Sonic depth sounder for laboratory and field use

USGS Publications Warehouse

Richardson, E.V.; Simons, Daryl B.; Posakony, G.J.

1961-01-01

The laboratory investigation of roughness in alluvial channels has led to the development of a special electronic device capable of mapping the streambed configuration under dynamic conditions. This electronic device employs an ultrasonic pulse-echo principle, similar to that of a fathometer, that utilizes microsecond techniques to give high accuracy in shallow depths. This instrument is known as the sonic depth sounder and was designed to cover a depth range of 0 to 4 feet with an accuracy of ? 0.5 percent. The sonic depth sounder is capable of operation at frequencies of 500, 1,000 and 2,000 kilocycles. The ultrasonic beam generated at the transducer is designed to give a minimum-diameter interrogating signal over the extended depth range. The information obtained from a sonic depth sounder is recorded on a strip-chart recorder. This permanent record allows an analysis to be made of the streambed configuration under different dynamic conditions. The model 1024 sonic depth sounder was designed principally as a research instrument to meet laboratory needs. As such, it is somewhat limited in its application as a field instrument on large streams and rivers. The principles employed in this instrument, however, have many potentials for field applications such as the indirect measurement of bed load when the bed roughness is ripples and (or) dunes, depth measurement, determination of bed configuration, and determination of depth of scour around bridge piers and abutments. For field application a modification of the present system into a battery-operated lightweight instrument designed to operate at a depth range of 0 to 30 feet is possible and desirable.

200 kHz Commercial Sonar Systems Generate Lower Frequency Side Lobes Audible to Some Marine Mammals

PubMed Central

Deng, Z. Daniel; Southall, Brandon L.; Carlson, Thomas J.; Xu, Jinshan; Martinez, Jayson J.; Weiland, Mark A.; Ingraham, John M.

2014-01-01

The spectral properties of pulses transmitted by three commercially available 200 kHz echo sounders were measured to assess the possibility that marine mammals might hear sound energy below the center (carrier) frequency that may be generated by transmitting short rectangular pulses. All three sounders were found to generate sound at frequencies below the center frequency and within the hearing range of some marine mammals, e.g. killer whales, false killer whales, beluga whales, Atlantic bottlenose dolphins, harbor porpoises, and others. The frequencies of these sub-harmonic sounds ranged from 90 to 130 kHz. These sounds were likely detectable by the animals over distances up to several hundred meters but were well below potentially harmful levels. The sounds generated by the sounders could potentially affect the behavior of marine mammals within fairly close proximity to the sources and therefore the exclusion of echo sounders from environmental impact analysis based solely on the center frequency output in relation to the range of marine mammal hearing should be reconsidered. PMID:24736608

Echo characteristics of two salmon species

NASA Astrophysics Data System (ADS)

Nealson, Patrick A.; Horne, John K.; Burwen, Debby L.

2005-04-01

The Alaska Department of Fish and Game relies on split-beam hydroacoustic techniques to estimate Chinook salmon (Oncorhynchus tshawytscha) returns to the Kenai River. Chinook counts are periodically confounded by large numbers of smaller sockeye salmon (O. nerka). Echo target-strength has been used to distinguish fish length classes, but was too variable to separate Kenai River chinook and sockeye distributions. To evaluate the efficacy of alternate echo metrics, controlled acoustic measurements of tethered chinook and sockeye salmon were collected at 200 kHz. Echo returns were digitally sampled at 48 kHz. A suite of descriptive metrics were collected from a series of 1,000 echoes per fish. Measurements of echo width were least variable at the -3 dB power point. Initial results show echo elongation and ping-to-ping variability in echo envelope width were significantly greater for chinook than for sockeye salmon. Chinook were also observed to return multiple discrete peaks from a single broadcast echo. These characteristics were attributed to the physical width of chinook exceeding half of the broadcast echo pulse width at certain orientations. Echo phase variability, correlation coefficient and fractal dimension distributions did not demonstrate significant discriminatory power between the two species. [Work supported by ADF&G, ONR.

Standard-target calibration of an acoustic backscatter system

USGS Publications Warehouse

Foote, Kenneth G.; Martini, Marinna A.

2010-01-01

The standard-target method used to calibrate scientific echo sounders and other scientific sonars by a single, solid elastic sphere is being adapted to acoustic backscatter (ABS) systems. Its first application, to the AQUAscat 1000, is described. The on-axis sensitivity and directional properties of transducer beams at three operating frequencies, nominally 1, 2.5, and 4 MHz, have been determined using a 10-mm-diameter sphere of tungsten carbide with 6% cobalt binder. Preliminary results are reported for the 1-MHz transducer. Their application to measurements of suspended sediment made in situ with the same device is described. This will enable the data to be expressed directly in physical units of volume backscattering.

The 3D Visualization of Slope Terrain in Sun Moon Lake.

NASA Astrophysics Data System (ADS)

Deng, F.; Gwo-shyn, S.; Pei-Kun, L.

2015-12-01

By doing topographical surveys in a reservoir, we can calculate siltation volume in the period of two measurements. It becomes basic requirement to provide more precise siltation value especially when the differential GPS positioning method and the multi-beams echo sounders have been prevailed; however, there are two problems making the result become challenging when doing the siltation-survey in reservoir. They are both relative with the difficulty in keeping survey accuracy to the area of side slope around the boundary of reservoir. Firstly, the efficiency or accuracy of horizontal positioning using the DGPS may decrease because of the satellite-blocking effect when the surveying ship nears the bank especially in the canyon type of reservoir. Secondly, measurement can only be acquired in the area covered by water using the echo sounder, such that the measuring data of side slope area above water surface are lack to decrease the accuracy or seriously affect the calculation of reservoir water volume. This research is to hold the terrain accuracy when measuring the reservoir side slope and the Sun Moon Lake Reservoir in central Taiwan is chosen as the experimental location. Sun Moon Lake is the most popular place for tourists in Taiwan and also the most important reservoir of the electricity facilities. Furthermore, it owns the biggest pumped-storage hydroelectricity in Asia. The water in the lake is self-contained, and its water supply has been input through two underground tunnels, such that a deposit fan is formed when the muds were settled down from the silty water of the Cho-Shui Shi. Three kinds of survey are conducted in this experiment. First, a close-range photogrammetry, around the border of the Sun Moon Lake is made, or it takes shoots along the bank using a camera linked with a computer running the software Pix4D. The result can provide the DTM data to the side slope above the water level. Second, the bathymetrical data can be obtained by sweeping the side-slope using the multi-beam sounder below the water surface. Finally, the image of the side-scan sonar is taken and merges with contour lines produced from underwater topographic DTM data. Combining those data, our purpose is by creating different 3D images to have good visualization checking the data of side-slope DTM surveys if they are in well qualified controlled.

Determination of film processing specifications for the Apollo 17 S-209 lunar sounder experiment

NASA Technical Reports Server (NTRS)

Weinstein, M. S.

1972-01-01

The lunar sounder is described as a radar system operating at carrier frequencies of 5, 15, and 150 MHz. The radar echoes are recorded onto Kodak type S0-394 film through the use of an optical recorder utilizing a cathode ray tube as the exposing device. A processing configuration is determined with regard to linearity, dynamic range, and noise.

Assessment of bridge scour in the lower, middle, and upper Yangtze River estuary with riverbed sonar profiling techniques.

PubMed

Zheng, Shuwei; Xu, Y Jun; Cheng, Heqin; Wang, Bo; Lu, Xuejun

2017-12-12

Riverbed scour of bridge piers can cause rapid loss in foundation strength, leading to sudden bridge collapse. This study used multi-beam echo sounders (Seabat 7125) to map riverbed surrounding the foundations of four major bridges in the lower, middle, and upper reaches of the 700-km Yangtze River Estuary (YRE) during June 2015 and September 2016. The high-resolution data were utilized to analyze the morphology of the bridge scour and the deformation of the wide-area riverbed (i.e., 5-18 km long and 1.3-8.3 km wide). In addition, previous bathymetric measurements collected in 1998, 2009, and 2013 were used to determine riverbed erosion and deposition at the bridge reaches. Our study shows that the scour depth surrounding the bridge foundations progressed up to 4.4-19.0 m in the YRE. Over the past 5-15 years, the total channel erosion in some river reaches was up to 15-17 m, possessing a threat to the bridge safety in the YRE. Tide cycles seemed to have resulted in significant variation in the scour morphology in the lower and middle YRE. In the lower YRE, the riverbed morphology displayed one long erosional ditch on both sides of the bridge foundations and a long-strip siltation area distributed upstream and downstream of the bridge foundations; in the middle YRE, the riverbed morphology only showed erosional morphology surrounding the bridge foundations. Large dunes caused deep cuts and steeper contours in the bridge scour. Furthermore, this study demonstrates that the high-resolution grid model formed by point cloud data of multi-beam echo sounders can clearly display the morphology of the bridge scour in terms of wide areas and that the sonar technique is a very useful tool in the assessment of bridge scours.

The 2006 Project Progress Report for 1987-099-00 Dworshak Kokanee Population and Entrainment Assessment (contract # 26850) is attached to project 2007-003-00, contract #31598. [POINTER

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

None

2008-12-18

During this contract, we continued testing underwater strobe lights to determine their effectiveness at repelling kokanee Oncorhynchus nerka away from Dworshak Dam. Strobe light tests were conducted on four nights from April 24-27, 2006, in front of the middle reservoir outlet (RO) 2. The density and distribution of fish, (thought to be mostly kokanee), were monitored with a split-beam echo sounder. We then compared fish counts and densities during nights when the lights were flashing to counts and densities during adjacent nights without the lights on. On two nights, April 25 and 27, 2006, when no lights were present, fishmore » counts near RO 2 averaged 12.4 fish and densities averaged 31.0 fish/ha. When strobe lights were turned on during the nights of April 24 and 26, mean counts dropped to 4.7 fish and densities dropped to 0.5 fish/ha. The decline in counts (62%) and densities (99%) was statistically significant (p = 0.009 and 0.002, respectively). Test results indicated that strobe lights were able to reduce fish densities by at least 50% in front of a discharging reservoir outlet, which would be sufficient to improve sport fish harvest. We also used split-beam hydroacoustics to monitor the kokanee population in Dworshak Reservoir during 2006. Estimated abundance of kokanee increased from the 2005 population estimate. Based on hydroacoustic surveys, we estimated approximately 5,815,000 kokanee (90% CI {+-} 27.6%) in Dworshak Reservoir in August 2006. This included 2,183,000 age-0 (90% CI {+-} 24.2%), 1,509,000 age-1 (90% CI {+-} 29.0%), and 2,124,000 age-2 (90% CI {+-} 27.6%) kokanee. This resulted in a density of age-2 kokanee above the management goal of 30-50 adults/ha. Entrainment sampling was conducted with fixed-site, split-beam hydroacoustics from May through September for a continuous 24 h period when dam operations permitted. The highest fish detection rates from entrainment assessments were found during dawn periods, unlike previous year's results, which were highest during nighttime. The lowest detection rate was found during the day period, which was consistent with previous findings. Fish detection rates were generally low during high discharges throughout the summer and highest during low discharges in May and June. Low detection rates were found during high discharge periods during drawdowns for anadromous fish flows in July and August, which resulted in low susceptibility to entrainment. Counts of spawning kokanee in four tributary streams totaled 29,743 fish. These data fit the previously developed relationship between spawner counts and adult kokanee abundance in the reservoir.« less

Dworshak Kokanee Population and Engrainment Assessment : 2006 Annual Report, March 1, 2006 - February 28, 2007.

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

Stark, Eric J.

2008-12-18

During this contract, we continued testing underwater strobe lights to determine their effectiveness at repelling kokanee Oncorhynchus nerka away from Dworshak Dam. Strobe light tests were conducted on four nights from April 24-27, 2006, in front of the middle reservoir outlet (RO) 2. The density and distribution of fish, (thought to be mostly kokanee), were monitored with a split-beam echo sounder. We then compared fish counts and densities during nights when the lights were flashing to counts and densities during adjacent nights without the lights on. On two nights, April 25 and 27, 2006, when no lights were present, fishmore » counts near RO 2 averaged 12.4 fish and densities averaged 31.0 fish/ha. When strobe lights were turned on during the nights of April 24 and 26, mean counts dropped to 4.7 fish and densities dropped to 0.5 fish/ha. The decline in counts (62%) and densities (99%) was statistically significant (p = 0.009 and 0.002, respectively). Test results indicated that strobe lights were able to reduce fish densities by at least 50% in front of a discharging reservoir outlet, which would be sufficient to improve sport fish harvest. We also used split-beam hydroacoustics to monitor the kokanee population in Dworshak Reservoir during 2006. Estimated abundance of kokanee increased from the 2005 population estimate. Based on hydroacoustic surveys, we estimated approximately 5,815,000 kokanee (90% CI {+-} 27.6%) in Dworshak Reservoir in August 2006. This included 2,183,000 age-0 (90% CI {+-} 24.2%), 1,509,000 age-1 (90% CI {+-} 29.0%), and 2,124,000 age-2 (90% CI {+-} 27.6%) kokanee. This resulted in a density of age-2 kokanee above the management goal of 30-50 adults/ha. Entrainment sampling was conducted with fixed-site, split-beam hydroacoustics from May through September for a continuous 24 h period when dam operations permitted. The highest fish detection rates from entrainment assessments were found during dawn periods, unlike previous year's results, which were highest during nighttime. The lowest detection rate was found during the day period, which was consistent with previous findings. Fish detection rates were generally low during high discharges throughout the summer and highest during low discharges in May and June. Low detection rates were found during high discharge periods during drawdowns for anadromous fish flows in July and August, which resulted in low susceptibility to entrainment. Counts of spawning kokanee in four tributary streams totaled 29,743 fish. These data fit the previously developed relationship between spawner counts and adult kokanee abundance in the reservoir.« less

The 2005 Project Progress Report for 1987-099-00 Dworshak Kokanee Population and Entrainment Assessment (contract # 16791) is attached to project 1987-099-00, contract # 26850. [POINTER

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

None

2008-12-18

During this contract, we continued testing underwater strobe lights to determine their effectiveness at repelling kokanee Oncorhynchus nerka away from Dworshak Dam. We tested one set of nine strobe lights flashing at a rate of 360 flashes/min in front of turbine 3 while operating at higher discharges than previously tested. The density and distribution of fish, (thought to be mostly kokanee), were monitored with a split-beam echo sounder. We then compared fish counts and densities during nights when the lights were flashing to counts and densities during adjacent nights without the lights on. On five nights between January 31 andmore » February 28, 2006, when no lights were present, fish counts near turbine 3 averaged eight fish and densities averaged 91 fish/ha. When strobe lights were turned on during five adjacent nights during the same period, mean counts dropped to four fish and densities dropped to 35 fish/ha. The decline in counts (49%) was not statistically significant (p = 0.182), but decline in densities (62%) was significant (p = 0.049). There appeared to be no tendency for fish to habituate to the lights during the night. Test results indicated that strobe lights were able to reduce fish densities by at least 50% in front of turbines operating at higher discharges, which would be sufficient to improve sportfish harvest. We also used split-beam hydroacoustics to monitor the kokanee population in Dworshak Reservoir during 2005. Estimated abundance of kokanee decreased from the 2004 population estimate. Based on hydroacoustic surveys, we estimated 3,011,626 kokanee (90% CI {+-} 15.2%) in Dworshak Reservoir, July 2005. This included 2,135,986 age-0 (90% CI {+-} 15.9%), 769,175 age-1 (90% CI {+-} 16.0%), and 107,465 age-2 (90% CI {+-} 15.2%). Poor survival of kokanee from age-1 to age-2 continued to keep age-2 densities below the management goal of 30-50 adults/ha. Entrainment sampling was conducted with fixed-site split-beam hydroacoustics a minimum of two days per month for a continuous 24 h period when dam operations permitted. The highest fish detection rates from entrainment assessments were again found during nighttime periods and lowest during the day. Fish detection rates were low during high discharges throughout the spring and summer and highest during low discharges in September and November. High discharge during drawdowns for anadromous fish flows in July and August again resulted in low detection rates and susceptibility to entrainment. Index counts of spawning kokanee in four tributary streams totaled 12,742 fish. This data fits the previously developed relationship between spawner counts and adult kokanee abundance in the reservoir.« less

The radio power reflected from rough and undulating ionospheric surfaces

NASA Astrophysics Data System (ADS)

Whitehead, J. D.; From, W. R.; Smith, L. G.

1984-08-01

It is shown for both rough and undulating surfaces that the mean radio power reflected by the ionosphere averaged over a sufficiently long time is exactly the same as for a smooth flat surface at the same height provided the sounder is equally sensitive for echoes from all directions. When making radio wave absorption measurements under spread conditions the total integrated power over the whole time the direct echoes are being received must be used but the distance attenuation factor must be calculated from the time of arrival of the first echo.

Coastal bathymetry data collected in May 2015 from Fire Island, New York—Wilderness breach and shoreface

USGS Publications Warehouse

Nelson, Timothy R.; Miselis, Jennifer L.; Hapke, Cheryl J.; Brenner, Owen T.; Henderson, Rachel E.; Reynolds, Billy J.; Wilson, Kathleen E.

2017-05-12

Scientists from the U.S. Geological Survey (USGS) St. Petersburg Coastal and Marine Science Center in St. Petersburg, Florida, conducted a bathymetric survey of Fire Island from May 6-20, 2015. The USGS is involved in a post-Hurricane Sandy effort to map and monitor the morphologic evolution of the wilderness breach as a part of the Hurricane Sandy Supplemental Project GS2-2B. During this study, bathymetry data were collected with single-beam echo sounders and Global Positioning Systems, which were mounted to personal watercraft, along the Fire Island shoreface and within the wilderness breach. Additional bathymetry and elevation data were collected using backpack Global Positioning Systems on flood shoals and in shallow channels within the wilderness breach.

Volcano-tectonic structures and CO2-degassing patterns in the Laacher See basin, Germany

NASA Astrophysics Data System (ADS)

Goepel, Andreas; Lonschinski, Martin; Viereck, Lothar; Büchel, Georg; Kukowski, Nina

2015-07-01

The Laacher See Volcano is the youngest (12,900 year BP) eruption center of the Quarternary East-Eifel Volcanic Field in Germany and has formed Laacher See, the largest volcanic lake in the Eifel area. New bathymetric data of Laacher See were acquired by an echo sounder system and merged with topographic light detection and ranging (LiDAR) data of the Laacher See Volcano area to form an integrated digital elevation model. This model provides detailed morphological information about the volcano basin and results of sediment transport therein. Morphological analysis of Laacher See Volcano indicates a steep inner crater wall (slope up to 30°) which opens to the south. The Laacher See basin is divided into a deep northern and a shallower southern part. The broader lower slopes inclined with up to 25° change to the almost flat central part (maximum water depth of 51 m) with a narrow transition zone. Erosion processes of the crater wall result in deposition of volcaniclastics as large deltas in the lake basin. A large subaqueous slide was identified at the northeastern part of the lake. CO2-degassing vents (wet mofettes) of Laacher See were identified by a single-beam echo sounder system through gas bubbles in the water column. These are more frequent in the northern part of the lake, where wet mofettes spread in a nearly circular-shaped pattern, tracing the crater rim of the northern eruption center of the Laacher See Volcano. Additionally, preferential paths for gas efflux distributed concentrically inside the crater rim are possibly related to volcano-tectonic faults. In the southern part of Laacher See, CO2 vents occur in a high spatial density only within the center of the arc-shaped structure Barschbuckel possibly tracing the conduit of a tuff ring.

Bathymetry of Ashokan, Cannonsville, Neversink, Pepacton, Rondout, and Schoharie Reservoirs, New York, 2013–15

USGS Publications Warehouse

Nystrom, Elizabeth A.

2018-02-01

Drinking water for New York City is supplied from several large reservoirs, including a system of reservoirs west of the Hudson River. To provide updated reservoir capacity tables and bathymetry maps of the City’s six West of Hudson reservoirs, bathymetric surveys were conducted by the U.S. Geological Survey from 2013 to 2015. Depths were surveyed with a single-beam echo sounder and real-time kinematic global positioning system along planned transects at predetermined intervals for each reservoir. A separate quality assurance dataset of echo sounder points was collected along transects at oblique angles to the main transects for accuracy assessment. Field-survey data were combined with water surface elevations in a geographic information system to create three-dimensional surfaces in the form of triangulated irregular networks (TINs) representing the elevations of the reservoir geomorphology. The TINs were linearly enforced to better represent geomorphic features within the reservoirs. The linearly enforced TINs were then used to create raster surfaces and 2-foot-interval contour maps of the reservoirs. Elevation-area-capacity tables were calculated at 0.01-foot intervals. The results of the surveys show that the total capacity of the West of Hudson reservoirs has decreased by 11.5 billion gallons (Ggal), or 2.3 percent, since construction, and the useable capacity (the volume above the minimum operating level required to deliver full flow for drinking water supply) has decreased by 7.9 Ggal (1.7 percent). The available capacity (the volume between the spillway elevation and the lowest intake or sill elevation used for drinking water supply) decreased by 9.6 Ggal (2.0 percent), and dead storage (the volume below the lowest intake or sill elevation) decreased by 1.9 Ggal (11.6 percent).

Toward a standard line for use in multibeam echo sounder calibration

NASA Astrophysics Data System (ADS)

Weber, Thomas C.; Rice, Glen; Smith, Michael

2018-06-01

A procedure is suggested in which a relative calibration for the intensity output of a multibeam echo sounder (MBES) can be performed. This procedure identifies a common survey line (i.e., a standard line), over which acoustic backscatter from the seafloor is collected with multiple MBES systems or by the same system multiple times. A location on the standard line which exhibits temporal stability in its seafloor backscatter response is used to bring the intensity output of the multiple MBES systems to a common reference. This relative calibration procedure has utility for MBES users wishing to generate an aggregate seafloor backscatter mosaic using multiple systems, revisiting an area to detect changes in substrate type, and comparing substrate types in the same general area but with different systems or different system settings. The calibration procedure is demonstrated using three different MBES systems over 3 different years in New Castle, NH, USA.

Processing RoxAnn sonar data to improve its categorization of lake bed surficial sediments

USGS Publications Warehouse

Cholwek, Gary; Bonde, John; Li, Xing; Richards, Carl; Yin, Karen

2000-01-01

To categorize spawning and nursery habitat for lake trout in Minnesota's near shore waters of Lake Superior, data was collected with a single beam echo sounder coupled with a RoxAnn bottom classification sensor. Test areas representative of different bottom surficial substrates were sampled. The collected data consisted of acoustic signals which showed both depth and substrate type. The location of the signals was tagged in real-time with a DGPS. All data was imported into a GIS database. To better interpret the output signal from the RoxAnn, several pattern classifiers were developed by multivariate statistical method. From the data a detailed and accurate map of lake bed bathymetry and surficial substrate types was produced. This map will be of great value to fishery and other natural resource managers.

Coastal bathymetry data collected in June 2014 from Fire Island, New York—The wilderness breach and shoreface

USGS Publications Warehouse

Nelson, Timothy R.; Miselis, Jennifer L.; Hapke, Cheryl J.; Wilson, Kathleen E.; Henderson, Rachel E.; Brenner, Owen T.; Reynolds, Billy J.; Hansen, Mark E.

2016-08-02

Scientists from the U.S. Geological Survey St. Petersburg Coastal and Marine Science Center in St. Petersburg, Florida, collected bathymetric data along the upper shoreface and within the wilderness breach at Fire Island, New York, in June 2014. The U.S. Geological Survey is involved in a post-Hurricane Sandy effort to map and monitor the morphologic evolution of the shoreface along Fire Island and model the evolution of the wilderness breach as a part of the Hurricane Sandy Supplemental Project GS2-2B. During this study, bathymetry was collected with single-beam echo sounders and global positioning systems, mounted to personal watercraft, along the Fire Island shoreface and within the wilderness breach. Additional bathymetry was collected using backpack global positioning systems along the flood shoals and shallow channels within the wilderness breach.

Acoustic detection of ice crystals in Antarctic waters

NASA Astrophysics Data System (ADS)

Penrose, John D.; Conde, M.; Pauly, T. J.

1994-06-01

During the voyage of the RSV Aurora Australis to the region of Prydz Bay, Antarctica in January-March 1991, ice crystals were encountered at depths from the surface to 125-m in the western area of the bay. On two occasions, crystals were retrieved by netting, and echo sounder records have been used to infer additional regions of occurrence. Acoustic target strength estimates made on the ice crystal assemblies encountered show significant spatial variation, which may relate to crystal size and/or aggregation. Data from a suite of conductivity-temperature-depth casts have been used to map regions of the study area where in situ water temperatures fell below the computed freezing point. Such regions correlate well with those selected on the basis of echogram type and imply that ice crystals occurred at depth over large areas of the bay during the cruise period. The ice crystal distribution described is consistent with that expected from a plume of supercooled water emerging from under the Amery Ice Shelf and forming part of the general circulation of the bay. The magnitude of the supercooled water plume is greater than those reported previously in the Prydz Bay region. If misinterpreted as biota on echo sounder records, ice crystals could significantly bias biomass estimates based on echo integration in this and potentially other areas.

Broadband infrared beam splitter for spaceborne interferometric infrared sounder.

PubMed

Yu, Tianyan; Liu, Dingquan; Qin, Yang

2014-10-01

A broadband infrared beam splitter (BS) on ZnSe substrate used for the spaceborne interferometric infrared sounder (SIIRS) is studied in the spectral range of 4.44-15 μm. Both broadband antireflection coating and broadband beam-splitter coating in this BS are designed and tested. To optimize the optical properties and the stability of the BS, suitable infrared materials were selected, and improved deposition techniques were applied. The designed structures matched experimental data well, and the properties of the BS met the application specification of SIIRS.

Microwave Atmospheric-Pressure Sensor

NASA Technical Reports Server (NTRS)

Flower, D. A.; Peckham, G. E.; Bradford, W. J.

1986-01-01

Report describes tests of microwave pressure sounder (MPS) for use in satellite measurements of atmospheric pressure. MPS is multifrequency radar operating between 25 and 80 GHz. Determines signal absorption over vertical path through atmosphere by measuring strength of echoes from ocean surface. MPS operates with cloud cover, and suitable for use on current meteorological satellites.

Bathymetric surveys at Highway Bridges Crossing the Missouri River in Kansas City, Missouri, using a multibeam echo sounder, 2010.

DOT National Transportation Integrated Search

2010-11-01

Bathymetric surveys were conducted by the U.S. Geological Survey, in cooperation with the Missouri Department of Transportation, on the Missouri River in the vicinity of nine bridges at seven highway crossings in Kansas City, Missouri, in March 2010....

The phase transition of methane caused by pressure change during its seeping up from seepage, revealed by video observation and acoustic reflection data

NASA Astrophysics Data System (ADS)

Aoyama, C.

2017-12-01

Methane plumes often exist in the vicinity sea area where shallow type methane hydrates are extracted and they are observed as images displayed on monitors of multi-beam sonar and echo sounder onboard, where methane hydrates are expected at sea bottom on ROV observation data. The hydrates are generally considered to be generated in shallow depths below the sea floor. In this study, author examined annual amount of methane dissolving into seawater by measuring the amount of plume in order to make a quantification of dissolving methane from seafloor. Measurement procedure is plume exploration using multi-beam and quantitative echo sounder , submerge ROV to gushing point at seafloor , calculate the rising speed of methane plumes and examine the phases by monitoring seeping plumes from seafloor with high-definition camera. Components of seeping plumes were defined as methane hydrate particles based on the result by measuring water temperature. From this procedure, it can be concluded that the minimum rising speed of methane hydrate particles from gushing point is 1.6×10-1(m/s) and the maximum of 2.0×10-1(m/s) indicating a difference of more than ten times the gaseous theoretical value of 2.74(m/s). This speed is theoretically closer to the solid speed of the material with physical property similar to hydrates, which is 3.05×10-1 (m/s). Therefore, it can be determined that those particles are in the solid state, immediately above seafloor. To measure the amount of plumes seeping from gushing points funnel-shaped instruments with 20cm diameter opening were used to collect methane plumes in this sea area. This was performed in three different gushing points. As a result, 300ml of methane plume was collected in 643 seconds. Assuming that gushing points exist evenly in the sea area, the annual amount of methane gas seeping from these points will be 7.7×105m3 /per m2. Result shows a large quantity of methane seeping from seafloor into the water. This data is an important factor when considering carbon cycle and future development the shallow methane hydrate resources.

Nonlinear theory of transverse beam echoes

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

Sen, Tanaji; Li, Yuan Shen

Transverse beam echoes can be excited with a single dipole kick followed by a single quadrupole kick. They have been used to measure diffusion in hadron beams and have other diagnostic capabilities. Here we develop theories of the transverse echo nonlinear in both the dipole and quadrupole kick strengths. The theories predict the maximum echo amplitudes and the optimum strength parameters. We find that the echo amplitude increases with smaller beam emittance and the asymptotic echo amplitude can exceed half the initial dipole kick amplitude. We show that multiple echoes can be observed provided the dipole kick is large enough.more » The spectrum of the echo pulse can be used to determine the nonlinear detuning parameter with small amplitude dipole kicks. Simulations are performed to check the theoretical predictions. In the useful ranges of dipole and quadrupole strengths, they are shown to be in reasonable agreement.« less

Nonlinear theory of transverse beam echoes

DOE PAGES

Sen, Tanaji; Li, Yuan Shen

2018-02-23

Transverse beam echoes can be excited with a single dipole kick followed by a single quadrupole kick. They have been used to measure diffusion in hadron beams and have other diagnostic capabilities. Here we develop theories of the transverse echo nonlinear in both the dipole and quadrupole kick strengths. The theories predict the maximum echo amplitudes and the optimum strength parameters. We find that the echo amplitude increases with smaller beam emittance and the asymptotic echo amplitude can exceed half the initial dipole kick amplitude. We show that multiple echoes can be observed provided the dipole kick is large enough.more » The spectrum of the echo pulse can be used to determine the nonlinear detuning parameter with small amplitude dipole kicks. Simulations are performed to check the theoretical predictions. In the useful ranges of dipole and quadrupole strengths, they are shown to be in reasonable agreement.« less

A retrospective on hydroacoustic assessment of fish passage in Alaskan rivers

NASA Astrophysics Data System (ADS)

Burwen, Debby; Fleischman, Steve; Maxwell, Suzanne; Pfisterer, Carl

2005-04-01

The Alaska Department of Fish and Game (ADFG) has enumerated fish stocks in rivers for over 30 years using a variety of acoustic technologies including single-, dual-, and split-beam sonar. Most recently, ADFG has evaluated a relatively new sonar technology at several sites in Alaska to determine its applicability to counting migrating fish in rivers. The new system, called a Dual frequency IDentification SONar (DIDSON), is a high-definition imaging sonar designed and manufactured by the University of Washington's Applied Physics Lab for military applications such as diver detection and underwater mine identification. Results from experiments conducted in 2002-2004 indicate that DIDSON provides significant improvements in our ability to detect, track, and determine the direction of travel of migrating fish in rivers. One of the most powerful uses of the DIDSON has been to combine its camera-like images of fish swimming behavior with corresponding split-beam data. These linked datasets have allowed us to evaluate the effects of fish orientation and swimming behavior on echo shape parameters that have proven useful in the classification of certain fish species.

Regional Characteristics for Interpreting Inverted Echo Sounder (IES) observations

DTIC Science & Technology

1987-06-01

rounding the IESs. There are seasonal warming and and ideally, we should like to have a series of hydro- cooling effects which may be missed with...thermocline This shallo, sanabihlit\\ , Is lkck to be spatialk and temporall , aliased: it ma\\ 01 ." b assoi ated ws.ith internal \\ awes or frontal tluctua

Simultaneous dual contrast weighting using double echo rapid acquisition with relaxation enhancement (RARE) imaging.

PubMed

Fuchs, Katharina; Hezel, Fabian; Klix, Sabrina; Mekle, Ralf; Wuerfel, Jens; Niendorf, Thoralf

2014-12-01

This work proposes a dual contrast rapid acquisition with relaxation enhancement (RARE) variant (2in1-RARE), which provides simultaneous proton density (PD) and T2 * contrast in a single acquisition. The underlying concept of 2in1-RARE is the strict separation of spin echoes and stimulated echoes. This approach offers independent weighting of spin echoes and stimulated echoes. 2in1-RARE was evaluated in phantoms including signal-to-noise ratio (SNR) and point spread function assessment. 2in1-RARE was benchmarked versus coherent RARE and a split-echo RARE variant. The applicability of 2in1-RARE for brain imaging was demonstrated in a small cohort of healthy subjects (n = 10) and, exemplary, a multiple sclerosis patient at 3 Tesla as a precursor to a broader clinical study. 2in1-RARE enables the simultaneous acquisition of dual contrast weighted images without any significant image degradation and without sacrificing SNR versus split-echo RARE. This translates into a factor of two speed gain over multi-contrast, sequential split-echo RARE. A 15% broadening of the point spread function was observed in 2in1-RARE. T1 relaxation effects during the mixing time can be neglected for brain tissue. 2in1-RARE offers simultaneous acquisition of images of anatomical (PD) and functional (T2 *) contrast. It presents an alternative to address scan time constraints frequently encountered during sequential acquisition of T2 * or PD-weighted RARE. © 2013 Wiley Periodicals, Inc.

Hydraulic alterations resulting from hydropower development in the Bonneville Reach of the Columbia River

USGS Publications Warehouse

Hatten, James R.; Batt, Thomas R.

2010-01-01

We used a two-dimensional (2D) hydrodynamic model to simulate and compare the hydraulic characteristics in a 74-km reach of the Columbia River (the Bonneville Reach) before and after construction of Bonneville Dam. For hydrodynamic modeling, we created a bathymetric layer of the Bonneville Reach from single-beam and multi-beam echo-sounder surveys, digital elevation models, and navigation surveys. We calibrated the hydrodynamic model at 100 and 300 kcfs with a user-defined roughness layer, a variable-sized mesh, and a U.S. Army Corps of Engineers backwater curve. We verified the 2D model with acoustic Doppler current profiler (ADCP) data at 14 transects and three flows. The 2D model was 88% accurate for water depths, and 77% accurate for velocities. We verified a pre-dam 2D model run at 126 kcfs using pre-dam aerial photos from September 1935. Hydraulic simulations indicated that mean water depths in the Bonneville Reach increased by 34% following dam construction, while mean velocities decreased by 58%. There are numerous activities that would benefit from data output from the 2D model, including biological sampling, bioenergetics, and spatially explicit habitat modeling.

Extraction of Ice Sheet Layers from Two Intersected Radar Echograms Near Neem Ice Core in Greenland

NASA Astrophysics Data System (ADS)

Xiong, S.; Muller, J.-P.

2016-06-01

Accumulation of snow and ice over time result in ice sheet layers. These can be remotely sensed where there is a contrast in electromagnetic properties, which reflect variations of the ice density, acidity and fabric orientation. Internal ice layers are assumed to be isochronous, deep beneath the ice surface, and parallel to the direction of ice flow. The distribution of internal layers is related to ice sheet dynamics, such as the basal melt rate, basal elevation variation and changes in ice flow mode, which are important parameters to model the ice sheet. Radar echo sounder is an effective instrument used to study the sedimentology of the Earth and planets. Ice Penetrating Radar (IPR) is specific kind of radar echo sounder, which extends studies of ice sheets from surface to subsurface to deep internal ice sheets depending on the frequency utilised. In this study, we examine a study site where folded ice occurs in the internal ice sheet south of the North Greenland Eemian ice drilling (NEEM) station, where two intersected radar echograms acquired by the Multi-channel Coherent Radar Depth Sounder (MCoRDS) employed in the NASA's Operation IceBridge (OIB) mission imaged this folded ice. We propose a slice processing flow based on a Radon Transform to trace and extract these two sets of curved ice sheet layers, which can then be viewed in 3-D, demonstrating the 3-D structure of the ice folds.

Observation of Moon Jellyfish Spatial Distribution Using a Scientific Echo Sounder and Underwater Camera

NASA Astrophysics Data System (ADS)

Mano, T.; Guo, X.; Fujii, N.; Yoshie, N.; Takeoka, H.

2016-02-01

Jellyfishes often form dense aggregation that causes a variety of social problems such as clogging seawater intake of power plant, breaking fisheries net and more. Understanding on jellyfish aggregation is not sufficient due to the difficulty of observation on this phenomenon. In this study, high-resolution observations using scientific echo sounder and underwater camera were carried out to reveal the fine structure of moon jellyfish distribution in a 3D space, as well as its abundance and temporal variation. In addition, water temperature, salinity and current speed were also measured for inferring formation mechanisms of jellyfish aggregation. The field observations with a target on moon jellyfish were carried out in August 2013 and August 2014, in a semi-enclosed bay in Japan. The ship equipped with scientific echo sounder was cruised over the entire bay to reveal the distribution and the form of the moon jellyfish aggregation. In August 2013, the jellyfish aggregations present a high density (maximum: 70 ind. /m3) and their outline shows spherical or zonal shape with a hollow structure. In August 2014, the jellyfish aggregations present a low density (maximum: 20 ind./m3) and the jellyfishes distributed in a layer structure over a wide area. The depth of jellyfish aggregation was consistent with thermocline. During three days of observations in 2014, the average population density of jellyfish reduced by one-tenth, showing a possibility that the jellyfish abundance in a bay may vary significantly in a short timescale of several days. Not only the active swimming of jellyfishes but also the ambient flow field associated with internal waves or Langmuir circulation may contribute to the jellyfish aggregations. In order to clarify the mechanisms for the formation of high density patchy aggregation, we plan to perform more detailed observations and numerical simulations that are able to capture the fine structure of these physical processes in the future.

Probing the magnetsophere with artificial electron beams

NASA Technical Reports Server (NTRS)

Winckler, J. R.

1981-01-01

An analysis is conducted of the University of Minnesota Electron Echo experiments, which so far have included five sounding rocket experiments. The concept of the Echo experiment is to inject electron beam pulses from a rocket into the ionosphere at altitudes in the range from 100 to 300 km. The electrons move to the conjugate hemisphere following magnetic field lines and return on neighboring field lines to the neighborhood of the rocket where the pulses may be detected and analyzed. Attention is given to the detection and analysis of echoes, the structure of echoes, and the Echo V experiment. The Echo V experiment showed clearly that detection of remote echo beams by atmospheric fluorescence using low light level TV system is not a viable technique. A future experiment is to use throw-away detectors for direct remote echo detection.

Integrating Sensors into a Marine Drone for Bathymetric 3D Surveys in Shallow Waters.

PubMed

Giordano, Francesco; Mattei, Gaia; Parente, Claudio; Peluso, Francesco; Santamaria, Raffaele

2015-12-29

This paper demonstrates that accurate data concerning bathymetry as well as environmental conditions in shallow waters can be acquired using sensors that are integrated into the same marine vehicle. An open prototype of an unmanned surface vessel (USV) named MicroVeGA is described. The focus is on the main instruments installed on-board: a differential Global Position System (GPS) system and single beam echo sounder; inertial platform for attitude control; ultrasound obstacle-detection system with temperature control system; emerged and submerged video acquisition system. The results of two cases study are presented, both concerning areas (Sorrento Marina Grande and Marechiaro Harbour, both in the Gulf of Naples) characterized by a coastal physiography that impedes the execution of a bathymetric survey with traditional boats. In addition, those areas are critical because of the presence of submerged archaeological remains that produce rapid changes in depth values. The experiments confirm that the integration of the sensors improves the instruments' performance and survey accuracy.

Integrating Sensors into a Marine Drone for Bathymetric 3D Surveys in Shallow Waters

PubMed Central

Giordano, Francesco; Mattei, Gaia; Parente, Claudio; Peluso, Francesco; Santamaria, Raffaele

2015-01-01

This paper demonstrates that accurate data concerning bathymetry as well as environmental conditions in shallow waters can be acquired using sensors that are integrated into the same marine vehicle. An open prototype of an unmanned surface vessel (USV) named MicroVeGA is described. The focus is on the main instruments installed on-board: a differential Global Position System (GPS) system and single beam echo sounder; inertial platform for attitude control; ultrasound obstacle-detection system with temperature control system; emerged and submerged video acquisition system. The results of two cases study are presented, both concerning areas (Sorrento Marina Grande and Marechiaro Harbour, both in the Gulf of Naples) characterized by a coastal physiography that impedes the execution of a bathymetric survey with traditional boats. In addition, those areas are critical because of the presence of submerged archaeological remains that produce rapid changes in depth values. The experiments confirm that the integration of the sensors improves the instruments’ performance and survey accuracy. PMID:26729117

Bathymetry data collected in October 2014 from Fire Island, New York—The wilderness breach, shoreface, and bay

USGS Publications Warehouse

Nelson, Timothy R.; Miselis, Jennifer L.; Hapke, Cheryl J.; Brenner, Owen T.; Henderson, Rachel E.; Reynolds, Billy J.; Wilson, Kathleen E.

2017-03-24

Scientists from the U.S. Geological Survey St. Petersburg Coastal and Marine Science Center in St. Petersburg, Florida, conducted a bathymetric survey of Fire Island, New York, from October 5 to 10, 2014. The U.S. Geological Survey is involved in a post-Hurricane Sandy effort to map and monitor the morphologic evolution of the wilderness breach, which formed in October 2012 during Hurricane Sandy, as part of the Hurricane Sandy Supplemental Project GS2-2B. During this study, bathymetry data were collected, using single-beam echo sounders and global positioning systems mounted to personal watercraft, along the Fire Island shoreface and within the wilderness breach, Fire Island Inlet, Narrow Bay, and Great South Bay east of Nicoll Bay. Additional bathymetry and elevation data were collected using backpack and wheel-mounted global positioning systems along the subaerial beach (foreshore and backshore), flood shoals, and shallow channels within the wilderness breach and adjacent shoreface.

Accelerated Fast Spin-Echo Magnetic Resonance Imaging of the Heart Using a Self-Calibrated Split-Echo Approach

PubMed Central

Klix, Sabrina; Hezel, Fabian; Fuchs, Katharina; Ruff, Jan; Dieringer, Matthias A.; Niendorf, Thoralf

2014-01-01

Purpose Design, validation and application of an accelerated fast spin-echo (FSE) variant that uses a split-echo approach for self-calibrated parallel imaging. Methods For self-calibrated, split-echo FSE (SCSE-FSE), extra displacement gradients were incorporated into FSE to decompose odd and even echo groups which were independently phase encoded to derive coil sensitivity maps, and to generate undersampled data (reduction factor up to R = 3). Reference and undersampled data were acquired simultaneously. SENSE reconstruction was employed. Results The feasibility of SCSE-FSE was demonstrated in phantom studies. Point spread function performance of SCSE-FSE was found to be competitive with traditional FSE variants. The immunity of SCSE-FSE for motion induced mis-registration between reference and undersampled data was shown using a dynamic left ventricular model and cardiac imaging. The applicability of black blood prepared SCSE-FSE for cardiac imaging was demonstrated in healthy volunteers including accelerated multi-slice per breath-hold imaging and accelerated high spatial resolution imaging. Conclusion SCSE-FSE obviates the need of external reference scans for SENSE reconstructed parallel imaging with FSE. SCSE-FSE reduces the risk for mis-registration between reference scans and accelerated acquisitions. SCSE-FSE is feasible for imaging of the heart and of large cardiac vessels but also meets the needs of brain, abdominal and liver imaging. PMID:24728341

Definition of Shifts of Optical Transitions Frequencies due to Pulse Perturbation Action by the Photon Echo Signal Form

NASA Astrophysics Data System (ADS)

Lisin, V. N.; Shegeda, A. M.; Samartsev, V. V.

2015-09-01

A relative phase shift between the different groups of excited dipoles, which appears as result of its frequency splitting due to action of a pulse of electric or magnetic fields, depends on a time, if the pulse overlaps in time with echo-pulse. As а consequence, the echo waveform is changed. The echo time form is modulated. The inverse modulation period well enough approximates Zeeman and pseudo-Stark splitting in the cases of magnetic and, therefore, electrical fields. Thus the g-factors of ground 4I15/2 and excited 4F9/2 optical states of Er3+ ion in LuLiF4 and YLiF4 have been measured and pseudo-Stark shift of R1 line in ruby has been determined.

Deep scattering layer migration and composition: observations from a diving saucer.

PubMed

Barham, E G

1966-03-18

The distribution of a myctophid fish and physonect siphonophores observed during dives in the Soucoupe off Baja California closely correlates with scattering layers recorded simultaneously with a 12-kcy/sec echo sounder. These organisms were observed while they were migrating vertically, and at their night and daytime levels. They are capable of rapid, extensive changes in depth.

RAWS: The spaceborne radar wind sounder

NASA Technical Reports Server (NTRS)

Moore, Richard K.

1991-01-01

The concept of the Radar Wind Sounder (RAWS) is discussed. The goals of the RAWS is to estimate the following three qualities: the echo power, to determine rain rate and surface wind velocity; the mean Doppler frequency, to determine the wind velocity in hydrometers; and the spread of the Doppler frequency, to determine the turbulent spread of the wind velocity. Researchers made significant progress during the first year. The feasibility of the concept seems certain. Studies indicate that a reasonably sized system can measure in the presence of ice clouds and dense water clouds. No sensitivity problems exist in rainy environments. More research is needed on the application of the radar to the measurement of rain rates and winds at the sea surface.

Inter-Comparison of GOES-8 Imager and Sounder Skin Temperature Retrievals

NASA Technical Reports Server (NTRS)

Haines, Stephanie L.; Suggs, Ronnie J.; Jedlovec, Gary J.; Arnold, James E. (Technical Monitor)

2001-01-01

Skin temperature (ST) retrievals derived from geostationary satellite observations have both high temporal and spatial resolutions and are therefore useful for applications such as assimilation into mesoscale forecast models, nowcasting, and diagnostic studies. Our retrieval method uses a Physical Split Window technique requiring at least two channels within the longwave infrared window. On current GOES satellites, including GOES-11, there are two Imager channels within the required spectral interval. However, beginning with the GOES-M satellite the 12-um channel will be removed, leaving only one longwave channel. The Sounder instrument will continue to have three channels within the longwave window, and therefore ST retrievals will be derived from Sounder measurements. This research compares retrievals from the two instruments and evaluates the effects of the spatial resolution and sensor calibration differences on the retrievals. Both Imager and Sounder retrievals are compared to ground-truth data to evaluate the overall accuracy of the technique. An analysis of GOES-8 and GOES-11 intercomparisons is also presented.

Beam echoes in the presence of coupling

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

Gross, Axel

2017-10-03

Transverse beam echoes could provide a new technique of measuring diusion characteristics orders of magnitude faster than the current methods; however, their interaction with many accelerator parameters is poorly understood. Using a program written in C, we explored the relationship between coupling and echo strength. We found that echoes could be generated in both dimensions, even with a dipole kick in only one dimension. We found that the echo eects are not destroyed even when there is strong coupling, falling o only at extremely high coupling values. We found that at intermediate values of skew quadrupole strength, the decoherence timemore » of the beam is greatly increased, causing a destruction of the echo eects. We found that this is caused by a narrowing of the tune width of the particles. Results from this study will help to provide recommendations to IOTA (Integrable Optics Test Accelerator) for their upcoming echo experiment.« less

Physical Oceanography Program Science Abstracts.

DTIC Science & Technology

1986-04-01

8217- % unit will be deployed from R/V Endeavor in a rapid sampling mode. It will be suspended along with an inverted echo sounder and video camera, below a...va r 4 1 i ty 0 Cal .5St i recK Jutc . Ph.2 .Ocemnonr. 15, i(15󈧝 Pedo ~k J ., N’. Sthand 3. Luytr-n, 1. t odynarics a -. of Thai o&?-anic surfce

Diffusion measurement from observed transverse beam echoes

DOE PAGES

Sen, Tanaji; Fischer, Wolfram

2017-01-09

For this research, we study the measurement of transverse diffusion through beam echoes. We revisit earlier observations of echoes in RHIC and apply an updated theoretical model to these measurements. We consider three possible models for the diffusion coefficient and show that only one is consistent with measured echo amplitudes and pulse widths. This model allows us to parameterize the diffusion coefficients as functions of bunch charge. We demonstrate that echoes can be used to measure diffusion much quicker than present methods and could be useful to a variety of hadron synchrotrons.

New Bottom Roughness Calculation from Multibeam Echo Sounders for Mine Warfare

DTIC Science & Technology

2012-09-01

complex including craters, gullies, seaweed , rocks, sand ridges, tall obstructions, deep holes and sloping regions. Underwater mines can be hidden...and shadows for detecting objects lying on the seafloor. The seafloor is rather complex including craters, gullies, seaweed , rocks, sand ridges, tall...roughness as craters, gullies, seaweed , sand ridges, tall obstructions, deep holes, or steeply sloping regions. Slopes can make it possible for mines to

Low-level water vapor fields from the VISSR atmospheric sounder (VAS) split window channels at 11 and 12 microns. [visible infrared spin scan radiometer

NASA Technical Reports Server (NTRS)

Chesters, D.; Uccellini, L.; Robinson, W.

1982-01-01

A series of high-resolution water vapor fields were derived from the 11 and 12 micron channels of the VISSR Atmospheric Sounder (VAS) on GOES-5. The low-level tropospheric moisture content was separated from the surface and atmospheric radiances by using the differential adsorption across the 'split window' along with the average air temperature from imbedded radiosondes. Fields of precipitable water are presented in a time sequence of five false color images taken over the United States at 3-hour intervals. Vivid subsynoptic and mesoscale patterns evolve at 15 km horizontal resolution over the 12-hour observing period. Convective cloud formations develop from several areas of enhanced low-level water vapor, especially where the vertical water vapor gradient relatively strong. Independent verification at radiosonde sites indicates fairly good absolute accuracy, and the spatial and temporal continuity of the water vapor features indicates very good relative accuracy. Residual errors are dominated by radiometer noise and unresolved clouds.

The Laser Atmospheric Wind Sounder (LAWS) Phase 2 Preliminary Laser Design

NASA Technical Reports Server (NTRS)

Lawrence, T. Rhidian; Pindroh, Albert L.; Bowers, Mark S.; Dehart, Terence E.; Mcdonald, Kenneth F.; Cousins, Ananda; Moody, Stephen E.

1992-01-01

The requirements for the Laser Atmospheric Wind Sounder (LAWS) were determined from system considerations and are summarized in tabular form. The laser subsystem provides for the generation and frequency control of two beams, the transmit high power and local oscillator beams, which are delivered to the optical and receiver subsystems, respectively. In our baseline approach, the excitation of the gain section is achieved by a self-sustaining uv-(corona) preionized discharge. Gas is recirculated within the laser loop using a transverse flow fan. An intra-flow-loop heat exchanger, catalyst monolith, and acoustic attenuators condition the gas to ensure uniform energy output and high beam quality during high pulse repetition rate operation. The baseline LAWS laser pulse temporal profile as calculated by in-house laser codes is given in graphical form.

An estimation method for echo signal energy of pipe inner surface longitudinal crack detection by 2-D energy coefficients integration

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

Zhou, Shiyuan, E-mail: redaple@bit.edu.cn; Sun, Haoyu, E-mail: redaple@bit.edu.cn; Xu, Chunguang, E-mail: redaple@bit.edu.cn

The echo signal energy is directly affected by the incident sound beam eccentricity or angle for thick-walled pipes inner longitudinal cracks detection. A method for analyzing the relationship between echo signal energy between the values of incident eccentricity is brought forward, which can be used to estimate echo signal energy when testing inside wall longitudinal crack of pipe, using mode-transformed compression wave adaptation of shear wave with water-immersion method, by making a two-dimension integration of “energy coefficient” in both circumferential and axial directions. The calculation model is founded for cylinder sound beam case, in which the refraction and reflection energymore » coefficients of different rays in the whole sound beam are considered different. The echo signal energy is calculated for a particular cylinder sound beam testing different pipes: a beam with a diameter of 0.5 inch (12.7mm) testing a φ279.4mm pipe and a φ79.4mm one. As a comparison, both the results of two-dimension integration and one-dimension (circumferential direction) integration are listed, and only the former agrees well with experimental results. The estimation method proves to be valid and shows that the usual method of simplifying the sound beam as a single ray for estimating echo signal energy and choosing optimal incident eccentricity is not so appropriate.« less

An estimation method for echo signal energy of pipe inner surface longitudinal crack detection by 2-D energy coefficients integration

NASA Astrophysics Data System (ADS)

Zhou, Shiyuan; Sun, Haoyu; Xu, Chunguang; Cao, Xiandong; Cui, Liming; Xiao, Dingguo

2015-03-01

The echo signal energy is directly affected by the incident sound beam eccentricity or angle for thick-walled pipes inner longitudinal cracks detection. A method for analyzing the relationship between echo signal energy between the values of incident eccentricity is brought forward, which can be used to estimate echo signal energy when testing inside wall longitudinal crack of pipe, using mode-transformed compression wave adaptation of shear wave with water-immersion method, by making a two-dimension integration of "energy coefficient" in both circumferential and axial directions. The calculation model is founded for cylinder sound beam case, in which the refraction and reflection energy coefficients of different rays in the whole sound beam are considered different. The echo signal energy is calculated for a particular cylinder sound beam testing different pipes: a beam with a diameter of 0.5 inch (12.7mm) testing a φ279.4mm pipe and a φ79.4mm one. As a comparison, both the results of two-dimension integration and one-dimension (circumferential direction) integration are listed, and only the former agrees well with experimental results. The estimation method proves to be valid and shows that the usual method of simplifying the sound beam as a single ray for estimating echo signal energy and choosing optimal incident eccentricity is not so appropriate.

Brainstem Cavernous Angioma

MedlinePlus

... echo” (as opposed to spin-echo or proton beam) imaging. Gradient-echo MRI is most efficient at ... radiosurgery for cavernous malformations: Kjellberg's experience with proton beam therapy in 98 cases at the Harvard Cyclotron. ...

A multi-frequency radar sounder for lava tubes detection on the Moon: Design, performance assessment and simulations

NASA Astrophysics Data System (ADS)

Carrer, Leonardo; Gerekos, Christopher; Bruzzone, Lorenzo

2018-03-01

Lunar lava tubes have attracted special interest as they would be suitable shelters for future human outposts on the Moon. Recent experimental results from optical images and gravitational anomalies have brought strong evidence of their existence, but such investigative means have very limited potential for global mapping of lava tubes. In this paper, we investigate the design requirement and feasibility of a radar sounder system specifically conceived for detecting subsurface Moon lava tubes from orbit. This is done by conducting a complete performance assessment and by simulating the electromagnetic signatures of lava tubes using a coherent 3D simulator. The results show that radar sounding of lava tubes is feasible with good performance margins in terms of signal-to-noise and signal-to-clutter ratio, and that a dual-frequency radar sounder would be able to detect the majority of lunar lava tubes based on their potential dimension with some limitations for very small lava tubes having width smaller than 250 m. The electromagnetic simulations show that lava tubes display an unique signature characterized by a signal phase inversion on the roof echo. The analysis is provided for different acquisition geometries with respect to the position of the sounded lava tube. This analysis confirms that orbiting multi-frequency radar sounder can detect and map in a reliable and unambiguous way the majority of Moon lava tubes.

EXPERIMENTS - APOLLO 17

NASA Image and Video Library

1972-11-17

S72-53472 (November 1972) --- An artist's concept illustrating how radar beams of the Apollo 17 lunar sounder experiment will probe three-quarters of a mile below the moon's surface from the orbiting spacecraft. The Lunar Sounder will be mounted in the SIM bay of the Apollo 17 Service Module. Electronic data recorded on film will be retrieved by the crew during trans-Earth EVA. Geologic information on the lunar interior obtained by the sounder will permit scientific investigation of underground rock layers, lava flow patterns, rille (canyon) structures, mascon properties, and any areas containing water. A prototype lunar sounder has been flight tested in aircraft over selected Earth sites to confirm the equipment design and develop scientific analysis techniques. The Lunar Sounder Experiment (S-209) was developed by North American Rockwell's (NR) Space Division for NASA's Manned Spacecraft Center to provide data for a scientific investigation team with representatives from the Jet Propulsion Laboratory, University of Utah, University of Michigan, U.S. Geological Survey, and NASA Ames Research Center.

Variability at Multiple Scales: Using an Array of Current and Pressure Sensor Equipped Inverted Echo Sounders to Measure the Ocean

DTIC Science & Technology

2016-11-29

travel time between the seafloor and the sea surface; bottom pressure and temperature; and near-bottom horizontal currents hourly for up to 5 years...pressure and current sensors (CPIESs). CPIESs (Figure 1) are moored instruments that measure (1) the round-trip acoustic travel time between the...measurements of surface-to-bottom round-trip acoustic- travel time (’c), bottom pressure and temperature, and near-bottom horizontal currents

Variability at Multiple Scales: Using an Array of Current- and Pressure-Sensor Equipped Inverted Echo Sounders to Measure the Ocean

DTIC Science & Technology

2016-11-29

travel time between the seafloor and the sea surface; bottom pressure and temperature; and near-bottom horizontal currents hourly for up to 5 years...pressure and current sensors (CPIESs). CPIESs (Figure 1) are moored instruments that measure (1) the round-trip acoustic travel time between the...measurements of surface-to-bottom round-trip acoustic- travel time (’c), bottom pressure and temperature, and near-bottom horizontal currents

Volcanic Structure of the Gakkel Ridge at 85°E

NASA Astrophysics Data System (ADS)

Willis, C.; Humphris, S.; Soule, S. A.; Reves-Sohn, R.; Shank, T.; Singh, H.

2007-12-01

We present an initial volcanologic interpretation of a magmatically-robust segment of the ultra-slow spreading (3- 7 mm/yr) Gakkel Ridge at 85°E in the eastern Arctic Basin based on surveys conducted during the July 2007 Arctic GAkkel Vents Expedition (AGAVE). A previous expedition (2001 AMORE) and seismic stations in the area found evidence for active hydrothermal circulation and seismicity that suggested volcanic activity may be ongoing at 85°E. We examine multi-beam bathymetric data, digital imagery, and rock and sediment samples in order to determine the nature of volcanic accretion that is occurring in this environment including the distribution of flow types and their relationship to features of the axial valley. Raw multi-beam bathymetric data was logged by the Kongsberg EM 120 1°x1° multi-beam echo sounder aboard the icbreaker IB Oden. Digital imagery was recorded on five video and still cameras mounted on the CAMPER fiber-optic wireline vehicle, which was towed 1-3m above the seafloor. Digital imagery was recorded on thirteen CAMPER drift-dives over interesting bathymetry including: a volcanic ridge in the axial valley named Duque's Hill, and Oden and Loke volcanoes that are part of the newly discovered Asgard volcanic chain. Talus, lava flows, and volcaniclastics were sampled with the clamshell grabber and slurp suction sampler on CAMPER. A variety of lava morphologies are identified in the imagery including large basalt pillows with buds and other surface ornamentation, lava tubes, lobates, sheet flows, and a thick cover of volcaniclastic sediment over extensive areas suggestive of explosive volcanic activity.

User expectations for multibeam echo sounders backscatter strength data-looking back into the future

NASA Astrophysics Data System (ADS)

Lucieer, Vanessa; Roche, Marc; Degrendele, Koen; Malik, Mashkoor; Dolan, Margaret; Lamarche, Geoffroy

2018-06-01

With the ability of multibeam echo sounders (MBES) to measure backscatter strength (BS) as a function of true angle of insonification across the seafloor, came a new recognition of the potential of backscatter measurements to remotely characterize the properties of the seafloor. Advances in transducer design, digital electronics, signal processing capabilities, navigation, and graphic display devices, have improved the resolution and particularly the dynamic range available to sonar and processing software manufacturers. Alongside these improvements the expectations of what the data can deliver has also grown. In this paper, we identify these user-expectations and explore how MBES backscatter is utilized by different communities involved in marine seabed research at present, and the aspirations that these communities have for the data in the future. The results presented here are based on a user survey conducted by the GeoHab (Marine Geological and Biological Habitat Mapping) association. This paper summarises the different processing procedures employed to extract useful information from MBES backscatter data and the various intentions for which the user community collect the data. We show how a range of backscatter output products are generated from the different processing procedures, and how these results are taken up by different scientific disciplines, and also identify common constraints in handling MBES BS data. Finally, we outline our expectations for the future of this unique and important data source for seafloor mapping and characterisation.

Environmental preferences of tuna and non-tuna species associated with drifting fish aggregating devices (DFADs) in the Atlantic Ocean, ascertained through fishers' echo-sounder buoys

NASA Astrophysics Data System (ADS)

Lopez, Jon; Moreno, Gala; Lennert-Cody, Cleridy; Maunder, Mark; Sancristobal, Igor; Caballero, Ainhoa; Dagorn, Laurent

2017-06-01

Understanding the relationship between environmental variables and pelagic species concentrations and dynamics is helpful to improve fishery management, especially in a changing environment. Drifting fish aggregating device (DFAD)-associated tuna and non-tuna biomass data from the fishers' echo-sounder buoys operating in the Atlantic Ocean have been modelled as functions of oceanographic (Sea Surface Temperature, Chlorophyll-a, Salinity, Sea Level Anomaly, Thermocline depth and gradient, Geostrophic current, Total Current, Depth) and DFAD variables (DFAD speed, bearing and soak time) using Generalized Additive Mixed Models (GAMMs). Biological interaction (presence of non-tuna species at DFADs) was also included in the tuna model, and found to be significant at this time scale. All variables were included in the analyses but only some of them were highly significant, and variable significance differed among fish groups. In general, most of the fish biomass distribution was explained by the ocean productivity and DFAD-variables. Indeed, this study revealed different environmental preferences for tunas and non-tuna species and suggested the existence of active habitat selection. This improved assessment of environmental and DFAD effects on tuna and non-tuna catchability in the purse seine tuna fishery will contribute to transfer of better scientific advice to regional tuna commissions for the management and conservation of exploited resources.

Vertical velocity structure and geometry of clear air convective elements

NASA Technical Reports Server (NTRS)

Rowland, J. R.; Arnold, A.

1975-01-01

The paper discusses observations of individual convective elements with a high-power narrow-beam scanning radar, an FM-CW radar, and an acoustic sounder, including the determination of the vertical air velocity patterns of convective structures with the FM-CW radar and acoustic sounder. Data are presented which link the observed velocity structure and geometrical patterns to previously proposed models of boundary layer convection. It is shown that the high-power radar provides a clear three-dimensional picture of convective cells and fields over a large area with a resolution of 150 m, where the convective cells are roughly spherical. Analysis of time-height records of the FM-CW radar and acoustic sounder confirms the downdraft-entrainment mechanism of the convective cell. The Doppler return of the acoustic sounder and the insect-trail slopes on FM-CW radar records are independent but redundant methods for obtaining the vertical velocity patterns of convective structures.

Neutron resonance spin echo with longitudinal DC fields

NASA Astrophysics Data System (ADS)

Krautloher, Maximilian; Kindervater, Jonas; Keller, Thomas; Häußler, Wolfgang

2016-12-01

We report on the design, construction, and performance of a neutron resonance spin echo (NRSE) instrument employing radio frequency (RF) spin flippers combining RF fields with DC fields, the latter oriented parallel (longitudinal) to the neutron propagation direction (longitudinal NRSE (LNRSE)). The advantage of the longitudinal configuration is the inherent homogeneity of the effective magnetic path integrals. In the center of the RF coils, the sign of the spin precession phase is inverted by a π flip of the neutron spins, such that non-uniform spin precession at the boundaries of the RF flippers is canceled. The residual inhomogeneity can be reduced by Fresnel- or Pythagoras-coils as in the case of conventional spin echo instruments (neutron spin echo (NSE)). Due to the good intrinsic homogeneity of the B0 coils, the current densities required for the correction coils are at least a factor of three less than in conventional NSE. As the precision and the current density of the correction coils are the limiting factors for the resolution of both NSE and LNRSE, the latter has the intrinsic potential to surpass the energy resolution of present NSE instruments. Our prototype LNRSE spectrometer described here was implemented at the resonance spin echo for diverse applications (RESEDA) beamline at the MLZ in Garching, Germany. The DC fields are generated by B0 coils, based on resistive split-pair solenoids with an active shielding for low stray fields along the beam path. One pair of RF flippers at a distance of 2 m generates a field integral of ˜0.5 Tm. The LNRSE technique is a future alternative for high-resolution spectroscopy of quasi-elastic excitations. In addition, it also incorporates the MIEZE technique, which allows to achieve spin echo resolution for spin depolarizing samples and sample environments. Here we present the results of numerical optimization of the coil geometry and first data from the prototype instrument.

Non-destructive splitter of twisted light based on modes splitting in a ring cavity.

PubMed

Li, Yan; Zhou, Zhi-Yuan; Ding, Dong-Sheng; Zhang, Wei; Shi, Shuai; Shi, Bao-Sen; Guo, Guang-Can

2016-02-08

Efficiently discriminating beams carrying different orbital angular momentum (OAM) is of fundamental importance for various applications including high capacity optical communication and quantum information processing. We design and experimentally verify a distinguished method for effectively splitting different OAM-carried beams by introducing Dove prisms in a ring cavity. Because of rotational symmetry broken of two OAM-carried beams with opposite topological charges, their transmission spectra will split. When mode and impedance matches between the cavity and one OAM-carried beam are achieved, this beam will transmit through the cavity and other beam will be reflected, both beams keep their spatial shapes. In this case, the cavity acts like a polarized beam splitter. Besides, the transmitting beam can be selected at your will, the splitting efficiency can reach unity if the cavity is lossless and it completely matches the beam. Furthermore, beams carry multi-OAMs can also be split by cascading ring cavities.

Electron Echo 6 - a Study by Particle Detectors of Electrons Artificially Injected Into the Magnetosphere.

NASA Astrophysics Data System (ADS)

Malcolm, Perry Robert

The ECHO-6 sounding rocket was launched from the Poker Flat Research Range, Alaska on 30 March 1983. A Terrier-Black Brant launch vehicle carried the payload on a northward trajectory over an auroral arc and to an apogee of 216 kilometers. The primary objective of the ECHO-6 experiment was to evaluate electric fields, magnetic fields, and plasma processes in the distant magnetosphere by injecting electron beams in the ionosphere and observing conjugate echoes. The experiment succeeded in injecting 10-36 KeV beams during the existence of a moderate growth phase aurora, an easterly electrojet system, and a pre -midnight inflation condition of the magnetosphere. The ECHO-6 payload system consisted of an accelerator MAIN payload, a free-flying Plasma Diagnostics Package (PDP), and four rocket propelled Throw Away Detectors (TADs). The PDP was ejected from the MAIN payload to analyze electric fields, plasma particles, energetic electrons, and photometric effects produced by beam injections. The TADs were ejected from the MAIN payload in a pattern to detect echoes in the conjugate echo region south of the beam emitting MAIN payload. The TADs reached distances exceeding 3 kilometers from the MAIN payload and made measurements of the ambient electrons by means of solid state detectors and electrostatic analyzers. In spite of the perfect operation of the TAD system and a rigorous analysis of the particle data, no conjugate echoes have been identified. Through the use of a new dynamic magnetic field model (Olson and Pfitzer, 1982) and satellite magnetometer measurements, it has been determined that the echoing electrons returned out of range of the TADs as a result of their bounce times and curvature-gradient drifts being increased beyond the expected limits for an inflated magnetic field. This dynamic model was then applied to the study of echoes seen during the ECHO-4 flight resulting in a significant increase in the calculated energy of the echo electrons and better agreement between the locally measured and bounce integrated electric field.

Studies based on global subsurface radar sounding of the Moon by SELENE (Kaguya) Lunar Radar Sounder (LRS): A summary

NASA Astrophysics Data System (ADS)

Kumamoto, A.; Yamaguchi, Y.; Yamaji, A.; Kobayashi, T.; Oshigami, S.; Ishiyama, K.; Nakamura, N.; Goto, Y.

2015-12-01

The Lunar Radar Sounder (LRS) onboard the SELENE (Kaguya) spacecraft has successfully performed radar sounder observations of the lunar subsurface structures and passive observations of natural radio and plasma waves from the lunar orbit. After the transfer of the spacecraft into the final lunar orbit and antenna deployment, the operation of LRS started on October 29, 2007. Through the operation until June 10, 2009, 130 million pulses worth of radar sounder data have been obtained [Ono et al., 2010]. Based on the datasets of the first lunar global subsurface radar sounding, Ono et al. [2009] revealed that there are distinct reflectors at a depth of several hundred meters in the nearside maria, which are inferred to be buried regolith layers covered by a basalt layer with a thickness of several hundred meters. Based on the further survey, Pommerol et al. [2010] pointed out the negative correlation of clear subsurface echoes with the maps of ilmenite, and suggested that dense ilmenite attenuates the radar pulse in the basaltic mare lava, and cause the absence of the clear subsurface echoes. That also suggests there are undetected subsurface reflectors especially below the young lava flow units with high ilmenite abundance. Kobayashi et al. [2012] applied synthetic aperture radar (SAR) processing to SELENE LRS data in order to obtain distinct radargram. Taking advantage of analyzing waveform data sent via high data rate telemetry from the Moon, we can perform advanced data analyses on the ground. We started providing the both SAR processed and waveform datasets via SELENE Data Archive (http://l2db.selene.darts.isas.jaxa.jp/index.html.en) since 2015. Oshigami et al. [2014] estimated volumes of basalt units in the ages of 2.7 Ga to 3.8 Ga in the nearside maria. The volume was derived from the depth of subsurface reflectors measured by LRS. The volumes of the geologic units were 103 to 104 km3. The average eruption rates were 10-5 to 10-3 km3 yr-1. The estimated volumes of the geologic mare units and average eruption rate showed clear positive correlations with their ages. In the presentation, we are going to review not only the studies mentioned above but also some recent studies such as Ishiyama et al. [2013], and Bando et al. [2015].

The Calibration and error analysis of Shallow water (less than 100m) Multibeam Echo-Sounding System

NASA Astrophysics Data System (ADS)

Lin, M.

2016-12-01

Multibeam echo-sounders(MBES) have been developed to gather bathymetric and acoustic data for more efficient and more exact mapping of the oceans. This gain in efficiency does not come without drawbacks. Indeed, the finer the resolution of remote sensing instruments, the harder they are to calibrate. This is the case for multibeam echo-sounding systems (MBES). We are no longer dealing with sounding lines where the bathymetry must be interpolated between them to engender consistent representations of the seafloor. We now need to match together strips (swaths) of totally ensonified seabed. As a consequence, misalignment and time lag problems emerge as artifacts in the bathymetry from adjacent or overlapping swaths, particularly when operating in shallow water. More importantly, one must still verify that bathymetric data meet the accuracy requirements. This paper aims to summarize the system integration involved with MBES and identify the various source of error pertaining to shallow water survey (100m and less). A systematic method for the calibration of shallow water MBES is proposed and presented as a set of field procedures. The procedures aim at detecting, quantifying and correcting systematic instrumental and installation errors. Hence, calibrating for variations of the speed of sound in the water column, which is natural in origin, is not addressed in this document. The data which used in calibration will reference International Hydrographic Organization(IHO) and other related standards to compare. This paper aims to set a model in the specific area which can calibrate the error due to instruments. We will construct a procedure in patch test and figure out all the possibilities may make sounding data with error then calculate the error value to compensate. In general, the problems which have to be solved is the patch test's 4 correction in the Hypack system 1.Roll 2.GPS Latency 3.Pitch 4.Yaw. Cause These 4 correction affect each others, we run each survey line to calibrate. GPS Latency is synchronized GPS to echo sounder. Future studies concerning any shallower portion of an area, by this procedure can be more accurate sounding value and can do more detailed research.

Bathymetric Surveys of Lake Arthur and Raccoon Lake, Pennsylvania, June 2007

USGS Publications Warehouse

Hittle, Clinton D.; Ruby, A. Thomas

2008-01-01

In spring of 2007, bathymetric surveys of two Pennsylvania State Park lakes were performed to collect accurate data sets of lake-bed elevations and to develop methods and techniques to conduct similar surveys across the state. The lake-bed elevations and associated geographical position data can be merged with land-surface elevations acquired through Light Detection and Ranging (LIDAR) techniques. Lake Arthur in Butler County and Raccoon Lake in Beaver County were selected for this initial data-collection activity. In order to establish accurate water-surface elevations during the surveys, benchmarks referenced to NAVD 88 were established on land at each lake by use of differential global positioning system (DGPS) surveys. Bathymetric data were collected using a single beam, 210 kilohertz (kHz) echo sounder and were coupled with the DGPS position data utilizing a computer software package. Transects of depth data were acquired at predetermined intervals on each lake, and the shoreline was delineated using a laser range finder and compass module. Final X, Y, Z coordinates of the geographic positions and lake-bed elevations were referenced to NAD 83 and NAVD 88 and are available to create bathymetric maps of the lakes.

Precision spectral manipulation of optical pulses using a coherent photon echo memory.

PubMed

Buchler, B C; Hosseini, M; Hétet, G; Sparkes, B M; Lam, P K

2010-04-01

Photon echo schemes are excellent candidates for high efficiency coherent optical memory. They are capable of high-bandwidth multipulse storage, pulse resequencing and have been shown theoretically to be compatible with quantum information applications. One particular photon echo scheme is the gradient echo memory (GEM). In this system, an atomic frequency gradient is induced in the direction of light propagation leading to a Fourier decomposition of the optical spectrum along the length of the storage medium. This Fourier encoding allows precision spectral manipulation of the stored light. In this Letter, we show frequency shifting, spectral compression, spectral splitting, and fine dispersion control of optical pulses using GEM.

Polarisation in spin-echo experiments: Multi-point and lock-in measurements

NASA Astrophysics Data System (ADS)

Tamtögl, Anton; Davey, Benjamin; Ward, David J.; Jardine, Andrew P.; Ellis, John; Allison, William

2018-02-01

Spin-echo instruments are typically used to measure diffusive processes and the dynamics and motion in samples on ps and ns time scales. A key aspect of the spin-echo technique is to determine the polarisation of a particle beam. We present two methods for measuring the spin polarisation in spin-echo experiments. The current method in use is based on taking a number of discrete readings. The implementation of a new method involves continuously rotating the spin and measuring its polarisation after being scattered from the sample. A control system running on a microcontroller is used to perform the spin rotation and to calculate the polarisation of the scattered beam based on a lock-in amplifier. First experimental tests of the method on a helium spin-echo spectrometer show that it is clearly working and that it has advantages over the discrete approach, i.e., it can track changes of the beam properties throughout the experiment. Moreover, we show that real-time numerical simulations can perfectly describe a complex experiment and can be easily used to develop improved experimental methods prior to a first hardware implementation.

Velocities of Auroral Coherent Echoes At 12 and 144 Mhz

NASA Astrophysics Data System (ADS)

Koustov, A. V.; Danskin, D. W.; Makarevitch, R. A.; Uspensky, M. V.; Janhunen, P.; Nishitani, N.; Nozawa, N.; Lester, M.; Milan, S.

Two Doppler coherent radar systems are currently working at Hankasalmi, Finland, the STARE and CUTLASS radars operating at 144 MHz and 12 MHz, respectively. The STARE beam 3 is nearly co-located with the CUTLASS beam 5 providing an opportunity for echo velocity comparison along the same direction but at significantly different radar frequencies. In this study we consider one event when STARE radar echoes are detected t the same ranges as CUTLASS radar echoes. The observations are complemented by EISCAT measurements of the ionospheric electric field and elec- tron density behavior at one range of 900 km. Two separate situations are studied; for the first one, CUTLASS observed F-region echoes (including the range of the EIS- CAT measurements) while for the second one CUTLASS observed E-region echoes. In both cases STARE E-region measurements were available. We show that F-region CUTLASS velocities agree well with the convection component along the CUTLASS radar beam while STARE velocities are sometimes smaller by a factor of 2-3. For the second case, STARE velocities are found to be either smaller or larger than CUTLASS velocities, depending on range. Plasma physics of E- and F-region irregularities is dis- cussed in attempt to explain inferred relationship between various velocities. Special attention is paid to ionospheric refraction that is important for the detection of 12-MHz echoes.

MR Fingerprinting Using The Quick Echo Splitting NMR Imaging Technique

PubMed Central

Jiang, Yun; Ma, Dan; Jerecic, Renate; Duerk, Jeffrey; Seiberlich, Nicole; Gulani, Vikas; Griswold, Mark A.

2016-01-01

Purpose The purpose of the study is to develop a quantitative method for the relaxation properties with a reduced radio frequency (RF) power deposition by combining Magnetic Resonance Fingerprinting (MRF) technique with Quick Echo Splitting NMR Imaging Technique (QUEST). Methods A QUEST-based MRF sequence was implemented to acquire high order echoes by increasing the gaps between RF pulses. Bloch simulations were used to calculate a dictionary containing the range of physically plausible signal evolutions using a range of T1 and T2 values based on the pulse sequence. MRF-QUEST was evaluated by comparing to the results of spin-echo methods. The SAR of QUEST-MRF was compared to the clinically available methods. Results MRF-QUEST quantifies the relaxation properties with good accuracy at the estimated head Specific Absorption Rate (SAR) of 0.03 W/kg. T1 and T2 values estimated by MRF-QUEST are in good agreement with the traditional methods. Conclusion The combination of the MRF and the QUEST provides an accurate quantification of T1 and T2 simultaneously with reduced RF power deposition. The resulting lower SAR may provide a new acquisition strategy for MRF when RF energy deposition is problematic. PMID:26924639

Mars radar clutter and surface roughness characteristics from MARSIS data

NASA Astrophysics Data System (ADS)

Campbell, Bruce A.; Schroeder, Dustin M.; Whitten, Jennifer L.

2018-01-01

Radar sounder studies of icy, sedimentary, and volcanic settings can be affected by reflections from surface topography surrounding the sensor nadir location. These off-nadir ;clutter; returns appear at similar time delays to subsurface echoes and complicate geologic interpretation. Additionally, broadening of the radar echo in delay by surface returns sets a limit on the detectability of subsurface interfaces. We use MARSIS 4 MHz data to study variations in the nadir and off-nadir clutter echoes, from about 300 km to 1000 km altitude, R, for a wide range of surface roughness. This analysis uses a new method of characterizing ionospheric attenuation to merge observations over a range of solar zenith angle and date. Mirror-like reflections should scale as R-2, but the observed 4 MHz nadir echoes often decline by a somewhat smaller power-law factor because MARSIS on-board processing increases the number of summed pulses with altitude. Prior predictions of the contributions from clutter suggest a steeper decline with R than the nadir echoes, but in very rough areas the ratio of off-nadir returns to nadir echoes shows instead an increase of about R1/2 with altitude. This is likely due in part to an increase in backscatter from the surface as the radar incidence angle at some round-trip time delay declines with increasing R. It is possible that nadir and clutter echo properties in other planetary sounding observations, including RIME and REASON flyby data for Europa, will vary in the same way with altitude, but there may be differences in the nature and scale of target roughness (e.g., icy versus rocky surfaces). We present global maps of the ionosphere- and altitude-corrected nadir echo strength, and of a ;clutter; parameter based on the ratio of off-nadir to nadir echoes. The clutter map offers a view of surface roughness at ∼75 m length scale, bridging the spatial-scale gap between SHARAD roughness estimates and MOLA-derived parameters.

Instrument technology for magnetosphere plasma imaging from high Earth orbit. Design of a radio plasma sounder

NASA Technical Reports Server (NTRS)

Haines, D. Mark; Reinisch, Bodo W.

1995-01-01

The use of radio sounding techniques for the study of the ionospheric plasma dates back to G. Briet and M. A. Tuve in 1926. Ground based swept frequency sounders can monitor the electron number density (N(sub e)) as a function of height (the N(sub e) profile). These early instruments evolved into a global network that produced high-resolution displays of echo time delay vs frequency on 35-mm film. These instruments provided the foundation for the success of the International Geophysical Year (1958). The Alouette and International Satellites for Ionospheric Studies (ISIS) programs pioneered the used of spaceborne, swept frequency sounders to obtain N(sub e) profiles of the topside of the ionosphere, from a position above the electron density maximum. Repeated measurements during the orbit produced an orbital plane contour which routinely provided density measurements to within 10%. The Alouette/ISIS experience also showed that even with a high powered transmitter (compared to the low power sounder possible today) a radio sounder can be compatible with other imaging instruments on the same satellite. Digital technology was used on later spacecraft developed by the Japanese (the EXOS C and D) and the Soviets (Intercosmos 19 and Cosmos 1809). However, a full coherent pulse compression and spectral integrating capability, such as exist today for ground-based sounders (Reinisch et al., 1992), has never been put into space. NASA's 1990 Space Physics Strategy Implementation Study "The NASA Space Physics Program from 1995 to 2010" suggested using radio sounders to study the plasmasphere and the magnetopause and its boundary layers (Green and Fung, 1993). Both the magnetopause and plasmasphere, as well as the cusp and boundary layers, can be observed by a radio sounder in a high-inclination polar orbit with an apogee greater than 6 R(sub e) (Reiff et al., 1994; Calvert et al., 1995). Magnetospheric radio sounding from space will provide remote density measurements of unprecedented precision and coverage in the plasmasphere, inner magnetosphere and magnetopause, from which the structure, inter-relationship, and variations of different plasma regions can be determined (Armstrong Johnson, 1995). A space-borne Radio Plasma Imager (RPI) could provide a unique global view of the magnetosphere revealing the underlying structure of remote plasma regions, thereby providing a framework for the interpretation of images obtained by other techniques as identified in the technical areas TA1 to TA4 in the MSFC NRA8-8.

Acoustical Measurement of Nonlinear Internal Waves Using the Inverted Echo Sounder

DTIC Science & Technology

2009-05-05

showed that the vertical round-trip travel time of an acoustic pulse allowed measurement of the variation of thermal stratification caused by internal...translate from distance to time , note that reflection from a position 56 m from zenith to a PIES at 1024-m depth would have a delay time of 2 ms. Note that...approximation of the travel time scatter, the delay to the arrival of the dis- tribution peak tp is directly related to the width b: t p 5 t 0 1 b. (24) The

Integrated Verification Experiment data collected as part of the Los Alamos National Laboratory's Source Region Program

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

Fitzgerald, T.J.; Carlos, R.C.; Argo, P.E.

As part of the integrated verification experiment (IVE), we deployed a network of hf ionospheric sounders to detect the effects of acoustic waves generated by surface ground motion following underground nuclear tests at the Nevada Test Site. The network sampled up to four geographic locations in the ionosphere from almost directly overhead of the surface ground zero out to a horizontal range of 60 km. We present sample results for four of the IVEs: Misty Echo, Texarkana, Mineral Quarry, and Bexar.

Siphonophores and the Deep Scattering Layer.

PubMed

Barham, E G

1963-05-17

Bathyscaphe dives in the San Diego Trough have revealed a close spatial relation between siphonophores and the deep scattering layer as recorded by precision depth recording echo-sounders. Measurements of gas bubbles within the flotation structures of Nanomia bijuga captured in a closing net in an ascended scattering layer indicate that these are very close to the resonant size for 12-kcy/sec sound. Because such organisms are capable of making prolonged vertical migrations, and are widespread geographically, they are very probably the major cause of stratified zones of scattering throughout the oceans of the world.

Seabed sediment classification for monitoring underwater nourishments using time series of multi-beam echo-soundings

NASA Astrophysics Data System (ADS)

Gaida, T. C.; Snellen, M.; van Dijk, T. A. G. P.; Simons, D. G.

2017-12-01

Coastal erosion induced by natural processes, such as wind, waves, tidal currents, or human interferences endangers human beings, infrastructure, fauna and flora at the oceans and rivers all over the world. In The Netherlands, in particular the North Sea islands are strongly affected by sediment erosion. To protect and stabilize the coastline, beach and shoreface nourishments are frequently performed. Thereby, sediment reservoirs are created that replace the eroded sediments. Increasing the long-term efficiency of coastal protection requires monitoring of the temporal and spatial development of the coastal nourishments. Multi-beam echo-sounders (MBES) allow for detailed and comprehensive investigations of the seabed composition and structure. To investigate the potential of using MBES for monitoring nourishments in a tidal inlet, four MBES surveys per year are carried out at the Dutch Wadden island Ameland. A pre-nourishment MBES survey was performed in April 2017 and the subsequent post-nourishment survey will take place in September 2017. Both surveys are equipped with a Kongsberg EM 2040C dual-head MBES and are supported with extensive grab sampling. In this study the use of MBES backscatter and bathymetry data are considered as an approach for monitoring coastal nourishments. The aim is to develop a monitoring procedure that allows for comparing MBES data taken during different surveys, i.e., with variations in environmental conditions, MBES characteristics and acquisition procedures. Different unsupervised and supervised acoustic seafloor classification techniques are applied to the processed MBES data to classify the seabed sediments. The analysis of the pre-nourishment MBES data indicates that the backscatter and consequently the classification are highly driven by the abundancy of shell fragments. These results will be used as a baseline to investigate the accumulation of the underwater nourishments. Independent grab samples will be used to select the optimal method for monitoring the development of underwater nourishments. This work will contribute to conventional and also to modern coastal protection strategies, e.g. using nature-based solutions, where natural processes (tides, waves) are used to redistribute coastal nourishments.

Development of the Advanced Technology Microwave Sounder (ATMS) for NPOESS C1

NASA Astrophysics Data System (ADS)

Brann, C.; Kunkee, D.

2008-12-01

The National Polar-orbiting Operational Environmental Satellite System's Advanced Technology Microwave Sounder (ATMS) is planned for flight on the first NPOESS mission (C1) in 2013. The C1 ATMS will be the second instrument of the ATMS series and will provide along with the companion Cross-track Infrared Sounder (CrIS), atmospheric temperature and moisture profiles for NPOESS. The first flight of the ATMS is scheduled in 2010 on the NPOESS Preparatory Project (NPP) satellite, which is an early instrument risk reduction component of the NPOESS mission. This poster will focus on the development of the ATMS for C1 including aspects of the sensor calibration, antenna beam and RF characteristics and scanning. New design aspects of the C1 ATMS, required primarily by parts obsolescence, will also be addressed in this poster.

Multispectral imaging probe

DOEpatents

Sandison, David R.; Platzbecker, Mark R.; Descour, Michael R.; Armour, David L.; Craig, Marcus J.; Richards-Kortum, Rebecca

1999-01-01

A multispectral imaging probe delivers a range of wavelengths of excitation light to a target and collects a range of expressed light wavelengths. The multispectral imaging probe is adapted for mobile use and use in confined spaces, and is sealed against the effects of hostile environments. The multispectral imaging probe comprises a housing that defines a sealed volume that is substantially sealed from the surrounding environment. A beam splitting device mounts within the sealed volume. Excitation light is directed to the beam splitting device, which directs the excitation light to a target. Expressed light from the target reaches the beam splitting device along a path coaxial with the path traveled by the excitation light from the beam splitting device to the target. The beam splitting device directs expressed light to a collection subsystem for delivery to a detector.

Multispectral imaging probe

DOEpatents

Sandison, D.R.; Platzbecker, M.R.; Descour, M.R.; Armour, D.L.; Craig, M.J.; Richards-Kortum, R.

1999-07-27

A multispectral imaging probe delivers a range of wavelengths of excitation light to a target and collects a range of expressed light wavelengths. The multispectral imaging probe is adapted for mobile use and use in confined spaces, and is sealed against the effects of hostile environments. The multispectral imaging probe comprises a housing that defines a sealed volume that is substantially sealed from the surrounding environment. A beam splitting device mounts within the sealed volume. Excitation light is directed to the beam splitting device, which directs the excitation light to a target. Expressed light from the target reaches the beam splitting device along a path coaxial with the path traveled by the excitation light from the beam splitting device to the target. The beam splitting device directs expressed light to a collection subsystem for delivery to a detector. 8 figs.

Improved Coal-Thickness Measurement

NASA Technical Reports Server (NTRS)

Barr, T. A.

1984-01-01

Summed signals and dielectric-filled antenna improve measurement. Improved FM radar for measuring thickness of coal seam eliminates spectrum splitting and reduces magnitude of echo from front coal surface.

Comparison of Measurements from Pressure-recording Inverted Echo Sounders and Satellite Altimetry in the North Equatorial Current Region of the Western Pacific

NASA Astrophysics Data System (ADS)

Jeon, Chanhyung; Park, Jae-Hun; Kim, Dong Guk; Kim, Eung; Jeon, Dongchull

2018-04-01

An array of 5 pressure-recording inverted echo sounders (PIESs) was deployed along the Jason-2 214 ground track in the North Equatorial Current (NEC) region of the western Pacific Ocean for about 2 years from June 2012. Round-trip acoustic travel time from the bottom to the sea surface and bottom pressure measurements from PIES were converted to sea level anomaly (SLA). AVISO along-track mono-mission SLA (Mono-SLA), reference mapped SLA (Ref-MSLA), and up-to-date mapped SLA (Upd-MSLA) products were used for comparison with PIESderived SLA (η tot). Comparisons of η tot with Mono-SLA revealed that hump artifact errors significantly contaminate the Mono-SLA. Differences of η tot from both Ref-MSLA and Upd-MSLA decreased as the hump errors were reduced in mapped SLA products. Comparisons of Mono-SLA measurements at crossover points of ground tracks near the observation sites revealed large differences though the time differences of their measurements were only 1.53 and 4.58 days. Comparisons between Mono-SLA and mapped SLA suggested that mapped SLA smooths out the hump artifact errors by taking values between the two discrepant Mono-SLA measurements at the crossover points. Consequently, mapped SLA showed better agreement with η tot at our observation sites. AVISO mapped sea surface height (SSH) products are the preferable dataset for studying SSH variability in the NEC region of the western Pacific, though some portions of hump artifact errors seem to still remain in them.

The Keelung Submarine volcanoes and gas plumes in the nearshore of northern Taiwan

NASA Astrophysics Data System (ADS)

Huang, J. C.; Tsia, C. H.; Hsu, S. K.; Lin, S. S.

2016-12-01

Taiwan is located in the collision zone between Philippine Sea Plate and Eurasian Plate. The Philippine Sea Plate subducts northward beneath the Ryukyu arc system while the Eurasian Plate subducts eastward beneath the Luzon arc system. The Taiwan mountain building started at 9 My ago and the most active collision has migrated to middle Taiwan. In consequence, the northern Taiwan has changed its stress pattern from forms a series of thrust faults to normal faults. The stress pattern change has probably induced the post-collisional extension and volcanism in and off northern Taiwan. Under such a tectonic environment, the volcanism and gas plumes are widespread in northern Taiwan and its offshore area. Among the volcanoes of the northern Taiwan volcanic zone, the Tatun Volcano Group is the most obvious one. In this study, we use sub-bottom profiler, EK500 echo sounder, and multibeam echo sounder to study the geophysical structure of a submarine volcano in the nearshore of northern Taiwan. We have analyzed the shallow structures and identified the locations of the gas plumes. The identification of the gas plumes can help us understand the nature of the submarine volcano. Our results show that the gas plumes appear near the Kanchiao Fault and Keelung islet. Some intrusive volcanoes can be observed in the subbottom profiler data. Finally, according to the observations, we found that the Keelung Submarine Volcano is still active. We need the monitor of the active Keelung Submarine Volcano to avoid the volcanic hazard. Additionally, we need to pay attention to the earthquakes related to the Keelung Submarine Volcano.

SSPARR: Development of an efficient autonomous sampling strategy

NASA Astrophysics Data System (ADS)

Chayes, D. N.

2013-12-01

The Seafloor Sounding in Polar and Remote Regions (SSPARR) effort was launched in 2004 with funding from the US National Science Foundation (Anderson et al. 2005.) Experiments with a prototype were encouraging (Greenspan et al., 2012, Chayes et al. 2012) and we are proceeding toward building and testing units for deployment during the 2014 season season in ice covered parts of the Arctic ocean. The simplest operational mode for a SSPARR buoy will be to wake and sample on a fixed time interval. A slightly more complex mode will check the distance traveled since the pervious sounding and potentially return to sleep-mode if it has not traveled far enough to make a significant new measurement. We are developing a mode that will use a sampling strategy based on querying an on-board copy of the best available digital terrain model (DTM) e.g. IBCAO in the Arctic, to help decide if it is appropriate to turn on the echo sounder and make a new measurement. We anticipate that a robust strategy of this type will allow a buoy to operate substantially longer on a fixed battery size. Anderson, R., D. Chayes, et al. (2005). "Seafloor Soundings in Polar and Remote Regions - A new instrument for unattended bathymetric observations," Eos Trans. AGU 86(18): Abstract C43A-10. Greenspan, D., D. Porter, et al. (2012). "IBuoy: Expendable Echo Sounder Buoy with Satellite Telemetry." EOS Fall Meeting Supplement C13E-0660. Chayes, D. N., S. A. Goemmer, et al. (2012). "SSPARR-3: A cost-effective autonomous drifting echosounder." EOS Fall Meeting supplement C13E-0659.

Detection to the DepositFan Occurring in the Sun Moon Lake Using Geophysical Sonar Data

NASA Astrophysics Data System (ADS)

Mimi, L.

2014-12-01

Located in central Taiwan, the Sun Moon Lake is an U-shaped basin with the waters capacity for 138.68 × 106m³. The water is input through two underground tunnels from the Wu-Jie dam in the upstream of the Zhuo-shui river. Although the Wu-Jie dam has been trying to keep the tunnels transporting clean water into the lake, the water is still mixed with muds. The silty water brings the deposits accumulating outwards from positions of the tunnel outlets resulting in a deposit fan formed in the lake. To monitor how the fan is accumulated is then very important in terms of environmental issue, tourism and electric power resources. Institute of Oceanography, National Taiwan University therefore conducted projects to use the multi-beam echo sounders to collect bathymetric data, and used the Chirp sub-bottom profiler to explore silted pattern inside the deposit fan. With these data, underwater topographic maps were plotted to observe the shape and internal structure of the fan. Moreover, two sets of data obtained in 2006 and 2012 were used to estimate the siltation magnitude and pattern in the six years period.The multi-beam sounder is Resons Seabat 9001s model; it collects 60 values in each of the swaths positioned by the DGPS method.The sub-bottom profiler is the EdgeTech 3100P Chirp Sonar, its acoustic wave frequency is in 2 ~ 16kHz. The data give the siltation amount in the Sun Moon Lake was around 3× 106 m³, which gives annual siltation rate at 5× 105 m³. The leading edge of the deposit fan has been expanded westwards 2 km from the water outlet since the tunnel was built 70 years ago; however, outside the deposit fan, the siltation shows insignificant amount on the water bottom.In the past few years the siltation mainly occurs outside in the east side of lake, more closer to the water outlets, the terrain had been increased from 744 m to 746 m (748.5 meters is stranded level of the lake).Observing sub-bottom profiler data, we can clearly see the location of the paleo-hard- bottom of the lake before the siltation occurred. These sub-bottom profiles can be used to check or to analyze episodic deposition behavior in producing the deposit fan.

MR fingerprinting using the quick echo splitting NMR imaging technique.

PubMed

Jiang, Yun; Ma, Dan; Jerecic, Renate; Duerk, Jeffrey; Seiberlich, Nicole; Gulani, Vikas; Griswold, Mark A

2017-03-01

The purpose of the study is to develop a quantitative method for the relaxation properties with a reduced radio frequency (RF) power deposition by combining magnetic resonance fingerprinting (MRF) technique with quick echo splitting NMR imaging technique (QUEST). A QUEST-based MRF sequence was implemented to acquire high-order echoes by increasing the gaps between RF pulses. Bloch simulations were used to calculate a dictionary containing the range of physically plausible signal evolutions using a range of T 1 and T 2 values based on the pulse sequence. MRF-QUEST was evaluated by comparing to the results of spin-echo methods. The specific absorption rate (SAR) of MRF-QUEST was compared with the clinically available methods. MRF-QUEST quantifies the relaxation properties with good accuracy at the estimated head SAR of 0.03 W/kg. T 1 and T 2 values estimated by MRF-QUEST are in good agreement with the traditional methods. The combination of the MRF and the QUEST provides an accurate quantification of T 1 and T 2 simultaneously with reduced RF power deposition. The resulting lower SAR may provide a new acquisition strategy for MRF when RF energy deposition is problematic. Magn Reson Med 77:979-988, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Neutron Zeeman beam-splitting for the investigation of magnetic nanostructures

NASA Astrophysics Data System (ADS)

Kozhevnikov, S. V.; Ott, F.; Semenova, E.

2017-03-01

Zeeman spatial splitting of a neutron beam takes place during a neutron spin-flip in magnetically non-collinear systems at grazing incidence geometry. We apply the neutron beam-splitting method for the investigation of magnetically non-collinear clusters of submicron size in a thin film. The experimental results are compared with ones obtained by other methods.

Low-cost ultra-thin broadband terahertz beam-splitter.

PubMed

Ung, Benjamin S-Y; Fumeaux, Christophe; Lin, Hungyen; Fischer, Bernd M; Ng, Brian W-H; Abbott, Derek

2012-02-27

A low-cost terahertz beam-splitter is fabricated using ultra-thin LDPE plastic sheeting coated with a conducting silver layer. The beam splitting ratio is determined as a function of the thickness of the silver layer--thus any required splitting ratio can be printed on demand with a suitable rapid prototyping technology. The low-cost aspect is a consequence of the fact that ultra-thin LDPE sheeting is readily obtainable, known more commonly as domestic plastic wrap or cling wrap. The proposed beam-splitter has numerous advantages over float zone silicon wafers commonly used within the terahertz frequency range. These advantages include low-cost, ease of handling, ultra-thin thickness, and any required beam splitting ratio can be readily fabricated. Furthermore, as the beam-splitter is ultra-thin, it presents low loss and does not suffer from Fabry-Pérot effects. Measurements performed on manufactured prototypes with different splitting ratios demonstrate a good agreement with our theoretical model in both P and S polarizations, exhibiting nearly frequency-independent splitting ratios in the terahertz frequency range.

Bathymetry of Totten Reservoir, Montezuma County, Colorado, 2011

USGS Publications Warehouse

Kohn, Michael S.

2012-01-01

In order to better characterize the water supply capacity of Totten Reservoir, Montezuma County, Colorado, the U.S. Geological Survey, in cooperation with the Dolores Water Conservancy District, conducted a bathymetric survey of Totten Reservoir. The study was performed in June 2011 using a man-operated boat-mounted multibeam echo sounder integrated with a global positioning system and a terrestrial real-time kinematic global positioning system. The two collected datasets were merged and imported into geographic information system software. A bathymetric map of the reservoir was generated in addition to plots for the stage-area and the stage-volume relations.

Bathymetry of Groundhog Reservoir, Dolores County, Colorado, 2011

USGS Publications Warehouse

Kohn, Michael S.

2012-01-01

In order to better characterize the water supply capacity of Groundhog Reservoir, Dolores County, Colorado, the U.S. Geological Survey, in cooperation with the Dolores Water Conservancy District, conducted a bathymetric survey of Groundhog Reservoir. The study was performed in June 2011 using a man-operated boat-mounted multibeam echo sounder integrated with a global positioning system and a terrestrial real-time kinematic global positioning system. The two collected datasets were merged and imported into geographic information system software. A bathymetric map of the reservoir was generated in addition to plots for the stage-area and the stage-volume relations.

A microwave pressure sounder. [for remote measurement of atmospheric pressure

NASA Technical Reports Server (NTRS)

Peckham, G. E.; Flower, D. A.

1981-01-01

A technique for the remote measurement of atmospheric surface pressure will be described. Such measurements could be made from a satellite in polar orbit and would cover many areas for which conventional meteorological data are not available. An active microwave instrument is used to measure the strength of return echoes from the ocean surface at a number of frequencies near the 60 GHz oxygen absorption band. Factors which affect the accuracy with which surface pressure can be deduced from these measurements will be discussed and an instrument designed to test the method by making measurements from an aircraft will be described.

Integrated Verification Experiment data collected as part of the Los Alamos National Laboratory`s Source Region Program. Appendix D: Ionospheric measurements for IVEs

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

Fitzgerald, T.J.; Carlos, R.C.; Argo, P.E.

As part of the integrated verification experiment (IVE), we deployed a network of hf ionospheric sounders to detect the effects of acoustic waves generated by surface ground motion following underground nuclear tests at the Nevada Test Site. The network sampled up to four geographic locations in the ionosphere from almost directly overhead of the surface ground zero out to a horizontal range of 60 km. We present sample results for four of the IVEs: Misty Echo, Texarkana, Mineral Quarry, and Bexar.

Dynamic splitting of Gaussian pencil beams in heterogeneity-correction algorithms for radiotherapy with heavy charged particles.

PubMed

Kanematsu, Nobuyuki; Komori, Masataka; Yonai, Shunsuke; Ishizaki, Azusa

2009-04-07

The pencil-beam algorithm is valid only when elementary Gaussian beams are small enough compared to the lateral heterogeneity of a medium, which is not always true in actual radiotherapy with protons and ions. This work addresses a solution for the problem. We found approximate self-similarity of Gaussian distributions, with which Gaussian beams can split into narrower and deflecting daughter beams when their sizes have overreached lateral heterogeneity in the beam-transport calculation. The effectiveness was assessed in a carbon-ion beam experiment in the presence of steep range compensation, where the splitting calculation reproduced a detour effect amounting to about 10% in dose or as large as the lateral particle disequilibrium effect. The efficiency was analyzed in calculations for carbon-ion and proton radiations with a heterogeneous phantom model, where the beam splitting increased computing times by factors of 4.7 and 3.2. The present method generally improves the accuracy of the pencil-beam algorithm without severe inefficiency. It will therefore be useful for treatment planning and potentially other demanding applications.

Asymmetric valley-resolved beam splitting and incident modes in slanted graphene junctions

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

Hsieh, S. H.; Chu, C. S.

2016-01-18

Electron injection into a graphene sheet through a slanted armchair graphene nanoribbon (AGNR) is investigated. An incident mode, or subband, in the AGNR is valley-unpolarized. Our attention is on the valley-resolved nature of the injected electron beams and its connection to the incident mode. It is known for a normal injection that an incident mode will split symmetrically into two valley-resolved beams of equal intensity. We show, in contrast, that slanted injections result in asymmetric valley-resolved beam splitting. The most asymmetric beam splitting cases, when one of the valley-resolved beams has basically disappeared, are found and the condition derived. Thismore » is shown not due to trigonal warping because it holds even in the low incident energy regime, as long as collimation allows. These most asymmetric beam splitting cases occur at energies within an energy interval near and include the subband edge of an incident mode. The physical picture is best illustrated by a projection of the slanted AGNR subband states onto that of the 2D graphene sheet. It follows that the disappearing of a valley-resolved beam coincides with the situation that the group velocities of the projected states in the corresponding valley are in backward directions.« less

Method and split cavity oscillator/modulator to generate pulsed particle beams and electromagnetic fields

DOEpatents

Clark, M. Collins; Coleman, P. Dale; Marder, Barry M.

1993-01-01

A compact device called the split cavity modulator whose self-generated oscillating electromagnetic field converts a steady particle beam into a modulated particle beam. The particle beam experiences both signs of the oscillating electric field during the transit through the split cavity modulator. The modulated particle beam can then be used to generate microwaves at that frequency and through the use of extractors, high efficiency extraction of microwave power is enabled. The modulated beam and the microwave frequency can be varied by the placement of resistive wires at nodes of oscillation within the cavity. The short beam travel length through the cavity permit higher currents because both space charge and pinching limitations are reduced. The need for an applied magnetic field to control the beam has been eliminated.

Method and split cavity oscillator/modulator to generate pulsed particle beams and electromagnetic fields

DOEpatents

Clark, M.C.; Coleman, P.D.; Marder, B.M.

1993-08-10

A compact device called the split cavity modulator whose self-generated oscillating electromagnetic field converts a steady particle beam into a modulated particle beam. The particle beam experiences both signs of the oscillating electric field during the transit through the split cavity modulator. The modulated particle beam can then be used to generate microwaves at that frequency and through the use of extractors, high efficiency extraction of microwave power is enabled. The modulated beam and the microwave frequency can be varied by the placement of resistive wires at nodes of oscillation within the cavity. The short beam travel length through the cavity permit higher currents because both space charge and pinching limitations are reduced. The need for an applied magnetic field to control the beam has been eliminated.

Cold water corals - Converting short term scientific excitement into long term public interest

NASA Astrophysics Data System (ADS)

Maestad, K.

2009-04-01

The Vesteraalen area off the Northern Norwegian coast is of ecological importance as a spawning ground for several fish stocks and as a corridor for migrating mature fish and drifting fish larvae for other stocks. The area is also of great interest to oil exploration companies for its hitherto untapped energy supplies. In the midst of it all, there are a number of cold-water coral reefs. Researchers at the Institute of Marine Research in Norway have constructed a sophisticated system for monitoring habitats around the cold-water corals and their environment over time. Two so-called landers will be placed next to coral reefs, will be equipped with echo sounders, camera, hydrophone, acoustic current profiler, CTD-sensor and sediment traps in March 09. This will provide high quality data regarding both physical conditions and biological activity. The sensors will make it possible to observe how different species interact with each other, with particular focus on the activity of fish and how they use the reef habitat. The system will have the capacity to transmit data live from the ocean floor. Creating attention in national media regarding such a ground-breaking project is not all that difficult. Already, the Norwegian national TV channel NRK has confirmed participation on the cruise that will deploy the landers. However, this project also presents communication challenges. One of which is to find a way of making echogram images of the reef understandable ("readable") to people not familiar with interpreting echo sounder signals. This will be especially important if it is decided to make the data from the coral reef available live on the internet. Furthermore, the aim will be to create interest amongst specific audiences in following the life in and around the coral reef over time.

A beam based method for target localization: inspiration from bats' directivity and binaural reception for ultrasonic sonar.

PubMed

Guarato, Francesco; Windmill, James; Gachagan, Anthony

2013-06-01

The process of echolocation is accomplished by bats partly using the beam profiles associated with their ear shapes that allow for discrimination between different echo directions. Indeed, knowledge of the emitted signal characteristic and measurement of the echo travel time from a target make it possible to compensate for attenuation due to distance, and to focus on filtering through the receivers' beam profiles by comparing received echoes to the original signal at all frequencies in the spectrum of interest. From this basis, a beam profile method to localize a target in three-dimensional space for an ultrasonic sensor system equipped with an emitter and two receivers is presented. Simulations were conducted with different noise levels, and only the contribution of the receivers' beam profiles was considered to estimate the orientation of the target with respect to the receivers. The beam pattern of the Phyllostomus discolor's ear was adopted as that of a receiver. Analyses of beam resolution and frequency ranges were conducted to enhance the accuracy of orientation estimates. The choice of appropriate resolution and frequency ranges guarantee that error mean values for most of the orientations are within [0.5°, 1.5°], even in noisy situations: Signal-to-noise ratio values considered in this work are 35 and 50 dB.

First Demonstration of ECHO: an External Calibrator for Hydrogen Observatories

NASA Astrophysics Data System (ADS)

Jacobs, Daniel C.; Burba, Jacob; Bowman, Judd D.; Neben, Abraham R.; Stinnett, Benjamin; Turner, Lauren; Johnson, Kali; Busch, Michael; Allison, Jay; Leatham, Marc; Serrano Rodriguez, Victoria; Denney, Mason; Nelson, David

2017-03-01

Multiple instruments are pursuing constraints on dark energy, observing reionization and opening a window on the dark ages through the detection and characterization of the 21 cm hydrogen line for redshifts ranging from ˜1 to 25. These instruments, including CHIME in the sub-meter and HERA in the meter bands, are wide-field arrays with multiple-degree beams, typically operating in transit mode. Accurate knowledge of their primary beams is critical for separation of bright foregrounds from the desired cosmological signals, but difficult to achieve through astronomical observations alone. Previous beam calibration work at low frequencies has focused on model verification and does not address the need of 21 cm experiments for routine beam mapping, to the horizon, of the as-built array. We describe the design and methodology of a drone-mounted calibrator, the External Calibrator for Hydrogen Observatories (ECHO), that aims to address this need. We report on a first set of trials to calibrate low-frequency dipoles at 137 MHz and compare ECHO measurements to an established beam-mapping system based on transmissions from the Orbcomm satellite constellation. We create beam maps of two dipoles at a 9° resolution and find sample noise ranging from 1% at the zenith to 100% in the far sidelobes. Assuming this sample noise represents the error in the measurement, the higher end of this range is not yet consistent with the desired requirement but is an improvement on Orbcomm. The overall performance of ECHO suggests that the desired precision and angular coverage is achievable in practice with modest improvements. We identify the main sources of systematic error and uncertainty in our measurements and describe the steps needed to overcome them.

Detection of delamination defects in CFRP materials using ultrasonic signal processing.

PubMed

Benammar, Abdessalem; Drai, Redouane; Guessoum, Abderrezak

2008-12-01

In this paper, signal processing techniques are tested for their ability to resolve echoes associated with delaminations in carbon fiber-reinforced polymer multi-layered composite materials (CFRP) detected by ultrasonic methods. These methods include split spectrum processing (SSP) and the expectation-maximization (EM) algorithm. A simulation study on defect detection was performed, and results were validated experimentally on CFRP with and without delamination defects taken from aircraft. Comparison of the methods for their ability to resolve echoes are made.

Split-screen display system and standardized methods for ultrasound image acquisition and multi-frame data processing

NASA Technical Reports Server (NTRS)

Selzer, Robert H. (Inventor); Hodis, Howard N. (Inventor)

2011-01-01

A standardized acquisition methodology assists operators to accurately replicate high resolution B-mode ultrasound images obtained over several spaced-apart examinations utilizing a split-screen display in which the arterial ultrasound image from an earlier examination is displayed on one side of the screen while a real-time "live" ultrasound image from a current examination is displayed next to the earlier image on the opposite side of the screen. By viewing both images, whether simultaneously or alternately, while manually adjusting the ultrasound transducer, an operator is able to bring into view the real-time image that best matches a selected image from the earlier ultrasound examination. Utilizing this methodology, dynamic material properties of arterial structures, such as IMT and diameter, are measured in a standard region over successive image frames. Each frame of the sequence has its echo edge boundaries automatically determined by using the immediately prior frame's true echo edge coordinates as initial boundary conditions. Computerized echo edge recognition and tracking over multiple successive image frames enhances measurement of arterial diameter and IMT and allows for improved vascular dimension measurements, including vascular stiffness and IMT determinations.

MAARSY - The new MST radar on Andøya: System description and first results

NASA Astrophysics Data System (ADS)

Latteck, Ralph; Zecha, Marius; Rapp, Markus; Stober, Gunter; Singer, Werner; Renkwitz, Toralf

2012-07-01

In 2011 the Leibniz-Institute of Atmospheric Physics in Kühlungsborn completed the installation of the Middle Atmosphere Alomar Radar System ({MAARSY}) on the North-Norwegian island Andøya. MAARSY is a 53.5 MHz monostatic radar with an active phased array antenna consisting of 433 Yagi antennas. The 3-element Yagi antennas are arranged in an equilateral triangular grid forming a circular aperture of approximately 6300 m^2. Each individual antenna is connected to its own transceiver with independent phase control and a scalable power output of up to 2 kW. This arrangement provides very high flexibility of beam forming and beam steering with a symmetric radar beam of a minimum beam width of 3.6°. The system allows classical beam swinging operation as well as experiments with simultaneous multiple beams and the use of interferometric applications for improved studies of the Arctic atmosphere from the troposphere up to the lower thermosphere with high spatio-temporal resolution. Standard observations of tropospheric winds and polar mesosphere summer echoes started immediately with an initial stage of expansion in spring 2010. Meteor head echo experiments and 3D observations of polar mesospheric winter echoes were conducted after an upgrade of the system in December 2010. Multi-beam experiments using up to 97 beams quasi-simultaneously in the mesosphere have been carried out during campaigns in summer 2011 with the completed system. We present a system description of MAARSY including beam pattern validation and show initial results from various campaigns obtained during the first 2 years of operation.

Precision sizing of moving large particles using diffraction splitting of Doppler lines

NASA Astrophysics Data System (ADS)

Kononenko, Vadim L.

1999-02-01

It is shown, that the Doppler line from a single large particle moving with a constant velocity through a finite- width laser beam, undergoes a doublet-type splitting under specific observation conditions. A general requirement is that particle size 2a is not negligibly small, compared with beam diameter 2w$0. Three optical mechanisms of line splitting are considered. The first one is based on nonsymmetric diffraction of a bounded laser beam by a moving particle. The second arises from the transient geometry of diffraction. The third mechanism, of photometric nature, originates from specific time variation of total illuminance of moving particles when 2a>Lambda, the interference fringe spacing in the measuring volume. The diffraction splitting is observed when a detector is placed near one of diffraction minima corresponding to either of probing beams, and 2a equals (n0.5)Lambda for n equals 1,2. The photometric splitting is observed with an image-forming optics, when 2a equals n(Lambda) . That gives the possibility of distant particles sizing based on the Doppler line splitting phenomenon. A general theory of line splitting is developed, and used to explain the experimental observations quantitatively. The influence of the scattering angels and observation angle on the line splitting characteristics is studied analytically and numerically.

Bathymetry of the Hong and Luoc River Junction, Red River Delta, Vietnam, 2010

USGS Publications Warehouse

Kinzel, Paul J.; Nelson, Jonathan M.; Toan, Duong Duc; Thanh, Mung Dinh; Shimizu, Yasuyuki

2012-01-01

The U.S. Geological Survey, in collaboration with the Water Resources University in Hanoi, Vietnam, conducted a bathymetric survey of the junction of the Hong and Luoc Rivers. The survey was done to characterize the channel morphology of this delta distributary network and provide input for hydrodynamic and sediment transport models. The survey was carried out in December 2010 using a boat-mounted multibeam echo sounder integrated with a global positioning system. A bathymetric map of the Hong and Luoc River junction was produced which was referenced to the datum of the Trieu Duong tide gage on the Luoc River.

Natural vs human-induced changes at the Tauranga Harbour area (New Zealand): a time -series acoustic seabed classification comparison

NASA Astrophysics Data System (ADS)

Capperucci, Ruggero Maria; Bartholomä, Alexander; Renken, Sabrina; De Lange, Willem

2013-04-01

The Tauranga Harbour Bay (New Zealand) is a mesotidal estuary system, enclosed by the Matakana barrier island. It hosts the leading export port in New Zealand and the second largest import port by value. Coastal changes are well documented over the last decades, mainly at the southern entrance of the area, between Matakana Island and Mt. Maunganui. It is an extremely dynamic environment, where natural processes are strongly influenced by human activities. In particular, the understanding of the recent evolution of the system is crucial for policymakers. In fact, the cumulative impact due to the maintenance of the port (mainly dredging activities, shipping, facilities construction, but also increasing tourism) and its already approved expansion clashes with the claim of the local Maori communities, which recently leaded to a court action. A hydroacoustic multiple-device survey (Side-scan Sonar SSS, Multibeam Echo-sounder MBES and Single Beam Echo-sounder) coupled with sediment sampling was carried out in March 2011 over an area of 0.8 km2, southern Matakana Island, along the Western Channel. The area is not directly impacted by dredging activities, resulting in an optimal testing site for assessing indirect effects of human disturbance on coastal dynamics. The main goals were: 1. To test the response of different acoustic systems in such a highly dynamic environment; 2. To study the influence of dredging activities on sediment dynamics and habitat changes, by means of comparing the current data with existing ones, in order to distinguish between natural and human induced changes Results demonstrate a good agreement between acoustic classifications from different systems. They seem to be mainly driven by the sediment distribution, with a distinctive fingerprint given by shells and shell fragments. Nevertheless, the presence of relevant topographic features (i.e. large bedform fields) influences swath-looking systems (SSS and MBES). SSS and MBES classifications tend to be described by a larger number of acoustic classes, allowing a better sub-division of acoustic zones that carries both the sedimentological and the topographic information into the final map. The evolution of the channel morphology and occurred largely in the past, thus the differences observed in the data can not be univocally ascribed to the dredging operations. Changes in the distribution of surface sediments, bedforms and shell lags can also be mapped. Although a general sedimentary pattern can be recognised over the time series data, a reduction in the shell coverage and the shallowing of the lower Western Channel could be related to an adjustment of the hydrodynamic conditions due to the dredging activities in the shipping channel nearby.

Modeling of beam customization devices in the pencil-beam splitting algorithm for heavy charged particle radiotherapy.

PubMed

Kanematsu, Nobuyuki

2011-03-07

A broad-beam-delivery system for radiotherapy with protons or ions often employs multiple collimators and a range-compensating filter, which offer complex and potentially useful beam customization. It is however difficult for conventional pencil-beam algorithms to deal with fine structures of these devices due to beam-size growth during transport. This study aims to avoid the difficulty with a novel computational model. The pencil beams are initially defined at the range-compensating filter with angular-acceptance correction for upstream collimation followed by stopping and scattering. They are individually transported with possible splitting near the aperture edge of a downstream collimator to form a sharp field edge. The dose distribution for a carbon-ion beam was calculated and compared with existing experimental data. The penumbra sizes of various collimator edges agreed between them to a submillimeter level. This beam-customization model will be used in the greater framework of the pencil-beam splitting algorithm for accurate and efficient patient dose calculation.

Helium and methane sources and fluxes of shallow submarine hydrothermal plumes near the Tokara Islands, Southern Japan

PubMed Central

Wen, Hsin-Yi; Sano, Yuji; Takahata, Naoto; Tomonaga, Yama; Ishida, Akizumi; Tanaka, Kentaro; Kagoshima, Takanori; Shirai, Kotaro; Ishibashi, Jun-ichiro; Yokose, Hisayoshi; Tsunogai, Urumu; Yang, Tsanyao F.

2016-01-01

Shallow submarine volcanoes have been newly discovered near the Tokara Islands, which are situated at the volcanic front of the northern Ryukyu Arc in southern Japan. Here, we report for the first time the volatile geochemistry of shallow hydrothermal plumes, which were sampled using a CTD-RMS system after analyzing water column images collected by multi-beam echo sounder surveys. These surveys were performed during the research cruise KS-14-10 of the R/V Shinsei Maru in a region stretching from the Wakamiko Crater to the Tokara Islands. The 3He flux and methane flux in the investigated area are estimated to be (0.99–2.6) × 104 atoms/cm2/sec and 6–60 t/yr, respectively. The methane in the region of the Tokara Islands is a mix between abiotic methane similar to that found in the East Pacific Rise and thermogenic one. Methane at the Wakamiko Crater is of abiotic origin but affected by isotopic fractionation through rapid microbial oxidation. The helium isotopes suggest the presence of subduction-type mantle helium at the Wakamiko Crater, while a larger crustal component is found close to the Tokara Islands. This suggests that the Tokara Islands submarine volcanoes are a key feature of the transition zone between the volcanic front and the spreading back-arc basin. PMID:27671524

Helium and methane sources and fluxes of shallow submarine hydrothermal plumes near the Tokara Islands, Southern Japan.

PubMed

Wen, Hsin-Yi; Sano, Yuji; Takahata, Naoto; Tomonaga, Yama; Ishida, Akizumi; Tanaka, Kentaro; Kagoshima, Takanori; Shirai, Kotaro; Ishibashi, Jun-Ichiro; Yokose, Hisayoshi; Tsunogai, Urumu; Yang, Tsanyao F

2016-09-27

Shallow submarine volcanoes have been newly discovered near the Tokara Islands, which are situated at the volcanic front of the northern Ryukyu Arc in southern Japan. Here, we report for the first time the volatile geochemistry of shallow hydrothermal plumes, which were sampled using a CTD-RMS system after analyzing water column images collected by multi-beam echo sounder surveys. These surveys were performed during the research cruise KS-14-10 of the R/V Shinsei Maru in a region stretching from the Wakamiko Crater to the Tokara Islands. The 3 He flux and methane flux in the investigated area are estimated to be (0.99-2.6) × 10 4 atoms/cm 2 /sec and 6-60 t/yr, respectively. The methane in the region of the Tokara Islands is a mix between abiotic methane similar to that found in the East Pacific Rise and thermogenic one. Methane at the Wakamiko Crater is of abiotic origin but affected by isotopic fractionation through rapid microbial oxidation. The helium isotopes suggest the presence of subduction-type mantle helium at the Wakamiko Crater, while a larger crustal component is found close to the Tokara Islands. This suggests that the Tokara Islands submarine volcanoes are a key feature of the transition zone between the volcanic front and the spreading back-arc basin.

The gas-hydrate-related seabed features in the Palm Ridge off southwest Taiwan

NASA Astrophysics Data System (ADS)

Su, Zheng-Wei; Hsu, Shu-Kun; Tsai, Ching-Hui; Chen, Song-Chuen; Lin, Hsiao-Shan

2016-04-01

The offshore area of the SW Taiwan is located in the convergence zone between the northern continental margin of the South China Sea and the Manila subduction complex. Our study area, the Palm Ridge, is located in the passive continental margin. According to the geophysical, geochemical and geothermal data, abundant gas hydrate may exist in the offshore area of SW Taiwan. In this study, we will study the relation between the seabed features and the gas hydrate formation of the Palm Ridge. The data used in this study include high-resolution sidescan sonar images, sub-bottom profiles, echo sounder system, multi-beam bathymetric data, multi-channel reflection seismic and submarine photography in the Palm Ridge. Our results show the existing authigenic carbonates, gas seepages and gas plumes are mainly distributed in the bathymetric high of the Palm Ridge. Numerous submarine landslides have occurred in the place where the BSR distribution is not continuous. We suggest that it may be because of rapid slope failure, causing the change of the gas hydrate stability zone. We also found several faults on the R3.1 anticline structure east of the deformation front. These features imply that abundant deep methane gases have migrated to shallow strata, causing submarine landslides or collapse. The detailed relationship of gas migration and submarine landslides need further studies.

Optimized retrievals of precipitable water from the VAS 'split window'

NASA Technical Reports Server (NTRS)

Chesters, Dennis; Robinson, Wayne D.; Uccellini, Louis W.

1987-01-01

Precipitable water fields have been retrieved from the VISSR Atmospheric Sounder (VAS) using a radiation transfer model for the differential water vapor absorption between the 11- and 12-micron 'split window' channels. Previous moisture retrievals using only the split window channels provided very good space-time continuity but poor absolute accuracy. This note describes how retrieval errors can be significantly reduced from plus or minus 0.9 to plus or minus 0.6 gm/sq cm by empirically optimizing the effective air temperature and absorption coefficients used in the two-channel model. The differential absorption between the VAS 11- and 12-micron channels, empirically estimated from 135 colocated VAS-RAOB observations, is found to be approximately 50 percent smaller than the theoretical estimates. Similar discrepancies have been noted previously between theoretical and empirical absorption coefficients applied to the retrieval of sea surface temperatures using radiances observed by VAS and polar-orbiting satellites. These discrepancies indicate that radiation transfer models for the 11-micron window appear to be less accurate than the satellite observations.

A simple X-ray source of two orthogonal beams for small samples imaging

NASA Astrophysics Data System (ADS)

Hrdý, J.

2018-04-01

A simple method for simultaneous imaging of small samples by two orthogonal beams is proposed. The method is based on one channel-cut crystal which is oriented such that the beam is diffracted on two crystallographic planes simultaneously. These planes are symmetrically inclined to the crystal surface. The beams are three times diffracted. After the first diffraction the beam is split. After the second diffraction the split beams become parallel. Finally, after the third diffraction the beams become convergent and may be used for imaging. The corresponding angular relations to obtain orthogonal beams are derived.

Radio Sounding Science at High Powers

NASA Technical Reports Server (NTRS)

Green, J. L.; Reinisch, B. W.; Song, P.; Fung, S. F.; Benson, R. F.; Taylor, W. W. L.; Cooper, J. F.; Garcia, L.; Markus, T.; Gallagher, D. L.

2004-01-01

Future space missions like the Jupiter Icy Moons Orbiter (JIMO) planned to orbit Callisto, Ganymede, and Europa can fully utilize a variable power radio sounder instrument. Radio sounding at 1 kHz to 10 MHz at medium power levels (10 W to kW) will provide long-range magnetospheric sounding (several Jovian radii) like those first pioneered by the radio plasma imager instrument on IMAGE at low power (less than l0 W) and much shorter distances (less than 5 R(sub E)). A radio sounder orbiting a Jovian icy moon would be able to globally measure time-variable electron densities in the moon ionosphere and the local magnetospheric environment. Near-spacecraft resonance and guided echoes respectively allow measurements of local field magnitude and local field line geometry, perturbed both by direct magnetospheric interactions and by induced components from subsurface oceans. JIMO would allow radio sounding transmissions at much higher powers (approx. 10 kW) making subsurface sounding of the Jovian icy moons possible at frequencies above the ionosphere peak plasma frequency. Subsurface variations in dielectric properties, can be probed for detection of dense and solid-liquid phase boundaries associated with oceans and related structures in overlying ice crusts.

Angular-momentum-dependent splitting of light through metal nanohole

NASA Astrophysics Data System (ADS)

Hu, Dejiao; Liu, Yu; Zhang, ZhiYou; Xiao, Xiao; Du, JingLei

2014-11-01

We numerically study the splitting of light beam which carries orbital angular momentum (OAM) through single metal nano-scale hole. A light beam carrying with OAM has a helical phase distribution in the transverse plane, where the electric field has the form: E(r,θ)=E0exp(lθ), and l is the topological charge which denotes the value of OAM. The circular polarization state is corresponding to the spin angular momentum (SAM), where s=+1 represents the left-handed polarization and s=-1 the right-handed polarization. Simulation results show l dependent splitting of beam through nano metal hole. When l is odd, the transmitted far field splits while no splitting happens when l is even. This phenomenon is attributed to the interaction between OAM beam and plasmonic mode of metal nano-hole. It is revealed that different OAM beam can excite different transverse mode in the metal cavity, which means the interaction should obey an OAM section rule. We show that even l can excite transverse mode with zero total AM and odd l can excite transverse mode with non-zero total AM within the hole. Orbital-spin conversion is also revealed in the free wave/plasmon interaction.

Over-under double-pass interferometer

NASA Technical Reports Server (NTRS)

Schindler, Rudolf A. (Inventor)

1980-01-01

An over-under double-pass interferometer in which the beamsplitter area and thickness can be reduced to conform only with optical flatness considerations is achieved by offsetting the optical center line of one cat's-eye retroreflector relative to the optical center line of the other in order that one split beam be folded into a plane distinct from the other folded split beam. The beamsplitter is made transparent in one area for a first folded beam to be passed to a mirror for doubling back and is made totally reflective in another area for the second folded beam to be reflected to a mirror for doubling back. The two beams thus doubled back are combined in the central, beam-splitting area of the beamsplitter and passed to a detector. This makes the beamsplitter insensitive to minimum-thickness requirements and selection of material.

Superconducting magnetic Wollaston prism for neutron spin encoding

NASA Astrophysics Data System (ADS)

Li, F.; Parnell, S. R.; Hamilton, W. A.; Maranville, B. B.; Wang, T.; Semerad, R.; Baxter, D. V.; Cremer, J. T.; Pynn, R.

2014-05-01

A magnetic Wollaston prism can spatially split a polarized neutron beam into two beams with different neutron spin states, in a manner analogous to an optical Wollaston prism. Such a Wollaston prism can be used to encode the trajectory of neutrons into the Larmor phase associated with their spin degree of freedom. This encoding can be used for neutron phase-contrast radiography and in spin echo scattering angle measurement (SESAME). In this paper, we show that magnetic Wollaston prisms with highly uniform magnetic fields and low Larmor phase aberration can be constructed to preserve neutron polarization using high temperature superconducting (HTS) materials. The Meissner effect of HTS films is used to confine magnetic fields produced electromagnetically by current-carrying HTS tape wound on suitably shaped soft iron pole pieces. The device is cooled to ˜30 K by a closed cycle refrigerator, eliminating the need to replenish liquid cryogens and greatly simplifying operation and maintenance. A HTS film ensures that the magnetic field transition within the prism is sharp, well-defined, and planar due to the Meissner effect. The spin transport efficiency across the device was measured to be ˜98.5% independent of neutron wavelength and energizing current. The position-dependent Larmor phase of neutron spins was measured at the NIST Center for Neutron Research facility and found to agree well with detailed simulations. The phase varies linearly with horizontal position, as required, and the neutron beam shows little depolarization. Consequently, the device has advantages over existing devices with similar functionality and provides the capability for a large neutron beam (20 mm × 30 mm) and an increase in length scales accessible to SESAME to beyond 10 μm. With further improvements of the external coupling guide field in the prototype device, a larger neutron beam could be employed.

Superconducting magnetic Wollaston prism for neutron spin encoding.

PubMed

Li, F; Parnell, S R; Hamilton, W A; Maranville, B B; Wang, T; Semerad, R; Baxter, D V; Cremer, J T; Pynn, R

2014-05-01

A magnetic Wollaston prism can spatially split a polarized neutron beam into two beams with different neutron spin states, in a manner analogous to an optical Wollaston prism. Such a Wollaston prism can be used to encode the trajectory of neutrons into the Larmor phase associated with their spin degree of freedom. This encoding can be used for neutron phase-contrast radiography and in spin echo scattering angle measurement (SESAME). In this paper, we show that magnetic Wollaston prisms with highly uniform magnetic fields and low Larmor phase aberration can be constructed to preserve neutron polarization using high temperature superconducting (HTS) materials. The Meissner effect of HTS films is used to confine magnetic fields produced electromagnetically by current-carrying HTS tape wound on suitably shaped soft iron pole pieces. The device is cooled to ~30 K by a closed cycle refrigerator, eliminating the need to replenish liquid cryogens and greatly simplifying operation and maintenance. A HTS film ensures that the magnetic field transition within the prism is sharp, well-defined, and planar due to the Meissner effect. The spin transport efficiency across the device was measured to be ~98.5% independent of neutron wavelength and energizing current. The position-dependent Larmor phase of neutron spins was measured at the NIST Center for Neutron Research facility and found to agree well with detailed simulations. The phase varies linearly with horizontal position, as required, and the neutron beam shows little depolarization. Consequently, the device has advantages over existing devices with similar functionality and provides the capability for a large neutron beam (20 mm × 30 mm) and an increase in length scales accessible to SESAME to beyond 10 μm. With further improvements of the external coupling guide field in the prototype device, a larger neutron beam could be employed.

Final report on technical work accomplished under contract NASw-2953

NASA Technical Reports Server (NTRS)

Fredricks, R. W.

1977-01-01

A report is given on the technical work accomplished in the area of plasma physics. The subjects covered are: (1) oblique whistler instabilities, (2) current-limited electron beam injection, (3) three-dimensional ion sound turbulence, (4) theoretical aspects of sounder antenna operation and (5) whistler modes in bow shock structures.

Singleshot T1 Mapping using Simultaneous Acquisitions of Spin- and STimulated-Echo Planar Imaging (2D ss-SESTEPI)

PubMed Central

Shi, Xianfeng; Kim, Seong-Eun; Jeong, Eun-Kee

2011-01-01

The conventional stimulated-echo NMR sequence only measures the longitudinal component, while discarding the transverse component, after tipping up the prepared magnetization. This transverse magnetization can be used to measure a spin-echo, in addition to the stimulated-echo. 2D ss-SESTEPI is an EPI-based singleshot imaging technique that simultaneously acquires a spin-echo-planar image (SEPI) and a stimulated-echo-planar image (STEPI) after a single RF excitation. The magnitudes of SEPI and STEPI differ by T1 decay and diffusion weighting for perfect 90° RF, and thus can be used to rapidly measure T1. However, the spatial variation of B1 amplitude induces un-even splitting of the transverse magnetization for SEPI and STEPI within the imaging FOV. Correction for B1 inhomogeneity is therefore critical for 2D ss-SESTEPI to be used for T1 measurement. We developed a method for B1 inhomogeneity correction by acquiring an additional STEPI with minimal mixing time, calculating the difference between the spin-echo and the stimulated-echo and multiplying the STEPI by the inverse functional map. Diffusion-induced decay is corrected by measuring the average diffusivity during the prescanning. Rapid singleshot T1 mapping may be useful for various applications, such as dynamic T1 mapping for real-time estimation of the concentration of contrast agent in DCE-MRI. PMID:20564579

Metal-dielectric composites for beam splitting and far-field deep sub-wavelength resolution for visible wavelengths.

PubMed

Yan, Changchun; Zhang, Dao Hua; Zhang, Yuan; Li, Dongdong; Fiddy, M A

2010-07-05

We report beam splitting in a metamaterial composed of a silver-alumina composite covered by a layer of chromium containing one slit. By simulating distributions of energy flow in the metamaterial for H-polarized waves, we find that the beam splitting occurs when the width of the slit is shorter than the wavelength, which is conducive to making a beam splitter in sub-wavelength photonic devices. We also find that the metamaterial possesses deep sub-wavelength resolution capabilities in the far field when there are two slits and the central silver layer is at least 36 nm in thickness, which has potential applications in superresolution imaging.

MAARSY: The new MST radar on Andøya—System description and first results

NASA Astrophysics Data System (ADS)

Latteck, R.; Singer, W.; Rapp, M.; Vandepeer, B.; Renkwitz, T.; Zecha, M.; Stober, G.

2012-02-01

The Middle Atmosphere Alomar Radar System (MAARSY) on the North-Norwegian island Andøya is a 53.5 MHz monostatic radar with an active phased array antenna consisting of 433 Yagi antennas. The 3-element Yagi antennas are arranged in an equilateral triangle grid forming a circular aperture of approximately 6300 m2. Each individual antenna is connected to its own transceiver with independent phase control and a scalable power output up to 2 kW. This arrangement provides a very high flexibility of beam forming and beam steering with a symmetric radar beam of a minimum beam width of 3.6° allowing classical beam swinging operation as well as experiments with simultaneous multiple beams and the use of interferometric applications for improved studies of the Arctic atmosphere from the troposphere up to the lower thermosphere with high spatio-temporal resolution. The installation of the antenna array was completed in August 2009. The radar control and data acquisition hardware as well as an initial expansion stage of 196 transceiver modules was installed in spring 2010 and upgraded to 343 transceiver modules in November 2010. The final extension to 433 transceiver modules has recently been completed in May 2011. Beside standard observations of tropospheric winds and Polar Mesosphere Summer Echoes, the first multi-beam experiments using up to 97 quasi-simultaneous beams in the mesosphere have been carried out in 2010 and 2011. These results provide a first insight into the horizontal variability of polar mesosphere summer and winter echoes with time resolutions between 3 and 9 minutes. In addition, first meteor head echo observations were conducted during the Geminid meteor shower in December 2010.

Dose calculation algorithm of fast fine-heterogeneity correction for heavy charged particle radiotherapy.

PubMed

Kanematsu, Nobuyuki

2011-04-01

This work addresses computing techniques for dose calculations in treatment planning with proton and ion beams, based on an efficient kernel-convolution method referred to as grid-dose spreading (GDS) and accurate heterogeneity-correction method referred to as Gaussian beam splitting. The original GDS algorithm suffered from distortion of dose distribution for beams tilted with respect to the dose-grid axes. Use of intermediate grids normal to the beam field has solved the beam-tilting distortion. Interplay of arrangement between beams and grids was found as another intrinsic source of artifact. Inclusion of rectangular-kernel convolution in beam transport, to share the beam contribution among the nearest grids in a regulatory manner, has solved the interplay problem. This algorithmic framework was applied to a tilted proton pencil beam and a broad carbon-ion beam. In these cases, while the elementary pencil beams individually split into several tens, the calculation time increased only by several times with the GDS algorithm. The GDS and beam-splitting methods will complementarily enable accurate and efficient dose calculations for radiotherapy with protons and ions. Copyright © 2010 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Note: A new design for a low-temperature high-intensity helium beam source

NASA Astrophysics Data System (ADS)

Lechner, B. A. J.; Hedgeland, H.; Allison, W.; Ellis, J.; Jardine, A. P.

2013-02-01

A high-intensity supersonic beam source is a key component of any atom scattering instrument, affecting the sensitivity and energy resolution of the experiment. We present a new design for a source which can operate at temperatures as low as 11.8 K, corresponding to a beam energy of 2.5 meV. The new source improves the resolution of the Cambridge helium spin-echo spectrometer by a factor of 5.5, thus extending the accessible timescales into the nanosecond range. We describe the design of the new source and discuss experiments characterizing its performance. Spin-echo measurements of benzene/Cu(100) illustrate its merit in the study of a typical slow-moving molecular adsorbate species.

Single photon at a configurable quantum-memory-based beam splitter

NASA Astrophysics Data System (ADS)

Guo, Xianxin; Mei, Yefeng; Du, Shengwang

2018-06-01

We report the demonstration of a configurable coherent quantum-memory-based beam splitter (BS) for a single-photon wave packet making use of laser-cooled 85Rb atoms and electromagnetically induced transparency. The single-photon wave packet is converted (stored) into a collective atomic spin state and later retrieved (split) into two nearly opposing directions. The storage time, beam-splitting ratio, and relative phase are configurable and can be dynamically controlled. We experimentally confirm that such a BS preserves the quantum particle nature of the single photon and the coherence between the two split wave packets of the single photon.

Physical-geometric optics method for large size faceted particles.

PubMed

Sun, Bingqiang; Yang, Ping; Kattawar, George W; Zhang, Xiaodong

2017-10-02

A new physical-geometric optics method is developed to compute the single-scattering properties of faceted particles. It incorporates a general absorption vector to accurately account for inhomogeneous wave effects, and subsequently yields the relevant analytical formulas effective and computationally efficient for absorptive scattering particles. A bundle of rays incident on a certain facet can be traced as a single beam. For a beam incident on multiple facets, a systematic beam-splitting technique based on computer graphics is used to split the original beam into several sub-beams so that each sub-beam is incident only on an individual facet. The new beam-splitting technique significantly reduces the computational burden. The present physical-geometric optics method can be generalized to arbitrary faceted particles with either convex or concave shapes and with a homogeneous or an inhomogeneous (e.g., a particle with a core) composition. The single-scattering properties of irregular convex homogeneous and inhomogeneous hexahedra are simulated and compared to their counterparts from two other methods including a numerically rigorous method.

Neutron resonance spin-echo upgrade at the three-axis spectrometer FLEXX

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

Groitl, F., E-mail: felix.groitl@psi.ch; Quintero-Castro, D. L.; Habicht, K.

2015-02-15

We describe the upgrade of the neutron resonance spin-echo setup at the cold neutron triple-axis spectrometer FLEXX at the BER II neutron source at the Helmholtz-Zentrum Berlin. The parameters of redesigned key components are discussed, including the radio frequency (RF) spin-flip coils, the magnetic shield, and the zero field coupling coils. The RF-flippers with larger beam windows allow for an improved neutron flux transfer from the source to the sample and further to the analyzer. The larger beam cross sections permit higher coil inclination angles and enable measurements on dispersive excitations with a larger slope of the dispersion. Due tomore » the compact design of the spin-echo units in combination with the increased coil tilt angles, the accessible momentum-range in the Larmor diffraction mode is substantially enlarged. In combination with the redesigned components of the FLEXX spectrometer, including the guide, the S-bender polarizer, the double focusing monochromator, and a Heusler crystal analyzer, the count rate increased by a factor of 15.5, and the neutron beam polarization is enhanced. The improved performance extends the range of feasible experiments, both for inelastic scattering on excitation lifetimes in single crystals, and for high-resolution Larmor diffraction. The experimental characterization of the instrument components demonstrates the reliable performance of the new neutron resonance spin-echo option, now available for the scientific community at FLEXX.« less

Effects of Energy Chirp on Echo-Enabled Harmonic Generation Free-Electron Lasers

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

Huang, Z.; Ratner, D.; Stupakov, G.

2009-02-23

We study effects of energy chirp on echo-enabled harmonic generation (EEHG). Analytical expressions are compared with numerical simulations for both harmonic and bunching factors. We also discuss the EEHG free-electron laser bandwidth increase due to an energy-modulated beam and its pulse length dependence on the electron energy chirp.

Seismic Imaging of Circumpolar Deep Water Exchange across the Shelf Break of the Antarctic Peninsula

NASA Astrophysics Data System (ADS)

Gunn, K.; White, N.; Larter, R. D.; Falder, M.; Caulfield, C. C. P.

2016-02-01

The western Antarctic Peninsula is an area of recent extreme atmospheric warming. In the adjacent ocean, there is particular interest in on-shelf movement of Circumpolar Deep Water as a possible link to changing climate by affecting ice shelf processes. Here, we investigate on-shelf intrusions using two-dimensional seismic imaging of the water column which has vertical and horizontal resolutions of 10 m. 8 seismic profiles were acquired in February 2015 using the RRS James Clark Ross. These profiles traverse the shelf break and cross two bathymetric features, the Marguerite and Biscoe troughs, which may play a role in water exchange processes. Seismic data were acquired using two Generator-Injector air guns fired every 10 s with a pressure of 2000 psi. Reflections were recorded on a 2.4 km streamer of 192 receivers spaced every 12.5 m. Observed reflections in the processed records are caused by rapid changes of temperature ( 80%) and salinity ( 20%), delineating water masses of different properties. 13 XCTDs and XBTs plus a 38 kHz echo-sounder profile were simultaneously acquired along seismic profiles and used for calibration. Preliminary results show the top of the Winter Water layer as a bright reflection at 50-120 m depth across the entire survey, corresponding to temperatures ≤ -1°C. Curved, discontinuous, eddy-like reflections, also seen on echo-sounder profiles, are attributed to modified Upper Circumpolar Deep Water with temperatures ≥ 1.34°C. A warm core eddy, 11 km long and 220 m high, is visible 2 km inland of the shelf break. Pure Upper Circumpolar Deep Water of temperatures ≥ 1.80°C is aligned with weak but discernible, lens-shaped reflections. Eddy-like structures and the overall reflective morphology yield useful insights into shelf exchange processes, suggestive of three potential mechanisms: (i) topography controlled flow; (ii) an 'ice-pump' mechanism; and (iii) mesoscale eddies.

Performance evaluation of a bigrating as a beam splitter.

PubMed

Hwang, R B; Peng, S T

1997-04-01

The design of a bigrating for use as a beam splitter is presented. It is based on a rigorous formulation of plane-wave scattering by a bigrating that is composed of two individual gratings oriented in different directions. Numerical results are carried out to optimize the design of a bigrating to perform 1 x 4 beam splitting in two dimensions and to examine its fabrication and operation tolerances. It is found that a bigrating can be designed to perform two functions: beam splitting and polarization purification.

Analysis of detection performance of multi band laser beam analyzer

NASA Astrophysics Data System (ADS)

Du, Baolin; Chen, Xiaomei; Hu, Leili

2017-10-01

Compared with microwave radar, Laser radar has high resolution, strong anti-interference ability and good hiding ability, so it becomes the focus of laser technology engineering application. A large scale Laser radar cross section (LRCS) measurement system is designed and experimentally tested. First, the boundary conditions are measured and the long range laser echo power is estimated according to the actual requirements. The estimation results show that the echo power is greater than the detector's response power. Secondly, a large scale LRCS measurement system is designed according to the demonstration and estimation. The system mainly consists of laser shaping, beam emitting device, laser echo receiving device and integrated control device. Finally, according to the designed lidar cross section measurement system, the scattering cross section of target is simulated and tested. The simulation results are basically the same as the test results, and the correctness of the system is proved.

Full-waveform data for building roof step edge localization

NASA Astrophysics Data System (ADS)

Słota, Małgorzata

2015-08-01

Airborne laser scanning data perfectly represent flat or gently sloped areas; to date, however, accurate breakline detection is the main drawback of this technique. This issue becomes particularly important in the case of modeling buildings, where accuracy higher than the footprint size is often required. This article covers several issues related to full-waveform data registered on building step edges. First, the full-waveform data simulator was developed and presented in this paper. Second, this article provides a full description of the changes in echo amplitude, echo width and returned power caused by the presence of edges within the laser footprint. Additionally, two important properties of step edge echoes, peak shift and echo asymmetry, were noted and described. It was shown that these properties lead to incorrect echo positioning along the laser center line and can significantly reduce the edge points' accuracy. For these reasons and because all points are aligned with the center of the beam, regardless of the actual target position within the beam footprint, we can state that step edge points require geometric corrections. This article presents a novel algorithm for the refinement of step edge points. The main distinguishing advantage of the developed algorithm is the fact that none of the additional data, such as emitted signal parameters, beam divergence, approximate edge geometry or scanning settings, are required. The proposed algorithm works only on georeferenced profiles of reflected laser energy. Another major advantage is the simplicity of the calculation, allowing for very efficient data processing. Additionally, the developed method of point correction allows for the accurate determination of points lying on edges and edge point densification. For this reason, fully automatic localization of building roof step edges based on LiDAR full-waveform data with higher accuracy than the size of the lidar footprint is feasible.

Echo power analysis and simulation of low altitude radio fuze

NASA Astrophysics Data System (ADS)

Chen, Xiaolu; Chen, Biao; Xu, Tao; Xu, Suqin

2013-01-01

The echo power from the earth gound which was received by fuze plays an important role in aerial defense missile, especially when the fuze is working in the look down mode. It is necessary to analyze and even simulate the echo power signals to enhance the missile's anti-jamming ability. In this paper, the quantity of echo power from the earth ground of low altitude radio fuze was analyzed in detail. Three boundary equations of area irradiated by electromagnetic beams were presented, which include two equidistant curve equations and one equal-Doppler curve equation. The relationship between the working mode and the critical height was analyzed. The calculating formula of echo power waveform was derived. And based on the derived formula, the correlation between the maximal echo power and the incident height was given and simulated, which would be helpful for the further researches of low altitude radio fuze.

Coherent and dynamic beam splitting based on light storage in cold atoms

PubMed Central

Park, Kwang-Kyoon; Zhao, Tian-Ming; Lee, Jong-Chan; Chough, Young-Tak; Kim, Yoon-Ho

2016-01-01

We demonstrate a coherent and dynamic beam splitter based on light storage in cold atoms. An input weak laser pulse is first stored in a cold atom ensemble via electromagnetically-induced transparency (EIT). A set of counter-propagating control fields, applied at a later time, retrieves the stored pulse into two output spatial modes. The high visibility interference between the two output pulses clearly demonstrates that the beam splitting process is coherent. Furthermore, by manipulating the control lasers, it is possible to dynamically control the storage time, the power splitting ratio, the relative phase, and the optical frequencies of the output pulses. With further improvements, the active beam splitter demonstrated in this work might have applications in photonic photonic quantum information and in all-optical information processing. PMID:27677457

X-ray Echo Spectroscopy

NASA Astrophysics Data System (ADS)

Shvyd'ko, Yuri

2016-02-01

X-ray echo spectroscopy, a counterpart of neutron spin echo, is being introduced here to overcome limitations in spectral resolution and weak signals of the traditional inelastic x-ray scattering (IXS) probes. An image of a pointlike x-ray source is defocused by a dispersing system comprised of asymmetrically cut specially arranged Bragg diffracting crystals. The defocused image is refocused into a point (echo) in a time-reversal dispersing system. If the defocused beam is inelastically scattered from a sample, the echo signal acquires a spatial distribution, which is a map of the inelastic scattering spectrum. The spectral resolution of the echo spectroscopy does not rely on the monochromaticity of the x rays, ensuring strong signals along with a very high spectral resolution. Particular schemes of x-ray echo spectrometers for 0.1-0.02 meV ultrahigh-resolution IXS applications (resolving power >108 ) with broadband ≃5 - 13 meV dispersing systems are introduced featuring more than 103 signal enhancement. The technique is general, applicable in different photon frequency domains.

Beam splitter and method for generating equal optical path length beams

DOEpatents

Qian, Shinan; Takacs, Peter

2003-08-26

The present invention is a beam splitter for splitting an incident beam into first and second beams so that the first and second beams have a fixed separation and are parallel upon exiting. The beam splitter includes a first prism, a second prism, and a film located between the prisms. The first prism is defined by a first thickness and a first perimeter which has a first major base. The second prism is defined by a second thickness and a second perimeter which has a second major base. The film is located between the first major base and the second major base for splitting the incident beam into the first and second beams. The first and second perimeters are right angle trapezoidal shaped. The beam splitter is configured for generating equal optical path length beams.

Photographs of the Sea Floor of Western Massachusetts Bay, Offshore of Boston, Massachusett, July 1999

USGS Publications Warehouse

Gutierrez, Benjamin T.; Butman, Bradford; Blackwood, Dann S.

2001-01-01

This CD-ROM contains photographs and sediment sample analyses of the sea floor obtained at 142 sites in western Massachusetts Bay (Figure 1) during a research cruise (USGS cruise ISBL99024) aboard the Fishing Vessel (FV) Isabel S. (Figure 2) conducted July 18-21, 1999. These photographs and samples provide critical ground truth information for the interpretation of shaded relief and backscatter intensity maps created using data collected with a multibeam echo sounder system (Butman and others, in press, a, b, c; Valentine and others, in press, a, b, c). Collection of these photographs and samples was undertaken in support of a large project whose overall objective is to map and describe the sea floor of Massachusetts Bay.

Theory and optical design of x-ray echo spectrometers

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

Shvyd'ko, Yuri

X-ray echo spectroscopy, a space-domain counterpart of neutron spin echo, is a recently proposed inelastic x-ray scattering (IXS) technique. X-ray echo spectroscopy relies on imaging IXS spectra and does not require x-ray monochromatization. Due to this, the echo-type IXS spectrometers are broadband, and thus have a potential to simultaneously provide dramatically increased signal strength, reduced measurement times, and higher resolution compared to the traditional narrow-band scanning-type IXS spectrometers. The theory of x-ray echo spectrometers presented earlier [Yu. Shvyd'ko, Phys. Rev. Lett. 116, 080801 (2016)] is developed here further with a focus on questions of practical importance, which could facilitate opticalmore » design and assessment of the feasibility and performance of the echo spectrometers. Among others, the following questions are addressed: spectral resolution, refocusing condition, echo spectrometer tolerances, refocusing condition adjustment, effective beam size on the sample, spectral window of imaging and scanning range, impact of the secondary source size on the spectral resolution, angular dispersive optics, focusing and collimating optics, and detector's spatial resolution. In conclusion, examples of optical designs and characteristics of echo spectrometers with 1-meV and 0.1-meV resolutions are presented.« less

Theory and optical design of x-ray echo spectrometers

DOE PAGES

Shvyd'ko, Yuri

2017-08-02

X-ray echo spectroscopy, a space-domain counterpart of neutron spin echo, is a recently proposed inelastic x-ray scattering (IXS) technique. X-ray echo spectroscopy relies on imaging IXS spectra and does not require x-ray monochromatization. Due to this, the echo-type IXS spectrometers are broadband, and thus have a potential to simultaneously provide dramatically increased signal strength, reduced measurement times, and higher resolution compared to the traditional narrow-band scanning-type IXS spectrometers. The theory of x-ray echo spectrometers presented earlier [Yu. Shvyd'ko, Phys. Rev. Lett. 116, 080801 (2016)] is developed here further with a focus on questions of practical importance, which could facilitate opticalmore » design and assessment of the feasibility and performance of the echo spectrometers. Among others, the following questions are addressed: spectral resolution, refocusing condition, echo spectrometer tolerances, refocusing condition adjustment, effective beam size on the sample, spectral window of imaging and scanning range, impact of the secondary source size on the spectral resolution, angular dispersive optics, focusing and collimating optics, and detector's spatial resolution. In conclusion, examples of optical designs and characteristics of echo spectrometers with 1-meV and 0.1-meV resolutions are presented.« less

Detection and Assessment of Wood Decay in Glulam Beams Using a Decay Rate Approach: A Review

Treesearch

C. Adam Senalik

2013-01-01

A glulam beam is subjected to X-ray computer tomography and acousto-ultrasonic measurements to detect and assess wood decay. A glulam beam without visible indications of wood decay was taken from field use. A modified impulse-echo technique is employed as an inspection method requiring access to only one side of the beam. It is observed that decay-rate analysis of the...

Displacement sensor based on intra-cavity tuning of dual-frequency gas laser

NASA Astrophysics Data System (ADS)

Niu, Haisha; Niu, Yanxiong; Liu, Ning; Li, Jiyang

2018-01-01

A nanometer-resolution displacement measurement instrument based on tunable cavity frequency-splitting method is presented. One beam is split into two orthogonally polarized beams when anisotropic element inserted in the cavity. The two beams with fixed frequency difference are modulated by the movement of the reflection mirror. The changing law of the power tuning curves between the total output and the two orthogonally polarized beams is researched, and a method splitting one tuning cycle to four equal parts is proposed based on the changing law, each part corresponds to one-eighth wavelength of displacement. A laser feedback interferometer (LFI) and piezoelectric ceramic are series connected to the sensor head to calibrate the displacement that less than one-eighth wavelength. The displacement sensor achieves to afford measurement range of 20mm with resolution of 6.93nm.

Ultrasonic device for measuring periodontal attachment levels

NASA Astrophysics Data System (ADS)

Lynch, J. E.; Hinders, M. K.

2002-07-01

Periodontal disease is manifested clinically by a degradation of the ligament that attaches the tooth to the bone. The most widely used diagnostic tool for assessment of periodontal diseases, measurement of periodontal attachment loss with a manual probe, may overestimate attachment loss by as much as 2 mm in untreated sites, while underestimating attachment loss by an even greater margin following treatment. Manual probing is also invasive, which causes patient discomfort. This work describes the development and testing of an ultrasonographic periodontal probe designed to replace manual probing. It uses a thin stream of water to project an ultrasonic beam into the periodontal pocket, and then measures echoes off features within the pocket. To do so, the ultrasonic beam must be narrowed from 2 (the diameter of the transducer) to 0.5 mm (the approximate width of the periodontal pocket at the gingival margin). The proper choice of transducer frequency, the proper method for controlling water flow from the probe, and a model for interpreting these echoes are also addressed. Initial results indicate that the device measures echoes from the hard tissue of the tooth surface, and that the periodontal attachment level can be inferred from these echoes.

Differential correction system of laser beam directional dithering based on symmetrical beamsplitter

NASA Astrophysics Data System (ADS)

Hongwei, Yang; Wei, Tao; Xiaoqia, Yin; Hui, Zhao

2018-02-01

This paper proposes a differential correction system with a differential optical path and a symmetrical beamsplitter for correcting the directional dithering of the laser beams. This system can split a collimated laser beam into two laser beams with equal and opposite movements. Thus, the positional averages of the two split laser beams remain constant irrespective of the dithering angle. The symmetrical beamsplitter designed based on transfer matrix principle is to balance the optical paths and irradiances of the two laser beams. Experimental results show that the directional dithering is reduced to less than one-pixel value. Finally, two examples show that this system can be widely used in one-dimensional measurement.

Temporal characteristics of coherent flow structures generated over alluvial sand dunes, Mississippi River, revealed by acoustic doppler current profiling and multibeam echo sounding

USGS Publications Warehouse

Czuba, John A.; Oberg, Kevin A.; Best, Jim L.; Parsons, Daniel R.; Simmons, S. M.; Johnson, K.K.; Malzone, C.

2009-01-01

This paper investigates the flow in the lee of a large sand dune located at the confluence of the Mississippi and Missouri Rivers, USA. Stationary profiles collected from an anchored boat using an acoustic Doppler current profiler (ADCP) were georeferenced with data from a real-time kinematic differential global positioning system. A multibeam echo sounder was used to map the bathymetry of the confluence and provided a morphological context for the ADCP measurements. The flow in the lee of a low-angle dune shows good correspondence with current conceptual models of flow over dunes. As expected, quadrant 2 events (upwellings of low-momentum fluid) are associated with high backscatter intensity. Turbulent events generated in the lower lee of a dune near the bed are associated with periods of vortex shedding and wake flapping. Remnant coherent structures that advect over the lower lee of the dune in the upper portion of the water column, have mostly dissipated and contribute little to turbulence intensities. The turbulent events that occupy most of the water column in the upper lee of the dune are associated with periods of wake flapping.

What multi-beam bathymetric data can tell about morphodynamics and sediment transport in an estuarine environment?

NASA Astrophysics Data System (ADS)

Winterscheid, Axel; Reiß, Marcel

2017-04-01

The Elbe River Estuary is one of the most important waterways for commercial shipping in Europe. It connects the North Sea with the Port of Hamburg located about 100 km inlands. To secure navigation, the Federal Waterways and Shipping Administration (WSV) is operating a fleet of survey vessels all equipped with a multi-beam echo sounder controlling the required water depths. Beyond navigational purposes, this monitoring is creating a comprehensive and ever-growing data base, which can be used for a consistent morphodynamical description of the river bed. The history of multi-beam records in the Elbe River Estuary reaches back to 2008. At particular river sections where large amounts of fine grained sediments accumulate surveys are taken biweekly; at other sections there are monthly surveys. Locally, sedimentation rates of up to 12 cm per day have been observed within the fairway. The time series of multiple multi-beam records have been analyzed with a particular focus on morphodynamics and sedimentation rates. Here we compare the morphodynamical characteristics of two river sections. The first section is located at the downstream end of the estuarine turbidity zone near the city of Cuxhaven; the second section is located 50 km away at the upstream end of the turbidity zone near the city of Hamburg. These two sections have been selected because in both the morphology of the river bed and the sedimentation processes are strongly influenced by the presence of fine grained sediments. The results show that changing sedimentation rates in both sections are conditioned by different site specific factors, e.g. the dynamic shifting of the turbidity zone along the estuary, which is resulting in a temporarily higher availability of suspended sediments and more intense sedimentation rates in the upper part of the estuary and the respective section. In contrast, in the downstream located river section more intense sedimentation rates could be related to periods of strong north-western wind conditions causing increased water levels and higher wave loads on the adjacent wadden areas of the German Bight. These processes were formerly inferred from theory and numerical studies but could not so far be supported on the basis of direct measurements due to a lack of continuous data records on sedimentation rates with a sufficiently high spatial and temporal resolution.

Diffractive-refractive optics: X-ray splitter.

PubMed

Hrdý, Jaromír

2010-01-01

The possibility of splitting a thin (e.g. undulator) X-ray beam based on diffraction-refraction effects is discussed. The beam is diffracted from a crystal whose diffracting surface has the shape of a roof with the ridge lying in the plane of diffraction. The crystal is cut asymmetrically. One half of the beam impinges on the left-hand part of the roof and the other half impinges on the right-hand side of the roof. Owing to refraction the left part of the beam is deviated to the left whereas the right part is deviated to the right. The device proposed consists of two channel-cut crystals with roof-like diffraction surfaces; the crystals are set in a dispersive position. The separation of the beams after splitting is calculated at a distance of 10 m from the crystals for various asymmetry and inclination angles. It is shown that such a splitting may be utilized for long beamlines. Advantages and disadvantages of this method are discussed.

X-ray luminescence computed tomography imaging based on X-ray distribution model and adaptively split Bregman method

PubMed Central

Chen, Dongmei; Zhu, Shouping; Cao, Xu; Zhao, Fengjun; Liang, Jimin

2015-01-01

X-ray luminescence computed tomography (XLCT) has become a promising imaging technology for biological application based on phosphor nanoparticles. There are mainly three kinds of XLCT imaging systems: pencil beam XLCT, narrow beam XLCT and cone beam XLCT. Narrow beam XLCT can be regarded as a balance between the pencil beam mode and the cone-beam mode in terms of imaging efficiency and image quality. The collimated X-ray beams are assumed to be parallel ones in the traditional narrow beam XLCT. However, we observe that the cone beam X-rays are collimated into X-ray beams with fan-shaped broadening instead of parallel ones in our prototype narrow beam XLCT. Hence we incorporate the distribution of the X-ray beams in the physical model and collected the optical data from only two perpendicular directions to further speed up the scanning time. Meanwhile we propose a depth related adaptive regularized split Bregman (DARSB) method in reconstruction. The simulation experiments show that the proposed physical model and method can achieve better results in the location error, dice coefficient, mean square error and the intensity error than the traditional split Bregman method and validate the feasibility of method. The phantom experiment can obtain the location error less than 1.1 mm and validate that the incorporation of fan-shaped X-ray beams in our model can achieve better results than the parallel X-rays. PMID:26203388

Neural field theory of perceptual echo and implications for estimating brain connectivity

NASA Astrophysics Data System (ADS)

Robinson, P. A.; Pagès, J. C.; Gabay, N. C.; Babaie, T.; Mukta, K. N.

2018-04-01

Neural field theory is used to predict and analyze the phenomenon of perceptual echo in which random input stimuli at one location are correlated with electroencephalographic responses at other locations. It is shown that this echo correlation (EC) yields an estimate of the transfer function from the stimulated point to other locations. Modal analysis then explains the observed spatiotemporal structure of visually driven EC and the dominance of the alpha frequency; two eigenmodes of similar amplitude dominate the response, leading to temporal beating and a line of low correlation that runs from the crown of the head toward the ears. These effects result from mode splitting and symmetry breaking caused by interhemispheric coupling and cortical folding. It is shown how eigenmodes obtained from functional magnetic resonance imaging experiments can be combined with temporal dynamics from EC or other evoked responses to estimate the spatiotemporal transfer function between any two points and hence their effective connectivity.

X-ray echo spectroscopy (Conference Presentation)

NASA Astrophysics Data System (ADS)

Shvyd'ko, Yuri V.

2016-09-01

X-ray echo spectroscopy, a counterpart of neutron spin-echo, was recently introduced [1] to overcome limitations in spectral resolution and weak signals of the traditional inelastic x-ray scattering (IXS) probes. An image of a point-like x-ray source is defocused by a dispersing system comprised of asymmetrically cut specially arranged Bragg diffracting crystals. The defocused image is refocused into a point (echo) in a time-reversal dispersing system. If the defocused beam is inelastically scattered from a sample, the echo signal acquires a spatial distribution, which is a map of the inelastic scattering spectrum. The spectral resolution of the echo spectroscopy does not rely on the monochromaticity of the x-rays, ensuring strong signals along with a very high spectral resolution. Particular schemes of x-ray echo spectrometers for 0.1-meV and 0.02-meV ultra-high-resolution IXS applications (resolving power > 10^8) with broadband 5-13 meV dispersing systems will be presented featuring more than 1000-fold signal enhancement. The technique is general, applicable in different photon frequency domains. [1.] Yu. Shvyd'ko, Phys. Rev. Lett. 116, accepted (2016), arXiv:1511.01526.

Symmetry-Based Variance Reduction Applied to 60Co Teletherapy Unit Monte Carlo Simulations

NASA Astrophysics Data System (ADS)

Sheikh-Bagheri, D.

A new variance reduction technique (VRT) is implemented in the BEAM code [1] to specifically improve the efficiency of calculating penumbral distributions of in-air fluence profiles calculated for isotopic sources. The simulations focus on 60Co teletherapy units. The VRT includes splitting of photons exiting the source capsule of a 60Co teletherapy source according to a splitting recipe and distributing the split photons randomly on the periphery of a circle, preserving the direction cosine along the beam axis, in addition to the energy of the photon. It is shown that the use of the VRT developed in this work can lead to a 6-9 fold improvement in the efficiency of the penumbral photon fluence of a 60Co beam compared to that calculated using the standard optimized BEAM code [1] (i.e., one with the proper selection of electron transport parameters).

Echolocation call intensity and directionality in flying short-tailed fruit bats, Carollia perspicillata (Phyllostomidae).

PubMed

Brinkløv, Signe; Jakobsen, Lasse; Ratcliffe, John M; Kalko, Elisabeth K V; Surlykke, Annemarie

2011-01-01

The directionality of bat echolocation calls defines the width of bats' sonar "view," while call intensity directly influences detection range since adequate sound energy must impinge upon objects to return audible echoes. Both are thus crucial parameters for understanding biosonar signal design. Phyllostomid bats have been classified as low intensity or "whispering bats," but recent data indicate that this designation may be inaccurate. Echolocation beam directionality in phyllostomids has only been measured through electrode brain-stimulation of restrained bats, presumably excluding active beam control via the noseleaf. Here, a 12-microphone array was used to measure echolocation call intensity and beam directionality in the frugivorous phyllostomid, Carollia perspicillata, echolocating in flight. The results showed a considerably narrower beam shape (half-amplitude beam angles of approximately 16° horizontally and 14° vertically) and louder echolocation calls [source levels averaging 99 dB sound pressure level (SPL) root mean square] for C. perspicillata than was found for this species when stationary. This suggests that naturally behaving phyllostomids shape their sound beam to achieve a longer and narrower sonar range than previously thought. C. perspicillata orient and forage in the forest interior and the narrow beam might be adaptive in clutter, by reducing the number and intensity of off-axis echoes.

Femtosecond laser fabrication of birefringent directional couplers as polarization beam splitters in fused silica.

PubMed

Fernandes, Luís A; Grenier, Jason R; Herman, Peter R; Aitchison, J Stewart; Marques, Paulo V S

2011-06-20

Integrated polarization beam splitters based on birefringent directional couplers are demonstrated. The devices are fabricated in bulk fused silica glass by femtosecond laser writing (300 fs, 150 nJ at 500 kHz, 522 nm). The birefringence was measured from the spectral splitting of the Bragg grating resonances associated with the vertically and horizontally polarized modes. Polarization splitting directional couplers were designed and demonstrated with 0.5 dB/cm propagation losses and -19 dB and -24 dB extinction ratios for the polarization splitting.

Examining Mars at Many Levels (Artist Concept)

NASA Image and Video Library

2005-03-23

This artist's concept represents the "Follow the Water" theme of NASA's Mars Reconnaissance Orbiter mission. The orbiter's science instruments monitor the present water cycle in the Mars atmosphere and the associated deposition and sublimation of water ice on the surface, while probing the subsurface to see how deep the water-ice reservoir detected by Mars Odyssey extends. At the same time, Mars Reconnaissance Orbiter will search for surface features and minerals (such as carbonates and sulfates) that record the extended presence of liquid water on the surface earlier in the planet's history. The instruments involved are the Shallow Subsurface Radar, the Compact Reconnaissance Imaging Spectrometer for Mars, the Mars Color Imager, the High Resolution Imaging Science Experiment, the Context Camera and the Mars Climate Sounder. To the far left, the radar antenna beams down and "sees" into the first few hundred feet (up to 1 kilometer) of Mars' crust. Just to the right of that, the next beam highlights the data received from the imaging spectrometer, which identifies minerals on the surface. The next beam represents the high-resolution camera, which can "zoom in" on local targets, providing the highest-resolution orbital images yet of features such as craters and gullies and rocks. The beam that shines almost horizontally is that of the Mars Climate Sounder. This instrument is critical to analyzing the current climate of Mars since it observes the temperature, humidity, and dust content of the martian atmosphere, and their seasonal and year-to-year variations. Meanwhile, the Mars Color Imager observes ice clouds, dust clouds and hazes, and the ozone distribution, producing daily global maps in multiple colors to monitor daily weather and seasonal changes. The electromagnetic spectrum is represented on the top right and individual instruments are placed where their capability lies. http://photojournal.jpl.nasa.gov/catalog/PIA07241

Superconducting magnetic Wollaston prism for neutron spin encoding

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

Li, F., E-mail: fankli@indiana.edu; Parnell, S. R.; Wang, T.

2014-05-15

A magnetic Wollaston prism can spatially split a polarized neutron beam into two beams with different neutron spin states, in a manner analogous to an optical Wollaston prism. Such a Wollaston prism can be used to encode the trajectory of neutrons into the Larmor phase associated with their spin degree of freedom. This encoding can be used for neutron phase-contrast radiography and in spin echo scattering angle measurement (SESAME). In this paper, we show that magnetic Wollaston prisms with highly uniform magnetic fields and low Larmor phase aberration can be constructed to preserve neutron polarization using high temperature superconducting (HTS)more » materials. The Meissner effect of HTS films is used to confine magnetic fields produced electromagnetically by current-carrying HTS tape wound on suitably shaped soft iron pole pieces. The device is cooled to ∼30 K by a closed cycle refrigerator, eliminating the need to replenish liquid cryogens and greatly simplifying operation and maintenance. A HTS film ensures that the magnetic field transition within the prism is sharp, well-defined, and planar due to the Meissner effect. The spin transport efficiency across the device was measured to be ∼98.5% independent of neutron wavelength and energizing current. The position-dependent Larmor phase of neutron spins was measured at the NIST Center for Neutron Research facility and found to agree well with detailed simulations. The phase varies linearly with horizontal position, as required, and the neutron beam shows little depolarization. Consequently, the device has advantages over existing devices with similar functionality and provides the capability for a large neutron beam (20 mm × 30 mm) and an increase in length scales accessible to SESAME to beyond 10 μm. With further improvements of the external coupling guide field in the prototype device, a larger neutron beam could be employed.« less

Mass Gauging Demonstrator for Any Gravitational Conditions

NASA Technical Reports Server (NTRS)

Korman, Valentin (Inventor); Pedersen, Kevin W. (Inventor); Witherow, William K. (Inventor)

2013-01-01

The present invention is a mass gauging interferometry system used to determine the volume contained within a tank. By using an optical interferometric technique to determine gas density and/or pressure a much smaller compression volume or higher fidelity measurement is possible. The mass gauging interferometer system is comprised of an optical source, a component that splits the optical source into a plurality of beams, a component that recombines the split beams, an optical cell operatively coupled to a tank, a detector for detecting fringes, and a means for compression. A portion of the beam travels through the optical cell operatively coupled to the tank, while the other beam(s) is a reference.

Quantum channel for the transmission of information

DOEpatents

Dress, William B.; Kisner, Roger A.; Richards, Roger K.

2004-01-13

Systems and methods are described for a quantum channel for the transmission of information. A method includes: down converting a beam of coherent energy to provide a beam of multi-color entangled photons; converging two spatially resolved portions of the beam of multi-color entangled photons into a converged multi-color entangled photon beam; changing a phase of at least a portion of the converged multi-color entangled photon beam to generate a first interferometric multi-color entangled photon beam; combining the first interferometric multi-color entangled photon beam with a second interferometric multi-color entangled photon beam within a single beam splitter; wherein combining includes erasing energy and momentum characteristics from both the first interferometric multi-color entangled photon beam and the second interferometric multi-color entangled photon beam; splitting the first interferometric multi-color entangled photon beam and the second interferometric multi-color entangled photon beam within the single beam splitter, wherein splitting yields a first output beam of multi-color entangled photons and a second output beam of multi-color entangled photons; and modulating the first output beam of multi-color entangled photons.

Accurate Ultrasonic Measurement of Surface Profile Using Phase Shift of Echo and Inverse Filtering

NASA Astrophysics Data System (ADS)

Arihara, Chihiro; Hasegawa, Hideyuki; Kanai, Hiroshi

2006-05-01

Atherosclerosis is the main cause of circulatory diseases such as myocardial infarction and cerebral infarction, and it is very important to diagnose atherosclerosis in its early stage. In the early stage of atherosclerosis, the luminal surface of an arterial wall becomes rough because of the injury of the endothelium [R. Ross: New Engl. J. Med. 340 (2004) 115]. Conventional ultrasonic diagnostic equipments cannot detect such roughness on the order of micrometer because of their low resolution of approximately 0.1 mm. In this study, for the accurate detection of surface roughness, an ultrasonic beam was scanned in the direction that is parallel to the surface of an object. When there is a gap on the surface, the phase of the echo from the surface changes because the distance between the probe and the surface changes during the scanning. Therefore, surface roughness can be assessed by estimating the phase shift of echoes obtained during the beam scanning. Furthermore, lateral resolution, which is deteriorated by a finite diameter of the ultrasound beam, was improved by an inverse filter. By using the proposed method, the surface profile of a phantom, which had surface roughness on the micrometer order, was detected, and the estimated surface profiles became more precise by applying the inverse filter.

Mine Sweeping System for Magnetic and Non-Magnetic Mines.

DTIC Science & Technology

1994-12-29

be detected. One example of the latter type of system is a conventional sonar device wherein a directional beam of acoustic energy periodically...Although satisfactory for many uses, sonar devices have several inherent limitations. Nearby objects can cause echoes and these may obscure the echo of...electromagnetic signal and sends it to the preamplifier 601. The preamplifier 601 increases the strength of the received electrical signal before sending it

Turbulent upwelling of mid-latitude ionosphere. 1. Observational results by the MU radar

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

Fukao, Shoichiro; Shirakawa, Tatsuya; Takami, Tomoyuki

1991-03-01

In this paper, the authors present the detailed results of a series of experiments designed to study the coherent backscatter of 50-MHz radar waves from the mid-latitude F region. Data were obtained with the active phased-array MU radar in Japan and include some auxiliary E region coherent echoes as well.The strongest echoes correspond to irregularities at least 20 dB stronger than thermal backscatter at the same frequency from typical F region densities at the same range. Simultaneous observations with ionosondes show that these echoes occur during strong mid-latitude spread F. As defined by ionosondes, the latter phenomenon is certainly muchmore » more widespread than the turbulent upwelling events described here, but they believe that in some sense these correspond to the most violent mid-latitude spread F. The strongest echoes occur in large patches which display away Doppler shifts corresponding to irregularity motion upward and northward from the radar. At the edges of these patches there is often a brief period of toward Doppler before the echoing region ceases. On rare occasions comparable patches of strong away and toward Doppler are detected, although in such cases the Doppler width of the toward echoes is much narrower than that of the away echoes. The multiple beam capability at MU allowed us to track the patches in the zonal direction on two days. The patches moved east to west in both cases at velocities of 125 m/s and 185 m/s, respectively. There is a distinct tendency for the bottom contour of the scattering region to be modulated at the same period as the patch occurence frequency as well as at higher frequencies. This higher-frequency component may correspond to substructures in the large patches and to the E region coherent scatter patches which were detected simultaneously in several multiple beam experiments.« less

SweepSAR: Beam-forming on Receive Using a Reflector-Phased Array Feed Combination for Spaceborne SAR

NASA Technical Reports Server (NTRS)

Freeman, A.; Krieger, G.; Rosen, P.; Younis, M.; Johnson, W. T. K.; Huber, S.; Jordan, R.; Moreira, A.

2012-01-01

In this paper, an alternative approach is described that is suited for longer wavelength SARs in particular, employing a large, deployable reflector antenna and a much simpler phased array feed. To illuminate a wide swath, a substantial fraction of the phased array feed is excited on transmit to sub-illuminate the reflector. Shorter transmit pulses are required than for conventional SAR. On receive, a much smaller portion of the phased array feed is used to collect the return echo, so that a greater portion of the reflector antenna area is used. The locus of the portion of the phased array used on receive is adjusted using an analog beam steering network, to 'sweep' the receive beam(s) across the illuminated swath, tracking the return echo. This is similar in some respects to the whiskbroom approach to optical sensors, hence the name: SweepSAR.SweepSAR has advantages over conventional SAR in that it requires less transmit power, and if the receive beam is narrow enough, it is relatively immune to range ambiguities. Compared to direct radiating arrays with digital beam- forming, it is much simpler to implement, uses currently available technologies, is better suited for longer wavelength systems, and does not require extremely high data rates or onboard processing.

Echo-Enabled X-Ray Vortex Generation

NASA Astrophysics Data System (ADS)

Hemsing, E.; Marinelli, A.

2012-11-01

A technique to generate high-brightness electromagnetic vortices with tunable topological charge at extreme ultraviolet and x-ray wavelengths is described. Based on a modified version of echo-enabled harmonic generation for free-electron lasers, the technique uses two lasers and two chicanes to produce high-harmonic microbunching of a relativistic electron beam with a corkscrew distribution that matches the instantaneous helical phase structure of the x-ray vortex. The strongly correlated electron distribution emerges from an efficient three-dimensional recoherence effect in the echo-enabled harmonic generation transport line and can emit fully coherent vortices in a downstream radiator for access to new research in x-ray science.

Sensitivity analysis and optimization method for the fabrication of one-dimensional beam-splitting phase gratings

PubMed Central

Pacheco, Shaun; Brand, Jonathan F.; Zaverton, Melissa; Milster, Tom; Liang, Rongguang

2015-01-01

A method to design one-dimensional beam-spitting phase gratings with low sensitivity to fabrication errors is described. The method optimizes the phase function of a grating by minimizing the integrated variance of the energy of each output beam over a range of fabrication errors. Numerical results for three 1x9 beam splitting phase gratings are given. Two optimized gratings with low sensitivity to fabrication errors were compared with a grating designed for optimal efficiency. These three gratings were fabricated using gray-scale photolithography. The standard deviation of the 9 outgoing beam energies in the optimized gratings were 2.3 and 3.4 times lower than the optimal efficiency grating. PMID:25969268

Angularly symmetric splitting of a light beam upon reflection and refraction at an air-dielectric plane boundary.

PubMed

Azzam, R M A

2015-12-01

Conditions for achieving equal and opposite angular deflections of a light beam by reflection and refraction at an air-dielectric boundary are determined. Such angularly symmetric beam splitting (ASBS) is possible only if the angle of incidence is >60° by exactly one third of the angle of refraction. This simple law, plus Snell's law, leads to several analytical results that clarify all aspects of this phenomenon. In particular, it is shown that the intensities of the two symmetrically deflected beams can be equalized by proper choice of the prism refractive index and the azimuth of incident linearly polarized light. ASBS enables a geometrically attractive layout of optical systems that employ multiple prism beam splitters.

Sensitivity of echo enabled harmonic generation to sinusoidal electron beam energy structure

DOE PAGES

Hemsing, E.; Garcia, B.; Huang, Z.; ...

2017-06-19

Here, we analytically examine the bunching factor spectrum of a relativistic electron beam with sinusoidal energy structure that then undergoes an echo-enabled harmonic generation (EEHG) transformation to produce high harmonics. The performance is found to be described primarily by a simple scaling parameter. The dependence of the bunching amplitude on fluctuations of critical parameters is derived analytically, and compared with simulations. Where applicable, EEHG is also compared with high gain harmonic generation (HGHG) and we find that EEHG is generally less sensitive to several types of energy structure. In the presence of intermediate frequency modulations like those produced by themore » microbunching instability, EEHG has a substantially narrower intrinsic bunching pedestal.« less

Shear wave arrival time estimates correlate with local speckle pattern.

PubMed

Mcaleavey, Stephen A; Osapoetra, Laurentius O; Langdon, Jonathan

2015-12-01

We present simulation and phantom studies demonstrating a strong correlation between errors in shear wave arrival time estimates and the lateral position of the local speckle pattern in targets with fully developed speckle. We hypothesize that the observed arrival time variations are largely due to the underlying speckle pattern, and call the effect speckle bias. Arrival time estimation is a key step in quantitative shear wave elastography, performed by tracking tissue motion via cross-correlation of RF ultrasound echoes or similar methods. Variations in scatterer strength and interference of echoes from scatterers within the tracking beam result in an echo that does not necessarily describe the average motion within the beam, but one favoring areas of constructive interference and strong scattering. A swept-receive image, formed by fixing the transmit beam and sweeping the receive aperture over the region of interest, is used to estimate the local speckle pattern. Metrics for the lateral position of the speckle are found to correlate strongly (r > 0.7) with the estimated shear wave arrival times both in simulations and in phantoms. Lateral weighting of the swept-receive pattern improved the correlation between arrival time estimates and speckle position. The simulations indicate that high RF echo correlation does not equate to an accurate shear wave arrival time estimate-a high correlation coefficient indicates that motion is being tracked with high precision, but the location tracked is uncertain within the tracking beam width. The presence of a strong on-axis speckle is seen to imply high RF correlation and low bias. The converse does not appear to be true-highly correlated RF echoes can still produce biased arrival time estimates. The shear wave arrival time bias is relatively stable with variations in shear wave amplitude and sign (-20 μm to 20 μm simulated) compared with the variation with different speckle realizations obtained along a given tracking vector. We show that the arrival time bias is weakly dependent on shear wave amplitude compared with the variation with axial position/ local speckle pattern. Apertures of f/3 to f/8 on transmit and f/2 and f/4 on receive were simulated. Arrival time error and correlation with speckle pattern are most strongly determined by the receive aperture.

Shear Wave Arrival Time Estimates Correlate with Local Speckle Pattern

PubMed Central

McAleavey, Stephen A.; Osapoetra, Laurentius O.; Langdon, Jonathan

2016-01-01

We present simulation and phantom studies demonstrating a strong correlation between errors in shear wave arrival time estimates and the lateral position of the local speckle pattern in targets with fully developed speckle. We hypothesize that the observed arrival time variations are largely due to the underlying speckle pattern, and call the effect speckle bias. Arrival time estimation is a key step in quantitative shear wave elastography, performed by tracking tissue motion via cross correlation of RF ultrasound echoes or similar methods. Variations in scatterer strength and interference of echoes from scatterers within the tracking beam result in an echo that does not necessarily describe the average motion within the beam, but one favoring areas of constructive interference and strong scattering. A swept-receive image, formed by fixing the transmit beam and sweeping the receive aperture over the region of interest, is used to estimate the local speckle pattern. Metrics for the lateral position of the speckle are found to correlate strongly (r>0.7) with the estimated shear wave arrival times both in simulations and in phantoms. Lateral weighting of the swept-receive pattern improved the correlation between arrival time estimates and speckle position. The simulations indicate that high RF echo correlation does not equate to an accurate shear wave arrival time estimate – a high correlation coefficient indicates that motion is being tracked with high precision, but the location tracked is uncertain within the tracking beam width. The presence of a strong on-axis speckle is seen to imply high RF correlation and low bias. The converse does not appear to be true – highly correlated RF echoes can still produce biased arrival time estimates. The shear wave arrival time bias is relatively stable with variations in shear wave amplitude and sign (−20 μm to 20 μm simulated) compared to the variation with different speckle realizations obtained along a given tracking vector. We show that the arrival time bias is weakly dependent on shear wave amplitude compared to the variation with axial position/local speckle pattern. Apertures of f/3 to f/8 on transmit and f/2 and f/4 on receive were simulated. Arrival time error and correlation with speckle pattern are most strongly determined by the receive aperture. PMID:26670847

Beam splitting of low-contrast binary gratings under second Bragg angle incidence.

PubMed

Zheng, Jiangjun; Zhou, Changhe; Wang, Bo; Feng, Jijun

2008-05-01

Beam splitting of low-contrast rectangular gratings under second Bragg angle incidence is studied. The grating period is between lambda and 2lambda. The diffraction behaviors of the three transmitted propagating orders are illustrated by analyzing the first three propagating grating modes. From a simplified modal approach, the design conditions of gratings as a high-efficiency element with most of its energy concentrated in the -2nd transmitted order (~90%) and of gratings as a 1 x 2 beam splitter with a total efficiency over 90% are derived. The grating parameters for achieving exactly the splitting pattern by use of rigorous coupled-wave analysis verified the design method. A 1 x 3 beam splitter is also demonstrated. Moreover, the polarization-dependent diffraction behaviors are investigated, which suggest the possibility of designing polarization-selective elements under such a configuration. The proposed concept of using the second Bragg angle should be helpful for developing new grating-based devices.

Mud volcano venting induced gas hydrate formation at the upper slope accretionary wedge, offshore SW Taiwan

NASA Astrophysics Data System (ADS)

Lin, Saulwood; Tseng, Yi-Ting; Cheng, Wan-Yen; Chou, Cheng-Tien; Chen, NeiChen; Hsieh, I.-Chih

2016-04-01

TsanYao Mud Volcano (TYMV) is the largest mud volcano cone in the Hengchun Mud Volcano Group (HCMVG), located at the upper slope of the accrretionary wedge, southwest of Taiwan. The region is under active tectonic activity with the Philippine Plate, moving northwestward at a rate of ~8 cm/year. This region also receives huge quantity of suspended particle load of ~100 mT/year at present time from adjacent small rivers of the Island of Taiwan. Large loads of suspended sediments influx become a major source of organic carbon and later gas and other hydrocarbon. Gas and fluid in the mud volcano are actively venting from deep to the sea floor on the upper slope of the accretionary wedge. In order to understand venting on the HCMVG, echo sounder, towcam and coring were carried out. Pore water sulfate, chloride, potassium, calcium, stable isotope O-18, gas compositions, dissolved sulfide were analysed. The HCMVG consists of 12 volcano cones of different sizes. Large quantity of gas and fluid are venting directly from deep to the TYMV structure high, as well as 50+ other vents as appeared as flares on the echo sounder. Some flares are reaching to the atmosphere and likely a source of green house gases to the atmosphere. Venting fluids include gas bubbles, suspended particle, mud, and breccia. Breccia size could reach more than 12 cm in diameter. Circular bands in different color appeared around the cone may represent stages of vent eruptions. Compositions of vent gas include methane, ethane and propane. High proportions of ethane and propane in the vent gas demonstrated that source of gas are thermogenic in origin. Patchy authigenic carbonate, bacterial mats, bivalves, tube worms and other chemosynthesis organisms were supported by venting gas AOM process near the sea floor. Pore water chloride concentrations show distinct variation pattern from center cone to the side of the volcano, with low in the center and high away from the cone. Pore water with higher than seawater chloride indicated gas hydrate formation in sediments away from the mud volcano cone.

Towards clinical computed ultrasound tomography in echo-mode: Dynamic range artefact reduction.

PubMed

Jaeger, Michael; Frenz, Martin

2015-09-01

Computed ultrasound tomography in echo-mode (CUTE) allows imaging the speed of sound inside tissue using hand-held pulse-echo ultrasound. This technique is based on measuring the changing local phase of beamformed echoes when changing the transmit beam steering angle. Phantom results have shown a spatial resolution and contrast that could qualify CUTE as a promising novel diagnostic modality in combination with B-mode ultrasound. Unfortunately, the large intensity range of several tens of dB that is encountered in clinical images poses difficulties to echo phase tracking and results in severe artefacts. In this paper we propose a modification to the original technique by which more robust echo tracking can be achieved, and we demonstrate in phantom experiments that dynamic range artefacts are largely eliminated. Dynamic range artefact reduction also allowed for the first time a clinical implementation of CUTE with sufficient contrast to reproducibly distinguish the different speed of sound in different tissue layers of the abdominal wall and the neck. Copyright © 2015. Published by Elsevier B.V.

Overview of the physics of US.

PubMed

Goldstein, A

1993-05-01

In ultrasonography (US), high-frequency sound waves are transmitted through the body by a transducer. When a transmitted ultrasound pulse encounters a tissue target, some of its energy is deflected back to the transducer. The time of flight of this ultrasound echo is used to calculate depth of the target in the transducer beam. The pulse-echo parameters used in the formation of images include echo amplitude, target spatial position, and frequency shift between the transmitted pulse and the received echo. The first two are displayed in gray-scale images and all three in color flow images. In gray-scale US, echo amplitude is encoded into shades of gray, with the lighter shades representing higher amplitude echoes. In color flow US, velocity of moving blood is usually presented in blue for motion toward the transducer and in red for motion away from it. A Doppler spectrum depicts changing blood velocity as a function of time. US has become more clinically valuable due to its ability to demonstrate soft-tissue structures, real-time imaging capability, relative safety, portability, and cost-effectiveness.

Generation and propagation of a sine-azimuthal wavefront modulated Gaussian beam

PubMed Central

Lao, Guanming; Zhang, Zhaohui; Luo, Meilan; Zhao, Daomu

2016-01-01

We introduce a method for modulating the Gaussian beam by means of sine-azimuthal wavefront and carry out the experimental generation. The analytical propagation formula of such a beam passing through a paraxial ABCD optical system is derived, by which the intensity properties of the sine-azimuthal wavefront modulated Gaussian (SWMG) beam are examined both theoretically and experimentally. Both of the experimental and theoretical results show that the SWMG beam goes through the process from beam splitting to a Gaussian-like profile, which is closely determined by the phase factor and the propagation distance. Appropriate phase factor and short distance are helpful for the splitting of beam. However, in the cases of large phase factor and focal plane, the intensity distributions tend to take a Gaussian form. Such unique features may be of importance in particle trapping and medical applications. PMID:27443798

Detecting deep sea hydrothermal vents with a split-beam echosounder

NASA Astrophysics Data System (ADS)

Gray, L. M.; Jerram, K.

2016-12-01

In May 2016, the NOAA Office of Exploration and Research exploration vessel, Okeanos Explorer, conducted a remotely operated vehicle (ROV) dive on a series of active `black smoker' hydrothermal vents at 3,300 m depth in the western Pacific Ocean near the Mariana Trench. The ROV system traversed 800 m along the seafloor and detected three distinct vent sites. The vent chimneys ranged in heights from 5 m to 30 m above the seafloor and vent fluid temperatures were measured as high as 337 °C. Immediately following the ROV dive, the Okeanos Explorer mapped the vent field with an 18 kHz split-beam echosounder traditionally used for fishery research and a 30 kHz multibeam echosounder with midwater capability. Six passes were made over the field, transiting at 4-5 knots on various headings. There was a clear and repeatable signal in the split-beam echogram from the venting but less obvious indication in the multibeam data. `Black smokers' have traditionally been detected using repeat conductivity-temperature-depth (CTD) `tow-yo' casts. Our field observations suggest an alternative, and potentially more efficient, method of detecting hydrothermal vent plumes within the beamwidth of the split-beam echosounder to inform ROV dive plans. Methods previously applied for locating marine gas seeps on the seafloor with split-beam echosounders can be applied to estimate the hydrothermal vent positions in this dataset and compared to the recorded ROV positions at each site. Additionally, assuming relatively stable venting and ambient conditions, the ROV position and CTD data recorded from the vehicles can be used to better understand the observed midwater acoustic backscatter signatures of the hydrothermal vent plumes.

Geometric metasurface enabling polarization independent beam splitting.

PubMed

Yoon, Gwanho; Lee, Dasol; Nam, Ki Tae; Rho, Junsuk

2018-06-21

A polarization independent holographic beam splitter that generates equal-intensity beams based on geometric metasurface is demonstrated. Although conventional geometric metasurfaces have the advantages of working over a broad frequency range and having intuitive design principles, geometric metasurfaces have the limitation that they only work for circular polarization. In this work, Fourier holography is used to overcome this limitation. A perfect overlap resulting from the origin-symmetry of the encoded image enables polarization independent operation of geometric metasurfaces. The designed metasurface beam splitter is experimentally demonstrated by using hydrogenated amorphous silicon, and the device performs consistent beam splitting regardless of incident polarizations as well as wavelengths. Our device can be applied to generate equal-intensity beams for entangled photon light sources in quantum optics, and the design approach provides a way to develop ultra-thin broadband polarization independent components for modern optics.

Broadband non-polarizing terahertz beam splitters with variable split ratio

NASA Astrophysics Data System (ADS)

Wei, Minggui; Xu, Quan; Wang, Qiu; Zhang, Xueqian; Li, Yanfeng; Gu, Jianqiang; Tian, Zhen; Zhang, Xixiang; Han, Jiaguang; Zhang, Weili

2017-08-01

Seeking effective terahertz functional devices has always aroused extensive attention. Of particular interest is the terahertz beam splitter. Here, we have proposed, designed, manufactured, and tested a broadband non-polarizing terahertz beam splitter with a variable split ratio based on an all-dielectric metasurface. The metasurface was created by patterning a dielectric surface of the N-step phase gradient and etching to a few hundred micrometers. The conversion efficiency as high as 81% under the normal incidence at 0.7 THz was achieved. Meanwhile, such a splitter works well over a broad frequency range. The split ratio of the proposed design can be continuously tuned by simply shifting the metasurface, and the angle of emergences can also be easily adjusted by choosing the step of phase gradients. The proposed design is non-polarizing, and its performance is kept under different polarizations.

An adaptive sparse deconvolution method for distinguishing the overlapping echoes of ultrasonic guided waves for pipeline crack inspection

NASA Astrophysics Data System (ADS)

Chang, Yong; Zi, Yanyang; Zhao, Jiyuan; Yang, Zhe; He, Wangpeng; Sun, Hailiang

2017-03-01

In guided wave pipeline inspection, echoes reflected from closely spaced reflectors generally overlap, meaning useful information is lost. To solve the overlapping problem, sparse deconvolution methods have been developed in the past decade. However, conventional sparse deconvolution methods have limitations in handling guided wave signals, because the input signal is directly used as the prototype of the convolution matrix, without considering the waveform change caused by the dispersion properties of the guided wave. In this paper, an adaptive sparse deconvolution (ASD) method is proposed to overcome these limitations. First, the Gaussian echo model is employed to adaptively estimate the column prototype of the convolution matrix instead of directly using the input signal as the prototype. Then, the convolution matrix is constructed upon the estimated results. Third, the split augmented Lagrangian shrinkage (SALSA) algorithm is introduced to solve the deconvolution problem with high computational efficiency. To verify the effectiveness of the proposed method, guided wave signals obtained from pipeline inspection are investigated numerically and experimentally. Compared to conventional sparse deconvolution methods, e.g. the {{l}1} -norm deconvolution method, the proposed method shows better performance in handling the echo overlap problem in the guided wave signal.

Highly coherent vacuum ultraviolet radiation at the 15th harmonic with echo-enabled harmonic generation technique

NASA Astrophysics Data System (ADS)

Hemsing, E.; Dunning, M.; Hast, C.; Raubenheimer, T. O.; Weathersby, S.; Xiang, D.

2014-07-01

X-ray free-electron lasers are enabling access to new science by producing ultrafast and intense x rays that give researchers unparalleled power and precision in examining the fundamental nature of matter. In the quest for fully coherent x rays, the echo-enabled harmonic generation technique is one of the most promising methods. In this technique, coherent radiation at the high harmonic frequencies of two seed lasers is generated from the recoherence of electron beam phase space memory. Here we report on the generation of highly coherent and stable vacuum ultraviolet radiation at the 15th harmonic of an infrared seed laser with this technique. The experiment demonstrates two distinct advantages that are intrinsic to the highly nonlinear phase space gymnastics of echo-enabled harmonic generation in a new regime, i.e., high frequency up-conversion efficiency and insensitivity to electron beam phase space imperfections. Our results allow comparison and confirmation of predictive models and scaling laws, and mark a significant step towards fully coherent x-ray free-electron lasers that will open new scientific research.

Operating Spin Echo in the Quantum Regime for an Atomic-Ensemble Quantum Memory

NASA Astrophysics Data System (ADS)

Rui, Jun; Jiang, Yan; Yang, Sheng-Jun; Zhao, Bo; Bao, Xiao-Hui; Pan, Jian-Wei

2015-09-01

Spin echo is a powerful technique to extend atomic or nuclear coherence times by overcoming the dephasing due to inhomogeneous broadenings. However, there are disputes about the feasibility of applying this technique to an ensemble-based quantum memory at the single-quanta level. In this experimental study, we find that noise due to imperfections of the rephasing pulses has both intense superradiant and weak isotropic parts. By properly arranging the beam directions and optimizing the pulse fidelities, we successfully manage to operate the spin echo technique in the quantum regime by observing nonclassical photon-photon correlations as well as the quantum behavior of retrieved photons. Our work for the first time demonstrates the feasibility of harnessing the spin echo method to extend the lifetime of ensemble-based quantum memories at the single-quanta level.

Parallel electric fields detected via conjugate electron echoes during the Echo 7 sounding rocket flight

NASA Technical Reports Server (NTRS)

Nemzek, R. J.; Winckler, J. R.

1991-01-01

Electron detectors on the Echo 7 active sounding rocket experiment measured 'conjugate echoes' resulting from artificial electron beam injections. Analysis of the drift motion of the electrons after a complete bounce leads to measurements of the magnetospheric convection electric field mapped to ionospheric altitudes. The magnetospheric field was highly variable, changing by tens of mV/m on time scales of as little as hundreds of millisec. While the smallest-scale magnetospheric field irregularities were mapped out by ionospheric conductivity, larger-scale features were enhanced by up to 50 mV/m in the ionosphere. The mismatch between magnetospheric and ionspheric convection fields indicates a violation of the equipotential field line condition. The parallel fields occurred in regions roughly 10 km across and probably supported a total potential drop of 10-100 V.

Vespertilionid bats control the width of their biosonar sound beam dynamically during prey pursuit

PubMed Central

Jakobsen, Lasse; Surlykke, Annemarie

2010-01-01

Animals using sound for communication emit directional signals, focusing most acoustic energy in one direction. Echolocating bats are listening for soft echoes from insects. Therefore, a directional biosonar sound beam greatly increases detection probability in the forward direction and decreases off-axis echoes. However, high directionality has context-specific disadvantages: at close range the detection space will be vastly reduced, making a broad beam favorable. Hence, a flexible system would be very advantageous. We investigated whether bats can dynamically change directionality of their biosonar during aerial pursuit of insects. We trained five Myotis daubentonii and one Eptesicus serotinus to capture tethered mealworms and recorded their echolocation signals with a multimicrophone array. The results show that the bats broaden the echolocation beam drastically in the terminal phase of prey pursuit. M. daubentonii increased the half-amplitude angle from approximately 40° to approximately 90° horizontally and from approximately 45° to more than 90° vertically. The increase in beam width is achieved by lowering the frequency by roughly one octave from approximately 55 kHz to approximately 27.5 kHz. The E. serotinus showed beam broadening remarkably similar to that of M. daubentonii. Our results demonstrate dynamic control of beam width in both species. Hence, we propose directionality as an explanation for the frequency decrease observed in the buzz of aerial hawking vespertilionid bats. We predict that future studies will reveal dynamic control of beam width in a broad range of acoustically communicating animals. PMID:20643943

Vespertilionid bats control the width of their biosonar sound beam dynamically during prey pursuit.

PubMed

Jakobsen, Lasse; Surlykke, Annemarie

2010-08-03

Animals using sound for communication emit directional signals, focusing most acoustic energy in one direction. Echolocating bats are listening for soft echoes from insects. Therefore, a directional biosonar sound beam greatly increases detection probability in the forward direction and decreases off-axis echoes. However, high directionality has context-specific disadvantages: at close range the detection space will be vastly reduced, making a broad beam favorable. Hence, a flexible system would be very advantageous. We investigated whether bats can dynamically change directionality of their biosonar during aerial pursuit of insects. We trained five Myotis daubentonii and one Eptesicus serotinus to capture tethered mealworms and recorded their echolocation signals with a multimicrophone array. The results show that the bats broaden the echolocation beam drastically in the terminal phase of prey pursuit. M. daubentonii increased the half-amplitude angle from approximately 40 degrees to approximately 90 degrees horizontally and from approximately 45 degrees to more than 90 degrees vertically. The increase in beam width is achieved by lowering the frequency by roughly one octave from approximately 55 kHz to approximately 27.5 kHz. The E. serotinus showed beam broadening remarkably similar to that of M. daubentonii. Our results demonstrate dynamic control of beam width in both species. Hence, we propose directionality as an explanation for the frequency decrease observed in the buzz of aerial hawking vespertilionid bats. We predict that future studies will reveal dynamic control of beam width in a broad range of acoustically communicating animals.

Laser Sounder for Global Measurement of CO2 Concentrations in the Troposphere from Space: Progress

NASA Technical Reports Server (NTRS)

Abshire, J. B.; Krainak, M.; Riris, H. J.; Sun, X.; Riris, H.; Andrews, A. E.; Collatz, J.

2004-01-01

We describe progress toward developing a laser-based technique for the remote measurement of the tropospheric CO2 concentrations from orbit. Our goal is to demonstrate a lidar technique and instrument technology that will permit measurements of the CO2 column abundance in the lower troposphere from aircraft at the few ppm level, with a capability of scaling to permit global CO2 measurements from orbit. Accurate measurements of the tropospheric CO2 mixing ratio from space are challenging due to the many potential error sources. These include possible interference from other trace gas species, the effects of temperature, clouds, aerosols & turbulence in the path, changes in surface reflectivity, and variability in dry air density caused by changes in atmospheric pressure, water vapor and topographic height. Some potential instrumental errors include frequency drifts in the transmitter, small transmission and sensitivity drifts in the instrument. High signal-to-noise ratios and measurement stability are needed for mixing ratio estimates at the few ppm level. We have been developing a laser sounder approach as a candidate for a future space mission. It utilizes multiple different laser transmitters to permit simultaneous measurement of CO2 and O2 extinction, and aerosol backscatter in the same measurement path. It directs the narrow co-aligned laser beams from the instrument's fiber lasers toward nadir, and measures the energy of the strong laser echoes reflected from the Earth's land and water surfaces. During the measurement its narrow linewidth lasers are rapidly tuned on- and off- selected CO2 line near 1572 nm and an O2 absorption line near 770 nm. The receiver measures the energies of the laser echoes from the surface and any clouds and aerosols in the path with photon counting detectors. Ratioing the on- to off-line echo pulse energies for each gas permits the column extinction and column densities of CO2 and O2 to be estimated simultaneously via the differential absorption lidar technique. For the on-line wavelengths, the side of the selected absorption lines are used, which due to pressure broadening, weights the measurements to the lower troposphere, where CO2 variations caused by surface sources and sinks are largest. Simultaneous measurements of O2 column abundance are made using an identical approach using an O2 line. The laser backscatter profiles from clouds and aerosols are measured with other lidar channels, which permits identifying measurements influenced by clouds and/or aerosol scattering in the path. For space use, our lidar would continuously measure at nadir in near polar circular orbit. Using dawn and dusk measurements made over the same region will make it possible to sample the diurnal variations in CO2 mixing ratios. A 1-m diameter telescope is used for the receiver for all wavelengths. When averaging over 50 seconds, our calculations show a SNR of approximately 1500 is achievable for each gas at each on- and off-line measurement. Measurements from such a mission can be used to generate monthly global maps of the lower tropospheric CO2 column abundance. Our calculations show global coverage with an accuracy of a few ppm with a spatial resolution of approximately 50,000 sq. km are achievable each month. We have demonstrated some key elements of the laser, detector and receiver approaches in the laboratory and with measurements over a 206 m horizontal path. These include stable measurements of CO2 line shapes in an absorption cell using a fiber laser amplifier seeded by a tunable diode laser, measurement of small amplitude changes at low optical signal levels with the PMT receiver, and comparison of the horizontal path measurements of CO2 against those from an in-situ instrument.

Modeling Statistics of Fish Patchiness and Predicting Associated Influence on Statistics of Acoustic Echoes

DTIC Science & Technology

2013-09-30

published 3-D multi-beam data. The Niwa and Anderson models were compared with 3-D multi-beam data collected by Paramo and Gerlotto. The data were...submitted, refereed] Bhatia, S., T.K. Stanton, J. Paramo , and F. Gerlotto (under revision), “Modeling statistics of fish school dimensions using 3-D

Laser Induced Breakdown Spectroscopy Based on Single Beam Splitting and Geometric Configuration for Effective Signal Enhancement

PubMed Central

Yang, Guang; Lin, Qingyu; Ding, Yu; Tian, Di; Duan, Yixiang

2015-01-01

A new laser induced breakdown spectroscopy (LIBS) based on single-beam-splitting (SBS) and proper optical geometric configuration has been initially explored in this work for effective signal enhancement. In order to improve the interaction efficiency of laser energy with the ablated material, a laser beam operated in pulse mode was divided into two streams to ablate/excite the target sample in different directions instead of the conventional one beam excitation in single pulse LIBS (SP-LIBS). In spatial configuration, the laser beam geometry plays an important role in the emission signal enhancement. Thus, an adjustable geometric configuration with variable incident angle between the two splitted laser beams was constructed for achieving maximum signal enhancement. With the optimized angles of 60° and 70° for Al and Cu atomic emission lines at 396.15 nm and 324.75 nm respectively, about 5.6- and 4.8-folds signal enhancements were achieved for aluminum alloy and copper alloy samples compared to SP-LIBS. Furthermore, the temporal analysis, in which the intensity of atomic lines in SP-LIBS decayed at least ten times faster than the SBS-LIBS, proved that the energy coupling efficiency of SBS-LIBS was significantly higher than that of SP-LIBS. PMID:25557721

Superconducting resonators as beam splitters for linear-optics quantum computation.

PubMed

Chirolli, Luca; Burkard, Guido; Kumar, Shwetank; Divincenzo, David P

2010-06-11

We propose and analyze a technique for producing a beam-splitting quantum gate between two modes of a ring-resonator superconducting cavity. The cavity has two integrated superconducting quantum interference devices (SQUIDs) that are modulated by applying an external magnetic field. The gate is accomplished by applying a radio frequency pulse to one of the SQUIDs at the difference of the two mode frequencies. Departures from perfect beam splitting only arise from corrections to the rotating wave approximation; an exact calculation gives a fidelity of >0.9992. Our construction completes the toolkit for linear-optics quantum computing in circuit quantum electrodynamics.

Modeling Statistics of Fish Patchiness and Predicting Associated Influence on Statistics of Acoustic Echoes

DTIC Science & Technology

2014-12-01

moving relative to the water in which they are immersed, reflecting the true school movement dynamics . There has also been work to implement this...Engineering Department Woods Hole Oceanographic Institution 98 Water Street, MS #11 Woods Hole, MA 02543 9. SPONSORING/MONITORING AGENCY NAME(S) AND...were measured with multi-beam sonars and quantified in terms of important aspects offish dynamics ; and predictions were made of echo statistics of a

Method and apparatus for making absolute range measurements

DOEpatents

Allison, S.W.; Cates, M.R.; Key, W.S.; Sanders, A.J.; Earl, D.D.

1999-06-22

This invention relates to a method and apparatus for making absolute distance or ranging measurements using Fresnel diffraction. The invention employs a source of electromagnetic radiation having a known wavelength or wavelength distribution, which sends a beam of electromagnetic radiation through an object which causes it to be split (hereinafter referred to as a beam splitter''), and then to a target. The beam is reflected from the target onto a screen containing an aperture spaced a known distance from the beam splitter. The aperture is sized so as to produce a Fresnel diffraction pattern. A portion of the beam travels through the aperture to a detector, spaced a known distance from the screen. The detector detects the central intensity of the beam. The distance from the object which causes the beam to be split to the target can then be calculated based upon the known wavelength, aperture radius, beam intensity, and distance from the detector to the screen. Several apparatus embodiments are disclosed for practicing the method embodiments of the present invention. 9 figs.

Bathymetry of Clear Creek Reservoir, Chaffee County, Colorado, 2016

USGS Publications Warehouse

Kohn, Michael S.; Kinzel, Paul J.; Mohrmann, Jacob S.

2017-03-06

To better characterize the water supply capacity of Clear Creek Reservoir, Chaffee County, Colorado, the U.S. Geological Survey, in cooperation with the Pueblo Board of Water Works and Colorado Mountain College, carried out a bathymetry survey of Clear Creek Reservoir. A bathymetry map of the reservoir is presented here with the elevation-surface area and the elevation-volume relations. The bathymetry survey was carried out June 6–9, 2016, using a man-operated boat-mounted, multibeam echo sounder integrated with a Global Positioning System and a terrestrial survey using real-time kinematic Global Navigation Satellite Systems. The two collected datasets were merged and imported into geographic information system software. The equipment and methods used in this study allowed water-resource managers to maintain typical reservoir operations, eliminating the need to empty the reservoir to carry out the survey.

Seafloor geology and benthic habitats, San Pedro Shelf, southern California

USGS Publications Warehouse

Wong, Florence L.; Dartnell, Peter; Edwards, Brian D.; Phillips, Eleyne L.

2012-01-01

Seafloor samples, videography, still photography, and real-time descriptions of geologic and biologic constituents at or near the seafloor of the San Pedro Shelf, southern California, advance the study of natural and man-made processes on this coastal area off the metropolitan Los Angeles area. Multibeam echo-sounder data collected by the U.S. Geological Survey in 1998 and 1999 guided sampling and camera work in 2004 resulting in a new seafloor character map that shows possible benthic habitats in much higher resolution (4- and 16-m pixels) than previously available. The seafloor is characterized by primarily muddy sand and sand with outcrops of Miocene and Pliocene bedrock along the Palos Verdes Fault Zone. Observed benthic populations indicate low abiotic complexity, low biotic complexity, and low biotic coverage. The data are provided for use in geographic information systems (GIS).

A novel and practical approach for determination of the acoustic nonlinearity parameter using a pulse-echo method

NASA Astrophysics Data System (ADS)

Jeong, Hyunjo; Zhang, Shuzeng; Barnard, Dan; Li, Xiongbing

2016-02-01

Measurements of the acoustic nonlinearity parameter β are frequently made for early detection of damage in various materials. The practical implementation of the measurement technique has been limited to the through-transmission setup for determining the nonlinearity parameter of the second harmonic wave. In this work, a feasibility study is performed to assess the possibility of using pulse-echo methods in determining the nonlinearity parameter β of solids with a stress-free boundary. The multi-Gaussian beam model is developed based on the quasilinear theory of the KZK equation. Simulation results and discussion are presented for the reflected beam fields of the fundamental and second harmonic waves, the uncorrected β behavior and the properties of total correction that incorporate reflection, attenuation and diffraction effects.

Experimental Demonstration of a Highly Efficient Fan-out Polarization Grating

PubMed Central

Wan, Chenhao; Chen, Jian; Tang, Xiahui; Zhan, Qiwen

2016-01-01

Highly efficient fan-out elements are crucial in coherent beam combining architectures especially in coupled laser resonators where the beam passes through the fan-out element twice per round trip. Although the theoretical efficiency is usually less than 86%, the Dammann gratings are ubiquitously utilized in a variety of types of coherent beam combining systems due to the facile design and fabrication. In the current paper, we experimentally demonstrate a highly efficient fan-out polarization grating. It is the first time to our knowledge that all the three space-variant parameters of a polarization grating are simultaneously optimized to achieve the function of multi-beam splitting. Besides the high fan-out efficiency, the ability to control the polarization states of individual split beams is another advantage of this polarization grating. The novel polarization grating is promising to find applications in laser beam combining systems. PMID:28008972

"Extracting Sun-Beams out of Cucumbers": The Retreat from Practice in Reconceptualized Curriculum Studies.

ERIC Educational Resources Information Center

Wraga, William G.

1999-01-01

Documents and explains three manifestations of the split between theory and practice in reconceptualized curriculum studies. Evaluates this split against the educational theory of John Dewey, considers the obligations of professional schools and land-grant universities, and suggests implications of the curriculum theory-practice split for…

Over-under double-pass interferometer

NASA Technical Reports Server (NTRS)

Schindler, R. A. (Inventor)

1977-01-01

An over-under double pass interferometer in which the beamsplitter area and thickness can be reduced to conform only with optical flatness considerations was achieved by offsetting the optical center line of one cat's-eye retroreflector relative to the optical center line of the other in order that one split beam be folded into a plane distinct from the other folded split beam. The beamsplitter is made transparent in one area for a first folded beam to be passed to a mirror for doubling back and is made totally reflective in another area for the second folded beam to be reflected to a mirror for doubling back. The two beams thus doubled back are combined in the central, beamsplitting area of the beamsplitting and passed to a detector. This makes the beamsplitter insensitive to minimum thickness requirements and selection of material.

Split-field pupil plane determination apparatus

DOEpatents

Salmon, Joseph T.

1996-01-01

A split-field pupil plane determination apparatus (10) having a wedge assembly (16) with a first glass wedge (18) and a second glass wedge (20) positioned to divide a laser beam (12) into a first laser beam half (22) and a second laser beam half (24) which diverge away from the wedge assembly (16). A wire mask (26) is positioned immediately after the wedge assembly (16) in the path of the laser beam halves (22, 24) such that a shadow thereof is cast as a first shadow half (30) and a second shadow half (32) at the input to a relay telescope (14). The relay telescope (14) causes the laser beam halves (22, 24) to converge such that the first shadow half (30) of the wire mask (26) is aligned with the second shadow half (32) at any subsequent pupil plane (34).

Thermal Stability of a 4 Meter Primary Reflector for the Scanning Microwave Limb Sounder

NASA Technical Reports Server (NTRS)

Cofield, Richard E.; Kasl, Eldon P.

2011-01-01

The Scanning Microwave Limb Sounder (SMLS) is a space-borne heterodyne radiometer which will measure pressure, temperature and atmospheric constituents from thermal emission in [180,680] GHz. SMLS, planned for the NRC Decadal Survey's Global Atmospheric Composition Mission, uses a novel toric Cassegrain antenna to perform both elevation and azimuth scanning. This provides better horizontal and temporal resolution and coverage than were possible with elevation-only scanning in the two previous MLS satellite instruments. SMLS is diffraction-limited in the vertical plane but highly astigmatic in the horizontal (beam aspect ratio approx. 1:20). Nadir symmetry ensures that beam shape is nearly invariant over plus or minus 65 deg azimuth. A low-noise receiver FOV is swept over the reflector system by a small azimuth-scanning mirror. We describe the fabrication and thermal-stability test of a composite demonstration primary reflector, having full 4m height and 1/3 the width planned for flight. Using finite-element models of reflectors and structure, we evaluate thermal deformations and optical performance for 4 orbital environments and isothermal soak. We compare deformations with photogrammetric measurements made during soak tests in a chamber. The test temperature range exceeds predicted orbital ranges by large factors, implying in-orbit thermal stability of 0.21 micron rms (root mean square)/C, which meets SMLS requirements.

Project Echo: Antenna Steering System

NASA Technical Reports Server (NTRS)

Klahn, R.; Norton, J. A.; Githens, J. A.

1961-01-01

The Project Echo communications experiment employed large, steerable,transmitting and receiving antennas at the ground terminals. It was necessary that these highly directional antennas be continuously and accurately pointed at the passing satellite. This paper describes a new type of special purpose data converter for directing narrow-beam communication antennas on the basis of predicted information. The system is capable of converting digital input data into real-time analog voltage commands with a dynamic accuracy of +/- 0.05 degree, which meets the requirements of the present antennas.

Combined action of corrugation and Weibel instabilities from electron-beam interaction with laser-irradiated plasma

NASA Astrophysics Data System (ADS)

Bai, Yafeng; Tian, Ye; Zhang, Zhijun; Cao, Lihua; Liu, Jiansheng

2018-03-01

The combined action of corrugation and Weibel instabilities was experimentally observed in the interaction between energetic electrons and a laser-irradiated insulated target. The energetic electron beam, driven by an ultrashort laser pulse, splits into filaments with a diameter of ˜10 μm while traversing an insulated target, owing to the corrugation instability. The filaments continued to split into thinner filaments owing to the Weibel instability if a preplasma was induced by a heating beam on the rear side of the target. When the time delay between the heating beam and electron beam was larger than 1 ps, a merging of the current filaments was observed. The characteristic filamentary structures disappeared when the time delay between the two beams was larger than 3 ps. A simplified model was developed to analyze this process; the obtained results were in good agreement with the experiment. Two-dimensional particle-in-cell simulations supported our analysis and reproduced the filamentation of the electron beam inside the plasma.

Effects of a modulated vortex structure on the diffraction dynamics of ring Airy Gaussian beams.

PubMed

Huang, Xianwei; Shi, Xiaohui; Deng, Zhixiang; Bai, Yanfeng; Fu, Xiquan

2017-09-01

The evolution of the ring Airy Gaussian beams with a modulated vortex in free space is numerically investigated. Compared with the unmodulated vortex, the unique property is that the beam spots first break up, and then gather. The evolution of the beams is influenced by the parameters of the vortex modulation, and the splitting phenomenon gets enhanced with multiple rings becoming light spots if the modulation depth increases. The symmetric branch pattern of the beam spots gets changed when the number of phase folds increases, and the initial modulation phase only impacts the angle of the beam spots. Moreover, a large distribution factor correlates to a hollow Gaussian vortex shape and weakens the splitting and gathering trend. By changing the initial parameters of the vortex modulation and the distribution factor, the peak intensity is greatly affected. In addition, the energy flow and the angular momentum are elucidated with the beam evolution features being confirmed.

Environmental DNA as a ‘Snapshot’ of Fish Distribution: A Case Study of Japanese Jack Mackerel in Maizuru Bay, Sea of Japan

PubMed Central

Takahashi, Kohji; Sawada, Hideki; Murakami, Hiroaki; Tsuji, Satsuki; Hashizume, Hiroki; Kubonaga, Shou; Horiuchi, Tomoya; Hongo, Masamichi; Nishida, Jo; Okugawa, Yuta; Fujiwara, Ayaka; Fukuda, Miho; Hidaka, Shunsuke; Suzuki, Keita W.; Miya, Masaki; Araki, Hitoshi; Yamanaka, Hiroki; Maruyama, Atsushi; Miyashita, Kazushi; Masuda, Reiji; Minamoto, Toshifumi; Kondoh, Michio

2016-01-01

Recent studies in streams and ponds have demonstrated that the distribution and biomass of aquatic organisms can be estimated by detection and quantification of environmental DNA (eDNA). In more open systems such as seas, it is not evident whether eDNA can represent the distribution and biomass of aquatic organisms because various environmental factors (e.g., water flow) are expected to affect eDNA distribution and concentration. To test the relationships between the distribution of fish and eDNA, we conducted a grid survey in Maizuru Bay, Sea of Japan, and sampled surface and bottom waters while monitoring biomass of the Japanese jack mackerel (Trachurus japonicus) using echo sounder technology. A linear model showed a high R2 value (0.665) without outlier data points, and the association between estimated eDNA concentrations from the surface water samples and echo intensity was significantly positive, suggesting that the estimated spatial variation in eDNA concentration can reflect the local biomass of the jack mackerel. We also found that a best-fit model included echo intensity obtained within 10–150 m from water sampling sites, indicating that the estimated eDNA concentration most likely reflects fish biomass within 150 m in the bay. Although eDNA from a wholesale fish market partially affected eDNA concentration, we conclude that eDNA generally provides a ‘snapshot’ of fish distribution and biomass in a large area. Further studies in which dynamics of eDNA under field conditions (e.g., patterns of release, degradation, and diffusion of eDNA) are taken into account will provide a better estimate of fish distribution and biomass based on eDNA. PMID:26933889

Curved Surface Beam Splitter

NASA Technical Reports Server (NTRS)

Minott, P. O.

1983-01-01

Beam splitter with curved entrance and exit surfaces introduces less chromatic aberration and Seidel aberrations in some optical systems than traditional plate or block beam splitters. Spherical-surface beam splitter is used in Schmidt-type mirror objective to split converging image-forming beam so two images are formed. Small aberrations introduced are corrected by compensator plate located at or near aperture stop.

Holographic memory using beam steering

NASA Technical Reports Server (NTRS)

Chao, Tien-Hsin (Inventor); Hanan, Jay C. (Inventor); Reyes, George F. (Inventor); Zhou, Hanying (Inventor)

2007-01-01

A method, apparatus, and system provide the ability for storing holograms at high speed. A single laser diode emits a collimated laser beam to both write to and read from a photorefractice crystal. One or more liquid crystal beam steering spatial light modulators (BSSLMs) steer a reference beam, split from the collimated laser beam, at high speed to the photorefractive crystal.

Atom beams split by gentle persuasion

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

Pool, R.

1994-02-25

Two different research teams have taken a big step toward atom interferometry. They have succeeded in splitting atomic beams by using atoms in spin states that neither absorb nor reemit laser light. By proper adjustment of experimental conditions, atoms are changed from one spin state to another, without passing through the intermediary excited state. The atoms in essence absorb momentum from the laser photons, without absorption or emission of photons. The change in momentum deflects atoms in the proper spin state.

Raman-Ramsey multizone spectroscopy in a pure rubidium vapor cell

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

Failache, H.; Lenci, L.; Lezama, A.

2010-02-15

In view of application to a miniaturized spectroscopy system, we consider an optical setup that splits a laser beam into several parallel narrow light sheets allowing an effective beam expansion and consequently longer atom-light interaction times. We analyze the multizone coherent population trapping (MZCPT) spectroscopy of alkali-metal-vapor atoms, without buffer gas, in the presence of a split light beam. We show that the MZCPT signal is largely insensitive to intensity broadening. Experimentally observed spectra are in qualitative agreement with the predictions of a simplified model that describes each spectrum as an integral over the atomic velocity distribution of Ramsey multizonemore » spectra.« less

Ponderomotive lower hybrid wave growth in electric fields associated with electron beam injection and transverse ion acceleration

NASA Astrophysics Data System (ADS)

Bale, S. D.; Kellogg, P. J.; Erickson, K. N.; Monson, S. J.; Arnoldy, R. L.

During electron beam injection, the Echo 7 rocket experiment observed large bursts of transversely accelerated ions. These ions seem to have been energized in the region of the beam or the payload return current. Electric field waveforms (<= 30 kHz) during gun operation show both low frequency fluctuations and broad band power. An analysis of the waveforms shows nonlinear mode coupling between waves near the ion cyclotron frequency and waves above the lower hybrid frequency.

Thermal Stability of a 4 Meter Primary Reflector for the Scanning Microwave Limb Sounder

NASA Technical Reports Server (NTRS)

Cofield, Richard; Kasl, Eldon P.

2010-01-01

We describe the fabrication and thermal-stability analysis and test of a composite demonstration model of the Scanning Microwave Limb Sounder (SMLS) primary reflector, having full 4m height and 1/3 the width planned for flight. SMLS is a space-borne heterodyne radiometer which will measure pressure, temperature and atmospheric constituents from thermal emission between 180 and 660 GHz. Current MLS instruments in low Earth orbit scan pencil-beam antennas (sized to resolve about one scale height) vertically over the atmospheric limb. SMLS, planned for the Global Atmospheric Composition Mission of the NRC Decadal Survey, adds azimuthal scanning for better horizontal and temporal resolution and coverage than typical orbit spacing provides. SMLS combines the wide scan range of the parabolic torus with unblocked offset Cassegrain optics. The resulting system is diffraction-limited in the vertical plane but highly astigmatic in the horizontal, having a beam aspect ratio [tilde operator]1:20. Symmetry about the nadir axis ensures that beam shape is nearly invariant over +/-65(white bullet) azimuth. The a feeds a low-noise SIS receiver whose FOV is swept over the reflector system by a small scanning mirror. Using finiteelement models of antenna reflectors and structure, we evaluate thermal deformations and the resulting optical performance for 4 orbital environments and isothermal soak. We compare deformations with photogrammetric measurements made during wide-range (ambient+[-97,+75](white bullet) C) thermal soak tests of the primary in a chamber. This range exceeds predicted orbital soak ranges by large factors, implying in-orbit thermal stability of 0.21(mu)m rms/(white bullet)C, which meets SMLS requirements.

Coherent hybrid electromagnetic field imaging

DOEpatents

Cooke, Bradly J [Jemez Springs, NM; Guenther, David C [Los Alamos, NM

2008-08-26

An apparatus and corresponding method for coherent hybrid electromagnetic field imaging of a target, where an energy source is used to generate a propagating electromagnetic beam, an electromagnetic beam splitting means to split the beam into two or more coherently matched beams of about equal amplitude, and where the spatial and temporal self-coherence between each two or more coherently matched beams is preserved. Two or more differential modulation means are employed to modulate each two or more coherently matched beams with a time-varying polarization, frequency, phase, and amplitude signal. An electromagnetic beam combining means is used to coherently combine said two or more coherently matched beams into a coherent electromagnetic beam. One or more electromagnetic beam controlling means are used for collimating, guiding, or focusing the coherent electromagnetic beam. One or more apertures are used for transmitting and receiving the coherent electromagnetic beam to and from the target. A receiver is used that is capable of square-law detection of the coherent electromagnetic beam. A waveform generator is used that is capable of generation and control of time-varying polarization, frequency, phase, or amplitude modulation waveforms and sequences. A means of synchronizing time varying waveform is used between the energy source and the receiver. Finally, a means of displaying the images created by the interaction of the coherent electromagnetic beam with target is employed.

Hybrid quantitative MRI using chemical shift displacement and recovery-based simultaneous water and lipid imaging: A preliminary study.

PubMed

Ohno, Naoki; Miyati, Tosiaki; Suzuki, Shuto; Kan, Hirohito; Aoki, Toshitaka; Nakamura, Yoshitaka; Hiramatsu, Yuki; Kobayashi, Satoshi; Gabata, Toshifumi

2018-07-01

To suppress olefinic signals and enable simultaneous and quantitative estimation of multiple functional parameters associated with water and lipid, we investigated a modified method using chemical shift displacement and recovery-based separation of lipid tissue (SPLIT) involving acquisitions with different inversion times (TIs), echo times (TEs), and b-values. Single-shot diffusion echo-planar imaging (SSD-EPI) with multiple b-values (0-3000 s/mm 2 ) was performed without fat suppression to separate water and lipid images using the chemical shift displacement of lipid signals in the phase-encoding direction. An inversion pulse (TI = 292 ms) was applied to SSD-EPI to remove olefinic signals. Consecutively, SSD-EPI (b = 0 s/mm 2 ) was performed with TI = 0 ms and TE = 31.8 ms for T 1 and T 2 measurements, respectively. Under these conditions, transverse water and lipid images at the maximum diameter of the right calf were obtained in six healthy subjects. T 1 , T 2 , and the apparent diffusion coefficients (ADC) were then calculated for the tibialis anterior (TA), gastrocnemius (GM), and soleus (SL) muscles, tibialis bone marrow (TB), and subcutaneous fat (SF). Perfusion-related (D*) and restricted diffusion coefficients (D) were calculated for the muscles. Lastly, the lipid fractions (LF) of the muscles were determined after T 1 and T 2 corrections. The modified SPLIT method facilitated sufficient separation of water and lipid images of the calf, and the inversion pulse with TI of 292 ms effectively suppressed olefinic signals. All quantitative parameters obtained with the modified SPLIT method were found to be in general agreement with those previously reported in the literature. The modified SPLIT technique enabled sufficient suppression of olefinic signals and simultaneous acquisition of quantitative parameters including diffusion, perfusion, T 1 and T 2 relaxation times, and LF. Copyright © 2018. Published by Elsevier Inc.

Lightning propagation and flash density in squall lines as determined with radar

NASA Technical Reports Server (NTRS)

Mazur, V.; Rust, W. D.

1983-01-01

Lightning echo rise times and range-time variations due to discharge propagation are determined using S and L band radars, and the evolution of precipitation reflectivity and the associated lightning activity in squall lines is investigated using VHF and L band radars. The rise time of radar echoes can be explained by ionized channel propagation through the radar beams. Speeds of at least 250,000 m/s are found from measurements of the radial velocity of streamer propagation along the antenna beam. The range-time variations in lightning echoes indicate that either new ionization occurs as streamers develop into different parts of the cloud, channel delay occurs during which adequate ionization exists for radar detection, or continuing current occurs. Determinations of the lightning flash density for a squall line in the U.S. show that the maximum lightning density tends to be near the leading edge of the precipitation cores in developing cells. Long discharges are produced as a cell in the squall line develops and the total lightning density increases, although short discharges predominate. As the cell dissipates, short flashes diminish or cease and the long flashes dominate the lightning activity.

Propagation dynamics of super-Gaussian beams in fractional Schrödinger equation: from linear to nonlinear regimes.

PubMed

Zhang, Lifu; Li, Chuxin; Zhong, Haizhe; Xu, Changwen; Lei, Dajun; Li, Ying; Fan, Dianyuan

2016-06-27

We have investigated the propagation dynamics of super-Gaussian optical beams in fractional Schrödinger equation. We have identified the difference between the propagation dynamics of super-Gaussian beams and that of Gaussian beams. We show that, the linear propagation dynamics of the super-Gaussian beams with order m > 1 undergo an initial compression phase before they split into two sub-beams. The sub-beams with saddle shape separate each other and their interval increases linearly with propagation distance. In the nonlinear regime, the super-Gaussian beams evolve to become a single soliton, breathing soliton or soliton pair depending on the order of super-Gaussian beams, nonlinearity, as well as the Lévy index. In two dimensions, the linear evolution of super-Gaussian beams is similar to that for one dimension case, but the initial compression of the input super-Gaussian beams and the diffraction of the splitting beams are much stronger than that for one dimension case. While the nonlinear propagation of the super-Gaussian beams becomes much more unstable compared with that for the case of one dimension. Our results show the nonlinear effects can be tuned by varying the Lévy index in the fractional Schrödinger equation for a fixed input power.

Observation of acoustic valley vortex states and valley-chirality locked beam splitting

NASA Astrophysics Data System (ADS)

Ye, Liping; Qiu, Chunyin; Lu, Jiuyang; Wen, Xinhua; Shen, Yuanyuan; Ke, Manzhu; Zhang, Fan; Liu, Zhengyou

2017-05-01

We report an experimental observation of the classical version of valley polarized states in a two-dimensional hexagonal sonic crystal. The acoustic valley states, which carry specific linear momenta and orbital angular momenta, were selectively excited by external Gaussian beams and conveniently confirmed by the pressure distribution outside the crystal, according to the criterion of momentum conservation. The vortex nature of such intriguing bulk crystal states was directly characterized by scanning the phase profile inside the crystal. In addition, we observed a peculiar beam-splitting phenomenon, in which the separated beams are constructed by different valleys and locked to the opposite vortex chirality. The exceptional sound transport, encoded with valley-chirality locked information, may serve as the basis of designing conceptually interesting acoustic devices with unconventional functions.

Creation of diffraction-limited non-Airy multifocal arrays using a spatially shifted vortex beam

NASA Astrophysics Data System (ADS)

Lin, Han; Gu, Min

2013-02-01

Diffraction-limited non-Airy multifocal arrays are created by focusing a phase-modulated vortex beam through a high numerical-aperture objective. The modulated phase at the back aperture of the objective resulting from the superposition of two concentric phase-modulated vortex beams allows for the generation of a multifocal array of cylindrically polarized non-Airy patterns. Furthermore, we shift the spatial positions of the phase vortices to manipulate the intensity distribution at each focal spot, leading to the creation of a multifocal array of split-ring patterns. Our method is experimentally validated by generating the predicted phase modulation through a spatial light modulator. Consequently, the spatially shifted circularly polarized vortex beam adopted in a dynamic laser direct writing system facilitates the fabrication of a split-ring microstructure array in a polymer material by a single exposure of a femtosecond laser beam.

Aura Microwave Limb Sounder Observations of Dynamics and Transport During the Record-Breaking 2009 Arctic Stratospheric Major Warming

NASA Technical Reports Server (NTRS)

Manney, Gloria L.; Schwartz, Michael J.; Krueger, Kirstin; Santee, Michelle L.; Pawson, Steven; Lee, Jae N.; Daffer, William H.; Fuller, Ryan A.; Livesey, Nathaniel J.

2009-01-01

A major stratospheric sudden warming (SSW) in January 2009 was the strongest and most prolonged on record. Aura Microwave Limb Sounder (MLS) observations are used to provide an overview of dynamics and transport during the 2009 SSW, and to compare with the intense, long-lasting SSW in January 2006. The Arctic polar vortex split during the 2009 SSW, whereas the 2006 SSW was a vortex displacement event. Winds reversed to easterly more rapidly and reverted to westerly more slowly in 2009 than in 2006. More mixing of trace gases out of the vortex during the decay of the vortex fragments, and less before the fulfillment of major SSW criteria, was seen in 2009 than in 2006; persistent well-defined fragments of vortex and anticyclone air were more prevalent in 2009. The 2009 SSW had a more profound impact on the lower stratosphere than any previously observed SSW, with no significant recovery of the vortex in that region. The stratopause breakdown and subsequent reformation at very high altitude, accompanied by enhanced descent into a rapidly strengthening upper stratospheric vortex, were similar in 2009 and 2006. Many differences between 2006 and 2009 appear to be related to the different character of the SSWs in the two years.

Angularly symmetric splitting of a light beam upon reflection and refraction at an air-dielectric plane boundary: reply.

PubMed

Azzam, R M A

2016-05-01

The simplified explicit expressions derived by Andersen [J. Opt. Soc. Am. A33, 984 (2016)JOAOD60740-323210.1364/JOSAA.32.000984], that relate to angularly symmetric beam splitting by reflection and refraction at an air-dielectric interface recently described by Azzam [J. Opt. Soc. Am. A32, 2436 (2015)JOAOD60740-323210.1364/JOSAA.32.002436], are welcome. A few additional remarks are also included in my reply to Andersen's comment.

Radar antenna pointing for optimized signal to noise ratio.

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

Doerry, Armin Walter; Marquette, Brandeis

2013-01-01

The Signal-to-Noise Ratio (SNR) of a radar echo signal will vary across a range swath, due to spherical wavefront spreading, atmospheric attenuation, and antenna beam illumination. The antenna beam illumination will depend on antenna pointing. Calculations of geometry are complicated by the curved earth, and atmospheric refraction. This report investigates optimizing antenna pointing to maximize the minimum SNR across the range swath.

Modeling and Analysis of Integrated Bathymetric and Geodetic Data for Inventory Surveys of Mining Water Reservoirs

NASA Astrophysics Data System (ADS)

Ochałek, Agnieszka; Lipecki, Tomasz; Jaśkowski, Wojciech; Jabłoński, Mateusz

2018-03-01

The significant part of the hydrography is bathymetry, which is the empirical part of it. Bathymetry is the study of underwater depth of waterways and reservoirs, and graphic presentation of measured data in form of bathymetric maps, cross-sections and three-dimensional bottom models. The bathymetric measurements are based on using Global Positioning System and devices for hydrographic measurements - an echo sounder and a side sonar scanner. In this research authors focused on introducing the case of obtaining and processing the bathymetrical data, building numerical bottom models of two post-mining reclaimed water reservoirs: Dwudniaki Lake in Wierzchosławice and flooded quarry in Zabierzów. The report includes also analysing data from still operating mining water reservoirs located in Poland to depict how bathymetry can be used in mining industry. The significant issue is an integration of bathymetrical data and geodetic data from tachymetry, terrestrial laser scanning measurements.

Advances in Inner Magnetosphere Passive and Active Wave Research

NASA Technical Reports Server (NTRS)

Green, James L.; Fung, Shing F.

2004-01-01

This review identifies a number of the principal research advancements that have occurred over the last five years in the study of electromagnetic (EM) waves in the Earth's inner magnetosphere. The observations used in this study are from the plasma wave instruments and radio sounders on Cluster, IMAGE, Geotail, Wind, Polar, Interball, and others. The data from passive plasma wave instruments have led to a number of advances such as: determining the origin and importance of whistler mode waves in the plasmasphere, discovery of the source of kilometric continuum radiation, mapping AKR source regions with "pinpoint" accuracy, and correlating the AKR source location with dipole tilt angle. Active magnetospheric wave experiments have shown that long range ducted and direct echoes can be used to obtain the density distribution of electrons in the polar cap and along plasmaspheric field lines, providing key information on plasmaspheric filling rates and polar cap outflows.

Estimating sub-surface dispersed oil concentration using acoustic backscatter response.

PubMed

Fuller, Christopher B; Bonner, James S; Islam, Mohammad S; Page, Cheryl; Ojo, Temitope; Kirkey, William

2013-05-15

The recent Deepwater Horizon disaster resulted in a dispersed oil plume at an approximate depth of 1000 m. Several methods were used to characterize this plume with respect to concentration and spatial extent including surface supported sampling and autonomous underwater vehicles with in situ instrument payloads. Additionally, echo sounders were used to track the plume location, demonstrating the potential for remote detection using acoustic backscatter (ABS). This study evaluated use of an Acoustic Doppler Current Profiler (ADCP) to quantitatively detect oil-droplet suspensions from the ABS response in a controlled laboratory setting. Results from this study showed log-linear ABS responses to oil-droplet volume concentration. However, the inability to reproduce ABS response factors suggests the difficultly in developing meaningful calibration factors for quantitative field analysis. Evaluation of theoretical ABS intensity derived from the particle size distribution provided insight regarding method sensitivity in the presence of interfering ambient particles. Copyright © 2013 Elsevier Ltd. All rights reserved.

Investigation of transverse oscillation method.

PubMed

Udesen, Jesper; Jensen, Jørgen Arendt

2006-05-01

Conventional ultrasound scanners can display only the axial component of the blood velocity vector, which is a significant limitation when vessels nearly parallel to the skin surface are scanned. The transverse oscillation (TO) method overcomes this limitation by introducing a TO and an axial oscillation in the pulse echo field. The theory behind the creation of the double oscillation pulse echo field is explained as well as the theory behind the estimation of the vector velocity. A parameter study of the method is performed, using the ultrasound simulation program Field II. A virtual linear-array transducer with center frequency 7 MHz and 128 active elements is created, and a virtual blood vessel of radius 6.4 mm is simulated. The performance of the TO method is found around an initial point in the parameter space. The parameters varied are: flow angle, transmit focus depth, receive apodization, pulse length, transverse wave length, number of emissions, signal-to-noise ratio (SNR), and type of echo-canceling filter used. Using an experimental scanner, the performance of the TO method is evaluated. An experimental flowrig is used to create laminar parabolic flow in a blood mimicking fluid, and the fluid is scanned under different flow-to-beam angles. The relative standard deviation on the transverse velocity estimate is found to be less than 10% for all angles between 50 degrees and 90 degrees. Furthermore, the TO method is evaluated in the flowrig using pulsatile flow, which resembles the flow in the femoral artery. The estimated volume flow as a function of time is compared to the volume flow derived from a conventional axial method at a flow-to-beam angle of 60 degrees. It is found that the method is highly sensitive to the angle between the flow and the beam direction. Also, the choice of echo canceling filter affects the performance significantly.

Method and apparatus for making absolute range measurements

DOEpatents

Allison, Stephen W.; Cates, Michael R.; Key, William S.; Sanders, Alvin J.; Earl, Dennis D.

1999-01-01

This invention relates to a method and apparatus for making absolute distance or ranging measurements using Fresnel diffraction. The invention employs a source of electromagnetic radiation having a known wavelength or wavelength distribution, which sends a beam of electromagnetic radiation through an object which causes it to be split (hereinafter referred to as a "beamsplitter"), and then to a target. The beam is reflected from the target onto a screen containing an aperture spaced a known distance from the beamsplitter. The aperture is sized so as to produce a Fresnel diffraction pattern. A portion of the beam travels through the aperture to a detector, spaced a known distance from the screen. The detector detects the central intensity of the beam. The distance from the object which causes the beam to be split to the target can then be calculated based upon the known wavelength, aperture radius, beam intensity, and distance from the detector to the screen. Several apparatus embodiments are disclosed for practicing the method embodiments of the present invention.

Controlling abruptly autofocusing vortex beams to mitigate crosstalk and vortex splitting in free-space optical communication.

PubMed

Yan, Xu; Guo, Lixin; Cheng, Mingjian; Li, Jiangting

2018-05-14

Orbital angular momentum (OAM) mode crosstalk induced by atmospheric turbulence is a challenging phenomenon commonly occurring in OAM-based free-space optical (FSO) communication. Recent advances have facilitated new practicable methods using abruptly autofocusing light beams for weakening the turbulence effect on the FSO link. In this work, we show that a circular phase-locked Airy vortex beam array (AVBA) with sufficient elements has the inherent ability to form an abruptly autofocusing light beam carrying OAM, and its focusing properties can be controlled on demand by adjusting the topological charge values and locations of these vortices embedded in the array elements. The performance of a tailored Airy vortex beam array (TAVBA) through atmospheric turbulence is numerically studied. In a comparison with the ring Airy vortex beam (RAVB), the results indicate that TAVBA can be a superior light source for effectively reducing the intermodal crosstalk and vortex splitting, thus leading to improvement in the FSO system performance.

Bathymetry and Sediment-Storage Capacity Change in Three Reservoirs on the Lower Susquehanna River, 1996-2008

USGS Publications Warehouse

Langland, Michael J.

2009-01-01

The Susquehanna River transports a substantial amount of the sediment and nutrient load to the Chesapeake Bay. Upstream of the bay, three large dams and their associated reservoirs trap a large amount of the transported sediment and associated nutrients. During the fall of 2008, the U.S. Geological Survey in cooperation with the Pennsylvania Department of Environmental Protection completed bathymetric surveys of three reservoirs on the lower Susquehanna River to provide an estimate of the remaining sediment-storage capacity. Previous studies indicated the upper two reservoirs were in equilibrium with long-term sediment storage; only the most downstream reservoir retained capacity to trap sediments. A differential global positioning system (DGPS) instrument was used to provide the corresponding coordinate position. Bathymetry data were collected using a single beam 210 kHz (kilohertz) echo sounder at pre-defined transects that matched previous surveys. Final horizontal (X and Y) and vertical (Z) coordinates of the geographic positions and depth to bottom were used to create bathymetric maps of the reservoirs. Results indicated that from 1996 to 2008 about 14,700,000 tons of sediment were deposited in the three reservoirs with the majority (12,000,000 tons) being deposited in Conowingo Reservoir. Approximately 20,000 acre-feet or 30,000,000 tons of remaining storage capacity is available in Conowingo Reservoir. At current transport (3,000,000 tons per year) and deposition (2,000,000 tons per year) rates and with no occurrence of major scour events due to floods, the remaining capacity may be filled in 15 to 20 years. Once the remaining sediment-storage capacity in the reservoirs is filled, sediment and associated phosphorus loads entering the Chesapeake Bay are expected to increase.

A giant mass failure in the northern flank of the Kueishantao Island off northeastern Taiwan: debris avalanches and related structures in the offshore downslope

NASA Astrophysics Data System (ADS)

Huang, P. C.; Hsu, S. K.; Tsai, C. H.; Chen, S. C.

2016-12-01

Based on the ignimbrite layers, previous studies have shown that Kueishantao volcanic island has probably erupted four times in 7000 years. Strong smell of sulfur can easily detect at east of the island with some plumes from the seabed. In May 2016, an earthquake with magnitude 5 occurred to northeast of the island which has triggered small collapse events in the eastern subaerial part. Recent geophysical surveys have also revealed the distribution of submarine debris avalanches in the north, south and east part off Kueishantao volcanic island. With high-resolution swath bathymetric data, we can observe some debris avalanches distributed with hummocky relief around the island. In this study, we present the marine geophysical data in order to have better understanding of the landslide mechanism from the offshore data of the Kueishantao island, especially with the multi-beam bathymetric data, acoustic backscatter analysis, subbottom profile, sidescan sonar and 3.5kHz echo-sounder. At the north of the island, large-scale debris avalanches extend around 4 km northward with the several blocks height up to more than twenty meters; and, the offshore area of deposit is about 5 km2 of hummocky topography distribution. The scale of debris avalanches may be related to the horseshoe scar of subaerial flank and also submarine flank collapsed events. Nevertheless, to identify the landslide history, we need to analyze the related core data in the future. By analyzing the high-resolution geophysical data, we will discuss the possible mechanism or factors that trigger subaerial flank collapse events and also the transportation of the debris avalanches to the submarine basin. The large-scale collapse events may produce tsunamis and directly affect the coast of northeastern Taiwan.

Optical distance measurement device and method thereof

DOEpatents

Bowers, Mark W.

2003-05-27

A system and method of efficiently obtaining distance measurements of a target. A modulated optical beam may be used to determine the distance to the target. A first beam splitter may be used to split the optical beam and a second beam splitter may be used to recombine a reference beam with a return ranging beam. An optical mixing detector may be used in a receiver to efficiently detect distance measurement information.

Nanophotonic photon echo memory based on rare-earth-doped crystals

NASA Astrophysics Data System (ADS)

Zhong, Tian; Kindem, Jonathan; Miyazono, Evan; Faraon, Andrei; Caltech nano quantum optics Team

2015-03-01

Rare earth ions (REIs) are promising candidates for implementing solid-state quantum memories and quantum repeater devices. Their high spectral stability and long coherence times make REIs a good choice for integration in an on-chip quantum nano-photonic platform. We report the coupling of the 883 nm transition of Neodymium (Nd) to a Yttrium orthosilicate (YSO) photonic crystal nano-beam resonator, achieving Purcell enhanced spontaneous emission by 21 times and increased optical absorption. Photon echoes were observed in nano-beams of different doping concentrations, yielding optical coherence times T2 up to 80 μs that are comparable to unprocessed bulk samples. This indicates the remarkable coherence properties of Nd are preserved during nanofabrication, therefore opening the possibility of efficient on-chip optical quantum memories. The nano-resonator with mode volume of 1 . 6(λ / n) 3 was fabricated using focused ion beam, and a quality factor of 3200 was measured. Purcell enhanced absorption of 80% by an ensemble of ~ 1 × 106 ions in the resonator was measured, which fulfills the cavity impedance matching condition that is necessary to achieve quantum storage of photons with unity efficiency.

A high temperature hybrid photovoltaic-thermal receiver employing spectral beam splitting for linear solar concentrators

NASA Astrophysics Data System (ADS)

Mojiri, Ahmad; Stanley, Cameron; Rosengarten, Gary

2015-09-01

Hybrid photovoltaic/thermal (PV-T) solar collectors are capable of delivering heat and electricity concurrently. Implementing such receivers in linear concentrators for high temperature applications need special considerations such as thermal decoupling of the photovoltaic (pv) cells from the thermal receiver. Spectral beam splitting of concentrated light provides an option for achieving this purpose. In this paper we introduce a relatively simple hybrid receiver configuration that spectrally splits the light between a high temperature thermal fluid and silicon pv cells using volumetric light filtering by semi-conductor doped glass and propylene glycol. We analysed the optical performance of this device theoretically using ray tracing and experimentally through the construction and testing of a full scale prototype. The receiver was mounted on a commercial parabolic trough concentrator in an outdoor experiment. The prototype receiver delivered heat and electricity at total thermal efficiency of 44% and electrical efficiency of 3.9% measured relative to the total beam energy incident on the primary mirror.

A satellite-based radar wind sensor

NASA Technical Reports Server (NTRS)

Xin, Weizhuang

1991-01-01

The objective is to investigate the application of Doppler radar systems for global wind measurement. A model of the satellite-based radar wind sounder (RAWS) is discussed, and many critical problems in the designing process, such as the antenna scan pattern, tracking the Doppler shift caused by satellite motion, and backscattering of radar signals from different types of clouds, are discussed along with their computer simulations. In addition, algorithms for measuring mean frequency of radar echoes, such as the Fast Fourier Transform (FFT) estimator, the covariance estimator, and the estimators based on autoregressive models, are discussed. Monte Carlo computer simulations were used to compare the performance of these algorithms. Anti-alias methods are discussed for the FFT and the autoregressive methods. Several algorithms for reducing radar ambiguity were studied, such as random phase coding methods and staggered pulse repitition frequncy (PRF) methods. Computer simulations showed that these methods are not applicable to the RAWS because of the broad spectral widths of the radar echoes from clouds. A waveform modulation method using the concept of spread spectrum and correlation detection was developed to solve the radar ambiguity. Radar ambiguity functions were used to analyze the effective signal-to-noise ratios for the waveform modulation method. The results showed that, with suitable bandwidth product and modulation of the waveform, this method can achieve the desired maximum range and maximum frequency of the radar system.

Beam-splitter switches based on zenithal bistable liquid-crystal gratings.

PubMed

Zografopoulos, Dimitrios C; Beccherelli, Romeo; Kriezis, Emmanouil E

2014-10-01

The tunable optical diffractive properties of zenithal bistable nematic liquid-crystal gratings are theoretically investigated. The liquid-crystal orientation is rigorously solved via a tensorial formulation of the Landau-de Gennes theory and the optical transmission properties of the gratings are investigated via full-wave finite-element frequency-domain simulations. It is demonstrated that by proper design the two stable states of the grating can provide nondiffracting and diffracting operation, the latter with equal power splitting among different diffraction orders. An electro-optic switching mechanism, based on dual-frequency nematic materials, and its temporal dynamics are further discussed. Such gratings provide a solution towards tunable beam-steering and beam-splitting components with extremely low power consumption.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Polarisation splitting of laser beams by large angles with minimal reflection losses

NASA Astrophysics Data System (ADS)

Davydov, B. L.

2006-05-01

New crystal anisotropic prisms for splitting orthogonally polarised components of laser radiation by large angles with minimal reflection losses caused by the Brewster refraction and total internal reflection of polarised waves from the crystal—air interface are considered and the method for their calculation is described. It is shown that, by assembling glue-free combinations of two or three prisms, thermally stable beamsplitters can be fabricated, which are free from the beam astigmatism and the wave dispersion of the output angles of the beams. The parameters and properties of new beamsplitters are presented in a convenient form in figures and tables.

Generating and Separating Twisted Light by gradient-rotation Split-Ring Antenna Metasurfaces.

PubMed

Zeng, Jinwei; Li, Ling; Yang, Xiaodong; Gao, Jie

2016-05-11

Nanoscale compact optical vortex generators promise substantially significant prospects in modern optics and photonics, leading to many advances in sensing, imaging, quantum communication, and optical manipulation. However, conventional vortex generators often suffer from bulky size, low vortex mode purity in the converted beam, or limited operation bandwidth. Here, we design and demonstrate gradient-rotation split-ring antenna metasurfaces as unique spin-to-orbital angular momentum beam converters to simultaneously generate and separate pure optical vortices in a broad wavelength range. Our proposed design has the potential for realizing miniaturized on-chip OAM-multiplexers, as well as enabling new types of metasurface devices for the manipulation of complex structured light beams.

Flat profile laser beam shaper

DOEpatents

Johnson, Todd R.

2017-09-12

A system for shaping a beam comprises an emitter for emitting coherent electromagnetic radiation. Birefringent displacers are configured between the emitter and a target wherein the at least two birefringent displacers split the coherent electromagnetic radiation into a plurality of coherent parallel beams of electromagnetic radiation thereby producing a shaped wave front of the coherent parallel beams of electromagnetic radiation.

Apparatus and method for improving radiation coherence and reducing beam emittance

DOEpatents

Csonka, P.L.

1992-05-12

A method and apparatus for increasing the coherence and reducing the emittance of a beam-shaped pulse operates by splitting the pulse into multiple sub-beams, delaying the propagation of the various sub-beams by varying amounts, and then recombining the sub-beams by means of a rotating optical element to form a pulse of longer duration with improved transverse coherence. 16 figs.

Holographic memory using beam steering

NASA Technical Reports Server (NTRS)

Chao, Tien-Hsin (Inventor); Hanan, Jay C. (Inventor); Reyes, George F. (Inventor); Zhou, Hanying (Inventor)

2006-01-01

A method, apparatus, and system provide the ability for storing holograms at high speed. A single laser diode emits a collimated laser beam to both write to and read from a photorefractice crystal. One or more liquid crystal beam steering spatial light modulators (BSSLMs) or Micro-Electro-Mechanical Systems (MEMS) mirrors steer a reference beam, split from the collimated laser beam, at high speed to the photorefractive crystal.

Apparatus and method for improving radiation coherence and reducing beam emittance

DOEpatents

Csonka, Paul L.

1992-01-01

A method and apparatus for increasing the coherence and reducing the emittance of a beam-shaped pulse operates by splitting the pulse into multiple sub-beams, delaying the propagation of the various sub-beams by varying amounts, and then recombining the sub-beams by means of a rotating optical element to form a pulse of longer duration with improved transverse coherence.

Combining split-beam and dual-frequency identification sonars to estimate abundance of anadromous fishes in the Roanoke River, North Carolina

USGS Publications Warehouse

Hughes, Jacob B.; Hightower, Joseph E.

2015-01-01

Riverine hydroacoustic techniques are an effective method for evaluating abundance of upstream migrating anadromous fishes. To use these methods in the Roanoke River, North Carolina, at a wide site with uneven bottom topography, we used a combination of split-beam sonar and dual-frequency identification sonar (DIDSON) deployments. We aimed a split-beam sonar horizontally to monitor midchannel and near-bottom zones continuously over the 3-month spring monitoring periods in 2010 and 2011. The DIDSON was rotated between seven cross-channel locations (using a vertical aim) and nearshore regions (using horizontal aims). Vertical deployment addressed blind spots in split-beam coverage along the bottom and provided reliable information about the cross-channel and vertical distributions of upstream migrants. Using a Bayesian framework, we modeled sonar counts within four cross-channel strata and apportioned counts by species using species proportions from boat electrofishing and gill netting. Modeled estimates (95% credible intervals [CIs]) of total upstream migrants in 2010 and 2011 were 2.5 million (95% CI, 2.4–2.6 million) and 3.6 million (95% CI, 3.4–3.9 million), respectively. Results indicated that upstream migrants are extremely shore- and bottom-oriented, suggesting nearshore DIDSON monitoring improved the accuracy and precision of our estimates. This monitoring protocol and model may be widely applicable to river systems regardless of their cross-sectional width or profile.

Electro-optic voltage sensor with Multiple Beam Splitting

DOEpatents

Woods, Gregory K.; Renak, Todd W.; Crawford, Thomas M.; Davidson, James R.

2000-01-01

A miniature electro-optic voltage sensor system capable of accurate operation at high voltages without use of the dedicated voltage dividing hardware. The invention achieves voltage measurement without significant error contributions from neighboring conductors or environmental perturbations. The invention employs a transmitter, a sensor, a detector, and a signal processor. The transmitter produces a beam of electromagnetic radiation which is routed into the sensor. Within the sensor the beam undergoes the Pockels electro-optic effect. The electro-optic effect produces a modulation of the beam's polarization, which is in turn converted to a pair of independent conversely-amplitude-modulated signals, from which the voltage of the E-field is determined by the signal processor. The use of converse AM signals enables the signal processor to better distinguish signal from noise. The sensor converts the beam by splitting the beam in accordance with the axes of the beam's polarization state (an ellipse) into at least two AM signals. These AM signals are fed into a signal processor and processed to determine the voltage between a ground conductor and the conductor on which voltage is being measured.

Optical microphone

DOEpatents

Veligdan, James T.

2000-01-11

An optical microphone includes a laser and beam splitter cooperating therewith for splitting a laser beam into a reference beam and a signal beam. A reflecting sensor receives the signal beam and reflects it in a plurality of reflections through sound pressure waves. A photodetector receives both the reference beam and reflected signal beam for heterodyning thereof to produce an acoustic signal for the sound waves. The sound waves vary the local refractive index in the path of the signal beam which experiences a Doppler frequency shift directly analogous with the sound waves.

Underwater single beam circumferentially scanning detection system using range-gated receiver and adaptive filter

NASA Astrophysics Data System (ADS)

Tan, Yayun; Zhang, He; Zha, Bingting

2017-09-01

Underwater target detection and ranging in seawater are of interest in unmanned underwater vehicles. This study presents an underwater detection system that synchronously scans a collimated laser beam and a narrow field of view to circumferentially detect an underwater target. Hybrid methods of range-gated and variable step-size least mean squares (VSS-LMS) adaptive filter are proposed to suppress water backscattering. The range-gated receiver eliminates the backscattering of near-field water. The VSS-LMS filter extracts the target echo in the remaining backscattering and the constant fraction discriminator timing method is used to improve ranging accuracy. The optimal constant fraction is selected by analysing the jitter noise and slope of the target echo. The prototype of the underwater detection system is constructed and tested in coastal seawater, then the effectiveness of backscattering suppression and high-ranging accuracy is verified through experimental results and analysis discussed in this paper.

Evaluation of the split cantilever beam for Mode 3 delamination testing

NASA Technical Reports Server (NTRS)

Martin, Roderick H.

1989-01-01

A test rig for testing a thick split cantilever beam for scissoring delamination (mode 3) fracture toughness was developed. A 3-D finite element analysis was conducted on the test specimen to determine the strain energy release rate, G, distribution along the delamination front. The virtual crack closure technique was used to calculate the G components resulting from interlaminar tension, GI, interlaminar sliding shear, GII, and interlaminar tearing shear, GIII. The finite element analysis showed that at the delamination front no GI component existed, but a GII component was present in addition to a GIII component. Furthermore, near the free edges, the GII component was significantly higher than the GIII component. The GII/GIII ratio was found to increase with delamination length but was insensitive to the beam depth. The presence of GII at the delamination front was verified experimentally by examination of the failure surfaces. At the center of the beam, where the failure was in mode 3, there was significant fiber bridging. However, at the edges of the beam where the failure was in mode 3, there was no fiber bridging and mode 2 shear hackles were observed. Therefore, it was concluded that the split cantilever beam configuration does not represent a pure mode 3 test. The experimental work showed that the mode 2 fracture toughness, GIIc, must be less than the mode 3 fracture toughness, GIIIc. Therefore, a conservative approach to characterizing mode 3 delamination is to equate GIIIc to GIIc.

Grating Beam Combiner.

DTIC Science & Technology

1982-12-01

with an nff-axis section of a 16-in. paraboloid. The expanded beam is split using a •• dielectrically coated 12.5-in. glass beam splitter at...equivalently the groove straightness). This was done prior to a recoating of the 12.5-in. beam splitter used in the interferometer after which it displayed...alternative to the full-aperture holographic sampler. It diffracts samples of an outgoing high-energy infrared (IR) beam and an incoming designator beam

Flush-mounting technique for composite beams

NASA Technical Reports Server (NTRS)

Harman, T. C.; Kay, B. F.

1980-01-01

Procedure permits mounting of heavy parts to surface of composite beams without appreciably weakening beam web. Web is split and held apart in region where attachment is to be made by lightweight precast foam filler. Bolt hole penetrates foam rather than web, and is secured by barrelnut in transverse bushing through web.

RAL Low-cost Ionosonde System

NASA Astrophysics Data System (ADS)

Stamper, R.; Davis, C. J.; Bradford, W. J.; Hapgood, M. A.; McCrea, I. W.

2009-04-01

Ionosondes continue to be important for the study of the ionosphere; they are relatively cheap and simple to install and operate, so can be distributed widely across the globe; they can give information on plasma density, structure and motion; their direct measurements of electron densities are also important for calibrating other more complicated observation methods such as incoherent scatter radar, satellite beacon tomography and radio occultation. The low cost of sounders, however, is relative to facilities such as space-based instrumentation and incoherent scatter radars; one type of ionosonde widely used for monitoring costs in excess of €150,000, representing a significant investment for many organisations. A new instrument design is under development at RAL for a low-power sounder using pulse-coding techniques to get good signal-to-noise. The design uses COTS components wherever possible, and has a projected cost in the region of €6,000 for the simplest version, making such a system accessible to all. The design is tiered so that the simplest version would give information about layer heights and electron densities, but adding multiple receivers would enable plasma velocities and echo direction to be determined, increasing the science output. The intention is that sounders of this new design be installed widely, in particular in developing nations. This would be especially beneficial for study of the equatorial and low-latitude ionosphere, which is relatively poorly understood because of a relative lack of instrumentation in this region. A wide range of studies would be enabled or enhanced by a much denser network of ionosondes across Africa, South America and Asia including: study of planetary-scale oscillations and gravity waves in the ionosphere; investigation of longitudinal variation in the equatorial electrojet and equatorial anomaly; examination of mechanisms for vertical coupling in the atmosphere with, for example, global thunderstorm activity being concentrated in Africa and South America; the study of ionospheric scintillation mechanisms and occurrence in the equatorial region; thorough characterisation of ionospheric variability on a wide range of spatial and temporal scales across a wide range of longitudes.

RAL Low-Cost Ionosonde System

NASA Astrophysics Data System (ADS)

Stamper, R.; Davis, C.; Bradford, J.

2005-12-01

Ionosondes continue to be important for the study of the ionosphere; they are relatively cheap and simple to install and operate, so can be distributed widely across the globe; they can give information on plasma density, structure and motion; their direct measurements of electron densities are also important for calibrating other more complicated observation methods such as incoherent scatter radar, satellite beacon tomography and radio occultation. The low cost of sounders, however, is relative to facilities such as space-based instrumentation and incoherent scatter radars; one type of ionosonde widely used for monitoring costs in excess of 200,000, representing a significant investment for many organisations. A new instrument design is under development at RAL for a low-power sounder using pulse-coding techniques to get good signal-to-noise. The design uses COTS components wherever possible, and has a projected cost in the region of 7,500 for the simplest version, making such a system accessible to all. The design is tiered so that the simplest version would give information about layer heights and electron densities, but adding multiple receivers would enable plasma velocities and echo direction to be determined, increasing the science output. The intention is that sounders of this new design be installed widely, in particular in developing nations. This would be especially beneficial for study of the equatorial and low-latitude ionosphere, which is relatively poorly understood because of a relative lack of instrumentation in this region. A wide range of studies would be enabled or enhanced by a much denser network of ionosondes across Africa, South America and Asia including: study of planetary-scale oscillations and gravity waves in the ionosphere; investigation of longitudinal variation in the equatorial electrojet and equatorial anomaly; examination of mechanisms for vertical coupling in the atmosphere with, for example, global thunderstorm activity being concentrated in Africa and South America; the study of ionospheric scintillation mechanisms and occurrence in the equatorial region; thorough characterisation of ionospheric variability on a wide range of spatial and temporal scales across a wide range of longitudes.

Results of a joint NOAA/NASA sounder simulation study

NASA Technical Reports Server (NTRS)

Phillips, N.; Susskind, Joel; Mcmillin, L.

1988-01-01

This paper presents the results of a joint NOAA and NASA sounder simulation study in which the accuracies of atmospheric temperature profiles and surface skin temperature measuremnents retrieved from two sounders were compared: (1) the currently used IR temperature sounder HIRS2 (High-resolution Infrared Radiation Sounder 2); and (2) the recently proposed high-spectral-resolution IR sounder AMTS (Advanced Moisture and Temperature Sounder). Simulations were conducted for both clear and partial cloud conditions. Data were analyzed at NASA using a physical inversion technique and at NOAA using a statistical technique. Results show significant improvement of AMTS compared to HIRS2 for both clear and cloudy conditions. The improvements are indicated by both methods of data analysis, but the physical retrievals outperform the statistical retrievals.

Temporal binding of neural responses for focused attention in biosonar

PubMed Central

Simmons, James A.

2014-01-01

Big brown bats emit biosonar sounds and perceive their surroundings from the delays of echoes received by the ears. Broadcasts are frequency modulated (FM) and contain two prominent harmonics sweeping from 50 to 25 kHz (FM1) and from 100 to 50 kHz (FM2). Individual frequencies in each broadcast and each echo evoke single-spike auditory responses. Echo delay is encoded by the time elapsed between volleys of responses to broadcasts and volleys of responses to echoes. If echoes have the same spectrum as broadcasts, the volley of neural responses to FM1 and FM2 is internally synchronized for each sound, which leads to sharply focused delay images. Because of amplitude–latency trading, disruption of response synchrony within the volleys occurs if the echoes are lowpass filtered, leading to blurred, defocused delay images. This effect is consistent with the temporal binding hypothesis for perceptual image formation. Bats perform inexplicably well in cluttered surroundings where echoes from off-side objects ought to cause masking. Off-side echoes are lowpass filtered because of the shape of the broadcast beam, and they evoke desynchronized auditory responses. The resulting defocused images of clutter do not mask perception of focused images for targets. Neural response synchronization may select a target to be the focus of attention, while desynchronization may impose inattention on the surroundings by defocusing perception of clutter. The formation of focused biosonar images from synchronized neural responses, and the defocusing that occurs with disruption of synchrony, quantitatively demonstrates how temporal binding may control attention and bring a perceptual object into existence. PMID:25122915

Phase modulation in dipolar-coupled A 2 spin systems: effect of maximum state mixing in 1H NMR in vivo

NASA Astrophysics Data System (ADS)

Schröder, Leif; Schmitz, Christian; Bachert, Peter

2004-12-01

Coupling constants of nuclear spin systems can be determined from phase modulation of multiplet resonances. Strongly coupled systems such as citrate in prostatic tissue exhibit a more complex modulation than AX connectivities, because of substantial mixing of quantum states. An extreme limit is the coupling of n isochronous spins (A n system). It is observable only for directly connected spins like the methylene protons of creatine and phosphocreatine which experience residual dipolar coupling in intact muscle tissue in vivo. We will demonstrate that phase modulation of this "pseudo-strong" system is quite simple compared to those of AB systems. Theory predicts that the spin-echo experiment yields conditions as in the case of weak interactions, in particular, the phase modulation depends linearly on the line splitting and the echo time.

Beam pointing angle optimization and experiments for vehicle laser Doppler velocimetry

NASA Astrophysics Data System (ADS)

Fan, Zhe; Hu, Shuling; Zhang, Chunxi; Nie, Yanju; Li, Jun

2015-10-01

Beam pointing angle (BPA) is one of the key parameters that affects the operation performance of the laser Doppler velocimetry (LDV) system. By considering velocity sensitivity and echo power, for the first time, the optimized BPA of vehicle LDV is analyzed. Assuming mounting error is within ±1.0 deg, the reflectivity and roughness are variable for different scenarios, the optimized BPA is obtained in the range from 29 to 43 deg. Therefore, velocity sensitivity is in the range of 1.25 to 1.76 MHz/(m/s), and the percentage of normalized echo power at optimized BPA with respect to that at 0 deg is greater than 53.49%. Laboratory experiments with a rotating table are done with different BPAs of 10, 35, and 66 deg, and the results coincide with the theoretical analysis. Further, vehicle experiment with optimized BPA of 35 deg is conducted by comparison with microwave radar (accuracy of ±0.5% full scale output). The root-mean-square error of LDV's results is smaller than the Microstar II's, 0.0202 and 0.1495 m/s, corresponding to LDV and Microstar II, respectively, and the mean velocity discrepancy is 0.032 m/s. It is also proven that with the optimized BPA both high velocity sensitivity and acceptable echo power can simultaneously be guaranteed.

Effective biosonar echo-to-clutter rejection ratio in a complex dynamic scene.

PubMed

Knowles, Jeffrey M; Barchi, Jonathan R; Gaudette, Jason E; Simmons, James A

2015-08-01

Biosonar guidance in a rapidly changing complex scene was examined by flying big brown bats (Eptesicus fuscus) through a Y-shaped maze composed of rows of strongly reflective vertical plastic chains that presented the bat with left and right corridors for passage. Corridors were 80-100 cm wide and 2-4 m long. Using the two-choice Y-shaped paradigm to compensate for left-right bias and spatial memory, a moveable, weakly reflective thin-net barrier randomly blocked the left or right corridor, interspersed with no-barrier trials. Flight path and beam aim were tracked using an array of 24 microphones surrounding the flight room. Each bat flew on a path centered in the entry corridor (base of Y) and then turned into the left or right passage, to land on the far wall or to turn abruptly, reacting to avoid a collision. Broadcasts were broadly beamed in the direction of flight, smoothly leading into an upcoming turn. Duration of broadcasts decreased slowly from 3 to 2 ms during flights to track the chains' progressively closer ranges. Broadcast features and flight velocity changed abruptly about 1 m from the barrier, indicating that echoes from the net were perceived even though they were 18-35 dB weaker than overlapping echoes from surrounding chains.

Modelling NDE pulse-echo inspection of misorientated planar rough defects using an elastic finite element method

NASA Astrophysics Data System (ADS)

Pettit, J. R.; Walker, A. E.; Lowe, M. J. S.

2015-03-01

Pulse-echo ultrasonic NDE examination of large pressure vessel forgings is a design and construction code requirement in the power generation industry. Such inspections aim to size and characterise potential defects that may have formed during the forging process. Typically these defects have a range of orientations and surface roughnesses which can greatly affect ultrasonic wave scattering behaviour. Ultrasonic modelling techniques can provide insight into defect response and therefore aid in characterisation. However, analytical approaches to solving these scattering problems can become inaccurate, especially when applied to increasingly complex defect geometries. To overcome these limitations a elastic Finite Element (FE) method has been developed to simulate pulse-echo inspections of embedded planar defects. The FE model comprises a significantly reduced spatial domain allowing for a Monte-Carlo based approach to consider multiple realisations of defect orientation and surface roughness. The results confirm that defects aligned perpendicular to the path of beam propagation attenuate ultrasonic signals according to the level of surface roughness. However, for defects orientated away from this plane, surface roughness can increase the magnitude of the scattered component propagating back along the path of the incident beam. This study therefore highlights instances where defect roughness increases the magnitude of ultrasonic scattered signals, as opposed to attenuation which is more often assumed.

Design of a 50/50 splitting ratio non-polarizing beam splitter based on the modal method with fused-silica transmission gratings

NASA Astrophysics Data System (ADS)

Zhao, Huajun; Yuan, Dairong; Ming, Hai

2011-04-01

The optical design of a beam splitter that has a 50/50 splitting ratio regardless of the polarization is presented. The non-polarizing beam splitter (NPBS) is based on the fused-silica rectangular transmission gratings with high intensity tolerance. The modal method has been used to estimate the effective index of the modes excited in the grating region for TE and TM polarizations. If a phase difference equals an odd multiples of π/2 for the first two modes (i.e. modes 0 and 1), the incident light will be diffracted into the 0 and -1 orders with about 50% and 50% diffraction efficiency for TM and TE polarizations, respectively.

Unveiling the photonic spin Hall effect of freely propagating fan-shaped cylindrical vector vortex beams.

PubMed

Zhang, Yi; Li, Peng; Liu, Sheng; Zhao, Jianlin

2015-10-01

An intriguing photonic spin Hall effect (SHE) for a freely propagating fan-shaped cylindrical vector (CV) vortex beam in a paraxial situation is theoretically and experimentally studied. A developed model to describe this kind of photonic SHE is proposed based on angular spectrum diffraction theory. With this model, the close dependences of spin-dependent splitting on the azimuthal order of polarization, the topological charge of the spiral phase, and the propagation distance are accurately revealed. Furthermore, it is demonstrated that the asymmetric spin-dependent splitting of a fan-shaped CV beam can be consciously managed, even with a constant azimuthal order of polarization. Such a controllable photonic SHE is experimentally verified by measuring the Stokes parameters.

Temporal and frequency characteristics of a narrow light beam in sea water.

PubMed

Luchinin, Alexander G; Kirillin, Mikhail Yu

2016-09-20

The structure of a light field in sea water excited by a unidirectional point-sized pulsed source is studied by Monte Carlo technique. The pulse shape registered at the distances up to 120 m from the source on the beam axis and in its axial region is calculated with a time resolution of 1 ps. It is shown that with the increase of the distance from the source the pulse splits into two parts formed by components of various scattering orders. Frequency and phase responses of the beam are calculated by means of the fast Fourier transform. It is also shown that for higher frequencies, the attenuation of harmonic components of the field is larger. In the range of parameters corresponding to pulse splitting on the beam axis, the attenuation of harmonic components in particular spectral ranges exceeds the attenuation predicted by Bouguer law. In this case, the transverse distribution of the amplitudes of these harmonics is minimal on the beam axis.

Topside Ionogram Scaler With True Height Algorithm (TOPIST): Automated processing of ISIS topside ionograms

NASA Astrophysics Data System (ADS)

Bilitza, Dieter; Huang, Xueqin; Reinisch, Bodo W.; Benson, Robert F.; Hills, H. Kent; Schar, William B.

2004-02-01

The United States/Canadian ISIS-1 and ISIS-2 satellites collected several million topside ionograms in the 1960s and 1970s with a multinational network of ground stations that provided good global coverage. However, processing of these ionograms into electron density profiles required time-consuming manual scaling of the traces from the analog ionograms, and as a result, only a few percent of the ionograms had been processed into electron density profiles. In recent years an effort began to digitize the analog recordings to prepare the ionograms for computerized analysis. As of November 2002, approximately 390,000 ISIS-1 and ISIS-2 digital topside-sounder ionograms have been produced. The Topside Ionogram Scaler With True Height Algorithm (TOPIST) program was developed for the automated scaling of the echo traces and for the inversion of these traces into topside electron density profiles. The program is based on the techniques that have been successfully applied in the analysis of ground-based Digisonde ionograms. The TOPIST software also includes an "editing option" for manual scaling of the more difficult ionograms, which could not be scaled during the automated TOPIST run. TOPIST is now successfully scaling ˜60% of the ISIS ionograms, and the electron density profiles are available through the online archive of the National Space Science Data Center at ftp://nssdcftp.gsfc.nasa.gov/spacecraft_data/isis/topside_sounder. This data restoration effort is producing a unique global database of topside electron densities over more than one solar cycle, which will be of particular importance for improvements of topside ionosphere models, especially the International Reference Ionosphere.

Miniature mechanical transfer optical coupler

DOEpatents

Abel, Philip [Overland Park, KS; Watterson, Carl [Kansas City, MO

2011-02-15

A miniature mechanical transfer (MT) optical coupler ("MMTOC") for optically connecting a first plurality of optical fibers with at least one other plurality of optical fibers. The MMTOC may comprise a beam splitting element, a plurality of collimating lenses, and a plurality of alignment elements. The MMTOC may optically couple a first plurality of fibers disposed in a plurality of ferrules of a first MT connector with a second plurality of fibers disposed in a plurality of ferrules of a second MT connector and a third plurality of fibers disposed in a plurality of ferrules of a third MT connector. The beam splitting element may allow a portion of each beam of light from the first plurality of fibers to pass through to the second plurality of fibers and simultaneously reflect another portion of each beam of light from the first plurality of fibers to the third plurality of fibers.

Seismo-acoustic imaging of marine hard substrate habitats: a case study from the German Bight (SE North Sea)

NASA Astrophysics Data System (ADS)

Papenmeier, Svenja; Hass, H. Christian

2016-04-01

The detection of hard substrate habitats in sublittoral environments is a considerable challenge in spite of modern high resolution hydroacoustic techniques. In offshore areas those habitats are mainly represented by either cobbles and boulders (stones) often located in wide areas of soft sediments or by glacial relict sediments (heterogeneous mixture of medium sand to gravel size with cobbles and boulders). Sediment classification and object detection is commonly done on the basis of hydroacoustic backscatter intensities recorded with e.g. sidescan sonar (SSS) and multibeam echo sounder (MBES). Single objects lying on the sediment such as stones can generally be recognized by the acoustic shadow behind the object. However, objects close to the sonar's nadir may remain undetected because their shadows are below the data resolution. Further limitation in the detection of objects is caused by sessile communities that thrive on the objects. The bio-cover tends to absorb most of the acoustic signal. Automated identification based on the backscatter signal is often not satisfactory, especially when stones are present in a setting with glacial deposits. Areas characterized by glacial relict sediments are hardly differentiable in their backscatter characteristics from rippled coarse sand and fine gravel (rippled coarse sediments) without an intensive ground-truthing program. From the ecological point of view the relict and rippled coarse sediments are completely different habitats and need to be distinguished. The case study represents a seismo-acoustic approach in which SSS and nonlinear sediment echo sounder (SES) data are combined to enable a reliable and reproducible differentiation between relict sediments (with stones and coarse gravels) and rippled coarse sediments. Elevated objects produce hyperbola signatures at the sediment surface in the echo data which can be used to complement the SSS data. The nonlinear acoustic propagation of the SES sound pulses produces a comparably small foot print which results in high spatial resolution (decimeter in the xyz directions) and hence allows a more precise demarcation of hard substrate areas. Data for this study were recorded in the "Sylt Outer Reef" (German Bight, North Sea) in May 2013 and March 2015. The investigated area is characterized by heterogeneously distributed moraine deposits and rippled coarse sediments partly draped with Holocene fine sands. The relict sediments and the rippled coarse sediments indicate both high backscatter intensities but can be distinguished by means of the hyperbola locations. The northeast of the study area is dominated by rippled coarse sediments (without hyperbolas) and the southwestern part by relict sediments with a high amount of stones represented by hyperbolas which is also proven by extensive ground-truthing (grab sampling and high quality underwater videos). An automated procedure to identify and export the hyperbola positions makes the demarcation of hard substrate grounds (here: relict sediments) reproducible, faster and less complex in comparison to the visual-manual identification on the basis of sidescan sonar data.

Design of collimating and rearrangement systems of laser diode array beam

NASA Astrophysics Data System (ADS)

Gao, Runmei; Fang, Tao; Fu, Rulian; Yao, Jianquan

2015-10-01

To improve the laser diode output beam quality, micro-cylindrical lens and the step-type lens combination are designed. The former is used to collimate beam in fast-axis direction, while the latter plays a role in the slow-axis of splitting and the rearrangement. The micro-column semi-elliptical lens is made with the drops of spherical zoom lensin electric field and with the help of the material properties of light-cured production, which can reduce the reflection of the front surface and total reflection loss of the after. The divergence angle in the fast axis is compressed to roughly the same as that in the slow-axis direction; Stepped lens splits compressed long strip beam in the slow axis, with parallelogram style of level equidistant and rearrange in the fast axis direction. The spot in the slow axis gets smaller and the spot becomes larger in the fast axis. At last divergence angle and the beam spot achieve balanced in the fast axis and slow axis, optical parameters BPP integrates approximate the same, and beam quality can be improved.

Propagation optical quarks after an uniaxial crystal: the experiment

NASA Astrophysics Data System (ADS)

Egorov, Yu. A.; Konovalenko, V. L.; Zinovev, A. O.; Anischenko, P. M.; Glumova, M. V.

2013-12-01

There is a lots of different papers reporting about the propagation of the different types of an optical beams in a uniaxial crystals are known by that time. This beams are: Lager-Gaussian and Bessel- Gaussian beams. It is common for all this types of beams, that if propagation axis and crystal axis coincides, and accident beam had a circular polarization, are can get type spiral type degenerated umbilici, which corresponds to the charge 2 optical vortex in the orthogonal polarized beam component, generated by crystal [1] (Fig 1). This generation accurse due to total angular momentum conservation law symmetry axis of the crystal. One to the changing of the spin momentum which is associated with the beam polarization, this leads to the orbital momentum changes that associated with topological charge of formed orthogonal circular component. Double charged optical vortex could be easily perturbed by tilting beam axis with respect to the crystal axis. If the tilt angles are small (<0.1°) central umbilici splits on two lemons and the surrounding ring umbilici splits on two pairs of monster-star. The further increasing of the tilt angle leads to the topological charge of circular components becomes, equal, and additional orbital moment correspond to the beam mass center displacement.

Using Neutron Spin Echo Resolved Grazing Incidence Scattering to Investigate Organic Solar Cell Materials

PubMed Central

Parnell, Andrew J.; Hobson, Adam; Dalgliesh, Robert M.; Jones, Richard A. L.; Dunbar, Alan D. F.

2014-01-01

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped crystallites. Neutrons are passed through two well defined regions of magnetic field; one before and one after the sample. The two magnetic field regions have opposite polarity and are tuned such that neutrons travelling through both regions, without being perturbed, will undergo the same number of precessions in opposing directions. In this case the neutron precession in the second arm is said to "echo" the first, and the original polarization of the beam is preserved. If the neutron interacts with a sample and scatters elastically the path through the second arm is not the same as the first and the original polarization is not recovered. Depolarization of the neutron beam is a highly sensitive probe at very small angles (<50 μrad) but still allows a high intensity, divergent beam to be used. The decrease in polarization of the beam reflected from the sample as compared to that from the reference sample can be directly related to structure within the sample. In comparison to scattering observed in neutron reflection measurements the SERGIS signals are often weak and are unlikely to be observed if the in-plane structures within the sample under investigation are dilute, disordered, small in size and polydisperse or the neutron scattering contrast is low. Therefore, good results will most likely be obtained using the SERGIS technique if the sample being measured consist of thin films on a flat substrate and contain scattering features that contains a high density of moderately sized features (30 nm to 5 µm) which scatter neutrons strongly or the features are arranged on a lattice. An advantage of the SERGIS technique is that it can probe structures in the plane of the sample. PMID:24457355

longitudinal space charge assisted echo seeding of a free electron laser

NASA Astrophysics Data System (ADS)

Hacker, Kirsten

2015-05-01

Seed lasers are employed to improve the temporal coherence of free-electron laser light. However, when seed pulses are short relative to the particle bunch, the noisy, temporally incoherent radiation from the un-seeded electrons can overwhelm the coherent, seeded radiation. In this paper a new seeding mechanism to improve the contrast between coherent and incoherent free electron laser radiation is employed together with a novel, simplified echo-seeding method. The concept relies on a combination of longitudinal space charge wakes and an echo-seeding technique to make a short, coherent pulse of FEL light together with noise background suppression. Several different simulation codes are used to illustrate the concept with conditions at the soft x-ray Free-electron LASer in Hamburg, FLASH. The impacts of coherent synchrotron radiation, intra beam scattering, and high peak current operation are investigated.

Ultrasonic ranging for the oculometer

NASA Technical Reports Server (NTRS)

Guy, W. J.

1981-01-01

Ultrasonic tracking techniques are investigated for an oculometer. Two methods are reported in detail. The first is based on measurements of time from the start of a transmit burst to a received echo. Knowing the sound velocity, distance can be calculated. In the second method, a continuous signal is transmitted. Target movement causes phase shifting of the echo. By accumulating these phase shifts, tracking from a set point can be achieved. Both systems have problems with contoured targets, but work well on flat plates and the back of a human head. Also briefly reported is an evaluation of an ultrasonic ranging system. Interface circuits make this system compatible with the echo time design. While the system is consistently accurate, it has a beam too narrow for oculometer use. Finally, comments are provided on a tracking system using the Doppler frequency shift to give range data.

Development of a Double-Gauss Lens Based Setup for Optoacoustic Applications

PubMed Central

Choi, Hojong; Ryu, Jae-Myung; Yeom, Jung-Yeol

2017-01-01

In optoacoustic (photoacoustic) systems, different echo signal intensities such as amplitudes, center frequencies, and bandwidths need to be compensated by utilizing variable gain or time-gain compensation amplifiers. However, such electronic components can increase system complexities and signal noise levels. In this paper, we introduce a double-Gauss lens to generate a large field of view with uniform light intensity due to the low chromatic aberrations of the lens, thus obtaining uniform echo signal intensities across the field of view of the optoacoustic system. In order to validate the uniformity of the echo signal intensities in the system, an in-house transducer was placed at various positions above a tissue sample and echo signals were measured and compared with each other. The custom designed double-Gauss lens demonstrated negligible light intensity variation (±1.5%) across the illumination field of view (~2 cm diameter). When the transducer was used to measure echo signal from an eye of a bigeye tuna within a range of ±1 cm, the peak-to-peak amplitude, center frequency, and their −6 dB bandwidth variations were less than 2 mV, 1 MHz, and 6%, respectively. The custom designed double-Gauss lens can provide uniform light beam across a wide area while generating insignificant echo signal variations, and thus can lower the burden of the receiving electronics or signal processing in the optoacoustic system. PMID:28273794

Application of GPS radio occultation to the assessment of temperature profile retrievals from microwave and infrared sounders

NASA Astrophysics Data System (ADS)

Feltz, M.; Knuteson, R.; Ackerman, S.; Revercomb, H.

2014-05-01

Comparisons of satellite temperature profile products from GPS radio occultation (RO) and hyperspectral infrared (IR)/microwave (MW) sounders are made using a previously developed matchup technique. The profile matchup technique matches GPS RO and IR/MW sounder profiles temporally, within 1 h, and spatially, taking into account the unique RO profile geometry and theoretical spatial resolution by calculating a ray-path averaged sounder profile. The comparisons use the GPS RO dry temperature product. Sounder minus GPS RO differences are computed and used to calculate bias and RMS profile statistics, which are created for global and 30° latitude zones for selected time periods. These statistics are created from various combinations of temperature profile data from the Constellation Observing System for Meteorology, Ionosphere & Climate (COSMIC) network, Global Navigation Satellite System Receiver for Atmospheric Sounding (GRAS) instrument, and the Atmospheric Infrared Sounder (AIRS)/Advanced Microwave Sounding Unit (AMSU), Infrared Atmospheric Sounding Interferometer (IASI)/AMSU, and Crosstrack Infrared Sounder (CrIS)/Advanced Technology Microwave Sounder (ATMS) sounding systems. By overlaying combinations of these matchup statistics for similar time and space domains, comparisons of different sounders' products, sounder product versions, and GPS RO products can be made. The COSMIC GPS RO network has the spatial coverage, time continuity, and stability to provide a common reference for comparison of the sounder profile products. The results of this study demonstrate that GPS RO has potential to act as a common temperature reference and can help facilitate inter-comparison of sounding retrieval methods and also highlight differences among sensor product versions.

Application of GPS radio occultation to the assessment of temperature profile retrievals from microwave and infrared sounders

NASA Astrophysics Data System (ADS)

Feltz, M.; Knuteson, R.; Ackerman, S.; Revercomb, H.

2014-11-01

Comparisons of satellite temperature profile products from GPS radio occultation (RO) and hyperspectral infrared (IR)/microwave (MW) sounders are made using a previously developed matchup technique. The profile matchup technique matches GPS RO and IR/MW sounder profiles temporally, within 1 h, and spatially, taking into account the unique RO profile geometry and theoretical spatial resolution by calculating a ray-path averaged sounder profile. The comparisons use the GPS RO dry temperature product. Sounder minus GPS RO differences are computed and used to calculate bias and rms profile statistics, which are created for global and 30° latitude zones for selected time periods. These statistics are created from various combinations of temperature profile data from the Constellation Observing System for Meteorology, Ionosphere & Climate (COSMIC) network, Global Navigation Satellite System Receiver for Atmospheric Sounding (GRAS) instrument, and the Atmospheric Infrared Sounder (AIRS)/Advanced Microwave Sounding Unit (AMSU), Infrared Atmospheric Sounding Interferometer (IASI)/AMSU, and Crosstrack Infrared Sounder (CrIS)/Advanced Technology Microwave Sounder (ATMS) sounding systems. By overlaying combinations of these matchup statistics for similar time and space domains, comparisons of different sounders' products, sounder product versions, and GPS RO products can be made. The COSMIC GPS RO network has the spatial coverage, time continuity, and stability to provide a common reference for comparison of the sounder profile products. The results of this study demonstrate that GPS RO has potential to act as a common temperature reference and can help facilitate inter-comparison of sounding retrieval methods and also highlight differences among sensor product versions.

Electro-optic voltage sensor with beam splitting

DOEpatents

Woods, Gregory K.; Renak, Todd W.; Davidson, James R.; Crawford, Thomas M.

2002-01-01

The invention is a miniature electro-optic voltage sensor system capable of accurate operation at high voltages without use of the dedicated voltage dividing hardware typically found in the prior art. The invention achieves voltage measurement without significant error contributions from neighboring conductors or environmental perturbations. The invention employs a transmitter, a sensor, a detector, and a signal processor. The transmitter produces a beam of electromagnetic radiation which is routed into the sensor. Within the sensor the beam undergoes the Pockels electro-optic effect. The electro-optic effect produces a modulation of the beam's polarization, which is in turn converted to a pair of independent conversely-amplitude-modulated signals, from which the voltage of the E-field is determined by the signal processor. The use of converse AM signals enables the signal processor to better distinguish signal from noise. The sensor converts the beam by splitting the beam in accordance with the axes of the beam's polarization state (an ellipse) into at least two AM signals. These AM signals are fed into a signal processor and processed to determine the voltage between a ground conductor and the conductor on which voltage is being measured.

Conjecture of plume components in hydrothermal sea area

NASA Astrophysics Data System (ADS)

Noda, K., IV; Aoyama, C.

2017-12-01

Investigation at Southern Okinawa Trough, western Kume Island, and Tokara Islands was performed from June 26 to July 12, 2016, as a part of Japan's cross ministerial Strategic Innovation Promotion Program (SIP) for a complete understanding of active hydrothermal vents. In this investigation, water column sonar data was obtained using multi-beam sonar (EM122) onboard YOKOSUKA (Japan Agency for Marine-Earth Science and Technology) and methane plumes were alsp monitored (YK16-07). Multi-beam sonar is an acoustic instrument used to measure submarine topography, and in this investigation, plumes were observed to successfully regenerate the data. It also became clear that volume backscattering strength (SV) of plumes varies, depending on the area where they are settled. On the other hand, components of plumes are still unknown. In this study, acoustic data obtained from YK16-07 will be reviewed using analytical software (echo view 7) to calculate volume backscattering strength (SV) of plumes. Likewise, multi-beam sonar (EM122) onboard DAIICHI KAIYOMARU (KAIYO ENGINEERING CO., LTD) was used to collect acoustic data. This already known data of methane plume from Sea of Japan will be analyzed using echo view 7. By comparing these data, plume components will be examined from plume size.

A dolphin lower jaw is a hydroacoustic antenna of the traveling wave

NASA Astrophysics Data System (ADS)

Ryabov, Vyacheslav A.

2003-10-01

The purpose of the work is the analysis of a possible function of mental foramens as channels through which the echo passes in the lower jaw fat body and the determination of a role of channels and a skull in formation of the directivity of the dolphin echolocation hearing. Concrete problems were studying of the lower jaw morphology, modeling and calculation of a dolphin, tursiops truncatus p., echolocation hearing beam pattern. The outcomes of the work indicate those morphological structures of the lower jaw; the left and right half represents two hydroacoustic receiving antennas of the traveling wave type, TWA farther. The mental foramens of a dolphin lower jaw represent nonequidistant array of waveguide delay lines, and determine the phase and amplitude distribution of each of the antenna's array. The beam pattern of the echolocation hearing was calculated with the usage of the TWA model, and the allowance of flat sound wave diffraction. The beam pattern shape is naturally determined by the echolocation hearing functionality. It is equally well adapted both for echolocation and for pulses echo detection. A steepness of the bearing characteristic is estimated; it reaches 0.7 dB per degree.

Temporal binding of neural responses for focused attention in biosonar.

PubMed

Simmons, James A

2014-08-15

Big brown bats emit biosonar sounds and perceive their surroundings from the delays of echoes received by the ears. Broadcasts are frequency modulated (FM) and contain two prominent harmonics sweeping from 50 to 25 kHz (FM1) and from 100 to 50 kHz (FM2). Individual frequencies in each broadcast and each echo evoke single-spike auditory responses. Echo delay is encoded by the time elapsed between volleys of responses to broadcasts and volleys of responses to echoes. If echoes have the same spectrum as broadcasts, the volley of neural responses to FM1 and FM2 is internally synchronized for each sound, which leads to sharply focused delay images. Because of amplitude-latency trading, disruption of response synchrony within the volleys occurs if the echoes are lowpass filtered, leading to blurred, defocused delay images. This effect is consistent with the temporal binding hypothesis for perceptual image formation. Bats perform inexplicably well in cluttered surroundings where echoes from off-side objects ought to cause masking. Off-side echoes are lowpass filtered because of the shape of the broadcast beam, and they evoke desynchronized auditory responses. The resulting defocused images of clutter do not mask perception of focused images for targets. Neural response synchronization may select a target to be the focus of attention, while desynchronization may impose inattention on the surroundings by defocusing perception of clutter. The formation of focused biosonar images from synchronized neural responses, and the defocusing that occurs with disruption of synchrony, quantitatively demonstrates how temporal binding may control attention and bring a perceptual object into existence. © 2014. Published by The Company of Biologists Ltd.

Acoustic properties of healthy and reconstructed cleft lip

NASA Astrophysics Data System (ADS)

Thijssen, Johan M.; van Hees, Nancy J.; Weijers, Gert G.; Huyskens, Rinske W.; Nillesen, Maartje; Katsaros, Christos; de Korte, Chris L.

2006-03-01

The feasibility of echographic imaging of the tissues in healthy lip and in reconstructed cleft lip and estimating the dimensions and the normalized echo level of these tissues is investigated. Echographic images of the upper lip were made with commercial medical ultrasound equipment, using a linear array transducer (7-11 MHz bandwidth) and a non-contact gel coupling. Tissue dimensions were measured by means of software calipers. Echo levels were calibrated and corrected for beam characteristics, gel path and tissue attenuation by using a tissue-mimicking phantom. At central position of philtrum, mean thickness (and standard deviation) of lip loose connective tissue layer, orbicularis oris muscle and dense connective layer was 4.0 (sd 0.1) mm, 2.3 (sd 0.7) mm, 2.2 (sd 0.7) mm, respectively, in healthy lip at rest. Mean (sd) echo level of muscle and dense connective tissue layer with respect to echo level of lip loose connective tissue layer was in relaxed condition: - 19.3 (sd 0.6) dB and - 10.7 (sd 4.0) dB, respectively. Echo level of loose connective tissue layer was +25.6 (sd 4.2) dB relative to phantom echo level obtained in the focus of the transducer. Color mode echo images were calculated, after adaptive filtering of the images, which show the tissues in separate colors and highlight the details of healthy lip and reconstructed cleft lip. Quantitative assessment of thickness and echo level of various lip tissues is feasible after proper calibration of the echographic equipment. Diagnostic potentials of the developed quantitative echographic techniques for non-invasive evaluation of the outcome of cleft lip reconstruction are promising.

Shot noise limits to sensitivity of optical interferometry

NASA Technical Reports Server (NTRS)

Prasad, Sudhakar

1992-01-01

By arguing that the limiting noise is the photoelectron shot noise, we show that the sensitivity of image synthesis by an ideal optical interferometer is independent of the details of beam-splitting and recombination. The signal-to-noise ratio of the synthesized image is proportional to the square root of the total number of photoelectrons detected by the entire array. For non-ideal interferometers, which are forced to employ a closure-phase method of indirect inference of the visibility data, essentially the same result holds for strong sources, but at weak light levels beam-splitting degrades sensitivity.

Retrieval of tropospheric profiles from IR emission spectra: preliminary results with the DBIS

NASA Astrophysics Data System (ADS)

Theriault, Jean-Marc; Anderson, Gail P.; Chetwynd, James H., Jr.; Murphy, Randall E.; Turner, Vernon; Cloutier, M.; Smith, A.; Moncet, Jean-Luc

1993-11-01

Recently, Smith and collaborators from University of Wisconsin-Madison have clearly established the possibilities of sounding tropospheric temperature and water vapor profiles with a ground-based uplooking interferometer. With the same perspective but for somewhat different applications, the Defence Research Establishment Valcartier (DREV) has initiated a project with the aim of exploring the many possible avenues of similar approaches. DREV, in collaboration with BOMEM (Quebec, Canada), has developed an instrument referred to as the Double Beam Interferometer Sounder (DBIS). This sounder has been conceived to match the needs encountered in many remote sensing scenarios: slant path capability, small field of view, very wide spectral coverage, and high spectral resolution. Preliminary tests with the DBIS have shown sufficient accuracy for remote sensing applications. In a series of field measurements, jointly organized by the Geophysics Directorate/PL, Hanscom AFB, and DREV, the instrument has been run in a wide variety of sky conditions. Several atmospheric emission spectra recorded with the sounder have been compared to calculations with FASCODE and MODTRAN models. The quality of measurement-model comparisons has prompted the development of an inversion algorithm based on these codes. The purpose of this paper is to report the recent progress achieved in this research. First, the design and operation of the instrument are reviewed. Second, recent field measurements of atmospheric emission spectra are analyzed and compared to models predictions. Finally, the simultaneous retrieval approach selected for the inversion of DBIS spectra to obtain temperature and water vapor profiles is described and preliminary results are presented.

ELF waves and ion resonances produced by an electron beam emitting rocket in the ionosphere

NASA Technical Reports Server (NTRS)

Winckler, J. R.; Abe, Y.; Erickson, K. N.

1986-01-01

Results are reported from the ECHO-6 electron-beam-injection experiment, performed in the auroral-zone ionosphere on March 30, 1983 using a sounding rocket equipped with two electron guns and a free-flying plasma-diagnostics instrument package. The data are presented in extensive graphs and diagrams and characterized in detail. Large ELF wave variations, superposed on the strong beam-sector-directed quasi-dc component, are observed in the 100-eV beam-induced plasma when the beam is injected in a transverse spiral, but not when it is injected upward parallel to the magnetic-field line. ELF activity is found to be suppressed whenever the rocket passed through field lines with auroral activity, suggesting that the waves are produced by the interaction of the beam potentials, plasma currents, and return currents neutralizing the accelerator payload.

Observations of the Upper Ocean Using a Multi-Beam Doppler Sonar

DTIC Science & Technology

1987-05-01

primary scatterers are biological, with various species of zooplankton (euphausiids, copepods, siphonophores , and pteropods) and occa- sional nekton...mesopelagic fishes (Hersey and Backus, 1962), or from other gas-bearing organ- isms such as siphonophores (Barham, 1963; 1966). Later observations using echo

Single-channel seismic-reflection profiles and sidescan-sonar records collected by the R/V Neecho, cruise NE 79-06, on the inner shelf east of Cape Cod, Massachusetts

USGS Publications Warehouse

Twichell, David C.

1981-01-01

Cruise NE 79-06 of the R/V NEECHO was conducted by the U.S. Geological Survey during September 27-0ctober 3, 1979, in the nearshore zone (3-30 m water depth) seaward of Coast Guard Beach and the northern part of Orleans Beach, east of Cape Cod, Massachusetts. The purpose of the study was to map the types and extent of nearshore bed forms and to define the late Pleistocene and Holocene history of the area.The equipment used on this cruise consisted of an EG&G Uniboom, Raytheon echo sounder, and Edo Western sidescan-sonar system. The Uniboom data were mostly filtered to 400-4000 Hz and were recorded at a 1/4-s sweep rate. The 60-kHz echo-sounding data were recorded on a 6-in strip chart on which the depth was calibrated in feet. The sidescan sonar had an operating frequency of 100 kHz and was set to scan 50 m or 100 m to each side of the towed fish. All three data types were collected along 153 km of trackline.Navigation during the survey was by Loran-C and Motorola miniranger systems. Two shore stations were set up for the miniranger system and fixes were collected at either 1- or 2-min intervals. This system malfunctioned during parts of the survey, and during these times navigation was by Loran-C using a Northstar system.The original records can be seen and studied at the U.S. Geological Survey Data Library at Woods Hole, MA 02543. Microfilm copies of the subbottom, echo-sounding, and sidescan-sonar records can be purchased only from the National Geophysical and Solar-Terrestrial Data Center, NOAA/EDIS/NGSDC, Code D621, 325 Broadway, Boulder, CO 80303, (303-497-6338).

Estimation of the Total Electron Content of the Martian Ionosphere using Radar Sounder Surface Echoes

NASA Technical Reports Server (NTRS)

Safaeinili, Ali; Kofman, Wlodek; Mouginot, Jeremie; Gim, Yonggyu; Herique, Alain; Ivanov, Anton B.; Plaut, Jeffrey J.; Picardi, Giovanni

2007-01-01

The Martian ionosphere's local total electron content (TEC) and the neutral atmosphere scale height can be derived from radar echoes reflected from the surface of the planet. We report the global distribution of the TEC by analyzing more than 750,000 echoes of the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS). This is the first direct measurement of the TEC of the Martian ionosphere. The technique used in this paper is a novel 'transmission-mode' sounding of the ionosphere of Mars in contrast to the Active Ionospheric Sounding experiment (AIS) on MARSIS, which generally operates in the reflection mode. This technique yields a global map of the TEC for the Martian ionosphere. The radar transmits a wideband chirp signal that travels through the ionosphere before and after being reflected from the surface. The received waves are attenuated, delayed and dispersed, depending on the electron density in the column directly below the spacecraft. In the process of correcting the radar signal, we are able to estimate the TEC and its global distribution with an unprecedented resolution of about 0.1 deg in latitude (5 km footprint). The mapping of the relative geographical variations in the estimated nightside TEC data reveals an intricate web of high electron density regions that correspond to regions where crustal magnetic field lines are connected to the solar wind. Our data demonstrates that these regions are generally but not exclusively associated with areas that have magnetic field lines perpendicular to the surface of Mars. As a result, the global TEC map provides a high-resolution view of where the Martian crustal magnetic field is connected to the solar wind. We also provide an estimate of the neutral atmospheric scale height near the ionospheric peak and observe temporal fluctuations in peak electron density related to solar activity.

Deep sea mega-geomorphology: Progress and problems

NASA Technical Reports Server (NTRS)

Bryan, W. B.

1985-01-01

Historically, marine geologists have always worked with mega-scale morphology. This is a consequence both of the scale of the ocean basins and of the low resolution of the observational remote sensing tools available until very recently. In fact, studies of deep sea morphology have suffered from a serious gap in observational scale. Traditional wide-beam echo sounding gave images on a scale of miles, while deep sea photography has been limited to scales of a few tens of meters. Recent development of modern narrow-beam echo sounding coupled with computer-controlled swath mapping systems, and development of high-resolution deep-towed side-scan sonar, are rapidly filling in the scale gap. These technologies also can resolve morphologic detail on a scale of a few meters or less. As has also been true in planetary imaging projects, the ability to observe phenomena over a range of scales has proved very effective in both defining processes and in placing them in proper context.

Active echolocation beam focusing in the false killer whale, Pseudorca crassidens.

PubMed

Kloepper, Laura N; Nachtigall, Paul E; Donahue, Megan J; Breese, Marlee

2012-04-15

The odontocete sound production system is highly complex and produces intense, directional signals that are thought to be focused by the melon and the air sacs. Because odontocete echolocation signals are variable and the emitted click frequency greatly affects the echolocation beam shape, investigations of beam focusing must account for frequency-related beam changes. In this study we tested whether the echolocation beam of a false killer whale changed depending on target difficulty and distance while also accounting for frequency-related changes in the echolocation beam. The data indicate that the false killer whale changes its beam size according to target distance and difficulty, which may be a strategy of maximizing the energy of the target echo. We propose that the animal is using a strategy of changing the focal region according to target distance and that this strategy is under active control.

Project Echo: 960-Megacycle, 10-Kilowatt Transmitter

NASA Technical Reports Server (NTRS)

Schafer, J. P.; Brandt, R. H.

1961-01-01

A 10-kw transmitter operating at 960 to 961 Mc was used at the eastern terminus of the Project Echo communications experiment. This transmitter is located on Crawford's Hill near Holmdel, New Jersey. The 10-kw output feeds into a waveguide line leading to a 60-foot dish antenna. Exciter-driver units are available to drive the power amplifier with various modulations, such as wide-deviation FM, low-index phase modulation, single-sideband or double-sideband modulation with or without carrier, 960.05 or 961.05 Mc constant-frequency CW, and radar on-off pulses at 961.05 Mc. The main output amplifier consists primarily of a four-stage, externally-tuned-cavity, water-cooled klystron, operating at a beam voltage of 16 to 18 kv. The transmitter has been operated during many Moonbounce, tropospheric scatter, and Echo I tests with very satisfactory results. This paper describes its use before March 1, 1961.

Whistler mode plasma waves observed on Electron Echo 2

NASA Technical Reports Server (NTRS)

Monson, S. J.; Kellogg, P. J.; Cartwright, D. G.

1976-01-01

Observations of whistler-mode waves associated with beams of electrons injected into the ionosphere are reported. The measurements are from the plasma-wave experiments carried on the Electron Echo 2 sounding rocket launched on September 24, 1972. Over 2000 electron injections were made with durations of 8 ms and 64 ms and pitch angles from 0 to 180 deg. The electric field receivers carried on the ejected nose cone observed strong whistler waves in the range from less than 100 kHz up to the electron cyclotron frequency of 1400 kHz. The whistler characteristics fall into four distinct types depending on pitch angle and gun energy. Both frequency and amplitude showed strong dependence on time from the start of the pulse and pitch angle. Cases of enhancement at the leading edge of a gun pulse, growth during a pulse, and echoes after the end of a pulse were all observed.

The hot plasma environment and floating potentials of an electron-beam-emitting rocket in the ionosphere

NASA Technical Reports Server (NTRS)

Arnoldy, R. L.; Winckler, J. R.

1981-01-01

The plasma environment surrounding the Echo III accelerator payload is examined with an extensive array of particle sensors. Suprathermal electrons are produced isotropically around the payload during the gun firings and decay away in approximately 32 ms. The largest directional intensities of this component are observed at the higher altitudes. Quick echo electrons are also observed to produce suprathermal electrons when they encounter the payload. The hot electrons surrounding the accelerator payload during gun injections bring sufficient charge to the payload to neutralize it provided the loss of charge by secondary production on the payload skin is small. Since the hot population exists for tens of milliseconds after the gun turnoff, it results in driving the payload up to 4 volts negative during this time. Quick echo electrons creating suprathermal electrons around the payload also drive the payload to a few volts negative.

Three & Four Product Surface-Wave Acousto-Optic Time Integrating Correlators.

DTIC Science & Technology

four product correlated signals. A laser beam is split and shaped into first and second sheet beams. The first beam is directed to a first acousto - optic medium...where it is doubly diffracted by first and second signals. The second beam is directed to a second acousto - optic medium which is spatially...rotated 90 degs relative to the first acousto - optic medium where the second sheet beam is either singly diffracted by a third signal or doubly diffracted

Effect of subaperture beamforming on phase coherence imaging.

PubMed

Hasegawa, Hideyuki; Kanai, Hiroshi

2014-11-01

High-frame-rate echocardiography using unfocused transmit beams and parallel receive beamforming is a promising method for evaluation of cardiac function, such as imaging of rapid propagation of vibration of the heart wall resulting from electrical stimulation of the myocardium. In this technique, high temporal resolution is realized at the expense of spatial resolution and contrast. The phase coherence factor has been developed to improve spatial resolution and contrast in ultrasonography. It evaluates the variance in phases of echo signals received by individual transducer elements after delay compensation, as in the conventional delay-andsum beamforming process. However, the phase coherence factor suppresses speckle echoes because phases of speckle echoes fluctuate as a result of interference of echoes. In the present study, the receiving aperture was divided into several subapertures, and conventional delay-and-sum beamforming was performed with respect to each subaperture to suppress echoes from scatterers except for that at a focal point. After subaperture beamforming, the phase coherence factor was obtained from beamformed RF signals from respective subapertures. By means of this procedure, undesirable echoes, which can interfere with the echo from a focal point, can be suppressed by subaperture beamforming, and the suppression of the phase coherence factor resulting from phase fluctuation caused by such interference can be avoided. In the present study, the effect of subaperture beamforming in high-frame-rate echocardiography with the phase coherence factor was evaluated using a phantom. By applying subaperture beamforming, the average intensity of speckle echoes from a diffuse scattering medium was significantly higher (-39.9 dB) than that obtained without subaperture beamforming (-48.7 dB). As for spatial resolution, the width at half-maximum of the lateral echo amplitude profile obtained without the phase coherence factor was 1.06 mm. By using the phase coherence factor, spatial resolution was improved significantly, and subaperture beamforming achieved a better spatial resolution of 0.75 mm than that of 0.78 mm obtained without subaperture beamforming.

Four Decades of Space-Borne Radio Sounding

NASA Technical Reports Server (NTRS)

Benson, Robert F.

2010-01-01

A review is given of the 38 rocket, satellite, and planetary payloads dedicated to ionospheric/magnetospheric radio sounding since 1961. Between 1961 and 1995, eleven sounding-rocket payloads from four countries evolved from proof-of-concept flights to sophisticated instruments. Some involved dual payloads, with the sounder transmitter on one and the sounder receiver on the other. The rocket sounders addressed specific space-plasma-wave questions, and provided improved measurements of ionospheric electron-density (N(sub e)) field-aligned irregularities (FAI). Four countries launched 12 ionospheric topside-sounder satellites between 1962 and 1994, and an ionospheric sounder was placed on the Mir Space Station in 1998. Eleven magnetospheric radio sounders, most of the relaxation type, were launched from 1977 to 2000. The relaxation sounders used low-power transmitters, designed to stimulate plasma resonances for accurate local Ne determinations. The latest magnetospheric sounder designed for remote sensing incorporated long antennas and digital signal processing techniques to overcome the challenges posed by low Ne values and large propagation distances. Three radio sounders from three countries were included on payloads to extraterrestrial destinations from 1990 to 2003. The scientific accomplishments of space-borne radio sounders included (1) a wealth of global N(sub e) information on the topside ionosphere and magnetosphere, based on vertical and magnetic-field-aligned N(sub e) profiles; (2) accurate in-situ N(sub e) values, even under low-density conditions; and (3) fundamental advances in our understanding of the excitation and propagation of plasma waves, which have even led to the prediction of a new plasma-wave mode.

Modelling NDE pulse-echo inspection of misorientated planar rough defects using an elastic finite element method

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

Pettit, J. R.; Lowe, M. J. S.; Walker, A. E.

2015-03-31

Pulse-echo ultrasonic NDE examination of large pressure vessel forgings is a design and construction code requirement in the power generation industry. Such inspections aim to size and characterise potential defects that may have formed during the forging process. Typically these defects have a range of orientations and surface roughnesses which can greatly affect ultrasonic wave scattering behaviour. Ultrasonic modelling techniques can provide insight into defect response and therefore aid in characterisation. However, analytical approaches to solving these scattering problems can become inaccurate, especially when applied to increasingly complex defect geometries. To overcome these limitations a elastic Finite Element (FE) methodmore » has been developed to simulate pulse-echo inspections of embedded planar defects. The FE model comprises a significantly reduced spatial domain allowing for a Monte-Carlo based approach to consider multiple realisations of defect orientation and surface roughness. The results confirm that defects aligned perpendicular to the path of beam propagation attenuate ultrasonic signals according to the level of surface roughness. However, for defects orientated away from this plane, surface roughness can increase the magnitude of the scattered component propagating back along the path of the incident beam. This study therefore highlights instances where defect roughness increases the magnitude of ultrasonic scattered signals, as opposed to attenuation which is more often assumed.« less

Effective biosonar echo-to-clutter rejection ratio in a complex dynamic scene

PubMed Central

Knowles, Jeffrey M.; Barchi, Jonathan R.; Gaudette, Jason E.; Simmons, James A.

2015-01-01

Biosonar guidance in a rapidly changing complex scene was examined by flying big brown bats (Eptesicus fuscus) through a Y-shaped maze composed of rows of strongly reflective vertical plastic chains that presented the bat with left and right corridors for passage. Corridors were 80–100 cm wide and 2–4 m long. Using the two-choice Y-shaped paradigm to compensate for left–right bias and spatial memory, a moveable, weakly reflective thin-net barrier randomly blocked the left or right corridor, interspersed with no-barrier trials. Flight path and beam aim were tracked using an array of 24 microphones surrounding the flight room. Each bat flew on a path centered in the entry corridor (base of Y) and then turned into the left or right passage, to land on the far wall or to turn abruptly, reacting to avoid a collision. Broadcasts were broadly beamed in the direction of flight, smoothly leading into an upcoming turn. Duration of broadcasts decreased slowly from 3 to 2 ms during flights to track the chains' progressively closer ranges. Broadcast features and flight velocity changed abruptly about 1 m from the barrier, indicating that echoes from the net were perceived even though they were 18–35 dB weaker than overlapping echoes from surrounding chains. PMID:26328724

Solitonic characteristics of Airy beam nonlinear propagation

NASA Astrophysics Data System (ADS)

Bouchet, Thomas; Marsal, Nicolas; Sciamanna, Marc; Wolfersberger, Delphine

2018-05-01

We analyze the nonlinear propagation of a one-dimensional Airy beam. Under nonlinear focusing conditions, the Airy beam splits into a weak accelerating structure and a beam that has been named an "off-shooting soliton." Experimental measurements and numerical results related to the off-shooting Airy beam are compared to soliton theoretical profiles and a good agreement is found in terms of transverse shape, width, and amplitude. We identify the different parameters to generate an Airy beam off-shooting soliton and demonstrate that its profile is also preserved through propagation over long distances.

Self-focusing and group-velocity dispersion of pulsed laser beams in the inhomogeneous atmosphere.

PubMed

Zhang, Yuqiu; Ji, Xiaoling; Zhang, Hao; Li, Xiaoqing; Wang, Tao; Wang, Huan; Deng, Yu

2018-05-28

We study self-focusing and group-velocity dispersion (GVD) effects in the inhomogeneous atmosphere on pulsed-laser space debris removal facilitated by a ground-based laser. It is found that changes of the pulse duration and the beam spot size with the propagation distance are noticeable due to the interplay of the GVD effect and the self-focusing effect, which is quite different from the behavior in the linear case. It is shown that the temporal pulse splitting may appear on the space debris, and the spatial side lobe usually appears together with the temporal pulse splitting. As compared with the linear case, the beam width and the pulse width on the debris target increase. On the other hand, crucial formulae of the modified focal length and the M 2 -factor for laser debris removal are also derived. It is found that the beam quality on the debris target becomes better if our modified focal length is adopted, and the beam quality on the debris target will be good if the value of M 2 -factor is less than 1.6.

Method for laser machining explosives and ordnance

DOEpatents

Muenchausen, Ross E.; Rivera, Thomas; Sanchez, John A.

2003-05-06

Method for laser machining explosives and related articles. A laser beam is directed at a surface portion of a mass of high explosive to melt and/or vaporize the surface portion while directing a flow of gas at the melted and/or vaporized surface portion. The gas flow sends the melted and/or vaporized explosive away from the charge of explosive that remains. The method also involves splitting the casing of a munition having an encased explosive. The method includes rotating a munition while directing a laser beam to a surface portion of the casing of an article of ordnance. While the beam melts and/or vaporizes the surface portion, a flow of gas directed at the melted and/or vaporized surface portion sends it away from the remaining portion of ordnance. After cutting through the casing, the beam then melts and/or vaporizes portions of the encased explosive and the gas stream sends the melted/vaporized explosive away from the ordnance. The beam is continued until it splits the article, after which the encased explosive, now accessible, can be removed safely for recycle or disposal.

Method and apparatus for optical communication by frequency modulation

DOEpatents

Priatko, Gordon J.

1988-01-01

Laser optical communication according to this invention is carried out by producing multi-frequency laser beams having different frequencies, splitting one or more of these constituent beams into reference and signal beams, encoding information on the signal beams by frequency modulation and detecting the encoded information by heterodyne techniques. Much more information can be transmitted over optical paths according to the present invention than with the use of only one path as done previously.

A search for muon neutrino to electron neutrino oscillation mediated by sterile neutrinos in MINOS+

NASA Astrophysics Data System (ADS)

Germani, Stefano; Schreckenberger, Adam P.

2017-09-01

The MINOS experiment made precision measurements of the neutrino oscillation parameters that are governed by the atmospheric mass-squared splitting. These measurements were made with data that were collected while the NuMI muon neutrino beam operated in a low energy mode that peaks around 3 GeV. Today the NuMI beam is running with a higher energy mode that produces a neutrino energy spectrum that peaks around 7 GeV, allowing the MINOS+ experiment to probe neutrino oscillation phenomena that could potentially be governed by a fourth mass-squared splitting. If observed, the presence of a fourth mass-squared splitting would be compelling evidence for a sterile neutrino state. In this analysis, we will present the results of a search for νµ → νe oscillation mediated by sterile neutrinos in MINOS+. The results will be contrasted against the measurements made by the LSND experiment.

Reflective echo tomographic imaging using acoustic beams

DOEpatents

Kisner, Roger; Santos-Villalobos, Hector J

2014-11-25

An inspection system includes a plurality of acoustic beamformers, where each of the plurality of acoustic beamformers including a plurality of acoustic transmitter elements. The system also includes at least one controller configured for causing each of the plurality of acoustic beamformers to generate an acoustic beam directed to a point in a volume of interest during a first time. Based on a reflected wave intensity detected at a plurality of acoustic receiver elements, an image of the volume of interest can be generated.

Design for beam splitting components employing silicon-on-insulator rib waveguide structures.

PubMed

Hsiao, C S; Wang, Likarn

2005-12-01

We present a new design for beam splitting components employing a silicon-on-insulator rib waveguide structures. In the new design, a high-index thin-film layer is deposited in the rib section to reduce the wave field dispersive tails in the slab section and accordingly render the mode field a confined spot. This in turn improves the beam splitting performance of some conventional waveguide components such as y branches and multimode interference couplers (MMICs), in terms of the excess loss, fiber coupling loss, and compactness of these components. For a 1 x 2 y-branch beam splitter, the excess loss can be as small as 0.43 dB in the new design, which is much lower than that for a conventional rib waveguide structure (which is 1.28 dB). For a 1 x 2 MMIC in our example, the new rib waveguide structure presents an excess loss of 0.064 dB for the TE mode and 0.046 dB for the TM mode, with negligible nonuniformity in dimensions of 30 microm x 1040 microm, whereas its counterpart (i.e., the one with the same dimensions but without a thin-film layer) presents an excess loss of approximately 0.86 dB for both modes. A conventional MMIC must have dimensions larger than 70 microm x 5650 microm to maintain almost the same low excess loss.

The effect of recombination and attachment on meteor radar diffusion coefficient profiles

NASA Astrophysics Data System (ADS)

Lee, C. S.; Younger, J. P.; Reid, I. M.; Kim, Y. H.; Kim, J.-H.

2013-04-01

Estimates of the ambipolar diffusion coefficient producedusing meteor radar echo decay times display an increasing trend below 80-85 km, which is inconsistent with a diffusion-only theory of the evolution of meteor trails. Data from the 33 MHz meteor radar at King Sejong Station, Antarctica, have been compared with observations from the Aura Earth Observing System Microwave Limb Sounder satellite instrument. It has been found that the height at which the diffusion coefficient gradient reverses follows the height of a constant neutral atmospheric density surface. Numerical simulations of meteor trail diffusion including dissociative recombination with atmospheric ions and three-body attachment of free electrons to neutral molecules indicate that three-body attachment is responsible for the distortion of meteor radar diffusion coefficient profiles at heights below 90 km, including the gradient reversal below 80-85 km. Further investigation has revealed that meteor trails with low initial electron line density produce decay times more consistent with a diffusion-only model of meteor trail evolution.

Sea floor maps showing topography, sun-illuminated topography, and backscatter intensity of the Stellwagen Bank National Marine Sanctuary region off Boston, Massachusetts

USGS Publications Warehouse

Valentine, P.C.; Middleton, T.J.; Fuller, S.J.

2000-01-01

This data set contains the sea floor topographic contours, sun-illuminated topographic imagery, and backscatter intensity generated from a multibeam sonar survey of the Stellwagen Bank National Marine Sanctuary region off Boston, Massachusetts, an area of approximately 1100 square nautical miles. The Stellwagen Bank NMS Mapping Project is designed to provide detailed maps of the Stellwagen Bank region's environments and habitats and the first complete multibeam topographic and sea floor characterization maps of a significant region of the shallow EEZ. Data were collected on four cruises over a two year period from the fall of 1994 to the fall of 1996. The surveys were conducted aboard the Candian Hydrographic Service vessel Frederick G. Creed, a SWATH (Small Waterplane Twin Hull) ship that surveys at speeds of 16 knots. The multibeam data were collected utilizing a Simrad Subsea EM 1000 Multibeam Echo Sounder (95 kHz) that is permanently installed in the hull of the Creed.

Automated benthic counting of living and non-living components in Ngedarrak Reef, Palau via subsurface underwater video.

PubMed

Marcos, Ma Shiela Angeli; David, Laura; Peñaflor, Eileen; Ticzon, Victor; Soriano, Maricor

2008-10-01

We introduce an automated benthic counting system in application for rapid reef assessment that utilizes computer vision on subsurface underwater reef video. Video acquisition was executed by lowering a submersible bullet-type camera from a motor boat while moving across the reef area. A GPS and echo sounder were linked to the video recorder to record bathymetry and location points. Analysis of living and non-living components was implemented through image color and texture feature extraction from the reef video frames and classification via Linear Discriminant Analysis. Compared to common rapid reef assessment protocols, our system can perform fine scale data acquisition and processing in one day. Reef video was acquired in Ngedarrak Reef, Koror, Republic of Palau. Overall success performance ranges from 60% to 77% for depths of 1 to 3 m. The development of an automated rapid reef classification system is most promising for reef studies that need fast and frequent data acquisition of percent cover of living and nonliving components.

Multifrequency acoustic observations of zooplankton in Knight Inlet, B.C

NASA Astrophysics Data System (ADS)

Trevorrow, Mark V.; Mackas, David L.; Benfield, Mark C.

2004-05-01

A collaborative investigation of midwater zooplankton aggregations in a coastal fjord was conducted in November 2002. Midwater aggregations of zooplankton in a coastal fjord were sampled and mapped using a calibrated, three-frequency (38, 120, and 200 kHz) vessel-based echo-sounder system, a multinet towed zooplankton net (BIONESS), and a high-resolution in situ camera system (ZOOVIS). Dense daytime layers of euphausiids and amphipods near 70- to 90-m depth were found in the lower reaches of the inlet, especially concentrated by tidal flows around a sill which rises above the layer. Quantitative euphausiid and amphipod backscattering measurements, combined with in situ species, size, and abundance estimates, were found to agree closely with recent size- and orientation-averaged fluid-cylinder scattering models produced by Stanton et al. Also, in situ scattering measurements of physonect siphonophores were found to have a much stronger low-frequency (38 kHz) scattering strength, in agreement with a simple bubble scattering model. [Work supported by Dr. J. Eckman, ONR code 322BC.

A GIS Library of Multibeam Data for Massachusetts Bay and the Stellwagen Bank National Marine Sanctuary, Offshore of Boston, Massachusetts

USGS Publications Warehouse

Butman, Bradford; Valentine, Page C.; Middleton, Tammie J.; Danforth, William W.

2007-01-01

Introduction The U.S. Geological Survey (USGS) has mapped the sea floor of the Stellwagen Bank National Marine Sanctuary and western Massachusetts Bay, offshore of Boston, Massachusetts (figure 1a, figure 1b). The mapping was carried out using a Simrad Subsea EM1000 Multibeam Echo Sounder (95 kHz) on the Frederick G. Creed on four cruises between 1994 and 1998. The mapping was conducted in cooperation with the National Oceanic and Atmospheric Administration (NOAA) and with support from the Canadian Hydrographic Service and the University of New Brunswick. This GIS Library contains images and grids of bathymetry, shaded relief bathymetry, and backscatter intensity data from these surveys in an Environmental Systems Research Institute (http://www.esri.com) (ESRI) ArcMap 9.1 Geographic Information System (GIS) project. The shapefiles, images, grids and associated metadata may also be downloaded individually. Descriptions and interpretations of the data are available in a series of published maps.

Discharge and other hydraulic measurements for characterizing the hydraulics of Lower Congo River

USGS Publications Warehouse

Oberg, Kevin; Shelton, John M.; Gardiner, Ned; Jackson, P. Ryan

2009-01-01

The first direct measurements of discharge of the Lower Congo River below Malebo Pool and upstream from Kinganga, Democratic Republic of Congo (DRC) were made in July 2008 using acoustic Doppler current profilers, differential GPS, and echo sounders. These measurements were made in support of research that is attempting to understand the distribution of fish species in the Lower Congo River and reasons for separation of species within this large river. Analyses of these measurements show that the maximum depth in the Lower Congo River was in excess of 200 m and maximum water velocities were greater than 4 m/s. The discharge measured near Luozi, DRC was 35,800 m3/s, and decreased slightly beginning midway through the study. Local bedrock controls seem to have a large effect on the flow in the river, even in reaches without waterfalls and rapids. Dramatic changes in bed topography are evident in transects across the river.

Fiber optic diffraction grating maker

DOEpatents

Deason, V.A.; Ward, M.B.

1991-05-21

A compact and portable diffraction grating maker is comprised of a laser beam, optical and fiber optics devices coupling the beam to one or more evanescent beam splitters, and collimating lenses or mirrors directing the split beam at an appropriate photosensitive material. The collimating optics, the output ends of the fiber optic coupler and the photosensitive plate holder are all mounted on an articulated framework so that the angle of intersection of the beams can be altered at will without disturbing the spatial filter, collimation or beam quality, and assuring that the beams will always intersect at the position of the plate. 4 figures.

Fiber optic diffraction grating maker

DOEpatents

Deason, Vance A.; Ward, Michael B.

1991-01-01

A compact and portable diffraction grating maker comprised of a laser beam, optical and fiber optics devices coupling the beam to one or more evanescent beam splitters, and collimating lenses or mirrors directing the split beam at an appropriate photosensitive material. The collimating optics, the output ends of the fiber optic coupler and the photosensitive plate holder are all mounted on an articulated framework so that the angle of intersection of the beams can be altered at will without disturbing the spatial filter, collimation or beam quality, and assuring that the beams will always intersect at the position of the plate.

Pyramid beam splitter

DOEpatents

McKeown, Mark H.; Beason, Steven C.; Fairer, George

1992-01-01

The apparatus of the present invention provides means for obtaining accurate, dependable, measurement of bearings and directions for geologic mapping in subterranean shafts, such as, for example, nuclear waste storage investigations. In operation, a laser beam is projected along a reference bearing. A pyramid is mounted such that the laser beam is parallel to the pyramid axis and can impinge on the apex of the pyramid thus splitting the beam several ways into several beams at right angles to each other and at right angles to the reference beam. The pyramid is also translatable and rotatable in a plane perpendicular to the reference beam.

1×3 optical drop splitter in a rod-type silicon photonic crystal

NASA Astrophysics Data System (ADS)

Zhuang, Dongxia; Chen, Xiyao; Li, Junjun; Lin, Guimin; Qiang, Zexuan; Qiu, Yishen; Li, Hui

2011-12-01

We report an 1×3 optical drop splitter (ODS) based on a self-collimation ring resonator (SCRR) in a rod-type silicon photonic crystal. The proposed 1×3 ODS consists of four beam splitters which are formed by changing the radius of one row of silicon rods. When the self-collimated light with resonance frequency is launched into the ODS, the light beam can be split into three parts come out from three drop ports while no light coming out from the through port. The splitting ratio of the three drop beams can be controlled by tuning the radii of the beam splitters. The FDTD method is employed to calculate the transmission of the 1×3 ODS. For the drop wavelength of 1550 nm, the free spectral range is 28.7 nm, which almost covers the whole optical communication C-band window. This 1×3 ODS may have applications in photonic integrated circuits.

Experimental study of broadband unidirectional splitting in photonic crystal gratings with broken structural symmetry

NASA Astrophysics Data System (ADS)

Colak, Evrim; Serebryannikov, Andriy E.; Ozgur Cakmak, A.; Ozbay, Ekmel

2013-04-01

It is experimentally demonstrated that the combination of diode and splitter functions can be realized in one broadband reciprocal device. The suggested performance is based on the dielectric photonic crystal grating whose structural symmetry is broken owing to non-deep corrugations placed at one of the two interfaces. The study has been performed at a normally incident beam-type illumination obtained from a microwave horn antenna. The two unidirectionally transmitted, deflected beams can show large magnitude and high contrast, while the angular distance between their maxima is 90° and larger. The dual-band unidirectional splitting is possible when using TM and TE polarizations.

Interferometer

NASA Technical Reports Server (NTRS)

Breckinridge, J. B. (Inventor)

1981-01-01

An interferometer of relatively simple design which is tilt compensated, and which facilitates adjustment of the path lengths of split light beams is described. The interferometer includes a pair of plate-like elements with a dielectric coating and an oil film between them, that forms a beamsplitter interface, and with a pair of reflector surfaces at the ends of the plates. A pair of retroreflectors are positioned so that each split beam component is directed by a retroreflector onto one of the reflector surfaces and is then returned to the beamsplitter interface, so that the reflector surfaces tilt in a direction and amount that compensates for tilting of the beamsplitter interface.

An optically passive method that doubles the rate of 2-Ghz timing fiducials

NASA Astrophysics Data System (ADS)

Boni, R.; Kendrick, J.; Sorce, C.

2017-08-01

Solid-state optical comb-pulse generators provide a convenient and accurate method to include timing fiducials in a streak camera image for time base correction. Commercially available vertical-cavity surface-emitting lasers (VCSEL's) emitting in the visible currently in use can be modulated up to 2 GHz. An optically passive method is presented to interleave a time-delayed path of the 2-GHz comb with itself, producing a 4-GHz comb. This technique can be applied to VCSEL's with higher modulation rates. A fiber-delivered, randomly polarized 2-GHz VCSEL comb is polarization split into s-polarization and p-polarization paths. One path is time delayed relative to the other by twice the 2-GHz rate with +/-1-ps accuracy; the two paths then recombine at the fiber-coupled output. High throughput (>=90%) is achieved by carefully using polarization beam-splitting cubes, a total internal reflection beam-path-steering prism, and antireflection coatings. The glass path-length delay block and turning prism are optically contacted together. The beam polarizer cubes that split and recombine the paths are precision aligned and permanently cemented into place. We expect the palm-sized, inline fiber-coupled, comb-rate-doubling device to maintain its internal alignment indefinitely.

Dynamics of a split torque helicopter transmission

NASA Astrophysics Data System (ADS)

Krantz, Timothy L.

1994-06-01

Split torque designs, proposed as alternatives to traditional planetary designs for helicopter main rotor transmissions, can save weight and be more reliable than traditional designs. This report presents the results of an analytical study of the system dynamics and performance of a split torque gearbox that uses a balance beam mechanism for load sharing. The Lagrange method was applied to develop a system of equations of motion. The mathematical model includes time-varying gear mesh stiffness, friction, and manufacturing errors. Cornell's method for calculating the stiffness of spur gear teeth was extended and applied to helical gears. The phenomenon of sidebands spaced at shaft frequencies about gear mesh fundamental frequencies was simulated by modeling total composite gear errors as sinusoid functions. Although the gearbox has symmetric geometry, the loads and motions of the two power paths differ. Friction must be considered to properly evaluate the balance beam mechanism. For the design studied, the balance beam is not an effective device for load sharing unless the coefficient of friction is less than 0.003. The complete system stiffness as represented by the stiffness matrix used in this analysis must be considered to precisely determine the optimal tooth indexing position.

Dynamics of a split torque helicopter transmission. M.S. Thesis - Cleveland State Univ.

NASA Technical Reports Server (NTRS)

Krantz, Timothy L.

1994-01-01

Split torque designs, proposed as alternatives to traditional planetary designs for helicopter main rotor transmissions, can save weight and be more reliable than traditional designs. This report presents the results of an analytical study of the system dynamics and performance of a split torque gearbox that uses a balance beam mechanism for load sharing. The Lagrange method was applied to develop a system of equations of motion. The mathematical model includes time-varying gear mesh stiffness, friction, and manufacturing errors. Cornell's method for calculating the stiffness of spur gear teeth was extended and applied to helical gears. The phenomenon of sidebands spaced at shaft frequencies about gear mesh fundamental frequencies was simulated by modeling total composite gear errors as sinusoid functions. Although the gearbox has symmetric geometry, the loads and motions of the two power paths differ. Friction must be considered to properly evaluate the balance beam mechanism. For the design studied, the balance beam is not an effective device for load sharing unless the coefficient of friction is less than 0.003. The complete system stiffness as represented by the stiffness matrix used in this analysis must be considered to precisely determine the optimal tooth indexing position.

Investigation of lunar maria structure from cross-analysis of GRAIL gravity and Kaguya radar data

NASA Astrophysics Data System (ADS)

Zuber, M. T.; Ermakov, A.; Smith, D. E.; Mastroguiseppe, M.; Raguso, M.

2016-12-01

The Lunar Radar Sounder (LRS) on JAXA's Kaguya spacecraft investigated the subsurface structure of the Moon to a depth of a few km. GRAIL gravity models are potentially sensitive to subsurface structure at such depths. GRAIL gravity and LRS radar data are complementary since both are sensitive to density/compositional heterogeneities. Cross-correlation of GRAIL and LRS data has the potential to produce new constraints on the structure and evolution of the lunar maria. Originally, subsurface reflections within the lunar maria were detected with Lunar Sounder Experiment aboard Apollo 17. Subsurface layering was attributed to multiple episodes of volcanism. Later, Kaguya's LRS produced similar measurements but with global-scale coverage. Laboratory measurements show that density variations among mare basalts can be up to 200 kg m-3 or 7%. The LRS measurements have detected subsurface reflection in the upper 1 km of the crust. Combining these two estimates and using the Bouguer slab approximation, we estimate that anomalies of order 1-10 mGal are expected due to potentially varying density of surface and/or subsurface horizons. This accuracy is achievable with the latest GRAIL gravity models. The LRS surface backscattering power is indicative of surface and near sub-surface dielectric properties, which are sensitive to target density and roughness. We investigate the northwestern part of the Procellarum basin because it is the region with the strongest signal-to-noise ratios in gravity models within maria. To examine shallow subsurface structure, we map the surface received power by tracking the first return of radar echoes and compare it with gravity gradients, which are particularly sensitive to small-scale structures.

Drag coefficients for spheres in free molecular flow in O at satellite velocities

NASA Technical Reports Server (NTRS)

Boring, J. W.; Humphris, R. R.

1973-01-01

The drag coefficients for the Echo 1 and Explorer 24 spherical surfaces in an O environment were experimentally determined over an energy range of 4 to 200 eV. The experiment was performed by generating a beam of atomic oxygen ions of the proper energy, neutralizing a portion of the beam, and then allowing only the neutral O particles to strike a very sensitive torsion balance. The momentum transferred to the surface was determined from the deflection of the torsion balance. At the lower energies, the more intense ion beam had to be used instead of the neutral beam. The drag coefficients are found to be slightly greater than 2 at energies corresponding to satellite velocities.

Plasma heating, electric fields and plasma flow by electron beam ionospheric injection

NASA Technical Reports Server (NTRS)

Winckler, J. R.; Erickson, K. N.

1990-01-01

The electric fields and the floating potentials of a Plasma Diagnostics Payload (PDP) located near a powerful electron beam injected from a large sounding rocket into the auroral zone ionosphere have been studied. As the PDP drifted away from the beam laterally, it surveyed a region of hot plasma extending nearly to 60 m radius. Large polarization electric fields transverse to B were imbedded in this hot plasma, which displayed large ELF wave variations and also an average pattern which has led to a model of the plasma flow about the negative line potential of the beam resembling a hydrodynamic vortex in a uniform flow field. Most of the present results are derived from the ECHO 6 sounding rocket mission.

Compact portable diffraction moire interferometer

DOEpatents

Deason, Vance A.; Ward, Michael B.

1989-01-01

A compact and portable moire interferometer used to determine surface deformations of an object. The improved interferometer is comprised of a laser beam, optical and fiber optics devices coupling the beam to one or more evanescent wave splitters, and collimating lenses directing the split beam at one or more specimen gratings. Observation means including film and video cameras may be used to view and record the resultant fringe patterns.

Polarimetric LIDAR with FRI sampling for target characterization

NASA Astrophysics Data System (ADS)

Wijerathna, Erandi; Creusere, Charles D.; Voelz, David; Castorena, Juan

2017-09-01

Polarimetric LIDAR is a significant tool for current remote sensing applications. In addition, measurement of the full waveform of the LIDAR echo provides improved ranging and target discrimination, although, data storage volume in this approach can be problematic. In the work presented here, we investigated the practical issues related to the implementation of a full waveform LIDAR system to identify polarization characteristics of multiple targets within the footprint of the illumination beam. This work was carried out on a laboratory LIDAR testbed that features a flexible arrangement of targets and the ability to change the target polarization characteristics. Targets with different retardance characteristics were illuminated with a linearly polarized laser beam and the return pulse intensities were analyzed by rotating a linear analyzer polarizer in front of a high-speed detector. Additionally, we explored the applicability and the limitations of applying a sparse sampling approach based on Finite Rate of Innovations (FRI) to compress and recover the characteristic parameters of the pulses reflected from the targets. The pulse parameter values extracted by the FRI analysis were accurate and we successfully distinguished the polarimetric characteristics and the range of multiple targets at different depths within the same beam footprint. We also demonstrated the recovery of an unknown target retardance value from the echoes by applying a Mueller matrix system model.

Ion resonances and ELF wave production by an electron beam injected into the ionosphere - ECHO 6

NASA Astrophysics Data System (ADS)

Winckler, J. R.; Steffen, J. E.; Malcolm, P. R.; Erickson, K. N.; Abe, Y.; Swanson, R. L.

1984-09-01

Two effects observed with electron antennas ejected from a sounding rocket launched into the ionosphere in March 1983 carrying electron beam guns are discussed. The sensor packages were ejected and travelled parallel to the vehicle trajectory. Electric potentials were measured between the single probes and a plasma diagnostic package while the gun injected electrons into the ionosphere in perpendicular and parallel 1 kHz directions. Signal pulses over the dc-1250 kHz range were detected. A kHz gun frequency caused a signal that decreased by two orders of magnitude between 45-90 m from the beam field line. However, the signal was detectable at 1 mV/m at 120 m, supporting earlier data that indicated that pulsed electron beams can cause ELF waves in space. Beam injection parallel to the magnetic field produced an 840 Hz resonance that could be quenched by activation of a transverse beam.

Monitoring a local extreme weather event with the scope of hyperspectral sounding

NASA Astrophysics Data System (ADS)

Satapathy, Jyotirmayee; Jangid, Buddhi Prakash

2018-06-01

Operational space-based hyperspectral Infrared sounders retrieve atmospheric temperature and humidity profiles from the measured radiances. These sounders like Atmospheric InfraRed Sounder, Infrared Atmospheric Sounding Interferometer as well as INSAT-3D sounders on geostationary orbit have proved to be very successful in providing these retrievals on global and regional scales, respectively, with good enough spatio-temporal resolutions and are well competent with that of traditional profiles from radiosondes and models fields. The aim of this work is to show how these new generation hyperspectral Infrared sounders can benefit in real-time weather monitoring. We have considered a regional extreme weather event to demonstrate how the profiles retrieved from these operational sounders are consistent with the environmental conditions which have led to this severe weather event. This work has also made use of data products of Moderate Resolution Imaging Spectroradiometer as well as by radiative transfer simulation of clear and cloudy atmospheric conditions using Numerical Weather Prediction profiles in conjunction with INSAT-3D sounder. Our results indicate the potential use of high-quality hyperspectral atmospheric profiles to aid in delineation of real-time weather prediction.

Report on the Radar/PIREP Cloud Top Discrepancy Study

NASA Technical Reports Server (NTRS)

Wheeler, Mark M.

1997-01-01

This report documents the results of the Applied Meteorology Unit's (AMU) investigation of inconsistencies between pilot reported cloud top heights and weather radar indicated echo top heights (assumed to be cloud tops) as identified by the 45 Weather Squadron (45WS). The objective for this study is to document and understand the differences in echo top characteristics as displayed on both the WSR-88D and WSR-74C radars and cloud top heights reported by the contract weather aircraft in support of space launch operations at Cape Canaveral Air Station (CCAS), Florida. These inconsistencies are of operational concern since various Launch Commit Criteria (LCC) and Flight Rules (FR) in part describe safe and unsafe conditions as a function of cloud thickness. Some background radar information was presented. Scan strategies for the WSR-74C and WSR-88D were reviewed along with a description of normal radar beam propagation influenced by the Effective Earth Radius Model. Atmospheric conditions prior to and leading up to both launch operations were detailed. Through the analysis of rawinsonde and radar data, atmospheric refraction or bending of the radar beam was identified as the cause of the discrepancies between reported cloud top heights by the contract weather aircraft and those as identified by both radars. The atmospheric refraction caused the radar beam to be further bent toward the Earth than normal. This radar beam bending causes the radar target to be displayed erroneously, with higher cloud top heights and a very blocky or skewed appearance.

Detailed structure and tectonics of the Ninetyeast Ridge near Site ODP 758 (on new geophysical data from KNOX06RR cruise of R/V Roger Revelle)

NASA Astrophysics Data System (ADS)

Levchenko, O.; Eisin, A. E.; Ivanenko, A. N.; Marinova, J. G.; Paul, C. F.; Sborshchikov, I. M.; Sager, W. W.

2008-12-01

Detailed geophysical survey was carried out during the NSF-funded KNOX06RR cruise of R/V Roger Revelle in July 2007 over the ~70×70 km area near ODP Site 758, the northern Ninetyeast Ridge (NER). In addition to multibeam echo-sounder bathymetry, 3.5 kHz echo-sounder profiles, magnetic, and gravity data, high-resolution multichannel seismic reflection data were collected on eight orthogonal profiles of total length ~270 km. Large NE-trending depressions with complicated horst and graben morphology dominate the whole detailed survey area. The numerous basement faults extend upward into overlying sediments filling out these depressions. Thickness of the sedimentary fill is highly variable due to very rough basement topography, and is up to 800 m maximum. This fill is divided in two clear sedimentary layers: transparent pelagic sediments above and stratified shallow-water ones below. Two high ~400-450 m isometric seamounts extend from the surrounding NER seafloor. High-resolution seismic records show that these igneous basement highs are covered by thin transparent pelagic sediments which hamper the dredging of volcanic rocks. Seismic stratigraphy analyses for sedimentary cover over the seamounts buried slopes suggest that they seem to be recent volcanoes superimposed on the main NER edifice. Both volcanoes are clearly delineated in the constructed map of total anomaly magnetic field. Since water depths are ~2.5 km above these seamounts, the lower edge of the magnetic body in these volcanoes is situated deep at ~7 km under sea level. That appears to represent deep roots of the volcanoes. Preliminary magnetic modeling shows that they were generated during negative chron of the geomagnetic scale rather not long ago and not far from their present location, seeming to confirm the inference that these volcanoes are recent in origin. In general, one may assume a secondary phase of magmatic activity on the NER. It is important to reveal, any recent phase of tectonic and magnetic activity occurred over the northern NER during the same time of well-known intense intraplate deformation in the Central Indian Basin which was initiated ~8 Ma in response to growing regional compression due to continental collision Hindustan and Eurasia. It appears to be nonrandom that this NER segment is located in an anomalous zone of high oceanic intraplate seismicity. Seismic stratigraphy analyses of high-resolution seismic records over the fault features simultaneously with careful study of reflectors on the buried slopes of the recent volcanoes will allow us to examine this problem.

Observations of Space Charge effects in the Spallation Neutron Source Accumulator Ring

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

Potts III, Robert E; Cousineau, Sarah M; Holmes, Jeffrey A

2012-01-01

The Spallation Neutron Source accumulator ring was designed to allow independent control of the transverse beam distribution in each plane. However, at high beam intensities, nonlinear space charge forces can strongly influence the final beam distribution and compromise our ability to independently control the transverse distributions. In this study we investigate the evolution of the beam at intensities of up to ~8x10^13 ppp through both simulation and experiment. Specifically, we analyze the evolution of the beam distribution for beams with different transverse aspect ratios and tune splits. We present preliminary results of simulations of our experiments.

Gd(III) complexes for electron-electron dipolar spectroscopy: Effects of deuteration, pH and zero field splitting.

PubMed

Garbuio, Luca; Zimmermann, Kaspar; Häussinger, Daniel; Yulikov, Maxim

2015-10-01

Spectral parameters of Gd(III) complexes are intimately linked to the performance of the Gd(III)-nitroxide or Gd(III)-Gd(III) double electron-electron resonance (DEER or PELDOR) techniques, as well as to that of relaxation induced dipolar modulation enhancement (RIDME) spectroscopy with Gd(III) ions. These techniques are of interest for applications in structural biology, since they can selectively detect site-to-site distances in biomolecules or biomolecular complexes in the nanometer range. Here we report relaxation properties, echo detected EPR spectra, as well as the magnitude of the echo reduction effect in Gd(III)-nitroxide DEER for a series of Gadolinium(III) complexes with chelating agents derived from tetraazacyclododecane. We observed that solvent deuteration does not only lengthen the relaxation times of Gd(III) centers but also weakens the DEER echo reduction effect. Both of these phenomena lead to an improved signal-to-noise ratios or, alternatively, longer accessible distance range in pulse EPR measurements. The presented data enrich the knowledge on paramagnetic Gd(III) chelate complexes in frozen solutions, and can help optimize the experimental conditions for most types of the pulse measurements of the electron-electron dipolar interactions. Copyright © 2015 Elsevier Inc. All rights reserved.

Effects of filtering of harmonics from biosonar echoes on delay acuity by big brown bats (Eptesicus fuscus).

PubMed

Bates, Mary E; Simmons, James A

2010-08-01

Big brown bats emit FM biosonar sounds containing two principal harmonics (FM1 approximately 55-22 kHz;FM2 approximately 105-45 kHz). To examine the role of harmonics, they were selectively filtered from stimuli in electronic-echo delay discrimination experiments. Positive stimuli were delayed by 3.16 ms (55 cm simulated target range); negative stimuli were by delayed by 3.96 ms (68 cm). This large 800-micros delay difference (nearly 14 cm) was easily discriminated for echoes containing equal-strength FM1 and FM2. Performance gradually decreased as highpass filters removed progressively larger segments from FM1. For echoes with FM2 alone, performance collapsed to chance, but performance remained good for lowpass echoes containing FM1 alone. Attenuation of FM2 by 3 dB relative to FM1 also decreased performance, but shortening electronic delay of the attenuated FM2 by 48 micros counteracted amplitude-latency trading and restored performance. Bats require the auditory representations of FM1 and FM2 to be in temporal register for high delay acuity. Misalignment of neuronal responses degrades acuity, but outright removal of FM2, leaving only FM1, causes little loss of acuity. Functional asymmetry of harmonics reflects lowpass effects from beaming and atmospheric propagation, which leave FM1 intact. It may cooperate with latency shifts to aid in suppression of clutter.

Security of subcarrier wave quantum key distribution against the collective beam-splitting attack.

PubMed

Miroshnichenko, G P; Kozubov, A V; Gaidash, A A; Gleim, A V; Horoshko, D B

2018-04-30

We consider a subcarrier wave quantum key distribution (QKD) system, where quantum encoding is carried out at weak sidebands generated around a coherent optical beam as a result of electro-optical phase modulation. We study security of two protocols, B92 and BB84, against one of the most powerful attacks for this class of systems, the collective beam-splitting attack. Our analysis includes the case of high modulation index, where the sidebands are essentially multimode. We demonstrate numerically and experimentally that a subcarrier wave QKD system with realistic parameters is capable of distributing cryptographic keys over large distances in presence of collective attacks. We also show that BB84 protocol modification with discrimination of only one state in each basis performs not worse than the original BB84 protocol in this class of QKD systems, thus significantly simplifying the development of cryptographic networks using the considered QKD technique.

View to the eastnortheast of the Sounder Antenna OvertheHorizon ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

View to the east-northeast of the Sounder Antenna - Over-the-Horizon Backscatter Radar Network, Christmas Valley Radar Site Transmit Sector Five Sounder Antennas, On unnamed road west of Lost Forest Road, Christmas Valley, Lake County, OR

View to the northeast of the Sounder Antenna OvertheHorizon ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

View to the northeast of the Sounder Antenna - Over-the-Horizon Backscatter Radar Network, Christmas Valley Radar Site Transmit Sector Five Sounder Antennas, On unnamed road west of Lost Forest Road, Christmas Valley, Lake County, OR

Control of secondary electrons from ion beam impact using a positive potential electrode

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

Crowley, T. P., E-mail: tpcrowley@xanthotechnologies.com; Demers, D. R.; Fimognari, P. J.

2016-11-15

Secondary electrons emitted when an ion beam impacts a detector can amplify the ion beam signal, but also introduce errors if electrons from one detector propagate to another. A potassium ion beam and a detector comprised of ten impact wires, four split-plates, and a pair of biased electrodes were used to demonstrate that a low-voltage, positive electrode can be used to maintain the beneficial amplification effect while greatly reducing the error introduced from the electrons traveling between detector elements.

A simple three dimensional wide-angle beam propagation method

NASA Astrophysics Data System (ADS)

Ma, Changbao; van Keuren, Edward

2006-05-01

The development of three dimensional (3-D) waveguide structures for chip scale planar lightwave circuits (PLCs) is hampered by the lack of effective 3-D wide-angle (WA) beam propagation methods (BPMs). We present a simple 3-D wide-angle beam propagation method (WA-BPM) using Hoekstra’s scheme along with a new 3-D wave equation splitting method. The applicability, accuracy and effectiveness of our method are demonstrated by applying it to simulations of wide-angle beam propagation and comparing them with analytical solutions.

A simple three dimensional wide-angle beam propagation method.

PubMed

Ma, Changbao; Van Keuren, Edward

2006-05-29

The development of three dimensional (3-D) waveguide structures for chip scale planar lightwave circuits (PLCs) is hampered by the lack of effective 3-D wide-angle (WA) beam propagation methods (BPMs). We present a simple 3-D wide-angle beam propagation method (WA-BPM) using Hoekstra's scheme along with a new 3-D wave equation splitting method. The applicability, accuracy and effectiveness of our method are demonstrated by applying it to simulations of wide-angle beam propagation and comparing them with analytical solutions.

Heterodyne interferometer with angstrom-level periodic nonlinearity

DOEpatents

Schmitz, Tony L.; Beckwith, John F.

2005-01-25

Displacement measuring interferometer systems and methods are disclosed. One or more acousto-optic modulators for receiving a laser light beam from a laser light source can be utilized to split the laser light beam into two or more laser light beams, while spatially separating frequencies thereof. One or more reflective mechanisms can be utilized to reflect one or more of the laser light beams back to the acousto-optic modulator. Interference of two or more of the laser light beams generally at the acousto-optic modulator can provide an interfered laser light beam thereof. A detector for receiving the interfered laser light beam can be utilized to provide interferometer measurement data.

Seafloor Mapping: We've Come a Long Way - But Still Have Far to Go……

NASA Astrophysics Data System (ADS)

Mayer, L. A.

2017-12-01

Our ability to map the seafloor has changed radically over the past century. For thousands of years a weight at the end of a rope (or wire) - a lead line - provided the only means to measure depth. By the end of the Second World War, single beam echo sounders had been perfected to the extent that they became common on oceanographic and other vessels providing more rapid but laterally averaged (typically over a distance commensurate with the water depth) measurements of seafloor depths. Towards the end of the 20th Century - two great advances were made in seafloor mapping - the development of techniques to use satellite altimetry to predict seafloor bathymetry and the evolution of multibeam sonar technology from classified military applications to the academic and commercial communities. Satellite-altimetry derived bathymetry provides an unprecedented view of seafloor topography and tremendous insight into tectonic-scale processes but is limited in achievable resolution. Multibeam sonars offer the potential of extremely high-resolution (a function of array size, beam footprint, and water depth), but are typically deployed from manned surface vessels that cover limited amount of seafloor at a relatively high daily cost. We have the technology to map the entire world ocean with multibeam sonar but It has been estimated that to map the world ocean deeper than about 150m (shallow water is very time-consuming and expensive because the coverage swath width is typically 3-5 times water) would take approximately 200 ship years and cost on the order of 3 billion dollars. We have demonstrated our willingness to spend billions to map other planets (e.g. Mars and the Moon) but for some reason, not our own. Recently, however, there has been growing momentum to see the entire world ocean mapped. The Nippon Foundation and GEBCO have recently announced the Seabed 2030 project with a goal of facilitating the mapping of the world ocean by 2030 and international agreements like The Galway Statement on Atlantic Cooperation are coordinating international efforts to see large portions of the seafloor mapped. Coupled with these international efforts, new technologies like autonomous mapping barges or large-scale multibeam sonar equipped Saildrones may greatly reduce costs and make the dream of mapping the world ocean at high-resolution a reality.

Coherent manipulation of mononuclear lanthanide-based single-molecule magnets

NASA Astrophysics Data System (ADS)

Datta, Saiti; Ghosh, Sanhita; Krzystek, Jurek; Hill, Stephen; Del Barco, Enrique; Cardona-Serra, Salvador; Coronado, Eugenio

2010-03-01

Using electron spin echo (ESE) spectroscopy, we report measurements of the longitudinal (T1) and transverse (T2) relaxation times of diluted single-crystals containing recently discovered mononuclear lanthanide-based single-molecule magnets (SMMs) encapsulated in polyoxometallate cages [AlDamen et al. J. Am. Chem. Soc. 130, 8874 -- 8875 (2008)]. This encapsulation offers the potential for preserving bulk SMM properties outside of a crystal, e.g. in molecular spintronic devices. The magnetic anisotropy in these complexes arises from the spin-orbit splitting of the ground state J multiplet of the lanthanide ion in the presence of a ligand field. At low frequencies only hyperfine-split transitions within the lowest ground state ±mJ doublet are observed. Spin relaxation times were measured for a holmium complex, and the results were compared for different hyperfine transitions and crystal dilutions. Clear Rabi oscillations were also observed, indicating that one can manipulate the spin coherently in these complexes.

Diffraction inspired unidirectional and bidirectional beam splitting in defect-containing photonic structures without interface corrugations

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

Colak, Evrim; Serebryannikov, Andriy E., E-mail: andser@amu.edu.pl; Usik, P. V.

2016-05-21

It is shown that strong diffractions and related dual-beam splitting can be obtained at transmission through the nonsymmetric structures that represent two slabs of photonic crystal (PhC) separated by a single coupled-cavity type defect layer, while there are no grating-like corrugations at the interfaces. The basic operation regimes include unidirectional and bidirectional splitting that occur due to the dominant contribution of the first positive and first negative diffraction orders to the transmission, which is typically connected with different manifestations of the asymmetric transmission phenomenon. Being the main component of the resulting transmission mechanism, diffractions appear owing to the effect exertedmore » by the defect layer that works like an embedded diffractive element. Two mechanisms can co-exist in one structure, which differ, among others, in that whether dispersion allows coupling of zero order to a wave propagating in the regular, i.e., defect-free PhC segments or not. The possibility of strong diffractions and efficient splitting related to it strongly depend on the dispersion properties of the Floquet-Bloch modes of the PhC. Existence of one of the studied transmission scenarios is not affected by location of the defect layer.« less

Modulated-splitting-ratio fiber-optic temperature sensor

NASA Technical Reports Server (NTRS)

Beheim, Glenn; Anthan, Donald J.; Rys, John R.; Fritsch, Klaus; Ruppe, Walter A.

1988-01-01

A fiber-optic temperature sensor is described, which uses a small silicon beamsplitter whose splitting ratio varies as a function of temperature. A four-beam technique is used to measure the sensor's temperature-indicating splitting ratio. This referencing method provides a measurement that is largely independent of the transmission properties of the sensor's optical fiber link. A significant advantage of this sensor, relative to other fiber-optic sensors, is its high stability, which permits the fiber-optic components to be readily substituted, thereby simplifying the sensor's installation and maintenance.

High power gas laser amplifier

DOEpatents

Leland, Wallace T.; Stratton, Thomas F.

1981-01-01

A high power output CO.sub.2 gas laser amplifier having a number of sections, each comprising a plurality of annular pumping chambers spaced around the circumference of a vacuum chamber containing a cold cathode, gridded electron gun. The electron beam from the electron gun ionizes the gas lasing medium in the sections. An input laser beam is split into a plurality of annular beams, each passing through the sections comprising one pumping chamber.

Compact portable diffraction moire interferometer

DOEpatents

Deason, V.A.; Ward, M.B.

1988-05-23

A compact and portable moire interferometer used to determine surface deformations of an object. The improved interferometer is comprised of a laser beam, optical and fiber optics devices coupling the beam to one or more evanescent wave splitters, and collimating lenses directing the split beam at one or more specimen gratings. Observations means including film and video cameras may be used to view and record the resultant fringe patterns. 7 figs.

Development of splitting convergent beam electron diffraction (SCBED).

PubMed

Houdellier, Florent; Röder, Falk; Snoeck, Etienne

2015-12-01

Using a combination of condenser electrostatic biprism with dedicated electron optic conditions for sample illumination, we were able to split a convergent beam electron probe focused on the sample in two half focused probes without introducing any tilt between them. As a consequence, a combined convergent beam electron diffraction pattern is obtained in the back focal plane of the objective lens arising from two different sample areas, which could be analyzed in a single pattern. This splitting convergent beam electron diffraction (SCBED) pattern has been tested first on a well-characterized test sample of Si/SiGe multilayers epitaxially grown on a Si substrate. The SCBED pattern contains information from the strained area, which exhibits HOLZ lines broadening induced by surface relaxation, with fine HOLZ lines observed in the unstrained reference part of the sample. These patterns have been analyzed quantitatively using both parts of the SCBED transmitted disk. The fine HOLZ line positions are used to determine the precise acceleration voltage of the microscope while the perturbed HOLZ rocking curves in the stained area are compared to dynamical simulated ones. The combination of these two information leads to a precise evaluation of the sample strain state. Finally, several SCBED setups are proposed to tackle fundamental physics questions as well as applied materials science ones and demonstrate how SCBED has the potential to greatly expand the range of applications of electron diffraction and electron holography. Copyright © 2015 Elsevier B.V. All rights reserved.

Differential phase acoustic microscope for micro-NDE

NASA Technical Reports Server (NTRS)

Waters, David D.; Pusateri, T. L.; Huang, S. R.

1992-01-01

A differential phase scanning acoustic microscope (DP-SAM) was developed, fabricated, and tested in this project. This includes the acoustic lens and transducers, driving and receiving electronics, scanning stage, scanning software, and display software. This DP-SAM can produce mechanically raster-scanned acoustic microscopic images of differential phase, differential amplitude, or amplitude of the time gated returned echoes of the samples. The differential phase and differential amplitude images provide better image contrast over the conventional amplitude images. A specially designed miniature dual beam lens was used to form two foci to obtain the differential phase and amplitude information of the echoes. High image resolution (1 micron) was achieved by applying high frequency (around 1 GHz) acoustic signals to the samples and placing two foci close to each other (1 micron). Tone burst was used in this system to obtain a good estimation of the phase differences between echoes from the two adjacent foci. The system can also be used to extract the V(z) acoustic signature. Since two acoustic beams and four receiving modes are available, there are 12 possible combinations to produce an image or a V(z) scan. This provides a unique feature of this system that none of the existing acoustic microscopic systems can provide for the micro-nondestructive evaluation applications. The entire system, including the lens, electronics, and scanning control software, has made a competitive industrial product for nondestructive material inspection and evaluation and has attracted interest from existing acoustic microscope manufacturers.

High spin states in 162Lu

NASA Astrophysics Data System (ADS)

Gupta, S. L.; Pancholi, S. C.; Juneja, P.; Mehta, D.; Kumar, Ashok; Bhowmik, R. K.; Muralithar, S.; Rodrigues, G.; Singh, R. P.

1997-09-01

An experimental investigation of the odd-odd 162Lu nucleus, following the 148Sm(19F,5n) reaction at beam energy Elab=112 MeV, has been performed through in-beam gamma-ray spectroscopy. It revealed three signature-split bands. The yrast band based on πh11/2⊗νi13/2 configuration exhibits anomalous signature splitting (the unfavored signature Routhian lying lower than the favored one) whose magnitude Δe'~25 keV, is considerably reduced in contrast to sizable normal signature splitting Δe'~125 and 60 keV observed in the yrast πh11/2 bands of the neighboring odd-A 161,163Lu nuclei, respectively. The signature inversion in this band occurs at spin ~20ħ (frequency=0.37 MeV). The second signature-split band, observed above the band crossing associated with the alignment of a pair of i13/2 quasineutrons, is a band based on the four-quasiparticle [πh11/2[523]7/2-⊗νh9/2[521]3/2-⊗(νi13/2)2], i.e., EABAp(Bp), configuration. The third signature-split band is also likely to be a four-quasiparticle band with configuration similar to the second band but involving F quasineutron, i.e., FABAp(Bp). The experimental results are discussed in comparison with the existing data in the neighboring nuclei and in the framework of the cranking shell model.

Design of a bullet beam pattern of a micro ultrasound transducer (Conference Presentation)

NASA Astrophysics Data System (ADS)

Roh, Yongrae; Lee, Seongmin

2016-04-01

Ultrasonic imaging transducer is often required to compose a beam pattern of a low sidelobe level and a small beam width over a long focal region to achieve good image resolution. Normal ultrasound transducers have many channels along its azimuth, which allows easy formation of the sound beam into a desired shape. However, micro-array transducers have no control of the beam pattern along their elevation. In this work, a new method is proposed to manipulate the beam pattern by using an acoustic multifocal lens and a shaded electrode on top of the piezoelectric layer. The shading technique split an initial uniform electrode into several segments and combined those segments to compose a desired beam pattern. For a given elevation width and frequency, the optimal pattern of the split electrodes was determined by means of the OptQuest-Nonlinear Program (OQ-NLP) algorithm to achieve the lowest sidelobe level. The requirement to achieve a small beam width with a long focal region was satisfied by employing an acoustic lens of three multiple focuses. Optimal geometry of the multifocal lens such as the radius of curvature and aperture diameter for each focal point was also determined by the OQ-NLP algorithm. For the optimization, a new index was devised to evaluate the on-axis response: focal region ratio = focal region / minimum beam width. The larger was the focal region ratio, the better was the beam pattern. Validity of the design has been verified through fabricating and characterizing an experimental prototype of the transducer.

Non-linear optical crystal vibration sensing device

DOEpatents

Kalibjian, R.

1994-08-09

A non-linear optical crystal vibration sensing device including a photorefractive crystal and a laser is disclosed. The laser produces a coherent light beam which is split by a beam splitter into a first laser beam and a second laser beam. After passing through the crystal the first laser beam is counter-propagated back upon itself by a retro-mirror, creating a third laser beam. The laser beams are modulated, due to the mixing effect within the crystal by vibration of the crystal. In the third laser beam, modulation is stable and such modulation is converted by a photodetector into a usable electrical output, intensity modulated in accordance with vibration applied to the crystal. 3 figs.

Wave front engineering by means of diffractive optical elements for applications in microscopy

NASA Astrophysics Data System (ADS)

Cojoc, Dan; Ferrari, Enrico; Garbin, Valeria; Cabrini, Stefano; Carpentiero, Alessandro; Prasciolu, Mauro; Businaro, Luca; Kaulich, Burchard; Di Fabrizio, Enzo

2006-05-01

We present a unified view regarding the use of diffractive optical elements (DOEs) for microscopy applications a wide range of electromagnetic spectrum. The unified treatment is realized through the design and fabrication of DOE through which wave front beam shaping is obtained. In particular we show applications ranging from micromanipulation using optical tweezers to X-ray differential interference contrast (DIC) microscopy. We report some details on the design and physical implementation of diffractive elements that beside focusing perform also other optical functions: beam splitting, beam intensity and phase redistribution or mode conversion. Laser beam splitting is used for multiple trapping and independent manipulation of spherical micro beads and for direct trapping and manipulation of biological cells with non-spherical shapes. Another application is the Gauss to Laguerre-Gaussian mode conversion, which allows to trap and transfer orbital angular momentum of light to micro particles with high refractive index and to trap and manipulate low index particles. These experiments are performed in an inverted optical microscope coupled with an infrared laser beam and a spatial light modulator for DOEs implementation. High resolution optics, fabricated by means of e-beam lithography, are demonstrated to control the intensity and the phase of the sheared beams in X-ray DIC microscopy. DIC experiments with phase objects reveal a dramatic increase in image contrast compared to bright-field X-ray microscopy.

Femtosecond laser-induced subwavelength ripples formed by asymmetrical grating splitting

NASA Astrophysics Data System (ADS)

Feng, Pin; Jiang, Lan; Li, Xin; Zhang, Kaihu; Shi, Xuesong; Li, Bo; Lu, Yongfeng

2016-05-01

The formation process and mechanism of subwavelength ripples were studied upon irradiation of ZnO by a femtosecond laser (800 nm, 50 fs, 1 kHz). An abnormally asymmetrical grating-splitting phenomenon was discovered. At relatively high laser fluences (F = 0.51-0.63 J/cm2), near-wavelength ripples were split asymmetrically to create subwavelength laser-induced periodic surface structures (LIPSS) with dual gaps (˜230 nm and ˜430 nm) on the primary grooves. At relatively low laser fluences (F = 0.4-0.45 J/cm2), near-wavelength ripples were split symmetrically, leading to the formation of uniform subwavelength structures with a period of ˜340 nm. The splitting phenomena are related to the varying laser beam dose induced by the overlapping during line scanning. The two grating-splitting types further imply that the dominated mechanism for LIPSS formation may be changed under different processing conditions.

The NPOESS Crosstrack Infrared Sounder (CrIS) and Advanced Technology Microwave Sounder (ATMS) as a Companion to the New Generation AIRS/AMSU and IASI/AMSU Sounder Suites

NASA Astrophysics Data System (ADS)

Bingham, G. E.; Pougatchev, N. S.; Zavyalov, V.; Esplin, M.; Blackwell, W. J.; Barnet, C.

2009-12-01

The NPOESS Preparatory Project is serving the operations and research community as the bridge mission between the Earth Observing System and the National Polar-orbiting Operational Environmental Satellite System. The Cross-track Infrared Sounder (CrIS), combined with the Advanced Technology Microwave Sounder (ATMS) are the core instruments to provide the key performance temperature and humidity profiles (along with some other atmospheric constituent information). Both the high spectral resolution CrIS and the upgraded microwave sounder (ATMS) will be working in parallel with already orbiting Advanced Atmospheric Infrared Sounder (AIRS/AMSU) on EOS AQUA platform and Infrared Atmospheric Sounding Interferometer (IASI/AMSU) on METOP-A satellite. This presentation will review the CrIS/ATMS capabilities in the context of continuity with the excellent performance records established by AIRS and IASI. The CrIS sensor is in the process of its final calibration and characterization testing and the results and Sensor Data Record process are being validated against this excellent dataset. The comparison between CrIS, AIRS, and IASI will include spectral, spatial, radiometric performance and sounding capability comparisons.

Optical Recorder of the Lunar Sounder Experiment

NASA Image and Video Library

1972-11-22

S72-49482 (November 1972) --- The Optical Recorder of the Lunar Sounder Experiment (S-209) which will be mounted in the SIM bay of the Apollo 17 Service Module. The three functional parts of the Lunar Sounder are the optical recorder, the coherent synthetic aperture radar, and the antennas, a retractable dipole for HF and a yagi for VHF. The Lunar Sounder will probe three-quarters of a mile below the moon's surface from the orbiting Apollo 17 spacecraft. Electronic data recorded on film will be retrieved by the crew during trans-Earth EVA. Geologic information on the lunar interior obtained by the sounder will permit scientific investigation of underground rock layers, lava flow patterns, rille (canyon) structures, mascon properties, and any areas containing water. A prototype lunar sounder has been flight tested in aircraft over selected Earth sites to confirm the equipment design and develop scientific analysis techniques. The Lunar Sounder Experiment was developed by North American Rockwell's (NR) Space Division for NASA's Manned Spacecraft Center to provide data for a scientific investigation team with representatives from the Jet Propulsion Laboratory, University of Utah, University of Michigan, U.S. Geological Survey, and NASA Ames Research Center.

A split-beam probe-pump-probe scheme for femtosecond time resolved protein X-ray crystallography

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

van Thor, Jasper J.; Madsen, Anders

In order to exploit the femtosecond pulse duration of X-ray Free-Electron Lasers (XFEL) operating in the hard X-ray regime for ultrafast time-resolved protein crystallography experiments, critical parameters that determine the crystallographic signal-to-noise (I/σI) must be addressed. For single-crystal studies under low absorbed dose conditions, it has been shown that the intrinsic pulse intensity stability as well as mode structure and jitter of this structure, significantly affect the crystallographic signal-to-noise. Here, geometrical parameters are theoretically explored for a three-beam scheme: X-ray probe, optical pump, X-ray probe (or “probe-pump-probe”) which will allow experimental determination of the photo-induced structure factor amplitude differences, ΔF,more » in a ratiometric manner, thereby internally referencing the intensity noise of the XFEL source. In addition to a non-collinear split-beam geometry which separates un-pumped and pumped diffraction patterns on an area detector, applying an additional convergence angle to both beams by focusing leads to integration over mosaic blocks in the case of well-ordered stationary protein crystals. Ray-tracing X-ray diffraction simulations are performed for an example using photoactive yellow protein crystals in order to explore the geometrical design parameters which would be needed. The specifications for an X-ray split and delay instrument that implements both an offset angle and focused beams are discussed, for implementation of a probe-pump-probe scheme at the European XFEL. We discuss possible extension of single crystal studies to serial femtosecond crystallography, particularly in view of the expected X-ray damage and ablation due to the first probe pulse.« less

A split-beam probe-pump-probe scheme for femtosecond time resolved protein X-ray crystallography

DOE PAGES

van Thor, Jasper J.; Madsen, Anders

2015-01-01

In order to exploit the femtosecond pulse duration of X-ray Free-Electron Lasers (XFEL) operating in the hard X-ray regime for ultrafast time-resolved protein crystallography experiments, critical parameters that determine the crystallographic signal-to-noise (I/σI) must be addressed. For single-crystal studies under low absorbed dose conditions, it has been shown that the intrinsic pulse intensity stability as well as mode structure and jitter of this structure, significantly affect the crystallographic signal-to-noise. Here, geometrical parameters are theoretically explored for a three-beam scheme: X-ray probe, optical pump, X-ray probe (or “probe-pump-probe”) which will allow experimental determination of the photo-induced structure factor amplitude differences, ΔF,more » in a ratiometric manner, thereby internally referencing the intensity noise of the XFEL source. In addition to a non-collinear split-beam geometry which separates un-pumped and pumped diffraction patterns on an area detector, applying an additional convergence angle to both beams by focusing leads to integration over mosaic blocks in the case of well-ordered stationary protein crystals. Ray-tracing X-ray diffraction simulations are performed for an example using photoactive yellow protein crystals in order to explore the geometrical design parameters which would be needed. The specifications for an X-ray split and delay instrument that implements both an offset angle and focused beams are discussed, for implementation of a probe-pump-probe scheme at the European XFEL. We discuss possible extension of single crystal studies to serial femtosecond crystallography, particularly in view of the expected X-ray damage and ablation due to the first probe pulse.« less

A split-beam probe-pump-probe scheme for femtosecond time resolved protein X-ray crystallography

PubMed Central

van Thor, Jasper J.; Madsen, Anders

2015-01-01

In order to exploit the femtosecond pulse duration of X-ray Free-Electron Lasers (XFEL) operating in the hard X-ray regime for ultrafast time-resolved protein crystallography experiments, critical parameters that determine the crystallographic signal-to-noise (I/σI) must be addressed. For single-crystal studies under low absorbed dose conditions, it has been shown that the intrinsic pulse intensity stability as well as mode structure and jitter of this structure, significantly affect the crystallographic signal-to-noise. Here, geometrical parameters are theoretically explored for a three-beam scheme: X-ray probe, optical pump, X-ray probe (or “probe-pump-probe”) which will allow experimental determination of the photo-induced structure factor amplitude differences, ΔF, in a ratiometric manner, thereby internally referencing the intensity noise of the XFEL source. In addition to a non-collinear split-beam geometry which separates un-pumped and pumped diffraction patterns on an area detector, applying an additional convergence angle to both beams by focusing leads to integration over mosaic blocks in the case of well-ordered stationary protein crystals. Ray-tracing X-ray diffraction simulations are performed for an example using photoactive yellow protein crystals in order to explore the geometrical design parameters which would be needed. The specifications for an X-ray split and delay instrument that implements both an offset angle and focused beams are discussed, for implementation of a probe-pump-probe scheme at the European XFEL. We discuss possible extension of single crystal studies to serial femtosecond crystallography, particularly in view of the expected X-ray damage and ablation due to the first probe pulse. PMID:26798786

View to the south with the Two Sounder Antennas on ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

View to the south with the Two Sounder Antennas on the left - Over-the-Horizon Backscatter Radar Network, Christmas Valley Radar Site Transmit Sector Four Sounder Antennas, On unnamed road west of Lost Forest Road, Christmas Valley, Lake County, OR

Analysis of test data film generated by the lunar sounder (S-209)

NASA Technical Reports Server (NTRS)

Massey, N.

1973-01-01

The analysis of test films pertaining to the readiness of the Apollo 17 radar equipment is discussed. Emphasis is placed on the evaluation of the lunar sounder equipment. The lunar sounder experiment was to examine the lunar surface at three different radar frequencies of 2 meters, 60 meters, and 20 meters. Test films were made on the lunar sounder system to describe the purpose of the test, to describe the experiments used for analysis, and to provide conclusions reached after analysis.

Proton beam deflection in MRI fields: Implications for MRI-guided proton therapy.

PubMed

Oborn, B M; Dowdell, S; Metcalfe, P E; Crozier, S; Mohan, R; Keall, P J

2015-05-01

This paper investigates, via magnetic modeling and Monte Carlo simulation, the ability to deliver proton beams to the treatment zone inside a split-bore MRI-guided proton therapy system. Field maps from a split-bore 1 T MRI-Linac system are used as input to geant4 Monte Carlo simulations which model the trajectory of proton beams during their paths to the isocenter of the treatment area. Both inline (along the MRI bore) and perpendicular (through the split-bore gap) orientations are simulated. Monoenergetic parallel and diverging beams of energy 90, 195, and 300 MeV starting from 1.5 and 5 m above isocenter are modeled. A phase space file detailing a 2D calibration pattern is used to set the particle starting positions, and their spatial location as they cross isocenter is recorded. No beam scattering, collimation, or modulation of the proton beams is modeled. In the inline orientation, the radial symmetry of the solenoidal style fringe field acts to rotate the protons around the beam's central axis. For protons starting at 1.5 m from isocenter, this rotation is 19° (90 MeV) and 9.8° (300 MeV). A minor focusing toward the beam's central axis is also seen, but only significant, i.e., 2 mm shift at 150 mm off-axis, for 90 MeV protons. For the perpendicular orientation, the main MRI field and near fringe field act as the strongest to deflect the protons in a consistent direction. When starting from 1.5 m above isocenter shifts of 135 mm (90 MeV) and 65 mm (300 MeV) were observed. Further to this, off-axis protons are slightly deflected toward or away from the central axis in the direction perpendicular to the main deflection direction. This leads to a distortion of the phase space pattern, not just a shift. This distortion increases from zero at the central axis to 10 mm (90 MeV) and 5 mm (300 MeV) for a proton 150 mm off-axis. In both orientations, there is a small but subtle difference in the deflection and distortion pattern between protons fired parallel to the beam axis and those fired from a point source. This is indicative of the 3D spatially variant nature of the MRI fringe field. For the first time, accurate magnetic and Monte Carlo modeling have been used to assess the transport of generic proton beams toward a 1 T split-bore MRI. Significant rotation is observed in the inline orientation, while more complex deflection and distortion are seen in the perpendicular orientation. The results of this study suggest that due to the complexity and energy-dependent nature of the magnetic deflection and distortion, the pencil beam scanning method will be the only choice for delivering a therapeutic proton beam inside a potential MRI-guided proton therapy system in either the inline or perpendicular orientation. Further to this, significant correction strategies will be required to account for the MRI fringe fields.

High spin states in 164Lu

NASA Astrophysics Data System (ADS)

Juneja, P.; Gupta, S. L.; Pancholi, S. C.; Kumar, Ashok; Mehta, D.; Chaturvedi, L.; Katoch, S. K.; Malik, S.; Shanker, G.; Bhowmik, R. K.; Muralithar, S.; Rodrigues, G.; Singh, R. P.

1996-03-01

High spin states in the odd-odd 164Lu nucleus have been investigated for the first time, through in-beam gamma-ray spectroscopy, following the 150Sm(19F,5n) reaction at beam energy Elab=105 MeV. Four bands, including two signature split bands are identified. The interpretation of the experimental results is discussed in comparison with the existing data in the neighboring nuclei and in the framework of the cranked shell model. The πh11/2⊗νi13/2 yrast band exhibits anomalous signature splitting and signature inversion is observed at a spin of 18ħ. This provides the missing datum for the systematics of staggering and signature inversion for the neighboring odd-odd N=93 isotones and supports the predictions of angular-momentum projection calculations by Hara and Sun. In the second signature split πh 11/2h9/2 band, the AB neutron crossing occurs at a rotational frequency of ~0.29 MeV. This is indicative of the disappearance of the blocking effect of the odd neutron.

MENTOR: Adding an outlying receiver to an ST radar for meteor-wind measurement

NASA Technical Reports Server (NTRS)

Roper, R. G.

1984-01-01

Radar scattering from ionized meteor trails has been used for many years as a way to determine mesopause-level winds. Scattering occurs perpendicular to the trails, and since the ionizing efficiency of the incoming meteoroids depends on the cosine of the zenith angle of the radiant, echoes directly overhead are rare. Stratosphere-troposphere (ST) radars normally sample within 15 deg of the vertical, and thus receive few meteor echoes. Even the higher powdered mesosphere-stratosphere-troposphere (MST) radars are not good meteor radars, although they were used to successfully retrieved meteor winds from the Poker Flat, Alaska MST radar by averaging long data intervals. It has been suggested that a receiving station some distance from an ST radar could receive pulses being scattered from meteor trails, determine the particular ST beam in which the scattering occurred, measure the radial Doppler velocity, and thus determine the wind field. This concept has been named MENTOR (Meteor Echoes; No Transmitter, Only Receivers).

An investigation of turbulent scatter from the mesosphere as observed by coherent-scatter radar

NASA Technical Reports Server (NTRS)

Gibbs, K. P.; Bowhill, S. A.

1983-01-01

Turbulent scatter from he mesosphere is observed using the Urbana coherent-scatter radar. The variation in signal-to-noise ratio as a function of time-of-day is examined. The origin of scattering regions is investigated by comparing the variations in scattered power and Doppler velocity. Nighttime echoes are shown for periods of enhanced electron concentration. The spectrum of the returned signal is studied with a resolution of ten seconds. Spectral information is used to increase altitude resolution and observe the motion of scatterers. The expected variation in signal-to-noise ratio with solar flux is observed. It is found that variations in the scattered power generally do not correspond to the gravity waves which are simultaneously observed. Turbulent layers are observed at altitudes with high shear in the horizontal velocity and at altitudes with low shear. The ten-second resolution is necessary to distinguish meteor echoes from echoes produced by the advection of a scattering layer through the radar beam.

Exploration Method Development for hydrothermal plume hunting by XCTD

NASA Astrophysics Data System (ADS)

Kitagawa, Y.; Ikeda, M.; Kadoshima, K.; Koizumi, Y.; Nakano, J.; Asakawa, E.; Sumi, T.

2017-12-01

J-MARES (Research and Development Partnership for Next Generation Technology of Marine Resources Survey, JAPAN) has been designing a low-cost and high-efficiency exploration system for seafloor hydrothermal massive sulfide deposits in "Cross-ministerial Strategic Innovation Promotion Program (SIP)" granted by the Cabinet Office, Government of Japan since 2014. We proposed hydrothermal plume hunting by XCTD (eXpendables Conductivity, Temperature and Depth). We applied this method to an area of interest more than 100km x 100km over Okinawa Trough, including some known seafloor massive sulfide deposits. Generally, hydrothermal plume exploration has been by ship mounted with MBES (Multi Beam Echo Sounder) or AUV with sound anomaly observation. However, these methods have to charter the sophisticated ship costly. On the other hand, throw-in type water quality meters (eg. XCTD and XBT) can be low-cost and easily operable. Moreover, that can make a quick look at seawater temperature and conductivity even in rough waters.Firstly, we confirmed XCTD probes position on the seafloor by ROV mounted deep-sea high vision camera. As a result of the test, probes swept downstream about 40 m in horizontal distance from throwing positions with about 1,600m in water depth. Following the previous test results, we had performed to the next test that confirmed detection range of hydrothermal plume at the chimney of North Mound in Izena Cauldron, so we had caught anomaly of seawater temperature and conductivity successfully which could be possibly derived from hydrothermal activities. Although averaged seawater temperature at a depth of 1500 m or more was about 3.95 degrees C, near the chimney was about 4.93 degrees C. The temperature anomalies originated from the hydrothermal plumes could be distributed at most 30m in horizontal distance and became smaller away from the chimney. Moreover, temperature anomaly mass of sea water tended to move upward in depth with distance away from the chimney.

R/V Kilo Moana's New Geophysical Instrumentation, Processing Methods, and Online Data Repository

NASA Astrophysics Data System (ADS)

Miller, J. E.; Chandler, M. T.; Taylor, B.; Shor, A.; Ferguson, J. S.; Wessel, P.

2012-12-01

In 2012 several upgrades were made to the underway geophysical systems on R/V Kilo Moana, which the University of Hawaii School of Ocean and Earth Science and Technology (SOEST) operates as part of the University-National Oceanographic Laboratory System (UNOLS) fleet. New instrumentation includes a Bell BGM-3 forced feedback-type gravimeter, a Kongsberg EM 122 12-kHz receiver array, and a high resolution 70-100 kHz EM 710 multibeam echo sounder. Multibeam acceptance trials carried out in June by the Multibeam Advisory Committee, Gates Acoustic Services and UH-SOEST found that both sonars are performing within expected levels with ~5x water depth (WD) for the EM 710 system in shallow water and ~19 km swath width at 4,700 m depth (~4x WD) for the EM 122 deep water system. UH-SOEST also took steps this year to fulfill its obligation to make Kilo Moana's geophysical data more accessible to the public. After an audit of Kilo Moana data at SOEST, Lamont's Rolling Deck to Repository (R2R) and the National Geophysical Data Center (NGDC), as of July 2012 all National Science Foundation-funded Kilo Moana multibeam, gravity, magnetics, center beam depth and Acoustic Doppler Current Profiler (ADCP) data have been submitted to R2R and any multibeam data over 2 years old is being transferred to NGDC. Because it had previously been difficult to access some of SOEST's geophysical data, updated data processing routines have been developed for converting raw gravity, magnetics, and centerbeam depth data to NGDC's standard marine data exchange format (MGD77) for archival and dissemination by NGDC. MGD77 files are being generated and inspected using rigorous along-track analytical techniques for ~270 surveys dating from 2002 to the present and are being submitted to NGDC. We are also developing an online data portal to further facilitate access to SOEST data.

Global Distribution of Seamounts as Inferred from Ship Depth Soundings and Satellite Altimetry

NASA Astrophysics Data System (ADS)

Wessel, P.; Kim, S.; Sandwell, D. T.

2006-12-01

Traditionally, seamounts are active or extinct undersea volcanoes rising more than 1 km above the abyssal plain, but scientists now regularly apply the seamount label to features of just a few tens of meters in height. As constructional features they represent a small but significant fraction of the total volcanic extrusive budget for oceanic seafloor and their distribution provides key information on the variations in intraplate volcanic activity through space and time. Furthermore, they sustain significant ecological communities, determine habitats for fish, and act as obstacles to ocean currents, thus enhancing tidal energy dissipation and ocean mixing. Consequently, it is of some importance to locate and characterize seamounts. Two approaches are used to map the global distribution of seamounts. Depth soundings from single- and multi-beam echo sounders can provide the most detailed maps with up to 100--200 m horizontal resolution. However, soundings from the 5600 publicly available cruises sample only a small fraction of the ocean floor. Direct radar measurements of the ocean surface by satellite-borne altimeters have been used to infer the marine gravity field. By examining such gravity data one can characterize seamounts taller than ~2 km and such studies have produced seamount catalogues holding almost 15,000 seamounts. Recent retracking of the original radar altimeter waveforms to improve the accuracy of the gravity field has resulted in a two-fold increase in resolution. By extrapolating the inferred power-law that relates seamount size to frequency we estimate that 45,000 smaller seamounts taller than 1.5 km still remain uncharted. Future altimetry missions could improve on resolution and decrease noise levels even further, allowing for an even larger number of small (1--1.5 km) seamounts to be separated from the background abyssal hill fabric. Mapping the complete global distribution of seamounts will help constrain competing models of seamount formation as well as facilitate the understanding of marine habitats and deep ocean circulation.

Innovation Technologies and Applications for Coastal Archaeological sites

NASA Astrophysics Data System (ADS)

Di Iorio, A.; Biliouris, D.; Guzinski, R.; Hansen, L. B.; Bagni, M.

2015-04-01

Innovation Technologies and Applications for Coastal Archaeological sites project (ITACA) aims to develop and test a management system for underwater archaeological sites in coastal regions. The discovering and monitoring service will use innovative satellite remote sensing techniques combined with image processing algorithms. The project will develop a set of applications integrated in a system pursuing the following objectives: - Search and location of ancient ship wrecks; - Monitoring of ship wrecks, ruins and historical artefacts that are now submerged; - Integration of resulting search and monitoring data with on-site data into a management tool for underwater sites; - Demonstration of the system's suitability for a service. High resolution synthetic aperture radar (TerraSAR-X, Cosmo-SkyMed) and multispectral satellite data (WorldView) will be combined to derive the relative bathymetry of the bottom of the sea up to the depth of 50 meters. The resulting data fusion will be processed using shape detection algorithms specific for archaeological items. The new algorithms, the physical modelling and the computational capabilities will be integrated into the Web-GIS, together with data recorded from surface (2D and 3D modelling) and from underwater surveys. Additional specific archaeological layers will be included into the WebGIS to facilitate the object identification through shape detection techniques and mapping. The system will be verified and validated through an extensive onground (sea) campaign carried out with both cutting edge technologies (side-scan sonar, multi beam echo sounder) and traditional means (professional scuba divers) in two test sites in Italy and Greece. The project is leaded by Planetek Hellas E.P.E. and include ALMA Sistemi sas for the "shape detection" and dissemination tasks, DHI-GRAS and Kell Srl for multispectral and SAR bathymetry. The complete consortium is composed by eleven partners and the project Kick-Off has been held in January 2014. The present contribution aims to present the project research achievements and finding at the mid-term review.

Electron beam injection during active experiments. I - Electromagnetic wave emissions

NASA Technical Reports Server (NTRS)

Winglee, R. M.; Kellogg, P. J.

1990-01-01

The wave emissions produced in Echo 7 experiment by active injections of electron beams were investigated to determine the properties of the electromagnetic and electrostatic fields for both the field-aligned and cross-field injection in such experiments and to evaluate the sources of free energy and relative efficiencies for the generation of the VLF and HF emissions. It is shown that, for typical beam energies in active experiments, electromagnetic effects do not substantially change the bulk properties of the beam, spacecraft charging, and plasma particle acceleration. Through simulations, beam-generated whistlers; fundamental z-mode and harmonic x-mode radiation; and electrostatic electron-cyclotron, upper-hybrid, Langmuir, and lower-hybrid waves were identified. The characteristics of the observed wave spectra were found to be sensitive to both the ratio of the electron plasma frequency to the cyclotron frequency and the angle of injection relative to the magnetic field.

Noise suppressing capillary separation system

DOEpatents

Yeung, Edward S.; Xue, Yongjun

1996-07-30

A noise-suppressing capillary separation system for detecting the real-time presence or concentration of an analyte in a sample is provided. The system contains a capillary separation means through which the analyte is moved, a coherent light source that generates a beam which is split into a reference beam and a sample beam that irradiate the capillary, and a detector for detecting the reference beam and the sample beam light that transmits through the capillary. The laser beam is of a wavelength effective to be absorbed by a chromophore in the capillary. The system includes a noise suppressing system to improve performance and accuracy without signal averaging or multiple scans.

Noise suppressing capillary separation system

DOEpatents

Yeung, E.S.; Xue, Y.

1996-07-30

A noise-suppressing capillary separation system for detecting the real-time presence or concentration of an analyte in a sample is provided. The system contains a capillary separation means through which the analyte is moved, a coherent light source that generates a beam which is split into a reference beam and a sample beam that irradiate the capillary, and a detector for detecting the reference beam and the sample beam light that transmits through the capillary. The laser beam is of a wavelength effective to be absorbed by a chromophore in the capillary. The system includes a noise suppressing system to improve performance and accuracy without signal averaging or multiple scans. 13 figs.

Retrieved Products from Simulated Hyperspectral Observations of a Hurricane

NASA Technical Reports Server (NTRS)

Susskind, Joel; Kouvaris, Louis; Iredell, Lena; Blaisdell, John

2015-01-01

Demonstrate via Observing System Simulation Experiments (OSSEs) the potential utility of flying high spatial resolution AIRS class IR sounders on future LEO and GEO missions.The study simulates and analyzes radiances for 3 sounders with AIRS spectral and radiometric properties on different orbits with different spatial resolutions: 1) Control run 13 kilometers AIRS spatial resolution at nadir on LEO in Aqua orbit; 2) 2 kilometer spatial resolution LEO sounder at nadir ARIES; 3) 5 kilometers spatial resolution sounder on a GEO orbit, radiances simulated every 72 minutes.

High throughput laser processing

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

Harley, Gabriel; Pass, Thomas; Cousins, Peter John

A solar cell is formed using a solar cell ablation system. The ablation system includes a single laser source and several laser scanners. The laser scanners include a master laser scanner, with the rest of the laser scanners being slaved to the master laser scanner. A laser beam from the laser source is split into several laser beams, with the laser beams being scanned onto corresponding wafers using the laser scanners in accordance with one or more patterns. The laser beams may be scanned on the wafers using the same or different power levels of the laser source.

Spatially-Heterodyned Holography

DOEpatents

Thomas, Clarence E [Knoxville, TN; Hanson, Gregory R [Clinton, TN

2006-02-21

A method of recording a spatially low-frequency heterodyne hologram, including spatially heterodyne fringes for Fourier analysis, includes: splitting a laser beam into a reference beam and an object beam; interacting the object beam with an object; focusing the reference beam and the object beam at a focal plane of a digital recorder to form a spatially low-frequency heterodyne hologram including spatially heterodyne fringes for Fourier analysis; digital recording the spatially low-frequency heterodyne hologram; Fourier transforming axes of the recorded spatially low-frequency heterodyne hologram including spatially heterodyne fringes in Fourier space to sit on top of a heterodyne carrier frequency defined by an angle between the reference beam and the object beam; cutting off signals around an origin; and performing an inverse Fourier transform.

Effects of filtering of harmonics from biosonar echoes on delay acuity by big brown bats (Eptesicus fuscus)

PubMed Central

Bates, Mary E.; Simmons, James A.

2010-01-01

Big brown bats emit FM biosonar sounds containing two principal harmonics (FM1∼55–22 kHz;FM2∼105–45 kHz). To examine the role of harmonics, they were selectively filtered from stimuli in electronic-echo delay discrimination experiments. Positive stimuli were delayed by 3.16 ms (55 cm simulated target range); negative stimuli were by delayed by 3.96 ms (68 cm). This large 800-μs delay difference (nearly 14 cm) was easily discriminated for echoes containing equal-strength FM1 and FM2. Performance gradually decreased as highpass filters removed progressively larger segments from FM1. For echoes with FM2 alone, performance collapsed to chance, but performance remained good for lowpass echoes containing FM1 alone. Attenuation of FM2 by 3 dB relative to FM1 also decreased performance, but shortening electronic delay of the attenuated FM2 by 48 μs counteracted amplitude-latency trading and restored performance. Bats require the auditory representations of FM1 and FM2 to be in temporal register for high delay acuity. Misalignment of neuronal responses degrades acuity, but outright removal of FM2, leaving only FM1, causes little loss of acuity. Functional asymmetry of harmonics reflects lowpass effects from beaming and atmospheric propagation, which leave FM1 intact. It may cooperate with latency shifts to aid in suppression of clutter. PMID:20707464

Development of a Novel Two Dimensional Surface Plasmon Resonance Sensor Using Multiplied Beam Splitting Optics

PubMed Central

Hemmi, Akihide; Mizumura, Ryosuke; Kawanishi, Ryuta; Nakajima, Hizuru; Zeng, Hulie; Uchiyama, Katsumi; Kaneki, Noriaki; Imato, Toshihiko

2013-01-01

A novel two dimensional surface plasmon resonance (SPR) sensor system with a multi-point sensing region is described. The use of multiplied beam splitting optics, as a core technology, permitted multi-point sensing to be achieved. This system was capable of simultaneously measuring nine sensing points. Calibration curves for sucrose obtained on nine sensing points were linear in the range of 0–10% with a correlation factor of 0.996–0.998 with a relative standard deviation of 0.090–4.0%. The detection limits defined as S/N = 3 were 1.98 × 10−6–3.91 × 10−5 RIU. This sensitivity is comparable to that of conventional SPR sensors. PMID:23299626

The Expected Impacts of NPOESS Microwave and Infrared Sounder Radiances on Operational Numerical Weather Prediction and Data Assimilation Systems

NASA Astrophysics Data System (ADS)

Swadley, S. D.; Baker, N.; Derber, J.; Collard, A.; Hilton, F.; Ruston, B.; Bell, W.; Candy, B.; Kleespies, T. J.

2009-12-01

The NPOESS atmospheric sounding functionality will be accomplished using two separate sensor suites, the combined infrared (IR) and microwave (MW) sensor suite (CrIMSS), and the Microwave Imager/Sounder (MIS) instrument. CrIMSS consists of the Cross Track Infrared Sounder (CrIS) and the cross track Advanced Technology Microwave Sounder (ATMS), and is scheduled to fly on the NPOESS Preparatory Project (NPP), and NPOESS operational flight units C1 and C3. The MIS is a conical scanning polarimetric imager and sounder patterned after the heritage WindSat, and DMSP Special Sensor Microwave Imagers and Sounders (SSMI and SSMIS), and is scheduled for flight units C2, C3 and C4. ATMS combines the current operational Advanced Microwave Sounding Unit (AMSU) and the Microwave Humidity Sounder (MHS), but with an additional channel in the 51.76 GHz oxygen absorption region and 3 additional channels in the 165.5 and 183 GHz water vapor absorption band. CrIS is a Fourier Transform Spectrometer and will provide 159 shortwave IR channels, 433 mid-range IR channels, and 713 longwave IR channels. The heritage sensors for CrIS are the NASA Advanced Infrared Sounder (AIRS) and the MetOp-A Infrared Atmospheric Sounding Interferometer (IASI). Both AIRS and IASI are high quality, high spectral resolution sounders which represent a significant improvement in the effective vertical resolution over previous IR sounders. This presentation will give an overview of preparations underway for day-1 monitoring of NPP/NPOESS radiances, and subsequent operational radiance assimilation. These preparations capitalize on experience gained during the pre-launch preparations, sensor calibration/validation and operational assimilation for the heritage sensors. One important step is to use pre-flight sensor channel specifications, noise estimates and knowledge of the antenna patterns, to generate and test proxy NPP/NPOESS sensor observations in existing assimilation systems. Other critical factors for successful radiance assimilation include low noise measurements, channel sets that span the vertical space defined within the NWP model, a fast and accurate radiative transfer model, and bias correction schemes designed to remove systematic biases in the departures between the observed versus calculated radiances.

Highly Directional Sonar Beam of Narwhals (Monodon monoceros) Measured with a Vertical 16 Hydrophone Array.

PubMed

Koblitz, Jens C; Stilz, Peter; Rasmussen, Marianne H; Laidre, Kristin L

2016-01-01

Recordings of narwhal (Monodon monoceros) echolocation signals were made using a linear 16 hydrophone array in the pack ice of Baffin Bay, West Greenland in 2013 at eleven sites. An average -3 dB beam width of 5.0° makes the narwhal click the most directional biosonar signal reported for any species to date. The beam shows a dorsal-ventral asymmetry with a narrower beam above the beam axis. This may be an evolutionary advantage for toothed whales to reduce echoes from the water surface or sea ice surface. Source level measurements show narwhal click intensities of up to 222 dB pp re 1 μPa, with a mean apparent source level of 215 dB pp re 1 μPa. During ascents and descents the narwhals perform scanning in the vertical plane with their sonar beam. This study provides valuable information for reference sonar parameters of narwhals and for the use of acoustic monitoring in the Arctic.

Highly Directional Sonar Beam of Narwhals (Monodon monoceros) Measured with a Vertical 16 Hydrophone Array

PubMed Central

Koblitz, Jens C.; Stilz, Peter; Rasmussen, Marianne H.; Laidre, Kristin L.

2016-01-01

Recordings of narwhal (Monodon monoceros) echolocation signals were made using a linear 16 hydrophone array in the pack ice of Baffin Bay, West Greenland in 2013 at eleven sites. An average -3 dB beam width of 5.0° makes the narwhal click the most directional biosonar signal reported for any species to date. The beam shows a dorsal-ventral asymmetry with a narrower beam above the beam axis. This may be an evolutionary advantage for toothed whales to reduce echoes from the water surface or sea ice surface. Source level measurements show narwhal click intensities of up to 222 dB pp re 1 μPa, with a mean apparent source level of 215 dB pp re 1 μPa. During ascents and descents the narwhals perform scanning in the vertical plane with their sonar beam. This study provides valuable information for reference sonar parameters of narwhals and for the use of acoustic monitoring in the Arctic. PMID:27828956

Two-Diffraction-Order, Beam-Splitting, Imaging Spectrometer

NASA Technical Reports Server (NTRS)

Labaw, Clayton C.; Burns, Ronald N.

1995-01-01

Two-octave imaging spectrometer utilizes light of two harmonically related wavelengths diffracted to harmonically related orders at same angles, followed by separation via dichroic beam splitter before final imaging. Conceptual design of spectrometer calls for minimum number of optical elements to achieve coverage of required visible and near-infrared wavelengths in instrument of reduced size, weight, and cost.

Eccentric superconducting RF cavity separator structure

DOEpatents

Aggus, John R.; Giordano, Salvatore T.; Halama, Henry J.

1976-01-01

Accelerator apparatus having an eccentric-shaped, iris-loaded deflecting cavity for an rf separator for a high energy high momentum, charged particle accelerator beam. In one embodiment, the deflector is superconducting, and the apparatus of this invention provides simplified machining and electron beam welding techniques. Model tests have shown that the electrical characteristics provide the desired mode splitting without adverse effects.

Modeling Statistics of Fish Patchiness and Predicting Associated Influence on Statistics of Acoustic Echoes

DTIC Science & Technology

2013-09-30

data. The Niwa and Anderson models were compared with 3-D multi-beam data collected by Paramo and Gerlotto. The data were consistent with the...Bhatia, S., T.K. Stanton, J. Paramo , and F. Gerlotto (under revision), “Modeling statistics of fish school dimensions using 3-D data from a

How Well Can Infrared Sounders Observe the Atmosphere and Surface Through Clouds?

NASA Technical Reports Server (NTRS)

Zhou, Daniel K.; Larar, Allen M.; Liu, Xu; Smith, William L.; Strow, L. Larrabee; Yang, Ping

2010-01-01

Infrared sounders, such as the Atmospheric Infrared Sounder (AIRS), the Infrared Atmospheric Sounding Interferometer (IASI), and the Cross-track Infrared sounder (CrIS), have a cloud-impenetrable disadvantage in observing the atmosphere and surface under opaque cloudy conditions. However, recent studies indicate that hyperspectral, infrared sounders have the ability to detect cloud effective-optical and microphysical properties and to penetrate optically thin clouds in observing the atmosphere and surface to a certain degree. We have developed a retrieval scheme dealing with atmospheric conditions with cloud presence. This scheme can be used to analyze the retrieval accuracy of atmospheric and surface parameters under clear and cloudy conditions. In this paper, we present the surface emissivity results derived from IASI global measurements under both clear and cloudy conditions. The accuracy of surface emissivity derived under cloudy conditions is statistically estimated in comparison with those derived under clear sky conditions. The retrieval error caused by the clouds is shown as a function of cloud optical depth, which helps us to understand how well infrared sounders can observe the atmosphere and surface through clouds.

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

Wu, J; Hill, G; Spiegel, J

Purpose: To investigate the clinical and dosimetric benefits of automatic gating of left breast mixed with breath-hold technique. Methods: Two Active Breathing Control systems, ABC2.0 and ABC3.0, were used during simulation and treatment delivery. The two systems are different such that ABC2.0 is a breath-hold system without beam control capability, while ABC3.0 has capability in both breath-hold and beam gating. At simulation, each patient was scanned twice: one with free breathing (FB) and one with breath hold through ABC. Treatment plan was generated on the CT with ABC. The same plan was also recalculated on the CT with FB. Thesemore » two plans were compared to assess plan quality. For treatments with ABC2.0, beams with MU > 55 were manually split into multiple subfields. All subfields were identical and shared the total MU. For treatment with ABC3.0, beam splitting was unnecessary. Instead, treatment was delivered in gating mode mixed with breath-hold technique. Treatment delivery efficiency using the two systems was compared. Results: The prescribed dose was 50.4Gy at 1.8Gy/fraction. The maximum heart dose averaged over 10 patients was 46.0±2.5Gy and 24.5±12.2Gy for treatments with FB and with ABC respectively. The corresponding heart V10 was 13.2±3.6% and 1.0±1.6% respectively. The averaged MUs were 99.8±7.5 for LMT, 99.2±9.4 for LLT. For treatment with ABC2.0, normally the original beam was split into 2 subfields. The averaged total time to delivery all beams was 4.3±0.4min for treatments with ABC2.0 and 3.3±0.6min for treatments with ABC3.0 in gating mode. Conclusion: Treatment with ABC tremendously reduced heart dose. Compared to treatments with ABC2.0, gating with ABC3.0 reduced the total treatment time by 23%. Use of ABC3.0 improved the delivery efficiency, and eliminated the possibility of mistreatments. The latter may happen with ABC2.0 where beam is not terminated when breath signal falls outside of the treatment window.« less

High-precision laser microcutting and laser microdrilling using diffractive beam-splitting and high-precision flexible beam alignment

NASA Astrophysics Data System (ADS)

Zibner, F.; Fornaroli, C.; Holtkamp, J.; Shachaf, Lior; Kaplan, Natan; Gillner, A.

2017-08-01

High-precision laser micro machining gains more importance in industrial applications every month. Optical systems like the helical optics offer highest quality together with controllable and adjustable drilling geometry, thus as taper angle, aspect ratio and heat effected zone. The helical optics is based on a rotating Dove-prism which is mounted in a hollow shaft engine together with other optical elements like wedge prisms and plane plates. Although the achieved quality can be interpreted as extremely high the low process efficiency is a main reason that this manufacturing technology has only limited demand within the industrial market. The objective of the research studies presented in this paper is to dramatically increase process efficiency as well as process flexibility. During the last years, the average power of commercial ultra-short pulsed laser sources has increased significantly. The efficient utilization of the high average laser power in the field of material processing requires an effective distribution of the laser power onto the work piece. One approach to increase the efficiency is the application of beam splitting devices to enable parallel processing. Multi beam processing is used to parallelize the fabrication of periodic structures as most application only require a partial amount of the emitted ultra-short pulsed laser power. In order to achieve highest flexibility while using multi beam processing the single beams are diverted and re-guided in a way that enables the opportunity to process with each partial beam on locally apart probes or semimanufactures.

Efficient Second Harmonic Generation in 3D Nonlinear Optical-Lattice-Like Cladding Waveguide Splitters by Femtosecond Laser Inscription

PubMed Central

Nie, Weijie; Jia, Yuechen; Vázquez de Aldana, Javier R.; Chen, Feng

2016-01-01

Integrated photonic devices with beam splitting function are intriguing for a broad range of photonic applications. Through optical-lattice-like cladding waveguide structures fabricated by direct femtosecond laser writing, the light propagation can be engineered via the track-confined refractive index profiles, achieving tailored output beam distributions. In this work, we report on the fabrication of 3D laser-written optical-lattice-like structures in a nonlinear KTP crystal to implement 1 × 4 beam splitting. Second harmonic generation (SHG) of green light through these nonlinear waveguide beam splitter structures provides the capability for the compact visible laser emitting devices. With Type II phase matching of the fundamental wavelength (@ 1064 nm) to second harmonic waves (@ 532 nm), the frequency doubling has been achieved through this three-dimensional beam splitter. Under 1064-nm continuous-wave fundamental-wavelength pump beam, guided-wave SHG at 532 nm are measured with the maximum power of 0.65 mW and 0.48 mW for waveguide splitters (0.67 mW and 0.51 mW for corresponding straight channel waveguides), corresponding to a SH conversion efficiency of approximately ~14.3%/W and 13.9%/W (11.2%/W, 11.3%/W for corresponding straight channel waveguides), respectively. This work paves a way to fabricate compact integrated nonlinear photonic devices in a single chip with beam dividing functions. PMID:26924255

Efficient Second Harmonic Generation in 3D Nonlinear Optical-Lattice-Like Cladding Waveguide Splitters by Femtosecond Laser Inscription.

PubMed

Nie, Weijie; Jia, Yuechen; Vázquez de Aldana, Javier R; Chen, Feng

2016-02-29

Integrated photonic devices with beam splitting function are intriguing for a broad range of photonic applications. Through optical-lattice-like cladding waveguide structures fabricated by direct femtosecond laser writing, the light propagation can be engineered via the track-confined refractive index profiles, achieving tailored output beam distributions. In this work, we report on the fabrication of 3D laser-written optical-lattice-like structures in a nonlinear KTP crystal to implement 1 × 4 beam splitting. Second harmonic generation (SHG) of green light through these nonlinear waveguide beam splitter structures provides the capability for the compact visible laser emitting devices. With Type II phase matching of the fundamental wavelength (@ 1064 nm) to second harmonic waves (@ 532 nm), the frequency doubling has been achieved through this three-dimensional beam splitter. Under 1064-nm continuous-wave fundamental-wavelength pump beam, guided-wave SHG at 532 nm are measured with the maximum power of 0.65 mW and 0.48 mW for waveguide splitters (0.67 mW and 0.51 mW for corresponding straight channel waveguides), corresponding to a SH conversion efficiency of approximately ~14.3%/W and 13.9%/W (11.2%/W, 11.3%/W for corresponding straight channel waveguides), respectively. This work paves a way to fabricate compact integrated nonlinear photonic devices in a single chip with beam dividing functions.

Self-interference of split HOLZ line (SIS-HOLZ) for z-dependent atomic displacement measurement: Theoretical discussion.

PubMed

Norouzpour, Mana; Rakhsha, Ramtin; Herring, Rodney

2017-06-01

A characteristic of the majority of semiconductors is the presence of lattice strain varying with the nanometer scale. Strain originates from the lattice mismatch between layers of different composition deposited during epitaxial growth. Strain can increase the mobility of the charge carriers by the band gap reduction. So, measuring atomic displacement inside crystals is an important field of interest in semiconductor industry. Among all available transmission electron microscopy techniques offering nano-scale resolution measurements, convergent beam electron diffraction (CBED) patterns show the highest sensitivity to the atomic displacement. Higher Order Laue Zone (HOLZ) lines split by small non-uniform variations of lattice constant allowing to measure the atomic displacement through the crystal. However, it could only reveal the atomic displacement in two dimensions, i.e., within the x-y plane of the thin film of TEM specimen. The z-axis atomic displacement which is along the path of the electron beam has been missing. This information can be obtained by recovering the phase information across the split HOLZ line using the self-interference of the split HOLZ line (SIS-HOLZ). In this work, we report the analytical approach used to attain the phase profile across the split HOLZ line. The phase profile is studied for three different atomic displacement fields in the Si substrate at 80nm away from its interface with Si/Si 0.8 Ge 0.2 superlattices. Copyright © 2017 Elsevier Ltd. All rights reserved.

Asymmetric adiabatic couplers for fully-integrated broadband quantum-polarization state preparation.

PubMed

Chung, Hung-Pin; Huang, Kuang-Hsu; Wang, Kai; Yang, Sung-Lin; Yang, Shih-Yuan; Sung, Chun-I; Solntsev, Alexander S; Sukhorukov, Andrey A; Neshev, Dragomir N; Chen, Yen-Hung

2017-12-04

Spontaneous parametric down-conversion (SPDC) is a widely used method to generate entangled photons, enabling a range of applications from secure communication to tests of quantum physics. Integrating SPDC on a chip provides interferometric stability, allows to reduce a physical footprint, and opens a pathway to true scalability. However, dealing with different photon polarizations and wavelengths on a chip presents a number of challenging problems. In this work, we demonstrate an on-chip polarization beam-splitter based on z-cut titanium-diffused lithium niobate asymmetric adiabatic couplers (AAC) designed for integration with a type-II SPDC source. Our experimental measurements reveal unique polarization beam-splitting regime with the ability to tune the splitting ratios based on wavelength. In particular, we measured a splitting ratio of 17 dB over broadband regions (>60 nm) for both H- and V-polarized lights and a specific 50%/50% splitting ratio for a cross-polarized photon pair from the AAC. The results show that such a system can be used for preparing different quantum polarization-path states that are controllable by changing the phase-matching conditions in the SPDC over a broad band. Furthermore, we propose a fully integrated electro-optically tunable type-II SPDC polarization-path-entangled state preparation circuit on a single lithium niobate photonic chip.

A simplified model of biosonar echoes from foliage and the properties of natural foliages.

PubMed

Ming, Chen; Zhu, Hongxiao; Müller, Rolf

2017-01-01

Foliage echoes could play an important role in the sensory ecology of echolocating bats, but many aspects of their sensory information content remain to be explored. A realistic numerical model for these echoes could support the development of hypotheses for the relationship between foliage properties and echo parameters. In prior work by the authors, a simple foliage model based on circular disks distributed uniformly in space has been developed. In the current work, three key simplifications used in this model have been examined: (i) representing leaves as circular disks, (ii) neglecting shading effects between leaves, and (iii) the uniform spatial distribution of the leaves. The target strengths of individual leaves and shading between them have been examined in physical experiments, whereas the impact of the spatial leaf distribution has been studied by modifying the numerical model to include leaf distributions according to a biomimetic model for natural branching patterns (L-systems). Leaf samples from a single species (leatherleaf arrowwood) were found to match the relationship between size and target strength of the disk model fairly well, albeit with a large variability part of which could be due to unaccounted geometrical features of the leaves. Shading between leaf-sized disks did occur for distances below 50 cm and could hence impact the echoes. Echoes generated with L-system models in two distinct tree species (ginkgo and pine) showed consistently more temporal inhomogeneity in the envelope amplitudes than a reference with uniform distribution. However, these differences were small compared to effects found in response to changes in the relative orientation of simulated sonar beam and foliage. These findings support the utility of the uniform leaf distribution model and suggest that bats could use temporal inhomogeneities in the echoes to make inferences regarding the relative positioning of their sonar and a foliage.

A simplified model of biosonar echoes from foliage and the properties of natural foliages

PubMed Central

Zhu, Hongxiao; Müller, Rolf

2017-01-01

Foliage echoes could play an important role in the sensory ecology of echolocating bats, but many aspects of their sensory information content remain to be explored. A realistic numerical model for these echoes could support the development of hypotheses for the relationship between foliage properties and echo parameters. In prior work by the authors, a simple foliage model based on circular disks distributed uniformly in space has been developed. In the current work, three key simplifications used in this model have been examined: (i) representing leaves as circular disks, (ii) neglecting shading effects between leaves, and (iii) the uniform spatial distribution of the leaves. The target strengths of individual leaves and shading between them have been examined in physical experiments, whereas the impact of the spatial leaf distribution has been studied by modifying the numerical model to include leaf distributions according to a biomimetic model for natural branching patterns (L-systems). Leaf samples from a single species (leatherleaf arrowwood) were found to match the relationship between size and target strength of the disk model fairly well, albeit with a large variability part of which could be due to unaccounted geometrical features of the leaves. Shading between leaf-sized disks did occur for distances below 50 cm and could hence impact the echoes. Echoes generated with L-system models in two distinct tree species (ginkgo and pine) showed consistently more temporal inhomogeneity in the envelope amplitudes than a reference with uniform distribution. However, these differences were small compared to effects found in response to changes in the relative orientation of simulated sonar beam and foliage. These findings support the utility of the uniform leaf distribution model and suggest that bats could use temporal inhomogeneities in the echoes to make inferences regarding the relative positioning of their sonar and a foliage. PMID:29240840

Sonar beam dynamics in leaf-nosed bats

PubMed Central

Linnenschmidt, Meike; Wiegrebe, Lutz

2016-01-01

Ultrasonic emissions of bats are directional and delimit the echo-acoustic space. Directionality is quantified by the aperture of the sonar beam. Recent work has shown that bats often widen their sonar beam when approaching movable prey or sharpen their sonar beam when navigating through cluttered habitats. Here we report how nose-emitting bats, Phyllostomus discolor, adjust their sonar beam to object distance. First, we show that the height and width of the bats sonar beam, as imprinted on a parabolic 45 channel microphone array, varies even within each animal and this variation is unrelated to changes in call level or spectral content. Second, we show that these animals are able to systematically decrease height and width of their sonar beam while focusing on the approaching object. Thus it appears that sonar beam sharpening is a further, facultative means of reducing search volume, likely to be employed by stationary animals when the object position is close and unambiguous. As only half of our individuals sharpened their beam onto the approaching object we suggest that this strategy is facultative, under voluntary control, and that beam formation is likely mediated by muscular control of the acoustic aperture of the bats’ nose leaf. PMID:27384865

Sonar beam dynamics in leaf-nosed bats.

PubMed

Linnenschmidt, Meike; Wiegrebe, Lutz

2016-07-07

Ultrasonic emissions of bats are directional and delimit the echo-acoustic space. Directionality is quantified by the aperture of the sonar beam. Recent work has shown that bats often widen their sonar beam when approaching movable prey or sharpen their sonar beam when navigating through cluttered habitats. Here we report how nose-emitting bats, Phyllostomus discolor, adjust their sonar beam to object distance. First, we show that the height and width of the bats sonar beam, as imprinted on a parabolic 45 channel microphone array, varies even within each animal and this variation is unrelated to changes in call level or spectral content. Second, we show that these animals are able to systematically decrease height and width of their sonar beam while focusing on the approaching object. Thus it appears that sonar beam sharpening is a further, facultative means of reducing search volume, likely to be employed by stationary animals when the object position is close and unambiguous. As only half of our individuals sharpened their beam onto the approaching object we suggest that this strategy is facultative, under voluntary control, and that beam formation is likely mediated by muscular control of the acoustic aperture of the bats' nose leaf.

Smart Optical Material Characterization System and Method

NASA Technical Reports Server (NTRS)

Choi, Sang Hyouk (Inventor); Park, Yeonjoon (Inventor)

2015-01-01

Disclosed is a system and method for characterizing optical materials, using steps and equipment for generating a coherent laser light, filtering the light to remove high order spatial components, collecting the filtered light and forming a parallel light beam, splitting the parallel beam into a first direction and a second direction wherein the parallel beam travelling in the second direction travels toward the material sample so that the parallel beam passes through the sample, applying various physical quantities to the sample, reflecting the beam travelling in the first direction to produce a first reflected beam, reflecting the beam that passes through the sample to produce a second reflected beam that travels back through the sample, combining the second reflected beam after it travels back though the sample with the first reflected beam, sensing the light beam produced by combining the first and second reflected beams, and processing the sensed beam to determine sample characteristics and properties.

High-speed volume measurement system

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

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

2018-01-30

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

Optical ionization detector

DOEpatents

Wuest, C.R.; Lowry, M.E.

1994-03-29

An optical ionization detector wherein a beam of light is split so that one arm passes through a fiber optics and the other arm passes through a gas-filled region, and uses interferometry to detect density changes in a gas when charged particles pass through it. The gas-filled region of the detector is subjected to a high electric field and as a charged particle traverses this gas region electrons are freed from the cathode and accelerated so as to generate an electron avalanche which is collected on the anode. The gas density is effected by the electron avalanche formation and if the index or refraction is proportional to the gas density the index will change accordingly. The detector uses this index change by modulating the one arm of the split light beam passing through the gas, with respect to the other arm that is passed through the fiber optic. Upon recombining of the beams, interference fringe changes as a function of the index change indicates the passage of charged particles through the gaseous medium. 3 figures.

Optical ionization detector

DOEpatents

Wuest, Craig R.; Lowry, Mark E.

1994-01-01

An optical ionization detector wherein a beam of light is split so that one arm passes through a fiber optics and the other arm passes through a gas-filled region, and uses interferometry to detect density changes in a gas when charged particles pass through it. The gas-filled region of the detector is subjected to a high electric field and as a charged particle traverses this gas region electrons are freed from the cathode and accelerated so as to generate an electron avalanche which is collected on the anode. The gas density is effected by the electron avalanche formation and if the index or refraction is proportional to the gas density the index will change accordingly. The detector uses this index change by modulating the one arm of the split light beam passing through the gas, with respect to the other arm that is passed through the fiber optic. Upon recombining of the beams, interference fringe changes as a function of the index change indicates the passage of charged particles through the gaseous medium.

An electronic beam splitter realized with crossed graphene nanoribbons

NASA Astrophysics Data System (ADS)

Frederiksen, Thomas; Brandimarte, Pedro; Engelund, Mads; Papior, Nick; Garcia-Lekue, Aran; Sanchez-Portal, Daniel

Graphene nanoribbons (GNRs) are promising components in future nanoelectronics. We have explored a prototype 4-terminal semiconducting device formed by two crossed armchair GNRs (AGNRs) using state-of-the-art first-principles transport methods. We analyze in detail the roles of intersection angle, stacking order, inter-GNR separation, and finite voltages on the transport characteristics. Interestingly, when the AGNRs intersect at θ =60° , electrons injected from one terminal can be split into two outgoing waves with a tunable ratio around 50 % and with almost negligible back-reflection. The splitted electron wave is found to propagate partly straight across the intersection region in one ribbon and partly in one direction of the other ribbon, i.e., in analogy of an optical beam splitter. Our simulations further identify realistic conditions for which this semiconducting device can act as a mechanically controllable electronic beam splitter with possible applications in carbon-based quantum electronic circuits and electron optics. FP7-FET-ICT PAMS (610446), MAT2013-46593-C6-2-P, IT-756-13.

Backscattering enhancement factor dependence of a Laguerre-Gaussian laser beam propagating on the location path in the atmosphere on optical turbulence intensity

NASA Astrophysics Data System (ADS)

Rytchkov, D. S.

2017-11-01

The paper presents the results of a study of the backscattering enhancement factor (BSE) dependence of vortex LaguerreGaussian beams propagating on monostatic location paths in the atmosphere on optical turbulence intensity. The numeric simulation split-step method of laser beam propagation was used to obtain BSE factor values of a laser beam propagated on monostatic location path in the turbulent atmosphere and reflected from a diffuse target. It is shown that BSE factor of the averaged intensity of a backscattered vortex laser beam of any topological charge is less than BSE factor values of backscattered Gaussian beam in arbitrary turbulent conditions.

Physical properties of meteoroids based on middle and upper atmosphere radar measurements

NASA Astrophysics Data System (ADS)

Gritsevich, M.; Kero, J.; Virtanen, J.; Szasz, C.; Nakamura, T.; Peltoniemi, J.; Koschny, D.

2014-07-01

We present a novel approach to reliably interpret the meteor head-echo scattering measurements detected by the 46.5 MHz MU radar system near Shigaraki, Japan. A meteor head echo is caused by radio waves scattered from the dense region of plasma surrounding and co-moving with a meteoroid during atmospheric flight. The signal Doppler shift and/or range rate of the target can therefore be used to determine meteoroid velocity. The data reduction steps include determining the exact trajectory of the meteoroids entering the observation volume of the antenna beam and calculating meteoroid mass and velocity as a function of time. The model is built using physically-based parametrization. The considered observation volume is narrow, elongated in the vertical direction, and its area of greatest sensitivity covers a circular area of about 10 km diameter at an altitude of 100 km above the radar. Over 100,000 meteor head echoes have been detected over past years of observations. Most of the events are faint with no alternative to be detected visually or with intensified video (ICCD) cameras. In this study we are focusing on objects which have entered the atmosphere with almost vertical trajectories, to ensure the observed segment of the trajectory to be as complete as possible, without loss of its beginning or end part due to beam-pattern-related loss of signal power. The analysis output parameters are range, altitude, radial velocity, meteoroid velocity, instantaneous target position, Radar Cross Section (RCS), meteor radiant, meteoroid ballistic and ablation coefficients, mass loss parameter and meteoroid mass, with possibility to derive other parameters.

Physical Properties of Meteoroids based on Middle and Upper Atmosphere Radar Measurements

NASA Astrophysics Data System (ADS)

Gritsevich, Maria; Nakamura, Takuji; Kero, Johan; Szasz, Csilla; Virtanen, Jenni; Peltoniemi, Jouni; Koschny, Detlef

We present a novel approach to reliably interpret the meteor head echo scattering measurements detected by the 46.5 MHz MU radar system near Shigaraki, Japan. A meteor head echo is caused by radio waves scattered from the dense region of plasma surrounding and co-moving with a meteoroid during atmospheric flight. The signal Doppler shift and/or range rate of the target can therefore be used to determine meteoroid velocity. The data reduction steps include determining the exact trajectory of the meteoroids entering the observation volume of the antenna beam and calculating meteoroid mass and velocity as a function of time. The model is built using physically based parameterization. The considered observation volume is narrow, elongated in the vertical direction, and its area of greatest sensitivity covers a circular area of about 10 km diameter at an altitude of 100 km above the radar. Over 100000 meteor head echoes have been detected over past years of observations. Most of the events are faint with no alternative to be detected visually or with intensified video (ICCD) cameras. In this study we are focusing on objects which have entered the atmosphere with almost vertical trajectories, to ensure the observed segment of the trajectory to be as complete as possible, without loss of its beginning or end part due to beam-pattern related loss of signal power. The analysis output parameters are range, altitude, radial velocity, meteoroid velocity, instantaneous target position, Radar Cross Section (RCS), meteor radiant, meteoroid ballistic and ablation coefficients, mass loss parameter and meteoroid mass, with possibility to derive other parameters.

Off-axis targets maximize bearing Fisher Information in broadband active sonar.

PubMed

Kloepper, Laura N; Buck, John R; Liu, Yang; Nachtigall, Paul E

2018-01-01

Broadband active sonar systems estimate range from time delay and velocity from Doppler shift. Relatively little attention has been paid to how the received echo spectrum encodes information about the bearing of an object. This letter derives the bearing Fisher Information encoded in the frequency dependent transmitter beampattern. This leads to a counter-intuitive result: directing the sonar beam so that a target of interest is slightly off-axis maximizes the bearing information about the target. Beam aim data from a dolphin biosonar experiment agree closely with the angle predicted to maximize bearing information.

Type III Solar Radio Burst Source Region Splitting due to a Quasi-separatrix Layer

NASA Astrophysics Data System (ADS)

McCauley, Patrick I.; Cairns, Iver H.; Morgan, John; Gibson, Sarah E.; Harding, James C.; Lonsdale, Colin; Oberoi, Divya

2017-12-01

We present low-frequency (80–240 MHz) radio imaging of type III solar radio bursts observed by the Murchison Widefield Array on 2015 September 21. The source region for each burst splits from one dominant component at higher frequencies into two increasingly separated components at lower frequencies. For channels below ∼132 MHz, the two components repetitively diverge at high speeds (0.1c–0.4c) along directions tangent to the limb, with each episode lasting just ∼2 s. We argue that both effects result from the strong magnetic field connectivity gradient that the burst-driving electron beams move into. Persistence mapping of extreme-ultraviolet jets observed by the Solar Dynamics Observatory reveals quasi-separatrix layers (QSLs) associated with coronal null points, including separatrix dome, spine, and curtain structures. Electrons are accelerated at the flare site toward an open QSL, where the beams follow diverging field lines to produce the source splitting, with larger separations at larger heights (lower frequencies). The splitting motion within individual frequency bands is interpreted as a projected time-of-flight effect, whereby electrons traveling along the outer field lines take slightly longer to excite emission at adjacent positions. Given this interpretation, we estimate an average beam speed of 0.2c. We also qualitatively describe the quiescent corona, noting in particular that a disk-center coronal hole transitions from being dark at higher frequencies to bright at lower frequencies, turning over around 120 MHz. These observations are compared to synthetic images based on the MHD algorithm outside a sphere (MAS) model, which we use to flux-calibrate the burst data.

Sustained ecological observing, how hard can it be?

NASA Astrophysics Data System (ADS)

Moltmann, T.; Proctor, R.

2016-02-01

Australia's Integrated Marine Observing System (IMOS) is a national scale, sustained observing system that has now been operating for a decade. The direction of IMOS has been strongly influenced by developments in the Global Ocean Observing System, particularly the integration of physical, chemical and biological observing, from open-ocean to coast. In addition to more mature approaches for measuring physical and chemical variables, IMOS has piloted sustained observing of benthic habitats, primary and secondary producers, mid-trophic, and higher trophic level organisms. Observing technologies used include autonomous underwater vehicles, continuous plankton recorders, underway measurements from ships of opportunity, monthly vessel-based sampling, bio-optical sensors on buoys and gliders, echo sounders, acoustic telemetry, bio-logging, noise logging and satellite remote sensing. Increased focus is now being placed on producing valued added products from biological time series, and working with biogeochemical and ecosystem modellers to help reduce model uncertainties, and to get feedback on future design of the observing system. Significant steps have been made towards the long term goal of sustained ecological observing, and important lessons learned along the way.

Acquision of Geometrical Data of Small Rivers with AN Unmanned Water Vehicle

NASA Astrophysics Data System (ADS)

Sardemann, H.; Eltner, A.; Maas, H.-G.

2018-05-01

Rivers with small- and medium-scaled catchments have been increasingly affected by extreme events, i.e. flash floods, in the last years. New methods to describe and predict these events are developed in the interdisciplinary research project EXTRUSO. Flash flood events happen on small temporal and spatial scales, stressing the necessity of high-resolution input data for hydrological and hydrodynamic modelling. Among others, the benefit of high-resolution digital terrain models (DTMs) will be evaluated in the project. This article introduces a boat-based approach for the acquisition of geometrical and morphological data of small rivers and their banks. An unmanned water vehicle (UWV) is used as a multi-sensor platform to collect 3D-point clouds of the riverbanks, as well as bathymetric measurements of water depth and river morphology. The UWV is equipped with a mobile Lidar, a panorama camera, an echo sounder and a positioning unit. Whole (sub-) catchments of small rivers can be digitalized and provided for hydrological modelling when UWV-based and UAV (unmanned aerial vehicle) based point clouds are fused.

Biological and physical oceanographic observations pertaining to the trawl fishery in a region of persistent coastal upwelling

NASA Technical Reports Server (NTRS)

Howe, J. T.; Gibson, D. B.; Evans, T. O.; Breaker, L.; Wrigley, R. C.; Broenkow, W. W.

1981-01-01

An upwelling episode in the Point Sal region of the central California coast is examined by using data obtained by a data buoy. The episodes was interrupted by the abrupt abatement of the strong wind which promotes coastal upwelling. The mean hourly upwelling index is calculated to be higher than the 20 year mean monthly value. During 3 days of light wind commercial bottom trawl operations were possible. Shipboard estimates of chlorophyll content in surface waters during trawling show the high concentrations that are indicative of a rich biomass of phytoplankton, a result of the upwelling episode. Satellite imagery shows the extent of the upwelling water to be of the order of 100 km offshore; the result of many upwelling episodes. Shipboard echo sounder data show the presence of various delmersal species and of zooplakton; the latter graze on the phytoplankton in the upper euphotic layers. The fish catch data are recorded according to species for 2 days of trawling, and the catch per trawl hour is recorded.

An integrated charge exchange recombination spectroscopy/beam emission spectroscopy diagnostic for Alcator C-Mod tokamak.

PubMed

Bespamyatnov, I O; Rowan, W L; Liao, K T; Granetz, R S

2010-10-01

A novel integrated charge exchange recombination spectroscopy (CXRS)/beam emission spectroscopy (BES) system is proposed for C-Mod, in which both measurements are taken from a shared viewing geometry. The supplementary BES system serves to quantify local beam densities and supplants the common calculation of beam attenuation. The new system employs two optical viewing arrays, 20 poloidal and 22 toroidal channels. A dichroic filter splits the light between two spectrometers operating at different wavelengths for impurity ion and beam neutrals emission. In this arrangement, the impurity density is inferred from the electron density, measured BES and CXRS spectral radiances, and atomic emission rates.

Dual surface interferometer

DOEpatents

Pardue, R.M.; Williams, R.R.

1980-09-12

A double-pass interferometer is provided which allows direct measurement of relative displacement between opposed surfaces. A conventional plane mirror interferometer may be modified by replacing the beam-measuring path cube-corner reflector with an additional quarterwave plate. The beam path is altered to extend to an opposed plane mirrored surface and the reflected beam is placed in interference with a retained reference beam split from dual-beam source and retroreflected by a reference cube-corner reflector mounted stationary with the interferometer housing. This permits direct measurement of opposed mirror surfaces by laser interferometry while doubling the resolution as with a conventional double-pass plane mirror laser interferometer system.

Dual surface interferometer

DOEpatents

Pardue, Robert M.; Williams, Richard R.

1982-01-01

A double-pass interferometer is provided which allows direct measurement of relative displacement between opposed surfaces. A conventional plane mirror interferometer may be modified by replacing the beam-measuring path cube-corner reflector with an additional quarter-wave plate. The beam path is altered to extend to an opposed plane mirrored surface and the reflected beam is placed in interference with a retained reference beam split from dual-beam source and retroreflected by a reference cube-corner reflector mounted stationary with the interferometer housing. This permits direct measurement of opposed mirror surfaces by laser interferometry while doubling the resolution as with a conventional double-pass plane mirror laser interferometer system.

Birefringence in a chiral medium, via temporal cloaking

NASA Astrophysics Data System (ADS)

Khan, Humayun; Haneef, Muhammad

2017-05-01

This paper reports theoretical investigation of birefringence in a chiral medium for the creation of temporal cloaking. The chiral medium splits the input probe beam into left/right circular polarized beams. These left/right circular polarized beams are then controlled and modified within the chiral medium. The left circular polarized beam delays by 24 ns whereas the right circular polarized beam advances by  -23 ns at a control field of rabbi frequency 6γ . This opens a 47 ns time gap for temporal cloaking to hide information without noise corruption and energy loss. The results have potential applications in communication devices for secure propagation of light pulse.

Macroscopic Violation of Three Cauchy-Schwarz Inequalities Using Correlated Light Beams From an Infra-Red Emitting Semiconductor Diode Array

NASA Technical Reports Server (NTRS)

Edwards, P. J.; Huang, X.; Li, Y. Q. (Editor); Wang, Y. Z. (Editor)

1996-01-01

We briefly review quantum mechanical and semi-classical descriptions of experiments which demonstrate the macroscopic violation of the three Cauchy-Schwarz inequalities: g(sup 2)(sub 11)(0) greater than or equal to 1; g(sup 2)(sub 11)(0) greater than or equal to g(sup 2)(sub 11)(t), (t approaches infinity); (the absolute value of g(sup 2)(sub 11)(0))(exp 2) less than or equal to g(sup 2)(sub 11)(0) g(sup 2)(sub 11)(0). Our measurements demonstrate the violation, at macroscopic intensities, of each of these inequalities. We show that their violation, although weak, can be demonstrated through photodetector current covariance measurements on correlated sub-Poissonian Poissonian, and super Poissonian light beams. Such beams are readily generated by a tandem array of infrared-emitting semiconductor junction diodes. Our measurements utilize an electrically coupled array of one or more infrared-emitting diodes, optically coupled to a detector array. The emitting array is operated in such a way as to generate highly correlated beams of variable photon Fano Factor. Because the measurements are made on time scales long compared with the first order coherence time and with detector areas large compared with the corresponding coherence areas, first order interference effects are negligible. The first and second inequalities are violated, as expected, when a sub-Poissonian light beam is split and the intensity fluctuations of the two split beams are measured by two photodetectors and subsequently cross-correlated. The third inequality is violated by bunched (as well as anti-bunched) beams of equal intensity provided the measured cross correlation coefficient exceeds (F - 1)/F, where F is the measured Fano Factor of each beam. We also investigate the violation for the case of unequal beams.

Non-linear optical crystal vibration sensing device

DOEpatents

Kalibjian, Ralph

1994-01-11

A non-linear optical crystal vibration sensing device (10) including a photorefractive crystal (26) and a laser (12). The laser (12 ) produces a coherent light beam (14) which is split by a beam splitter (18) into a first laser beam (20) and a second laser beam (22). After passing through the crystal (26) the first laser beam (20) is counter-propagated back upon itself by a retro-mirror (32), creating a third laser beam (30). The laser beams (20, 22, 30) are modulated, due to the mixing effect within the crystal (26) by vibration of the crystal (30). In the third laser beam (30), modulation is stable and such modulation is converted by a photodetector (34) into a usable electrical output, intensity modulated in accordance with vibration applied to the crystal (26).

Method for using acoustic sounder categories to determine atmospheric stability

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

Schubert, J.F.

1979-01-01

Capabilities of the diffusion meteorologist have been expanded by the acoustic sounder, an economical tool for monitoring in real time the height of the mixed layer. The acoustic sounder continuously measures the rate of change in the height of the mixed layer which is an important parameter in calculating the transport and diffusion of radioactive and nonradioactive air pollutants. Continuous record of convective cells, gravity waves, inversions, and frontal systems permit analysis of the synoptic (analysis of stability in terms of simultaneous weather information) and complex (analysis of the stability of a single place by the relative frequencies of variousmore » stability types or groups of such types) stabilities of the local area. Sounder data obtained at the Savannah River Plant was compared on an hourly basis to data obtained at the WJBF-TV tower located approximately 20 km northwest of the acoustic sounder site.« less

Recent improvements of the JET lithium beam diagnostica)

NASA Astrophysics Data System (ADS)

Brix, M.; Dodt, D.; Dunai, D.; Lupelli, I.; Marsen, S.; Melson, T. F.; Meszaros, B.; Morgan, P.; Petravich, G.; Refy, D. I.; Silva, C.; Stamp, M.; Szabolics, T.; Zastrow, K.-D.; Zoletnik, S.; JET-EFDA Contributors

2012-10-01

A 60 kV neutral lithium diagnostic beam probes the edge plasma of JET for the measurement of electron density profiles. This paper describes recent enhancements of the diagnostic setup, new procedures for calibration and protection measures for the lithium ion gun during massive gas puffs for disruption mitigation. New light splitting optics allow in parallel beam emission measurements with a new double entrance slit CCD spectrometer (spectrally resolved) and a new interference filter avalanche photodiode camera (fast density and fluctuation studies).

Design technique for all-dielectric non-polarizing beam splitter plate

NASA Astrophysics Data System (ADS)

Rizea, A.

2012-03-01

There are many situations when, for the proper working, an opto-electronic device requiring optical components does not change the polarization state of light after a reflection, splitting or filtering. In this paper, a design for a non-polarizing beam splitter plate is proposed. Based on certain optical properties of homogeneous dielectric materials we will establish a reliable thin film package formula, excellent for the start of optimization to obtain a 20-nm bandwidth non-polarizing beam splitter.

A tunable electronic beam splitter realized with crossed graphene nanoribbons

NASA Astrophysics Data System (ADS)

Brandimarte, Pedro; Engelund, Mads; Papior, Nick; Garcia-Lekue, Aran; Frederiksen, Thomas; Sánchez-Portal, Daniel

2017-03-01

Graphene nanoribbons (GNRs) are promising components in future nanoelectronics due to the large mobility of graphene electrons and their tunable electronic band gap in combination with recent experimental developments of on-surface chemistry strategies for their growth. Here, we explore a prototype 4-terminal semiconducting device formed by two crossed armchair GNRs (AGNRs) using state-of-the-art first-principles transport methods. We analyze in detail the roles of intersection angle, stacking order, inter-GNR separation, GNR width, and finite voltages on the transport characteristics. Interestingly, when the AGNRs intersect at θ =60° , electrons injected from one terminal can be split into two outgoing waves with a tunable ratio around 50% and with almost negligible back-reflection. The split electron wave is found to propagate partly straight across the intersection region in one ribbon and partly in one direction of the other ribbon, i.e., in analogy with an optical beam splitter. Our simulations further identify realistic conditions for which this semiconducting device can act as a mechanically controllable electronic beam splitter with possible applications in carbon-based quantum electronic circuits and electron optics. We rationalize our findings with a simple model suggesting that electronic beam splitters can generally be realized with crossed GNRs.

Optical beam forming techniques for phased array antennas

NASA Technical Reports Server (NTRS)

Wu, Te-Kao; Chandler, C.

1993-01-01

Conventional phased array antennas using waveguide or coax for signal distribution are impractical for large scale implementation on satellites or spacecraft because they exhibit prohibitively large system size, heavy weight, high attenuation loss, limited bandwidth, sensitivity to electromagnetic interference (EMI) temperature drifts and phase instability. However, optical beam forming systems are smaller, lighter, and more flexible. Three optical beam forming techniques are identified as applicable to large spaceborne phased array antennas. They are (1) the optical fiber replacement of conventional RF phased array distribution and control components, (2) spatial beam forming, and (3) optical beam splitting with integrated quasi-optical components. The optical fiber replacement and the spatial beam forming approaches were pursued by many organizations. Two new optical beam forming architectures are presented. Both architectures involve monolithic integration of the antenna radiating elements with quasi-optical grid detector arrays. The advantages of the grid detector array in the optical process are the higher power handling capability and the dynamic range. One architecture involves a modified version of the original spatial beam forming approach. The basic difference is the spatial light modulator (SLM) device for controlling the aperture field distribution. The original liquid crystal light valve SLM is replaced by an optical shuffling SLM, which was demonstrated for the 'smart pixel' technology. The advantages are the capability of generating the agile beams of a phased array antenna and to provide simultaneous transmit and receive functions. The second architecture considered is the optical beam splitting approach. This architecture involves an alternative amplitude control for each antenna element with an optical beam power divider comprised of mirrors and beam splitters. It also implements the quasi-optical grid phase shifter for phase control and grid amplifier for RF power. The advantages are no SLM is required for this approach, and the complete antenna system is capable of full monolithic integration.

Dual-etalon cavity ring-down frequency-comb spectroscopy with broad band light source

DOEpatents

Chandler, David W; Strecker, Kevin E

2014-04-01

In an embodiment, a dual-etalon cavity-ring-down frequency-comb spectrometer system is described. A broad band light source is split into two beams. One beam travels through a first etalon and a sample under test, while the other beam travels through a second etalon, and the two beams are recombined onto a single detector. If the free spectral ranges ("FSR") of the two etalons are not identical, the interference pattern at the detector will consist of a series of beat frequencies. By monitoring these beat frequencies, optical frequencies where light is absorbed may be determined.

High throughput solar cell ablation system

DOEpatents

Harley, Gabriel; Pass, Thomas; Cousins, Peter John; Viatella, John

2014-10-14

A solar cell is formed using a solar cell ablation system. The ablation system includes a single laser source and several laser scanners. The laser scanners include a master laser scanner, with the rest of the laser scanners being slaved to the master laser scanner. A laser beam from the laser source is split into several laser beams, with the laser beams being scanned onto corresponding wafers using the laser scanners in accordance with one or more patterns. The laser beams may be scanned on the wafers using the same or different power levels of the laser source.

High throughput solar cell ablation system

DOEpatents

Harley, Gabriel; Pass, Thomas; Cousins, Peter John; Viatella, John

2012-09-11

A solar cell is formed using a solar cell ablation system. The ablation system includes a single laser source and several laser scanners. The laser scanners include a master laser scanner, with the rest of the laser scanners being slaved to the master laser scanner. A laser beam from the laser source is split into several laser beams, with the laser beams being scanned onto corresponding wafers using the laser scanners in accordance with one or more patterns. The laser beams may be scanned on the wafers using the same or different power levels of the laser source.

Double-clad photonic crystal fiber coupler for compact nonlinear optical microscopy imaging.

PubMed

Fu, Ling; Gu, Min

2006-05-15

A 1 x 2 double-clad photonic crystal fiber coupler is fabricated by the fused tapered method, showing a low excess loss of 1.1 dB and a splitting ratio of 97/3 over the entire visible and near-infrared wavelength range. In addition to the property of splitting the laser power, the double-clad feature of the coupler facilitates the separation of a near-infrared single-mode beam from a visible multimode beam, which is ideal for nonlinear optical microscopy imaging. In conjunction with a gradient-index lens, this coupler is used to construct a miniaturized microscope based on two-photon fluorescence and second-harmonic generation. Three-dimensional nonlinear optical images demonstrate potential applications of the coupler to compact all-fiber and nonlinear optical microscopy and endoscopy.

Space-Borne Radio-Sounding Investigations Facilitated by the Virtual Wave Observatory (VWO)

NASA Technical Reports Server (NTRS)

Benson, Robert F.; Fung, Shing F.; Bilitza,Dieter; Garcia, Leonard N.; Shao, Xi; Galkin, Ivan A.

2011-01-01

The goal of the Virtual Wave Observatory (VWO) is to provide userfriendly access to heliophysics wave data. While the VWO initially emphasized the vast quantity of wave data obtained from passive receivers, the VWO infrastructure can also be used to access active sounder data sets. Here we use examples from some half-million Alouette-2, ISIS-1, and ISIS-2 digital topside-sounder ionograms to demonstrate the desirability of such access to the actual ionograms for investigations of both natural and sounder-stimulated plasma-wave phenomena. By this demonstration, we wish to encourage investigators to make other valuable space-borne sounder data sets accessible via the VWO.

Spectral Resolution and Coverage Impact on Advanced Sounder Information Content

NASA Technical Reports Server (NTRS)

Larar, Allen M.; Liu, Xu; Zhou, Daniel K.; Smith, William L.

2010-01-01

Advanced satellite sensors are tasked with improving global measurements of the Earth s atmosphere, clouds, and surface to enable enhancements in weather prediction, climate monitoring capability, and environmental change detection. Achieving such measurement improvements requires instrument system advancements. This presentation focuses on the impact of spectral resolution and coverage changes on remote sensing system information content, with a specific emphasis on thermodynamic state and trace species variables obtainable from advanced atmospheric sounders such as the Infrared Atmospheric Sounding Interferometer (IASI) and Cross-track Infrared Sounder (CrIS) systems on the MetOp and NPP/NPOESS series of satellites. Key words: remote sensing, advanced sounders, information content, IASI, CrIS

Modeling Statistics of Fish Patchiness and Predicting Associated Influence on Statistics of Acoustic Echoes

DTIC Science & Technology

2014-09-30

were compared with 3-D multi-beam data collected by Paramo and Gerlotto. The data were consistent with the Anderson model in that both the data and...column of a random, oceanic waveguide,” J. Acoust. Soc. Am., DOI 10.1121/1.4881925 [published, refereed] Stanton, T.K., Bhatia, S., J. Paramo , and F

Modeling the Effects of Beam Size and Flaw Morphology on Ultrasonic Pulse/Echo Sizing of Delaminations in Carbon Composites

NASA Technical Reports Server (NTRS)

Margetan, Frank J.; Leckey, Cara A.; Barnard, Dan

2012-01-01

The size and shape of a delamination in a multi-layered structure can be estimated in various ways from an ultrasonic pulse/echo image. For example the -6dB contours of measured response provide one simple estimate of the boundary. More sophisticated approaches can be imagined where one adjusts the proposed boundary to bring measured and predicted UT images into optimal agreement. Such approaches require suitable models of the inspection process. In this paper we explore issues pertaining to model-based size estimation for delaminations in carbon fiber reinforced laminates. In particular we consider the influence on sizing when the delamination is non-planar or partially transmitting in certain regions. Two models for predicting broadband sonic time-domain responses are considered: (1) a fast "simple" model using paraxial beam expansions and Kirchhoff and phase-screen approximations; and (2) the more exact (but computationally intensive) 3D elastodynamic finite integration technique (EFIT). Model-to-model and model-to experiment comparisons are made for delaminations in uniaxial composite plates, and the simple model is then used to critique the -6dB rule for delamination sizing.

Using a binaural biomimetic array to identify bottom objects ensonified by echolocating dolphins

USGS Publications Warehouse

Heiweg, D.A.; Moore, P.W.; Martin, S.W.; Dankiewicz, L.A.

2006-01-01

The development of a unique dolphin biomimetic sonar produced data that were used to study signal processing methods for object identification. Echoes from four metallic objects proud on the bottom, and a substrate-only condition, were generated by bottlenose dolphins trained to ensonify the targets in very shallow water. Using the two-element ('binaural') receive array, object echo spectra were collected and submitted for identification to four neural network architectures. Identification accuracy was evaluated over two receive array configurations, and five signal processing schemes. The four neural networks included backpropagation, learning vector quantization, genetic learning and probabilistic network architectures. The processing schemes included four methods that capitalized on the binaural data, plus a monaural benchmark process. All the schemes resulted in above-chance identification accuracy when applied to learning vector quantization and backpropagation. Beam-forming or concatenation of spectra from both receive elements outperformed the monaural benchmark, with higher sensitivity and lower bias. Ultimately, best object identification performance was achieved by the learning vector quantization network supplied with beam-formed data. The advantages of multi-element signal processing for object identification are clearly demonstrated in this development of a first-ever dolphin biomimetic sonar. ?? 2006 IOP Publishing Ltd.

Bedform dynamics in a large sand-bedded river using multibeam echo sounding

NASA Astrophysics Data System (ADS)

Elliott, C. M.; Jacobson, R. B.; Erwin, S.; Eric, A. B.; DeLonay, A. J.

2014-12-01

High-resolution repeat multibeam Echo Sounder (MBES) surveys of the Lower Missouri River in Missouri, USA demonstrate sand bedform movement at a variety of scales over a range of discharges. Understanding dune transport rates and the temporal and spatial variability in sizes across the channel has implications for how sediment transport measurements are made and for understanding the dynamics of habitats utilized by benthic organisms over a range of life stages. Nearly 800 miles of the Lower Missouri River has been altered through channelization and bank stabilization that began in the early 1900's for navigation purposes. Channelization of the Lower Missouri River has created a self-scouring navigation channel with large dunes that migrate downstream over a wide range of discharges. Until the use of MBES surveys on the Missouri River the spatial variability of dune forms in the Missouri River navigation channel was poorly understood. MBES surveys allow for visualization of a range of sand bedforms and repeat measurements demonstrate that dunes are moving over a wide range of discharges on the river. Understanding the spatial variability of dunes and dune movement across the channel and in different channel settings (bends, channel cross-overs, near channel structures) will inform emerging methods in sediment transport measurement that use bedform differencing calculations and provide context for physical bedload sediment sampling on large sand-bedded rivers. Multiple benthic fish species of interest including the endangered pallid sturgeon utilize Missouri River dune fields and adjacent regions for migration, feeding, spawning, early development and dispersal. Surveys using MBES and other hydroacoustic tools provide fisheries biologists with broad new insights into the functionality of bedforms as habitat for critical life stages of large river fish species in the Missouri River, and similar sand-bedded systems.

Preliminary Field Demonstration of Passive Radio Sounding Using the Sun as a Signal for Echo Detection

NASA Astrophysics Data System (ADS)

Peters, S. T.; Schroeder, D. M.; Romero-Wolf, A.; Haynes, M.

2017-12-01

The Radar for Icy Moon Exploration (RIME) and the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) have been identified as potential candidates for the implementation of passive sounding as additional observing modes for the ESA and NASA missions to Ganymede and Europa. Recent work has shown the theoretical potential for Jupiter's decametric radiation to be used as a source for passive radio sounding of its icy moons. We are further developing and adapting this geophysical approach for use in terrestrial glaciology. Here, we present results from preliminary field testing of a prototype passive radio sounder from cliffs along the California coast. This includes both using a Lloyd's mirror to measure the Sun's direct path and its reflection off the ocean's surface and exploiting autocorrelation to detect the delay time of the echo. This is the first in-situ demonstration of the autocorrelation-based passive-sounding approach using an astronomical white noise signal. We also discuss preliminary field tests on rougher terrestrial and subglacial surfaces, including at Store Glacier in Greenland. Additionally, we present modeling and experimental results that demonstrate the feasibility of applying presumming approaches to the autocorrelations to achieve coherent gain from an inherently random signal. We note that while recording with wider bandwidths and greater delays places fundamental limits on the Lloyd's mirror approach, our new autocorrelation method has no such limitation. Furthermore, we show how achieving wide bandwidths via spectral-stitching methods allows us to obtain a finer range resolution than given by the receiver's instantaneous bandwidth. Finally, we discuss the potential for this technique to eliminate the need for active transmitters in certain types of ice sounding experiments, thereby reducing the complexity, power consumption, and cost of systems and observations.

Wavelength-independent constant period spin-echo modulated small angle neutron scattering

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

Sales, Morten, E-mail: lsp260@alumni.ku.dk; Plomp, Jeroen; Bouwman, Wim

2016-06-15

Spin-Echo Modulated Small Angle Neutron Scattering (SEMSANS) in Time-of-Flight (ToF) mode has been shown to be a promising technique for measuring (very) small angle neutron scattering (SANS) signals and performing quantitative Dark-Field Imaging (DFI), i.e., SANS with 2D spatial resolution. However, the wavelength dependence of the modulation period in the ToF spin-echo mode has so far limited the useful modulation periods to those resolvable with the limited spatial resolution of the detectors available. Here we present our results of an approach to keep the period of the induced modulation constant for the wavelengths utilised in ToF. This is achieved bymore » ramping the magnetic fields in the coils responsible for creating the spatially modulated beam in synchronisation with the neutron pulse, thus keeping the modulation period constant for all wavelengths. Such a setup enables the decoupling of the spatial detector resolution from the resolution of the modulation period by the use of slits or gratings in analogy to the approach in grating-based neutron DFI.« less

Achromatic vector vortex beams from a glass cone

PubMed Central

Radwell, N.; Hawley, R. D.; Götte, J. B.; Franke-Arnold, S.

2016-01-01

The reflection of light is governed by the laws first described by Augustin-Jean Fresnel: on internal reflection, light acquires a phase shift, which depends on its polarization direction with respect to the plane of incidence. For a conical reflector, the cylindrical symmetry is echoed in an angular variation of this phase shift, allowing us to create light modes with phase and polarization singularities. Here we observe the phase and polarization profiles of light that is back reflected from a solid glass cone and, in the case of circular input light, discover that not only does the beam contain orbital angular momentum but can trivially be converted to a radially polarized beam. Importantly, the Fresnel coefficients are reasonably stable across the visible spectrum, which we demonstrate by measuring white light polarization profiles. This discovery provides a highly cost-effective technique for the generation of broadband orbital angular momentum and radially polarized beams. PMID:26861191

Achromatic vector vortex beams from a glass cone

NASA Astrophysics Data System (ADS)

Radwell, N.; Hawley, R. D.; Götte, J. B.; Franke-Arnold, S.

2016-02-01

The reflection of light is governed by the laws first described by Augustin-Jean Fresnel: on internal reflection, light acquires a phase shift, which depends on its polarization direction with respect to the plane of incidence. For a conical reflector, the cylindrical symmetry is echoed in an angular variation of this phase shift, allowing us to create light modes with phase and polarization singularities. Here we observe the phase and polarization profiles of light that is back reflected from a solid glass cone and, in the case of circular input light, discover that not only does the beam contain orbital angular momentum but can trivially be converted to a radially polarized beam. Importantly, the Fresnel coefficients are reasonably stable across the visible spectrum, which we demonstrate by measuring white light polarization profiles. This discovery provides a highly cost-effective technique for the generation of broadband orbital angular momentum and radially polarized beams.

Work of PZT ceramics sounder for sound source artificial larynx

NASA Astrophysics Data System (ADS)

Sugio, Yuuichi; Kanetake, Ryota; Tanaka, Akimitsu; Ooe, Katsutoshi

2007-04-01

We aim to develop the easy-to-use artificial larynx with high tone quality. We focus on using a PZT ceramics sounder as its sound source, because it is small size, low power consumption, and harmless to humans. But conventional PZT ceramics sounder have the problem that it cannot generate an enough sound in the low frequency range, thus they cannot be used for artificial larynx. Then, we aim to develop the PZT ceramics sounder which can generate enough volume in the low frequency range. If we can lower the resonance frequency of the sounder, it can generate low pitch sound easily. Therefore I created the new diaphragm with low resonance frequency. In addition, we could obtain the high amplitude by changing method of driving. This time, we report on the characteristic comparison of this new PZT ceramics sounder and conventional one. Furthermore, for this new one, we analyzed the best alignment of PZT ceramics and the shape of the diaphragm to obtain low resonance frequency and big amplitude. In fact we analyzed the optimization of the structure. The analysis is done by computer simulation of ANSYS and Laser Doppler Vibrometer. In the future, we will add intonation to the generated sound by input wave form which is developed concurrently, and implant the sounder inside of the body by the method of fixing metal to biomolecule which is done too. And so high tone quality and convenient artificial larynx will be completed.

How exciton-vibrational coherences control charge separation in the photosystem II reaction center.

PubMed

Novoderezhkin, Vladimir I; Romero, Elisabet; van Grondelle, Rienk

2015-12-14

In photosynthesis absorbed sun light produces collective excitations (excitons) that form a coherent superposition of electronic and vibrational states of the individual pigments. Two-dimensional (2D) electronic spectroscopy allows a visualization of how these coherences are involved in the primary processes of energy and charge transfer. Based on quantitative modeling we identify the exciton-vibrational coherences observed in 2D photon echo of the photosystem II reaction center (PSII-RC). We find that the vibrations resonant with the exciton splittings can modify the delocalization of the exciton states and produce additional states, thus promoting directed energy transfer and allowing a switch between the two charge separation pathways. We conclude that the coincidence of the frequencies of the most intense vibrations with the splittings within the manifold of exciton and charge-transfer states in the PSII-RC is not occurring by chance, but reflects a fundamental principle of how energy conversion in photosynthesis was optimized.

Eddy-Kuroshio Interactions: Local and Remote Effects

NASA Astrophysics Data System (ADS)

Jan, Sen; Mensah, Vigan; Andres, Magdalena; Chang, Ming-Huei; Yang, Yiing Jang

2017-12-01

Quasi-geostrophic mesoscale eddies regularly impinge on the Kuroshio in the western North Pacific, but the processes underlying the evolution of these eddy-Kuroshio interactions have not yet been thoroughly investigated in the literature. Here this interaction is examined with results from a semi-idealized three-dimensional numerical model and observations from four pressure-sensor equipped inverted echo sounders (PIESs) in a zonal section east of Taiwan and satellite altimeters. Both the observations and numerical simulations suggest that, during the interaction of a cyclonic eddy with the Kuroshio, the circular eddy is deformed into an elliptic shape with the major axis in the northwest-southeast direction, before being dissipated; the poleward velocity and associated Kuroshio transport decrease and the sea level and pycnocline slopes across the Kuroshio weaken. In contrast, for an anticyclonic eddy during the eddy-Kuroshio interaction, variations in the velocity, sea level, and isopycnal depth are reversed; the circular eddy is also deformed to an ellipse but with the major axis parallel to the Kuroshio. The model results also demonstrate that the velocity field is modified first and consequently the SSH and isopycnal depth evolve during the interaction. Furthermore, due to the combined effect of impingement latitude and realistic topography, some eddy-Kuroshio interactions east of Taiwan are found to have remote effects, both in the Luzon Strait and on the East China Sea shelf northeast of Taiwan.