Distribution and Origin of Multiple Bottom Simulating Reflectors in the Danube Deep-Sea Fan, Black Sea

NASA Astrophysics Data System (ADS)

Zander, T.; Berndt, C.; Haeckel, M.; Klaucke, I.; Bialas, J.; Klaeschen, D.

2015-12-01

The sedimentary succession of the anoxic, deep Black Sea Basin is an ideal location for organic matter preservation and microbial methane generation. In the depth range of the gas hydrate stability zone (GHSZ) methane gas forms methane hydrates and presumably large accumulations of gas hydrate exist in porous sediments, such as those encountered on the Danube deep-sea fan. High-resolution P-Cable 3D seismic data reveals the character and distribution of up to four stacked bottom simulating reflectors (BSR) within the channel-levee systems of the Danube deep-sea fan. These anomalous BSRs were first described by Popescu et al. (2006). The geological processes that lead to multiple BSRs are still poorly understood. The theoretical base of the GHSZ calculated from regional temperature gradients and salinity data is in agreement with the shallowest BSR in the area. We have tested two hypotheses that may explain the formation of the lower BSRs. The first hypothesis is that the lower BSRs are formed by overpressure compartments. Large amounts of free gas below the BSRs are trapped in the pore space increasing the pressure above hydrostatic condition up to a level where gas hydrates are stable again. The second hypothesis is that the lower BSRs are linked to the growth of the Danube fan. Sediment deposits from the outer levee of the youngest channel cover the area hosting multiple BSRs. The youngest channel developed during the last sea level lowstand that is correlated with the Neo-Euxinian that started 23,000 yrs. BP. We propose that the rapid sediment loading during sea level lowstands is a key factor for the preservation of paleo-BSRs in the study area. References Popescu, I., De Batist, M., Lericolais, G., Nouzé, H., Poort, J., Panin, N., Versteeg, W., Gillet, H., 2006. Multiple bottom-simulating reflections in the Black Sea: Potential proxies of past climate conditions. Marine Geology 227, 163-176.

Seismic evidence for mass-transport deposits and BSR occurrence on the forearc region along the central Ryukyu Islands, Japan

NASA Astrophysics Data System (ADS)

Komatsu, Y.; Kobayashi, T.; Fujii, T.

2017-12-01

Mass-transport deposits (MTDs) are widely observed from many continental margins and are a significant component of both slope and basin-floor settings. Although MTDs are typically mud-prone, some MTDs above certain porosity thresholds can act as important hydrocarbon reservoirs. MTDs associated with gas hydrate occurrence in the Ulleung basin were documented. The recovery of gas hydrate by drilling and piston coring has confirmed the gas hydrate accumulations in the basin. Gas hydrate dissociation may have played a role in the slide-initiation at the Storegga Slide offshore Norway. In this study, to identify the gas hydrate reservoir potential of MTDs, we focus on seismic characteristics (seismic facies, attributes, and velocity) of MTDs associated with bottom simulating reflectors (BSR). Our study area is in the forearc region along the central Ryukyu Islands (southeast Japan). In this area, BSR have been widely observed. However, the studies were insufficient for the evaluation of gas hydrate due to poor-quality 2-D seismic data. We use high-quality 3-D seismic volumes in water depths ranging from approximately 150 to 2000 m between Okinawa Island and Miyako Island. BSR in the eastern region of the study area was interpreted within Neogene to Quaternary MTDs. Strata in MTDs are correlated with the upper Shimajiri group based on the characteristics of well data outside of the seismic exploration area and stratigraphy of land areas. The Shimajiri group is composed of homogeneous siltstone intercalated with lenticular, thin-bedded, fine sandstone. Their group is water-dissolved gas reservoir in Okinawa Island and Miyako Island. On our seismic data, MTDs are shown as chaotic, poorly discontinuous strata of low amplitude, partially continuous moderate- to high-amplitude reflections. The seismic velocity profile shows a relative increase in MTD intervals above the BSR, similar to gas hydrate-bearing sediments. It is also indicative of over-consolidation that was result of compression caused by slumping.

Using Temperature as a Tracer to Study Fluid Flow Patterns On and Offshore Taiwan

NASA Astrophysics Data System (ADS)

Chi, W. C.

2017-12-01

Fluid flows are a dynamic system in the crust that affect crustal deformation and formation of natural resources. It is difficult to study fluid flow velocity instrumentally, but temperature data offers a quantitative tool that can be used as a tracer to study crustal hydrogeology. Here we present numerical techniques we have applied to study the fluid migration velocity along conduits including faults in on and offshore settings. Offshore SW Taiwan, we use a bottom-simulating reflector (BSR) from seismic profiles to study the temperature field at several hundred meters subbottom depth. The BSR is interpreted as the base of a gas hydrate stability zone under the seabed. Gas hydrates are solid-state water with gas molecules enclosed, which can be found where the temperature, pressure, and salinity conditions allow hydrates to be stable. Using phase diagrams and hydro pressure information we can derive the temperature at the BSR. BSRs are widespread in the study area, providing very dense temperature field information which shows upward bending of the BSR near faults. We have quantitatively estimated the 1D and 2D fluid flow patterns required to fit the BSR-based temperature field. This shows that fault zones can act as conduits with high permeability parallel to the fault planes. On the other hand, fault zones can also act as barriers to fluid flow, as demonstrated in our onland temperature data. We have collected temperature profiles at several bore holes onland that are very close together. The preliminary results show that the fault zones separate the ground water systems, causing very different geothermal gradients. Our results show that the physical properties of fault zones can be anisotropic, as demonstrated in previous work. Future work includes estimating the regional water expulsion budget offshore SW Taiwan, in particular for several gas hydrate sites.

Inverse-Ray Imaging of Gas Hydrates Along a MCS/OBS Profile at the Continental Slope Offshore SW Taiwan

NASA Astrophysics Data System (ADS)

Wang, T. K.; Chen, C.; Yang, B.; Lee, C.

2006-12-01

Prevalence of gas hydrates offshore SW Taiwan has been proposed due to lots of bottom-simulated reflectors (BSR) appeared on the seismic data. In this paper, we analyze a MCS/OBS profile with intensive BSR signals at the continental slope of the northern South China Sea. Firstly, MCS data with 160 channels collected by R/V Maurice-Ewing in September 1995 is re-processed through vertical velocity analysis, horizon velocity analysis, and prestack depth migration. Then, OBS data collected by the first Micro-OBS survey from NTOU team in August 2005 is analyzed through travel-time inversion of reflected and refracted arrivals for which the initial model is constructed from the MCS result. Finally, a novel technique of inverse reflected rays by considering both MCS and OBS data is applied for layer-stripping imaging of sedimentary layers. Velocity models imaged from three methods are confirmed the prevalence of BSR at 100-400 m depth below the sea floor along the whole profile. Relatively smooth sedimentary layers are observed below the lower slope of the continent whereas several mud diapers are imaged below the upper slope of the continent. Above the mud diapers, we find gas hydrates with high velocity of about 1.9-2.1 km/s and thickness of about 100 m immediately above the strong BSR. Similarly, near the mud diapers, free gas with low velocity of about 1.4-1.7 km/s and thickness of about 200 m is imaged. Migration of free gas through diapirism may result in lots of gas hydrates accumulated below the upper slope of the continent offshore SW Taiwan.

On the origin of multiple BSRs in the Danube deep-sea fan, Black Sea

NASA Astrophysics Data System (ADS)

Zander, Timo; Haeckel, Matthias; Berndt, Christian; Chi, Wu-Cheng; Klaucke, Ingo; Bialas, Joerg; Klaeschen, Dirk; Koch, Stephanie; Atgın, Orhan

2017-03-01

High-resolution 2D seismic data reveal the character and distribution of up to four stacked bottom simulating reflectors (BSR) within the channel-levee systems of the Danube deep-sea fan. The theoretical base of the gas hydrate stability zone (GHSZ) calculated from regional geothermal gradients and salinity data is in agreement with the shallowest BSR. For the deeper BSRs, BSR formation due to overpressure compartments can be excluded because the necessary gas column would exceed the vertical distance between two overlying BSRs. We show instead that the deeper BSRs are likely paleo BSRs caused by a change in pressure and temperature conditions during different limnic phases of the Black Sea. This is supported by the observation that the BSRs correspond to paleo seafloor horizons located in a layer between a buried channel-levee system and the levee deposits of the Danube channel. The good match of the observed BSRs and the BSRs predicted from deposition of these sediment layers indicates that the multiple BSRs reflect stages of stable sealevel lowstands possibly during glacial times. The observation of sharp BSRs several 10,000 of years but possibly up to 300,000 yr after they have left the GHSZ demonstrates that either hydrate dissociation does not take place within this time frame or that only small amounts of gas are released that can be transported by diffusion. The gas underneath the previous GHSZ does not start to migrate for several thousands of years.

In0.53Ga0.47As/InP conventional and inverted thermophotovoltaic cells with back surface reflector

NASA Astrophysics Data System (ADS)

Karlina, L. B.; Kulagina, M. M.; Timoshina, N. Kh.; Vlasov, A. S.; Andreev, V. M.

2007-02-01

Characteristics of conventional and inverted InGaAs/InP thermophotovoltaic (TPV) cells with a back surface reflector (BSR) fabricated on electrically active n-type InP substrates are presented. Thermophotovoltaic cells based on lattice matched InP-In0.53Ga0.47As heterostructures were fabricated with the use of LPE and Zn,P diffusion technologies. In the p-n TPV cells (conventional type, spectral range 600÷1800 nm) with a frontal p-InGaAs layer, BSR was made on a n-InP substrate. In the n-p structure (inverted type, spectral range1000-1800 nm) with a frontal bulk n-InP-window-substrate, BSR was formed on a p-InGaAs layer. Antireflection coating (ARC) on the frontal cell surface consists of ZnS/MgF2 layers. Results of investigation of sub-bangap photons reflection from InP substrates with a backside MgF2/Au mirror in the range of 1800÷2000nm are described. The reflection of BSR for InP samples with the doping level in the range of 1×1017÷6×1018cm-3 evidenced a weak dependence on their thickness and doping level. A reflection of 86÷90% has been measured for substrates 100μm thick and 80% for ones 400μm thick with ARC. Study of sub-bandgap photon reflection of p-InGaAs (Zn,P) layers with surface concentration of 1÷3×1019cm-3 has been also carried out. A reflection of 68÷77% for 2÷4μm layers with "hybrid" (ohmic contact plus mirror) back-surface reflector consisted of deposited Cr/Au layers was measured. It was found, that p-n and n-p thermophotovoltaic 1×1cm2 cells with identical grid design reveal similar parameters for up to 1A/cm2 current density (VOC=465mV and FF=64%) and the 76÷80% reflection of the sub-bandgap photons for wavelengths longer than 1.86μm. The developed inverted InGaAs TPV cells have been tested under illumination of silicon carbide high temperature emitter. The photocurrent density Jsc=7A/cm2, open circuit voltage Voc=0.476V and fill factor FF=0.691 have been measured in the inverted (without BSR) InGaAs cell under SiC emitter heated to the temperature of about 1550°C. Both types of devices can successfully be used as TPV cells for conversion of radiation in the range of 1500-1900K, with 14-15% efficiency.

A Study of Contacts and Back-Surface Reflectors for 0.6eV Ga0.32In0.68As/InAs0.32P0.68 Thermophotovoltaic Monolithically Interconnected Modules

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

Wu, X.; Duda, A.; Carapella, J. J.

1998-12-23

Thermophotovoltaic (TPV) systems have recently rekindled a high level of interest for a number of applications. In order to meet the requirement of low-temperature ({approx}1000 C) TPV systems, 0.6-eV Ga0.32In0.68As/InAs0.32P0.68 TPV monolithically interconnected modules (MIMs) have been developed at the National Renewable energy Laboratory (NREL)[1]. The successful fabrication of Ga0.32In0.68As/InAs0.32P0.68 MIMs depends on developing and optimizing of several key processes. Some results regarding the chemical vapor deposition (CVD)-SiO2 insulating layer, selective chemical etch via sidewall profiles, double-layer antireflection coatings, and metallization via interconnects have previously been given elsewhere [2]. In this paper, we report on the study of contacts andmore » back-surface reflectors. In the first part of this paper, Ti/Pd/Ag and Cr/Pd/Ag contact to n-InAs0.32P0.68and p-Ga0.32In0.68As are investigated. The transfer length method (TLM) was used for measuring of specific contact resistance Rc. The dependence of Rc on different doping levels and different pre-treatment of the two semiconductors will be reported. Also, the adhesion and the thermal stability of Ti/Pd/Ag and Cr/Pd/Ag contacts to n-InAs0.32P0.68and p-Ga0.32In0.68As will be presented. In the second part of this paper, we discuss an optimum back-surface reflector (BSR) that has been developed for 0.6-eV Ga0.32In0.68As/InAs0.32P0.68 TPV MIM devices. The optimum BSR consists of three layers: {approx}1300{angstrom} MgF2 (or {approx}1300{angstrom} CVD SiO2) dielectric layer, {approx}25{angstrom} Ti adhesion layer, and {approx}1500{angstrom} Au reflection layer. This optimum BSR has high reflectance, good adhesion, and excellent thermal stability.« less

Amplitude Variation of Bottom Simulating Reflection with Respect to Frequency - Transitional Base or Attenuation?

USGS Publications Warehouse

Lee, Myung W.

2007-01-01

The amplitude of a bottom simulating reflection (BSR), which occurs near the phase boundary between gas hydrate-bearing sediments and underlying gas-filled sediments, strongly depends on the frequency content of a seismic signal, as well as the impedance contrast across the phase boundary. A strong-amplitude BSR, detectable in a conventional seismic profile, is a good indicator of the presence of free gas beneath the phase boundary. However, the BSR as observed in low-frequency multichannel seismic data is generally difficult to identify in high-frequency, single-channel seismic data. To investigate the frequency dependence of BSR amplitudes, single-channel seismic data acquired with an air gun source at Blake Ridge, which is located off the shore of South Carolina, were analyzed in the frequency range of 10-240 Hz. The frequency-dependent impedance contrast caused by the velocity dispersion in partially gas saturated sediments is important to accurately analyze BSR amplitude. Analysis indicates that seismic attenuation of gas hydrate-bearing sediments, velocity dispersion, and a transitional base all contribute to the frequency-dependent BSR amplitude variation in the frequency range of 10-500 Hz. When velocity dispersion is incorporated into the BSR amplitude analysis, the frequency-dependent BSR amplitude at Blake Ridge can be explained with gas hydrate-bearing sediments having a quality factor of about 250 and a transitional base with a thickness of about 1 meter.

Evidence of focused fluid flow associated to the gas hydrate wedge on the angolan margin

NASA Astrophysics Data System (ADS)

Casenave, Viviane; Imbert, Patrice; Gay, Aurélien

2013-04-01

The Lower Congo basin, offshore south west Africa, is a prolific petroleum province, which has been extensively investigated and exploited for more than 30 years. The study area is located above a producing oil and gas field, the hydrocarbons being trapped in turbidite channels on a tectonic horst. The work is based on the analysis of 3-D seismic and site survey data (2D AUV, grab samples and ROV photos) above a deeper oil and gas field called Moho. The analysis of this seismic data set reveals numerous evidence of focused fluid flow through the Mio-Pliocene interval, including present-day seafloor seep features and shallow buried paleo-seeps, indicating past activity of the system. The main fluid migration-related structures are the followings: 1. Stacked amplitude anomalies, interpreted as the result of vertical migrations of gas are pervasive. Most of these seep features seem to correspond to fossil events as they are interpreted as successive precipitation at the seafloor of patches of seep carbonates (MDAC, Methane Derived Authigenic Carbonates) stacked during the activity of a seep. 2. Another phenomenon of gas migration through the sediment pile is visible on the seismic data of the Moho area: it is the BSR (Bottom Simulating Reflector) located above a horst. The BSR is formed by 2 patches, which cover a small area about 1.5 km² for the largest and 0.5 km2 for the smallest. These two BSRs are located under a depth of water included between 600 and 700 m, into the BSR wedging area. 3. A 'spider morphology' is visible on the seafloor. It corresponds to depressions forming variable-sized furrows oriented slightly oblique to the slope dip direction, directly above the upslope limit of the BSR patches. ROV photos and movies from these furrows showed the presence of seep carbonates and of bacterial carpets, linked with methane leak at the seafloor. A similar 'spider morphology' was also identified in subsurface, at 20 ms under the seafloor, further down the slope, in present-day water depth ranging from 750 to 850 m. These buried depressions cover a stripe in that depth range all over the area covered by the 3D seismic data. These two observations, made both on the seafloor and on it subsurface, seem to correspond to the same phenomenon of fluid expulsion, for the views of the seismic morphology similarities, but in different periods. It is interpreted as a result of a downward migration of the BSR, because of the last sea-level rise, which would have meant an upslope migration of the intersection of the BSR with the seafloor. Based on the evidence of gas hydrate dissociation phenomenon in the Lower Congo Basin, the pinch-out of the BSR may be considered as a natural laboratory for investigating a possible massive greenhouse gas release due to global warming.

Impact of Gas Hydrate and Related Fluid Seepage on Submarine Slope Failures along the Margins of the Ulleung Basin, East Sea (Japan Sea)

NASA Astrophysics Data System (ADS)

Horozal, S.; Bahk, J. J.; Urgeles, R.; Kim, G. Y.; Cukur, D.; Lee, G. H.; Lee, S. H.; Kim, S. P.; Ryu, B. J.; Kim, J. H.

2016-12-01

The Ulleung Basin is a back-arc basin that is known to retain gas hydrate reservoirs in the East (Japan) Sea. The basin contains large volumes of mass-transport deposits (MTDs) due to submarine slope failures along its margins since the Neogene. In this study, seismic indicators of gas hydrate and associated gas and fluid flow were re-compiled on a regional multi-channel seismic reflection data. The gas hydrate occurrence zone (GHOZ) is defined by the BSR (bottom-simulating reflector) distribution. It is more pronounced along the southwestern slope with a minimum depth of 100 mbsf (meters below seafloor) at 295 mbsl (meter below sea level) on the southern, while its thickness is the greatest (250 mbsf) at the southwestern margin. Flow and seepage structures reflected on the seismic data as columnar acoustic-blanking zones varying in width and height (up to hundreds of meters) were classified into: (a) buried seismic chimneys (BSC), (b) chimneys with a mound (SCM), and (c) chimneys with a depression (SCD) on the seafloor. Pockmarks which are not associated with seismic chimneys, reflection anomalies (i.e., enhanced reflections below the BSR and hyperbolic reflections), and SCD are predominant features in the western margin, while the BSR, BSC and SCM are densely distributed in the south-southwestern margin. Present-day gas hydrate stability zone (GHSZ) is calculated using in-situ bottom-water temperature and geothermal gradient measurements (ranging between 0-17.5 oC and 25-200 oC/km, respectively) and multibeam bathymetry data. The GHSZ thickness exceeds 190 m, and the upslope limit of GHSZ ranges between about 180 and 260 mbsl. This depth range is in the proximity of the uppermost depths of landslide scars ( 190 mbsl) which are common features on the slopes along with glide planes, slides/slumps and MTDs. Overall, the base of GHSZ (BGHSZ) and the BSR depths are well-correlated in the basin. However, the BSR depths are typically greater (up to 50 m) than the BGHSZ depths on the slopes suggesting that the GHOZ is not stable. A close correlation exists between the spatial distributions of the landslides, and indicators of gas hydrate and gas/fluid flow and the GHSZ. This may imply that excess pore-pressure caused by dissociation/dissolution of gas hydrates could have played a role on slope failures.

The history and future trends of ocean warming-induced gas hydrate dissociation in the SW Barents Sea

NASA Astrophysics Data System (ADS)

Vadakkepuliyambatta, Sunil; Chand, Shyam; Bünz, Stefan

2017-01-01

The Barents Sea is a major part of the Arctic where the Gulf Stream mixes with the cold Arctic waters. Late Cenozoic uplift and glacial erosion have resulted in hydrocarbon leakage from reservoirs, evolution of fluid flow systems, shallow gas accumulations, and hydrate formation throughout the Barents Sea. Here we integrate seismic data observations of gas hydrate accumulations along with gas hydrate stability modeling to analyze the impact of warming ocean waters in the recent past and future (1960-2060). Seismic observations of bottom-simulating reflectors (BSRs) indicate significant thermogenic gas input into the hydrate stability zone throughout the SW Barents Sea. The distribution of BSR is controlled primarily by fluid flow focusing features, such as gas chimneys and faults. Warming ocean bottom temperatures over the recent past and in future (1960-2060) can result in hydrate dissociation over an area covering 0.03-38% of the SW Barents Sea.

Role of gas hydrates in slope failure on frontal ridge of northern Cascadia margin

NASA Astrophysics Data System (ADS)

Yelisetti, Subbarao; Spence, George D.; Riedel, Michael

2014-10-01

Several slope failures are observed near the deformation front on the frontal ridges of the northern Cascadia accretionary margin off Vancouver Island. The cause for these events is not clear, although several lines of evidence indicate a possible connection between the occurrence of gas hydrate and submarine landslide features. The presence of gas hydrate is indicated by a prominent bottom-simulating reflector (BSR), at a depth of ˜265-275 m beneath the seafloor (mbsf), as interpreted from vertical-incidence and wide-angle seismic data beneath the ridge crests of the frontal ridges. For one slide, informally called Slipstream Slide, the velocity structure inferred from tomography analyses shows anomalous high velocities values of about 2.0 km s-1 at shallow depths of 100 mbsf. The estimated depth of the glide plane (100 ± 10 m) closely matches the depth of these shallow high velocities. In contrast, at a frontal ridge slide just to the northwest (informally called Orca Slide), the glide plane occurs at the same depth as the current BSR. Our new results indicate that the glide plane of the Slipstream slope failure is associated with the contrast between sediments strengthened by gas hydrate and overlying sediments where little or no hydrate is present. In contrast, the glide plane of Orca Slide is between sediment strengthened by hydrate underlain by sediments beneath the gas hydrate stability zone, possibly containing free gas. Additionally, a set of margin perpendicular normal faults are imaged from seafloor down to BSR depth at both frontal ridges. As inferred from the multibeam bathymetry, the estimated volume of the material lost during the slope failure at Slipstream Slide is about 0.33 km3, and ˜0.24 km3 of this volume is present as debris material on the ocean basin floor. The 20 per cent difference is likely due to more widely distributed fine sediments not easily detectable as bathymetric anomalies. These volume estimates on the Cascadia margin are approaching the mass failure volume for other slides that have generated large tsunamis-for example 1-3 km3 for a 1998 Papua New Guinea slide.

Gas hydrate distribution identified from wireline logging data and seismic data in the Pearl River Mouth Basin,northern slope of South China Sea

NASA Astrophysics Data System (ADS)

Wang, X.; Wu, S.; Yang, S.

2012-12-01

Wireline logging data acquired during China's first gas hydrate drilling expedition (GMGS-1) in April-June of 2007 and seismic data indicate the occurrences of gas hydrate above the base of gas hydrate stability (BGHS). Bottom simulating reflectors (BSRs) are widespread in the drilling zone, predominantly occurring beneath the ridges of migrating submarine canyons. Higher P-wave velocities and higher resistivity above BGHS at sites SH3, SH2 and SH7 indicate the presence of gas hydrate in the thickness range from 10 to 25 meters below seafloor. However, the measured compressional (P-wave) velocities at site SH3 show there are three abnormal P-wave velocities zones above the BGHS, which are lower than those of water-saturated sediments, indicating the presence of free gas in the pore space. The P-wave velocities drop as low as 1.0 m/s at the depth of 125 m. While the recovered core at 100 bars degassed show that methane was under unsaturated. Below the BSR, seismic data show enhanced reflections and the P-impedances have lower values, which inferred these reflections to be caused by free gas. To determine whether the low well-log P-wave velocity is caused by in-situ gas, synthetic seismograms were generated using the measured well-log P-wave velocity and calculated assuming water-saturated in the pore space. Comparing the surface seismic data with synthetic seismograms suggests that low P-wave velocities are likely caused by migrating gas due to borehole drilling. Three dimensional (3D) multi-channel seismic (MCS) data, inverted P-wave velocity, and RMS amplitude are used to study the detailed distribution and occurrences of the BSR and associated with the migration of gas in this basin. Three types of BSR and amplitude anomalies zones are identified from 3D seismic data. Gas hydrate in this basin are linked to and associated with gas accumulation below gas hydrate stability zone, which has a closerelationship with focused fluid flow features such as gas chimneys, faults, diapir, pipe.

Possible Causes of Double-BSRs on the Hikurangi Margin, New Zealand

NASA Astrophysics Data System (ADS)

Pecher, I. A.; Mountjoy, J. J.; Crutchley, G. J.; Krastel, S.; Koch, S.; Dannowski, A.; Bialas, J.; Henrys, S. A.

2014-12-01

Bottom Simulating Reflections (BSRs) are commonly thought to be caused by free gas at the base of gas hydrate stability (BGHS). BSRs usually occur at the pressure-temperature conditions for the phase boundary of gas hydrate, which depends on gas composition, pore water chemistry, and various other factors. Hence, BSRs should only occur at a single depth level beneath the seafloor. At several locations worldwide however, double and multiple BSRs have been observed. We have recently discovered localized double-BSRs on the Hikurangi Margin east of New Zealand and present first results from studying the possible origin of these double-BSRs. Both BSRs display negative polarity compared to the seafloor ruling out diagenetic origins. The deeper BSR (BSR-2) is found to be anomalously deep, while the shallower BSR (BSR-1) is at similar depths as BSRs regionally. BSR-2 and BSR-1 are clearly separated on seismic lines from east to west, while they converge from north to south. We propose two possible models for formation of these double-BSRs: 1. Uplift leads to depressurization and an upward movement of the BGHS with respect to the seafloor. BSR-1 may have formed at the new BGHS while immobile gas may remain in place at the original level of the BGHS causing BSR-2. 2. Thermogenic gas may leak from a deeper hydrocarbon reservoir. Gas mixes of thermogenic origin are predicted to form hydrate that is more stable than pure methane hydrate, in particular if the mix contains gases that lead to formation of Structure-II hydrate. BSR-2 may form at a level of the BGHS for a more stable gas mix; residual gases may migrate further until they reach the phase boundary for less stable hydrates at BSR-1. We currently slightly favour uplift as cause of the double-BSRs largely because of the smooth topography of BSR-2: Small-scale lateral variations of gas composition should lead to significant BSR topography. More importantly, we note that the process of fractionation of gas during hydrate formation from thermogenic gas mixes in nature is only poorly understood.

Improved image quality using monolithic scintillator detectors with dual-sided readout in a whole-body TOF-PET ring: a simulation study.

PubMed

Tabacchini, Valerio; Surti, Suleman; Borghi, Giacomo; Karp, Joel S; Schaart, Dennis R

2017-02-13

We have recently built and characterized the performance of a monolithic scintillator detector based on a 32 mm  ×  32 mm  ×  22 mm LYSO:Ce crystal read out by digital silicon photomultiplier (dSiPM) arrays coupled to the crystal front and back surfaces in a dual-sided readout (DSR) configuration. The detector spatial resolution appeared to be markedly better than that of a detector consisting of the same crystal with conventional back-sided readout (BSR). Here, we aim to evaluate the influence of this difference in the detector spatial response on the quality of reconstructed images, so as to quantify the potential benefit of the DSR approach for high-resolution, whole-body time-of-flight (TOF) positron emission tomography (PET) applications. We perform Monte Carlo simulations of clinical PET systems based on BSR and DSR detectors, using the results of our detector characterization experiments to model the detector spatial responses. We subsequently quantify the improvement in image quality obtained with DSR compared to BSR, using clinically relevant metrics such as the contrast recovery coefficient (CRC) and the area under the localized receiver operating characteristic curve (ALROC). Finally, we compare the results with simulated rings of pixelated detectors with DOI capability. Our results show that the DSR detector produces significantly higher CRC and increased ALROC values than the BSR detector. The comparison with pixelated systems indicates that one would need to choose a crystal size of 3.2 mm with three DOI layers to match the performance of the BSR detector, while a pixel size of 1.3 mm with three DOI layers would be required to get on par with the DSR detector.

Improved image quality using monolithic scintillator detectors with dual-sided readout in a whole-body TOF-PET ring: a simulation study

NASA Astrophysics Data System (ADS)

Tabacchini, Valerio; Surti, Suleman; Borghi, Giacomo; Karp, Joel S.; Schaart, Dennis R.

2017-03-01

We have recently built and characterized the performance of a monolithic scintillator detector based on a 32 mm  ×  32 mm  ×  22 mm LYSO:Ce crystal read out by digital silicon photomultiplier (dSiPM) arrays coupled to the crystal front and back surfaces in a dual-sided readout (DSR) configuration. The detector spatial resolution appeared to be markedly better than that of a detector consisting of the same crystal with conventional back-sided readout (BSR). Here, we aim to evaluate the influence of this difference in the detector spatial response on the quality of reconstructed images, so as to quantify the potential benefit of the DSR approach for high-resolution, whole-body time-of-flight (TOF) positron emission tomography (PET) applications. We perform Monte Carlo simulations of clinical PET systems based on BSR and DSR detectors, using the results of our detector characterization experiments to model the detector spatial responses. We subsequently quantify the improvement in image quality obtained with DSR compared to BSR, using clinically relevant metrics such as the contrast recovery coefficient (CRC) and the area under the localized receiver operating characteristic curve (ALROC). Finally, we compare the results with simulated rings of pixelated detectors with DOI capability. Our results show that the DSR detector produces significantly higher CRC and increased ALROC values than the BSR detector. The comparison with pixelated systems indicates that one would need to choose a crystal size of 3.2 mm with three DOI layers to match the performance of the BSR detector, while a pixel size of 1.3 mm with three DOI layers would be required to get on par with the DSR detector.

P-Wave and S-Wave Velocity Structure of Submarine Landslide Associated With Gas Hydrate Layer on Frontal Ridge of Northern Cascadia Margin

NASA Astrophysics Data System (ADS)

He, T.; Lu, H.; Yelisetti, S.; Spence, G.

2015-12-01

The submarine landslide associated with gas hydrate is a potential risk for environment and engineering projects, and thus from long time ago it has been a hot topic of hydrate research. The study target is Slipstream submarine landslide, one of the slope failures observed on the frontal ridges of the Northern Cascadia accretionary margin off Vancouver Island. The previous studies indicated a possible connection between this submarine landslide feature and gas hydrate, whose occurrence is indicated by a prominent bottom-simulating reflector (BSR), at a depth of ~265-275 m beneath the seafloor (mbsf). The OBS (Ocean Bottom Seismometer) data collected during SeaJade (Seafloor Earthquake Array - Japan Canada Cascadia Experiment) project were used to derive the subseafloor velocity structure for both P- and S-wave using travel times picked from refraction and reflection events. The P-wave velocity structure above the BSR showed anomalous high velocities of about 2.0 km/s at shallow depths of 100 mbsf, closely matching the estimated depth of the glide plane (100 ± 10 m). Forward modelling of S-waves was carried out using the data from the OBS horizontal components. The S-wave velocities, interpreted in conjunction with the P-wave results, provide the key constraints on the gas hydrate distribution within the pores. The hydrate distribution in the pores is important for determining concentrations, and also for determining the frame strength which is critical for controlling slope stability of steep frontal ridges. The increase in S-wave velocity suggests that the hydrate is distributed as part of the load-bearing matrix to increase the rigidity of the sediment.

3D seismic analysis of the gas hydrate system and the fluid migration paths in part of the Niger Delta Basin, Nigeria

NASA Astrophysics Data System (ADS)

Akinsanpe, Olumuyiwa T.; Adepelumi, Adekunle A.; Benjamin, Uzochukwu K.; Falebita, Dele E.

2017-12-01

Comprehensive qualitative and semi-quantitative seismic analysis was carried out on 3-dimensional seismic data acquired in the deepwater compressional and shale diapiric zone of the Niger Delta Basin using an advanced seismic imaging tool. The main aim of this work is to obtain an understanding of the forming mechanism of the gas hydrate system, and the fluid migration paths associated with this part of the basin. The results showed the presence of pockmarks on the seafloor and bottom simulating reflectors (BSRs) in the field, indicating the active fluid flux and existence of gas hydrate system in the area. In the area of approximately 195 km2 occupying nearly 24% of the entire study field, three major zones with continuous or discontinuous BSRs of 3 to 7 km in length which are in the northeastern, southern and eastern part of the field respectively were delineated. The BSR is interpreted to be the transition between the free gas zone and the gas hydrate zone. The geologic structures including faults (strike-slip and normal faults), chimneys and diapirs were deduced to be the main conduits for gas migration. It is concluded that the biogenic gases generated in the basin were possibly transported via faults and chimneys by advection processes and subsequently accumulated under low temperature and high pressure conditions in the free gas zone below the BSR forming gas hydrate. A plausible explanation for the presence of the ubiquitous pockmarks of different diameters and sizes in the area is the transportation of the excessive gas to the seafloor through these mapped geologic structures.

Two-Dimensional Heat Transfer Modeling of the Formosa Ridge Offshore SW Taiwan: Implication for Fluid Migrating Paths of a Cold Seep Site

NASA Astrophysics Data System (ADS)

Tsai, Y.; Chi, W.; Liu, C.; Shyu, C.

2011-12-01

The Formosa Ridge, a small ridge located on the passive China continental slope offshore southwestern Taiwan, is an active cold seep site. Large and dense chemosynthetic communities were found there by the ROV Hyper-Dolphin during the 2007 NT0705 cruise. A vertical blank zone is clearly observed on all the seismic profiles across the cold seep site. This narrow zone is interpreted to be the fluid conduit of the seep site. Previous studies suggest that cold sea water carrying large amount of sulfate could flow into the fluid system from flanks of the ridge, and forms a very effective fluid circulation system that emits both methane and hydrogen sulfide to feed the unusual chemosynthetic communities observed at the Formosa Ridge cold seep site. Here we use thermal signals to study possible fluid flow migration paths. In 2008 and 2010, we have collected vdense thermal probe data at this site. We also study the temperatures at Bottom-Simulating Reflectors (BSRs) based on methane hydrate phase diagram. We perform 2D finite element thermal conductive simulations to study the effects of bathymetry on the temperature field in the ridge, and compare the simulation result with thermal probe and BSR-derived datasets. The boundary conditions include insulated boundaries on both sides, and we assign a fix temperature at the bottom of the model using an average regional geothermal gradient. Sensitivity tests and thermal probe data from a nearby region give a regional background geothermal gradient of 0.04 to 0.05 °C/m. The outputs of the simulation runs include geothermal gradient and temperature at different parts of the model. The model can fit the geothermal gradient at a distance away from the ridge where there is less geophysics evidence of fluid flow. However our model over-predicts the geothermal gradient by 50% at the ridge top. We also compare simulated temperature field and found that under the flanks of the ridge the temperature is cooled by 2 °C compared with the BSR-derived temperatures. These results are consistent with the interpretation of cold seawater being pumped into the ridge from both flanks, cooling the temperature field. In summary, the thermal data are consistence with previously proposed fluid circulation model.

Gas and porewater composition of shallow sediments in the Tuaheni Basin, New Zealand

NASA Astrophysics Data System (ADS)

Rose, P. S.; Coffin, R. B.; Yoza, B.; Boyd, T. J.; Crutchley, G. J.; Mountjoy, J. J.; Pecher, I. A.

2015-12-01

Seismic profiles collected during previous investigations on the Hikurangi Margin, off the North Island, New Zealand showed bottom simulating reflectors (BSRs), which are generally indicative of the presence of free gas. Further, double BSRs clearly identified in the Tuaheni Basin were hypothesized to result from differences in gas composition and fluid migration. During a cruise on the RV Tangaroa in June 2015 (TAN 1508) additional seismic data were collected and used to identify piston coring targets. Coring locations were selected to sample around BSR pinch-outs and possible fluid migration pathways to determine gas composition and flux. Shallow sediments collected in June 2015 in the Tuaheni Basin had relatively low sediment headspace CH4 concentrations (6000ppm. Higher molecular weight alkanes were not detected in the sediment headspace gas at any location. Sediment porewater sulfate, chloride and sulfide concentrations will be presented with CH4concentration profiles and geophysical data.

The character and amplitude of ‘discontinuous’ bottom-simulating reflections in marine seismic data

DOE PAGES

Hillman, Jess I. T.; Cook, Ann E.; Sawyer, Derek E.; ...

2016-11-22

Bottom-simulating reflections (BSRs) identified in seismic data are well documented; and are commonly interpreted to indicate the presence of gas hydrates along continental margins, as well as to estimate regional volumes of gas hydrate. A BSR is defined as a reflection that sub-parallels the seafloor but is opposite in polarity and cross-cuts dipping sedimentary strata. BSRs form as a result of a strong negative acoustic impedance contrast. BSRs, however, are a diverse seismic phenomena that manifest in strikingly contrasting ways in different geological settings, and in different seismic data types. We investigate the characteristics of BSRs, using conventional and highmore » resolution, 2D and 3D seismic data sets in three locations: the Terrebonne and Orca Basins in the Gulf of Mexico, and Blake Ridge on the US Atlantic Margin. The acquisition geometry and frequency content of the seismic data significantly impact the resultant character of BSRs, as observed with depth and amplitude maps of the BSRs. Furthermore, our amplitude maps reinforce the concept that the BSR represents a zone, over which the transition from hydrate to free gas occurs, as opposed to the conventional model of the BSR occurring at a single interface. Our results show that a BSR can be mapped in three dimensions but it is not spatially continuous, at least not at the basin scale. Rather, a BSR manifests itself as a discontinuous, or patchy, reflection and only at local scales is it continuous. We suggest the discontinuous nature of BSRs is the result of variable saturation and distribution of free gas and hydrate, acquisition geometry and frequency content of the recorded seismic data. Lastly, the commonly accepted definition of a BSR should be broadened with careful consideration of these factors, to represent the uppermost extent of enhanced amplitude at the shallowest occurrence of free gas trapped by overlying hydrate-bearing sediments.« less

The character and amplitude of 'discontinuous' bottom-simulating reflections in marine seismic data

NASA Astrophysics Data System (ADS)

Hillman, Jess I. T.; Cook, Ann E.; Sawyer, Derek E.; Küçük, H. Mert; Goldberg, David S.

2017-02-01

Bottom-simulating reflections (BSRs) identified in seismic data are well documented; and are commonly interpreted to indicate the presence of gas hydrates along continental margins, as well as to estimate regional volumes of gas hydrate. A BSR is defined as a reflection that sub-parallels the seafloor but is opposite in polarity and cross-cuts dipping sedimentary strata. BSRs form as a result of a strong negative acoustic impedance contrast. BSRs, however, are a diverse seismic phenomena that manifest in strikingly contrasting ways in different geological settings, and in different seismic data types. We investigate the characteristics of BSRs, using conventional and high resolution, 2D and 3D seismic data sets in three locations: the Terrebonne and Orca Basins in the Gulf of Mexico, and Blake Ridge on the US Atlantic Margin. The acquisition geometry and frequency content of the seismic data significantly impact the resultant character of BSRs, as observed with depth and amplitude maps of the BSRs. Furthermore, our amplitude maps reinforce the concept that the BSR represents a zone, over which the transition from hydrate to free gas occurs, as opposed to the conventional model of the BSR occurring at a single interface. Our results show that a BSR can be mapped in three dimensions but it is not spatially continuous, at least not at the basin scale. Rather, a BSR manifests itself as a discontinuous, or patchy, reflection and only at local scales is it continuous. We suggest the discontinuous nature of BSRs is the result of variable saturation and distribution of free gas and hydrate, acquisition geometry and frequency content of the recorded seismic data. The commonly accepted definition of a BSR should be broadened with careful consideration of these factors, to represent the uppermost extent of enhanced amplitude at the shallowest occurrence of free gas trapped by overlying hydrate-bearing sediments.

The character and amplitude of ‘discontinuous’ bottom-simulating reflections in marine seismic data

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

Hillman, Jess I. T.; Cook, Ann E.; Sawyer, Derek E.

Bottom-simulating reflections (BSRs) identified in seismic data are well documented; and are commonly interpreted to indicate the presence of gas hydrates along continental margins, as well as to estimate regional volumes of gas hydrate. A BSR is defined as a reflection that sub-parallels the seafloor but is opposite in polarity and cross-cuts dipping sedimentary strata. BSRs form as a result of a strong negative acoustic impedance contrast. BSRs, however, are a diverse seismic phenomena that manifest in strikingly contrasting ways in different geological settings, and in different seismic data types. We investigate the characteristics of BSRs, using conventional and highmore » resolution, 2D and 3D seismic data sets in three locations: the Terrebonne and Orca Basins in the Gulf of Mexico, and Blake Ridge on the US Atlantic Margin. The acquisition geometry and frequency content of the seismic data significantly impact the resultant character of BSRs, as observed with depth and amplitude maps of the BSRs. Furthermore, our amplitude maps reinforce the concept that the BSR represents a zone, over which the transition from hydrate to free gas occurs, as opposed to the conventional model of the BSR occurring at a single interface. Our results show that a BSR can be mapped in three dimensions but it is not spatially continuous, at least not at the basin scale. Rather, a BSR manifests itself as a discontinuous, or patchy, reflection and only at local scales is it continuous. We suggest the discontinuous nature of BSRs is the result of variable saturation and distribution of free gas and hydrate, acquisition geometry and frequency content of the recorded seismic data. Lastly, the commonly accepted definition of a BSR should be broadened with careful consideration of these factors, to represent the uppermost extent of enhanced amplitude at the shallowest occurrence of free gas trapped by overlying hydrate-bearing sediments.« less

Equivalent formation strength as a proxy tool for exploring the existence and distribution of gas hydrates

NASA Astrophysics Data System (ADS)

Hamada, Y.; Yamada, Y.; Sanada, Y.; Nakamura, Y.; Kido, Y. N.; Moe, K.

2017-12-01

Gas hydrates bearing layer can be normally identified by a basement simulating reflector (BSR) or well logging because of their high acoustic- and electric impedance compared to the surrounding formation. These characteristics of the gas hydrate can also represent contrast of in-situ formation strength. We here attempt to describe gas hydrate bearing layers based on the equivalent strength (EST). The Indian National Gas Hydrate Program (NGHP) Expedition 02 was executed 2015 off the eastern margin of the Indian Peninsula to investigate distribution and occurrence of gas hydrates. From 25 drill sites, downhole logging data, cored samples, and drilling performance data were collected. Recorded drilling performance data was converted to the EST, which is a developed mechanical strength calculated only by drilling parameters (top drive torque, rotation per minute , rate of penetration , and drill bit diameter). At a representative site, site 23, the EST shows constant trend of 5 to 10 MPa, with some positive peaks at 0 - 270 mbsf interval, and sudden increase up to 50 MPa above BSR depth (270 - 290 mbsf). Below the BSR, the EST stays at 5-10 MPa down to the bottom of the hole (378 mbsf). Comparison of the EST with logging data and core sample description suggests that the depth profiles of the EST reflect formation lithology and gas hydrate content: the EST increase in the sand-rich layer and the gas hydrate bearing zone. Especially in the gas hydrate zone, the EST curve indicates approximately the same trend with that of P-wave velocity and resistivity measured by downhole logging. Cross plot of the increment of the EST and resistivity revealed the relation between them is roughly logarithmic, indicating the increase and decrease of the EST strongly depend on the saturation factor of gas hydrate. These results suggest that the EST, proxy of in-situ formation strength, can be an indicator of existence and amount of the gas-hydrate layer. Although the EST was calculated after drilling utilizing recorded surface drilling parameter in this study, the EST can be acquired during drilling by using real-time drilling parameters. In addition, the EST only requires drilling performance parameters without any additional tools or measurements, making it a simplified and economical tool for the exploration of gas hydrates.

Density structure of submarine slump and normal sediments of the first gas production test site at Daini-Atsumi Knoll near Nankai Trough, estimated by LWD logging data

NASA Astrophysics Data System (ADS)

Suzuki, K.; Takayama, T.; Fujii, T.; Yamamoto, K.

2014-12-01

Many geologists have discussed slope instability caused by gas-hydrate dissociation, which could make movable fluid in pore space of sediments. However, physical property changes caused by gas hydrate dissociation would not be so simple. Moreover, during the period of natural gas-production from gas-hydrate reservoir applying depressurization method would be completely different phenomena from dissociation processes in nature, because it could not be caused excess pore pressure, even though gas and water exist. Hence, in all cases, physical properties of gas-hydrate bearing sediments and that of their cover sediments are quite important to consider this phenomena, and to carry out simulation to solve focusing phenomena during gas hydrate dissociation periods. Daini-Atsumi knoll that was the first offshore gas-production test site from gas-hydrate is partially covered by slumps. Fortunately, one of them was penetrated by both Logging-While-Drilling (LWD) hole and pressure-coring hole. As a result of LWD data analyses and core analyses, we have understood density structure of sediments from seafloor to Bottom Simulating Reflector (BSR). The results are mentioned as following. ・Semi-confined slump showed high-density, relatively. It would be explained by over-consolidation that was result of layer-parallel compression caused by slumping. ・Bottom sequence of slump has relative high-density zones. It would be explained by shear-induced compaction along slide plane. ・Density below slump tends to increase in depth. It is reasonable that sediments below slump deposit have been compacting as normal consolidation. ・Several kinds of log-data for estimating physical properties of gas-hydrate reservoir sediments have been obtained. It will be useful for geological model construction from seafloor until BSR. We can use these results to consider geological model not only for slope instability at slumping, but also for slope stability during depressurized period of gas production from gas-hydrate. AcknowledgementThis study was supported by funding from the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) planned by the Ministry of Economy, Trade and Industry (METI).

Baseline seismic survey for the 2nd offshore methane hydrate production test in the Eastern Nankai Trough

NASA Astrophysics Data System (ADS)

Teranishi, Y.; Inamori, T.; Kobayashi, T.; Fujii, T.; Saeki, T.; Takahashi, H.; Kobayashi, F.

2017-12-01

JOGMEC carries out seismic monitoring surveys before and after the 2nd offshore methane hydrate (MH) production test in the Eastern Nankai Trough and evaluates MH dissociation behavior from the time-lapse seismic response. In 2016, JOGMEC deployed Ocean Bottom Cable (OBC) system provided by OCC in the Daini Atsumi Knoll with water depths of 900-1100 m. The main challenge of the seismic survey was to optimize the cable layout for ensuring an effective time-lapse seismic detectability while overcoming the following two issues: 1. OBC receiver lines were limited to only two lines. It was predicted that the imaging of shallow reflectors would suffer from lack of continuity and resolution due to this limitation of receiver lines. 2. The seafloor and shallow sedimentary layers including monitoring target are dipping to the Northwest direction. It was predicted that the refection points would laterally shift to up-dip direction (Southeast direction). In order to understand the impact of the issues above, the seismic survey was designed with elastic wave field simulation. The reflection seismic survey for baseline data was conducted in August 2016. A total of 70 receiver stations distributed along one cable were deployed successfully and a total of 9952 shots were fired. After the baseline seismic survey, the hydrophone and geophone vertical component datasets were processed as outlined below: designaturing, denoising, surface consistent deconvolution and surface consistent amplitude correction. High-frequency imaging with Reverse Time Migration (RTM) was introduced to these data sets. Improvements in imaging from the RTM are remarkable compared to the Kirchhoff migration and the existing Pre-stack time migration with 3D marine surface seismic data obtained and processed in 2002, especially in the following parts. The MH concentrated zone which has complex structures. Below the Bottom Simulating Reflector (BSR) which is present as a impedance-contrast boundary

A first application of marine-controlled source method on gas-hydrate study off SW Taiwan

NASA Astrophysics Data System (ADS)

Chiang, C.; Hsu, S.; Chen, C.; Evans, R. L.

2011-12-01

Bottom simulating reflector (BSR), high methane flux, shallow sulfide/methane interface, fluid gushed from the seafloor, self-carbonate within sediment, methane reef, and self-biome are widely distributed in the offshore of the southwestern Taiwan. These geophysical and geochemistry signatures imply a high gas hydrate reservoir area. However, the upper bound of the gas hydrate and shallow section of the sediment are still unclear. This study shows the results of our first marine controlled-source electromagnetic survey in 2010 and provides the information of shallow sediment around the offshore of southwestern Taiwan. Three target areas were conducted: the southeast of Small Ryukyu Islands (seepage, G96), west of Yung-An Ridge (YAR) and northwest of Good Weather Ridge (GWR). In total, fourteen survey lines have been carried out, and the total survey length is about 72 km. Our preliminary result shows that the resistivity/porosity anomalies within pockmarks and seepages correspond to the features from the sub-bottom profilers. The range of porosity change is 4 % in G96 and YAR sites, while in the GWR site there is up to 8 % of porosity change and implies a high gas hydrate potential area.

Gas Migration Processes through the Gas Hydrate Stability Zone at Four-Way Closure Ridge Offshore SW Taiwan

NASA Astrophysics Data System (ADS)

Kunath, P.; Chi, W. C.; Berndt, C.; Liu, C. S.

2016-12-01

We have used 3D P-Cable seismic data from Four-Way-Closure Ridge, a NW-SE trending anticlinal ridge within the lower slope domain of accretionary wedge, to investigate the geological constraints influencing the fluid migration pattern in the shallow marine sediments. In the seismic data, fluid migration feature manifests itself as high reflection layers of dipping strata, which originate underneath a bottom simulating reflector (BSR) and extend towards the seafloor. Shoaling of the BSR near fluid migration pathways indicates a focused fluid flux, perturbing the temperature field. Furthermore, seafloor video footage confirmed the presence of recent methane seepage above seismically imaged fluid migration pathways. We plan to test two hypotheses for the occurrence of these fluid migration pathways: 1) the extensional regime under the anticlinal ridge crest caused the initiation of localized fault zones, acting as fluid conduits in the gas hydrate stability zone (GHSZ). 2) sediment deformation induced by focused fluid flow and massive growth and dissolution of gas hydrate, similar to processes controlling the evolution of pockmarks on the Nigerian continental margin. We suggest that these processes may be responsible for the formation of a massive hydrate core in the crest of the anticline, as inferred from other geophysical datasets. Triggering process for fluid migration cannot be clearly defined. However, the existence of blind thrust faults may help to advect deep-seated fluids. This may be augmented by biogenic production of shallow gas underneath the ridge, where the excess of gas enables the coexistence of gas, water, and gas hydrate within the GHSZ. Fluid migration structures may exists because of the buoyancy of gas-bearing fluids. This study shows a potential model on how gas-bearing fluids migrate upward towards structural highs, which might occur in other anticlinal structures around the world. Keywords: P-Cable, gas-hydrate, fluid flow, fault-related fold, methane seepage

Fluid flow and methane occurrences in the Disko Bugt area offshore West Greenland: indications for gas hydrates?

NASA Astrophysics Data System (ADS)

Nielsen, Tove; Laier, Troels; Kuijpers, Antoon; Rasmussen, Tine L.; Mikkelsen, Naja E.; Nørgård-Pedersen, Niels

2014-12-01

The present study is the first to directly address the issue of gas hydrates offshore West Greenland, where numerous occurrences of shallow hydrocarbons have been documented in the vicinity of Disko Bugt (Bay). Furthermore, decomposing gas hydrate has been implied to explain seabed features in this climate-sensitive area. The study is based on archive data and new (2011, 2012) shallow seismic and sediment core data. Archive seismic records crossing an elongated depression (20×35 km large, 575 m deep) on the inner shelf west of Disko Bugt (Bay) show a bottom simulating reflector (BSR) within faulted Mesozoic strata, consistent with the occurrence of gas hydrates. Moreover, the more recently acquired shallow seismic data reveal gas/fluid-related features in the overlying sediments, and geochemical data point to methane migration from a deeper-lying petroleum system. By contrast, hydrocarbon signatures within faulted Mesozoic strata below the strait known as the Vaigat can be inferred on archive seismics, but no BSR was visible. New seismic data provide evidence of various gas/fluid-releasing features in the overlying sediments. Flares were detected by the echo-sounder in July 2012, and cores contained ikaite and showed gas-releasing cracks and bubbles, all pointing to ongoing methane seepage in the strait. Observed seabed mounds also sustain gas seepages. For areas where crystalline bedrock is covered only by Pleistocene-Holocene deposits, methane was found only in the Egedesminde Dyb (Trough). There was a strong increase in methane concentration with depth, but no free gas. This is likely due to the formation of gas hydrate and the limited thickness of the sediment infill. Seabed depressions off Ilulissat Isfjord (Icefjord) previously inferred to express ongoing gas release from decomposing gas hydrate show no evidence of gas seepage, and are more likely a result of neo-tectonism.

A Long-Term Geothermal Observatory Spanning Subseafloor Gas Hydrates in IODP Hole U1364A, Cascadia Accretionary Prism

NASA Astrophysics Data System (ADS)

Becker, K.; Davis, E.; Heesemann, M.; McGuire, J. J.; Collins, J. A.; O'Brien, J. K.; von der Heydt, K.

2017-12-01

We report the configuration of and initial results from a 24-thermistor cable installed to 268 m below seafloor (mbsf) in IODP Hole U1364A in the frontal accretionary prism of the Cascadia subduction zone. The thermistor array spans the gas hydrate stability zone and a clear bottom-simulating reflector at 225-230 mbsf. The thermistor string was deployed in July 2016 along with a seismic-strain observatory into the cased section of a pressure-monitoring Advanced CORK (ACORK) that had been installed in 2010 during IODP Expedition 328. Formation pressures are monitored via permeable screens on the outside of solid steel casing that is sealed at the bottom by a bridge plug and cement up to 302 mbsf. All three observatory systems were connected to the Ocean Networks Canada NEPTUNE cabled observatory Clayoquot Slope node in June of 2017, with the thermistor temperatures being logged by ONC every minute. The thermistor array was designed with concentrated vertical spacing around the BSR and two pressure-monitoring screens at 203 and 244 mbsf, with wider thermistor spacing elsewhere to document the geothermal state up to seafloor. The initial six weeks of data logged via the ONC connection show a generally linear temperature gradient, with temperatures of about 15.8°C at the BSR depth, consistent with methane hydrate stability at that depth and pressure. Sensor temperatures at most depths are quite stable over this period, with the exceptions of two sensors at 76 and 256 mbsf that show slowly rising temperatures; these could be due to cellular convection of borehole fluids, sensor degradation, or formation processes, but this requires a longer time series to resolve. We will report updated results after four more months of data recording through November 2017, along with any correlations to the pressure records. The data are freely available to all registered ONC users via the ONC data management and archiving system.

Multichannel Seismic Imaging of the Rivera Plate Subduction at the Seismogenic Jalisco Block Area (Western Mexican Margin)

NASA Astrophysics Data System (ADS)

Bartolome, R.; Gorriz, E.; Danobeitia, J.; Barba, D. C., Sr.; Martí, D.; L Cameselle, A.; Nuñez-Cornu, F. J.; Bandy, W. L.; Mortera, C.; Nunez, D.; Alonso, J. L.; Castellon, A.; Prada, M.

2016-12-01

During the TSUJAL marine geophysical survey, conducted in February and March 2014 Spanish, Mexican and British scientists and technicians explored the western margin of Mexico, considered one of the most active seismic zones in America. This work aims to characterize the internal structure of the subduction zone of the Rivera plate beneath the North American plate in the offshore part of the Jalisco Block, to link the geodynamic and the recent tectonic deformation occurring there with the possible generation of tsunamis and earthquakes. For this purpose, it has been carried out acquisition, processing and geological interpretation of a multichannel seismic reflection profile running perpendicular to the margin. Crustal images show an oceanic domain, dominated by subduction-accretion along the lower slope of the margin with a subparallel sediment thickness of up to 1.6 s two way travel time (approx. 2 km) in the Middle American Trench. Further, from these data the region appears to be prone to giant earthquake production. The top of the oceanic crust (intraplate reflector) is very well imaged. It is almost continuous along the profile with a gentle dip (<10°); however, it is disrupted by normal faulting resulting from the bending of the plate during subduction. The continental crust presents a well-developed accretionary prism consisting of highly deformed sediments with prominent slumping towards the trench that may be the result of past tsunamis. Also, a Bottom Simulating Reflector (BSR) is identified in the first half a second (twtt) of the section. High amplitude reflections at around 7-8 s twtt clearly image a discontinuous Moho, defining a very gentle dipping subduction plane.

Multichannel Seismic Imaging of the Rivera Plate Subduction at the Seismogenic Jalisco Block Area (Western Mexican Margin)

NASA Astrophysics Data System (ADS)

Bartolome, Rafael; Górriz, Estefanía; Dañobeitia, Juanjo; Cordoba, Diego; Martí, David; Cameselle, Alejandra L.; Núñez-Cornú, Francisco; Bandy, William L.; Mortera-Gutiérrez, Carlos A.; Nuñez, Diana; Castellón, Arturo; Alonso, Jose Luis

2016-10-01

During the TSUJAL marine geophysical survey, conducted in February and March 2014, Spanish, Mexican and British scientists and technicians explored the western margin of Mexico, considered one of the most active seismic zones in America. This work aims to characterize the internal structure of the subduction zone of the Rivera plate beneath the North American plate in the offshore part of the Jalisco Block, to link the geodynamic and the recent tectonic deformation occurring there with the possible generation of tsunamis and earthquakes. For this purpose, it has been carried out acquisition, processing and geological interpretation of a multichannel seismic reflection profile running perpendicular to the margin. Crustal images show an oceanic domain, dominated by subduction-accretion along the lower slope of the margin with a subparallel sediment thickness of up to 1.6 s two-way travel time (approx. 2 km) in the Middle American Trench. Further, from these data the region appears to be prone to giant earthquake production. The top of the oceanic crust (intraplate reflector) is very well imaged. It is almost continuous along the profile with a gentle dip (<10°); however, it is disrupted by normal faulting resulting from the bending of the plate during subduction. The continental crust presents a well-developed accretionary prism consisting of highly deformed sediments with prominent slumping towards the trench that may be the result of past tsunamis. Also, a bottom simulating reflector (BSR) is identified in the first half a second (twtt) of the section. High amplitude reflections at around 7-8 s twtt clearly image a discontinuous Moho, defining a very gentle dipping subduction plane.

Software Reviews.

ERIC Educational Resources Information Center

Kimball, Jeffrey P.; And Others

1987-01-01

Describes a variety of computer software. The packages reviewed include a variety of simulations, a spread sheet, a printer driver and an alternative operating system for DBM.PCs and compatible programs. (BSR)

Identification of QTLs for rice brown spot resistance in backcross inbred lines derived from a cross between Koshihikari and CH45.

PubMed

Matsumoto, Kengo; Ota, Yuya; Seta, Satomi; Nakayama, Yukinori; Ohno, Teppei; Mizobuchi, Ritsuko; Sato, Hiroyuki

2017-12-01

Rice brown spot (BS), caused by Bipolaris oryzae , is one of the major diseases of rice in Japan. Quantitative resistance has been observed in local cultivars (e.g., CH45), but no economically useful resistant variety has been bred. Using simple sequence repeat (SSR) polymorphic markers, we conducted quantitative trait locus (QTL) analysis of BS resistance in backcross inbred lines (BILs) from a cross between indica CH45 (resistant) and japonica Koshihikari (susceptible). On the basis of field disease evaluations in 2015 and 2016, four QTLs contributing to BS resistance were identified on chromosomes 2 ( qBSR2-kc ), 7 ( qBSR7-kc ), 9 ( qBSR9-kc ), and 11 ( qBSR11-kc ). The 'CH45' alleles at qBSR2-kc , qBSR7-kc , and qBSR11-kc and the 'Koshihikari' allele at qBSR9-kc increased resistance. The major QTL qBSR11-kc explained 23.0%-25.9% of the total phenotypic variation. Two QTLs ( qBSR9-kc and qBSR11-kc ) were detected in both years, whereas the other two were detected only in 2016. Genetic markers flanking these four QTLs will be powerful tools for marker-assisted selection to improve BS resistance.

The receptor-like cytoplasmic kinase BSR1 mediates chitin-induced defense signaling in rice cells.

PubMed

Kanda, Yasukazu; Yokotani, Naoki; Maeda, Satoru; Nishizawa, Yoko; Kamakura, Takashi; Mori, Masaki

2017-08-01

Broad-Spectrum Resistance 1 (BSR1) encodes a rice receptor-like cytoplasmic kinase, and enhances disease resistance when overexpressed. Rice plants overexpressing BSR1 are highly resistant to diverse pathogens, including rice blast fungus. However, the mechanism responsible for this resistance has not been fully characterized. To analyze the BSR1 function, BSR1-knockout (BSR1-KO) plants were generated using a clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 9 (Cas9) system. Experiments using suspension-cultured cells revealed that defense responses including H 2 O 2 production (i.e. oxidative burst) and expression of defense-related genes induced by autoclaved conidia of the rice blast fungus significantly decreased in BSR1-KO cells. Furthermore, a treatment with chitin oligomers which function as microbe-associated molecular patterns (MAMPs) of the rice blast fungus resulted in considerably suppressed defense responses in BSR1-KO cells. These results suggest that BSR1 is important for the rice innate immunity triggered by the perception of chitin.

Geochemical Investigation of Slope Failure on the Northern Cascadia Margin Frontal Ridge

NASA Astrophysics Data System (ADS)

Pohlman, J. W.; Riedel, M.; Waite, W.; Rose, K.; Lapham, L.; Hamilton, T. S.; Enkin, R.; Spence, G. D.; Hyndman, R.; Haacke, R.

2008-12-01

Numerous submarine landslides occur along the seaward side of the northern Cascadia margin's frontal ridge. Bottom simulating reflectors (BSRs) are also prevalent beneath the ridge at a sediment depth (~255 mbsf) coincident with the failure of at least one potentially recent slump. By one scenario, the most recent megathrust earthquake on the northern Cascadia margin, which occurred in 1700 A.D., raised the pore pressure and destabilized gas-charged sediment at the BSR depth. If true, the exposed seafloor within the slide's sole would contain gas-charged, sulfate-free sediment immediately following the slope failure. Over time, sulfate would diffuse into the exposed sediment and re-establish an equilibrium sulfate gradient. In this study, three 1-5 km wide collapse structures and the surrounding areas were cored during the Natural Resources Canada (NRCan) supported cruise PGC0807 to determine if the failures were related to over- pressurized gas and constrain the age of the slumps. Sulfate and methane gradients were measured from cores typically collected along a transect from the headwall scarp, and down to the toe of the slide. Rapidly decreasing sulfate concentrations with depth (a proxy for enhanced methane flux toward the seafloor) above the headwall of Lopez slump confirms a high background flux on the crest of the ridge. However, within the cores we recovered from the headwall, slide sole and slide deposits at all sites investigated, sulfate was abundant, methane was largely absent and, correspondingly, sulfate gradients were relatively low. On the basis of these results, methane was either lost from the system during or since the slope failure, or was never present in the high concentrations expected at an exhumed BSR. Numerical models that simulate sulfate diffusion following the slump-induced pore water profile perturbations will be utilized to constrain the age of the slope failures. Complementary sedimentological and geotechnical studies from the geochemically analyzed cores are ongoing to understand the primary factors that initiate and trigger slope failures along the frontal ridge of the northern Cascadia margin. Shipboard scientific party in alphabetical order: R. Enkin (NRCan), L. Esteban (NRCan), R. Haacke (NRCan), T.S. Hamilton (Camosun College), M. Hogg (Camosun), L. Lapham (Florida State), G. Middleton (NRCan), P. Neelands (NRCan), J. Pohlman (USGS), M. Riedel (McGill), K. Rose (USDOE), A. Schlesinger (UVic), G. Standen (Geoforce), A. Stephenson (UVic), S. Taylor (NRCan), W. Waite (USGS), X. Wang (McGill)

When a Model Needs a Model: Convincing Skeptics of Counterintuitive Results--An Example from Affirmative Action Modeling.

ERIC Educational Resources Information Center

Feinberg, William E.

1988-01-01

This article describes a monte carlo computer simulation of affirmative action employment policies. The counterintuitive results of the model are explained through a thought device involving urns and marbles. States that such model simulations have implications for social policy. (BSR)

Characterization of three types of silicon solar cells for SEPS Deep Space Mission. Volume 3: Current-voltage characteristics of spectrolab sculptured BSR/P+ (K7), BSR/P+ (K6.5) and BSR (K4.5) cells as a function of temperature and intensity

NASA Technical Reports Server (NTRS)

Whitaker, A. F.; Little, S. A.; Wooden, V. A.; Carter, D. E.; Cothren, B. E.; Torstenson, C. A.

1980-01-01

Three types of high performance silicon solar cells, sculptured BSR/P+(K7), BSR/P+(K6.5) and BSR(K4.5) manufactured by Spectrolab were evaluated for their low temperature and low intensity performance. Sixteen cells of each type were subjected to 11 temperatures and 9 intensities. The sculptured BSR/P+(K7) cells provided the greatest maximum power output both at 1 AU and at LTLI conditions. The average efficiencies of this cell were 14.4 percent at 1 SC/+25 deg C and 18.5 percent at 0.086 SC/-100 deg C.

Characterization of three types of silicon solar cells for SEPS deep space missions. Volume 1: Current-voltage characteristics of OCLI BSF/BSR 10 ohm-cm, and BSR 2 ohm-cm cells as a function of temperature and intensity

NASA Technical Reports Server (NTRS)

Whitaker, A. F.; Little, S. A.; Smith, C. F., Jr.; Wooden, V. A.

1979-01-01

Three types of high performance silicon solar cells, BSF/BSR 10 ohm-cm, BSR 10 ohm-cm, and BSR 2 ohm-cm, were evaluated for their low temperature and low intensity performance. Sixteen cells of each type were subjected to ten temperatures and nine intensities. The BSF/BSR 10 ohm-cm cells provided the best performance at 1 solar constant and +25 C with an efficiency of 14.1% while the BSR 2 ohm-cm cells had the highest low temperature and low intensity performance with an efficiency of 22.2% at 0.04 solar constant and -170 C and the most consistent cell-to-cell characteristics.

InGaAs monolithic interconnected modules (MIM)

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

Fatemi, N.S.; Jenkins, P.P.; Weizer, V.G.

1997-12-31

A monolithic interconnected module (MIM) structure has been developed for thermophotovoltaic (TPV) applications. The MIM device consists of many individual InGaAs cells series-connected on a single semi-insulating (S.I.) InP substrate. An infrared (IR) back surface reflector (BSR), placed on the rear surface of the substrate, returns the unused portion of the TPV radiator output spectrum back to the emitter for recycling, thereby providing for high system efficiencies. Also, the use of a BSR obviates the need to use a separate filtering element. As a result, MIMs are exposed to the entire emitter output, thereby maximizing output power density. MIMs withmore » an active area of 1 x 1-cm were comprised of 15 cells monolithically connected in series. Both lattice-matched and lattice-mismatched InGaAs/InP devices were produced, with bandgaps of 0.74 and 0.55 eV, respectively. The 0.74-eV modules demonstrated an open-circuit voltage (Voc) of 6.158 V and a fill factor of 74.2% at a short-circuit current (Jsc) of 842 mA/cm{sup 2}, under flashlamp testing. The 0.55-eV modules demonstrated a Voc of 4.849 V and a fill factor of 57.8% at a Jsc of 3.87 A/cm{sup 2}. IR reflectance measurements (i.e., {lambda} > 2 {micro}m) of these devices indicated a reflectivity of {ge} 83%. Latest electrical and optical performance results for the MIMs will be presented.« less

Hydrates in the California Borderlands Revisited: Results from a Controlled-Source Electromagnetic Survey of the Santa Cruz Basin.

NASA Astrophysics Data System (ADS)

Kannberg, P. K.; Constable, S.

2014-12-01

Methane hydrate, an ice-like clathrate of water and methane, forms in shallow continental slope sediments, and is both a potential energy source and geologic hazard. Hydrates presence is traditionally inferred from the presence of the bottom simulating reflector (BSR), a seismic velocity inversion resulting from free gas pooling at the base of the hydrate stability field. The BSR is not a measure of hydrate, but rather a proxy for free gas presence. Whereas seismic methods are sensitive to velocity anomalies, controlled-source electromagnetic (CSEM) methods are sensitive to conductivity anomalies. The electrically resistive methane hydrate makes a favorable target for CSEM surveys, which are capable of detecting and potentially quantifying the presence of methane hydrate directly. Building on previous work 100km to the south in the San Nicolas Basin, we present initial results from a 6-day June 2014 survey in the Santa Cruz Basin, located 100km west of Los Angeles. CSEM surveys are performed by deep-towing an EM source that is transmitting a known signal; this signal is detected by towed and seafloor receivers. The initial EM source signal is altered by the electrical properties of the surrounding environment. Conductors such as brine and seawater are attenuating mediums, while resistors such as methane hydrate, gas, and oil are preservative of the original signal. Twenty-one seafloor receivers, as well as a 4 receiver towed array were deployed to image the resistivity structure of the Santa Cruz Basin. Using 30-year-old 2D seismic profiles as a guide, potential hydrate targets were identified, and the transmitter and array were towed over 150 km on 6 lines with 5 seafloor receivers each. The 6 towed lines were coincident with legacy seismic lines. The towed array is sensitive to sediment depths less than 1km, allowing for high data density through the hydrate stability field. The larger transmitter-receiver offsets of the seafloor receivers allow sensitivity to at least 3km below the seafloor. Combining the two data sets allows for both high resolution in the near-seafloor hydrate accumulations as well as imaging the potential gas-source regions of the hydrate field.

Characterization of a stratigraphically constrained gas hydrate system along the western continental margin of Svalbard from ocean bottom seismometer data

NASA Astrophysics Data System (ADS)

Chabert, Anne; Minshull, Tim A.; Westbrook, Graham K.; Berndt, Christian; Thatcher, Kate E.; Sarkar, Sudipta

2011-12-01

The ongoing warming of bottom water in the Arctic region is anticipated to destabilize some of the gas hydrate present in shallow seafloor sediment, potentially causing the release of methane from dissociating hydrate into the ocean and the atmosphere. Ocean-bottom seismometer (OBS) experiments were conducted along the continental margin of western Svalbard to quantify the amount of methane present as hydrate or gas beneath the seabed. P- and S-wave velocities were modeled for five sites along the continental margin, using ray-trace forward modeling. Two southern sites were located in the vicinity of a 30 km long zone where methane gas bubbles escaping from the seafloor were observed during the cruise. The three remaining sites were located along an E-W orientated line in the north of the margin. At the deepest northern site, Vp anomalies indicate the presence of hydrate in the sediment immediately overlying a zone containing free gas up to 100-m thick. The acoustic impedance contrast between the two zones forms a bottom-simulating reflector (BSR) at approximately 195 m below the seabed. The two other sites within the gas hydrate stability zone (GHSZ) do not show the clear presence of a BSR or of gas hydrate. However, anomalously low Vp, indicating the presence of free gas, was modeled for both sites. The hydrate content was estimated from Vp and Vs, using effective-medium theory. At the deepest northern site, modeling suggests a pore-space hydrate concentration of 7-12%, if hydrate forms as part of a connected framework, and about 22% if it is pore-filling. At the two other northern sites, located between the deepest site and the landward limit of the GHSZ, we suggest that hydrate is present in the sediment as inclusions. Hydrate may be present in small quantities at these two sites (4-5%) of the pore space. The variation in lithology for the three sites indicated by high-resolution seismic profiles may control the distribution, concentration and formation of hydrate and free gas.

Baseline monitoring using aircraft laser ranging. [spaceborne laser simulation and aircraft laser tracking

NASA Technical Reports Server (NTRS)

Krabill, W. B.; Hoge, F. E.; Martin, C. F.

1982-01-01

The use of aircraft laser ranging for the determination of baselines between ground based retroreflectors was investigated via simulations and with tests at Wallops Flight Center using the Airborne Oceanographic Lidar (AOL) on the Wallops C-54 aircraft ranging to a reflector array deployed around one of the Wallops runways. The aircraft altitude and reflector spacing were chosen on the basis of scaled down modeling of spacecraft tracking from 1000 km of reflectors separated by some 52 km, or of high altitude (10 km) aircraft tracking of reflectors separated by some 500 m. Aircraft altitudes flown for different passes across the runway reflector array varied from 800 m to 1350 m, with 32 reflectors deployed over an approximtely 300 m x 500 m ground pattern. The AOL transmitted 400 pulses/sec with a scan rate of 5/sec in a near circular pattern, so that the majority of the pulses were reflected by the runway surface or its environs rather than by retroreflectors. The return pulse characteristics clearly showed the high reflectivity of portions of the runway, with several returns indistinguishable in amplitude from reflector returns. For each pass across the reflector field, typically six to ten reflector hits were identified, consistent with that predicted by simulations and the observed transmitted elliptical pulse size.

Bifacial PV cell with reflector for stand-alone mast for sensor powering purposes

NASA Astrophysics Data System (ADS)

Jakobsen, Michael L.; Thorsteinsson, Sune; Poulsen, Peter B.; Riedel, N.; Rødder, Peter M.; Rødder, Kristin

2017-09-01

Reflectors to bifacial PV-cells are simulated and prototyped in this work. The aim is to optimize the reflector to specific latitudes, and particularly northern latitudes. Specifically, by using minimum semiconductor area the reflector must be able to deliver the electrical power required at the condition of minimum solar travel above the horizon, worst weather condition etc. We will test a bifacial PV-module with a retroreflector, and compare the output with simulations combined with local solar data.

Comparative genomic and plasmid analysis of beer-spoiling and non-beer-spoiling Lactobacillus brevis isolates.

PubMed

Bergsveinson, Jordyn; Ziola, Barry

2017-12-01

Beer-spoilage-related lactic acid bacteria (BSR LAB) belong to multiple genera and species; however, beer-spoilage capacity is isolate-specific and partially acquired via horizontal gene transfer within the brewing environment. Thus, the extent to which genus-, species-, or environment- (i.e., brewery-) level genetic variability influences beer-spoilage phenotype is unknown. Publicly available Lactobacillus brevis genomes were analyzed via BlAst Diagnostic Gene findEr (BADGE) for BSR genes and assessed for pangenomic relationships. Also analyzed were functional coding capacities of plasmids of LAB inhabiting extreme niche environments. Considerable genetic variation was observed in L. brevis isolated from clinical samples, whereas 16 candidate genes distinguish BSR and non-BSR L. brevis genomes. These genes are related to nutrient scavenging of gluconate or pentoses, mannose, and metabolism of pectin. BSR L. brevis isolates also have higher average nucleotide identity and stronger pangenome association with one another, though isolation source (i.e., specific brewery) also appears to influence the plasmid coding capacity of BSR LAB. Finally, it is shown that niche-specific adaptation and phenotype are plasmid-encoded for both BSR and non-BSR LAB. The ultimate combination of plasmid-encoded genes dictates the ability of L. brevis to survive in the most extreme beer environment, namely, gassed (i.e., pressurized) beer.

Geologic and Site Survey Setting for JIP Gulf of Mexico Gas Hydrate Drilling

NASA Astrophysics Data System (ADS)

Hutchinson, D. R.; Snyder, F.; Hart, P. E.; Ruppel, C. D.; Pohlman, J.; Wood, W. T.; Coffin, R. B.; Edwards, K. M.

2005-12-01

The JIP Gulf of Mexico drilling program targeted two contrasting geologic settings to understand natural gas hydrates: a salt-withdrawal minibasin and a mound/seep site, both at mid-slope water depths of about 1300 m. The minibasin site (lease block Keathley Canyon 151) contains a Bottom Simulating Reflection (BSR) that deepens from 260 m below the sea floor near the edge of the basin to 500 mbsf towards the center of the basin. Drilling was conducted at a site in which the BSR is about 415 mbsf. Seismic stratigraphy of the minibasin consists of continuous laminated sequences of variable thicknesses alternating with more massive units of discontinuous reflections. These sequences represent uniform hemipelagic deposition, which drapes the basin, and turbidite deposition, which pinches out along the basin edges. The BSR crosses several of these sequences. A map of amplitude values at the BSR shows a strong banding pattern indicative of the layering, with the highest amplitudes interpreted to be trapped gas in the coarser-grained units. Prior to drilling, piston-core data indicated extensive shallow mass wasting near the edges of the minibasin. Heat flow data indicated thermal gradients that in general predicted a BSR deeper than observed in the seismic data. Full-waveform inversion of 3D multichannel data indicated a probable thick zone of low-saturation hydrate immediately above the BSR. There is little coherent seismic stratigraphy at the mound/seep site in the Mississippi Canyon (lease blocks Atwater Valley 13/14), as the canyon fill is dominated by a complex mix of turbidite and mass-wasting deposits. Hints of a possible BSR that is warped upwards beneath the mound can be seen in both 3D and 2D multichannel seismic data, but it cannot be traced laterally away from the mound with any certainty. A seismic pull-down pseudo-structure beneath the mound suggests the presence of a free-gas low-velocity zone at shallow depths. Pore-water analyses from shallow piston cores and closely-spaced heat-flow data indicate the mound is a site of probable fluid venting. A transect of bottom photographs crosses a possible mud flow and numerous bacterial mats, consistent with features seen in fluid venting at other sites in the Gulf. Prestack inversion of the multichannel data did not predict significant gas hydrate at the site on the edge of the mound. However, at the control site off the mound, predictions were more favorable for low hydrate saturations in the deeper part of the drill hole.

Convergence studies of deterministic methods for LWR explicit reflector methodology

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

Canepa, S.; Hursin, M.; Ferroukhi, H.

2013-07-01

The standard approach in modem 3-D core simulators, employed either for steady-state or transient simulations, is to use Albedo coefficients or explicit reflectors at the core axial and radial boundaries. In the latter approach, few-group homogenized nuclear data are a priori produced with lattice transport codes using 2-D reflector models. Recently, the explicit reflector methodology of the deterministic CASMO-4/SIMULATE-3 code system was identified to potentially constitute one of the main sources of errors for core analyses of the Swiss operating LWRs, which are all belonging to GII design. Considering that some of the new GIII designs will rely on verymore » different reflector concepts, a review and assessment of the reflector methodology for various LWR designs appeared as relevant. Therefore, the purpose of this paper is to first recall the concepts of the explicit reflector modelling approach as employed by CASMO/SIMULATE. Then, for selected reflector configurations representative of both GII and GUI designs, a benchmarking of the few-group nuclear data produced with the deterministic lattice code CASMO-4 and its successor CASMO-5, is conducted. On this basis, a convergence study with regards to geometrical requirements when using deterministic methods with 2-D homogenous models is conducted and the effect on the downstream 3-D core analysis accuracy is evaluated for a typical GII deflector design in order to assess the results against available plant measurements. (authors)« less

Poor outcome prediction by burst suppression ratio in adults with post-anoxic coma without hypothermia.

PubMed

Yang, Qinglin; Su, Yingying; Hussain, Mohammed; Chen, Weibi; Ye, Hong; Gao, Daiquan; Tian, Fei

2014-05-01

Burst suppression ratio (BSR) is a quantitative electroencephalography (qEEG) parameter. The purpose of our study was to compare the accuracy of BSR when compared to other EEG parameters in predicting poor outcomes in adults who sustained post-anoxic coma while not being subjected to therapeutic hypothermia. EEG was registered and recorded at least once within 7 days of post-anoxic coma onset. Electrodes were placed according to the international 10-20 system, using a 16-channel layout. Each EEG expert scored raw EEG using a grading scale adapted from Young and scored amplitude-integrated electroencephalography tracings, in addition to obtaining qEEG parameters defined as BSR with a defined threshold. Glasgow outcome scales of 1 and 2 at 3 months, determined by two blinded neurologists, were defined as poor outcome. Sixty patients with Glasgow coma scale score of 8 or less after anoxic accident were included. The sensitivity (97.1%), specificity (73.3%), positive predictive value (82.5%), and negative prediction value (95.0%) of BSR in predicting poor outcome were higher than other EEG variables. BSR1 and BSR2 were reliable in predicting death (area under the curve > 0.8, P < 0.05), with the respective cutoff points being 39.8% and 61.6%. BSR1 was reliable in predicting poor outcome (area under the curve  =  0.820, P < 0.05) with a cutoff point of 23.9%. BSR1 was also an independent predictor of increased risk of death (odds ratio  =  1.042, 95% confidence intervals: 1.012-1.073, P  =  0.006). BSR may be a better predictor in prognosticating poor outcomes in patients with post-anoxic coma who do not undergo therapeutic hypothermia when compared to other qEEG parameters.

Light-Output Enhancement of GaN-Based Light-Emitting Diodes with Three-Dimensional Backside Reflectors Patterned by Microscale Cone Array

PubMed Central

Hu, Jinyong; Wang, Hong

2014-01-01

Three-dimensional (3D) backside reflector, compared with flat reflectors, can improve the probability of finding the escape cone for reflecting lights and thus enhance the light-extraction efficiency (LEE) for GaN-based light-emitting diode (LED) chips. A triangle-lattice of microscale SiO2 cone array followed by a 16-pair Ti3O5/SiO2 distributed Bragg reflector (16-DBR) was proposed to be attached on the backside of sapphire substrate, and the light-output enhancement was demonstrated by numerical simulation and experiments. The LED chips with flat reflectors or 3D reflectors were simulated using Monte Carlo ray tracing method. It is shown that the LEE increases as the reflectivity of backside reflector increases, and the light-output can be significantly improved by 3D reflectors compared to flat counterparts. It can also be observed that the LEE decreases as the refractive index of the cone material increases. The 3D 16-DBR patterned by microscale SiO2 cone array benefits large enhancement of LEE. This microscale pattern was prepared by standard photolithography and wet-etching technique. Measurement results show that the 3D 16-DBR can provide 12.1% enhancement of wall-plug efficiency, which is consistent with the simulated value of 11.73% for the enhancement of LEE. PMID:25133262

Design method of LED rear fog lamp based on freeform micro-surface reflectors

NASA Astrophysics Data System (ADS)

Yu, Jindong; Wu, Heng

2017-11-01

We propose a practical method for the design of a light-emitting diode (LED) rear fog lamp based on freeform micro-surface reflectors. The lamp consists of nine LEDs and each of them has a freeform micro-surface reflector correspondingly. The micro-surface reflector design includes three steps. An initial freeform reflector is first built based on the light energy maps. The micro-surface reflector is then constructed on the bias of the initial one. Finally, a two-step method is designed to optimize the micro-surface reflector. With the proposed method, a module is designed and LCW DURIS E5 LED source whose emitting surface is 5.7 mm × 3.0 mm is adopted for simulation. A prototype is also assembled and fabricated to verify the real performance. Both the simulation and experimental results demonstrate that the luminous intensity distribution can well fulfill the requirements of ECE No.38 regulation. Furthermore, more than 79% energy can be saved when compared with the rear fog lamps using conventional sources.

Lead foil wrapping of the plastic scintillators for the gamma ray detection: optical reflector or spectrum intensifier?

NASA Astrophysics Data System (ADS)

Taheri, A.; Askari, M.; Taghan Sasanpour, M.

2017-08-01

This paper studies the effect of lead wrapping on the response of the plastic scintillators as gamma detectors. Experimental tests and Geant4 simulations showed that lead wrapping cannot increase the gamma absorption efficiency of the detector but, as a reflector, it can improve the optical properties of the detector. The reflectivity of the lead foil as an optical reflector was determined equal to 66% using an experimental-simulation combined method. Based on the obtained results, the optical collection efficiency of the detector was also increased about 4% after employing the lead reflector.

A new type of lamp and reflector for I.R. simulation

NASA Technical Reports Server (NTRS)

Saenger, G.

1986-01-01

The lamps and reflectors used for infrared radiation simulation tests at ESTEC did not allow researchers to predict the intensity needed for test conditions with the desired accuracy. This was due to poor reproducibility of the polar diagrams, the unknown contribution of the radiation in the long wavelength range in vacuum, imperfections in the quartz bulbs, and misalignment of the lamp in the reflector. When using a 1000 W coiled spiral quartz lamp with a diffuse reflector, these shortcomings are overcome. Due to the good reproducibility, an overall accuracy within plus or minus 2 percent should be obtained.

Toward Protein Structure In Situ: Comparison of Two Bifunctional Rhodamine Adducts of Troponin C

PubMed Central

Julien, Olivier; Sun, Yin-Biao; Knowles, Andrea C.; Brandmeier, Birgit D.; Dale, Robert E.; Trentham, David R.; Corrie, John E. T.; Sykes, Brian D.; Irving, Malcolm

2007-01-01

As part of a program to develop methods for determining protein structure in situ, sTnC was labeled with a bifunctional rhodamine (BR or BSR), cross-linking residues 56 and 63 of its C-helix. NMR spectroscopy of the N-terminal domain of BSR-labeled sTnC in complex with Ca2+ and the troponin I switch peptide (residues 115–131) showed that BSR labeling does not significantly affect the secondary structure of the protein or its dynamics in solution. BR-labeling was previously shown to have no effect on the solution structure of this complex. Isometric force generation in isolated demembranated fibers from rabbit psoas muscle into which BR- or BSR-labeled sTnC had been exchanged showed reduced Ca2+-sensitivity, and this effect was larger with the BSR label. The orientation of rhodamine dipoles with respect to the fiber axis was determined by polarized fluorescence. The mean orientations of the BR and BSR dipoles were almost identical in relaxed muscle, suggesting that both probes accurately report the orientation of the C-helix to which they are attached. The BSR dipole had smaller orientational dispersion, consistent with less flexible linkers between the rhodamine dipole and cysteine-reactive groups. PMID:17483167

Registration of an oilseed sunflower germplasm line HA-BSR1 highly tolerant to Sclerotinia basal stalk rot

USDA-ARS?s Scientific Manuscript database

Basal stalk rot (BSR) caused by Sclerotinia sclerotiorum (Lib.) de Bary is a devastating disease that causes a significant damage to worldwide sunflower (Helianthus annuus L.) production by reducing seed yield and quality. The objective of this research was to develop highly BSR tolerant sunflower g...

Brain Stimulation Reward Supports More Consistent and Accurate Rodent Decision-Making than Food Reward.

PubMed

McMurray, Matthew S; Conway, Sineadh M; Roitman, Jamie D

2017-01-01

Animal models of decision-making rely on an animal's motivation to decide and its ability to detect differences among various alternatives. Food reinforcement, although commonly used, is associated with problematic confounds, especially satiety. Here, we examined the use of brain stimulation reward (BSR) as an alternative reinforcer in rodent models of decision-making and compared it with the effectiveness of sugar pellets. The discriminability of various BSR frequencies was compared to differing numbers of sugar pellets in separate free-choice tasks. We found that BSR was more discriminable and motivated greater task engagement and more consistent preference for the larger reward. We then investigated whether rats prefer BSR of varying frequencies over sugar pellets. We found that animals showed either a clear preference for sugar reward or no preference between reward modalities, depending on the frequency of the BSR alternative and the size of the sugar reward. Overall, these results suggest that BSR is an effective reinforcer in rodent decision-making tasks, removing food-related confounds and resulting in more accurate, consistent, and reliable metrics of choice.

InGaAs monolithic interconnected modules (MIMs)

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

Fatemi, N.S.; Jenkins, P.P.; Weizer, V.G.

1997-12-31

A monolithic interconnected module (MIM) structure has been developed for thermophotovoltaic (TPV) applications. The MIM device consists of many individual InGaAs cells series-connected on a single semi-insulating (S.I.) InP substrate. An infrared (IR) back surface reflector (BSR), placed on the rear surface of the substrate, returns the unused portion of the TPV radiator output spectrum back to the radiator for recuperation, thereby providing for high system efficiencies. Also, the use of a BSR reduces the requirements imposed on a front surface interference filter and may lead to using only an anti-reflection coating. As a result, MIMs are exposed to themore » entire radiator output, and with increasing output power density. MIMs were fabricated with an active area of 0.9 x 1 cm, and with 15 cells monolithically connected in series. Both lattice-matched and lattice-mismatched InGaAs/InP devices were fabricated, with bandgaps of 0.74 and 0.55 eV, respectively. The 0.74 eV MIMs demonstrated an open-circuit voltage (Voc) of 6.16 V and a fill factor of 74.2% at a short-circuit current (Jsc) of 0.84 A/cm{sup 2}, under flashlamp testing. The 0.55 eV modules demonstrated a Voc of 4.85 V and a fill factor of 57.8% at a Jsc of 3.87 A/cm{sup 2}. The near IR reflectance (2--4 {micro}m) for both lattice-matched and lattice-mismatched structures was measured to be in the range of 80--85%. Latest electrical and optical performance results for these MIMs is presented.« less

Shallow subsurface imaging of northern Cascadia margin using downward continued short-streamer data

NASA Astrophysics Data System (ADS)

Yelisetti, S.; Ghosal, D.; Spence, G.

2017-12-01

Since Eocene, the Juan de Fuca plate has been subducting beneath the North American plate, scrapping off sediments from the down going plate, accreting to the margin forming frontal accretionary wedge, Crescent terrane and the Pacific Rim terrane, which are separated by landward dipping Crescent thrust and Tofino faults. In 1989, the Geological Survey of Canada has acquired several multichannel seismic lines along the northern Cascadia margin to study the subduction zone processes and the formation and distribution of methane hydrates in the accreted sediment section. Seismic reflections and refractions are recorded on a 3.6 km streamer up to 14 s using 4 ms sample rate with 183 m near-offset. In this study, we present the migrated image of line 89-06 which indicate the top of the down-going plate and several landward dipping frontal thrusts. Additionally, a bottom simulating reflector (BSR) is identified over a 20 km distance at a depth of 250 m beneath the seafloor within the accretionary wedge sediments where the water depth is around 1500-2000 m. Preliminary velocity analyses corresponding to the BSR reflection using semblance method indicate high-velocity sediment with P-wave velocities of 2.0 km/s. To better constrain the velocity distribution of such shallow subsurface features, we have analyzed the refracted arrivals from the seaward part of the Tofino basin sediment section. Specifically, we have downward continued the shot and receiver gathers to the seafloor bringing the far offset refracted phases to near offset as first arrivals. Since the refractions are not well captured over the trench deposits due to large water depth ( 2500 m) and limited streamer length, the downward continued results do not show refracted arrivals very clearly at the near offset. In contrast, moving landward along the frontal slope with gradual decrease in water depth to 1300 m and less, the effect of downward continuation seems to be more prominent bringing the refracted phases to near offset more clearly as first arrivals. More detailed first arrival tomographic velocity analysis is currently underway using these downward continued datasets. The tomographic velocity model will then be used as a starting model for future full waveform inversion to obtain the high-resolution velocity and attenuation models of the accreted sediments.

Types and Evolution of Gas Hydrate System along the Tectonically Active Zones of the Western Pacific: Nankai Trough vs. Eastern Margin of Japan Sea

NASA Astrophysics Data System (ADS)

Matsumoto, R.; Tomaru, H.; Takeuchi, L.; Hiruta, A.; Ishizaki, O.; Aoyama, C.; Machiyama, H.; Goto, T.

2007-12-01

A series of sea-going surveys of marine gas hydrates around Japan Islands for more than a decade has revealed characteristic and contrasting features and evolution of gas hydrate system between the Nankai subduction zone and the Joetsu Basin of Japan Sea. Gas hydrate of the Nankai trough largely occurs as pore-filling type, laterally extending in turbidites. Methane is depleted in C-13, mostly derived from microbial brake-down of organic matters. Strong and continuous BSRs occur at around 270 mbsf, corresponding to the base of gas hydrate stability (BGHS). Furthermore, double BSRs with weak reflector (BSR-2) 20-30 m below BSR appear in uplifting knolls. BSR-2 is explained as a relic BSR, which coincides with BGHS. Combination effects of uplifting of gas hydrate bearing sediments and sea-level fall are likely to have caused shoaling of BGHS and BSRs, dissociation of gas hydrate between old and new BRSs, and further accumulation of gas hydrates above BSR. Thus the recycling of methane at BGHS triggered by glacial sea level fall contributed for the development of subsurface gas hydrate deposits. Joetsu basin is located on a newly formed convergent boundary between Eurasia and Philippine Sea Plates. Well-defined circular pockmarks with ca.500 m in diameter develop on the folded and faulted Umitaka spur and Joetsu knoll in the basin. A number of circular swells and mounds, 200-500 m in diameter, have been also recognized nearby the pockmarks. Thus the Umitaka spur and perhaps Joetsu knoll are characterized by rough topography of pockmarks and mounds. Methane of plumes and gas hydrate originates in deep-seated thermogenic gases with relatively heavy carbon. 3D seismic profiles clearly depict gas chimney structures below pockmark-mound zones, and gigantic methane plumes stand on the mounds not in the pockmarks. Pockmarks are often considered as vent holes, however, those of the Joestu Basin are quite. BSRs occur at about 150 mbsr, corresponding to very high heat flow, and are widely distributed throughout the area, while no double BSRs are observed. BSRs within gas chimneys are very strong and often exhibit pull-up structure. A number of piston corers have recovered chunks of massive gas hydrate from the mounds. ROV dives observed gas hydrates exposed atop the mounds. Furthermore, electric ocean floor survey has revealed that sediments below the pockmark-mound zones were not conductive. These lines of evidence suggest that the mounds are more-or-less composed of or at least contain significant amounts of methane. Sea-level fall during the last glacial, 120 m in Japan Sea, should have caused instability of gas hydrate, in particular, those within pockmarks. Pull-up structures within the chimney seem to support the model that the mounds are gas hydrate dome and the pockmark, probably a relic hydrate mound. Glacial sea level fall should have caused massive dissociation of subsurface methane hydrate as in case of the Nankai trough. However the methane from the dissociation of massive hydrate in the chimney should escape to seawater to form a crater-like depression pockmarks. Considering active venting, gigantic plumes, inferred violent venting and perhaps floating of massive gas hydrates, gas hydrate deposits are to be formed during warmer, high-sea level periods, and episodic dissociation and massive emission of methane to ocean/atmosphere system.

Prestack Waveform Inversion and Well Log Examination at GC955 and WR313 in the Gulf of Mexico for Estimation of Methane Hydrate Concentrations

NASA Astrophysics Data System (ADS)

Fortin, W.; Goldberg, D.; Kucuk, H. M.

2017-12-01

Gas hydrates are naturally occurring compounds, which, at a molecular scale, are lattice structures of ice embedded with various gas molecules in the lattice voids. Volumetric estimates of associated hydrocarbons vary greatly due to the difficulty in remotely estimating hydrate concentrations in marine sediments but embedded hydrocarbon stores are thought to represent a significant portion of global deposits. Inherent hydrate instabilities obscure our understanding of and complicates processes related to resource extraction and hydrate response to disturbances in the local environment. Understanding the spatial extent and variability of hydrate deposits have important implications for potential economic production, climate change, and assessing natural hazards risks. Seismic reflection techniques are capable of determining the extent of gas hydrate deposits, often through the observation of bottom simulating reflectors (BSRs). However, BSRs are not present everywhere gas hydrates exist. Using high resolution prestack time migrated seismic data and prestack waveform inversion (PWI) we produce highly resolved velocity models and compare them to co-located well logs. Coupling our PWI results with velocity-porosity relationships and nearby well control, we map hydrate properties at GC955 and WR313. Integrating small scale heterogeneities and variations along the velocity model with in-situ measurements, we develop a workflow aimed to quantify hydrate concentrations observed in seismic data over large areas in great detail regardless of the existence of a BSR.

Reflectivity Spectra for Commonly Used Reflectors

NASA Astrophysics Data System (ADS)

Janecek, Martin

2012-06-01

Monte Carlo simulations play an important role in developing and evaluating the performance of radiation detection systems. To accurately model a reflector in an optical Monte Carlo simulation, the reflector's spectral response has to be known. We have measured the reflection coefficient for many commonly used reflectors for wavelengths from 250 nm to 800 nm. The reflectors were also screened for fluorescence and angular distribution changes with wavelength. The reflectors examined in this work include several polytetrafluoroethylene (PTFE) reflectors, Spectralon, GORE diffuse reflector, titanium dioxide paint, magnesium oxide, nitrocellulose filter paper, Tyvek paper, Lumirror, Melinex, ESR films, and aluminum foil. All PTFE films exhibited decreasing reflectivity with longer wavelengths due to transmission. To achieve >;0.95 reflectivity in the 380 to 500 nm range, the PTFE films have to be at least 0.5 mm thick-nitrocellulose is a good alternative if a thin diffuse reflector is needed. Several of the reflectors have sharp declines in reflectivity below a cut-off wavelength, including TiO2 (420 nm), ESR film (395 nm), nitrocellulose (330 nm), Lumirror (325 nm), and Melinex (325 nm). PTFE-like reflectors were the only examined reflectors that had reflectivity above 0.90 for wavelengths below 300 nm. Lumirror, Melinex, and ESR film exhibited fluorescence. Lumirror and Melinex are excited by wavelengths between 320 and 420 nm and have their emission peaks located at 440 nm, while ESR film is excited by wavelengths below 400 nm and the emission peak is located at 430 nm. Lumirror and Melinex also exhibited changing angular distributions with wavelength.

Large area, low cost space solar cells with optional wraparound contacts

NASA Technical Reports Server (NTRS)

Michaels, D.; Mendoza, N.; Williams, R.

1981-01-01

Design parameters for two large area, low cost solar cells are presented, and electron irradiation testing, thermal alpha testing, and cell processing are discussed. The devices are a 2 ohm-cm base resistivity silicon cell with an evaporated aluminum reflector produced in a dielectric wraparound cell, and a 10 ohm-cm silicon cell with the BSF/BSR combination and a conventional contact system. Both cells are 5.9 x 5.9 cm and require 200 micron thick silicon material due to mission weight constraints. Normalized values for open circuit voltage, short circuit current, and maximum power calculations derived from electron radiation testing are given. In addition, thermal alpha testing values of absorptivity and emittance are included. A pilot cell processing run produced cells averaging 14.4% efficiencies at AMO 28 C. Manufacturing for such cells will be on a mechanized process line, and the area of coverslide application technology must be considered in order to achieve cost effective production.

Seismic character of gas hydrates on the Southeastern U.S. continental margin

USGS Publications Warehouse

Lee, M.W.; Hutchinson, D.R.; Agena, W.F.; Dillon, William P.; Miller, J.J.; Swift, B.A.

1994-01-01

Gas hydrates are stable at relatively low temperature and high pressure conditions; thus large amounts of hydrates can exist in sediments within the upper several hundred meters below the sea floor. The existence of gas hydrates has been recognized and mapped mostly on the basis of high amplitude Bottom Simulating Reflections (BSRs) which indicate only that an acoustic contrast exists at the lower boundary of the region of gas hydrate stability. Other factors such as amplitude blanking and change in reflection characteristics in sediments where a BSR would be expected, which have not been investigated in detail, are also associated with hydrated sediments and potentially disclose more information about the nature of hydratecemented sediments and the amount of hydrate present. Our research effort has focused on a detailed analysis of multichannel seismic profiles in terms of reflection character, inferred distribution of free gas underneath the BSR, estimation of elastic parameters, and spatial variation of blanking. This study indicates that continuous-looking BSRs in seismic profiles are highly segmented in detail and that the free gas underneath the hydrated sediment probably occurs as patches of gas-filled sediment having variable thickness. We also present an elastic model for various types of sediments based on seismic inversion results. The BSR from sediments of high ratio of shear to compressional velocity, estimated as about 0.52, encased in sediments whose ratios are less than 0.35 is consistent with the interpretation of gasfilled sediments underneath hydrated sediments. This model contrasts with recent results in which the BSR is explained by increased concentrations of hydrate near the base of the hydrate stability field and no underlying free gas is required. 

Learning-related skills and academic achievement in academically at-risk first graders

PubMed Central

Cerda, Carissa A.; Im, Myung Hee; Hughes, Jan N.

2015-01-01

Using an academically at-risk, ethnically diverse sample of 744 first-grade children, this study tested a multi-method (i.e., child performance measures, teacher ratings, and peer ratings) measurement model of learning-related skills (i.e., effortful control [EC], behavioral self-regulation [BSR], and social competence [SC]), and their shared and unique contributions to children's reading and math achievement, above the effect of demographic variables. The hypothesized correlated factor measurement model demonstrated relatively good fit, with BSR and SC correlated highly with one another and moderately with EC. When entered in separate regression equations, EC and BSR each predicted children's reading and math achievement; SC only predicted reading achievement. When considered simultaneously, neither EC, BSR, nor SC contributed independently to reading achievement; however, EC had a direct effect on math achievement and an indirect effect on reading achievement via both BSR and SC. Implications for research and early intervention efforts are discussed. PMID:25908886

Enhanced light absorption of silicon solar cells with dielectric nanostructured back reflector

NASA Astrophysics Data System (ADS)

Ren, Rui; Zhong, Zheng

2018-06-01

This paper investigates the light absorption property of nanostructured dielectric reflectors in silicon thin film solar cells using numerical simulation. Flat thin film solar cell with ZnO nanostructured back reflector can produce comparable photocurrent to the control model with Ag nanostructured back reflector. Furthermore, when it is integrated with nano-pillar surface decoration, a photocurrent density of 29.5 mA/cm2 can be achieved, demonstrating a photocurrent enhancement of 5% as compared to the model with Ag nanostructured back reflector.

A Nonlinear Dynamic Model and Free Vibration Analysis of Deployable Mesh Reflectors

NASA Technical Reports Server (NTRS)

Shi, H.; Yang, B.; Thomson, M.; Fang, H.

2011-01-01

This paper presents a dynamic model of deployable mesh reflectors, in which geometric and material nonlinearities of such a space structure are fully described. Then, by linearization around an equilibrium configuration of the reflector structure, a linearized model is obtained. With this linearized model, the natural frequencies and mode shapes of a reflector can be computed. The nonlinear dynamic model of deployable mesh reflectors is verified by using commercial finite element software in numerical simulation. As shall be seen, the proposed nonlinear model is useful for shape (surface) control of deployable mesh reflectors under thermal loads.

Genotyping-by-sequencing uncovers the introgression alien segments associated with Sclerotinia basal stalk rot resistance from wild species—I. Helianthus argophyllus and H. petiolaris

USDA-ARS?s Scientific Manuscript database

Basal stalk rot (BSR), caused by Sclerotinia Sclerotiorum, is a devastating disease in sunflower worldwide. The progress of breeding for Sclerotinia BSR resistance has been hampered due to the lack of effective sources of resistance for cultivated sunflower. Our objective was to transfer BSR resista...

Insect-cell expression, crystallization and X-ray data collection of the bradyzoite-specific antigen BSR4 from Toxoplasma gondii

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

Grujic, Ognjen; Grigg, Michael E.; Boulanger, Martin J., E-mail: mboulang@uvic.ca

2008-05-01

Preliminary X-ray diffraction studies of the bradyzoite-specific surface antigen BSR4 from T. gondii are described. Toxoplasma gondii is an important global pathogen that infects nearly one third of the world’s adult population. A family of developmentally expressed structurally related surface-glycoprotein adhesins (SRSs) mediate attachment to and are utilized for entry into host cells. The latent bradyzoite form of T. gondii persists for the life of the host and expresses a distinct family of SRS proteins, of which the bradyzoite-specific antigen BSR4 is a prototypical member. Structural studies of BSR4 were initiated by first recombinantly expressing BSR4 in insect cells, whichmore » was followed by crystallization and preliminary X-ray data collection to 1.95 Å resolution. Data processing showed that BSR4 crystallized with one molecule in the asymmetric unit of the P4{sub 1}2{sub 1}2 or P4{sub 3}2{sub 1}2 space group, with a solvent content of 60% and a corresponding Matthews coefficient of 2.98 Å{sup 3} Da{sup −1}.« less

BSRs Elevated by Fluid Upwelling on the Upper Amazon Fan : Bottom-up Controls on Gas Hydrate Stability

NASA Astrophysics Data System (ADS)

Praeg, D.; Silva, C. G.; dos Reis, A. T.; Ketzer, J. M.; Unnithan, V.; Perovano Da Silva, R. J.; Cruz, A. M.; Gorini, C.

2017-12-01

The stability of natural gas hydrate accumulations on continental margins has mainly been considered in terms of changes in seawater pressures and temperatures driven from above by climate. We present evidence from the Amazon deep-sea fan for stability zone changes driven from below by fluid upwelling. A grid of 2D and 3D multichannel seismic data show the upper Amazon fan in water depths of 1200-2000 m to contain a discontinuous bottom-simulating seismic reflection (BSR) that forms `patches' 10-50 km wide and up to 140 km long, over a total area of at least 5000 km2. The elongate BSR patches coincide with anticlinal thrust-folds that record on-going gravitational collapse of the fan above décollements at depths of up to 10 km. The BSR lies within 100-300 m of seafloor, in places rising beneath features that seafloor imagery show to be pockmarks and mud volcanoes, some venting gas to the water column. The BSR patches are up to 500 m shallower than predicted for methane hydrate based on geothermal gradients as low as 17˚C/km measured within the upper fan, and inversion of the BSR to obtain temperatures at the phase boundary indicates gradients 2-5 times background levels. We interpret the strongly elevated BSR patches to record upwelling of warm gas-rich fluids through thrust-fault zones 101 km wide. We infer this process to favour gas hydrate occurrences that are concentrated in proportion to flux and locally pierced by vents, and that will be sensitive to temporal variations in the upward flux of heat and gas. Thus episodes of increased flux, e.g. during thrusting, could dissociate gas hydrates to trigger slope failures and/or enhanced gas venting to the ocean. Structurally-driven fluid flow episodes could account for evidence of recurrent large-scale failures from the compressive belt on the upper fan during its Neogene collapse, and provide a long-term alternative to sea level triggering. The proposed mechanism of upward flux links the distribution and stability of gas hydrate occurrences (and gas vents) to the internal dynamics of deep-sea depocentres, in all water depths that structural pathways for fluid migration may form. Gravitational collapse is increasingly recognized to affect passive continental margins, and our findings challenge global models of hydrate inventory over time based solely on in situ methanogenesis.

Effects of deterministic surface distortions on reflector antenna performance

NASA Technical Reports Server (NTRS)

Rahmat-Samii, Y.

1985-01-01

Systematic distortions of reflector antenna surfaces can cause antenna radiation patterns to be undesirably different from those of perfectly smooth reflector surfaces. In this paper, a simulation model for systematic distortions is described which permits an efficient computation of the effects of distortions in the reflector pattern. The model uses a vector diffraction physical optics analysis for the determination of both the co-polar and cross-polar fields. An interpolation scheme is also presented for the description of reflector surfaces which are prescribed by discrete points. Representative numerical results are presented for reflectors with sinusoidally and thermally distorted surfaces. Finally, comparisons are made between the measured and calculated patterns of a slowly-varying distorted offset parabolic reflector.

Geologic and tributary influences on the chemistry of a headwater stream

Treesearch

Alexander C. Wooten; James Preer; Pamela J. Edwards

1999-01-01

Water samples were collected weekly from June 12 to August 14, 1995, from Big Spring Run (BSR) in West Virginia. BSR originates in Big Spring Cave, where three stream samples were collected. In addition, 18 BSR sites were sampled downstream from the cave, three from its tributaries, and one above and below the stream?s confluence with Elklick Run. Along its length (653...

Overexpression of BSR1 confers broad-spectrum resistance against two bacterial diseases and two major fungal diseases in rice

PubMed Central

Maeda, Satoru; Hayashi, Nagao; Sasaya, Takahide; Mori, Masaki

2016-01-01

Broad-spectrum disease resistance against two or more types of pathogen species is desirable for crop improvement. In rice, Xanthomonas oryzae pv. oryzae (Xoo), the causal bacteria of rice leaf blight, and Magnaporthe oryzae, the fungal pathogen causing rice blast, are two of the most devastating pathogens. We identified the rice BROAD-SPECTRUM RESISTANCE 1 (BSR1) gene for a BIK1-like receptor-like cytoplasmic kinase using the FOX hunting system, and demonstrated that BSR1-overexpressing (OX) rice showed strong resistance to the bacterial pathogen, Xoo and the fungal pathogen, M. oryzae. Here, we report that BSR1-OX rice showed extended resistance against two other different races of Xoo, and to at least one other race of M. oryzae. In addition, the rice showed resistance to another bacterial species, Burkholderia glumae, which causes bacterial seedling rot and bacterial grain rot, and to Cochliobolus miyabeanus, another fungal species causing brown spot. Furthermore, BSR1-OX rice showed slight resistance to rice stripe disease, a major viral disease caused by rice stripe virus. Thus, we demonstrated that BSR1-OX rice shows remarkable broad-spectrum resistance to at least two major bacterial species and two major fungal species, and slight resistance to one viral pathogen. PMID:27436950

Cardiopulmonary resuscitation using the cardio vent device in a resuscitation model.

PubMed

Suner, Selim; Jay, Gregory D; Kleinman, Gary J; Woolard, Robert H; Jagminas, Liudvikas; Becker, Bruce M

2002-05-01

To compare the "Bellows on Sternum Resuscitation" (BSR) device that permits simultaneous compression and ventilation by one rescuer with two person cardiopulmonary resuscitation (CPR) with bag-valve-mask (BVM) ventilation in a single blind crossover study performed in the laboratory setting. Tidal volume and compression depth were recorded continuously during 12-min CPR sessions with the BSR device and two person CPR. Six CPR instructors performed a total of 1,894 ventilations and 10,532 compressions in 3 separate 12-min sessions. Mean tidal volume (MTV) and compression rate (CR) with the BSR device differed significantly from CPR with the BVM group (1242 mL vs. 1065 mL, respectively, p = 0.0018 and 63.2 compressions per minute (cpm) vs. 81.3 cpm, respectively, p = 0.0076). Error in compression depth (ECD) rate of 9.78% was observed with the BSR device compared to 8.49% with BMV CPR (p = 0.1815). Error rate was significantly greater during the second half of CPR sessions for both BSR and BVM groups. It is concluded that one-person CPR with the BSR device is equivalent to two-person CPR with BVM in all measured parameters except for CR. Both groups exhibited greater error rate in CPR performance in the latter half of 12-min CPR sessions.

Overexpression of BSR1 confers broad-spectrum resistance against two bacterial diseases and two major fungal diseases in rice.

PubMed

Maeda, Satoru; Hayashi, Nagao; Sasaya, Takahide; Mori, Masaki

2016-06-01

Broad-spectrum disease resistance against two or more types of pathogen species is desirable for crop improvement. In rice, Xanthomonas oryzae pv. oryzae (Xoo), the causal bacteria of rice leaf blight, and Magnaporthe oryzae, the fungal pathogen causing rice blast, are two of the most devastating pathogens. We identified the rice BROAD-SPECTRUM RESISTANCE 1 (BSR1) gene for a BIK1-like receptor-like cytoplasmic kinase using the FOX hunting system, and demonstrated that BSR1-overexpressing (OX) rice showed strong resistance to the bacterial pathogen, Xoo and the fungal pathogen, M. oryzae. Here, we report that BSR1-OX rice showed extended resistance against two other different races of Xoo, and to at least one other race of M. oryzae. In addition, the rice showed resistance to another bacterial species, Burkholderia glumae, which causes bacterial seedling rot and bacterial grain rot, and to Cochliobolus miyabeanus, another fungal species causing brown spot. Furthermore, BSR1-OX rice showed slight resistance to rice stripe disease, a major viral disease caused by rice stripe virus. Thus, we demonstrated that BSR1-OX rice shows remarkable broad-spectrum resistance to at least two major bacterial species and two major fungal species, and slight resistance to one viral pathogen.

Monte Carlo simulation of the radiant field produced by a multiple-lamp quartz heating system

NASA Technical Reports Server (NTRS)

Turner, Travis L.

1991-01-01

A method is developed for predicting the radiant heat flux distribution produced by a reflected bank of tungsten-filament tubular-quartz radiant heaters. The method is correlated with experimental results from two cases, one consisting of a single lamp and a flat reflector and the other consisting of a single lamp and a parabolic reflector. The simulation methodology, computer implementation, and experimental procedures are discussed. Analytical refinements necessary for comparison with experiment are discussed and applied to a multilamp, common reflector heating system.

Contrasting Effects of Lithium Chloride and CB1 Receptor Blockade on Enduring Changes in the Valuation of Reward.

PubMed

Hernandez, Giovanni; Bernstein, David; Schoenbaum, Geoffrey; Cheer, Joseph F

2011-01-01

When an organism responds for a reward, its learned behavior can be characterized as goal-directed or habitual based on whether or not it is susceptible to reward devaluation. Here, we evaluated whether instrumental responding for brain stimulation reward (BSR) can be devalued using a paradigm traditionally used for natural rewards. Rats were trained to lever press for BSR; afterward, BSR was paired with either lithium chloride (LiCl, 5 mg/kg, i.p.), a pro-emetic, or AM251, a CB1 receptor antagonist (3 mg/kg, i.p.) or the vehicle of these compounds. Pairings of BSR with these compounds and their vehicles were performed in a novel environment so that only unconditional effects of BSR would be affected by the pharmacological manipulations. Subsequently, in a probe test, all rats were returned in the drug-free state to the boxes where they had received training and instrumental responding was reassessed in the absence of BSR delivery. When compared to control, LiCl produced a significant decrease in the number of responses during the test session, whereas AM251 did not. These results show that instrumental responding for BSR is susceptible to devaluation, in accord with the proposal that this behavior is supported at least in part by associations between the response and the rewarding outcome. Further, they suggest that reward modulation observed in studies involving the use of CB1 receptor antagonists arises from changes in the organism's motivation rather than drug-induced changes in the intrinsic value of reward.

Retrieval of background surface reflectance with BRD components from pre-running BRDF

NASA Astrophysics Data System (ADS)

Choi, Sungwon; Lee, Kyeong-Sang; Jin, Donghyun; Lee, Darae; Han, Kyung-Soo

2016-10-01

Many countries try to launch satellite to observe the Earth surface. As important of surface remote sensing is increased, the reflectance of surface is a core parameter of the ground climate. But observing the reflectance of surface by satellite have weakness such as temporal resolution and being affected by view or solar angles. The bidirectional effects of the surface reflectance may make many noises to the time series. These noises can lead to make errors when determining surface reflectance. To correct bidirectional error of surface reflectance, using correction model for normalized the sensor data is necessary. A Bidirectional Reflectance Distribution Function (BRDF) is making accuracy higher method to correct scattering (Isotropic scattering, Geometric scattering, Volumetric scattering). To correct bidirectional error of surface reflectance, BRDF was used in this study. To correct bidirectional error of surface reflectance, we apply Bidirectional Reflectance Distribution Function (BRDF) to retrieve surface reflectance. And we apply 2 steps for retrieving Background Surface Reflectance (BSR). The first step is retrieving Bidirectional Reflectance Distribution (BRD) coefficients. Before retrieving BSR, we did pre-running BRDF to retrieve BRD coefficients to correct scatterings (Isotropic scattering, Geometric scattering, Volumetric scattering). In pre-running BRDF, we apply BRDF with observed surface reflectance of SPOT/VEGETATION (VGT-S1) and angular data to get BRD coefficients for calculating scattering. After that, we apply BRDF again in the opposite direction with BRD coefficients and angular data to retrieve BSR as a second step. As a result, BSR has very similar reflectance to one of VGT-S1. And reflectance in BSR is shown adequate. The highest reflectance of BSR is not over 0.4μm in blue channel, 0.45μm in red channel, 0.55μm in NIR channel. And for validation we compare reflectance of clear sky pixel from SPOT/VGT status map data. As a result of comparing BSR with VGT-S1, bias is from 0.0116 to 0.0158 and RMSE is from 0.0459 to 0.0545. They are very reasonable results, so we confirm that BSR is similar to VGT-S1. And weakness of this study is missing pixel in BSR which are observed less time to retrieve BRD components. If missing pixels are filled, BSR is better to retrieve surface products with more accuracy. And we think that after filling the missing pixel and being more accurate, it can be useful data to retrieve surface product which made by surface reflectance like cloud masking and retrieving aerosol.

Elastic velocity models for gas-hydrate-bearing sediments-a comparison

NASA Astrophysics Data System (ADS)

Chand, Shyam; Minshull, Tim A.; Gei, Davide; Carcione, José M.

2004-11-01

The presence of gas hydrate in oceanic sediments is mostly identified by bottom-simulating reflectors (BSRs), reflection events with reversed polarity following the trend of the seafloor. Attempts to quantify the amount of gas hydrate present in oceanic sediments have been based mainly on the presence or absence of a BSR and its relative amplitude. Recent studies have shown that a BSR is not a necessary criterion for the presence of gas hydrates, but rather its presence depends on the type of sediments and the in situ conditions. The influence of hydrate on the physical properties of sediments overlying the BSR is determined by the elastic properties of their constituents and on sediment microstructure. In this context several approaches have been developed to predict the physical properties of sediments, and thereby quantify the amount of gas/gas hydrate present from observed deviations of these properties from those predicted for sediments without gas hydrate. We tested four models: the empirical weighted equation (WE); the three-phase effective-medium theory (TPEM); the three-phase Biot theory (TPB) and the differential effective-medium theory (DEM). We compared these models for a range of variables (porosity and clay content) using standard values for physical parameters. The comparison shows that all the models predict sediment properties comparable to field values except for the WE model at lower porosities and the TPB model at higher porosities. The models differ in the variation of velocity with porosity and clay content. The variation of velocity with hydrate saturation is also different, although the range is similar. We have used these models to predict velocities for field data sets from sediment sections with and without gas hydrates. The first is from the Mallik 2L-38 well, Mackenzie Delta, Canada, and the second is from Ocean Drilling Program (ODP) Leg 164 on Blake Ridge. Both data sets have Vp and Vs information along with the composition and porosity of the matrix. Models are considered successful if predictions from both Vp and Vs match hydrate saturations inferred from other data. Three of the models predict consistent hydrate saturations of 60-80 per cent from both Vp and Vs from log and vertical seismic profiling data for the Mallik 2L-38 well data set, but the TPEM model predicts 20 per cent higher saturations, as does the DEM model with a clay-water starting medium. For the clay-rich sediments of Blake Ridge, the DEM, TPEM and WE models predict 10-20 per cent hydrate saturation from Vp data, comparable to that inferred from resistivity data. The hydrate saturation predicted by the TPB model from Vp is higher. Using Vs data, the DEM and TPEM models predict very low or zero hydrate saturation while the TPB and WE models predict hydrate saturation very much higher than those predicted from Vp data. Low hydrate saturations are observed to have little effect on Vs. The hydrate phase appears to be connected within the sediment microstructure even at low saturations.

Numerical and experimental analyses of the radiant heat flux produced by quartz heating systems

NASA Technical Reports Server (NTRS)

Turner, Travis L.; Ash, Robert L.

1994-01-01

A method is developed for predicting the radiant heat flux distribution produced by tungsten filament, tubular fused-quartz envelope heating systems with reflectors. The method is an application of Monte Carlo simulation, which takes the form of a random walk or ray tracing scheme. The method is applied to four systems of increasing complexity, including a single lamp without a reflector, a single lamp with a Hat reflector, a single lamp with a parabolic reflector, and up to six lamps in a six-lamp contoured-reflector heating unit. The application of the Monte Carlo method to the simulation of the thermal radiation generated by these systems is discussed. The procedures for numerical implementation are also presented. Experiments were conducted to study these quartz heating systems and to acquire measurements of the corresponding empirical heat flux distributions for correlation with analysis. The experiments were conducted such that several complicating factors could be isolated and studied sequentially. Comparisons of the experimental results with analysis are presented and discussed. Good agreement between the experimental and simulated results was obtained in all cases. This study shows that this method can be used to analyze very complicated quartz heating systems and can account for factors such as spectral properties, specular reflection from curved surfaces, source enhancement due to reflectors and/or adjacent sources, and interaction with a participating medium in a straightforward manner.

Electrically switchable polymer stabilised broadband infrared reflectors and their potential as smart windows for energy saving in buildings.

PubMed

Khandelwal, Hitesh; Loonen, Roel C G M; Hensen, Jan L M; Debije, Michael G; Schenning, Albertus P H J

2015-07-01

Electrically switchable broadband infrared reflectors that are relatively transparent in the visible region have been fabricated using polymer stabilised cholesteric liquid crystals. The IR reflectors can change their reflection/transmission properties by applying a voltage in response to changes in environmental conditions. Simulations predict that a significant amount of energy can be saved on heating, cooling and lighting of buildings in places such as Madrid by using this switchable IR reflector. We have also fabricated a switchable IR reflector which can also generate electricity. These polymer based switchable IR reflectors are of high potential as windows of automobiles and buildings to control interior temperatures and save energy.

Electrically switchable polymer stabilised broadband infrared reflectors and their potential as smart windows for energy saving in buildings

PubMed Central

Khandelwal, Hitesh; Loonen, Roel C. G. M.; Hensen, Jan L. M.; Debije, Michael G.; Schenning, Albertus P. H. J.

2015-01-01

Electrically switchable broadband infrared reflectors that are relatively transparent in the visible region have been fabricated using polymer stabilised cholesteric liquid crystals. The IR reflectors can change their reflection/transmission properties by applying a voltage in response to changes in environmental conditions. Simulations predict that a significant amount of energy can be saved on heating, cooling and lighting of buildings in places such as Madrid by using this switchable IR reflector. We have also fabricated a switchable IR reflector which can also generate electricity. These polymer based switchable IR reflectors are of high potential as windows of automobiles and buildings to control interior temperatures and save energy. PMID:26132328

Focusing electrode and coaxial reflector used for reducing the guiding magnetic field of the Ku-band foilless transit-time oscillator

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

Ling, Junpu; Zhang, Jiande; He, Juntao, E-mail: hejuntao12@163.com

2014-08-15

Based on the theoretical analysis of the intense relativistic electron beam propagation in the coaxial drift-tube, a focusing electrode and a coaxial reflector is proposed to lessen the demand of the coaxial Ku-band foilless transit-time oscillator (TTO) for the guiding magnetic field. Moreover, a Ku-band TTO with the focusing electrode and the coaxial reflector is designed and studied by particle in cell simulation. When the diode voltage is 390 kV, the beam current 7.8 kA, and the guiding magnetic field is only 0.3 T, the device can output 820 MW microwave pulse at 14.25 GHz by means of the simulation.more » However, for the device without them, the output power is only 320 MW. The primary experiments are also carried out. When the guiding magnetic field is 0.3 T, the output power of the device with the focusing electrode and the coaxial reflector is double that of the one without them. The simulation and experimental results prove that the focusing electrode and the coaxial reflector are effective on reducing the guiding magnetic field of the device.« less

Different contributions of dopamine D1 and D2 receptor activity to alcohol potentiation of brain stimulation reward in C57BL/6J and DBA/2J mice.

PubMed

Fish, Eric W; DiBerto, Jeffrey F; Krouse, Michael C; Robinson, J Elliott; Malanga, C J

2014-08-01

C57BL/6J (C57) and DBA/2J (DBA) mice respond differently to drugs that affect dopamine systems, including alcohol. The current study compared effects of D1 and D2 receptor agonists and antagonists, and the interaction between D1/D2 antagonists and alcohol, on intracranial self-stimulation in male C57 and DBA mice to determine the role of dopamine receptors in the effects of alcohol on brain stimulation reward (BSR). In the initial strain comparison, dose effects on BSR thresholds and maximum operant response rates were determined for the D1 receptor agonist SKF-82958 (±-6-chloro-7,8-dihydroxy-3-allyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine; 0.1-0.56 mg/kg) and antagonist SCH 23390 (+-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepinehydrochloride; 0.003-0.056 mg/kg), and the D2 receptor agonist quinpirole (0.1-3.0 mg/kg) and antagonist raclopride (0.01-0.56 mg/kg). For the alcohol interaction, SCH 23390 (0.003 mg/kg) or raclopride (0.03 mg/kg) was given before alcohol (0.6-2.4 g/kg p.o.). D1 antagonism dose-dependently elevated and SKF-82958 dose-dependently lowered BSR threshold in both strains; DBA mice were more sensitive to SKF-82958 effects. D2 antagonism dose-dependently elevated BSR threshold only in C57 mice. Low doses of quinpirole elevated BSR threshold equally in both strains, whereas higher doses of quinpirole lowered BSR threshold only in C57 mice. SCH 23390, but not raclopride, prevented lowering of BSR threshold by alcohol in DBA mice. Conversely, raclopride, but not SCH 23390, prevented alcohol potentiation of BSR in C57 mice. These results extend C57 and DBA strain differences to D1/D2 sensitivity of BSR, and suggest differential involvement of D1 and D2 receptors in the acute rewarding effects of alcohol in these two mouse strains. Copyright © 2014 by The American Society for Pharmacology and Experimental Therapeutics.

Iron bioavailability and weight gains to iron-deficient rats fed a commonly consumed Tunisian meal 'bean seeds ragout' with or without beef and with green or black tea decoction.

PubMed

Hamdaoui, Mohamed Hédi; Chabchoub, Soufia; Hédhili, Abderrazek

2003-01-01

The Fe bioavailability and the weight gains were evaluated in rats fed a commonly consumed Tunisian meal 'bean seeds ragout' (BSR), with or without beef and with black or green tea decoction. The Fe bioavailability was evaluated in Fe-deficient rats by the hemoglobin repletion method and the Fe stored in the liver. The addition of beef to the BSR significantly increased the Fe bioavailability from this meal by 147% and the reserve of Fe stored in the liver by 77% (P < 0.001). In contrast, both black and green tea decoctions caused a significant decrease of the Fe bioavailability from BSR meal (-19.6 +/- 4.9% and -14.9 +/- 4.1%, respectively). The reserve of Fe stored in the liver was significantly lower in the BSR, the black and the green tea groups than in the positive control group (FeSO4). The weight gains were significantly lower in the black and the green tea groups (3.9 +/- 5.7 g, 13 +/- 1.9 g, respectively) than in the BSR group (24.9 +/- 6 g). The addition of beef to BSR meal counteracted the inhibitory effect of the kidney bean and considerably improved the Fe bioavailability and the Fe stored in the liver of rats. The green tea decoction, which constitutes an important source of antioxidant factors, had the same inhibitory effect as the black tea decoction on the Fe bioavailability from BSR meal. In addition, both black and green teas significantly reduced the weight gains, where the black tea decoction has the most effect.

Characterization of Desulfovibrio salinus sp. nov., a slightly halophilic sulfate-reducing bacterium isolated from a saline lake in Tunisia.

PubMed

Ben Ali Gam, Zouhaier; Thioye, Abdoulaye; Cayol, Jean-Luc; Joseph, Manon; Fauque, Guy; Labat, Marc

2018-03-01

A novel slightly halophilic sulfate-reducing bacterium, designated strain P1BSR T , was isolated from water of a saline lake in Tunisia. Strain P1BSR T had motile (single polar flagellum), Gram-negative, rod-shaped, non-spore-forming cells, occurring singly or in pairs. Strain P1BSR T grew at temperatures between 15 and 45 °C (optimum 40 °C), and in a pH range between 6 and 8.5 (optimum pH 6.7). The strain required NaCl for growth (1 % w/v), and tolerated high NaCl concentration (up to 12 % w/v) with an optimum of 3 % (w/v). Sulfate, thiosulfate and sulfite served as terminal electron acceptors, but not elemental sulfur, fumarate, nitrate and nitrite. Strain P1BSR T utilized lactate, pyruvate, formate, d-fructose and glycerol as carbon and energy sources. The main cellular fatty acid was C16 : 0 (50.8 %). The genomic DNA G+C content was 47.7 mol%. Phylogenetic analysis of 16S rRNA gene sequence similarity indicated that strain P1BSR T was affiliated to the genus Desulfovibrio, with the type strains Desulfovibrio salexigens (96.51 %), Desulfovibrio zosterae (95.68 %), Desulfovibrio hydrothermalis (94.81 %) and Desulfovibrio ferrireducens (94.73 %) as its closest phylogenetic relatives. On the basis of genotypic, phenotypic and phylogenetic characteristics, it is proposed to assign strain P1BSR T to a novel species of the genus Desulfovibrio, Desulfovibrio salinus sp. nov. The type strain is P1BSR T (=DSM 101510 T =JCM 31065 T ).

Simulation of parabolic reflectors for ultraviolet phototherapy

NASA Astrophysics Data System (ADS)

Grimes, David Robert

2016-08-01

Ultraviolet (UVR) phototherapy is widely used to treat an array of skin conditions, including psoriasis, eczema and vitiligo. For such interventions, a quantified dose is vital if the treatment is to be both biologically effective and to avoid the detrimental effects of over-dosing. As dose is absorbed at surface level, the orientation of patient site with respect to the UVR lamps modulates effective dose. Previous investigations have modelled this behaviour, and examined the impact of shaped anodized aluminium reflectors typically placed around lamps in phototherapy cabins. These mirrors are effective but tend to yield complex patterns of reflection around the cabin which can result in substantial dose inhomogeneity. There has been some speculation over whether using the reflective property of parabolic mirrors might improve dose delivery or homogeneity through the treatment cabin. In this work, the effects of parabolic mirrors are simulated and compared with standard shaped mirrors. Simulation results strongly suggest that parabolic reflectors reduce total irradiance relative to standard shaped reflectors, and have a negligible impact on dose homogeneity.

A Physical Model for Shallow Groundwater Studies and the Simulation of Land Drain Performance.

ERIC Educational Resources Information Center

Parkinson, Robert; Reid, Ian

1987-01-01

Describes a two-dimensional sand-tank model that illustrates the influence of ground slope on tile drain discharge and the movement of groundwater in general. The model can be used to demonstrate the effect of topography on sub-surface water movement in agricultural catchments, thus it is a useful hydrological teaching aid. (Author/BSR)

Bandwidth Study of the Microwave Reflectors with Rectangular Corrugations

NASA Astrophysics Data System (ADS)

Zhang, Liang; He, Wenlong; Donaldson, Craig R.; Cross, Adrian W.

2016-09-01

The mode-selective microwave reflector with periodic rectangular corrugations in the inner surface of a circular metallic waveguide is studied in this paper. The relations between the bandwidth and reflection coefficient for different numbers of corrugation sections were studied through a global optimization method. Two types of reflectors were investigated. One does not consider the phase response and the other does. Both types of broadband reflectors operating at W-band were machined and measured to verify the numerical simulations.

The effect of reflector geometry on the acoustic field and bubble dynamics produced by an electrohydraulic shock wave lithotripter.

PubMed

Zhou, Yufeng; Zhong, Pei

2006-06-01

A theoretical model for the propagation of shock wave from an axisymmetric reflector was developed by modifying the initial conditions for the conventional solution of a nonlinear parabolic wave equation (i.e., the Khokhlov-Zabolotskaya-Kuznestsov equation). The ellipsoidal reflector of an HM-3 lithotripter is modeled equivalently as a self-focusing spherically distributed pressure source. The pressure wave form generated by the spark discharge of the HM-3 electrode was measured by a fiber optic probe hydrophone and used as source conditions in the numerical calculation. The simulated pressure wave forms, accounting for the effects of diffraction, nonlinearity, and thermoviscous absorption in wave propagation and focusing, were compared with the measured results and a reasonably good agreement was found. Furthermore, the primary characteristics in the pressure wave forms produced by different reflector geometries, such as that produced by a reflector insert, can also be predicted by this model. It is interesting to note that when the interpulse delay time calculated by linear geometric model is less than about 1.5 micros, two pulses from the reflector insert and the uncovered bottom of the original HM-3 reflector will merge together. Coupling the simulated pressure wave form with the Gilmore model was carried out to evaluate the effect of reflector geometry on resultant bubble dynamics in a lithotripter field. Altogether, the equivalent reflector model was found to provide a useful tool for the prediction of pressure wave form generated in a lithotripter field. This model may be used to guide the design optimization of reflector geometries for improving the performance and safety of clinical lithotripters.

The effect of reflector geometry on the acoustic field and bubble dynamics produced by an electrohydraulic shock wave lithotripter

PubMed Central

Zhou, Yufeng; Zhong, Pei

2007-01-01

A theoretical model for the propagation of shock wave from an axisymmetric reflector was developed by modifying the initial conditions for the conventional solution of a nonlinear parabolic wave equation (i.e., the Khokhlov–Zabolotskaya–Kuznestsov equation). The ellipsoidal reflector of an HM-3 lithotripter is modeled equivalently as a self-focusing spherically distributed pressure source. The pressure wave form generated by the spark discharge of the HM-3 electrode was measured by a fiber optic probe hydrophone and used as source conditions in the numerical calculation. The simulated pressure wave forms, accounting for the effects of diffraction, nonlinearity, and thermoviscous absorption in wave propagation and focusing, were compared with the measured results and a reasonably good agreement was found. Furthermore, the primary characteristics in the pressure wave forms produced by different reflector geometries, such as that produced by a reflector insert, can also be predicted by this model. It is interesting to note that when the interpulse delay time calculated by linear geometric model is less than about 1.5 μs, two pulses from the reflector insert and the uncovered bottom of the original HM-3 reflector will merge together. Coupling the simulated pressure wave form with the Gilmore model was carried out to evaluate the effect of reflector geometry on resultant bubble dynamics in a lithotripter field. Altogether, the equivalent reflector model was found to provide a useful tool for the prediction of pressure wave form generated in a lithotripter field. This model may be used to guide the design optimization of reflector geometries for improving the performance and safety of clinical lithotripters. PMID:16838506

Trapping and migration of methane associated with the gas hydrate stability zone at the Blake Ridge Diapir: New insights from seismic data

USGS Publications Warehouse

Taylor, M.H.; Dillon, William P.; Pecher, I.A.

2000-01-01

The Blake Ridge Diapir is the southernmost of a line of salt diapirs along the Carolina trough. Diapirs cause faulting of the superjacent sediments, creating pathways for migration of fluids and gas to the seafloor. We analyzed reflection seismic data from the Blake Ridge Diapir, which is located in a region with known abundant gas hydrate occurrence. A striking feature in these data is a significant shallowing of the base of gas hydrate stability (BGHS) over the center of the diapir. The seafloor is warped up by about 100 m above the diapir, from about 2300 m to about 2200 m. The BGHS, as indicated by a bottom simulating reflection (BSR), is about 4.5 s off the flanks of the diapir, rising to about 4.15 s at the center. Above the diapir, a fault system appears to rise vertically from the BGHS to about 0.05 s below the seafloor (40-50 m); it then diverges into several steeply dipping faults that breach the seafloor and cover an area ~700 m in diameter. Other secondary faults diverge from the main fault or emerge directly from the BGHS near the crest of the diapir. Gas and other fluids may migrate upward through the faults. We performed complex trace analysis to compare the reflection strength and instantaneous frequency along individual reflections. A low-frequency anomaly over the center of the diapir indicates high seismic attenuation. This is interpreted to be caused by migration of fluids (probably methane) along fault pathways. The migration of gas (i.e. probably mainly methane) through the gas hydrate stability zone is not yet understood. We speculate that pore fluids in the faults may be too warm and too salty to form gas hydrate, even at depths where gas hydrate is stable away from the diapir. Alternatively, gas hydrates may seal the fault walls such that water supply is too low to transform all the gas into gas hydrates. The shallowing of the BSR may reflect increased heatflow above the diapir either caused by the high thermal conductivity of the underlying salt or by advective heat transport along with fluids. High pore water salinity shifts the gas hydrate stability to lower temperatures and may also play a significant role in BSR shallowing. We, therefore, investigated the possible effect of pore water salinity on shallowing of the BSR. We found that BSR shallowing may theoretically be entirely caused by increased salinity over the diapir, although geologically this would not be reasonable. This observation demonstrates the potential importance of pore water salinity for lateral variations of BSR depths, in particular, above salt structures: (C) 2000 Elsevier Science B.V.

The development of composite materials for spacecraft precision reflector panels

NASA Technical Reports Server (NTRS)

Tompkins, Stephen S.; Bowles, David E.; Funk, Joan G.; Towell, Timothy W.; Lavoie, J. A.

1990-01-01

One of the critical technology needs for large precision reflectors required for future astrophysics and optical communications is in the area of structural materials. Therefore, a major area of the Precision Segmented Reflector Program at NASA is to develop lightweight composite reflector panels with durable, space environmentally stable materials which maintain both surface figure and required surface accuracy necessary for space telescope applications. Results from the materials research and development program at NASA Langley Research Center are discussed. Advanced materials that meet the reflector panel requirements are identified. Thermal, mechanical and durability properties of candidate materials after exposure to simulated space environments are compared to the baseline material.

Reconfigurable Yagi-Uda antenna based on a silicon reflector with a solid-state plasma.

PubMed

Kim, Da-Jin; Park, Jang-Soon; Kim, Cheol Ho; Hur, Jae; Kim, Choong-Ki; Cho, Young-Kyun; Ko, Jun-Bong; Park, Bonghyuk; Kim, Dongho; Choi, Yang-Kyu

2017-12-08

This paper describes the fabrication and characterization of a reconfigurable Yagi-Uda antenna based on a silicon reflector with a solid-state plasma. The silicon reflector, composed of serially connected p-i-n diodes, forms a highly dense solid-state plasma by injecting electrons and holes into the intrinsic region. When this plasma silicon reflector is turned on, the front-realized gain of the antenna increases by more than 2 dBi beyond 5.3 GHz. To achieve the large gain increment, the structure of the antenna is carefully designed with the aid of semiconductor device simulation and antenna simulation. By using an aluminum nitride (AlN) substrate with high thermal conductivity, self-heating effects from the high forward current in the p-i-n diode are efficiently suppressed. By comparing the antenna simulation data and the measurement data, we estimated the conductivity of the plasma silicon reflector in the on-state to be between 10 4 and 10 5  S/m. With these figures, silicon material with its technology is an attractive tunable material for a reconfigurable antenna, which has attracted substantial interest from many areas, such as internet of things (IoT) applications, wireless network security, cognitive radio, and mobile and satellite communications as well as from multiple-input-multiple-output (MIMO) systems.

Molecular defense response of oil palm to Ganoderma infection.

PubMed

Ho, C-L; Tan, Y-C

2015-06-01

Basal stem rot (BSR) of oil palm roots is due to the invasion of fungal mycelia of Ganoderma species which spreads to the bole of the stem. In addition to root contact, BSR can also spread by airborne basidiospores. These fungi are able to break down cell wall components including lignin. BSR not only decreases oil yield, it also causes the stands to collapse thus causing severe economic loss to the oil palm industry. The transmission and mode of action of Ganoderma, its interactions with oil palm as a hemibiotroph, and the molecular defence responses of oil palm to the infection of Ganoderma boninense in BSR are reviewed, based on the transcript profiles of infected oil palms. The knowledge gaps that need to be filled in oil palm-Ganoderma molecular interactions i.e. the associations of hypersensitive reaction (HR)-induced cell death and reactive oxygen species (ROS) kinetics to the susceptibility of oil palm to Ganoderma spp., the interactions of phytohormones (salicylate, jasmonate and ethylene) at early and late stages of BSR, and cell wall strengthening through increased production of guaiacyl (G)-type lignin, are also discussed. Copyright © 2014 Elsevier Ltd. All rights reserved.

Radioactive Demonstration Of Mineralized Waste Forms Made From Hanford Low Activity Waste (Tank Farm Blend) By Fluidized Bed Steam Reformation (FBSR)

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

Jantzen, C. M.; Crawford, C. L.; Bannochie, C. J.

The U.S. Department of Energy’s Office of River Protection (ORP) is responsible for the retrieval, treatment, immobilization, and disposal of Hanford’s tank waste. A key aspect of the River Protection Project (RPP) cleanup mission is to construct and operate the Hanford Tank Waste Treatment and Immobilization Plant (WTP). The WTP will separate the tank waste into high-level and low-activity waste (LAW) fractions, both of which will subsequently be vitrified. The projected throughput capacity of the WTP LAW Vitrification Facility is insufficient to complete the RPP mission in the time frame required by the Hanford Federal Facility Agreement and Consent Order,more » also known as the Tri-Party Agreement (TPA), i.e. December 31, 2047. Supplemental Treatment is likely to be required both to meet the TPA treatment requirements as well as to more cost effectively complete the tank waste treatment mission. The Supplemental Treatment chosen will immobilize that portion of the retrieved LAW that is not sent to the WTP’s LAW Vitrification facility into a solidified waste form. The solidified waste will then be disposed on the Hanford site in the Integrated Disposal Facility (IDF). Fluidized Bed Steam Reforming (FBSR) offers a moderate temperature (700-750°C) continuous method by which LAW can be processed irrespective of whether the waste contain organics, nitrates, sulfates/sulfides, chlorides, fluorides, volatile radionuclides or other aqueous components. The FBSR technology can process these wastes into a crystalline ceramic (mineral) waste form. The mineral waste form that is produced by co-processing waste with kaolin clay in an FBSR process has been shown to be comparable to LAW glass, i.e. leaches Tc-99, Re and Na at <2g/m 2 during ASTM C1285 (Product Consistency) durability testing. Monolithing of the granular FBSR product was investigated to prevent dispersion during transport or burial/storage. Monolithing in an inorganic geopolymer binder, which is amorphous, macro-encapsulates the granules, and the monoliths pass ANSI/ANS 16.1 and ASTM C1308 durability testing with Re achieving a Leach Index (LI) of 9 (the Hanford Integrated Disposal Facility, IDF, criteria for Tc-99) after a few days and Na achieving an LI of >6 (the Hanford IDF criteria for Na) in the first few hours. The granular and monolithic waste forms also pass the EPA Toxicity Characteristic Leaching Procedure (TCLP) for all Resource Conservation and Recovery Act (RCRA) components at the Universal Treatment Standards (UTS). Two identical Benchscale Steam Reformers (BSR) were designed and constructed at SRNL, one to treat non-radioactive simulants and the other to treat actual radioactive wastes. The results from the non-radioactive BSR were used to determine the parameters needed to operate the radioactive BSR in order to confirm the findings of non-radioactive FBSR pilot scale and engineering scale tests and to qualify an FBSR LAW waste form for applications at Hanford. Radioactive testing commenced using SRS LAW from Tank 50 chemically trimmed to look like Hanford’s blended LAW known as the Rassat simulant as this simulant composition had been tested in the non-radioactive BSR, the non-radioactive pilot scale FBSR at the Science Applications International Corporation-Science and Technology Applications Research (SAIC-STAR) facility in Idaho Falls, ID and in the TTT Engineering Scale Technology Demonstration (ESTD) at Hazen Research Inc. (HRI) in Denver, CO. This provided a “tie back” between radioactive BSR testing and non-radioactive BSR, pilot scale, and engineering scale testing. Approximately six hundred grams of non-radioactive and radioactive BSR product were made for extensive testing and comparison to the non-radioactive pilot scale tests performed in 2004 at SAIC-STAR and the engineering scale test performed in 2008 at HRI with the Rassat simulant. The same mineral phases and off-gas species were found in the radioactive and non-radioactive testing. The granular ESTD and BSR products (radioactive and non-radioactive) were analyzed for total constituents and durability tested as a granular waste form. A subset of the granular material was stabilized in a clay based geopolymer matrix at 42% and 65% FBSR loadings and durability tested as a monolith waste form. The 65 wt% FBSR loaded monolith made with clay (radioactive) was more durable than the 67-68 wt% FBSR loaded monoliths made from fly ash (non-radioactive) based on short term PCT testing. Long term, 90 to 107 day, ASTM C1308 testing (similar to ANSI/ANS 16.1 testing) was only performed on two fly ash geopolymer monoliths at 67-68 wt% FBSR loading and three clay geopolymer monoliths at 42 wt% FBSR loading. More clay geopolymers need to be made and tested at longer times at higher FBSR loadings for comparison to the fly ash monoliths. Monoliths made with metakaolin (heat treated) clay are of a more constant composition and are very reactive as the heat treated clay is amorphous and alkali activated. The monoliths made with fly ash are subject to the inherent compositional variation found in fly ash as it is a waste product from burning coal and it contains unreactive components such as mullite. However, both the fly ash and the clay based monoliths perform well in long term ASTM C1308 testing.« less

Non-periodic high-index contrast gratings reflector with large-angle beam forming ability

NASA Astrophysics Data System (ADS)

Fang, Wenjing; Huang, Yongqing; Duan, Xiaofeng; Fei, Jiarui; Ren, Xiaomin; Mao, Min

2016-05-01

A non-periodic high-index contrast gratings (HCGs) reflector on SOI wafer with large-angle beam forming ability has been proposed and fabricated. The proposed reflector was designed using rigorous coupled-wave analysis (RCWA) and finite-element-method (FEM). A deflection angle of 17.35° and high reflectivity of 92.31% are achieved under transverse magnetic (TM) polarized light in numerical simulation. Experimental results show that the reflected power peaked at 17.2° under a 1550 nm incident light, which is in good accordance with the simulation results. Moreover, the reflected power spectrum was also measured. Under different incident wavelengths around 1550 nm, reflected powers all peaked at 17.2°. The results show that the proposed non-periodic HCGs reflector has a good reflection and beam forming ability in a wavelength range as wide as 40 nm around 1550 nm.

The optical design and simulation of the collimated solar simulator

NASA Astrophysics Data System (ADS)

Zhang, Jun; Ma, Tao

2018-01-01

The solar simulator is a lighting device that can simulate the solar radiation. It has been widely used in the testing of solar cells, satellite space environment simulation and ground experiment, test and calibration precision of solar sensor. The solar simulator mainly consisted of short—arc xenon lamp, ellipsoidal reflectors, a group of optical integrator, field stop, aspheric folding mirror and collimating reflector. In this paper, the solar simulator's optical system basic size are given by calculation. Then the system is optically modeled with the Lighttools software, and the simulation analysis on solar simulator using the Monte Carlo ray -tracing technique is conducted. Finally, the simulation results are given quantitatively by diagrammatic form. The rationality of the design is verified on the basis of theory.

Application of Vision Metrology to In-Orbit Measurement of Large Reflector Onboard Communication Satellite for Next Generation Mobile Satellite Communication

NASA Astrophysics Data System (ADS)

Akioka, M.; Orikasa, T.; Satoh, M.; Miura, A.; Tsuji, H.; Toyoshima, M.; Fujino, Y.

2016-06-01

Satellite for next generation mobile satellite communication service with small personal terminal requires onboard antenna with very large aperture reflector larger than twenty meters diameter because small personal terminal with lower power consumption in ground base requires the large onboard reflector with high antenna gain. But, large deployable antenna will deform in orbit because the antenna is not a solid dish but the flexible structure with fine cable and mesh supported by truss. Deformation of reflector shape deteriorate the antenna performance and quality and stability of communication service. However, in case of digital beam forming antenna with phased array can modify the antenna beam performance due to adjustment of excitation amplitude and excitation phase. If we can measure the reflector shape precisely in orbit, beam pattern and antenna performance can be compensated with the updated excitation amplitude and excitation phase parameters optimized for the reflector shape measured every moment. Softbank Corporation and National Institute of Information and Communications Technology has started the project "R&D on dynamic beam control technique for next generation mobile communication satellite" as a contracted research project sponsored by Ministry of Internal Affairs and Communication of Japan. In this topic, one of the problem in vision metrology application is a strong constraints on geometry for camera arrangement on satellite bus with very limited space. On satellite in orbit, we cannot take many images from many different directions as ordinary vision metrology measurement and the available area for camera positioning is quite limited. Feasibility of vision metrology application and general methodology to apply to future mobile satellite communication satellite is to be found. Our approach is as follows: 1) Development of prototyping simulator to evaluate the expected precision for network design in zero order and first order 2) Trial measurement for large structure with similar dimension with large deployable reflector to confirm the validity of the network design and instrumentation. In this report, the overview of this R&D project and the results of feasibility study of network design based on simulations on vision metrology and beam pattern compensation of antenna with very large reflector in orbit is discussed. The feasibility of assumed network design for vision metrology and satisfaction of accuracy requirements are discussed. The feasibility of beam pattern compensation by using accurately measured reflector shape is confirmed with antenna pattern simulation for deformed parabola reflector. If reflector surface of communication satellite can be measured routinely in orbit, the antenna pattern can be compensated and maintain the high performance every moment.

Fault structure, properties and activity of the Makran Accretionary Prism and implications for seismogenic potential

NASA Astrophysics Data System (ADS)

Smith, G. L.; McNeill, L. C.; Henstock, T.; Bull, J. M.

2011-12-01

The Makran subduction zone is the widest accretionary prism in the world (~400km), generated by convergence between the Arabian and Eurasian tectonic plates. It represents a global end-member, with a 7km thick incoming sediment section. Accretionary prisms have traditionally been thought to be aseismic due to the presence of unconsolidated sediment and elevated basal pore pressures. The seismogenic potential of the Makran subduction zone is unclear, despite a Mw 8.1 earthquake in 1945 that may have been located on the plate boundary beneath the prism. In this study, a series of imbricate landward dipping (seaward verging) thrust faults have been interpreted across the submarine prism (outer 70 km) using over 6000km of industry multichannel seismic data and bathymetric data. A strong BSR (bottom simulating reflector) is present throughout the prism (excluding the far east). An unreflective décollement is interpreted from the geometry of the prism thrusts. Two major sedimentary units are identified in the input section, the lower of which contains the extension of the unreflective décollement surface. Between 60%-100% of the input section is currently being accreted. The geometry of piggy-back basin stratigraphy shows that the majority of thrusts, including those over 50km from the trench, are recently active. Landward thrusts show evidence for reactivation after periods of quiescence. Negative polarity fault plane reflectors are common in the frontal thrusts and in the eastern prism, where they may be related to increased fault activity and fluid expulsion, and are rarer in older landward thrusts. Significant NE-SW trending basement structures (The Murray Ridge and Little Murray Ridge) on the Arabian plate intersect the deformation front and affect sediment input to the subduction zone. Prism taper and structure are apparently primarily controlled by sediment supply and the secondary influence of subducting basement ridges. The thick, likely distal, sediment section in the west produces a prism with a simple imbricate structure. As basement depth is reduced over the Little Murray Ridge, the accretionary prism structure (fault spacing and deformation front position) changes. In the east, proximity to the Murray Ridge and triple junction is expressed through a reduction in prism width and reduced fault activity. The resulting prism structure and morphology can ultimately be used to assess likely sediment properties and hence seismic potential at the plate boundary.

Loss of function of a rice TPR-domain RNA-binding protein confers broad-spectrum disease resistance.

PubMed

Zhou, Xiaogang; Liao, Haicheng; Chern, Mawsheng; Yin, Junjie; Chen, Yufei; Wang, Jianping; Zhu, Xiaobo; Chen, Zhixiong; Yuan, Can; Zhao, Wen; Wang, Jing; Li, Weitao; He, Min; Ma, Bingtian; Wang, Jichun; Qin, Peng; Chen, Weilan; Wang, Yuping; Liu, Jiali; Qian, Yangwen; Wang, Wenming; Wu, Xianjun; Li, Ping; Zhu, Lihuang; Li, Shigui; Ronald, Pamela C; Chen, Xuewei

2018-03-20

Crops carrying broad-spectrum resistance loci provide an effective strategy for controlling infectious disease because these loci typically confer resistance to diverse races of a pathogen or even multiple species of pathogens. Despite their importance, only a few crop broad-spectrum resistance loci have been reported. Here, we report the identification and characterization of the rice bsr-k1 (broad-spectrum resistance Kitaake-1) mutant, which confers broad-spectrum resistance against Magnaporthe oryzae and Xanthomonas oryzae pv oryzae with no major penalty on key agronomic traits. Map-based cloning reveals that Bsr-k1 encodes a tetratricopeptide repeats (TPRs)-containing protein, which binds to mRNAs of multiple OsPAL ( OsPAL1-7 ) genes and promotes their turnover. Loss of function of the Bsr-k1 gene leads to accumulation of OsPAL1-7 mRNAs in the bsr-k1 mutant. Furthermore, overexpression of OsPAL1 in wild-type rice TP309 confers resistance to M. oryzae , supporting the role of OsPAL1 Our discovery of the bsr-k1 allele constitutes a significant conceptual advancement and provides a valuable tool for breeding broad-spectrum resistant rice. Copyright © 2018 the Author(s). Published by PNAS.

A Possible Origin of the Gas Hydrate in Southwest Taiwan Offshore Area

NASA Astrophysics Data System (ADS)

Lee, C.; Lee, J.; Oung, J.

2003-12-01

The southwest Taiwan locate at the eastward subduction zone of the Eurasian plate, which is currently converging with the Philippine Sea plate at a rate of several few centimeters per year. The geological setting of this region is characterized by the appearance of thick accreted sediments up to several kilometers, numerous submarine canyons, active faults, and mud diapirs/volcanoes. The origin of mud diapir/volcano is probably related to the plate convergence. During the tectonic processes, the organic matters were "cooked" thermogenically and biogenically to produce the natural gases, and possibly the oil in the sediment. Beneath the seafloor, if the natural gases were at the appropriate temperature and pressure condition, they would become the gas hydrate, and preserved in the top sediment layers. The formation of gas hydrate is situated under the water depth at about 300 to 3000 meters in this region. In the seismic profiles, the Bottom Simulation Reflector (BSR) probably represents the boundary between the solid-state and gas-state natural gas. The BSR is also regarded as an important marker as an existence of gas hydrate. It is extensively distributed in the continental margin off southwest Taiwan, but unstable, especially along the active fault zones. The natural gas as well as the mud and hydraulic fluid in the deep sediment are pushed into the surface layer. In order to investigate the relationship between mud diapir and gas hydrate, we conduct the geophysical and geological methods: using a 38/150 kHz high-frequency echo sounder system to guide and select the sites for mud diapirs, and take 1-3 m gravity core samples. We, then, adopt an up-side-down "headspace" tin-can technique to preserve the gases, and use a gas chromatography to analyze its contents. Oil companies commonly use the method. The first result shows that the existence of methane, ethane, propane and possible other higher hydrocarbon contents in the core samples. The methane is the most abundant gas, up to 1859 parts per million in volume (ppm); the others are not significant, probably due to a leaking in the sampling and transportation. We have reduced the "headspace" in order to preserve more concentrated gases in the second attempt, and the result shows similar. Nonetheless, our results suggest that the gases are probably a mixture of thermogenic and biogenic origin. Due to the existence of higher hydrocarbon contents, we believe that the thermogenic gases are produced in the deep source sediments, while the shallow biogenic methane is mixing with them in the top sediment. In the mud diapir/volcano area, the contents of natural gases are usually higher than that in a flat seafloor. As several high gas values have been founded in the near shore area (e.g., 1604 ppm of C1 plus C2 and C3 found at a water depth of 23 m), we suggest that the 300-3000 m gas hydrate zone is probably in a dynamic balance of which the deep gases are continuously migrating to the BSR and the free gases are being evaporating from this zone. Our data illustrate the potential existence of natural gases in this region; however, we cannot quantify the reserve at this time. Further investigations with a long core and better-improved techniques are needed.

Bacterial and Thermochemical Sulfate Reduction in Diagenetic Settings - Old and New Insights

NASA Astrophysics Data System (ADS)

Machel, H.

2006-12-01

The association of dissolved sulfate and hydrocarbons is thermodynamically unstable in virtually all diagenetic environments. Hence, redox-reactions occur, whereby sulfate is reduced by hydrocarbons either bacterially (bacterial sulfate reduction = BSR) or inorganically (thermochemical sulfate reduction = TSR). Based on empirical evidence, BSR and TSR occur in two mutually exclusive thermal regimes, i.e., low-T and high-T diagenetic environments, respectively. BSR is common in diagenetic settings at T = 0 - 80 ° C. Above this T range, almost all sulfate reducers cease to metabolize. Those few types of hyperthermophiles that can form H2S at higher T appear to be very rare and do not normally occur and/or metabolize in geologic settings that are otherwise conducive to BSR. TSR appears to be common in geologic settings at T = 100 - 140 ° C, but in some settings T up to 180 ° C appears to be necessary. TSR does not have a sharply defined, generally valid minimum T because the onset and rate of TSR are governed by several factors that vary from place to place, i.e., the composition of the available organic reactants, kinetic inhibitors and/or catalysts, anhydrite dissolution rates, wettability, as well as migration and diffusion rates of the major reactants. A well- defined, specific minimum T for TSR can be expected only where the reservoir conditions are fairly homogeneous on the scale of a field or a play. BSR is geologically instantaneous in most geologic settings. Rates of TSR are much lower, but still geologically significant. TSR may form sour gas reservoirs and/or MVT deposits in several tens of thousands to a few million years at T = 100 - 140 ° C. BSR and TSR may be exothermic or endothermic, depending mainly on the presence or absence of specific organic reactants. The main organic reactants for BSR are organic acids and other products of aerobic or fermentative biodegradation, and those for TSR are branched and n-alkanes, followed by cyclic and mono-aromatic species, in the gasoline range. Sulfate is derived almost invariably from the dissolution of gypsum and/or anhydrite, which may be primary or secondary deposits at or near the redox-reaction site(s). The products of BSR and TSR are similar, but their relative amounts vary widely and are determined by a number of locally variable factors, including availability of reactants, formation water chemistry, and wettability. The primary inorganic reaction products in both thermal regimes are H2S (HS-) and HCO3- (CO2). The presence of alkali earth metals often results in the formation of carbonates, particularly calcite and dolomite. Iron sulfides, galena, and sphalerite form as by-products of H2S generation, if the respective transition or base metals are present or transported to a BSR/TSR reaction site. Elemental sulfur may accumulate as a volumetrically significant net reaction product, usually when the system runs out of reactive hydrocarbons. Solid bitumen may form as a by-product of both BSR and TSR.

Effect of the incidence angle to free space optical communication based on cat-eye modulating retro-reflector

NASA Astrophysics Data System (ADS)

Zhang, Lai-xian; Sun, Hua-yan; Zhao, Yan-zhong; Zheng, Yong-hui; Shan, Cong-miao

2013-08-01

Based on the cat-eye effect of optical system, free space optical communication based on cat-eye modulating retro-reflector can build communication link rapidly. Compared to classical free space optical communication system, system based on cat-eye modulating retro-reflector has great advantages such as building communication link more rapidly, a passive terminal is smaller, lighter and lower power consuming. The incident angle is an important factor of cat-eye effect, so it will affect the retro-reflecting communication link. In this paper, the principle and work flow of free space optical communication based on cat-eye modulating retro-reflector were introduced. Then, using the theory of geometric optics, the equivalent model of modulating retro-reflector with incidence angle was presented. The analytical solution of active area and retro-reflected light intensity of cat-eye modulating retro-reflector were given. Noise of PIN photodetector was analyzed, based on which, bit error rate of free space optical communication based on cat-eye modulating retro-reflector was presented. Finally, simulations were done to study the effect of incidence angle to the communication. The simulation results show that the incidence angle has little effect on active area and retro-reflected light intensity when the incidence beam is in the active field angle of cat-eye modulating retro-reflector. With certain system and condition, the communication link can rapidly be built when the incidence light beam is in the field angle, and the bit error rate increases greatly with link range. When link range is smaller than 35Km, the bit error rate is less than 10-16.

Simulation and Testing of a Linear Array of Modified Four-Square Feed Antennas for the Tianlai Cylindrical Radio Telescope

NASA Astrophysics Data System (ADS)

Cianciara, Aleksander J.; Anderson, Christopher J.; Chen, Xuelei; Chen, Zhiping; Geng, Jingchao; Li, Jixia; Liu, Chao; Liu, Tao; Lu, Wing; Peterson, Jeffrey B.; Shi, Huli; Steffel, Catherine N.; Stebbins, Albert; Stucky, Thomas; Sun, Shijie; Timbie, Peter T.; Wang, Yougang; Wu, Fengquan; Zhang, Juyong

A wide bandwidth, dual polarized, modified four-square antenna is presented as a feed antenna for radio astronomical measurements. A linear array of these antennas is used as a line-feed for cylindrical reflectors for Tianlai, a radio interferometer designed for 21cm intensity mapping. Simulations of the feed antenna beam patterns and scattering parameters are compared to experimental results at multiple frequencies across the 650-1420MHz range. Simulations of the beam patterns of the combined feed array/reflector are presented as well.

Geometric and boundary element method simulations of acoustic reflections from rough, finite, or non-planar surfaces

NASA Astrophysics Data System (ADS)

Rathsam, Jonathan

This dissertation seeks to advance the current state of computer-based sound field simulations for room acoustics. The first part of the dissertation assesses the reliability of geometric sound-field simulations, which are approximate in nature. The second part of the dissertation uses the rigorous boundary element method (BEM) to learn more about reflections from finite reflectors: planar and non-planar. Acoustical designers commonly use geometric simulations to predict sound fields quickly. Geometric simulation of reflections from rough surfaces is still under refinement. The first project in this dissertation investigates the scattering coefficient, which quantifies the degree of diffuse reflection from rough surfaces. The main result is that predicted reverberation time varies inversely with scattering coefficient if the sound field is nondiffuse. Additional results include a flow chart that enables acoustical designers to gauge how sensitive predicted results are to their choice of scattering coefficient. Geometric acoustics is a high-frequency approximation to wave acoustics. At low frequencies, more pronounced wave phenomena cause deviations between real-world values and geometric predictions. Acoustical designers encounter the limits of geometric acoustics in particular when simulating the low frequency response from finite suspended reflector panels. This dissertation uses the rigorous BEM to develop an improved low-frequency radiation model for smooth, finite reflectors. The improved low frequency model is suggested in two forms for implementation in geometric models. Although BEM simulations require more computation time than geometric simulations, BEM results are highly accurate. The final section of this dissertation uses the BEM to investigate the sound field around non-planar reflectors. The author has added convex edges rounded away from the source side of finite, smooth reflectors to minimize coloration of reflections caused by interference from boundary waves. Although the coloration could not be fully eliminated, the convex edge increases the sound energy reflected into previously nonspecular zones. This excess reflected energy is marginally audible using a standard of 20 dB below direct sound energy. The convex-edged panel is recommended for use when designers want to extend reflected energy spatially beyond the specular reflection zone of a planar panel.

Self-stigma and empowerment in combined-CMHA and consumer-run services: two controlled trials.

PubMed

Segal, Steven P; Silverman, Carol J; Temkin, Tanya L

2013-10-01

Self-help agencies (SHAs) are consumer-operated service organizations managed as participatory democracies involving members in all management tasks. Hierarchically organized board- and staff-run consumer-operated service programs (BSR-COSPs) are consumer managed, but they afford members less decision-making power. This study considered the relative effectiveness of SHAs and BSR-COSPs working jointly with community mental health agencies (CMHAs) and the role of organizational empowerment in reducing self-stigma. Clients seeking CMHA services were assigned in separate randomized controlled trials to a trial of combined SHA and CMHA services versus regular CMHA services (N=505) or to a trial of combined BSR-COSP and CMHA services versus regular CMHA services (N=139). Self-stigma, organizational empowerment, and self-efficacy were assessed at baseline and eight months with the Attitudes Toward Persons With Mental Illness Scale, the Organizationally Mediated Empowerment Scale, and the Self-Efficacy Scale. Outcomes were evaluated with fully recursive path analysis models. SHA-CMHA participants experienced greater positive change in self-stigma than CMHA-only participants, a result attributable to participation in the combined condition (b=1.20, p=.016) and increased organizational empowerment (b=.27, p=.003). BSR-COSP-CMHA participants experienced greater negative change in self-stigma than CMHA-only participants, a result attributable to participation in the combined service (b=-4.73, p=.031). In the SHA-CMHA trial, participants showed positive change in self-efficacy, whereas the change among BSR-COSP-CMHA participants was negative. Differential organizational empowerment efforts in the SHA and BSR-COSP appeared to account for the differing outcomes. Members experienced reduced self-stigma and increases in self-efficacy when they were engaged in responsible roles.

Analysis of ParB-centromere interactions by multiplex SPR imaging reveals specific patterns for binding ParB in six centromeres of Burkholderiales chromosomes and plasmids

PubMed Central

Pillet, Flavien; Passot, Fanny Marie

2017-01-01

Bacterial centromeres–also called parS, are cis-acting DNA sequences which, together with the proteins ParA and ParB, are involved in the segregation of chromosomes and plasmids. The specific binding of ParB to parS nucleates the assembly of a large ParB/DNA complex from which ParA—the motor protein, segregates the sister replicons. Closely related families of partition systems, called Bsr, were identified on the chromosomes and large plasmids of the multi-chromosomal bacterium Burkholderia cenocepacia and other species from the order Burkholeriales. The centromeres of the Bsr partition families are 16 bp palindromes, displaying similar base compositions, notably a central CG dinucleotide. Despite centromeres bind the cognate ParB with a narrow specificity, weak ParB-parS non cognate interactions were nevertheless detected between few Bsr partition systems of replicons not belonging to the same genome. These observations suggested that Bsr partition systems could have a common ancestry but that evolution mostly erased the possibilities of cross-reactions between them, in particular to prevent replicon incompatibility. To detect novel similarities between Bsr partition systems, we have analyzed the binding of six Bsr parS sequences and a wide collection of modified derivatives, to their cognate ParB. The study was carried out by Surface Plasmon Resonance imaging (SPRi) mulitplex analysis enabling a systematic survey of each nucleotide position within the centromere. We found that in each parS some positions could be changed while maintaining binding to ParB. Each centromere displays its own pattern of changes, but some positions are shared more or less widely. In addition from these changes we could speculate evolutionary links between these centromeres. PMID:28562673

Analysis of ParB-centromere interactions by multiplex SPR imaging reveals specific patterns for binding ParB in six centromeres of Burkholderiales chromosomes and plasmids.

PubMed

Pillet, Flavien; Passot, Fanny Marie; Pasta, Franck; Anton Leberre, Véronique; Bouet, Jean-Yves

2017-01-01

Bacterial centromeres-also called parS, are cis-acting DNA sequences which, together with the proteins ParA and ParB, are involved in the segregation of chromosomes and plasmids. The specific binding of ParB to parS nucleates the assembly of a large ParB/DNA complex from which ParA-the motor protein, segregates the sister replicons. Closely related families of partition systems, called Bsr, were identified on the chromosomes and large plasmids of the multi-chromosomal bacterium Burkholderia cenocepacia and other species from the order Burkholeriales. The centromeres of the Bsr partition families are 16 bp palindromes, displaying similar base compositions, notably a central CG dinucleotide. Despite centromeres bind the cognate ParB with a narrow specificity, weak ParB-parS non cognate interactions were nevertheless detected between few Bsr partition systems of replicons not belonging to the same genome. These observations suggested that Bsr partition systems could have a common ancestry but that evolution mostly erased the possibilities of cross-reactions between them, in particular to prevent replicon incompatibility. To detect novel similarities between Bsr partition systems, we have analyzed the binding of six Bsr parS sequences and a wide collection of modified derivatives, to their cognate ParB. The study was carried out by Surface Plasmon Resonance imaging (SPRi) mulitplex analysis enabling a systematic survey of each nucleotide position within the centromere. We found that in each parS some positions could be changed while maintaining binding to ParB. Each centromere displays its own pattern of changes, but some positions are shared more or less widely. In addition from these changes we could speculate evolutionary links between these centromeres.

Interfacial characteristics and multiferroic properties of ion-doped BiFeO3/NiFe2O4 thin films

NASA Astrophysics Data System (ADS)

Guo, Meiyou; Tan, Guoqiang; Zheng, Yujuan; Liu, Wenlong; Ren, Huijun; Xia, Ao

2017-05-01

Multi-ion doped BiFeO3/NiFe2O4 bilayered thin films were successfully prepared on fluorine-doped SnO2/glass (SnO2:F) substrates by sol-gel method. The crystalline structure, leakage current, interfacial characteristics, and multiferroic properties were investigated in detail. The results of Rietveld refinement showed that the structure of BSrSFMC layer is transformed from rhombohedral to tetragonal structure by the means of ion-doping. The difference of leakage current density of the BSrSFMC/NiFe2O4 (NFO) bilayered films of the -40 V to 40 V and 40 V to -40 V are 0.32 × 10-5 and 1.13 × 10-5 A/cm2, respectively. It was observed that there are obvious interface effects between BSrSFMC and NFO layers, which will cause the accumulation of space charges and the establishment of built-in internal electric field (EI) at the interface. Therefore, different EI directions will affect the dipoles reversal and migration of carriers in the BSrSFMC layer, which will result in different values of transient current with the same applied voltage in the opposite directions. The larger coercive field (Ec ˜ 750 kV/cm) of BSrSFMC/NFO film indicated that there is a tensile stress at the interface between BSrSFMC and NFO layers, making the polarization difficult. These results showed that the above interesting phenomena of the J-V are closely related to the interface effects between the layer of BiFeO3 and NiFe2O4.

Retrieving background surface reflectance of Himawari-8/AHI using BRDF modeling

NASA Astrophysics Data System (ADS)

Choi, Sungwon; Seo, Minji; Lee, Kyeong-sang; Han, Kyung-soo

2017-04-01

In these days, remote sensing is more important than past. And retrieving surface reflectance in remote sensing is also important. So there are many ways to retrieve surface reflectance by my countries with polar orbit and geostationary satellite. We studied Bidirectional Reflectance Distribution Function (BRDF) which is used to retrieve surface reflectance. In BRDF equation, we calculate surface reflectance using BRD components and angular data. BRD components are to calculate 3 of scatterings, isotropic geometric and volumetric scattering. To make Background Surface Reflectance (BSR) of Himawari-8/AHI. We used 5 bands (band1, band2, band3, band4, band5) with BRDF. And we made 5 BSR for 5 channels. For validation, we compare BSR with Top of canopy (TOC) reflectance of AHI. As a result, bias are from -0.00223 to 0.008328 and Root Mean Square Error (RMSE) are from 0.045 to 0.049. We think BSR can be used to replace TOC reflectance in remote sensing to improve weakness of TOC reflectance.

Seismic reflection profile of the Blake Ridge near sites 994, 995, and 997: Chapter 4

USGS Publications Warehouse

Dillon, William P.; Hutchinson, Deborah R.; Drury, Rebecca M.

1996-01-01

Seismic reflection profiles near Sites 994, 995, and 997 were collected with seismic sources that provide maximum resolution with adequate power to image the zone of gas hydrate stability and the region direction beneath it. The overall structure of the sediment drift deposit that constitutes the Blake Ridge consists of southwestward-dipping strata. These strata are approximately conformal to the seafloor on the southwest side of the ridge and are truncated by erosion on the northeast side. A bottom-simulating reflection (BSR) marks the velocity contrast between gas hydrate-bearing sediment and regions containing free gas beneath the zone of gas hydrate stability. The BSR is strong and continuous near the ridge crest but becomes discontinuous on the flanks, where concentration of gas is reduced and dipping strata pass through the level of the base o fgas hydrate stability or the strata are disrupted by faults. Seismic reflection amplitudes appear to be reduced in the region of gas hydrate formation compared to normal amplitudes. A faulted zone ~0.5-0.6 s thick parallels reflections from strata. We infer that this may represent a formerly gas hydrate-bearing zone that was faulted because of a breakdown of hydrate near its phase limit (at the base of the zone). Strong reflections at the top of the faulted zone are caused by free-gas acccumulation at Site 994. Similar strong reflections probably are caused by free-gas accumulations where the top of the faulted zone rises above the BSR, although this would require local free gas within the hydrate-stable zone.

Application of arbuscular mycorrhizal fungi with Pseudomonas aeruginosa UPMP3 reduces the development of Ganoderma basal stem rot disease in oil palm seedlings.

PubMed

Sundram, Shamala; Meon, Sariah; Seman, Idris Abu; Othman, Radziah

2015-07-01

The effect of arbuscular mycorrhizal fungi (AMF) in combination with endophytic bacteria (EB) in reducing development of basal stem rot (BSR) disease in oil palm (Elaeis guineensis) was investigated. BSR caused by Ganoderma boninense leads to devastating economic loss and the oil palm industry is struggling to control the disease. The application of two AMF with two EB as biocontrol agents was assessed in the nursery and subsequently, repeated in the field using bait seedlings. Seedlings pre-inoculated with a combination of Glomus intraradices UT126, Glomus clarum BR152B and Pseudomonas aeruginosa UPMP3 significantly reduced disease development measured as the area under disease progression curve (AUDPC) and the epidemic rate (R L) of disease in the nursery. A 20-month field trial using similar treatments evaluated disease development in bait seedlings based on the rotting area/advancement assessed in cross-sections of the seedling base. Data show that application of Glomus intraradices UT126 singly reduced disease development of BSR, but that combination of the two AMF with P. aeruginosa UPMP3 significantly improved biocontrol efficacy in both nursery and fields reducing BSR disease to 57 and 80%, respectively. The successful use of bait seedlings in the natural environment to study BSR development represents a promising alternative to nursery trial testing in the field with shorter temporal assessment.

The Serotonin 2C Receptor Agonist Lorcaserin Attenuates Intracranial Self-Stimulation and Blocks the Reward-Enhancing Effects of Nicotine.

PubMed

Zeeb, Fiona D; Higgins, Guy A; Fletcher, Paul J

2015-07-15

Lorcaserin, a serotonin (5-hydroxytryptamine, 5-HT) 2C receptor agonist, was recently approved for the treatment of obesity. We previously suggested that 5-HT2C receptor agonists affect reward processes and reduce the rewarding effects of drugs of abuse. Here, we determined whether lorcaserin (1) decreases responding for brain stimulation reward (BSR) and (2) prevents nicotine from enhancing the efficacy of BSR. Rats were trained on the intracranial self-stimulation (ICSS) paradigm to nosepoke for BSR of either the dorsal raphé nucleus or left medial forebrain bundle. In Experiment 1, lorcaserin (0.3-1.0 mg/kg) dose-dependently reduced the efficacy of BSR. This effect was blocked by prior administration of the 5-HT2C receptor antagonist SB242084. In Experiment 2, separate groups of rats received saline or nicotine (0.4 mg/kg) for eight sessions prior to testing. Although thresholds were unaltered in saline-treated rats, nicotine reduced reward thresholds. An injection of lorcaserin (0.3 mg/kg) prior to nicotine prevented the reward-enhancing effect of nicotine across multiple test sessions. These results demonstrated that lorcaserin reduces the rewarding value of BSR and also prevents nicotine from facilitating ICSS. Hence, lorcaserin may be effective in treating psychiatric disorders, including obesity and nicotine addiction, by reducing the value of food or drug rewards.

The Use of Decentralized Control in the Design of a Large Segmented Space Reflector

NASA Technical Reports Server (NTRS)

Ryaciotaki-Boussalis, Helen; Mirmirani, Maj; Rad, Khosrow; Morales, Mauricio; Velazquez, Efrain; Chassiakos, Anastasios; Luzardo, Jose-Alberto

1997-01-01

The 3-dimensional model for a segmented reflector telescope is developed using finite element techniques. The structure is decomposed into six subsystems. System control design using neural networks is performed. Performance evaluation is demonstrated via simulation using PRO-MATLAB and SIMULINK.

The effects of stainless steel radial reflector on core reactivity for small modular reactor

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

Kang, Jung Kil, E-mail: jkkang@email.kings.ac.kr; Hah, Chang Joo, E-mail: changhah@kings.ac.kr; Cho, Sung Ju, E-mail: sungju@knfc.co.kr

Commercial PWR core is surrounded by a radial reflector, which consists of a baffle and water. Radial reflector is designed to reflect neutron back into the core region to improve the neutron efficiency of the reactor and to protect the reactor vessels from the embrittling effects caused by irradiation during power operation. Reflector also helps to flatten the neutron flux and power distributions in the reactor core. The conceptual nuclear design for boron-free small modular reactor (SMR) under development in Korea requires to have the cycle length of 4∼5 years, rated power of 180 MWth and enrichment less than 5more » w/o. The aim of this paper is to analyze the effects of stainless steel radial reflector on the performance of the SMR using UO{sub 2} fuels. Three types of reflectors such as water, water/stainless steel 304 mixture and stainless steel 304 are selected to investigate the effect on core reactivity. Additionally, the thickness of stainless steel and double layer reflector type are also investigated. CASMO-4/SIMULATE-3 code system is used for this analysis. The results of analysis show that single layer stainless steel reflector is the most efficient reflector.« less

Evaluation of Hardware and Procedures for Astronaut Assembly and Repair of Large Precision Reflectors

NASA Technical Reports Server (NTRS)

Lake, Mark S.; Heard, Walter L., Jr.; Watson, Judith J.; Collins, Timothy J.

2000-01-01

A detailed procedure is presented that enables astronauts in extravehicular activity (EVA) to efficiently assemble and repair large (i.e., greater than 10m-diameter) segmented reflectors, supported by a truss, for space-based optical or radio-frequency science instruments. The procedure, estimated timelines, and reflector hardware performance are verified in simulated 0-g (neutral buoyancy) assembly tests of a 14m-diameter, offset-focus, reflector test article. The test article includes a near-flight-quality, 315-member, doubly curved support truss and 7 mockup reflector panels (roughly 2m in diameter) representing a portion of the 37 total panels needed to fully populate the reflector. Data from the tests indicate that a flight version of the design (including all reflector panels) could be assembled in less than 5 hours - less than the 6 hours normally permitted for a single EVA. This assembly rate essentially matches pre-test predictions that were based on a vast amount of historical data on EVA assembly of structures produced by NASA Langley Research Center. Furthermore, procedures and a tool for the removal and replacement of a damaged reflector panel were evaluated, and it was shown that EVA repair of this type of reflector is feasible with the use of appropriate EVA crew aids.

Flight Simulation Model Exchange. Volume 1

NASA Technical Reports Server (NTRS)

Murri, Daniel G.; Jackson, E. Bruce

2011-01-01

The NASA Engineering and Safety Center Review Board sponsored an assessment of the draft Standard, Flight Dynamics Model Exchange Standard, BSR/ANSI-S-119-201x (S-119) that was conducted by simulation and guidance, navigation, and control engineers from several NASA Centers. The assessment team reviewed the conventions and formats spelled out in the draft Standard and the actual implementation of two example aerodynamic models (a subsonic F-16 and the HL-20 lifting body) encoded in the Extensible Markup Language grammar. During the implementation, the team kept records of lessons learned and provided feedback to the American Institute of Aeronautics and Astronautics Modeling and Simulation Technical Committee representative. This document contains the results of the assessment.

Flight Simulation Model Exchange. Volume 2; Appendices

NASA Technical Reports Server (NTRS)

Murri, Daniel G.; Jackson, E. Bruce

2011-01-01

The NASA Engineering and Safety Center Review Board sponsored an assessment of the draft Standard, Flight Dynamics Model Exchange Standard, BSR/ANSI-S-119-201x (S-119) that was conducted by simulation and guidance, navigation, and control engineers from several NASA Centers. The assessment team reviewed the conventions and formats spelled out in the draft Standard and the actual implementation of two example aerodynamic models (a subsonic F-16 and the HL-20 lifting body) encoded in the Extensible Markup Language grammar. During the implementation, the team kept records of lessons learned and provided feedback to the American Institute of Aeronautics and Astronautics Modeling and Simulation Technical Committee representative. This document contains the appendices to the main report.

The novel support structure design of high stability for space borne primary reflector

NASA Astrophysics Data System (ADS)

Yu, Fei; Ding, Lin; Tan, Ting; Pei, Jing-yang.; Zhao, Xue-min; Bai, Shao-jun

2018-01-01

The novel support structure design of high stability for space borne primary mirror is presented. The structure is supported by a ball head support rod, for statically determinate support of reflector. The ball head assembly includes the supporting rod, nesting, bushing and other important parts. The liner bushing of the resistant material is used to fit for ball head approximated with the reflector material, and then the bad impact of thermal mismatch could be minimized to minimum. In order to ensure that the structure of the support will not be damaged, the glue spots for limitation is added around the reflector, for position stability of reflector. Through analysis and calculation, it can be seen that the novel support structure would not transfer the external stresses to the reflector, and the external stresses usually result from thermal mismatch and assembly misalignment. The novel method is useful for solving the problem of the bad influence form thermal stress and assembly force. In this paper, the supporting structure is introduced and analyzed in detail. The simulation results show that the ball head support reflector works more stably.

Neutral buoyancy test evaluation of hardware and extravehicular activity procedures for on-orbit assembly of a 14 meter precision reflector

NASA Technical Reports Server (NTRS)

Heard, Walter L., Jr.; Lake, Mark S.

1993-01-01

A procedure that enables astronauts in extravehicular activity (EVA) to perform efficient on-orbit assembly of large paraboloidal precision reflectors is presented. The procedure and associated hardware are verified in simulated Og (neutral buoyancy) assembly tests of a 14 m diameter precision reflector mockup. The test article represents a precision reflector having a reflective surface which is segmented into 37 individual panels. The panels are supported on a doubly curved tetrahedral truss consisting of 315 struts. The entire truss and seven reflector panels were assembled in three hours and seven minutes by two pressure-suited test subjects. The average time to attach a panel was two minutes and three seconds. These efficient assembly times were achieved because all hardware and assembly procedures were designed to be compatible with EVA assembly capabilities.

Multijunction InGaAs thermophotovoltaic devices

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

Fatemi, N.S.; Jenkins, P.P.; Weizer, V.G.

1998-12-31

A monolithic interconnected module (MIM) structure has been developed for thermophotovoltaic (TPV) applications. The MIM consists of many individual InGaAs cells series-connected on a single semi-insulating (S.I.) InP substrate. An infrared (IR) back surface reflector (BSR), placed on the rear surface of the substrate, returns the unused portion of the TPV radiator output spectrum back to the radiator for recuperation, thereby providing for high system efficiencies. MIMs were fabricated with an active area of 0.9 {times} 1 cm, and with 15 cells monolithically connected in series. Both lattice-matched and lattice-mismatched InGaAs/InP devices were fabricated, with bandgaps of 0.74 and 0.55more » eV, respectively. The 0.74 eV MIMs demonstrated an open-circuit voltage (Voc) of 6.16 V and a fill factor of 74.2% at a short-circuit current (Jsc) of 0.84 A/cm{sup 2}, under flashlamp testing. The 0.55 eV MIMs demonstrated a Voc of 4.85 V and a fill factor of 57.8% at a Jsc of 3.87 A/cm{sup 2}. Electrical performance results for these MIMs are presented.« less

Composite materials for precision space reflector panels

NASA Technical Reports Server (NTRS)

Tompkins, Stephen S.; Funk, Joan G.; Bowles, David E.; Towell, Timothy W.; Connell, John W.

1992-01-01

One of the critical technology needs of large precision reflectors for future astrophysical and optical communications satellites lies in the area of structural materials. Results from a materials research and development program at NASA Langley Research Center to provide materials for these reflector applications are discussed. Advanced materials that meet the reflector panel requirements are identified, and thermal, mechanical and durability properties of candidate materials after exposure to simulated space environments are compared. A parabolic, graphite-phenolic honeycomb composite panel having a surface accuracy of 70.8 microinches rms and an areal weight of 1.17 lbm/sq ft was fabricated with T50/ERL1962 facesheets, a PAEI thermoplastic surface film, and Al and SiO(x) coatings.

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

Mohanty, Subhasish; Majumdar, Saurindranath

Irradiation creep plays a major role in the structural integrity of the graphite components in high temperature gas cooled reactors. Finite element procedures combined with a suitable irradiation creep model can be used to simulate the time-integrated structural integrity of complex shapes, such as the reactor core graphite reflector and fuel bricks. In the present work a comparative study was undertaken to understand the effect of linear and nonlinear irradiation creep on results of finite element based stress analysis. Numerical results were generated through finite element simulations of a typical graphite reflector.

Rise Time of the Simulated VERITAS 12 m Davies-Cotton Reflector

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

White, Richard J.

The Very Energetic Radiation Imaging Telescope Array System (VERITAS) will utilise Imaging Atmospheric Cherenkov Telescopes (IACTs) based on a Davies-Cotton design with f-number f/1.0 to detect cosmic gamma-rays. Unlike a parabolic reflector, light from the Davies-Cotton does not arrive isochronously at the camera. Here the effect of the telescope geometry on signal rise-time is examined. An almost square-pulse arrival time profile with a rise time of 1.7 ns is found analytically and confirmed through simulation.

Active feed array compensation for reflector antenna surface distortions. Ph.D. Thesis - Akron Univ., Ohio

NASA Technical Reports Server (NTRS)

Acosta, Roberto J.

1988-01-01

The feasibility of electromagnetic compensation for reflector antenna surface distortions is investigated. The performance characteristics of large satellite communication reflector antenna systems degrade as the reflector surface distorts, mainly due to thermal effects from solar radiation. The technique developed can be used to maintain the antenna boresight directivity and sidelobe level independent of thermal effects on the reflector surface. With the advent of monolithic microwave integrated circuits (MMIC), a greater flexibility in array fed reflector antenna systems can be achieved. MMIC arrays provide independent control of amplitude and phase for each of the many radiating elements in the feed array. By assuming a known surface distortion profile, a simulation study is carried out to examine the antenna performance as a function of feed array size and number of elements. Results indicate that the compensation technique can effectively control boresight directivity and sidelobe level under peak surface distortion in the order of tenth of a wavelength.

Wave-optics simulation of the double-pass beam propagation in modulating retro-reflector FSO systems using a corner cube reflector.

PubMed

Yang, Guowei; You, Shengzui; Bi, Meihua; Fan, Bing; Lu, Yang; Zhou, Xuefang; Li, Jing; Geng, Hujun; Wang, Tianshu

2017-09-10

Free-space optical (FSO) communication utilizing a modulating retro-reflector (MRR) is an innovative way to convey information between the traditional optical transceiver and the semi-passive MRR unit that reflects optical signals. The reflected signals experience turbulence-induced fading in the double-pass channel, which is very different from that in the traditional single-pass FSO channel. In this paper, we consider the corner cube reflector (CCR) as the retro-reflective device in the MRR. A general geometrical model of the CCR is established based on the ray tracing method to describe the ray trajectory inside the CCR. This ray tracing model could treat the general case that the optical beam is obliquely incident on the hypotenuse surface of the CCR with the dihedral angle error and surface nonflatness. Then, we integrate this general CCR model into the wave-optics (WO) simulation to construct the double-pass beam propagation simulation. This double-pass simulation contains the forward propagation from the transceiver to the MRR through the atmosphere, the retro-reflection of the CCR, and the backward propagation from the MRR to the transceiver, which can be realized by a single-pass WO simulation, the ray tracing CCR model, and another single-pass WO simulation, respectively. To verify the proposed CCR model and double-pass WO simulation, the effective reflection area, the incremental phase, and the reflected beam spot on the transceiver plane of the CCR are analyzed, and the numerical results are in agreement with the previously published results. Finally, we use the double-pass WO simulation to investigate the double-pass channel in the MRR FSO systems. The histograms of the turbulence-induced fading in the forward and backward channels are obtained from the simulation data and are fitted by gamma-gamma (ΓΓ) distributions. As the two opposite channels are highly correlated, we model the double-pass channel fading by the product of two correlated ΓΓ random variables (RVs).

Low Earth orbit atomic oxygen simulation for durability evaluation of solar reflector surfaces

NASA Technical Reports Server (NTRS)

Degroh, Kim K.; Banks, Bruce A.

1992-01-01

To evaluate the performance and durability of solar reflector surfaces in the atomic oxygen environment typical of low Earth orbit (LEO), one must expose the reflector surface either directly to LEO or to ground-laboratory atomic oxygen environments. Although actual LEO exposures are most desired, such opportunities are typically scarce, expensive, and of limited duration. As a result, ground-laboratory exposures must be relied upon as the most practical long-term durability evaluation technique. Plasma ashers are widely used as LEO simulation facilities by producing atomic oxygen environments for durability evaluation of potential spacecraft materials. Atomic oxygen arrival differs between ground and space exposure in that plasma asher exposure produces isotropic arrival and space solar tracking produces sweeping arrival. Differences in initial impact reaction probability occur, dependent upon the energy and species existing in these environments. Due to the variations in ground-laboratory and space atomic oxygen, quantification of in-space performance based on plasma asher testing is not straightforward. The various atomic oxygen interactions that can occur with reflector surfaces, such as undercutting in organic substrates at protective coating defect sites, ground-laboratory techniques recommended for evaluating the atomic oxygen durability of reflectors based on asher exposures, and computational techniques which make use of ground-laboratory atomic oxygen exposure to predict in-space LEO durability are addressed.

Simulation requirements for the Large Deployable Reflector (LDR)

NASA Technical Reports Server (NTRS)

Soosaar, K.

1984-01-01

Simulation tools for the large deployable reflector (LDR) are discussed. These tools are often the transfer function variety equations. However, transfer functions are inadequate to represent time-varying systems for multiple control systems with overlapping bandwidths characterized by multi-input, multi-output features. Frequency domain approaches are the useful design tools, but a full-up simulation is needed. Because of the need for a dedicated computer for high frequency multi degree of freedom components encountered, non-real time smulation is preferred. Large numerical analysis software programs are useful only to receive inputs and provide output to the next block, and should be kept out of the direct loop of simulation. The following blocks make up the simulation. The thermal model block is a classical heat transfer program. It is a non-steady state program. The quasistatic block deals with problems associated with rigid body control of reflector segments. The steady state block assembles data into equations of motion and dynamics. A differential raytrace is obtained to establish a change in wave aberrations. The observation scene is described. The focal plane module converts the photon intensity impinging on it into electron streams or into permanent film records.

The Effects of Reinforcer Magnitude on Timing in Rats

ERIC Educational Resources Information Center

Ludvig, Elliot A.; Conover, Kent; Shizgal, Peter

2007-01-01

The relation between reinforcer magnitude and timing behavior was studied using a peak procedure. Four rats received multiple consecutive sessions with both low and high levels of brain stimulation reward (BSR). Rats paused longer and had later start times during sessions when their responses were reinforced with low-magnitude BSR. When estimated…

Proposed suitable electron reflector layer materials for thin-film CuIn1-xGaxSe2 solar cells

NASA Astrophysics Data System (ADS)

Sharbati, Samaneh; Gharibshahian, Iman; Orouji, Ali A.

2018-01-01

This paper investigates the electrical properties of electron reflector layer to survey materials as an electron reflector (ER) for chalcopyrite CuInGaSe solar cells. The purpose is optimizing the conduction-band and valence-band offsets at ER layer/CIGS junction that can effectively reduce the electron recombination near the back contact. In this work, an initial device model based on an experimental solar cell is established, then the properties of a solar cell with electron reflector layer are physically analyzed. The electron reflector layer numerically applied to baseline model of thin-film CIGS cell fabricated by ZSW (efficiency = 20.3%). The improvement of efficiency is achievable by electron reflector layer materials with Eg > 1.3 eV and -0.3 < Δχ < 0.7, depends on bandgap. Our simulations examine various electron reflector layer materials and conclude the most suitable electron reflector layer for this real CIGS solar cells. ZnSnP2, CdSiAs2, GaAs, CdTe, Cu2ZnSnS4, InP, CuO, Pb10Ag3Sb11S28, CuIn5S8, SnS, PbCuSbS3, Cu3AsS4 as well as CuIn1-xGaxSe (x > 0.5) are efficient electron reflector layer materials, so the potential improvement in efficiency obtained relative gain of 5%.

Influence of surface error on electromagnetic performance of reflectors based on Zernike polynomials

NASA Astrophysics Data System (ADS)

Li, Tuanjie; Shi, Jiachen; Tang, Yaqiong

2018-04-01

This paper investigates the influence of surface error distribution on the electromagnetic performance of antennas. The normalized Zernike polynomials are used to describe a smooth and continuous deformation surface. Based on the geometrical optics and piecewise linear fitting method, the electrical performance of reflector described by the Zernike polynomials is derived to reveal the relationship between surface error distribution and electromagnetic performance. Then the relation database between surface figure and electric performance is built for ideal and deformed surfaces to realize rapidly calculation of far-field electric performances. The simulation analysis of the influence of Zernike polynomials on the electrical properties for the axis-symmetrical reflector with the axial mode helical antenna as feed is further conducted to verify the correctness of the proposed method. Finally, the influence rules of surface error distribution on electromagnetic performance are summarized. The simulation results show that some terms of Zernike polynomials may decrease the amplitude of main lobe of antenna pattern, and some may reduce the pointing accuracy. This work extracts a new concept for reflector's shape adjustment in manufacturing process.

Reconfigurable antenna using plasma reflector

NASA Astrophysics Data System (ADS)

Jusoh, Mohd Taufik; Ahmad, Khairol Amali; Din, Muhammad Faiz Md; Hashim, Fakroul Ridzuan

2018-02-01

This paper presents the feasibility study and design of plasma implementation in industrial, scientific and medical (ISM) communication band. A reflector antenna with rounded shaped is proposed to collimate beam in particular direction radiated by a quarter wave antenna operating at 2.4GHz. The simulations result has shown that by using plasma as the reflector elements, the gain, directivity and radiation patterns are identical with metal elements with only small different in the broadside direction. The versatility of the antenna is achievable by introducing electrical reconfigurable option to change the beam pattern.

Tectonic Setting of NGHP-1 Site 17, Andaman Forearc

NASA Astrophysics Data System (ADS)

Cochran, J. R.

2008-12-01

The National Gas Hydrate Program (NGHP) Expedition 1 was an 'IODP-like' coring and logging program to investigate gas hydrate occurrences along the margins of India. Although most sites were located along the east coast of India, Site NGHP-01-17 was located near 10° 45'N on the Andaman forearc approximately 50 km east of Little Andaman Island in a water depth of 1325 m. Seismic lines across the site show an anomalously deep bottom simulating reflector (BSR) at a depth of about 600 mbsf. Coring and logging results confirmed that the BSR does mark the base of the gas hydrate stability zone. The age of the sediments at the base of the hole was estimated as 12.3 Ma. The Andaman Sea is an extensional basin resulting from strain partitioning during oblique subduction at the Sunda trench. The site is located within the eastern portion of the Andaman-Nicobar outer arc accretionary ridge on a long sliver of crust between the Eastern Margin Fault and the Diligent Fault. They are both down-to-the-east normal faults that form the eastern edge of the accretionary prism. The West Andaman Fault (WAF), which forms the principal active plate boundary between the Sumatra Fault and the Andaman Spreading Center, is located about 45 km further east along the eastern side of Invisible Bank. The Eastern Margin Fault forms the eastern edge of the block containing Little Andaman Island and extends northward for at least 100 km along the eastern side of South Andaman Island where it appears to die out. It can be traced south to about 8° 20'N where it dies out east of Tarasa Island. The Diligent Fault extends south to about 9° N where it apparently merges with the WAF. It forms the eastern edge of the accretionary prism northward to at least to 13° N and most likely to the Mynamar shelf at 14° N. It probably continues on to join the Kabaw Fault, which marks the eastern boundary of the accretionary prism in Myanmar. Although there is a significant vertical offset across both faults near the NGDP-1-17 site, the Diligent Fault appears to have also experienced strike-slip faulting at some point, probably prior to formation of the Andaman Spreading Center at about 4 Ma. At that time the situation may have been similar to that now found between about 7° N and 4° N where the northern motion of the sliver plate is concentrated at two locations, a fault system along the landward margin of the accretionary prism and another system further landward that forms the main plate boundary.

Assessing submarine gas hydrate at active seeps on the Hikurangi Margin, New Zealand, using controlled source electromagnetic data with constraints from seismic, geochemistry, and heatflow data

NASA Astrophysics Data System (ADS)

Schwalenberg, K.; Haeckel, M.; Pecher, I. A.; Toulmin, S. J.; Hamdan, L. J.; Netzeband, G.; Wood, W.; Poort, J.; Jegen, M. D.; Coffin, R. B.

2009-12-01

Electrical resistivity is one of the key properties useful for evaluating submarine gas hydrate deposits. Gas hydrates are electrically insulating in contrast to the conductive pore fluid. Where they form in sufficient quantities the bulk resistivity of the sub-seafloor is elevated. CSEM data were collected in 2007 as part of the German - International “New Vents” project on R/V Sonne, cruise SO191, at three target areas on the Hikurangi subduction margin, New Zealand. The margin is characterized by widespread bottom simulating reflectors (BSR), seep structures, and active methane and fluid venting indicating the potential for gas hydrate formation. Opouawe Bank is one of the ridge and basin systems on the accretionary wedge and is located off the Wairarapa coast at water depths of 1000-1100 m. The first observed seep sites (North Tower, South Tower, Pukeko, Takahe, and Tui) were identified from individual gas flares in hydro-acoustic data and video observations during voyages on R/V Tangaroa. Seismic reflection data collected during SO191 subsequently identified more than 25 new seep structures. Two intersecting CSEM profiles have been surveyed across North Tower, South Tower, and Takahe. 1-D inversion of the data reveals anomalously high resistivities at North Tower and South Tower, moderately elevated resistivities at Takahe, and normal background resistivities away from the seeps. The high resistivities are attributed to gas hydrate layers at intermediate depths beneath the seeps. At South Tower the hydrate concentration could be possibly as much as 25% of the total sediment volume within a 50m thick layer. This conforms with geochemical pore water analyses which show a trend of increased methane flux towards South Tower. At Takahe, gas pockets and patchy gas hydrate, as well as sediment heterogeneities and carbonates, or temperature driven upward fluid flow indicated by the observed higher heat flow at this site may explain the resistivity pattern. Porangahau Ridge is located further north on the margin in water depths of 1900-2000m. A high amplitude reflection zone extending from the BSR around 700mbsf towards the seafloor has been observed at the western flank of the ridge. This is attributed to local shoaling at the base of the hydrate stability zone caused by upward migrating warm fluids. A CSEM profile was surveyed across the same seismic line. The data reveal a pronounced resistivity anomaly at the western rim suggesting a zone of concentrated gas hydrate above the reflection band. Heat flow and geochemistry data collected along the same transect show concave temperature profiles indicating mildly advective heat flow and massive gas and fluid transport on the western flank, particularly at the location where the resistivity anomaly has been observed.

Simulation numerique de l'effet du reflecteur radial sur les cellules rep en utilisant les codes DRAGON et DONJON

NASA Astrophysics Data System (ADS)

Bejaoui, Najoua

The pressurized water nuclear reactors (PWRs) is the largest fleet of nuclear reactors in operation around the world. Although these reactors have been studied extensively by designers and operators using efficient numerical methods, there are still some calculation weaknesses, given the geometric complexity of the core, still unresolved such as the analysis of the neutron flux's behavior at the core-reflector interface. The standard calculation scheme is a two steps process. In the first step, a detailed calculation at the assembly level with reflective boundary conditions, provides homogenized cross-sections for the assemblies, condensed to a reduced number of groups; this step is called the lattice calculation. The second step uses homogenized properties in each assemblies to calculate reactor properties at the core level. This step is called the full-core calculation or whole-core calculation. This decoupling of the two calculation steps is the origin of methodological bias particularly at the interface core reflector: the periodicity hypothesis used to calculate cross section librairies becomes less pertinent for assemblies that are adjacent to the reflector generally represented by these two models: thus the introduction of equivalent reflector or albedo matrices. The reflector helps to slowdown neutrons leaving the reactor and returning them to the core. This effect leads to two fission peaks in fuel assemblies localised at the core/reflector interface, the fission rate increasing due to the greater proportion of reentrant neutrons. This change in the neutron spectrum arises deep inside the fuel located on the outskirts of the core. To remedy this we simulated a peripheral assembly reflected with TMI-PWR reflector and developed an advanced calculation scheme that takes into account the environment of the peripheral assemblies and generate equivalent neutronic properties for the reflector. This scheme is tested on a core without control mechanisms and charged with fresh fuel. The results of this study showed that explicit representation of reflector and calculation of peripheral assembly with our advanced scheme allow corrections to the energy spectrum at the core interface and increase the peripheral power by up to 12% compared with that of the reference scheme.

Estimating the effects of potential climate and land use changes on hydrologic processes of a large agriculture dominated watershed

NASA Astrophysics Data System (ADS)

Neupane, Ram P.; Kumar, Sandeep

2015-10-01

Land use and climate are two major components that directly influence catchment hydrologic processes, and therefore better understanding of their effects is crucial for future land use planning and water resources management. We applied Soil and Water Assessment Tool (SWAT) to assess the effects of potential land use change and climate variability on hydrologic processes of large agriculture dominated Big Sioux River (BSR) watershed located in North Central region of USA. Future climate change scenarios were simulated using average output of temperature and precipitation data derived from Special Report on Emission Scenarios (SRES) (B1, A1B, and A2) for end-21st century. Land use change was modeled spatially based on historic long-term pattern of agricultural transformation in the basin, and included the expansion of corn (Zea mays L.) cultivation by 2, 5, and 10%. We estimated higher surface runoff in all land use scenarios with maximum increase of 4% while expanding 10% corn cultivation in the basin. Annual stream discharge was estimated higher with maximum increase of 72% in SRES-B1 attributed from higher groundwater contribution of 152% in the same scenario. We assessed increased precipitation during spring season but the summer precipitation decreased substantially in all climate change scenarios. Similar to decreased summer precipitation, discharge of the BSR also decreased potentially affecting agricultural production due to reduced future water availability during crop growing season in the basin. However, combined effects of potential land use change with climate variability enhanced for higher annual discharge of the BSR. Therefore, these estimations can be crucial for implications of future land use planning and water resources management of the basin.

Fabrication of SiC membrane HCG blue reflector using nanoimprint lithography

NASA Astrophysics Data System (ADS)

Lai, Ying-Yu; Matsutani, Akihiro; Lu, Tien-Chang; Wang, Shing-Chung; Koyama, Fumio

2015-02-01

We designed and fabricated a suspended SiC-based membrane high contrast grating (HCG) reflectors. The rigorous coupled-wave analysis (RCWA) was employed to verify the structural parameters including grating periods, grating height, filling factors and air-gap height. From the optimized simulation results, the designed SiC-based membrane HCG has a wide reflection stopband (reflectivity (R) <90%) of 135 nm for the TE polarization, which centered at 480 nm. The suspended SiC-based membrane HCG reflectors were fabricated by nanoimprint lithography and two-step etching technique. The corresponding reflectivity was measured by using a micro-reflectivity spectrometer. The experimental results show a high reflectivity (R<90%), which is in good agreement with simulation results. This achievement should have an impact on numerous III-N based photonic devices operating in the blue wavelength or even ultraviolet region.

Fine mapping of resistance genes from five brown stem rot resistance sources in soybean

USDA-ARS?s Scientific Manuscript database

Brown stem rot (BSR) of soybean [Glycine max (L.) Merr.] caused by Cadophora gregata (Allington & Chamb.) T.C. Harr. & McNew, can be controlled effectively with genetic host resistance. Three BSR resistance genes Rbs1, Rbs2, and Rbs3, have been identified and mapped to a large region on chromosome 1...

SNP discovery and QTL mapping of Sclerotinia basal stalk rot resistance in sunflower using genotyping-by-sequencing (GBS)

USDA-ARS?s Scientific Manuscript database

Basal stalk rot (BSR) caused by the ascomycete fungus Sclerotinia sclerotiorum (Lib.) de Bary is a serious disease of sunflower (Helianthus annuus L.) in the cool and humid production areas of the world. Quantitative trait loci (QTL) for BSR resistance were identified in a sunflower recombinant inbr...

Creep behavior for advanced polycrystalline SiC fibers

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

Youngblood, G.E.; Jones, R.H.; Kohyama, Akira

1997-04-01

A bend stress relaxation (BSR) test has been utilized to examine irradiation enhanced creep in polycrystalline SiC fibers which are under development for use as fiber reinforcement in SiC/SiC composite. Qualitative, S-shaped 1hr BSR curves were compared for three selected advanced SiC fiber types and standard Nicalon CG fiber. The temperature corresponding to the middle of the S-curve (where the BSR parameter m = 0.5) is a measure of a fiber`s thermal stability as well as it creep resistance. In order of decreasing thermal creep resistance, the measured transition temperatures were Nicalon S (1450{degrees}C), Sylramic (1420{degrees}C), Hi-Nicalon (1230{degrees}C) and Nicalonmore » CG (1110{degrees}C).« less

Structural-electromagnetic bidirectional coupling analysis of space large film reflector antennas

NASA Astrophysics Data System (ADS)

Zhang, Xinghua; Zhang, Shuxin; Cheng, ZhengAi; Duan, Baoyan; Yang, Chen; Li, Meng; Hou, Xinbin; Li, Xun

2017-10-01

As used for energy transmission, a space large film reflector antenna (SLFRA) is characterized by large size and enduring high power density. The structural flexibility and the microwave radiation pressure (MRP) will lead to the phenomenon of structural-electromagnetic bidirectional coupling (SEBC). In this paper, the SEBC model of SLFRA is presented, then the deformation induced by the MRP and the corresponding far field pattern deterioration are simulated. Results show that, the direction of the MRP is identical to the normal of the reflector surface, and the magnitude is proportional to the power density and the square of cosine incident angle. For a typical cosine function distributed electric field, the MRP is a square of cosine distributed across the diameter. The maximum deflections of SLFRA linearly increase with the increasing microwave power densities and the square of the reflector diameters, and vary inversely with the film thicknesses. When the reflector diameter becomes 100 m large and the microwave power density exceeds 102 W/cm2, the gain loss of the 6.3 μm-thick reflector goes beyond 0.75 dB. When the MRP-induced deflection degrades the reflector performance, the SEBC should be taken into account.

Deployment simulation of a deployable reflector for earth science application

NASA Astrophysics Data System (ADS)

Wang, Xiaokai; Fang, Houfei; Cai, Bei; Ma, Xiaofei

2015-10-01

A novel mission concept namely NEXRAD-In-Space (NIS) has been developed for monitoring hurricanes, cyclones and other severe storms from a geostationary orbit. It requires a space deployable 35-meter diameter Ka-band (35 GHz) reflector. NIS can measure hurricane precipitation intensity, dynamics and its life cycle. These information is necessary for predicting the track, intensity, rain rate and hurricane-induced floods. To meet the requirements of the radar system, a Membrane Shell Reflector Segment (MSRS) reflector technology has been developed and several technologies have been evaluated. However, the deployment analysis of this large size and high-precision reflector has not been investigated. For a pre-studies, a scaled tetrahedral truss reflector with spring driving deployment system has been made and tested, deployment dynamics analysis of this scaled reflector has been performed using ADAMS to understand its deployment dynamic behaviors. Eliminating the redundant constraints in the reflector system with a large number of moving parts is a challenging issue. A primitive joint and flexible struts were introduced to the analytical model and they can effectively eliminate over constraints of the model. By using a high-speed camera and a force transducer, a deployment experiment of a single-bay tetrahedral module has been conducted. With the tested results, an optimization process has been performed by using the parameter optimization module of ADAMS to obtain the parameters of the analytical model. These parameters were incorporated to the analytical model of the whole reflector. It is observed from the analysis results that the deployment process of the reflector with a fixed boundary experiences three stages. These stages are rapid deployment stage, slow deployment stage and impact stage. The insight of the force peak distributions of the reflector can help the optimization design of the structure.

Use of a compact range approach to evaluate rf and dual-mode missiles

NASA Astrophysics Data System (ADS)

Willis, Kenneth E.; Weiss, Yosef

2000-07-01

This paper describes a hardware-in-the-loop (HWIL) system developed for testing Radio Frequency (RF), Infra-Red (IR), and Dual-Mode missile seekers. The system consists of a unique hydraulic five-axis (three seeker axes plus two target axes) Flight Motion Table (FMT), an off-axis parabolic reflector, and electronics required to generate the signals to the RF feeds. RF energy that simulates the target is fed into the reflector from three orthogonal feeds mounted on the inner target axis, at the focal point area of the parabolic reflector. The parabolic reflector, together with the three RF feeds (the Compact Range), effectively produces a far-field image of the target. Both FMT target axis motion and electronic control of the RF beams (deflection) modify the simulated line-of-sight target angles. Multiple targets, glint, multi-path, ECM, and clutter can be introduced electronically. To evaluate dual-mode seekers, the center section of the parabolic reflector is replaced with an IR- transparent, but RF-reflective section. An IR scene projector mounts to the FMT target axes, with its image focused on the intersection of the FMT seeker axes. The system eliminates the need for a large anechoic chamber and 'Target Wall' or target motion system used with conventional HWIL systems. This reduces acquisition and operating costs of the facility.

Design optimization of a smooth headlamp reflector to SAE/DOT beam-shape requirements

NASA Astrophysics Data System (ADS)

Shatz, Narkis E.; Bortz, John C.; Dassanayake, Mahendra S.

1999-10-01

The optical design of Ford Motor Company's 1992 Mercury Grand Marquis headlamp utilized a Sylvania 9007 filament source, a paraboloidal reflector and an array of cylindrical lenses (flutes). It has been of interest to Ford to determine the practicality of closely reproducing the on- road beam pattern performance of this headlamp, with an alternate optical arrangement whereby the control of the beam would be achieved solely by means of the geometry of the surface of the reflector, subject to a requirement of smooth-surface continuity; replacing the outer lens with a clear plastic cover having no beam-forming function. To this end the far-field intensity distribution produced by the 9007 bulb was measured at the low-beam setting. These measurements were then used to develop a light-source model for use in ray tracing simulations of candidate reflector geometries. An objective function was developed to compare candidate beam patterns with the desired beam pattern. Functional forms for the 3D reflector geometry were developed with free parameters to be subsequently optimized. A solution was sought meeting the detailed US SAE/DOT constraints for minimum and maximum permissible levels of illumination in the different portions of the beam pattern. Simulated road scenes were generated by Ford Motor Company to compare the illumination properties of the new design with those of the original Grand Marquis headlamp.

Nonuniform sampling techniques for antenna applications

NASA Technical Reports Server (NTRS)

Rahmat-Samii, Yahya; Cheung, Rudolf Lap-Tung

1987-01-01

A two-dimensional sampling technique, which can employ irregularly spaced samples (amplitude and phase) in order to generate the complete far-field patterns is presented. The technique implements a matrix inversion algorithm, which depends only on the nonuniform sampled data point locations and with no dependence on the actual field values at these points. A powerful simulation algorithm is presented to allow a real-life simulation of many reflector/feed configurations and to determine the usefulness of the nonuniform sampling technique for the copolar and cross-polar patterns. Additionally, an overlapped window concept and a generalized error simulation model are discussed to identify the stability of the technique for recovering the field data among the nonuniform sampled data. Numerical results are tailored for the pattern reconstruction of a 20-m offset reflector antenna operating at L-band. This reflector is planned to be used in a proposed measurement concept of large antenna aboard the Space Shuttle, whereby it would be almost impractical to accurately control the movement of the Shuttle with respect to the RF source in prescribed directions in order to generate uniform sampled points. Also, application of the nonuniform sampling technique to patterns obtained using near-field measured data is demonstrated. Finally, results of an actual far-field measurement are presented for the construction of patterns of a reflector antenna from a set of nonuniformly distributed measured amplitude and phase data.

Characterization of solar cells for space applications. Volume 6: Electrical characteristics of Spectrolab BSF, BSR, textured, 10 ohm-cm, 50 micron advanced OAST solar cells as a function of intensity, temperature, and irradiation

NASA Technical Reports Server (NTRS)

Anspaugh, B. E.; Downing, R. G.; Miyahira, T. F.; Weiss, R. S.

1979-01-01

Electrical parametric data are presented on BSF, BSR, textured 10 ohm cm, 50 micron advanced OAST cells in graphical and tabular form as functions of solar illumination intensity, temperature, and 1 MeV electron fluence.

Beaufort Sea deep-water gas hydrate recovery from a seafloor mound in a region of widespread BSR occurrence

USGS Publications Warehouse

Hart, Patrick E.; Pohlman, John W.; Lorenson, T.D.; Edwards, Brian D.

2011-01-01

Gas hydrate was recovered from the Alaskan Beaufort Sea slope north of Camden Bay in August 2010 during a U.S. Coast Guard Cutter Healy expedition (USCG cruise ID HLY1002) under the direction of the U.S. Geological Survey (USGS). Interpretation of multichannel seismic (MCS) reflection data collected in 1977 by the USGS across the Beaufort Sea continental margin identified a regional bottom simulating reflection (BSR), indicating that a large segment of the Beaufort Sea slope is underlain by gas hydrate. During HLY1002, gas hydrate was sampled by serendipity with a piston core targeting a steep-sided bathymetric high originally thought to be an outcrop of older, exposed strata. The feature cored is an approximately 1100m diameter, 130 m high conical mound, referred to here as the Canning Seafloor Mound (CSM), which overlies the crest of a buried anticline in a region of sub-parallel compressional folds beneath the eastern Beaufort outer slope. An MCS profile shows a prominent BSR upslope and downslope from the mound. The absence of a BSR beneath the CSM and occurrence of gas hydrate near the summit indicates that free gas has migrated via deep-rooted thrust faults or by structural focusing up the flanks of the anticline to the seafloor. Gas hydrate recovered from near the CSM summit at a subbottom depth of about 5.7 meters in a water depth of 2538 m was of nodular and vein-filling morphology. Although the hydrate was not preserved, residual gas from the core liner contained >95% methane by volume when corrected for atmospheric contamination. The presence of trace C4+hydrocarbons (<0.1% by volume) confirms at least a minor thermogenic component. Authigenic carbonates and mollusk shells found throughout the core indicate sustained methane-rich fluid advection and possible sediment extrusion contributing to the development of the mound. Blister-like inflation of the seafloor caused by formation and accumulation of shallow hydrate lenses is also a likely factor in CSM growth. Pore water analysis shows the sulfate-methane transition to be very shallow (0-1 mbsf), also supporting an active high-flux interpretation. Pore water with chloride concentrations as low as 160 mM suggest fluid migration pathways may extend to the mound from buried non-marine sediments containing low-salinity fluids.

Automotive Insulation

NASA Technical Reports Server (NTRS)

1997-01-01

Under a Space Act Agreement between Boeing North America and BSR Products, Space Shuttle Thermal Protection System (TPS) materials are now used to insulate race cars. BSR has created special TPS blanket insulation kits for use on autos that take part in NASCAR events, and other race cars through its nationwide catalog distribution system. Temperatures inside a race car's cockpit can soar to a sweltering 140 to 160 degrees, with the extreme heat coming through the engine firewall, transmission tunnel, and floor. It is common for NASCAR drivers to endure blisters and burns due to the excessive heat. Tests on a car insulated with the TPS material showed a temperature drop of some 50 degrees in the driver's cockpit. BSR-TPS Products, Inc. now manufactures insulation kits for distribution to race car teams around the world.

Optically-free-standing InGaN microdisks with metallic reflectors

NASA Astrophysics Data System (ADS)

Zhang, Xuhui; To, Chap Hang; Choi, Hoi Wai

2017-01-01

The optical properties of free-standing thin-film microdisks with NiAg metallic reflectors are compared with those with an indium tin oxide (ITO) interfacial layer. The microdisks have been fabricated by a combination of microsphere lithography and laser lift-off processes. Optical-pumped lasing from the microdisk with NiAg reflector has been observed, with reduced threshold and higher quality factor compared those with ITO layers, attributed to improved optical confinement due to the reflectivity of the Ag coating. The results are supported by three-dimensional (3D) finite-difference-time-domain (FDTD) simulations.

An experimental investigation with artificial sunlight of a solar hot-water heater

NASA Technical Reports Server (NTRS)

Simon, F. F.

1976-01-01

Thermal performance measurements were made of a commercial solar hot-water heater in a solar simulator. The objective of the test was to determine basic performance characteristics of a traditional type of flat-plate collector, with and without side reflectors (to increase the solar flux). Due to the fact that collector testing in the solar simulator permits control of the variables that affect collector performance, it was possible to obtain information on each of the following: (1) the effect of flow and incidence angle on the efficiency of a flat-plate collector (but only without side reflectors), (2) transient performance under flow and nonflow conditions, (3) the effectiveness of reflectors in increasing collector efficiency for a zero radiation angle at fluid temperatures required for solar air conditioning, and (4) the limits of applicability of a collector efficiency correlation based on the Hottel-Whillier equation (1958).

Novel types of surface acoustic wave microreflectors - Performance analysis and simulations

NASA Astrophysics Data System (ADS)

Golan, G.; Griffel, G.; Seidman, A.; Croitoru, N.

1990-06-01

Surface acoustic waves for micrograting reflectors have been characterized. Based on the perturbation theory, eight different types of structures on an acoustic waveguide were analyzed. Results of simulations of all eight types of corrugation structures were evaluated in order to find the least leaky waveguide, the most efficient reflector (with minimum necessary perturbations), and the optimal mode shape for improved performances. General design curves are presented in order to illustrate the behavior of the incident and reflected waves under a variety of structural conditions. Analytic expressions for the calculations of the mode amplitude and mode shape, and for general acoustic corrugations are derived and then the simulations results are presented.

Crustal Structure of Southern Baja California Peninsula, Mexico, and its Margins

NASA Astrophysics Data System (ADS)

Gonzalez, A.; Robles-Vazquez, L. N.; Requena-Gonzalez, N. A.; Fletcher, J.; Lizarralde, D.; Kent, G.; Harding, A.; Holbrook, S.; Umhoefer, P.; Axen, G.

2007-05-01

Data from 6 deep 2D multichannel seismic (MCS) lines, 1 wide-angle seismic transect and gravity were used to investigate the crustal structure and stratigraphy of the southern Baja California peninsula and its margins. An array of air guns was used as seismic source shooting each 50 m. Each signal was recorded during 16 s by a 6 km long streamer with 480 channels and a spacing of 12.5 m. Seismic waves were also recorded by Ocean Bottom Seismometers (OBS) in the Pacific and the Gulf of California and by portable seismic instruments onshore southern Baja California. MCS data were conventionally processed, to obtain post-stack time-migrated seismic sections. We used a direct method for the interpretation of the wide-angle data, including ray tracing and travel times calculation. In addition to the gravity data recorded onboard, satellite and land public domain data were also used in the gravity modeling. The combined MCS, wide-angle and gravity transect between the Magdalena microplate to the center of Farallon basin in the Gulf of California, crossing the southern Baja California Peninsula to the north of La Paz, allows to verify the existence of the Magdalena microplate under Baja California. We have also confirmed an extensional component of the Tosco-Abreojos fault zone and we have calculated crustal thicknesses. We have also observed the continuation to the south of the Santa Margarita detachment. The MCS seismic sections show a number of fault scarps, submarine canyons and grabens and horsts associated to normal faults offshore southern Baja California peninsula. The normal displacement observed in the Tosco-Abreojos fault zone and some basins in the continental platform, as well as the presence of faulted acoustic basement blocks, evidence that not all extension was accommodated by the Gulf Extensional Province during the middle to late Miocene. Part of the extension was (and is) accommodated in the Baja California Pacific margin. This confirms the observations from previous seismic lines that suggest that the peninsula is a tectonic block not completely transferred to the Pacific plate. In agreement with the seismic facies and the correlations with the available stratigraphic columns of Deep Sea Drilling Program 471 and 474, we generally identify at least three seismostratigraphic units over the acoustic basement. The lower unit reflectors dip towards the palaeo-trench. We identified a Bottom Simulating Reflector (BSR) probably associated to the presence of gas hydrates, which extends at least 200 km along three seismic lines.

Artificially controlled backscattering in single mode fibers based on femtosecond laser fabricated reflectors

NASA Astrophysics Data System (ADS)

Wang, Xiaoliang; Chen, Daru; Li, Haitao; Wu, Qiong

2018-04-01

A novel method to artificially control the backscattering of the single-mode fiber (SMF) is proposed and investigated for the first time. This method can help to fabricate a high backscattering fiber (HBSF), such as by fabricating reflectors in every one meter interval of an SMF based on the exposure of the femtosecond laser beam. The artificially controlled backscattering (ACBS) can be much higher than the natural Rayleigh backscattering (RB) of the SMF. The RB power and ACBS power in the unit length fiber are derived according to the theory of the RBS. The total relative power and the relative back power reflected in the unit length of the HBSF have been simulated and presented. The simulated results show that the HBSF has the characteristics of both low optical attenuation and high backscattering. The relative back power reflected in the unit length of the HBSF is 25dB larger than the RB power of the SMF when the refractive index modulation quantity of the reflectors is 0.009. Some preliminary experiments also indicate that the method fabricating reflectors to increase the backscattering power of the SMF is practical and promising.

Simultaneous travel time tomography for updating both velocity and reflector geometry in triangular/tetrahedral cell model

NASA Astrophysics Data System (ADS)

Bai, Chao-ying; He, Lei-yu; Li, Xing-wang; Sun, Jia-yu

2018-05-01

To conduct forward and simultaneous inversion in a complex geological model, including an irregular topography (or irregular reflector or velocity anomaly), we in this paper combined our previous multiphase arrival tracking method (referred as triangular shortest-path method, TSPM) in triangular (2D) or tetrahedral (3D) cell model and a linearized inversion solver (referred to as damped minimum norms and constrained least squares problem solved using the conjugate gradient method, DMNCLS-CG) to formulate a simultaneous travel time inversion method for updating both velocity and reflector geometry by using multiphase arrival times. In the triangular/tetrahedral cells, we deduced the partial derivative of velocity variation with respective to the depth change of reflector. The numerical simulation results show that the computational accuracy can be tuned to a high precision in forward modeling and the irregular velocity anomaly and reflector geometry can be accurately captured in the simultaneous inversion, because the triangular/tetrahedral cell can be easily used to stitch the irregular topography or subsurface interface.

Simultaneous travel time tomography for updating both velocity and reflector geometry in triangular/tetrahedral cell model

NASA Astrophysics Data System (ADS)

Bai, Chao-ying; He, Lei-yu; Li, Xing-wang; Sun, Jia-yu

2017-12-01

To conduct forward and simultaneous inversion in a complex geological model, including an irregular topography (or irregular reflector or velocity anomaly), we in this paper combined our previous multiphase arrival tracking method (referred as triangular shortest-path method, TSPM) in triangular (2D) or tetrahedral (3D) cell model and a linearized inversion solver (referred to as damped minimum norms and constrained least squares problem solved using the conjugate gradient method, DMNCLS-CG) to formulate a simultaneous travel time inversion method for updating both velocity and reflector geometry by using multiphase arrival times. In the triangular/tetrahedral cells, we deduced the partial derivative of velocity variation with respective to the depth change of reflector. The numerical simulation results show that the computational accuracy can be tuned to a high precision in forward modeling and the irregular velocity anomaly and reflector geometry can be accurately captured in the simultaneous inversion, because the triangular/tetrahedral cell can be easily used to stitch the irregular topography or subsurface interface.

Reflectivity quenching of ESR multilayer polymer film reflector in optically bonded scintillator arrays

NASA Astrophysics Data System (ADS)

Loignon-Houle, Francis; Pepin, Catherine M.; Charlebois, Serge A.; Lecomte, Roger

2017-04-01

The 3M-ESR multilayer polymer film is a widely used reflector in scintillation detector arrays. As specified in the datasheet and confirmed experimentally by measurements in air, it is highly reflective (> 98 %) over the entire visible spectrum (400-1000 nm) for all angles of incidence. Despite these outstanding characteristics, it was previously found that light crosstalk between pixels in a bonded LYSO scintillator array with ESR reflector can be as high as ∼30-35%. This unexplained light crosstalk motivated further investigation of ESR optical performance. Analytical simulation of a multilayer structure emulating the ESR reflector showed that the film becomes highly transparent to incident light at large angles when surrounded on both sides by materials of refractive index higher than air. Monte Carlo simulations indicate that a considerable fraction (∼25-35%) of scintillation photons are incident at these leaking angles in high aspect ratio LYSO scintillation crystals. The film transparency was investigated experimentally by measuring the scintillation light transmission through the ESR film sandwiched between a scintillation crystal and a photodetector with or without layers of silicone grease. Strong light leakage, up to nearly 30%, was measured through the reflector when coated on both sides with silicone, thus elucidating the major cause of light crosstalk in bonded arrays. The reflector transparency was confirmed experimentally for angles of incidence larger than 60 ° using a custom designed setup allowing illumination of the bonded ESR film at selected grazing angles. The unsuspected ESR film transparency can be beneficial for detector arrays exploiting light sharing schemes, but it is highly detrimental for scintillator arrays designed for individual pixel readout.

Characterization of Streptomyces spp. isolated from the rhizosphere of oil palm and evaluation of their ability to suppress basal stem rot disease in oil palm seedlings when applied as powder formulations in a glasshouse trial.

PubMed

Shariffah-Muzaimah, S A; Idris, A S; Madihah, A Z; Dzolkhifli, O; Kamaruzzaman, S; Maizatul-Suriza, M

2017-12-18

Ganoderma boninense, the main causal agent of oil palm (Elaeis guineensis) basal stem rot (BSR), severely reduces oil palm yields around the world. To reduce reliance on fungicide applications to control BSR, we are investigating the efficacy of alternative control methods, such as the application of biological control agents. In this study, we used four Streptomyces-like actinomycetes (isolates AGA43, AGA48, AGA347 and AGA506) that had been isolated from the oil palm rhizosphere and screened for antagonism towards G. boninense in a previous study. The aim of this study was to characterize these four isolates and then to assess their ability to suppress BSR in oil palm seedlings when applied individually to the soil in a vermiculite powder formulation. Analysis of partial 16S rRNA gene sequences (512 bp) revealed that the isolates exhibited a very high level of sequence similarity (> 98%) with GenBank reference sequences. Isolates AGA347 and AGA506 showed 99% similarity with Streptomyces hygroscopicus subsp. hygroscopicus and Streptomyces ahygroscopicus, respectively. Isolates AGA43 and AGA48 also belonged to the Streptomyces genus. The most effective formulation, AGA347, reduced BSR in seedlings by 73.1%. Formulations using the known antifungal producer Streptomyces noursei, AGA043, AGA048 or AGA506 reduced BSR by 47.4, 30.1, 54.8 and 44.1%, respectively. This glasshouse trial indicates that these Streptomyces spp. show promise as potential biological control agents against Ganoderma in oil palm. Further investigations are needed to determine the mechanism of antagonism and to increase the shelf life of Streptomyces formulations.

Temperature Distribution and Influence Mechanism on Large Reflector Antennas under Solar Radiation

NASA Astrophysics Data System (ADS)

Wang, C. S.; Yuan, S.; Liu, X.; Xu, Q.; Wang, M.; Zhu, M. B.; Chen, G. D.; Duan, Y. H.

2017-10-01

The solar impact on antenna must be lessened for the large reflector antenna operating at high frequencies to have great electromagnetic performances. Therefore, researching the temperature distribution and its influence on large reflector antenna is necessary. The variation of solar incidence angle is first calculated. Then the model is simulated by the I-DEAS software, with the temperature, thermal stress, and thermal distortion distribution through the day obtained. In view of the important influence of shadow on antenna structure, a newly proposed method makes a comprehensive description of the temperature distribution on the reflector and its influence through the day by dividing a day into three different periods. The sound discussions and beneficial summary serve as the scientific foundation for the engineers to compensate the thermal distortion and optimize the antenna structure.

Uncertainty-enabled design of electromagnetic reflectors with integrated shape control

NASA Astrophysics Data System (ADS)

Haque, Samiul; Kindrat, Laszlo P.; Zhang, Li; Mikheev, Vikenty; Kim, Daewa; Liu, Sijing; Chung, Jooyeon; Kuian, Mykhailo; Massad, Jordan E.; Smith, Ralph C.

2018-03-01

We implemented a computationally efficient model for a corner-supported, thin, rectangular, orthotropic polyvinylidene fluoride (PVDF) laminate membrane, actuated by a two-dimensional array of segmented electrodes. The laminate can be used as shape-controlled electromagnetic reflector and the model estimates the reflector's shape given an array of control voltages. In this paper, we describe a model to determine the shape of the laminate for a given distribution of control voltages. Then, we investigate the surface shape error and its sensitivity to the model parameters. Subsequently, we analyze the simulated deflection of the actuated bimorph using a Zernike polynomial decomposition. Finally, we provide a probabilistic description of reflector performance using statistical methods to quantify uncertainty. We make design recommendations for nominal parameter values and their tolerances based on optimization under uncertainty using multiple methods.

Optical design of a robotic TV camera probe for minimally invasive abdominal surgery

NASA Astrophysics Data System (ADS)

Todaro, Susanna; He, Weiyi; Killinger, Dennis

2011-03-01

Minimally invasive techniques are a promising new field of surgery; however, they limit the surgeon's access points and maneuverability. In order to increase the number of access points in minimally invasive abdominal surgery, a proposed implantable medical probe braces to the abdominal wall and provides illumination and video signal. The probe is cylindrical, about 25 mm long and 10 mm in diameter. A ring of LEDs on the end of the probe illuminates the tissue, and the resulting image is focused onto an HD video detector. It was necessary to apply beam-shaping reflectors to collimate the light onto a small target area, to avoid illuminating areas not picked up by the video. These reflectors were designed and simulated using the optical ray tracing software TracePro. Two LED chip geometries and three types of reflector geometries were analyzed, and the parameters for each geometry were optimized. For the straight-edged reflectors, the intensity patterns and optimization were compared to experimental results. Although parabolic reflectors produced the best collimation, cone reflectors with a 20-degree half-angle produced significant collimation at a much cheaper price. This work was supported by NSF REU program (award No DMR-1004873).

Genetic versus census estimators of the opportunity for sexual selection in the wild.

PubMed

Dunn, Stacey J; Waits, Lisette P; Byers, John A

2012-04-01

Abstract The existence of a direct link between intensity of sexual selection and mating-system type is widely accepted. However, the quantification of sexual selection has proven problematic. Several measures of sexual selection have been proposed, including the operational sex ratio (OSR), the breeding sex ratio (BSR), and the opportunity for sexual selection (I(mates)). For a wild population of pronghorn (Antilocapra americana), we calculated OSR and BSR. We estimated I(mates) from census data on the spatial and temporal distribution of receptive females in rut and from a multigenerational genetic pedigree. OSR and BSR indicated weak sexual selection on males, but census and pedigree I(mates) suggested stronger sexual selection on males than on females. OSR and BSR correlated with census but not pedigree estimates of I(mates), and census I(mates) did not correlate with pedigree estimates. This suggests that the behavioral mating system, as deduced from the spatial and temporal distribution of females, does not predict the genetic mating system of pronghorn. The differences we observed between estimators were primarily due to female mate sampling and choice and to the sex ratio. For most species, behavioral data are not perfectly accurate and therefore will be an insufficient alternative to using multigenerational pedigrees to quantify sexual selection.

Tn5-Mob transposon mediated transfer of salt tolerance and symbiotic characteristics between Rhizobia genera.

PubMed

Yang, S; Wu, Z; Gao, W; Li, J

1993-01-01

Rhizobium meliloti 042B is a fast-growing, salt-tolerant and high efficiency nitrogen-fixing symbiont with alfalfa. Bradyrhizobium japonicum USDA110 grows slowly, and cannot grow in YMA medium containing 0.1M NaCl, but nodulates and fixed nitrogen efficiently with soybean. Eighty-six transconjugants, called SR, were obtained by inserting Tn5-Mob randomly into genomes of 042B using pSUP5011 and helper plasmid RP4. Selecting 4 SR strains randomly and introducing DNA fragment of SR into USDA110 with helper plasmid R68.45 by triparental mating, 106 transconjugants, called BSR, were constructed. Most of BSR strains had the fast-growing phenotype and could tolerate 0.3-0.5M NaCl generally. Some of them produced melanine. When soybean and alfalfa were inoculated with these transconjugants BSR, 47 out of 90 BSR were found to nodulate in both of these plants, but no nitrogenase activity was observed with alfalfa; 26 strains could only nodulate and fix nitrogen in soybean; 13 strains could nodulate in alfalfa but did not fix nitrogen; 4 strains failed to nodulate in either soybean or alfalfa. Among them, 4 transconjugants which tolerated and fixed nitrogen efficiently in soybean were constructed.

Optimization of wave-guided luminescence for higher efficiency of bifacial thin-film microscale GaAs solar cells

NASA Astrophysics Data System (ADS)

Shen, Ling; Shen, Yifeng; Li, Feng

2018-01-01

In pursuit of capturing more wave-guided luminescence for surface-printed bifacial GaAs μ-cells, the pyramid structure has been incorporated with specular back side reflector (BSR) to change the direction of photon propagation. Based on ray tracing model, the calculated photon capturing efficiency of GaAs μ-cells from back side via pyramid, dependent on the parameters of pyramid structure, achieve the largest 1.7× increase for dye absorption peak of 480 nm compared to the case without pyramid. More significantly, the short circuit current in experiment has been improved from original 16.5 mA/cm2 to 23.75 mA/cm2 for the AM 1.5G solar spectrum. Further experiment demonstrates that the optimized pyramid structure enables the integrated luminescent intensity to reach ∼3× increase in a smaller distance of optical transport, which means the advantages in photon capturing efficiency for cells with higher aspect ratio. The calculation further confirms that the cells with higher aspect ratio, among all cells with the same area, realize the higher concentration ratio for the same geometric gain. This provides a guideline for design of cell geometries to guarantee a higher power output in terms of cell modules.

Matrix method for acoustic levitation simulation.

PubMed

Andrade, Marco A B; Perez, Nicolas; Buiochi, Flavio; Adamowski, Julio C

2011-08-01

A matrix method is presented for simulating acoustic levitators. A typical acoustic levitator consists of an ultrasonic transducer and a reflector. The matrix method is used to determine the potential for acoustic radiation force that acts on a small sphere in the standing wave field produced by the levitator. The method is based on the Rayleigh integral and it takes into account the multiple reflections that occur between the transducer and the reflector. The potential for acoustic radiation force obtained by the matrix method is validated by comparing the matrix method results with those obtained by the finite element method when using an axisymmetric model of a single-axis acoustic levitator. After validation, the method is applied in the simulation of a noncontact manipulation system consisting of two 37.9-kHz Langevin-type transducers and a plane reflector. The manipulation system allows control of the horizontal position of a small levitated sphere from -6 mm to 6 mm, which is done by changing the phase difference between the two transducers. The horizontal position of the sphere predicted by the matrix method agrees with the horizontal positions measured experimentally with a charge-coupled device camera. The main advantage of the matrix method is that it allows simulation of non-symmetric acoustic levitators without requiring much computational effort.

Polarized edge emission from GaN-based light-emitting diodes sandwiched by dielectric/metal hybrid reflectors

NASA Astrophysics Data System (ADS)

Yan, L. J.; Sheu, J. K.; Huang, F. W.; Lee, M. L.

2010-12-01

Edge-emitting c-plane GaN/sapphire-based light-emitting diodes (LEDs) sandwiched by two dielectric/metal hybrid reflectors on both sapphire and GaN surfaces were studied to determine their light emission polarization. The hybrid reflectors comprised dielectric multiple thin films and a metal layer. The metal layers of Au or Ag used in this study were designed to enhance the polarization ratio from S-polarization (transverse electric wave, TE) to P-polarization (transverse magnetic wave, TM). The two sets of optimized dielectric multi thin films served as matching layers for wide-angle incident light on both sapphire and GaN surfaces. To determine which reflector scheme would achieve a higher polarization ratio, simulations of the reflectance at the hybrid reflectors on sapphire (or GaN) interface were performed before the fabrication of experimental LEDs. Compared with conventional c-plane InGaN/GaN/sapphire LEDs without dielectric/metal hybrid reflectors, the experimental LEDs exhibited higher polarization ratio (ITE-max/ITM-max) with r=2.174 (˜3.37 dB) at a wavelength of 460 nm. In contrast, the original polarized light (without dielectric/metal hybrid reflectors) was partially contributed (r=1.398) by C-HH or C-LH (C band to the heavy-hole sub-band or C band to the crystal-field split-off sub-band) transitions along the a-plane or m-plane direction.

A simple test for thermomechanical evaluation of ceramic fibers

NASA Technical Reports Server (NTRS)

Morscher, Gregory N.; Dicarlo, James A.

1991-01-01

A simple bend stress relaxation (BSR) test was developed to measure the creep related properties of ceramic fibers and whiskers. The test was applied to a variety of commercial and developmental Si based fibers to demonstrate capabilities and to evaluate the relative creep resistance of the fibers at 1200 to 1400 C. The implications of these results and the advantages of the BSR test over typical tensile creep tests are discussed.

Velocity Structure and 3D Finite Element Modeling for Critical Instability of Gas Hydrate-related Slipstream Submarine Slide, offshore Vancouver Island, Canada

NASA Astrophysics Data System (ADS)

LONG, S.; He, T.; Lan, K.; Spence, G.; Yelisetti, S.

2016-12-01

The previous study indicated that Slipstream submarine landslide is one of a gas hydrate-related slope failures on the frontal ridges of the Northern Cascadia accretionary margin, off Vancouver Island, Canada. The OBS data collected during SeaJade project were used to derive the subseafloor Vp & Vs structures. The anomalous high Vp of about 2.0 km/s at shallow depths of 100 (± 10) mbsf closely matches the estimated depth of the glide plane. The modelled Vs above the BSR at a depth of 265-275 mbsf is about 100-150 m/s higher than a theoretical 100% water saturated background value, indicating that the hydrate acts as part of the load-bearing matrix to increase the rigidity of the sediment. Also, the Vp & Vs above BSR both indicate a consistent 40% saturation of gas hydrate. On the basis of high accurate submarine bathymetry obtained by multibeam sounding system, the submarine landform before slump is reconstructed by comparing the slump headwall geometry with surrounding ridges. Using the elastic moduli determined from Vp & Vs, the stress status was calculated by the finite element method for different conditions and confirmed that the undersea sliding process related with gas hydrate starts from the toe of the slope and then progressively retreats to the place of current headwall, in a series of triangular blocks or wedges. The shear stress are then compared with the frame shear strength of geological model, which is critical for controlling slope stability of steep frontal ridges The simulation results found that the ridge was stable under its own weight, but gas hydrate saturation decrease and pore-water pressure increase will greatly reduce shear strength of sediments and may cause a landslide. Since the study area is in the earthquake belt, the large seismic acceleration will greatly affect pore pressure distribution within the ridge. The simulation results indicated that the shallow high-velocity gas hydrate layer coincident with glide plane depth is more likely to fail than the current BSR observations during an earthquake. Combining with regional tectonic background, it is initially deduced that the large earthquake is the most possible trigger of Slipstream landslide.

The calculation of electromagnetic fields in the Fresnel and Fraunhofer regions using numerical integration methods

NASA Technical Reports Server (NTRS)

Schmidt, R. F.

1971-01-01

Some results obtained with a digital computer program written at Goddard Space Flight Center to obtain electromagnetic fields scattered by perfectly reflecting surfaces are presented. For purposes of illustration a paraboloidal reflector was illuminated at radio frequencies in the simulation for both receiving and transmitting modes of operation. Fields were computed in the Fresnel and Fraunhofer regions. A dual-reflector system (Cassegrain) was also simulated for the transmitting case, and fields were computed in the Fraunhofer region. Appended results include derivations which show that the vector Kirchhoff-Kottler formulation has an equivalent form requiring only incident magnetic fields as a driving function. Satisfaction of the radiation conditions at infinity by the equivalent form is demonstrated by a conversion from Cartesian to spherical vector operators. A subsequent development presents the formulation by which Fresnel or Fraunhofer patterns are obtainable for dual-reflector systems. A discussion of the time-average Poynting vector is also appended.

Neutron-beam-shaping assembly for boron neutron-capture therapy

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

Zaidi, L.; Kashaeva, E. A.; Lezhnin, S. I.

A neutron-beam-shaping assembly consisting of a moderator, a reflector, and an absorber is used to form a therapeutic neutron beam for the boron neutron-capture therapy of malignant tumors at accelerator neutron sources. A new structure of the moderator and reflector is proposed in the present article, and the results of a numerical simulation of the neutron spectrum and of the absorbed dose in a modified Snyder head phantom are presented. The application of a composite moderator and of a composite reflector and the implementation of neutron production at the proton energy of 2.3MeV are shown to permit obtaining a high-qualitymore » therapeutic neutron beam.« less

An experimental investigation with artificial sunlight of a solar hot-water heater

NASA Technical Reports Server (NTRS)

Simon, F. F.

1976-01-01

Thermal performance measurements were made of a commercial solar hot water heater in a solar simulator to determine basic performance characteristics of a traditional type of flat plate collector, with and without side reflectors (to increase the solar flux). Information on each of the following was obtained; (1) the effect of flow and incidence angle on the efficiency of a flat plate collector (but only without side reflectors); (2) transient performance under flow and nonflow conditions; (3) the effectiveness of reflectors to increase collector efficiency for a zero radiation angle at fluid temperatures required for solar air conditioning; and (4) the limits of applicability of a collector efficiency correlation based on the Hottel Whillier equation.

Measurement of thermal neutrons reflection coefficients for two-layer reflectors.

PubMed

Azimkhani, S; Zolfagharpour, F; Ziaie, F

2018-05-01

In this research, thermal neutrons albedo coefficients and relative number of excess counts have been measured experimentally for different thicknesses of two-layer reflectors by using 241 Am-Be neutron source (5.2Ci) and BF 3 detector. Our used reflectors consist of two-layer which are combinations of water, graphite, polyethylene, and lead materials. Experimental results reveal that thermal neutron reflection coefficients slightly increased by addition of the second layer. The maximum value of growth for thermal neutrons albedo is obtained for lead-polyethylene compound (0.72 ± 0.01). Also, there is suitable agreement between the experimental values and simulation results by using MCNPX code. Copyright © 2018 Elsevier Ltd. All rights reserved.

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

Bihani, Abhishek; Daigle, Hugh; Cook, Ann

Coexistence of three methane phases (liquid (L), gas (G), hydrate (H)) in marine gas hydrate systems may occur according to in-situ pressure, temperature, salinity and pore size. In sediments with salinity close to seawater, a discrete zone of three-phase (3P) equilibrium may occur near the base of the regional hydrate stability zone (RHSZ) due to capillary effects. The existence of a 3P zone influences the location of the bottom-simulating reflection (BSR) and has implications for methane fluxes at the base of the RHSZ. We studied hydrate stability conditions in two wells, WR313-G and WR313-H, at Walker Ridge Block 313 inmore » the northern Gulf of Mexico. We determined pore size distributions (PSD) by constructing a synthetic nuclear magnetic resonance (NMR) relaxation time distribution. Correlations were obtained by non-linear regression on NMR, gamma ray, and bulk density logs from well KC-151 at Keathley Canyon. The correlations enabled construction of relaxation time distributions for WR313-G and WR313-H, which were used to predict PSD through comparison with mercury injection capillary pressure measurements. With the computed PSD, L+H and L+G methane solubility was determined from in-situ pressure and temperature. The intersection of the L+G and L+H curves for various pore sizes allowed calculation of the depth range of the 3P equilibrium zone. As in previous studies at Blake Ridge and Hydrate Ridge, the top of the 3P zone moves upwards with increasing water depth and overlies the bulk 3P equilibrium depth. In clays at Walker Ridge, the predicted thickness of the 3P zone is approximately 35 m, but in coarse sands it is only a few meters due to the difference in absolute pore sizes and the width of the PSD. The thick 3P zone in the clays may explain in part why the BSR is only observed in the sand layers at Walker Ridge, although other factors may influence the presence or absence of a BSR.« less

3D Finite Element Modeling for Possible Creeping Behavior of Gas Hydrate-related Slipstream Submarine Slide, offshore Vancouver Island, Canada

NASA Astrophysics Data System (ADS)

LONG, S.; He, T.; Lan, K.; Spence, G.; Yelisetti, S.

2017-12-01

Natural gas hydrate-related submarine landslides have been identified on worldwide continental slope. Being a potential risk for marine environment and engineering projects, it has been a hot topic of hydrate research in recent decades. The study target is Slipstream submarine landslide, one of the slope failures on the frontal ridges of the Northern Cascadia accretionary margin, off Vancouver Island, Canada. The previous studies of P- & S-wave velocity structure based on OBS (Ocean Bottom Seismometer) data of SeaJade (Seafloor Earthquake Array - Japan Canada Cascadia Experiment) project indicated that there are two high concentration gas-hydrate layers within the ridge, one is at a depth of 100 mbsf (meter beneath the seafloor) with anomalous high P-wave velocities and the other is just above the prominent BSR (bottom-simulating reflector) at a depth of 265-275 mbsf. In this study we investigated the possible creeping behavior of gas hydrate layer to examine the critical instability of the ridge slope using the finite element method for self weight and additional stress (e.g., mega earthquake) conditions. The elastic and elasticoplasticity moduli of gas hydrate layer were obtained from laboratory measurements for different uniaxial pressure tests, which indicated that the sediments behave elastically for uniaxial pressures below 6 MPa, but elasticoplastically between 6-6.77 MPa. The modeled shear stress distribution indicated that the current sliding surface is more likely connected with the shallow high-velocity gas hydrate layer and sliding process related with gas hydrate starts from the toe of the slope and then progressively retreats to the place of current headwall, in a series of triangular blocks or wedges. Since the study area is in the earthquake belt, the large seismic acceleration will greatly affect the stress field and pore pressure distribution within the ridge, and the landslide is going to happen and supposedly at the shallow high-velocity gas hydrate layer.

Determining gas hydrate distribution in sands using integrated analysis of well log and seismic data in the Terrebonne Basin, Gulf of Mexico

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

Hillman, Jess; Cook, Ann; Daigle, Hugh

The Terrebonne Basin is a salt bounded mini-basin in the northeast section of the Walker Ridge protraction area in the Gulf of Mexico, and the main site for an upcoming gas-hydrate focused International Ocean Discovery Program (IODP) cruise. The basin is infilled by an increasingly mud rich sedimentary sequence with several 5-15 meter gas-hydrate filled sand units of Miocene to Pliocene age overlying the up-domed salt. These gas-hydrate filled sand units can be identified in logging while drilling data from two existing wells in the Terrebonne Basin, drilled in 2009 by the Gas Hydrate Joint Industry Project (JIP) Leg 2.more » The sand units are cross cut by a distinct bottom-simulating reflector (BSR), and are clearly characterized by a polarity reversal in the sand units. The polarity reversal is caused by a positive gas-hydrate filled sand within the stability zone changing to negative gas-bearing sand. Using well data and calculated synthetic seismogram well ties we are able to identify several additional 1-4 meter gas-hydrate and water-saturated sand units associated with thick (100-200 m-thick), fine grained, hydrate bearing fractured units in the upper sedimentary sequence on the seismic data. Following on previous work, we propose that microbial generation of methane occurring within the fine-grained, fractured units acts as a source for gas hydrate formation in the thin sands. In contrast, it has been proposed that the gas hydrate in the 5-15 m-thick sands first discovered by the JIP was originates from a deeper thermogenic source. Through correlating hydrate occurrence in sands from well data, to amplitudes derived from the seismic data, we can estimate possible distribution of hydrate across the basin. Overall, we find the Terrebonne basin to be a complex gas hydrate system with multiple mechanisms of methane generation and migration.« less

Endoluminal ultrasound applicator configurations utilizing deployable arrays, reflectors and lenses to augment and dynamically adjust treatment volume, gain, and depth

NASA Astrophysics Data System (ADS)

Adams, Matthew S.; Salgaonkar, Vasant A.; Sommer, Graham; Diederich, Chris J.

2017-02-01

Endoluminal high-intensity ultrasound offers spatially-precise thermal ablation of tissues adjacent to body lumens, but is constrained in treatment volume and penetration depth by the effective aperture of integrated transducers, which are limited in size to enable delivery through anatomical passages, endoscopic instrumentation, or laparoscopic ports. This study introduced and investigated three distinct endoluminal ultrasound applicator designs that can be delivered in a compact state then deployed or expanded at the target luminal site to increase the effective therapeutic aperture. The first design incorporated an array of planar transducers which could be unfolded at specific angles of convergence between the transducers. Two alternative designs consisted of fixed transducer sources surrounded by an expandable multicompartment balloon that contained acoustic reflector and dynamically-adjustable fluid lenses compartments. Parametric studies of acoustic output were performed across device design parameters via the rectangular radiator and secondary sources methods. Biothermal models were used to simulate resulting temperature distributions in three-dimensional heterogeneous tissue models. Simulations indicate that a deployable transducer array can increase volumetric coverage and penetration depth by 80% and 20%, respectively, while permitting more conformal thermal lesion shapes based on the degree of convergence between the transducers. The applicator designs incorporating reflector and fluid lenses demonstrated enhanced focal gain and penetration depth that increased with the diameter of the expanded reflector-lens balloon. Thermal simulations of assemblies with 12 mm compact profiles and 50 mm expanded balloon diameters demonstrated generation of localized thermal lesions at depths up to 10 cm in liver tissue.

Final Scientific/Technical Report of Gas Hydrate Dynamics on the Alaskan Beaufort Continental Slope: Modeling and Field Characterization

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

Hornbach, Matthew J; Colwell, Frederick S; Harris, Robert

Methane Hydrates, a solid form of methane and water, exist at high pressures and low temperatures, occurs on every continental margin on Earth, represents one of the largest reservoirs of carbon on the planet, and, if destabilized, may play an important role in both slope stability and climate change. For decades, researchers have studied methane hydrates with the hope of determining if methane hydrates are destabilizing, and if so, how this destabilization might impact slope stability and ocean/atmosphere carbon budgets. In the past ~5 years, it has become well established that the upper “feather-edge” of methane hydrate stability (intermediate watermore » depths of ~200-500 meters below sea level) represents an important frontier for methane hydrates stability research, as this zone is most susceptible to destabilization due to minor fluctuations in ocean temperature in space and time. The Arctic Ocean—one of the fastest warming regions on Earth—is perhaps the best place to study possible changes to methane hydrate stability due to ocean warming. To address the stability of methane hydrates at intermediate ocean depths, Southern Methodist University in partnership with Oregon State University and The United State Geological Survey at Woods Hole began investigating methane hydrate stability in intermediate water depths below both the US Beaufort Sea and the Atlantic Margin, from 2012-2017. The work was funded by the Department of Energy’s (DOE) National Energy Technology Laboratory (NETL). The key goal of the SMU component of this study was to collect the first ever heat flow data in the Beaufort Sea and compare measured shallow (probe-based1) heat flow values with deeper (BSR-derived2) heat flow values, and from this, determine whether hydrates were in thermal equilibrium. In September 2016, SMU/OSU collected the first ever heat flow measurements in the US Beaufort Sea. Despite poor weather and rough seas, the cruise was a success, with 116 heat flow measurements acquired across the margin, spanning 4 transects separated by more than 400 km. Useable heat flow data exists for 97% (113) of probe heat flow measurements, revealing a clear picture of regional heat flow across the basin. During the past 8 months since the cruise, SMU researchers have processed the heat flow and thermal conductivity measurements and compared results to deeper heat flow estimates obtained from seismic data. The analysis reveals clear, consistent trends: All probe heat flow measurements in depths greater than 800 mbsl are consistent with BSR-derived values; heat flow measurements obtained in water depths between ~250-750 mbsl are systematically lower than those estimated from BSRs; and heat flow estimates in water depths shallower than ~250 mbsl are systematically warmer than deeper estimates. The consistency between shallow (probe) and deep (BSR) heat flow measurements at depths greater than ~750 m where ocean temperature changes are minimal supports the premise that the hydrates consist primarily of methane and represent a valuable tool for estimating heat flow. The anomalous cooling trend observed in the upper 250 m is consistent with expected seasonal effects observed in shallow ocean buoy measurements in the arctic, when cold, less dense melting sea ice cools the upper 200 m of the ocean during the summer as ice melting occurs. The discrepancy in heat flow at intermediate water depths is best explained via recent intermediate ocean temperature warming, where long-term (annual or longer) warming intermediate ocean bottom waters result in an anomalously low heat flow in shallow heat flow measurements. Using the characteristic 1D time-length scale for diffusion, we estimate that ocean temperature warming began no later than ~1200 years ago but arguably much more recently as results are limited by seismic resolution. More importantly, our analysis indicates methane hydrate is destabilizing not only in the upper feather edge (200-500 mbsl) but at depths as great as 750 mbsl. The intermediate ocean warming rate supports previous studies suggesting geologically rapid warming (>0.1 deg C/decade) at intermediate ocean depths in the Beaufort Sea. Assuming no further changes or additional warming, our analysis indicates methane hydrates will destabilize at seafloor depths shallower than 750 mbsl in the Beaufort Sea within the next ~3000 years. 1 Probe outfitted with sensors inserted into the seafloor sediment 2 Bottom-simulating reflector (BSR) seismic data indicates presence of hydrate deposits« less

Comparison of indoor-outdoor thermal performance for the Sunpak evacuated tube liquid collector

NASA Technical Reports Server (NTRS)

1980-01-01

Performance data for current Sunpak production collectors is presented. The effects of an improved manifold are seen from the test results. The test results show excellent correlation between the solar simulator derived test results and outdoor test results. Also, because of different incident angle modifiers, the all-day efficiency of this collector with a diffuse reflector is comparable to the performance with the standard shaped specular reflector.

A fast RCS accuracy assessment method for passive radar calibrators

NASA Astrophysics Data System (ADS)

Zhou, Yongsheng; Li, Chuanrong; Tang, Lingli; Ma, Lingling; Liu, QI

2016-10-01

In microwave radar radiometric calibration, the corner reflector acts as the standard reference target but its structure is usually deformed during the transportation and installation, or deformed by wind and gravity while permanently installed outdoor, which will decrease the RCS accuracy and therefore the radiometric calibration accuracy. A fast RCS accuracy measurement method based on 3-D measuring instrument and RCS simulation was proposed in this paper for tracking the characteristic variation of the corner reflector. In the first step, RCS simulation algorithm was selected and its simulation accuracy was assessed. In the second step, the 3-D measuring instrument was selected and its measuring accuracy was evaluated. Once the accuracy of the selected RCS simulation algorithm and 3-D measuring instrument was satisfied for the RCS accuracy assessment, the 3-D structure of the corner reflector would be obtained by the 3-D measuring instrument, and then the RCSs of the obtained 3-D structure and corresponding ideal structure would be calculated respectively based on the selected RCS simulation algorithm. The final RCS accuracy was the absolute difference of the two RCS calculation results. The advantage of the proposed method was that it could be applied outdoor easily, avoiding the correlation among the plate edge length error, plate orthogonality error, plate curvature error. The accuracy of this method is higher than the method using distortion equation. In the end of the paper, a measurement example was presented in order to show the performance of the proposed method.

Effect-site half-time for burst suppression is longer than for hypnosis during anaesthesia with sevoflurane.

PubMed

Kennedy, R R; Minto, C; Seethepalli, A

2008-01-01

The relationship between measures of drug effect such as bispectral index (BIS) and end-tidal (ET) levels of anaesthetic agents is described by the 'effect site equilibrium half-time', t(1/2)(ke0). There are limited data available on sevoflurane t(1/2)(ke0) during routine anaesthesia and surgery. Preliminary observations suggested t(1/2)(ke0) for the degree of hypnosis as estimated by BIS is different from that for burst suppression of the electroencephalograph, occurring at 'deep' levels of anaesthesia. This study aimed to determine and compare t(1/2)(ke0) for these two 'effects'. Large changes in ET sevoflurane were produced in 13 subjects during surgery. ET sevoflurane, BIS, and burst suppression ratio (BSR) were recorded every 10 s. Data were divided into epochs with BIS>30 (BIS) or with BSR>10% (burst suppression). Using a non-parametric modelling technique, t(1/2)(ke0) was determined for each epoch. There were 36 'BIS' and 20 burst suppression zones. Mean (sd) t(1/2)(ke0) for BIS was 3.48 (1.12) min and for BSR 9.9 (6.4) min. In all subjects, t(1/2)(ke0) BIS

Relativistic twistron based on backward-wave oscillator with modulating reflector and an efficiency of 56%

NASA Astrophysics Data System (ADS)

Totmeninov, E. M.; Pegel, I. V.; Tarakanov, V. P.

2017-06-01

Using numerical simulation, the operating mode of a relativistic Cherenkov microwave generator of the twistronic type has been demonstrated. The generator includes an electrodynamic system based on a backward-wave oscillator and modulating reflector with nonmonotonous, highly nonuniform energy exchange along the length of the system. The efficiency of power conversion from the electron beam to electromagnetic radiation is 56%, and the electronic efficiency is 66%. For an accelerating voltage of 340 kV and an electron beam current of 3.3 kA, the simulated generation power is 630 MW at a frequency of 9.7 GHz and a guiding magnetic field of 2.2 T.

On-chip broadband spectral filtering using planar double high-contrast grating reflectors

NASA Astrophysics Data System (ADS)

Horie, Yu; Arbabi, Amir; Faraon, Andrei

2015-02-01

We propose a broadband free-space on-chip spectrometer based on an array of integrated narrowband filters consisting of Fabry-Perot resonators formed by two high-contrast grating (HCG) based reflectors separated by a low-index thin layer with a fixed cavity thickness. Using numerical simulations, broadband tunability of resonance wavelengths was achieved only by changing the in-plane grating parameters such as period or duty cycle of HCGs while the substrate geometry was kept fixed. Experimentally, the HCG reflectors were fabricated on silicon on insulator (SOI) substrates and high reflectivity was measured, fabrication process for the proposed double HCG-based narrowband filter array was developed. The filtering function that can be spanned over a wide range of wavelengths was measured.

Structured surface reflector design for oblique incidence beam splitter at 610 GHz.

PubMed

Defrance, F; Casaletti, M; Sarrazin, J; Wiedner, M C; Gibson, H; Gay, G; Lefèvre, R; Delorme, Y

2016-09-05

An iterative alternate projection-based algorithm is developed to design structured surface reflectors to operate as beam splitters at GHz and THz frequencies. To validate the method, a surface profile is determined to achieve a reflector at 610 GHz that generates four equal-intensity beams towards desired directions of ±12.6° with respect to the specular reflection axis. A prototype is fabricated and the beam splitter behavior is experimentally demonstrated. Measurements confirm a good agreement (within 1%) with computer simulations using Feko, validating the method. The beam splitter at 610 GHz has a measured efficiency of 78% under oblique incidence illumination that ensures a similar intensity between the four reflected beams (variation of about 1%).

Compact high-flux two-stage solar collectors based on tailored edge-ray concentrators

NASA Astrophysics Data System (ADS)

Friedman, Robert P.; Gordon, Jeffrey M.; Ries, Harald

1995-08-01

Using the recently-invented tailored edge-ray concentrator (TERC) approach for the design of compact two-stage high-flux solar collectors--a focusing primary reflector and a nonimaging TERC secondary reflector--we present: 1) a new primary reflector shape based on the TERC approach and a secondary TERC tailored to its particular flux map, such that more compact concentrators emerge at flux concentration levels in excess of 90% of the thermodynamic limit; and 2) calculations and raytrace simulations result which demonstrate the V-cone approximations to a wide variety of TERCs attain the concentration of the TERC to within a few percent, and hence represent practical secondary concentrators that may be superior to corresponding compound parabolic concentrator or trumpet secondaries.

Polymorphisms in exons 1B and 1C of the type I interleukin-1 receptor gene in patients with endometriosis.

PubMed

D'Amora, Paulo; Sato, Hélio; Girão, Manoel J B C; Silva, Ismael D C G; Schor, Eduardo

2006-09-01

To study possible correlation between the prevalence of polymorphisms in the type I interleukin-1 receptor gene and pelvic endometriosis. Genotypes of 223 women were analyzed: 109 women with surgically and histologically confirmed endometriosis and 114 healthy women. Distributions of two single-base polymorphisms of the human interleukin-1 receptor type I (IL-1RI) gene were evaluated: PstI, due to a C-->T transition in exon 1B and BsrBI a C-->A transition at position 52 in exon 1C. Polymorphisms were detected by polymerase chain reaction (PCR) followed by restriction fragment length polymorphism analysis (RFLP) resolved on 3% agarose gels stained with ethidium bromide. Genotypes for PstI polymorphisms did not differ significantly among control and endometriosis (P = 0.058). However, in relation to BsrBI polymorphism, protective risk was observed for the development of endometriosis [OR 0.39-IC 95% (0.2-0.9)]. BsrBI heterozygote genotype (C/A) showed protective effect against endometriosis development.

Additive manufacturing of reflective optics: evaluating finishing methods

NASA Astrophysics Data System (ADS)

Leuteritz, G.; Lachmayer, R.

2018-02-01

Individually shaped light distributions become more and more important in lighting technologies and thus the importance of additively manufactured reflectors increases significantly. The vast field of applications ranges from automotive lighting to medical imaging and bolsters the statement. However, the surfaces of additively manufactured reflectors suffer from insufficient optical properties even when manufactured using optimized process parameters for the Selective Laser Melting (SLM) process. Therefore post-process treatments of reflectors are necessary in order to further enhance their optical quality. This work concentrates on the effectiveness of post-process procedures for reflective optics. Based on already optimized aluminum reflectors, which are manufactured with a SLM machine, the parts are differently machined after the SLM process. Selected finishing methods like laser polishing, sputtering or sand blasting are applied and their effects quantified and compared. The post-process procedures are investigated on their impact on surface roughness and reflectance as well as geometrical precision. For each finishing method a demonstrator will be created and compared to a fully milled sample and among themselves. Ultimately, guidelines are developed in order to figure out the optimal treatment of additively manufactured reflectors regarding their optical and geometrical properties. Simulations of the light distributions will be validated with the developed demonstrators.

Deployable reflector antenna performance optimization using automated surface correction and array-feed compensation

NASA Technical Reports Server (NTRS)

Schroeder, Lyle C.; Bailey, M. C.; Mitchell, John L.

1992-01-01

Methods for increasing the electromagnetic (EM) performance of reflectors with rough surfaces were tested and evaluated. First, one quadrant of the 15-meter hoop-column antenna was retrofitted with computer-driven and controlled motors to allow automated adjustment of the reflector surface. The surface errors, measured with metric photogrammetry, were used in a previously verified computer code to calculate control motor adjustments. With this system, a rough antenna surface (rms of approximately 0.180 inch) was corrected in two iterations to approximately the structural surface smoothness limit of 0.060 inch rms. The antenna pattern and gain improved significantly as a result of these surface adjustments. The EM performance was evaluated with a computer program for distorted reflector antennas which had been previously verified with experimental data. Next, the effects of the surface distortions were compensated for in computer simulations by superimposing excitation from an array feed to maximize antenna performance relative to an undistorted reflector. Results showed that a 61-element array could produce EM performance improvements equal to surface adjustments. When both mechanical surface adjustment and feed compensation techniques were applied, the equivalent operating frequency increased from approximately 6 to 18 GHz.

Effect of Facet Displacement on Radiation Field and Its Application for Panel Adjustment of Large Reflector Antenna

NASA Astrophysics Data System (ADS)

Wang, Wei; Lian, Peiyuan; Zhang, Shuxin; Xiang, Binbin; Xu, Qian

2017-05-01

Large reflector antennas are widely used in radars, satellite communication, radio astronomy, and so on. The rapid developments in these fields have created demands for development of better performance and higher surface accuracy. However, low accuracy and low efficiency are the common disadvantages for traditional panel alignment and adjustment. In order to improve the surface accuracy of large reflector antenna, a new method is presented to determinate panel adjustment values from far field pattern. Based on the method of Physical Optics (PO), the effect of panel facet displacement on radiation field value is derived. Then the linear system is constructed between panel adjustment vector and far field pattern. Using the method of Singular Value Decomposition (SVD), the adjustment value for all panel adjustors are obtained by solving the linear equations. An experiment is conducted on a 3.7 m reflector antenna with 12 segmented panels. The results of simulation and test are similar, which shows that the presented method is feasible. Moreover, the discussion about validation shows that the method can be used for many cases of reflector shape. The proposed research provides the instruction to adjust surface panels efficiently and accurately.

Characterizing subcritical assemblies with time of flight fixed by energy estimation distributions

NASA Astrophysics Data System (ADS)

Monterial, Mateusz; Marleau, Peter; Pozzi, Sara

2018-04-01

We present the Time of Flight Fixed by Energy Estimation (TOFFEE) as a measure of the fission chain dynamics in subcritical assemblies. TOFFEE is the time between correlated gamma rays and neutrons, subtracted by the estimated travel time of the incident neutron from its proton recoil. The measured subcritical assembly was the BeRP ball, a 4.482 kg sphere of α-phase weapons grade plutonium metal, which came in five configurations: bare, 0.5, 1, and 1.5 in iron, and 1 in nickel closed fitting shell reflectors. We extend the measurement with MCNPX-PoliMi simulations of shells ranging up to 6 inches in thickness, and two new reflector materials: aluminum and tungsten. We also simulated the BeRP ball with different masses ranging from 1 to 8 kg. A two-region and single-region point kinetics models were used to model the behavior of the positive side of the TOFFEE distribution from 0 to 100 ns. The single region model of the bare cases gave positive linear correlations between estimated and expected neutron decay constants and leakage multiplications. The two-region model provided a way to estimate neutron multiplication for the reflected cases, which correlated positively with expected multiplication, but the nature of the correlation (sub or superlinear) changed between material types. Finally, we found that the areal density of the reflector shells had a linear correlation with the integral of the two-region model fit. Therefore, we expect that with knowledge of reflector composition, one could determine the shell thickness, or vice versa. Furthermore, up to a certain amount and thickness of the reflector, the two-region model provides a way of distinguishing bare and reflected plutonium assemblies.

A fast method for optical simulation of flood maps of light-sharing detector modules.

PubMed

Shi, Han; Du, Dong; Xu, JianFeng; Moses, William W; Peng, Qiyu

2015-12-01

Optical simulation of the detector module level is highly desired for Position Emission Tomography (PET) system design. Commonly used simulation toolkits such as GATE are not efficient in the optical simulation of detector modules with complicated light-sharing configurations, where a vast amount of photons need to be tracked. We present a fast approach based on a simplified specular reflectance model and a structured light-tracking algorithm to speed up the photon tracking in detector modules constructed with polished finish and specular reflector materials. We simulated conventional block detector designs with different slotted light guide patterns using the new approach and compared the outcomes with those from GATE simulations. While the two approaches generated comparable flood maps, the new approach was more than 200-600 times faster. The new approach has also been validated by constructing a prototype detector and comparing the simulated flood map with the experimental flood map. The experimental flood map has nearly uniformly distributed spots similar to those in the simulated flood map. In conclusion, the new approach provides a fast and reliable simulation tool for assisting in the development of light-sharing-based detector modules with a polished surface finish and using specular reflector materials.

Highly accurate photogrammetric measurements of the Planck reflectors

NASA Astrophysics Data System (ADS)

Amiri Parian, Jafar; Gruen, Armin; Cozzani, Alessandro

2017-11-01

The Planck mission of the European Space Agency (ESA) is designed to image the anisotropies of the Cosmic Background Radiation Field over the whole sky. To achieve this aim, sophisticated reflectors are used as part of the Planck telescope receiving system. The system consists of secondary and primary reflectors which are sections of two different ellipsoids of revolution with mean diameters of 1 and 1.6 meters. Deformations of the reflectors which influence the optical parameters and the gain of receiving signals are investigated in vacuum and at very low temperatures. For this investigation, among the various high accuracy measurement techniques, photogrammetry was selected. With respect to the photogrammetric measurements, special considerations had to be taken into account in design steps, measurement arrangement and data processing to achieve very high accuracies. The determinability of additional parameters of the camera under the given network configuration, datum definition, reliability and precision issues as well as workspace limits and propagating errors from different sources are considered. We have designed an optimal photogrammetric network by heuristic simulation for the flight model of the primary and the secondary reflectors with relative precisions better than 1:1000'000 and 1:400'000 to achieve the requested accuracies. A least squares best fit ellipsoid method was developed to determine the optical parameters of the reflectors. In this paper we will report about the procedures, the network design and the results of real measurements.

Fine Mapping of Resistance Genes from Five Brown Stem Rot Resistance Sources in Soybean.

PubMed

Rincker, Keith; Hartman, Glen L; Diers, Brian W

2016-03-01

Brown stem rot (BSR) of soybean [ (L.) Merr.] caused by (Allington & Chamb.) T.C. Harr. & McNew can be controlled effectively with genetic host resistance. Three BSR resistance genes , , and , have been identified and mapped to a large region on chromosome 16. Marker-assisted selection (MAS) will be more efficient and gene cloning will be facilitated with a narrowed genomic interval containing an gene. The objective of this study was to fine map the positions of genes from five sources. Mapping populations were developed by crossing the resistant sources 'Bell', PI 84946-2, PI 437833, PI 437970, L84-5873, and PI 86150 with either the susceptible cultivar Colfax or Century 84. Plants identified as having a recombination event near genes were selected and individually harvested to create recombinant lines. Progeny from recombinant lines were tested in a root-dip assay and evaluated for foliar and stem BSR symptom development. Overall, 4878 plants were screened for recombination, and progeny from 52 recombinant plants were evaluated with simple-sequence repeat (SSR) genetic markers and assessed for symptom development. Brown stem rot resistance was mapped to intervals ranging from 0.34 to 0.04 Mb in the different sources. In all sources, resistance was fine mapped to intervals inclusive of BARCSOYSSR_16_1114 and BARCSOYSSR_16_1115, which provides further evidence that one locus provides BSR resistance in soybean. Copyright © 2016 Crop Science Society of America.

Extravehicular activity compatibility evaluation of developmental hardware for assembly and repair of precision reflectors

NASA Technical Reports Server (NTRS)

Heard, Walter L., Jr.; Lake, Mark S.; Bush, Harold G.; Jensen, J. Kermit; Phelps, James E.; Wallsom, Richard E.

1992-01-01

This report presents results of tests performed in neutral buoyancy by two pressure-suited test subjects to simulate Extravehicular Activity (EVA) tasks associated with the on-orbit construction and repair of a precision reflector spacecraft. Two complete neutral buoyancy assemblies of the test article (tetrahedral truss with three attached reflector panels) were performed. Truss joint hardware, two different panel attachment hardware concepts, and a panel replacement tool were evaluated. The test subjects found the operation and size of the truss joint hardware to be acceptable. Both panel attachment concepts were found to be EVA compatible, although one concept was judged by the test subjects to be considerably easier to operate. The average time to install a panel from a position within arm's reach of the test subjects was 1 min 14 sec. The panel replacement tool was used successfully to demonstrate the removal and replacement of a damaged reflector panel in 10 min 25 sec.

Standing wave acoustic levitation on an annular plate

NASA Astrophysics Data System (ADS)

Kandemir, Mehmet Hakan; Çalışkan, Mehmet

2016-11-01

In standing wave acoustic levitation technique, a standing wave is formed between a source and a reflector. Particles can be attracted towards pressure nodes in standing waves owing to a spring action through which particles can be suspended in air. This operation can be performed on continuous structures as well as in several numbers of axes. In this study an annular acoustic levitation arrangement is introduced. Design features of the arrangement are discussed in detail. Bending modes of the annular plate, known as the most efficient sound generation mechanism in such structures, are focused on. Several types of bending modes of the plate are simulated and evaluated by computer simulations. Waveguides are designed to amplify waves coming from sources of excitation, that are, transducers. With the right positioning of the reflector plate, standing waves are formed in the space between the annular vibrating plate and the reflector plate. Radiation forces are also predicted. It is demonstrated that small particles can be suspended in air at pressure nodes of the standing wave corresponding to a particular bending mode.

A SIMS Study of Sulfur Isotopes of Accessory Pyrites Associated with Barites from Methane Cold Seeps in the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Morelli, E. C.; Aharon, P.

2017-12-01

Bacteria and archaea associated with seeps can fix methane from sublimating gas hydrates through coupled bacterial sulfate reduction/ anaerobic methane oxidation (BSR/AMO) and prevent outgassing to the atmosphere. The occurrence of such microbial processes has been established on the basis of the sulfur isotope compositions of microbial byproducts (pyrites; FeS2) that reflect the degree of fractionation between SO4 and FeS2 via the production of the H2S intermediate phase. BSR/AMO coupling has been discerned in accessory sulfides associated with carbonates from gas hydrate sites. Whether BSR/AMO coupling is also active in barites, another ubiquitous product of gas hydrate sublimation, has so far been overlooked. Here we present results of a new sulfur isotope study of accessory sulfides in barites associated with gas hydrates at the threshold of stability occurring on the Gulf of Mexico slope. Using a fractionation factor of 1.009 and a seawater δ34SSO4 value of 20.3‰ and assuming a Rayleigh distillation closed system model for marine sulfide precipitation, pyrites from barite gas seeps are predicted to exhibit a range of δ34S values (about -1‰ to 20‰ CDT) as the pool of sulfate is continuously depleted. Actual δ34S values could fall outside of the predicted range because the system in question is likely only partially closed and kinetic fractionations are likely. δ34S of accessory pyrites from three Garden Banks Lease Block 382 (510 - 640m water depth) and one Mississippi Canyon Lease Block 929 (590m) barite samples have been determined using an ims-1290 Secondary Ion Mass Spectrometer (SIMS). Two Garden Banks samples and one Mississippi Canyon sample reveal a spread of values from 5.30 ± 0.04 to 25.90 ± 0.09 (‰ CDT), which follow the predicted trend for gas seeps and indicate the source of fractionation is likely from the coupled BSR/AMO process. One Garden Banks sample yields a wide spread of values from -26.2 ± 0.05 to 20.5 ± 0.4 (‰ CDT). The negative values are unexpected because such values typically suggest a sole contribution by BSR. This sample was the youngest (12.8 ± 0.6 yrs versus 21.5 ± 1.9 to 44.23 ± 2.92 yrs) at time of collection, and thus some of the negative values could reflect kinetic effects governed by the BSR pathway or anaerobic bacterial disproportionation (BDS) of elemental sulfur.

Development of optical ground verification method for μm to sub-mm reflectors

NASA Astrophysics Data System (ADS)

Stockman, Y.; Thizy, C.; Lemaire, P.; Georges, M.; Mazy, E.; Mazzoli, A.; Houbrechts, Y.; Rochus, P.; Roose, S.; Doyle, D.; Ulbrich, G.

2017-11-01

Large reflectors and antennas for the IR to mm wavelength range are being planned for many Earth observation and astronomical space missions and for commercial communication satellites as well. Scientific observatories require large telescopes with precisely shaped reflectors for collecting the electro-magnetic radiation from faint sources. The challenging tasks of on-ground testing are to achieve the required accuracy in the measurement of the reflector shapes and antenna structures and to verify their performance under simulated space conditions (vacuum, low temperatures). Due to the specific surface characteristics of reflectors operating in these spectral regions, standard optical metrology methods employed in the visible spectrum do not provide useful measurement results. The current state-of-the-art commercial metrology systems are not able to measure these types of reflectors because they have to face the measurement of shape and waviness over relatively large areas with a large deformation dynamic range and encompassing a wide range of spatial frequencies. 3-D metrology (tactile coordinate measurement) machines are generally used during the manufacturing process. Unfortunately, these instruments cannot be used in the operational environmental conditions of the reflector. The application of standard visible wavelength interferometric methods is very limited or impossible due to the large relative surface roughnesses involved. A small number of infrared interferometers have been commercially developed over the last 10 years but their applications have also been limited due to poor dynamic range and the restricted spatial resolution of their detectors. These restrictions affect also the surface error slopes that can be captured and makes their application to surfaces manufactured using CRFP honeycomb technologies rather difficult or impossible. It has therefore been considered essential, from the viewpoint of supporting future ESA exploration missions, to develop and realise suitable verification tools based on infrared interferometry and other optical techniques for testing large reflector structures, telescope configurations and their performances under simulated space conditions. Two methods and techniques are developed at CSL. The first one is an IR-phase shifting interferometer with high spatial resolution. This interferometer shall be used specifically for the verification of high precision IR, FIR and sub-mm reflector surfaces and telescopes under both ambient and thermal vacuum conditions. The second one presented hereafter is a holographic method for relative shape measurement. The holographic solution proposed makes use of a home built vacuum compatible holographic camera that allows displacement measurements from typically 20 nanometres to 25 microns in one shot. An iterative process allows the measurement of a total of up to several mm of deformation. Uniquely the system is designed to measure both specular and diffuse surfaces.

Simulation and experiment for the inspection of stainless steel bolts in servicing using an ultrasonic phased array

NASA Astrophysics Data System (ADS)

Chen, Jinzhong; He, Renyang; Kang, Xiaowei; Yang, Xuyun

2015-10-01

The non-destructive testing of small-sized (M12-M20) stainless steel bolts in servicing is always a technical problem. This article focuses on the simulation and experimental research of stainless steel bolts with an artificial defect reflector using ultrasonic phased array inspection. Based on the observation of the sound field distribution of stainless steel bolts in ultrasonic phased array as well as simulation modelling and analysis of the phased array probes' detection effects with various defect sizes, different artificial defect reflectors of M16 stainless steel bolts are machined in reference to the simulation results. Next, those bolts are tested using a 10-wafer phased array probe with 5 MHz. The test results finally prove that ultrasonic phased array can detect 1-mm cracks in diameter with different depths of M16 stainless steel bolts and a metal loss of Φ1 mm of through-hole bolts, which provides technical support for future non-destructive testing of stainless steel bolts in servicing.

Lunar surface structural concepts and construction studies

NASA Technical Reports Server (NTRS)

Mikulas, Martin

1991-01-01

The topics are presented in viewgraph form and include the following: lunar surface structures construction research areas; lunar crane related disciplines; shortcomings of typical mobile crane in lunar base applications; candidate crane cable suspension systems; NIST six-cable suspension crane; numerical example of natural frequency; the incorporation of two new features for improved performance of the counter-balanced actively-controlled lunar crane; lunar crane pendulum mechanics; simulation results; 1/6 scale lunar crane testbed using GE robot for global manipulation; basic deployable truss approaches; bi-pantograph elevator platform; comparison of elevator platforms; perspective of bi-pantograph beam; bi-pantograph synchronously deployable tower/beam; lunar module off-loading concept; module off-loader concept packaged; starburst deployable precision reflector; 3-ring reflector deployment scheme; cross-section of packaged starburst reflector; and focal point and thickness packaging considerations.

Magnetically tunable graphene-based reflector under linear polarized incidence at room temperature

NASA Astrophysics Data System (ADS)

Yang, Liang; Tian, Jing; Giddens, Henry; Poumirol, Jean-Marie; Wu, JingBo; Kuzmenko, Alexey B.; Hao, Yang

2018-04-01

At the terahertz spectrum, the 2D material graphene has diagonal and Hall conductivities in the presence of a magnetic field. These peculiar properties provide graphene-based structures with a magnetically tunable response to electromagnetic waves. In this work, the absolute reflection intensity was measured for a graphene-based reflector illuminated by linearly polarized incident waves at room temperature, which demonstrated the intensity modulation depth (IMD) under different magnetostatic biases by up to 15%. Experimental data were fitted and analyzed by a modified equivalent circuit model. In addition, as an important phenomenon of the graphene gyrotropic response, Kerr rotation is discussed according to results achieved from full-wave simulations. It is concluded that the IMD is reduced for the best Kerr rotation in the proposed graphene-based reflector.

Novel back-reflector architecture with nanoparticle based buried light-scattering microstructures for improved solar cell performance

NASA Astrophysics Data System (ADS)

Desta, Derese; Ram, Sanjay K.; Rizzoli, Rita; Bellettato, Michele; Summonte, Caterina; Jeppesen, Bjarke R.; Jensen, Pia B.; Tsao, Yao-Chung; Wiggers, Hartmut; Pereira, Rui N.; Balling, Peter; Larsen, Arne Nylandsted

2016-06-01

A new back-reflector architecture for light-management in thin-film solar cells is proposed that includes a morphologically smooth top surface with light-scattering microstructures buried within. The microstructures are pyramid shaped, fabricated on a planar reflector using TiO2 nanoparticles and subsequently covered with a layer of Si nanoparticles to obtain a flattened top surface, thus enabling growth of good quality thin-film solar cells. The optical properties of this back-reflector show high broadband haze parameter and wide angular distribution of diffuse light-scattering. The n-i-p amorphous silicon thin-film solar cells grown on such a back-reflector show enhanced light absorption resulting in improved external quantum efficiency. The benefit of the light trapping in those solar cells is evidenced by the gains in short-circuit current density and efficiency up to 15.6% and 19.3% respectively, compared to the reference flat solar cells. This improvement in the current generation in the solar cells grown on the flat-topped (buried pyramid) back-reflector is observed even when the irradiation takes place at large oblique angles of incidence. Finite-difference-time-domain simulation results of optical absorption and ideal short-circuit current density values agree well with the experimental findings. The proposed approach uses a low cost and simple fabrication technique and allows effective light manipulation by utilizing the optical properties of micro-scale structures and nanoscale constituent particles.

The Science of Inaccurate Temperatures: Explaining How the Bahamas Did Not Form in a Jacuzzi

NASA Astrophysics Data System (ADS)

Murray, S.; Swart, P. K.; McNeill, D. F.

2016-12-01

The Bahamas archipelago is a carbonate platform that formed in the warm waters of the Gulf Stream current. Using clumped isotope paleothermometry, it has been shown that carbonates extending back through the Miocene taken from cores throughout the Bahamas have all precipitated from fluids at temperatures similar to what is found in the Bahamas in the present day (15 to 35°C). However, in a single core, (Clino), collected off the western edge of Great Bahama Bank, Δ47 values have been measured which suggest formation at significantly warmer temperatures (42 to 53°C). These values are present in spite of the fact that the sediments have never been deeply buried. In a parallel study, these same cores were measured for their carbonate associated sulfate (CAS). The only core that presented evidence of elevated CAS, indicative of bacterial sulfate reduction (BSR), was the Clino core. In this core the clumped isotope temperatures are correlated with changes in the δ34S of the CAS. This finding suggests that BSR can have a significant effect on the Δ47 value producing erroneous temperatures. This is further supported by examining a carbonate concretion with extreme negative δ13C values (-30‰) taken as evidence of BSR. The clumped isotope temperatures in this nodule are elevated relative to its burial history with an increase of 15 °C from the outer edge of the concretion to the center. The increase in temperature correlates well with the decreasing δ13C suggesting increasing fractionation associated with BSR is directly impacting the clumped isotope measurements.

High aperture efficiency symmetric reflector antennas with up to 60 deg field of view

NASA Astrophysics Data System (ADS)

Rappaport, Carey M.; Craig, William P.

1991-03-01

A microwave single-reflector scanning antenna derived from an ellipse (rather than the usual parabola) which gives a much greater field of view is presented. This reflector combines reasonable scanning in one plane with good focusing in the other, and its scanning ability is superior to the torus and other single reflectors because it has much greater aperture efficiency and is thus smaller while having the same performance. The reflector surface is derived in two steps: a fourth-order even polynomial profile curve in the scan plane is found using least squares to minimize the scanned ray errors; then even polynomial terms in x and y that minimize astigmatism for both the unscanned and maximally scanned beams are added to form the three-dimensional surface. Numerical simulations of radiation patterns for a variety of antenna diameter and field-of-view cases give excellent results. The 60 deg scan case with 30-lambda-diameter aperture has only 0.2-dB peak gain deviation from ideal and first sidelobe levels below 14 dB down from peak gain. The 17 deg, 500-lambda case has only 0.8-dB gain variation and -14 to -11 dB sidelobe levels for approximately +/-68 beamwidths of scan, with focal length to aperture diameter ratio equal to about one.

A fast method for optical simulation of flood maps of light-sharing detector modules

PubMed Central

Shi, Han; Du, Dong; Xu, JianFeng; Moses, William W.; Peng, Qiyu

2016-01-01

Optical simulation of the detector module level is highly desired for Position Emission Tomography (PET) system design. Commonly used simulation toolkits such as GATE are not efficient in the optical simulation of detector modules with complicated light-sharing configurations, where a vast amount of photons need to be tracked. We present a fast approach based on a simplified specular reflectance model and a structured light-tracking algorithm to speed up the photon tracking in detector modules constructed with polished finish and specular reflector materials. We simulated conventional block detector designs with different slotted light guide patterns using the new approach and compared the outcomes with those from GATE simulations. While the two approaches generated comparable flood maps, the new approach was more than 200–600 times faster. The new approach has also been validated by constructing a prototype detector and comparing the simulated flood map with the experimental flood map. The experimental flood map has nearly uniformly distributed spots similar to those in the simulated flood map. In conclusion, the new approach provides a fast and reliable simulation tool for assisting in the development of light-sharing-based detector modules with a polished surface finish and using specular reflector materials. PMID:27660376

A fast method for optical simulation of flood maps of light-sharing detector modules

DOE PAGES

Shi, Han; Du, Dong; Xu, JianFeng; ...

2015-09-03

Optical simulation of the detector module level is highly desired for Position Emission Tomography (PET) system design. Commonly used simulation toolkits such as GATE are not efficient in the optical simulation of detector modules with complicated light-sharing configurations, where a vast amount of photons need to be tracked. Here, we present a fast approach based on a simplified specular reflectance model and a structured light-tracking algorithm to speed up the photon tracking in detector modules constructed with polished finish and specular reflector materials. We also simulated conventional block detector designs with different slotted light guide patterns using the new approachmore » and compared the outcomes with those from GATE simulations. And while the two approaches generated comparable flood maps, the new approach was more than 200–600 times faster. The new approach has also been validated by constructing a prototype detector and comparing the simulated flood map with the experimental flood map. The experimental flood map has nearly uniformly distributed spots similar to those in the simulated flood map. In conclusion, the new approach provides a fast and reliable simulation tool for assisting in the development of light-sharing-based detector modules with a polished surface finish and using specular reflector materials.« less

Monte Carlo Analysis of the Battery-Type High Temperature Gas Cooled Reactor

NASA Astrophysics Data System (ADS)

Grodzki, Marcin; Darnowski, Piotr; Niewiński, Grzegorz

2017-12-01

The paper presents a neutronic analysis of the battery-type 20 MWth high-temperature gas cooled reactor. The developed reactor model is based on the publicly available data being an `early design' variant of the U-battery. The investigated core is a battery type small modular reactor, graphite moderated, uranium fueled, prismatic, helium cooled high-temperature gas cooled reactor with graphite reflector. The two core alternative designs were investigated. The first has a central reflector and 30×4 prismatic fuel blocks and the second has no central reflector and 37×4 blocks. The SERPENT Monte Carlo reactor physics computer code, with ENDF and JEFF nuclear data libraries, was applied. Several nuclear design static criticality calculations were performed and compared with available reference results. The analysis covered the single assembly models and full core simulations for two geometry models: homogenous and heterogenous (explicit). A sensitivity analysis of the reflector graphite density was performed. An acceptable agreement between calculations and reference design was obtained. All calculations were performed for the fresh core state.

Monolithic integration of elliptic-symmetry diffractive optical element on silicon-based 45 degrees micro-reflector.

PubMed

Lan, Hsiao-Chin; Hsiao, Hsu-Liang; Chang, Chia-Chi; Hsu, Chih-Hung; Wang, Chih-Ming; Wu, Mount-Learn

2009-11-09

A monolithically integrated micro-optical element consisting of a diffractive optical element (DOE) and a silicon-based 45 degrees micro-reflector is experimentally demonstrated to facilitate the optical alignment of non-coplanar fiber-to-fiber coupling. The slanted 45 degrees reflector with a depth of 216 microm is fabricated on a (100) silicon wafer by anisotropic wet etching. The DOE with a diameter of 174.2 microm and a focal length of 150 microm is formed by means of dry etching. Such a compact device is suitable for the optical micro-system to deflect the incident light by 90 degrees and to focus it on the image plane simultaneously. The measured light pattern with a spot size of 15 microm has a good agreement with the simulated result of the elliptic-symmetry DOE with an off-axis design for eliminating the strongly astigmatic aberration. The coupling efficiency is enhanced over 10-folds of the case without a DOE on the 45 degrees micro-reflector. This device would facilitate the optical alignment of non-coplanar light coupling and further miniaturize the volume of microsystem.

Choice of crystal surface finishing for a dual-ended readout depth-of-interaction (DOI) detector.

PubMed

Fan, Peng; Ma, Tianyu; Wei, Qingyang; Yao, Rutao; Liu, Yaqiang; Wang, Shi

2016-02-07

The objective of this study was to choose the crystal surface finishing for a dual-ended readout (DER) DOI detector. Through Monte Carlo simulations and experimental studies, we evaluated 4 crystal surface finishing options as combinations of crystal surface polishing (diffuse or specular) and reflector (diffuse or specular) options on a DER detector. We also tested one linear and one logarithm DOI calculation algorithm. The figures of merit used were DOI resolution, DOI positioning error, and energy resolution. Both the simulation and experimental results show that (1) choosing a diffuse type in either surface polishing or reflector would improve DOI resolution but degrade energy resolution; (2) crystal surface finishing with a diffuse polishing combined with a specular reflector appears a favorable candidate with a good balance of DOI and energy resolution; and (3) the linear and logarithm DOI calculation algorithms show overall comparable DOI error, and the linear algorithm was better for photon interactions near the ends of the crystal while the logarithm algorithm was better near the center. These results provide useful guidance in DER DOI detector design in choosing the crystal surface finishing and DOI calculation methods.

Operating manual for the Bulk Shielding Reactor

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

Not Available

1983-04-01

The BSR is a pool-type reactor. It has the capabilities of continuous operation at a power level of 2 MW or at any desired lower power level. This manual presents descriptive and operational information. The reactor and its auxillary facilities are described from physical and operational viewpoints. Detailed operating procedures are included which are applicable from source-level startup to full-power operation. Also included are procedures relative to the safety of personnel and equipment in the areas of experiments, radiation and contamination control, emergency actions, and general safety. This manual supercedes all previous operating manuals for the BSR.

Operating manual for the Bulk Shielding Reactor

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

Not Available

1987-03-01

The BSR is a pool-type reactor. It has the capabilities of continuous operation at a power level of 2 MW or at any desired lower power level. This manual presents descriptive and operational information. The reactor and its auxiliary facilities are described from physical and operational viewpoints. Detailed operating procedures are included which are applicable from source-level startup to full-power operation. Also included are procedures relative to the safety of personnel and equipment in the areas of experiments, radiation and contamination control, emergency actions, and general safety. This manual supersedes all previous operating manuals for the BSR.

A perfect Fresnel acoustic reflector implemented by a Fano-resonant metascreen

NASA Astrophysics Data System (ADS)

Amin, M.; Siddiqui, O.; Farhat, M.; Khelif, A.

2018-04-01

We propose a perfectly reflecting acoustic metasurface which is designed by replacing the curved segments of the traditional Fresnel reflector by flat Fano-resonant sub-wavelength unit cells. To preserve the original Fresnel focusing mechanism, the unit cell phase follows a specific phase profile which is obtained by applying the generalized Snell's law and Fermat's principle. The reflected curved phase fronts are thus created at the air-metasurface boundary by tailoring the metasurface dispersion as dictated by Huygens' principle. Since the unit cells are implemented by sub-wavelength double slit-shaped cavity resonators, the impinging sound waves are perfectly reflected producing acoustic focusing with negligible absorption. We use plane-wave solution and full-wave simulations to demonstrate the focusing effects. The simulation results closely follow the analytical predictions.

Two-state semiconductor laser self-mixing velocimetry exploiting coupled quantum-dot emission-states: experiment, simulation and theory

PubMed Central

Gioannini, Mariangela; Dommermuth, Marius; Drzewietzki, Lukas; Krestnikov, Igor; Livshits, Daniil; Krakowski, Michel; Breuer, Stefan

2014-01-01

We exploit the coupled emission-states of a single-chip semiconductor InAs/GaAs quantum-dot laser emitting simultaneously on ground-state (λGS = 1245 nm) and excited-state (λES = 1175 nm) to demonstrate coupled-two-state self-mixing velocimetry for a moving diffuse reflector. A 13 Hz-narrow Doppler beat frequency signal at 317 Hz is obtained for a reflector velocity of 3 mm/s, which exemplifies a 66-fold improvement in width as compared to single-wavelength self-mixing velocimetry. Simulation results reveal the physical origin of this signal, the coupling of excited-state and ground-state photons via the carriers, which is unique for quantum-dot lasers and reproduce the experimental results with excellent agreement. PMID:25321809

The precision segmented reflectors: Moderate mission figure control subsystem

NASA Technical Reports Server (NTRS)

Sevaston, G.; Redding, D.; Lau, K.; Breckenridge, W.; Levine, B.; Nerheim, N.; Sirlin, S.; Kadogawa, H.

1991-01-01

A system concept for a space based segmented reflector telescope figure control subsystem is described. The concept employs a two phase architecture in which figure initialization and figure maintenance are independent functions. Figure initialization is accomplished by image sharpening using natural reference targets. Figure maintenance is performed by monitoring the relative positions and alignments of the telescope components using an optical truss. Actuation is achieved using precision positioners. Computer simulation results of figure initialization by pairwise segment coalignment/cophasing and simulated annealing are presented along with figure maintenance results using a wavefront error regulation algorithm. Both functions are shown to perform at acceptable levels for the class of submillimeter telescopes that are serving as the focus of this technology development effort. Component breadboard work as well as plans for a system testbed are discussed.

Sub-wavelength grating structure on the planar waveguide (Conference Presentation)

NASA Astrophysics Data System (ADS)

Qing-Song, Zhu; Sheng-Hui, Chen

2016-10-01

Making progress in recent years, with the technology of the grating, the grating period can be reduced to shrink the size of the light coupler on a waveguide. The working wavelength of the light coupler can be in the range from the near-infrared to visible. In this study , we used E-gun evaporation system with ion-beam-assisted deposition system to fabricate bottom cladding (SiO2), guiding layer (Ta2O5) and Distributed Bragg Reflector(DBR) of the waveguide on the silicon substrate. Electron-beam lithography is used to make sub-wavelength gratings and reflector grating on the planar waveguide which is a coupling device on the guiding layer. The best fabrication parameters were analyzed to deposit the film. The exposure and development times also influenced to fabricate the grating quality. The purpose is to reduce the device size and enhance coupling efficiency which maintain normal incidence of the light . We designed and developed the device using the Finite-Difference Time-Domain (FDTD) method. The grating period, depth, fill factor, film thickness, Distributed Bragg Reflector(DBR) numbers and reflector grating period have been discussed to enhance coupling efficiency and maintained normal incidence of the light. According to the simulation results, when the wavelength is 1300 nm, the coupling grating period is 720 nm and the Ta2O5 film is 460 nm with 360 nm of reflector grating period and 2 layers of Distributed Bragg Reflector, which had the optimum coupling efficiency and normal incidence angle. In the measurement, We successfully measured the TE wave coupling efficiency of the photoresist grating coupling device.

Is Slow-Onset Long-Acting Monoamine Transport Blockade to Cocaine as Methadone is to Heroin? Implication for Anti-Addiction Medications

PubMed Central

Peng, Xiao-Qing; Xi, Zheng-Xiong; Li, Xia; Spiller, Krista; Li, Jie; Chun, Lauren; Wu, Kuo-Ming; Froimowitz, Mark; Gardner, Eliot L

2010-01-01

The success of methadone in treating opiate addiction has suggested that long-acting agonist therapies may be similarly useful for treating cocaine addiction. Here, we examined this hypothesis, using the slow-onset long-acting monoamine reuptake inhibitor 31,345, a trans-aminotetralin analog, in a variety of addiction-related animal models, and compared it with methadone's effects on heroin's actions in the same animal models. Systemic administration of 31,345 produced long-lasting enhancement of electrical brain-stimulation reward (BSR) and extracellular nucleus accumbens (NAc) dopamine (DA). Pretreatment with 31,345 augmented cocaine-enhanced BSR, prolonged cocaine-enhanced NAc DA, and produced a long-term (24-48 h) reduction in cocaine self-administration rate without obvious extinction pattern, suggesting an additive effect of 31,345 with cocaine. In contrast, methadone pretreatment not only dose-dependently inhibited heroin self-administration with an extinction pattern but also dose-dependently inhibited heroin-enhanced BSR and NAc DA, suggesting functional antagonism by methadone of heroin's actions. In addition, 31,345 appears to possess significant abuse liability, as it produces dose-dependent enhancement of BSR and NAc DA, maintains a low rate of self-administration behavior, and dose-dependently reinstates drug-seeking behavior. In contrast, methadone only partially maintains self-administration with an extinction pattern, and fails to induce reinstatement of drug-seeking behavior. These findings suggest that 31,345 is a cocaine-like slow-onset long-acting monoamine transporter inhibitor that may act as an agonist therapy for cocaine addiction. However, its pattern of action appears to be significantly different from that of methadone. Ideal agonist substitutes for cocaine should fully emulate methadone's actions, that is, functionally antagonizing cocaine's action while blocking monoamine transporters to augment synaptic DA. PMID:20827272

Evidence-based management of systemic sclerosis: Navigating recommendations and guidelines.

PubMed

Pellar, Russell Edward; Pope, Janet Elizabeth

2017-06-01

Systemic sclerosis (SSc) is a rare heterogeneous connective tissue disease. Recommendations addressing the major issues in the management of SSc including screening and treatment of organ complications are needed. The updated European League Against Rheumatism/European Scleroderma Trial and Research (EULAR/EUSTAR) and the British Society of Rheumatology (BSR) and British Health Professionals in Rheumatology (BHPR) guidelines were compared and contrasted. The updated EULAR/EUSTAR guidelines focus specifically on the management of SSc features and include data on newer therapeutic modalities and mention a research agenda. These recommendations are pharmacologic, with few guidelines regarding investigations and non-pharmacologic management. Recommendations from BSR/BHPR are similar to the organ manifestations mentioned in the EULAR/EUSTAR recommendations, and expand on several domains of treatment, including general measures, non-pharmacologic treatment, cardiac involvement, calcinosis, and musculoskeletal features. The guidelines usually agree with one another. Limitations include the lack of guidance for combination or second-line therapy, algorithmic suggestions, the absence of evidence-based recommendations regarding the treatment of specific complications (i.e., gastric antral ectasia and erectile dysfunction). Consensus for when to treat interstitial lung disease in SSc is lacking. There are differences between Europe and North American experts due to access and indications for certain therapies. Care gaps in SSc have been demonstrated so the EULAR/EUSTAR and BSR/BHP guidelines can promote best practices. Certain complications warrant active investigation to further improve outcomes in SSc and future updates of these recommendations. Care gaps in SSc have been demonstrated so the EULAR/EUSTAR and BSR/BHP guidelines can promote best practices. Certain complications warrant active investigation to further improve outcomes in SSc. Copyright © 2017 Elsevier Inc. All rights reserved.

Spatial statistical analysis of basal stem root disease under natural field epidemic of oil palm

NASA Astrophysics Data System (ADS)

Kamu, Assis; Phin, Chong Khim; Seman, Idris Abu; Wan, Hoong Hak; Mun, Ho Chong

2015-02-01

Oil palm or scientifically known as Elaeis guineensis Jacq. is the most important commodity crop in Malaysia and has greatly contributed to the economy growth of the country. As far as disease is concerned in the industry, Basal Stem Rot (BSR) caused by Ganoderma boninence remains the most important disease. BSR disease is the most widely studied with information available for oil palm disease in Malaysia. However, there is still limited study on the spatial as well as temporal pattern or distribution of the disease especially under natural field epidemic condition in oil palm plantation. The objective of this study is to spatially identify the pattern of BSR disease under natural field epidemic using two geospatial analytical techniques, which are quadrat analysis for the first order properties of partial pattern analysis and nearest-neighbor analysis (NNA) for the second order properties of partial pattern analysis. Two study sites were selected with different age of tree. Both sites are located in Tawau, Sabah and managed by the same company. The results showed that at least one of the point pattern analysis used which is NNA (i.e. the second order properties of partial pattern analysis) has confirmed the disease is complete spatial randomness. This suggests the spread of the disease is not from tree to tree and the age of palm does not play a significance role in determining the spatial pattern of the disease. From the spatial pattern of the disease, it would help in the disease management program and for the industry in the future. The statistical modelling is expected to help in identifying the right model to estimate the yield loss of oil palm due to BSR disease in the future.

Fabrication and characterization of TiO2/SiO2 based Bragg reflectors for light trapping applications

NASA Astrophysics Data System (ADS)

Dubey, R. S.; Ganesan, V.

Distributed Bragg reflectors (DBRs) have received an intensive attention due to their increasing demand in optoelectronic and photonic devices. Such reflectors are capable to prohibit the light propagation within the specified wavelength range of interest. In this paper, we present the fabrication of TiO2/SiO2 stacks based Bragg reflectors by using a simple and in-expensive sol-gel spin coating technique. The prepared single-layer thin films of TiO2 and SiO2 onto glass substrates were characterized for their optical constants. By tuning the process parameters, one-seven DBR stacks of TiO2/SiO2 were prepared. The corresponding shift of the Bragg reflection peak was observed with the increased number of DBR stacks and as much as about 90% reflectance is observed from the 7DBR stacks. The experimentally measured reflectance was compared with the simulated one, which showed good in agreement. FESEM measurement has confirmed the formation of bright and dark strips of TiO2 and SiO2 films with their thicknesses 80 and 115 nm respectively. The simulation study was explored to a design of thin film silicon solar cell using 7DBR stacks. An enhancement in light absorption in the visible wavelength range is observed which coincides with the experimental result of the reflectance. The use of DBR at the bottom of the solar cell could felicitate the better light harvesting with the occurrence of Fabry-Perot resonances in the absorbing layer.

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

DTIC Science & Technology

2016-01-22

Numerical electromagnetic simulations based on the multilevel fast multipole method (MLFMM) were used to analyze and optimize the antenna...and are not necessarily endorsed by the United States Government. numerical simulations with the multilevel fast multipole method (MLFMM...and optimized using numerical simulations conducted with the multilevel fast multipole method (MLFMM) using FEKO software (www.feko.info). The

Design and analysis of reflector for uniform light-emitting diode illuminance.

PubMed

Tsai, Chung-Yu

2013-05-01

A light-emitting diode (LED) projection system is proposed, composed of an LED chip and a variable-focus-parabolic (VFP) reflector, in which the focal length varies as a function of the vertical displacement of the incidence point relative to the horizontal centerline of the LED chip. The light-ray paths within the projection system are analyzed using an exact analytical model and a skew-ray tracing approach. The profile of the proposed VFP reflector and the position of the LED chip are then optimized in such a way as to enhance the uniformity of the illuminance distribution on the target region of the image plane. The validity of the optimized design is demonstrated by means of ZEMAX simulations. It is shown that the optimized VFP projector system yields a significant improvement in illuminance uniformity compared to conventional spherical and parabolic projectors and therefore minimizes the glare effect.

Broadband Integrated Lens for Illuminating Reflector Antenna With Constant Aperture Efficiency

NASA Astrophysics Data System (ADS)

Fernandes, Carlos A.; Lima, Eduardo B.; Costa, Jorge R.

2010-12-01

A new integrated shaped lens antenna configuration is described with frequency stable radiation pattern and phase center position across a broad 1:3 frequency band, which can be used for focal plane reflector feeding in quasi-optical radio telescope systems. The lens is compatible with the integration of ultrawideband uniplanar printed feeds at its base and equally broadband mixing devices, like the Hot Electron Bolometer (HEB), although these are not used in the present work. Measurements on a scaled mm-wave lab prototype have confirmed stable performance versus frequency, with only dB directivity variation, and better than 94% Gaussicity, thanks to the possibility to impose a predefined output radiation pattern template. Simulations were performed to test the illumination of an off-set parabolic reflector by the lens radiation pattern, which confirmed reasonably constant aperture efficiency in the order of 78% across the 100% bandwidth.

Human postural responses to motion of real and virtual visual environments under different support base conditions.

PubMed

Mergner, T; Schweigart, G; Maurer, C; Blümle, A

2005-12-01

The role of visual orientation cues for human control of upright stance is still not well understood. We, therefore, investigated stance control during motion of a visual scene as stimulus, varying the stimulus parameters and the contribution from other senses (vestibular and leg proprioceptive cues present or absent). Eight normal subjects and three patients with chronic bilateral loss of vestibular function participated. They stood on a motion platform inside a cabin with an optokinetic pattern on its interior walls. The cabin was sinusoidally rotated in anterior-posterior (a-p) direction with the horizontal rotation axis through the ankle joints (f=0.05-0.4 Hz; A (max)=0.25 degrees -4 degrees ; v (max)=0.08-10 degrees /s). The subjects' centre of mass (COM) angular position was calculated from opto-electronically measured body sway parameters. The platform was either kept stationary or moved by coupling its position 1:1 to a-p hip position ('body sway referenced', BSR, platform condition), by which proprioceptive feedback of ankle joint angle became inactivated. The visual stimulus evoked in-phase COM excursions (visual responses) in all subjects. (1) In normal subjects on a stationary platform, the visual responses showed saturation with both increasing velocity and displacement of the visual stimulus. The saturation showed up abruptly when visually evoked COM velocity and displacement reached approximately 0.1 degrees /s and 0.1 degrees , respectively. (2) In normal subjects on a BSR platform (proprioceptive feedback disabled), the visual responses showed similar saturation characteristics, but at clearly higher COM velocity and displacement values ( approximately 1 degrees /s and 1 degrees , respectively). (3) In patients on a stationary platform (no vestibular cues), the visual responses were basically similar to those of the normal subjects, apart from somewhat higher gain values and less-pronounced saturation effects. (4) In patients on a BSR platform (no vestibular and proprioceptive cues, presumably only somatosensory graviceptive and visual cues), the visual responses showed an abnormal increase in gain with increasing stimulus frequency in addition to a displacement saturation. On the normal subjects we performed additional experiments in which we varied the gain of the visual response by using a 'virtual reality' visual stimulus or by applying small lateral platform tilts. This did not affect the saturation characteristics of the visual response to a considerable degree. We compared the present results to previous psychophysical findings on motion perception, noting similarities of the saturation characteristics in (1) with leg proprioceptive detection thresholds of approximately 0.1 degrees /s and 0.1 degrees and those in (2) with vestibular detection thresholds of 1 degrees /s and 1 degrees , respectively. From the psychophysical data one might hypothesise that a proprioceptive postural mechanism limits the visually evoked body excursions if these excursions exceed 0.1 degrees /s and 0.1 degrees in condition (1) and that a vestibular mechanism is doing so at 1 degrees /s and 1 degrees in (2). To better understand this, we performed computer simulations using a posture control model with multiple sensory feedbacks. We had recently designed the model to describe postural responses to body pull and platform tilt stimuli. Here, we added a visual input and adjusted its gain to fit the simulated data to the experimental data. The saturation characteristics of the visual responses of the normals were well mimicked by the simulations. They were caused by central thresholds of proprioceptive, vestibular and somatosensory signals in the model, which, however, differed from the psychophysical thresholds. Yet, we demonstrate in a theoretical approach that for condition (1) the model can be made monomodal proprioceptive with the psychophysical 0.1 degrees /s and 0.1 degrees thresholds, and for (2) monomodal vestibular with the psychophysical 1 degrees /s and 1 degrees thresholds, and still shows the corresponding saturation characteristics (whereas our original model covers both conditions without adjustments). The model simulations also predicted the almost normal visual responses of patients on a stationary platform and their clearly abnormal responses on a BSR platform.

Multi-element array signal reconstruction with adaptive least-squares algorithms

NASA Technical Reports Server (NTRS)

Kumar, R.

1992-01-01

Two versions of the adaptive least-squares algorithm are presented for combining signals from multiple feeds placed in the focal plane of a mechanical antenna whose reflector surface is distorted due to various deformations. Coherent signal combining techniques based on the adaptive least-squares algorithm are examined for nearly optimally and adaptively combining the outputs of the feeds. The performance of the two versions is evaluated by simulations. It is demonstrated for the example considered that both of the adaptive least-squares algorithms are capable of offsetting most of the loss in the antenna gain incurred due to reflector surface deformations.

Correlation Between Geological Stuctures and Gas Hydrate amount Offshore the South Shetland Island — Preliminary Results

NASA Astrophysics Data System (ADS)

Loreto, M. F.; Tinivella, U.; Accaino, F.; Giustiniani, M.

2010-05-01

Sediments of the accretionary prism, present along the continental margin of the Peninsula Antarctica SW of Elephant Island, are filled by gas hydrates as evidenced by a strong BSR. A multidisciplinary geophysical dataset, represented by seismic data, multibeam, chirp profiles, CTD and core samples, was acquired during three oceanographic cruises. The estimation of gas hydrate and free gas concentrations is based on the P-wave velocity analysis. In order to extract a detailed and reliable velocity field, we have developed and optimized a procedure that includes the pre-stack depth migration to determine, iteratively and with a layer stripping approach method, the velocity field and the depth-migrated seismic section. The final velocity field is then translated in terms of gas hydrate and free gas amounts by using theoretical approaches. Several seismic sections have been processed in the investigated area. The final 2D velocity sections have been translated in gas-phase concentration sections, considering the gas distribution within sediments both uniformly and patchly distributed. The free gas layer is locally present and, consequently, the base of the free gas reflector was identified only in some lines or part of them. The hydrate layer shows important lateral variations of hydrate concentration in correspondence of geological features, such as faults and folds. The intense fluid migration along faults and different fluid accumulation in correspondence of geological structures can control the gas hydrate concentration and modify the geothermal field in the surrounding area.

Multiple-Band Linear-Polarization Conversion and Circular Polarization in Reflection Mode Using a Symmetric Anisotropic Metasurface

NASA Astrophysics Data System (ADS)

Lin, Bao-Qin; Guo, Jian-Xin; Chu, Peng; Huo, Wen-Jun; Xing, Zhuo; Huang, Bai-Gang; Wu, Lan

2018-02-01

In this work, we propose a multiband linear-polarization (LP) conversion and circular polarization (CP) maintaining reflector using a symmetric anisotropic metasurface. The anisotropic metasurface is composed of a square array of a two-corner-cut square multiring disk printed on a grounded dielectric substrate, which is a symmetric structure with a pair of mutually perpendicular symmetric axes u and v along the ±45 ° directions with respect to the y -axis direction. The simulated results show that the reflector can realize LP conversion in five frequency bands at both x - and y -polarized incidence, the first four bands all have a certain bandwidth, and the fourth one, especially, is an ultrawideband. In addition, because of the symmetry of the reflector structure, the polarization state of a CP wave can be maintained after reflection, and the magnitude of the copolarized reflection coefficient at the CP incidence is just equal to that of the cross-polarized reflection coefficient at the x - and y -polarized incidence. We analyze the root cause of the multiband LP conversion and CP maintaining reflection, and carry out one experiment to verify the proposed reflector.

High-output LED-based light engine for profile lighting fixtures with high color uniformity using freeform reflectors.

PubMed

Gadegaard, Jesper; Jensen, Thøger Kari; Jørgensen, Dennis Thykjær; Kristensen, Peter Kjær; Søndergaard, Thomas; Pedersen, Thomas Garm; Pedersen, Kjeld

2016-02-20

In the stage lighting and entertainment market, light engines (LEs) for lighting fixtures are often based on high-intensity discharge (HID) bulbs. Switching to LED-based light engines gives possibilities for fast switching, additive color mixing, a longer lifetime, and potentially, more energy-efficient systems. The lumen output of a single LED is still not sufficient to replace an HID source in high-output profile fixtures, but combining multiple LEDs can create an LE with a similar output, but with added complexity. This paper presents the results of modeling and testing such a light engine. Custom ray-tracing software was used to design a high-output red, green and blue LED-based light engine with twelve CBT-90 LEDs using a dual-reflector principle. The simulated optical system efficiency was 0.626 with a perfect (R=1) reflector coating for light delivered on a target surface through the entire optical system. A profile lighting fixture prototype was created, and provided an output of 6744 lumen and an efficiency of 0.412. The lower efficiency was mainly due to a non-optimal reflector coating, and the optimized design is expected to reach a significantly higher efficiency.

Evaluation of the first simulation tool to quantitatively interpret the measurements of the ExoMars mission's Wisdom GPR

NASA Astrophysics Data System (ADS)

Dorizon, Sophie; Ciarletti, Valérie

2013-04-01

The Water Ice Sub-surface Deposits Observation on Mars (WISDOM) (500MHz - 3GHz) GPR is one of the instruments that have been selected as part of the Pasteur payload of ESA's 2018 ExoMars Rover mission. One of the main scientific objectives of the mission is to characterize the nature of the shallow sub-surface on Mars and WISDOM has been designed to explore the first 3 meters of the sub-surface with a vertical resolution of a few centimetres. Laboratory and field tests using the prototype developed for the ExoMars mission by LATMOS (Laboratoire Atmosphère, Milieux, Observations Spatiales) in collaboration with the AOB (Bordeaux) and the university of Dresden (Germany) are regularly performed to assess and improve the radar performances. In order to quantitatively interpret the experimental data obtained, we developed a simulation tool based on ray-tracing. This code proves to be a fast practical way even if simplified to help radargrams interpretation. The WISDOM GPR, unlike most traditional GPRs, is operated approximately 30 centimetres above the surface. This configuration implies that the propagation between the antenna and the surface cannot be neglected especially because the instrument's aim is to characterise the very shallow subsurface. As a consequence, while we can draw advantage of this specific configuration by using the surface echo's amplitude to retrieve information about the top layer's roughness and permittivity value, precise location of buried reflector becomes more complicated. Indeed, the signature distinctive of individual reflectors buried in the sub-surface is not more an exact mathematical hyperbola. When the individual reflector is buried deep enough in the subsurface, the adjustment by an hyperbolic function still allows the retrieval of the reflector's location and the permittivity value of the surrounding medium. But in case of a reflector closer to the surface, the approximation is no longer valid. We propose a robust model adjustment that can be used for any reflector's depth. The physical assumptions taken into account are presented. Finally, results for different configurations and the validation of the limit conditions for which this adjustment method is reliable are shown. Preliminary analyzes on real data show the good performance of the method developed. Other modelling techniques will be considered to complete a full data interpretation taking the best from the instrument capacities

Carbon isotopes of benthic foraminifera associated with methane seeps in Four-Way Closure Ridge, offshore southwestern Taiwan

NASA Astrophysics Data System (ADS)

Wang, W. R.; Wei, K. Y.; Mii, H. S.; Lin, Y. S.; Huang, J. J.; Wang, P. L.; Lin, A. T.

2015-12-01

Release of large amounts of methane from marine gas hydrate reservoirs has been considered as a possible trigger of climate change, which can be recorded by the variation of carbon isotopes (δ13C) of the benthic foraminifera. In modern analogs, previous studies have suggested that δ13C becomes more negative when influenced by methane seeps. However, values of δ13C of benthic foraminifera might vary with different species and sedimentary settings in different regions. Seismic profiles in offshore southwestern Taiwan show the existence of Bottom Simulating Reflector (BSR) in the region, indicative of gas hydrate reservoirs. Various methane seepages have been found, and they are suspected to be related to the gas hydrates buried underneath. A better understanding of the δ13C signals of benthic foraminifera near the methane seepages can further clarify the origin of the methane and to evaluate it as a proxy of methane release for the geologic past. We have analyzed δ13C of benthic foraminifera Uvigerina proboscidea (150-250 mm) in the topmost 15 cm sediments in five marine cores (OR1-1092-WFWC-1, OR1-1092-WFWC-4, OR1-1092-WFWC-6, OR3-1806-C5-2 and OR3-1806-C10) collected from the Four-Way Closure Ridge in offshore southwestern Taiwan (water depth from 1330 to 1580 m). Our results show that δ13C values of U. proboscidea range from -0.98‰ to -6.21‰ (VPDB) for core OR3-1806-C5-2, which is considered as a seeps-influenced site. On the other hand, δ13C values of U. proboscidea from the background sites range from -0.40‰ to -1.00‰. The difference between the methane seep-affected and the background sites is in the range of 0.00‰ to 5.01‰, comparable to those documented in previous studies in other areas. The significant negative excursion in carbon isotopes in the seep site foraminifera is likely caused by incorporation of light inorganic carbon generated by methanotrophy in the system.

High precision gas hydrate imaging of small-scale and high-resolution marine sparker multichannel seismic data

NASA Astrophysics Data System (ADS)

Luo, D.; Cai, F.

2017-12-01

Small-scale and high-resolution marine sparker multi-channel seismic surveys using large energy sparkers are characterized by a high dominant frequency of the seismic source, wide bandwidth, and a high resolution. The technology with a high-resolution and high-detection precision was designed to improve the imaging quality of shallow sedimentary. In the study, a 20KJ sparker and 24-channel streamer cable with a 6.25m group interval were used as a seismic source and receiver system, respectively. Key factors for seismic imaging of gas hydrate are enhancement of S/N ratio, amplitude compensation and detailed velocity analysis. However, the data in this study has some characteristics below: 1. Small maximum offsets are adverse to velocity analysis and multiple attenuation. 2. Lack of low frequency information, that is, information less than 100Hz are invisible. 3. Low S/N ratio since less coverage times (only 12 times). These characteristics make it difficult to reach the targets of seismic imaging. In the study, the target processing methods are used to improve the seismic imaging quality of gas hydrate. First, some technologies of noise suppression are combined used in pre-stack seismic data to suppression of seismic noise and improve the S/N ratio. These technologies including a spectrum sharing noise elimination method, median filtering and exogenous interference suppression method. Second, the combined method of three technologies including SRME, τ-p deconvolution and high precision Radon transformation is used to remove multiples. Third, accurate velocity field are used in amplitude energy compensation to highlight the Bottom Simulating Reflector (short for BSR, the indicator of gas hydrates) and gas migration pathways (such as gas chimneys, hot spots et al.). Fourth, fine velocity analysis technology are used to improve accuracy of velocity analysis. Fifth, pre-stack deconvolution processing technology is used to compensate for low frequency energy and suppress of ghost, thus formation reflection characteristics are highlighted. The result shows that the small-scale and high resolution marine sparker multi-channel seismic surveys are very effective in improving the resolution and quality of gas hydrate imaging than the conventional seismic acquisition technology.

Gas hydrate identified in sand-rich inferred sedimentary section using downhole logging and seismic data in Shenhu area, South China Sea

USGS Publications Warehouse

Wang, Xiujuan; Lee, Myung W.; Collett, Timothy S.; Yang, Shengxiong; Guo, Yiqun; Wu, Shiguo

2014-01-01

Downhole wireline log (DWL) data was acquired from eight drill sites during China's first gas hydrate drilling expedition (GMGS-1) in 2007. Initial analyses of the acquired well log data suggested that there were no significant gas hydrate occurrences at Site SH4. However, the re-examination of the DWL data from Site SH4 indicated that there are two intervals of high resistivity, which could be indicative of gas hydrate. One interval of high resistivity at depth of 171–175 m below seafloor (mbsf) is associated with a high compressional- wave (P-wave) velocities and low gamma ray log values, which suggests the presence of gas hydrate in a potentially sand-rich (low clay content) sedimentary section. The second high resistivity interval at depth of 175–180 mbsf is associated with low P-wave velocities and low gamma values, which suggests the presence of free gas in a potentially sand-rich (low clay content) sedimentary section. Because the occurrence of free gas is much shallower than the expected from the regional depth of the bottom simulating reflector (BSR), the free gas could be from the dissociation of gas hydrate during drilling or there may be a local anomaly in the depth to the base of the gas hydrate stability zone. In order to determine whether the low P-wave velocity with high resistivity is caused by in-situ free gas or dissociated free gas from the gas hydrate, the surface seismic data were also used in this analysis. The log analysis incorporating the surface seismic data through the construction of synthetic seismograms using various models indicated the presence of free gas directly in contact with an overlying gas hydrate-bearing section. The occurrence of the anomalous base of gas hydrate stability at Site SH4 could be caused by a local heat flow conditions. This paper documents the first observation of gas hydrate in what is believed to be a sand-rich sediment in Shenhu area of the South China Sea.

MOEMS Fabry-Pérot interferometer with point-anchored Si-air mirrors for middle infrared

NASA Astrophysics Data System (ADS)

Tuohiniemi, Mikko; Näsilä, Antti; Akujärvi, Altti; Blomberg, Martti

2014-09-01

We studied how a micromachined Fabry-Pérot interferometer, realized with wide point-anchored Si/air-gap reflectors, performs at the middle-infrared. A computational analysis of the anchor mechanical behavior is also presented. Compared with solid-film reflectors, this technology features better index contrast, which enables a wider stop band and potentially higher resolution. In this work, we investigate whether the performance is improved according to the index-contrast benefit, or whether the mechanical differences play a role. For comparison, we manufactured and characterized another design that applies solid-film reflectors of Si/SiO2 structure. This data is exploited as a reference for a middle-infrared interferometer and as a template for mapping the performance from the simulation results to the measured data. The novel Si/air-gap device was realized as a non-tunable proof-of-concept version. The measured data is mapped into an estimate of the achievable performance of a tunable version. We present the measured transmission and resolution data and compare the simulation models that reproduce the data. The prediction for the tunable middle-infrared Si/air-gap device is then presented. The results indicate that the interferometer’s resolution is expected to have improved twofold and have a much wider stop band compared with the prior art.

Monte Carlo simulation of moderator and reflector in coal analyzer based on a D-T neutron generator.

PubMed

Shan, Qing; Chu, Shengnan; Jia, Wenbao

2015-11-01

Coal is one of the most popular fuels in the world. The use of coal not only produces carbon dioxide, but also contributes to the environmental pollution by heavy metals. In prompt gamma-ray neutron activation analysis (PGNAA)-based coal analyzer, the characteristic gamma rays of C and O are mainly induced by fast neutrons, whereas thermal neutrons can be used to induce the characteristic gamma rays of H, Si, and heavy metals. Therefore, appropriate thermal and fast neutrons are beneficial in improving the measurement accuracy of heavy metals, and ensure that the measurement accuracy of main elements meets the requirements of the industry. Once the required yield of the deuterium-tritium (d-T) neutron generator is determined, appropriate thermal and fast neutrons can be obtained by optimizing the neutron source term. In this article, the Monte Carlo N-Particle (MCNP) Transport Code and Evaluated Nuclear Data File (ENDF) database are used to optimize the neutron source term in PGNAA-based coal analyzer, including the material and shape of the moderator and neutron reflector. The optimized targets include two points: (1) the ratio of the thermal to fast neutron is 1:1 and (2) the total neutron flux from the optimized neutron source in the sample increases at least 100% when compared with the initial one. The simulation results show that, the total neutron flux in the sample increases 102%, 102%, 85%, 72%, and 62% with Pb, Bi, Nb, W, and Be reflectors, respectively. Maximum optimization of the targets is achieved when the moderator is a 3-cm-thick lead layer coupled with a 3-cm-thick high-density polyethylene (HDPE) layer, and the neutron reflector is a 27-cm-thick hemispherical lead layer. Copyright © 2015 Elsevier Ltd. All rights reserved.

Optical analysis of a photovoltaic V-trough system installed in western India.

PubMed

Maiti, Subarna; Sarmah, Nabin; Bapat, Pratap; Mallick, Tapas K

2012-12-20

The low concentrating photovoltaic (PV) system such as a 2× V-trough system can be a promising choice for enhancing the power output from conventional PV panels with the inclusion of thermal management. This system is more attractive when the reflectors are retrofitted to the stationary PV panels installed in a high aspect ratio in the north-south direction and are tracked 12 times a year manually according to preset angles, thus eliminating the need of diurnal expensive tracking. In the present analysis, a V-trough system facing exactly the south direction is considered, where the tilt angle of the PV panels' row is kept constant at 18.34°. The system is installed on the terrace of CSIR-Central Salt and Marine Chemicals Research Institute in Bhavnagar, Gujarat, India (21.47 N, 71.15 E). The dimension of the entire PV system is 9.64 m×0.55 m. The V-troughs made of anodized aluminum reflectors (70% specular reflectivity) had the same dimensions. An in-house developed; experimentally validated Monte Carlo ray-trace model was used to study the effect of the angular variation of the reflectors throughout a year for the present assembly. Results of the ray trace for the optimized angles showed the maximum simulated optical efficiency to be 85.9%. The spatial distribution of solar intensity over the 0.55 m dimension of the PV panel due to the V-trough reflectors was also studied for the optimized days in periods that included solstices and equinoxes. The measured solar intensity profiles with and without the V-trough system were used to calculate the actual optical efficiencies for several sunny days in the year, and results were validated with the simulated efficiencies within an average error limit of 10%.

Thin film concentrator panel development

NASA Technical Reports Server (NTRS)

Zimmerman, D. K.

1982-01-01

The development and testing of a rigid panel concept that utilizes a thin film reflective surface for application to a low-cost point-focusing solar concentrator is discussed. It is shown that a thin film reflective surface is acceptable for use on solar concentrators, including 1500 F applications. Additionally, it is shown that a formed steel sheet substrate is a good choice for concentrator panels. The panel has good optical properties, acceptable forming tolerances, environmentally resistant substrate and stiffeners, and adaptability to low to mass production rates. Computer simulations of the concentrator optics were run using the selected reflector panel design. Experimentally determined values for reflector surface specularity and reflectivity along with dimensional data were used in the analysis. The simulations provided intercept factor and net energy into the aperture as a function of aperture size for different surface errors and pointing errors. Point source and Sun source optical tests were also performed.

Self-Assembled InAs Nanowires as Optical Reflectors

PubMed Central

Floris, Francesco; Fornasari, Lucia; Marini, Andrea; Roddaro, Stefano; Beltram, Fabio; Cecchini, Marco; Sorba, Lucia; Rossella, Francesco

2017-01-01

Subwavelength nanostructured surfaces are realized with self-assembled vertically-aligned InAs nanowires, and their functionalities as optical reflectors are investigated. In our system, polarization-resolved specular reflectance displays strong modulations as a function of incident photon energy and angle. An effective-medium model allows one to rationalize the experimental findings in the long wavelength regime, whereas numerical simulations fully reproduce the experimental outcomes in the entire frequency range. The impact of the refractive index of the medium surrounding the nanostructure assembly on the reflectance was estimated. In view of the present results, sensing schemes compatible with microfluidic technologies and routes to innovative nanowire-based optical elements are discussed. PMID:29160860

FDTD and transfer matrix methods for evaluating the performance of photonic crystal based microcavities for exciton-polaritons

NASA Astrophysics Data System (ADS)

Liu, Yi-Cheng; Byrnes, Tim

2016-11-01

We investigate alternative microcavity structures for exciton-polaritons consisting of photonic crystals instead of distributed Bragg reflectors. Finite-difference time-domain simulations and scattering transfer matrix methods are used to evaluate the cavity performance. The results are compared with conventional distributed Bragg reflectors. We find that in terms of the photon lifetime, the photonic crystal based microcavities are competitive, with typical lifetimes in the region of ∼20 ps being achieved. The photonic crystal microcavities have the advantage that they are compact and are frequency adjustable, showing that they are viable to investigate exciton-polariton condensation physics.

Further evaluation of the constrained least squares electromagnetic compensation method

NASA Technical Reports Server (NTRS)

Smith, William T.

1991-01-01

Technologies exist for construction of antennas with adaptive surfaces that can compensate for many of the larger distortions caused by thermal and gravitational forces. However, as the frequency and size of reflectors increase, the subtle surface errors become significant and degrade the overall electromagnetic performance. Electromagnetic (EM) compensation through an adaptive feed array offers means for mitigation of surface distortion effects. Implementation of EM compensation is investigated with the measured surface errors of the NASA 15 meter hoop/column reflector antenna. Computer simulations are presented for: (1) a hybrid EM compensation technique, and (2) evaluating the performance of a given EM compensation method when implemented with discretized weights.

A behavioral task for investigating action discovery, selection and switching: comparison between types of reinforcer

PubMed Central

Fisher, Simon D.; Gray, Jason P.; Black, Melony J.; Davies, Jennifer R.; Bednark, Jeffery G.; Redgrave, Peter; Franz, Elizabeth A.; Abraham, Wickliffe C.; Reynolds, John N. J.

2014-01-01

Action discovery and selection are critical cognitive processes that are understudied at the cellular and systems neuroscience levels. Presented here is a new rodent joystick task suitable to test these processes due to the range of action possibilities that can be learnt while performing the task. Rats learned to manipulate a joystick while progressing through task milestones that required increasing degrees of movement accuracy. In a switching phase designed to measure action discovery, rats were repeatedly required to discover new target positions to meet changing task demands. Behavior was compared using both food and electrical brain stimulation reward (BSR) of the substantia nigra as reinforcement. Rats reinforced with food and those with BSR performed similarly overall, although BSR-treated rats exhibited greater vigor in responding. In the switching phase, rats learnt new actions to adapt to changing task demands, reflecting action discovery processes. Because subjects are required to learn different goal-directed actions, this task could be employed in further investigations of the cellular mechanisms of action discovery and selection. Additionally, this task could be used to assess the behavioral flexibility impairments seen in conditions such as Parkinson's disease and obsessive-compulsive disorder. The versatility of the task will enable cross-species investigations of these impairments. PMID:25477795

Creep and stress relaxation modeling of polycrystalline ceramic fibers

NASA Technical Reports Server (NTRS)

Dicarlo, James A.; Morscher, Gregory N.

1994-01-01

A variety of high performance polycrystalline ceramic fibers are currently being considered as reinforcement for high temperature ceramic matrix composites. However, under mechanical loading about 800 C, these fibers display creep related instabilities which can result in detrimental changes in composite dimensions, strength, and internal stress distributions. As a first step toward understanding these effects, this study examines the validity of a mechanism-based empirical model which describes primary stage tensile creep and stress relaxation of polycrystalline ceramic fibers as independent functions of time, temperature, and applied stress or strain. To verify these functional dependencies, a simple bend test is used to measure stress relaxation for four types of commercial ceramic fibers for which direct tensile creep data are available. These fibers include both nonoxide (SCS-6, Nicalon) and oxide (PRD-166, FP) compositions. The results of the Bend Stress Relaxation (BSR) test not only confirm the stress, time, and temperature dependencies predicted by the model, but also allow measurement of model empirical parameters for the four fiber types. In addition, comparison of model tensile creep predictions based on the BSR test results with the literature data show good agreement, supporting both the predictive capability of the model and the use of the BSR text as a simple method for parameter determination for other fibers.

Comparative proteomic analysis of oil palm leaves infected with Ganoderma boninense revealed changes in proteins involved in photosynthesis, carbohydrate metabolism, and immunity and defense.

PubMed

Jeffery Daim, Leona Daniela; Ooi, Tony Eng Keong; Ithnin, Nalisha; Mohd Yusof, Hirzun; Kulaveerasingam, Harikrishna; Abdul Majid, Nazia; Karsani, Saiful Anuar

2015-08-01

The basidiomycete fungal pathogen Ganoderma boninense is the causative agent for the incurable basal stem rot (BSR) disease in oil palm. This disease causes significant annual crop losses in the oil palm industry. Currently, there is no effective method for disease control and elimination, nor is any molecular marker for early detection of the disease available. An understanding of how BSR affects protein expression in plants may help identify and/or assist in the development of an early detection protocol. Although the mode of infection of BSR disease is primarily via the root system, defense-related genes have been shown to be expressed in both the root and leafs. Thus, to provide an insight into the changes in the global protein expression profile in infected plants, comparative 2DE was performed on leaf tissues sampled from palms with and without artificial inoculation of the Ganoderma fungus. Comparative 2DE revealed that 54 protein spots changed in abundance. A total of 51 protein spots were successfully identified by LC-QTOF MS/MS. The majority of these proteins were those involved in photosynthesis, carbohydrate metabolism as well as immunity and defense. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Creep and stress relaxation modeling of polycrystalline ceramic fibers

NASA Technical Reports Server (NTRS)

Dicarlo, James A.; Morscher, Gregory N.

1991-01-01

A variety of high performance polycrystalline ceramic fibers are currently being considered as reinforcement for high temperature ceramic matrix composites. However, under mechanical loading above 800 C, these fibers display creep-related instabilities which can result in detrimental changes in composite dimensions, strength, and internal stress distributions. As a first step toward understanding these effects, this study examines the validity of mechanistic-based empirical model which describes primary stage tensile creep and stress relaxation of polycrystalline ceramic fibers as independent functions of time, temperature, and applied stress or strain. To verify these functional dependencies, a simple bend test is used to measure stress relaxation for four types of commercial ceramic fibers for which direct tensile creep data are available. These fibers include both nonoxide (SCS-6, Nicalon) and oxide (PRD-166, FP) compositions. The results of the bend stress relaxation (BSR) test not only confirm the stress, time, and temperature dependencies predicted by the model but also allow measurement of model empirical parameters for the four fiber types. In addition, comparison of model predictions and BSR test results with the literature tensile creep data show good agreement, supporting both the predictive capability of the model and the use of the BSR test as a simple method for parameter determination for other fibers.

Comparative study of protective activities of Neospora caninum bradyzoite antigens, NcBAG1, NcBSR4, NcMAG1, and NcSAG4, in a mouse model of acute parasitic infection.

PubMed

Uchida, Masaki; Nagashima, Kotomi; Akatsuka, Yui; Murakami, Takashi; Ito, Akira; Imai, Soichi; Ike, Kazunori

2013-02-01

Neospora caninum is an obligate intracellular protozoan parasite that causes severe neuromuscular diseases, repeated abortion, stillbirth, and congenital infection in livestock and companion animals. The development of an effective vaccine against neosporosis in cattle is an important issue due to the significant worldwide economic impact of this disease. We evaluated the immunogenicity of four bradyzoite antigens, NcBAG1 (first described in this study), NcBSR4, NcMAG1, and NcSAG4, using an acute infection mouse model to determine synergistic effects with the tachyzoite antigen as a candidate for vaccine production. Mice were inoculated with the recombinant vaccines (r-)NcBAG1, rNcBSR4, rNcMAG1, rNcSAG4, or phosphate-buffered saline (PBS) (adjuvant control group) in an oil-in-water emulsion with bitter gourd extract, a Th1 immune stimulator, or PBS alone as the infection control group. Mice inoculated with each vaccine developed antigen-specific IgG1 and IgG2a antibodies and isolated splenocytes from mice produced high levels of interferon-γ when infected with the N. caninum tachyzoite. The mice inoculated with rNcBAG1, rNcMAG1, or rNcSAG4 developed slight to moderate clinical symptoms but did not succumb to infection. In contrast, rNcBSR4 and both control groups developed severe disease and some mice required euthanasia. The parasitic burden in the brain tissues of vaccinated mice was assessed by N. caninum-specific real-time PCR at 5 weeks after infection. The parasite load in rNcBAG1-, rNcMAG1-, and rNcSAG4-inoculated mice was significantly lower than that in adjuvant and infection control mice. Therefore, these antigens may be useful for the production of a N. caninum-specific vaccination protocol.

Correlation between clinical signs of depth of anaesthesia and cerebral state index responses in dogs with different target-controlled infusions of propofol.

PubMed

Ribeiro, Lénio M; Ferreira, David A; Brás, Susana; Gonzalo-Orden, Jose M; Antunes, Luis M

2012-01-01

To evaluate if the cerebral state index (CSI), measured by a Cerebral State Monitor (CSM), can predict depth of anaesthesia as assessed clinically or by estimated propofol plasma concentrations. Prospective clinical study. Fourteen mixed breed dogs, weighing 24.5 ± 4.7 kg, scheduled to undergo neutering procedures. Dogs were premedicated with 0.05 mg kg(-1) acepromazine intramuscularly. The CSM and cardiovascular monitoring equipment were attached. Anaesthesia was induced with propofol using a target controlled infusion (TCI) to varying plasma propofol targets (PropCp). Following endotracheal intubation the dogs were ventilated with oxygen. Anaesthetic maintenance was with propofol by TCI. A PropCp of 3 μg dL(-1) was set initially, then PropCps were increased in 1 μg dL(-1) steps to 7, 9 and then 11 μg dL(-1). Each PropCp was held constant for a 5 minute period, at the end of which depth of anaesthesia was classified using a previously evaluated scale of 'planes' based on palpebral and corneal reflexes and eye position. Cerebral state index (CSI), burst suppression (BSR) and electromyogram were measured at these time points. The prediction probability (PK) of these variables, or of the PropCp in predicting depth of anaesthesia was calculated. The PKs for predicting anaesthetic planes were 0.74, 0.91, 0.76 and 0.78 for CSI, BSR, EMG and PropCp, respectively. The PKs for PropCp to predict CSI, BSR and EMG were 0.65, 0.71 and 0.65 respectively. The Cerebral State Monitor was able to detect very deep planes of anaesthesia when BSR occurs, but was not able to distinguish between the intermediate anaesthetic planes likely to be used in clinical anaesthesia. © 2011 The Authors. Veterinary Anaesthesia and Analgesia. © 2011 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesiologists.

Efficiency enhancement and angle-dependent color change in see-through organic photovoltaics using distributed Bragg reflectors

NASA Astrophysics Data System (ADS)

Dong, Wan Jae; Lo, Nhat-Truong; Jung, Gwan Ho; Ham, Juyoung; Lee, Jong-Lam

2016-03-01

A distributed Bragg reflector (DBR) is conducted as a bottom reflector in see-through organic photovoltaics (OPVs) with an active layer of poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester (P3HT:PCBM). The DBR consists of alternative layers of the high- and low-refractive index materials of Ta2O5 (n = 2.16) and SiO2 (n = 1.46). The DBR selectively reflects the light within a specific wavelength region (490 nm-630 nm) where the absorbance of P3HT:PCBM is maximum. The see-through OPVs fabricated on DBR exhibit efficiency enhancement by 31% compared to the device without DBR. Additionally, the angle-dependent transmittance of DBR is analysed using optical simulation and verified by experimental results. As the incident angle of light increases, peak of reflectance shifts to shorter wavelength and the bandwidth gets narrower. This unique angle-dependent optical properties of DBR allows the facile color change of see-through OPVs.

Design and deploying study of a new petal-type deployable solid surface antenna

NASA Astrophysics Data System (ADS)

Huang, He; Guan, Fu-Ling; Pan, Liang-Lai; Xu, Yan

2018-07-01

Deployable solid surface reflector is still one of the most important ways to fulfill the ultra-high-accuracy and ultra-large-aperture reflector antennas. However the drawback of integrate stiffness is still a main problem for solid surface reflectors in the former research. To figure out this problem, a New Petal-type Deployable Solid Surface Antenna (NPDSSA) is developed in this study. A kind of drag springs are applied as linkages with adjacent petals to improve the integrate rigidity. The structural design is introduced and the geometric parameters are analyzed to find their effects on the rotation and package capacities. The software simulations and laboratory model tests are conducted to verify the deploying process of NPDSSA. Two models are employed to study the property of linkage butts and drag springs. It is indicated that model NPDSSA with the application of linkage butts and drag springs has better integrality and stability during the deploying. Finally it is concluded that NPDSSA is feasible for space applications.

Large incidence angle and defocus influence cat's eye retro-reflector

NASA Astrophysics Data System (ADS)

Zhang, Lai-xian; Sun, Hua-yan; Zhao, Yan-zhong; Yang, Ji-guang; Zheng, Yong-hui

2014-11-01

Cat's eye lens make the laser beam retro-reflected exactly to the opposite direction of the incidence beam, called cat's eye effect, which makes rapid acquiring, tracking and pointing of free space optical communication possible. Study the influence of cat's eye effect to cat's eye retro-reflector at large incidence angle is useful. This paper analyzed the process of how the incidence angle and focal shit affect effective receiving area, retro-reflected beam divergence angle, central deviation of cat's eye retro-reflector at large incidence angle and cat's eye effect factor using geometrical optics method, and presented the analytic expressions. Finally, numerical simulation was done to prove the correction of the study. The result shows that the efficiency receiving area of cat's eye retro-reflector is mainly affected by incidence angle when the focal shift is positive, and it decreases rapidly when the incidence angle increases; the retro-reflected beam divergence and central deviation is mainly affected by focal shift, and within the effective receiving area, the central deviation is smaller than beam divergence in most time, which means the incidence beam can be received and retro-reflected to the other terminal in most time. The cat's eye effect factor gain is affected by both incidence angle and focal shift.

Salinity effect of irrigation with treated wastewater in basal soil respiration in SE of Spain

NASA Astrophysics Data System (ADS)

Morugan, A.; Garcia-Orenes, F.; Mataix-Solera, J.

2012-04-01

The use of treated wastewater for the irrigation of agricultural soils is an alternative to utilizing better-quality water, especially in semiarid regions where water shortage is a very serious problem. Wastewater use in agriculture is not a new practice, all over the world this reuse has been common practice for a long time, but the concept is of greater importance currently because of the global water crisis. Replacement of freshwater by treated wastewater is seen as an important conservation strategy contributing to agricultural production, substantial benefits can derive from using this nutrient-rich waste water but there can also be a negative impact. For this reason it is necessary to know precisely the composition of water before applying it to the soil in order to guarantee minimal impact in terms of contamination and salinization. In this work we have been studying, for more than three years, different parameters in calcareous soils irrigated with treated wastewater in an agricultural Mediterranean area located at Biar (Alicante, SE Spain), with a crop of grape (Vitis labrusca). Three types of waters were used for the irrigation of the soil: fresh water (control) (TC), and treated wastewater from secondary (T2) and tertiary treatment (T3). Three different doses of irrigation have been applied to fit the efficiency of the irrigation to the crop and soil type during the study period. A soil sampling was carried out every four months. We show the results of the evolution of basal soil respiration (BSR), and its relationship with other parameters. We observed a similar pattern of behavior for BSR between treatments, a decrease at the first eighteen months of irrigation and an increase at the end of study. In our study case, the variations of BSR obtained for all the treatments seem to be closely related to the dose and frequency of irrigation and the related soil wetting and drying cycles. However, the results showed a negative correlation between BSR and saline content in soils irrigated with wastewater. The lower values of BSR were detected at T2 and T3 treatments and higher in TC, corresponding with an increase of electrical conductivity (EC) in soil especially in that irrigated with the secondary treatment. The increase of EC in any case was so high as to produce big problems with crop productivity or soil salinization. An increasing trend was observed in BSR after a period of leaching of salts and a decrease of EC. An exhaustive control of EC of treated wastewater is necessary to avoid undesirable effects on crop yield and to assess the feasibility of using these waters in this type of soil. Aknowledgements: This research was supported by the Water Reuse project (Reference STREP- FP6-2003-INCO-Russia+NIS-1. PL 516731). A. Morugán acknowledges the grants from "Caja Mediterraneo". The authors also acknowledge the "Biar waste water treatment station", "Entidad pública de saneamiento de aguas residuales de la Comunidad Valenciana" and "Proaguas Costablanca" for the collaboration.

Short-range/Long-range Integrated Target (SLIT) for Video Guidance Sensor Rendezvous and Docking

NASA Technical Reports Server (NTRS)

Roe, Fred D. (Inventor); Bryan, Thomas C. (Inventor)

2009-01-01

A laser target reflector assembly for mounting upon spacecraft having a long-range reflector array formed from a plurality of unfiltered light reflectors embedded in an array pattern upon a hemispherical reflector disposed upon a mounting plate. The reflector assembly also includes a short-range reflector array positioned upon the mounting body proximate to the long-range reflector array. The short-range reflector array includes three filtered light reflectors positioned upon extensions from the mounting body. The three filtered light reflectors retro-reflect substantially all incident light rays that are transmissive by their monochromatic filters and received by the three filtered light reflectors. In one embodiment the short-range reflector array is embedded within the hemispherical reflector,

900-m high gas plumes rising from marine sediments containing structure II hydrates at Vestnesa Ridge, offshore W-Svalbard

NASA Astrophysics Data System (ADS)

Smith, Andrew J.; Mienert, Jürgen; Bünz, Stefan; Greinert, Jens; Rasmussen, Tine L.

2013-04-01

We study an arctic sediment drift in ~1200 m water depth at Vestnesa Ridge, offshore western Svalbard. The ridge is spotted with pockmarks that range in size from a few meters to hundreds of meters in diameter and centimeters to tens of meters in height (e.g. Vogt et al., 1994). There is a strong negative-polarity seismic reflection below the ridge that is interpreted to record a negative impedance contrast marking the boundary between gas hydrate and water above and free gas and water below: it is the bottom-simulating reflector (BSR). Seismically transparent zones, interpreted as gas chimneys, extend from pockmarks at the seafloor to depths below the BSR (180-220 meters below the seafloor) (Bünz et al., 2012). Gas flares, gas hydrate, and methane-seep-specific biological communities (pogonphora and begiatoa bacterial mats) have been observed adjacent to pockmarks at the ridge (Bünz et al., 2012). We present new single-beam echosounding data that were acquired during 2010 and 2012 cruises on the R/V Helmer Hanssen at Vestnesa Ridge using a Simrad EK60 system that operates at frequencies of 18 and 38 kHz. During both cruises which lasted 3-5 days, we detected continuous bubble release from 4 separate pockmarks in 2010 and 6 separate pockmarks in 2012. There were no noticeable, short-term (hourly or daily) variations in the bubble release from the pockmarks, indicating that the venting from the pockmarks does not undergo rapid changes. Plumes from the pockmarks rise between 875 to 925m above the seafloor to a final water depth of 325 to 275m, respectively. This depth is in excellent agreement with the top of the hydrate stability zone (275 meters below sea level) for the gas composition of hydrate sampled at the ridge (96.31% C1; 3.36% C2; 0.21% C3; 0.11% IC4; 0.01% NC4). This suggests that hydrate skins are forming around the gas bubbles, inhibiting the dissolution of gas, and allowing the bubbles to rise to such great heights in the water column. Our results provide hard constraints for bubble-dissolution models (e.g. McGinnis et al., 2006) that can validate whether a gas-hydrate-rimmed bubble can survive the ~900m rise through the water column. Long-term monitoring of such gas-hydrate and fluid-flow systems is important for quantifying methane fluxes to the ocean, for identifying the source(s) of the venting gas, and for better understanding the environmental conditions under which deep-sea biological communities exist. References Bünz, S., Polyanov, S., Vadakkepuliyambatta, S., Consolaro, C., and Mienert, J., 2012, Active gas venting through hydrate-bearing sediments on the Vestnesa Ridge, offshore W-Svalbard. : Marine Geology v. 332-334, p. 189-197. McGinnis, D.F., Greinert, J., Artemov, Y., Beaubien, S.E., and Wüest, A., 2006, The fate of rising methane bubbles in stratified waters: What fraction reaches the atmosphere?: Journal of Geophysical Research, v. 111, C09007, doi:10.1029/2005JC003183. Vogt, P. R., Crane, K., Sundvor, E., Max, M. D., and Pfirman, S. L., 1994, Methane-generated(?) pockmarks on young, thickly sedimented oceanic crust in the Arctic: Vestnesa ridge, Fram strait: Geology, v. 22, no. 3, p. 255-258.

Thermo-spectral properties of plastic lasers

NASA Astrophysics Data System (ADS)

Dawson, Nathan J.; Aviles, Michael; Andrews, James H.; Crescimanno, Michael; Petrus, Joshua B.; Mazzocco, Anthony; Singer, Kenneth D.; Baer, Eric; Song, Hyunmin

2013-09-01

We study the effects of temperature changes on the operating wavelength of all-polymer microresonator lasers, particularly on multilayered defect distributed feedback and distributed Bragg reflector lasers. The parameters that change the operating wavelength are discussed with comparisons between experiments and simulations.

Criminal Law Wrap-Up.

ERIC Educational Resources Information Center

Coplan, Carol

1987-01-01

Examines four recent Supreme Court decisions. The decisions involve Miranda rights, alleged Fourth Amendment violations (good faith exception and vehicle searches), and the right to confront witnesses. (BSR)

Preliminary research on overmoded high-power millimeter-wave Cerenkov generator with dual-cavity reflector in low guiding magnetic field

NASA Astrophysics Data System (ADS)

Ye, Hu; Chen, Changhua; Ning, Hui; Tan, Weibing; Teng, Yan; Shi, Yanchao; Wu, Ping; Song, Zhimin; Cao, Yibing; Du, Zhaoyu

2015-12-01

This paper presents preliminary research on a V-band overmoded Cerenkov generator with dual-cavity reflector operating in a low guiding magnetic field. It is found that the fluctuation of the electron envelope in the low guiding magnetic field can be predicted using an equivalent coaxial model of a foilless diode, and a dual-cavity reflector based on the model matching method can provide strong reflection at the front end of the overmoded structures so that any microwave power that leaks into the diode region can be effectively suppressed. Numerical simulations indicate that the control of the beam envelope and the use of the dual-cavity reflector ease generator operation in the low guiding magnetic field. In the experimental research, the fluctuation of the annular electron beam with the outer radius of 7.5 mm measures approximately 0.7 mm, which is in good agreement with the theoretical results. The disturbance caused by power leaking from the overmoded slow wave structure is eliminated by the dual-cavity reflector. With accurate fabrication and assembly processes, an operating frequency of 61.6 GHz is attained by the fifth harmonic heterodyne method, and the output power is measured to be approximately 123 MW by the far-field measurement method at a diode voltage of 445 kV, a beam current of 4.45 kA, and under a guiding magnetic field of 1.45 T. The output mode is measured using an array of neon flash bulbs, and the pulse shortening phenomenon is both observed and analyzed.

Effect of back reflectors on photon absorption in thin-film amorphous silicon solar cells

NASA Astrophysics Data System (ADS)

Hossain, Mohammad I.; Qarony, Wayesh; Hossain, M. Khalid; Debnath, M. K.; Uddin, M. Jalal; Tsang, Yuen Hong

2017-10-01

In thin-film solar cells, the photocurrent conversion productivity can be distinctly boosted-up utilizing a proper back reflector. Herein, the impact of different smooth and textured back reflectors was explored and effectuated to study the optical phenomena with interface engineering strategies and characteristics of transparent contacts. A unique type of wet-chemically textured glass-substrate 3D etching mask used in superstrate (p-i-n) amorphous silicon-based solar cell along with legitimated back reflector permits joining the standard light-trapping methodologies, which are utilized to upgrade the energy conversion efficiency (ECE). To investigate the optical and electrical properties of solar cell structure, the optical simulations in three-dimensional measurements (3D) were performed utilizing finite-difference time-domain (FDTD) technique. This design methodology allows to determine the power losses, quantum efficiencies, and short-circuit current densities of various layers in such solar cell. The short-circuit current densities for different reflectors were varied from 11.50 to 13.27 and 13.81 to 16.36 mA/cm2 for the smooth and pyramidal textured solar cells, individually. Contrasted with the comparable flat reference cell, the short-circuit current density of textured solar cell was increased by around 24%, and most extreme outer quantum efficiencies rose from 79 to 86.5%. The photon absorption was fundamentally improved in the spectral region from 600 to 800 nm with no decrease of photocurrent shorter than 600-nm wavelength. Therefore, these optimized designs will help to build the effective plans next-generation amorphous silicon-based solar cells.

Initial evaluation of acoustic reflectors for the preservation of sensitive abdominal skin areas during MRgFUS treatment.

PubMed

Gorny, Krzysztof R; Chen, Shigao; Hangiandreou, Nicholas J; Hesley, Gina K; Woodrum, David A; Brown, Douglas L; Felmlee, Joel P

2009-04-21

During MR-guided focused ultrasound (MRgFUS) treatments of uterine fibroids using ExAblate(R)2000 (InSightec, Haifa, Israel), individual tissue ablations are performed extracorporeally through the patient's abdomen using an annular array FUS transducer embedded within the MR table. Ultrasound intensities in the near field are below therapeutic levels and, under normal conditions, heating of the patient skin is minimal. However, increased absorption of ultrasound energy within sensitive skin areas or areas with differing acoustic properties, such as scars, may lead to skin burns and therefore these areas must be kept outside the near field of the FUS beam. Depending on their location and size the sensitive areas may either obstruct parts of the fibroid from being treated or prevent the entire MRgFUS treatment altogether. The purpose of this work is to evaluate acoustic reflector materials that can be applied to protect skin and the underlying sensitive areas. Reflection coefficients of cork (0.88) and foam (0.91) based materials were evaluated with a hydrophone. An ExAblate 2000 MRgFUS system was used to simulate clinical treatment with discs of reflector materials placed in a near field underneath a gel phantom. MR thermometry was used to monitor temperature elevations as well as the integrity of the focal spot. The phantom measurements showed acoustic shadow zones behind the reflectors with zone depths changing between 7 and 27 mm, for reflector disc diameters increasing from 10 to 30 mm (40 mm diameter discs completely blocked the FUS beam at the depth evaluated). The effects on thermal lesions due to the presence of the reflectors in the FUS beam were found to diminish with decreasing disc diameter and increasing sonication depth. For a 20 mm diameter disc and beyond 50 mm sonication depth, thermal lesions were minimally affected by the presence of the disc. No heating was observed on the skin side of the foam reflectors, as confirmed by measurements performed with adhesive temperature labels. We present these data and discuss possible applications to clinical MRgFUS treatments.

Progress toward the development of dual junction GaAs/Ge solar cells

NASA Technical Reports Server (NTRS)

Lillington, D. R.; Krut, D. D.; Cavicchi, B. T.; Ralph, E.; Chung, M.

1991-01-01

Large area GaAs/Ge cells offer substantial promise for increasing the power output from existing silicon solar array designs and for providing an enabled technology for missions hitherto impossible using silicon. Single junction GaAs/Ge cells offer substantial advantages in both size, weight, and cost compared to GaAs cells but the efficiency is limited to approximately 19.2 to 20 percent AMO. The thermal absorptance of GaAs/Ge cells is also worse than GaAs/GaAs cells (0.88 vs 0.81 typ.) due to the absorption in the Ge substrate. On the other hand dual junction GaAs/Ge cells offer efficiencies up to ultimately 24 percent AMO in sizes up to 8 x 8 cm but there are still technological issues remaining to achieve current matching in the GaAs and Ge cells. This can be achieved through tuned antireflection (AR) coatings, improved quality of the GaAs growth, improved quality Ge wafers and the use of a Back Surface Field (BSF)/Back Surface Reflector (BSR) in the Ge cell. Although the temperature coefficients of efficiency and voltage are higher for dual junction GaAs/Ge cells, it has been shown elsewhere that for typical 28 C cell efficiencies of 22 percent (dual junction) vs 18.5 percent (single junction) there is a positive power tradeoff up to temperatures as high as 120 C. Due to the potential ease of fabrication of GaAs/Ge dual junction cells there is likely to be only a small cost differential compared to single junction cells.

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

NASA Technical Reports Server (NTRS)

Stutzman, W. L.; Takamizawa, K.; Werntz, P.; Lapean, J.; Barts, R.

1991-01-01

The following subject areas are covered: General Reflector Antenna Systems Program version 7(GRASP7); Multiple Reflector Analysis Program for Cylindrical Antennas (MRAPCA); Tri-Reflector 2D Synthesis Code (TRTDS); a geometrical optics and a physical optics synthesis techniques; beam scanning reflector, the type 2 and 6 reflectors, spherical reflector, and multiple reflector imaging systems; and radiometric array design.

Exploring brainstem function in multiple sclerosis by combining brainstem reflexes, evoked potentials, clinical and MRI investigations.

PubMed

Magnano, Immacolata; Pes, Giovanni Mario; Pilurzi, Giovanna; Cabboi, Maria Paola; Ginatempo, Francesca; Giaconi, Elena; Tolu, Eusebio; Achene, Antonio; Salis, Antonio; Rothwell, John C; Conti, Maurizio; Deriu, Franca

2014-11-01

To investigate vestibulo-masseteric (VMR), acoustic-masseteric (AMR), vestibulo-collic (VCR) and trigemino-collic (TCR) reflexes in patients with multiple sclerosis (MS); to relate abnormalities of brainstem reflexes (BSRs) to multimodal evoked potentials (EPs), clinical and Magnetic Resonance Imaging (MRI) findings. Click-evoked VMR, AMR and VCR were recorded from active masseter and sternocleidomastoid muscles, respectively; TCR was recorded from active sternocleidomastoid muscles, following electrical stimulation of the infraorbital nerve. EPs and MRI were performed with standard techniques. Frequencies of abnormal BSRs were: VMR 62.1%, AMR 55.1%, VCR 25.9%, TCR 58.6%. Brainstem dysfunction was identified by these tests, combined into a four-reflex battery, in 86.9% of cases, by EPs in 82.7%, MRI in 71.7% and clinical examination in 37.7% of cases. The sensitivity of paired BSRs/EPs (93.3%) was significantly higher than combined MRI/clinical testing (70%) in patients with disease duration ⩽6.4years. BSR alterations significantly correlated with clinical, EP and MRI findings. The four-BSR battery effectively increases the performance of standard EPs in early detection of brainstem impairment, otherwise undetected by clinical examination and neuroimaging. Multiple BSR assessment usefully supplements conventional testing and monitoring of brainstem function in MS, especially in newly diagnosed patients. Copyright © 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Control of Basal Stem Rot Disease in Oil Palm by Supplementation of Calcium, Copper, and Salicylic Acid.

PubMed

Bivi, M Shahul Hamid Rahamah; Paiko, Adamu Saidu; Khairulmazmi, Ahmad; Akhtar, M S; Idris, Abu Seman

2016-10-01

Continuous supplementation of mineral nutrients and salicylic acid (SA) as foliar application could improve efficacy in controlling basal stem rot (BSR) disease in oil palm seedling. It is revealed from the results that the highest disease severity index (58.3%) was recorded in T8 treatments at 9 months after inoculation. The best disease control was achieved by T7 treatments (calcium/copper/SA [Ca/Cu/SA]) (5.0%) followed by T1 (5.5%), T5 (5.8%), T3 (8.3%), T6 (8.3%), T4 (13.3%), and T2 (15.8%) treatments. Continuous supplementation of Ca/Cu/SA was found to be the most effective in controlling the disease and the high performance liquid chromatography results showed the detection of ergosterol at very low concentration in the treated samples. Moreover, the transmission electron microscopy analysis results clearly indicated that T7 treatment was also enhancing lignification, which was responsible for the thickness of the secondary cell walls and middle lamella compared to untreated samples. It was therefore, concluded that continuous supplementation of minerals nutrients and SA could effectively suppress disease severity by reducing ergosterol activity and also improve the process of lignification in the treated plants. Furthermore, this treatment also managed to delay the onset of BSR symptoms and promote the growth of the seedlings and eventually suppress the BSR disease.

Control of Basal Stem Rot Disease in Oil Palm by Supplementation of Calcium, Copper, and Salicylic Acid

PubMed Central

Bivi, M. Shahul Hamid Rahamah; Paiko, Adamu Saidu; Khairulmazmi, Ahmad; Akhtar, M. S.; Idris, Abu Seman

2016-01-01

Continuous supplementation of mineral nutrients and salicylic acid (SA) as foliar application could improve efficacy in controlling basal stem rot (BSR) disease in oil palm seedling. It is revealed from the results that the highest disease severity index (58.3%) was recorded in T8 treatments at 9 months after inoculation. The best disease control was achieved by T7 treatments (calcium/copper/SA [Ca/Cu/SA]) (5.0%) followed by T1 (5.5%), T5 (5.8%), T3 (8.3%), T6 (8.3%), T4 (13.3%), and T2 (15.8%) treatments. Continuous supplementation of Ca/Cu/SA was found to be the most effective in controlling the disease and the high performance liquid chromatography results showed the detection of ergosterol at very low concentration in the treated samples. Moreover, the transmission electron microscopy analysis results clearly indicated that T7 treatment was also enhancing lignification, which was responsible for the thickness of the secondary cell walls and middle lamella compared to untreated samples. It was therefore, concluded that continuous supplementation of minerals nutrients and SA could effectively suppress disease severity by reducing ergosterol activity and also improve the process of lignification in the treated plants. Furthermore, this treatment also managed to delay the onset of BSR symptoms and promote the growth of the seedlings and eventually suppress the BSR disease. PMID:27721689

Comparative and bioinformatics analyses of pathogenic bacterial secretomes identified by mass spectrometry in Burkholderia species.

PubMed

Nguyen, Thao Thi; Chon, Tae-Soo; Kim, Jaehan; Seo, Young-Su; Heo, Muyoung

2017-07-01

Secreted proteins (secretomes) play crucial roles during bacterial pathogenesis in both plant and human hosts. The identification and characterization of secretomes in the two plant pathogens Burkholderia glumae BGR1 and B. gladioli BSR3, which cause diseases in rice such as seedling blight, panicle blight, and grain rot, are important steps to not only understand the disease-causing mechanisms but also find remedies for the diseases. Here, we identified two datasets of secretomes in B. glumae BGR1 and B. gladioli BSR3, which consist of 118 and 111 proteins, respectively, using mass spectrometry approach and literature curation. Next, we characterized the functional properties, potential secretion pathways and sequence information properties of secretomes of two plant pathogens in a comparative analysis by various computational approaches. The ratio of potential non-classically secreted proteins (NCSPs) to classically secreted proteins (CSPs) in B. glumae BGR1 was greater than that in B. gladioli BSR3. For CSPs, the putative hydrophobic regions (PHRs) which are essential for secretion process of CSPs were screened in detail at their N-terminal sequences using hidden Markov model (HMM)-based method. Total 31 pairs of homologous proteins in two bacterial secretomes were indicated based on the global alignment (identity ≥ 70%). Our results may facilitate the understanding of the species-specific features of secretomes in two plant pathogenic Burkholderia species.

All-reflective optical target illumination system with high numerical aperture

DOEpatents

Sigler, Robert D.

1978-01-01

An all-reflective optical system for providing illumination of a target focal region at high numerical aperture from a pair of co-axially, confluent collimated light beams. A target cavity is defined by a pair of opposed inner ellipsoidal reflectors having respective first focal points within a target region and second focal points at a vertex opening in the opposing reflector. Outwardly of each inner reflector is the opposed combination of a spherical reflector, and an outer generally ellipsoidal reflector having an aberrated first focal point coincident with the focus of the opposing spherical reflector and a second focal point coincident with the second focal point of the opposing inner ellipsoidal reflector through a vertex opening in the spherical reflector. The confluent collimated beams are incident through vertex openings in the outer ellipsoidal reflectors onto respective opposing spherical reflectors. Each beam is reflected by the associated spherical reflector onto the opposing outer ellipsoidal reflector and focused thereby onto the opposing inner ellipsoidal reflector, and then onto the target region.

Boundary conditions for simulating large SAW devices using ANSYS.

PubMed

Peng, Dasong; Yu, Fengqi; Hu, Jian; Li, Peng

2010-08-01

In this report, we propose improved substrate left and right boundary conditions for simulating SAW devices using ANSYS. Compared with the previous methods, the proposed method can greatly reduce computation time. Furthermore, the longer the distance from the first reflector to the last one, the more computation time can be reduced. To verify the proposed method, a design example is presented with device center frequency 971.14 MHz.

EXPERIMENTAL AND ANALYTICAL STUDIES OF REFLECTRO CONTROL FOR THE ADVANCED ENGINEERING TEST REACTOR. PART A. EXPERIMENTAL STUDIES WITH THE REFLECTOR CONTROL SYSTEM MODEL. PART B. ANALYTICAL STUDIES OF REFLECTOR CONTROL

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

Bertelson, P.C.; Francis, T.L.

1959-10-21

Studies of reflector control for the Advanced Engineering Test Reactor were made. The performance of various parts of the reflector control system model such as the safety reflector and the water jet educator, boric acid injection, and demineralizer systems is discussed. The experimental methods and results obtained are discussed. Four reflector control schemes were studied. The schemes were a single-region and three-region reflector schemes two separate reflectors, and two connected reflectors. Calculations were made of shim and safety reflector worth for a variety of parameters. Safety reflector thickness was varied from 7.75 to 0 inches, with and without boron. Boricmore » acid concentration was varied from 100 to 2% of saturation in the shim reflectors. Neutron flux plots are presented (C.J.G.)« less

An examination of the sensitivity and systematic error of the NASA GEMS Bragg Reflection Polarimeter using Monte-Carlo simulations

NASA Astrophysics Data System (ADS)

Allured, Ryan; Okajima, Takashi; Soufli, Regina; Fernández-Perea, Mónica; Daly, Ryan O.; Marlowe, Hannah; Griffiths, Scott T.; Pivovaroff, Michael J.; Kaaret, Philip

2012-10-01

The Bragg Reflection Polarimeter (BRP) on the NASA Gravity and Extreme Magnetism Small Explorer Mission is designed to measure the linear polarization of astrophysical sources in a narrow band centered at about 500 eV. X-rays are focused by Wolter I mirrors through a 4.5 m focal length to a time projection chamber (TPC) polarimeter, sensitive between 2{10 keV. In this optical path lies the BRP multilayer reflector at a nominal 45 degree incidence angle. The reflector reflects soft X-rays to the BRP detector and transmits hard X-rays to the TPC. As the spacecraft rotates about the optical axis, the reflected count rate will vary depending on the polarization of the incident beam. However, false polarization signals may be produced due to misalignments and spacecraft pointing wobble. Monte-Carlo simulations have been carried out, showing that the false modulation is below the statistical uncertainties for the expected focal plane offsets of < 2 mm.

Reflector system for a lighting fixture

DOEpatents

Siminovitch, Michael J.; Page, Erik; Gould, Carl T.

1998-01-01

Disclosed herein is a reflector system for a lighting fixture having a illumination source surrounded by an envelope. The reflector system includes a first reflector surrounding the illumination source. The reflector system also includes a second reflector which is non-contiguous with the first reflector and which surrounds the illumination source. The illumination source creates light rays which are reflected by the first and second reflectors. The first reflector directs light rays toward the center line of the fixture. However, the reflected rays despite being so reflected do not substantially intersect the envelope. The reflected light rays from the second reflector being directed so that they diverge from the center line of the fixture avoiding intersection with the semi-transparent envelope.

Reflector system for a lighting fixture

DOEpatents

Siminovitch, Michael J.; Page, Erik; Gould, Carl T.

2001-01-01

Disclosed herein is a reflector system for a lighting fixture having a illumination source surrounded by an envelope. The reflector system includes a first reflector surrounding the illumination source. The reflector system also includes a second reflector which is non-contiguous with the first reflector and which surrounds the illumination source. The illumination source creates light rays which are reflected by the first and second reflectors. The first reflector directs light rays toward the center line of the fixture. However, the reflected rays despite being so reflected do not substantially intersect the envelope. The reflected light rays from the second reflector being directed so that they diverge from the center line of the fixture avoiding intersection with the semi-transparent envelope.

Annealing Effects on Creep and Rupture of Polycrystalline Alumina-Based Fibers

NASA Technical Reports Server (NTRS)

Goldsby, J. C.; Yun, H. M.; Morscher, G. N.; DiCarlo, J. A.

1998-01-01

Continuous-length polycrystalline aluminum-oxide-based fibers are being considered as reinforcements for advanced high-temperature composite materials. For these fine-grained fibers, basic issues arise concerning grain growth and microstructural instability during composite fabrication and the resulting effects on the fiber's thermo-mechanical properties. To examine these issues, commercially available Nextel 610 (alumina) and Altex (alumina-silica) fibers were annealed at 1100 and 1300 C for up to 100 hr in air. Changes in fiber microstructure, fiber tensile creep, stress rupture, and bend stress relaxation (BSR) that occurred with annealing were then determined. BSR tests were also used to compare as-received and annealed fibers to other polycrystalline oxide fibers. Annealing was shown to have a significant effect, particularly on the Altex fiber, and caused it to have increased creep resistance.

Terrace retro-reflector array for poloidal polarimeter on ITER.

PubMed

Imazawa, R; Kawano, Y; Ono, T; Kusama, Y

2011-02-01

A new concept of a terrace retro-reflector array (TERRA) as part of the poloidal polarimeter for ITER is proposed in this paper. TERRA reflects a laser light even from a high incident angle in the direction of the incident-light path, while a conventional retro-reflector array cannot. Besides, TERRA can be installed in a smaller space than a corner-cube retro-reflector. In an optical sense, TERRA is equivalent to a Littrow grating, the blaze angle of which varies, depending on the incident angle. The reflected light generates a bright and dark fringe, and the bright fringe is required to travel along the incident-light path to achieve the objects of laser-aided diagnostics. In order to investigate the propagation properties of laser light reflected by TERRA, we have developed a new diffraction formula. Conditions for the propagation of the bright fringe in the direction of the incident light have been obtained using the Littrow grating model and have been confirmed in a simulation applying the new diffraction formula. Finally, we have designed laser transmission optics using TERRA for the ITER poloidal polarimeter and have calculated the light propagation of the system. The optical design obtains a high transmission efficiency, with 88.6% of the incident power returned. These results demonstrate the feasibility of applying TERRA to the ITER poloidal polarimeter.

Analysis of the Thermo-Elastic Response of Space Reflectors to Simulated Space Environment

NASA Astrophysics Data System (ADS)

Allegri, G.; Ivagnes, M. M.; Marchetti, M.; Poscente, F.

2002-01-01

The evaluation of space environment effects on materials and structures is a key matter to develop a proper design of long duration missions: since a large part of satellites operating in the earth orbital environment are employed for telecommunications, the development of space antennas and reflectors featured by high dimensional stability versus space environment interactions represents a major challenge for designers. The structural layout of state of the art space antennas and reflectors is very complex, since several different sensible elements and materials are employed: particular care must be placed in evaluating the actual geometrical configuration of the reflectors operating in the space environment, since very limited distortions of the designed layout can produce severe effects on the quality of the signal both received and transmitted, especially for antennas operating at high frequencies. The effects of thermal loads due to direct sunlight exposition and to earth and moon albedo can be easily taken into account employing the standard methods of structural analysis: on the other hand the thermal cycling and the exposition to the vacuum environment produce a long term damage accumulation which affects the whole structure. The typical effects of the just mentioned exposition are the outgassing of polymeric materials and the contamination of the exposed surface, which can affect sensibly the thermo-mechanical properties of the materials themselves and, therefore, the structural global response. The main aim of the present paper is to evaluate the synergistic effects of thermal cycling and of the exposition to high vacuum environment on an innovative antenna developed by Alenia Spazio S.p.a.: to this purpose, both an experimental and numerical research activity has been developed. A complete prototype of the antenna has been exposed to the space environment simulated by the SAS facility: this latter is constituted by an high vacuum chamber, equipped by high pressure Xenon lamps to simulate the direct solar irradiation and a cryogenic heat exchanger to reproduce the earth shadowing of sunlight. The temperature of the thermal cycles ranges from -80°C up to 100°C: the thermo-elastic response of the antenna has been surveyed by employing strain gauges place on the structures at several different locations. The structure has been subjected to 100 thermal cycles, each of which lasting two hours: the total duration of the exposition to the vacuum environment has been equal to 300 hours. Finally the antenna has been disassembled and its elements have been examined to evaluate the effects of the simulated exposition on each of them: the total mass loss and the final thermo-mechanical properties of the polymeric based materials which constitute the structural core of the antenna have been surveyed. The experimental results have been compared to numerical simulation performed by the NASTRAN code: the basic FEM model, developed for the unexposed antenna, has been updated to take into account the thermo-mechanical degradation of the structural elements and materials. This has allowed to obtain, by extrapolation, a FEM based prevision of the antenna thermo-elastic response for long-term operative conditions. References. [1] D. Hastings, H. Garret "Spacecraft environment interactions", Cambridge University Press, Atmospheric Series, Cambridge, 1996. [2] IAF-01-I.6.05 "On the Reliability of Honeycomb Core Bonding Joint in Sandwich Composite Materials for Space Applications" G. Allegri, U. Lecci, M. Marchetti, F. Poscente, 52° IAF Congress, 2001. [3] Meguro A. and alii, "Technology status of the 13 m aperture deployment antenna reflectors for Engineering Test Satellite VIII", Acta Astronautica, Volume: 47, Issue: 2-9, July - November, 2000, pp. 147-152. [4] Novikov L. S. "Contemporary state of spacecraft/environment interaction research" Radiation Measurements, Volume: 30, Issue: 5, October, 1999, pp. 661-667. [5] IAF-01-I.1.02 "Development of High Performance Large Single Shaped Reflectors" Paul Archer, C. Abegg, T. Le Goff, EADS/LV, Les Mureaux, France.

Preliminary research on overmoded high-power millimeter-wave Cerenkov generator with dual-cavity reflector in low guiding magnetic field

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

Ye, Hu; Wu, Ping; Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi'an, Shaanxi 710024

2015-12-15

This paper presents preliminary research on a V-band overmoded Cerenkov generator with dual-cavity reflector operating in a low guiding magnetic field. It is found that the fluctuation of the electron envelope in the low guiding magnetic field can be predicted using an equivalent coaxial model of a foilless diode, and a dual-cavity reflector based on the model matching method can provide strong reflection at the front end of the overmoded structures so that any microwave power that leaks into the diode region can be effectively suppressed. Numerical simulations indicate that the control of the beam envelope and the use ofmore » the dual-cavity reflector ease generator operation in the low guiding magnetic field. In the experimental research, the fluctuation of the annular electron beam with the outer radius of 7.5 mm measures approximately 0.7 mm, which is in good agreement with the theoretical results. The disturbance caused by power leaking from the overmoded slow wave structure is eliminated by the dual-cavity reflector. With accurate fabrication and assembly processes, an operating frequency of 61.6 GHz is attained by the fifth harmonic heterodyne method, and the output power is measured to be approximately 123 MW by the far-field measurement method at a diode voltage of 445 kV, a beam current of 4.45 kA, and under a guiding magnetic field of 1.45 T. The output mode is measured using an array of neon flash bulbs, and the pulse shortening phenomenon is both observed and analyzed.« less

TOMO3D: 3-D joint refraction and reflection traveltime tomography parallel code for active-source seismic data—synthetic test

NASA Astrophysics Data System (ADS)

Meléndez, A.; Korenaga, J.; Sallarès, V.; Miniussi, A.; Ranero, C. R.

2015-10-01

We present a new 3-D traveltime tomography code (TOMO3D) for the modelling of active-source seismic data that uses the arrival times of both refracted and reflected seismic phases to derive the velocity distribution and the geometry of reflecting boundaries in the subsurface. This code is based on its popular 2-D version TOMO2D from which it inherited the methods to solve the forward and inverse problems. The traveltime calculations are done using a hybrid ray-tracing technique combining the graph and bending methods. The LSQR algorithm is used to perform the iterative regularized inversion to improve the initial velocity and depth models. In order to cope with an increased computational demand due to the incorporation of the third dimension, the forward problem solver, which takes most of the run time (˜90 per cent in the test presented here), has been parallelized with a combination of multi-processing and message passing interface standards. This parallelization distributes the ray-tracing and traveltime calculations among available computational resources. The code's performance is illustrated with a realistic synthetic example, including a checkerboard anomaly and two reflectors, which simulates the geometry of a subduction zone. The code is designed to invert for a single reflector at a time. A data-driven layer-stripping strategy is proposed for cases involving multiple reflectors, and it is tested for the successive inversion of the two reflectors. Layers are bound by consecutive reflectors, and an initial velocity model for each inversion step incorporates the results from previous steps. This strategy poses simpler inversion problems at each step, allowing the recovery of strong velocity discontinuities that would otherwise be smoothened.

Reflector system for a lighting fixture

DOEpatents

Siminovitch, M.J.; Page, E.; Gould, C.T.

1998-09-08

Disclosed herein is a reflector system for a lighting fixture having a illumination source surrounded by an envelope. The reflector system includes a first reflector surrounding the illumination source. The reflector system also includes a second reflector which is non-contiguous with the first reflector and which surrounds the illumination source. The illumination source creates light rays which are reflected by the first and second reflectors. The first reflector directs light rays toward the center line of the fixture. However, the reflected rays despite being so reflected do not substantially intersect the envelope. The reflected light rays from the second reflector being directed so that they diverge from the center line of the fixture avoiding intersection with the semi-transparent envelope. 5 figs.

A Response to the Question of Elitism.

ERIC Educational Resources Information Center

Hausman, Jerome J.

1987-01-01

Points out that Ralph Smith's article, "A Question of Elitism," offers useful distinctions for advancing the cause of elitism in education. Contends that excellence and democratic values are indeed compatible. (BSR)

Education and Equality of Opportunity for Girls and Women.

ERIC Educational Resources Information Center

Cels-Offermans, Anne

1987-01-01

Discusses findings of a questionnaire about the improvement of educational opportunities for women in Western Europe. Summarizes recent developments, measures, and initiatives and concludes by recommending further improvements. (BSR)

Teaching Public Administration in a Post-Literate Society.

ERIC Educational Resources Information Center

Brumback, Richard A.

1988-01-01

The problem of students entering universities and graduate programs with sub-standard communication skills is becoming more pronounced. Teaching communication skills is an important vehicle for enhancing student work. (BSR)

Effects of isoflurane, sevoflurane and methoxyflurane on the electroencephalogram of the chicken.

PubMed

McIlhone, Amanda E; Beausoleil, Ngaio J; Johnson, Craig B; Mellor, David J

2014-11-01

Anaesthetics have differing effects on mammalian electroencephalogram (EEG) but little is known about the effects on avian EEG. This study explored how inhalant anaesthetics affect chicken EEG. Experimental study. Twelve female Hyline Brown chickens aged 6-11 weeks. Each chicken was anaesthetized with isoflurane, sevoflurane, and methoxyflurane. For each, anaesthesia was adjusted to 1, 1.5 and 2 times Minimum Anaesthetic Concentration (MAC). Total Power (Ptot), Median Frequency (F50), Spectral Edge Frequency (F95) and Burst Suppression Ratio (BSR) were calculated at each volume concentration. BSR data were analyzed using doubly repeated measures anova. Neither isoflurane nor sevoflurane could be included in analysis of F50, F95 and Ptot because of extensive burst suppression; Methoxyflurane data were analyzed using RM anova. There was a significant interaction between anaesthetic and concentration on BSR [F(4,22) = 10.65, p < 0.0001]. For both isoflurane and sevoflurane, BSR increased with concentration. Isoflurane caused less suppression than sevoflurane at 1.5 MAC and at final 1 MAC while methoxyflurane caused virtually no burst suppression. Methoxyflurane concentration had a significant effect on F50 [F(2,20) = 3.83, p = 0.04], F95 [F(2,20) = 4.03, p = 0.03] and Ptot [F(2,20) = 5.22, p = 0.02]. Decreasing methoxyflurane from 2 to 1 MAC increased F50 and F95. Ptot increased when concentration decreased from 1.5 to 1 MAC and tended to be higher at 1 MAC than at 2 MAC. Isoflurane and sevoflurane suppressed chicken EEG in a dose-dependent manner. Higher concentrations of methoxyflurane caused an increasing degree of synchronization of EEG. Isoflurane and sevoflurane suppressed EEG activity to a greater extent than did methoxyflurane at equivalent MAC multiples. Isoflurane caused less suppression than sevoflurane at intermediate concentrations. These results indicate the similarity between avian and mammalian EEG responses to inhalant anaesthetics and reinforce the difference between MAC and anaesthetic effects on brain activity in birds. © 2014 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia.

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.

The coating design of phase-shifting reflector array with high reflectance and specified reflection phase shifts for static Michelson interferometer

NASA Astrophysics Data System (ADS)

Zhang, Xuanni; Zhang, Hui; Wang, Yijun

2016-02-01

The optical Doppler Michelson imaging interferometer is widely used for wind measurements. Four interferograms obtained simultaneously are needed to immune to environmental disturbances. Thus, a static and divided mirror Michelson interferometer is proposed. Its highlight is the phase-shifting reflector array, which divides one mirror into four quadrants coated by different multilayer films with high reflectance, specified phase steps π/2 and little polarization effects. By combining analytical and empirical method, four coatings are designed with software TFCalc. The simulated results showed good agreement with the desired optical properties. Due to the limitation of the optical material and function of the software TFCalc, there are some design errors within tolerance.

Polarization-independent beam focusing by high-contrast grating reflectors

NASA Astrophysics Data System (ADS)

Su, Wei; Zheng, Gaige; Jiang, Liyong; Li, Xiangyin

2014-08-01

A kind of high-contrast grating (HCG) reflector for beam focusing has been proposed. We design a planar grating structure with a parabolic surface and numerical simulations using a finite different time domain (FDTD) method to verify that the structure has the capability of focusing both transverse-magnetic (TM) and transverse-electric (TE) polarized lights. Finally, we expand the design structure into a three-dimensional (3D) case. Numerical results demonstrate that the power intensities at the focal point are all greater than 8.5 dB compared with incident intensity, which means the structure has a better focusing effect. Further analysis of incident wavelength sensitivity (1.55, 1.79 and 2 μm) reveals that the proposed structure has a wide range of working wavelength.

Improved optical design of nontracking concentrators

NASA Astrophysics Data System (ADS)

Kwan, B. M.; Bannerot, R. B.

1984-08-01

Optical designs based on a two reflections or less criterion have been developed for one and two-facet trapezoidal concentrators. Collector designs resulting from this criterion have been evaluated with the aid of a ray-trace computer simulation which includes the effects of nonideal reflectors. Results indicate a marked increase in performance, particularly for the one-facet designs, as compared to the collectors previously designed with the one reflection or less criterion. A significant result is that when a proper accounting is made for the actual acceptance angle for the concentrators, the performances of the optimal one and two-facet designs become nearly identical, indicating that the previously held contention that improved performance could be achieved with multifaceted reflectors (geometrically approaching the compound parabolic shape) may be incorrect.

Control of the spontaneous emission from a single quantum dash using a slow-light mode in a two-dimensional photonic crystal on a Bragg reflector

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

Chauvin, N.; Fiore, A.; Nedel, P.

2009-07-15

We demonstrate the coupling of a single InAs/InP quantum, emitting around 1.55 {mu}m, to a slow-light mode in a two-dimensional photonic crystal on Bragg reflector. These surface addressable 2.5D photonic crystal band-edge modes present the advantages of a vertical emission and the mode area and localization may be controlled, leading to a less critical spatial alignment with the emitter. An increase in the spontaneous emission rate by a factor of 1.5-2 is measured at low temperature and is compared to the Purcell factor predicted by three-dimensional time-domain electromagnetic simulations.

Evaluation of Gas Hydrate at Alaminos Canyon 810, Northern Gulf of Mexico Slope

NASA Astrophysics Data System (ADS)

Yang, C.; Cook, A.; Sawyer, D.; Hillman, J. I. T.

2016-12-01

We characterize the gas hydrate reservoir in Alaminos Canyon Block 810 (AC810) on the northern Gulf of Mexico slope, approximately 400 km southeast of Houston, Texas, USA. Three-dimensional seismic data shows a bottom-simulating-reflection (BSR), over 30 km2, which suggests that a significant gas hydrate accumulation may occur at AC810. Furthermore, logging while drilling (LWD) data acquired from a Statoil well located that penetrated the BSR near the crest of the regional anticline indicates two possible gas hydrate units (Hydrate Unit A and Hydrate Unit B). LWD data in this interval are limited to gamma ray and resistivity only. Resistivity curve separations are observed in Hydrate Unit A (131 to 253 mbsf) suggesting hydrate-filled fractures in marine mud. A spiky high resistivity response in Hydrate Unit B (308 to 354 mbsf) could either be a marine mud or a sand-prone interval. The abrupt decrease (from 7 to 1 Ωm) in resistivity logs at 357 mbsf generally corresponds with the interpreted base of hydrate stability, as the BSR is observed near 350 mbsf on the seismic data. To further investigate the formation characteristics, we generate synthetic traces using general velocity and density trends for marine sediments to match the seismic trace extracted at the Statoil well. We consider models with 1) free gas and 2) water only below the base of hydrate stability. In our free gas-below models, we find the velocity of Hydrate Unit A and Hydrate Unit B is generally low and does not deviate significantly from the general velocity trends, suggesting that gas hydrate is present in a marine mud. In the water-below model, the compressional velocity of Hydrate Unit B ranges from 2450 m/s to 3150 m/s. This velocity is similar to the velocity of high hydrate saturation in sand; typically greater than 2500 m/s. This may indicate that Hydrate Unit B is sand with high hydrate saturation; however, to achieve a suitable match between the water-below synthetic seismogram and the trace, a high velocity layer was required below the base of hydrate stability, which is not indicated by the well logs. Our models indicate that at AC810, Hydrate Unit A probably contains hydrate filled fractures in a marine mud. For Hydrate Unit B, our models suggest hydrate may occur in a sand-prone interval, but is more likely to be gas hydrate filled fractures in marine mud.

Bifocal reflector for electrohydraulic lithotripters.

PubMed

Prieto, F E; Loske, A M

1999-03-01

To describe the design and construction of a bifocal reflector that could be used in electrohydraulic extracorporeal shockwave lithotripters in order to increase their efficiency. The new reflector is obtained by joining two sectors of two rotationally symmetric ellipsoidal reflectors having different distances between their foci, which results in a bifocal composite reflector with the F1 foci in coincidence and the two F2 foci separated by a certain distance. As in conventional reflectors, shockwaves are generated by the electrical breakdown of water between two electrodes, located at the focus (F1) closest to the reflector. A prototype was constructed and tested in an experimental shockwave generator of our own make, using two different types of kidney-stone models, one to test the stone fragmentation abilities, and the other to test the stone pitting abilities. Fragmentation data for the new reflector were compared with those of a conventional ellipsoidal reflector tested on the same device. The new design appeared to be more efficient in breaking up both types of kidney-stone models than the conventional reflector. Pressure measurements were obtained with both reflectors using needle hydrophones. The physical background of shockwave reflection on both reflectors is also explained. With this new reflector, it could be possible, in principle, to reduce the treatment time of extracorporeal shockwave lithotripsy.

What Did Peel County Do In the Great War?

ERIC Educational Resources Information Center

Morton, Desmond

1987-01-01

Describes the strengths and weaknesses of the Canadian War effort during World War I. Specifically focuses on Peel County, Ontario and the particular problems its inhabitants experienced during the war. (BSR)

De novo transcriptome analyses of host-fungal interactions in oil palm (Elaeis guineensis Jacq.).

PubMed

Ho, Chai-Ling; Tan, Yung-Chie; Yeoh, Keat-Ai; Ghazali, Ahmad-Kamal; Yee, Wai-Yan; Hoh, Chee-Choong

2016-01-19

Basal stem rot (BSR) is a fungal disease in oil palm (Elaeis guineensis Jacq.) which is caused by hemibiotrophic white rot fungi belonging to the Ganoderma genus. Molecular responses of oil palm to these pathogens are not well known although this information is crucial to strategize effective measures to eradicate BSR. In order to elucidate the molecular interactions between oil palm and G. boninense and its biocontrol fungus Trichoderma harzianum, we compared the root transcriptomes of untreated oil palm seedlings with those inoculated with G. boninense and T. harzianum, respectively. Differential gene expression analyses revealed that jasmonate (JA) and salicylate (SA) may act in an antagonistic manner in affecting the hormone biosynthesis, signaling, and downstream defense responses in G. boninense-treated oil palm roots. In addition, G. boninense may compete with the host to control disease symptom through the transcriptional regulation of ethylene (ET) biosynthesis, reactive oxygen species (ROS) production and scavenging. The strengthening of host cell walls and production of pathogenesis-related proteins as well as antifungal secondary metabolites in host plants, are among the important defense mechanisms deployed by oil palm against G. boninense. Meanwhile, endophytic T. harzianum was shown to improve the of nutrition status and nutrient transportation in host plants. The findings of this analysis have enhanced our understanding on the molecular interactions of G. boninense and oil palm, and also the biocontrol mechanisms involving T. harzianum, thus contributing to future formulations of better strategies for prevention and treatment of BSR.

Kinematically complete study of low-energy electron-impact ionization of argon: Internormalized cross sections in three-dimensional kinematics

NASA Astrophysics Data System (ADS)

Ren, Xueguang; Amami, Sadek; Zatsarinny, Oleg; Pflüger, Thomas; Weyland, Marvin; Dorn, Alexander; Madison, Don; Bartschat, Klaus

2016-06-01

As a further test of advanced theoretical methods to describe electron-impact single-ionization processes in complex atomic targets, we extended our recent work on Ne (2 p ) ionization [X. Ren, S. Amami, O. Zatsarinny, T. Pflüger, M. Weyland, W. Y. Baek, H. Rabus, K. Bartschat, D. Madison, and A. Dorn, Phys. Rev. A 91, 032707 (2015), 10.1103/PhysRevA.91.032707] to Ar (3 p ) ionization at the relatively low incident energy of E0=66 eV. The experimental data were obtained with a reaction microscope, which can cover nearly the entire 4 π solid angle for the secondary electron emission. We present experimental data for detection angles of 10, 15, and 20∘ for the faster of the two outgoing electrons as a function of the detection angle of the secondary electron with energies of 3, 5, and 10 eV, respectively. Comparison with theoretical predictions from a B -spline R -matrix (BSR) with pseudostates approach and a three-body distorted-wave (3DW) approach, for detection of the secondary electron in three orthogonal planes as well as the entire solid angle, shows overall satisfactory agreement between experiment and the BSR results, whereas the 3DW approach faces difficulties in predicting some of the details of the angular distributions. These findings are different from our earlier work on Ne (2 p ), where both the BSR and 3DW approaches yielded comparable levels of agreement with the experimental data.

Benthic iron cycling in a high-oxygen environment: Implications for interpreting the Archean sedimentary iron isotope record.

PubMed

McCoy, V E; Asael, D; Planavsky, N

2017-09-01

The most notable trend in the sedimentary iron isotope record is a shift at the end of the Archean from highly variable δ 56 Fe values with large negative excursions to less variable δ 56 Fe values with more limited negative values. The mechanistic explanation behind this trend has been extensively debated, with two main competing hypotheses: (i) a shift in marine redox conditions and the transition to quantitative iron oxidation; and (ii) a decrease in the signature of microbial iron reduction in the sedimentary record because of increased bacterial sulfate reduction (BSR). Here, we provide new insights into this debate and attempt to assess these two hypotheses by analyzing the iron isotope composition of siderite concretions from the Carboniferous Mazon Creek fossil site. These concretions precipitated in an environment with water column oxygenation, extensive sediment pile dissimilatory iron reduction (DIR) but limited bacterial sulfate reduction (BSR). Most of the concretions have slightly positive iron isotope values, with a mean of 0.15‰ and limited iron isotope variability compared to the Archean sedimentary record. This limited variability in an environment with high DIR and low BSR suggests that these conditions alone are insufficient to explain Archean iron isotope compositions. Therefore, these results support the idea that the unusually variable and negative iron isotope values in the Archean are due to dissimilatory iron reduction (DIR) coupled with extensive water column iron cycling. © 2017 John Wiley & Sons Ltd.

Extreme Precision Antenna Reflector Study Results

NASA Technical Reports Server (NTRS)

Sharp, G. R.; Gilger, L. D.; Ard, K. E.

1985-01-01

Thermal and mechanical distortion degrade the RF performance of antennas. The complexity of future communications antennas requires accurate, dimensionally stable antenna reflectors and structures built from materials other than those currently used. The advantages and disadvantages of using carbon fibers in an epoxy matrix are reviewed as well as current reflector fabrications technology and adjustment. The manufacturing sequence and coefficient of thermal expansion of carbon fiber/borosilicate glass composites is described. The construction of a parabolic reflector from this material and the assembling of both reflector and antenna are described. A 3M-aperture-diameter carbon/glass reflector that can be used as a subassembly for large reflectors is depicted. The deployment sequence for a 10.5M-aperture-diameter antenna, final reflector adjustment, and the deployment sequence for large reflectors are also illustrated.

Dual annular rotating "windowed" nuclear reflector reactor control system

DOEpatents

Jacox, Michael G.; Drexler, Robert L.; Hunt, Robert N. M.; Lake, James A.

1994-01-01

A nuclear reactor control system is provided in a nuclear reactor having a core operating in the fast neutron energy spectrum where criticality control is achieved by neutron leakage. The control system includes dual annular, rotatable reflector rings. There are two reflector rings: an inner reflector ring and an outer reflector ring. The reflectors are concentrically assembled, surround the reactor core, and each reflector ring includes a plurality of openings. The openings in each ring are capable of being aligned or non-aligned with each other. Independent driving means for each of the annular reflector rings is provided so that reactor criticality can be initiated and controlled by rotation of either reflector ring such that the extent of alignment of the openings in each ring controls the reflection of neutrons from the core.

Computer prediction of dual reflector antenna radiation properties

NASA Technical Reports Server (NTRS)

Christodoulou, C.

1981-01-01

A program for calculating radiation patterns for reflector antennas with either smooth analytic surfaces or with surfaces composed of a number of panels. Techniques based on the geometrical optics (GO) approach were used in tracing rays over the following regions: from a feed antenna to the first reflector surface (subreflector); from this reflector to a larger reflector surface (main reflector); and from the main reflector to a mathematical plane (aperture plane) in front of the main reflector. The equations of GO were also used to calculate the reflected field components for each ray making use of the feed radiation pattern and the parameters defining the surfaces of the two reflectors. These resulting fields form an aperture distribution which is integrated numerically to compute the radiation pattern for a specified set of angles.

Tsujal Marine Survey: Crustal Characterization of the Rivera Plate-Jalisco Block Boundary and its Implications for Seismic and Tsunami Hazard Assessment

NASA Astrophysics Data System (ADS)

Bartolome, R.; Danobeitia, J.; Barba, D. C., Sr.; Nunez-Cornu, F. J.; Cameselle, A. L.; Estrada, F.; Prada, M.; Bandy, W. L.

2014-12-01

During the spring of 2014, a team of Spanish and Mexican scientists explored the western margin of Mexico in the frame of the TSUJAL project. The two main objectives were to characterize the nature and structure of the lithosphere and to identify potential sources triggering earthquakes and tsunamis at the contact between Rivera plate-Jalisco block with the North American Plate. With these purposes a set of marine geophysical data were acquired aboard the RRS James Cook. This work is focus in the southern part of the TSUJAL survey, where we obtain seismic images from the oceanic domain up to the continental shelf. Thus, more than 800 km of MCS data, divided in 7 profiles, have been acquired with a 6km long streamer and using an air-gun sources ranging from 5800 c.i. to 3540 c.i. Furthermore, a wide-angle seismic profile of 190 km length was recorded in 16 OBS deployed perpendicular to the coast of Manzanillo. Gravity and magnetic, multibeam bathymetry and sub-bottom profiler data were recorded simultaneously with seismic data in the offshore area. Preliminary stacked MCS seismic sections reveal the crustal structure in the different domains of the Mexican margin. The contact between the Rivera and NA Plates is observed as a strong reflection at 6 s two way travel time (TWTT), in a parallel offshore profile (TS01), south of Manzanillo. This contact is also identified in a perpendicular profile, TS02, along a section of more than 100 km in length crossing the Rivera transform zone, and the plate boundary between Cocos and Rivera Plates. Northwards, offshore Pto. Vallarta, the MCS data reveals high amplitude reflections at around 7-8.5 s TWTT, roughly 2.5-3.5 s TWTT below the seafloor, that conspicuously define the subduction plane (TS06b). These strong reflections which we interpret as the Moho discontinuity define the starting bending of subduction of Rivera Plate. Another clear pattern observed within the first second of the MCS data shows evidences of a bottom simulating reflector (BSR) along the continental margin, particularly strong offshore Pto. Vallarta. The integration of all these acquired geophysical information will allow obtaining a comprehensive image of the lithosphere that will be valuable for the seismic and tsunamigenic hazard assessment.

The Successful Deployment of a New Sub-Seafloor Observatory

NASA Astrophysics Data System (ADS)

Lado Insua, T.; Moran, K.; Kulin, I.; Farrington, S.; Newman, J. B.; Riedel, M.; Iturrino, G. J.; Masterson, W. A.; Furman, C. R.; Klaus, A.; Storms, M.; Attryde, J.; Hetmaniak, C.; Huey, D.

2013-12-01

The Simple Cabled Instrument for Measuring Parameters In-Situ (SCIMPI) is a new ocean observatory instrument designed to study dynamic processes in the sub-seafloor. The first SCIMPI prototype comprises nine modules that collect time series measurements of temperature, pressure and electrical resistivity of sediments at pre-selected depths below seafloor. These modules are joined in an array by flexible cables. Floats are attached to the cables of the system to keep the cabling taught against the weight of a sinker bar at the bottom of the string. The system was designed for deployment through drillpipe using D/V JOIDES Resolution. SCIMPI is designed for sediments that will collapse around the observatory after deployment. After five years in development, SCIMPI was successfully deployed within the NEPTUNE Canada observatory in May 2013. The IODP Expedition 341S took place on the Cascadia Margin. The deployment Site U1416 is within an active gas hydrate vent field. Spacing of SCIMPI modules was tailored to measure parameters in the accreted sediment and above and below the Bottom Simulating Reflector (BSR). The location of the modules was dimensioned based on a multivariate analysis of physical properties derived from IODP boreholes located nearby. Members of the SCIMPI team, science party, technical support, crew and participants of the School of Rock assembled the instrument on deck during the days leading up to the deployment. During deployment, SCIMPI was connected to the Multi-Function-Telemetry-Module (from LDEO) and was lowered through drillpipe on the wireline logging cable. SCIMPI communicated data to a shipboard computer until its release, providing assurance that measurements were active on all sensors. The observatory was released with the Electronic Release System (ERS) and the drillpipe was pulled out of the borehole. A camera system was used to check on the installation immediately after deployment. An Ocean Networks Canada expedition revisited the site a month later to assess the borehole collapse around SCIMPI. Its four year battery life will allow SCIMPI to record data on its command module while waiting to be connected to the NEPTUNE Canada observatory in 2014. The modular design of SCIMPI allows adapting its configuration for different situations and environments. SCIMPI is now available for exploring other dynamic sub-seafloor settings in future expeditions.

Lunar regolith stratigraphy analysis based on the simulation of lunar penetrating radar signals

NASA Astrophysics Data System (ADS)

Lai, Jialong; Xu, Yi; Zhang, Xiaoping; Tang, Zesheng

2017-11-01

The thickness of lunar regolith is an important index of evaluating the quantity of lunar resources such as 3He and relative geologic ages. Lunar penetrating radar (LPR) experiment of Chang'E-3 mission provided an opportunity of in situ lunar subsurface structure measurement in the northern mare imbrium area. However, prior work on analyzing LPR data obtained quite different conclusions of lunar regolith structure mainly because of the missing of clear interface reflectors in radar image. In this paper, we utilized finite-difference time-domain (FDTD) method and three models of regolith structures with different rock density, number of layers, shapes of interfaces, and etc. to simulate the LPR signals for the interpretation of radar image. The simulation results demonstrate that the scattering signals caused by numerous buried rocks in the regolith can mask the horizontal reflectors, and the die-out of radar echo does not indicate the bottom of lunar regolith layer and data processing such as migration method could recover some of the subsurface information but also result in fake signals. Based on analysis of simulation results, we conclude that LPR results uncover the subsurface layered structure containing the rework zone with multiple ejecta blankets of small crater, the ejecta blanket of Chang'E-3 crater, and the transition zone and estimate the thickness of the detected layer is about 3.25 m.

Dependence of acoustic levitation capabilities on geometric parameters.

PubMed

Xie, W J; Wei, B

2002-08-01

A two-cylinder model incorporating boundary element method simulations is developed, which builds up the relationship between the levitation capabilities and the geometric parameters of a single-axis acoustic levitator with reference to wavelength. This model proves to be successful in predicting resonant modes of the acoustic field and explaining axial symmetry deviation of the levitated samples near the reflector and emitter. Concave reflecting surfaces of a spherical cap, a paraboloid, and a hyperboloid of revolution are investigated systematically with regard to the dependence of the levitation force on the section radius R(b) and curvature radius R (or depth D) of the reflector. It is found that the levitation force can be remarkably enhanced by choosing an optimum value of R or D, and the possible degree of this enhancement for spherically curved reflectors is the largest. The degree of levitation force enhancement by this means can also be facilitated by enlarging R(b) and employing a lower resonant mode. The deviation of the sample near the reflector is found likely to occur in case of smaller R(b), larger D, and a higher resonant mode. The calculated dependence of levitation force on R, R(b), and the resonant mode is also verified by experiment and finally demonstrated to be in good agreement with experimental results, in which considerably a strong levitation force is achieved to levitate an iridium sphere which has the largest density of 22.6 g/cm(3).

An innovative, highly sensitive receiver system for the Square Kilometre Array Mid Radio Telescope

NASA Astrophysics Data System (ADS)

Tan, Gie Han; Lehmensiek, Robert; Billade, Bhushan; Caputa, Krzysztof; Gauffre, Stéphane; Theron, Isak P.; Pantaleev, Miroslav; Ljusic, Zoran; Quertier, Benjamin; Peens-Hough, Adriaan

2016-07-01

The Square Kilometre Array (SKA) Project is a global science and engineering project realizing the next-generation radio telescopes operating in the metre and centimetre wavelengths regions. This paper addresses design concepts of the broadband, exceptionally sensitive receivers and reflector antennas deployed in the SKA1-Mid radio telescope to be located in South Africa. SKA1-Mid (350 MHz - 13.8 GHz with an option for an upper limit of 24 GHz) will consist of 133 reflector antennas using an unblocked aperture, offset Gregorian configuration with an effective diameter of 15 m. Details on the unblocked aperture Gregorian antennas, low noise front ends and advanced direct digitization receivers, are provided from a system design perspective. The unblocked aperture results in increased aperture efficiency and lower side-lobe levels compared to a traditional on-axis configuration. The low side-lobe level reduces the noise contribution due to ground pick-up but also makes the antenna less susceptible to ground-based RFI sources. The addition of extra shielding on the sub-reflector provides a further reduction of ground pick-up. The optical design of the SKA1-Mid reflector antenna has been tweaked using advanced EM simulation tools in combination with sophisticated models for sky, atmospheric and ground noise contributions. This optimal antenna design in combination with very low noise, partially cryogenic, receivers and wide instantaneous bandwidth provide excellent receiving sensitivity in combination with instrumental flexibility to accommodate a wide range of astronomical observation modes.

Large Deployable Reflector Technologies for Future European Telecom and Earth Observation Missions

NASA Astrophysics Data System (ADS)

Ihle, A.; Breunig, E.; Dadashvili, L.; Migliorelli, M.; Scialino, L.; van't Klosters, K.; Santiago-Prowald, J.

2012-07-01

This paper presents requirements, analysis and design results for European large deployable reflectors (LDR) for space applications. For telecommunications, the foreseeable use of large reflectors is associated to the continuous demand for improved performance of mobile services. On the other hand, several earth observation (EO) missions can be identified carrying either active or passive remote sensing instruments (or both), in which a large effective aperture is needed e.g. BIOMASS. From the European point of view there is a total dependence of USA industry as such LDRs are not available from European suppliers. The RESTEO study is part of a number of ESA led activities to facilitate European LDR development. This paper is focused on the structural-mechanical aspects of this study. We identify the general requirements for LDRs with special emphasis on launcher accommodation for EO mission. In the next step, optimal concepts for the LDR structure and the RF-Surface are reviewed. Regarding the RF surface, both, a knitted metal mesh and a shell membrane based on carbon fibre reinforced silicon (CFRS) are considered. In terms of the backing structure, the peripheral ring concept is identified as most promising and a large number of options for the deployment kinematics are discussed. Of those, pantographic kinematics and a conical peripheral ring are selected. A preliminary design for these two most promising LDR concepts is performed which includes static, modal and kinematic simulation and also techniques to generate the reflector nets.

Experimental detailed power distribution in a fast spectrum thermionic reactor fuel element at the core/BeO reflector interface region

NASA Technical Reports Server (NTRS)

Klann, P. G.; Lantz, E.

1973-01-01

A zero-power critical assembly was designed, constructed, and operated for the prupose of conducting a series of benchmark experiments dealing with the physics characteristics of a UN-fueled, Li-7-cooled, Mo-reflected, drum-controlled compact fast reactor for use with a space-power conversion system. The critical assembly was modified to simulate a fast spectrum advanced thermionics reactor by: (1) using BeO as a reflector in place of some of the existing molybdenum, (2) substituting Nb-1Zr tubing for some of the existing Ta tubing, and (3) inserting four full-scale mockups of thermionic type fuel elements near the core and BeO reflector boundary. These mockups were surrounded with a buffer zone having the equivalent thermionic core composition. In addition to measuring the critical mass of this thermionic configuration, a detailed power distribution in one of the thermionic element stages in the mixed spectrum region was measured. A power peak to average ratio of two was observed for this fuel stage at the midplane of the core and adjacent to the reflector. Also, the power on the outer surface adjacent to the BeO was slightly more than a factor of two larger than the power on the inside surface of a 5.08 cm (2.0 in.) high annular fuel segment with a 2.52 cm (0.993 in. ) o.d. and a 1.86 cm (0.731 in.) i.d.

The Situation Oriented Approach to Preschool Curriculum.

ERIC Educational Resources Information Center

Oertel, Frithjof M.

1987-01-01

Describes preschool education in West Germany in terms of the various aspects of reform that changed function-oriented classrooms to situation-oriented learning environments. Argues for the priority of social education in early childhood. (BSR)

Dual annular rotating [open quotes]windowed[close quotes] nuclear reflector reactor control system

DOEpatents

Jacox, M.G.; Drexler, R.L.; Hunt, R.N.M.; Lake, J.A.

1994-03-29

A nuclear reactor control system is provided in a nuclear reactor having a core operating in the fast neutron energy spectrum where criticality control is achieved by neutron leakage. The control system includes dual annular, rotatable reflector rings. There are two reflector rings: an inner reflector ring and an outer reflector ring. The reflectors are concentrically assembled, surround the reactor core, and each reflector ring includes a plurality of openings. The openings in each ring are capable of being aligned or non-aligned with each other. Independent driving means for each of the annular reflector rings is provided so that reactor criticality can be initiated and controlled by rotation of either reflector ring such that the extent of alignment of the openings in each ring controls the reflection of neutrons from the core. 4 figures.

Optical design of free-form bicycle lamp

NASA Astrophysics Data System (ADS)

Tian, Chao; Cen, Zaofeng; Deng, Shitao; Wang, Jing

2008-03-01

Bicycle lamp used for road lighting is becoming popular now. However, few people have realized its potential market and correlative researches are far from enough. Generally speaking, researches on bicycle lamps are mostly focused on how to design a reflector which will collect light energy more efficiently and can transfer it to certain areas forward when the light source is determinated. In traditional angle of view, the reflector is usually a paraboloid or ellipsoid. However, both of them can not meet the requirement in practice most of the cases. Therefore, free form reflectors (FFRs) instead are widely used. In this paper, a new approach to design FFR which is convenient and rapid is presented. To do computer-aided simulation, certain light source should be selected first. Usually, light sources that behavior like a Lambertian emitter are modeled. To examine the correctness of this approach, a bicycle lamp is designed according to this approach to see if it can meet the requirements of the Germany standard which will be introduced in the text later. The standard requires specific illuminance values for particular points at the test screen with a distance of 10m from the source. The simulation results is exciting and can meet all the requirement. For example, 10lx is expected at the point (0, 0) while the obtained value is 10.42lx, under the conditions that the total luminous flux of the light source is 42lm and the reflectivity of FFR is 0.8. This method has certain universal significance and can provide references for the design of other illumination systems.

Plasmonic silicon solar cells: impact of material quality and geometry.

PubMed

Pahud, Celine; Isabella, Olindo; Naqavi, Ali; Haug, Franz-Josef; Zeman, Miro; Herzig, Hans Peter; Ballif, Christophe

2013-09-09

We study n-i-p amorphous silicon solar cells with light-scattering nanoparticles in the back reflector. In one configuration, the particles are fully embedded in the zinc oxide buffer layer; In a second configuration, the particles are placed between the buffer layer and the flat back electrode. We use stencil lithography to produce the same periodic arrangement of the particles and we use the same solar cell structure on top, thus establishing a fair comparison between a novel plasmonic concept and its more traditional counterpart. Both approaches show strong resonances around 700 nm in the external quantum efficiency the position and intensity of which vary strongly with the nanoparticle shape. Moreover, disagreement between simulations and our experimental results suggests that the dielectric data of bulk silver do not correctly represent the reality. A better fit is obtained by introducing a porous interfacial layer between the silver and zinc oxide. Without the interfacial layer, e.g. by improved processing of the nanoparticles, our simulations show that the nanoparticles concept could outperform traditional back reflectors.

Improved foilless Ku-band transit-time oscillator for generating gigawatt level microwave with low guiding magnetic field

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

Ling, Junpu; He, Juntao, E-mail: hejuntao12@163.com; Zhang, Jiande

2014-09-15

An improved foilless Ku-band transit-time oscillator with low guiding magnetic field is proposed and investigated in this paper. With a non-uniform buncher and a coaxial TM{sub 02} mode dual-resonant reflector, this improved device can output gigawatt level Ku-band microwave with relatively compact radial dimensions. Besides the above virtue, this novel reflector also has the merits of high TEM reflectance, being more suitable for pre-modulating the electron beam and enhancing the conversion efficiency. Moreover, in order to further increase the conversion efficiency and lower the power saturation time, a depth-tunable coaxial collector and a resonant cavity located before the extractor aremore » employed in our device. Main structure parameters of the device are optimized by particle in cell simulations. The typical simulation result is that, with a 380 kV, 8.2 kA beam guided by a magnetic field of about 0.6 T, 1.15 GW microwave pulse at 14.25 GHz is generated, yielding a conversion efficiency of about 37%.« less

Precision pointing compensation for DSN antennas with optical distance measuring sensors

NASA Technical Reports Server (NTRS)

Scheid, R. E.

1989-01-01

The pointing control loops of Deep Space Network (DSN) antennas do not account for unmodeled deflections of the primary and secondary reflectors. As a result, structural distortions due to unpredictable environmental loads can result in uncompensated boresight shifts which degrade pointing accuracy. The design proposed here can provide real-time bias commands to the pointing control system to compensate for environmental effects on pointing performance. The bias commands can be computed in real time from optically measured deflections at a number of points on the primary and secondary reflectors. Computer simulations with a reduced-order finite-element model of a DSN antenna validate the concept and lead to a proposed design by which a ten-to-one reduction in pointing uncertainty can be achieved under nominal uncertainty conditions.

Multi-mode horn antenna simulation

NASA Technical Reports Server (NTRS)

Dod, L. R.; Wolf, J. D.

1980-01-01

Radiation patterns were computed for a circular multimode horn antenna using waveguide electric field radiation expressions. The circular multimode horn was considered as a possible reflector feed antenna for the Large Antenna Multifrequency Microwave Radiometer (LAMMR). This horn antenna uses a summation of the TE sub 11 deg and TM sub 11 deg modes to generate far field primary radiation patterns with equal E and H plane beamwidths and low sidelobes. A computer program for the radiation field expressions using the summation of waveguide radiation modes is described. The sensitivity of the multimode horn antenna radiation patterns to phase variations between the two modes is given. Sample radiation pattern calculations for a reflector feed horn for LAMMR are shown. The multimode horn antenna provides a low noise feed suitable for radiometric applications.

Design of a Shape Memory Alloy deployment hinge for reflector facets

NASA Technical Reports Server (NTRS)

Anders, W. S.; Rogers, C. A.

1991-01-01

A design concept for a Shape Memory Alloy (SMA) actuated hinge mechanism for deploying segmented facet-type reflector surfaces on antenna truss structures is presented. The mechanism uses nitinol, a nickel-titanium shape memory alloy, as a displacement-force micro-actuator. An electrical current is used to resistively heat a 'plastically' elongated SMA actuator wire, causing it to contract in response to a thermally-induced phase transformation. The resulting tension creates a moment, imparting rotary motion between two adjacent panels. Mechanical stops are designed into the device to limit its range of motion and to establish positioning accuracy at the termination of deployment. The concept and its operation are discussed in detail, and an analytical dynamic simulation model is presented. The model has been used to perform nondimensionalized parametric design studies.

A method for development of efficient 3D models for neutronic calculations of ASTRA critical facility using experimental information

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

Balanin, A. L.; Boyarinov, V. F.; Glushkov, E. S.

The application of experimental information on measured axial distributions of fission reaction rates for development of 3D numerical models of the ASTRA critical facility taking into account azimuthal asymmetry of the assembly simulating a HTGR with annular core is substantiated. Owing to the presence of the bottom reflector and the absence of the top reflector, the application of 2D models based on experimentally determined buckling is impossible for calculation of critical assemblies of the ASTRA facility; therefore, an alternative approach based on the application of the extrapolated assembly height is proposed. This approach is exemplified by the numerical analysis ofmore » experiments on measurement of efficiency of control rods mockups and protection system (CPS).« less

THERMAL NEUTRONIC REACTOR

DOEpatents

Spinrad, B.I.

1960-01-12

A novel thermal reactor was designed in which a first reflector formed from a high atomic weight, nonmoderating material is disposed immediately adjacent to the reactor core. A second reflector composed of a moderating material is disposed outwardly of the first reflector. The advantage of this novel reflector arrangement is that the first reflector provides a high slow neutron flux in the second reflector, where irradiation experiments may be conducted with a small effect on reactor reactivity.

Prospects for Geostationary Doppler Weather Radar

NASA Technical Reports Server (NTRS)

Tanelli, Simone; Fang, Houfei; Durden, Stephen L.; Im, Eastwood; Rhamat-Samii, Yahya

2009-01-01

A novel mission concept, namely NEXRAD in Space (NIS), was developed for detailed monitoring of hurricanes, cyclones, and severe storms from a geostationary orbit. This mission concept requires a space deployable 35-m diameter reflector that operates at 35-GHz with a surface figure accuracy requirement of 0.21 mm RMS. This reflector is well beyond the current state-of-the-art. To implement this mission concept, several potential technologies associated with large, lightweight, spaceborne reflectors have been investigated by this study. These spaceborne reflector technologies include mesh reflector technology, inflatable membrane reflector technology and Shape Memory Polymer reflector technology.

Laser beam alignment system

DOEpatents

Kasner, William H.; Racki, Daniel J.; Swenson, Clark E.

1984-01-01

A plurality of pivotal reflectors direct a high-power laser beam onto a workpiece, and a rotatable reflector is movable to a position wherein it intercepts the beam and deflects a major portion thereof away from its normal path, the remainder of the beam passing to the pivotal reflectors through an aperture in the rotating reflector. A plurality of targets are movable to positions intercepting the path of light traveling to the pivotal reflectors, and a preliminary adjustment of the latter is made by use of a low-power laser beam reflected from the rotating reflector, after which the same targets are used to make a final adjustment of the pivotal reflectors with the portion of the high-power laser beam passed through the rotating reflector.

Reducing Operating Temperature in Photovoltaic Modules

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

Silverman, Timothy J.; Deceglie, Michael G.; Subedi, Indra

Reducing the operating temperature of photovoltaic modules increases their efficiency and lifetime. This can be achieved by reducing the production of waste heat or by improving the rejection of waste heat. We tested, using a combination of simulation and experiment, several thermal modifications in each category. To predict operating temperature and energy yield changes in response to changes to the module, we implemented a physics-based transient simulation framework based almost entirely on measured properties. The most effective thermal modifications reduced the production of waste heat by reflecting unusable light from the cell or the module. Consistent with previous results andmore » verified in this work through year-long simulations, the ideal reflector resulted in an annual irradiance-weighted temperature reduction of 3.8 K for crystalline silicon (c-Si). Our results illustrate that more realistic reflector concepts must balance detrimental optical effects with the intended thermal effects to realize the optimal energy production advantage. Methods improving thermal conductivity or back-side emissivity showed only modest improvements of less than 1 K. We also studied a GaAs module, which uses high-efficiency and high-subbandgap reflectivity to operate at an annual irradiance-weighted temperature 12 K cooler than that of a c-Si module under the same conditions.« less

Reducing Operating Temperature in Photovoltaic Modules

DOE PAGES

Silverman, Timothy J.; Deceglie, Michael G.; Subedi, Indra; ...

2018-01-09

Reducing the operating temperature of photovoltaic modules increases their efficiency and lifetime. This can be achieved by reducing the production of waste heat or by improving the rejection of waste heat. We tested, using a combination of simulation and experiment, several thermal modifications in each category. To predict operating temperature and energy yield changes in response to changes to the module, we implemented a physics-based transient simulation framework based almost entirely on measured properties. The most effective thermal modifications reduced the production of waste heat by reflecting unusable light from the cell or the module. Consistent with previous results andmore » verified in this work through year-long simulations, the ideal reflector resulted in an annual irradiance-weighted temperature reduction of 3.8 K for crystalline silicon (c-Si). Our results illustrate that more realistic reflector concepts must balance detrimental optical effects with the intended thermal effects to realize the optimal energy production advantage. Methods improving thermal conductivity or back-side emissivity showed only modest improvements of less than 1 K. We also studied a GaAs module, which uses high-efficiency and high-subbandgap reflectivity to operate at an annual irradiance-weighted temperature 12 K cooler than that of a c-Si module under the same conditions.« less

Z-path SAW RFID tag.

PubMed

Härmä, Sanna; Plessky, Victor P; Hartmann, Clinton S; Steichen, William

2008-01-01

Surface acoustic wave (SAW) radio-frequency identification (RFID) tags are soon expected to be produced in very high volumes. The size and cost of a SAW RFID tag will be key parameters for many applications. Therefore, it is of primary importance to reduce the chip size. In this work, we describe the design principles of a 2.4-GHz SAW RFID tag that is significantly smaller than earlier reported tags. We also present simulated and experimental results. The coded signal should arrive at the reader with a certain delay (typically about 1 micros), i.e., after the reception of environmental echoes. If the tag uses a bidirectional interdigital transducer (IDT), space for the initial delay is needed on both sides of the IDT. In this work, we replace the bidirectional IDT by a unidirectional one. This halves the space required by the initial delay because all the code reflectors must now be placed on the same side of the IDT. We reduce tag size even further by using a Z-path geometry in which the same space in x-direction is used for both the initial delay and the code reflectors. Chip length is thus determined only by the space required by the code reflectors.

Embeded photonic crystal at the interface of p-GaN and Ag reflector to improve light extraction of GaN-based flip-chip light-emitting diode

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

Zhen, Aigong; Ma, Ping, E-mail: maping@semi.ac.cn; Zhang, Yonghui

2014-12-22

In this experiment, a flip-chip light-emitting diode with photonic crystal was fabricated at the interface of p-GaN and Ag reflector via nanospheres lithography technique. In this structure, photonic crystal could couple with the guide-light efficiently by reason of the little distance between photonic crystal and active region. The light output power of light emitting diode with embedded photonic crystal was 1.42 times larger than that of planar flip-chip light-emitting diode. Moreover, the embedded photonic crystal structure makes the far-field divergence angle decreased by 18° without spectra shift. The three-dimensional finite difference time domain simulation results show that photonic crystal couldmore » improve the light extraction, and enhance the light absorption caused by Ag reflector simultaneously, because of the roughed surface. The depth of photonic crystal is the key parameter affecting the light extraction and absorption. Light extraction efficiency increases with the depth photonic crystal structure rapidly, and reaches the maximum at the depth 80 nm, beyond which light extraction decrease drastically.« less

A Philosophical Rationale and Practical Guide to Raising the "CQ" - Caring Quality - in Education ... A Moral Imperative.

ERIC Educational Resources Information Center

Kobak, Dorothy

1987-01-01

Argues that successful education must include teaching children to care. Outlines how a caring capacity can be developed and incorporated into educational methodology through action oriented projects. (BSR)

GammaScorpion: mobile gamma-ray tomography system for early detection of basal stem rot in oil palm plantations

NASA Astrophysics Data System (ADS)

Abdullah, Jaafar; Hassan, Hearie; Shari, Mohamad Rabaie; Mohd, Salzali; Mustapha, Mahadi; Mahmood, Airwan Affendi; Jamaludin, Shahrizan; Ngah, Mohd Rosdi; Hamid, Noor Hisham

2013-03-01

Detection of the oil palm stem rot disease Ganoderma is a major issue in estate management and production in Malaysia. Conventional diagnostic techniques are difficult and time consuming when using visual inspection, and destructive and expensive when based on the chemical analysis of root or stem tissue. As an alternative, a transportable gamma-ray computed tomography system for the early detection of basal stem rot (BSR) of oil palms due to Ganoderma was developed locally at the Malaysian Nuclear Agency, Kajang, Malaysia. This system produces high quality tomographic images that clearly differentiate between healthy and Ganoderma infected oil palm stems. It has been successfully tested and used to detect the extent of BSR damage in oil palm plantations in Malaysia without the need to cut down the trees. This method offers promise for in situ inspection of oil palm stem diseases compared to the more conventional methods.

Off-axis reflective optical apparatus

NASA Technical Reports Server (NTRS)

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

2005-01-01

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

Inline microring reflector for photonic applications

NASA Astrophysics Data System (ADS)

Kang, Young Mo

The microring is a compact resonator that is used as a versatile building block in photonic circuits ranging from filters, modulators, logic gates, sensors, switches, multiplexers, and laser cavities. The Bragg grating is a periodic structure that allows the selection of a narrow bandwidth of spectrum for stable lasing operation. In this dissertation, we study analysis and simulations of a compact microring based reflector assembled by forming a Bragg grating into a loop. With the appropriate design, the microring resonance can precisely align with the reflection peak of the grating while all other peaks are suppressed by reflection nulls of the grating. The field buildup at the resonance effectively amplifies small reflection of the grating, thereby producing significant overall reflection from the ring, and it is possible to achieve a stable narrow linewidth compact laser by forming a single mode laser cavity. The device operation principle is studied from two distinct perspectives; the first looks at coupling of two contra-directional traveling waves within the ring whereas the second aspect investigates relative excitation of the two competing microring resonant modes. In the former method, we relate the steady state amplitudes of the two traveling waves to the reflection spectrum of the grating and solve for the reflection and transmission response for each wavelength of interest. In the latter approach, we expand the field in terms of the resonant modes of the ring cavity and derive transfer functions for reflection and transmission from the nearby mode frequencies. The angular periodicity of the reflective microring geometry allows us to effectively simulate the resonant modes from a computational domain of a single period grating when the continuity boundary condition is applied. We successfully predict the reflection and transmission response of a Si3N 4/SiO2 microring reflector using this method---otherwise too large to carry out full-wave simulation---and show that the prediction agrees very well with the measurement result.

Performance simulation in high altitude platforms (HAPs) communications systems

NASA Astrophysics Data System (ADS)

Ulloa-Vásquez, Fernando; Delgado-Penin, J. A.

2002-07-01

This paper considers the analysis by simulation of a digital narrowband communication system for an scenario which consists of a High-Altitude aeronautical Platform (HAP) and fixed/mobile terrestrial transceivers. The aeronautical channel is modelled considering geometrical (angle of elevation vs. horizontal distance of the terrestrial reflectors) and statistical arguments and under these circumstances a serial concatenated coded digital transmission is analysed for several hypothesis related to radio-electric coverage areas. The results indicate a good feasibility for the communication system proposed and analysed.

The Position and Attitude of Sub-reflector Modeling for TM65 m Radio Telescope

NASA Astrophysics Data System (ADS)

Sun, Z. X.; Chen, L.; Wang, J. Q.

2016-01-01

In the course of astronomical observations, with changes in angle of pitch, the large radio telescope will have different degrees of deformation in the sub-reflector support, back frame, main reflector etc, which will lead to the dramatic decline of antenna efficiency in both high and low elevation. A sub-reflector system of the Tian Ma 65 m radio telescope has been installed in order to compensate for the gravitational deformations of the sub-reflector support and the main reflector. The position and attitude of the sub-reflector are variable in order to improve the pointing performance and the efficiency at different elevations. In this paper, it is studied that the changes of position and attitude of the sub-reflector have influence on the efficiency of antenna in the X band and Ku band. A model has been constructed to determine the position and attitude of the sub-reflector with elevation, as well as the point compensation model, by observing the radio source. In addition, antenna efficiency was tested with sub-reflector position adjusted and fixed. The results show that the model of sub-reflector can effectively improve the efficiency of the 65 m radio telescope. In X band, the aperture efficiency of the radio telescope reaches more than 60% over the entire elevation range.

A new fabrication method for precision antenna reflectors for space flight and ground test

NASA Technical Reports Server (NTRS)

Sharp, G. Richard; Wanhainen, Joyce S.; Ketelsen, Dean A.

1991-01-01

Communications satellites are using increasingly higher frequencies that require increasingly precise antenna reflectors for use in space. Traditional industry fabrication methods for space antenna reflectors employ successive modeling techniques using high- and low-temperature molds for reflector face sheets and then a final fit-up of the completed honeycomb sandwich panel antenna reflector to a master pattern. However, as new missions are planned at much higher frequencies, greater accuracies will be necessary than are achievable using these present methods. A new approach for the fabrication of ground-test solid-surface antenna reflectors is to build a rigid support structure with an easy-to-machine surface. This surface is subsequently machined to the desired reflector contour and coated with a radio-frequency-reflective surface. This method was used to fabricate a 2.7-m-diameter ground-test antenna reflector to an accuracy of better than 0.013 mm (0.0005 in.) rms. A similar reflector for use on spacecraft would be constructed in a similar manner but with space-qualified materials. The design, analysis, and fabrication of the 2.7-m-diameter precision antenna reflector for antenna ground tests and the extension of this technology to precision, space-based antenna reflectors are described.

The broad spectrum revisited: Evidence from plant remains

PubMed Central

Weiss, Ehud; Wetterstrom, Wilma; Nadel, Dani; Bar-Yosef, Ofer

2004-01-01

The beginning of agriculture is one of the most important developments in human history, with enormous consequences that paved the way for settled life and complex society. Much of the research on the origins of agriculture over the last 40 years has been guided by Flannery's [Flannery, K. V. (1969) in The Domestication and Exploitation of Plants and Animals, eds. Ucko, P. J. & Dimbleby, G. W. (Duckworth, London), pp. 73–100] “broad spectrum revolution” (BSR) hypothesis, which posits that the transition to farming in southwest Asia entailed a period during which foragers broadened their resource base to encompass a wide array of foods that were previously ignored in an attempt to overcome food shortages. Although these resources undoubtedly included plants, nearly all BSR hypothesis-inspired research has focused on animals because of a dearth of Upper Paleolithic archaeobotanical assemblages. Now, however, a collection of >90,000 plant remains, recently recovered from the Stone Age site Ohalo II (23,000 B.P.), Israel, offers insights into the plant foods of the late Upper Paleolithic. The staple foods of this assemblage were wild grasses, pushing back the dietary shift to grains some 10,000 years earlier than previously recognized. Besides the cereals (wild wheat and barley), small-grained grasses made up a large component of the assemblage, indicating that the BSR in the Levant was even broader than originally conceived, encompassing what would have been low-ranked plant foods. Over the next 15,000 years small-grained grasses were gradually replaced by the cereals and ultimately disappeared from the Levantine diet. PMID:15210984

The broad spectrum revisited: evidence from plant remains.

PubMed

Weiss, Ehud; Wetterstrom, Wilma; Nadel, Dani; Bar-Yosef, Ofer

2004-06-29

The beginning of agriculture is one of the most important developments in human history, with enormous consequences that paved the way for settled life and complex society. Much of the research on the origins of agriculture over the last 40 years has been guided by Flannery's [Flannery, K. V. (1969) in The Domestication and Exploitation of Plants and Animals, eds. Ucko, P. J. & Dimbleby, G. W. (Duckworth, London), pp. 73-100] "broad spectrum revolution" (BSR) hypothesis, which posits that the transition to farming in southwest Asia entailed a period during which foragers broadened their resource base to encompass a wide array of foods that were previously ignored in an attempt to overcome food shortages. Although these resources undoubtedly included plants, nearly all BSR hypothesis-inspired research has focused on animals because of a dearth of Upper Paleolithic archaeobotanical assemblages. Now, however, a collection of >90,000 plant remains, recently recovered from the Stone Age site Ohalo II (23,000 B.P.), Israel, offers insights into the plant foods of the late Upper Paleolithic. The staple foods of this assemblage were wild grasses, pushing back the dietary shift to grains some 10,000 years earlier than previously recognized. Besides the cereals (wild wheat and barley), small-grained grasses made up a large component of the assemblage, indicating that the BSR in the Levant was even broader than originally conceived, encompassing what would have been low-ranked plant foods. Over the next 15,000 years small-grained grasses were gradually replaced by the cereals and ultimately disappeared from the Levantine diet.

A Wideband Corner-Reflector Antenna for 240 to 400 MHz.

DTIC Science & Technology

1983-09-19

8217 .; ,:,:. .-.:.,.;.. - -... - .- . -.. .-- v...- ..... .-. .-.- 1,.:..- FIGURES 1. Corner Reflector with Open-Sleeve Dipole Feed ............ ...... 7 2...Open-Sleeve Dipole Feed for Corner Reflector, 240-400 MHz........ 8 3. Closeup Photo of Open-Sleeve Dpole ..................... ...... 8 4. VSWR of...4-ft Corner Reflector, Open-Sleeve Dipole Feed .......... 9 5. Gain of Corner Reflector............ .............. . ....... 9 6. Measured E- and H

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

NASA Technical Reports Server (NTRS)

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

1992-01-01

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

Slab Penetration vs. Slab Stagnation: Mantle Reflectors as an Indicator

NASA Astrophysics Data System (ADS)

Okeler, A.; Gu, Y. J.; Schultz, R.; Contenti, S. M.

2011-12-01

Subducting oceanic lithosphere along convergent margins may stagnate near the base of the upper mantle or penetrate into the lower mantle. These dynamic processes cause extensive thermal and compositional variations, which can be observed in terms of impedance contrast (reflectivity) and topography of mantle transition zone (MTZ) discontinuities, i.e., 410- and 660-km discontinuities. In this study, we utilize ~ 15000 surface-reflected shear waves (SS) and their precursory arrivals (S410S and S660S) to analyze subduction related deformations on mantle reflectivity structure. We apply pre-stack, time-to-depth migration technique to SS precursors, and move weak underside reflections using PREM-predicted travel-time curves. Common Mid-point gathers are formed to investigate structure under the western Pacific, south America, and Mediterranean convergent boundaries. In general, mantle reflectivity structures are consistent with previous seismic tomography models. In regions of slab penetration (e.g., southern Kurile arc, Aegean Sea), our results show 1) a substantial decrease in S660S amplitude, and 2) strong lower mantle reflector(s) at ~ 900 km depth. These reflective structures are supported by zones of high P and S velocities extending into the lower mantle. Our 1-D synthetic simulations suggest that the decreasing S660S amplitudes are, at least partially, associated with shear wave defocusing due to changes in reflector depth (by ±20 km) within averaging bin. Assuming a ~500 km wide averaging area, a dipping reflector with 6-8 % slope can reduce the amplitude of a SS precursor by ~50%. On the other hand, broad depressions with strong impedance contrast at the base of the MTZ characterize the regions of slab stagnation, such as beneath the Tyrrhenian Sea and northeastern China. For the latter region, substantial topography on the 660-km discontinuity west of the Wadati-Benioff zone suggests that the stagnant part of the Pacific plate across Honshu arc is not nearly as flat as previously suggested.

Measurement and interpretation of crustal deformation rates associated with postglacial rebound

NASA Technical Reports Server (NTRS)

Davis, James L.

1994-01-01

Analysis of Global Positioning System (GPS) data from two sites separated by horizontal distance of only approximately 2.2 m yielded phase residuals exhibiting a systematic elevation angle dependence. One of the two GPS antennas was mounted on an approximately 1 m high concrete pillar, and the other was mounted on a standard wooden tripod. We performed elevation angle cutoff tests with these data, and established that the vertical coordinate of site position was sensitive to the minimum elevation angle (elevation cutoff) of the data analyzed. For example, the vertical coordinate of site position changed by 9.7 plus or minus 0.8 mm when the minimum elevation angle was increased from 10 to 25. We performed simulations based on a simple (ray tracing) multipath model with a single horizontal reflector, and demonstrated that the elevation angle cutoff test results and the pattern of the residual versus elevation angle could be qualitatively reproduced if the reflector were located 0.1-0.2 m beneath the antenna phase center. We therefore, hypothesized that the source of the elevation-angle-dependent error were multipath reflections and scattering and that the horizontal surface of the pillar, located a distance of approximately 0.2 m beneath the antenna phase center, was the primary reflector. We tested this hypothesis by placing microwave absorbing material between the antenna and the pillar in a number of configurations and analyzed the changes in apparent position of the antenna. The results indicate that (1) the horizontal surface of the pillar is indeed the main reflector, (2) both the concrete and the metal plate embedded in the pillar are significant reflectors, and (3) the reflection can be reduced to a great degree by the use of microwave absorbing materials. These results have significant implications for the accuracy of global GPS geodetic tracking networks which use pillar-antenna configuration identical or similar to the one used here (at the Westford WFRD GPS site).

Pressure-release versus rigid reflector for extracorporeal shockwave lithotripsy.

PubMed

Loske, Achim M; Prieto, Fernando E

2002-06-01

To evaluate the advantages and disadvantages of using a pressure-release reflector instead of a rigid reflector to concentrate shockwaves for extracorporeal shockwave lithotripsy (SWL). As in all electrohydraulic lithotripters, shockwaves were generated by electrical breakdown of water between two electrodes, located at the focus (F1) closest to a paraellipsoidal reflector. A pressure-release reflector, made out of polyurethane foam, was constructed and tested on a research lithotripter using kidney stone models. Fragmentation data and pressure measurements were compared with those of a conventional rigid reflector tested on the same device. The weight of stone model fragments remaining after shockwave exposure was less with the pressure-release reflector after screening through a 3.0 x 3.0-mm mesh. The residual fragment weight was less with the rigid reflector using 1.0 x 1.0- and 0.6 x 0.6-mm meshes. Pressure-release reflectors may maintain acceptable stone fragmentation while offering improved patient safety and should be considered for SWL.

Siting Patterns of Nuclear Waste Repositories.

ERIC Educational Resources Information Center

Solomon, Barry D.; Shelley, Fred M.

1988-01-01

Provides an inventory of international radioactive waste-management policies and repository siting decisions for North America, Central and South America, Europe, Asia, and Africa. This discussion stresses the important role of demographic, geologic, and political factors in siting decisions. (Author/BSR)

An Angle of Vision: Black Women and the United States Constitution, 1787-1987.

ERIC Educational Resources Information Center

Hine, Darlene Clark

1988-01-01

Analyzes how Black women fought for and won basic citizenship rights in the United States. Cites examples which show how the struggle of Black women helped to transform the U.S. Constitution. (Author/BSR)

The Peace Movement: An Exercise in Micro-Macro Linkages.

ERIC Educational Resources Information Center

Galtung, Johan

1988-01-01

Contends that the basic assumption of the peace movement is the abuse of military power by the state. Argues that the peace movement is most effective through linkages with cultural, political, and economic forces in society. (BSR)

Anticipating the Social Consequences of AIDS: A Position Paper.

ERIC Educational Resources Information Center

Berk, Richard A.; And Others

1981-01-01

Focuses on the social consequences of the AIDS epidemic, arguing that sociologists have an important contribution to make in planning for the long-range social consequences of AIDS. Concludes with three different commentaries on Berk's article. (Author/BSR)

The Challenge of Training in Applied Sociology.

ERIC Educational Resources Information Center

Johnson, Doyle Paul; And Others

1987-01-01

Explores the challenge of expanding nonacademic employment opportunities for sociologists and training sociology students for such employment. Suggests several interrelated strategies for these students that address issues of marketing and public relations as well as curriculum revision. (Author/BSR)

What Is High School Economics? Posttest Knowledge, Attitudes, and Course Content.

ERIC Educational Resources Information Center

Soper, John C.; Walstad, William B.

1988-01-01

Reports a study designed to measure the effectiveness of teaching and learning major economic concepts and concept clusters in high school. Includes findings on student attitudes toward the subject of economics and toward economic issues. (BSR)

Demonstration of a Single-Crystal Reflector-Filter for Enhancing Slow Neutron Beams

DOE PAGES

Muhrer, Guenter; Schönfeldt, Troels; Iverson, Erik B.; ...

2016-06-14

The cold polycrystalline beryllium reflector-filter concept has been used to enhance the cold neutron emission of cryogenic hydrogen moderators, while suppressing the intermediate wavelength and fast neutron emission at the same time. While suppressing the fast neutron emission is often desired, the suppression of intermediate wavelength neutrons is often unwelcome. It has been hypothesized that replacing the polycrystalline reflector-filter concept with a single-crystal reflector-filter concept would overcome the suppression of intermediate wavelength neutrons and thereby extend the usability of the reflector-filter concept to shorter but still important wavelengths. In this paper we present the first experimental data on a single-crystalmore » reflector-filter and compare experimental results with hypothesized performance. We find that a single-crystal reflector-filter retains the long-wavelength benefit of the polycrystalline reflector-filter, without suffering the same loss of important intermediate wavelength neutrons. Ultimately, this finding extends the applicability of the reflector-filter concept to intermediate wavelengths, and furthermore indicates that the reflector-filter benefits arise from its interaction with fast (background) neutrons, not with intermediate wavelength neutrons of potential interest in many types of neutron scattering.« less

Acoustic Levitation System

NASA Technical Reports Server (NTRS)

Gammell, P. M.; Wang, T. G.; Croonquist, A.; Lee, M. C.

1985-01-01

Dense materials, such as steel balls, continuously levitated with energy provided by efficient high-powered siren in combination with shaped reflector. Reflector system, consisting of curved top reflector and flat lower reflector, eliminates instability in spatial positioning of sample.

Chemical and explosive detections using photo-acoustic effect and quantum cascade lasers

NASA Astrophysics Data System (ADS)

Choa, Fow-Sen

2013-12-01

Photoacoustic (PA) effect is a sensitive spectroscopic technique for chemical sensing. In recent years, with the development of quantum cascade lasers (QCLs), significant progress has been achieved for PA sensing applications. Using high-power, tunable mid-IR QCLs as laser sources, PA chemical sensor systems have demonstrated parts-pertrillion- level detection sensitivity. Many of these high sensitivity measurements were demonstrated locally in PA cells. Recently, we have demonstrated standoff PA detection of isopropanol vapor for more than 41 feet distance using a quantum cascade laser and a microphone with acoustic reflectors. We also further demonstrated solid phase TNT detections at a standoff distance of 8 feet. To further calibrate the detection sensitivity, we use nerve gas simulants that were generated and calibrated by a commercial vapor generator. Standoff detection of gas samples with calibrated concentration of 2.3 ppm was achieved at a detection distance of more than 2 feet. An extended detection distance up to 14 feet was observed for a higher gas concentration of 13.9 ppm. For field operations, array of microphones and microphone-reflector pairs can be utilized to achieve noise rejection and signal enhancement. We have experimentally demonstrated that the signal and noise spectra of the 4 microphone/4 reflector system with a combined SNR of 12.48 dB. For the 16-microphone and one reflector case, an SNR of 17.82 was achieved. These successful chemical sensing demonstrations will likely create new demands for widely tunable QCLs with ultralow threshold (for local fire-alarm size detection systems) and high-power (for standoff detection systems) performances.

Baseline tests of an autonomous telerobotic system for assembly of space truss structures

NASA Technical Reports Server (NTRS)

Rhodes, Marvin D.; Will, Ralph W.; Quach, Coung

1994-01-01

Several proposed space missions include precision reflectors that are larger in diameter than any current or proposed launch vehicle. Most of these reflectors will require a truss structure to accurately position the reflector panels and these reflectors will likely require assembly in orbit. A research program has been conducted at the NASA Langley Research Center to develop the technology required for the robotic assembly of truss structures. The focus of this research has been on hardware concepts, computer software control systems, and operator interfaces necessary to perform supervised autonomous assembly. A special facility was developed and four assembly and disassembly tests of a 102-strut tetrahedral truss have been conducted. The test procedures were developed around traditional 'pick-and-place' robotic techniques that rely on positioning repeatability for successful operation. The data from two of the four tests were evaluated and are presented in this report. All operations in the tests were controlled by predefined sequences stored in a command file, and the operator intervened only when the system paused because of the failure of an actuator command. The tests were successful in identifying potential pitfalls in a telerobotic system, many of which would not have been readily anticipated or incurred through simulation studies. Addressing the total integrated task, instead of bench testing the component parts, forced all aspects of the task to be evaluated. Although the test results indicate that additional developments should be pursued, no problems were encountered that would preclude automated assembly in space as a viable construction method.

Concepts and analysis for precision segmented reflector and feed support structures

NASA Technical Reports Server (NTRS)

Miller, Richard K.; Thomson, Mark W.; Hedgepeth, John M.

1990-01-01

Several issues surrounding the design of a large (20-meter diameter) Precision Segmented Reflector are investigated. The concerns include development of a reflector support truss geometry that will permit deployment into the required doubly-curved shape without significant member strains. For deployable and erectable reflector support trusses, the reduction of structural redundancy was analyzed to achieve reduced weight and complexity for the designs. The stiffness and accuracy of such reduced member trusses, however, were found to be affected to a degree that is unexpected. The Precision Segmented Reflector designs were developed with performance requirements that represent the Reflector application. A novel deployable sunshade concept was developed, and a detailed parametric study of various feed support structural concepts was performed. The results of the detailed study reveal what may be the most desirable feed support structure geometry for Precision Segmented Reflector/Large Deployable Reflector applications.

Neutron beam optimization based on a 7Li(p,n)7Be reaction for treatment of deep-seated brain tumors by BNCT

NASA Astrophysics Data System (ADS)

Zahra Ahmadi, Ganjeh; S. Farhad, Masoudi

2014-10-01

Neutron beam optimization for accelerator-based Boron Neutron Capture Therapy (BNCT) is investigated using a 7Li(p,n)7Be reaction. Design and optimization have been carried out for the target, cooling system, moderator, filter, reflector, and collimator to achieve a high flux of epithermal neutron and satisfy the IAEA criteria. Also, the performance of the designed beam in tissue is assessed by using a simulated Snyder head phantom. The results show that the optimization of the collimator and reflector is critical to finding the best neutron beam based on the 7Li(p,n)7Be reaction. Our designed beam has 2.49×109n/cm2s epithermal neutron flux and is suitable for BNCT of deep-seated brain tumors.

A tunable Fabry-Perot filter (λ/18) based on all-dielectric metamaterials

NASA Astrophysics Data System (ADS)

Ao, Tianhong; Xu, Xiangdong; Gu, Yu; Jiang, Yadong; Li, Xinrong; Lian, Yuxiang; Wang, Fu

2018-05-01

A tunable Fabry-Perot filter composed of two separated all-dielectric metamaterials is proposed and numerically investigated. Different from metallic metamaterials reflectors, the all-dielectric metamaterials are constructed by high-permittivity TiO2 cylinder arrays and exhibit high reflection in a broadband of 2.49-3.08 THz. The high reflection is attributed to the first and second Mie resonances, by which the all-dielectric metamaterials can serve as reflectors in the Fabry-Perot filter. Both the results from phase analysis method and CST simulations reveal that the resonant frequency of the as-proposed filter appears at 2.78 THz, responding to a cavity with λ/18 wavelength thickness. Particularly, the resonant frequency can be adjusted by changing the cavity thickness. This work provides a feasible approach to design low-loss terahertz filters with a thin air cavity.

Nanoimprinted backside reflectors for a-Si:H thin-film solar cells: critical role of absorber front textures.

PubMed

Tsao, Yao-Chung; Fisker, Christian; Pedersen, Thomas Garm

2014-05-05

The development of optimal backside reflectors (BSRs) is crucial for future low cost and high efficiency silicon (Si) thin-film solar cells. In this work, nanostructured polymer substrates with aluminum coatings intended as BSRs were produced by positive and negative nanoimprint lithography (NIL) techniques, and hydrogenated amorphous silicon (a-Si:H) was deposited hereon as absorbing layers. The relationship between optical properties and geometry of front textures was studied by combining experimental reflectance spectra and theoretical simulations. It was found that a significant height variation on front textures plays a critical role for light-trapping enhancement in solar cell applications. As a part of sample preparation, a transfer NIL process was developed to overcome the problem of low heat deflection temperature of polymer substrates during solar cell fabrication.

Modeling and stability of segmented reflector telescopes - A decentralized approach

NASA Technical Reports Server (NTRS)

Ryaciotaki-Boussalis, Helen A.; Ih, Che-Hang Charles

1990-01-01

The decentralization of a segmented reflector telescope based on a finite-element model of its structure is considered. The decentralization of the system at the panel level is considered. Each panel is originally treated as an isolated subsystem so that the controller design is performed independently at the local level, and then applied to the composite system for stability analysis. The panel-level control laws were designed by means of pole placement using local output feedback. Simulation results show a better 1000:1 vibration attenuation in panel position when compared to the open-loop system. It is shown that the overall closed-loop system is exponentially stable provided that certain conditions are met. The advantage to the decentralized approach is that the design is performed in terms of the low-dimensionality subsystems, thus drastically reducing the design computational complexities.

Deployable reflector structure

NASA Technical Reports Server (NTRS)

Mikulas, Martin, Jr. (Inventor); Hoberman, Charles (Inventor)

1993-01-01

A deployable reflector structure is presented. The structure has a number of movable reflector panels pivotably supported on rigid arms. Several such arms are pivotably connected to a central structure. The arm can move in starburst fashion from a packaged stage, where all arms are vertical, to a deployed stage, where all arms are horizontal. All of the movable reflector panels are maintained at a predetermined angle to an axis of the reflector structure when the arms are pivoted. The reflector panels are stacked tightly on top of each other in the packaged state of the reflector structure. Simple mechanisms are used for avoiding interference between panels on different arms in the packaged stage and for fitting the movable panels together like tiles in the deployed stage.

The Knitting Lesson.

ERIC Educational Resources Information Center

Smith, Pamela

1987-01-01

Based on Jean-Francois Millet's 1869 painting, "The Knitting Lesson," this lesson's goal is to introduce students in grades seven through nine to genre (everyday life) painting the nineteenth century. The lesson is also designed to show that some aspects of genre may be timeless. (BSR)

The Spirit and Action of Citizenship: Alex Taylor Community School.

ERIC Educational Resources Information Center

Haggerson, Nelson L.; And Others

1987-01-01

Describes a study of the prosocial atmosphere and citizenship spirit found at Alex Taylor Community School in Edmonton, Canada. Includes a brief background of the project and a description of several motivating citizenship activities within the school. (BSR)

Global Community Education: A Curriculum Trend for the '80s.

ERIC Educational Resources Information Center

Matriano, Estela

1987-01-01

Defines global community education and examines two major topics considered essential for understanding it. The topics are: (1) perspectives and imperatives of global education; and (2) the realities and possibilities of globalizing a curriculum for a new age. (BSR)

Economic Education in Japanese and American Secondary Schools.

ERIC Educational Resources Information Center

Ellington, J. Lucien; Tadahisa, Uozumi

1988-01-01

Reports a study that compared and contrasted economic education in U.S. and Japanese secondary schools. Examines economics in the curricula; textbooks; characteristics of teachers responsible for economics instruction; and the level of emphasis teachers assign to economic concepts. (Author/BSR)

VizieR Online Data Catalog: Inelastic e+Mg collision data (Barklem+, 2017)

NASA Astrophysics Data System (ADS)

Barklem, P. S.; Osorio, Y.; Fursa, D. V.; Bray, I.; Zatsarinny, O.; Bartschat, K.; Jerkstrand, A.

2017-06-01

The file states.dat lists the considered states. The remaining files then provide the effective collision strength matrices for various temperatures from the convergent close coupling (CCC) and B-spline R-matrix (BSR) calculations. (27 data files).

Evaluation of deer warning reflectors in Virginia.

DOT National Transportation Integrated Search

2003-01-01

A deer warning reflector consists of a red, double-sided reflector mounted on posts, similar to those used for roadside delineators along roadways. As vehicles approach and move through the road section, it is purported that the reflector reflects th...

Experimental study of an adaptive CFRC reflector for high order wave-front error correction

NASA Astrophysics Data System (ADS)

Lan, Lan; Fang, Houfei; Wu, Ke; Jiang, Shuidong; Zhou, Yang

2018-03-01

The recent radio frequency communication system developments are generating the need for creating space antennas with lightweight and high precision. The carbon fiber reinforced composite (CFRC) materials have been used to manufacture the high precision reflector. The wave-front errors caused by fabrication and on-orbit distortion are inevitable. The adaptive CFRC reflector has received much attention to do the wave-front error correction. Due to uneven stress distribution that is introduced by actuation force and fabrication, the high order wave-front errors such as print-through error is found on the reflector surface. However, the adaptive CFRC reflector with PZT actuators basically has no control authority over the high order wave-front errors. A new design architecture assembled secondary ribs at the weak triangular surfaces is presented in this paper. The virtual experimental study of the new adaptive CFRC reflector has conducted. The controllability of the original adaptive CFRC reflector and the new adaptive CFRC reflector with secondary ribs are investigated. The virtual experimental investigation shows that the new adaptive CFRC reflector is feasible and efficient to diminish the high order wave-front error.

Simulation of reflecting surface deviations of centimeter-band parabolic space radiotelescope (SRT) with the large-size mirror

NASA Astrophysics Data System (ADS)

Kotik, A.; Usyukin, V.; Vinogradov, I.; Arkhipov, M.

2017-11-01

he realization of astrophysical researches requires the development of high-sensitive centimeterband parabolic space radiotelescopes (SRT) with the large-size mirrors. Constructively such SRT with the mirror size more than 10 m can be realized as deployable rigid structures. Mesh-structures of such size do not provide the reflector reflecting surface accuracy which is necessary for the centimeter band observations. Now such telescope with the 10 m diameter mirror is developed in Russia in the frame of "SPECTR - R" program. External dimensions of the telescope is more than the size of existing thermo-vacuum chambers used to prove SRT reflecting surface accuracy parameters under the action of space environment factors. That's why the numerical simulation turns out to be the basis required to accept the taken designs. Such modeling should be based on experimental working of the basic constructive materials and elements of the future reflector. In the article computational modeling of reflecting surface deviations of a centimeter-band of a large-sized deployable space reflector at a stage of his orbital functioning is considered. The analysis of the factors that determines the deviations - both determined (temperatures fields) and not-determined (telescope manufacturing and installation faults; the deformations caused by features of composite materials behavior in space) is carried out. The finite-element model and complex of methods are developed. They allow to carry out computational modeling of reflecting surface deviations caused by influence of all factors and to take into account the deviations correction by space vehicle orientation system. The results of modeling for two modes of functioning (orientation at the Sun) SRT are presented.

A new approach for shaping of dual-reflector antennas

NASA Technical Reports Server (NTRS)

Lee, Teh-Hong; Burnside, W. D.; Rudduck, Roger C.

1987-01-01

The shaping of 2-D dual-reflector antenna systems to generate a prescribed distribution with uniform phase at the aperture of the second reflector is examined. This method is based on the geometrical nature of Cassegrain and Gregorian dual-reflector antennas. The method of syntheses satisfies the principles of geometrical optics which are the foundations of dual-reflector designs. Instead of setting up differential equations or heuristically designing the subreflector, a set of algebraic equations is formulated and solved numerically to obtain the desired surfaces. The caustics of the reflected rays from the subreflector can be obtained and examined. Several examples of 2-D dual-reflector shaping are shown to validate the study. Geometrical optics and physical optics are used to calculate the scattered fields from the reflectors.

Transcending a Patriarchal Past: Teaching the History of Women in Sociology.

ERIC Educational Resources Information Center

Deegan, Mary Jo

1988-01-01

Contends that the ideas of early female sociologists are rarely documented in textbooks, classrooms, or historical accounts of the profession. Provides a guide to reference works, autobiographies, and biographies about 10 early female founders of American sociology. (Author/BSR)

16 CFR 1512.16 - Requirements for reflectors.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 1512.16 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FEDERAL HAZARDOUS SUBSTANCES ACT... vehicle headlamps. The use of reflector combinations off the center plane of the bicycle (defined in...) Front reflector. The reflector or mount shall not contact the ground plane when the bicycle is resting...

Investigation of structure in the modular light pipe component for LED automotive lamp

NASA Astrophysics Data System (ADS)

Chen, Hsi-Chao; Zhou, Yang; Huang, Chien-Sheng; Jhong, Wan-Ling; Cheng, Bo-Wei; Jhang, Jhe-Ming

2014-09-01

Light-Emitting Diodes (LEDs) have the advantages of small length, long lifetime, fast response time (μs), low voltage, good mechanical properties and environmental protection. Furthermore, LEDs could replace the halogen lamps to avoid the mercury pollution and economize the use of energy. Therefore, the LEDs could instead of the traditional lamp in the future and became an important light source. The proposal of this study was to investigate the effects of the structure and length of the reflector component for a LED automotive lamp. The novel LED automotive lamp was assembled by several different modularization columnar. The optimized design of the different structure and the length to the reflector was simulated by software TracePro. The design result must met the vehicle regulation of United Nations Economic Commission for Europe (UNECE) such as ECE-R19 etc. The structure of the light pipe could be designed by two steps structure. Then constitute the proper structure and choose different power LED to meet the luminous intensity of the vehicle regulation. The simulation result shows the proper structure and length has the best total luminous flux and a high luminous efficiency for the system. Also, the stray light could meet the vehicle regulation of ECE R19. Finally, the experimental result of the selected structure and length of the light pipe could match the simulation result above 80%.

Design of a high efficiency relativistic backward wave oscillator with low guiding magnetic field

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

Li, Xiaoze; Song, Wei; Tan, Weibing

2016-07-15

A high efficiency relativistic backward wave oscillator working at a low guiding magnetic field is designed and simulated. A trapezoidal resonant reflector is used to reduce the modulation field in the resonant reflector to avoid overmodulation of the electron beam which will lead to a large momentum spread and then low conversion efficiency. The envelope of the inner radius of the slow wave structure (SWS) increases stepwise to keep conformal to the trajectory of the electron beam which will alleviate the bombardment of the electron on the surface of the SWS. The length of period of the SWS is reducedmore » gradually to make a better match between phase velocity and electron beam, which decelerates continually and improves the RF current distribution. Meanwhile the modulation field is reduced by the introduction of nonuniform SWS also. The particle in cell simulation results reveal that a microwave with a power of 1.8 GW and a frequency of 14.7 GHz is generated with an efficiency of 47% when the diode voltage is 620 kV, the beam current 6.1 kA, and the guiding magnetic field 0.95 T.« less

Solar energy collection system

NASA Technical Reports Server (NTRS)

Miller, C. G.; Stephens, J. B. (Inventor)

1979-01-01

A fixed, linear, ground-based primary reflector having an extended curved sawtooth-contoured surface covered with a metalized polymeric reflecting material, reflects solar energy to a movably supported collector that is kept at the concentrated line focus reflector primary. The primary reflector may be constructed by a process utilizing well known freeway paving machinery. The solar energy absorber is preferably a fluid transporting pipe. Efficient utilization leading to high temperatures from the reflected solar energy is obtained by cylindrical shaped secondary reflectors that direct off-angle energy to the absorber pipe. A seriatim arrangement of cylindrical secondary reflector stages and spot-forming reflector stages produces a high temperature solar energy collection system of greater efficiency.

Theoretical modeling of the dynamics of a semiconductor laser subject to double-reflector optical feedback

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

Bakry, A.; Abdulrhmann, S.; Ahmed, M., E-mail: mostafa.farghal@mu.edu.eg

2016-06-15

We theoretically model the dynamics of semiconductor lasers subject to the double-reflector feedback. The proposed model is a new modification of the time-delay rate equations of semiconductor lasers under the optical feedback to account for this type of the double-reflector feedback. We examine the influence of adding the second reflector to dynamical states induced by the single-reflector feedback: periodic oscillations, period doubling, and chaos. Regimes of both short and long external cavities are considered. The present analyses are done using the bifurcation diagram, temporal trajectory, phase portrait, and fast Fourier transform of the laser intensity. We show that adding themore » second reflector attracts the periodic and perioddoubling oscillations, and chaos induced by the first reflector to a route-to-continuous-wave operation. During this operation, the periodic-oscillation frequency increases with strengthening the optical feedback. We show that the chaos induced by the double-reflector feedback is more irregular than that induced by the single-reflector feedback. The power spectrum of this chaos state does not reflect information on the geometry of the optical system, which then has potential for use in chaotic (secure) optical data encryption.« less

Special test equipment and fixturing for MSAT reflector assembly alignment

NASA Technical Reports Server (NTRS)

Young, Jeffrey A.; Zinn, Michael R.; Mccarten, David R.

1994-01-01

The MSAT Reflector Assembly is a state of the art subsystem for Mobile Satellite (MSAT), a geosynchronous-based commercial mobile telecommunication satellite program serving North America. The Reflector Assembly consisted of a deployable, three-hinge, folding-segment Boom, deployable 5.7 x 5.3-meter 16-rib Wrap-Rib Reflector, and a Reflector Pointing Mechanism (RPM). The MSAT spacecraft was based on a Hughes HS601 spacecraft bus carrying two Reflector Assemblies independently dedicated for L-band transmit and receive operations. Lockheed Missiles and Space Company (LMSC) designed and built the Reflector Assembly for MSAT under contract to SPAR Aerospace Ltd. Two MSAT satellites were built jointly by SPAR Aerospace Ltd. and Hughes Space and Communications Co. for this program, the first scheduled for launch in 1994. When scaled for wavelength, the assembly and alignment requirements for the Reflector Assembly were in many instances equivalent to or exceeded that of a diffraction-limited visible light optical system. Combined with logistical constraints inherent to large, compliant, lightweight structures; 'bolt-on' alignment; and remote, indirect spacecraft access; the technical challenges were formidable. This document describes the alignment methods, the special test equipment, and fixturing for Reflector Assembly assembly and alignment.

78 FR 14357 - Certain Compact Fluorescent Reflector Lamps, Products Containing Same and Components Thereof...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-05

... Reflector Lamps, Products Containing Same and Components Thereof; Institution of Investigation AGENCY: U.S... fluorescent reflector lamps, products containing same and components thereof by reason of infringement of... compact fluorescent reflector lamps, products containing same and components thereof by reason of...

Breeding sex ratio and population size of loggerhead turtles from Southwestern Florida.

PubMed

Lasala, Jacob A; Hughes, Colin R; Wyneken, Jeanette

2018-01-01

Species that display temperature-dependent sex determination are at risk as a result of increasing global temperatures. For marine turtles, high incubation temperatures can skew sex ratios towards females. There are concerns that temperature increases may result in highly female-biased offspring sex ratios, which would drive a future sex ratio skew. Studying the sex ratios of adults in the ocean is logistically very difficult because individuals are widely distributed and males are inaccessible because they remain in the ocean. Breeding sex ratios (BSR) are sought as a functional alternative to study adult sex ratios. One way to examine BSR is to determine the number of males that contribute to nests. Our goal was to evaluate the BSR for loggerhead turtles (Caretta caretta) nesting along the eastern Gulf of Mexico in Florida, from 2013-2015, encompassing three nesting seasons. We genotyped 64 nesting females (approximately 28% of all turtles nesting at that time) and up to 20 hatchlings from their nests (n = 989) using 7 polymorphic microsatellite markers. We identified multiple paternal contributions in 70% of the nests analyzed and 126 individual males. The breeding sex ratio was approximately 1 female for every 2.5 males. We did not find repeat males in any of our nests. The sex ratio and lack of repeating males was surprising because of female-biased primary sex ratios. We hypothesize that females mate offshore of their nesting beaches as well as en route. We recommend further comparisons of subsequent nesting events and of other beaches as it is imperative to establish baseline breeding sex ratios to understand how growing populations behave before extreme environmental effects are evident.

Breeding sex ratio and population size of loggerhead turtles from Southwestern Florida

PubMed Central

Hughes, Colin R.; Wyneken, Jeanette

2018-01-01

Species that display temperature-dependent sex determination are at risk as a result of increasing global temperatures. For marine turtles, high incubation temperatures can skew sex ratios towards females. There are concerns that temperature increases may result in highly female-biased offspring sex ratios, which would drive a future sex ratio skew. Studying the sex ratios of adults in the ocean is logistically very difficult because individuals are widely distributed and males are inaccessible because they remain in the ocean. Breeding sex ratios (BSR) are sought as a functional alternative to study adult sex ratios. One way to examine BSR is to determine the number of males that contribute to nests. Our goal was to evaluate the BSR for loggerhead turtles (Caretta caretta) nesting along the eastern Gulf of Mexico in Florida, from 2013–2015, encompassing three nesting seasons. We genotyped 64 nesting females (approximately 28% of all turtles nesting at that time) and up to 20 hatchlings from their nests (n = 989) using 7 polymorphic microsatellite markers. We identified multiple paternal contributions in 70% of the nests analyzed and 126 individual males. The breeding sex ratio was approximately 1 female for every 2.5 males. We did not find repeat males in any of our nests. The sex ratio and lack of repeating males was surprising because of female-biased primary sex ratios. We hypothesize that females mate offshore of their nesting beaches as well as en route. We recommend further comparisons of subsequent nesting events and of other beaches as it is imperative to establish baseline breeding sex ratios to understand how growing populations behave before extreme environmental effects are evident. PMID:29370223

Solar thermal collectors using planar reflector

NASA Technical Reports Server (NTRS)

Espy, P. N.

1978-01-01

Specular reflectors have been used successfully with flat-plate collectors to achieve exceptionally high operating temperatures and high delivered energy per unit collector area. Optimal orientation of collectors and reflectors can result in even higher performance with an improved relationship between energy demand and supply. This paper reports on a study providing first order optimization of collector-reflector arrays in which single- and multiple-faceted reflectors in fixed or singly adjustable configurations provide delivered energy maxima in either summer or winter.

Photogrammetry research for FAST eleven-meter reflector panel surface shape measurement

NASA Astrophysics Data System (ADS)

Zhou, Rongwei; Zhu, Lichun; Li, Weimin; Hu, Jingwen; Zhai, Xuebing

2010-10-01

In order to design and manufacture the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) active reflector measuring equipment, measurement on each reflector panel surface shape was presented, static measurement of the whole neutral spherical network of nodes was performed, real-time dynamic measurement at the cable network dynamic deformation was undertaken. In the implementation process of the FAST, reflector panel surface shape detection was completed before eleven-meter reflector panel installation. Binocular vision system was constructed based on the method of binocular stereo vision in machine vision, eleven-meter reflector panel surface shape was measured with photogrammetry method. Cameras were calibrated with the feature points. Under the linearity camera model, the lighting spot array was used as calibration standard pattern, and the intrinsic and extrinsic parameters were acquired. The images were collected for digital image processing and analyzing with two cameras, feature points were extracted with the detection algorithm of characteristic points, and those characteristic points were matched based on epipolar constraint method. Three-dimensional reconstruction coordinates of feature points were analyzed and reflective panel surface shape structure was established by curve and surface fitting method. The error of reflector panel surface shape was calculated to realize automatic measurement on reflector panel surface shape. The results show that unit reflector panel surface inspection accuracy was 2.30mm, within the standard deviation error of 5.00mm. Compared with the requirement of reflector panel machining precision, photogrammetry has fine precision and operation feasibility on eleven-meter reflector panel surface shape measurement for FAST.

33 CFR 118.120 - Radar reflectors and racons.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Radar reflectors and racons. 118... BRIDGES BRIDGE LIGHTING AND OTHER SIGNALS § 118.120 Radar reflectors and racons. The District Commander may require or authorize the installation of radar reflectors and racons on bridge structures, stakes...

46 CFR 169.726 - Radar reflector.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 7 2011-10-01 2011-10-01 false Radar reflector. 169.726 Section 169.726 Shipping COAST... Control, Miscellaneous Systems, and Equipment § 169.726 Radar reflector. Each nonmetallic vessel less than 90 feet in length must exhibit a radar reflector of suitable size and design while underway. Markings ...

33 CFR 118.120 - Radar reflectors and racons.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Radar reflectors and racons. 118... BRIDGES BRIDGE LIGHTING AND OTHER SIGNALS § 118.120 Radar reflectors and racons. The District Commander may require or authorize the installation of radar reflectors and racons on bridge structures, stakes...

46 CFR 169.726 - Radar reflector.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 7 2010-10-01 2010-10-01 false Radar reflector. 169.726 Section 169.726 Shipping COAST... Control, Miscellaneous Systems, and Equipment § 169.726 Radar reflector. Each nonmetallic vessel less than 90 feet in length must exhibit a radar reflector of suitable size and design while underway. Markings ...

46 CFR 169.726 - Radar reflector.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 7 2012-10-01 2012-10-01 false Radar reflector. 169.726 Section 169.726 Shipping COAST... Control, Miscellaneous Systems, and Equipment § 169.726 Radar reflector. Each nonmetallic vessel less than 90 feet in length must exhibit a radar reflector of suitable size and design while underway. Markings ...

33 CFR 118.120 - Radar reflectors and racons.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Radar reflectors and racons. 118... BRIDGES BRIDGE LIGHTING AND OTHER SIGNALS § 118.120 Radar reflectors and racons. The District Commander may require or authorize the installation of radar reflectors and racons on bridge structures, stakes...

46 CFR 169.726 - Radar reflector.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 7 2014-10-01 2014-10-01 false Radar reflector. 169.726 Section 169.726 Shipping COAST... Control, Miscellaneous Systems, and Equipment § 169.726 Radar reflector. Each nonmetallic vessel less than 90 feet in length must exhibit a radar reflector of suitable size and design while underway. Markings ...

33 CFR 118.120 - Radar reflectors and racons.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Radar reflectors and racons. 118... BRIDGES BRIDGE LIGHTING AND OTHER SIGNALS § 118.120 Radar reflectors and racons. The District Commander may require or authorize the installation of radar reflectors and racons on bridge structures, stakes...

46 CFR 169.726 - Radar reflector.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 7 2013-10-01 2013-10-01 false Radar reflector. 169.726 Section 169.726 Shipping COAST... Control, Miscellaneous Systems, and Equipment § 169.726 Radar reflector. Each nonmetallic vessel less than 90 feet in length must exhibit a radar reflector of suitable size and design while underway. Markings ...

33 CFR 118.120 - Radar reflectors and racons.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Radar reflectors and racons. 118... BRIDGES BRIDGE LIGHTING AND OTHER SIGNALS § 118.120 Radar reflectors and racons. The District Commander may require or authorize the installation of radar reflectors and racons on bridge structures, stakes...

Positive Action Programmes in the Fields of Education, Training, Retraining, Employment, and Promotion for Women.

ERIC Educational Resources Information Center

Michel, Andree

1987-01-01

Reviews efforts by individual governments in the European Economic Community to improve the rights of women in the workplace. Focuses on the objectives of these efforts, and concludes by evaluating strengths and weaknesses of these programs. (BSR)

Evaluation of spectral entropy to measure anaesthetic depth and antinociception in sevoflurane-anaesthetised Beagle dogs.

PubMed

Morgaz, Juan; Granados, María del Mar; Domínguez, Juan Manuel; Navarrete, Rocío; Fernández, Andrés; Galán, Alba; Muñoz, Pilar; Gómez-Villamandos, Rafael J

2011-06-01

The use of spectral entropy to determine anaesthetic depth and antinociception was evaluated in sevoflurane-anaesthetised Beagle dogs. Dogs were anaesthetised at each of five multiples of their individual minimum alveolar concentrations (MAC; 0.75, 1, 1.25, 1.5 and 1.75 MAC), and response entropy (RE), state entropy (SE), RE-SE difference, burst suppression rate (BSR) and cardiorespiratory parameters were recorded before and after a painful stimulus. RE, SE and RE-SE difference did not change significantly after the stimuli. The correlation between MAC-entropy parameters was weak, but these values increased when 1.75 MAC results were excluded from the analysis. BSR was different to zero at 1.5 and 1.75 MAC. It was concluded that RE and RE-SE differences were not adequate indicators of antinociception and SE and RE were unable to detect deep planes of anaesthesia in dogs, although they both distinguished the awake and unconscious states. Copyright © 2010 Elsevier Ltd. All rights reserved.

Shear Ram Verification Test Protocol (VTP) Best Practices

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

Lindley, Roy A.; Braun, Joseph C.

A blowout preventer (BOP) is a critical component used on subsea oil and gas wells during drilling, completion, and workover operations on the U. S. outer continental shelf (OCS). The purpose of the BOP is to seal oil and gas wells, and in the case of an emergency well-control event, to prevent the uncontrolled release of hydrocarbons. One of the most important components of the BOP is the hydraulically operated blind shear ram (BSR) that shears drilling-related components, such as drill pipes, casings, tubings, and wire-related tools that may have been placed in the well. In addition to shearing thesemore » components, the BSR must form a seal to keep hydrocarbons within the well bore, even when under the highest well-fluid pressures expected. The purpose of this document is for Argonne National Laboratory (ANL) to provide an independent view, based on current regulations, and best practices for testing and confirming the operability and suitability of BSRs under realistic (or actual) well conditions.« less

Developments in rheumatology consultant manpower provision: the BSR/arc Workforce Register 2003-05.

PubMed

Harrison, M J; Morley, K D; Symmons, D P M

2006-11-01

To summarize the changes and continuing inequalities in rheumatology service provision in the UK between 2001 and 2005. Questionnaires about demographics and workload were sent to all consultants on the BSR/arc Workforce Register in January 2003 and 2005. A total of 94% of 506 consultants responded in 2003 and 89% of 542 in 2005. About 19% of the consultants practice rheumatology with acute medicine. Levels of optimal provision exceed 60% in England and Wales, but are below 50% in Scotland and Northern Ireland. The levels of provision in London are substantially higher than anywhere else. The median number of hours worked per week has increased from 35.2 in 2003 to 41 in 2005. Rheumatology continues to expand. There is inequality with better provision in England (especially London) and Wales than Scotland and Northern Ireland. Patterns of nurse and Senior House Officer (SHO) provision correlate with consultant numbers. Thus, the catalyst for improved service is consultant expansion.

Coherence parameter measurements for neon and hydrogen

NASA Astrophysics Data System (ADS)

Wright, Robert; Hargreaves, Leigh; Khakoo, Murtadha; Zatsarinny, Oleg; Bartschat, Klaus; Stauffer, Al

2015-09-01

We present recent coherence parameter measurements for excitation of neon and hydrogen by 50 eV electrons. The measurements were made using a crossed electron/gas beam spectrometer, featuring a hemispherically selected electron energy analyzer for detecting scattered electrons and double-reflection VUV polarization analyzer to register fluorescence photons. Time-coincidence counting methods on the electron and photon signals were employed to determine Stokes Parameters at each scattering angle, with data measured at angles between 20 - 115 degrees. The data are compared with calculated results using the B-Spline R-Matrix (BSR) and Relativistic Distorted Wave (RDW) approaches. Measurements were made of both the linear (Plin and γ) and circular (Lperp) parameters for the lowest lying excited states in these two targets. We particularly focus on results in the Lperp parameter, which shows unusual behavior in these particular targets, including strong sign changes implying reversal of the angular momentum transfer. In the case of neon, the unusual behavior is well captured by the BSR, but not by other models.

The Boundaries of Woman's Spirituality in the Beliefs-Spirituality-Religiousness (B-S-R) Model: A Third Perspective-Beliefs as a Cognitive Basis.

PubMed

Skrzypińska, Katarzyna

2017-10-01

The real nature of the phenomenon of woman's Spirituality is the main contemporary challenge for empirical research. The literature needs many more examples of the cognitive genesis of worldviews, Spirituality and Religiousness. The first aim of this article is to present the central tenet of the Threefold Nature of Spirituality model which theoretically explains the nature of Spirituality and the theoretical relationship between beliefs (worldviews), Spirituality and Religiousness (B-S-R model). The second aim is the empirical verification of this relationship through the application of an analysis of mediation. The 308 participants were women aged 18-50 years (M = 25.25, SD = 9.42). The results obtained indicate that is a good mediator between an individual's worldview and Religiousness. Presented analysis of mediation allows us to describe the basic functioning mechanism of the spiritual sphere and the relationship between the three elements: worldview, Spirituality and Religiousness.

Relativistic backward wave oscillator operating in TM02 with cutoff-type resonant reflector

NASA Astrophysics Data System (ADS)

Teng, Yan; Shi, Yanchao; Yang, Dewen; Cao, Yibing; Zhang, Zhijun

2017-04-01

This paper proposes an overmoded relativistic backward wave oscillator (RBWO) operating in the TM02 mode with the cutoff-type resonant reflector characterized by the advantages of the cutoff neck and the single resonant cavity. In order to protect the explosive emission of the annular cathode from the disturbance of the microwave leakage, the cutoff-type resonant reflector can effectively prevent the microwave consisting of several modes from propagating into the diode region. Attributed to the strong reflections caused by the cutoff-type resonant reflector at the front end of the overmoded slow-wave structure (SWS), the overmoded RBWO works in the state of the strong resonance, which enhances the beam-to-microwave power conversion efficiency. TM02 is selected as the operation mode so as to increase the power handling capability. The nonuniform SWS depresses the cross-excitation of the unwanted longitudinal modes of TM02 and improves the synchronous interaction between the electron beam and the structure wave. It is found that when we make the peak values of the longitudinal electric field and the modulated current appear nearly at the same position in the overmoded SWS by optimizing the electrodynamic structure, the conversion efficiency will be enhanced significantly. In the numerical simulation, the microwave generation with power 2.99 GW and efficiency 0.45 is obtained under the diode voltage 851 kV and current 7.8 kA with the guide magnetic field of 4.3 T. The microwave generation with the pure frequency spectrum of 10.083 GHz radiates in the TM01 mode. The conversion efficiency keeps above 0.40 over the diode voltage range of 220 kV.

A novel concentrator with zero-index metamaterial for space solar power station

NASA Astrophysics Data System (ADS)

Huang, Jin; Chu, Xue-mei; Fan, Jian-yu; Jin, Qi-bao; Duan, Zhu-zhu

2017-03-01

Space solar power station (SSPS) is a comprehensive system that continuously collects solar energy in space and transmits it to ground with a wireless power transmission (WPT) system. These systems have great potential to provide large-scale energy. To increase the efficiency and reduce the weight and cost of the photovoltaic (PV) components, a huge light-weighted concentrator was introduced in the latest SSPS concepts, such as integrated symmetrical concentrator (ISC) and arbitrarily large phased array (ALPHA). However, for typical SSPS running in Geostationary Earth Orbit (GEO), the sunlight direction varies with time, leading to a great challenge for concentrator design. In ISC, the two-dimensional mast is used to realize sun-tracking. However, a multi-thousand-ton structure is difficult to control precisely in space. For this reason, ALPHA comprises a large number of individually pointed thin-film reflectors to intercept sunlight, mounted on the non-moving structure. However, the real-time adjustment of the thousands of reflectors is still an open problem. Furthermore, the uniformity of the time of the power generation (UTPG) is another factor evaluating the system. Therefore, this paper proposes a novel concentrator based on zero-index metamaterial (ZIM) called Thin-film Energy Terminator (SSPS-TENT). This will aid the control of the massive reflectors while avoiding the rotation of the overall system, the control of the massive reflectors and the influence of the obliquity of the ecliptic. Also, an optimization design method is proposed to increase its solar energy collecting efficiency (ECE) and flux distribution (FD). The ray-tracing simulation results show that the ECE is more than 96% of the day. In terms of the FD, the uniformity varies from 0.3057 to 0.5748. Compared with ALPHA, the UTPG is more stable.

Reflectors with directional-mixed reflection properties for application in luminaries with high-power LED diodes

NASA Astrophysics Data System (ADS)

Zaremba, Krzysztof

2008-06-01

Application of directional-mixed reflectors results in a luminance decrease of the apparent image of light emitting diodes (LEDs), which is advantageous as far as glare reduction is concerned. On the other hand, reflectors have a negative impact on luminous intensity curves of the luminaries. This work analyzes an impact of surfaces with directional-mixed reflection properties in a mirror reflector designed for a luminary equipped with high-power LEDs. We present an algorithm used to determine the shape of the reflector of the surface with small scattering, where the axis twist angle for a parabolic reflector varies in a predefined range and follows a power function.

Back surface reflectors for solar cells

NASA Technical Reports Server (NTRS)

Chai, A. T.

1980-01-01

Sample solar cells were fabricated to study the effects of various back surface reflectors on the device performance. They are typical 50 micrometers thick, space quality, silicon solar cells except for variations of the back contact configuration. The back surfaces of the sample cells are polished to a mirror like finish, and have either conventional full contacts or grid finger contacts. Measurements and evaluation of various metallic back surface reflectors, as well as cells with total internal reflection, are presented. Results indicate that back surface reflectors formed using a grid finger back contact are more effective reflectors than cells with full back metallization and that Au, Ag, or Cu are better back surface reflector metals than Al.

Implementation of a small-angle scattering model in MCNPX for very cold neutron reflector studies

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

Grammer, Kyle B.; Gallmeier, Franz X.

Current neutron moderator media do not sufficiently moderate neutrons below the cold neutron regime into the very cold neutron (VCN) regime that is desirable for some physics applications. Nesvizhevsky et al [1] have demonstrated that nanodiamond powder efficiently reflect VCN via small angle scattering. He suggests that these effects could be exploited to boost the neutron output of a VCN moderator. Simulation studies of nanoparticle reflectors are being investigated as part of the development of a VCN source option for the SNS second target station. We are pursuing an expansion of the MCNPX code by implementation of an analytical small-anglemore » scattering function [2], which is adaptable by scattering particle sizes, distributions, and packing fractions in order to supplement currently existing scattering kernels. The analytical model and preliminary studies using MCNPX will be discussed.« less

Tunable electromagnetically induced transparency in integrated silicon photonics circuit.

PubMed

Li, Ang; Bogaerts, Wim

2017-12-11

We comprehensively simulate and experimentally demonstrate a novel approach to generate tunable electromagnetically induced transparency (EIT) in a fully integrated silicon photonics circuit. It can also generate tunable fast and slow light. The circuit is a single ring resonator with two integrated tunable reflectors inside, which form an embedded Fabry-Perot (FP) cavity inside the ring cavity. The mode of the FP cavity can be controlled by tuning the reflections using integrated thermo-optic tuners. Under correct tuning conditions, the interaction of the FP mode and the ring resonance mode will generate a Fano resonance and an EIT response. The extinction ratio and bandwidth of the EIT can be tuned by controlling the reflectors. Measured group delay proves that both fast light and slow light can be generated under different tuning conditions. A maximum group delay of 1100 ps is observed because of EIT. Pulse advance around 1200 ps is also demonstrated.

Suspended light-emitting diode featuring a bottom dielectric distributed Bragg reflector

NASA Astrophysics Data System (ADS)

Cai, Wei; Wang, Wei; Zhu, Bingcheng; Gao, Xumin; Zhu, Guixia; Yuan, Jialei; Wang, Yongjin

2018-01-01

Here, we propose, fabricate and characterize the light manipulation of a suspended-membrane InGaN/GaN multiple-quantum-well light-emitting diode (MQW-LED) with a dielectric distributed Bragg reflector (DBR) positioned at the bottom, implemented on a GaN-on-silicon platform. Silicon removal is conducted to obtain the suspended MQW-LED architecture, and back wafer thinning of the epitaxial film is performed to improve the device performance. A 6-pair SiO2/Ta2O5 DBR is deposited on the backside to manipulate the emitted light. The experimental results demonstrate that the bottom dielectric DBR exhibits high reflectivity and distinctly changes the light emission, which are consistent with the performed simulation results. This work represents a significant step towards the realization of inexpensive, electrically driven and simply fabricated GaN VCSELs for potential use in number of applications.

A Ka-band radial relativistic backward wave oscillator with GW-class output power

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

Zhu, Jiaxin; Zhang, Xiaoping, E-mail: zhangxiaoping@nudt.edu.cn; Dang, Fangchao

A novel radial relativistic backward wave oscillator with a reflector is proposed and designed to generate GW-level high power microwaves at Ka-band. The segmented radial slow wave structure and the reflector are matched to enhance interaction efficiency. We choose the volume wave TM{sub 01} mode as the working mode due to the volume wave characteristic. The main structural parameters of the novel device are optimized by particle-in-cell simulation. High power microwaves with power of 2 GW and a frequency of 29.4 GHz are generated with 30% efficiency when the electron beam voltage is 383 kV, the beam current is 17 kA, and themore » guiding magnetic field is only 0.6 T. Simultaneously, the highest electric field in the novel Ka-band device is just about 960 kV/cm in second slow wave structure.« less

Workshop on Technology Development Issues for the Large Deployable Reflector (LDR)

NASA Technical Reports Server (NTRS)

Nishioka, Kenji (Editor)

1986-01-01

The results of the 2nd Large Deployable Reflector (LDR) Technology Review Workshop held at Asilomar, California, March 17 to 22, 1985, are summarized. The workshop was convened to update LDR Technology status and to revise as necessary the results for the first LDR Workshop held in June 1982. There were some 100 participants representing government agencies, industry, and universities. This Workshop's goal was to assess, identify, and set priorities for the LDR technology issues based on requirements identified in the first workshop. Four high-priority technology areas were identified: (1) mirror materials and construction; (2) sensing and controls; (3) system-simulation and modeling capability; and (4) submillimeter instruments. The results of the workshop were used to provide a list of technolgy issues for the development of a technology initiatives plan for the LDR by NASA's Office of Aeronautics and Space Technology.

Light interaction in sapphire/MgF2/Al triple-layer omnidirectional reflectors in AlGaN-based near ultraviolet light-emitting diodes

PubMed Central

Lee, Keon Hwa; Moon, Yong-Tae; Song, June-O; Kwak, Joon Seop

2015-01-01

This study examined systematically the mechanism of light interaction in the sapphire/MgF2/Al triple-layer omnidirectional reflectors (ODR) and its effects on the light output power in near ultraviolet light emitting diodes (NUV-LEDs) with the ODR. The light output power of NUV-LEDs with the triple-layer ODR structure increased with decreasing surface roughness of the sapphire backside in the ODR. Theoretical modeling of the roughened surface suggests that the dependence of the reflectance of the triple-layer ODR structure on the surface roughness can be attributed mainly to light absorption by the Al nano-structures and the trapping of scattered light in the MgF2 layer. Furthermore, the ray tracing simulation based upon the theoretical modeling showed good agreement with the measured reflectance of the ODR structure in diffuse mode. PMID:26010378

Light interaction in sapphire/MgF2/Al triple-layer omnidirectional reflectors in AlGaN-based near ultraviolet light-emitting diodes.

PubMed

Lee, Keon Hwa; Moon, Yong-Tae; Song, June-O; Kwak, Joon Seop

2015-05-26

This study examined systematically the mechanism of light interaction in the sapphire/MgF2/Al triple-layer omnidirectional reflectors (ODR) and its effects on the light output power in near ultraviolet light emitting diodes (NUV-LEDs) with the ODR. The light output power of NUV-LEDs with the triple-layer ODR structure increased with decreasing surface roughness of the sapphire backside in the ODR. Theoretical modeling of the roughened surface suggests that the dependence of the reflectance of the triple-layer ODR structure on the surface roughness can be attributed mainly to light absorption by the Al nano-structures and the trapping of scattered light in the MgF2 layer. Furthermore, the ray tracing simulation based upon the theoretical modeling showed good agreement with the measured reflectance of the ODR structure in diffuse mode.

Scanning wind-vector scatterometers with two pencil beams

NASA Technical Reports Server (NTRS)

Kirimoto, T.; Moore, R. K.

1984-01-01

A scanning pencil-beam scatterometer for ocean windvector determination has potential advantages over the fan-beam systems used and proposed heretofore. The pencil beam permits use of lower transmitter power, and at the same time allows concurrent use of the reflector by a radiometer to correct for atmospheric attenuation and other radiometers for other purposes. The use of dual beams based on the same scanning reflector permits four looks at each cell on the surface, thereby improving accuracy and allowing alias removal. Simulation results for a spaceborne dual-beam scanning scatterometer with a 1-watt radiated power at an orbital altitude of 900 km is described. Two novel algorithms for removing the aliases in the windvector are described, in addition to an adaptation of the conventional maximum likelihood algorithm. The new algorithms are more effective at alias removal than the conventional one. Measurement errors for the wind speed, assuming perfect alias removal, were found to be less than 10%.

System concept for a moderate cost Large Deployable Reflector (LDR)

NASA Technical Reports Server (NTRS)

Swanson, P. N.; Breckinridge, J. B.; Diner, A.; Freeland, R. E.; Irace, W. R.; Mcelroy, P. M.; Meinel, A. B.; Tolivar, A. F.

1986-01-01

A study was carried out at JPL during the first quarter of 1985 to develop a system concept for NASA's LDR. Major features of the concept are a four-mirror, two-stage optical system; a lightweight structural composite segmented primary reflector; and a deployable truss backup structure with integral thermal shield. The two-stage optics uses active figure control at the quaternary reflector located at the primary reflector exit pupil, allowing the large primary to be passive. The lightweight composite reflector panels limit the short-wavelength operation to approximately 30 microns but reduce the total primary reflector weight by a factor of 3 to 4 over competing technologies. On-orbit thermal analysis indicates a primary reflector equilibrium temperature of less than 200 K with a maximum gradient of about 5 C across the 20-m aperture. Weight and volume estimates are consistent with a single Shuttle launch, and are based on Space Station assembly and checkout.

75 FR 34656 - Energy Conservation Program for Consumer Products: Energy Conservation Standards for Certain...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-18

... diameter, elliptical reflector (ER), and bulged reflector (BR) incandescent reflector lamps. In that... document or any other aspect of the rulemaking for certain small diameter, ER, and BR incandescent..., ER, and BR incandescent reflector lamps, and provide docket number EERE-2010- BT-STD-0005 and/or RIN...

Corrosion protection for silver reflectors

DOEpatents

Arendt, Paul N.; Scott, Marion L.

1991-12-31

A method of protecting silver reflectors from damage caused by contact with gaseous substances which are often present in the atmosphere and a silver reflector which is so protected. The inventive method comprises at least partially coating a reflector with a metal oxide such as aluminum oxide to a thickness of 15 .ANG. or less.

Approaching conversion limit with all-dielectric solar cell reflectors.

PubMed

Fu, Sze Ming; Lai, Yi-Chun; Tseng, Chi Wei; Yan, Sheng Lun; Zhong, Yan Kai; Shen, Chang-Hong; Shieh, Jia-Min; Li, Yu-Ren; Cheng, Huang-Chung; Chi, Gou-chung; Yu, Peichen; Lin, Albert

2015-02-09

Metallic back reflectors has been used for thin-film and wafer-based solar cells for very long time. Nonetheless, the metallic mirrors might not be the best choices for photovoltaics. In this work, we show that solar cells with all-dielectric reflectors can surpass the best-configured metal-backed devices. Theoretical and experimental results all show that superior large-angle light scattering capability can be achieved by the diffuse medium reflectors, and the solar cell J-V enhancement is higher for solar cells using all-dielectric reflectors. Specifically, the measured diffused scattering efficiency (D.S.E.) of a diffuse medium reflector is >0.8 for the light trapping spectral range (600nm-1000nm), and the measured reflectance of a diffuse medium can be as high as silver if the geometry of embedded titanium oxide(TiO(2)) nanoparticles is optimized. Moreover, the diffuse medium reflectors have the additional advantage of room-temperature processing, low cost, and very high throughput. We believe that using all-dielectric solar cell reflectors is a way to approach the thermodynamic conversion limit by completely excluding metallic dissipation.

Lightweight composite reflectors for space optics

NASA Astrophysics Data System (ADS)

Williams, Brian E.; McNeal, Shawn R.; Ono, Russell M.

1998-01-01

The primary goal of this work was to advance the state of the art in lightweight, high optical quality reflectors for space- and Earth-based telescopes. This was accomplished through the combination of a precision silicon carbide (SiC) reflector surface and a high specific strength, low-mass SiC structural support. Reducing the mass of components launched into space can lead to substantial cost savings, but an even greater benefit of lightweight reflectors for both space- and Earth-based optics applications is the fact that they require far less complex and less expensive positioning systems. While Ultramet is not the first company to produce SiC by chemical vapor deposition (CVD) for reflector surfaces, it is the first to propose and demonstrate a lightweight, open-cell SiC structural foam that can support a thin layer of the highly desirable polished SiC reflector material. SiC foam provides a substantial structural and mass advantage over conventional honeycomb supports and alternative finned structures. The result is a reflector component that meets or exceeds the optical properties of current high-quality glass, ceramic, and metal reflectors while maintaining a substantially lower areal density.

Shape adjustment optimization and experiment of cable-membrane reflectors

NASA Astrophysics Data System (ADS)

Du, Jingli; Gu, Yongzhen; Bao, Hong; Wang, Congsi; Chen, Xiaofeng

2018-05-01

Cable-membrane structures are widely employed for large space reflectors due to their lightweight, compact and easy package. In these structures, membranes are attached to cable net, serving as reflectors themselves or as supporting structures for other reflective surface. The cable length and membrane shape have to be carefully designed and fabricated to guarantee the desired reflector surface shape. However, due to inevitable error in cable length and membrane shape during the manufacture and assembly of cable-membrane reflectors, some cables have to be designed to be capable of length adjustment. By carefully adjusting the length of these cables, the degeneration in reflector shape precision due to this inevitable error can be effectively reduced. In the paper a shape adjustment algorithm for cable-membrane reflectors is proposed. Meanwhile, model updating is employed during shape adjustment to decrease the discrepancy of the numerical model with respect to the actual reflector. This discrepancy has to be considered because during attaching membranes to cable net, the accuracy of the membrane shape is hard to guarantee. Numerical examples and experimental results demonstrate the proposed method.

Tracking reflector assembly for a skylight

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

Dominquez, R.L.

1984-02-07

A tracking reflector assembly for a skylight includes a ring-shaped base member rotatably supported above the skylight by a plurality of rollers which engage a channel formed within an annular wall of the ring. A reflector is pivotally coupled to the ring for reflecting light into the skylight to supplement light which strikes the skylight directly. A vertical drive motor operates in response to a pair of photosensors for raising and lowering the reflector to follow changes in the angular elevation of the sun. The ring-shaped base member includes a toothed lower surface engaged by a gear coupled to amore » horizontal drive motor for rotating the ring-shaped base member in response to a third photosensor for following east-to-west movement of the sun. Each of the aforementioned photosensors is normally shaded and actuates the associated drive motor only when being struck by direct sunlight. A vertical limit switch limits the amount by which the reflector may be pivotally raised to avoid reflecting midday summer sunlight into the skylight. Another switch is responsive to closure of the reflector over the base member for preventing the vertical drive motor from attempting to further pivot the reflector downwardly. A fourth photosensor senses darkness resulting from sunset or heavy overcast conditions for pivoting the reflector downwardly and returning the base member and reflector to an easterly direction. A limit switch senses the return of the base member to the full east position for terminating actuation of the horizontal drive motor. A user operated switch selectively enables the tracking reflector assembly to operate automatically or causes the reflector to be lowered and the base member to be returned to the full east position until the user again enables the automatic control circuitry.« less

Criticality Safety Analysis on the Mixed Be, Nat-U, and C (Graphite) Reflectors in 55-Gallon Waste Drums and Their Equivalents for HWM Applications

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

Chou, P

The objective of this analysis is to develop and establish the technical basis on the criticality safety controls for the storage of mixed beryllium (Be), natural uranium (Nat-U), and carbon (C)/graphite reflectors in 55-gallon waste containers and/or their equivalents in Hazardous Waste Management (HWM) facilities. Based on the criticality safety limits and controls outlined in Section 3.0, the operations involving the use of mixed-reflector drums satisfy the double-contingency principle as required by DOE Order 420.1 and are therefore criticality safe. The mixed-reflector mass limit is 120 grams for each 55-gallon drum or its equivalent. a reflector waiver of 50 gramsmore » is allowed for Be, Nat-U, or C/graphite combined. The waived reflectors may be excluded from the reflector mass calculations when determining if a drum is compliant. The mixed-reflector drums are allowed to mix with the typical 55-gallon one-reflector drums with a Pu mass limit of 120 grams. The fissile mass limit for the mixed-reflector container is 65 grams of Pu equivalent each. The corresponding reflector mass limits are 300 grams of Be, and/or 100 kilograms of Nat-U, and/or 110 kilograms of C/graphite for each container. All other unaffected control parameters for the one-reflector containers remain in effect for the mixed-reflector drums. For instance, Superior moderators, such as TrimSol, Superla white mineral oil No. 9, paraffin, and polyethylene, are allowed in unlimited quantities. Hydrogenous materials with a hydrogen density greater than 0.133 gram/cc are not allowed. Also, an isolation separation of no less than 76.2 cm (30-inch) is required between a mixed array and any other array. Waste containers in the action of being transported are exempted from this 76.2-cm (30-inch) separation requirement. All deviations from the CS controls and mass limits listed in Section 3.0 will require individual criticality safety analyses on a case-by-case basis for each of them to confirm their criticality safety prior to their deployment and implementation.« less

Suppression of large intraluminal bubble expansion in shock wave lithotripsy without compromising stone comminution: Methodology and in vitro experiments

NASA Astrophysics Data System (ADS)

Zhong, Pei; Zhou, Yufeng

2001-12-01

To reduce the potential of vascular injury without compromising the stone comminution capability of a Dornier HM-3 lithotripter, we have devised a method to suppress intraluminal bubble expansion via in situ pulse superposition. A thin shell ellipsoidal reflector insert was designed and fabricated to fit snugly into the original reflector of an HM-3 lithotripter. The inner surface of the reflector insert shares the same first focus with the original HM-3 reflector, but has its second focus located 5 mm proximal to the generator than that of the HM-3 reflector. With this modification, the original lithotripter shock wave is partitioned into a leading lithotripter pulse (peak positive pressure of 46 MPa and positive pulse duration of 1 μs at 24 kV) and an ensuing second compressive wave of 10 MPa peak pressure and 2 μs pulse duration, separated from each other by about 4 μs. Superposition of the two waves leads to a selective truncation of the trailing tensile component of the lithotripter shock wave, and consequently, a reduction in the maximum bubble expansion up to 41% compared to that produced by the original reflector. The pulse amplitude and -6 dB beam width of the leading lithotripter shock wave from the upgraded reflector at 24 kV are comparable to that produced by the original HM-3 reflector at 20 kV. At the lithotripter focus, while only about 30 shocks are needed to cause a rupture of a blood vessel phantom made of cellulose hollow fiber (i.d.=0.2 mm) using the original HM-3 reflector at 20 kV, no rupture could be produced after 200 shocks using the upgraded reflector at 24 kV. On the other hand, after 100 shocks the upgraded reflector at 24 kV can achieve a stone comminution efficiency of 22%, which is better than the 18% efficiency produced by the original reflector at 20 kV (p=0.043). All together, it has been shown in vitro that the upgraded reflector can produce satisfactory stone comminution while significantly reducing the potential for vessel rupture in shock wave lithotripsy.

Planar shock reflection on a wedged concave reflector

NASA Astrophysics Data System (ADS)

Yu, Fan-Ming; Sheu, Kuen-Dong

2001-04-01

The investigation of shock reflection and shock diffraction phenomena upon a wedged concave reflector produced by a planar incident shock wave has been done in the shock tube facility of Institute of Aeronautics and Astronautics, National Cheng- Kung University. The experiment proceeds upon three wedged concave reflectors models the upper and lower wedge angles arrangement of them are (50 degrees, 50 degrees) - 35 degrees, 35 degrees) and (50 degrees, 35 degrees), respectively. They were tested at Mach numbers of 1.2 - 1.65 and 2.0. On the first reflector, following the regular reflection on the 50 degree-wedged surface by the incident shock wave, a Mach shock diffraction behavior has been observed as shock moves outward from the apex of the reflector. On the apex of the reflector, it behaviors as a sector of the blast shock moving on a diverging channel. On the shadowgraph pictures it has been observed there exists a pattern of gas dynamics focus upon the second reflector. The Mach reflection from the 35 degree- wedged surface as being generated by the planar incident shock wave, on which the overlapping of the two triple points from both wedged surface offers the focusing mechanism. The shock interference, which proceeds by the Mach shock reflection and the regular shock diffraction from the reflector, generates a very complicate rolling-up of slip lines system. On the third reflector, the mixed shock interference behavior has been observed of which two diffraction shocks from concave 50 degree-wedged surface and 35 degree-wedged surface interfere with each other. The measurement of the peak pressure along a ray from the model apex parallel to incident shock direction indicates that the measured maximum pressure rising is larger near the apex of the reflector. Considering the measured maximum pressure increment due to the reflection shocks indicate that the wave strength upon large apex angle reflector is greater than it is upon small apex angle reflector. However, as considering the measured maximum pressure increment following the diffraction shocks, the results show that due to the focusing process upon (35 degree, 35 degree) reflector, it is of the largest increment.

The thermal structure of the mud diapir/volcano and its influence on gas hydrate stability in northern South China Sea

NASA Astrophysics Data System (ADS)

Wan, Z.; Xu, X.; Wang, X.

2016-12-01

The mud diapir/volcano is an important indicator for gas hydrate exploration, which develops widely in continental slopes. There are many mud diapirs/volcanoes developed in northern South China Sea continental slope. Guangzhou Marine Geological Survey (GMGS) of the Chinese Ministry of Land and Resources targeted mud diapirs/volcanoes and deployed gas hydrate drilling in the Shenhu area. An obvious mud diapir developed below borehole number SH5, and bottom-simulating reflection (BSR) was also detected, but no gas hydrates were found at this borehole. We analyzed the thermal structure of mud diapirs and their relationship to the occurrence of gas hydrates. The in situ temperature at the seafloor is approximately 2.2 2.5oC in the study area. Seafloor heat flow values of SH5 is 71.4mW/m2. Temperature increases rapidly to 17oC from 40 m to 100 m and stays in the range of 17 to 19oC below 100 m. And the thermal conductivity value of SH5 is approximately 1.0 W/m·k from top to bottom. The evolution of the mud diapir/volcanoes can be divided into three stages within a continuous geological process controlling the gas hydrate reservoir. During the late stage, liquid from the mud diapir/volcanoes begins to invade the gas hydrate stability zone . Because of the high unit heat capacity of liquid, the whole temperature field of the surrounding layers increases significantly when the mud diapir/volcanoes pierces upwards. This high heat flow leads to decomposition of the gas hydrates. Therefore, the reason of SH5 did not find gas hydrates may be that the mud diapir had pierced through during the late stage, leading to gas hydrate decomposition, even though there is an obvious BSR. This work was supported by Science and Technology Program of Guangzhou (No. 201607010214) and National Nature Science Foundation of China (No. 91128203,41102077).

Prospecting for Natural Gas Gydrate in the Orca & Choctaw Basins in the Northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Cook, A.; Hillman, J. I. T.; Sawyer, D.; Frye, M.; Palmes, S.; Shedd, W. W.

2016-12-01

The Orca and Choctaw salt bounded mini-basins, which occur in 1.5 to 2.5 km water depth on the northern Gulf of Mexico slope, are currently under consideration as an IODP scientific drilling location for coarse-grained natural gas hydrate systems. We use a 3D seismic dataset for gas hydrate prospecting that covers parts of eleven lease blocks ( 200 km2) in the Walker Ridge protraction area. The study area includes the southern section of the Orca Basin and a smaller section of the northern Choctaw Basin. We have mapped a discontinuous bottom-simulating reflection (BSR) over nearly 30% of our seismic dataset, which varies significantly in both amplitude and depth throughout the area. The southeastern section of our dataset contains three positive impedance amplitude horizons with possible phase reversals at the BSR. Detailed mapping in the area also reveals at the base of gas hydrate stability, a complicated intercalation of an east-west trending fault system and an amalgamated deepwater depositional system comprising channel levee deposits and turbidite sheet sands. Three industry wells drilled in the southwestern section of our study area indicate that the sedimentary sequence infilling the basins consists of predominantly mud rich units with interbedded turbidite sands, forming a 2 km thick supra-salt sequence of late Miocene to Pleistocene sediments. Two of the industry wells have strong evidence for natural gas hydrate in clay-rich sediment, with moderate resistivity (between 2-10 Ωm) increases above background resistivity in zones that exceed 60 m thick. Additionally, the electromagnetic resistivity curves in these wells separate suggesting that the gas hydrate occurs in high-angle fractures. We will present our seismic dataset, our continuing analysis and selected drill sites in the Orca and Choctaw basins. Furthermore, our analysis in the southeastern section of the study area underscores the importance of interpreting faults when considering phase reversals in hydrate systems.

Instructional Innovation - MOS: A Model Involving Student Participation.

ERIC Educational Resources Information Center

Malloy, Elizabeth; O'Donnell, Terrence P.

1987-01-01

Asserts that new models of instructional methodology are needed to meet the demands of a changing world community. Describes a small-group teaching method called MOS, which calls for students to read, analyze, and shape meaning gained from material while instructors encourage and provide insight. (BSR)

10 CFR 429.35 - Bare or covered (no reflector) medium base compact fluorescent lamps.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 10 Energy 3 2012-01-01 2012-01-01 false Bare or covered (no reflector) medium base compact....35 Bare or covered (no reflector) medium base compact fluorescent lamps. (a) Sampling plan for... reflector) medium base compact fluorescent lamps; and (2) For each basic model of bare or covered (no...

10 CFR 429.35 - Bare or covered (no reflector) medium base compact fluorescent lamps.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 10 Energy 3 2014-01-01 2014-01-01 false Bare or covered (no reflector) medium base compact....35 Bare or covered (no reflector) medium base compact fluorescent lamps. (a) Sampling plan for... reflector) medium base compact fluorescent lamps; and (2) For each basic model of bare or covered (no...

10 CFR 429.35 - Bare or covered (no reflector) medium base compact fluorescent lamps.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 10 Energy 3 2013-01-01 2013-01-01 false Bare or covered (no reflector) medium base compact....35 Bare or covered (no reflector) medium base compact fluorescent lamps. (a) Sampling plan for... reflector) medium base compact fluorescent lamps; and (2) For each basic model of bare or covered (no...

43 CFR 2806.43 - How does BLM calculate rent for passive reflectors and local exchange networks?

Code of Federal Regulations, 2011 CFR

2011-10-01

... reflectors and local exchange networks? 2806.43 Section 2806.43 Public Lands: Interior Regulations Relating...-Of-Way § 2806.43 How does BLM calculate rent for passive reflectors and local exchange networks? (a) BLM calculates rent for passive reflectors and local exchange networks by using the same rent...

How clear-cutting affects fire severity and soil properties in a Mediterranean ecosystem.

PubMed

Francos, Marcos; Pereira, Paulo; Mataix-Solera, Jorge; Arcenegui, Victoria; Alcañiz, Meritxell; Úbeda, Xavier

2018-01-15

Forest management practices in Mediterranean ecosystems are frequently employed to reduce both the risk and severity of wildfires. However, these pre-fire treatments may influence the effects of wildfire events on soil properties. The aim of this study is to examine the short-term effects of a wildfire that broke out in 2015 on the soil properties of three sites: two exposed to management practices in different years - 2005 (site M05B) and 2015 (site M15B) - and one that did not undergo any management (NMB) and to compare their properties with those recorded in a plot (Control) unaffected by the 2015 wildfire. We analyzed aggregate stability (AS), soil organic matter (SOM) content, total nitrogen (TN), carbon/nitrogen ratio (C/N), inorganic carbon (IC), pH, electrical conductivity (EC), extractable calcium (Ca), magnesium (Mg), sodium (Na), and potassium (K), microbial biomass carbon (C mic ) and basal soil respiration (BSR). In the managed plots, a clear-cutting operation was conducted, whereby part of the vegetation was cut and left covering the soil surface. The AS values recorded at the Control site were significantly higher than those recorded at M05B, whereas the TN and SOM values at NMB were significantly higher than those recorded at M05B. IC was significantly higher at M05B than at the other plots. There were no significant differences in C/N ratio between the analyzed sites. Soil pH at M05B was significantly higher than the value recorded at the Control plot. Extractable Ca was significantly higher at NMB than at both M05B and the Control, while extractable Mg was significantly lower at M05B than at NMB. Extractable K was significantly lower at the Control than at the three fire-affected plots. C mic was significantly higher at NMB than at the Control. BSR, BSR/C and BSR/C mic values at the fire-affected sites were significantly lower than those recorded at the Control. No significant differences were identified in C mic /C. Overall, a comparison of the pre-fire treatments showed that NMB was the practice that had the least negative effects on the soil properties studied, followed by M15B, and that fire severity was highest at M05B due to the accumulation of dead plant fuel. Copyright © 2017 Elsevier Ltd. All rights reserved.

Surface measuring technique. [using a laser to scan the surface of a reflector

NASA Technical Reports Server (NTRS)

Spiers, R. B., Jr.

1980-01-01

Measurement of the surface contour of a large electrostatically formed concave reflector using a modified Foucault or knife edge test is described. The curve of the actual electrostatically formed reflector surface is compared to a curve representing a reference sphere. Measurements of surface slope and deviation are calculated every 15 cm along the reflector's horizontal and vertical diameters. Characterization of surface roughness on a small scale compared to the laser spot size at the reflector are obtained from the increased laser spot size at a distant projection screen.

Weighted SAW reflector gratings for orthogonal frequency coded SAW tags and sensors

NASA Technical Reports Server (NTRS)

Puccio, Derek (Inventor); Malocha, Donald (Inventor)

2011-01-01

Weighted surface acoustic wave reflector gratings for coding identification tags and sensors to enable unique sensor operation and identification for a multi-sensor environment. In an embodiment, the weighted reflectors are variable while in another embodiment the reflector gratings are apodized. The weighting technique allows the designer to decrease reflectively and allows for more chips to be implemented in a device and, consequently, more coding diversity. As a result, more tags and sensors can be implemented using a given bandwidth when compared with uniform reflectors. Use of weighted reflector gratings with OFC makes various phase shifting schemes possible, such as in-phase and quadrature implementations of coded waveforms resulting in reduced device size and increased coding.

Electromagnetic Simulations for an Axisymmetric Gregorian Reflector System for a Space Deployed Inflatable Antenna

DTIC Science & Technology

2016-01-22

Q. J. Wei, S. Pan, S. Mohan, and S. Seager, Inflatable antenna for CubeSat : fabrication, deployment and results of experimental tests, 2014 IEEE...Aerospace Conference, pp. 1- 12. [8] A. Babuscia, T. Choi, C. Lee, and K-M. Cheung, Inflatable antennas and arrays for interplanetary communication using CubeSats and SmallSats, 2015 IEEE Aerospace Conference, pp. 1-9.

SU-F-T-183: Design of a Beam Shaping Assembly of a Compact DD-Based Boron Neutron Capture Therapy System

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

Hsieh, M; Liu, Y; Nie, L

Purpose: To design a beam shaping assembly (BSA) to shape the 2.45-MeV neutrons produced by a deuterium-deuterium (DD) neutron generator and to optimize the beam output for boron neutron capture therapy of brain tumors Methods: MCNP is used for this simulation study. The simulation model consists of a neutron surface source that resembles an actual DD source and is surrounded by a BSA. The neutron source emits 2.45-MeV neutrons isotropically. The BSA is composed of a moderator, reflector, collimator and filter. Various types of materials and geometries are tested for each component to optimize the neutron output. Neutron characteristics aremore » measured with an 2×2×2-cm{sup 3} air-equivalent cylinder at the beam exit. The ideal BSA is determined by evaluating the in-air parameters, which include epithermal neutron per source neutron, fast neutron dose per epithermal neutron, and photon dose per epithermal neutron. The parameter values are compared to those recommended by the IAEA. Results: The ideal materials for reflector and thermal neutron filter were lead and cadmium, respectively. The thickness for reflector was 43 cm and for filter was 0.5 mm. At present, the best-performing moderator has 25 cm of AlF{sub 3} and 5 cm of MgF{sub 2}. This layout creates a neutron spectrum that has a peak at approximately 10 keV and produces 1.35E-4 epithermal neutrons per source neutron per cm{sup 2}. Additional neutron characteristics, fast neutrons per epithermal neutron and photon per epithermal neutron, are still under investigation. Conclusion: Working is ongoing to optimize the final layout of the BSA. The neutron spectrum at the beam exit window of the final configuration will have the maximum number of epithermal neutrons and limited photon and fast neutron contaminations within the recommended values by IAEA. Future studies will also include phantom experiments to validate the simulation results.« less

Piezocomposite Actuator Arrays for Correcting and Controlling Wavefront Error in Reflectors

NASA Technical Reports Server (NTRS)

Bradford, Samuel Case; Peterson, Lee D.; Ohara, Catherine M.; Shi, Fang; Agnes, Greg S.; Hoffman, Samuel M.; Wilkie, William Keats

2012-01-01

Three reflectors have been developed and tested to assess the performance of a distributed network of piezocomposite actuators for correcting thermal deformations and total wave-front error. The primary testbed article is an active composite reflector, composed of a spherically curved panel with a graphite face sheet and aluminum honeycomb core composite, and then augmented with a network of 90 distributed piezoelectric composite actuators. The piezoelectric actuator system may be used for correcting as-built residual shape errors, and for controlling low-order, thermally-induced quasi-static distortions of the panel. In this study, thermally-induced surface deformations of 1 to 5 microns were deliberately introduced onto the reflector, then measured using a speckle holography interferometer system. The reflector surface figure was subsequently corrected to a tolerance of 50 nm using the actuators embedded in the reflector's back face sheet. Two additional test articles were constructed: a borosilicate at window at 150 mm diameter with 18 actuators bonded to the back surface; and a direct metal laser sintered reflector with spherical curvature, 230 mm diameter, and 12 actuators bonded to the back surface. In the case of the glass reflector, absolute measurements were performed with an interferometer and the absolute surface was corrected. These test articles were evaluated to determine their absolute surface control capabilities, as well as to assess a multiphysics modeling effort developed under this program for the prediction of active reflector response. This paper will describe the design, construction, and testing of active reflector systems under thermal loads, and subsequent correction of surface shape via distributed peizeoelctric actuation.

Near ultraviolet InGaN/AlGaN-based light-emitting diodes with highly reflective tin-doped indium oxide/Al-based reflectors.

PubMed

Choi, Chang-Hoon; Han, Jaecheon; Park, Jae-Seong; Seong, Tae-Yeon

2013-11-04

The enhanced light output power of a InGaN/AlGaN-based light-emitting diodes (LEDs) using three different types of highly reflective Sn-doped indium oxide (ITO)/Al-based p-type reflectors, namely, ITO/Al, Cu-doped indium oxide (CIO)/s-ITO(sputtered)/Al, and Ag nano-dots(n-Ag)/CIO/s-ITO/Al, is presented. The ITO/Al-based reflectors exhibit lower reflectance (76 - 84% at 365 nm) than Al only reflector (91.1%). However, unlike Al only n-type contact, the ITO/Al-based contacts to p-GaN show good ohmic characteristics. Near-UV (365 nm) InGaN/AlGaN-based LEDs with ITO/Al, CIO/s-ITO/Al, and n-Ag/CIO/s-ITO/Al reflectors exhibit forward-bias voltages of 3.55, 3.48, and 3.34 V at 20 mA, respectively. The LEDs with the ITO/Al and CIO/s-ITO/Al reflectors exhibit 9.5% and 13.5% higher light output power (at 20 mA), respectively, than the LEDs with the n-Ag/CIO/s-ITO/Al reflector. The improved performance of near UV LEDs is attributed to the high reflectance and low contact resistivity of the ITO/Al-based reflectors, which are better than those of conventional Al-based reflectors.

Conformal Membrane Reflectors for Deployable Optics

NASA Technical Reports Server (NTRS)

Hood, Patrick J.; Keys, Andrew S. (Technical Monitor)

2002-01-01

This presentation reports the Phase I results on NASA's Gossamer Spacecraft Exploratory Research and Technology Program. Cornerstone Research Group, Inc., the University of Rochester, and International Photonics Consultants collaborated to investigate the feasibility of free-standing, liquid-crystal-polymer (LCP) reflectors for integration into space-based optical systems. The goal of the program was to achieve large-diameter, broadband. reflective membranes that are resistant to the effects of space, specifically cryogenic environments and gamma-ray irradiation. Additionally, we assessed the applicability of utilizing the technology as tight sails, since, by their very nature, these films offer high-reflectivity at specified wavelengths. Previous research programs have demonstrated all-polymer, narrow-band Specular reflectors and diffuse membrane reflectors. The feasibility of fabricating an all-polymer broadband specular reflector and a narrow-band specular membrane reflector was assessed in the Phase I Gossamer program. In addition, preliminary gamma irradiation studies were conducted to determine the stability of the polymer reflectors to radiation. Materials and process technology were developed to fabricate coupon-scale reflectors of both broad- and narrow-band specular reflectors in Phase 1. This presentation will report the results of these studies, including, the performance of a narrow-band specular membrane. Gamma irradiation exposures indicate limited impact on the optical performance although additional exposure studies are warranted. Plans to scale up the membrane fabrication process will be presented.

76 FR 56678 - Energy Efficiency Program for Consumer Products: Public Meeting and Availability of the Framework...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-14

... reflector (ER) and bulged reflector (BR) bulb shapes, and with diameters of 2.75 inches or less. Therefore....25 and 2.75 inches, as well as lamps with ER, BR, bulged parabolic aluminized reflector (BPAR), or... certain reflector (R), ER and BR IRLs. DOE has concluded, for the reasons that follow, that it has the...

Primary reflector for solar energy collection systems

NASA Technical Reports Server (NTRS)

Miller, C. G. (Inventor); Stephens, J. B.

1978-01-01

A fixed, linear, ground-based primary reflector is disclosed which has an extended curved sawtooth-contoured surface covered with a metalized polymeric reflecting material. The device reflects solar energy to a movably supported collector that is kept at the concentrated line focus of the reflector primary. The primary reflector may be constructed by a process utilizing well-known freeway paving machinery.

Primary reflector for solar energy collection systems and method of making same

NASA Technical Reports Server (NTRS)

Miller, C. G.; Stephens, J. B. (Inventor)

1979-01-01

Solar energy is reflected to a movably supported collector that is kept at the concentrated line focus of the reflector primary by a fixed, linear, ground-based primary reflector having an extended curved sawtooth contoured surface covered with a metalized polymeric reflecting material. The primary reflector was constructed by a process utilizing well-known freeway paving machinery.

Electrophoretic deposited TiO 2 pigment-based back reflectors for thin film solar cells

DOE PAGES

Bills, Braden; Morris, Nathan; Dubey, Mukul; ...

2015-01-16

Highly reflective coatings with strong light scattering effect have many applications in optical components and optoelectronic devices. This paper reports titanium dioxide (TiO 2) pigment-based reflectors that have 2.5 times higher broadband diffuse reflection than commercially produced aluminum or silver based reflectors and result in efficiency enhancements of a single-junction amorphous Si solar cell. Electrophoretic deposition is used to produce pigment-based back reflectors with high pigment density, controllable film thickness and site-specific deposition. Electrical conductivity of the pigment-based back reflectors is improved by creating electrical vias throughout the pigment-based back reflector by making holes using an electrical discharge / dielectricmore » breakdown approach followed by a second electrophoretic deposition of conductive nanoparticles into the holes. While previous studies have demonstrated the use of pigment-based back reflectors, for example white paint, on glass superstrate configured thin film Si solar cells, this work presents a scheme for producing pigment-based reflectors on complex shape and flexible substrates. Finally, mechanical durability and scalability are demonstrated on a continuous electrophoretic deposition roll-to-roll system which has flexible metal substrate capability of 4 inch wide and 300 feet long.« less

Beam shaping assembly of a D-T neutron source for BNCT and its dosimetry simulation in deeply-seated tumor

NASA Astrophysics Data System (ADS)

Faghihi, F.; Khalili, S.

2013-08-01

This article involves two aims for BNCT. First case includes a beam shaping assembly estimation for a D-T neutron source to find epi-thermal neutrons which are the goal in the BNCT. Second issue is the percent depth dose calculation in the adult Snyder head phantom. Monte-Carlo simulations and verification of a suggested beam shaping assembly (including internal neutron multiplier, moderator, filter, external neutron multiplier, collimator, and reflector dimensions) for thermalizing a D-T neutron source as well as increasing neutron flux are carried out and our results are given herein. Finally, we have simulated its corresponding doses for treatment planning of a deeply-seated tumor.

Wide scanning spherical antenna

NASA Technical Reports Server (NTRS)

Shen, Bing (Inventor); Stutzman, Warren L. (Inventor)

1995-01-01

A novel method for calculating the surface shapes for subreflectors in a suboptic assembly of a tri-reflector spherical antenna system is introduced, modeled from a generalization of Galindo-Israel's method of solving partial differential equations to correct for spherical aberration and provide uniform feed to aperture mapping. In a first embodiment, the suboptic assembly moves as a single unit to achieve scan while the main reflector remains stationary. A feed horn is tilted during scan to maintain the illuminated area on the main spherical reflector fixed throughout the scan thereby eliminating the need to oversize the main spherical reflector. In an alternate embodiment, both the main spherical reflector and the suboptic assembly are fixed. A flat mirror is used to create a virtual image of the suboptic assembly. Scan is achieved by rotating the mirror about the spherical center of the main reflector. The feed horn is tilted during scan to maintain the illuminated area on the main spherical reflector fixed throughout the scan.

Feasibility Study of Graphite Epoxy Antenna for a Microwave Limb Sounder Radiometer (MLSR)

NASA Technical Reports Server (NTRS)

1979-01-01

Results are presented of a feasibility study to design graphite epoxy antenna reflectors for a jet propulsion laboratory microwave limb sounder instrument (MLSR). Two general configurations of the offset elliptic parabolic reflectors are presented that will meet the requirements on geometry and reflector accuracy. The designs consist of sandwich construction for the primary reflectors, secondary reflector support structure and cross-tie members between reflector pairs. Graphite epoxy materials of 3 and 6 plies are used in the facesheets of the sandwich. An aluminum honeycomb is used for the core. A built-in adjustment system is proposed to reduce surface distortions during assembly. The manufacturing and environmental effects are expected to result in surface distortions less than .0015 inch and pointing errors less than .002 degree.

Reflector and Protections in a Sodium-cooled Fast Reactor: Modelling and Optimization

NASA Astrophysics Data System (ADS)

Blanchet, David; Fontaine, Bruno

2017-09-01

The ASTRID project (Advanced Sodium Technological Reactor for Industrial Demonstration) is a Generation IV nuclear reactor concept under development in France [1]. In this frame, studies are underway to optimize radial reflectors and protections. Considering radial protections made in natural boron carbide, this study is conducted to assess the neutronic performances of the MgO as the reference choice for reflector material, in comparison with other possible materials including a more conventional stainless steel. The analysis is based upon a simplified 1-D and 2-D deterministic modelling of the reactor, providing simplified interfaces between core, reflector and protections. Such models allow examining detailed reaction rate distributions; they also provide physical insights into local spectral effects occurring at the Core-Reflector and at the Reflector-Protection interfaces.

Interaction of acoustic levitation field with liquid reflecting surface

NASA Astrophysics Data System (ADS)

Hong, Z. Y.; Xie, W. J.; Wei, B.

2010-01-01

Single-axis acoustic levitation of substances, such as foam, water, polymer, and aluminum, is achieved by employing various liquids as the sound reflectors. The interaction of acoustic levitation field with liquid reflecting surface is investigated theoretically by considering the deformation of the liquid surface under acoustic radiation pressure. Numerical calculations indicate that the deformation degree of the reflecting surface shows a direct proportion to the acoustic radiation power. Appropriate deformation is beneficial whereas excessive deformation is unfavorable to enhance the levitation capability. Typically, the levitation capability with water reflector is smaller than that with the concave rigid reflector but slightly larger than that with the planar rigid reflector at low emitter vibration intensity. Liquid reflectors with larger surface tension and higher density behave more closely to the planar rigid reflector.

Separation of Powers in Foreign and Domestic Contexts.

ERIC Educational Resources Information Center

Bennett, Robert W.

1987-01-01

Explores the concept of separation of powers in terms of recent conflicts between the executive and legislative branches of the U.S. government. Points out that what the Supreme Court has said about separation of powers in the domestic context may complicate resolution of more serious problems in foreign affairs. (BSR)

Resources for Teaching about Nationalism, 1812 to the Civil War.

ERIC Educational Resources Information Center

Seiter, David

1987-01-01

Highlights five resources for teaching about the rise of U.S. nationalism between 1812 and 1865 available from the Educational Resource Information Center (ERIC). Items included are: (1) the War of 1812; (2) the annexation of Texas; (3) the Kansas-Nebraska Act; and (4) the question of slavery. (BSR)

Education for Coping with Conflict - A Participatory Approach to Discipline Using Negotiation and Mediation.

ERIC Educational Resources Information Center

Masheder, Mildred

1987-01-01

Examines the use of corporal punishment and contends that a more democratic educational system demand its abolition. States that two essentials of democratic education are a caring atmosphere and a true spirit of reconciliation. Outlines assertion techniques that enhance conflict resolution. (BSR)

The Call for Balance: Implications of Chinese Educational History and Philosophy.

ERIC Educational Resources Information Center

Prillaman, A. Renee; Day, Barbara D.

1987-01-01

Examines data gathered from a survey of literature, observations, and interviews conducted during a 1985 trip to China. Specifically focuses on changes in Chinese education as influenced by politics, economics, and social values. Includes a comparison of similarities and differences in current Chinese and U.S. education. (BSR)

Basic Realities of Global Education.

ERIC Educational Resources Information Center

Johnson, Judith A.

1987-01-01

States the need for global education and suggests ways in which it might be accomplished most effectively. Suggestions include focusing on (1) the oneness of humankind; (2) the innate goodness of human beings; (3) equality between men and women; (4) the right to education; and (5) the necessity of ecological harmony. (BSR)

The Rise and Fall of the Schools Science Project in East Africa.

ERIC Educational Resources Information Center

Lillis, Kevin M.; Lowe, John

1987-01-01

Reviews problems associated with implementing the School Science Project (SSP) in Kenya, and the subsequent downfall of the project in the late 1970s. Concludes that the SSP experience raises fundamental questions about secondary science education in Kenya and the rest of the developing world. (BSR)

Threshold of Withdrawal from Schoolwork among Children of Divorced Parents.

ERIC Educational Resources Information Center

Guttmann, Joseph; And Others

1987-01-01

Examines whether there is a difference in the threshold of withdrawal from schoolwork between children of divorced parents and children from intact families. Results showed that children of divorced parents have lower levels of achievement and lower withdrawal thresholds than do children from intact families. (Author/BSR)

Test Anxiety and Performance of Adolescent Children of Divorced Parents.

ERIC Educational Resources Information Center

Guttmann, Joseph

1987-01-01

This study examined the level of test anxiety of adolescent children of divorced parents. It suggests such anxiety is a possible explanation of the lower scholastic achievement of such children. Results indicated children of divorced parents had significantly higher anxiety scores than did children of intact families. (Author/BSR)

What Is High School Economics? TEL Revision and Pretest Findings.

ERIC Educational Resources Information Center

Walstad, William B.; Soper, John C.

1988-01-01

Argues there is limited research data about student knowledge of economic concepts at the secondary school education level. Describes the development, validation, and national norming of the revised Test of Economic Literacy (TEL) and presents findings from the 1986 pretest analysis of the revised TEL. (BSR)

Nuclear reactor reflector

DOEpatents

Hopkins, Ronald J.; Land, John T.; Misvel, Michael C.

1994-01-01

A nuclear reactor reflector is disclosed that comprises a stack of reflector blocks with vertical water flow passages to cool the reflector. The interface between blocks is opposite support points for reactor fuel rods. Water flows between the reflector and the reactor barrel from passages in a bottom block. The top block contains a flange to limit this flow and the flange has a slot to receive an alignment pin that is welded to the barrel. The pin is held in the slot by two removable shims. Alignment bars extend the length of the stack in slots machined in each block when the stack is assembled.

Nuclear reactor reflector

DOEpatents

Hopkins, R.J.; Land, J.T.; Misvel, M.C.

1994-06-07

A nuclear reactor reflector is disclosed that comprises a stack of reflector blocks with vertical water flow passages to cool the reflector. The interface between blocks is opposite support points for reactor fuel rods. Water flows between the reflector and the reactor barrel from passages in a bottom block. The top block contains a flange to limit this flow and the flange has a slot to receive an alignment pin that is welded to the barrel. The pin is held in the slot by two removable shims. Alignment bars extend the length of the stack in slots machined in each block when the stack is assembled. 12 figs.

Tailored reflectors for illumination.

PubMed

Jenkins, D; Winston, R

1996-04-01

We report on tailored reflector design methods that allow the placement of general illumination patterns onto a target plane. The use of a new integral design method based on the edge-ray principle of nonimaging optics gives much more compact reflector shapes by eliminating the need for a gap between the source and the reflector profile. In addition, the reflectivity of the reflector is incorporated as a design parameter. We show the performance of design for constant irradiance on a distant plane, and we show how a leading-edge-ray method may be used to achieve general illumination patterns on nearby targets.

Data appendix: F-number=1.0 EMR with a flexible back electrode

NASA Technical Reports Server (NTRS)

Mihora, D. J.

1984-01-01

A 12.5 micron Tedlar low f-number electrostatic membrane reflector was tested. The antenna reflector was designed to achieve a spherical reflector surface with a focal length to diameter ratio f(sub n) of one and a potential accuracy of 1.0 over its 4.88 m diameter. The configuration required the cutting and joining of twelve pie-shaped panels to form the reflector surface. Electrostatic forces are used to tension this preformed membrane reflector. The test data is spare-only three sets of measurements were taken due to lack of funds.

Photonic generation of ultra-wideband signals by direct current modulation on SOA section of an SOA-integrated SGDBR laser.

PubMed

Lv, Hui; Yu, Yonglin; Shu, Tan; Huang, Dexiu; Jiang, Shan; Barry, Liam P

2010-03-29

Photonic ultra-wideband (UWB) pulses are generated by direct current modulation of a semiconductor optical amplifier (SOA) section of an SOA-integrated sampled grating distributed Bragg reflector (SGDBR) laser. Modulation responses of the SOA section of the laser are first simulated with a microwave equivalent circuit model. Simulated results show a resonance behavior indicating the possibility to generate UWB signals with complex shapes in the time domain. The UWB pulse generation is then experimentally demonstrated for different selected wavelength channels with an SOA-integrated SGDBR laser.

Gulf of Mexico Gas Hydrate Joint Industry Project Leg II: Results from the Walker Ridge 313 Site

NASA Astrophysics Data System (ADS)

Shedd, W.; Frye, M.; Boswell, R. M.; Collett, T. S.; McConnell, D.; Jones, E.; Shelander, D.; Dai, J.; Guerin, G.; Cook, A.; Mrozewski, S.; Godfriaux, P. D.; Dufrene, R.; Hutchinson, D. R.; Roy, R.

2009-12-01

The Gulf of Mexico Gas Hydrate Joint Industry Project Leg II drilling program visited three sites in the Gulf of Mexico during a 21 day drilling program in April and May, 2009. Using both petroleum systems and seismic stratigraphic approaches, the exploration focus for Leg II was to identify sites with the potential for gas hydrate-saturated sand reservoirs. The data acquired consist of a comprehensive suite of high resolution LWD logs including gamma ray, density, porosity, sonic, and resistivity tools. No physical samples were taken in the field. Two holes, locations G and H, were drilled at the Walker Ridge 313 site (WR 313)in the central Gulf of Mexico, just updip of the “salt sheet province”. The primary objective of each well was to determine the presence or absence of gas hydrate from the log data at the predetermined primary targets, picked from industry 3-D seismic data, in dipping Pleistocene turbidite derived sands on the flanks of a salt withdrawal minibasin. The seismic targets were high amplitude positive reflections just updip of phase reversals at the interpreted base of hydrate stability, corresponding to the so-called bottom simulating reflector, or “BSR”. Downdip of the BSR, the sands were clearly troughs, or negative reflections, suggesting free gas charge. An existing industry well, located updip of both JIP locations, contains a slightly sandy zone in the same stratigraphic interval as the JIP targets, that has elevated resistivities correlated to the target sands, suggesting low saturation “shows” of hydrate. Stratigraphically bounded fractured fine grained sediments with probable gas hydrate fill were found in both holes between 800 ft and 1300 ft at G, and between 600 ft and 1000 ft below the seafloor at H. At the primary targets, high saturation gas hydrates in sand were interpreted from logs at both holes. LWD data indicate 50 ft of high saturation gas hydrate in sands starting at 2722 ft below seafloor at the G hole. At H, 37 ft of high saturation gas hydrate was found in the target sand. Numerous minor occurrences of probable pore filling gas hydrate in thin sands were found at both locations. The likely discovery of thick gas hydrate-filled sands at the WR 313 site validates the exploration approach, and strongly indicates that gas hydrate can be found in reservoir quality marine sands. Additionally, the depth below mudline to which these wells were drilled without risers or drivepipe is unprecedented and the information gleaned will aid in marine hydrate exploration efforts worldwide.

Gas hydrate occurrences in the Danube Delta, Western Black Sea: Results from 2D and 3D controlled source electromagnetics

NASA Astrophysics Data System (ADS)

Schwalenberg, Katrin; Hölz, Sebastian; Gehrmann, Romina; Rippe, Dennis; Dannowski, Anke; Zander, Timo; Duan, Shuangmin; Jegen, Marion; Bialas, Jörg

2017-04-01

Marine controlled source electromagnetic (CSEM) data have been collected over gas hydrate targets in the Danube Delta off the coasts of Bulgaria and Romania in early 2014 during voyage MSM35 on R/V Maria S. MERIAN. The cruise was part of the German SUGAR Project, a joint venture project with the goal to study submarine gas hydrates as a source of methane. Within European waters the Black Sea is one of the most prospective hydrocarbon areas. Thick sedimentary basins, the existence of an extended gas hydrate stability zone and the observation of multiple bottom simulating reflectors (BSR) in the western part indicate a huge gas hydrate potential in sandy sediments. Low pore-water salinities between 1 and 4 ppt have been observed in borehole data at depths below 30 mbsf, and are attributed to sea level low stands in the past. 2D and 3D CSEM data sets have been collected over one of the channel levee systems of the Danube Delta fan. High-resolution 2D and 3D seismic, and OBS data are available in the same target area providing structural information and porosity profiles from seismic velocity data. Analysis of subsets of the 3D CSEM data reveal pore-water salinities around 4 ppt for the shallow sediment section, thus are not as low as suggested by the borehole data. The inversion of both 2D and 3D CSEM data sets reveal highly anomalous resistivities within the gas hydrate stability field. We believe that high gas hydrate saturations are the likely cause, as low pore-water salinities are not sufficient to explain the high resistivities, seismic data indicate no clear gas migration pathways through the stability field, nor do hydro-acoustic data show areas of gas seepage which are confined to the landward edge of the stability field. Estimates of the gas hydrate saturation are commonly derived from Archie's Law, and strongly depend on the proper choice of input parameters. We apply porosities from seismic velocity profiles, pore-water resistivities derived from salinity and temperature profiles, and Archie coefficients a, m, and n derived from laboratory studies with various sands and porosities. Gas hydrate saturation estimates vary between 20 and 60 % due to the wide range of input parameter, but are generally higher than estimates from seismic velocity data, an outcome also observed in other gas hydrate areas.

Gravity deformation measurements of 70m reflector surfaces

NASA Technical Reports Server (NTRS)

Brenner, Michael; Imbriale, William A.; Britcliffe, Michael K.

2001-01-01

Two of NASA's Deep Space Network (DSN) 70-meter reflectors are measured using a Leica TDM-5000 theodolite. The main reflector surface was measured at five elevation angles so that a gravity deformation model could be derived that described the main reflector distortions over the entire range of elevation angles. The report describes the measurement equipment and accuracy and the results derived from the data.

Impact of HFIR LEU Conversion on Beryllium Reflector Degradation Factors

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

Ilas, Dan

2013-10-01

An assessment of the impact of low enriched uranium (LEU) conversion on the factors that may cause the degradation of the beryllium reflector is performed for the High Flux Isotope Reactor (HFIR). The computational methods, models, and tools, comparisons with previous work, along with the results obtained are documented and discussed in this report. The report documents the results for the gas and neutronic poison production, and the heating in the beryllium reflector for both the highly enriched uranium (HEU) and LEU HFIR configurations, and discusses the impact that the conversion to LEU may have on these quantities. A time-averagingmore » procedure was developed to calculate the isotopic (gas and poisons) production in reflector. The sensitivity of this approach to different approximations is gauged and documented. The results show that the gas is produced in the beryllium reflector at a total rate of 0.304 g/cycle for the HEU configuration; this rate increases by ~12% for the LEU case. The total tritium production rate in reflector is 0.098 g/cycle for the HEU core and approximately 11% higher for the LEU core. A significant increase (up to ~25%) in the neutronic poisons production in the reflector during the operation cycles is observed for the LEU core, compared to the HEU case, for regions close to the core s horizontal midplane. The poisoning level of the reflector may increase by more than two orders of magnitude during long periods of downtime. The heating rate in the reflector is estimated to be approximately 20% lower for the LEU core than for the HEU core. The decrease is due to a significantly lower contribution of the heating produced by the gamma radiation for the LEU core. Both the isotopic (gas and neutronic poisons) production and the heating rates are spatially non-uniform throughout the beryllium reflector volume. The maximum values typically occur in the removable reflector and close to the midplane.« less

Detection of reflector surface from near field phase measurements

NASA Technical Reports Server (NTRS)

Ida, Nathan

1991-01-01

The deviation of a reflector antenna surface from a perfect parabolic shape causes degradation of the performance of the antenna. The problem of determining the shape of the reflector surface in a reflector antenna using near field phase measurements is not a new one. A recent issue of the IEEE tansactions on Antennas and Propagation (June 1988) contained numerous descriptions of the use of these measurements: holographic reconstruction or inverse Fourier transform. Holographic reconstruction makes use of measurement of the far field of the reflector and then applies the Fourier transform relationship between the far field and the current distribution on the reflector surface. Inverse Fourier transformation uses the phase measurements to determine the far field pattern using the method of Kerns. After the far field pattern is established, an inverse Fourier transform is used to determine the phases in a plane between the reflector surface and the plane in which the near field measurements were taken. These calculations are time consuming since they involve a relatively large number of operations. A much faster method can be used to determine the position of the reflector. This method makes use of simple geometric optics to determine the path length of the ray from the feed to the reflector and from the reflector to the measurement point. For small physical objects and low frequencies, diffraction effects have a major effect on the error, and the algorithm provides incorrect results. It is believed that the effect is less noticeable for large distortions such as antenna warping, and more noticeable for small, localized distortions such as bumps and depressions such as might be caused by impact damage.

Continuous adaptive beam pointing and tracking for laser power transmission.

PubMed

Schäfer, Christian A

2010-06-21

The adaptive beam pointing concept has been revisited for the purpose of controlled transmission of laser energy from an optical transmitter to a target. After illumination, a bidirectional link is established by a retro-reflector on the target and an amplifier-phase conjugate mirror (A-PCM) on the transmitter. By setting the retro-reflector's aperture smaller than the diffraction limited spot size but big enough to provide sufficient amount of optical feedback, a stable link can be maintained and light that hits the retro-reflector's surrounded area can simultaneously be reconverted into usable electric energy. The phase conjugate feedback ensures that amplifier's distortions are compensated and the target tracked accurately.After deriving basic arithmetic expressions for the proposed system, a section is devoted for the motivation of free-space laser power transmission which is supposed to find varied applicability in space. As an example, power transmission from a satellite to the earth is described where recently proposed solar power generating structures on high-altitudes receive the power above the clouds to provide constant energy supply.In the experimental part, an A-PCM setup with reflectivity of about R(A-PCM) = 100 was realized using a semiconductor optical amplifier and a photorefractive self-pumped PCM. Simulation results show that a reflectivity of R(A-PCM)>1000 could be obtained by improving the self-pumped PCM's efficiency. That would lead to a transmission efficiency of eta>90%.

Optical Reflectance Measurements for Commonly Used Reflectors

NASA Astrophysics Data System (ADS)

Janecek, Martin; Moses, William W.

2008-08-01

When simulating light collection in scintillators, modeling the angular distribution of optical light reflectance from surfaces is very important. Since light reflectance is poorly understood, either purely specular or purely diffuse reflectance is generally assumed. In this paper we measure the optical reflectance distribution for eleven commonly used reflectors. A 440 nm, output power stabilized, un-polarized laser is shone onto a reflector at a fixed angle of incidence. The reflected light's angular distribution is measured by an array of silicon photodiodes. The photodiodes are movable to cover 2pi of solid angle. The light-induced current is, through a multiplexer, read out with a digital multimeter. A LabVIEW program controls the motion of the laser and the photodiode array, the multiplexer, and the data collection. The laser can be positioned at any angle with a position accuracy of 10 arc minutes. Each photodiode subtends 6.3deg, and the photodiode array can be positioned at any angle with up to 10 arc minute angular resolution. The dynamic range for the current measurements is 10 5:1. The measured light reflectance distribution was measured to be specular for several ESR films as well as for aluminum foil, mostly diffuse for polytetrafluoroethylene (PTFE) tape and titanium dioxide paint, and neither specular nor diffuse for Lumirrorreg, Melinexreg and Tyvekreg. Instead, a more complicated light distribution was measured for these three materials.

Reflector for efficient coupling of a laser beam to air or other fluids

DOEpatents

Kare, Jordin T.

1992-01-01

A reflector array is disclosed herein that provides a controlled region or regions of plasma breakdowns from a laser beam produced at a remotely-based laser source. The plasma may be applied to produce thrust to propel a spacecraft, or to diagnose a laser beam, or to produce shockwaves. The spacecraft propulsion system comprises a reflector array attached to the vehicle. The reflector array comprises a plurality of reflectors spaced apart on a reflective surface, with each reflector acting as an independent focusing mirror. The reflectors are spaced closely together to form a continuous or partially-continuous surface. The reflector array may be formed from a sheet of reflective material, such as copper or aluminum. In operation, a beam of electromagnetic energy, such as a laser beam, is directed at the reflectors which focus the reflected electromagnetic energy at a plurality of regions off the surface. The energy concentrated in the focal region causes a breakdown of the air or other fluid in the focal region, creating a plasma. Electromagnetic energy is absorbed in the plasma and it grows in volume, compressing and heating the adjacent fluid thereby providing thrust. Laser pulses may be applied repetitively. After each such thrust pulse, fresh air can be introduced next to the surface either laterally, or through a perforated surface. If air or some other gas or vapor is supplied, for example from a tank carried on board a vehicle, this invention may also be used to provide thrust in a vacuum environment.

Analysis of a generalized dual reflector antenna system using physical optics

NASA Technical Reports Server (NTRS)

Acosta, Roberto J.; Lagin, Alan R.

1992-01-01

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

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Stationary force produced by an optical pulsating discharge in a laser engine model

NASA Astrophysics Data System (ADS)

Grachev, Gennadii N.; Tishchenko, V. N.; Apollonov, V. V.; Gulidov, A. I.; Smirnov, A. L.; Sobolev, A. V.; Zimin, M. I.

2007-07-01

An optical pulsating discharge produced by repetitively pulses laser radiation (with a pulse repetition rate of up to 100 kHz) is studied in a cylindrical tube simulating the reflector of a laser engine. The pressure of shock waves and the propulsion produced by them are measured. The discharge produced the stationary propulsion ~1 N kW-1.

Optimization of Neutron Spectrum in Northwest Beam Tube of Tehran Research Reactor for BNCT, by MCNP Code

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

Zamani, M.; End of North Kargar st, Atomic Energy Organization of Iran, P.O. Box: 14155-1339, Tehran; Kasesaz, Y.

2015-07-01

In order to gain the neutron spectrum with proper components specification for BNCT, it is necessary to design a Beam Shape Assembling (BSA), include of moderator, collimator, reflector, gamma filter and thermal neutrons filter, in front of the initial radiation beam from the source. According to the result of MCNP4C simulation, the Northwest beam tube has the most optimized neuron flux between three north beam tubes of Tehran Research Reactor (TRR). So, it has been chosen for this purpose. Simulation of the BSA has been done in four above mentioned phases. In each stage, ten best configurations of materials withmore » different length and width were selected as the candidates for the next stage. The last BSA configuration includes of: 78 centimeters of air as an empty space, 40 centimeters of Iron plus 52 centimeters of heavy-water as moderator, 30 centimeters of water or 90 centimeters of Aluminum-Oxide as a reflector, 1 millimeters of lithium (Li) as thermal neutrons filter and finally 3 millimeters of Bismuth (Bi) as a filter of gamma radiation. The result of Calculations shows that if we use this BSA configuration for TRR Northwest beam tube, then the best neutron flux and spectrum will be achieved for BNCT. (authors)« less

Assembly considerations for large reflectors

NASA Technical Reports Server (NTRS)

Bush, H.

1988-01-01

The technologies developed at LaRC in the area of erectable instructures are discussed. The information is of direct value to the Large Deployable Reflector (LDR) because an option for the LDR backup structure is to assemble it in space. The efforts in this area, which include development of joints, underwater assembly simulation tests, flight assembly/disassembly tests, and fabrication of 5-meter trusses, led to the use of the LaRC concept as the baseline configuration for the Space Station Structure. The Space Station joint is linear in the load and displacement range of interest to Space Station; the ability to manually assemble and disassemble a 45-foot truss structure was demonstrated by astronauts in space as part of the ACCESS Shuttle Flight Experiment. The structure was built in 26 minutes 46 seconds, and involved a total of 500 manipulations of untethered hardware. Also, the correlation of the space experience with the neutral buoyancy simulation was very good. Sections of the proposed 5-meter bay Space Station truss have been built on the ground. Activities at LaRC have included the development of mobile remote manipulator systems (which can traverse the Space Station 5-meter structure), preliminary LDR sun shield concepts, LDR construction scenarios, and activities in robotic assembly of truss-type structures.

Panel positioning error and support mechanism for a 30-m THz radio telescope

NASA Astrophysics Data System (ADS)

Yang, De-Hua; Okoh, Daniel; Zhou, Guo-Hua; Li, Ai-Hua; Li, Guo-Ping; Cheng, Jing-Quan

2011-06-01

A 30-m TeraHertz (THz) radio telescope is proposed to operate at 200 μm with an active primary surface. This paper presents sensitivity analysis of active surface panel positioning errors with optical performance in terms of the Strehl ratio. Based on Ruze's surface error theory and using a Monte Carlo simulation, the effects of six rigid panel positioning errors, such as piston, tip, tilt, radial, azimuthal and twist displacements, were directly derived. The optical performance of the telescope was then evaluated using the standard Strehl ratio. We graphically illustrated the various panel error effects by presenting simulations of complete ensembles of full reflector surface errors for the six different rigid panel positioning errors. Study of the panel error sensitivity analysis revealed that the piston error and tilt/tip errors are dominant while the other rigid errors are much less important. Furthermore, as indicated by the results, we conceived of an alternative Master-Slave Concept-based (MSC-based) active surface by implementating a special Series-Parallel Concept-based (SPC-based) hexapod as the active panel support mechanism. A new 30-m active reflector based on the two concepts was demonstrated to achieve correction for all the six rigid panel positioning errors in an economically feasible way.

Bragg Reflector-Induced Increased Nonradiative Lifetime in Gallium Arsenide (GaAs)/Aluminum Gallium Arsenide (AlGaAs) Double Heterostructures

DTIC Science & Technology

2015-09-01

ARL-TR-7473 ● SEP 2015 US Army Research Laboratory Bragg Reflector-Induced Increased Nonradiative Lifetime in Gallium Arsenide...return it to the originator. ARL-TR-7473 ● SEP 2015 US Army Research Laboratory Bragg Reflector-Induced Increased Nonradiative ...3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE Bragg Reflector-Induced Increased Nonradiative Lifetime in Gallium Arsenide (GaAs)/Aluminum

The DART Cylindrical, Infrared, 1 Meter Membrane Reflector

NASA Technical Reports Server (NTRS)

Morgan, Rhonda M.; Agnes, Greg S.; Barber, Dan; Dooley, Jennifer; Dragovan, Mark; Hatheway, Al E.; Marcin, Marty

2004-01-01

The Dual Anamorphic Reflector Telescopes (DART) is an architecture for large aperture space telescopes that enables the use of membranes. A membrane can be readily shaped in one direction of curvature using a combination of boundary control and tensioning, yielding a cylindrical reflector. Two cylindrical reflectors (orthogonal and confocal) comprise the 'primary mirror' of the telescope system. The aperture is completely unobstructed and ideal for infrared and high contrast observations.

Coaxial Virtual Cathode Enhancement

DTIC Science & Technology

2004-10-20

need more solid evidence to clarify them. Table 2. Frequency list for geometries without reflectors, showing the microwave frequencies based on their...frequency. V. The Functions of the Reflectors Table 3 is a frequency list with the donut reflector at different positions. From Table 3, we can see that...both cases. We do observe that the microwave power generally is decreased by the donut reflector. Table 3. Frequency list for geometries with a donut

Fabrication of Spherical Reflectors in Outer Space

NASA Technical Reports Server (NTRS)

Wang, Yu; Dooley, Jennifer; Dragovan, Mark; Serivens, Wally

2005-01-01

A process is proposed for fabrication of lightweight spherical reflectors in outer space for telescopes, radio antennas, and light collectors that would be operated there. The process would obviate the relatively massive substrates and frames needed to support such reflectors in normal Earth gravitation. According to the proposal, fabrication of a reflector would begin with blowing of a bubble to the specified reflector radius. Taking advantage of the outer-space vacuum as a suitable environment for evaporative deposition of metal, a metal-evaporation source would be turned on and moved around the bubble to deposit a reflective metal film over the specified reflector area to a thickness of several microns. Then the source would be moved and aimed to deposit more metal around the edge of the reflector area, increasing the thickness there to approximately equal to 100 micron to form a frame. Then the bubble would be deflated and peeled off the metal, leaving a thin-film spherical mirror having an integral frame. The mirror would then be mounted for use. The feasibility of this technology has been proved by fabricating a prototype at JPL. As shown in the figure, a 2-in. (.5-cm) diameter hemispherical prototype reflector was made from a polymer bubble coated with silver, forming a very smooth surface.

A method to design blended rolled edges for compact range reflectors

NASA Technical Reports Server (NTRS)

Gupta, Inder J.; Burnside, Walter D.

1989-01-01

A method to design blended rolled edges for arbitrary rim shape compact range reflectors is presented. The reflectors may be center-fed or offset-fed. The method leads to rolled edges with minimal surface discontinuities. It is shown that the reflectors designed using the prescribed method can be defined analytically using simple expressions. A procedure to obtain optimum rolled edges parameter is also presented. The procedure leads to blended rolled edges that minimize the diffracted fields emanating from the junction between the paraboloid and the rolled edge surface while satisfying certain constraints regarding the reflector size and the minimum operating frequency of the system.

A Method for Producing a Shaped Contour Radiation Pattern Using a Single Shaped Reflector and a Single Feed

NASA Technical Reports Server (NTRS)

Cherrette, A. R.; Lee, S. W.; Acosta, R. J.

1988-01-01

Eliminating the corporate feed network in shaped contour beam antennas will reduce the expense, weight, and RF loss of the antenna system. One way of producing a shaped contour beam without using a feed network is to use a single shaped reflector with a single feed element. For a prescribed contour beam and feed, an optimization method for designing the reflector shape is given. As a design example, a shaped reflector is designed to produce a continental U.S. coverage (CONUS) beam. The RF performance of the shaped reflector is then verified by physical optics.

A method to design blended rolled edges for compact range reflectors

NASA Technical Reports Server (NTRS)

Gupta, Inder J.; Ericksen, Kurt P.; Burnside, Walter D.

1990-01-01

A method to design blended rolled edges for arbitrary rim shape compact range reflectors is presented. The reflectors may be center-fed or offset-fed. The method leads to rolled edges with minimal surface discontinuities. It is shown that the reflectors designed using the prescribed method can be defined analytically using simple expressions. A procedure to obtain optimum rolled edges parameters is also presented. The procedure leads to blended rolled edges that minimize the diffracted fields emanating from the junction between the paraboloid and the rolled edge surface while satisfying certain constraints regarding the reflector size and the minimum operating frequency of the system.

Analytical approximation of a distorted reflector surface defined by a discrete set of points

NASA Technical Reports Server (NTRS)

Acosta, Roberto J.; Zaman, Afroz A.

1988-01-01

Reflector antennas on Earth orbiting spacecrafts generally cannot be described analytically. The reflector surface is subjected to a large temperature fluctuation and gradients, and is thus warped from its true geometrical shape. Aside from distortion by thermal stresses, reflector surfaces are often purposely shaped to minimize phase aberrations and scanning losses. To analyze distorted reflector antennas defined by discrete surface points, a numerical technique must be applied to compute an interpolatory surface passing through a grid of discrete points. In this paper, the distorted reflector surface points are approximated by two analytical components: an undistorted surface component and a surface error component. The undistorted surface component is a best fit paraboloid polynomial for the given set of points and the surface error component is a Fourier series expansion of the deviation of the actual surface points, from the best fit paraboloid. By applying the numerical technique to approximate the surface normals of the distorted reflector surface, the induced surface current can be obtained using physical optics technique. These surface currents are integrated to find the far field radiation pattern.

Scanning properties of large dual-shaped offset and symmetric reflector antennas

NASA Astrophysics Data System (ADS)

Galindo-Israel, Victor; Veruttipong, Watt; Norrod, Roger D.; Imbriale, William A.

1992-04-01

Several characteristics of dual offset (DOSR) and symmetric shaped reflectors are examined. Among these is the amelioration of the added cost of manufacturing a shaped reflector antenna, particularly a doubly curved surface for the DOSR, if adjustable panels, which may be necessary for correction of gravity and wind distortions, are also used for improving gain by shaping. The scanning properties of shaped reflectors, both offset and circularly symmetric, are examined and compared to conic section scanning characteristics. Scanning of the pencil beam is obtained by lateral and axial translation of a single point-source feed. The feed is kept pointed toward the center of the subreflector. The effects of power spillover and aperture phase error as a function of beam scanning is examined for several different types of large reflector designs including DOSR, circularly symmetric large f/D and smaller f/D dual reflector antenna systems. It is graphically illustrated that the Abbe-sine condition for improving scanning of an optical system cannot, inherently, be satisfied in a dual-shaped reflector system shaped for high gain and low feed spillover.

Materials and process optimization for dual-shell satellite antenna reflectors

NASA Astrophysics Data System (ADS)

Balaski, Darcy R.; van Oyen, Hans J.; Nissan, Sorin J.

A comprehensive, design-optimization test program was conducted for satellite antenna reflectors composed of two offset paraboloidal Kevlar-reinforced sandwich shells separated by a circular sandwich structure. In addition to standard mechanical properties testing, coefficient of thermal expansion and hygroscopic tests were conducted to predict reflector surface accuracy in the thermal cycling environment of orbital space. Attention was given to the relative placement of components during assembly, in view of reflector surface measurements.

Lamp with a truncated reflector cup

DOEpatents

Li, Ming; Allen, Steven C.; Bazydola, Sarah; Ghiu, Camil-Daniel

2013-10-15

A lamp assembly, and method for making same. The lamp assembly includes first and second truncated reflector cups. The lamp assembly also includes at least one base plate disposed between the first and second truncated reflector cups, and a light engine disposed on a top surface of the at least one base plate. The light engine is configured to emit light to be reflected by one of the first and second truncated reflector cups.

Wideband QAMC reflector's antenna for low profile applications

NASA Astrophysics Data System (ADS)

Grelier, M.; Jousset, M.; Mallégol, S.; Lepage, A. C.; Begaud, X.; LeMener, J. M.

2011-06-01

A wideband reflector's antenna based on quasi-artificial magnetic conductor is proposed. To validate the design, an Archimedean spiral has been backed to this new reflector. In comparison to classical solution using absorbent material, the prototype presents a very low thickness of λ/15 at the lowest operating frequency and an improved gain over a 2.4:1 bandwidth. The whole methodology to design this reflector can be applied to other wideband antennas.

Terrestrial Laser Scanner Two-Face Measurements for Analyzing the Elevation-Dependent Deformation of the Onsala Space Observatory 20-m Radio Telescope's Main Reflector in a Bundle Adjustment.

PubMed

Holst, Christoph; Schunck, David; Nothnagel, Axel; Haas, Rüdiger; Wennerbäck, Lars; Olofsson, Henrik; Hammargren, Roger; Kuhlmann, Heiner

2017-08-09

For accurate astronomic and geodetic observations based on radio telescopes, the elevation-dependent deformation of the radio telescopes' main reflectors should be known. Terrestrial laser scanning has been used for determining the corresponding changes of focal lengths and areal reflector deformations at several occasions before. New in this publication is the situation in which we minimize systematic measurement errors by an improved measurement and data-processing concept: Sampling the main reflector in both faces of the laser scanner and calibrating the laser scanner in situ in a bundle adjustment. This concept is applied to the Onsala Space Observatory 20-m radio telescope: The focal length of the main reflector decreases by 9.6 mm from 85 ∘ to 5 ∘ elevation angle. Further local deformations of the main reflector are not detected.

Graphical method to design multilayer phase retarders.

PubMed

Apfel, J H

1981-03-15

When multilayer reflectors are used at nonnormal incidence, the two planes of polarization generally have different phase shifts. This difference, known as phase retardance, depends on the multilayer design, the incidence angle, and the wavelength. Heretofore, the design of reflectors with specific phase retardance has been carried out by computer optimization except for the case of a single layer on a metal substrate. A graph of phase retardance D vs the average phase shift A as a function of layer thickness provides a means for visualization that is useful in reflector designs. A D-A graph predicts the phase properties of a reflector as a function of the index and thickness of an added layer. Graphs of phase retardance vs average phase for two different materials can be superposed to predict the composite performance of a multilayer reflector. This graphical technique is employed to design and analyze reflectors with specified phase retardance.

Main-Reflector Manufacturing Technology for the Deep Space Optical Communications Ground Station

NASA Technical Reports Server (NTRS)

Britcliffe, M. J.; Hoppe, D. J.

2001-01-01

The Deep Space Network (DSN) has plans to develop a 10-m-diameter optical communications receiving station. The system uses the direct detection technique, which has much different requirements from a typical astronomical telescope. The receiver must operate in daylight and nighttime conditions. This imposes special requirements on the optical system to reject stray light from the Sun and other sources. One of the biggest challenges is designing a main-reflector surface that meets these requirements and can be produced at a reasonable cost. The requirements for the performance of the reflector are presented. To date, an aspherical primary reflector has been assumed. A reflector with a spherical reflector has a major cost advantage over an aspherical design, with no sacrifice in performance. A survey of current manufacturing techniques for optical mirrors of this type was performed. Techniques including solid glass, lightweight glass, diamond-turned aluminum, and composite mirrors were investigated.

State-of-the-art low-cost solar reflector materials

NASA Astrophysics Data System (ADS)

Kennedy, C.; Jorgensen, G.

1994-11-01

Solar thermal technologies generate power by concentrating sunlight with large mirrors. The National Renewable Energy Laboratory (NREL) is working with industrial partners to develop the optical reflector materials needed for the successful deployment of this technology. The reflector materials must be low in cost and maintain high specular reflectance for extended lifetimes in severe outdoor environments. Currently, the best candidate materials for solar mirrors are silver-coated low-iron glass and silvered polymer films. Polymer reflectors are lighter in weight, offer greater flexibility in system design, and have the potential for lower cost than glass mirrors. In parallel with collaborative activities, several innovative candidate reflector-material constructions were investigated at NREL. The low-cost material requirement necessitates manufacturing compatible with mass-production techniques. Future cooperative efforts with the web-coating industry offers the promise of exciting new alternative materials and the potential for dramatic cost savings in developing advanced solar reflector materials.

Flat Engineered Multichannel Reflectors

NASA Astrophysics Data System (ADS)

Asadchy, V. S.; Díaz-Rubio, A.; Tcvetkova, S. N.; Kwon, D.-H.; Elsakka, A.; Albooyeh, M.; Tretyakov, S. A.

2017-07-01

Recent advances in engineered gradient metasurfaces have enabled unprecedented opportunities for light manipulation using optically thin sheets, such as anomalous refraction, reflection, or focusing of an incident beam. Here, we introduce a concept of multichannel functional metasurfaces, which are able to control incoming and outgoing waves in a number of propagation directions simultaneously. In particular, we reveal a possibility to engineer multichannel reflectors. Under the assumption of reciprocity and energy conservation, we find that there exist three basic functionalities of such reflectors: specular, anomalous, and retroreflections. Multichannel response of a general flat reflector can be described by a combination of these functionalities. To demonstrate the potential of the introduced concept, we design and experimentally test three different multichannel reflectors: three- and five-channel retroreflectors and a three-channel power splitter. Furthermore, by extending the concept to reflectors supporting higher-order Floquet harmonics, we forecast the emergence of other multichannel flat devices, such as isolating mirrors, complex splitters, and multi-functional gratings.

Interferometric Polarization Control

NASA Technical Reports Server (NTRS)

Wollack, Edward J. (Inventor); Moseley, Samuel H. (Inventor); Chuss, David T. (Inventor); Novak, Giles A. (Inventor)

2008-01-01

A signal conditioning module provides a polarimeter capability in a photometric system. The module may include multiple variable delay polarization modulators. Each modulator may include an input port, and a first arm formed to include a first reflector and first rooftop mirror arranged in opposed relationship. The first reflector may direct an input radiation signal to the first rooftop mirror. Each modulator also may include an output port and a second arm formed to include a second reflector and second rooftop mirror arranged in opposed relationship. The second reflector can guide a signal from the second rooftop mirror towards the output port to provide an output radiation signal. A beamsplitting grid may be placed between the first reflector and the first rooftop mirror, and also between the second reflector and the second rooftop mirror. A translation apparatus can provide adjustment relative to optical path length vis-a-vis the first arm, the second arm and the grid.

Interferometric polarization control

NASA Technical Reports Server (NTRS)

Wollack, Edward J. (Inventor); Novak, Giles A. (Inventor); Moseley, Samuel H. (Inventor); Chuss, David T. (Inventor)

2009-01-01

A signal conditioning module provides a polarimeter capability in a photometric system. The module may include multiple variable delay polarization modulators. Each modulator may include an input port, and a first arm formed to include a first reflector and first rooftop mirror arranged in opposed relationship. The first reflector may direct an input radiation signal to the first rooftop mirror. Each modulator also may include an output port and a second arm formed to include a second reflector and second rooftop mirror arranged in opposed relationship. The second reflector can guide a signal from the second rooftop mirror towards the output port to provide an output radiation signal. A beamsplitting grid may be placed between the first reflector and the first rooftop mirror, and also between the second reflector and the second rooftop mirror. A translation apparatus can provide adjustment relative to optical path length vis-a-vis the first arm, the second arm and the grid.

Terrestrial Laser Scanner Two-Face Measurements for Analyzing the Elevation-Dependent Deformation of the Onsala Space Observatory 20-m Radio Telescope’s Main Reflector in a Bundle Adjustment

PubMed Central

Schunck, David; Nothnagel, Axel; Haas, Rüdiger; Wennerbäck, Lars; Olofsson, Henrik; Hammargren, Roger; Kuhlmann, Heiner

2017-01-01

For accurate astronomic and geodetic observations based on radio telescopes, the elevation-dependent deformation of the radio telescopes’ main reflectors should be known. Terrestrial laser scanning has been used for determining the corresponding changes of focal lengths and areal reflector deformations at several occasions before. New in this publication is the situation in which we minimize systematic measurement errors by an improved measurement and data-processing concept: Sampling the main reflector in both faces of the laser scanner and calibrating the laser scanner in situ in a bundle adjustment. This concept is applied to the Onsala Space Observatory 20-m radio telescope: The focal length of the main reflector decreases by 9.6 mm from 85∘ to 5∘ elevation angle. Further local deformations of the main reflector are not detected. PMID:28792449

Beyond Wires and Seeds: Reflector-guided Breast Lesion Localization and Excision.

PubMed

Mango, Victoria L; Wynn, Ralph T; Feldman, Sheldon; Friedlander, Lauren; Desperito, Elise; Patel, Sejal N; Gomberawalla, Ameer; Ha, Richard

2017-08-01

Purpose To evaluate outcomes of Savi Scout (Cianna Medical, Aliso Viejo, Calif) reflector-guided localization and excision of breast lesions by analyzing reflector placement, localization, and removal, along with target excision and rates of repeat excision (referred to as re-excision). Materials and Methods A single-institution retrospective review of 100 women who underwent breast lesion localization and excision by using the Savi Scout surgical guidance system from June 2015 to May 2016 was performed. By using image guidance 0-8 days before surgery, 123 nonradioactive, infrared-activated, electromagnetic wave reflectors were percutaneously inserted adjacent to or within 111 breast targets. Twenty patients had two or three reflectors placed for bracketing or for localizing multiple lesions, and when ipsilateral, they were placed as close as 2.6 cm apart. Target and reflector were localized intraoperatively by one of two breast surgeons who used a handpiece that emitted infrared light and electromagnetic waves. Radiographs of the specimen and pathologic analysis helped verify target and reflector removal. Target to reflector distance was measured on the mammogram and radiograph of the specimen, and reflector depth was measured on the mammogram. Pathologic analysis was reviewed. Re-excision rates and complications were recorded. By using statistics software, descriptive statistics were generated with 95% confidence intervals (CIs) calculated. Results By using sonographic (40 of 123; 32.5%; 95% CI: 24.9%, 41.2%) or mammographic (83 of 123; 67.5%; 95% CI: 58.8% 75.1%) guidance, 123 (100%; 95% CI: 96.4%, 100%) reflectors were placed. Mean mammographic target to reflector distance was 0.3 cm. All 123 (100%; 95% CI: 96.4%, 100%) targets and reflectors were excised. Pathologic analysis yielded 54 of 110 malignancies (49.1%; 95% CI: 39.9%, 58.3%; average, 1.0 cm; range, 0.1-5 cm), 32 high-risk lesions (29.1%; 95% CI: 21.4%, 38.2%), and 24 benign lesions (21.8%; 95% CI: 115.1%, 30.4%). Four of 54 malignant cases (7.4%; 95% CI: 2.4%, 18.1%) demonstrated margins positive for cancer that required re-excision. Five of 110 radiographs of the specimen (4.5%; 95% CI: 1.7%, 10.4%) demonstrated increased distance between the target and reflector distance of greater than 1.0 cm (range, 1.1-2.6 cm) compared with postprocedure mammogram the day of placement, three of five were associated with hematomas, two of five migrated without identifiable cause. No related postoperative complications were identified. Conclusion Savi Scout is an accurate, reliable method to localize and excise breast lesions with acceptable margin positivity and re-excision rates. Bracketing is possible with reflectors as close as 2.6 cm. Savi Scout overcomes many limitations of other localization methods, which warrants further study. © RSNA, 2017.

Development of a transportable neutron activation analysis system to quantify manganese in bone in vivo: feasibility and methodology.

PubMed

Liu, Yingzi; Koltick, David; Byrne, Patrick; Wang, Haoyu; Zheng, Wei; Nie, Linda H

2013-12-01

This study was conducted to investigate the methodology and feasibility of developing a transportable neutron activation analysis (NAA) system to quantify manganese (Mn) in bone using a portable deuterium-deuterium (DD) neutron generator as the neutron source. Since a DD neutron generator was not available in our laboratory, a deuterium-tritium (DT) neutron generator was used to obtain experimental data and validate the results from Monte Carlo (MC) simulations. After validation, MC simulations using a DD generator as the neutron source were then conducted. Different types of moderators and reflectors were simulated, and the optimal thicknesses for the moderator and reflector were determined. To estimate the detection limit (DL) of the system, and to observe the interference of the magnesium (Mg) γ line at 844 keV to the Mn γ line at 847 keV, three hand phantoms with Mn concentrations of 30 parts per million (ppm), 150 ppm, and 500 ppm were made and irradiated by the DT generator system. The Mn signals in these phantoms were then measured using a 50% high-efficiency high-purity germanium (HPGe) detector. The DL was calculated to be about 4.4 ppm for the chosen irradiation, decay, and measurement time. This was calculated to be equivalent to a DL of about 3.3 ppm for the DD generator system. To achieve this DL with one 50% high-efficiency HPGe detector, the dose to the hand was simulated to be about 37 mSv, with the total body equivalent dose being about 23µSv. In conclusion, it is feasible to develop a transportable NAA system to quantify Mn in bone in vivo with an acceptable radiation exposure to the subject.

Development of a transportable neutron activation analysis system to quantify manganese in bone in vivo: feasibility and methodology

PubMed Central

Liu, Yingzi; Koltick, David; Byrne, Patrick; Wang, Haoyu; Zheng, Wei; Nie, Linda H

2014-01-01

This study was conducted to investigate the methodology and feasibility of developing a transportable neutron activation analysis (NAA) system to quantify manganese (Mn) in bone using a portable deuterium–deuterium (DD) neutron generator as the neutron source. Since a DD neutron generator was not available in our laboratory, a deuterium–tritium (DT) neutron generator was used to obtain experimental data and validate the results from Monte Carlo (MC) simulations. After validation, MC simulations using a DD generator as the neutron source were then conducted. Different types of moderators and reflectors were simulated, and the optimal thicknesses for the moderator and reflector were determined. To estimate the detection limit (DL) of the system, and to observe the interference of the magnesium (Mg) γ line at 844 keV to the Mn γ line at 847 keV, three hand phantoms with Mn concentrations of 30 parts per million (ppm), 150 ppm, and 500 ppm were made and irradiated by the DT generator system. The Mn signals in these phantoms were then measured using a 50% high-efficiency high-purity germanium (HPGe) detector. The DL was calculated to be about 4.4 ppm for the chosen irradiation, decay, and measurement time. This was calculated to be equivalent to a DL of about 3.3 ppm for the DD generator system. To achieve this DL with one 50% high-efficiency HPGe detector, the dose to the hand was simulated to be about 37 mSv, with the total body equivalent dose being about 23μSv. In conclusion, it is feasible to develop a transportable NAA system to quantify Mn in bone in vivo with an acceptable radiation exposure to the subject. PMID:24165395

Sources of resistance to sunflower diseases in a global collection of domesticated USDA plant introductions

USDA-ARS?s Scientific Manuscript database

Basal stalk rot (BSR) and head rot (HR) caused by Sclerotinia sclerotiorum (Lib.) de Bary are traditionally major diseases of sunflower (Helianthus annuus L.) in the United States, while Phomopsis stem canker (PSC) caused by Phomopsis helianthi Munt.-Cvet. et. al. has increasingly become damaging in...

Teaching about the U.S. Constitution through Metaphor: Government as a Machine.

ERIC Educational Resources Information Center

Mills, Randy K.

1988-01-01

Briefly reviews theories of brain hemisphere functions and draws implications for social studies instruction. Maintains that the metaphor aids the development of understanding because it connects right and left brain functions. Provides a learning activity based on the metaphor of the U.S. government functioning as a machine. (BSR)

Anand Niketan Ashram, Rangpur, India: An Education for Meaningful Participation.

ERIC Educational Resources Information Center

Desai, Prakash O.; Haggerson, Nelson L.

1987-01-01

Describes a visit to the Anand Niketan Ashram in the interior of the State of Gujarat India, an internationally known school with a model education for meaningful citizen participation. Explores the program's philosophy activities and describes how the authors came together to have this experience and write this article. (BSR)

Why Did the Founding Fathers Write the Constitution of the United States?

ERIC Educational Resources Information Center

Singer, Alan

1987-01-01

Presents a mock dialogue among Thomas Jefferson, John Adams, James Madison, Alexander Hamilton, and Abigail Adams that questions whether the Founding Fathers wrote the U.S. Constitution as defenders of hard-won liberty or as self-serving aristocrats whose sole interest was in preserving their own economic and political positions. (BSR)

Reflector for efficient coupling of a laser beam to air or other fluids

DOEpatents

Kare, J.T.

1992-10-06

A reflector array is disclosed herein that provides a controlled region or regions of plasma breakdowns from a laser beam produced at a remotely-based laser source. The plasma may be applied to produce thrust to propel a spacecraft, or to diagnose a laser beam, or to produce shock waves. The spacecraft propulsion system comprises a reflector array attached to the vehicle. The reflector array comprises a plurality of reflectors spaced apart on a reflective surface, with each reflector acting as an independent focusing mirror. The reflectors are spaced closely together to form a continuous or partially-continuous surface. The reflector array may be formed from a sheet of reflective material, such as copper or aluminum. In operation, a beam of electromagnetic energy, such as a laser beam, is directed at the reflectors which focus the reflected electromagnetic energy at a plurality of regions off the surface. The energy concentrated in the focal region causes a breakdown of the air or other fluid in the focal region, creating a plasma. Electromagnetic energy is absorbed in the plasma and it grows in volume, compressing and heating the adjacent fluid thereby providing thrust. Laser pulses may be applied repetitively. After each such thrust pulse, fresh air can be introduced next to the surface either laterally, or through a perforated surface. If air or some other gas or vapor is supplied, for example from a tank carried on board a vehicle, this invention may also be used to provide thrust in a vacuum environment. 10 figs.

Preliminary design approach for large high precision segmented reflectors

NASA Technical Reports Server (NTRS)

Mikulas, Martin M., Jr.; Collins, Timothy J.; Hedgepeth, John M.

1990-01-01

A simplified preliminary design capability for erectable precision segmented reflectors is presented. This design capability permits a rapid assessment of a wide range of reflector parameters as well as new structural concepts and materials. The preliminary design approach was applied to a range of precision reflectors from 10 meters to 100 meters in diameter while considering standard design drivers. The design drivers considered were: weight, fundamental frequency, launch packaging volume, part count, and on-orbit assembly time. For the range of parameters considered, on-orbit assembly time was identified as the major design driver. A family of modular panels is introduced which can significantly reduce the number of reflector parts and the on-orbit assembly time.

Optical properties of nonimaging concentrators with corrugated reflectors

NASA Astrophysics Data System (ADS)

Roennelid, Mats; Perers, Bengt; Karlsson, Bjorn

1994-09-01

A ray tracing study has been performed on the optical properties of cylindrical nonimaging concentrators with linear corrugated reflectors. The corrugations are assumed to be V-formed and to have an extension parallel to the meridian plane of the concentrators. It is shown that the acceptance angle for radiation incident in the meridian plane can be increased for moderate corrugations. This increased acceptance is balanced by a decreased acceptance of radiation from other directions. Calculations of angular acceptance for a 2X compound parabolic concentrator is presented. It is shown that the annual irradiation on a solar collector with booster reflector can be increased if corrugated reflectors are used instead of smooth reflectors.