The Moored Acoustic Buoy System (MABS)

DTIC Science & Technology

1975-04-04

STAQOG, Ocean Sciences & Technology Department Indirect. REVIEWED AND APPROY 4 April lq75 A)R. Hse Associate Director for Sonar Retsearch The authors...It consists of a subsurface instrumentation buoy in conjunction with a family of lightweight hydrophone arrays designed to measure a variety of...vertical to horizontal in the water column. Recent de- velopments in lightweight synthetic-cable technology have been incorporated into the design to make

Killer whale caller localization using a hydrophone array in an oceanarium pool

NASA Astrophysics Data System (ADS)

Bowles, Ann E.; Greenlaw, Charles F.; McGehee, Duncan E.; van Holliday, D.

2004-05-01

A system to localize calling killer whales was designed around a ten-hydrophone array in a pool at SeaWorld San Diego. The array consisted of nine ITC 8212 and one ITC 6050H hydrophones mounted in recessed 30×30 cm2 niches. Eight of the hydrophones were connected to a Compaq Armada E500 laptop computer through a National Instruments DAQ 6024E PCMCIA A/D data acquisition card and a BNC-2120 signal conditioner. The system was calibrated with a 139-dB, 4.5-kHz pinger. Acoustic data were collected during four 48-72 h recording sessions, simultaneously with video recorded from a four-camera array. Calling whales were localized by one of two methods, (1) at the hydrophone reporting the highest sound exposure level and (2) using custom-designed 3-D localization software based on time-of-arrival (ORCA). Complex reverberations in the niches and pool made locations based on time of arrival difficult to collect. Based on preliminary analysis of data from four sessions (400+ calls/session), the hydrophone reporting the highest level reliably attributed callers 51%-100% of the time. This represents a substantial improvement over attribution rates of 5%-15% obtained with single hydrophone recordings. [Funding provided by Hubbs-SeaWorld Research Institute and the Hubbs Society.

On measurement of acoustic pulse arrival angles using a vertical array

NASA Astrophysics Data System (ADS)

Makarov, D. V.

2017-11-01

We consider a recently developed method to analyze the angular structure of pulsed acoustic fields in an underwater sound channel. The method is based on the Husimi transform that allows us to approximately link a wave field with the corresponding ray arrivals. The advantage of the method lies in the possibility of its practical realization by a vertical hydrophone array crossing only a small part of the oceanic depth. The main aim of the present work is to find the optimal parameter values of the array that ensure good angular accuracy and sufficient reliability of the algorithm to calculate the arrival angles. Broadband pulses with central frequencies of 80 and 240 Hz are considered. It is shown that an array with a length of several hundred meters allows measuring the angular spectrum with an accuracy of up to 1 degree. The angular resolution is lowered with an increase of the sound wavelength due to the fundamental limitations imposed by the uncertainty relation.

Coherent acoustic communication in a tidal estuary with busy shipping traffic.

PubMed

van Walree, Paul A; Neasham, Jeffrey A; Schrijver, Marco C

2007-12-01

High-rate acoustic communication experiments were conducted in a dynamic estuarine environment. Two current profilers deployed in a shipping lane were interfaced with acoustic modems, which modulated and transmitted the sensor readings every 200 s over a period of four days. QPSK modulation was employed at a raw data rate of 8 kbits on a 12-kHz carrier. Two 16-element hydrophone arrays, one horizontal and one vertical, were deployed near the shore. A multichannel decision-feedback equalizer was used to demodulate the modem signals received on both arrays. Long-term statistical analysis reveals the effects of the tidal cycle, subsea unit location, attenuation by the wake of passing vessels, and high levels of ship-generated noise on the fidelity of the communication links. The use of receiver arrays enables vast improvement in the overall reliability of data delivery compared with a single-receiver system, with performance depending strongly on array orientation. The vertical array offers the best performance overall, although the horizontal array proves more robust against shipping noise. Spatial coherence estimates, variation of array aperture, and inspection of array angular responses point to adaptive beamforming and coherent combining as the chief mechanisms of array gain.

Underwater sound radiation patterns of contemporary merchant ships

NASA Astrophysics Data System (ADS)

Gassmann, M.; Wiggins, S. M.; Hildebrand, J. A.

2016-12-01

Merchant ships radiate underwater sound as an unintended by-product of their operation and as consequence contribute significantly to low-frequency, man-made noise in the ocean. Current measurement standards for the description of underwater sound from ships (ISO 17208-1:2016 and ANSI S12.64-2009) require nominal hydrophone depths of 15°, 30° and 45° at the starboard and portside of the test vessel.To opportunistically study the underwater sound of contemporary merchant ships that were tracked by the Automatic Identification System (AIS), an array of seven high-frequency acoustic recording packages (HARPs) with a sampling frequency of 200 kHz was deployed in the Santa Barbara Channel in the primary outgoing shipping lane for the port of Los Angeles and Long Beach. The vertical and horizontal aperture of the array allowed for starboard and portside measurements at all standard-required nominal hydrophone depths in addition to measurements taken at the keel aspect. Based on these measurements, frequency-dependent radiation patterns of contemporary merchant ships were estimated and used to evaluate current standards for computing ship source levels.

Continental-shelf Scale Passive Ocean AcousticWaveguide Remote Sensing of Marine Mammals and other Submerged Objects including Detection, Localization, and Classification

NASA Astrophysics Data System (ADS)

Wang, Delin

In this thesis, we develop the basics of the Passive Ocean Acoustic Waveguide Remote Sensing (POAWRS) technique for the instantaneous continental-shelf scale detection, localization and species classification of marine mammal vocalizations. POAWRS uses a large-aperture, densely sampled coherent hydrophone array system with orders of magnitude higher array gain to enhance signal-to-noise ratios (SNR) by coherent beamforming, enabling detection of underwater acoustic signals either two orders of magnitude more distant in range or lower in SNR than a single hydrophone. The ability to employ coherent spatial processing of signals with the POAWRS technology significantly improves areal coverage, enabling detection of oceanic sound sources over instantaneous wide areas spanning 100 km or more in diameter. The POAWRS approach was applied to analyze marine mammal vocalizations from diverse species received on a 160-element Office Naval Research Five Octave Research Array (ONR-FORA) deployed during their feeding season in Fall 2006 in the Gulf of Maine. The species-dependent temporal-spatial distribution of marine mammal vocalizations and correlation to the prey fish distributions have been determined. Furthermore, the probability of detection regions, source level distributions and pulse compression gains of the vocalization signals from diverse marine mammal species have been estimated. We also develop an approach for enhancing the angular resolution and improving bearing estimates of acoustic signals received on a coherent hydrophone array with multiple-nested uniformly-spaced subapertures, such as the ONR-FORA, by nonuniform array beamforming. Finally we develop a low-cost non-oil-filled towable prototype hydrophone array that consists of eight hydrophone elements with real-time data acquisition and 100 m tow cable. The approach demonstrated here will be applied in the development of a full 160 element POAWRS-type low-cost coherent hydrophone array system in the future.

The evolution and exploitation of the fiber-optic hydrophone

NASA Astrophysics Data System (ADS)

Hill, David J.

2007-07-01

In the late 1970s one of the first applications identified for fibre-optic sensing was the fibre-optic hydrophone. It was recognised that the technology had the potential to provide a cost effective solution for large-scale arrays of highly sensitive hydrophones which could be interrogated over large distances. Consequently both the United Kingdom and United States navies funded the development of this sonar technology to the point that it is now deployed on submarines and as seabed arrays. The basic design of a fibre-optic hydrophone has changed little; comprising a coil of optical fibre wound on a compliant mandrel, interrogated using interferometric techniques. Although other approaches are being investigated, including the development of fibre-laser hydrophones, the interferometric approach remains the most efficient way to create highly multiplexed arrays of acoustic sensors. So much so, that the underlying technology is now being exploited in civil applications. Recently the exploration and production sector of the oil and gas industry has begun funding the development of fibre-optic seismic sensing using seabed mounted, very large-scale arrays of four component (three accelerometers and a hydrophone) packages based upon the original technology developed for sonar systems. This has given new impetus to the development of the sensors and the associated interrogation systems which has led to the technology being adopted for other commercial uses. These include the development of networked in-road fibre-optic Weigh-in-Motion sensors and of intruder detection systems which are able to acoustically monitor long lengths of border, on both land and at sea. After two decades, the fibre-optic hydrophone and associated technology has matured and evolved into a number of highly capable sensing solutions used by a range of industries.

Compressional velocities from multichannel refraction arrivals on Georges Bank: northwest Atlantic Ocean

USGS Publications Warehouse

McGinnis, L. D.; Otis, R. M.

1979-01-01

Velocities were obtained from unreversed, refracted arrivals on analog records from a 48‐channel, 3.6-km hydrophone cable (3.89 km from the airgun array to the last hydrophone array). Approximately 200 records were analyzed along 1500 km of ship track on Georges Bank, northwest Atlantic Ocean, to obtain regional sediment velocity distribution to a depth of 1.4 km below sea level. This technique provides nearly continuous coverage of refraction velocities and vertical velocity gradients. Because of the length of the hydrophone cable and the vertical velocity gradients, the technique is applicable only to the Continental Shelf and the shallower parts of the Continental Slope in water depths less than 300 m. Sediment diagenesis, the influence of overburden pressure on compaction, lithology, density, and porosity are inferred from these data. Velocities of the sediment near the water‐sediment interface range from less than 1500 m/sec on the north edge of Georges Bank to 1830 m/sec for glacial deposits in the northcentral part of the bank. Velocity gradients in the upper 400 m range from 1.0km/sec/km(sec−1) on the south edge of the bank to 1.7sec−1 on the north. Minimum gradients of 0.8sec−1 were observed south of Nantucket Island. Velocities and velocity gradients are explained in relation to physical properties of the Cretaceous, Tertiary, and Pleistocene sediments. Isovelocity contours at 100-m/sec intervals are nearly horizontal in the upper 400 m. Isovelocity contours at greater depths show a greater difference from a mean depth because of the greater structural and lithological variation. Bottom densities inferred from the velocities range from 1.7 to 1.9g/cm3 and porosities range from 48 to 62 percent. The most significant factor controlling velocity distribution on Georges Bank is overburden pressure and resulting compaction. From the velocity data we conclude that Georges Bank has been partially overridden by a continental ice sheet.

Blue-Whale Calls Detected at the Pioneer Seamount Underwater Observatory

NASA Astrophysics Data System (ADS)

Hoffman, M. D.; Vuosalo, C. O.; Bland, R. W.; Garfield, N.

2002-12-01

In September of 2001 a cabled vertical linear array (VLA) of hydrophones was deployed on Pioneer Seamount, 90 km off the California coast near Half Moon Bay, by the NOAA-PMEL and University of Washington-APL. The array of 4 hydrophones is at a depth of 950 m, and the four signals are digitized at the shore end of the cable at 1000 Hz. The data are archived by PMEL, and are available to the public over the internet. Spectrograms of all of the data are accessible on the SFSU web site. A large number of blue-whale calls are evident in the spectrograms. We have employed spectrogram correlation [Mellinger 2000] and a matched-filter detection scheme [Stafford 1998] to automatically identify these whale calls in three months of data. Results on the frequency of calls and their variability will be presented. Mellinger, David K., and Christopher W. Clark [2000], "Recognizing transient low-frequency whale sounds by spectrogram correlation," J. Acoust. Soc. Am. 107 (3518). Stafford, Kathleen M., Christopher G. Fox, and Davis S. Clark [1998], "Long-range acoustic detection and localization of blue whale calls in the northeast Pacific Ocean," J. Acoust. Soc. Am. 104 (3616).

High-resolution bottom-loss estimation using the ambient-noise vertical coherence function.

PubMed

Muzi, Lanfranco; Siderius, Martin; Quijano, Jorge E; Dosso, Stan E

2015-01-01

The seabed reflection loss (shortly "bottom loss") is an important quantity for predicting transmission loss in the ocean. A recent passive technique for estimating the bottom loss as a function of frequency and grazing angle exploits marine ambient noise (originating at the surface from breaking waves, wind, and rain) as an acoustic source. Conventional beamforming of the noise field at a vertical line array of hydrophones is a fundamental step in this technique, and the beamformer resolution in grazing angle affects the quality of the estimated bottom loss. Implementation of this technique with short arrays can be hindered by their inherently poor angular resolution. This paper presents a derivation of the bottom reflection coefficient from the ambient-noise spatial coherence function, and a technique based on this derivation for obtaining higher angular resolution bottom-loss estimates. The technique, which exploits the (approximate) spatial stationarity of the ambient-noise spatial coherence function, is demonstrated on both simulated and experimental data.

An intelligent subsurface buoy design for measuring ocean ambient noise

NASA Astrophysics Data System (ADS)

Li, Bing; Wang, Lei

2012-11-01

A type of ultra-low power subsurface buoy system is designed to measure and record ocean ambient noise data. The buoy utilizes a vector hydrophone (pass band 20Hz-1.2kHz) and a 6-element vertical hydrophone array (pass band 20Hz-2kHz) to measure ocean ambient noise. The acoustic signals are passed through an automatically modified gain, a band pass filter, and an analog-to-digital (A/D) conversion module. They are then stored in high-capacity flash memory. In order to identify the direction of noise source, the vector sensor measuring system has integrated an electric-magnetic compass. The system provides a low-rate underwater acoustic communication system which is used to report the buoy state information and a high-speed USB interface which is used to retrieve the recorded data on deck. The whole system weighs about 125kg and can operate autonomously for more than 72 hours. The system's main architecture and the sea-trial test results are provided in this paper.

Matched Field Processing Based on Least Squares with a Small Aperture Hydrophone Array.

PubMed

Wang, Qi; Wang, Yingmin; Zhu, Guolei

2016-12-30

The receiver hydrophone array is the signal front-end and plays an important role in matched field processing, which usually covers the whole water column from the sea surface to the bottom. Such a large aperture array is very difficult to realize. To solve this problem, an approach called matched field processing based on least squares with a small aperture hydrophone array is proposed, which decomposes the received acoustic fields into depth function matrix and amplitudes of the normal modes at the beginning. Then all the mode amplitudes are estimated using the least squares in the sense of minimum norm, and the amplitudes estimated are used to recalculate the received acoustic fields of the small aperture array, which means the recalculated ones contain more environmental information. In the end, lots of numerical experiments with three small aperture arrays are processed in the classical shallow water, and the performance of matched field passive localization is evaluated. The results show that the proposed method can make the recalculated fields contain more acoustic information of the source, and the performance of matched field passive localization with small aperture array is improved, so the proposed algorithm is proved to be effective.

Matched Field Processing Based on Least Squares with a Small Aperture Hydrophone Array

PubMed Central

Wang, Qi; Wang, Yingmin; Zhu, Guolei

2016-01-01

The receiver hydrophone array is the signal front-end and plays an important role in matched field processing, which usually covers the whole water column from the sea surface to the bottom. Such a large aperture array is very difficult to realize. To solve this problem, an approach called matched field processing based on least squares with a small aperture hydrophone array is proposed, which decomposes the received acoustic fields into depth function matrix and amplitudes of the normal modes at the beginning. Then all the mode amplitudes are estimated using the least squares in the sense of minimum norm, and the amplitudes estimated are used to recalculate the received acoustic fields of the small aperture array, which means the recalculated ones contain more environmental information. In the end, lots of numerical experiments with three small aperture arrays are processed in the classical shallow water, and the performance of matched field passive localization is evaluated. The results show that the proposed method can make the recalculated fields contain more acoustic information of the source, and the performance of matched field passive localization with small aperture array is improved, so the proposed algorithm is proved to be effective. PMID:28042828

Crosstalk analyse of DFB fiber laser hydrophone array based on time division multiplexing

NASA Astrophysics Data System (ADS)

Li, Yu; Huang, Junbin; Gu, Hongcan; Tang, Bo; Wu, Jing

2014-12-01

In this paper, the crosstalk of a time division multiplexed (TDM) system of distributed feedback (DFB) fiber laser (FL)hydrophones based on optical switch using Phase Generated Carrier (PGC) method was quantitatively analyzed. After mathematical deduction, the relationship among crosstalk, multiplexing scale and extinction ratio of optical switch was given. The simulation results show that to realize a TDM system of DFB fiber laser hydrophones with crosstalk lower than -40dB, the average extinction ratio should be higher than 24.78dB for a 4- channel system, while higher than 28.45dB for an 8- channel system. Two experiments to analyze the array crosstalk to a certain channel in an 8- channel array were conducted in this paper. Firstly, by testing the powers of leak laser to a certain channel from others, the array crosstalk to this channel was obtained according to the equation mathematically deduced in this paper. The result shows the array crosstalk to a certain channel of the 8-channel array was -7.6dB. An experiment of underwater acoustic detection was carried out finally to get the real array crosstalk to this certain channel, and the experimental result shows that the array crosstalk to this channel is -8.8dB, which is close to the calculated result.

Seismic fiber optic multiplexed sensors for exploration and reservoir management

NASA Astrophysics Data System (ADS)

Houston, Mark H.

2000-12-01

Reliable downhole communications, control and sensor networks will dramatically improve oil reservoir management practices and will enable the construction of intelligent or smart-well completions. Fiber optic technology will play a key role in the implementation of these communication, control and sensing systems because of inherent advantages of power, weight and reliability over more conventional electronic-based systems. Field test data, acquired using an array of fiber optic seismic hydrophones within a steam-flood, heavy oil- production filed, showed a significant improvement (10X in this specific case) in subsurface resolution as compared to conventional surface seismic acquisition. These results demonstrate the viability of using multiplexed fiber optic sensors for exploration and reservoir management in 3D vertical seismic profiling (VSP) surveys and in permanent sensor arrays for 4D surveys.

Structural Imaging around the SMS Deposit by the Multi-Source ZVCS Survey Method in the Izena Hole, Mid-Okinawa Trough

NASA Astrophysics Data System (ADS)

Tara, K.; Asakawa, E.; Murakami, F.; Tsukahara, H.; Saito, S.; Lee, S.; Katou, M.; Jamali Hondori, E.; Sumi, T.; Kadoshima, K.; Kose, M.

2017-12-01

Seafloor Massive Sulfide (SMS) deposits typically show rugged topography such as abundant chimney structures and sulfide mounds. However, buried SMS deposits are not well studied because of few efficient methods to detect and characterize them. Therefore, we proposed a Zero-offset Vertical Cable Seismic (ZVCS) survey using a Sparker and a Remotely Operated Vehicle (ROV) which was equipped with autonomous hydrophone arrays and a sub-bottom profiler (SBP). Zero-offset shooting and near-bottom recording can acquire high resolution acoustic data that could separate the reflection and scattered wave by vertically towed hydrophone arrays. We conducted the multi-source ZVCS survey in the Hakurei site, where the existence of the exposed and the buried SMS deposits has been reported, in Izena Hole, the Mid-Okinawa Trough, during the exploration cruise JM16-04. We obtained the two source's cross-sections of the buried SMS that enabled us to identify the area from the viewpoint of seismic facies. Buried SMS area is characterized by wavy to subparallel internal configuration and semi-continuously reflections. These features suggest that results from collapse of original sedimentary structure and hydrothermal alteration. Previous our exploration of the entire Izena Hole by the Autonomous Cable Seismic (ACS) were conducted in the JM16-02. Comparison between the ZVCS and ACS results gave us not only structural features in the surrounding area of SMS, but also the hydrothermal system of the Izena Hole. These results suggest that the hydrothermal circulation in the Izena Hole is vertically limited to the fracture zone caused by the depression and the buried SMS occurs in a sedimentary layer in the fracture zone. We conclude that ZVCS and ACS imaging of the shallow sub-seafloor structures will be useful for discussion about the geological background of SMS deposits.

Ocean Bottom Seismometer Augmentation of the Philippine Sea Experiment (OBSAPS) Cruise Report

DTIC Science & Technology

2011-09-01

single 77.5Hz M-sequence on six OBSAPS receivers: (from bottom to top) the vertical geophone on the North OBS ( blue ), the hydrophone module on the...wet end electronics (pressure sensor, hydrophone and octopus ) to the spare J15-3 S/N 14 and re-deployed the transducer and tow body assembly. We then...our wet end electronics (hydrophone, pressure sensor and octopus ) to the S/N 11 unit and re-deployed. The repaired J15-3 S/N 11 unit performed

Radiated noise from commercial ships in the Gulf of Maine: implications for whale/vessel collisions.

PubMed

Allen, J Kaitlyn; Peterson, Michael L; Sharrard, George V; Wright, Dana L; Todd, Sean K

2012-09-01

To understand mysticete acoustic-based detection of ships, radiated noise from high-speed craft, cruise ships, catamarans and fishing vessels was recorded June-September 2009. Calibrated acoustic data (<2500 Hz) from a vertical hydrophone array was combined with ship passage information. A cruise ship had the highest broadband source level, while a fishing vessel had the lowest. Ship noise radiated asymmetrically and varied with depth. Bow null-effect acoustic shadow zones were observed for all ship classes and were correlated with ship-length-to-draft-ratios. These shadow zones may reduce ship detection by near-surface mysticetes.

Vertical Cable Seismic Survey for SMS exploration

NASA Astrophysics Data System (ADS)

Asakawa, Eiichi; Murakami, Fumitoshi; Tsukahara, Hotoshi; Mizohata, Shigeharu

2014-05-01

The Vertical Cable Seismic (VCS) survey is one of the reflection seismic methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by sea-surface, deep-towed or ocean bottom sources. Analyzing the reflections from the sub-seabed, we could look into the subsurface structure. Because the VCS is an efficient high-resolution 3D seismic survey method for a spatially-bounded area, we proposed it for the SMS survey tool development program that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) started in 2009. We have been developing the VCS survey system, including not only data acquisition hardware but data processing and analysis technique. We carried out several VCS surveys combining with surface towed source, deep towed source and ocean bottom source. The water depths of these surveys are from 100m up to 2100 m. Through these experiments, our VCS data acquisition system has been also completed. But the data processing techniques are still on the way. One of the most critical issues is the positioning in the water. The uncertainty in the positions of the source and of the hydrophones in water degraded the quality of subsurface image. GPS navigation system is available on sea surface, but in case of deep-towed source or ocean bottom source, the accuracy of shot position with SSBL/USBL is not sufficient for the very high-resolution imaging. We have developed a new approach to determine the positions in water using the travel time data from the source to VCS hydrophones. In 2013, we have carried out the second VCS survey using the surface-towed high-voltage sparker and ocean bottom source in the Izena Cauldron, which is one of the most promising SMS areas around Japan. The positions of ocean bottom source estimated by this method are consistent with the VCS field records. The VCS data with the sparker have been processed with 3D PSTM. It gives the very high resolution 3D volume deeper than two hundred meters. Our VCS system has been demonstrated as a promising survey tool for the SMS exploration.

Development of Vertical Cable Seismic System (3)

NASA Astrophysics Data System (ADS)

Asakawa, E.; Murakami, F.; Tsukahara, H.; Mizohata, S.; Ishikawa, K.

2013-12-01

The VCS (Vertical Cable Seismic) is one of the reflection seismic methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by surface, deep-towed or ocean bottom sources. Analyzing the reflections from the sub-seabed, we could look into the subsurface structure. Because VCS is an efficient high-resolution 3D seismic survey method for a spatially-bounded area, we proposed the method for the hydrothermal deposit survey tool development program that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) started in 2009. We are now developing a VCS system, including not only data acquisition hardware but data processing and analysis technique. We carried out several VCS surveys combining with surface towed source, deep towed source and ocean bottom source. The water depths of the survey are from 100m up to 2100m. The target of the survey includes not only hydrothermal deposit but oil and gas exploration. Through these experiments, our VCS data acquisition system has been completed. But the data processing techniques are still on the way. One of the most critical issues is the positioning in the water. The uncertainty in the positions of the source and of the hydrophones in water degraded the quality of subsurface image. GPS navigation system are available on sea surface, but in case of deep-towed source or ocean bottom source, the accuracy of shot position with SSBL/USBL is not sufficient for the very high-resolution imaging. We have developed another approach to determine the positions in water using the travel time data from the source to VCS hydrophones. In the data acquisition stage, we estimate the position of VCS location with slant ranging method from the sea surface. The deep-towed source or ocean bottom source is estimated by SSBL/USBL. The water velocity profile is measured by XCTD. After the data acquisition, we pick the first break times of the VCS recorded data. The estimated positions of shot points and receiver points in the field include the errors. We use these data as initial guesses, we invert iteratively shot and receiver positions to match the travel time data. After several iterations we could finally estimate the most probable positions. Integration of the constraint of VCS hydrophone positions, such as the spacing is 10m, can accelerate the convergence of the iterative inversion and improve results. The accuracy of the estimated positions from the travel time date is enough for the VCS data processing.

Ocean Acoustic Observatory Federation

DTIC Science & Technology

2001-09-30

range detection and localization of blue whale calls in the northeast Pacific Ocean ousing military hydrophone arrays, Jour. Acoust . Soc. Am., vol. 104...3616- 3624, 1998 . 5 Stafford , Kathleen M., Sharon L. Nieukirk, and Christopher G. Fox, Low-frequency whale sounds recorded on hydrophones... Stafford , Kathleen M., Blue Whale (Balaenoptera musculus) Vocalizations recorded in the North Pacific Ocean: Geographic, Seasonal, and Diel Variation,

Onboard Acoustic Data-Processing for the Statistical Analysis of Array Beam-Noise,

DTIC Science & Technology

1980-12-15

performance of the sonar system as a measurement tool and others that can assess the character of the ambient- noise field at the time of the measurement. In...the plot as would "dead" hydrophones. A reduction in sensitivity of a hydrophone, a faulty preamplifier , or any other fault in the acoustic channel

Echolocation signals of wild Atlantic spotted dolphin (Stenella frontalis)

NASA Astrophysics Data System (ADS)

Au, Whitlow W. L.; Herzing, Denise L.

2003-01-01

An array of four hydrophones arranged in a symmetrical star configuration was used to measure the echolocation signals of the Atlantic spotted dolphin (Stenella frontalis) in the Bahamas. The spacing between the center hydrophone and the other hydrophones was 45.7 cm. A video camera was attached to the array and a video tape recorder was time synchronized with the computer used to digitize the acoustic signals. The echolocation signals had bi-modal frequency spectra with a low-frequency peak between 40 and 50 kHz and a high-frequency peak between 110 and 130 kHz. The low-frequency peak was dominant when the signal the source level was low and the high-frequency peak dominated when the source level was high. Peak-to-peak source levels as high as 210 dB re 1 μPa were measured. The source level varied in amplitude approximately as a function of the one-way transmission loss for signals traveling from the animals to the array. The characteristics of the signals were similar to those of captive Tursiops truncatus, Delphinapterus leucas and Pseudorca crassidens measured in open waters under controlled conditions.

Improvements to Passive Acoustic Tracking Methods for Marine Mammal Monitoring

DTIC Science & Technology

2016-05-02

individual animals . 15. SUBJECT TERMS Marine mammal; Passive acoustic monitoring ; Localization; Tracking ; Multiple source ; Sparse array 16. SECURITY...al. 2004; Thode 2005; Nosal 2007] to localize animals in situations where straight-line propagation assumptions made by conventional marine mammal...Objective 1: Inveti for sound speed profiles. hydrophone position and hydrophone timing offset in addition to animal position Almost all marine mammal

Recording and quantification of ultrasonic echolocation clicks from free-ranging toothed whales

NASA Astrophysics Data System (ADS)

Madsen, P. T.; Wahlberg, M.

2007-08-01

Toothed whales produce short, ultrasonic clicks of high directionality and source level to probe their environment acoustically. This process, termed echolocation, is to a large part governed by the properties of the emitted clicks. Therefore derivation of click source parameters from free-ranging animals is of increasing importance to understand both how toothed whales use echolocation in the wild and how they may be monitored acoustically. This paper addresses how source parameters can be derived from free-ranging toothed whales in the wild using calibrated multi-hydrophone arrays and digital recorders. We outline the properties required of hydrophones, amplifiers and analog to digital converters, and discuss the problems of recording echolocation clicks on the axis of a directional sound beam. For accurate localization the hydrophone array apertures must be adapted and scaled to the behavior of, and the range to, the clicking animal, and precise information on hydrophone locations is critical. We provide examples of localization routines and outline sources of error that lead to uncertainties in localizing clicking animals in time and space. Furthermore we explore approaches to time series analysis of discrete versions of toothed whale clicks that are meaningful in a biosonar context.

Vertical array measurements of humpback whale songs

NASA Astrophysics Data System (ADS)

Au, Whitlow W. L.; Lammers, Marc O.; Pack, Adam A.; Herman, Louis

2004-05-01

The songs of eight male humpback whales were recorded at ranges varying from 20 to 40 m with a vertical array of hydrophones that had a flat frequency response to 24 kHz. The songs consisted of bursts of sounds called units. Units were organized into phrases and phrases into themes. Most of the units had mean duration between 1 and 2 s and mean silent periods between units between 1 and 2 s. Many of the recorded songs contained units that had high-frequency harmonics that extended beyond 22 kHz. These harmonic results suggest that humpback whale songs have a broadband quality not previously reported and may provide some insights on the high-frequency limit of hearing in these whales. The source levels of the songs were also estimated by considering the root-mean-square sound-pressure level referenced to 1 m for the unit with the largest level for different phrase within a song. Source levels varied between 171 to 189 dB re: 1 μPa. Singing escorts have been regularly observed within two whale lengths of females and these observations and knowledge of source levels provide estimates of sound-pressure levels that male humpback whales expose female whales to.

Array design considerations for exploitation of stable weakly dispersive modal pulses in the deep ocean

NASA Astrophysics Data System (ADS)

Udovydchenkov, Ilya A.

2017-07-01

Modal pulses are broadband contributions to an acoustic wave field with fixed mode number. Stable weakly dispersive modal pulses (SWDMPs) are special modal pulses that are characterized by weak dispersion and weak scattering-induced broadening and are thus suitable for communications applications. This paper investigates, using numerical simulations, receiver array requirements for recovering information carried by SWDMPs under various signal-to-noise ratio conditions without performing channel equalization. Two groups of weakly dispersive modal pulses are common in typical mid-latitude deep ocean environments: the lowest order modes (typically modes 1-3 at 75 Hz), and intermediate order modes whose waveguide invariant is near-zero (often around mode 20 at 75 Hz). Information loss is quantified by the bit error rate (BER) of a recovered binary phase-coded signal. With fixed receiver depths, low BERs (less than 1%) are achieved at ranges up to 400 km with three hydrophones for mode 1 with 90% probability and with 34 hydrophones for mode 20 with 80% probability. With optimal receiver depths, depending on propagation range, only a few, sometimes only two, hydrophones are often sufficient for low BERs, even with intermediate mode numbers. Full modal resolution is unnecessary to achieve low BERs. Thus, a flexible receiver array of autonomous vehicles can outperform a cabled array.

In-vivo fetal ultrasound exposimetry.

PubMed

Daft, C W; Siddiqi, T A; Fitting, D W; Meyer, R A; O'Brien, W R

1990-01-01

An instrument has been developed to measure the acoustic pressure field in vivo during an obstetric ultrasound examination. This provides for improved intensity values for exposure calculations, to assist in assessment of bioeffects. The ultrasonic field is sampled using a calibrated seven-element linear array hydrophone of poly(vinylidene difluoride) transducers, which is placed as close as possible to the ovary, embryo, or fetus using a vaginal approach. The RF signals from the hydrophone are digitized at 50 MHz, and the maximum amplitude waveform received in the examination is recorded. The output of the clinical B-scanner is calibrated by a measurement with the hydrophone in a water bath. From the hydrophone measurements, the in vivo I(SPTA), I(SPTP), and I(SPPA) are computed. Further analysis allows the frequency-dependent tissue attenuation to be assessed.

On Modeling Eavesdropping Attacks in Underwater Acoustic Sensor Networks †

PubMed Central

Wang, Qiu; Dai, Hong-Ning; Li, Xuran; Wang, Hao; Xiao, Hong

2016-01-01

The security and privacy of underwater acoustic sensor networks has received extensive attention recently due to the proliferation of underwater activities. This paper proposes an analytical model to investigate the eavesdropping attacks in underwater acoustic sensor networks. Our analytical framework considers the impacts of various underwater acoustic channel conditions (such as the acoustic signal frequency, spreading factor and wind speed) and different hydrophones (isotropic hydrophones and array hydrophones) in terms of network nodes and eavesdroppers. We also conduct extensive simulations to evaluate the effectiveness and the accuracy of our proposed model. Empirical results show that our proposed model is quite accurate. In addition, our results also imply that the eavesdropping probability heavily depends on both the underwater acoustic channel conditions and the features of hydrophones. PMID:27213379

Lesson learned from monitoring the environmental effects of construction of the first offshore wind farm in the US

NASA Astrophysics Data System (ADS)

Miller, J.; Potty, G. R.; King, J. W.; Gallien, D. R.; Khan, A. A.; Vigness Raposa, K.; Giard, J. L.; Frankel, A. S.; Mason, T.; Popper, A. N.; Hawkins, A. D.; Crocker, S. E.

2016-02-01

Noise radiation from pile driving activities were monitored using multiple sensors during the construction of the USA's first offshore wind farm located 3 nm off Block Island, RI. The 30-megawatt Block Island Wind Farm (BIWF) consists of five turbines in water depths of approximately 30 m and is scheduled to be online in 2016. The substructure for these turbines consists of jacket type construction with piles driven to pin the structure to the seabed. Pile driving operations generate intense sound, impulsive in nature at close range, which radiates into the surrounding air, water and sediment. The underwater acoustic measurement platforms consisted of a towed array consisting of eight hydrophones, two fixed moorings with four hydrophones each, a fixed sensor package for measuring particle velocity, and boat-deployed dipping hydrophones. The hydrophone array was towed from a position 1 km from the pile driving location to 15 km distance from the construction. The fixed moorings were deployed at 10 km and 15 km from the pile location. The fixed moorings consisted of four hydrophones each at depths of 10, 15, 20 and 25 m. Near field measurements of the underwater acoustic signals from the pile driving were collected with a tetrahedral array deployed at 500 m from the pile driving location about 1 m above the seabed. The boat-deployed dipping hydrophones sampled the acoustic field at locations from 0.5 km to 20 km from the pile driving locations. Based on these acoustic measurements and propagation modeling, the acoustic pressure field as a function of range and depth from the pile is estimated. The transition from fast-rise-time impulsive signals at close range to slow-rise-time non-impulsive signals at longer ranges will be addressed. This study will provide the required information to qualify the different zones of potential marine mammal effects (zones of injury, behavioral effects etc.) and to estimate exposure to fishes and other species. [Work supported by Bureau of Ocean Energy Management (BOEM)

Characteristic Analysis of Air-gun Source Wavelet based on the Vertical Cable Data

NASA Astrophysics Data System (ADS)

Xing, L.

2016-12-01

Air guns are important sources for marine seismic exploration. Far-field wavelets of air gun arrays, as a necessary parameter for pre-stack processing and source models, plays an important role during marine seismic data processing and interpretation. When an air gun fires, it generates a series of air bubbles. Similar to onshore seismic exploration, the water forms a plastic fluid near the bubble; the farther the air gun is located from the measurement, the more steady and more accurately represented the wavelet will be. In practice, hydrophones should be placed more than 100 m from the air gun; however, traditional seismic cables cannot meet this requirement. On the other hand, vertical cables provide a viable solution to this problem. This study uses a vertical cable to receive wavelets from 38 air guns and data are collected offshore Southeast Qiong, where the water depth is over 1000 m. In this study, the wavelets measured using this technique coincide very well with the simulated wavelets and can therefore represent the real shape of the wavelets. This experiment fills a technology gap in China.

Seismic and Biological Sources of Ambient Ocean Sound

NASA Astrophysics Data System (ADS)

Freeman, Simon Eric

Sound is the most efficient radiation in the ocean. Sounds of seismic and biological origin contain information regarding the underlying processes that created them. A single hydrophone records summary time-frequency information from the volume within acoustic range. Beamforming using a hydrophone array additionally produces azimuthal estimates of sound sources. A two-dimensional array and acoustic focusing produce an unambiguous two-dimensional `image' of sources. This dissertation describes the application of these techniques in three cases. The first utilizes hydrophone arrays to investigate T-phases (water-borne seismic waves) in the Philippine Sea. Ninety T-phases were recorded over a 12-day period, implying a greater number of seismic events occur than are detected by terrestrial seismic monitoring in the region. Observation of an azimuthally migrating T-phase suggests that reverberation of such sounds from bathymetric features can occur over megameter scales. In the second case, single hydrophone recordings from coral reefs in the Line Islands archipelago reveal that local ambient reef sound is spectrally similar to sounds produced by small, hard-shelled benthic invertebrates in captivity. Time-lapse photography of the reef reveals an increase in benthic invertebrate activity at sundown, consistent with an increase in sound level. The dominant acoustic phenomenon on these reefs may thus originate from the interaction between a large number of small invertebrates and the substrate. Such sounds could be used to take census of hard-shelled benthic invertebrates that are otherwise extremely difficult to survey. A two-dimensional `map' of sound production over a coral reef in the Hawaiian Islands was obtained using two-dimensional hydrophone array in the third case. Heterogeneously distributed bio-acoustic sources were generally co-located with rocky reef areas. Acoustically dominant snapping shrimp were largely restricted to one location within the area surveyed. This distribution of sources could reveal small-scale spatial ecological limitations, such as the availability of food and shelter. While array-based passive acoustic sensing is well established in seismoacoustics, the technique is little utilized in the study of ambient biological sound. With the continuance of Moore's law and advances in battery and memory technology, inferring biological processes from ambient sound may become a more accessible tool in underwater ecological evaluation and monitoring.

Demonstration of an advanced fibre laser hydrophone array in Gulf St Vincent

NASA Astrophysics Data System (ADS)

Foster, Scott; Tikhomirov, Alexei; Harrison, Joanne; van Velzen, John

2015-09-01

We have developed an 8-element fibre laser seabed array demonstrating state-of-the art performance characteristics for a fibre laser sensing system. The system employs sea-state-zero sensitivity hydrophones with a flat acoustic response over a bandwidth exceeding 5kHz and very low inertial sensitivity. The system contains no outboard electronics and few metal components making it extremely light, compact, and low complexity. The array may be deployed up to 4 km from a land or sea based platform to a depth of up to 80m. Power delivery and telemetry for all 8 sensors is achieved via a single 2mm diameter optical fibre cable weighing less than 5kg per km. We report here results of the first field trials of this system.

Single-lobed frequency-dependent beam shape in an echolocating false killer whale (Pseudorca crassidens).

PubMed

Kloepper, Laura N; Nachtigall, Paul E; Quintos, Christopher; Vlachos, Stephanie A

2012-01-01

Recent studies indicate some odontocetes may produce echolocation beams with a dual-lobed vertical structure. The shape of the odontocete echolocation beam was further investigated in a false killer whale performing an echolocation discrimination task. Clicks were recorded with an array of 16 hydrophones and frequency-dependent amplitude plots were constructed to assess beam shape. The majority of the echolocation clicks were single-lobed in structure with most energy located between 20 and 80 kHz. These data indicate the false killer whale does not produce a dual-lobed structure, as has been shown in bottlenose dolphins, which may be a function of lowered frequencies in the emitted signal due to hearing loss. © 2012 Acoustical Society of America.

Source parameter estimates of echolocation clicks from wild pygmy killer whales (Feresa attenuata) (L)

NASA Astrophysics Data System (ADS)

Madsen, P. T.; Kerr, I.; Payne, R.

2004-10-01

Pods of the little known pygmy killer whale (Feresa attenuata) in the northern Indian Ocean were recorded with a vertical hydrophone array connected to a digital recorder sampling at 320 kHz. Recorded clicks were directional, short (25 μs) transients with estimated source levels between 197 and 223 dB re. 1 μPa (pp). Spectra of clicks recorded close to or on the acoustic axis were bimodal with peak frequencies between 45 and 117 kHz, and with centroid frequencies between 70 and 85 kHz. The clicks share characteristics of echolocation clicks from similar sized, whistling delphinids, and have properties suited for the detection and classification of prey targeted by this odontocete. .

Three-dimensional tracking of Cuvier's beaked whales' echolocation sounds using nested hydrophone arrays.

PubMed

Gassmann, Martin; Wiggins, Sean M; Hildebrand, John A

2015-10-01

Cuvier's beaked whales (Ziphius cavirostris) were tracked using two volumetric small-aperture (∼1 m element spacing) hydrophone arrays, embedded into a large-aperture (∼1 km element spacing) seafloor hydrophone array of five nodes. This array design can reduce the minimum number of nodes that are needed to record the arrival of a strongly directional echolocation sound from 5 to 2, while providing enough time-differences of arrivals for a three-dimensional localization without depending on any additional information such as multipath arrivals. To illustrate the capabilities of this technique, six encounters of up to three Cuvier's beaked whales were tracked over a two-month recording period within an area of 20 km(2) in the Southern California Bight. Encounter periods ranged from 11 min to 33 min. Cuvier's beaked whales were found to reduce the time interval between echolocation clicks while alternating between two inter-click-interval regimes during their descent towards the seafloor. Maximum peak-to-peak source levels of 179 and 224 dB re 1 μPa @ 1 m were estimated for buzz sounds and on-axis echolocation clicks (directivity index = 30 dB), respectively. Source energy spectra of the on-axis clicks show significant frequency components between 70 and 90 kHz, in addition to their typically noted FM upsweep at 40-60 kHz.

Earthquake Source Parameters Inferred from T-Wave Observations

NASA Astrophysics Data System (ADS)

Perrot, J.; Dziak, R.; Lau, T. A.; Matsumoto, H.; Goslin, J.

2004-12-01

The seismicity of the North Atlantic Ocean has been recorded by two networks of autonomous hydrophones moored within the SOFAR channel on the flanks of the Mid-Atlantic Ridge (MAR). In February 1999, a consortium of U.S. investigators (NSF and NOAA) deployed a 6-element hydrophone array for long-term monitoring of MAR seismicity between 15o-35oN south of the Azores. In May 2002, an international collaboration of French, Portuguese, and U.S. researchers deployed a 6-element hydrophone array north of the Azores Plateau from 40o-50oN. The northern network (referred to as SIRENA) was recovered in September 2003. The low attenuation properties of the SOFAR channel for earthquake T-wave propagation results in a detection threshold reduction from a magnitude completeness level (Mc) of ˜ 4.7 for MAR events recorded by the land-based seismic networks to Mc=3.0 using hydrophone arrays. Detailed focal depth and mechanism information, however, remain elusive due to the complexities of seismo-acoustic propagation paths. Nonetheless, recent analyses (Dziak, 2001; Park and Odom, 2001) indicate fault parameter information is contained within the T-wave signal packet. We investigate this relationship further by comparing an earthquake's T-wave duration and acoustic energy to seismic magnitude (NEIC) and radiation pattern (for events M>5) from the Harvard moment-tensor catalog. First results show earthquake energy is well represented by the acoustic energy of the T-waves, however T-wave codas are significantly influenced by acoustic propagation effects and do not allow a direct determination of the seismic magnitude of the earthquakes. Second, there appears to be a correlation between T-wave acoustic energy, azimuth from earthquake source to the hydrophone, and the radiation pattern of the earthquake's SH waves. These preliminary results indicate there is a relationship between the T-wave observations and earthquake source parameters, allowing for additional insights into T-wave propagation.

Field demonstration of an eight-element fiber laser hydrophone array

NASA Astrophysics Data System (ADS)

Foster, Scott; Tikhomirov, Alexei; Harrison, Joanne; van Velzen, John

2014-05-01

We have developed an 8-element fibre laser seabed array demonstrating state-of-the art performance characteristics for a fibre laser sensing system and highlighting the advantage this technology provides in the underwater sensing domain. The system employs sea-state-zero sensitivity hydrophones with a flat acoustic response over a bandwidth exceeding 5kHz and very low inertial sensitivity. The system contains no outboard electronics and few metal components making it extremely light, compact, and low complexity. The array may be deployed up to 4 km from a land or sea based platform to a depth of up to 80m. Power delivery and telemetry for all 8 sensors is achieved via a single 2mm diameter optical fibre cable weighing less than 5kg per km. We report here results of the first field trials of this system.

Development of high sensitivity eight-element multiplexed fiber laser acoustic pressure hydrophone array and interrogation system

NASA Astrophysics Data System (ADS)

Li, Ming; Sun, Zhihui; Zhang, Xiaolei; Li, Shujuan; Song, Zhiqiang; Wang, Meng; Guo, Jian; Ni, Jiasheng; Wang, Chang; Peng, Gangding; Xu, Xiangang

2017-09-01

Fiber laser hydrophones have got widespread concerns due to the unique advantages and broad application prospects. In this paper, the research results of the eight-element multiplexed fiber laser acoustic pressure array and the interrogation system are introduced, containing low-noise distributed feedback fiber laser (DFB-FL) fabrication, sensitivity enhancement packaging, and interferometric signal demodulation. The frequency response range of the system is 10Hz-10kHz, the laser frequency acoustic pressure sensitivity reaches 115 dB re Hz/Pa, and the equivalent noise acoustic pressure is less than 60μPa/Hz1/2. The dynamic range of the system is greater than 120 dB.

Analysis of Low Frequency Ocean Noise: (1) From a Long-Term Experiment Across the U.S. East Coast, and (2) From the Wake Island Hydrophone Array During Northwest Pacific Typhoons

DTIC Science & Technology

1994-07-22

1944). "Mouvements ondulatoires de la mer en profondeur constante on decroissante," Ann. Ponts Chaussees 114, 25-87. Nichols, R.H. (1981). "Infrasonic...I I II 0 0 06 05 I 2 5 i0 20 50 o0 ---,, bL ....... *. BOT TOM HYDROPHONE FR EQ U EN CY (H Z) o SOFAR HYDROPHONE SEISMIC FIG. 2. Estimated response...Trans. R. Soc. London Ser. A 243, 1-35 (1950). Gauge," J. Atmos. Ocean Technol. 1, 237-246 (1984). 2 M. Miche, "Mouvements Ondulatoires de la Mer en

T-phase and tsunami signals recorded by IMS hydrophone triplets during the 2011 Tohoku earthquake

NASA Astrophysics Data System (ADS)

Matsumoto, H.; Haralabus, G.; Zampolli, M.; Ozel, N. M.; Yamada, T.; Mark, P. K.

2016-12-01

A hydrophone station of the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) is used to estimate the back-azimuth of T-phase signals generated by the 2011 Tohoku earthquake. Among the 6 IMS hydrophone stations required by the Treaty, 5 stations consist of two triplets, with the exception of HA1 (Australia), which has only one. The hydrophones of each triplet are suspended in the SOFAR channel and arranged to form an equilateral triangle with each side being approximately two kilometers long. The waveforms from the Tohoku earthquake were received at HA11, located on Wake Island, which is located approximately 3100 km south-east of the earthquake epicenter. The frequency range used in the array analysis was chosen to be less than 0.375 Hz, which assumed the target phase velocity to be 1.5 km/s for T-phases. The T-phase signals that originated from the seismic source however show peaks in the frequency band above one Hz. As a result of the inter-element distances of 2 km, spatial aliasing is observed in the frequency-wavenumber analysis (F-K analysis) if the entire 100 Hz bandwidth of the hydrophones is used. This spatial aliasing is significant because the distance between hydrophones in the triplet is large in comparison to the ratio between the phase velocity of T-phase signals and the frequency. To circumvent this spatial aliasing problem, a three-step processing technique used in seismic array analysis is applied: (1) high-pass filtering above 1 Hz to retrieve the T-phase, followed by (2) extraction of the envelope of this signal to highlight the T-phase contribution, and finally (3) low-pass filtering of the envelope below 0.375 Hz. The F-K analysis provides accurate back-azimuth and slowness estimations without spatial aliasing. Deconvolved waveforms are also processed to retrieve tsunami components by using a three-pole model of the frequency-amplitude-phase (FAP) response below 0.1 Hz and the measured sensor response for higher frequencies. It is also shown that short-period pressure fluctuations recorded by the IMS hydrophones correspond to theoretical dispersion curves of tsunamis. Thus, short-period dispersive tsunami signals can be identified by the IMS hydrophone triplets.

Optimization of Concurrent Deployments of the Juvenile Salmon Acoustic Telemetry System and Other Hydroacoustic Equipment at John Day Dam

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

Ploskey, Gene R.; Hughes, James S.; Khan, Fenton

The purpose of this report is to document the results of the acoustic optimization study conducted at John Day Dam during January and February 2008. The goal of the study was to optimize performance of the Juvenile Salmon Acoustic Telemetry System (JSATS) by determining deployment and data acquisition methods to minimize electrical and acoustic interference from various other acoustic sampling devices. Thereby, this would allow concurrent sampling by active and passive acoustic methods during the formal evaluations of the prototype surface flow outlets at the dam during spring and summer outmigration seasons for juvenile salmonids. The objectives for the optimizationmore » study at John Day Dam were to: 1. Design and test prototypes and provide a total needs list of pipes and trolleys to deploy JSATS hydrophones on the forebay face of the powerhouse and spillway. 2. Assess the effect on mean percentage decoded of JSATS transmissions from tags arrayed in the forebay and detected on the hydrophones by comparing: turbine unit OFF vs. ON; spill bay OPEN vs. CLOSED; dual frequency identification sonar (DIDSON) and acoustic Doppler current profiler (ADCP) both OFF vs. ON at a spill bay; and, fixed-aspect hydroacoustic system OFF vs. ON at a turbine unit and a spill bay. 3. Determine the relationship between fixed-aspect hydroacoustic transmit level and mean percentage of JSATS transmissions decoded. The general approach was to use hydrophones to listen for transmissions from JSATS tags deployed in vertical arrays in a series perpendicular to the face of the dam. We used acoustic telemetry equipment manufactured by Technologic and Sonic Concepts. In addition, we assessed old and new JSATS signal detectors and decoders and two different types of hydrophone baffling. The optimization study consisted of a suite of off/on tests. The primary response variable was mean percentage of tag transmissions decoded. We found that there was no appreciable adverse effect on mean percentage decoded for JSATS transmitters from: turbine operations; spillway operations; DIDSON/ADCP acoustic energy; and PAS hydroacoustic systems at transmit level of -12 dB, although there was a significant impact at all higher transmit levels (-11 to -6 dB). The main conclusion from this optimization study is that valid JSATS telemetry data can be collected simultaneously with a DIDSON/ADCP and a PAS hydroacoustic system at transmit level -12 dB. Multiple evaluation tools should be considered to increase the robustness and thoroughness of future fish passage evaluations at John Day and other dams.« less

Using a coherent hydrophone array for observing sperm whale range, classification, and shallow-water dive profiles.

PubMed

Tran, Duong D; Huang, Wei; Bohn, Alexander C; Wang, Delin; Gong, Zheng; Makris, Nicholas C; Ratilal, Purnima

2014-06-01

Sperm whales in the New England continental shelf and slope were passively localized, in both range and bearing, and classified using a single low-frequency (<2500 Hz), densely sampled, towed horizontal coherent hydrophone array system. Whale bearings were estimated using time-domain beamforming that provided high coherent array gain in sperm whale click signal-to-noise ratio. Whale ranges from the receiver array center were estimated using the moving array triangulation technique from a sequence of whale bearing measurements. Multiple concurrently vocalizing sperm whales, in the far-field of the horizontal receiver array, were distinguished and classified based on their horizontal spatial locations and the inter-pulse intervals of their vocalized click signals. The dive profile was estimated for a sperm whale in the shallow waters of the Gulf of Maine with 160 m water-column depth located close to the array's near-field where depth estimation was feasible by employing time difference of arrival of the direct and multiply reflected click signals received on the horizontal array. By accounting for transmission loss modeled using an ocean waveguide-acoustic propagation model, the sperm whale detection range was found to exceed 60 km in low to moderate sea state conditions after coherent array processing.

Acoustic Environment of Admiralty Inlet: Broadband Noise Measurements

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

Xu, Jinshan; Deng, Zhiqun; Martinez, Jayson J.

2011-09-30

Admiralty Inlet has been selected as a potential tidal energy site. It is located near shipping lanes, is a highly variable acoustic environment, and is frequented by the highly endangered southern resident killer whale (SRKW). Resolving environmental impacts is the first step to receiving approval to deploy tidal turbines at Admiralty Inlet. Of particular concern is the potential for blade strike or other negative interactions between the SRKW and the tidal turbine. A variety of technologies including passive and active monitoring systems are being considered as potential tools to determine the presence of SRKW in the vicinity of the turbines.more » Broadband noise level measurements are critical for the determination of design and operation specifications of all marine and hydrokinetic energy capture technologies. Acoustic environment data at the proposed site was acquired at different depths using a cabled vertical line array (VLA) with four calibrated hydrophones. The sound pressure level (SPL) power spectrum density was estimated based on the fast Fourier transform. This study describes the first broadband SPL measurements for this site at different depths with frequency ranging from 10 kHz to 480 kHz in combination with other information. To understand the SPL caused by this bedload transport, three different pressure sensors with temperature and conductivity were also assembled on the VLA to measure the conditions at the hydrophone deployment depth. The broadband SPL levels at frequency ranges of 3 kHz to 7 kHz as a function of depth were estimated. Only the hydrophone at an average depth of 40 m showed the strong dependence of SPL with distance from the bottom, which was possibly caused by the cobbles shifting on the seabed. Automatic Identification System data were also studied to understand the SPL measurements.« less

Versatile Experimental Kevlar Array Hydrophones: USRD Type H78

DTIC Science & Technology

1979-04-05

the design of a small deop-submergence noise-measuring hydropl,one for the infra - sonic and low-audio frequency range, three hydrophone...llenriquez and L.-E. Ivey, -Standard Ilydrophone for the Infrasonic and Audio- F.-equency Range at H~ydrostatic Pressure to 10,000 psig," J. A cous. qoc. Am...Piezoelectric Ceramic Ilydrophone for Infrasonic and Audio Frequencies IJSRD Type 1148," NRL Report 7260, 15 Mar. 1971. 9. S.W. Meeks and R.W. Timme, "Effects

Amazon river dolphins (Inia geoffrensis) modify biosonar output level and directivity during prey interception in the wild.

PubMed

Ladegaard, Michael; Jensen, Frants Havmand; Beedholm, Kristian; da Silva, Vera Maria Ferreira; Madsen, Peter Teglberg

2017-07-15

Toothed whales have evolved to live in extremely different habitats and yet they all rely strongly on echolocation for finding and catching prey. Such biosonar-based foraging involves distinct phases of searching for, approaching and capturing prey, where echolocating animals gradually adjust sonar output to actively shape the flow of sensory information. Measuring those outputs in absolute levels requires hydrophone arrays centred on the biosonar beam axis, but this has never been done for wild toothed whales approaching and capturing prey. Rather, field studies make the assumption that toothed whales will adjust their biosonar in the same manner to arrays as they will when approaching prey. To test this assumption, we recorded wild botos ( Inia geoffrensis ) as they approached and captured dead fish tethered to a hydrophone in front of a star-shaped seven-hydrophone array. We demonstrate that botos gradually decrease interclick intervals and output levels during prey approaches, using stronger adjustment magnitudes than predicted from previous boto array data. Prey interceptions are characterised by high click rates, but although botos buzz during prey capture, they do so at lower click rates than marine toothed whales, resulting in a much more gradual transition from approach phase to buzzing. We also demonstrate for the first time that wild toothed whales broaden biosonar beamwidth when closing in on prey, as is also seen in captive toothed whales and bats, thus resulting in a larger ensonified volume around the prey, probably aiding prey tracking by decreasing the risk of prey evading ensonification. © 2017. Published by The Company of Biologists Ltd.

Vertical Cable Seismic Survey for Hydrothermal Deposit

NASA Astrophysics Data System (ADS)

Asakawa, E.; Murakami, F.; Sekino, Y.; Okamoto, T.; Ishikawa, K.; Tsukahara, H.; Shimura, T.

2012-04-01

The vertical cable seismic is one of the reflection seismic methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by surface, deep-towed or ocean bottom sources. Analyzing the reflections from the sub-seabed, we could look into the subsurface structure. This type of survey is generally called VCS (Vertical Cable Seismic). Because VCS is an efficient high-resolution 3D seismic survey method for a spatially-bounded area, we proposed the method for the hydrothermal deposit survey tool development program that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) started in 2009. We are now developing a VCS system, including not only data acquisition hardware but data processing and analysis technique. Our first experiment of VCS surveys has been carried out in Lake Biwa, JAPAN in November 2009 for a feasibility study. Prestack depth migration is applied to the 3D VCS data to obtain a high quality 3D depth volume. Based on the results from the feasibility study, we have developed two autonomous recording VCS systems. After we carried out a trial experiment in the actual ocean at a water depth of about 400m and we carried out the second VCS survey at Iheya Knoll with a deep-towed source. In this survey, we could establish the procedures for the deployment/recovery of the system and could examine the locations and the fluctuations of the vertical cables at a water depth of around 1000m. The acquired VCS data clearly shows the reflections from the sub-seafloor. Through the experiment, we could confirm that our VCS system works well even in the severe circumstances around the locations of seafloor hydrothermal deposits. We have, however, also confirmed that the uncertainty in the locations of the source and of the hydrophones could lower the quality of subsurface image. It is, therefore, strongly necessary to develop a total survey system that assures a accurate positioning and a deployment techniques. We have carried out two field surveys in FY2011. One is a 3D survey with a boomer for a high-resolution surface source and the other one for an actual field survey in the Izena Cauldron an active hydrothermal area in the Okinawa Trough. Through these surveys, the VCS will become a practical exploration tool for the exploration of seafloor hydrothermal deposits.

Polarization maintaining fiber magnetic sensor based on the digital phase generated carrier technology

NASA Astrophysics Data System (ADS)

Zhang, Xueliang; Meng, Zhou; Hu, Zhengliang; Yang, Huayong; Song, Zhangqi; Hu, Yongming

2008-12-01

A polarization maintaining fiber (PMF) magnetic field sensor based on a digital phase generated carrier (PGC) technology is presented. A magnetic sensor constructed with two magnetostrictive strips attached on the sensing fiber is joined in the sensing arm of a fiber Michelson interferometer. The fiber optic interferometric system is made of all PMF, which inhibits the polarization-induced signal fading. The light source is a fiber laser which can be modulated directly. The PGC metnod is used to demodulate magnetic field signal avoiding phase induced interferometric signal fading, and ensure the sensing partto be all fiber structure. A fiber optic magnetic field sensor with appreciate size for the fiber optic hydrophone towed array is obtained, which can be used to sense the enviromental magnetic field along the sensing direction.This sensor is a good choice for the directional angle measurement through sensing the Earth magnetic field in the array shape measurement of a fiber optic hydrophone towed array.

Distributed acoustic sensing system based on continuous wide-band ultra-weak fiber Bragg grating array

NASA Astrophysics Data System (ADS)

Tang, Jianguan; Li, Liang; Guo, Huiyong; Yu, Haihu; Wen, Hongqiao; Yang, Minghong

2017-04-01

A distributed acoustic sensing system (DAS) with low-coherence ASE and Michelson interferometer based on continuous width-band ultra-weak fiber Bragg grating (UW-FBG) array is proposed and experimentally demonstrated. The experimental result shows that the proposed system has better performance in detecting acoustic waves than the conventional hydrophone.

The echolocation transmission beam of free-ranging Indo-Pacific humpback dolphins (Sousa chinensis).

PubMed

Fang, Liang; Wu, Yuping; Wang, Kexiong; Pine, Matthew K; Wang, Ding; Li, Songhai

2017-08-01

While the transmission beam of odontocetes has been described in a number of studies, the majority of them that have measured the transmission beam in two dimensions were focused on captive animals. Within the current study, a dedicated cross hydrophone array with nine elements was used to investigate the echolocation transmission beam of free-ranging Indo-Pacific humpback dolphins. A total of 265 on-axis clicks were analyzed, from which the apparent peak to peak source levels ranged between 168 to 207 dB (mean 184.5 dB ± 6.6 dB). The 3-dB beam width along the horizontal and vertical plane was 9.6° and 7.4°, respectively. Measured separately, the directivity index of the horizontal and vertical plane was 12.6 and 13.5 dB, respectively, and the overall directivity index (both planes combined) was 29.5 dB. The beam shape was slightly asymmetrical along the horizontal and vertical axis. Compared to other species, the characteristics of the transmitting beam of Indo-Pacific humpback dolphins were relatively close to the bottlenose dolphin (Tursiops truncatus), likely due to the similarity in the peak frequency and waveform of echolocation clicks and comparable body sizes of the two species.

Transmission beam characteristics of a Risso's dolphin (Grampus griseus).

PubMed

Smith, Adam B; Kloepper, Laura N; Yang, Wei-Cheng; Huang, Wan-Hsiu; Jen, I-Fan; Rideout, Brendan P; Nachtigall, Paul E

2016-01-01

The echolocation system of the Risso's dolphin (Grampus griseus) remains poorly studied compared to other odontocete species. In this study, echolocation signals were recorded from a stationary Risso's dolphin with an array of 16 hydrophones and the two-dimensional beam shape was explored using frequency-dependent amplitude plots. Click source parameters were similar to those already described for this species. Centroid frequency of click signals increased with increasing sound pressure level, while the beamwidth decreased with increasing center frequency. Analysis revealed primarily single-lobed, and occasionally vertically dual-lobed, beam shapes. Overall beam directivity was found to be greater than that of the harbor porpoise, bottlenose dolphin, and a false killer whale. The relationship between frequency content, beam directivity, and head size for this Risso's dolphin deviated from the trend described for other species. These are the first reported measurements of echolocation beam shape and directivity in G. griseus.

A beamforming study for implementation of vibro-acoustography with a 1.75-D array transducer.

PubMed

Urban, Matthew W; Chalek, Carl; Haider, Bruno; Thomenius, Kai E; Fatemi, Mostafa; Alizad, Azra

2013-03-01

Vibro-acoustography (VA) is an ultrasound-based imaging modality that uses radiation force produced by two cofocused ultrasound beams separated by a small frequency difference, Δf, to vibrate tissue at Δf. An acoustic field is created by the object vibration and measured with a nearby hydrophone. This method has recently been implemented on a clinical ultrasound system using 1-D linear-array transducers. In this article, we discuss VA beamforming and image formation using a 1.75-D array transducer. A 1.75-D array transducer has several rows of elements in the elevation direction which can be controlled independently for focusing. The advantage of the 1.75-D array over a 1-D linear-array transducer is that multiple rows of elements can be used for improving elevation focus for imaging formation. Six configurations for subaperture design for the two ultrasound beams necessary for VA imaging were analyzed. The point-spread functions for these different configurations were evaluated using a numerical simulation model. Four of these configurations were then chosen for experimental evaluation with a needle hydrophone as well as for scanning two phantoms. Images were formed by scanning a urethane breast phantom and an ex vivo human prostate. VA imaging using a 1.75-D array transducer offers several advantages over scanning with a linear-array transducer, including improved image resolution and contrast resulting from better elevation focusing of the imaging point-spread function.

A Beamforming Study for Implementation of Vibro-acoustography with a 1.75D Array Transducer

PubMed Central

Urban, Matthew W.; Chalek, Carl; Haider, Bruno; Thomenius, Kai E.; Fatemi, Mostafa; Alizad, Azra

2013-01-01

Vibro-acoustography (VA) is an ultrasound-based imaging modality that uses radiation force produced by two cofocused ultrasound beams separated by a small frequency difference, Δf, to vibrate tissue at Δf. An acoustic field is created by the object vibration and measured with a nearby hydrophone. This method has recently been implemented on a clinical ultrasound system using one-dimensional (1D) linear array transducers. In this article, we discuss VA beamforming and image formation using a 1.75D array transducer. A 1.75D array transducer has several rows of elements in the elevation direction which can be controlled independently for focusing. The advantage of the 1.75D array over a 1D linear array transducer is that multiple rows of elements can be used for improving elevation focus for imaging formation. Six configurations for subaperture design for the two ultrasound beams necessary for VA imaging were analyzed. The point-spread functions for these different configurations were evaluated using a numerical simulation model. Four of these configurations were then chosen for experimental evaluation with a needle hydrophone as well as for scanning two phantoms. Images were formed by scanning a urethane breast phantom and an ex vivo human prostate. VA imaging using a 1.75D array transducer offers several advantages over scanning with a linear array transducer including improved image resolution and contrast due to better elevation focusing of the imaging point-spread function. PMID:23475919

Cross-correlation, triangulation, and curved-wavefront focusing of coral reef sound using a bi-linear hydrophone array.

PubMed

Freeman, Simon E; Buckingham, Michael J; Freeman, Lauren A; Lammers, Marc O; D'Spain, Gerald L

2015-01-01

A seven element, bi-linear hydrophone array was deployed over a coral reef in the Papahãnaumokuãkea Marine National Monument, Northwest Hawaiian Islands, in order to investigate the spatial, temporal, and spectral properties of biological sound in an environment free of anthropogenic influences. Local biological sound sources, including snapping shrimp and other organisms, produced curved-wavefront acoustic arrivals at the array, allowing source location via focusing to be performed over an area of 1600 m(2). Initially, however, a rough estimate of source location was obtained from triangulation of pair-wise cross-correlations of the sound. Refinements to these initial source locations, and source frequency information, were then obtained using two techniques, conventional and adaptive focusing. It was found that most of the sources were situated on or inside the reef structure itself, rather than over adjacent sandy areas. Snapping-shrimp-like sounds, all with similar spectral characteristics, originated from individual sources predominantly in one area to the east of the array. To the west, the spectral and spatial distributions of the sources were more varied, suggesting the presence of a multitude of heterogeneous biological processes. In addition to the biological sounds, some low-frequency noise due to distant breaking waves was received from end-fire north of the array.

Single-shot measurements of the acoustic field of an electrohydraulic lithotripter using a hydrophone array

PubMed Central

Alibakhshi, Mohammad A.; Kracht, Jonathan M.; Cleveland, Robin O.; Filoux, Erwan; Ketterling, Jeffrey A.

2013-01-01

Piezopolymer-based hydrophone arrays consisting of 20 elements were fabricated and tested for use in measuring the acoustic field from a shock-wave lithotripter. The arrays were fabricated from piezopolymer films and were mounted in a housing to allow submersion into water. The motivation was to use the array to determine how the shot-to-shot variability of the spark discharge in an electrohydraulic lithotripter affects the resulting focused acoustic field. It was found that the dominant effect of shot-to-shot variability was to laterally shift the location of the focus by up to 5 mm from the nominal acoustic axis of the lithotripter. The effect was more pronounced when the spark discharge was initiated with higher voltages. The lateral beamwidth of individual, instantaneous shock waves were observed to range from 1.5 mm to 24 mm. Due to the spatial variation of the acoustic field, the average of instantaneous beamwidths were observed to be 1 to 2 mm narrower than beamwidths determined from traditional single-point measurements that average the pressure measured at each location before computing beamwidth. PMID:23654419

Quantitative assessment of acoustic intensity in the focused ultrasound field using hydrophone and infrared imaging.

PubMed

Yu, Ying; Shen, Guofeng; Zhou, Yufeng; Bai, Jingfeng; Chen, Yazhu

2013-11-01

With the popularity of ultrasound therapy in clinics, characterization of the acoustic field is important not only to the tolerability and efficiency of ablation, but also for treatment planning. A quantitative method was introduced to assess the intensity distribution of a focused ultrasound beam using a hydrophone and an infrared camera with no prior knowledge of the acoustic and thermal parameters of the absorber or the configuration of the array elements. This method was evaluated in both theoretical simulations and experimental measurements. A three-layer model was developed to calculate the acoustic field in the absorber, the absorbed acoustic energy during the sonication and the consequent temperature elevation. Experiments were carried out to measure the acoustic pressure with the hydrophone and the temperature elevation with the infrared camera. The percentage differences between the derived results and the simulation are <4.1% for on-axis intensity and <21.1% for -6-dB beam width at heating times up to 360 ms in the focal region of three phased-array ultrasound transducers using two different absorbers. The proposed method is an easy, quick and reliable approach to calibrating focused ultrasound transducers with satisfactory accuracy. Copyright © 2013 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Low-frequency whale and seismic airgun sounds recorded in the mid-Atlantic Ocean.

PubMed

Nieukirk, Sharon L; Stafford, Kathleen M; Mellinger, David K; Dziak, Robert P; Fox, Christopher G

2004-04-01

Beginning in February 1999, an array of six autonomous hydrophones was moored near the Mid-Atlantic Ridge (35 degrees N-15 degrees N, 50 degrees W-33 degrees W). Two years of data were reviewed for whale vocalizations by visually examining spectrograms. Four distinct sounds were detected that are believed to be of biological origin: (1) a two-part low-frequency moan at roughly 18 Hz lasting 25 s which has previously been attributed to blue whales (Balaenoptera musculus); (2) series of short pulses approximately 18 s apart centered at 22 Hz, which are likely produced by fin whales (B. physalus); (3) series of short, pulsive sounds at 30 Hz and above and approximately 1 s apart that resemble sounds attributed to minke whales (B. acutorostrata); and (4) downswept, pulsive sounds above 30 Hz that are likely from baleen whales. Vocalizations were detected most often in the winter, and blue- and fin whale sounds were detected most often on the northern hydrophones. Sounds from seismic airguns were recorded frequently, particularly during summer, from locations over 3000 km from this array. Whales were detected by these hydrophones despite its location in a very remote part of the Atlantic Ocean that has traditionally been difficult to survey.

The temporal characteristics of humpback whale songs

NASA Astrophysics Data System (ADS)

Au, Whitlow W. L.; Lammers, Marc O.; Stimpert, Alison; Schotten, Michiel

2005-09-01

Songs sung by male humpback whales consist of distinct, pulsed sounds that are designated as units. Units are produced in some sequence to form a phrase, a repeated set of phrases forms a theme, and repeated themes form a song. A song can last from minutes to hours. The songs of eight humpback whales were recorded with a vertical array of five hydrophones spaced 7 m apart with the array located within 100 m of the whales. At least seven distinct units were identified aurally from this data set obtained during the 2002 winter humpback whale session in Hawaii. Four distinct recurring themes were found in the songs, and for each whale at least two themes were recorded. The average duration of each unit sampled and the silent interval following the unit were determined in order to describe the temporal characteristics of the songs. From the data the temporal consistency and cadence control of unit production by each humpback whale and between whales were determined. Understanding the temporal and spectral characteristics of units within songs and how these units vary between whales could ultimately help in the design of computer algorithms to automatically identify individual whales.

Adaptive spatial combining for passive time-reversed communications.

PubMed

Gomes, João; Silva, António; Jesus, Sérgio

2008-08-01

Passive time reversal has aroused considerable interest in underwater communications as a computationally inexpensive means of mitigating the intersymbol interference introduced by the channel using a receiver array. In this paper the basic technique is extended by adaptively weighting sensor contributions to partially compensate for degraded focusing due to mismatch between the assumed and actual medium impulse responses. Two algorithms are proposed, one of which restores constructive interference between sensors, and the other one minimizes the output residual as in widely used equalization schemes. These are compared with plain time reversal and variants that employ postequalization and channel tracking. They are shown to improve the residual error and temporal stability of basic time reversal with very little added complexity. Results are presented for data collected in a passive time-reversal experiment that was conducted during the MREA'04 sea trial. In that experiment a single acoustic projector generated a 24-PSK (phase-shift keyed) stream at 200400 baud, modulated at 3.6 kHz, and received at a range of about 2 km on a sparse vertical array with eight hydrophones. The data were found to exhibit significant Doppler scaling, and a resampling-based preprocessing method is also proposed here to compensate for that scaling.

The Quasi-Eulerian Hydrophone: A New Approach for Ocean Acoustics

NASA Astrophysics Data System (ADS)

Matsumoto, H.; Dziak, R. P.; Fowler, M. J.; Hammond, S. R.; Meinig, C.

2005-12-01

For the last 10 years Oregon State University and NOAA/Pacific Marine Environmental Laboratory have successfully operated and maintained autonomous hydrophone arrays to monitor low frequency acoustic energy of earthquakes and marine mammal calls in remote ocean areas where no historical record existed. These hydrophones are moored at mid-water depth and require a routine servicing cruise to retrieve the stored data. The system is robust, but it is not real-time and it takes up to a year before acoustic events can be identified from the raw acoustic data. As a result, we frequently miss opportunities to observe ocean acoustic events as they occur. A new type of autonomous hydrophone called a Quasi-Eulerian hydrophone (QUEphone) is under development at OSU/PMEL. This instrument allows near-real-time monitoring of a selected study area. It is a tether-free float with a built-in hydrophone monitoring system and a buoyancy controller. It is capable of repeat ascent/descent cycles in up to 2000 m of water. In contrast to the conventional Lagrangean float, the QUEphone float stays in the same area by maintaining negative buoyancy and remaining on the seafloor for most of its life span. While on the seafloor the QUEphone runs an intelligent event detection algorithm, and upon detection of a significant number of events will surface to transmit a small data file to shore. We have conducted brief test deployments of the QUEphone in both a fresh-water lake and marine waters off Oregon coast, and the results of these tests will be discussed and compared with other hydrophone data. Once fully developed the QUEphone is expected to provide near real-time analysis capability of earthquakes that affect seafloor hydrothermal vents and their associated ecosystems. Such fast reaction will allow for a rapid response to seismic events, enabling researchers to examine how changes in hydrothermal activity affect deep-ocean vent ecosystems.

Fiber Optic Towed Arrays

DTIC Science & Technology

2007-01-01

Fabry - Perot inter- ferometers. The hydrophones are passively multiplexed both in time and in wavelength to allow hundreds of channels to be carried...sensing fiber wrapped on a solid plastic mandrel. For this demon- stration, the laser and the demodulation electronics were collocated with the fiber

Seismicity And Accretion Processes Along The Mid-Atlantic Ridge south of the Azores using data from the MARCHE Autonomous Hydrophone Array

NASA Astrophysics Data System (ADS)

Perrot, Julie; Cevatoglu, Melis; Cannat, Mathilde; Escartin, Javier; Maia, Marcia; Tisseau, Chantal; Dziak, Robert; Goslin, Jean

2013-04-01

The seismicity of the South Atlantic Ocean has been recorded by the MARCHE network of 4 autonomous underwater hydrophones (AUH) moored within the SOFAR channel on the flanks of the Mid-Atlantic Ridge (MAR). The instruments were deployed south of the Azores Plateau between 32° and 39°N from July 2005 to August 2008. The low attenuation properties of the SOFAR channel for earthquake T-wave propagation result in a detection threshold reduction from a magnitude completeness level (Mc) of ~4.3 for MAR events recorded by the land-based seismic networks to Mc=2.1 using this hydrophone array. A spatio-temporal analysis has been performed among the 5600 events recorded inside the MARCHE array. Most events are distributed along the ridge between lat. 39°N on the Azores Platform and the Rainbow (36°N) segment. In the hydrophone catalogue, acoustic magnitude (Source Level, SL) is used as a measure of earthquake size. The source level above which the data set is complete is SLc=205 dB. We look for seismic swarms using the cluster software of the SEISAN package. The criterion used are a minimum SL of 210 to detect a possible mainshock, and a radius of 30 km and a time window of 40 days after this mainshock (Cevatoglu, 2010, Goslin et al., 2012). 7 swarms with more than 15 events are identified using this approach between 32°et 39°N of latitude. The maximum number of earthquake in a swarm is 57 events. This result differs from the study of Simao et al. (2010) as we processed a further year of data and selected sequences with fewer events. Looking at the distribution of the SL as a function of time after the mainshock, we discuss the possible mechanism of these earthquakes : tectonic events with a "mainshock-aftershock" distribution fitting a modified Omori law or volcanic events showing more constant SL values. We also present the geophysical setting of these 7 swarms, using gravity, bathymetry, and available local geological data. This study illustrates the potential of hydrophone data to monitor segment-scale ridges processes in the vicinity of the Lucky Strike seafloor observatory (lat. 37°20'N), the Azores node of the EMSO (European Multidiciplinary Subsea Observatory) system. - M. Cevatoglu, Analyse de la sismicité médio-atlantique et son apport dans la compréhension des processus d'accrétion : Expérience MARCHE3, master's thesis , IUEM, University of Brest, 52 p., june 2010. - J. Goslin, J. Perrot, J.-Y. Royer, C. Martin, N. Lourenco, J. Luis, R. P. Dziak, H. Matsumoto, J. Haxel, M. J. Fowler, C. G. Fox, A. T.-K. Lau and S.Bazin. Spatiotemporal distribution of the seismicity along the Mid-Atlantic Ridge north of the Azores from hydroacoustic data: Insights into seismogenic processes in a ridge-hot spot context, 2012, Geochem. Geophys. Geosyst., 13, Q02010, doi:10.1029/2011GC003828. - N. Simao and J. Escartin and J. Goslin and J. Haxel and M. Cannat and R. Dziak, Regional Seismicity of the Mid-Atlantic Ridge: Observations from autonomous hydrophone arrays, 2010, Geophys. J. Int., 183, 1559-1578.

APL - North Pacific Acoustic Laboratory

DTIC Science & Technology

2015-03-04

PhilSea10 cruise were spent in a series of upgrades and associated tests of the TCTD system. Electronic upgrades in conjunction with the manufacturers, ADM...amplitude at positions sufficiently removed from caustics . Mr. White computed eigenrays to all tracked upper array hydrophone positions relative to each

Baird's beaked whale echolocation signals.

PubMed

Baumann-Pickering, Simone; Yack, Tina M; Barlow, Jay; Wiggins, Sean M; Hildebrand, John A

2013-06-01

Echolocation signals from Baird's beaked whales were recorded during visual and acoustic shipboard surveys of cetaceans in the California Current ecosystem and with autonomous, long-term recorders in the Southern California Bight. The preliminary measurement of the visually validated Baird's beaked whale echolocation signals from towed array data were used as a basis for identifying Baird's signals in the autonomous recorder data. Two distinct signal types were found, one being a beaked whale-like frequency modulated (FM) pulse, the other being a dolphin-like broadband click. The median FM inter-pulse interval was 230 ms. Both signal types showed a consistent multi-peak structure in their spectra with peaks at ~9, 16, 25, and 40 kHz. Depending on signal type, as well as recording aspect and distance to the hydrophone, these peaks varied in relative amplitude. The description of Baird's echolocation signals will allow for studies of their distribution and abundance using towed array data without associated visual sightings and from autonomous seafloor hydrophones.

Characterization of a Multi-element Clinical HIFU System Using Acoustic Holography and Nonlinear Modeling

PubMed Central

Kreider, Wayne; Yuldashev, Petr V.; Sapozhnikov, Oleg A.; Farr, Navid; Partanen, Ari; Bailey, Michael R.; Khokhlova, Vera A.

2014-01-01

High-intensity focused ultrasound (HIFU) is a treatment modality that relies on the delivery of acoustic energy to remote tissue sites to induce thermal and/or mechanical tissue ablation. To ensure the safety and efficacy of this medical technology, standard approaches are needed for accurately characterizing the acoustic pressures generated by clinical ultrasound sources under operating conditions. Characterization of HIFU fields is complicated by nonlinear wave propagation and the complexity of phased-array transducers. Previous work has described aspects of an approach that combines measurements and modeling, and here we demonstrate this approach for a clinical phased array transducer. First, low-amplitude hydrophone measurements were performed in water over a scan plane between the array and the focus. Second, these measurements were used to holographically reconstruct the surface vibrations of the transducer and to set a boundary condition for a 3-D acoustic propagation model. Finally, nonlinear simulations of the acoustic field were carried out over a range of source power levels. Simulation results were compared to pressure waveforms measured directly by hydrophone at both low and high power levels, demonstrating that details of the acoustic field including shock formation are quantitatively predicted. PMID:25004539

Characteristics and Use of a Parametric End-Fired Array for Acoustics in Air

DTIC Science & Technology

2007-03-01

as a sonar application for underwater use. The vast majority of the research for parametric arrays was devoted to underwater applications until the...and also for the calibration of hydrophones and receivers for wide band sonar . All of the researchers mentioned above mainly focused their efforts on...features, which include very high directivity at low frequencies without unwanted side lobes. They are generally used as a wide band sonar system

Passive Localization of Multiple Sources Using Widely-Spaced Arrays with Application to Marine Mammals

DTIC Science & Technology

2007-09-30

the behavioral ecology of marine mammals by simultaneously tracking multiple vocalizing individuals in space and time. OBJECTIVES The ...goal is to contribute to the behavioral ecology of marine mammals by simultaneously tracking multiple vocalizing individuals in space and time. 15...OA Graduate Traineeship for E-M Nosal) LONG-TERM GOALS The goal of our research is to develop systems that use a widely spaced hydrophone array

Near-bottom hydrophone measurements of ambient noise and sperm whale vocalizations in the northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Newcomb, Joal; Fisher, Robert; Field, Robert; Turgut, Altan; Ioup, George; Ioup, Juliette; Rayborn, Grayson; Kuczaj, Stan; Caruthers, Jerald; Goodman, Ralph; Sidorovskaia, Natalia

2002-05-01

Three bottom-moored hydrophones, 50 m above the bottom, were placed on a downslope line, ending at the largest concentration of sperm whale sightings in the northern Gulf of Mexico, in 600 m, 800 m, and 1000 m water depths. These depths were chosen after upslope propagation modeling, using historical databases, showed transmission losses greater than 110 dB at hydrophones near the bottom in water shallower than 600 m for a 500 m deep source at the 1000 m contour. These autonomously recording hydrophones were environmental acoustic recording system (EARS) buoys obtained from the Naval Oceanographic Office. They were capable of recording signals up to 5500 Hz continuously for 36 days and were deployed from July 17 through August 21. During this period a major marine mammal exercise was being conducted at the surface by the Minerals Management Service and the National Marine Fisheries Service, with other government and university scientists, in which temporary acoustic recording devices were attached to the whales and the whales were monitored by a surface towed array. Our near-bottom measurements of ambient noise and sperm whale vocalizations are discussed and compared to those surface and on-whale measurements. [Research supported by ONR.

Temporal-Spectral Characterization and Classification of Marine Mammal Vocalizations and Diesel-Electric Ships Radiated Sound over Continental Shelf Scale Regions with Coherent Hydrophone Array Measurements

NASA Astrophysics Data System (ADS)

Huang, Wei

The passive ocean acoustic waveguide remote sensing (POAWRS) technology is capable of monitoring a large variety of underwater sound sources over instantaneous wide areas spanning continental-shelf scale regions. POAWRS uses a large-aperture densely-sampled coherent hydrophone array to significantly enhance the signal-to-noise ratio via beamforming, enabling detection of sound sources roughly two-orders of magnitude more distant in range than that possible with a single hydrophone. The sound sources detected by POAWRS include ocean biology, geophysical processes, and man-made activities. POAWRS provides detection, bearing-time estimation, localization, and classification of underwater sound sources. The volume of underwater sounds detected by POAWRS is immense, typically exceeding a million unique signal detections per day, in the 10-4000 Hz frequency range, making it a tremendously challenging task to distinguish and categorize the various sound sources present in a given region. Here we develop various approaches for characterizing and clustering the signal detections for various subsets of data acquired using the POAWRS technology. The approaches include pitch tracking of the dominant signal detections, time-frequency feature extraction, clustering and categorization methods. These approaches are essential for automatic processing and enhancing the efficiency and accuracy of POAWRS data analysis. The results of the signal detection, clustering and classification analysis are required for further POAWRS processing, including localization and tracking of a large number of oceanic sound sources. Here the POAWRS detection, localization and clustering approaches are applied to analyze and elucidate the vocalization behavior of humpback, sperm and fin whales in the New England continental shelf and slope, including the Gulf of Maine from data acquired using coherent hydrophone arrays. The POAWRS technology can also be applied for monitoring ocean vehicles. Here the approach is calibrated by application to known ships present in the Gulf of Maine and in the Norwegian Sea from their underwater sounds received using a coherent hydrophone array. The vocalization behavior of humpback whales was monitored over vast areas of the Gulf of Maine using the POAWRS technique over multiple diel cycles in Fall 2006. The humpback vocalizations, received at a rate of roughly 1800+/-1100 calls per day, comprised of both song and non-song. The song vocalizations, composed of highly structured and repeatable set of phrases, are characterized by inter-pulse intervals of 3.5 +/- 1.8 s. Songs were detected throughout the diel cycle, occuring roughly 40% during the day and 60% during the night. The humpback non-song vocalizations, dominated by shorter duration (≤3 s) downsweep and bow-shaped moans, as well as a small fraction of longer duration (˜5 s) cries, have significantly larger mean and more variable inter-pulse intervals of 14.2 +/- 11 s. The non-song vocalizations were detected at night with negligible detections during the day, implying they probably function as nighttime communication signals. The humpback song and non-song vocalizations are separately localized using the moving array triangulation and array invariant techniques. The humpback song and non-song moan calls are both consistently localized to a dense area on northeastern Georges Bank and a less dense region extended from Franklin Basin to the Great South Channel. Humpback cries occur exclusively on northeastern Georges Bank and during nights with coincident dense Atlantic herring shoaling populations, implying the cries are feeding-related. Sperm whales in the New England continental shelf and slope were passively localized and classified from their vocalizations received using a single low-frequency (<2500 Hz) densely-sampled horizontal coherent hydrophone array deployed in Spring 2013 in Gulf of Maine. Whale bearings were estimated using time-domain beamforming that provided high coherent array gain in sperm whale click signal-to-noise ratio. Whale ranges from the receiver array center were estimated using the moving array triangulation technique from a sequence of whale bearing measurements. Multiple concurrently vocalizing sperm whales, in the far-field of the horizontal receiver array, were distinguished and classified based on their horizontal spatial locations and the inter-pulse intervals of their vocalized click signals. We provide detailed analysis of over 15,000 fin whale 20 Hz vocalizations received on Oct 1-3, 2006 in the Gulf of Maine. These vocalizations are separated into 16 clusters following the clustering approaches. Seven of these types are prominent, each acounting for between 8% to 16% and together comprise roughly 85% of all the analyzed vocalizations. The 7 prominent clusters are each more abundant during nighttime hours by a factor of roughly 2.5 times than that of the daytime. The diel-spatial correlation of the 7 prominent clusters to the simultaneously observed densities of their fish prey, the Atlantic herring in the Gulf of Maine, is provided which implies that the factor of roughly 2.5 increase in call rate during night-time hours can be attributed to increased fish-feeding activities. (Abstract shortened by ProQuest.).

Environmentally adaptive processing for shallow ocean applications: A sequential Bayesian approach.

PubMed

Candy, J V

2015-09-01

The shallow ocean is a changing environment primarily due to temperature variations in its upper layers directly affecting sound propagation throughout. The need to develop processors capable of tracking these changes implies a stochastic as well as an environmentally adaptive design. Bayesian techniques have evolved to enable a class of processors capable of performing in such an uncertain, nonstationary (varying statistics), non-Gaussian, variable shallow ocean environment. A solution to this problem is addressed by developing a sequential Bayesian processor capable of providing a joint solution to the modal function tracking and environmental adaptivity problem. Here, the focus is on the development of both a particle filter and an unscented Kalman filter capable of providing reasonable performance for this problem. These processors are applied to hydrophone measurements obtained from a vertical array. The adaptivity problem is attacked by allowing the modal coefficients and/or wavenumbers to be jointly estimated from the noisy measurement data along with tracking of the modal functions while simultaneously enhancing the noisy pressure-field measurements.

Seafloor seismicity, Antarctic ice-sounds, cetacean vocalizations and long-term ambient sound in the Indian Ocean basin

NASA Astrophysics Data System (ADS)

Royer, J.-Y.; Chateau, R.; Dziak, R. P.; Bohnenstiehl, D. R.

2015-08-01

This paper presents the results from the Deflo-hydroacoustic experiment in the Southern Indian Ocean using three autonomous underwater hydrophones, complemented by two permanent hydroacoustic stations. The array monitored for 14 months, from November 2006 to December 2007, a 3000 × 3000 km wide area, encompassing large segments of the three Indian spreading ridges that meet at the Indian Triple Junction. A catalogue of 11 105 acoustic events is derived from the recorded data, of which 55 per cent are located from three hydrophones, 38 per cent from 4, 6 per cent from five and less than 1 per cent by six hydrophones. From a comparison with land-based seismic catalogues, the smallest detected earthquakes are mb 2.6 in size, the range of recorded magnitudes is about twice that of land-based networks and the number of detected events is 5-16 times larger. Seismicity patterns vary between the three spreading ridges, with activity mainly focused on transform faults along the fast spreading Southeast Indian Ridge and more evenly distributed along spreading segments and transforms on the slow spreading Central and ultra-slow spreading Southwest Indian ridges; the Central Indian Ridge is the most active of the three with an average of 1.9 events/100 km/month. Along the Sunda Trench, acoustic events mostly radiate from the inner wall of the trench and show a 200-km-long seismic gap between 2 °S and the Equator. The array also detected more than 3600 cryogenic events, with different seasonal trends observed for events from the Antarctic margin, compared to those from drifting icebergs at lower (up to 50°S) latitudes. Vocalizations of five species and subspecies of large baleen whales were also observed and exhibit clear seasonal variability. On the three autonomous hydrophones, whale vocalizations dominate sound levels in the 20-30 and 100 Hz frequency bands, whereas earthquakes and ice tremor are a dominant source of ambient sound at frequencies <20 Hz.

The North Pacific Acoustic Laboratory deep-water acoustic propagation experiments in the Philippine Sea.

PubMed

Worcester, Peter F; Dzieciuch, Matthew A; Mercer, James A; Andrew, Rex K; Dushaw, Brian D; Baggeroer, Arthur B; Heaney, Kevin D; D'Spain, Gerald L; Colosi, John A; Stephen, Ralph A; Kemp, John N; Howe, Bruce M; Van Uffelen, Lora J; Wage, Kathleen E

2013-10-01

A series of experiments conducted in the Philippine Sea during 2009-2011 investigated deep-water acoustic propagation and ambient noise in this oceanographically and geologically complex region: (i) the 2009 North Pacific Acoustic Laboratory (NPAL) Pilot Study/Engineering Test, (ii) the 2010-2011 NPAL Philippine Sea Experiment, and (iii) the Ocean Bottom Seismometer Augmentation of the 2010-2011 NPAL Philippine Sea Experiment. The experimental goals included (a) understanding the impacts of fronts, eddies, and internal tides on acoustic propagation, (b) determining whether acoustic methods, together with other measurements and ocean modeling, can yield estimates of the time-evolving ocean state useful for making improved acoustic predictions, (c) improving our understanding of the physics of scattering by internal waves and spice, (d) characterizing the depth dependence and temporal variability of ambient noise, and (e) understanding the relationship between the acoustic field in the water column and the seismic field in the seafloor. In these experiments, moored and ship-suspended low-frequency acoustic sources transmitted to a newly developed distributed vertical line array receiver capable of spanning the water column in the deep ocean. The acoustic transmissions and ambient noise were also recorded by a towed hydrophone array, by acoustic Seagliders, and by ocean bottom seismometers.

Transcranial ultrasonic therapy based on time reversal of acoustically induced cavitation bubble signature

PubMed Central

Gâteau, Jérôme; Marsac, Laurent; Pernot, Mathieu; Aubry, Jean-Francois; Tanter, Mickaël; Fink, Mathias

2010-01-01

Brain treatment through the skull with High Intensity Focused Ultrasound (HIFU) can be achieved with multichannel arrays and adaptive focusing techniques such as time-reversal. This method requires a reference signal to be either emitted by a real source embedded in brain tissues or computed from a virtual source, using the acoustic properties of the skull derived from CT images. This non-invasive computational method focuses with precision, but suffers from modeling and repositioning errors that reduce the accessible acoustic pressure at the focus in comparison with fully experimental time-reversal using an implanted hydrophone. In this paper, this simulation-based targeting has been used experimentally as a first step for focusing through an ex vivo human skull at a single location. It has enabled the creation of a cavitation bubble at focus that spontaneously emitted an ultrasonic wave received by the array. This active source signal has allowed 97%±1.1% of the reference pressure (hydrophone-based) to be restored at the geometrical focus. To target points around the focus with an optimal pressure level, conventional electronic steering from the initial focus has been combined with bubble generation. Thanks to step by step bubble generation, the electronic steering capabilities of the array through the skull were improved. PMID:19770084

15 CFR Supplement No. 7 to Part 774 - Very Sensitive List

Code of Federal Regulations, 2014 CFR

2014-01-01

... designed” for real time application with towed acoustic hydrophone arrays, having “user accessible....2.f—Processing equipment, “specially designed” for real time application with bottom or bay cable...” “specially designed” for a defense article not on the USML or a commodity controlled by a “600 series” ECCN...

Catheter Hydrophone Aberration Correction for Transcranial Histotripsy Treatment of Intracerebral Hemorrhage: Proof-of-Concept.

PubMed

Gerhardson, Tyler; Sukovich, Jonathan R; Pandey, Aditya S; Hall, Timothy L; Cain, Charles A; Xu, Zhen

2017-11-01

Histotripsy is a minimally invasive ultrasound therapy that has shown rapid liquefaction of blood clots through human skullcaps in an in vitro intracerebral hemorrhage model. However, the efficiency of these treatments can be compromised if the skull-induced aberrations are uncorrected. We have developed a catheter hydrophone which can perform aberration correction (AC) and drain the liquefied clot following histotripsy treatment. Histotripsy pulses were delivered through an excised human skullcap using a 256-element, 500-kHz hemisphere array transducer with a 15-cm focal distance. A custom hydrophone was fabricated using a mm PZT-5h crystal interfaced to a coaxial cable and integrated into a drainage catheter. An AC algorithm was developed to correct the aberrations introduced between histotripsy pulses from each array element. An increase in focal pressure of up to 60% was achieved at the geometric focus and 27%-62% across a range of electronic steering locations. The sagittal and axial -6-dB beam widths decreased from 4.6 to 2.2 mm in the sagittal direction and 8 to 4.4 mm in the axial direction, compared to 1.5 and 3 mm in the absence of aberration. After performing AC, lesions with diameters ranging from 0.24 to 1.35 mm were generated using electronic steering over a mm grid in a tissue-mimicking phantom. An average volume of 4.07 ± 0.91 mL was liquefied and drained after using electronic steering to treat a 4.2-mL spherical volume in in vitro bovine clots through the skullcap.

A small towed beamforming array to identify vocalizing resident killer whales ( Orcinus orca) concurrent with focal behavioral observations

NASA Astrophysics Data System (ADS)

Miller, Patrick J.; Tyack, Peter L.

Investigations of communication systems benefit from concurrent observation of vocal and visible behaviors of individual animals. A device has been developed to identify individual vocalizing resident killer whales ( Orcinus orca) during focal behavioral observations. The device consists of a 2-m, 15-element hydrophone array, which is easily towed behind a small vessel, on-board multi-channel recorders, and real-time signal processing equipment. Acoustic data from the hydrophones are digitized and processed using broadband frequency-domain beamforming to yield frequency-azimuth (FRAZ) and "directo-gram" displays of arriving sounds. Based upon statistical analysis of independent portions of typical killer whale calls, the precision of the angle-of-arrival estimate ranges from ±0° to ±2.5° with a mean precision of ±1.5°. Echolocation clicks also are resolved precisely with a typical -6 dB mainlobe width of ±2.0°. Careful positioning of the array relative to the animals minimizes the effects of depth ambiguities and allows identification of individual sources in many circumstances. Several strategies for identifying vocalizing individuals are discussed and an example of a successful identification is described. Use of the array with resident killer whales did not interfere with vessel maneuverability, animal tracking, or behavioral sampling of focal individuals. This localization technique has promise for advancing the abilities of researchers to conduct unbiased behavioral and acoustic sampling of individual free-ranging cetaceans.

Porosity, Fracturing and Alteration of Young Oceanic Crust: New Seismic Analyses at Borehole 504B

NASA Astrophysics Data System (ADS)

Gregory, E. P. M.; Hobbs, R. W.; Peirce, C.; Wilson, D. J.

2017-12-01

DSDP/ODP borehole 504B, drilled 2111 m into 6.9 Ma oceanic crust, provides in-situ core and logging measurements of the lithology, fracturing and porosity of crust originally formed at the Costa Rica Rift and its subsequent alteration by hydrothermal fluids. A recent active seismic survey over the borehole and surrounding area reveals wider spatial variations in velocity that can be related to this porosity and fracturing. Over 10,000 airgun shots were fired in a 30 x 30 km grid over the borehole region, using both high-frequency and low-frequency airgun arrays. The shots were recorded on a 4.5 km-long streamer and 24 ocean-bottom seismographs, each equipped with a three-component geophone and an hydrophone. A vertical hydrophone array recorded the downgoing source wavelet, and underway gravity, magnetic field and multibeam bathymetry data were also recorded. This combined dataset enables the most comprehensive geophysical analysis of this area of crust to date, while the ground-truthing provided by 504B enables us to address the questions of what do the seismic oceanic crustal layers represent and what controls their characteristics as the crust ages? Wide-angle seismic modelling with a Monte Carlo based uncertainty analysis reveals new 2D and 3D Vp and Vs models of the area, which show relatively homogeneous crust around borehole 504B, and place the seismic layer 2B/2C, and seismic layer 2/3 boundaries coincident with fracturing and alteration fronts rather than the lithological boundaries between lavas and dykes, and dykes and gabbros, respectively. Analysis of Poisson's ratio, seismic anisotropy and particle motions reveal patterns in fracturing and porosity across the survey area, and locate possible fossilised hydrothermal circulation cells. These cells appear to have influenced the porosity of the crust through alteration and mineralisation processes, with faults inherited from initial crustal accretion influencing basement topographic highs and providing conduits for mineralising fluids to flow. This research is part of a major, interdisciplinary NERC-funded research collaboration entitled: Oceanographic and Seismic Characterisation of heat dissipation and alteration by hydrothermal fluids at an Axial Ridge (OSCAR).

Pico-strain multiplexed fiber optic sensor array operating down to infra-sonic frequencies.

PubMed

Littler, Ian C M; Gray, Malcolm B; Chow, Jong H; Shaddock, Daniel A; McClelland, David E

2009-06-22

An integrated sensor system is presented which displays passive long range operation to 100 km at pico-strain (pepsilon) sensitivity to low frequencies (4 Hz) in wavelength division multiplexed operation with negligible cross-talk (better than -75 dB). This has been achieved by pre-stabilizing and multiplexing all interrogation lasers for the sensor array to a single optical frequency reference. This single frequency reference allows each laser to be locked to an arbitrary wavelength and independently tuned, while maintaining suppression of laser frequency noise. With appropriate packaging, such a multiplexed strain sensing system can form the core of a low frequency accelerometer or hydrophone array.

50 CFR 218.34 - Requirements for monitoring and reporting.

Code of Federal Regulations, 2013 CFR

2013-10-01

... beyond the border of the exclusion zone (i.e., the circumference of the area from the border of the... (hydrophone or towed array) could be used to determine if marine mammals are in the area before and/or after a... participation shall take into account safety, logistics, and operational concerns. (iv) MMOs shall observe from...

50 CFR 218.34 - Requirements for monitoring and reporting.

Code of Federal Regulations, 2012 CFR

2012-10-01

... beyond the border of the exclusion zone (i.e., the circumference of the area from the border of the... (hydrophone or towed array) could be used to determine if marine mammals are in the area before and/or after a... participation shall take into account safety, logistics, and operational concerns. (iv) MMOs shall observe from...

50 CFR 218.34 - Requirements for monitoring and reporting.

Code of Federal Regulations, 2011 CFR

2011-10-01

... beyond the border of the exclusion zone (i.e., the circumference of the area from the border of the... (hydrophone or towed array) could be used to determine if marine mammals are in the area before and/or after a... participation shall take into account safety, logistics, and operational concerns. (iv) MMOs shall observe from...

Vocalizations produced by humpback whale (Megaptera novaeangliae) calves recorded in Hawaii.

PubMed

Zoidis, Ann M; Smultea, Mari A; Frankel, Adam S; Hopkins, Julia L; Day, Andy; McFarland, A Sasha; Whitt, Amy D; Fertl, Dagmar

2008-03-01

Although humpback whale (Megaptera novaeangliae) calves are reported to vocalize, this has not been measurably verified. During March 2006, an underwater video camera and two-element hydrophone array were used to record nonsong vocalizations from a mother-calf escort off Hawaii. Acoustic data were analyzed; measured time delays between hydrophones provided bearings to 21 distinct vocalizations produced by the male calf. Signals were pulsed (71%), frequency modulated (19%), or amplitude modulated (10%). They were of simple structure, low frequency (mean=220 Hz), brief duration (mean=170 ms), and relatively narrow bandwidth (mean=2 kHz). The calf produced three series of "grunts" when approaching the diver. During winters of the years 2001-2005 in Hawaii, nonsong vocalizations were recorded in 109 (65%) of 169 groups with a calf using an underwater video and single (omnidirectional) hydrophone. Nonsong vocalizations were most common (34 of 39) in lone mother-calf pairs. A subsample from this dataset of 60 signals assessed to be vocalizations provided strong evidence that 10 male and 18 female calves vocalized based on statistical similarity to the 21 verified calf signals, proximity to an isolated calf (27 of 28 calves), strong signal-to-noise ratio, and/or bubble emissions coincident to sound.

Acoustic wave propagation and intensity fluctuations in shallow water 2006 experiment

NASA Astrophysics Data System (ADS)

Luo, Jing

Fluctuations of low frequency sound propagation in the presence of nonlinear internal waves during the Shallow Water 2006 experiment are analyzed. Acoustic waves and environmental data including on-board ship radar images were collected simultaneously before, during, and after a strong internal solitary wave packet passed through a source-receiver acoustic track. Analysis of the acoustic wave signals shows temporal intensity fluctuations. These fluctuations are affected by the passing internal wave and agrees well with the theory of the horizontal refraction of acoustic wave propagation in shallow water. The intensity focusing and defocusing that occurs in a fixed source-receiver configuration while internal wave packet approaches and passes the acoustic track is addressed in this thesis. Acoustic ray-mode theory is used to explain the modal evolution of broadband acoustic waves propagating in a shallow water waveguide in the presence of internal waves. Acoustic modal behavior is obtained from the data through modal decomposition algorithms applied to data collected by a vertical line array of hydrophones. Strong interference patterns are observed in the acoustic data, whose main cause is identified as the horizontal refraction referred to as the horizontal Lloyd mirror effect. To analyze this interference pattern, combined Parabolic Equation model and Vertical-mode horizontal-ray model are utilized. A semi-analytic formula for estimating the horizontal Lloyd mirror effect is developed.

Vertical Structure of Shadow Zone Arrivals: Comparison of Parabolic Equation Simulations and Acoustic Data

DTIC Science & Technology

2011-01-01

676 677 Travel Time (sec) 678 45 95 £ 85 ? 75 £ 65 3 55 *§ 85 75 65 55 85 75 65 55 45’— 673 dB re 1 uPa A :,. 1.. i b , u . k , AL...1. u * .1 t., J. .1. 674 675 676 677 Travel Time (sec) 678 673 674 675 676 677 Travel Time (sec) 678 Range...hydrophone data at the 3892 -meter depth (Figure 2(d)). A more quantitative measure of the vertical extension of the cusp is the energy profile of the cusp

Analysis of the Spatial and Temporal Distribution of the Seismicity of the Mid-Atlantic Ridge Using the SIRENA and the South Azores Autonomous Hydrophone Arrays

NASA Astrophysics Data System (ADS)

Simão, N.; Goslin, J.; Perrot, J.; Haxel, J.; Dziak, R.

2006-12-01

Acoustic data recorded by two Autonomous Hydrophone Arrays (AHA) were jointly processed in Brest (IUEM) and Newport (PMEL-VENTS) to monitor the seismicity of the Mid-Atlantic Ridge (MAR) over a ten month period, at a wide range of spatial scales. Over the deployment period, nearly 6000 T-phase generating earthquakes were localized using a semi-automatic algorithm. Our analysis of the temporal and spatial distribution of these events combined with their acoustic energy source levels provides important insights for the generation mechanisms and characteristic behavior of MAR seismicity. It shows for the AHA catalog a variation of the cumulative number of events with time almost linear. Taking in account the area inside the arrays, the section of the ridge north of the Azores is more seismically active than the southern part of it and the seismic activity occurs in large localized clusters. Our (AHA) catalog of acoustic events was used to compare locations, focal mechanisms and magnitude observations with correlated data from land-based stations of the NEIC global seismic network to establish completeness levels from both within and outside of the hydrophone array. The (AHA) catalog has a Source Level of Completeness (SLc) of 204dB, and a b-value of 0.0605. The NEIC catalog for this region during this period has a Magnitude of Completeness (Mc) of 4.6 and a b-value of 1.01. Regressing the AHA values onto the NEIC derived Mc/b-value relationship suggests a Mc of 3.2 for the AHA catalog. By restricting the events to the region inside the AHA, the NEIC catalog has an Mc of 4.7 with a b-value of 1.09, while the AHA catalog has a SLc of 205dB with a b-value of 0.0753. Comparing the b-values of the NEIC catalog with the AHA catalog, we obtain an improved Mc of 3.0 for the AHA inside the array. A time- and space-dependent Single-Link-Cluster algorithm was applied to the events localized inside the AHA. This allowed us to gather cluster sequences of earthquakes for higher temporal and spatial resolution Mc and b-value computations. The cumulative number of events and time series for several of these clusters were used in a Modified Omori Law simulation. Some of the identified sequences correlated well with a main-shock /aftershock mechanism associated with the older and colder crustal characteristics related to a tectonically dominated MAR regime.

Discriminating different type waves from pressure and ground motion observation in the seafloor by DONET cabled observation network.

NASA Astrophysics Data System (ADS)

Araki, E.; Kawaguchi, K.; Kaneda, Y.

2011-12-01

We developed and deployed seafloor cabled observatory called "Dense Ocean-floor Network for Earthquake and Tsunamis (DONET)" in the Nankai Trough, south of Japan. The main purpose of the DONET network is to observe large earthquake such as Tonankai earthquake in the deployed seafloor and associate Tsunamis in real-time to help disaster mitigation, and as well to monitor inter-seismic crustal activities such as micro earthquakes, very low frequency earthquakes, and slower crustal deformation. In each DONET seafloor observatory, high-sensitive broadband set of instruments for seismic and seafloor pressure monitoring, consisted from Guralp CMG3T broadband seismometer, Metrozet TSA100S accelerometer, Paroscientific 8B7000-2 pressure gauge, a deep-sea differential pressure gauge, a hydrophone, and a seawater thermometer, are installed. The density of seafloor observatories are 20 observatories distributed in 15-30 km interval which is optimized for monitoring of events in the plate boundary beneath the network. DONET may be regarded as a large-scale, high sensitive high density seismic array for monitoring teleseismic events in the Philippine Sea and the Pacific Ocean. The DONET seafloor observatories are situated in wide range of seafloor depth between 1800m and 4500m, from the seafloor basin about 50 km off Japanese Island through the slope of accerecionary prism to the deep trench axis 150 km off the coast, that may also regarded as a vertical array in the 4.5km thick ocean. This variation of depths helps identify T-phases from the array record. In data analysis, it is necessary to identify propagation mode of each observed wave which may often be mixed together. In our design of DONET observation system, we took care to help identification of seismic phase by obtaining both ground motion and seafloor pressure in the same location. This is simply achieved by combining seafloor pressure gauges and seismometer in a single observatory package, but care was taken to observe both in the similar level of sensitivity and dynamic range in wide frequencies from near DC to over 100 Hz. In the case of DONET, the broadband seismometer and the differential pressure gauge have similar level of sensitivity in 0.005 - 10 Hz, and similarly the accelerometer and the hydrophone cover between 1-100Hz, in total covering most frequencies of our interest, 0.005 Hz to 100 Hz. With both ground motion and seafloor pressure measurement, we may distinguish types of waves relatively easily, and it is also possible to filter particular types of waves from the array dataset to help our data analysis. For example, it has been commonly practiced to distinguish up-going and down-going seismic phases from pressure and ground motion, but this is relatively difficult only with sparse seismometer array. This technique may also be applied to correct teleseismic record with sea surface reflection in receiver function analysis for exploring deep crustal structure.

Passive Mode Carbon Nanotube Underwater Acoustic Transducer

DTIC Science & Technology

2016-09-20

Acoustical transducer arrays can reflect a sound signal in reverse to the sender which can be used for echo location devices. [0008] In Jiang...of this layer of the medium determines the amplitude of the resulting sound waves. [0005] Recently, there has been development of underwater...structures. The energy is partially reflected from interfaces between the geologic structure and is detected with geophone or hydrophone sensors

Marine Bioacoustics: Soundtracks for the Future

DTIC Science & Technology

2013-09-30

studying humpback whale ecology. During summer courses, we provide students 1.) with a strong conceptual understanding of marine bioacoustics theory...localize and track vocalizing humpback whales . 2 During the summer course, we conducted a multi-frequency acoustic survey of Saanich Inlet, BC... humpback whales can be localized and tracked with hydrophone array deployed on Wave Gliders. Paper from this project will be presented at the 20th

Improvements to Passive Acoustic Tracking Methods for Marine Mammal Monitoring

DTIC Science & Technology

2016-05-02

separate and associate calls from individual animals . Marine mammal; Passive acoustic monitoring; Localization; Tracking; Multiple source; Sparse array...position and hydrophone timing offset in addition to animal position Almost all marine mammal tracking methods treat animal position as the only unknown...Workshop on Detection, Classification and Localization (DCL) of Marine Mammals). The animals were expected to be relatively close to the surface

Hydroacoustic Signals Recorded by the International Monitoring System

NASA Astrophysics Data System (ADS)

Blackman, D.; de Groot-Hedlin, C.; Orcutt, J.; Harben, P.

2002-12-01

Networks of hydrophones, such as the hydroacoustic part of the International Monitoring System (IMS), and hydrophone arrays, such as the U.S. Navy operates, record many types of signals, some of which travel thousands of kilometers in the oceanic sound channel. Abyssal earthquakes generate many such individual events and occasionally occur in swarms. Here we focus on signals generated by other types of sources, illustrating their character with recent data, mostly from the Indian Ocean. Shipping generates signals in the 5-40 Hz band. Large airgun arrays can generate T-waves that travel across an ocean basin if the near-source seafloor has appropriate depth/slope. Airgun array shots from our 2001 experiment were located with an accuracy of 25-40 km at 700-1000 km ranges, using data from a Diego Garcia tripartite sensor station. Shots at greater range (up to 4800 km) were recorded at multiple stations but their higher background noise levels in the 5-30 Hz band resulted in location errors of ~100 km. Imploding glass spheres shattered within the sound channel produce a very impulsive arrival, even after propagating 4400 km. Recordings of the sphere signal have energy concentrated in the band above 40 Hz. Natural sources such as undersea volcanic eruptions and marine mammals also produce signals that are clearly evident in hydrophone recordings. For whales, the frequency range is 20~120Hz and specific patterns of vocalization characterize different species. Volcanic eruptions typically produce intense swarms of acoustic activity that last days-weeks and the source area can migrate tens of kms during the period. The utility of these types of hydroacoustic sources for research and/or monitoring purposes depends on the accuracy with which recordings can be used to locate and quantitatively characterize the source. Oceanic weather, both local and regional, affect background noise levels in key frequency bands at the recording stations. Databases used in forward modeling of propagation and acoustic losses can be sparse in remote regions. Our Indian Ocean results suggest that when bathymetric coverage is poor, predictions for 8 Hz propagation/loss match observations better than those for propagation of 30 Hz signals over 1000-km distances.

A Summary of the Naval Postgraduate School Research Program.

DTIC Science & Technology

1983-05-01

environment . Of particular note here are the activities of the Environmental Physics Group, our work in electro-optics, and work anticipated in the...of natural light and the optical beam spread function of the ocean. The sponsor is DARPA. ENVIRONMENTAL ACOUSTICS G. H. Jung, R. H. Bourke, C. R... environmental phenomena determine the nature of ambient noise signals received at hydrophone arrays. Summary: During FY82, additional data bases were

Deployment of Autonomous Hydrophone Array in the Scotia Sea

DTIC Science & Technology

2008-09-01

originated by the Clarence Island in the Bransfield strait near the Antarctic Peninsula (Figure 3). The signals originated from a 10x5 km iceberg ...Atlantic Ocean near the Antarctic Peninsula and the South Scotia Sea is a region where acoustic surveillance by International Monitoring System (IMS...study sound propagation through the Antarctic Convergence Zone (ACZ), as well as acoustic blockage and reflection caused by islands and associated

Analysis and localization of blue whale vocalizations in the Solomon Sea using waveform amplitude data.

PubMed

Frank, Scott D; Ferris, Aaron N

2011-08-01

During the Woodlark Basin seismic experiment in eastern Papua New Guinea (1999-2000), an ocean-bottom seismic array recorded marine mammal vocalizations along with target earthquake signals. The array consisted of 14 instruments, 7 of which were three-component seismometers with a fourth component hydrophone. They were deployed at 2.0-3.2 km water depth and operated from September 1999 through February 2000. While whale vocalizations were recorded throughout the deployment, this study focuses on 3 h from December 21, 1999 during which the signals are particularly clear. The recordings show a blue whale song composed of a three-unit phrase. That song does not match vocalization characteristics of other known Pacific subpopulations and may represent a previously undocumented blue whale song. Animal tracking and source level estimates are obtained with a Bayesian inversion method that generates probabilistic source locations. The Bayesian method is augmented to include travel time estimates from seismometers and hydrophones and acoustic signal amplitude. Tracking results show the whale traveled northeasterly over the course of 3 h, covering approximately 27 km. The path followed the edge of the Woodlark Basin along a shelf that separates the shallow waters of the Trobriand platform from the deep waters of the basin.

Process for Assembly of Multimode Hydrophone Ceramic Stack

DTIC Science & Technology

2016-09-20

PROCESS FOR ASSEMBLY OF MULTIMODE HYDROPHONE CERAMIC STACK STATEMENT OF GOVERNMENT INTEREST [0001] The invention described herein may be...invention relates to a method of assembly for a multimode acoustic hydrophone. (2) Description of the Prior Art [0004] An acoustic hydrophone can...performance difference of a hydrophone that does not have uniform axial stress/voltage on each ring, when the hydrophone is assembled and FIG. 13 thru FIG

Thin-film sparse boundary array design for passive acoustic mapping during ultrasound therapy.

PubMed

Coviello, Christian M; Kozick, Richard J; Hurrell, Andrew; Smith, Penny Probert; Coussios, Constantin-C

2012-10-01

A new 2-D hydrophone array for ultrasound therapy monitoring is presented, along with a novel algorithm for passive acoustic mapping using a sparse weighted aperture. The array is constructed using existing polyvinylidene fluoride (PVDF) ultrasound sensor technology, and is utilized for its broadband characteristics and its high receive sensitivity. For most 2-D arrays, high-resolution imagery is desired, which requires a large aperture at the cost of a large number of elements. The proposed array's geometry is sparse, with elements only on the boundary of the rectangular aperture. The missing information from the interior is filled in using linear imaging techniques. After receiving acoustic emissions during ultrasound therapy, this algorithm applies an apodization to the sparse aperture to limit side lobes and then reconstructs acoustic activity with high spatiotemporal resolution. Experiments show verification of the theoretical point spread function, and cavitation maps in agar phantoms correspond closely to predicted areas, showing the validity of the array and methodology.

Development of Vertical Cable Seismic System (2)

NASA Astrophysics Data System (ADS)

Asakawa, E.; Murakami, F.; Tsukahara, H.; Ishikawa, K.

2012-12-01

The vertical cable seismic is one of the reflection seismic methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by surface, deep-towed or ocean bottom sources. Analyzing the reflections from the sub-seabed, we could look into the subsurface structure. This type of survey is generally called VCS (Vertical Cable Seismic). Because VCS is an efficient high-resolution 3D seismic survey method for a spatially-bounded area, we proposed the method for the hydrothermal deposit survey tool development program that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) started in 2009. We are now developing a VCS system, including not only data acquisition hardware but data processing and analysis technique. Our first experiment of VCS surveys has been carried out in Lake Biwa, JAPAN in November 2009 for a feasibility study. Prestack depth migration is applied to the 3D VCS data to obtain a high quality 3D depth volume. Based on the results from the feasibility study, we have developed two autonomous recording VCS systems. After we carried out a trial experiment in the actual ocean at a water depth of about 400m and we carried out the second VCS survey at Iheya Knoll with a deep-towed source. In this survey, we could establish the procedures for the deployment/recovery of the system and could examine the locations and the fluctuations of the vertical cables at a water depth of around 1000m. The acquired VCS data clearly shows the reflections from the sub-seafloor. Through the experiment, we could confirm that our VCS system works well even in the severe circumstances around the locations of seafloor hydrothermal deposits. We have carried out two field surveys in 2011. One is a 3D survey with a boomer for a high-resolution surface source and the other one for an actual field survey in the Izena Cauldron an active hydrothermal area in the Okinawa Trough. Through these surveys, we have confirmed that the uncertainty in the locations of the source and of the hydrophones in water could lower the quality of subsurface image. It is, therefore, strongly necessary to develop a total survey system that assures an accurate positioning and a deployment techniques. In case of shooting on sea surface, GPS navigation system are available, but in case of deep-towed source or ocean bottom source, the accuracy of shot position with SSBL/USBL is not sufficient for the very high-resolution imaging as requested for the SMS survey. We will incorporate the accurate LBL navigation systems with VCs. The LBL navigation system has been developed by IIS of the University of Tokyo. The error is estimated less than 10cm at the water depth of 3000m. Another approach is that the shot points can be calculated using the first break of the VCS after the VCS locations are estimated by slant-ranging from the sea surface. Our VCS system has been designed as a survey tool for hydrothermal deposit, but it will be also applicable for deep water site surveys or geohazard assessment such as active faults.

Extreme Morphologic and Venting Changes in Methane Seeps at Southern Hydrate Ridge, Cascadia Margin

NASA Astrophysics Data System (ADS)

Bigham, K.; Kelley, D. S.; Solomon, E. A.; Delaney, J. R.

2017-12-01

Two highly active methane hydrate seeps have been visited over a 7-year period as part of the construction and operation of NSF's Ocean Observatory Initiative's Regional Cable Array at Southern Hydrate Ridge. The site is located 90 km west of Newport, Oregon, at a water depth of 800 m. The seeps, Einstein's Grotto (OOI instrument deployment site) and Smokey Tavern (alternate site to the north), have been visited yearly from 2010 to 2017 with ROVs. Additionally, a digital still camera deployed from 2014 to 2017 at Einstein's Grotto, has been documenting the profound morphologic and biological changes at this site. A cabled pressure sensor, Acoustic Doppler Current Profiler, hydrophone, seismometer array, and uncabled fluid samplers have also been operational at the site for the duration of the camera's deployment. During this time, Einstein's Grotto has evolved from a gentle mound with little venting, to a vigorously bubbling pit bounded by a near vertical wall. Early on bubble emissions blew significant amounts of sediment into the water column and thick Beggiatoa mats coverd the mound. Most recently the face of the pit has collapsed, although bubble plumes are still emitted from the site. The Smokey Tavern site has undergone more extreme changes. Similar to Einstein's Grotto it was first characterized by gentle hummocks with dispersed bacterial mats. In subsequent years, it developed an extremely rugged, elongated collapsed area with vertical walls and jets of methane bubbles rising from small pits near the base of the collapse zone. Meter-across nearly sediment-free blocks of methane hydrate were exposed on the surface and in the walls of the collapse zone. In 2016, this area was unrecognizable with a much more subdued topography, and weak venting of bubbles. Exposed methane hydrate was not visible. From these observations new evolutionary models for methane seeps are being developed for Southern Hydrate Ridge.

Evaluation of an experimental electrohydraulic discharge device for extracorporeal shock wave lithotripsy: Pressure field of sparker array.

PubMed

Li, Guangyan; Connors, Bret A; Schaefer, Ray B; Gallagher, John J; Evan, Andrew P

2017-11-01

In this paper, an extracorporeal shock wave source composed of small ellipsoidal sparker units is described. The sparker units were arranged in an array designed to produce a coherent shock wave of sufficient strength to fracture kidney stones. The objective of this paper was to measure the acoustical output of this array of 18 individual sparker units and compare this array to commercial lithotripters. Representative waveforms acquired with a fiber-optic probe hydrophone at the geometric focus of the sparker array indicated that the sparker array produces a shock wave (P + ∼40-47 MPa, P - ∼2.5-5.0 MPa) similar to shock waves produced by a Dornier HM-3 or Dornier Compact S. The sparker array's pressure field map also appeared similar to the measurements from a HM-3 and Compact S. Compared to the HM-3, the electrohydraulic technology of the sparker array produced a more consistent SW pulse (shot-to-shot positive pressure value standard deviation of ±4.7 MPa vs ±3.3 MPa).

Freely Drifting Swallow Float Array: August 1990 NATIVE 1 Experiment (First Deployment)

DTIC Science & Technology

1991-02-01

jump around record 1520, indicating that the apparent increase in float 2’s hydrophone sensitivity occurred only at the lower infra - sonic ...and d) the infrasonic acoustic data. The infrasonic data include the RMS levels of the pressure and the three components of parti- cle velocity for all...active intensity spectra. A description of the Swallow float infrasonic data acquisition system, along with calibration curves, is given in Appendix 1

Sperm whale assessment in the Western Ionian Sea using acoustic data from deep sea observatories

NASA Astrophysics Data System (ADS)

Caruso, Francesco; Bellia, Giorgio; Beranzoli, Laura; De Domenico, Emilio; Larosa, Giuseppina; Marinaro, Giuditta; Papale, Elena; Pavan, Gianni; Pellegrino, Carmelo; Pulvirenti, Sara; Riccobene, Giorgio; Scandura, Danila; Sciacca, Virginia; Viola, Salvatore

2015-04-01

The Italian National Institute of Nuclear Physics (INFN) operates two deep sea infrastructures: Capo Passero, Western Ionian Sea 3,600 meters of depth, and Catania Wester Ionian Sea 2,100 m depth. At the two sites, several research observatories have been run: OnDE, NEMO-SN1, SMO, KM3NeT-Italia most of them jointly operated between INFN and INGV. In all these observatories, passive acoustic sensors (hydrophones) have been installed. Passive Acoustics Monitoring (PAM) is nowadays the main tool of the bioacoustics to study marine mammals. In particular, receiving the sounds emitted by cetaceans from a multi-hydrophones array installed in a cabled seafloor observatory, a research about the ecological dynamics of the species may be performed. Data acquired with the hydrophones installed aboard the OnDE, SMO and KM3NeT-Italia observatories will be reported. Thanks to acquired data, the acoustic presence of the sperm whales was assessed and studied for several years (2005:2013). An "ad hoc" algorithm was also developed to allow the automatic identification of the "clicks" emitted by the sperm whales and measure the size of detected animals. According to the results obtained, the sperm whale population in the area is well-distributed in size, sex and sexual maturity. Although specimens more than 14 meters of length (old males) seem to be absent.

Twelve years of tracking 52-Hz whale calls from a unique source in the North Pacific

NASA Astrophysics Data System (ADS)

Watkins, William A.; Daher, Mary Ann; George, Joseph E.; Rodriguez, David

2004-12-01

A unique whale call with 50-52 Hz emphasis from a single source has been tracked over 12 years in the central and eastern North Pacific. These calls, referred to as 52-Hz calls, were monitored and analyzed from acoustic data recorded by hydrophones of the US Navy Sound Surveillance System (SOSUS) and other arrays. The calls were noticed first in 1989, and have been detected and tracked since 1992. No other calls with similar characteristics have been identified in the acoustic data from any hydrophone system in the North Pacific basin. Only one series of these 52-Hz calls has been recorded at a time, with no call overlap, suggesting that a single whale produced the calls. The calls were recorded from August to February with most in December and January. The species producing these calls is unknown. The tracks of the 52-Hz whale were different each year, and varied in length from 708 to 11,062 km with travel speeds ranging from 0.7 to 3.8 km/h. Tracks included (A) meandering over short ranges, (B) predominantly west-to-east movement, and (C) mostly north-to-south travel. These tracks consistently appeared to be unrelated to the presence or movement of other whale species (blue, fin and humpback) monitored year-round with the same hydrophones.

Explosive processes during the 2015 eruption of Axial Seamount, as recorded by seafloor hydrophones

NASA Astrophysics Data System (ADS)

Caplan-Auerbach, J.; Dziak, R. P.; Haxel, J.; Bohnenstiehl, D. R.; Garcia, C.

2017-04-01

Following the installation of the Ocean Observatories Initiative cabled array, the 2015 eruption of Axial Seamount, Juan de Fuca ridge, became the first submarine eruption to be captured in real time by seafloor seismic and acoustic instruments. This eruption also marked the first instance where the entire eruption cycle of a submarine volcano, from the previous eruption in 2011 to the end of the month-long 2015 event, was monitored continuously using autonomous ocean bottom hydrophones. Impulsive sounds associated with explosive lava-water interactions are identified within hydrophone records during both eruptions. Explosions within the caldera are acoustically distinguishable from those occurring in association with north rift lava flows erupting in 2015. Acoustic data also record a series of broadband diffuse events, occurring in the waning phase of the eruption, and are interpreted as submarine Hawaiian explosions. This transition from gas-poor to gas-rich eruptive activity coincides with an increase in water temperature within the caldera and with a decrease in the rate of deflation. The last recorded diffuse events coincide with the end of the eruption, represented by the onset of inflation. All the observed explosion signals couple strongly into the water column, and only weakly into the solid Earth, demonstrating the importance of hydroacoustic observations as a complement to seismic and geodetic studies of submarine eruptions.

Smart materials systems through mesoscale patterning

NASA Astrophysics Data System (ADS)

Aksay, Ilhan A.; Groves, John T.; Gruner, Sol M.; Lee, P. C. Y.; Prud'homme, Robert K.; Shih, Wei-Heng; Torquato, Salvatore; Whitesides, George M.

1996-02-01

We report work on the fabrication of smart materials with two unique strategies: (1) self- assembly and (2) laser stereolithography. Both methods are akin to the processes used by biological systems. The first one is ideal for pattern development and the fabrication of miniaturized units in the submicron range and the second one in the 10 micrometer to 1 mm size range. By using these miniaturized units as building blocks, one can also produce smart material systems that can be used at larger length scales such as smart structural components. We have chosen to focus on two novel piezoceramic systems: (1) high-displacement piezoelectric actuators, and (2) piezoceramic hydrophone composites possessing negative Poisson ratio matrices. High-displacement actuators are essential in such applications as linear motors, pumps, switches, loud speakers, variable-focus mirrors, and laser deflectors. Arrays of such units can potentially be used for active vibration control of helicopter rotors as well as the fabrication of adaptive rotors. In the case of piezoceramic hydrophone composites, we utilize matrices having a negative Poisson's ratio in order to produce highly sensitive, miniaturized sensors. We envision such devices having promising new application areas such as the implantation of hydrophones in small blood vessels to monitor blood pressure. Negative Poisson ratio materials have promise as robust shock absorbers, air filters, and fasteners, and hence, can be used in aircraft and land vehicles.

Uncertainty of High Intensity Therapeutic Ultrasound (HITU) Field Characterization with Hydrophones: Effects of Nonlinearity, Spatial Averaging, and Complex Sensitivity

PubMed Central

Liu, Yunbo; Wear, Keith A.; Harris, Gerald R.

2017-01-01

Reliable acoustic characterization is fundamental for patient safety and clinical efficacy during high intensity therapeutic ultrasound (HITU) treatment. Technical challenges, such as measurement uncertainty and signal analysis still exist for HITU exposimetry using ultrasound hydrophones. In this work, four hydrophones were compared for pressure measurement: a robust needle hydrophone, a small PVDF capsule hydrophone and two different fiber-optic hydrophones. The focal waveform and beam distribution of a single element HITU transducer (1.05 MHz and 3.3 MHz) were evaluated. Complex deconvolution between the hydrophone voltage signal and frequency-dependent complex sensitivity was performed to obtain pressure waveform. Compressional pressure, rarefactional pressure, and focal beam distribution were compared up to 10.6/−6.0 MPa (p+ and p−) (1.05 MHz) and 20.65/−7.20 MPa (3.3 MHz). In particular, the effects of spatial averaging, local nonlinear distortion, complex deconvolution and hydrophone damage thresholds were investigated. This study showed an uncertainty of no better than 10–15% on hydrophone-based HITU pressure characterization. PMID:28735734

Variation of High-Intensity Therapeutic Ultrasound (HITU) Pressure Field Characterization: Effects of Hydrophone Choice, Nonlinearity, Spatial Averaging and Complex Deconvolution.

PubMed

Liu, Yunbo; Wear, Keith A; Harris, Gerald R

2017-10-01

Reliable acoustic characterization is fundamental for patient safety and clinical efficacy during high-intensity therapeutic ultrasound (HITU) treatment. Technical challenges, such as measurement variation and signal analysis, still exist for HITU exposimetry using ultrasound hydrophones. In this work, four hydrophones were compared for pressure measurement: a robust needle hydrophone, a small polyvinylidene fluoride capsule hydrophone and two fiberoptic hydrophones. The focal waveform and beam distribution of a single-element HITU transducer (1.05 MHz and 3.3 MHz) were evaluated. Complex deconvolution between the hydrophone voltage signal and frequency-dependent complex sensitivity was performed to obtain pressure waveforms. Compressional pressure (p + ), rarefactional pressure (p - ) and focal beam distribution were compared up to 10.6/-6.0 MPa (p + /p - ) (1.05 MHz) and 20.65/-7.20 MPa (3.3 MHz). The effects of spatial averaging, local non-linear distortion, complex deconvolution and hydrophone damage thresholds were investigated. This study showed a variation of no better than 10%-15% among hydrophones during HITU pressure characterization. Published by Elsevier Inc.

The Development of the Differential MEMS Vector Hydrophone

PubMed Central

Zhang, Guojun; Liu, Mengran; Shen, Nixin; Wang, Xubo; Zhang, Wendong

2017-01-01

To solve the problem that MEMS vector hydrophones are greatly interfered with by the vibration of the platform and flow noise in applications, this paper describes a differential MEMS vector hydrophone that could simultaneously receive acoustic signals and reject acceleration signals. Theoretical and simulation analyses have been carried out. Lastly, a prototype of the differential MEMS vector hydrophone has been created and tested using a standing wave tube and a vibration platform. The results of the test show that this hydrophone has a high sensitivity, Mv = −185 dB (@ 500 Hz, 0 dB reference 1 V/μPa), which is almost the same as the previous MEMS vector hydrophones, and has a low acceleration sensitivity, Mv = −58 dB (0 dB reference 1 V/g), which has decreased by 17 dB compared with the previous MEMS vector hydrophone. The differential MEMS vector hydrophone basically meets the requirements of acoustic vector detection when it is rigidly fixed to a working platform, which lays the foundation for engineering applications of MEMS vector hydrophones. PMID:28594384

Design and simulation of MEMS vector hydrophone with reduced cross section based meander beams

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

Kumar, Manoj; Dutta, S.; Pal, Ramjay

MEMS based vector hydrophone is being one of the key device in the underwater communications. In this paper, we presented a bio-inspired MEMS vector hydrophone. The hydrophone structure consists of a proof mass suspended by four meander type beams with reduced cross-section. Modal patterns of the structure were studied. First three modal frequencies of the hydrophone structure were found to be 420 Hz, 420 Hz and 1646 Hz respectively. The deflection and stress of the hydrophone is found have linear behavior in the 1 µPa – 1Pa pressure range.

Seismicity And Accretion Process Along The North Mid-Atlantic Ridge From The SIRENA Autonomous Hydrophone Data

NASA Astrophysics Data System (ADS)

Perrot, J.; Goslin, J.; Dziak, R. P.; Haxel, J. H.; Maia, M. A.; Tisseau, C.; Royer, J.

2009-12-01

The seismicity of the North Atlantic Ocean was recorded by the SIRENA array of 6 autonomous underwater hydrophones (AUH) moored within the SOFAR channel on the flanks of the Mid-Atlantic Ridge (MAR). The instruments were deployed north of the Azores Plateau between 40° and 50°N from June 2002 to September 2003. The low attenuation properties of the SOFAR channel for earthquake T-wave propagation result in a detection threshold reduction to a magnitude completeness level (Mc) of ~2.8, to be compared to a Mc~4.7 for MAR events recorded by land-based seismic networks. A spatio-temporal analysis was performed over the 1696 events localized inside the SIRENA array. For hydrophone-derived catalogs, the acoustic magnitude, or Source Level (SL), is used as a measure of earthquake size. The ''source level completeness'', above which the data set is complete, is SLc=208 dB. The SIRENA catalog was searched for swarms using the cluster software of the SEISAN distribution. A minimum SL of 210 dB was chosen to detect a possible mainshock, and all subsequent events within 40 days following the possible mainshock, located within a radius of 15 km from the mainshock were considered as events of the swarm. 15 km correspond to the maximum fault length in a slow-ridge context. 11 swarms with more than 15 events were detected along the MAR between 40°et 50°N during the SIRENA deployment. The maximum number of earthquakes in a swarm is 40 events. The SL vs. time distribution within each swarm allowed a first discrimination between the swarms occurring in a tectonic context and those which can be attributed to volcanic processes, the latter showing a more constant SL vs. time distribution. Moreover, the swarms occurring in a tectonic context show a "mainshock-afterschock" distribution of the cumulative number of events vs. time, fitting a Modified Omori Law. The location of tectonic and volcanic swarms correlates well with regions where a positive and negative Mantle Bouguer Anomalies (MBAs)(Maia et al., 2007) are observed, indicating the presence of thinner/colder and thicker/warmer crust respectively. Our results thus show that hydrophone data can be fruitfully used to help and characterize active ridge processes at various spatial scales. Maia M., J. Goslin, and P. Gente (2007), Evolution of accretion processes along the Mid-Atlantic Ridge north of the Azores since 5.5 Ma: An insight into the interactions between the ridge and the plume, Geochem. Geophys. Geosyst., 8.

Fine-scale pathways used by adult sea lampreys during riverine spawning migrations

USGS Publications Warehouse

Holbrook, Christopher; Bergstedt, Roger A.; Adams, Noah S.; Hatton, Tyson; McLaughlin, Robert L.

2015-01-01

Better knowledge of upstream migratory patterns of spawning Sea Lampreys Petromyzon marinus, an invasive species in the Great Lakes, is needed to improve trapping for population control and assessment. Although trapping of adult Sea Lampreys provides the basis for estimates of lake-wide abundance that are used to evaluate the Sea Lamprey control program, traps have only been operated at dams due to insufficient knowledge of Sea Lamprey behavior in unobstructed channels. Acoustic telemetry and radiotelemetry were used to obtain movement tracks for 23 Sea Lampreys in 2008 and 18 Sea Lampreys in 2009 at two locations in the Mississagi River, Ontario. Cabled hydrophone arrays provided two-dimensional geographic positions from acoustic transmitters at 3-s intervals; depth-encoded radio tag detections provided depths. Upstream movements occurred at dusk or during the night (2015–0318 hours). Sea Lampreys were closely associated with the river bottom and showed some preference to move near banks in shallow glide habitats, suggesting that bottom-oriented gears could selectively target adult Sea Lampreys in some habitats. However, Sea Lampreys were broadly distributed across the river channel, suggesting that the capture efficiency of nets and traps in open channels would depend heavily on the proportion of the channel width covered. Lack of vertical movements into the water column may have reflected lamprey preference for low water velocities, suggesting that energy conservation was more beneficial for lampreys than was vertical searching in rivers. Improved understanding of Sea Lamprey movement will assist in the development of improved capture strategies for their assessment and control in the Great Lakes.

Geophysical Inversion with Adaptive Array Processing of Ambient Noise

NASA Astrophysics Data System (ADS)

Traer, James

2011-12-01

Land-based seismic observations of microseisms generated during Tropical Storms Ernesto and Florence are dominated by signals in the 0.15--0.5Hz band. Data from seafloor hydrophones in shallow water (70m depth, 130 km off the New Jersey coast) show dominant signals in the gravity-wave frequency band, 0.02--0.18Hz and low amplitudes from 0.18--0.3Hz, suggesting significant opposing wave components necessary for DF microseism generation were negligible at the site. Both storms produced similar spectra, despite differing sizes, suggesting near-coastal shallow water as the dominant region for observed microseism generation. A mathematical explanation for a sign-inversion induced to the passive fathometer response by minimum variance distortionless response (MVDR) beamforming is presented. This shows that, in the region containing the bottom reflection, the MVDR fathometer response is identical to that obtained with conventional processing multiplied by a negative factor. A model is presented for the complete passive fathometer response to ocean surface noise, interfering discrete noise sources, and locally uncorrelated noise in an ideal waveguide. The leading order term of the ocean surface noise produces the cross-correlation of vertical multipaths and yields the depth of sub-bottom reflectors. Discrete noise incident on the array via multipaths give multiple peaks in the fathometer response. These peaks may obscure the sub-bottom reflections but can be attenuated with use of Minimum Variance Distortionless Response (MVDR) steering vectors. A theory is presented for the Signal-to-Noise-Ratio (SNR) for the seabed reflection peak in the passive fathometer response as a function of seabed depth, seabed reflection coefficient, averaging time, bandwidth and spatial directivity of the noise field. The passive fathometer algorithm was applied to data from two drifting array experiments in the Mediterranean, Boundary 2003 and 2004, with 0.34s of averaging time. In the 2004 experiment, the response showed the array depth varied periodically with an amplitude of 1 m and a period of 7 s consistent with wave driven motion of the array. This introduced a destructive interference which prevents the SNR growing with averaging time, unless the motion is removed by use of a peak tracker.

Enhancing active and passive remote sensing in the ocean using broadband acoustic transmissions and coherent hydrophone arrays

NASA Astrophysics Data System (ADS)

Tran, Duong Duy

The statistics of broadband acoustic signal transmissions in a random continental shelf waveguide are characterized for the fully saturated regime. The probability distribution of broadband signal energies after saturated multi-path propagation is derived using coherence theory. The frequency components obtained from Fourier decomposition of a broadband signal are each assumed to be fully saturated, where the energy spectral density obeys the exponential distribution with 5.6 dB standard deviation and unity scintillation index. When the signal bandwidth and measurement time are respectively larger than the correlation bandwidth and correlation time of its energy spectral density components, the broadband signal energy obtained by integrating the energy spectral density across the signal bandwidth then follows the Gamma distribution with standard deviation smaller than 5.6 dB and scintillation index less than unity. The theory is verified with broadband transmissions in the Gulf of Maine shallow water waveguide in the 300-1200 Hz frequency range. The standard deviations of received broadband signal energies range from 2.7 to 4.6 dB for effective bandwidths up to 42 Hz, while the standard deviations of individual energy spectral density components are roughly 5.6 dB. The energy spectral density correlation bandwidths of the received broadband signals are found to be larger for signals with higher center frequency. Sperm whales in the New England continental shelf and slope were passively localized, in both range and bearing using a single low-frequency (< 2500 Hz), densely sampled, towed horizontal coherent hydrophone array system. Whale bearings were estimated using time-domain beamforming that provided high coherent array gain in sperm whale click signal-to-noise ratio. Whale ranges from the receiver array center were estimated using the moving array triangulation technique from a sequence of whale bearing measurements. The dive profile was estimated for a sperm whale in the shallow waters of the Gulf of Maine with 160 m water-column depth, located close to the array's near-field where depth estimation was feasible by employing time difference of arrival of the direct and multiply reflected click signals received on the array. The dependence of broadband energy on bandwidth and measurement time was verified employing recorded sperm whale clicks in the Gulf of Maine.

Comparative study of absorption in tilted silicon nanowire arrays for photovoltaics

PubMed Central

2014-01-01

Silicon nanowire arrays have been shown to demonstrate light trapping properties and promising potential for next-generation photovoltaics. In this paper, we show that the absorption enhancement in vertical nanowire arrays on a perfectly electric conductor can be further improved through tilting. Vertical nanowire arrays have a 66.2% improvement in ultimate efficiency over an ideal double-pass thin film of the equivalent amount of material. Tilted nanowire arrays, with the same amount of material, exhibit improved performance over vertical nanowire arrays across a broad range of tilt angles (from 38° to 72°). The optimum tilt of 53° has an improvement of 8.6% over that of vertical nanowire arrays and 80.4% over that of the ideal double-pass thin film. Tilted nanowire arrays exhibit improved absorption over the solar spectrum compared with vertical nanowires since the tilt allows for the excitation of additional modes besides the HE 1m modes that are excited at normal incidence. We also observed that tilted nanowire arrays have improved performance over vertical nanowire arrays for a large range of incidence angles (under about 60°). PMID:25435833

Comparative study of absorption in tilted silicon nanowire arrays for photovoltaics.

PubMed

Kayes, Md Imrul; Leu, Paul W

2014-01-01

Silicon nanowire arrays have been shown to demonstrate light trapping properties and promising potential for next-generation photovoltaics. In this paper, we show that the absorption enhancement in vertical nanowire arrays on a perfectly electric conductor can be further improved through tilting. Vertical nanowire arrays have a 66.2% improvement in ultimate efficiency over an ideal double-pass thin film of the equivalent amount of material. Tilted nanowire arrays, with the same amount of material, exhibit improved performance over vertical nanowire arrays across a broad range of tilt angles (from 38° to 72°). The optimum tilt of 53° has an improvement of 8.6% over that of vertical nanowire arrays and 80.4% over that of the ideal double-pass thin film. Tilted nanowire arrays exhibit improved absorption over the solar spectrum compared with vertical nanowires since the tilt allows for the excitation of additional modes besides the HE 1m modes that are excited at normal incidence. We also observed that tilted nanowire arrays have improved performance over vertical nanowire arrays for a large range of incidence angles (under about 60°).

Fabrication of high thermal conductivity arrays of carbon nanotubes and their composites

DOEpatents

Geohegan, David B [Knoxville, TN; Ivanov, Ilya N [Knoxville, TN; Puretzky, Alexander A [Knoxville, TN

2010-07-27

Methods and apparatus are described for fabrication of high thermal conductivity arrays of carbon nanotubes and their composites. A composition includes a vertically aligned nanotube array including a plurality of nanotubes characterized by a property across substantially all of the vertically aligned nanotube array. A method includes depositing a vertically aligned nanotube array that includes a plurality of nanotubes; and controlling a deposition rate of the vertically aligned nanotubes array as a function of an in situ monitored property of the plurality of nanotubes.

TRISTEN/FRAM II Cruise Report, East Arctic, April 1980.

DTIC Science & Technology

1981-04-13

is not readily accessible by air from Alaska. The Eurasia Basin contains the Arctic Midoceanic Ridge, which extends in a straight line for 2000 km...13 6 Bottom Refraction - Shot- Lines Overlain on FRAM II Positions 14 7 Waterfall Display of Successive Spectral Estimates of Single...Northeast leg of the array was oriented 341T and the NW leg 304 ’T. After a windstorm and flow break-up on 16 April, hydrophones 11 and 12 and 21-24 were

Characterizing Broadband Acoustic Propagation Scintillation and Modelling Scattering and Reverberation for Sensing in a Random Ocean Waveguide

DTIC Science & Technology

2014-09-30

34Ecosystem scale acoustic sensing reveals humpback whale behavior synchronous with herring spawning processes and re-evaluation finds no effect of sonar...on humpback song occurrence in the Gulf of Maine in Fall 2006." PlosOne (accepted, in print for 2014). 2. D. Tran, W. Huang, A. Bohn, D. Wang, Z...Gong, N. Makris and P. Ratilal, "Using a coherent hydrophone array for observing sperm whale range, classification, and shallow-water dive profiles

Extensible 3D (X3D) Graphics for Visualizing Marine Mammal Reaction to Underwater Sound on the Southern California ASW Range (SOAR)

DTIC Science & Technology

2007-06-01

file ARC- 20060811T130816.txt, where color is used to represent points in time (red being the earliest, transitioning to orange, yellow , then white...Administration (NOAA), using passive hydrophone arrays along the mid-Atlantic ridge to listen for underwater earthquakes and volcanoes , have found that a...appeared. The earliest data points were designated red, and later points were shades of orange and yellow , until the last points (relative to the

Design and optimization of stress centralized MEMS vector hydrophone with high sensitivity at low frequency

NASA Astrophysics Data System (ADS)

Zhang, Guojun; Ding, Junwen; Xu, Wei; Liu, Yuan; Wang, Renxin; Han, Janjun; Bai, Bing; Xue, Chenyang; Liu, Jun; Zhang, Wendong

2018-05-01

A micro hydrophone based on piezoresistive effect, "MEMS vector hydrophone" was developed for acoustic detection application. To improve the sensitivity of MEMS vector hydrophone at low frequency, we reported a stress centralized MEMS vector hydrophone (SCVH) mainly used in 20-500 Hz. Stress concentration area was actualized in sensitive unit of hydrophone by silicon micromachining technology. Then piezoresistors were placed in stress concentration area for better mechanical response, thereby obtaining higher sensitivity. Static analysis was done to compare the mechanical response of three different sensitive microstructure: SCVH, conventional micro-silicon four-beam vector hydrophone (CFVH) and Lollipop-shaped vector hydrophone (LVH) respectively. And fluid-structure interaction (FSI) was used to analyze the natural frequency of SCVH for ensuring the measurable bandwidth. Eventually, the calibration experiment in standing wave field was done to test the property of SCVH and verify the accuracy of simulation. The results show that the sensitivity of SCVH has nearly increased by 17.2 dB in contrast to CFVH and 7.6 dB in contrast to LVH during 20-500 Hz.

Effect on High-Intensity Fields of a Tough Hydrophone With Hydrothermal PZT Thick-Film Vibrator and Titanium Front Layer.

PubMed

Okada, Nagaya; Takeuchi, Shinichi

2017-07-01

A novel tough hydrophone was fabricated by depositing hydrothermally synthesized lead zirconate titanate polycrystalline film on the back-side surface of a titanium plate. Our developed tough hydrophone resisted damage in a high-pressure field (15 MPa) at a focal point of a sinusoidal continuous wave driven by a concave high-intensity focused ultrasound (HIFU) transducer with up to 50 W of power input to the sound source. The hydrophone was suitable for the HIFU field, even though the hydrophone has a flat-shape tip of 3.5 mm diameter, which is slightly larger than the wavelength of a few megahertz. In this paper, experiments are performed to assess the effect on the HIFU field of changing the shape of the tough hydrophone, with the aim of developing a tough hydrophone. The spatial distribution of the acoustic bubbles around the focal point was visualized by using ultrasonic diagnostic equipment with the tough hydrophone located at the focal point of the HIFU transducer. From the visualization, the trapped acoustic bubbles were seen to arise from the standing wave, which implies that the acoustic pressure is reduced by this cloud of acoustic bubbles that appeared during hydrophone measurement. Although cavitation and acoustic bubbles may be unavoidable when using high-intensity ultrasound, the estimated result of evaluating acoustic fields without misunderstanding by acoustic bubbles can be obtained by the aid of visualizing bubbles around the tough hydrophone.

Ultrasonic fingerprint sensor using a piezoelectric micromachined ultrasonic transducer array integrated with complementary metal oxide semiconductor electronics

NASA Astrophysics Data System (ADS)

Lu, Y.; Tang, H.; Fung, S.; Wang, Q.; Tsai, J. M.; Daneman, M.; Boser, B. E.; Horsley, D. A.

2015-06-01

This paper presents an ultrasonic fingerprint sensor based on a 24 × 8 array of 22 MHz piezoelectric micromachined ultrasonic transducers (PMUTs) with 100 μm pitch, fully integrated with 180 nm complementary metal oxide semiconductor (CMOS) circuitry through eutectic wafer bonding. Each PMUT is directly bonded to a dedicated CMOS receive amplifier, minimizing electrical parasitics and eliminating the need for through-silicon vias. The array frequency response and vibration mode-shape were characterized using laser Doppler vibrometry and verified via finite element method simulation. The array's acoustic output was measured using a hydrophone to be ˜14 kPa with a 28 V input, in reasonable agreement with predication from analytical calculation. Pulse-echo imaging of a 1D steel grating is demonstrated using electronic scanning of a 20 × 8 sub-array, resulting in 300 mV maximum received amplitude and 5:1 contrast ratio. Because the small size of this array limits the maximum image size, mechanical scanning was used to image a 2D polydimethylsiloxane fingerprint phantom (10 mm × 8 mm) at a 1.2 mm distance from the array.

Membrane hydrophone phase characteristics through nonlinear acoustics measurements.

PubMed

Bloomfield, Philip E; Gandhi, Gaurav; Lewin, Peter A

2011-11-01

This work considers the need for both the amplitude and phase to fully characterize polyvinylidene fluoride (PVDF) membrane hydrophones and presents a comprehensive discussion of the nonlinear acoustic measurements utilized to extract the phase information and the experimental results taken with two widely used PVDF membrane hydrophones up to 100 MHz. A semi-empirical computer model utilized the hyperbolic propagation operator to predict the nonlinear pressure field and provide the complex frequency response of the corresponding source transducer. The PVDF hydrophone phase characteristics, which were obtained directly from the difference between the computer-modeled nonlinear field simulation and the corresponding measured harmonic frequency phase values, agree to within 10% with the phase predictions obtained from receive-transfer-function simulations based on software modeling of the membrane's physical properties. Cable loading effects and membrane hydrophone resonances were distinguished and identified through a series of impedance measurements and receive transfer function simulations on the hydrophones including their hard-wired coaxial cables. The results obtained indicate that the PVDF membrane hydrophone's phase versus frequency plot exhibits oscillations about a monotonically decreasing line. The maxima and minima inflection point slopes occur at the membrane thickness resonances and antiresonances, respectively. A cable resonance was seen at 100 MHz for the hydrophone with a 1-m cable attached, but not seen for the hydrophone with a shorter 0.65-m cable.

Passive acoustic monitoring using a towed hydrophone array results in identification of a previously unknown beaked whale habitat.

PubMed

Yack, Tina M; Barlow, Jay; Calambokidis, John; Southall, Brandon; Coates, Shannon

2013-09-01

Beaked whales are diverse and species rich taxa. They spend the vast majority of their time submerged, regularly diving to depths of hundreds to thousands of meters, typically occur in small groups, and behave inconspicuously at the surface. These factors make them extremely difficult to detect using standard visual survey methods. However, recent advancements in acoustic detection capabilities have made passive acoustic monitoring (PAM) a viable alternative. Beaked whales can be discriminated from other odontocetes by the unique characteristics of their echolocation clicks. In 2009 and 2010, PAM methods using towed hydrophone arrays were tested. These methods proved highly effective for real-time detection of beaked whales in the Southern California Bight (SCB) and were subsequently implemented in 2011 to successfully detect and track beaked whales during the ongoing Southern California Behavioral Response Study. The three year field effort has resulted in (1) the successful classification and tracking of Cuvier's (Ziphius cavirostris), Baird's (Berardius bairdii), and unidentified Mesoplodon beaked whale species and (2) the identification of areas of previously unknown beaked whale habitat use. Identification of habitat use areas will contribute to a better understanding of the complex relationship between beaked whale distribution, occurrence, and preferred habitat characteristics on a relatively small spatial scale. These findings will also provide information that can be used to promote more effective management and conservation of beaked whales in the SCB, a heavily used Naval operation and training region.

Separation control with fluidic oscillators in water

NASA Astrophysics Data System (ADS)

Schmidt, H.-J.; Woszidlo, R.; Nayeri, C. N.; Paschereit, C. O.

2017-08-01

The present study assesses the applicability of fluidic oscillators for separation control in water. The first part of this work evaluates the properties of the fluidic oscillators including frequency, cavitation effects, and exerted thrust. Derived from the governing internal dynamics, the oscillation frequency is found to scale directly with the jet's exit velocity and the size of the fluidic oscillator independent of the working fluid. Frequency data from various experiments collapse onto a single curve. The occurrence of cavitation is examined by visual inspection and hydrophone measurements. The oscillation frequency is not affected by cavitation because it does not occur inside the oscillators. The spectral information obtained with the hydrophone provide a reliable indicator for the onset of cavitation at the exit. The performance of the fluidic oscillators for separation control on a bluff body does not seem to be affected by the presence of cavitation. The thrust exerted by an array of fluidic oscillators with water as the working fluid is measured to be even larger than theoretically estimated values. The second part of the presented work compares the performance of fluidic oscillators for separation control in water with previous results in air. The array of fluidic oscillators is installed into the rear end of a bluff body model. The drag improvements based on force balance measurements agree well with previous wind tunnel experiments on the same model. The flow field is examined by pressure measurements and with particle image velocimetry. Similar performance and flow field characteristics are observed in both water and air.

Analysis of the low-level seismicity along the Southern Indian Ocean spreading ridges recorded by the OHASISBIO array of hydrophones in 2012

NASA Astrophysics Data System (ADS)

Tsang-Hin-Sun, Eve; Royer, Jean-Yves; Sukhovich, Alexey; Perrot, Julie

2014-05-01

Arrays of autonomous hydrophones (AUHs) proved to be a very valuable tool for monitoring the seismic activity of mid-ocean ridges. AUHs take advantage of the ocean acoustic properties to detect many low-magnitude underwater earthquakes undetected by land-based stations. This allows for a significant improvement in the magnitude completeness level of seismic catalogs in remote oceanic areas. This study presents some results from the deployment of the OHASISBIO array comprising 7 AUHs deployed in the southern Indian Ocean. The source of acoustic events, i.e. site where - conversion from seismic to acoustic waves occur and proxy to epicenters for shallow earthquakes - can be precisely located within few km, inside the AUH array. The distribution of the uncertainties in the locations and time-origins shows that the OHASISBIO array reliably covers a wide region encompassing the Indian Ocean triple junction and large extent of the three mid-oceanic Indian spreading ridges, from 52°E to 80°E and from 25°S to 40°S. During its one year long deployment in 2012 and in this area the AUH array recorded 1670 events, while, for the same period, land-based networks only detected 470 events. A comparison of the background seismicity along the South-east (SEIR) and South-west (SWIR) Indian ridges suggests that the microseismicity, even over a year period, could be representative of the steady-state of stress along the SEIR and SWIR; this conclusion is based on very high Spearman's correlations between our one-year long AUH catalog and teleseismic catalogs over nearly 40 years. Seismicity along the ultra-slow spreading SWIR is regularly distributed in space and time, along spreading segments and transform faults, whereas the intermediate spreading SEIR diplays clusters of events in the vicinity of some transform faults or near specific geological structures such as the St-Paul and Amsterdam hotspot. A majority of these clusters seem to be related to magmatic processes, such as dyke intrusion or propagation. The analysis of mainshock-aftershock sequences reveals that flew clusters fit a modified Omori law, non-withstanding of their location (on transform faults or not), reflecting complex rupture mechanisms along both spreading ridges.

Correction for frequency-dependent hydrophone response to nonlinear pressure waves using complex deconvolution and rarefactional filtering: application with fiber optic hydrophones.

PubMed

Wear, Keith; Liu, Yunbo; Gammell, Paul M; Maruvada, Subha; Harris, Gerald R

2015-01-01

Nonlinear acoustic signals contain significant energy at many harmonic frequencies. For many applications, the sensitivity (frequency response) of a hydrophone will not be uniform over such a broad spectrum. In a continuation of a previous investigation involving deconvolution methodology, deconvolution (implemented in the frequency domain as an inverse filter computed from frequency-dependent hydrophone sensitivity) was investigated for improvement of accuracy and precision of nonlinear acoustic output measurements. Timedelay spectrometry was used to measure complex sensitivities for 6 fiber-optic hydrophones. The hydrophones were then used to measure a pressure wave with rich harmonic content. Spectral asymmetry between compressional and rarefactional segments was exploited to design filters used in conjunction with deconvolution. Complex deconvolution reduced mean bias (for 6 fiber-optic hydrophones) from 163% to 24% for peak compressional pressure (p+), from 113% to 15% for peak rarefactional pressure (p-), and from 126% to 29% for pulse intensity integral (PII). Complex deconvolution reduced mean coefficient of variation (COV) (for 6 fiber optic hydrophones) from 18% to 11% (p+), 53% to 11% (p-), and 20% to 16% (PII). Deconvolution based on sensitivity magnitude or the minimum phase model also resulted in significant reductions in mean bias and COV of acoustic output parameters but was less effective than direct complex deconvolution for p+ and p-. Therefore, deconvolution with appropriate filtering facilitates reliable nonlinear acoustic output measurements using hydrophones with frequency-dependent sensitivity.

Vessel Noise Affects Beaked Whale Behavior: Results of a Dedicated Acoustic Response Study

PubMed Central

Pirotta, Enrico; Milor, Rachael; Quick, Nicola; Moretti, David; Di Marzio, Nancy; Tyack, Peter; Boyd, Ian; Hastie, Gordon

2012-01-01

Some beaked whale species are susceptible to the detrimental effects of anthropogenic noise. Most studies have concentrated on the effects of military sonar, but other forms of acoustic disturbance (e.g. shipping noise) may disrupt behavior. An experiment involving the exposure of target whale groups to intense vessel-generated noise tested how these exposures influenced the foraging behavior of Blainville’s beaked whales (Mesoplodon densirostris) in the Tongue of the Ocean (Bahamas). A military array of bottom-mounted hydrophones was used to measure the response based upon changes in the spatial and temporal pattern of vocalizations. The archived acoustic data were used to compute metrics of the echolocation-based foraging behavior for 16 targeted groups, 10 groups further away on the range, and 26 non-exposed groups. The duration of foraging bouts was not significantly affected by the exposure. Changes in the hydrophone over which the group was most frequently detected occurred as the animals moved around within a foraging bout, and their number was significantly less the closer the whales were to the sound source. Non-exposed groups also had significantly more changes in the primary hydrophone than exposed groups irrespective of distance. Our results suggested that broadband ship noise caused a significant change in beaked whale behavior up to at least 5.2 kilometers away from the vessel. The observed change could potentially correspond to a restriction in the movement of groups, a period of more directional travel, a reduction in the number of individuals clicking within the group, or a response to changes in prey movement. PMID:22880022

Detection Performance of Horizontal Linear Hydrophone Arrays in Shallow Water.

DTIC Science & Technology

1980-12-15

random phase G gain G angle interval covariance matrix h processor vector H matrix matched filter; generalized beamformer I unity matrix 4 SACLANTCEN SR...omnidirectional sensor is h*Ph P G = - h [Eq. 47] G = h* Q h P s The following two sections evaluate a few examples of application of the OLP. Following the...At broadside the signal covariance matrix reduces to a dyadic: P 󈧬 s s*;therefore, the gain (e.g. Eq. 37) becomes tr(H* P H) Pn * -1 Q -1 Pn G ~OQp

Biological and Behavioral Response Studies of Marine Mammals in Southern California, 2011 (SOCAL-11)

DTIC Science & Technology

2012-09-01

Hildebrand, C. Kyburg, R. Carlson, T. Yack, and J. Barlow ) EXECUTIVE SUMMARY PROJECT OBJECTIVES METHODOLOGY AND FOCAL SPECIES SOCAL-11...HYDROPHONE ARRAY. ( Tina M. Yack, Shannon Coates, Jay Barlow , John Calambokidis, Annie Douglas, and Shannon Rankin) INTRODUCTION MATERIALS AND...E. Falcone, G. Schorr, A. Douglas,  A. Stimpert, J. Hildebrand, C. Kyburg, R. Carlson, T. Yack, J.  Barlow        SOCAL‐11 PROJECT REPORT  2

An interferometric fiber optic hydrophone with large upper limit of dynamic range

NASA Astrophysics Data System (ADS)

Zhang, Lei; Kan, Baoxi; Zheng, Baichao; Wang, Xuefeng; Zhang, Haiyan; Hao, Liangbin; Wang, Hailiang; Hou, Zhenxing; Yu, Wenpeng

2017-10-01

Interferometric fiber optic hydrophone based on heterodyne detection is used to measure the missile dropping point in the sea. The signal caused by the missile dropping in the water will be too large to be detected, so it is necessary to boost the upper limit of dynamic range (ULODR) of fiber optic hydrophone. In this article we analysis the factors which influence the ULODR of fiber optic hydrophone based on heterodyne detection, the ULODR is decided by the sampling frequency fsam and the heterodyne frequency Δf. The sampling frequency and the heterodyne frequency should be satisfied with the Nyquist sampling theorem which fsam will be two times larger than Δf, in this condition the ULODR is depended on the heterodyne frequency. In order to enlarge the ULODR, the Nyquist sampling theorem was broken, and we proposed a fiber optic hydrophone which the heterodyne frequency is larger than the sampling frequency. Both the simulation and experiment were done in this paper, the consequences are similar: When the sampling frequency is 100kHz, the ULODR of large heterodyne frequency fiber optic hydrophone is 2.6 times larger than that of the small heterodyne frequency fiber optic hydrophone. As the heterodyne frequency is larger than the sampling frequency, the ULODR is depended on the sampling frequency. If the sampling frequency was set at 2MHz, the ULODR of fiber optic hydrophone based on heterodyne detection will be boosted to 1000rad at 1kHz, and this large heterodyne fiber optic hydrophone can be applied to locate the drop position of the missile in the sea.

Ultrasonic fingerprint sensor using a piezoelectric micromachined ultrasonic transducer array integrated with complementary metal oxide semiconductor electronics

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

Lu, Y.; Fung, S.; Wang, Q.

2015-06-29

This paper presents an ultrasonic fingerprint sensor based on a 24 × 8 array of 22 MHz piezoelectric micromachined ultrasonic transducers (PMUTs) with 100 μm pitch, fully integrated with 180 nm complementary metal oxide semiconductor (CMOS) circuitry through eutectic wafer bonding. Each PMUT is directly bonded to a dedicated CMOS receive amplifier, minimizing electrical parasitics and eliminating the need for through-silicon vias. The array frequency response and vibration mode-shape were characterized using laser Doppler vibrometry and verified via finite element method simulation. The array's acoustic output was measured using a hydrophone to be ∼14 kPa with a 28 V input, in reasonable agreement with predication from analyticalmore » calculation. Pulse-echo imaging of a 1D steel grating is demonstrated using electronic scanning of a 20 × 8 sub-array, resulting in 300 mV maximum received amplitude and 5:1 contrast ratio. Because the small size of this array limits the maximum image size, mechanical scanning was used to image a 2D polydimethylsiloxane fingerprint phantom (10 mm × 8 mm) at a 1.2 mm distance from the array.« less

Coda-wave and ambient noise interferometry using an offset vertical array at Iwanuma site, northeast Japan

NASA Astrophysics Data System (ADS)

Minami, K.; Yamamoto, M.; Nishimura, T.; Nakahara, H.; Shiomi, K.

2013-12-01

Seismic interferometry using vertical borehole arrays is a powerful tool to estimate the shallow subsurface structure and its time lapse changes. However, the wave fields surrounding borehole arrays are non-isotropic due to the existence of ground surface and non-uniform distribution of sources, and do not meet the requirements of the seismic interferometry in a strict sense. In this study, to examine differences between wave fields of coda waves and ambient noise, and to estimate their effects on the results of seismic interferometry, we conducted a temporal seismic experiment using zero-offset and offset vertical arrays. We installed two 3-components seismometers (hereafter called Surface1 and Surface2) at the ground surface in the vicinity of NIED Iwanuma site (Miyagi Pref., Japan). Surface1 is placed just above the Hi-net downhole seismometer whose depth is 101 m, and Surface2 is placed 70 m away from Surface1. To extract the wave propagation between these 3 seismometers, we compute the cross-correlation functions (CCFs) of coda-wave and ambient noise for each pair of the zero-offset vertical (Hi-net-Surface1), finite-offset vertical (Hi-net-Surface2), and horizontal (Surface1-Surface2) arrays. We use the frequency bands of 4-8, 8-16 Hz in the CCF computation. The characteristics of obtained CCFs are summarized as follows; (1) in all frequency bands, the peak lag times of CCFs from coda waves are almost the same between the vertical and offset-vertical arrays irrespective of different inter-station distance, and those for the horizontal array are around 0 s. (2) the peak lag times of CCFs from ambient noise show slight differences, that is, those obtained from the vertical array are earlier than those from the offset-vertical array, and those from the horizontal array are around 0.05 s. (3) the peak lag times of CCFs for the vertical array obtained from ambient noise analyses are earlier than those from the coda-wave analyses. These results indicate that wave fields of coda-wave are mainly composed of vertically propagating waves, while those of ambient noise are composed of both vertically and horizontally propagating waves. To explain these characteristics of the CCFs obtained from different wave fields, we conducted a numerical simulation of interferometry based on the concept of stationary phase. Here, we assume isotropic upward incidence of SV-wave into a homogeneous half-space, and compute CCFs for the zero-offset and finite-offset vertical arrays by taking into account the reflection and conversion of P-SV waves at the free surface. Due to the effectively non-isotropic wave field, the simulated CCF for the zero-offset vertical array shows slight delay in peak lag time and its amplitudes decrease in the acausal part. On the other hand, the simulated CCF for finite-offset vertical array shows amplitude decrease and no peak lag time shift. These results are consistent with the difference in peak lag times obtained from coda-wave and ambient noise analyses. Our observations and theoretical consideration suggest that the careful consideration of wave fields is important in the application of seismic interferometry to borehole array data.

Preliminary Results from an Hydroacoustic Experiment in the Indian Ocean

NASA Astrophysics Data System (ADS)

Royer, J.; Dziak, R. P.; Delatre, M.; Brachet, C.; Haxel, J. H.; Matsumoto, H.; Goslin, J.; Brandon, V.; Bohnenstiehl, D. R.; Guinet, C.; Samaran, F.

2008-12-01

We report initial results from a 14-month hydroacoustic experiment in the Indian Ocean conducted by CNRS/University of Brest and NOAA/Oregon State University. The objective was to monitor the low-level seismic activity associated with the three contrasting spreading ridges and deforming zones in the Indian Ocean. Three autonomous hydrophones, moored in the SOFAR channel, were deployed in October 2006 and recovered early 2008 by R/V Marion Dufresne, in the Madagascar Basin, and northeast and southwest of Amsterdam Island, complementing the two permanent hydroacoustic stations of the Comprehensive nuclear-Test-Ban Treaty Organization (CTBTO) located near Diego Garcia Island and off Cape Leeuwin. Our temporary network detected more than 2000 events. Inside the array, we located 592 events (compared to 49 in the NEIC earthquake catalog) with location errors less than 5 km and time error less than 2s. The hydrophone array detected on average 5 to 40 times more events per month than land-based networks. First-order observations indicate that hydroacoustic seismicity along the Southeast Indian ridge (SEIR) occurs predominantly along the transform faults. The Southwest Indian Ridge exhibits some periodicity in earthquake activity between adjacent ridge segments. Two large tectonic/volcanic earthquake swarms are observed along the Central Indian Ridge (near the triple junction) in September and December 2007. Moreover, many off ridge-axis events are also observed both south and north of the SEIR axis. Improved localization using the CTBTO records will help refine these preliminary results and further investigate extended volcanic sequences along the SEIR east of 80°E and other events outside of the temporary array. The records also display numerous vocalizations of baleen whales in the 20-40Hz bandwidth. The calls are attributed to fin whales, Antarctic blue whales and pygmy blue whales of Madagascar and Australian type. Their vocal activity is found to be highly seasonal, occurring mainly from April to October with subspecies variations. This array thus provides a unique data set to improve our understanding of the seismic activity in this region and to establish the occurrence and migration pattern of critically endangered whale species.

High power transcranial beam steering for ultrasonic brain therapy

PubMed Central

Pernot, Mathieu; Aubry, Jean-François; Tanter, Mickaël; Thomas, Jean-Louis; Fink, Mathias

2003-01-01

A sparse phased array is specially designed for non-invasive ultrasound transskull brain therapy. The array is made of 200 single-elements corresponding to a new generation of high power transducers developed in collaboration with Imasonic (Besançon, France). Each element has a surface of 0.5cm2 and works at 0.9 MHz central frequency with a maximum 20W.cm−2 intensity on the transducer surface. In order to optimize the steering capabilities of the array, several transducers distributions on a spherical surface are simulated: hexagonal, annular, and quasi-random distributions. Using a quasi-random distribution significantly reduces the grating lobes. Furthermore, the simulations show the capability of the quasi-random array to electronically move the focal spot in the vicinity of the geometrical focus (up to +/− 15 mm). Based on the simulation study, the array is constructed and tested. The skull aberrations are corrected by using a time reversal mirror with amplitude correction achieved thanks to an implantable hydrophone, and a sharp focus is obtained through a human skull. Several lesions are induced in fresh liver and brain samples through human skulls, demonstrating the accuracy and the steering capabilities of the system. PMID:12974575

High power transcranial beam steering for ultrasonic brain therapy

NASA Astrophysics Data System (ADS)

Pernot, M.; Aubry, J.-F.; Tanter, M.; Thomas, J.-L.; Fink, M.

2003-08-01

A sparse phased array is specially designed for non-invasive ultrasound transskull brain therapy. The array is made of 200 single elements corresponding to a new generation of high power transducers developed in collaboration with Imasonic (Besançon, France). Each element has a surface of 0.5 cm2 and works at 0.9 MHz central frequency with a maximum 20 W cm-2 intensity on the transducer surface. In order to optimize the steering capabilities of the array, several transducer distributions on a spherical surface are simulated: hexagonal, annular and quasi-random distributions. Using a quasi-random distribution significantly reduces the grating lobes. Furthermore, the simulations show the capability of the quasi-random array to electronically move the focal spot in the vicinity of the geometrical focus (up to +/-15 mm). Based on the simulation study, the array is constructed and tested. The skull aberrations are corrected by using a time reversal mirror with amplitude correction achieved thanks to an implantable hydrophone, and a sharp focus is obtained through a human skull. Several lesions are induced in fresh liver and brain samples through human skulls, demonstrating the accuracy and the steering capabilities of the system.

Broadband spectra of seismic survey air-gun emissions, with reference to dolphin auditory thresholds.

PubMed

Goold, J C; Fish, P J

1998-04-01

Acoustic emissions from a 2120 cubic in air-gun array were recorded through a towed hydrophone assembly during an oil industry 2-D seismic survey off the West Wales Coast of the British Isles. Recorded seismic pulses were sampled, calibrated, and analyzed post-survey to investigate power levels of the pulses in the band 200 Hz-22 kHz at 750-m, 1-km, 2.2-km, and 8-km range from source. At 750-m range from source, seismic pulse power at the 200-Hz end of the spectrum was 140 dB re: 1 microPa2/Hz, and at the 20-kHz end of the spectrum seismic pulse power was 90 dB re: 1 microPa2/Hz. Although the background noise levels of the seismic recordings were far in excess of ambient, due to the proximity of engine, propeller, and flow sources of the ship towing the hydrophone, seismic power dominated the entire recorded bandwidth of 200 Hz-22 kHz at ranges of up to 2 km from the air-gun source. Even at 8-km range seismic power was still clearly in excess of the high background noise levels up to 8 kHz. Acoustic observations of common dolphins during preceding seismic surveys suggest that these animals avoided the immediate vicinity of the air-gun array while firing was in progress, i.e., localized disturbance occurred during seismic surveying. Although a general pattern of localized disturbance is suggested, one specific observation revealed that common dolphins were able to tolerate the seismic pulses at 1-km range from the air-gun array. Given the high broadband seismic pulse power levels across the entire recorded bandwidth, and known auditory thresholds for several dolphin species, we consider such seismic emissions to be clearly audible to dolphins across a bandwidth of tens on kilohertz, and at least out to 8-km range.

Working Towards Deep-Ocean Temperature Monitoring by Studying the Acoustic Ambient Noise Field in the South Pacific Ocean

NASA Astrophysics Data System (ADS)

Sambell, K.; Evers, L. G.; Snellen, M.

2017-12-01

Deriving the deep-ocean temperature is a challenge. In-situ observations and satellite observations are hardly applicable. However, knowledge about changes in the deep ocean temperature is important in relation to climate change. Oceans are filled with low-frequency sound waves created by sources such as underwater volcanoes, earthquakes and seismic surveys. The propagation of these sound waves is temperature dependent and therefore carries valuable information that can be used for temperature monitoring. This phenomenon is investigated by applying interferometry to hydroacoustic data measured in the South Pacific Ocean. The data is measured at hydrophone station H03 which is part of the International Monitoring System (IMS). This network consists of several stations around the world and is in place for the verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). The station consists of two arrays located north and south of Robinson Crusoe Island separated by 50 km. Both arrays consist of three hydrophones with an intersensor distance of 2 km located at a depth of 1200 m. This depth is in range of the SOFAR channel. Hydroacoustic data measured at the south station is cross-correlated for the time period 2014-2017. The results are improved by applying one-bit normalization as a preprocessing step. Furthermore, beamforming is applied to the hydroacoustic data in order to characterize ambient noise sources around the array. This shows the presence of a continuous source at a backazimuth between 180 and 200 degrees throughout the whole time period, which is in agreement with the results obtained by cross-correlation. Studies on source strength show a seasonal dependence. This is an indication that the sound is related to acoustic activity in Antarctica. Results on this are supported by acoustic propagation modeling. The normal mode technique is used to study the sound propagation from possible source locations towards station H03.

Improvements to Passive Acoustic Tracking Methods for Marine Mammal Monitoring

DTIC Science & Technology

2015-09-30

applicable for highly directional sources). The MTOA+RL method was applied to a dolphin click sequence from a single hydrophone dataset. Using arrival...arrival and 3 multipath arrivals for a dolphin click recorded on a single seafloor-mounted hydrophone. The hydrophone [described in Fedenczuk et al

HIFU Transducer Characterization Using a Robust Needle Hydrophone

NASA Astrophysics Data System (ADS)

Howard, Samuel M.; Zanelli, Claudio I.

2007-05-01

A robust needle hydrophone has been developed for HIFU transducer characterization and reported on earlier. After a brief review of the hydrophone design and performance, we demonstrate its use to characterize a 1.5 MHz, 10 cm diameter, F-number 1.5 spherically focused source driven to exceed an intensity of 1400 W/cm2at its focus. Quantitative characterization of this source at high powers is assisted by deconvolving the hydrophone's calibrated frequency response in order to accurately reflect the contribution of harmonics generated by nonlinear propagation in the water testing environment. Results are compared to measurements with a membrane hydrophone at 0.3% duty cycle and to theoretical calculations, using measurements of the field at the source's radiating surface as input to a numerical solution of the KZK equation.

The relationship among oceanography, prey fields, and beaked whale foraging habitat in the Tongue of the Ocean.

PubMed

Hazen, Elliott L; Nowacek, Douglas P; St Laurent, Louis; Halpin, Patrick N; Moretti, David J

2011-04-27

Beaked whales, specifically Blainville's (Mesoplodon densirostris) and Cuvier's (Ziphius cavirostris), are known to feed in the Tongue of the Ocean, Bahamas. These whales can be reliably detected and often localized within the Atlantic Undersea Test and Evaluation Center (AUTEC) acoustic sensor system. The AUTEC range is a regularly spaced bottom mounted hydrophone array covering >350 nm(2) providing a valuable network to record anthropogenic noise and marine mammal vocalizations. Assessments of the potential risks of noise exposure to beaked whales have historically occurred in the absence of information about the physical and biological environments in which these animals are distributed. In the fall of 2008, we used a downward looking 38 kHz SIMRAD EK60 echosounder to measure prey scattering layers concurrent with fine scale turbulence measurements from an autonomous turbulence profiler. Using an 8 km, 4-leaf clover sampling pattern, we completed a total of 7.5 repeat surveys with concurrently measured physical and biological oceanographic parameters, so as to examine the spatiotemporal scales and relationships among turbulence levels, biological scattering layers, and beaked whale foraging activity. We found a strong correlation among increased prey density and ocean vertical structure relative to increased click densities. Understanding the habitats of these whales and their utilization patterns will improve future models of beaked whale habitat as well as allowing more comprehensive assessments of exposure risk to anthropogenic sound.

Sequential Bayesian geoacoustic inversion for mobile and compact source-receiver configuration.

PubMed

Carrière, Olivier; Hermand, Jean-Pierre

2012-04-01

Geoacoustic characterization of wide areas through inversion requires easily deployable configurations including free-drifting platforms, underwater gliders and autonomous vehicles, typically performing repeated transmissions during their course. In this paper, the inverse problem is formulated as sequential Bayesian filtering to take advantage of repeated transmission measurements. Nonlinear Kalman filters implement a random-walk model for geometry and environment and an acoustic propagation code in the measurement model. Data from MREA/BP07 sea trials are tested consisting of multitone and frequency-modulated signals (bands: 0.25-0.8 and 0.8-1.6 kHz) received on a shallow vertical array of four hydrophones 5-m spaced drifting over 0.7-1.6 km range. Space- and time-coherent processing are applied to the respective signal types. Kalman filter outputs are compared to a sequence of global optimizations performed independently on each received signal. For both signal types, the sequential approach is more accurate but also more efficient. Due to frequency diversity, the processing of modulated signals produces a more stable tracking. Although an extended Kalman filter provides comparable estimates of the tracked parameters, the ensemble Kalman filter is necessary to properly assess uncertainty. In spite of mild range dependence and simplified bottom model, all tracked geoacoustic parameters are consistent with high-resolution seismic profiling, core logging P-wave velocity, and previous inversion results with fixed geometries.

Circadian Rhythm of Ambient Noise Off the Southeast Coast of India

NASA Astrophysics Data System (ADS)

Kannan, R.; Latha, G.; Prashanthi Devi, M.

An ambient noise system consisting of a vertical linear hydrophone array was deployed in the shallow waters off Chennai, southeast coast of India from 1 August to 16 September 2013 to record ambient ocean noise of frequencies up to 10kHz. Biological sounds, which are broadband, short duration signals resulting from Terapon theraps, a native species, are a prominent feature of the ocean soundscape. Terapon activity peaks at 8pm and 11pm, and its presence is not observed after 12 midnight in both the months. In the other period, the ambient noise fluctuation is due to wind and vessel traffic. Hence, the present study focuses on the description of the ambient noise fluctuation over two 12h periods, i.e., 12 midnight-12 noon considered as period I, and 12 noon-12 midnight as period II in order to show the circadian rhythm of ambient noise. In this study area, Terapon vocalization reached 25dB above the ambient noise level and it dominates the short-term spectra records in the 0.4-4kHz range. All Terapon signals had daily patterns of sound production with highest levels of activity after dusk during the study period. The result shows that the circadian rhythm of ambient noise is mainly of biological sound generated by Terapon and it is reported first time in the shallow waters off the southeast coast of India.

The Relationship among Oceanography, Prey Fields, and Beaked Whale Foraging Habitat in the Tongue of the Ocean

PubMed Central

Hazen, Elliott L.; Nowacek, Douglas P.; St. Laurent, Louis; Halpin, Patrick N.; Moretti, David J.

2011-01-01

Beaked whales, specifically Blainville's (Mesoplodon densirostris) and Cuvier's (Ziphius cavirostris), are known to feed in the Tongue of the Ocean, Bahamas. These whales can be reliably detected and often localized within the Atlantic Undersea Test and Evaluation Center (AUTEC) acoustic sensor system. The AUTEC range is a regularly spaced bottom mounted hydrophone array covering >350 nm2 providing a valuable network to record anthropogenic noise and marine mammal vocalizations. Assessments of the potential risks of noise exposure to beaked whales have historically occurred in the absence of information about the physical and biological environments in which these animals are distributed. In the fall of 2008, we used a downward looking 38 kHz SIMRAD EK60 echosounder to measure prey scattering layers concurrent with fine scale turbulence measurements from an autonomous turbulence profiler. Using an 8 km, 4-leaf clover sampling pattern, we completed a total of 7.5 repeat surveys with concurrently measured physical and biological oceanographic parameters, so as to examine the spatiotemporal scales and relationships among turbulence levels, biological scattering layers, and beaked whale foraging activity. We found a strong correlation among increased prey density and ocean vertical structure relative to increased click densities. Understanding the habitats of these whales and their utilization patterns will improve future models of beaked whale habitat as well as allowing more comprehensive assessments of exposure risk to anthropogenic sound. PMID:21556355

A rapid and non-invasive method for measuring the peak positive pressure of HIFU fields by a laser beam.

PubMed

Wang, Hua; Zeng, Deping; Chen, Ziguang; Yang, Zengtao

2017-04-12

Based on the acousto-optic interaction, we propose a laser deflection method for rapidly, non-invasively and quantitatively measuring the peak positive pressure of HIFU fields. In the characterization of HIFU fields, the effect of nonlinear propagation is considered. The relation between the laser deflection length and the peak positive pressure is derived. Then the laser deflection method is assessed by comparing it with the hydrophone method. The experimental results show that the peak positive pressure measured by laser deflection method is little higher than that obtained by the hydrophone, confirming that they are in reasonable agreement. Considering that the peak pressure measured by hydrophones is always underestimated, the laser deflection method is assumed to be more accurate than the hydrophone method due to the absence of the errors in hydrophone spatial-averaging measurement and the influence of waveform distortion on hydrophone corrections. Moreover, noting that the Lorentz formula still remains applicable to high-pressure environments, the laser deflection method exhibits a great potential for measuring HIFU field under high-pressure amplitude. Additionally, the laser deflection method provides a rapid way for measuring the peak positive pressure, without the scan time, which is required by the hydrophones.

A nonlinear propagation model-based phase calibration technique for membrane hydrophones.

PubMed

Cooling, Martin P; Humphrey, Victor F

2008-01-01

A technique for the phase calibration of membrane hydrophones in the frequency range up to 80 MHz is described. This is achieved by comparing measurements and numerical simulation of a nonlinearly distorted test field. The field prediction is obtained using a finite-difference model that solves the nonlinear Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation in the frequency domain. The measurements are made in the far field of a 3.5 MHz focusing circular transducer in which it is demonstrated that, for the high drive level used, spatial averaging effects due to the hydrophone's finite-receive area are negligible. The method provides a phase calibration of the hydrophone under test without the need for a device serving as a phase response reference, but it requires prior knowledge of the amplitude sensitivity at the fundamental frequency. The technique is demonstrated using a 50-microm thick bilaminar membrane hydrophone, for which the results obtained show functional agreement with predictions of a hydrophone response model. Further validation of the results is obtained by application of the response to the measurement of the high amplitude waveforms generated by a modern biomedical ultrasonic imaging system. It is demonstrated that full deconvolution of the calculated complex frequency response of a nonideal hydrophone results in physically realistic measurements of the transmitted waveforms.

Tracking blue whales in the eastern tropical Pacific with an ocean-bottom seismometer and hydrophone array.

PubMed

Dunn, Robert A; Hernandez, Olga

2009-09-01

Low frequency northeastern Pacific blue whale calls were recorded near the northern East Pacific Rise (9 degrees N latitude) on 25 ocean-bottom-mounted hydrophones and three-component seismometers during a 5-day period (November 22-26, 1997). Call types A, B, C, and D were identified; the most common pattern being approximately 130-135 s repetitions of the AB sequence that, for any individual whale, persisted for hours. Up to eight individual blue whales were recorded near enough to the instruments to determine their locations and were tracked call-by-call using the B components of the calls and a Bayesian inversion procedure. For four of these eight whales, the entire call sequences and swim tracks were determined for 20-26-h periods; the other whales were tracked for much shorter periods. The eight whales moved into the area during a period of airgun activity conducted by the academic seismic ship R/V Maurice Ewing. The authors examined the whales' locations and call characteristics with respect to the periods of airgun activity. Although the data do not permit a thorough investigation of behavioral responses, no correlation in vocalization or movement with airgun activity was observed.

Measurement of Complex Sensitivity of Data Channels in Hydrophone Line Array at Very Low Frequency

DTIC Science & Technology

2015-03-25

minimum frequency at which the acoustic projectors commonly used for acoustic calibrations can transmit a useful acoustic signal. Dkt . No. 300041...Crane Water Surface 10 inch move Dkt . No. 300041 Application No. ?? REPLACEMENT SHEET? 1st DRAFT FIG. 2 62 60 66 64 70 12 66 68 2 1 11 1 12 12 2 Dkt . No...5-5 0.6 0.8 1.0 = 51ms = 0.86 Dkt . No. 300041 Application No. ?? REPLACEMENT SHEET? 1st DRAFT FIG. 4 0 1 210 10 10 -10 -5 0 5 M ag ni tu de ( dB

Killer whales (Orcinus orca) produce ultrasonic whistles.

PubMed

Samarra, Filipa I P; Deecke, Volker B; Vinding, Katja; Rasmussen, Marianne H; Swift, René J; Miller, Patrick J O

2010-11-01

This study reports that killer whales, the largest dolphin, produce whistles with the highest fundamental frequencies ever reported in a delphinid. Using wide-band acoustic sampling from both animal-attached (Dtag) and remotely deployed hydrophone arrays, ultrasonic whistles were detected in three Northeast Atlantic populations but not in two Northeast Pacific populations. These results are inconsistent with analyses suggesting a correlation of maximum frequency of whistles with body size in delphinids, indicate substantial intraspecific variation in whistle production in killer whales, and highlight the importance of appropriate acoustic sampling techniques when conducting comparative analyses of sound repertoires.

A 3D approximate maximum likelihood localization solver

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

2016-09-23

A robust three-dimensional solver was needed to accurately and efficiently estimate the time sequence of locations of fish tagged with acoustic transmitters and vocalizing marine mammals to describe in sufficient detail the information needed to assess the function of dam-passage design alternatives and support Marine Renewable Energy. An approximate maximum likelihood solver was developed using measurements of time difference of arrival from all hydrophones in receiving arrays on which a transmission was detected. Field experiments demonstrated that the developed solver performed significantly better in tracking efficiency and accuracy than other solvers described in the literature.

A comparison of light spot hydrophone and fiber optic probe hydrophone for lithotripter field characterization.

PubMed

Smith, N; Sankin, G N; Simmons, W N; Nanke, R; Fehre, J; Zhong, P

2012-01-01

The performance of a newly developed light spot hydrophone (LSHD) in lithotripter field characterization was compared to that of the fiber optic probe hydrophone (FOPH). Pressure waveforms produced by a stable electromagnetic shock wave source were measured by the LSHD and FOPH under identical experimental conditions. In the low energy regime, focus and field acoustic parameters matched well between the two hydrophones. At clinically relevant high energy settings for shock wave lithotripsy, the measured leading compressive pressure waveforms matched closely with each other. However, the LSHD recorded slightly larger |P_| (p < 0.05) and secondary peak compressive pressures (p < 0.01) than the FOPH, leading to about 20% increase in total acoustic pulse energy calculated in a 6 mm radius around the focus (p = 0.06). Tensile pulse durations deviated ~5% (p < 0.01) due to tensile wave shortening from cavitation activity using the LSHD. Intermittent compression spikes and laser light reflection artifacts have been correlated to bubble activity based on simultaneous high-speed imaging analysis. Altogether, both hydrophones are adequate for lithotripter field characterization as specified by the international standard IEC 61846.

Vertical directivities of seismic arrays on the ground surface

NASA Astrophysics Data System (ADS)

Shiraishi, H.; Asanuma, H.

2012-12-01

Microtremor survey method (MSM) is a technique to estimate subsurface velocity structures by inverting phase velocities of the surface waves in the microtremors. We can explorer the S-wave velocity structures at significantly lower expenses by the MSM than the conventional geophysical techniques because of its passive nature. Coherent waves across an array are identified in the MSM, and, therefore, all the existing velocity inversion methods have been deduced under an implicit assumption of horizontal velocity structure. However, it is expected that the development of the 3D inversion theory would drastically enhance applicability and reliability of the MSM. We, hence, investigated the characteristics of vertical directivities of the arrays deployed on the ground surface as an initial step for deriving the 3D MSM. We have firstly examined the response of an elemental two sensor array to which plane waves propagates from the deep crust with a certain angle of incident, and then examined the characteristics of several types of arrays, including triangular and circular arrays to clarify the characteristics of practical arrays. Real part of the complex coherence function, which has been derived to evaluate coherence of the Rayleigh wave between sensors for plane waves (Shiraishi et al., 2006), has been applied for this investigation. Our results showed that the directivity varies according to a parameter kr ( k : wave number, r : separation of the sensors ). A vertical directivity of two sensor array at kr = π shows a rotationally-symmetrical shape (Figure (a)). In contrast, an equilateral triangle array has a conspicuous directivity toward the vertical direction (cf. Figure (b)). This divergence suggests that the shape of the vertical directivity significantly depend on the geometry, and a sharp directivity toward just beneath the array can be realized by designing the vertical directivity. We concluded from this study that 3D MSM is feasible and further study to investigate measurement and processing theories will be made by the authors. An example of the vertical directivity at kr=π. Red circles represent the sensors.

Using a heterodyne vibrometer in combination with pulse excitation for primary calibration of ultrasonic hydrophones in amplitude and phase

NASA Astrophysics Data System (ADS)

Weber, Martin; Wilkens, Volker

2017-08-01

A high-frequency vibrometer was used with ultrasonic pulse excitation in order to perform a primary hydrophone calibration. This approach enables the simultaneous characterization of the amplitude and phase transfer characteristic of ultrasonic hydrophones. The method allows a high frequency resolution in a considerably short time for the measurement. Furthermore, the uncertainty contributions of this approach were investigated and quantified. A membrane hydrophone was calibrated and the uncertainty budget for this measurement was determined. The calibration results are presented up to 70~\\text{MHz} . The measurement results show good agreement with the results obtained by sinusoidal burst excitation through the use of the vibrometer and by a homodyne laser interferometer, with RMS deviation of approximately 3% -4% in the frequency range from 1 to 60~\\text{MHz} . Further hydrophones were characterized up to 100~\\text{MHz} with this procedure to demonstrate the suitability for very high frequency calibration.

Beam steering via resonance detuning in coherently coupled vertical cavity laser arrays

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

Johnson, Matthew T., E-mail: matthew.johnson.9@us.af.mil; Siriani, Dominic F.; Peun Tan, Meng

2013-11-11

Coherently coupled vertical-cavity surface-emitting laser arrays offer unique advantages for nonmechanical beam steering applications. We have applied dynamic coupled mode theory to show that the observed temporal phase shift between vertical-cavity surface-emitting array elements is caused by the detuning of their resonant wavelengths. Hence, a complete theoretical connection between the differential current injection into array elements and the beam steering direction has been established. It is found to be a fundamentally unique beam-steering mechanism with distinct advantages in efficiency, compactness, speed, and phase-sensitivity to current.

Sub-1-V-60 nm vertical body channel MOSFET-based six-transistor static random access memory array with wide noise margin and excellent power delay product and its optimization with the cell ratio on static random access memory cell

NASA Astrophysics Data System (ADS)

Ogasawara, Ryosuke; Endoh, Tetsuo

2018-04-01

In this study, with the aim to achieve a wide noise margin and an excellent power delay product (PDP), a vertical body channel (BC)-MOSFET-based six-transistor (6T) static random access memory (SRAM) array is evaluated by changing the number of pillars in each part of a SRAM cell, that is, by changing the cell ratio in the SRAM cell. This 60 nm vertical BC-MOSFET-based 6T SRAM array realizes 0.84 V operation under the best PDP and up to 31% improvement of PDP compared with the 6T SRAM array based on a 90 nm planar MOSFET whose gate length and channel width are the same as those of the 60 nm vertical BC-MOSFET. Additionally, the vertical BC-MOSFET-based 6T SRAM array achieves an 8.8% wider read static noise margin (RSNM), a 16% wider write margin (WM), and an 89% smaller leakage. Moreover, it is shown that changing the cell ratio brings larger improvements of RSNM, WM, and write time in the vertical BC-MOSFET-based 6T SRAM array.

Estimating the location of baleen whale calls using dual streamers to support mitigation procedures in seismic reflection surveys.

PubMed

Abadi, Shima H; Tolstoy, Maya; Wilcock, William S D

2017-01-01

In order to mitigate against possible impacts of seismic surveys on baleen whales it is important to know as much as possible about the presence of whales within the vicinity of seismic operations. This study expands on previous work that analyzes single seismic streamer data to locate nearby calling baleen whales with a grid search method that utilizes the propagation angles and relative arrival times of received signals along the streamer. Three dimensional seismic reflection surveys use multiple towed hydrophone arrays for imaging the structure beneath the seafloor, providing an opportunity to significantly improve the uncertainty associated with streamer-generated call locations. All seismic surveys utilizing airguns conduct visual marine mammal monitoring surveys concurrent with the experiment, with powering-down of seismic source if a marine mammal is observed within the exposure zone. This study utilizes data from power-down periods of a seismic experiment conducted with two 8-km long seismic hydrophone arrays by the R/V Marcus G. Langseth near Alaska in summer 2011. Simulated and experiment data demonstrate that a single streamer can be utilized to resolve left-right ambiguity because the streamer is rarely perfectly straight in a field setting, but dual streamers provides significantly improved locations. Both methods represent a dramatic improvement over the existing Passive Acoustic Monitoring (PAM) system for detecting low frequency baleen whale calls, with ~60 calls detected utilizing the seismic streamers, zero of which were detected using the current R/V Langseth PAM system. Furthermore, this method has the potential to be utilized not only for improving mitigation processes, but also for studying baleen whale behavior within the vicinity of seismic operations.

Estimating the location of baleen whale calls using dual streamers to support mitigation procedures in seismic reflection surveys

PubMed Central

Abadi, Shima H.; Tolstoy, Maya; Wilcock, William S. D.

2017-01-01

In order to mitigate against possible impacts of seismic surveys on baleen whales it is important to know as much as possible about the presence of whales within the vicinity of seismic operations. This study expands on previous work that analyzes single seismic streamer data to locate nearby calling baleen whales with a grid search method that utilizes the propagation angles and relative arrival times of received signals along the streamer. Three dimensional seismic reflection surveys use multiple towed hydrophone arrays for imaging the structure beneath the seafloor, providing an opportunity to significantly improve the uncertainty associated with streamer-generated call locations. All seismic surveys utilizing airguns conduct visual marine mammal monitoring surveys concurrent with the experiment, with powering-down of seismic source if a marine mammal is observed within the exposure zone. This study utilizes data from power-down periods of a seismic experiment conducted with two 8-km long seismic hydrophone arrays by the R/V Marcus G. Langseth near Alaska in summer 2011. Simulated and experiment data demonstrate that a single streamer can be utilized to resolve left-right ambiguity because the streamer is rarely perfectly straight in a field setting, but dual streamers provides significantly improved locations. Both methods represent a dramatic improvement over the existing Passive Acoustic Monitoring (PAM) system for detecting low frequency baleen whale calls, with ~60 calls detected utilizing the seismic streamers, zero of which were detected using the current R/V Langseth PAM system. Furthermore, this method has the potential to be utilized not only for improving mitigation processes, but also for studying baleen whale behavior within the vicinity of seismic operations. PMID:28199400

Migratory behavior of eastern North Pacific gray whales tracked using a hydrophone array

PubMed Central

Helble, Tyler A.; D’Spain, Gerald L.; Weller, David W.; Wiggins, Sean M.; Hildebrand, John A.

2017-01-01

Eastern North Pacific gray whales make one of the longest annual migrations of any mammal, traveling from their summer feeding areas in the Bering and Chukchi Seas to their wintering areas in the lagoons of Baja California, Mexico. Although a significant body of knowledge on gray whale biology and behavior exists, little is known about their vocal behavior while migrating. In this study, we used a sparse hydrophone array deployed offshore of central California to investigate how gray whales behave and use sound while migrating. We detected, localized, and tracked whales for one full migration season, a first for gray whales. We verified and localized 10,644 gray whale M3 calls and grouped them into 280 tracks. Results confirm that gray whales are acoustically active while migrating and their swimming and acoustic behavior changes on daily and seasonal time scales. The seasonal timing of the calls verifies the gray whale migration timing determined using other methods such as counts conducted by visual observers. The total number of calls and the percentage of calls that were part of a track changed significantly over both seasonal and daily time scales. An average calling rate of 5.7 calls/whale/day was observed, which is significantly greater than previously reported migration calling rates. We measured a mean speed of 1.6 m/s and quantified heading, direction, and water depth where tracks were located. Mean speed and water depth remained constant between night and day, but these quantities had greater variation at night. Gray whales produce M3 calls with a root mean square source level of 156.9 dB re 1 μPa at 1 m. Quantities describing call characteristics were variable and dependent on site-specific propagation characteristics. PMID:29084266

Migratory behavior of eastern North Pacific gray whales tracked using a hydrophone array.

PubMed

Guazzo, Regina A; Helble, Tyler A; D'Spain, Gerald L; Weller, David W; Wiggins, Sean M; Hildebrand, John A

2017-01-01

Eastern North Pacific gray whales make one of the longest annual migrations of any mammal, traveling from their summer feeding areas in the Bering and Chukchi Seas to their wintering areas in the lagoons of Baja California, Mexico. Although a significant body of knowledge on gray whale biology and behavior exists, little is known about their vocal behavior while migrating. In this study, we used a sparse hydrophone array deployed offshore of central California to investigate how gray whales behave and use sound while migrating. We detected, localized, and tracked whales for one full migration season, a first for gray whales. We verified and localized 10,644 gray whale M3 calls and grouped them into 280 tracks. Results confirm that gray whales are acoustically active while migrating and their swimming and acoustic behavior changes on daily and seasonal time scales. The seasonal timing of the calls verifies the gray whale migration timing determined using other methods such as counts conducted by visual observers. The total number of calls and the percentage of calls that were part of a track changed significantly over both seasonal and daily time scales. An average calling rate of 5.7 calls/whale/day was observed, which is significantly greater than previously reported migration calling rates. We measured a mean speed of 1.6 m/s and quantified heading, direction, and water depth where tracks were located. Mean speed and water depth remained constant between night and day, but these quantities had greater variation at night. Gray whales produce M3 calls with a root mean square source level of 156.9 dB re 1 μPa at 1 m. Quantities describing call characteristics were variable and dependent on site-specific propagation characteristics.

"Lollipop-shaped" high-sensitivity Microelectromechanical Systems vector hydrophone based on Parylene encapsulation

NASA Astrophysics Data System (ADS)

Liu, Yuan; Wang, Renxin; Zhang, Guojun; Du, Jin; Zhao, Long; Xue, Chenyang; Zhang, Wendong; Liu, Jun

2015-07-01

This paper presents methods of promoting the sensitivity of Microelectromechanical Systems (MEMS) vector hydrophone by increasing the sensing area of cilium and perfect insulative Parylene membrane. First, a low-density sphere is integrated with the cilium to compose a "lollipop shape," which can considerably increase the sensing area. A mathematic model on the sensitivity of the "lollipop-shaped" MEMS vector hydrophone is presented, and the influences of different structural parameters on the sensitivity are analyzed via simulation. Second, the MEMS vector hydrophone is encapsulated through the conformal deposition of insulative Parylene membrane, which enables underwater acoustic monitoring without any typed sound-transparent encapsulation. Finally, the characterization results demonstrate that the sensitivity reaches up to -183 dB (500 Hz 0dB at 1 V/ μPa ), which is increased by more than 10 dB, comparing with the previous cilium-shaped MEMS vector hydrophone. Besides, the frequency response takes on a sensitivity increment of 6 dB per octave. The working frequency band is 20-500 Hz and the concave point depth of 8-shaped directivity is beyond 30 dB, indicating that the hydrophone is promising in underwater acoustic application.

Ultrasonic brain therapy: First trans-skull in vivo experiments on sheep using adaptive focusing

NASA Astrophysics Data System (ADS)

Pernot, Mathieu; Aubry, Jean-Francois; Tanter, Michael; Fink, Mathias; Boch, Anne-Laure; Kujas, Michèle

2004-05-01

A high-power prototype dedicated to trans-skull therapy has been tested in vivo on 20 sheep. The array is made of 200 high-power transducers working at 1-MHz central and is able to reach 260 bars at focus in water. An echographic array connected to a Philips HDI 1000 system has been inserted in the therapeutic array in order to perform real-time monitoring of the treatment. A complete craniotomy has been performed on half of the treated animal models in order to get a reference model. On the other animals, a minimally invasive surgery has been performed thanks to a time-reversal experiment: a hydrophone was inserted at the target inside the brain thanks to a 1-mm2 craniotomy. A time-reversal experiment was then conducted through the skull bone with the therapeutic array to treat the targeted point. For all the animals a specified region around the target was treated thanks to electronic beam steering. Animals were finally divided into three groups and sacrificed, respectively, 0, 1, and 2 weeks after treatment. Finally, histological examination confirmed tissue damage. These in vivo experiments highlight the strong potential of high-power time-reversal technology.

Advanced Unmanned Search System (AUSS) Surface Navigation, Underwater Tracking, and Transponder Network Calibration

DTIC Science & Technology

1992-09-01

5 ENTER PULSE REP PERIOD ................................ 900 ENTER RETURN TO TOP LEVEL C-5 26. SBS1 RECEIVER ----- HYDROPHONE ----- HYDRI ...HYDROPHONE ----- HYDRI PRECISION RETURN 1 LEVEL 29. HEADING INPUT ------ GYRO 1 ------ CONTINUE RANGE GATE OFF ----- FILTER OFF RETURN TO TOP LEVEL 30...700 ENTER RETURN TO TOP LEVEL 12. SBSI RECEIVER ------ HYDROPHONE ------ HYDRI PRECISION RETURN 1 LEVEL 13. HEADING INPUT ------ GYRO 1

Geophysical monitoring of the submerged area of the Campi Flegrei caldera (Southern Italy): experiences and perspectives

NASA Astrophysics Data System (ADS)

Iannaccone, Giovanni; Guardato, Sergio; De Martino, Prospero; Donnarumma, Gian Paolo; Bobbio, Antonella; Chierici, Francesco; Pignagnoli, Luca; Beranzoli, Laura

2016-04-01

The monitoring system of the Campi Flegrei caldera is made up of a dense geophysical network of seismological and geodetic instruments with data acquired and processed at the Monitoring Center of INGV in Naples. As one third of the caldera is covered by the sea, a marine monitoring system has been operating since 2008 in the center of the gulf of Pozzuoli, where the sea depth is about 100 m at ~2.5 km from the coast. The main component of the monitoring system is CUMAS (Cabled Underwater Multidisciplinary Acquisition System), which consists of a sea floor module equipped with geophysical and oceanographic sensors (broad band seismometer, accelerometer, hydrophone, bottom pressure recorder and single point three component water-current meter) and status and control sensors. CUMAS is connected by cable to the top of an elastic beacon buoy equipped with the power supply and data transmission devices. The buoy consists of a float placed below sea level, surrounding and holding a steel pole that supports a turret structure above sea level. The pole, turret and float system are rigidly connected to the ballast on the sea bottom. Thus a GPS installed on the turret can record the vertical sea floor displacement related to the volcanic activity of the area. The GPS has operated since January 2012 with continuous acquisition lasting more than three years and has recorded a cumulative seafloor uplift of about 7-8 cm. The comparison of the pattern of the GPS buoy data with those of the land stations confirms a quasi-symmetrical vertical displacement field of the caldera area. Measurement of vertical sea floor displacement has also been obtained by the analysis of bottom pressure recorder data. These results, in conjunction with the analysis of seismic and hydrophone data, have encouraged us to extend the marine monitoring system with the deployment in the Gulf of Pozzuoli of three new similar systems. We also present preliminary results of the first few months of activity of these new systems.

Ranging bowhead whale calls in a shallow-water dispersive waveguide.

PubMed

Abadi, Shima H; Thode, Aaron M; Blackwell, Susanna B; Dowling, David R

2014-07-01

This paper presents the performance of three methods for estimating the range of broadband (50-500 Hz) bowhead whale calls in a nominally 55-m-deep waveguide: Conventional mode filtering (CMF), synthetic time reversal (STR), and triangulation. The first two methods use a linear vertical array to exploit dispersive propagation effects in the underwater sound channel. The triangulation technique used here, while requiring no knowledge about the propagation environment, relies on a distributed array of directional autonomous seafloor acoustics recorders (DASARs) arranged in triangular grid with 7 km spacing. This study uses simulations and acoustic data collected in 2010 from coastal waters near Kaktovik, Alaska. At that time, a 12-element vertical array, spanning the bottom 63% of the water column, was deployed alongside a distributed array of seven DASARs. The estimated call location-to-array ranges determined from CMF and STR are compared with DASAR triangulation results for 19 whale calls. The vertical-array ranging results are generally within ±10% of the DASAR results with the STR results providing slightly better agreement. The results also indicate that the vertical array can range calls over larger ranges and with greater precision than the particular distributed array discussed here, whenever the call locations are beyond the distributed array boundaries.

High-frequency modulated signals of killer whales (Orcinus orca) in the North Pacific.

PubMed

Simonis, Anne E; Baumann-Pickering, Simone; Oleson, Erin; Melcón, Mariana L; Gassmann, Martin; Wiggins, Sean M; Hildebrand, John A

2012-04-01

Killer whales in the North Pacific, similar to Atlantic populations, produce high-frequency modulated signals, based on acoustic recordings from ship-based hydrophone arrays and autonomous recorders at multiple locations. The median peak frequency of these signals ranged from 19.6-36.1 kHz and median duration ranged from 50-163 ms. Source levels were 185-193 dB peak-to-peak re: 1 μPa at 1 m. These uniform, repetitive, down-swept signals are similar to bat echolocation signals and possibly could have echolocation functionality. A large geographic range of occurrence suggests that different killer whale ecotypes may utilize these signals.

Echolocation clicks from killer whales (Orcinus orca) feeding on herring (Clupea harengus).

PubMed

Simon, Malene; Wahlberg, Magnus; Miller, Lee A

2007-02-01

Echolocation clicks from Norwegian killer whales feeding on herring schools were recorded using a four-hydrophone array. The clicks had broadband bimodal frequency spectra with low and high frequency peaks at 24 and 108 kHz, respectively. The -10 dB bandwidth was 35 kHz. The average source level varied from 173 to 202 dB re 1 microPa (peak-to-peak) at 1 m. This is considerably lower than source levels described for Canadian killer whales foraging on salmon. It is suggested that biosonar clicks of Norwegian killer whales are adapted for localization of prey with high target strength and acute hearing abilities.

Development and Testing of a Dual Accelerometer Vector Sensor for AUV Acoustic Surveys †

PubMed Central

Mantouka, Agni; Felisberto, Paulo; Santos, Paulo; Zabel, Friedrich; Saleiro, Mário; Jesus, Sérgio M.; Sebastião, Luís

2017-01-01

This paper presents the design, manufacturing and testing of a Dual Accelerometer Vector Sensor (DAVS). The device was built within the activities of the WiMUST project, supported under the Horizon 2020 Framework Programme, which aims to improve the efficiency of the methodologies used to perform geophysical acoustic surveys at sea by the use of Autonomous Underwater Vehicles (AUVs). The DAVS has the potential to contribute to this aim in various ways, for example, owing to its spatial filtering capability, it may reduce the amount of post processing by discriminating the bottom from the surface reflections. Additionally, its compact size allows easier integration with AUVs and hence facilitates the vehicle manoeuvrability compared to the classical towed arrays. The present paper is focused on results related to acoustic wave azimuth estimation as an example of its spatial filtering capabilities. The DAVS device consists of two tri-axial accelerometers and one hydrophone moulded in one unit. Sensitivity and directionality of these three sensors were measured in a tank, whilst the direction estimation capabilities of the accelerometers paired with the hydrophone, forming a vector sensor, were evaluated on a Medusa Class AUV, which was sailing around a deployed sound source. Results of these measurements are presented in this paper. PMID:28594342

Development and Testing of a Dual Accelerometer Vector Sensor for AUV Acoustic Surveys.

PubMed

Mantouka, Agni; Felisberto, Paulo; Santos, Paulo; Zabel, Friedrich; Saleiro, Mário; Jesus, Sérgio M; Sebastião, Luís

2017-06-08

This paper presents the design, manufacturing and testing of a Dual Accelerometer Vector Sensor (DAVS). The device was built within the activities of the WiMUST project, supported under the Horizon 2020 Framework Programme, which aims to improve the efficiency of the methodologies used to perform geophysical acoustic surveys at sea by the use of Autonomous Underwater Vehicles (AUVs). The DAVS has the potential to contribute to this aim in various ways, for example, owing to its spatial filtering capability, it may reduce the amount of post processing by discriminating the bottom from the surface reflections. Additionally, its compact size allows easier integration with AUVs and hence facilitates the vehicle manoeuvrability compared to the classical towed arrays. The present paper is focused on results related to acoustic wave azimuth estimation as an example of its spatial filtering capabilities. The DAVS device consists of two tri-axial accelerometers and one hydrophone moulded in one unit. Sensitivity and directionality of these three sensors were measured in a tank, whilst the direction estimation capabilities of the accelerometers paired with the hydrophone, forming a vector sensor, were evaluated on a Medusa Class AUV, which was sailing around a deployed sound source. Results of these measurements are presented in this paper.

High-resolution measurement of a bottlenose dolphin's (Tursiops truncatus) biosonar transmission beam pattern in the horizontal plane.

PubMed

Finneran, James J; Branstetter, Brian K; Houser, Dorian S; Moore, Patrick W; Mulsow, Jason; Martin, Cameron; Perisho, Shaun

2014-10-01

Previous measurements of toothed whale echolocation transmission beam patterns have utilized few hydrophones and have therefore been limited to fine angular resolution only near the principal axis or poor resolution over larger azimuthal ranges. In this study, a circular, horizontal planar array of 35 hydrophones was used to measure a dolphin's transmission beam pattern with 5° to 10° resolution at azimuths from -150° to +150°. Beam patterns and directivity indices were calculated from both the peak-peak sound pressure and the energy flux density. The emitted pulse became smaller in amplitude and progressively distorted as it was recorded farther off the principal axis. Beyond ±30° to 40°, the off-axis signal consisted of two distinct pulses whose difference in time of arrival increased with the absolute value of the azimuthal angle. A simple model suggests that the second pulse is best explained as a reflection from internal structures in the dolphin's head, and does not implicate the use of a second sound source. Click energy was also more directional at the higher source levels utilized at longer ranges, where the center frequency was elevated compared to that of the lower amplitude clicks used at shorter range.

Echolocation parameters of Australian humpback dolphins (Sousa sahulensis) and Indo-Pacific bottlenose dolphins (Tursiops aduncus) in the wild.

PubMed

de Freitas, Mafalda; Jensen, Frants H; Tyne, Julian; Bejder, Lars; Madsen, Peter T

2015-06-01

Echolocation is a key sensory modality for toothed whale orientation, navigation, and foraging. However, a more comparative understanding of the biosonar properties of toothed whales is necessary to understand behavioral and evolutionary adaptions. To address this, two free-ranging sympatric delphinid species, Australian humpback dolphins (Sousa sahulensis) and Indo-Pacific bottlenose dolphins (Tursiops aduncus), were studied. Biosonar clicks from both species were recorded within the same stretch of coastal habitat in Exmouth Gulf, Western Australia, using a vertical seven element hydrophone array. S. sahulensis used biosonar clicks with a mean source level of 199 ± 3 dB re 1 μPa peak-peak (pp), mean centroid frequency of 106 ± 11 kHz, and emitted at interclick intervals (ICIs) of 79 ± 33 ms. These parameters were similar to click parameters of sympatric T. aduncus, characterized by mean source levels of 204 ± 4 dB re 1 μPa pp, centroid frequency of 112 ± 9 kHz, and ICIs of 73 ± 29 ms. These properties are comparable to those of other similar sized delphinids and suggest that biosonar parameters are independent of sympatric delphinids and possibly driven by body size. The dynamic biosonar behavior of these delphinids may have, consequently, allowed for adaptations to local environments through high levels of control over sonar beam properties.

Calibration of Hydrophone Stations: Lessons Learned from the Ascension Island Experiment

DTIC Science & Technology

2000-09-01

source based on the implosion of a glass sphere for future long-range calibrations. RESEARCH ACCOMPLISHED The J.C. Ross, an icebreaker class...waters around Ascension Island. The blow - ups show the track in the immediate vicinity of the three hydrophones and plots their nominal location. The...used has practical and cost-driven limitations. Small implosive sources such as lightbulbs have been used from ships as hydrophone calibration sources

Shallow 3-D vertical seismic profiling around a contaminant withdrawal well on the Lawrence Livermore National Laboratory Site

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

Rector, J.; Bainer, R.; Milligan, P.

1997-01-30

One of the major problems associated with ground water contaminant remediation is well placement. Optimal-placement of wells requires an accurate knowledge of geologic structure and stratigraphy in the near surface sediments and rock (0 to 100 m). Without the development of remote imaging provided by geophysical techniques, the required spacing between treatment wells may be less than 2 m in order to be confident that all contaminant reservoirs had been remediated. One method for characterizing geologic structure and stratigraphy in the near surface is vertical seismic profiling (VSP), a technique often used on deep exploration wells to calibrate surface seismicmore » reflection data. For near-surface applications, VSP data can be acquired efficiently using an array of hydrophones lowered into a fluid-filled borehole (Milligan et al, 1997). In this paper we discuss the acquisition and processing of a 3-D VSP collected at a shallow remediation site located on the grounds of the Lawrence Livermore National Laboratory (LLNL) near Livermore, California. The site was used by the United States Navy as an air training base. At this time, initial releases of hazardous materials to the environment occurred in the form of solvents [volatile organic compounds (VOCs)] that were used for the cleaning of airplanes and their parts. Gasoline, diesel and other petroleum-based compounds are also known to have leaked into the ground. California Research and Development Company, a subsidy of Standard Oil, occupied the southeastern portion of the site from 1950 to 1954. The first releases of radioactive materials to the environment occurred at this time, with the beginning of testing of radioactive materials at the site. In 1952, LLNL acquired the site. Additional releases of VOCS, polychlorinated biphenyls (PCBs), metals, radionuclides (primarily tritium), gasoline and pesticides have occurred since. These releases were due to localized spills, landfills, surface impoundments, disposal pits, broken sewer lines and pipes, and leaking tanks.« less

Copper vertical micro dendrite fin arrays and their superior boiling heat transfer capability

NASA Astrophysics Data System (ADS)

Wang, Ya-Qiao; Lyu, Shu-Shen; Luo, Jia-Li; Luo, Zhi-Yong; Fu, Yuan-Xiang; Heng, Yi; Zhang, Jian-Hui; Mo, Dong-Chuan

2017-11-01

Micro pin fin arrays have been widely used in electronic cooling, micro reactors, catalyst support, and wettability modification and so on, and a facile way to produce better micro pin fin arrays is demanded. Herein, a simple electrochemical method has been developed to fabricate copper vertical micro dendrite fin arrays (Cu-VMDFA) with controllable shapes, number density and height. High copper sulphate concentration is one key point to make the dendrite stand vertically. Besides, the applied current should rise at an appropriate rate to ensure the copper dendrite can grow vertically on its own. The Cu-VMDFA can significantly enhance the heat transfer coefficient by approximately twice compared to the plain copper surface. The Cu-VMDFA may be widely used in boiling heat transfer areas such as nuclear power plants, electronic cooling, heat exchangers, and so on.

Seismic reflection and refraction data acquired in Canada Basin, Northwind Ridge and Northwind Basin, Arctic Ocean in 1988, 1992 and 1993

USGS Publications Warehouse

Grantz, Arthur; Hart, Patrick E.; May, Steven D.

2004-01-01

Seismic reflection and refraction data were collected in generally ice-covered waters of the Canada Basin and the eastern part of the Chukchi Continental Borderland of the Amerasia Basin, Arctic Ocean, during the late summers of 1988, 1992, and 1993. The data were acquired from a Polar class icebreaker, the U.S. Coast Guard Cutter Polar Star, using a seismic reflection system designed by the U.S. Geological Survey (USGS). The northernmost data extend to 78? 48' N latitude. In 1988, 155 km of reflection data were acquired with a prototype system consisting of a single 195 cubic inch air gun seismic source and a two-channel hydrophone streamer with a 150-m active section. In 1992 and 1993, 500 and 1,900 km, respectively, of seismic reflection profile data were acquired with an improved six air gun, 674 to 1303 cubic inch tuned seismic source array and the same two-channel streamer. In 1993, a 12-channel streamer with a 150-m active section was used to record five of the reflection lines and one line was acquired using a three air gun, 3,000 cubic inch source. All data were recorded with a DFS-V digital seismic recorder. Processed sections feature high quality vertical incidence images to more than 6 km of sub-bottom penetration in the Canada Basin. Refraction data were acquired with U.S. Navy sonobuoys recorded simultaneously with the seismic reflection profiles. In 1988 eight refraction profiles were recorded with the single air gun, and in 1992 and 1993 a total of 47 refraction profiles were recorded with the six air gun array. The sonobuoy refraction records, with offsets up to 35 km, provide acoustic velocity information to complement the short-offset reflection data. The report includes trackline maps showing the location of the data, as well as both digital data files (SEG-Y) and images of all of the profiles.

Trip Report - June 1989 Swallow Float Deployment with RUM

DTIC Science & Technology

1990-12-01

Float 1. with its external geophone package resting on the sediment, and float 3, equipped with an infra - sonic hydrophone and tethered to the bottom...an external, triaxial geophone package resting on the ocean bottom and the other equippd with an infrasonic hydrophone and bottom-tethered by a 0.5... infrasonic hydrophone and bottom-tethered by a 0.5-meter line, are presented in this report Introduction An experiment designed to compare the ambient sound

Plasmonic Properties of Vertically Aligned Nanowire Arrays

DTIC Science & Technology

2012-01-01

scattering (SERS) applications. In this investigation, two types of vertical NW arrays were studied; those of ZnO NWs grown on nanosphere lithography...plasmonic nanowires to investigate this SERS effect. Here we used two types of vertical NWs, ZnO NWs, and Si NWs, respectively, to investigate SERS...successfully grow vertically aligned ZnO nanowires by the well-known VLS process. In this way, the ZnO NWs can be arranged in a repeatable hexagonal pattern

COOMET pilot comparison 473/RU-a/09: Comparison of hydrophone calibrations in the frequency range 250 Hz to 200 kHz

NASA Astrophysics Data System (ADS)

Yi, Chen; Isaev, A. E.; Yuebing, Wang; Enyakov, A. M.; Teng, Fei; Matveev, A. N.

2011-01-01

A description is given of the COOMET project 473/RU-a/09: a pilot comparison of hydrophone calibrations at frequencies from 250 Hz to 200 kHz between Hangzhou Applied Acoustics Research Institute (HAARI, China)—pilot laboratory—and Russian National Research Institute for Physicotechnical and Radio Engineering Measurements (VNIIFTRI, Designated Institute of Russia of the CIPM MRA). Two standard hydrophones, B&K 8104 and TC 4033, were calibrated and compared to assess the current state of hydrophone calibration of HAARI (China) and Russia. Three different calibration methods were applied: a vibrating column method, a free-field reciprocity method and a comparison method. The standard facilities of each laboratory were used, and three different sound fields were applied: pressure field, free-field and reverberant field. The maximum deviation of the sensitivities of two hydrophones between the participants' results was 0.36 dB. Main text. To reach the main text of this paper, click on Final Report. The final report has been peer-reviewed and approved for publication by the CCAUV-KCWG.

A risk function for behavioral disruption of Blainville's beaked whales (Mesoplodon densirostris) from mid-frequency active sonar.

PubMed

Moretti, David; Thomas, Len; Marques, Tiago; Harwood, John; Dilley, Ashley; Neales, Bert; Shaffer, Jessica; McCarthy, Elena; New, Leslie; Jarvis, Susan; Morrissey, Ronald

2014-01-01

There is increasing concern about the potential effects of noise pollution on marine life in the world's oceans. For marine mammals, anthropogenic sounds may cause behavioral disruption, and this can be quantified using a risk function that relates sound exposure to a measured behavioral response. Beaked whales are a taxon of deep diving whales that may be particularly susceptible to naval sonar as the species has been associated with sonar-related mass stranding events. Here we derive the first empirical risk function for Blainville's beaked whales (Mesoplodon densirostris) by combining in situ data from passive acoustic monitoring of animal vocalizations and navy sonar operations with precise ship tracks and sound field modeling. The hydrophone array at the Atlantic Undersea Test and Evaluation Center, Bahamas, was used to locate vocalizing groups of Blainville's beaked whales and identify sonar transmissions before, during, and after Mid-Frequency Active (MFA) sonar operations. Sonar transmission times and source levels were combined with ship tracks using a sound propagation model to estimate the received level (RL) at each hydrophone. A generalized additive model was fitted to data to model the presence or absence of the start of foraging dives in 30-minute periods as a function of the corresponding sonar RL at the hydrophone closest to the center of each group. This model was then used to construct a risk function that can be used to estimate the probability of a behavioral change (cessation of foraging) the individual members of a Blainville's beaked whale population might experience as a function of sonar RL. The function predicts a 0.5 probability of disturbance at a RL of 150 dBrms re µPa (CI: 144 to 155) This is 15dB lower than the level used historically by the US Navy in their risk assessments but 10 dB higher than the current 140 dB step-function.

Detection, location, and characterization of hydroacoustic signals using seafloor cable networks offshore Japan (Invited)

NASA Astrophysics Data System (ADS)

Sugioka, H.; Suyehiro, K.; Shinohara, M.

2009-12-01

The hydroacoustic monitoring by the International Monitoring System (IMS) for Comprehensive Nuclear-Test-Treaty (CTBT) verification system utilize hydrophone stations and seismic stations called T-phase stations for worldwide detection. Some signals of natural origin include those from earthquakes, submarine volcanic eruptions, or whale calls. Among artificial sources there are non-nuclear explosions and air-gun shots. It is important for IMS system to detect and locate hydroacoustic events with sufficient accuracy and correctly characterize the signals and identify the source. As there are a number of seafloor cable networks operated offshore Japanese islands basically facing the Pacific Ocean for monitoring regional seismicity, the data from these stations (pressures, hydrophones and seismic sensors) may be utilized to verify and increase the capability of the IMS. We use these data to compare some selected event parameters with those by Pacific in the time period of 2004-present. These anomalous examples and also dynamite shots used for seismic crustal structure studies and other natural sources will be presented in order to help improve the IMS verification capabilities for detection, location and characterization of anomalous signals. The seafloor cable networks composed of three hydrophones and six seismometers and a temporal dense seismic array detected and located hydroacoustic events offshore Japanese island on 12th of March in 2008, which had been reported by the IMS. We detected not only the reverberated hydroacoustic waves between the sea surface and the sea bottom but also the seismic waves going through the crust associated with the events. The determined source of the seismic waves is almost coincident with the one of hydroacoustic waves, suggesting that the seismic waves are converted very close to the origin of the hydroacoustic source. We also detected very similar signals on 16th of March in 2009 to the ones associated with the event of 12th of March in 2008.

A Risk Function for Behavioral Disruption of Blainville’s Beaked Whales (Mesoplodon densirostris) from Mid-Frequency Active Sonar

PubMed Central

Moretti, David; Thomas, Len; Marques, Tiago; Harwood, John; Dilley, Ashley; Neales, Bert; Shaffer, Jessica; McCarthy, Elena; New, Leslie; Jarvis, Susan; Morrissey, Ronald

2014-01-01

There is increasing concern about the potential effects of noise pollution on marine life in the world’s oceans. For marine mammals, anthropogenic sounds may cause behavioral disruption, and this can be quantified using a risk function that relates sound exposure to a measured behavioral response. Beaked whales are a taxon of deep diving whales that may be particularly susceptible to naval sonar as the species has been associated with sonar-related mass stranding events. Here we derive the first empirical risk function for Blainville’s beaked whales (Mesoplodon densirostris) by combining in situ data from passive acoustic monitoring of animal vocalizations and navy sonar operations with precise ship tracks and sound field modeling. The hydrophone array at the Atlantic Undersea Test and Evaluation Center, Bahamas, was used to locate vocalizing groups of Blainville’s beaked whales and identify sonar transmissions before, during, and after Mid-Frequency Active (MFA) sonar operations. Sonar transmission times and source levels were combined with ship tracks using a sound propagation model to estimate the received level (RL) at each hydrophone. A generalized additive model was fitted to data to model the presence or absence of the start of foraging dives in 30-minute periods as a function of the corresponding sonar RL at the hydrophone closest to the center of each group. This model was then used to construct a risk function that can be used to estimate the probability of a behavioral change (cessation of foraging) the individual members of a Blainville’s beaked whale population might experience as a function of sonar RL. The function predicts a 0.5 probability of disturbance at a RL of 150dBrms re µPa (CI: 144 to 155) This is 15dB lower than the level used historically by the US Navy in their risk assessments but 10 dB higher than the current 140 dB step-function. PMID:24465477

Multifrequency tomography of the La Reunion mantle plume with P and S waves using ocean bottom seismometers in the Indian Ocean

NASA Astrophysics Data System (ADS)

Tsekhmistrenko, M.; Sigloch, K.; Hosseini, K.

2017-12-01

The RHUM-RUM experiment (Reunion Hotspot Upper Mantle - Reunions Unterer Mantel) investigates the presence or absence of a whole mantle plume beneath the volcanic hotspot island of La Reunion. From 2011 to 2016, RHUM-RUM instrumented a 2000 km x 2000 km area of western Indian Ocean seafloor, islands and Madagascar with broadband seismometers and hydrophones. The central component was a 13-month deployment of 57 German and French Ocean Bottom Seismometers (OBS) in 2300-5600 m depth. This was supplemented by 2-3 years deployments of 37 island stations on Reunion, Mauritius, Rodrigues, the southern Seychelles, the Iles Eparses and southern Madagascar. Two partner projects contributed another 30+ stations on Madagascar. We present results of multifrequency P- and S-waveform tomography of the entire mantle column beneath the Reunion hotspot. We use all frequency passbands that efficiently transmit body waves and rise above the considerable noise floor of OBS measurements. More than 200 teleseismic events during the 13-month long OBS deployment yielded usable measurements, and another 400 events before and after. We present our methods, discuss data yield and quality of ocean-bottom versus island/land seismometers and hydrophones. 150,000 combined cross-correlations measurements were used in multifrequency P-wave tomography, in passbands between 30 s and 2.7 s dominant period. Cross-correlation coefficients at permanent and temporal land stations are generally higher than on OBS, which are more affected by both microseismic and self-noise. Hydrophones worked more reliably, but strong reverberations from the water column mean that they are still less usable than seismograms. All measurements of the RHUM-RUM array are embedded in a global P-wave inversion. Mantle structures obtained from this new, high resolution tomographic model of the La Reunion area are compared to existing tomographies. We also compare to local and global convection models in order to understand the relation between mantle flow and the development of mantle plumes through time.

Ultrasound therapy transducers with space-filling non-periodic arrays.

PubMed

Raju, Balasundar I; Hall, Christopher S; Seip, Ralf

2011-05-01

Ultrasound transducers designed for therapeutic purposes such as tissue ablation, histotripsy, or drug delivery require large apertures for adequate spatial localization while providing sufficient power and steerability without the presence of secondary grating lobes. In addition, it is highly preferred to minimize the total number of channels and to maintain simplicity in electrical matching network design. To this end, we propose array designs that are both space-filling and non-periodic in the placement of the elements. Such array designs can be generated using the mathematical concept of non-periodic or aperiodic tiling (tessellation) and can lead to reduced grating lobes while maintaining full surface area coverage to deliver maximum power. For illustration, we designed two 2-D space-filling therapeutic arrays with 128 elements arranged on a spherical shell. One was based on the two-shape Penrose rhombus tiling, and the other was based on a single rectangular shape arranged non-periodically. The steerability performance of these arrays was studied using acoustic field simulations. For comparison, we also studied two other arrays, one with circular elements distributed randomly, and the other a periodic array with square elements. Results showed that the two space-filling non-periodic arrays were able to steer to treat a volume of 16 x 16 x 20 mm while ensuring that the grating lobes were under -10 dB compared with the main lobe. The rectangular non-periodic array was able to generate two and half times higher power than the random circles array. The rectangular array was then fabricated by patterning the array using laser scribing methods and its steerability performance was validated using hydrophone measurements. This work demonstrates that the concept of space-filling aperiodic/non-periodic tiling can be used to generate therapy arrays that are able to provide higher power for the same total transducer area compared with random arrays while maintaining acceptable grating lobe levels.

Broadband continuous wave source localization via pair-wise, cochleagram processing

NASA Astrophysics Data System (ADS)

Nosal, Eva-Marie; Frazer, L. Neil

2005-04-01

A pair-wise processor has been developed for the passive localization of broadband continuous-wave underwater sources. The algorithm uses sparse hydrophone arrays and does not require previous knowledge of the source signature. It is applicable in multiple source situations. A spectrogram/cochleagram version of the algorithm has been developed in order to utilize higher frequencies at longer ranges where signal incoherence, and limited computational resources, preclude the use of full waveforms. Simulations demonstrating the robustness of the algorithm with respect to noise and environmental mismatch will be presented, together with initial results from the analysis of humpback whale song recorded at the Pacific Missile Range Facility off Kauai. [Work supported by MHPCC and ONR.

An experimental assessment of resistance reduction and wake modification of a kvlcc model by using outer-layer vertical blades

NASA Astrophysics Data System (ADS)

An, Nam Hyun; Ryu, Sang Hoon; Chun, Ho Hwan; Lee, Inwon

2014-03-01

In this study, an experimental investigation has been made of the applicability of outer-layer vertical blades to real ship model. After first devised by Hutchins and Choi (2003), the outer-layer vertical blades demonstrated its effectiveness in reducing total drag of flat plate (Park et al., 2011) with maximum drag reduction of 9.6%. With a view to assessing the effect in the flow around a ship, the arrays of outer-layer vertical blades have been installed onto the side bottom and flat bottom of a 300k KVLCC model. A series of towing tank test has been carried out to investigate resistance (CTM) reduction efficiency and improvement of stern wake distribution with varying geometric parameters of the blades array. The installation of vertical blades led to the CTM reduction of 2.15~2.76% near the service speed. The nominal wake fraction was affected marginally by the blades array and the axial velocity distribution tended to be more uniform by the blades array.

The Surface Interface Characteristics of Vertically Aligned Carbon Nanotube and Graphitic Carbon Fiber Arrays Grown by Thermal and Plasma Enhanced Chemical Vapor Deposition

NASA Technical Reports Server (NTRS)

Delzeit, Lance; Nguyen, Cattien; Li, Jun; Han, Jie; Meyyappan, M.

2002-01-01

The development of nano-arrays for sensors and devices requires the growth of arrays with the proper characteristics. One such application is the growth of vertically aligned carbon nanotubes (CNTs) and graphitic carbon fibers (GCFs) for the chemical attachment of probe molecules. The effectiveness of such an array is dependent not only upon the effectiveness of the probe and the interface between that probe and the array, but also the array and the underlaying substrate. If that array is a growth of vertically aligned CNTs or GCFs then the attachment of that array to the surface is of the utmost importance. This attachment provides the mechanical stability and durability of the array, as well as, the electrical properties of that array. If the detection is to be acquired through an electrical measurement, then the appropriate resistance between the array and the surface need to be fabricated into the device. I will present data on CNTs and GCFs grown from both thermal and plasma enhanced chemical vapor deposition. The focus will be on the characteristics of the metal film from which the CNTs and GCFs are grown and the changes that occur due to changes within the growth process.

Broadband calibration of the R/V Marcus G. Langseth four-string seismic sources

NASA Astrophysics Data System (ADS)

Tolstoy, M.; Diebold, J.; Doermann, L.; Nooner, S.; Webb, S. C.; Bohnenstiehl, D. R.; Crone, T. J.; Holmes, R. C.

2009-08-01

The R/V Marcus G. Langseth is the first 3-D seismic vessel operated by the U.S. academic community. With up to a four-string, 36-element source and four 6-km-long solid state hydrophone arrays, this vessel promises significant new insights into Earth science processes. The potential impact of anthropogenic sound sources on marine life is an important topic to the marine seismic community. To ensure that operations fully comply with existing and future marine mammal permitting requirements, a calibration experiment was conducted in the Gulf of Mexico in 2007-2008. Results are presented from deep (˜1.6 km) and shallow (˜50 m) water sites, obtained using the full 36-element (6600 cubic inches) seismic source. This array configuration will require the largest safety radii, and the deep and shallow sites provide two contrasting operational environments. Results show that safety radii and the offset between root-mean-square and sound exposure level measurements were highly dependent on water depth.

Matched Bearing Processing for Airborne Source Localization by an Underwater Horizontal Line Array

NASA Astrophysics Data System (ADS)

Peng, Zhao-Hui; Li, Zheng-Lin; Wang, Guang-Xu

2010-11-01

Location of an airborne source is estimated from signals measured by a horizontal line array (HLA), based on the fact that a signal transmitted by an airborne source will reach a underwater hydrophone in different ways: via a direct refracted path, via one or more bottom and surface reflections, via the so-called lateral wave. As a result, when an HLA near the airborne source is used for beamforming, several peaks at different bearing angles will appear. By matching the experimental beamforming outputs with the predicted outputs for all source locations, the most likely location is the one which gives minimum difference. An experiment is conducted for airborne source localization in the Yellow Sea in October 2008. An HLA was laid on the sea bottom at the depth of 30m. A high-power loudspeaker was hung on a research ship floating near the HLA and sent out LFM pulses. The estimated location of the loudspeaker is in agreement well with the GPS measurements.

Fabrication of graphene/titanium carbide nanorod arrays for chemical sensor application.

PubMed

Fu, Chong; Li, Mingji; Li, Hongji; Li, Cuiping; Qu, Changqing; Yang, Baohe

2017-03-01

Vertically stacked graphene nanosheet/titanium carbide nanorod array/titanium (graphene/TiC nanorod array) wires were fabricated using a direct current arc plasma jet chemical vapor deposition (DC arc plasma jet CVD) method. The graphene/TiC nanorod arrays were characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction spectroscopy. The TiO 2 nanotube array was reduced to the TiC nanorod array, and using those TiC nanorods as nucleation sites, the vertical graphene layer was formed on the TiC nanorod surface. The multi-target response mechanisms of the graphene/TiC nanorod array were investigated for ascorbic acid (AA), dopamine (DA), uric acid (UA), and hydrochlorothiazide (HCTZ). The vertically stacked graphene sheets facilitated the electron transfer and reactant transport with a unique porous surface, high surface area, and high electron transport network of CVD graphene sheets. The TiC nanorod array facilitated the electron transfer and firmly held the graphene layer. Thus, the graphene/TiC nanorod arrays could simultaneously respond to trace biomarkers and antihypertensive drugs. Copyright © 2016 Elsevier B.V. All rights reserved.

T-phase and tsunami pressure waveforms recorded by near-source IMS water-column hydrophone triplets during the 2015 Chile earthquake

NASA Astrophysics Data System (ADS)

Matsumoto, H.; Haralabus, G.; Zampolli, M.; Özel, N. M.

2016-12-01

Underwater acoustic signal waveforms recorded during the 2015 Chile earthquake (Mw 8.3) by the hydrophones of hydroacoustic station HA03, located at the Juan Fernandez Islands, are analyzed. HA03 is part of the Comprehensive Nuclear-Test-Ban Treaty International Monitoring System. The interest in the particular data set stems from the fact that HA03 is located only approximately 700 km SW from the epicenter of the earthquake. This makes it possible to study aspects of the signal associated with the tsunamigenic earthquake, which would be more difficult to detect had the hydrophones been located far from the source. The analysis shows that the direction of arrival of the T phase can be estimated by means of a three-step preprocessing technique which circumvents spatial aliasing caused by the hydrophone spacing, the latter being large compared to the wavelength. Following this preprocessing step, standard frequency-wave number analysis (F-K analysis) can accurately estimate back azimuth and slowness of T-phase signals. The data analysis also shows that the dispersive tsunami signals can be identified by the water-column hydrophones at the time when the tsunami surface gravity wave reaches the station.

Vertically Free-Standing Ordered Pb(Zr0.52Ti0.48)O3 Nanocup Arrays by Template-Assisted Ion Beam Etching

NASA Astrophysics Data System (ADS)

Zhang, Xiaoyan; Tang, Dan; Huang, Kangrong; Hu, Die; Zhang, Fengyuan; Gao, Xingsen; Lu, Xubing; Zhou, Guofu; Zhang, Zhang; Liu, Junming

2016-04-01

In this report, vertically free-standing lead zirconate titanate Pb(Zr0.52Ti0.48)O3 (PZT) nanocup arrays with good ordering and high density (1.3 × 1010 cm-2) were demonstrated. By a template-assisted ion beam etching (IBE) strategy, the PZT formed in the pore-through anodic aluminum oxide (AAO) membrane on the Pt/Si substrate was with a cup-like nanostructure. The mean diameter and height of the PZT nanocups (NCs) was about 80 and 100 nm, respectively, and the wall thickness of NCs was about 20 nm with a hole depth of about 80 nm. Uppermost, the nanocup structure with low aspect ratio realized vertically free-standing arrays when losing the mechanical support from templates, avoiding the collapse or bundling when compared to the typical nanotube arrays. X-ray diffraction (XRD) and Raman spectrum revealed that the as-prepared PZT NCs were in a perovskite phase. By the vertical piezoresponse force microscopy (VPFM) measurements, the vertically free-standing ordered ferroelectric PZT NCs showed well-defined ring-like piezoresponse phase and hysteresis loops, which indicated that the high-density PZT nanocup arrays could have potential applications in ultra-high non-volatile ferroelectric memories (NV-FRAM) or other nanoelectronic devices.

Statistical analysis of kinetic energy entrainment in a model wind turbine array boundary layer

NASA Astrophysics Data System (ADS)

Cal, Raul Bayoan; Hamilton, Nicholas; Kang, Hyung-Suk; Meneveau, Charles

2012-11-01

For large wind farms, kinetic energy must be entrained from the flow above the wind turbines to replenish wakes and enable power extraction in the array. Various statistical features of turbulence causing vertical entrainment of mean-flow kinetic energy are studied using hot-wire velocimetry data taken in a model wind farm in a scaled wind tunnel experiment. Conditional statistics and spectral decompositions are employed to characterize the most relevant turbulent flow structures and determine their length-scales. Sweep and ejection events are shown to be the largest contributors to the vertical kinetic energy flux, although their relative contribution depends upon the location in the wake. Sweeps are shown to be dominant in the region above the wind turbine array. A spectral analysis of the data shows that large scales of the flow, about the size of the rotor diameter in length or larger, dominate the vertical entrainment. The flow is more incoherent below the array, causing decreased vertical fluxes there. The results show that improving the rate of vertical kinetic energy entrainment into wind turbine arrays is a standing challenge and would require modifying the large-scale structures of the flow. This work was funded in part by the National Science Foundation (CBET-0730922, CBET-1133800 and CBET-0953053).

Wavelength shift in vertical cavity laser arrays on a patterned substrate

NASA Astrophysics Data System (ADS)

Eng, L. E.; Bacher, K.; Yuen, W.; Larson, M.; Ding, G.; Harris, J. S., Jr.; Chang-Hasnain, C. J.

1995-03-01

The authors demonstrate a spatially chirped emission wavelength in vertical cavity surface emitting laser (VCSEL) arrays grown by molecular beam epitaxy. The wavelength shift is due to a lateral thickness variation in the Al(0.2)Ga(0.8)As cavity, which is induced by a substrate temperature profile during growth. A 20 nm shift in lasing wavelength is obtained in a VCSEL array.

NEMO-SMO acoustic array: A deep-sea test of a novel acoustic positioning system for a km3-scale underwater neutrino telescope

NASA Astrophysics Data System (ADS)

Viola, S.; Ardid, M.; Bertin, V.; Enzenhöfer, A.; Keller, P.; Lahmann, R.; Larosa, G.; Llorens, C. D.; NEMO Collaboration; SMO Collaboration

2013-10-01

Within the activities of the NEMO project, the installation of a 8-floors tower (NEMO-Phase II) at a depth of 3500 m is foreseen in 2012. The tower will be installed about 80 km off-shore Capo Passero, in Sicily. On board the NEMO tower, an array of 18 acoustic sensors will be installed, permitting acoustic detection of biological sources, studies for acoustic neutrino detection and primarily acoustic positioning of the underwater structures. For the latter purpose, the sensors register acoustic signals emitted by five acoustic beacons anchored on the sea-floor. The data acquisition system of the acoustic sensors is fully integrated with the detector data transport system and is based on an “all data to shore” philosophy. Signals coming from hydrophones are continuously sampled underwater at 192 kHz/24 bit and transmitted to shore through an electro-optical cable for real-time analysis. A novel technology for underwater GPS time-stamping of data has been implemented and tested. The operation of the acoustic array will permit long-term test of sensors and electronics technologies that are proposed for the acoustic positioning system of KM3NeT.

Long-term seismicity of the Reykjanes Ridge (North Atlantic) recorded by a regional hydrophone array

NASA Astrophysics Data System (ADS)

Goslin, Jean; Lourenço, Nuno; Dziak, Robert P.; Bohnenstiehl, DelWayne R.; Haxel, Joe; Luis, Joaquim

2005-08-01

The seismicity of the northern Mid-Atlantic Ridge was recorded by two hydrophone networks moored in the sound fixing and ranging (SOFAR) channel, on the flanks of the Mid-Atlantic Ridge, north and south of the Azores. During its period of operation (05/2002-09/2003), the northern `SIRENA' network, deployed between latitudes 40° 20'N and 50° 30'N, recorded acoustic signals generated by 809 earthquakes on the hotspot-influenced Reykjanes Ridge. This activity was distributed between five spatio-temporal event clusters, each initiated by a moderate-to-large magnitude (4.0-5.6 M) earthquake. The rate of earthquake occurrence within the initial portion of the largest sequence (which began on 2002 October 6) is described adequately by a modified Omori law aftershock model. Although this is consistent with triggering by tectonic processes, none of the Reykjanes Ridge sequences are dominated by a single large-magnitude earthquake, and they appear to be of relatively short duration (0.35-4.5 d) when compared to previously described mid-ocean ridge aftershock sequences. The occurrence of several near-equal magnitude events distributed throughout each sequence is inconsistent with the simple relaxation of mainshock-induced stresses and may reflect the involvement of magmatic or fluid processes along this deep (>2000 m) section of the Reykjanes Ridge.

Chemical growth of ZnO nanorod arrays on textured nanoparticle nanoribbons and its second-harmonic generation performance

NASA Astrophysics Data System (ADS)

Gui, Zhou; Wang, Xian; Liu, Jian; Yan, Shanshan; Ding, Yanyan; Wang, Zhengzhou; Hu, Yuan

2006-07-01

On the basis of the highly oriented ZnO nanoparticle nanoribbons as the growth seed layer (GSL) and solution growth technique, we have synthesized vertical ZnO nanorod arrays with high density over a large area and multi-teeth brush nanostructure, respectively, according to the density degree of the arrangement of nanoparticle nanoribbons GSL on the glass substrate. This controllable and convenient technique opens the possibility of creating nanostructured film for industrial fabrication and may represent a facile way to get similar structures of other compounds by using highly oriented GSL to promote the vertical arrays growth. The growth mechanism of the formation of the ordered nanorod arrays is also discussed. The second-order nonlinear optical coefficient d31 of the vertical ZnO nanorod arrays measured by the Maker fringes technique is 11.3 times as large as that of d36 KH 2PO 4 (KDP).

Highly uniform and vertically aligned SnO2 nanochannel arrays for photovoltaic applications

NASA Astrophysics Data System (ADS)

Kim, Jae-Yup; Kang, Jin Soo; Shin, Junyoung; Kim, Jin; Han, Seung-Joo; Park, Jongwoo; Min, Yo-Sep; Ko, Min Jae; Sung, Yung-Eun

2015-04-01

Nanostructured electrodes with vertical alignment have been considered ideal structures for electron transport and interfacial contact with redox electrolytes in photovoltaic devices. Here, we report large-scale vertically aligned SnO2 nanochannel arrays with uniform structures, without lateral cracks fabricated by a modified anodic oxidation process. In the modified process, ultrasonication is utilized to avoid formation of partial compact layers and lateral cracks in the SnO2 nanochannel arrays. Building on this breakthrough, we first demonstrate the photovoltaic application of these vertically aligned SnO2 nanochannel arrays. These vertically aligned arrays were directly and successfully applied in quasi-solid state dye-sensitized solar cells (DSSCs) as photoanodes, yielding reasonable conversion efficiency under back-side illumination. In addition, a significantly short process time (330 s) for achieving the optimal thickness (7.0 μm) and direct utilization of the anodized electrodes enable a simple, rapid and low-cost fabrication process. Furthermore, a TiO2 shell layer was coated on the SnO2 nanochannel arrays by the atomic layer deposition (ALD) process for enhancement of dye-loading and prolonging the electron lifetime in the DSSC. Owing to the presence of the ALD TiO2 layer, the short-circuit photocurrent density (Jsc) and conversion efficiency were increased by 20% and 19%, respectively, compared to those of the DSSC without the ALD TiO2 layer. This study provides valuable insight into the development of efficient SnO2-based photoanodes for photovoltaic application by a simple and rapid fabrication process.Nanostructured electrodes with vertical alignment have been considered ideal structures for electron transport and interfacial contact with redox electrolytes in photovoltaic devices. Here, we report large-scale vertically aligned SnO2 nanochannel arrays with uniform structures, without lateral cracks fabricated by a modified anodic oxidation process. In the modified process, ultrasonication is utilized to avoid formation of partial compact layers and lateral cracks in the SnO2 nanochannel arrays. Building on this breakthrough, we first demonstrate the photovoltaic application of these vertically aligned SnO2 nanochannel arrays. These vertically aligned arrays were directly and successfully applied in quasi-solid state dye-sensitized solar cells (DSSCs) as photoanodes, yielding reasonable conversion efficiency under back-side illumination. In addition, a significantly short process time (330 s) for achieving the optimal thickness (7.0 μm) and direct utilization of the anodized electrodes enable a simple, rapid and low-cost fabrication process. Furthermore, a TiO2 shell layer was coated on the SnO2 nanochannel arrays by the atomic layer deposition (ALD) process for enhancement of dye-loading and prolonging the electron lifetime in the DSSC. Owing to the presence of the ALD TiO2 layer, the short-circuit photocurrent density (Jsc) and conversion efficiency were increased by 20% and 19%, respectively, compared to those of the DSSC without the ALD TiO2 layer. This study provides valuable insight into the development of efficient SnO2-based photoanodes for photovoltaic application by a simple and rapid fabrication process. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00202h

Hydroacoustic monitoring of seafloor earthquake and cryogenic sounds in the Bransfield Strait, Antarctica

NASA Astrophysics Data System (ADS)

Park, M.; Lee, W.; Dziak, R. P.; Matsumoto, H.; Bohnenstiehl, D. R.; Haxel, J. H.

2008-12-01

To record signals from submarine tectonic activity and ice-generated sound around the Antarctic Peninsula, we have operated an Autonomous Underwater Hydrophone (AUH) array from 2005 to 2007. The objectives of this experiment are to improve detection capability in the study area which is poorly covered by global seismic networks and to reveal characteristics of cryogenic sound which is hard to detect using low-latitude hydrophone array. NEIC has reported ~10-20 earthquakes per year in this region, while the efficiency of sound propagation in the ocean allows detection of greater than two orders of magnitude more earthquakes. A total of 5,160 earthquakes including 12 earthquake swarms are located during the deployment period. A total of 6 earthquake swarms (3,008) occurred in the western part of the Bransfield Strait (WBS), show an epicenter migration of 1-2 km/hr, exhibit a deficiency in high-frequency energy, and occurred near submarine volcanic centers along the back-arc rift axis. Cross-correlation analysis with ocean and solid earth tides indicates the WBS seismicity is modulated by tidal stress, where volcanic earthquake activity reflects variations in tidal forcing than do tectonic earthquakes. On-the-other hand, earthquake swarms from the eastern part of the BS (EBS) show features typical of tectonic earthquakes such as widely distributed epicenters with no clear spatio-temporal pattern and full-spectrum (broadband) signals. These results are consistent with previous crustal models indicating the WBS is undergoing volcanically dominated rifting, whereas rifting in the EBS is tectonically driven. A total of 5,929 ice-generated signals were also derived from the data and are the first detailed observation of various cryogenic phenomena in the region. These cryogenic signals exhibit unusual, tremor-like signals with a high-frequency fundamental (~40 Hz) and 5-6 overtones caused by iceberg resonance, as well as impulsive, short-duration "icequakes" caused by ice break-up and iceberg flow directed along seafloor canyons.

Ambient & Vessel Noise Measurement and Marine Mammal Monitoring in the Stait of Georgia, British-Columbia, Canada.

NASA Astrophysics Data System (ADS)

Moloney, J. E.; Hannay, D.; Mouy, X.; Mouy, P. A.; Urazghildiiev, I.; Dakin, T.

2016-02-01

Recently JASCO Applied Sciences (Canada) Ltd (JASCO), Ocean Networks Canada (ONC) and the Port of Metro Vancouver (PMV) have collaborated in the installation of a novel, real-time ocean observing (listening) system (PMV-ECHO system deployed in the Strait of Georgia, BC. This system was designed specifically to measure ambient noise, vessel source levels, and to detect, classify, localize and track marine mammals using their vocalization in order to estimate population density. The listening station deployment and monitoring activities are part of the Enhancing Cetacean Habitat and Observation (ECHO) Program. The program aims to better understand and manage the impact of shipping activities on at-risk whales throughout the southern coast of British Columbia. The PMV-ECHO system is composed of two unique spatial arrays of four hydrophones and one active projector each. Both arrays are used to measure and monitor the environment and calibrate the hydrophones over time. Further, a new shored-based data processing and visualization system (JMesh) is used automatically process the data and to enable operators to easily provide measurement information, navigate through large time series of detections, examine spectrograms, listen to detected sounds, validate detections, and compare detections for different species over time and space. The JMesh web platform has been designed to overcome the otherwise overwhelming volume of acoustic data collected by the PMV-ECHO sensor systems. This paper will describe how the PMV-ECHO system along with the automated real-time analysis and visualization software suite can be used study marine mammal distribution and behavior, variation of vessel noises and potential effects of anthropogenic activities on marine mammals. The goal of the PMV-ECHO program is to find ways to reduce shipping impact on at-risk species especially in the approaches to large ports. This program and its scientific and technical approaches should be of interest to many marine organizations, industries, researchers and enforcement agencies.

Vertically aligned carbon nanotubes for microelectrode arrays applications.

PubMed

Castro Smirnov, J R; Jover, Eric; Amade, Roger; Gabriel, Gemma; Villa, Rosa; Bertran, Enric

2012-09-01

In this work a methodology to fabricate carbon nanotube based electrodes using plasma enhanced chemical vapour deposition has been explored and defined. The final integrated microelectrode based devices should present specific properties that make them suitable for microelectrode arrays applications. The methodology studied has been focused on the preparation of highly regular and dense vertically aligned carbon nanotube (VACNT) mat compatible with the standard lithography used for microelectrode arrays technology.

Vertical Si nanowire arrays fabricated by magnetically guided metal-assisted chemical etching

NASA Astrophysics Data System (ADS)

Chun, Dong Won; Kim, Tae Kyoung; Choi, Duyoung; Caldwell, Elizabeth; Kim, Young Jin; Paik, Jae Cheol; Jin, Sungho; Chen, Renkun

2016-11-01

In this work, vertically aligned Si nanowire arrays were fabricated by magnetically guided metal-assisted directional chemical etching. Using an anodized aluminum oxide template as a shadow mask, nanoscale Ni dot arrays were fabricated on an Si wafer to serve as a mask to protect the Si during the etching. For the magnetically guided chemical etching, we deposited a tri-layer metal catalyst (Au/Fe/Au) in a Swiss-cheese configuration and etched the sample under the magnetic field to improve the directionality of the Si nanowire etching and increase the etching rate along the vertical direction. After the etching, the nanowires were dried with minimal surface-tension-induced aggregation by utilizing a supercritical CO2 drying procedure. High-resolution transmission electron microscopy (HR-TEM) analysis confirmed the formation of single-crystal Si nanowires. The method developed here for producing vertically aligned Si nanowire arrays could find a wide range of applications in electrochemical and electronic devices.

Influence of packing density and surface roughness of vertically-aligned carbon nanotubes on adhesive properties of gecko-inspired mimetics.

PubMed

Chen, Bingan; Zhong, Guofang; Oppenheimer, Pola Goldberg; Zhang, Can; Tornatzky, Hans; Esconjauregui, Santiago; Hofmann, Stephan; Robertson, John

2015-02-18

We have systematically studied the macroscopic adhesive properties of vertically aligned nanotube arrays with various packing density and roughness. Using a tensile setup in shear and normal adhesion, we find that there exists a maximum packing density for nanotube arrays to have adhesive properties. Too highly packed tubes do not offer intertube space for tube bending and side-wall contact to surfaces, thus exhibiting no adhesive properties. Likewise, we also show that the surface roughness of the arrays strongly influences the adhesion properties and the reusability of the tubes. Increasing the surface roughness of the array strengthens the adhesion in the normal direction, but weakens it in the shear direction. Altogether, these results allow progress toward mimicking the gecko's vertical mobility.

Development of Deep-tow Autonomous Cable Seismic (ACS) for Seafloor Massive Sulfides (SMSs) Exploration.

NASA Astrophysics Data System (ADS)

Asakawa, Eiichi; Murakami, Fumitoshi; Tsukahara, Hitoshi; Saito, Shutaro; Lee, Sangkyun; Tara, Kenji; Kato, Masafumi; Jamali Hondori, Ehsan; Sumi, Tomonori; Kadoshima, Kazuyuki; Kose, Masami

2017-04-01

Within the EEZ of Japan, numerous surveys exploring ocean floor resources have been conducted. The exploration targets are gas hydrates, mineral resources (manganese, cobalt or rare earth) and especially seafloor massive sulphide (SMS) deposits. These resources exist in shallow subsurface areas in deep waters (>1500m). For seismic explorations very high resolution images are required. These cannot be effectively obtained with conventional marine seismic techniques. Therefore we have been developing autonomous seismic survey systems which record the data close to the seafloor to preserve high frequency seismic energy. Very high sampling rate (10kHz) and high accurate synchronization between recording systems and shot time are necessary. We adopted Cs-base atomic clock considering its power consumption. At first, we developed a Vertical Cable Seismic (VCS) system that uses hydrophone arrays moored vertically from the ocean bottom to record close to the target area. This system has been successfully applied to SMS exploration. Specifically it fixed over known sites to assess the amount of reserves with the resultant 3D volume. Based on the success of VCS, we modified the VCS system to use as a more efficient deep-tow seismic survey system. Although there are other examples of deep-tow seismic systems, signal transmission cables present challenges in deep waters. We use our autonomous recording system to avoid these problems. Combining a high frequency piezoelectric source (Sub Bottom Profiler:SBP) that automatically shots with a constant interval, we achieve the high resolution deep-tow seismic without data transmission/power cable to the board. Although the data cannot be monitored in real-time, the towing system becomes very simple. We have carried out survey trial, which showed the systems utility as a high-resolution deep-tow seismic survey system. Furthermore, the frequency ranges of deep-towed source (SBP) and surface towed sparker are 700-2300Hz and 10-200Hz respectively. Therefore we can use these sources simultaneously and distinguish the records of each source in the data processing stage. We have developed new marine seismic survey systems with autonomous recording for the exploration of the ocean floor resources. The applications are vertical cable seismic (VCS) and deep-tow seismic (ACS). These enable us the recording close to the seafloor and give the high resolution results with a simple, cost-effective configuration.

Hydrophone area-averaging correction factors in nonlinearly generated ultrasonic beams

NASA Astrophysics Data System (ADS)

Cooling, M. P.; Humphrey, V. F.; Wilkens, V.

2011-02-01

The nonlinear propagation of an ultrasonic wave can be used to produce a wavefield rich in higher frequency components that is ideally suited to the calibration, or inter-calibration, of hydrophones. These techniques usually use a tone-burst signal, limiting the measurements to harmonics of the fundamental calibration frequency. Alternatively, using a short pulse enables calibration at a continuous spectrum of frequencies. Such a technique is used at PTB in conjunction with an optical measurement technique to calibrate devices. Experimental findings indicate that the area-averaging correction factor for a hydrophone in such a field demonstrates a complex behaviour, most notably varying periodically between frequencies that are harmonics of the centre frequency of the original pulse and frequencies that lie midway between these harmonics. The beam characteristics of such nonlinearly generated fields have been investigated using a finite difference solution to the nonlinear Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation for a focused field. The simulation results are used to calculate the hydrophone area-averaging correction factors for 0.2 mm and 0.5 mm devices. The results clearly demonstrate a number of significant features observed in the experimental investigations, including the variation with frequency, drive level and hydrophone element size. An explanation for these effects is also proposed.

Passive acoustic localization of the Atlantic bottlenose dolphin using whistles and echolocation clicks.

PubMed

Freitag, L E; Tyack, P L

1993-04-01

A method for localization and tracking of calling marine mammals was tested under realistic field conditions that include noise, multipath, and arbitrarily located sensors. Experiments were performed in two locations using four and six hydrophones with captive Atlantic bottlenose dolphins (Tursiops truncatus). Acoustic signals from the animals were collected in the field using a digital acoustic data acquisition system. The data were then processed off-line to determine relative hydrophone positions and the animal locations. Accurate hydrophone position estimates are achieved by pinging sequentially from each hydrophone to all the others. A two-step least-squares algorithm is then used to determine sensor locations from the calibration data. Animal locations are determined by estimating the time differences of arrival of the dolphin signals at the different sensors. The peak of a matched filter output or the first cycle of the observed waveform is used to determine arrival time of an echolocation click. Cross correlation between hydrophones is used to determine inter-sensor time delays of whistles. Calculation of source location using the time difference of arrival measurements is done using a least-squares solution to minimize error. These preliminary experimental results based on a small set of data show that realistic trajectories for moving animals may be generated from consecutive location estimates.

Vertically Free-Standing Ordered Pb(Zr0.52Ti0.48)O3 Nanocup Arrays by Template-Assisted Ion Beam Etching.

PubMed

Zhang, Xiaoyan; Tang, Dan; Huang, Kangrong; Hu, Die; Zhang, Fengyuan; Gao, Xingsen; Lu, Xubing; Zhou, Guofu; Zhang, Zhang; Liu, Junming

2016-12-01

In this report, vertically free-standing lead zirconate titanate Pb(Zr0.52Ti0.48)O3 (PZT) nanocup arrays with good ordering and high density (1.3 × 10(10) cm(-2)) were demonstrated. By a template-assisted ion beam etching (IBE) strategy, the PZT formed in the pore-through anodic aluminum oxide (AAO) membrane on the Pt/Si substrate was with a cup-like nanostructure. The mean diameter and height of the PZT nanocups (NCs) was about 80 and 100 nm, respectively, and the wall thickness of NCs was about 20 nm with a hole depth of about 80 nm. Uppermost, the nanocup structure with low aspect ratio realized vertically free-standing arrays when losing the mechanical support from templates, avoiding the collapse or bundling when compared to the typical nanotube arrays. X-ray diffraction (XRD) and Raman spectrum revealed that the as-prepared PZT NCs were in a perovskite phase. By the vertical piezoresponse force microscopy (VPFM) measurements, the vertically free-standing ordered ferroelectric PZT NCs showed well-defined ring-like piezoresponse phase and hysteresis loops, which indicated that the high-density PZT nanocup arrays could have potential applications in ultra-high non-volatile ferroelectric memories (NV-FRAM) or other nanoelectronic devices.

The depth-dependence of rain noise in the Philippine Sea.

PubMed

Barclay, David R; Buckingham, Michael J

2013-05-01

During the Philippine Sea experiment in May 2009, Deep Sound, a free-falling instrument platform, descended to a depth of 5.1 km and then returned to the surface. Two vertically aligned hydrophones monitored the ambient noise continuously throughout the descent and ascent. A heavy rainstorm passed over the area during the deployment, the noise from which was recorded over a frequency band from 5 Hz to 40 kHz. Eight kilometers from the deployment site, a rain gauge on board the R/V Kilo Moana provided estimates of the rainfall rate. The power spectral density of the rain noise shows two peaks around 5 and 30 kHz, elevated by as much as 20 dB above the background level, even at depths as great as 5 km. Periods of high noise intensity in the acoustic data correlate well with the rainfall rates recovered from the rain gauge. The vertical coherence function of the rain noise has well-defined zeros between 1 and 20 kHz, which are characteristic of a localized source on the sea surface. A curve-fitting procedure yields the vertical directional density function of the noise, which is sharply peaked, accurately tracking the storm as it passed over the sensor station.

FIBER AND INTEGRATED OPTICS: Multiplexed optical-fiber sensors with autodyne detection

NASA Astrophysics Data System (ADS)

Potapov, V. T.; Mamedov, A. M.; Shatalin, S. V.; Yushkaĭtis, R. V.

1993-09-01

A method is proposed for multiplexing optical-fiber interference sensors. The method involves autodyne reception of frequency-modulated radiation reflected back to the laser. The response of a He-Ne laser with a linearly varying generation frequency to radiation reflected back from a single-mode fiber is studied. The spectrum of beats caused in the laser radiation by the reflection is shown to be governed by the distribution of reflectors along the fiber. The phases of the spectral components contain information about the phase shift of the reflected optical signal. A hydrophone array with a sensitivity of 30 μrad/Hz1/2 is described. A distributed temperature sensor with a spatial resolution of 1 m is also described.

Comparison of PAM Systems for Acoustic Monitoring and Further Risk Mitigation Application.

PubMed

Ludwig, Stefan; Kreimeyer, Roman; Knoll, Michaela

2016-01-01

We present results of the SIRENA 2011 research cruises conducted by the NATO Undersea Research Centre (NURC) and joined by the Research Department for Underwater Acoustics and Geophysics (FWG), Bundeswehr Technical Centre (WTD 71) and the Universities of Kiel and Pavia. The cruises were carried out in the Ligurian Sea. The main aim of the FWG was to test and evaluate the newly developed towed hydrophone array as a passive acoustic monitoring (PAM) tool for risk mitigation applications. The system was compared with the PAM equipment used by the other participating institutions. Recorded sounds were used to improve an automatic acoustic classifier for marine mammals, and validated acoustic detections by observers were compared with the results of the classifier.

Development of a portable passive-acoustic bedload monitoring system

USDA-ARS?s Scientific Manuscript database

A hydrophone-based passive acoustic bedload-monitoring system was designed, tested and deployed by researchers at the University of Mississippi and the National Sedimentation Laboratory in Oxford, MS. The hydrophone system was designed to be easily deployed and operated by non-experts. In addition, ...

Vertical viewing angle enhancement for the 360  degree integral-floating display using an anamorphic optic system.

PubMed

Erdenebat, Munkh-Uchral; Kwon, Ki-Chul; Yoo, Kwan-Hee; Baasantseren, Ganbat; Park, Jae-Hyeung; Kim, Eun-Soo; Kim, Nam

2014-04-15

We propose a 360 degree integral-floating display with an enhanced vertical viewing angle. The system projects two-dimensional elemental image arrays via a high-speed digital micromirror device projector and reconstructs them into 3D perspectives with a lens array. Double floating lenses relate initial 3D perspectives to the center of a vertically curved convex mirror. The anamorphic optic system tailors the initial 3D perspectives horizontally and vertically disperse light rays more widely. By the proposed method, the entire 3D image provides both monocular and binocular depth cues, a full-parallax demonstration with high-angular ray density and an enhanced vertical viewing angle.

Method of varying a characteristic of an optical vertical cavity structure formed by metalorganic vapor phase epitaxy

DOEpatents

Hou, Hong Q.; Coltrin, Michael E.; Choquette, Kent D.

2001-01-01

A process for forming an array of vertical cavity optical resonant structures wherein the structures in the array have different detection or emission wavelengths. The process uses selective area growth (SAG) in conjunction with annular masks of differing dimensions to control the thickness and chemical composition of the materials in the optical cavities in conjunction with a metalorganic vapor phase epitaxy (MOVPE) process to build these arrays.

Study of phase-locked diode laser array and DFB/DBR surface emitting laser diode

NASA Astrophysics Data System (ADS)

Hsin, Wei

New types of phased-array and surface-emitting lasers are designed. The importance and approaches (or structures) of different phased array and surface emitting laser diodes are reviewed. The following are described: (1) a large optical cavity channel substrate planar laser array with layer thickness chirping; (2) a vertical cavity surface emitter with distributed feedback (DFB) optical cavity and a transverse junction buried heterostructure; (3) a microcavity distributed Bragg reflector (DBR) surface emitter; and (4) two surface emitting laser structures which utilized lateral current injection schemes to overcome the problems occurring in the vertical injection scheme.

Fabrication of flexible and vertical silicon nanowire electronics.

PubMed

Weisse, Jeffrey M; Lee, Chi Hwan; Kim, Dong Rip; Zheng, Xiaolin

2012-06-13

Vertical silicon nanowire (SiNW) array devices directly connected on both sides to metallic contacts were fabricated on various non-Si-based substrates (e.g., glass, plastics, and metal foils) in order to fully exploit the nanomaterial properties for final applications. The devices were realized with uniform length Ag-assisted electroless etched SiNW arrays that were detached from their fabrication substrate, typically Si wafers, reattached to arbitrary substrates, and formed with metallic contacts on both sides of the NW array. Electrical characterization of the SiNW array devices exhibits good current-voltage characteristics consistent with the SiNW morphology.

Matrix addressable vertical cavity surface emitting laser array

NASA Astrophysics Data System (ADS)

Orenstein, M.; von Lehmen, A. C.; Chang-Hasnain, C.; Stoffel, N. G.; Harbison, J. P.

1991-02-01

The design, fabrication and characterization of 1024-element matrix-addressable vertical-cavity surface-emitting laser (VCSEL) arrays are described. A strained InGaAs quantum-well VCSEL structure was grown by MBE, and an array of 32 x 32 lasers was defined using a proton implantation process. A matrix addressing architecture was employed, which enables the individual addressing of each of the 1024 lasers using only 64 electrical contacts. All the lasers in the array, measured after the laser definition step, were operating with fairly homogeneous characteristics; threshold current of 6.8 mA and output quantum differential efficiency of about 8 percent.

Nonlinear propagation model for ultrasound hydrophones calibration in the frequency range up to 100 MHz.

PubMed

Radulescu, E G; Wójcik, J; Lewin, P A; Nowicki, A

2003-06-01

To facilitate the implementation and verification of the new ultrasound hydrophone calibration techniques described in the companion paper (somewhere in this issue) a nonlinear propagation model was developed. A brief outline of the theoretical considerations is presented and the model's advantages and disadvantages are discussed. The results of simulations yielding spatial and temporal acoustic pressure amplitude are also presented and compared with those obtained using KZK and Field II models. Excellent agreement between all models is evidenced. The applicability of the model in discrete wideband calibration of hydrophones is documented in the companion paper somewhere in this volume.

Nanostructured pillars based on vertically aligned carbon nanotubes as the stationary phase in micro-CEC.

PubMed

Wu, Ren-Guei; Yang, Chung-Shi; Wang, Pen-Cheng; Tseng, Fan-Gang

2009-06-01

We present a micro-CEC chip carrying out a highly efficient separation of dsDNA fragments through vertically aligned multi-wall carbon nanotubes (MWCNTs) in a microchannel. The vertically aligned MWCNTs were grown directly in the microchannel to form straight nanopillar arrays as ordered and directional chromatographic supports. 1-Pyrenedodecanoic acid was employed for the surface modification of the MWCNTs' stationary phase to adsorb analytes by hydrophobic interactions. This device was used for separating dsDNA fragments of three different lengths (254, 360, and 572 bp), and fluorescence detection was employed to verify the electrokinetic transport in the MWCNT array. The micro-CEC separation of the three compounds was achieved in less than 300 s at a field strength of 66 V/cm due to superior laminar flow patterns and a lower flow resistance resulting from the vertically aligned MWCNTs being used as the stationary phase medium. In addition, a fivefold reduction of band broadening was obtained when the analyte was separated by the chromatographic MWCNT array channel instead of the CE channel. From all of the results, we suggest that an in situ grown and directional MWCNT array can potentially be useful for preparing more diversified forms of stationary phases for vertically efficient chip-based electrochromatography.

Development of a High Intensity Focused Ultrasound (HIFU) Hydrophone System

NASA Astrophysics Data System (ADS)

Schafer, Mark E.; Gessert, James; Moore, Wayne

2006-05-01

Concomitant with the growing clinical use of High Intensity Focused Ultrasound (HIFU), there has been a need for reliable, economical and reproducible measurements of HIFU acoustic fields. A number of approaches have been proposed and investigated, most notably by Kaczkowski et al [Proc. 2003 IEEE Ultrasonics Symposium, 982-985]. We are developing a similar reflective scatterer approach, incorporating several novel features which improve the hydrophone's bandwidth, reliability, and reproducibility. For the scattering element, we have used a fused silica optical fiber with a polyamide protective coating. The receiver is designed as a segmented, truncated spherical structure with a 10cm radius; the scattering element is positioned at the center of the sphere. The receiver is made from 25 micron thick, biaxially stretched PVDF, with a Pt-Au electrode on the front surface. Each segment has its own high impedance, wideband preamplifier, and the signals from multiple segments are summed coherently. As an additional feature, the system is designed to pulse the PVDF elements so that the pulse-echo response can be used to align the fiber at the center. Initial tests of the system have demonstrated a receiver array sensitivity of -279 dB re 1 microVolt/Pa (before preamplification), with a scattering loss at the fiber of approximately 39dB, producing an effective sensitivity of -318 dB re 1 micro Volt/Pa. The addition of the closely coupled wideband preamplifiers boosts the signal to a range which is sufficient for the measurement of HIFU transducers. The effective bandwidth of the system exceeds 15MHz, through careful design and the use of PVDF as a sensor material. In order to test the system, a HIFU transducer in the 4.0MHz frequency range was tested at low output settings using a conventional PVDF membrane hydrophone. The prototype system was then used to characterize the same HIFU transducer at full power. The results showed good correlation between waveforms and cross-axis beam measurements, taking into account the additional shock losses at higher output settings.

Laser-assisted simultaneous transfer and patterning of vertically aligned carbon nanotube arrays on polymer substrates for flexible devices.

PubMed

In, Jung Bin; Lee, Daeho; Fornasiero, Francesco; Noy, Aleksandr; Grigoropoulos, Costas P

2012-09-25

We demonstrate a laser-assisted dry transfer technique for assembling patterns of vertically aligned carbon nanotube arrays on a flexible polymeric substrate. A laser beam is applied to the interface of a nanotube array and a polycarbonate sheet in contact with one another. The absorbed laser heat promotes nanotube adhesion to the polymer in the irradiated regions and enables selective pattern transfer. A combination of the thermal transfer mechanism with rapid direct writing capability of focused laser beam irradiation allows us to achieve simultaneous material transfer and direct micropatterning in a single processing step. Furthermore, we demonstrate that malleability of the nanotube arrays transferred onto a flexible substrate enables post-transfer tailoring of electric conductance by collapsing the aligned nanotubes in different directions. This work suggests that the laser-assisted transfer technique provides an efficient route to using vertically aligned nanotubes as conductive elements in flexible device applications.

Growth of Vertically Aligned ZnO Nanowire Arrays Using Bilayered Metal Catalysts

DTIC Science & Technology

2012-01-01

12] J. P. Liu, C. X. Guo, C. M. Li et al., “Carbon-decorated ZnO nanowire array: a novel platform for direct electrochemistry of enzymes and...cited. Vertically aligned, high-density ZnO nanowires (NWs) were grown for the first time on c-plane sapphire using binary alloys of Ni/Au or Cu/Au as...deleterious to the ZnO NW array growth. Significant improvement of the Au adhesion on the substrate was noted, opening the potential for direct

Optimal design of aperiodic, vertical silicon nanowire structures for photovoltaics.

PubMed

Lin, Chenxi; Povinelli, Michelle L

2011-09-12

We design a partially aperiodic, vertically-aligned silicon nanowire array that maximizes photovoltaic absorption. The optimal structure is obtained using a random walk algorithm with transfer matrix method based electromagnetic forward solver. The optimal, aperiodic structure exhibits a 2.35 times enhancement in ultimate efficiency compared to its periodic counterpart. The spectral behavior mimics that of a periodic array with larger lattice constant. For our system, we find that randomly-selected, aperiodic structures invariably outperform the periodic array.

Vertically aligned ZnO nanorod core-polypyrrole conducting polymer sheath and nanotube arrays for electrochemical supercapacitor energy storage

PubMed Central

2014-01-01

Nanocomposite electrodes having three-dimensional (3-D) nanoscale architecture comprising of vertically aligned ZnO nanorod array core-polypyrrole (PPy) conducting polymer sheath and the vertical PPy nanotube arrays have been investigated for supercapacitor energy storage. The electrodes in the ZnO nanorod core-PPy sheath structure are formed by preferential nucleation and deposition of PPy layer over hydrothermally synthesized vertical ZnO nanorod array by controlled pulsed current electropolymerization of pyrrole monomer under surfactant action. The vertical PPy nanotube arrays of different tube diameter are created by selective etching of the ZnO nanorod core in ammonia solution for different periods. Cyclic voltammetry studies show high areal-specific capacitance approximately 240 mF.cm-2 for open pore and approximately 180 mF.cm-2 for narrow 30-to-36-nm diameter PPy nanotube arrays attributed to intensive faradic processes arising from enhanced access of electrolyte ions through nanotube interior and exterior. Impedance spectroscopy studies show that capacitive response extends over larger frequency domain in electrodes with PPy nanotube structure. Simulation of Nyquist plots by electrical equivalent circuit modeling establishes that 3-D nanostructure is better represented by constant phase element which accounts for the inhomogeneous electrochemical redox processes. Charge-discharge studies at different current densities establish that kinetics of the redox process in PPy nanotube electrode is due to the limitation on electron transport rather than the diffusive process of electrolyte ions. The PPy nanotube electrodes show deep discharge capability with high coulomb efficiency and long-term charge-discharge cyclic studies show nondegrading performance of the specific areal capacitance tested for 5,000 cycles. PMID:25246867

ORPC RivGen Acoustic Measurements

DOE Data Explorer

Brian Polagye

2016-06-06

Drifting hydrophone measurements obtained around the Ocean Renewable Power Company RivGen turbine near the village of Igiugig, Alaska in August, 2014. Each data set contains hydrophone voltage (as well as gain and sensitivity), position on the river (LAT, LONG, and proximity to turbine [xt, yt]), drift velocity, and contextual meteorological data.

Ensuring very shallow-water sediment properties: case study from Capo Granitola harbour, Sicily (Italy)

NASA Astrophysics Data System (ADS)

Punzo, Michele; Cavuoto, Giuseppe; Tarallo, Daniela; Di Fiore, Vincenzo

2017-09-01

We present high-resolution Vp models of the Capo Granitola harbor, Sicily (Italy) obtained by first arrival traveltime tomography. Seismic data were collected along four hydrophone arrays on the sea-bottom and via a Watergun as seismic source, in order to plan dredging operations in the harbor. Using a hydrophone spacing of 2.5 m and shot spacing of 5 m, very high resolution quality data were recorded. Seismic tomography expands existing knowledge of the harbour subsoil with a penetration of about 20 m, illuminating the Lower Pleistocene bedrock (Marsala calcarenites) that corresponds to high-Vp regions (Vp > 4.5 km/s). Low Vp (1.8-4.5 km/s) deposits belonging to terraced calcarenites (Upper Pleistocene in age) are also well imaged; they are about 8 m thick and lie below loose sand deposits (Vp = 1.5 km/s). The substratum has an articulated morphology; Vp images unravel small steps in the basement probably related to structural discontinuities (e.g., faults). Processing data with 3D techniques enables images of the structure and the thickness of the lithotypes to be reconstructed, thus leading to large-scale, realistic estimates of the total quantity of material to be excavated or dredged. Tomographic profiles permit clear discrimination of the soft sediment above the basement and thus allow the determination of the total volume of sediment above the seismic bedrock, estimated at about 265,000 m3.

Support for the beam focusing hypothesis in the false killer whale.

PubMed

Kloepper, Laura N; Buck, John R; Smith, Adam B; Supin, Alexander Ya; Gaudette, Jason E; Nachtigall, Paul E

2015-08-01

The odontocete sound production system is complex and composed of tissues, air sacs and a fatty melon. Previous studies suggested that the emitted sonar beam might be actively focused, narrowing depending on target distance. In this study, we further tested this beam focusing hypothesis in a false killer whale. Using three linear arrays of hydrophones, we recorded the same emitted click at 2, 4 and 7 m distance and calculated the beamwidth, intensity, center frequency and bandwidth as recorded on each array at every distance. If the whale did not focus her beam, acoustics predicts the intensity would decay with range as a function of spherical spreading and the angular beamwidth would remain constant. On the contrary, our results show that as the distance from the whale to the array increases, the beamwidth is narrower and the received click intensity is higher than that predicted by a spherical spreading function. Each of these measurements is consistent with the animal focusing her beam on a target at a given range. These results support the hypothesis that the false killer whale is 'focusing' its sonar beam, producing a narrower and more intense signal than that predicted by spherical spreading. © 2015. Published by The Company of Biologists Ltd.

Echolocation signals of foraging killer whales (Orcinus orca)

NASA Astrophysics Data System (ADS)

Au, Whitlow W. L.; Ford, John K. B.; Allman, Kelly A.

2002-05-01

Fish eating resident killer whales that frequent the coastal waters of Vancouver Island, Canada have a strong preference for chinook salmon. The whales in Johnston Strait often forage along the steep cliffs that extend into the water, echolocating their prey. Echolocation signals were measured with a four hydrophone symmetrical star array and the signals were simultaneous digitized at a sample rate of 500 kHz using a lunch-box PC. A portable VCR recorded the images from an underwater camera located close to the array center. Only signals emanated from close to the beam axis (1185 total) were chosen for a detailed analysis. Killer whales project very broad band echolocation signals (Q 1.3 to 1.5) that tend to have a bimodal frequency structure. Ninety seven percent of the signals had center frequencies between 45 and 80 kHz with a band-width between 35 and 50 kHz. The peak-to-peak source level of the echolocation signal decreased as a function of the one way transmission loss to the array. Source levels varied between 200 and 225 dB re 1 μPa. Using a model of target strength for chinook salmons, the echo levels from the echolocation signals are estimated for different ranges between whale and salmon.

Evaluation of high frequency ghost cavitation emissions for two different seismic air-gun arrays using numerical modelling

NASA Astrophysics Data System (ADS)

Khodabandeloo, Babak; Landrø, Martin

2017-04-01

Sound is deployed by marine mammals for variety of vital purposes such as finding food, communication, echolocation, etc. On the other hand human activities generate underwater noise. One major type of acoustic source is marine seismic acquisition which is carried out to image layers beneath the seabed exploiting reflected acoustic and elastic waves. Air-gun arrays are the most common and efficient marine seismic sources. Field measurements using broad band hydrophones have revealed that acoustic energies emitted by air-gun arrays contains frequencies from a few Hz up to tens of kHz. Frequencies below 200 Hz benefit seismic imaging and the rest is normally considered as wasted energy. On the other hand, the high frequency range (above 200 Hz) overlaps with hearing curves of many marine mammals and especially toothed whales and may have an impact on their behavior. A phenomenon called ghost cavitation is recently recognized to be responsible for a major part of these high frequencies (> 5 kHz). Acoustic pressure waves of individual air guns reflected from sea surface can cause the hydrostatic pressure to drop towards zero close to the source array. In these regions there is a high probability for water vapor cavity growth and subsequent collapse. We have simulated ghost cavitation cloud using numerical modelling and the results are validated by comparing with field measurements. The model is used to compare the amount of high frequency noise due to ghost cavitation for two different air gun arrays. Both of the arrays have three subarrays but the array distance for the one with 2730 in3 air volume is 6 meters and for the slightly bigger array (3250 in3 in air volume) the subarrays are separated by 8 meters. Simulation results indicate that the second array, despite larger subarray distance, generates stronger ghost cavitation signal.

Shallow Water Propagation

DTIC Science & Technology

2010-02-26

bottom waveguide. The lower contour plot demonstrates that this method, unlike other parabolic equations, can treat seismic sources. 20100308162...solitons. One illustration in Figure 8 shows depth-averaged data at the Naval Research Laboratory vertical line array (VLA) [dashed blue curves...vertical line array about 15 km from the source. The right panel [blue curves] compares corresponding simulations from a three-dimensional adiabatic mode

Number Prompts Left-to-Right Spatial Mapping in Toddlerhood

ERIC Educational Resources Information Center

McCrink, Koleen; Perez, Jasmin; Baruch, Erica

2017-01-01

Toddlers performed a spatial mapping task in which they were required to learn the location of a hidden object in a vertical array and then transpose this location information 90° to a horizontal array. During the vertical training, they were given (a) no labels, (b) alphabetical labels, or (c) numerical labels for each potential spatial location.…

Localization of Southern Resident Killer Whales Using Two Star Arrays to Support Marine Renewable Energy

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

Ren, Huiying; Deng, Zhiqun; Carlson, Thomas J.

2012-10-19

Tidal power has been identified as one of the most potential commercial-scale renewable energy sources. Puget Sound, Washington, is a potential site to deploy tidal power generating devices. The risk of injury for killer whales needs to be managed before the deployment of these types of devices can be approved by regulating authorities. A passive acoustic system consisting of two star arrays, each with four hydrophones, was designed and implemented for the detection and localization of Southern Resident killer whales. Deployment of the passive acoustic system was conducted at Sequim Bay, Washington. A total of nine test locations were chosen,more » within a radius of 250 m around the star arrays, to test our localization approach. For the localization algorithm, a least square solver was applied to obtain a bearing location from each star array. The final source location was determined by the intersection of the bearings given by each of the two star arrays. Bearing and distance errors were obtained to conduct comparison between the calculated and true (from Global Positioning System) locations. The results indicated that bearing errors were within 1.04º for eight of the test locations; one location had bearing errors slightly larger than expected due to the strong background noise at that position. For the distance errors, six of the test locations were within the range of 1.91 to 32.36 m. The other two test locations were near the intersection line between the centers of the two star arrays, which were expected to have large errors from the theoretical sensitivity analysis performed.« less

Simulation of non-linear acoustic field and thermal pattern of phased-array high-intensity focused ultrasound (HIFU).

PubMed

Wang, Mingjun; Zhou, Yufeng

2016-08-01

HIFU becomes an effective and non-invasive modality of solid tumour/cancer ablation. Simulation of the non-linear acoustic wave propagation using a phased-array transducer in multiple layered media using different focusing strategies and the consequent lesion formation are essential in HIFU planning in order to enhance the efficacy and efficiency of treatment. An angular spectrum approach with marching fractional steps was applied in the wave propagation from phased-array HIFU transducer, and diffraction, attenuation, and non-linearity effects were accounted for by a second-order operator splitting scheme. The simulated distributions of the first three harmonics along and transverse to the transducer axis were compared to the hydrophone measurements. The bioheat equation was used to simulate the subsequent temperature elevation using the deposited acoustic energy, and lesion formation was determined by the thermal dose. Better agreement was found between the measured harmonics distribution and simulation using the proposed algorithm than the Khokhlov-Zabozotskaya-Kuznetsov equation. Variable focusing of the phased-array transducer (geometric focusing, transverse shifting and the generation of multiple foci) can be simulated successfully. The shifting and splitting of focus was found to result in significantly less temperature elevation at the focus and the subsequently, the smaller lesion size, but the larger grating lobe grating lobe in the pre-focal region. The proposed algorithm could simulate the non-linear wave propagation from the source with arbitrary shape and distribution of excitation through multiple tissue layers in high computation accuracy. The performance of phased-array HIFU can be optimised in the treatment planning.

Ocean Basin Impact of Ambient Noise on Marine Mammal Detectability, Distribution, and Acoustic Communication - YIP

DTIC Science & Technology

2011-09-30

when applying the 4 passive sonar equation. The integration of acoustic time series from different ocean basins will provide a synoptic...Penn State ARL Hydrophone Analog signal (V) Preamplifiers & 24-bit AiD 1-100 HzBP filter Signal Flow for a Single Hydrophone Digital signal

Balancing Mitigation Against Impact: A Case Study From the 2005 Chicxulub Seismic Survey

NASA Astrophysics Data System (ADS)

Barton, P.; Diebold, J.; Gulick, S.

2006-05-01

In early 2005 the R/V Maurice Ewing conducted a large-scale deep seismic reflection-refraction survey offshore Yucatan, Mexico, to investigate the internal structure of the Chicxulub impact crater, centred on the coastline. Shots from a tuned 20 airgun, 6970 cu in array were recorded on a 6 km streamer and 25 ocean bottom seismometers (OBS). The water is exceptionally shallow to large distances offshore, reaching 30 m about 60 km from the land, making it unattractive to the larger marine mammals, although there are small populations of Atlantic and spotted dolphins living in the area, as well as several turtle breeding and feeding grounds on the Yucatan peninsula. In the light of calibrated tests of the Ewing's array (Tolstoy et al., 2004, Geophysical Research Letters 31, L14310), a 180 dB safety radius of 3.5 km around the gun array was adopted. An energetic campaign was organised by environmentalists opposing the work. In addition to the usual precautions of visual and listening watches by independent observers, gradual ramp-ups of the gun arrays, and power-downs or shut-downs for sightings, constraints were also placed to limit the survey to daylight hours and weather conditions not exceeding Beaufort 4. The operations were subject to several on-board inspections by the Mexican environmental authorities, causing logistical difficulties. Although less than 1% of the total working time was lost to shutdowns due to actual observation of dolphins or turtles, approximately 60% of the cruise time was taken up in precautionary inactivity. A diver in the water 3.5 km from the profiling ship reported that the sound in the water was barely noticeable, leading us to examine the actual sound levels recorded by both the 6 km streamer and the OBS hydrophones. The datasets are highly self-consistent, and give the same pattern of decay with distance past about 2 km offset, but with different overall levels: this may be due to geometry or calibration differences under investigation. Both datasets indicate significantly lower levels than reported by Tolstoy et al. (2004). There was no evidence of environmental damage created by this survey. It can be concluded that the mitigation measures were extremely successful, but there is also a concern that the overhead cost of the environmental protection made this one of the most costly academic surveys ever undertaken, and that not all of this protection was necessary. In particular, the predicted 180 dB safety radius appeared to be overly conservative, even though based on calibrated measurements in very similar physical circumstances, and we suggest that these differences were a result of local seismic velocity structure in the water column and/or shallow seabed, which resulted in different partitioning of the energy. These results suggest that real time monitoring of hydrophone array data may provide a method of determining the safety radius dynamically, in response to local conditions.

Detection of baleen whales on an ocean-bottom seismometer array in the Lau Basin

NASA Astrophysics Data System (ADS)

Brodie, D.; Dunn, R.

2011-12-01

Long-term deployment of ocean-bottom seismometer arrays provides a unique opportunity for identifying and tracking whales in a manner not usually possible in biological studies. Large baleen whales emit low frequency (>5Hz) sounds called 'calls' or 'songs' that can be detected on either the hydrophone or vertical channel of the instrument at distances in excess of 50 km. The calls are distinct to individual species and even geographical groups among species, and are thought to serve a variety of purposes. Distinct repeating calls can be automatically identified using matched-filter processing, and whales can be located in a manner similar to that of earthquakes. Many baleen whale species are endangered, and little is known about their geographic distribution, population dynamics, and basic behaviors. The Lau back-arc basin, a tectonically active, elongated basin bounded by volcanic shallows, lies in the southwestern Pacific Ocean between Fiji and Tonga. Although whales are known to exist around Fiji and Tonga, little is understood about the population dynamics and migration patterns throughout the basin. Twenty-nine broadband ocean-bottom seismometers deployed in the basin recorded data for approximately ten months during the years 2009-2010. To date, four species of whales have been identified in the data: Blue (one call type), Humpback (two call types, including long-lasting 'songs'), Bryde's (one call type), and Fin whales (three call types). Three as-yet-unknown call types have also been identified. After the calls were identified, idealized spectrograms of the known calls were matched against the entire data set using an auto-detection algorithm. The auto-detection output provides the number of calls and times of year when each call type was recorded. Based on the results, whales migrate seasonally through the basin with some overlapping of species. Initial results also indicate that different species of whales are more common in some parts of the basin than others, suggesting preferences in water depth and distance to land. In future work, whales will be tracked through the basin using call localization information to illustrate migration patterns of the various species.

Whistle source levels of free-ranging beluga whales in Saguenay-St. Lawrence marine park.

PubMed

Le Bot, Olivier; Simard, Yvan; Roy, Nathalie; Mars, Jérôme I; Gervaise, Cédric

2016-07-01

Wild beluga whistle source levels (SLs) are estimated from 52 three-dimensional (3D) localized calls using a 4-hydrophone array. The probability distribution functions of the root-mean-square (rms) SL in the time domain, and the peak, the strongest 3-dB, and 10-dB SLs from the spectrogram, were non-Gaussian. The average rms SL was 143.8 ± 6.7 dB re 1 μPa at 1 m. SL spectral metrics were, respectively, 145.8 ± 8 dB, 143.2 ± 7.1 dB, and 138.5 ± 6.9 dB re 1 μPa(2)·Hz(-1) at 1 m.

Design Considerations and Performance of MEMS Acoustoelectric Ultrasound Detectors

PubMed Central

Wang, Zhaohui; Ingram, Pier; Greenlee, Charles L.; Olafsson, Ragnar; Norwood, Robert A.; Witte, Russell S.

2014-01-01

Most single-element hydrophones depend on a piezoelectric material that converts pressure changes to electricity. These devices, however, can be expensive, susceptible to damage at high pressure, and/or have limited bandwidth and sensitivity. We have previously described the acoustoelectric (AE) hydrophone as an inexpensive alternative for mapping an ultrasound beam and monitoring acoustic exposure. The device exploits the AE effect, an interaction between electrical current flowing through a material and a propagating pressure wave. Previous designs required imprecise fabrication methods using common laboratory supplies, making it difficult to control basic features such as shape and size. This study describes a different approach based on microelectromechanical systems (MEMS) processing that allows for much finer control of several design features. In an effort to improve the performance of the AE hydrophone, we combine simulations with bench-top testing to evaluate key design features, such as thickness, shape, and conductivity of the active and passive elements. The devices were evaluated in terms of sensitivity, frequency response, and accuracy for reproducing the beam pattern. Our simulations and experimental results both indicated that designs using a combination of indium tin oxide (ITO) for the active element and gold for the passive electrodes (conductivity ratio = ~20) produced the best result for mapping the beam of a 2.25-MHz ultrasound transducer. Also, the AE hydrophone with a rectangular dumbbell configuration achieved a better beam pattern than other shape configurations. Lateral and axial resolutions were consistent with images generated from a commercial capsule hydrophone. Sensitivity of the best-performing device was 1.52 nV/Pa at 500 kPa using a bias voltage of 20 V. We expect a thicker AE hydrophone closer to half the acoustic wavelength to produce even better sensitivity, while maintaining high spectral bandwidth for characterizing medical ultrasound transducers. AE ultrasound detectors may also be useful for monitoring acoustic exposure during therapy or as receivers for photoacoustic imaging. PMID:24658721

Vector Acoustics, Vector Sensors, and 3D Underwater Imaging

NASA Astrophysics Data System (ADS)

Lindwall, D.

2007-12-01

Vector acoustic data has two more dimensions of information than pressure data and may allow for 3D underwater imaging with much less data than with hydrophone data. The vector acoustic sensors measures the particle motions due to passing sound waves and, in conjunction with a collocated hydrophone, the direction of travel of the sound waves. When using a controlled source with known source and sensor locations, the reflection points of the sound field can be determined with a simple trigonometric calculation. I demonstrate this concept with an experiment that used an accelerometer based vector acoustic sensor in a water tank with a short-pulse source and passive scattering targets. The sensor consists of a three-axis accelerometer and a matched hydrophone. The sound source was a standard transducer driven by a short 7 kHz pulse. The sensor was suspended in a fixed location and the hydrophone was moved about the tank by a robotic arm to insonify the tank from many locations. Several floats were placed in the tank as acoustic targets at diagonal ranges of approximately one meter. The accelerometer data show the direct source wave as well as the target scattered waves and reflections from the nearby water surface, tank bottom and sides. Without resorting to the usual methods of seismic imaging, which in this case is only two dimensional and relied entirely on the use of a synthetic source aperture, the two targets, the tank walls, the tank bottom, and the water surface were imaged. A directional ambiguity inherent to vector sensors is removed by using collocated hydrophone data. Although this experiment was in a very simple environment, it suggests that 3-D seismic surveys may be achieved with vector sensors using the same logistics as a 2-D survey that uses conventional hydrophones. This work was supported by the Office of Naval Research, program element 61153N.

Functionalized vertical GaN micro pillar arrays with high signal-to-background ratio for detection and analysis of proteins secreted from breast tumor cells.

PubMed

Choi, Mun-Ki; Kim, Gil-Sung; Jeong, Jin-Tak; Lim, Jung-Taek; Lee, Won-Yong; Umar, Ahmad; Lee, Sang-Kwon

2017-11-02

The detection of cancer biomarkers has recently attracted significant attention as a means of determining the correct course of treatment with targeted therapeutics. However, because the concentration of these biomarkers in blood is usually relatively low, highly sensitive biosensors for fluorescence imaging and precise detection are needed. In this study, we have successfully developed vertical GaN micropillar (MP) based biosensors for fluorescence sensing and quantitative measurement of CA15-3 antigens. The highly ordered vertical GaN MP arrays result in the successful immobilization of CA15-3 antigens on each feature of the arrays, thereby allowing the detection of an individual fluorescence signal from the top surface of the arrays owing to the high regularity of fluorophore-tagged MP spots and relatively low background signal. Therefore, our fluorescence-labeled and CA15-3 functionalized vertical GaN-MP-based biosensor is suitable for the selective quantitative analysis of secreted CA15-3 antigens from MCF-7 cell lines, and helps in the early diagnosis and prognosis of serious diseases as well as the monitoring of the therapeutic response of breast cancer patients.

Design and performance of a horizontal mooring for upper-ocean research

USGS Publications Warehouse

Grosenbaugh, Mark; Anderson, Steven; Trask, Richard; Gobat, Jason; Paul, Walter; Butman, Bradford; Weller, Robert

2002-01-01

This paper describes the design and performance of a two-dimensional moored array for sampling horizontal variability in the upper ocean. The mooring was deployed in Massachusetts Bay in a water depth of 84 m for the purpose of measuring the horizontal structure of internal waves. The mooring was instrumented with three acoustic current meters (ACMs) spaced along a 170-m horizontal cable that was stretched between two subsurface buoys 20 m below the sea surface. Five 25-m-long vertical instrument strings were suspended from the horizontal cable. A bottom-mounted acoustic Doppler current profiler (ADCP) was deployed nearby to measure the current velocity throughout the water column. Pressure sensors mounted on the subsurface buoys and the vertical instrument strings were used to measure the vertical displacements of the array in response to the currents. Measurements from the ACMs and the ADCP were used to construct time-dependent, two-dimensional current fields. The current fields were used as input to a numerical model that calculated the deformation of the array with respect to the nominal zero-current configuration. Comparison of the calculated vertical offsets of the downstream subsurface buoy and downstream vertical instrument string with the pressure measurements were used to verify the numerical code. These results were then used to estimate total deformation of the array due to the passage of the internal waves. Based on the analysis of the three internal wave events with the highest measured vertical offsets, it is concluded that the geometry of the main structure (horizontal cable and anchor legs) was kept to within ±2.0 m, and the geometry of the vertical instrument strings was kept to within ±4.0 m except for one instance when the current velocity reached 0.88 m s−1.

Hydrophone calibration for MERMAID seismic network

NASA Astrophysics Data System (ADS)

Joubert, C.; Nolet, G.; Sukhovich, A.; Ogé, A.; Argentino, J.; Hello, Y.

2013-12-01

The MERMAID float (Mobile Earthquake Recorder in Marine Areas by Independent Divers) is a new oceanic seismometer which has already successfully recorded P-waves from teleseismic events, when deployed in the Mediterranean Sea and the Indian Ocean. The frequency band of teleseismic acquisition is for frequencies up to 2 Hz. The P-waves are recorded with a Rafos II hydrophone. The hydrophone has a flat frequency response from 5 Hz to 10 kHz but its behavior below 5 Hz is not documented. In this work we determine the Rafos II response with the electronic card used for MERMAID in the frequency band of 0.1 to 2 Hz. A simple and low-cost calibration method at low frequencies was developed and applied to the Rafos II but can be used for any hydrophone. In this calibration method a brief pressure increase of 1000 Pa is applied to the hydrophone. We record response after filtering and digitizing by the electronic card. To create the pressure increase, the hydrophone is placed in a calibration chamber filled with water and making sure no air bubbles are present. By opening a solenoid valve connected to a tube with 10 cm extra water on top of the chamber, an abrupt pressure of 1000 Pa is applied. The output signal is fitted to an empirical response function, that characterizes it with four parameters: A, B, α and τ which control the shape of the signal: h(t) = t^(ατ) e^(-αt) (A + Bt). A represents the magnification, α defines the exponential relaxation of the signal, B models the overshoot and τ allows for a slightly delayed response due to the low-pass filtering in the electronics. A set of 20 experiments is used to characterize the Rafos II instrumental response in association with the electronic card. The method developed here offers a good and simple way to estimate the response at low frequencies. The MERMAID hydrophone response to the step function input of 1000 Pa can be defined by A = 0.36 × 0.02 mV/Pa, B = - 0.08 × 0.01 mV Pa^(-1) s^(-1), α = 0.28 × 0.02 s^(-1) and τ = 0.41 × 0.14 s.

Three-dimensional parabolic equation models of the acoustic coverage of the CTBT hydrophone station at Crozet

NASA Astrophysics Data System (ADS)

Zampolli, Mario; Haralabus, Georgios; Prior, Mark K.; Heaney, Kevin D.; Campbell, Richard

2014-05-01

Hydrophone stations of the Comprehensive Nuclear-Test-Ban Organisation (CTBTO) International Monitoring System (IMS), with the exception of one in Australia, comprise two triplets of submerged moored hydrophones, one North and one South of the island from which the respective system is deployed. Triplet distances vary approximately between 50 - 100 km from the island, with each triplet connected to the receiving shore equipment by fibre-optic submarine data cables. Once deployed, the systems relay underwater acoustic waveforms in the band 1 - 100 Hz in real time to Vienna via a shore based satellite link. The design life of hydroacoustic stations is at least 20 years, without need for any maintenance of the underwater system. The re-establishment of hydrophone monitoring station HA04 at Crozet (French Southern and Antarctic Territories) in the South-Western Indian Ocean is currently being investigated. In order to determine appropriate locations and depths for the installation of the hydrophones a number of constraints need to be taken into account and balanced against each other. The most important of these are (i) hydrophone depth in a region where the sound-speed profile is mostly upward refracting and the Sound Fixing and Ranging (SOFAR) channel is not well defined, (ii) a safe distance from the surface currents which occupy the first few hundred meters of the water column, (iii) seabed slopes that enable the safe deployment of the hydrophone mooring bases, (iv) avoidance of regions of high internal tide activity, (v) choice of locations to optimize basin and cross-basin scale acoustic coverage of each triplet and (vi) redundancy considerations so that one triplet can partially cover for the other one in case of necessity. A state-of-the-art three-dimensional (3-D) parabolic equation acoustic propagation model was used to model the propagation for a number of potential triplet locations. Criteria for short-listing candidate triplet locations were based on acoustic coverage towards the North and South, as well as overall acoustic coverage, taking into account different scales of source strength. An increase in the predicted area coverage compared to predictions based on 2-D modelling was observed and attributed to diffraction around sharp localized features such as islands or sea-mounts.

Self-assembled vertically aligned Au nanorod arrays for surface-enhanced Raman scattering (SERS) detection of Cannabinol

NASA Astrophysics Data System (ADS)

Milliken, Sarah; Fraser, Jeff; Poirier, Shawn; Hulse, John; Tay, Li-Lin

2018-05-01

Self-assembled multi-layered vertically aligned gold nanorod (AuNR) arrays have been fabricated by a simple preparation process that requires a balance between the particle concentration and the ionic strength of the solvent. An experimentally determined critical AuNR concentration of 2.0 nM and 50 mM NaCl produces well-ordered vertically aligned hexagonally close-packed AuNR arrays. We demonstrate surface treatment via UV Ozone cleaning of such samples to allow introduction of analyte molecules (benzenethiol and cannabinol) for effective surface enhanced Raman scattering detection. This is the first demonstration of the SERS analysis of cannabinol. This approach demonstrates a cost-effective, high-yield and simple fabrication route to SERS sensors with application in the screening for the cannabinoids.

High yield of self-catalyzed GaAs nanowire arrays grown on silicon via gallium droplet positioning.

PubMed

Plissard, S; Larrieu, G; Wallart, X; Caroff, P

2011-07-08

We report and detail a method to achieve growth of vertical self-catalyzed GaAs nanowires directly on Si(111) with a near-perfect vertical yield, using electron-beam-defined arrays of holes in a dielectric layer and molecular beam epitaxy. In our conditions, GaAs nanowires are grown along a vapor-liquid-solid mechanism, using in situ self-forming Ga droplets. The focus of this paper is to understand the role of the substrate preparation and of the pre-growth conditioning. Without changing temperature or the V/III ratio, the yield of vertical nanowires is increased incrementally up to 95%. The possibility to achieve very dense arrays, with center-to-center inter-wire distances less than 100 nm, is demonstrated.

Deformations and Rotational Ground Motions Inferred from Downhole Vertical Array Observations

NASA Astrophysics Data System (ADS)

Graizer, V.

2017-12-01

Only few direct reliable measurements of rotational component of strong earthquake ground motions are obtained so far. In the meantime, high quality data recorded at downhole vertical arrays during a number of earthquakes provide an opportunity to calculate deformations based on the differences in ground motions recorded simultaneously at different depths. More than twenty high resolution strong motion downhole vertical arrays were installed in California with primary goal to study site response of different geologic structures to strong motion. Deformation or simple shear strain with the rate γ is the combination of pure shear strain with the rate γ/2 and rotation with the rate of α=γ/2. Deformations and rotations were inferred from downhole array records of the Mw 6.0 Parkfield 2004, the Mw 7.2 Sierra El Mayor (Mexico) 2010, the Mw 6.5 Ferndale area in N. California 2010 and the two smaller earthquakes in California. Highest amplitude of rotation of 0.60E-03 rad was observed at the Eureka array corresponding to ground velocity of 35 cm/s, and highest rotation rate of 0.55E-02 rad/s associated with the S-wave was observed at a close epicentral distance of 4.3 km from the ML 4.2 event in Southern California at the La Cienega array. Large magnitude Sierra El Mayor earthquake produced long duration rotational motions of up to 1.5E-04 rad and 2.05E-03 rad/s associated with shear and surface waves at the El Centro array at closest fault distance of 33.4km. Rotational motions of such levels, especially tilting can have significant effect on structures. High dynamic range well synchronized and properly oriented instrumentation is necessary for reliable calculation of rotations from vertical array data. Data from the dense Treasure Island array near San Francisco demonstrate consistent change of shape of rotational motion with depth and material. In the frequency range of 1-15 Hz Fourier amplitude spectrum of vertical ground velocity is similar to the scaled tilt spectrum. Amplitudes of rotations at the site depend upon the size of the base and usually decrease with depth. They are also amplified by soft material. Earthquake data used in this study were downloaded from the Center for Engineering Strong Motion Data at http://www.strongmotioncenter.org/.

Field emission from in situ-grown vertically aligned SnO2 nanowire arrays

PubMed Central

2012-01-01

Vertically aligned SnO2 nanowire arrays have been in situ fabricated on a silicon substrate via thermal evaporation method in the presence of a Pt catalyst. The field emission properties of the SnO2 nanowire arrays have been investigated. Low turn-on fields of 1.6 to 2.8 V/μm were obtained at anode-cathode separations of 100 to 200 μm. The current density fluctuation was lower than 5% during a 120-min stability test measured at a fixed applied electric field of 5 V/μm. The favorable field-emission performance indicates that the fabricated SnO2 nanowire arrays are promising candidates as field emitters. PMID:22330800

Super non-linear RRAM with ultra-low power for 3D vertical nano-crossbar arrays.

PubMed

Luo, Qing; Xu, Xiaoxin; Liu, Hongtao; Lv, Hangbing; Gong, Tiancheng; Long, Shibing; Liu, Qi; Sun, Haitao; Banerjee, Writam; Li, Ling; Gao, Jianfeng; Lu, Nianduan; Liu, Ming

2016-08-25

Vertical crossbar arrays provide a cost-effective approach for high density three-dimensional (3D) integration of resistive random access memory. However, an individual selector device is not allowed to be integrated with the memory cell separately. The development of V-RRAM has impeded the lack of satisfactory self-selective cells. In this study, we have developed a high performance bilayer self-selective device using HfO2 as the memory switching layer and a mixed ionic and electron conductor as the selective layer. The device exhibits high non-linearity (>10(3)) and ultra-low half-select leakage (<0.1 pA). A four layer vertical crossbar array was successfully demonstrated based on the developed self-selective device. High uniformity, ultra-low leakage, sub-nA operation, self-compliance, and excellent read/write disturbance immunity were achieved. The robust array level performance shows attractive potential for low power and high density 3D data storage applications.

Vertically Integrated MEMS SOI Composite Porous Silicon-Crystalline Silicon Cantilever-Array Sensors: Concept for Continuous Sensing of Explosives and Warfare Agents

NASA Astrophysics Data System (ADS)

Stolyarova, Sara; Shemesh, Ariel; Aharon, Oren; Cohen, Omer; Gal, Lior; Eichen, Yoav; Nemirovsky, Yael

This study focuses on arrays of cantilevers made of crystalline silicon (c-Si), using SOI wafers as the starting material and using bulk micromachining. The arrays are subsequently transformed into composite porous silicon-crystalline silicon cantilevers, using a unique vapor phase process tailored for providing a thin surface layer of porous silicon on one side only. This results in asymmetric cantilever arrays, with one side providing nano-structured porous large surface, which can be further coated with polymers, thus providing additional sensing capabilities and enhanced sensing. The c-Si cantilevers are vertically integrated with a bottom silicon die with electrodes allowing electrostatic actuation. Flip Chip bonding is used for the vertical integration. The readout is provided by a sensitive Capacitance to Digital Converter. The fabrication, processing and characterization results are reported. The reported study is aimed towards achieving miniature cantilever chips with integrated readout for sensing explosives and chemical warfare agents in the field.

Air-bridged Ohmic contact on vertically aligned si nanowire arrays: application to molecule sensors.

PubMed

Han, Hee; Kim, Jungkil; Shin, Ho Sun; Song, Jae Yong; Lee, Woo

2012-05-02

A simple, cost-effective, and highly reliable method for constructing an air-bridged electrical contact on large arrays of vertically aligned nanowires was developed. The present method may open up new opportunities for developing advanced nanowire-based devices for energy harvest and storage, power generation, and sensing applications. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Physically Damped Noise Canceling Hydrophone

DTIC Science & Technology

2016-06-24

Description of the Prior Art [0004] An acoustic hydrophone can transfer underwater pressure waves to electrical energy. As a result, an output charge...includes two types of piezoelectric transducers coupled together. One transducer maintains voids and is sensitive to hydrostatic acoustic signals. The...the cable assembly. [0009] Cray (United States Patent No. 6,370,084) discloses an acoustic vector sensor. An accelerometer of the acoustic vector

Investigation of methods for successful installation and operation of Juvenile Salmon Acoustic Telemetry System (JSATS) hydrophones in the Willamette River, Oregon, 2012

USGS Publications Warehouse

Rutz, Gary L.; Sholtis, Matthew D.; Adams, Noah S.; Beeman, John W.

2014-01-01

Acoustic telemetry equipment was installed at three sites in the Willamette River during October 2012 to test the effectiveness of using the Juvenile Salmon Acoustic Telemetry System to monitor the movements of fish in a high-flow, high-velocity riverine environment. Hydrophones installed on concrete blocks were placed on the bottom of the river, and data cables were run from the hydrophones to shore where they were attached to anchor points. Under relatively low-flow conditions (less than approximately 10,000 cubic feet per second) the monitoring system remained in place and could be used to detect tagged fish as they traveled downstream during their seaward migration. At river discharge over approximately 10,000 cubic feet per second, the hydrophones were damaged and cables were lost because of the large volume of woody debris in the river and the increase in water velocity. Damage at two of the sites was sufficient to prevent data collection. A limited amount of data was collected from the equipment at the third site. Site selection and deployment strategies were re-evaluated, and an alternate deployment methodology was designed for implementation in 2013.

Diameter modulation of vertically aligned single-walled carbon nanotubes.

PubMed

Xiang, Rong; Einarsson, Erik; Murakami, Yoichi; Shiomi, Junichiro; Chiashi, Shohei; Tang, Zikang; Maruyama, Shigeo

2012-08-28

We demonstrate wide-range diameter modulation of vertically aligned single-walled carbon nanotubes (SWNTs) using a wet chemistry prepared catalyst. In order to ensure compatibility to electronic applications, the current minimum mean diameter of 2 nm for vertically aligned SWNTs is challenged. The mean diameter is decreased to about 1.4 nm by reducing Co catalyst concentrations to 1/100 or by increasing Mo catalyst concentrations by five times. We also propose a novel spectral analysis method that allows one to distinguish absorbance contributions from the upper, middle, and lower parts of a nanotube array. We use this method to quantitatively characterize the slight diameter change observed along the array height. On the basis of further investigation of the array and catalyst particles, we conclude that catalyst aggregation-rather than Ostwald ripening-dominates the growth of metal particles.

Self-assembled vertically aligned Au nanorod arrays for surface-enhanced Raman scattering (SERS) detection of Cannabinol.

PubMed

Milliken, Sarah; Fraser, Jeff; Poirier, Shawn; Hulse, John; Tay, Li-Lin

2018-05-05

Self-assembled multi-layered vertically aligned gold nanorod (AuNR) arrays have been fabricated by a simple preparation process that requires a balance between the particle concentration and the ionic strength of the solvent. An experimentally determined critical AuNR concentration of 2.0nM and 50mM NaCl produces well-ordered vertically aligned hexagonally close-packed AuNR arrays. We demonstrate surface treatment via UV Ozone cleaning of such samples to allow introduction of analyte molecules (benzenethiol and cannabinol) for effective surface enhanced Raman scattering detection. This is the first demonstration of the SERS analysis of cannabinol. This approach demonstrates a cost-effective, high-yield and simple fabrication route to SERS sensors with application in the screening for the cannabinoids. Copyright © 2018. Published by Elsevier B.V.

Vertical comb-drive microscanner with 4x4 array of micromirrors for phase-shifting Mirau microinterferometry

NASA Astrophysics Data System (ADS)

Bargiel, Sylwester; Lullin, Justine; Lemoal, Patrice; Perrin, Stéphane; Passilly, Nicolas; Albero, Jorge; Froehly, Luc; Lardet-Vieudrin, Franck; Gorecki, Christophe

2016-04-01

In this paper, we present construction, fabrication and characterization of an electrostatic MOEMS vertical microscanner for generation of an optical phase shift in array-type interferometric microsystems. The microscanner employs asymmetric comb-drives for a vertical displacement of a large 4x4 array of reference micromirrors and for in-situ position sensing. The device is designed to be fully compatible with Mirau configuration and with vertical integration strategy. This enables further integration of the device within an "active" multi-channel Mirau micro-interferometer and implementation of the phase shifting interferometry (PSI) technique for imaging applications. The combination of micro-interferometer and PSI is particularly interesting in the swept-source optical coherence tomography, since it allows not only strong size reduction of a system but also improvement of its performance (sensitivity, removal of the image artefacts). The technology of device is based on double-side DRIE of SOI wafer and vapor HF releasing of the suspended platform. In the static mode, the device provides vertical displacement of micromirrors up to 2.8μm (0 - 40V), whereas at resonance (fo=500 Hz), it reaches 0.7 μm for only 1VDC+1VAC. In both operation modes, the measured displacement is much more than required for PSI implementation (352nm peak-to-peak). The presented device is a key component of array-type Mirau micro-interferometer that enables the construction of portable, low-cost interferometric systems, e.g. for in vivo medical diagnostics.

On fiber optic probe hydrophone measurements in a cavitating liquid.

PubMed

Zijlstra, Aaldert; Ohl, Claus Dieter

2008-01-01

The measurement of high-pressure signals is often hampered by cavitation activity. The usage of a fiber optic probe hydrophone possesses advantages over other hydrophones, yet when measuring in a cavitating liquid large variations in the signal amplitude are found; in particular when the pressure signal recovers back to positive values. With shadowgraphy the wave propagation and cavity dynamics are imaged and the important contributions of secondary shock waves emitted from collapsing cavitation bubbles are revealed. Interestingly, just adding a small amount of acidic acid reduces the cavitation activity to a large extent. With this treatment an altered primary pressure profile which does not force the cavitation bubbles close to fiber tip into collapse has been found. Thereby, the shot-to-shot variations are greatly reduced.

Flexible Dye-Sensitized Solar Cell Based on Vertical ZnO Nanowire Arrays

PubMed Central

2011-01-01

Flexible dye-sensitized solar cells are fabricated using vertically aligned ZnO nanowire arrays that are transferred onto ITO-coated poly(ethylene terephthalate) substrates using a simple peel-off process. The solar cells demonstrate an energy conversion efficiency of 0.44% with good bending tolerance. This technique paves a new route for building large-scale cost-effective flexible photovoltaic and optoelectronic devices. PMID:27502660

Monolithic integration of multiple wavelength vertical-cavity surface-emitting lasers by mask molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Saito, Hideaki; Ogura, Ichiro; Sugimoto, Yoshimasa; Kasahara, Kenichi

1995-05-01

The monolithic incorporation and performance of vertical-cavity surface-emitting lasers (VCSELs) emitting at two distinct wavelengths, which were suited for application to wavelength division multiplexing (WDM) systems were reported. The monolithic integration of two-wavelength VCSEL arrays was achieved by using mask molecular beam epitaxy. This method can generate arrays that have the desired integration area size and wavelength separation.

Sources and levels of ambient ocean sound near the Antarctic Peninsula.

PubMed

Dziak, Robert P; Bohnenstiehl, DelWayne R; Stafford, Kathleen M; Matsumoto, Haruyoshi; Park, Minkyu; Lee, Won Sang; Fowler, Matt J; Lau, Tai-Kwan; Haxel, Joseph H; Mellinger, David K

2015-01-01

Arrays of hydrophones were deployed within the Bransfield Strait and Scotia Sea (Antarctic Peninsula region) from 2005 to 2009 to record ambient ocean sound at frequencies of up to 125 and 500 Hz. Icequakes, which are broadband, short duration signals derived from fracturing of large free-floating icebergs, are a prominent feature of the ocean soundscape. Icequake activity peaks during austral summer and is minimum during winter, likely following freeze-thaw cycles. Iceberg grounding and rapid disintegration also releases significant acoustic energy, equivalent to large-scale geophysical events. Overall ambient sound levels can be as much as ~10-20 dB higher in the open, deep ocean of the Scotia Sea compared to the relatively shallow Bransfield Strait. Noise levels become lowest during the austral winter, as sea-ice cover suppresses wind and wave noise. Ambient noise levels are highest during austral spring and summer, as surface noise, ice cracking and biological activity intensifies. Vocalizations of blue (Balaenoptera musculus) and fin (B. physalus) whales also dominate the long-term spectra records in the 15-28 and 89 Hz bands. Blue whale call energy is a maximum during austral summer-fall in the Drake Passage and Bransfield Strait when ambient noise levels are a maximum and sea-ice cover is a minimum. Fin whale vocalizations were also most common during austral summer-early fall months in both the Bransfield Strait and Scotia Sea. The hydrophone data overall do not show sustained anthropogenic sources (ships and airguns), likely due to low coastal traffic and the typically rough weather and sea conditions of the Southern Ocean.

Sources and Levels of Ambient Ocean Sound near the Antarctic Peninsula

PubMed Central

Dziak, Robert P.; Bohnenstiehl, DelWayne R.; Stafford, Kathleen M.; Matsumoto, Haruyoshi; Park, Minkyu; Lee, Won Sang; Fowler, Matt J.; Lau, Tai-Kwan; Haxel, Joseph H.; Mellinger, David K.

2015-01-01

Arrays of hydrophones were deployed within the Bransfield Strait and Scotia Sea (Antarctic Peninsula region) from 2005 to 2009 to record ambient ocean sound at frequencies of up to 125 and 500 Hz. Icequakes, which are broadband, short duration signals derived from fracturing of large free-floating icebergs, are a prominent feature of the ocean soundscape. Icequake activity peaks during austral summer and is minimum during winter, likely following freeze-thaw cycles. Iceberg grounding and rapid disintegration also releases significant acoustic energy, equivalent to large-scale geophysical events. Overall ambient sound levels can be as much as ~10–20 dB higher in the open, deep ocean of the Scotia Sea compared to the relatively shallow Bransfield Strait. Noise levels become lowest during the austral winter, as sea-ice cover suppresses wind and wave noise. Ambient noise levels are highest during austral spring and summer, as surface noise, ice cracking and biological activity intensifies. Vocalizations of blue (Balaenoptera musculus) and fin (B. physalus) whales also dominate the long-term spectra records in the 15–28 and 89 Hz bands. Blue whale call energy is a maximum during austral summer-fall in the Drake Passage and Bransfield Strait when ambient noise levels are a maximum and sea-ice cover is a minimum. Fin whale vocalizations were also most common during austral summer-early fall months in both the Bransfield Strait and Scotia Sea. The hydrophone data overall do not show sustained anthropogenic sources (ships and airguns), likely due to low coastal traffic and the typically rough weather and sea conditions of the Southern Ocean. PMID:25875205

A dimensional comparison between embedded 3D-printed and silicon microchannels

NASA Astrophysics Data System (ADS)

O'Connor, J.; Punch, J.; Jeffers, N.; Stafford, J.

2014-07-01

The subject of this paper is the dimensional characterization of embedded microchannel arrays created using contemporary 3D-printing fabrication techniques. Conventional microchannel arrays, fabricated using deep reactive ion etching techniques (DRIE) and wet-etching (KOH), are used as a benchmark for comparison. Rectangular and trapezoidal cross-sectional shapes were investigated. The channel arrays were 3D-printed in vertical and horizontal directions, to examine the influence of print orientation on channel characteristics. The 3D-printed channels were benchmarked against Silicon channels in terms of the following dimensional characteristics: cross-sectional area (CSA), perimeter, and surface profiles. The 3D-printed microchannel arrays demonstrated variances in CSA of 6.6-20% with the vertical printing approach yielding greater dimensional conformity than the horizontal approach. The measured CSA and perimeter of the vertical channels were smaller than the nominal dimensions, while the horizontal channels were larger in both CSA and perimeter due to additional side-wall roughness present throughout the channel length. This side-wall roughness caused significant shape distortion. Surface profile measurements revealed that the base wall roughness was approximately the resolution of current 3D-printers. A spatial periodicity was found along the channel length which appeared at different frequencies for each channel array. This paper concludes that vertical 3D-printing is superior to the horizontal printing approach, in terms of both dimensional fidelity and shape conformity and can be applied in microfluidic device applications.

Central solar-energy receiver

DOEpatents

Not Available

1981-10-27

An improved tower-mounted central solar energy receiver for heating air drawn through the receiver by an induced draft fan is described. A number of vertically oriented, energy absorbing, fin-shaped slats are radially arranged in a number of concentric cylindrical arrays on top of the tower coaxially surrounding a pipe having air holes through which the fan draws air which is heated by the slats which receive the solar radiation from a heliostat field. A number of vertically oriented and wedge-shaped columns are radially arranged in a number of concentric cylindrical clusters surrounding the slat arrays. The columns have two mirror-reflecting sides to reflect radiation into the slat arrays and one energy absorbing side to reduce reradiation and reflection from the slat arrays.

Central solar energy receiver

DOEpatents

Drost, M. Kevin

1983-01-01

An improved tower-mounted central solar energy receiver for heating air drawn through the receiver by an induced draft fan. A number of vertically oriented, energy absorbing, fin-shaped slats are radially arranged in a number of concentric cylindrical arrays on top of the tower coaxially surrounding a pipe having air holes through which the fan draws air which is heated by the slats which receive the solar radiation from a heliostat field. A number of vertically oriented and wedge-shaped columns are radially arranged in a number of concentric cylindrical clusters surrounding the slat arrays. The columns have two mirror-reflecting sides to reflect radiation into the slat arrays and one energy absorbing side to reduce reradiation and reflection from the slat arrays.

High-Isolation Low Cross-Polarization Phased-Array Antenna for MPAR Application

NASA Astrophysics Data System (ADS)

Saeidi-Manesh, Hadi; Karimkashi, Shaya; Zhang, Guifu; Doviak, Richard J.

2017-12-01

The design and analysis of 12 × 12-element planar array of a dual-polarized aperture-coupled microstrip patch antenna operating in the frequency band of 2.7 GHz to 3.0 GHz for multifunction applications are presented. High-isolation between horizontal and vertical polarization ports and low cross-polarization are achieved through an aperture-coupled feed. The reflection coefficient and the isolation of horizontal and vertical ports at different scan angles are examined. The array antenna is fabricated and its radiation patterns are measured in the far-field and near-field chambers. The embedded element pattern of designed element is measured in the near-field chamber and is used for calculating the array scanning radiation pattern.

Sea level history in 3D: Data acquisition and processing for an ultra-high resolution MCS survey across IODP Expedition 313 drillsite

NASA Astrophysics Data System (ADS)

Nedimovic, M. R.; Mountain, G. S.; Austin, J. A., Jr.; Fulthorpe, C.; Aali, M.; Baldwin, K.; Bhatnagar, T.; Johnson, C.; Küçük, H. M.; Newton, A.; Stanley, J.

2015-12-01

In June-July 2015, we acquired the first 3D/2D hybrid (short/long streamer) multichannel seismic (MCS) reflection dataset. These data were collected simultaneously across IODP Exp. 313 drillsites, off New Jersey, using R/V Langsethand cover ~95% of the planned 12x50 km box. Despite the large survey area, the lateral and vertical resolution for the 3D dataset is almost a magnitude of order higher than for data gathered for standard petroleum exploration. Such high-resolution was made possible by collection of common midpoint (CMP) lines whose combined length is ~3 times the Earth's circumference (~120,000 profile km) and a source rich in high-frequencies. We present details on the data acquisition, ongoing data analysis, and preliminary results. The science driving this project is presented by Mountain et al. The 3D component of this innovative survey used an athwartship cross cable, extended laterally by 2 barovanes roughly 357.5 m apart and trailed by 24 50-m P-Cables spaced ~12.5 m with near-trace offset of 53 m. Each P-Cable had 8 single hydrophone groups spaced at 6.25 m for a total of 192 channels. Record length was 4 s and sample rate 0.5 ms, with no low cut and an 824 Hz high cut filter. We ran 77 sail lines spaced ~150 m. Receiver locations were determined using 2 GPS receivers mounted on floats and 2 compasses and depth sensors per streamer. Streamer depths varied from 2.1 to 3.7 m. The 2D component used a single 3 km streamer, with 240 9-hydrophone groups spaced at 12.5 m, towed astern with near-trace offset of 229 m. The record length was 4 s and sample rate 0.5 ms, with low cut filter at 2 Hz and high cut at 412 Hz. Receiver locations were recorded using GPS at the head float and tail buoy, combined with 12 bird compasses spaced ~300 m. Nominal streamer depth was 4.5 m. The source for both systems was a 700 in3 linear array of 4 Bolt air guns suspended at 4.5 m towing depth, 271.5 m behind the ship's stern. Shot spacing was 12.5 m. Data analysis to prestack time migration is being carried out by Absolute Imaging, a commercial company. The shipboard QC analysis and brute stacks indicate that the final product will be superb. Key advantages of the hybrid 3D/2D dataset are: (1) Velocity control from the 2D long-streamer data combined with the ultra-high resolution of the P-Cable 3D dataset; (2) Opportunity for prestack and poststack attribute analysis.

The sounds of science

NASA Astrophysics Data System (ADS)

Carlowicz, Michael

As scientists carefully study some aspects of the ocean environment, are they unintentionally distressing others? That is a question to be answered by Robert Benson and his colleagues in the Center for Bioacoustics at Texas A&M University.With help from a 3-year, $316,000 grant from the U.S. Office of Naval Research, Benson will study how underwater noise produced by naval operations and other sources may affect marine mammals. In Benson's study, researchers will generate random sequences of low-frequency, high-intensity (180-decibel) sounds in the Gulf of Mexico, working at an approximate distance of 1 km from sperm whale herds. Using an array of hydrophones, the scientists will listen to the characteristic clicks and whistles of the sperm whales to detect changes in the animals' direction, speed, and depth, as derived from fluctuations in their calls.

Study of a new design of p-N semiconductor detector array for nuclear medicine imaging by monte carlo simulation codes.

PubMed

Hajizadeh-Safar, M; Ghorbani, M; Khoshkharam, S; Ashrafi, Z

2014-07-01

Gamma camera is an important apparatus in nuclear medicine imaging. Its detection part is consists of a scintillation detector with a heavy collimator. Substitution of semiconductor detectors instead of scintillator in these cameras has been effectively studied. In this study, it is aimed to introduce a new design of P-N semiconductor detector array for nuclear medicine imaging. A P-N semiconductor detector composed of N-SnO2 :F, and P-NiO:Li, has been introduced through simulating with MCNPX monte carlo codes. Its sensitivity with different factors such as thickness, dimension, and direction of emission photons were investigated. It is then used to configure a new design of an array in one-dimension and study its spatial resolution for nuclear medicine imaging. One-dimension array with 39 detectors was simulated to measure a predefined linear distribution of Tc(99_m) activity and its spatial resolution. The activity distribution was calculated from detector responses through mathematical linear optimization using LINPROG code on MATLAB software. Three different configurations of one-dimension detector array, horizontal, vertical one sided, and vertical double-sided were simulated. In all of these configurations, the energy windows of the photopeak were ± 1%. The results show that the detector response increases with an increase of dimension and thickness of the detector with the highest sensitivity for emission photons 15-30° above the surface. Horizontal configuration array of detectors is not suitable for imaging of line activity sources. The measured activity distribution with vertical configuration array, double-side detectors, has no similarity with emission sources and hence is not suitable for imaging purposes. Measured activity distribution using vertical configuration array, single side detectors has a good similarity with sources. Therefore, it could be introduced as a suitable configuration for nuclear medicine imaging. It has been shown that using semiconductor P-N detectors such as P-NiO:Li, N-SnO2 :F for gamma detection could be possibly applicable for design of a one dimension array configuration with suitable spatial resolution of 2.7 mm for nuclear medicine imaging.

A hydrophone prototype for ultra high energy neutrino acoustic detection

NASA Astrophysics Data System (ADS)

Cotrufo, A.; Plotnikov, A.; Yershova, O.; Anghinolfi, M.; Piombo, D.

2009-06-01

The design of an air-backed fiber-optic hydrophone is presented. With respect to the previous models this prototype is optimized to provide a bandwidth sufficiently large to detect acoustic signals produced by high energy hadronic showers in water. In addiction to the geometrical configuration and to the choice of the materials, the preliminary results of the measured performances in air are presented.

Using hydrophones as a surrogate monitoring technique to detect temporal and spatial variability in bedload transport

USGS Publications Warehouse

Marineau, Mathieu D.; Minear, J. Toby; Wright, Scott A.

2015-01-01

Collecting physical bedload measurements is an expensive and time-consuming endeavor that rarely captures the spatial and temporal variability of sediment transport. Technological advances can improve monitoring of sediment transport by filling in temporal gaps between physical sampling periods. We have developed a low-cost hydrophone recording system designed to record the sediment-generated noise (SGN) resulting from collisions of coarse particles (generally larger than 4 mm) in gravel-bedded rivers. The sound level of the signal recorded by the hydrophone is assumed to be proportional to the magnitude of bedload transport as long as the acoustic frequency of the SGN is known, the grain-size distribution of the bedload is assumed constant, and the frequency band of the ambient noise is known and can be excluded from the analysis. Each system has two hydrophone heads and samples at half-hour intervals. Ten systems were deployed on the San Joaquin River, California, and its tributaries for ten months during water year 2014, and two systems were deployed during a flood event on the Gunnison River, Colorado in 2014. A mobile hydrophone system was also tested at both locations to collect longitudinal profiles of SGN. Physical samples of bedload were not collected in this study. In lieu of physical measurements, several audio recordings from each site were aurally reviewed to confirm the presence or absence of SGN, and hydraulic data were compared to historical measurements of bedload transport or transport capacity estimates to verify if hydraulic conditions during the study would likely produce bedload transport. At one site on the San Joaquin River, the threshold of movement was estimated to have occurred around 30 m 3 /s based on SGN data. During the Gunnison River flood event, continuous data showed clockwise hysteresis, indicating that bedload transport was generally less at any given streamflow discharge during the recession limb of the hydrograph. Spatial variability in transport was also detected in the longitudinal profiles audibly and using signal processing algorithms. These experiments demonstrate the ability of hydrophone technology to capture the temporal and spatial variability of sediment transport, which may be missed when samples are collected using conventional methods.

Two-dimensional fluid droplet arrays generated using a single nozzle

DOEpatents

Lee, Eric R.; Perl, Martin L.

1999-11-02

Amplitudes of drive pulses received by a horizontally-placed dropper determine the horizontal displacements of droplets relative to an ejection aperture of the dropper. The drive pulses are varied such that the dropper generates a two-dimensional array of vertically-falling droplets. Vertical and horizontal interdroplet spacings may be varied in real time. Applications include droplet analysis experiments such as Millikan fractional charge searches and aerosol characterization, as well as material deposition applications.

Bottom Interaction in Ocean Acoustic Propagation

DTIC Science & Technology

2014-09-30

deep seafloor (greater than the critical depth). What is the relationship between the seismic (ground motion) noise on the seafloor and the acoustic...ocean bottom seismometers (OBSs), but were very weak on the deep vertical line array (Deep VLA), located above 750 m from the seafloor. Stephen et al...was carried out in April-May 2011 near the location of the PhilSea10 Distributed Vertical Line Array (DVLA) (Stephen et al., 2011). The second

Bottom Interaction in Ocean Acoustic Propagation

DTIC Science & Technology

2015-09-30

the deep seafloor (greater than the critical depth). What is the relationship between the seismic (ground motion) noise on the seafloor and the...ocean bottom seismometers (OBSs), but were very weak on the deep vertical line array (Deep VLA), located above 750 m from the seafloor. Stephen et...carried out in April-May 2011 near the location of the PhilSea10 Distributed Vertical Line Array (DVLA) (Stephen et al., 2011). The second experiment

Vertical nanopillars for in situ probing of nuclear mechanics in adherent cells

PubMed Central

Hanson, Lindsey; Zhao, Wenting; Lou, Hsin-Ya; Lin, Ziliang Carter; Lee, Seok Woo; Chowdary, Praveen; Cui, Yi; Cui, Bianxiao

2016-01-01

The mechanical stability and deformability of the cell nucleus are crucial to many biological processes, including migration, proliferation and polarization. In vivo, the cell nucleus is frequently subjected to deformation on a variety of length and time scales, but current techniques for studying nuclear mechanics do not provide access to subnuclear deformation in live functioning cells. Here we introduce arrays of vertical nanopillars as a new method for the in situ study of nuclear deformability and the mechanical coupling between the cell membrane and the nucleus in live cells. Our measurements show that nanopillar-induced nuclear deformation is determined by nuclear stiffness, as well as opposing effects from actin and intermediate filaments. Furthermore, the depth, width and curvature of nuclear deformation can be controlled by varying the geometry of the nanopillar array. Overall, vertical nanopillar arrays constitute a novel approach for non-invasive, subcellular perturbation of nuclear mechanics and mechanotransduction in live cells. PMID:25984833

Uniform, dense arrays of vertically aligned, large-diameter single-walled carbon nanotubes.

PubMed

Han, Zhao Jun; Ostrikov, Kostya

2012-04-04

Precisely controlled reactive chemical vapor synthesis of highly uniform, dense arrays of vertically aligned single-walled carbon nanotubes (SWCNTs) using tailored trilayered Fe/Al(2)O(3)/SiO(2) catalyst is demonstrated. More than 90% population of thick nanotubes (>3 nm in diameter) can be produced by tailoring the thickness and microstructure of the secondary catalyst supporting SiO(2) layer, which is commonly overlooked. The proposed model based on the atomic force microanalysis suggests that this tailoring leads to uniform and dense arrays of relatively large Fe catalyst nanoparticles on which the thick SWCNTs nucleate, while small nanotubes and amorphous carbon are effectively etched away. Our results resolve a persistent issue of selective (while avoiding multiwalled nanotubes and other carbon nanostructures) synthesis of thick vertically aligned SWCNTs whose easily switchable thickness-dependent electronic properties enable advanced applications in nanoelectronic, energy, drug delivery, and membrane technologies.

Conformal atomic layer deposition of alumina on millimeter tall, vertically-aligned carbon nanotube arrays.

PubMed

Stano, Kelly L; Carroll, Murphy; Padbury, Richard; McCord, Marian; Jur, Jesse S; Bradford, Philip D

2014-11-12

Atomic layer deposition (ALD) can be used to coat high aspect ratio and high surface area substrates with conformal and precisely controlled thin films. Vertically aligned arrays of multiwalled carbon nanotubes (MWCNTs) with lengths up to 1.5 mm were conformally coated with alumina from base to tip. The nucleation and growth behaviors of Al2O3 ALD precursors on the MWCNTs were studied as a function of CNT surface chemistry. CNT surfaces were modified through a series of post-treatments including pyrolytic carbon deposition, high temperature thermal annealing, and oxygen plasma functionalization. Conformal coatings were achieved where post-treatments resulted in increased defect density as well as the extent of functionalization, as characterized by X-ray photoelectron spectroscopy and Raman spectroscopy. Using thermogravimetric analysis, it was determined that MWCNTs treated with pyrolytic carbon and plasma functionalization prior to ALD coating were more stable to thermal oxidation than pristine ALD coated samples. Functionalized and ALD coated arrays had a compressive modulus more than two times higher than a pristine array coated for the same number of cycles. Cross-sectional energy dispersive X-ray spectroscopy confirmed that Al2O3 could be uniformly deposited through the entire thickness of the vertically aligned MWCNT array by manipulating sample orientation and mounting techniques. Following the ALD coating, the MWCNT arrays demonstrated hydrophilic wetting behavior and also exhibited foam-like recovery following compressive strain.

Toward optimized light utilization in nanowire arrays using scalable nanosphere lithography and selected area growth.

PubMed

Madaria, Anuj R; Yao, Maoqing; Chi, Chunyung; Huang, Ningfeng; Lin, Chenxi; Li, Ruijuan; Povinelli, Michelle L; Dapkus, P Daniel; Zhou, Chongwu

2012-06-13

Vertically aligned, catalyst-free semiconducting nanowires hold great potential for photovoltaic applications, in which achieving scalable synthesis and optimized optical absorption simultaneously is critical. Here, we report combining nanosphere lithography (NSL) and selected area metal-organic chemical vapor deposition (SA-MOCVD) for the first time for scalable synthesis of vertically aligned gallium arsenide nanowire arrays, and surprisingly, we show that such nanowire arrays with patterning defects due to NSL can be as good as highly ordered nanowire arrays in terms of optical absorption and reflection. Wafer-scale patterning for nanowire synthesis was done using a polystyrene nanosphere template as a mask. Nanowires grown from substrates patterned by NSL show similar structural features to those patterned using electron beam lithography (EBL). Reflection of photons from the NSL-patterned nanowire array was used as a measure of the effect of defects present in the structure. Experimentally, we show that GaAs nanowires as short as 130 nm show reflection of <10% over the visible range of the solar spectrum. Our results indicate that a highly ordered nanowire structure is not necessary: despite the "defects" present in NSL-patterned nanowire arrays, their optical performance is similar to "defect-free" structures patterned by more costly, time-consuming EBL methods. Our scalable approach for synthesis of vertical semiconducting nanowires can have application in high-throughput and low-cost optoelectronic devices, including solar cells.

Enhancing Thermal Conductive Performance of Vertically Aligned Carbon Nanotube Array Composite by Pre-Annealing Treatment.

PubMed

Wang, Miao; Chen, Hong-Yuan; Xing, Ya-Juan; Wei, Han-Xing; Li, Qiang; Chen, Ming-Hai; Li, Qing-Wen; Xuan, Yi-Min

2015-04-01

Vertically aligned carbon nanotube (VACNT) array/polymer composite has already been recognized as a promising candidate for advanced thermal pad in thermal management of high-power electronic devices. However, the thermal conductive performance of this composite was limited by the quality of CNTs arrays. In this study, pre-annealing treatment was used to purify CNT arrays and improve thermal conductive performance of VACNT arrays/silicone composite. The thermal conductivity of the composite was enhanced by 34.52% and the thermal interface resistance was also reduced by 65.94% at a pre-annealing temperature of 490 °C for 5 min. The annealing process could remove some amorphous carbon and open the tips of CNTs. As a result, the interfacial compatibility in composite between carbon nanotube and polymer matrix was improved. The cyclic compression and tension performance of VACNT/S160 composite was investigated for further application.

Acoustic monitoring of earthquakes along the Blanco Transform Fault zone and Gorda Plate and their tectonic implications

NASA Astrophysics Data System (ADS)

Dziak, Robert Paul

Hydroacoustic tertiary (T-) waves are seismically generated acoustic waves that propagate over great distances in the ocean sound channel with little loss in signal strength. Hydrophone recorded T-waves can provide a lower earthquake detection threshold and an improved epicenter location accuracy for oceanic earthquakes than land-based seismic networks. Thus detection and location of NE Pacific ocean earthquakes along the Blanco Transform Fault (BTFZ) and Gorda plate using the U.S. Navy's SOSUS (SOund SUrveillance System) hydrophone arrays afford greater insight into the current state of stress and crustal deformation mechanics than previously available. Acoustic earthquake information combined with bathymetry, submersible observations, earthquake source- parameter estimates, petrologic samples, and water-column chemistry renders a new tectonic view of the southern Juan de Fuca plate boundaries. Chapter 2 discusses development of seismo-acoustic analysis techniques using the well-documented April 1992 Cape Mendocino earthquake sequence. Findings include a hydrophone detection threshold estimate (M ~ 2.4), and T-wave propagation path modeling to approximate earthquake acoustic source energy. Empirical analyses indicate that acoustic energy provides a reasonable magnitude and seismic moment estimate of oceanic earthquakes not detected by seismic networks. Chapters 3 documents a probable volcanogenic T-wave event swarm along a pull-apart basin within the western BTFZ during January 1994. Response efforts yielded evidence of anomalous water-column 3He concentrations, pillow- lava volcanism, and the first discovery of active hydrothermal vents along an oceanic fracture zone. Chapter 4 discusses the detection of a NE-SW trending microearthquake band along the mid-Gorda plate which was active from initiation of SOSUS recording in August 1991 through July 1992, then abruptly ceased. It is proposed that eventual termination of the Gorda plate seismicity band is due to strain reduction associated with the Cape Mendocino earthquake sequence. Chapter 5 combines bathymetric, hydro-acoustic, seismic, submersible, and gravity data to investigate the active tectonics of the transform parallel Blanco Ridge (BR), along the eastern BTFZ. The BR formation mechanism preferred here is uplift through strike-slip motion (with a normal component) followed by formation and intrusion of mantle-derived serpentinized-peridotite into the shallow ocean crust. The conclusion considers a potential link between the deformation patterns observed along the BTFZ and Gorda plate regions.

A random phased-array for MR-guided transcranial ultrasound neuromodulation in non-human primates

NASA Astrophysics Data System (ADS)

Chaplin, Vandiver; Phipps, Marshal A.; Caskey, Charles F.

2018-05-01

Transcranial focused ultrasound (FUS) is a non-invasive technique for therapy and study of brain neural activation. Here we report on the design and characterization of a new MR-guided FUS transducer for neuromodulation in non-human primates at 650 kHz. The array is randomized with 128 elements 6.6 mm in diameter, radius of curvature 7.2 cm, opening diameter 10.3 cm (focal ratio 0.7), and 46% coverage. Simulations were used to optimize transducer geometry with respect to focus size, grating lobes, and directivity. Focus size and grating lobes during electronic steering were quantified using hydrophone measurements in water and a three-axis stage. A novel combination of optical tracking and acoustic mapping enabled measurement of the 3D pressure distribution in the cortical region of an ex vivo skull to within ~3.5 mm of the surface, and allowed accurate modelling of the experiment via non-homogeneous 3D acoustic simulations. The data demonstrates acoustic focusing beyond the skull bone, with the focus slightly broadened and shifted proximal to the skull. The fabricated design is capable of targeting regions within the S1 sensorimotor cortex of macaques.

Time reversal technique for gas leakage detection.

PubMed

Maksimov, A O; Polovinka, Yu A

2015-04-01

The acoustic remote sensing of subsea gas leakage traditionally uses sonars as active acoustic sensors and hydrophones picking up the sound generated by a leak as passive sensors. When gas leaks occur underwater, bubbles are produced and emit sound at frequencies intimately related to their sizes. The experimental implementation of an acoustic time-reversal mirror (TRM) is now well established in underwater acoustics. In the basic TRM experiment, a probe source emits a pulse that is received on an array of sensors, time reversed, and re-emitted. After time reversal, the resulting field focuses back at the probe position. In this study, a method for enhancing operation of the passive receiving system has been proposed by using it in the regime of TRM. Two factors, the local character of the acoustic emission signal caused by the leakage and a resonant nature of the bubble radiation at their birth, make particularly effective scattering with the conjugate wave (CW). Analytical calculations are performed for the scattering of CW wave on a single bubble when CW is formed by bubble birthing wail received on an array, time reversed, and re-emitted. The quality of leakage detection depends on the spatio-temporal distribution of ambient noise.

Diurnal vocal activity of gray whales in Laguna San Ignacio, BCS, Mexico

NASA Astrophysics Data System (ADS)

Guerra, Melania; Thode, Aaron; Wisdom, Sheyna; Gonzalez, Sergio; Urban, Jorge; Sumich, James

2005-09-01

Three sets of portable horizontal acoustic arrays were deployed during a week in February 2005 to gather acoustic recordings of gray whales (Eschrichtius robustus) in Laguna San Ignacio, one of the three major breeding/calving lagoons in Baja California, Mexico. These arrays, which were constructed by attaching a pair of autonomous flash-memory acoustic sensors to a rope, were deployed for 36 consecutive hours on two occasions, spatially covering the narrowest point of the lagoon near Punta Piedra, the area of the highest concentration of whales. Additionally a single hydrophone was deployed off a small boat to record during friendly encounters with single whales and cow/calf pairs. Each recorder's time series was analyzed for Type 1 gray whale sounds (called pops), which are pulsive, broadband, and have substantial acoustic energy between 100 and 600 Hz. The number of automated acoustic detections per hour can be compared with population sizes estimated by two visual surveys conducted by scientists of the Autonomous University of Baja California Sur, La Paz. The results of several automated analyses of both the bottom-mounted and boat-deployed recordings will be presented, with a focus on potential diurnal patterns in the vocal activity.

A random phased-array for MR-guided transcranial ultrasound neuromodulation in non-human primates.

PubMed

Chaplin, Vandiver; Phipps, Marshal A; Caskey, Charles F

2018-05-17

Transcranial focused ultrasound (FUS) is a non-invasive technique for therapy and study of brain neural activation. Here we report on the design and characterization of a new MR-guided FUS transducer for neuromodulation in non-human primates at 650 kHz. The array is randomized with 128 elements 6.6 mm in diameter, radius of curvature 7.2 cm, opening diameter 10.3 cm (focal ratio 0.7), and 46% coverage. Simulations were used to optimize transducer geometry with respect to focus size, grating lobes, and directivity. Focus size and grating lobes during electronic steering were quantified using hydrophone measurements in water and a three-axis stage. A novel combination of optical tracking and acoustic mapping enabled measurement of the 3D pressure distribution in the cortical region of an ex vivo skull to within ~3.5 mm of the surface, and allowed accurate modelling of the experiment via non-homogeneous 3D acoustic simulations. The data demonstrates acoustic focusing beyond the skull bone, with the focus slightly broadened and shifted proximal to the skull. The fabricated design is capable of targeting regions within the S1 sensorimotor cortex of macaques.

Adaptive Focusing For Ultrasonic Transcranial Brain Therapy: First In Vivo Investigation On 22 Sheep

NASA Astrophysics Data System (ADS)

Pernot, Mathieu; Aubry, Jean-François; Tanter, Mickael; Boch, Anne Laure; Kujas, Michelle; Fink, Mathias

2005-03-01

A high power prototype dedicated to trans-skull therapy has been tested in vivo on 22 sheep. The array is made of 300 high power transducers working at 1MHz central frequency and is able to achieve 400 bars at focus in water during five seconds with a 50% percent duty cycle. In the first series of experiments, 10 sheep were treated and sacrificed immediately after treatment. A complete craniotomy was performed on half of the treated animal models in order to get a reference model. On the other half, minimally invasive surgery has been performed: a hydrophone was inserted at a given target location inside the brain through a craniotomy of a few mm2. A time reversal experiment was then conducted through the skull bone with the therapeutic array to treat the targeted point. Thanks to the high power technology of the prototype, trans-skull adaptive treatment could be achieved. In a second series of experiments, 12 animals were divided into three groups and sacrificed respectively one, two or three weeks after treatment. Finally, Magnetic Resonance Imaging and histological examination were performed to confirm tissue damage.

Fiber optic hydrophone

DOEpatents

Kuzmenko, Paul J.; Davis, Donald T.

1994-01-01

A miniature fiber optic hydrophone based on the principles of a Fabry-Perot interferometer. The hydrophone, in one embodiment, includes a body having a shaped flexible bladder at one end which defines a volume containing air or suitable gas, and including a membrane disposed adjacent a vent. An optic fiber extends into the body with one end terminating in spaced relation to the membrane. Acoustic waves in the water that impinge on the bladder cause the pressure of the volume therein to vary causing the membrane to deflect and modulate the reflectivity of the Fabry-Perot cavity formed by the membrane surface and the cleaved end of the optical fiber disposed adjacent to the membrane. When the light is transmitted down the optical fiber, the reflected signal is amplitude modulated by the incident acoustic wave. Another embodiment utilizes a fluid filled volume within which the fiber optic extends.

Vertically aligned diamond-graphite hybrid nanorod arrays with superior field electron emission properties

NASA Astrophysics Data System (ADS)

Ramaneti, R.; Sankaran, K. J.; Korneychuk, S.; Yeh, C. J.; Degutis, G.; Leou, K. C.; Verbeeck, J.; Van Bael, M. K.; Lin, I. N.; Haenen, K.

2017-06-01

A "patterned-seeding technique" in combination with a "nanodiamond masked reactive ion etching process" is demonstrated for fabricating vertically aligned diamond-graphite hybrid (DGH) nanorod arrays. The DGH nanorod arrays possess superior field electron emission (FEE) behavior with a low turn-on field, long lifetime stability, and large field enhancement factor. Such an enhanced FEE is attributed to the nanocomposite nature of the DGH nanorods, which contain sp2-graphitic phases in the boundaries of nano-sized diamond grains. The simplicity in the nanorod fabrication process renders the DGH nanorods of greater potential for the applications as cathodes in field emission displays and microplasma display devices.

Biosonar adjustments to target range of echolocating bottlenose dolphins (Tursiops sp.) in the wild.

PubMed

Jensen, F H; Bejder, L; Wahlberg, M; Madsen, P T

2009-04-01

Toothed whales use echolocation to locate and track prey. Most knowledge of toothed whale echolocation stems from studies on trained animals, and little is known about how toothed whales regulate and use their biosonar systems in the wild. Recent research suggests that an automatic gain control mechanism in delphinid biosonars adjusts the biosonar output to the one-way transmission loss to the target, possibly a consequence of pneumatic restrictions in how fast the sound generator can be actuated and still maintain high outputs. This study examines the relationships between target range (R), click intervals, and source levels of wild bottlenose dolphins (Tursiops sp.) by recording regular (non-buzz) echolocation clicks with a linear hydrophone array. Dolphins clicked faster with decreasing distance to the array, reflecting a decreasing delay between the outgoing echolocation click and the returning array echo. However, for interclick intervals longer than 30-40 ms, source levels were not limited by the repetition rate. Thus, pneumatic constraints in the sound-production apparatus cannot account for source level adjustments to range as a possible automatic gain control mechanism for target ranges longer than a few body lengths of the dolphin. Source level estimates drop with reducing range between the echolocating dolphins and the target as a function of 17 log(R). This may indicate either (1) an active form of time-varying gain in the biosonar independent of click intervals or (2) a bias in array recordings towards a 20 log(R) relationship for apparent source levels introduced by a threshold on received click levels included in the analysis.

Impacts of short-time scale water column variability on broadband high-frequency acoustic wave propagation

NASA Astrophysics Data System (ADS)

Eickmeier, Justin

Acoustical oceanography is one way to study the ocean, its internal layers, boundaries and all processes occurring within using underwater acoustics. Acoustical sensing techniques allows for the measurement of ocean processes from within that logistically or financially preclude traditional in-situ measurements. Acoustic signals propagate as pressure wavefronts from a source to a receiver through an ocean medium with variable physical parameters. The water column physical parameters that change acoustic wave propagation in the ocean include temperature, salinity, current, surface roughness, seafloor bathymetry, and vertical stratification over variable time scales. The impacts of short-time scale water column variability on acoustic wave propagation include coherent and incoherent surface reflections, wavefront arrival time delay, focusing or defocusing of the intensity of acoustic beams and refraction of acoustic rays. This study focuses on high-frequency broadband acoustic waves, and examines the influence of short-time scale water column variability on broadband high-frequency acoustics, wavefronts, from 7 to 28 kHz, in shallow water. Short-time scale variability is on the order of seconds to hours and the short-spatial scale variability is on the order of few centimeters. Experimental results were collected during an acoustic experiment along 100 m isobaths and data analysis was conducted using available acoustic wave propagation models. Three main topics are studied to show that acoustic waves are viable as a remote sensing tool to measure oceanographic parameters in shallow water. First, coherent surface reflections forming striation patterns, from multipath receptions, through rough surface interaction of broadband acoustic signals with the dynamic sea surface are analyzed. Matched filtered results of received acoustic waves are compared with a ray tracing numerical model using a sea surface boundary generated from measured water wave spectra at the time of signal propagation. It is determined that on a time scale of seconds, corresponding to typical periods of surface water waves, the arrival time of reflected acoustic signals from surface waves appear as striation patterns in measured data and can be accurately modelled by ray tracing. Second, changes in acoustic beam arrival angle and acoustic ray path influenced by isotherm depth oscillations are analyzed using an 8-element delay-sum beamformer. The results are compared with outputs from a two-dimensional (2-D) parabolic equation (PE) model using measured sound speed profiles (SSPs) in the water column. Using the method of beamforming on the received signal, the arrival time and angle of an acoustic beam was obtained for measured acoustic signals. It is determined that the acoustic ray path, acoustic beam intensity and angular spread are a function of vertical isotherm oscillations on a time scale of minutes and can be modeled accurately by a 2-D PE model. Third, a forward problem is introduced which uses acoustic wavefronts received on a vertical line array, 1.48 km from the source, in the lower part of the water column to infer range dependence or independence in the SSP. The matched filtering results of received acoustic wavefronts at all hydrophone depths are compared with a ray tracing routine augmented to calculate only direct path and bottom reflected signals. It is determined that the SSP range dependence can be inferred on a time scale of hours using an array of hydrophones spanning the water column. Sound speed profiles in the acoustic field were found to be range independent for 11 of the 23 hours in the measurements. A SSP cumulative reconstruction process, conducted from the seafloor to the sea surface, layer-by-layer, identifies critical segments in the SSP that define the ray path, arrival time and boundary interactions. Data-model comparison between matched filtered arrival time spread and arrival time output from the ray tracing was robust when the SSP measured at the receiver was input to the model. When the SSP measured nearest the source (at the same instant in time) was input to the ray tracing model, the data-model comparison was poor. It was determined that the cumulative sound speed change in the SSP near the source was 1.041 m/s greater than that of the SSP at the receiver and resulted in the poor data-model comparison. In this study, the influences on broadband acoustic wave propagation in the frequency range of 7 to 28 kHz of spatial and temporal changes in the oceanography of shallow water regions are addressed. Acoustic waves can be used as remote sensing tools to measure oceanographic parameters in shallow water and data-model comparison results show a direct relationship between the oceanographic variations and acoustic wave propagations.

Large-scale synthesis of arrays of high-aspect-ratio rigid vertically aligned carbon nanofibres

NASA Astrophysics Data System (ADS)

Melechko, A. V.; McKnight, T. E.; Hensley, D. K.; Guillorn, M. A.; Borisevich, A. Y.; Merkulov, V. I.; Lowndes, D. H.; Simpson, M. L.

2003-09-01

We report on techniques for catalytic synthesis of rigid, high-aspect-ratio, vertically aligned carbon nanofibres by dc plasma enhanced chemical vapour deposition that are tailored for applications that require arrays of individual fibres that feature long fibre lengths (up to 20 µm) such as scanning probe microscopy, penetrant cell and tissue probing arrays and mechanical insertion approaches for gene delivery to cell cultures. We demonstrate that the definition of catalyst nanoparticles is the critical step that enables growth of individual, long-length fibres and discuss methods for catalyst particle preparation that allow the growth of individual isolated nanofibres from catalyst dots with diameters as large as 500 nm. This development enables photolithographic definition of catalyst and therefore the inexpensive, large-scale production of such arrays.

Studies of the Propagation of Elastic Waves in Fluids and Solids.

DTIC Science & Technology

1983-12-15

and scattering of ultrasound ; studies of the generation, propagation, and detection of acoustic transients, including laser induced pressure pulses... ultrasound in water and other liquids. The wide band acoustic pulses used to calibrate the various hydrophones were produced by driving thick PZT...Analysis of Pulsed Ultrasonic Fields by PVDF Spot-Poled Membrane Hydrophones, G. R. Harris, E. F. Carome and H. D. Dardy, IEEE Trans. Sonics Ultrason., SU

Application of Density Estimation Methods to Datasets Collected From a Glider

DTIC Science & Technology

2015-09-30

species that occur in the locations where the acoustic data was recorded. For example, the data recorded off the west coast of Sardinia, Italy...fixed passive acoustic recordings to datasets recorded from an underwater glider. The current project will benefit from data collections with combined...Electromagnetics and Acoustics Research (NEAR) Laboratory was fitted with two High Tech, Inc., hydrophones (model # HTI-92-WB). The hydrophones were mounted one

A novel method for determining calibration and behavior of PVDF ultrasonic hydrophone probes in the frequency range up to 100 MHz.

PubMed

Bleeker, H J; Lewin, P A

2000-01-01

A new calibration technique for PVDF ultrasonic hydrophone probes is described. Current implementation of the technique allows determination of hydrophone frequency response between 2 and 100 MHz and is based on the comparison of theoretically predicted and experimentally determined pressure-time waveforms produced by a focused, circular source. The simulation model was derived from the time domain algorithm that solves the non linear KZK (Khokhlov-Zabolotskaya-Kuznetsov) equation describing acoustic wave propagation. The calibration technique data were experimentally verified using independent calibration procedures in the frequency range from 2 to 40 MHz using a combined time delay spectrometry and reciprocity approach or calibration data provided by the National Physical Laboratory (NPL), UK. The results of verification indicated good agreement between the results obtained using KZK and the above-mentioned independent calibration techniques from 2 to 40 MHz, with the maximum discrepancy of 18% at 30 MHz. The frequency responses obtained using different hydrophone designs, including several membrane and needle probes, are presented, and it is shown that the technique developed provides a desirable tool for independent verification of primary calibration techniques such as those based on optical interferometry. Fundamental limitations of the presented calibration method are also examined.

Observations and Bayesian location methodology of transient acoustic signals (likely blue whales) in the Indian Ocean, using a hydrophone triplet.

PubMed

Le Bras, Ronan J; Kuzma, Heidi; Sucic, Victor; Bokelmann, Götz

2016-05-01

A notable sequence of calls was encountered, spanning several days in January 2003, in the central part of the Indian Ocean on a hydrophone triplet recording acoustic data at a 250 Hz sampling rate. This paper presents signal processing methods applied to the waveform data to detect, group, extract amplitude and bearing estimates for the recorded signals. An approximate location for the source of the sequence of calls is inferred from extracting the features from the waveform. As the source approaches the hydrophone triplet, the source level (SL) of the calls is estimated at 187 ± 6 dB re: 1 μPa-1 m in the 15-60 Hz frequency range. The calls are attributed to a subgroup of blue whales, Balaenoptera musculus, with a characteristic acoustic signature. A Bayesian location method using probabilistic models for bearing and amplitude is demonstrated on the calls sequence. The method is applied to the case of detection at a single triad of hydrophones and results in a probability distribution map for the origin of the calls. It can be extended to detections at multiple triads and because of the Bayesian formulation, additional modeling complexity can be built-in as needed.

Ultrasonic immersion probes characterization for use in nondestructive testing according to EN 12668-2:2001

NASA Astrophysics Data System (ADS)

Silva, C. E. R.; Alvarenga, A. V.; Costa-Felix, R. P. B.

2011-02-01

Ultrasound is often used as a Non-Destructive Testing (NDT) technique to analyze components and structures to detect internal and surface flaws. To guarantee reliable measurements, it is necessary to calibrate instruments and properly assess related uncertainties. An important device of an ultrasonic instrument system is its probe, which characterization should be performed according to EN 12668-2. Concerning immersion probes beam profile, the parameters to be assessed are beam divergence, focal distance, width, and zone length. Such parameters are determined by scanning a reflector or a hydrophone throughout the transducer beam. Within the present work, a methodology developed at Inmetro's Laboratory of Ultrasound to evaluate relevant beam parameters is presented, based on hydrophone scan. Water bath and positioning system to move the hydrophone were used to perform the scan. Studied probes were excited by a signal generator, and the waterborne signals were detected by the hydrophone and acquired using an oscilloscope. A user-friendly virtual instrument was developed in LabVIEW to automate the system. The initial tests were performed using 1 and 2.25 MHz-ultrasonic unfocused probes (Ø 1.27 cm), and results were consistent with the manufacturer's specifications. Moreover, expanded uncertainties were lower than 6% for all parameters under consideration.

Computational investigation of hydrokinetic turbine arrays in an open channel using an actuator disk-LES model

NASA Astrophysics Data System (ADS)

Kang, Seokkoo; Yang, Xiaolei; Sotiropoulos, Fotis

2012-11-01

While a considerable amount of work has focused on studying the effects and performance of wind farms, very little is known about the performance of hydrokinetic turbine arrays in open channels. Unlike large wind farms, where the vertical fluxes of momentum and energy from the atmospheric boundary layer comprise the main transport mechanisms, the presence of free surface in hydrokinetic turbine arrays inhibits vertical transport. To explore this fundamental difference between wind and hydrokinetic turbine arrays, we carry out LES with the actuator disk model to systematically investigate various layouts of hydrokinetic turbine arrays mounted on the bed of a straight open channel with fully-developed turbulent flow fed at the channel inlet. Mean flow quantities and turbulence statistics within and downstream of the arrays will be analyzed and the effect of the turbine arrays as means for increasing the effective roughness of the channel bed will be extensively discussed. This work was supported by Initiative for Renewable Energy & the Environment (IREE) (Grant No. RO-0004-12), and computational resources were provided by Minnesota Supercomputing Institute.

Visualizing the movement of the contact between vocal folds during vibration by using array-based transmission ultrasonic glottography

PubMed Central

Jing, Bowen; Chigan, Pengju; Ge, Zhengtong; Wu, Liang; Wang, Supin; Wan, Mingxi

2017-01-01

For the purpose of noninvasively visualizing the dynamics of the contact between vibrating vocal fold medial surfaces, an ultrasonic imaging method which is referred to as array-based transmission ultrasonic glottography is proposed. An array of ultrasound transducers is used to detect the ultrasound wave transmitted from one side of the vocal folds to the other side through the small-sized contact between the vocal folds. A passive acoustic mapping method is employed to visualize and locate the contact. The results of the investigation using tissue-mimicking phantoms indicate that it is feasible to use the proposed method to visualize and locate the contact between soft tissues. Furthermore, the proposed method was used for investigating the movement of the contact between the vibrating vocal folds of excised canine larynges. The results indicate that the vertical movement of the contact can be visualized as a vertical movement of a high-intensity stripe in a series of images obtained by using the proposed method. Moreover, a visualization and analysis method, which is referred to as array-based ultrasonic kymography, is presented. The velocity of the vertical movement of the contact, which is estimated from the array-based ultrasonic kymogram, could reach 0.8 m/s during the vocal fold vibration. PMID:28599522

Metal-modified and vertically aligned carbon nanotube sensors array for landfill gas monitoring applications.

PubMed

Penza, M; Rossi, R; Alvisi, M; Serra, E

2010-03-12

Vertically aligned carbon nanotube (CNT) layers were synthesized on Fe-coated low-cost alumina substrates using radio-frequency plasma enhanced chemical vapour deposition (RF-PECVD) technology. A miniaturized CNT-based gas sensor array was developed for monitoring landfill gas (LFG) at a temperature of 150 degrees C. The sensor array was composed of 4 sensing elements with unmodified CNT, and CNT loaded with 5 nm nominally thick sputtered nanoclusters of platinum (Pt), ruthenium (Ru) and silver (Ag). Chemical analysis of multicomponent gas mixtures constituted of CO(2), CH(4), H(2), NH(3), CO and NO(2) has been performed by the array sensor responses and pattern recognition based on principal component analysis (PCA). The PCA results demonstrate that the metal-decorated and vertically aligned CNT sensor array is able to discriminate the NO(2) presence in the multicomponent mixture LFG. The NO(2) gas detection in the mixture LFG was proved to be very sensitive, e.g.: the CNT:Ru sensor shows a relative change in the resistance of 1.50% and 0.55% for NO(2) concentrations of 3.3 ppm and 330 ppb dispersed in the LFG, respectively, with a wide NO(2) gas concentration range measured from 0.33 to 3.3 ppm, at the sensor temperature of 150 degrees C. The morphology and structure of the CNT networks have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. A forest-like nanostructure of vertically aligned CNT bundles in the multi-walled form appeared with a height of about 10 microm and a single-tube diameter varying in the range of 5-35 nm. The intensity ratio of the Raman spectroscopy D-peak and G-peak indicates the presence of disorder and defects in the CNT networks. The size of the metal (Pt, Ru, Ag) nanoclusters decorating the CNT top surface varies in the range of 5-50 nm. Functional characterization based on electrical charge transfer sensing mechanisms in the metal-modified CNT-chemoresistor array demonstrates high sensitivity by providing minimal sub-ppm level detection, e.g., download up to 100 ppb NO(2), at the sensor temperature of 150 degrees C. The gas sensitivity of the CNT sensor array depends on operating temperature, showing a lower optimal temperature of maximum sensitivity for the metal-decorated CNT sensors compared to unmodified CNT sensors. Results indicate that the recovery mechanisms in the CNT chemiresistors can be altered by a rapid heating pulse from room temperature to about 110 degrees C. A comparison of the NO(2) gas sensitivity for the chemiresistors based on disorderly networked CNTs and vertically aligned CNTs is also reported. Cross-sensitivity towards relative humidity of the CNT sensors array is investigated. Finally, the sensing properties of the metal-decorated and vertically aligned CNT sensor arrays are promising to monitor gas events in the LFG for practical applications with low power consumption and moderate sensor temperature.

Polymeric waveguide array with 45 degree slopes fabricated by bottom side tilted exposure

NASA Astrophysics Data System (ADS)

Lin, Xiaohui; Dou, Xinyuan; Wang, Alan X.; Chen, Ray T.

2011-01-01

This paper demonstrated a practical fabrication process of polymeric waveguide array (12 channels) with 50μm(W)×50μm(H)×23mm(L) dimension and mirror embedded 45° degree slopes for vertical coupling purpose. The entire process contained three main parts: a SU8 pre-mold with 45° slope, a PDMS mold and the final waveguide array device. The key step of fabricating the pre-mold included a bottom side tilted exposure of SU8 photo resist. By placing the sample upside down, tilting by 58.7° and immersing into DI water, the ultraviolet (UV) beam that shined vertically was directed to go through from the bottom of the glass substrate into top side SU8 resist with 45° angle to form the surface. This method was able to guarantee no-gap contact between the mask pattern and the photo resist when exposing. By comparing the process complexity and achieved structure of the top and bottom side exposure, the later was proved to be a promising method for making high quality tilted structure without any tailing effect. The reversed PDMS mold was then fabricated on the SU8 pre-mold. The PDMS mold was used to imprint the cladding layer of the waveguide array. After metal deposition, core filling and top cladding layer coating, the final polymeric waveguide array device was achieved. For performance evaluation, 850nm laser beam from VCSEL was modulated to 10Gbps signals and vertically coupled into the waveguide array. The eye diagrams revealed high Q factor when transmitting signals along these waveguide array.

Vertical group III-V nanowires on si, heterostructures, flexible arrays and fabrication

DOEpatents

Wang, Deli; Soci, Cesare; Bao, Xinyu; Wei, Wei; Jing, Yi; Sun, Ke

2015-01-13

Embodiments of the invention provide a method for direct heteroepitaxial growth of vertical III-V semiconductor nanowires on a silicon substrate. The silicon substrate is etched to substantially completely remove native oxide. It is promptly placed in a reaction chamber. The substrate is heated and maintained at a growth temperature. Group III-V precursors are flowed for a growth time. Preferred embodiment vertical Group III-V nanowires on silicon have a core-shell structure, which provides a radial homojunction or heterojunction. A doped nanowire core is surrounded by a shell with complementary doping. Such can provide high optical absorption due to the long optical path in the axial direction of the vertical nanowires, while reducing considerably the distance over which carriers must diffuse before being collected in the radial direction. Alloy composition can also be varied. Radial and axial homojunctions and heterojunctions can be realized. Embodiments provide for flexible Group III-V nanowire structures. An array of Group III-V nanowire structures is embedded in polymer. A fabrication method forms the vertical nanowires on a substrate, e.g., a silicon substrate. Preferably, the nanowires are formed by the preferred methods for fabrication of Group III-V nanowires on silicon. Devices can be formed with core/shell and core/multi-shell nanowires and the devices are released from the substrate upon which the nanowires were formed to create a flexible structure that includes an array of vertical nanowires embedded in polymer.

Construction of a Fiber Optic Gradient Hydrophone Using a Michelson Configuration.

DTIC Science & Technology

1986-03-27

Michelson interferometers; * Fabry - Perot interferometers; • Intermode interferometers; • Sagnac interferometers. Of these, the first two categories show the...most promise for hydrophone applications. The Fabry - Perot design is an excellent tool for precision length measurements but is extremely sensitive to...Pa was measured. Using the demodulation technique in Mills, [Ref. 13: pp. 94-95], one can make a comparison to the USRD type G63 stan- dard pressure

Fiber optic hydrophone

DOEpatents

Kuzmenko, P.J.; Davis, D.T.

1994-05-10

A miniature fiber optic hydrophone based on the principles of a Fabry-Perot interferometer is disclosed. The hydrophone, in one embodiment, includes a body having a shaped flexible bladder at one end which defines a volume containing air or suitable gas, and including a membrane disposed adjacent a vent. An optical fiber extends into the body with one end terminating in spaced relation to the membrane. Acoustic waves in the water that impinge on the bladder cause the pressure of the volume therein to vary causing the membrane to deflect and modulate the reflectivity of the Fabry-Perot cavity formed by the membrane surface and the cleaved end of the optical fiber disposed adjacent to the membrane. When the light is transmitted down the optical fiber, the reflected signal is amplitude modulated by the incident acoustic wave. Another embodiment utilizes a fluid filled volume within which the fiber optic extends. 2 figures.

A primary method for the complex calibration of a hydrophone from 1 Hz to 2 kHz

NASA Astrophysics Data System (ADS)

Slater, W. H.; E Crocker, S.; Baker, S. R.

2018-02-01

A primary calibration method is demonstrated to obtain the magnitude and phase of the complex sensitivity for a hydrophone at frequencies between 1 Hz and 2 kHz. The measurement is performed in a coupler reciprocity chamber (‘coupler’) a closed test chamber where time harmonic oscillations in pressure can be achieved and the reciprocity conditions required for a primary calibration can be realized. Relevant theory is reviewed and the reciprocity parameter updated for the complex measurement. Systematic errors and corrections for magnitude are reviewed and more added for phase. The combined expanded uncertainties of the magnitude and phase of the complex sensitivity at 1 Hz were 0.1 dB re 1 V μ Pa-1 and  ± 1\\circ , respectively. Complex sensitivity, sensitivity magnitude, and phase measurements are presented on an example primary reference hydrophone.

Bio-inspired piezoelectric artificial hair cell sensor fabricated by powder injection molding

NASA Astrophysics Data System (ADS)

Han, Jun Sae; Oh, Keun Ha; Moon, Won Kyu; Kim, Kyungseop; Joh, Cheeyoung; Seo, Hee Seon; Bollina, Ravi; Park, Seong Jin

2015-12-01

A piezoelectric artificial hair cell sensor was fabricated by the powder injection molding process in order to make an acoustic vector hydrophone. The entire process of powder injection molding was developed and optimized for PMN-PZT ceramic powder. The artificial hair cell sensor, which consists of high aspect ratio hair cell and three rectangular mechanoreceptors, was precisely fabricated through the developed powder injection molding process. The density and the dielectric property of the fabricated sensor shows 98% of the theoretical density and 85% of reference dielectric property of PMN-PZT ceramic powder. With regard to homogeneity, three rectangular mechanoreceptors have the same dimensions, with 3 μm of tolerance with 8% of deviation of dielectric property. Packaged vector hydrophones measure the underwater acoustic signals from 500 to 800 Hz with -212 dB of sensitivity. Directivity of vector hydrophone was acquired at 600 Hz as analyzing phase differences of electric signals.

Characterization of nonlinear ultrasound fields of 2D therapeutic arrays

PubMed Central

Yuldashev, Petr V.; Kreider, Wayne; Sapozhnikov, Oleg A.; Farr, Navid; Partanen, Ari; Bailey, Michael R.; Khokhlova, Vera

2015-01-01

A current trend in high intensity focused ultrasound (HIFU) technologies is to use 2D focused phased arrays that enable electronic steering of the focus, beamforming to avoid overheating of obstacles (such as ribs), and better focusing through inhomogeneities of soft tissue using time reversal methods. In many HIFU applications, the acoustic intensity in situ can reach thousands of W/cm2 leading to nonlinear propagation effects. At high power outputs, shock fronts develop in the focal region and significantly alter the bioeffects induced. Clinical applications of HIFU are relatively new and challenges remain for ensuring their safety and efficacy. A key component of these challenges is the lack of standard procedures for characterizing nonlinear HIFU fields under operating conditions. Methods that combine low-amplitude pressure measurements and nonlinear modeling of the pressure field have been proposed for axially symmetric single element transducers but have not yet been validated for the much more complex 3D fields generated by therapeutic arrays. Here, the method was tested for a clinical HIFU source comprising a 256-element transducer array. A numerical algorithm based on the Westervelt equation was used to enable 3D full-diffraction nonlinear modeling. With the acoustic holography method, the magnitude and phase of the acoustic field were measured at a low power output and used to determine the pattern of vibrations at the surface of the array. This pattern was then scaled to simulate a range of intensity levels near the elements up to 10 W/cm2. The accuracy of modeling was validated by comparison with direct measurements of the focal waveforms using a fiber-optic hydrophone. Simulation results and measurements show that shock fronts with amplitudes up to 100 MPa were present in focal waveforms at clinically relevant outputs, indicating the importance of strong nonlinear effects in ultrasound fields generated by HIFU arrays. PMID:26203345

Angular dependent anisotropic terahertz response of vertically aligned multi-walled carbon nanotube arrays with spatial dispersion.

PubMed

Zhou, Yixuan; E, Yiwen; Xu, Xinlong; Li, Weilong; Wang, Huan; Zhu, Lipeng; Bai, Jintao; Ren, Zhaoyu; Wang, Li

2016-12-14

Spatial dispersion effect of aligned carbon nanotubes (CNTs) in the terahertz (THz) region has significance for both theoretical and applied consideration due to the unique intrinsically anisotropic physical properties of CNTs. Herein, we report the angular dependent reflection of p-polarized THz wave from vertically aligned multi-walled CNT arrays in both experiment and theory. The spectra indicate that the reflection depends on the film thickness of vertically aligned CNTs, the incident angle, and the frequency. The calculation model is based on the spatial dispersion effect of aligned CNTs and performed with effective impedance method and the Maxwell-Garnett approximation. The results fit well with the experiment when the thickness of CNT film is thin, which reveals a coherent superposition mechanism of the CNT surface reflection and CNTs/Si interface reflection. For thick CNT films, the CNTs/Si interface response determines the reflection at small incident angles, while the CNTs surface effect dominates at large incident angles. This work investigates the spatial dispersion effect of vertically aligned CNT arrays in the THz region, and paves a way for potential anisotropic THz applications based on CNTs with oblique incidence requirements.

Angular dependent anisotropic terahertz response of vertically aligned multi-walled carbon nanotube arrays with spatial dispersion

NASA Astrophysics Data System (ADS)

Zhou, Yixuan; Yiwen, E.; Xu, Xinlong; Li, Weilong; Wang, Huan; Zhu, Lipeng; Bai, Jintao; Ren, Zhaoyu; Wang, Li

2016-12-01

Spatial dispersion effect of aligned carbon nanotubes (CNTs) in the terahertz (THz) region has significance for both theoretical and applied consideration due to the unique intrinsically anisotropic physical properties of CNTs. Herein, we report the angular dependent reflection of p-polarized THz wave from vertically aligned multi-walled CNT arrays in both experiment and theory. The spectra indicate that the reflection depends on the film thickness of vertically aligned CNTs, the incident angle, and the frequency. The calculation model is based on the spatial dispersion effect of aligned CNTs and performed with effective impedance method and the Maxwell-Garnett approximation. The results fit well with the experiment when the thickness of CNT film is thin, which reveals a coherent superposition mechanism of the CNT surface reflection and CNTs/Si interface reflection. For thick CNT films, the CNTs/Si interface response determines the reflection at small incident angles, while the CNTs surface effect dominates at large incident angles. This work investigates the spatial dispersion effect of vertically aligned CNT arrays in the THz region, and paves a way for potential anisotropic THz applications based on CNTs with oblique incidence requirements.

A 3D approximate maximum likelihood solver for localization of fish implanted with acoustic transmitters

DOE PAGES

Li, Xinya; Deng, Z. Daniel; USA, Richland Washington; ...

2014-11-27

Better understanding of fish behavior is vital for recovery of many endangered species including salmon. The Juvenile Salmon Acoustic Telemetry System (JSATS) was developed to observe the out-migratory behavior of juvenile salmonids tagged by surgical implantation of acoustic micro-transmitters and to estimate the survival when passing through dams on the Snake and Columbia Rivers. A robust three-dimensional solver was needed to accurately and efficiently estimate the time sequence of locations of fish tagged with JSATS acoustic transmitters, to describe in sufficient detail the information needed to assess the function of dam-passage design alternatives. An approximate maximum likelihood solver was developedmore » using measurements of time difference of arrival from all hydrophones in receiving arrays on which a transmission was detected. Field experiments demonstrated that the developed solver performed significantly better in tracking efficiency and accuracy than other solvers described in the literature.« less

A 3D approximate maximum likelihood solver for localization of fish implanted with acoustic transmitters

NASA Astrophysics Data System (ADS)

Li, Xinya; Deng, Z. Daniel; Sun, Yannan; Martinez, Jayson J.; Fu, Tao; McMichael, Geoffrey A.; Carlson, Thomas J.

2014-11-01

Better understanding of fish behavior is vital for recovery of many endangered species including salmon. The Juvenile Salmon Acoustic Telemetry System (JSATS) was developed to observe the out-migratory behavior of juvenile salmonids tagged by surgical implantation of acoustic micro-transmitters and to estimate the survival when passing through dams on the Snake and Columbia Rivers. A robust three-dimensional solver was needed to accurately and efficiently estimate the time sequence of locations of fish tagged with JSATS acoustic transmitters, to describe in sufficient detail the information needed to assess the function of dam-passage design alternatives. An approximate maximum likelihood solver was developed using measurements of time difference of arrival from all hydrophones in receiving arrays on which a transmission was detected. Field experiments demonstrated that the developed solver performed significantly better in tracking efficiency and accuracy than other solvers described in the literature.

A 3D approximate maximum likelihood solver for localization of fish implanted with acoustic transmitters

PubMed Central

Li, Xinya; Deng, Z. Daniel; Sun, Yannan; Martinez, Jayson J.; Fu, Tao; McMichael, Geoffrey A.; Carlson, Thomas J.

2014-01-01

Better understanding of fish behavior is vital for recovery of many endangered species including salmon. The Juvenile Salmon Acoustic Telemetry System (JSATS) was developed to observe the out-migratory behavior of juvenile salmonids tagged by surgical implantation of acoustic micro-transmitters and to estimate the survival when passing through dams on the Snake and Columbia Rivers. A robust three-dimensional solver was needed to accurately and efficiently estimate the time sequence of locations of fish tagged with JSATS acoustic transmitters, to describe in sufficient detail the information needed to assess the function of dam-passage design alternatives. An approximate maximum likelihood solver was developed using measurements of time difference of arrival from all hydrophones in receiving arrays on which a transmission was detected. Field experiments demonstrated that the developed solver performed significantly better in tracking efficiency and accuracy than other solvers described in the literature. PMID:25427517

A 3D approximate maximum likelihood solver for localization of fish implanted with acoustic transmitters.

PubMed

Li, Xinya; Deng, Z Daniel; Sun, Yannan; Martinez, Jayson J; Fu, Tao; McMichael, Geoffrey A; Carlson, Thomas J

2014-11-27

Better understanding of fish behavior is vital for recovery of many endangered species including salmon. The Juvenile Salmon Acoustic Telemetry System (JSATS) was developed to observe the out-migratory behavior of juvenile salmonids tagged by surgical implantation of acoustic micro-transmitters and to estimate the survival when passing through dams on the Snake and Columbia Rivers. A robust three-dimensional solver was needed to accurately and efficiently estimate the time sequence of locations of fish tagged with JSATS acoustic transmitters, to describe in sufficient detail the information needed to assess the function of dam-passage design alternatives. An approximate maximum likelihood solver was developed using measurements of time difference of arrival from all hydrophones in receiving arrays on which a transmission was detected. Field experiments demonstrated that the developed solver performed significantly better in tracking efficiency and accuracy than other solvers described in the literature.

Seismic and hydroacoustic analysis relevant to MH370

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

Stead, Richard J.

2014-07-03

The vicinity of the Indian Ocean is searched for open and readily available seismic and/or hydroacoustic stations that might have recorded a possible impact of MH370 with the ocean surface. Only three stations are identified: the IMS hydrophone arrays H01 and H08, and the Geoscope seismic station AIS. Analysis of the data from these stations shows an interesting arrival on H01 that has some interference from an Antarctic ice event, large amplitude repeating signals at H08 that obscure any possible arrivals, and large amplitude chaotic noise at AIS precludes any analysis at higher frequencies of interest. The results are thereforemore » rather inconclusive but may point to a more southerly impact location within the overall Indian Ocean search region. The results would be more useful if they can be combined with any other data that are not readily available.« less

A 3D approximate maximum likelihood solver for localization of fish implanted with acoustic transmitters

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

Li, Xinya; Deng, Z. Daniel; USA, Richland Washington

Better understanding of fish behavior is vital for recovery of many endangered species including salmon. The Juvenile Salmon Acoustic Telemetry System (JSATS) was developed to observe the out-migratory behavior of juvenile salmonids tagged by surgical implantation of acoustic micro-transmitters and to estimate the survival when passing through dams on the Snake and Columbia Rivers. A robust three-dimensional solver was needed to accurately and efficiently estimate the time sequence of locations of fish tagged with JSATS acoustic transmitters, to describe in sufficient detail the information needed to assess the function of dam-passage design alternatives. An approximate maximum likelihood solver was developedmore » using measurements of time difference of arrival from all hydrophones in receiving arrays on which a transmission was detected. Field experiments demonstrated that the developed solver performed significantly better in tracking efficiency and accuracy than other solvers described in the literature.« less

Sources and levels of ambient ocean sound near the antarctic peninsula

DOE PAGES

Dziak, Robert P.; Bohnenstiehl, DelWayne R.; Stafford, Kathleen M.; ...

2015-04-14

Arrays of hydrophones were deployed within the Bransfield Strait and Scotia Sea (Antarctic Peninsula region) from 2005 to 2009 to record ambient ocean sound at frequencies of up to 125 and 500 Hz. Icequakes, which are broadband, short duration signals derived from fracturing of large free-floating icebergs, are a prominent feature of the ocean soundscape. Icequake activity peaks during austral summer and is minimum during winter, likely following freeze-thaw cycles. Iceberg grounding and rapid disintegration also releases significant acoustic energy, equivalent to large-scale geophysical events. Overall ambient sound levels can be as much as ~10–20 dB higher in the open,more » deep ocean of the Scotia Sea compared to the relatively shallow Bransfield Strait. Noise levels become lowest during the austral winter, as sea-ice cover suppresses wind and wave noise. Ambient noise levels are highest during austral spring and summer, as surface noise, ice cracking and biological activity intensifies. Vocalizations of blue ( Balaenoptera musculus) and fin ( B. physalus) whales also dominate the long-term spectra records in the 15–28 and 89 Hz bands. Blue whale call energy is a maximum during austral summer-fall in the Drake Passage and Bransfield Strait when ambient noise levels are a maximum and sea-ice cover is a minimum. Fin whale vocalizations were also most common during austral summer-early fall months in both the Bransfield Strait and Scotia Sea. The hydrophone data overall do not show sustained anthropogenic sources (ships and airguns), likely due to low coastal traffic and the typically rough weather and sea conditions of the Southern Ocean.« less

Vertically aligned CdSe nanowire arrays for energy harvesting and piezotronic devices.

PubMed

Zhou, Yu Sheng; Wang, Kai; Han, Weihua; Rai, Satish Chandra; Zhang, Yan; Ding, Yong; Pan, Caofeng; Zhang, Fang; Zhou, Weilie; Wang, Zhong Lin

2012-07-24

We demonstrated the energy harvesting potential and piezotronic effect in vertically aligned CdSe nanowire (NW) arrays for the first time. The CdSe NW arrays were grown on a mica substrate by the vapor-liquid-solid process using a CdSe thin film as seed layer and platinum as catalyst. High-resolution transmission electron microscopy image and selected area electron diffraction pattern indicate that the CdSe NWs have a wurtzite structure and growth direction along (0001). Using conductive atomic force microscopy (AFM), an average output voltage of 30.7 mV and maximum of 137 mV were obtained. To investigate the effect of strain on electron transport, the current-voltage characteristics of the NWs were studied by positioning an AFM tip on top of an individual NW. By applying normal force/stress on the NW, the Schottky barrier between the Pt and CdSe was found to be elevated due to the piezotronic effect. With the change of strain of 0.12%, a current decreased from 84 to 17 pA at 2 V bias. This paper shows that the vertical CdSe NW array is a potential candidate for future piezo-phototronic devices.

Separating light absorption layer from channel in ZnO vertical nanorod arrays based photodetectors for high-performance image sensors

NASA Astrophysics Data System (ADS)

Ma, Yang; Wu, Congjun; Xu, Zhihao; Wang, Fei; Wang, Min

2018-05-01

Photoconductor arrays with both high responsivity and large ON/OFF ratios are of great importance for the application of image sensors. Herein, a ZnO vertical nanorod array based photoconductor with a light absorption layer separated from the device channel has been designed, in which the photo-generated carriers along the axial ZnO nanorods drive to the external electrodes through nanorod-nanorod junctions in the dense layer at the bottom. This design allows us to enhance the photocurrent with unchanged dark current by increasing the ratio between the ZnO nanorod length and the thickness of the dense layer to achieve both high responsivity and large ON/OFF ratios. As a result, the as-fabricated devices possess a high responsivity of 1.3 × 105 A/W, a high ON/OFF ratio of 790, a high detectivity of 1.3 × 1013 Jones, and a low detectable light intensity of 1 μW/cm2. More importantly, the developed approach enables the integration of ZnO vertical nanorod array based photodetectors as image sensors with uniform device-to-device performance.

GaN nanowire arrays with nonpolar sidewalls for vertically integrated field-effect transistors

NASA Astrophysics Data System (ADS)

Yu, Feng; Yao, Shengbo; Römer, Friedhard; Witzigmann, Bernd; Schimpke, Tilman; Strassburg, Martin; Bakin, Andrey; Schumacher, Hans Werner; Peiner, Erwin; Suryo Wasisto, Hutomo; Waag, Andreas

2017-03-01

Vertically aligned gallium nitride (GaN) nanowire (NW) arrays have attracted a lot of attention because of their potential for novel devices in the fields of optoelectronics and nanoelectronics. In this work, GaN NW arrays have been designed and fabricated by combining suitable nanomachining processes including dry and wet etching. After inductively coupled plasma dry reactive ion etching, the GaN NWs are subsequently treated in wet chemical etching using AZ400K developer (i.e., with an activation energy of 0.69 ± 0.02 eV and a Cr mask) to form hexagonal and smooth a-plane sidewalls. Etching experiments using potassium hydroxide (KOH) water solution reveal that the sidewall orientation preference depends on etchant concentration. A model concerning surface bonding configuration on crystallography facets has been proposed to understand the anisotropic wet etching mechanism. Finally, NW array-based vertical field-effect transistors with wrap-gated structure have been fabricated. A device composed of 99 NWs exhibits enhancement mode operation with a threshold voltage of 1.5 V, a superior electrostatic control, and a high current output of >10 mA, which prevail potential applications in next-generation power switches and high-temperature digital circuits.

GaN nanowire arrays with nonpolar sidewalls for vertically integrated field-effect transistors.

PubMed

Yu, Feng; Yao, Shengbo; Römer, Friedhard; Witzigmann, Bernd; Schimpke, Tilman; Strassburg, Martin; Bakin, Andrey; Schumacher, Hans Werner; Peiner, Erwin; Wasisto, Hutomo Suryo; Waag, Andreas

2017-03-03

Vertically aligned gallium nitride (GaN) nanowire (NW) arrays have attracted a lot of attention because of their potential for novel devices in the fields of optoelectronics and nanoelectronics. In this work, GaN NW arrays have been designed and fabricated by combining suitable nanomachining processes including dry and wet etching. After inductively coupled plasma dry reactive ion etching, the GaN NWs are subsequently treated in wet chemical etching using AZ400K developer (i.e., with an activation energy of 0.69 ± 0.02 eV and a Cr mask) to form hexagonal and smooth a-plane sidewalls. Etching experiments using potassium hydroxide (KOH) water solution reveal that the sidewall orientation preference depends on etchant concentration. A model concerning surface bonding configuration on crystallography facets has been proposed to understand the anisotropic wet etching mechanism. Finally, NW array-based vertical field-effect transistors with wrap-gated structure have been fabricated. A device composed of 99 NWs exhibits enhancement mode operation with a threshold voltage of 1.5 V, a superior electrostatic control, and a high current output of >10 mA, which prevail potential applications in next-generation power switches and high-temperature digital circuits.

Piezoelectric and Electrostrictive Materials for Transducer Applications. Volume 1.

DTIC Science & Technology

1988-03-01

3 Composites for Hydrophone Applications ...................... 2 2.3.1 Lead Bismuth Titanate Ferrate Compositions ................. 2 2.3.2...external variables are considered. 2.3 0:3 Composites for Hydrophone Applications 2.3.1 Lead Bismuth Titanate Ferrate Compositions the-"Following up...34" Even for doped samples however, the best results were obtained at the 50% bismuth ferrate composition. 0.. W* . - ’ w-w~-,wn~ , 7WI W W PP7W-w7WnM

Morphology-controlled cactus-like branched anatase TiO2 arrays with high light-harvesting efficiency for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Wu, Wu-Qiang; Rao, Hua-Shang; Feng, Hao-Lin; Guo, Xin-Dong; Su, Cheng-Yong; Kuang, Dai-Bin

2014-08-01

The present work establishes a facile process for one-step hydrothermal growth of vertically aligned anatase cactus-like branched TiO2 (CBT) arrays on a transparent conducting oxide (TCO) substrate. Various CBT morphologies are obtained by adjusting the potassium titanium oxide oxalate (PTO) reactant concentration (from 0.05 M to 0.15 M) and this yields a morphologically-controllable branched TiO2 arrays geometry. The CBT arrays consist of a vertically oriented nanowire (NW) or nanosheet (NS) stem and a host of short nanorod (NR) branches. The hierarchical CBT arrays demonstrate their excellent candidatures as photoanodes, which are capable of exhibiting high light-harvesting efficiency in dye-sensitized solar cells (DSSCs). Consequently, DSSCs based on 7 μm long optimized CBT arrays (0.05 M PTO), which are assembled with high density and high aspect-ratio NR branches, exhibit an impressive power conversion efficiency of 6.43% under AM 1.5G one sun illumination. The high performance can be attributed to the prominent light-harvesting efficiency, resulting from larger surface area and superior light-scattering capability.

Effects of Nanowire Length and Surface Roughness on the Electrochemical Sensor Properties of Nafion-Free, Vertically Aligned Pt Nanowire Array Electrodes

PubMed Central

Li, Zhiyang; Leung, Calvin; Gao, Fan; Gu, Zhiyong

2015-01-01

In this paper, vertically aligned Pt nanowire arrays (PtNWA) with different lengths and surface roughnesses were fabricated and their electrochemical performance toward hydrogen peroxide (H2O2) detection was studied. The nanowire arrays were synthesized by electroplating Pt in nanopores of anodic aluminum oxide (AAO) template. Different parameters, such as current density and deposition time, were precisely controlled to synthesize nanowires with different surface roughnesses and various lengths from 3 μm to 12 μm. The PtNWA electrodes showed better performance than the conventional electrodes modified by Pt nanowires randomly dispersed on the electrode surface. The results indicate that both the length and surface roughness can affect the sensing performance of vertically aligned Pt nanowire array electrodes. Generally, longer nanowires with rougher surfaces showed better electrochemical sensing performance. The 12 μm rough surface PtNWA presented the largest sensitivity (654 μA·mM−1·cm−2) among all the nanowires studied, and showed a limit of detection of 2.4 μM. The 12 μm rough surface PtNWA electrode also showed good anti-interference property from chemicals that are typically present in the biological samples such as ascorbic, uric acid, citric acid, and glucose. The sensing performance in real samples (river water) was tested and good recovery was observed. These Nafion-free, vertically aligned Pt nanowires with surface roughness control show great promise as versatile electrochemical sensors and biosensors. PMID:26404303

Highly organised and dense vertical silicon nanowire arrays grown in porous alumina template on <100> silicon wafers

PubMed Central

2013-01-01

In this work, nanoimprint lithography combined with standard anodization etching is used to make perfectly organised triangular arrays of vertical cylindrical alumina nanopores onto standard <100>−oriented silicon wafers. Both the pore diameter and the period of alumina porous array are well controlled and can be tuned: the periods vary from 80 to 460 nm, and the diameters vary from 15 nm to any required diameter. These porous thin layers are then successfully used as templates for the guided epitaxial growth of organised mono-crystalline silicon nanowire arrays in a chemical vapour deposition chamber. We report the densities of silicon nanowires up to 9 × 109 cm−2 organised in highly regular arrays with excellent diameter distribution. All process steps are demonstrated on surfaces up to 2 × 2 cm2. Specific emphasis was made to select techniques compatible with microelectronic fabrication standards, adaptable to large surface samples and with a reasonable cost. Achievements made in the quality of the porous alumina array, therefore on the silicon nanowire array, widen the number of potential applications for this technology, such as optical detectors or biological sensors. PMID:23773702

Design of a hydrophone for an Ocean World lander

NASA Astrophysics Data System (ADS)

Smith, Heather D.; Duncan, Andrew G.

2017-10-01

For this presentation we describe the science return, and design of a microphone on- board a Europa lander mission. In addition to the E/PO benefit of a hydrophone to listen to the Europa Ocean, a microphone also provides scientific data on the properties of the subsurface ocean.A hydrophone is a small light-weight instrument that could be used to achieve two of the three Europa Lander mission anticipated science goals of: 1) Asses the habitability (particularly through quantitative compositional measurements of Europa via in situ techniques uniquely available to a landed mission. And 2) Characterize surface properties at the scale of the lander to support future exploration, including the local geologic context.Acoustic properties of the ocean would lead to a better understanding of the water density, currents, seafloor topography and other physical properties of the ocean as well as lead to an understanding of the salinity of the ocean. Sound from water movement (tidal movement, currents, subsurface out-gassing, ocean homogeneity (clines), sub-surface morphology, and biological sounds.The engineering design of the hydrophone instrument will be designed to fit within a portion of the resource allocation of the current best estimates of the Europa lander payload (26.6 Kg, 24,900 cm3, 2,500 W-hrs and 2700 Mbits). The hydrophone package will be designed to ensure planetary protection is maintained and will function under the cur- rent Europa lander mission operations scenario of a two-year cruise phase, and 30-day surface operational phase on Europa.Although the microphone could be used on the surface, it is designed to be lowered into the subsurface ocean. As such, planetary protection (forward contamination) is a primary challenge for a subsurface microphone/ camera. The preliminary design is based on the Navy COTS optical microphone.Reference: Pappalardo, R. T., et al. "Science potential from a Europa lander." Astrobiology 13.8 (2013): 740-773.

An 'Orca-stra' of Science and Sound: The Reverberations of Northeast Pacific Whales and How We're Helping People Understand Them Though Games, Demos and Listening

NASA Astrophysics Data System (ADS)

Pelz, M.; Dewey, R. K.; Hoeberechts, M.; Kanes, K.; Ewing, N.

2015-12-01

Presented by the Ocean Networks Canada (ONC) Leaning and Engagement team, this demonstration focuses on our strategy for engaging and inspiring the next generation of ocean advocates by introducing them to one of the ocean's most charismatic inhabitants: marine mammals (and don't worry, we don't need any tanks or neoprene suits to do it). Using bioacoustic data, we can bring the essence of the animals with us. ONC, an initiative of the University of Victoria, operates cabled ocean observatories which supply continuous power and Internet connectivity to a broad suite of subsea instruments from the coast to the deep sea. This Internet connectivity permits researchers, students and members of the public to download freely available data onto their computers from anywhere around the globe, in real-time. Our demo focuses on the story of bioacoustics from instrument to animal. When visiting classrooms or hosting booths, we enhance user knowledge and experience by connecting familiar animals with their acoustic data from hydrophones. This includes listening to hydrophone clips collected from the network, analyzing sounds using interactive, real-time software and playing interactive games designed to get participants thinking like a scientist and taking a whale's perspective. For example, participants listen to recordings and guess the sound, identify frequencies and try a working hydrophone. The presentation consists of a suite of activities that meet a broad range of Next Generation Science Standards and includes links to the SoundCloud, https://soundcloud.com/oceannetworkscanada the ONC hydrophone FAQ, http://www.oceannetworks.ca/smart-hydrophone-faq and a classroom ready resource, Shouting Whales http://openschool.bc.ca/shouting_whales/index.html . The included links allow users anywhere to have a similar whale "experience" as the data are classroom ready, accessible and free.

Finite frequency P-wave traveltime measurements on ocean bottom seismometers and hydrophones in the western Indian Ocean

NASA Astrophysics Data System (ADS)

Tsekhmistrenko, Maria; Sigloch, Karin; Hosseini, Kasra; Barruol, Guilhem

2016-04-01

From 2011 to 2014, the RHUM-RUM project (Reunion Hotspot Upper Mantle - Reunions Unterer Mantel) instrumented a 2000x2000km2 area of Indian Ocean seafloor, islands and Madagascar with broadband seismometers and hydrophones. The central component was a 13-month deployment of 57 German and French Ocean Bottom Seismometers (OBS) in 2300-5600 m depth. This was supplemented by 2-3 year deployments of 37 island stations on Reunion, Mauritius, Rodrigues, the southern Seychelles, the Iles Eparses and southern Madagascar. Two partner projects contributed another 30+ stations on Madagascar. Our ultimate objective is multifrequency waveform tomography of the entire mantle column beneath the Reunion hotspot. Ideally we would use all passbands that efficiently transmit body waves but this meets practical limits in the noise characteristics of ocean-bottom recordings in particular. Here we present the preliminary data set of frequency-dependent P-wave traveltime measurements on seismometers and hydrophones, obtained by cross-correlation of observed with predicted waveforms. The latter are synthesized from fully numerical Green's functions and carefully estimated, broadband source time functions. More than 200 teleseismic events during the 13-month long deployment yielded usable P-waveform measurements. We present our methods and discuss data yield and quality of ocean-bottom versus land seismometers, and of OBS versus broadband hydrophones. Above and below the microseismic noise band, data yields are higher than within it, especially for OBS. The 48 German OBS, equipped with Guralp 60 s sensors, were afflicted by relatively high self-noise compared to the 9 French instruments equipped with Nanometrics Trillium 240 s sensors. The HighTechInc (model HTI-01 and HTI-04-PCA/ULF) hydrophones (100 s corner period) functioned particularly reliably but their waveforms are relatively more challenging to model due to reverberations in the water column. We obtain ~15000 combined cross-correlations measurements that should be usable in multifrequency P-wave tomography, in passbands between 30 s and 2.7 s dominant period.

Evaluation of the shear force of single cancer cells by vertically aligned carbon nanotubes suitable for metastasis diagnosis.

PubMed

Abdolahad, M; Mohajerzadeh, S; Janmaleki, M; Taghinejad, H; Taghinejad, M

2013-03-01

Vertically aligned carbon nanotube (VACNT) arrays have been demonstrated as probes for rapid quantifying of cancer cell deformability with high resolution. Through entrapment of various cancer cells on CNT arrays, the deflections of the nanotubes during cell deformation were used to derive the lateral cell shear force using a large deflection mode method. It is observed that VACNT beams act as sensitive and flexible agents, which transfer the shear force of cells trapped on them by an observable deflection. The metastatic cancer cells have significant deformable structures leading to a further cell traction force (CTF) than primary cancerous one on CNT arrays. The elasticity of different cells could be compared by their CTF measurement on CNT arrays. This study presents a nanotube-based methodology for quantifying the single cell mechanical behavior, which could be useful for understanding the metastatic behavior of cells.

Ultra-high aggregate bandwidth two-dimensional multiple-wavelength diode laser arrays

NASA Astrophysics Data System (ADS)

Chang-Hasnain, Connie

1994-04-01

Two-dimensional (2D) multi-wavelength vertical cavity surface emitting laser (VCSEL) arrays is promising for ultrahigh aggregate capacity optical networks. A 2D VCSEL array emitting 140 distinct wavelengths was reported by implementing a spatially graded layer in the VCSEL structure, which in turn creates a wavelength spread. In this program, we concentrated on novel epitaxial growth techniques to make reproducible and repeatable multi-wavelength VCSEL arrays.

Surface-restrained growth of vertically aligned carbon nanotube arrays with excellent thermal transport performance.

PubMed

Ping, Linquan; Hou, Peng-Xiang; Liu, Chang; Li, Jincheng; Zhao, Yang; Zhang, Feng; Ma, Chaoqun; Tai, Kaiping; Cong, Hongtao; Cheng, Hui-Ming

2017-06-22

A vertically aligned carbon nanotube (VACNT) array is a promising candidate for a high-performance thermal interface material in high-power microprocessors due to its excellent thermal transport property. However, its rough and entangled free tips always cause poor interfacial contact, which results in serious contact resistance dominating the total thermal resistance. Here, we employed a thin carbon cover to restrain the disorderly growth of the free tips of a VACNT array. As a result, all the free tips are seamlessly connected by this thin carbon cover and the top surface of the array is smoothed. This unique structure guarantees the participation of all the carbon nanotubes in the array in the heat transport. Consequently the VACNT array grown on a Cu substrate shows a record low thermal resistance of 0.8 mm 2 K W -1 including the two-sided contact resistances, which is 4 times lower than the best result previously reported. Remarkably, the VACNT array can be easily peeled away from the Cu substrate and act as a thermal pad with excellent flexibility, adhesive ability and heat transport capability. As a result the CNT array with a thin carbon cover shows great potential for use as a high-performance flexible thermal interface material.

Deployment/retraction ground testing of a large flexible solar array

NASA Technical Reports Server (NTRS)

Chung, D. T.

1982-01-01

The simulated zero-gravity ground testing of the flexible fold-up solar array consisting of eighty-four full-size panels (.368 m x .4 m each) is addressed. Automatic, hands-off extension, retraction, and lockup operations are included. Three methods of ground testing were investigated: (1) vertical testing; (2) horizontal testing, using an overhead water trough to support the panels; and (3) horizontal testing, using an overhead track in conjunction with a counterweight system to support the panels. Method 3 was selected as baseline. The wing/assembly vertical support structure, the five-tier overhead track, and the mast-element support track comprise the test structure. The flexible solar array wing assembly was successfully extended and retracted numerous times under simulated zero-gravity conditions.

Board-to-Board Free-Space Optical Interconnections Passing through Boards for a Bookshelf-Assembled Terabit-Per-Second-Class ATM Switch.

PubMed

Hirabayashi, K; Yamamoto, T; Matsuo, S; Hino, S

1998-05-10

We propose free-space optical interconnections for a bookshelf-assembled terabit-per-second-class ATM switch. Thousands of arrayed optical beams, each having a rate of a few gigabits per second, propagate vertically to printed circuit boards, passing through some boards, and are connected to arbitrary transmitters and receivers on boards by polarization controllers and prism arrays. We describe a preliminary experiment using a 1-mm-pitch 2 x 2 beam-collimator array that uses vertical-cavity surface-emitting laser diodes. These optical interconnections can be made quite stable in terms of mechanical shock and temperature fluctuation by the attachment of reinforcing frames to the boards and use of an autoalignment system.

Surface Craft Motion Parameter Estimation Using Multipath Delay Measurements from Hydrophones

DTIC Science & Technology

2011-12-01

the sensor is cd . The slant range of the source from the sensor at time t is given by 21222 ])([)( cc RtvtR +−= τ ( 1 ) where 2122 ])[( crtc dhhR...Surface Craft Motion Parameter Estimation Using Multipath Delay Measurements from Hydrophones Kam W. Lo # 1 and Brian G. Ferguson #2 # Maritime...Eveleigh, NSW 2015 Australia 1 kam.lo@dsto.defence.gov.au 2 brian.ferguson@dsto.defence.gov.au Abstract— An equation-error (EE) method is

Cheap DECAF: Density Estimation for Cetaceans from Acoustic Fixed Sensors Using Separate, Non-Linked Devices

DTIC Science & Technology

2015-09-30

interpolation was used to estimate fin whale density in between the hydrophone locations , and the result plotted as a density image. This was repeated every 5...singing fin whale density throughout the year for the study location off Portugal. Color indicates whale density, with calibration scale at right; yellow...spots are hydrophone locations ; timeline at top indicates the time of year; circle at lower right is 1000 km 2 , the area used in the unit of whale

ULF/VLF (0.001 to 50 Hz) Seismo-Acoustic Noise in the Ocean. Proceedings of a Workshop Held at Austin, Texas on November 29-December 1, 1988

DTIC Science & Technology

1989-08-03

holes drilled in the seafloor from the D/V JOIDES Resolution through petrological , geochemical and paleomagnetic studies of the samples and logging...seismome- ters and/or hydrophones (or differential pressure gauges , DPG). Testing of the new instruments at very early stages is important to ensure...resolved using ocean bottom seismometers, suspended hydrophones and differential pressure gauges assisted by an orbiting radar altimeter (GEOSAT

Assessment of the Performance of the Near-Bottom Hydrophones of the U.S. Navy Southern California Offshore Range in Detecting, Localizing and Reconstructing 10-20 kHz Odontocete Whistles

DTIC Science & Technology

2008-03-01

Stafford et al. ( 1998 ) utilized MSP for long range and acoustic detection and localization of blue whale calls in the northeast Pacific Ocean...J. Acoust . Soc. Am. 107 (6):3496:3508 (2000). Stafford , K. M., Fox, C. G., Clark, D. S., “ Long - range acoustic detection and localization of blue ...OF THE PERFORMANCE OF THE NEAR- BOTTOM HYDROPHONES OF THE U.S. NAVY SOUTHERN CALIFORNIA OFFSHORE

Hydroacoustic Propagation Through the Antarctic Convergence Zone: Study of Errors in Yield and Location Estimates for Explosive Charges

DTIC Science & Technology

2007-09-01

since water depth was only 800 m. Interestingly the signal from the 3rd drop has charge-seafloor range and bubble pulse frequency closer to what would...Hydrophone. A near-source hydrophone recording system was put together by Scripps Institution of Oceanography’s (SIO’s) Ocean Bottom Seismograph ...needed. We have thus proposed another research cruise to obtain more detailed measurements . Our new plan calls for several improvements to the previous

Final Environmental Impact Statement for the Kauai Acoustic Thermometry of Ocean Climate Project and Its Associated Marine Mammal Research Program: Vol 1

DTIC Science & Technology

1995-05-01

at zero source level to allow time for any mobile marine animal who was annoyed by the sound to depart the affected area; and project facilities would...using conventional thermometers); autonomous polar hydrophones; and a dual site experiment using mobile playback experiments. Of the twelve alternatives...HYDROPHONES (ICE NOISE 2-43 MEASUREMENTS) (ALTERNATIVE 11) 2.2.12 DUAL SITE EXPERIMENT; ALTERNATIVE MMRP 2-44 TECHNIQUES -- MOBILE PLAYBACK EXPERIMENTS

Wavelength control of vertical cavity surface-emitting lasers by using nonplanar MOCVD

NASA Astrophysics Data System (ADS)

Koyama, F.; Mukaihara, T.; Hayashi, Y.; Ohnoki, N.; Hatori, N.; Iga, K.

1995-01-01

We present a novel approach of on-wafer wavelength control for vertical cavity surface-emitting lasers (VCSEL's) using nonplanar metalorganic chemical vapor deposition. The resonant wavelength of 980 nm VCSEL's grown on a patterned substrate can be controlled in the wavelength range over 45 nm by changing the size of circular patterns. A multi-wavelength VCSEL linear array was fabricated by using this technique. The proposed method will be useful for multi-wavelength VCSEL arrays as well as for the cancellation of wavelength nonuniformity over a wafer.

Water Quality Monitor

NASA Technical Reports Server (NTRS)

1982-01-01

An automated water quality monitoring system was developed by Langley Research Center to meet a need of the Environmental Protection Agency (EPA). Designed for unattended operation in water depths up to 100 feet, the system consists of a subsurface buoy anchored in the water, a surface control unit (SCU) and a hydrophone link for acoustic communication between buoy and SCU. Primary functional unit is the subsurface buoy. It incorporates 16 cells for water sampling, plus sensors for eight water quality measurements. Buoy contains all the electronic equipment needed for collecting and storing sensor data, including a microcomputer and a memory unit. Power for the electronics is supplied by a rechargeable nickel cadmium battery that is designed to operate for about two weeks. Through hydrophone link the subsurface buoy reports its data to the SCU, which relays it to land stations. Link allows two-way communications. If system encounters a problem, it automatically shuts down and sends alert signal. Sequence of commands sent via hydrophone link causes buoy to release from anchor and float to the surface for recovery.

Effect of nonlinearity on lesion formation for high-intensity focused ultrasound (HIFU) exposures

NASA Astrophysics Data System (ADS)

Lee, Paul; Lizzi, Frederic L.; Ketterling, Jeffrey A.; Vecchio, Christopher J.

2004-05-01

This study examined the effects of nonlinear propagation phenomena on two types of HIFU transducers (5 MHz) being used for thermal treatments of disease. The first transducer is a 5-element annular array. The second is a transducer with a 5-strip electrode; its multilobed focused beam is designed to efficiently produce broad, paddle-shaped lesions. The beam patterns of these transducers were computed using a variety of excitation patterns for electronic focusing of the annular array and variation of lesion size for the strip-electrode transducer. A range of intensities was studied to determine how nonlinear propagation affects the beam shape, constituent frequency content, grating lobes, etc. These 3D computations used a finite-amplitude beam propagation model that combined the angular spectrum method and Burger's equation to compute the diffraction and nonlinear effects, respectively. Computed beam patterns were compared with hydrophone measurements for each transducer. The linear and nonlinear beam patterns were used to compute the absorbed thermal dose, and the bioheat equation was evaluated to calculate 3D temperature rises and geometry of induced lesions. Computed lesion sizes and shapes were compared to in vitro lesions created by each HIFU transducer. [Work supported by NCI and NHLBI Grant 5R01 CA84588.

Underwater behavior of sperm whales off Kaikoura, New Zealand, as revealed by a three-dimensional hydrophone array.

PubMed

Miller, Brian; Dawson, Stephen; Vennell, Ross

2013-10-01

Observations are presented of the vocal behavior and three dimensional (3D) underwater movements of sperm whales measured with a passive acoustic array off the coast of Kaikoura, New Zealand. Visual observations and vocal behaviors of whales were used to divide dive tracks into different phases, and depths and movements of whales are reported for each of these phases. Diving depths and movement information from 75 3D tracks of whales in Kaikoura are compared to one and two dimensional tracks of whales studied in other oceans. While diving, whales in Kaikoura had a mean swimming speed of 1.57 m/s, and, on average, dived to a depth of 427 m (SD = 117 m), spending most of their time at depths between 300 and 600 m. Creak vocalizations, assumed to be the prey capture phase of echolocation, occurred throughout the water column from sea surface to sea floor, but most occurred at depths of 400-550 m. Three dimensional measurement of tracking revealed several different "foraging" strategies, including active chasing of prey, lining up slow-moving or unsuspecting prey, and foraging on demersal or benthic prey. These movements provide the first 3D descriptions underwater behavior of whales at Kaikoura.

Facile construction of vertically aligned EuS-ZnO hybrid core shell nanorod arrays for visible light driven photocatalytic properties

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

Ranjith, K. S.; Kumar, D. Ranjith; Kumar, R. T. Rajendra, E-mail: rtrkumar@buc.edu.in

2015-06-24

We demonstrated the development of coupled semiconductor in the form of hybrid heterostructures for significant advancement in catalytic functional materials. In this article, we report the preparation of vertically aligned core shell ZnO-EuS nanorod photocatalyst arrays by a simple chemical solution process followed by sulfudation process. The XRD pattern confirmed formation of the hexagonal wurtzite structure of ZnO and cubic nature of the EuS. Cross sectional FESEM images show vertical rod array structure, and the size of the nanorods ranges from 80 to 120 nm. UV-Vis DRS spectra showed that the optical absorption of ZnO was significantly enhanced to the visiblemore » region by modification with EuS surfaces. TEM study confirmed that the surface of ZnO was drastically improved by the modification with EuS nanoparticle. The catalytic activity of EuS−ZnO core shell nanorod arrays were evaluated by the photodegradation of Methylene Blue (MB) dye under visible irradiation. The results revealed that the photocatalytic activity of EuS−ZnO was much higher than that of ZnO under natural sunlight. EuS−ZnO was found to be stable and reusable without appreciable loss of catalytic activity up to four consecutive cycles.« less

Vertical Gravimeter Array Observations and Their Performance in Groundwater-Level Monitoring

NASA Astrophysics Data System (ADS)

Tanaka, T.; Honda, R.

2018-03-01

The gravitational effects of the atmosphere and subsurface water are significant obstacles to observing gravity variations on the sub-μGal (1 μGal = 10 nm/s2) scale. The goal of this study is to detect changes in gravity that are caused by mass redistributions deep underground related to seismological phenomena by reducing environmental gravity effects using multiple gravimeters belowground and aboveground, which we term a "vertical gravimeter array." Based on an evaluation of the responses to atmospheric effects and rainfall events identified in observations made with individual relative gravimeters, the vertical gravimeter array succeeds in stacking the target signals from deep underground and in reducing errors due to rainfall or free groundwater and atmospheric effects. To enable accurate interpretation, we introduce a physical approach that is based on attraction and loading deformation effects for atmospheric reduction using state-of-the-art gridded weather data products. Changes in the water levels of confined groundwater can be regarded as a signal from deep underground, and a response coefficient of approximately -15 μGal/m was obtained. In addition, the response coefficient of the free groundwater level was determined to be approximately 5 μGal/m. Such array observations are expected to contribute to monitoring crustal activity and hydrological studies.

Acoustic tracking of sperm whales in the Gulf of Alaska using a two-element vertical array and tags.

PubMed

Mathias, Delphine; Thode, Aaron M; Straley, Jan; Andrews, Russel D

2013-09-01

Between 15 and 17 August 2010, a simple two-element vertical array was deployed off the continental slope of Southeast Alaska in 1200 m water depth. The array was attached to a vertical buoy line used to mark each end of a longline fishing set, at 300 m depth, close to the sound-speed minimum of the deep-water profile. The buoy line also served as a depredation decoy, attracting seven sperm whales to the area. One animal was tagged with both a LIMPET dive depth-transmitting satellite and bioacoustic "B-probe" tag. Both tag datasets were used as an independent check of various passive acoustic schemes for tracking the whale in depth and range, which exploited the elevation angles and relative arrival times of multiple ray paths recorded on the array. Analytical tracking formulas were viable up to 2 km range, but only numerical propagation models yielded accurate locations up to at least 35 km range at Beaufort sea state 3. Neither localization approach required knowledge of the local bottom bathymetry. The tracking system was successfully used to estimate the source level of an individual sperm whale's "clicks" and "creaks" and predict the maximum detection range of the signals as a function of sea state.

High-Performance Flexible All-Solid-State Asymmetric Supercapacitors Based on Vertically Aligned CuSe@Co(OH) 2 Nanosheet Arrays

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

Gong, Jiangfeng; Tian, Yazhou; Yang, Ziyuan

The developments of electrode active materials provide the opportunities for next-generation energy storage devices. The arrangement of electrode materials on the substrate has recently emerged as a promising strategy for preparing high-performance supercapacitors. In this paper, we demonstrate a novel vertically aligned CuSe@Co(OH) 2 nanosheet arrays electrode for supercapacitor application. The materials are thoroughly characterized by structural and spectroscopic techniques. Electrochemical performance of CuSe@Co(OH) 2 nanosheet arrays are investigated in detail, which exhibit a specific capacitance as much as 1180 F g -1 at a current density of 1 A g -1. A flexible asymmetric all-solid-state supercapacitor is fabricated usingmore » CuSe@Co(OH) 2 nanosheet arrays as the positive electrode and activated carbon as the negative electrode. The device delivers a volumetric capacitance of 441.4 mF cm -3 with maximum energy density and maximum power density is 0.17 and 62.1 mW cm -3, as well as robust cycling stability (~80.4% capacitance retention after 10 000 cycles), excellent flexibility, and mechanical stability. Finally, the excellent electrochemical performance can be attributed to its unique vertically aligned configuration.« less

High-Performance Flexible All-Solid-State Asymmetric Supercapacitors Based on Vertically Aligned CuSe@Co(OH) 2 Nanosheet Arrays

DOE PAGES

Gong, Jiangfeng; Tian, Yazhou; Yang, Ziyuan; ...

2018-01-04

The developments of electrode active materials provide the opportunities for next-generation energy storage devices. The arrangement of electrode materials on the substrate has recently emerged as a promising strategy for preparing high-performance supercapacitors. In this paper, we demonstrate a novel vertically aligned CuSe@Co(OH) 2 nanosheet arrays electrode for supercapacitor application. The materials are thoroughly characterized by structural and spectroscopic techniques. Electrochemical performance of CuSe@Co(OH) 2 nanosheet arrays are investigated in detail, which exhibit a specific capacitance as much as 1180 F g -1 at a current density of 1 A g -1. A flexible asymmetric all-solid-state supercapacitor is fabricated usingmore » CuSe@Co(OH) 2 nanosheet arrays as the positive electrode and activated carbon as the negative electrode. The device delivers a volumetric capacitance of 441.4 mF cm -3 with maximum energy density and maximum power density is 0.17 and 62.1 mW cm -3, as well as robust cycling stability (~80.4% capacitance retention after 10 000 cycles), excellent flexibility, and mechanical stability. Finally, the excellent electrochemical performance can be attributed to its unique vertically aligned configuration.« less

Integration of photoactive and electroactive components with vertical cavity surface emitting lasers

DOEpatents

Bryan, R.P.; Esherick, P.; Jewell, J.L.; Lear, K.L.; Olbright, G.R.

1997-04-29

A monolithically integrated optoelectronic device is provided which integrates a vertical cavity surface emitting laser and either a photosensitive or an electrosensitive device either as input or output to the vertical cavity surface emitting laser either in parallel or series connection. Both vertical and side-by-side arrangements are disclosed, and optical and electronic feedback means are provided. Arrays of these devices can be configured to enable optical computing and neural network applications. 9 figs.

Integration of photoactive and electroactive components with vertical cavity surface emitting lasers

DOEpatents

Bryan, Robert P.; Esherick, Peter; Jewell, Jack L.; Lear, Kevin L.; Olbright, Gregory R.

1997-01-01

A monolithically integrated optoelectronic device is provided which integrates a vertical cavity surface emitting laser and either a photosensitive or an electrosensitive device either as input or output to the vertical cavity surface emitting laser either in parallel or series connection. Both vertical and side-by-side arrangements are disclosed, and optical and electronic feedback means are provided. Arrays of these devices can be configured to enable optical computing and neural network applications.

Pitch variable liquid lens array using electrowetting

NASA Astrophysics Data System (ADS)

Kim, YooKwang; Lee, Jin Su; Kim, Junoh; Won, Yong Hyub

2017-02-01

These days micro lens array is used in various fields such as fiber coupling, laser collimation, imaging and sensor system and beam homogenizer, etc. One of important thing in using micro lens array is, choice of its pitch. Especially imaging systems like integral imaging or light-field camera, pitch of micro lens array defines the system property and thus it could limit the variability of the system. There are already researches about lens array using liquid, and droplet control by electrowetting. This paper reports the result of combining them, the liquid lens array that could vary its pitch by electrowetting. Since lens array is a repeated system, realization of a small part of lens array is enough to show its property. The lens array is composed of nine (3 by 3) liquid droplets on flat surface. On substrate, 11 line electrodes are patterned along vertical and horizontal direction respectively. The width of line electrodes is 300um and interval is 200um. Each droplet is positioned to contain three electrode lines for both of vertical and horizontal direction. So there is one remaining electrode line in each of outermost side for both direction. In original state the voltage is applied to inner electrodes. When voltage of outermost electrodes are turned on, eight outermost droplets move to outer side, thereby increasing pitch of lens array. The original pitch was 1.5mm and it increased to 2.5mm after electrodes of voltage applied is changed.

Long-Term Seismicity of Northern (15° N-60° N) Mid-Atlantic Ridge (MAR) Recorded by two Regional Hydrophone Arrays: a Widespread Along-Ridge Influence of the Azores and Iceland Hotspots

NASA Astrophysics Data System (ADS)

Goslin, J.; Bazin, S.; Dziak, R. P.; Fox, C.; Fowler, M.; Haxel, J.; Lourenco, N.; Luis, J.; Martin, C.; Matsumoto, H.; Perrot, J.; Royer, J.

2004-12-01

The seismicity of the North Atlantic was recorded by two networks of hydrophones moored in the SOFAR channel, north and south of the Azores Plateau. The interpretation of the hydro-acoustic signals recorded during the first six-month common period of operation of the two networks (June 2002 to Nov. 2002) provides a unique data set on the spatial and time distributions of the numerous low-magnitude earthquakes which occurred along the Mid-Atlantic Ridge. Close to 2000 events were localized during this six-month period between latitudes 15° N and 63° N, 501 of which are localized within the SIRENA network (40° N-51° N) and 692 within the wider South Azores network (17° N-33° N). Using hydrophones to locate seafloor earthquakes by interpreting T-wave signals lowers the detection threshold of Mid-Atlantic Ridge events to 3.0 mb from the 4.7 mb of global seismic networks. This represents an average thirty-fold increase in the number of events: 62 events were detected by global seismological networks within the same area during the same period. An along-ridge spatial distribution of the seismicity is obtained by computing the cumulated numbers of events in 1° -wide latitudinal bins. When plotted vs. latitude, this first-order distribution shows remarkable long-wavelength patterns: the seismicity rate is low when approaching the Azores and Iceland (reaching values as low as 10 events/d° ), while it peaks to 70 events/d° in the vicinity of the Gibbs FZ. Moreover, the latitudinal distribution of the seismicity hints at an asymmetric influence of the Azores hotpot on the MAR. Finally, the spatial distribution of the seismicity anti-correlates well at long wavelengths with the zero-age depths along the MAR and correlates with the zero-age Mantle Bouguer (MBA) anomaly values and the Vs velocity anomalies at 100 km in the upper mantle. It is thus proposed that the seismicity level would be partly tied to the rheology and thickness of the brittle layer and be thus dependant on the thermal regime of the upper mantle. The seismicity distribution could then be used as an additional tool to characterize the along-ridge influence of the Azores and Iceland hotspots on the MAR slow-spreading center.

ESONET LIDO Demonstration Mission: the East Sicily node

NASA Astrophysics Data System (ADS)

Riccobene, Giorgio; Favali, Paolo; Andrè, Michel; Chierici, Francesco; Pavan, Gianni; Esonet Lido Demonstration Mission Team

2010-05-01

Off East Sicily (at 2100 m depth, 25 km off the harbour of Catania) a prototype of a cabled deep-sea observatory (NEMO-SN1) was set up and has been operational in real-time since 2005 (the cabled deep-sea multi-parameter station SN1, equipped with geophysical and environmental sensors and the cabled NEMO-OνDE, equipped with 4 broadband hydrophones). The Western Ionian Sea is one of the node sites for the upcoming European permanent underwater network (EMSO). Within the activities of the EC project ESONET-NoE some demonstration missions have been funded. The LIDO-DM (Listening to the Deep Ocean-Demonstration Mission) is one of these and is related to two sites, East Sicily and Iberian Margin (Gulf of Cadiz), the main aims being geo-hazards monitoring and warning (seismic, tsunami, and volcanic) and bio-acoustics. The LIDO-DM East Sicily installation represents a further major step within ESONET-NoE, resulting in a fully integrated system for multidisciplinary deep-sea science, capable to transmit and distribute data in real time to the scientific community and to the general public. LIDO-DM East Sicily hosts a large number of sensors aimed at monitoring and studying oceanographic and environmental parameters (by means of CTD, ADCP, 3-C single point current meter, turbidity meter), geophysical phenomena (low frequency hydrophones, accelerometer, gravity meter, vector and scalar magnetometers, seismometer, absolute and differential pressure gauges), ocean noise monitoring and identification and tracking of biological acoustic sources in deep sea. The latter will be performed using two tetrahedral arrays of 4 hydrophones, located at a relative distance of about 5 km, and at about 25 km from the shore. The whole system will be connected and powered from shore, by means of the electro-optical cable net installed at the East Sicily Site Infrastructure, and synchronised with GPS. Sensors data sampling is performed underwater and transmitted via optical fibre link, with optimal S/N ratio for all signals. This will also permit real-time data acquisition, analysis and distribution on-shore. Innovative electronics for the off-shore data acquisition and transmission systems has been designed, built and tested. A dedicated computing and networking infrastructure for data acquisition, storage and distribution through the internet has been also created. The deployment and connection of the deep sea structures will be performed using the dedicated ROV and Deep Sea Shuttle handling facilities (PEGASO, owned by INGV and INFN). LIDO-DM constitutes the enhancement of the Western Ionian site in view of the EMSO Research Infrastructure.

Optical bandgap modelling from the structural arrangement of carbon nanotubes.

PubMed

Butler, Timothy P; Rashid, Ijaz; Montelongo, Yunuen; Amaratunga, Gehan A J; Butt, Haider

2018-06-14

The optical bandgap properties of vertically-aligned carbon nanotube (VACNT) arrays were probed through their interaction with white light, with the light reflected from the rotating arrays measured with a spectrometer. The precise deterministic control over the structure of vertically-aligned carbon nanotube arrays through electron beam lithography and well-controlled growth conditions brings with it the ability to produce exotic photonic crystals over a relatively large area. The characterisation of the behaviour of these materials in the presence of light is a necessary first step toward application. Relatively large area array structures of high-quality VACNTs were fabricated in square, hexagonal, circular and pseudorandom patterned arrays with length scales on the order of those of visible light for the purpose of investigating how they may be used to manipulate an impinging light beam. In order to investigate the optical properties of these arrays a set of measurement apparatus was designed which allowed the accurate measurement of their optical bandgap characteristics. The patterned samples were rotated under the illuminating white light beam, revealing interesting optical bandgap results caused by the changing patterns and relative positions of the scattering elements (VACNTs).

Modelling clustering of vertically aligned carbon nanotube arrays.

PubMed

Schaber, Clemens F; Filippov, Alexander E; Heinlein, Thorsten; Schneider, Jörg J; Gorb, Stanislav N

2015-08-06

Previous research demonstrated that arrays of vertically aligned carbon nanotubes (VACNTs) exhibit strong frictional properties. Experiments indicated a strong decrease of the friction coefficient from the first to the second sliding cycle in repetitive measurements on the same VACNT spot, but stable values in consecutive cycles. VACNTs form clusters under shear applied during friction tests, and self-organization stabilizes the mechanical properties of the arrays. With increasing load in the range between 300 µN and 4 mN applied normally to the array surface during friction tests the size of the clusters increases, while the coefficient of friction decreases. To better understand the experimentally obtained results, we formulated and numerically studied a minimalistic model, which reproduces the main features of the system with a minimum of adjustable parameters. We calculate the van der Waals forces between the spherical friction probe and bunches of the arrays using the well-known Morse potential function to predict the number of clusters, their size, instantaneous and mean friction forces and the behaviour of the VACNTs during consecutive sliding cycles and at different normal loads. The data obtained by the model calculations coincide very well with the experimental data and can help in adapting VACNT arrays for biomimetic applications.

Ultra-fast microwave-assisted hydrothermal synthesis of long vertically aligned ZnO nanowires for dye-sensitized solar cell application.

PubMed

Mahpeykar, S M; Koohsorkhi, J; Ghafoori-Fard, H

2012-04-27

Long vertically aligned ZnO nanowire arrays were synthesized using an ultra-fast microwave-assisted hydrothermal process. Using this method, we were able to grow ZnO nanowire arrays at an average growth rate as high as 200 nm min(-1) for maximum microwave power level. This method does not suffer from the growth stoppage problem at long growth times that, according to our investigations, a normal microwave-assisted hydrothermal method suffers from. Longitudinal growth of the nanowire arrays was investigated as a function of microwave power level and growth time using cross-sectional FESEM images of the grown arrays. Effect of seed layer on the alignment of nanowires was also studied. X-ray diffraction analysis confirmed c-axis orientation and single-phase wurtzite structure of the nanowires. J-V curves of the fabricated ZnO nanowire-based mercurochrome-sensitized solar cells indicated that the short-circuit current density is increased with increasing the length of the nanowire array. According to the UV-vis spectra of the dyes detached from the cells, these increments were mainly attributed to the enlarged internal surface area and therefore dye loading enhancement in the lengthened nanowire arrays.

Scalar Fluxes Near a Tall Building in an Aligned Array of Rectangular Buildings

NASA Astrophysics Data System (ADS)

Fuka, Vladimír; Xie, Zheng-Tong; Castro, Ian P.; Hayden, Paul; Carpentieri, Matteo; Robins, Alan G.

2018-04-01

Scalar dispersion from ground-level sources in arrays of buildings is investigated using wind-tunnel measurements and large-eddy simulation (LES). An array of uniform-height buildings of equal dimensions and an array with an additional single tall building (wind tunnel) or a periodically repeated tall building (LES) are considered. The buildings in the array are aligned and form long streets. The sensitivity of the dispersion pattern to small changes in wind direction is demonstrated. Vertical scalar fluxes are decomposed into the advective and turbulent parts and the influences of wind direction and of the presence of the tall building on the scalar flux components are evaluated. In the uniform-height array turbulent scalar fluxes are dominant, whereas the tall building produces an increase of the magnitude of advective scalar fluxes that yields the largest component. The presence of the tall building causes either an increase or a decrease to the total vertical scalar flux depending on the position of the source with respect to the tall building. The results of the simulations can be used to develop parametrizations for street-canyon dispersion models and enhance their capabilities in areas with tall buildings.

Extremely Black Vertically Aligned Carbon Nanotube Arrays for Solar Steam Generation.

PubMed

Yin, Zhe; Wang, Huimin; Jian, Muqiang; Li, Yanshen; Xia, Kailun; Zhang, Mingchao; Wang, Chunya; Wang, Qi; Ma, Ming; Zheng, Quan-Shui; Zhang, Yingying

2017-08-30

The unique structure of a vertically aligned carbon nanotube (VACNT) array makes it behave most similarly to a blackbody. It is reported that the optical absorptivity of an extremely black VACNT array is about 0.98-0.99 over a large spectral range of 200 nm-200 μm, inspiring us to explore the performance of VACNT arrays in solar energy harvesting. In this work, we report the highly efficient steam generation simply by laminating a layer of VACNT array on the surface of water to harvest solar energy. It is found that under solar illumination the temperature of upper water can significantly increase with obvious water steam generated, indicating the efficient solar energy harvesting and local temperature rise by the thin layer of VACNTs. We found that the evaporation rate of water assisted by VACNT arrays is 10 times that of bare water, which is the highest ratio for solar-thermal-steam generation ever reported. Remarkably, the solar thermal conversion efficiency reached 90%. The excellent performance could be ascribed to the strong optical absorption and local temperature rise induced by the VACNT layer, as well as the ultrafast water transport through the VACNT layer due to the frictionless wall of CNTs. Based on the above, we further demonstrated the application of VACNT arrays in solar-driven desalination.

Analysis of the moments of the sensitivity function for resistivity over a homogeneous half-space: Rules of thumb for pseudoposition, offline sensitivity and resolution

NASA Astrophysics Data System (ADS)

Butler, S. L.

2017-08-01

It is instructive to consider the sensitivity function for a homogeneous half space for resistivity since it has a simple mathematical formula and it does not require a priori knowledge of the resistivity of the ground. Past analyses of this function have allowed visualization of the regions that contribute most to apparent resistivity measurements with given array configurations. The horizontally integrated form of this equation gives the sensitivity function for an infinitesimally thick horizontal slab with a small resistivity contrast and analysis of this function has admitted estimates of the depth of investigation for a given electrode array. Recently, it has been shown that the average of the vertical coordinate over this function yields a simple formula that can be used to estimate the depth of investigation. The sensitivity function for a vertical inline slab has also been previously calculated. In this contribution, I show that the sensitivity function for a homogeneous half-space can also be integrated so as to give sensitivity functions to semi-infinite vertical slabs that are perpendicular to the array axis. These horizontal sensitivity functions can, in turn, be integrated over the spatial coordinates to give the mean horizontal positions of the sensitivity functions. The mean horizontal positions give estimates for the centres of the regions that affect apparent resistivity measurements for arbitrary array configuration and can be used as horizontal positions when plotting pseudosections even for non-collinear arrays. The mean of the horizontal coordinate that is perpendicular to a collinear array also gives a simple formula for estimating the distance over which offline resistivity anomalies will have a significant effect. The root mean square (rms) widths of the sensitivity functions are also calculated in each of the coordinate directions as an estimate of the inverse of the resolution of a given array. For depth and in the direction perpendicular to the array, the rms thickness is shown to be very similar to the mean distance. For the direction parallel to the array, the rms thickness is shown to be proportional to the array length and similar to the array length divided by 2 for many arrays. I expect that these formulas will provide useful rules of thumb for estimating the centres and extents of regions influencing apparent resistivity measurements for survey planning and for education.

Vertically oriented metamaterial broadband linear polariser

DOE PAGES

Campione, Salvatore; Burckel, David Bruce

2018-03-14

Control and manipulation of polarization is an important topic for imaging and light matter interactions. In the infrared regime, the large wavelengths make wire grid polarizers a viable option, as it is possible to create periodic arrays of metallic wires at that scale. The recent advent of metamaterials has spurred an increase in non-traditional polarizer motifs centred around more complicated repeat units, which potentially provide more functionality. In this paper we explore the use of two-dimensional (2D) arrays of single and back-to-back vertically oriented cross dipoles arranged in a cubic in-plane silicon matrix. Here, we show that both single andmore » back-to-back versions have higher rejection ratios and larger bandwidths than either wire grid polarizers or 2D arrays of linear dipoles.« less

Multispectral InGaAs/GaAs/AlGaAs laser arrays by MBE growth on patterned substrates

NASA Astrophysics Data System (ADS)

Kamath, K.; Bhattacharya, P.; Singh, J.

1997-05-01

Multispectral semiconductor laser arrays on single chip is demonstrated by molecular beam epitaxial (MBE) growth of {In0.2Ga0.8As}/{GaAs} quantum well lasers on GaAs (1 0 0) substrates patterned by dry etching. No regrowth is needed for simple edge emitting lasers. It was observed that the laser characteristics are not degraded by the patterned growth. The shift in the emission wavelength obtained by this method can be controlled by varying the width of the pre-patterned ridges as well as by selecting the regions with different number of vertical sidewalls on both sides. We have also shown that multispectral vertical cavity surface emitting laser (VCSEL) arrays can be made by this technique with a single regrowth.

Optical levitation and translation of a microscopic particle by use of multiple beams generated by vertical-cavity surface-emitting laser array sources.

PubMed

Ogura, Yusuke; Shirai, Nobuhiro; Tanida, Jun

2002-09-20

An optical levitation and translation method for a microscopic particle by use of the resultant force induced by multiple light beams is studied. We show dependence of the radiation pressure force on the illuminating distribution by numerical calculation, and we find that the strongest axial force is obtained by a specific spacing period of illuminating beams. Extending the optical manipulation technique by means of vertical-cavity surface-emitting laser (VCSEL) array sources [Appl. Opt. 40, 5430 (2001)], we are the first, to our knowledge, to demonstrate levitation of a particle and its translation while levitated by using a VCSEL array. The vertical position of the target particle can be controlled in a range of a few tens of micrometers with an accuracy of 2 microm or less. The analytical and experimental results suggest that use of multiple beams is an effective method to levitate a particle with low total illumination power. Some issues on the manipulation method that uses multiple beams are discussed.

GaInNAsSb/GaAs vertical cavity surface-emitting lasers (VCSELs): current challenges and techniques to realize multiple-wavelength laser arrays at 1.55 μm

NASA Astrophysics Data System (ADS)

Gobet, Mathilde; Bae, Hopil P.; Sarmiento, Tomas; Harris, James S.

2008-02-01

Multiple-wavelength laser arrays at 1.55 μm are key components of wavelength division multiplexing (WDM) systems for increased bandwidth. Vertical cavity surface-emitting lasers (VCSELs) grown on GaAs substrates outperform their InP counterparts in several points. We summarize the current challenges to realize continuous-wave (CW) GaInNAsSb VCSELs on GaAs with 1.55 μm emission wavelength and explain the work in progress to realize CW GaInNAsSb VCSELs. Finally, we detail two techniques to realize GaInNAsSb multiple-wavelength VCSEL arrays at 1.55 μm. The first technique involves the incorporation of a photonic crystal into the upper mirror. Simulation results for GaAs-based VCSEL arrays at 1.55 μm are shown. The second technique uses non-uniform molecular beam epitaxy (MBE). We have successfully demonstrated 1x6 resonant cavity light-emitting diode arrays at 850 nm using this technique, with wavelength spacing of 0.4 nm between devices and present these results.

Piezo-Phototronic Enhanced UV Sensing Based on a Nanowire Photodetector Array.

PubMed

Han, Xun; Du, Weiming; Yu, Ruomeng; Pan, Caofeng; Wang, Zhong Lin

2015-12-22

A large array of Schottky UV photodetectors (PDs) based on vertical aligned ZnO nanowires is achieved. By introducing the piezo-phototronic effect, the performance of the PD array is enhanced up to seven times in photoreponsivity, six times in sensitivity, and 2.8 times in detection limit. The UV PD array may have applications in optoelectronic systems, adaptive optical computing, and communication. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Amazon river dolphins (Inia geoffrensis) use a high-frequency short-range biosonar.

PubMed

Ladegaard, Michael; Jensen, Frants Havmand; de Freitas, Mafalda; Ferreira da Silva, Vera Maria; Madsen, Peter Teglberg

2015-10-01

Toothed whales produce echolocation clicks with source parameters related to body size; however, it may be equally important to consider the influence of habitat, as suggested by studies on echolocating bats. A few toothed whale species have fully adapted to river systems, where sonar operation is likely to result in higher clutter and reverberation levels than those experienced by most toothed whales at sea because of the shallow water and dense vegetation. To test the hypothesis that habitat shapes the evolution of toothed whale biosonar parameters by promoting simpler auditory scenes to interpret in acoustically complex habitats, echolocation clicks of wild Amazon river dolphins were recorded using a vertical seven-hydrophone array. We identified 404 on-axis biosonar clicks having a mean SLpp of 190.3 ± 6.1 dB re. 1 µPa, mean SLEFD of 132.1 ± 6.0 dB re. 1 µPa(2)s, mean Fc of 101.2 ± 10.5 kHz, mean BWRMS of 29.3 ± 4.3 kHz and mean ICI of 35.1 ± 17.9 ms. Piston fit modelling resulted in an estimated half-power beamwidth of 10.2 deg (95% CI: 9.6-10.5 deg) and directivity index of 25.2 dB (95% CI: 24.9-25.7 dB). These results support the hypothesis that river-dwelling toothed whales operate their biosonars at lower amplitude and higher sampling rates than similar-sized marine species without sacrificing high directivity, in order to provide high update rates in acoustically complex habitats and simplify auditory scenes through reduced clutter and reverberation levels. We conclude that habitat, along with body size, is an important evolutionary driver of source parameters in toothed whale biosonars. © 2015. Published by The Company of Biologists Ltd.

Influence of Ultrasonic Nonlinear Propagation on Hydrophone Calibration Using Two-Transducer Reciprocity Method

NASA Astrophysics Data System (ADS)

Yoshioka, Masahiro; Sato, Sojun; Kikuchi, Tsuneo; Matsuda, Yoichi

2006-05-01

In this study, the influence of ultrasonic nonlinear propagation on hydrophone calibration by the two-transducer reciprocity method is investigated quantitatively using the Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation. It is proposed that the correction for the diffraction and attenuation of ultrasonic waves used in two-transducer reciprocity calibration can be derived using the KZK equation to remove the influence of nonlinear propagation. The validity of the correction is confirmed by comparing the sensitivities calibrated by the two-transducer reciprocity method and laser interferometry.

Growing vertical ZnO nanorod arrays within graphite: efficient isolation of large size and high quality single-layer graphene.

PubMed

Ding, Ling; E, Yifeng; Fan, Louzhen; Yang, Shihe

2013-07-18

We report a unique strategy for efficiently exfoliating large size and high quality single-layer graphene directly from graphite into DMF dispersions by growing ZnO nanorod arrays between the graphene layers in graphite.

Lithographic fine-tuning of vertical cavity surface emitting laser-pumped two-dimensional photonic crystal lasers.

PubMed

Cao, J R; Lee, Po-Tsung; Choi, Sang-Jun; O'Brien, John D; Dapkus, P Daniel

2002-01-01

Lithographic tuning of operating wavelengths in a photonic crystal laser array is demonstrated. The photonic crystal lattice constant is varied by 2 nm between elements of the array, and a wavelength spacing of approximately 4 nm is achieved.

Array invariant-based ranging of a source of opportunity.

PubMed

Byun, Gihoon; Kim, J S; Cho, Chomgun; Song, H C; Byun, Sung-Hoon

2017-09-01

The feasibility of tracking a ship radiating random and anisotropic noise is investigated using ray-based blind deconvolution (RBD) and array invariant (AI) with a vertical array in shallow water. This work is motivated by a recent report [Byun, Verlinden, and Sabra, J. Acoust. Soc. Am. 141, 797-807 (2017)] that RBD can be applied to ships of opportunity to estimate the Green's function. Subsequently, the AI developed for robust source-range estimation in shallow water can be applied to the estimated Green's function via RBD, exploiting multipath arrivals separated in beam angle and travel time. In this letter, a combination of the RBD and AI is demonstrated to localize and track a ship of opportunity (200-900 Hz) to within a 5% standard deviation of the relative range error along a track at ranges of 1.8-3.4 km, using a 16-element, 56-m long vertical array in approximately 100-m deep shallow water.

Application of a silicon photodiode array for solar edge tracking in the Halogen Occultation Experiment

NASA Technical Reports Server (NTRS)

Mauldin, L. E., III; Moore, A. S.; Stump, C. S.; Mayo, L. S.

1985-01-01

The optical and electronic design of the Halogen Occultation Experiment (HALOE) elevation sunsensor is described. This system uses a Galilean telescope to form a solar image on a linear silicon photodiode array. The array is a self-scanned, monolithic charge coupled device. The addresses of both solar edges imaged on the array are used by the control/pointing system to scan the HALOE science instantaneous-field-of-view (IFOV) across the vertical solar diameter during instrument calibration, and then maintain the science IFOV four arcmin below the top edge during the science data occultation event. Vertical resolution of 16 arcsec and a radiometric dynamic range of 100 are achieved at the 0.7 micrometer operating wavelength. The design provides for loss of individual photodiode elements without loss of angular tracking capability. The HALOE instrument is a gas correlation radiometer that is now being developed by NASA Langley Research Center for the Upper Atmospheric Research Satellite.

Carbon Nanofiber Electrode Array for Neurochemical Monitoring

NASA Technical Reports Server (NTRS)

Koehne, Jessica E.

2017-01-01

A sensor platform based on vertically aligned carbon nanofibers (CNFs) has been developed. Their inherent nanometer scale, high conductivity, wide potential window, good biocompatibility and well-defined surface chemistry make them ideal candidates as biosensor electrodes. Here, we report using vertically aligned CNF as neurotransmitter recording electrodes for application in a smart deep brain stimulation (DBS) device. Our approach combines a multiplexed CNF electrode chip, developed at NASA Ames Research Center, with the Wireless Instantaneous Neurotransmitter Concentration Sensor (WINCS) system, developed at the Mayo Clinic. Preliminary results indicate that the CNF nanoelectrode arrays are easily integrated with WINCS for neurotransmitter detection in a multiplexed array format. In the future, combining CNF based stimulating and recording electrodes with WINCS may lay the foundation for an implantable smart therapeutic system that utilizes neurochemical feedback control while likely resulting in increased DBS application in various neuropsychiatric disorders. In total, our goal is to take advantage of the nanostructure of CNF arrays for biosensing studies requiring ultrahigh sensitivity, high-degree of miniaturization, and selective biofunctionalization.

The effects of DRIE operational parameters on vertically aligned micropillar arrays

NASA Astrophysics Data System (ADS)

Miller, Kane; Li, Mingxiao; Walsh, Kevin M.; Fu, Xiao-An

2013-03-01

Vertically aligned silicon micropillar arrays have been created by deep reactive ion etching (DRIE) and used for a number of microfabricated devices including microfluidic devices, micropreconcentrators and photovoltaic cells. This paper delineates an experimental design performed on the Bosch process of DRIE of micropillar arrays. The arrays are fabricated with direct-write optical lithography without photomask, and the effects of DRIE process parameters, including etch cycle time, passivation cycle time, platen power and coil power on profile angle, scallop depth and scallop peak-to-peak distance are studied by statistical design of experiments. Scanning electron microscope images are used for measuring the resultant profile angles and characterizing the scalloping effect on the pillar sidewalls. The experimental results indicate the effects of the determining factors, etch cycle time, passivation cycle time and platen power, on the micropillar profile angles and scallop depths. An optimized DRIE process recipe for creating nearly 90° and smooth surface (invisible scalloping) has been obtained as a result of the statistical design of experiments.

Highly-Ordered 3D Vertical Resistive Switching Memory Arrays with Ultralow Power Consumption and Ultrahigh Density.

PubMed

Al-Haddad, Ahmed; Wang, Chengliang; Qi, Haoyuan; Grote, Fabian; Wen, Liaoyong; Bernhard, Jörg; Vellacheri, Ranjith; Tarish, Samar; Nabi, Ghulam; Kaiser, Ute; Lei, Yong

2016-09-07

Resistive switching random access memories (RRAM) have attracted great scientific and industrial attention for next generation data storage because of their advantages of nonvolatile properties, high density, low power consumption, fast writing/erasing speed, good endurance, and simple and small operation system. Here, by using a template-assisted technique, we demonstrate a three-dimensional highly ordered vertical RRAM device array with density as high as that of the nanopores of the template (10(8)-10(9) cm(-2)), which can also be fabricated in large area. The high crystallinity of the materials, the large contact area and the intimate semiconductor/electrode interface (3 nm interfacial layer) make the ultralow voltage operation (millivolt magnitude) and ultralow power consumption (picowatt) possible. Our procedure for fabrication of the nanodevice arrays in large area can be used for producing many other different materials and such three-dimensional electronic device arrays with the capability to adjust the device densities can be extended to other applications of the next generation nanodevice technology.

Methods for monitoring hydroacoustic events using direct and reflected T waves in the Indian Ocean

NASA Astrophysics Data System (ADS)

Hanson, Jeffrey A.; Bowman, J. Roger

2006-02-01

The recent installation of permanent, three-element hydrophone arrays in the Indian Ocean offshore Diego Garcia and Cape Leeuwin, Australia, provides an opportunity to study hydroacoustic sources in more detail than previously possible. We developed and applied methods for coherent processing of the array data, for automated association of signals detected at more than one array, and for source location using only direct arrivals and using signals reflected from coastlines and other bathymetric features. During the 286-day study, 4725 hydroacoustic events were defined and located in the Indian and Southern oceans. Events fall into two classes: tectonic earthquakes and ice-related noise. The tectonic earthquakes consist of mid-ocean ridge, trench, and intraplate earthquakes. Mid-ocean ridge earthquakes are the most common tectonic events and often occur in clusters along transform offsets. Hydroacoustic signal levels for earthquakes in a standard catalog suggest that the hydroacoustic processing threshold for ridge events is one magnitude below the seismic network. Fewer earthquakes are observed along the Java Trench than expected because the large bathymetric relief of the source region complicates coupling between seismic and hydroacoustic signals, leading to divergent signal characteristics at different stations. We located 1843 events along the Antarctic coast resulting from various ice noises, most likely thermal fracturing and ice ridge forming events. Reflectors of signals from earthquakes are observed along coastlines, the mid-Indian Ocean and Ninety East ridges, and other bathymetric features. Reflected signals are used as synthetic stations to reduce location uncertainty and to enable event location with a single station.

The Development of High-Density Vertical Silicon Nanowires and Their Application in a Heterojunction Diode.

PubMed

Chang, Wen-Chung; Su, Sheng-Chien; Wu, Chia-Ching

2016-06-30

Vertically aligned p-type silicon nanowire (SiNW) arrays were fabricated through metal-assisted chemical etching (MACE) of Si wafers. An indium tin oxide/indium zinc oxide/silicon nanowire (ITO/IZO/SiNW) heterojunction diode was formed by depositing ITO and IZO thin films on the vertically aligned SiNW arrays. The structural and electrical properties of the resulting ITO/IZO/SiNW heterojunction diode were characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and current-voltage (I-V) measurements. Nonlinear and rectifying I-V properties confirmed that a heterojunction diode was successfully formed in the ITO/IZO/SiNW structure. The diode had a well-defined rectifying behavior, with a rectification ratio of 550.7 at 3 V and a turn-on voltage of 2.53 V under dark conditions.

Toward highly stable solid-state unconventional thin-film battery-supercapacitor hybrid devices: Interfacing vertical core-shell array electrodes with a gel polymer electrolyte

NASA Astrophysics Data System (ADS)

Pandey, Gaind P.; Klankowski, Steven A.; Liu, Tao; Wu, Judy; Li, Jun

2017-02-01

A novel solid-state battery-supercapacitor hybrid device is fabricated for high-performance electrical energy storage using a Si anode and a TiO2 cathode in conjunction with a flexible, solid-like gel polymer electrolyte film as the electrolyte and separator. The electrodes were fabricated as three-dimensional nanostructured vertical arrays by sputtering active materials as conformal shells on vertically aligned carbon nanofibers (VACNFs) which serve as the current collector and structural template. Such nanostructured vertical core-shell array-electrodes enable short Li-ion diffusion path and large pseudocapacitive contribution by fast surface reactions, leading to the hybrid features of batteries and supercapacitors that can provide high specific energy over a wide range of power rates. Due to the improved mechanical stability of the infiltrated composite structure, the hybrid cell shows excellent cycling stability and is able to retain more than 95% of the original capacity after 3500 cycles. More importantly, this solid-state device can stably operate in a temperature range from -20 to 60 °C with a very low self-discharge rate and an excellent shelf life. This solid-state architecture is promising for the development of highly stable thin-film hybrid energy storage devices for unconventional applications requiring largely varied power, wider operation temperature, long shelf-life and higher safety standards.

Vertically aligned p-type single-crystalline GaN nanorod arrays on n-type Si for heterojunction photovoltaic cells.

PubMed

Tang, Y B; Chen, Z H; Song, H S; Lee, C S; Cong, H T; Cheng, H M; Zhang, W J; Bello, I; Lee, S T

2008-12-01

Vertically aligned Mg-doped GaN nanorods have been epitaxially grown on n-type Si substrate to form a heterostructure for fabricating p-n heterojunction photovoltaic cells. The p-type GaN nanorod/n-Si heterojunction cell shows a well-defined rectifying behavior with a rectification ratio larger than 10(4) in dark. The cell has a high short-circuit photocurrent density of 7.6 mAlcm2 and energy conversion efficiency of 2.73% under AM 1.5G illumination at 100 mW/cm2. Moreover, the nanorod array may be used as an antireflection coating for solar cell applications to effectively reduce light loss due to reflection. This study provides an experimental demonstration for integrating one-dimensional nanostructure arrays with the substrate to directly fabricate heterojunction photovoltaic cells.

Modeling and optimization of atomic layer deposition processes on vertically aligned carbon nanotubes.

PubMed

Yazdani, Nuri; Chawla, Vipin; Edwards, Eve; Wood, Vanessa; Park, Hyung Gyu; Utke, Ivo

2014-01-01

Many energy conversion and storage devices exploit structured ceramics with large interfacial surface areas. Vertically aligned carbon nanotube (VACNT) arrays have emerged as possible scaffolds to support large surface area ceramic layers. However, obtaining conformal and uniform coatings of ceramics on structures with high aspect ratio morphologies is non-trivial, even with atomic layer deposition (ALD). Here we implement a diffusion model to investigate the effect of the ALD parameters on coating kinetics and use it to develop a guideline for achieving conformal and uniform thickness coatings throughout the depth of ultra-high aspect ratio structures. We validate the model predictions with experimental data from ALD coatings of VACNT arrays. However, the approach can be applied to predict film conformality as a function of depth for any porous topology, including nanopores and nanowire arrays.

Large-scale horizontally aligned ZnO microrod arrays with controlled orientation, periodic distribution as building blocks for chip-in piezo-phototronic LEDs.

PubMed

Guo, Zhen; Li, Haiwen; Zhou, Lianqun; Zhao, Dongxu; Wu, Yihui; Zhang, Zhiqiang; Zhang, Wei; Li, Chuanyu; Yao, Jia

2015-01-27

A novel method of fabricating large-scale horizontally aligned ZnO microrod arrays with controlled orientation and periodic distribution via combing technology is introduced. Horizontally aligned ZnO microrod arrays with uniform orientation and periodic distribution can be realized based on the conventional bottom-up method prepared vertically aligned ZnO microrod matrix via the combing method. When the combing parameters are changed, the orientation of horizontally aligned ZnO microrod arrays can be adjusted (θ = 90° or 45°) in a plane and a misalignment angle of the microrods (0.3° to 2.3°) with low-growth density can be obtained. To explore the potential applications based on the vertically and horizontally aligned ZnO microrods on p-GaN layer, piezo-phototronic devices such as heterojunction LEDs are built. Electroluminescence (EL) emission patterns can be adjusted for the vertically and horizontally aligned ZnO microrods/p-GaN heterojunction LEDs by applying forward bias. Moreover, the emission color from UV-blue to yellow-green can be tuned by investigating the piezoelectric properties of the materials. The EL emission mechanisms of the LEDs are discussed in terms of band diagrams of the heterojunctions and carrier recombination processes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Vertical displacement of Ips Latidens and Ips Pini

Treesearch

Daniel R. Miller

2000-01-01

The effect of semiochemical interruptants was examined for Ips latidens (LeConte) and Ips pini (Say) using artificial trees (tall-traps) consisting of an array of seven Lindgren multiple-funnel traps suspended vertically on a rope ladder. S-(+)- Ipsdienol reduced the numbers of I. latidens captured in (±)-ipsenol...

Improved field emission properties of carbon nanotubes grown on stainless steel substrate and its application in ionization gauge

NASA Astrophysics Data System (ADS)

Li, Detian; Cheng, Yongjun; Wang, Yongjun; Zhang, Huzhong; Dong, Changkun; Li, Da

2016-03-01

Vertically aligned carbon nanotube (CNT) arrays were fabricated by chemical vapor deposition (CVD) technique on different substrates. Microstructures and field emission characteristics of the as-grown CNT arrays were investigated systematically, and its application in ionization gauge was also evaluated preliminarily. The results indicate that the as-grown CNT arrays are vertically well-aligned relating to the substrate surfaces, but the CNTs grown on stainless steel substrate are longer and more crystalline than the ones grown on silicon wafer substrate. The field emission behaviors of the as-grown CNT arrays are strongly dependent upon substrate properties. Namely, the CNT array grown on stainless steel substrate has better field emission properties, including lower turn on and threshold fields, better emission stability and repeatability, compared with the one grown on silicon wafer substrate. The superior field emission properties of the CNT array grown on stainless steel substrate are mainly attributed to low contact resistance, high thermal conductivity, good adhesion strength, etc. In addition, the metrological behaviors of ionization gauge with the CNT array grown on stainless steel substrate as an electron source were investigated, and this novel cathode ionization gauge extends the lower limit of linear pressure measurement to 10-8 Pa, which is one order of magnitude lower than the result reported for the same of gauge with CNT cathode.

AUV Positioning Method Based on Tightly Coupled SINS/LBL for Underwater Acoustic Multipath Propagation.

PubMed

Zhang, Tao; Shi, Hongfei; Chen, Liping; Li, Yao; Tong, Jinwu

2016-03-11

This paper researches an AUV (Autonomous Underwater Vehicle) positioning method based on SINS (Strapdown Inertial Navigation System)/LBL (Long Base Line) tightly coupled algorithm. This algorithm mainly includes SINS-assisted searching method of optimum slant-range of underwater acoustic propagation multipath, SINS/LBL tightly coupled model and multi-sensor information fusion algorithm. Fuzzy correlation peak problem of underwater LBL acoustic propagation multipath could be solved based on SINS positional information, thus improving LBL positional accuracy. Moreover, introduction of SINS-centered LBL locating information could compensate accumulative AUV position error effectively and regularly. Compared to loosely coupled algorithm, this tightly coupled algorithm can still provide accurate location information when there are fewer than four available hydrophones (or within the signal receiving range). Therefore, effective positional calibration area of tightly coupled system based on LBL array is wider and has higher reliability and fault tolerance than loosely coupled. It is more applicable to AUV positioning based on SINS/LBL.

AUV Positioning Method Based on Tightly Coupled SINS/LBL for Underwater Acoustic Multipath Propagation

PubMed Central

Zhang, Tao; Shi, Hongfei; Chen, Liping; Li, Yao; Tong, Jinwu

2016-01-01

This paper researches an AUV (Autonomous Underwater Vehicle) positioning method based on SINS (Strapdown Inertial Navigation System)/LBL (Long Base Line) tightly coupled algorithm. This algorithm mainly includes SINS-assisted searching method of optimum slant-range of underwater acoustic propagation multipath, SINS/LBL tightly coupled model and multi-sensor information fusion algorithm. Fuzzy correlation peak problem of underwater LBL acoustic propagation multipath could be solved based on SINS positional information, thus improving LBL positional accuracy. Moreover, introduction of SINS-centered LBL locating information could compensate accumulative AUV position error effectively and regularly. Compared to loosely coupled algorithm, this tightly coupled algorithm can still provide accurate location information when there are fewer than four available hydrophones (or within the signal receiving range). Therefore, effective positional calibration area of tightly coupled system based on LBL array is wider and has higher reliability and fault tolerance than loosely coupled. It is more applicable to AUV positioning based on SINS/LBL. PMID:26978361

Joint Bearing and Range Estimation of Multiple Objects from Time-Frequency Analysis.

PubMed

Liu, Jeng-Cheng; Cheng, Yuang-Tung; Hung, Hsien-Sen

2018-01-19

Direction-of-arrival (DOA) and range estimation is an important issue of sonar signal processing. In this paper, a novel approach using Hilbert-Huang transform (HHT) is proposed for joint bearing and range estimation of multiple targets based on a uniform linear array (ULA) of hydrophones. The structure of this ULA based on micro-electro-mechanical systems (MEMS) technology, and thus has attractive features of small size, high sensitivity and low cost, and is suitable for Autonomous Underwater Vehicle (AUV) operations. This proposed target localization method has the following advantages: only a single snapshot of data is needed and real-time processing is feasible. The proposed algorithm transforms a very complicated nonlinear estimation problem to a simple nearly linear one via time-frequency distribution (TFD) theory and is verified with HHT. Theoretical discussions of resolution issue are also provided to facilitate the design of a MEMS sensor with high sensitivity. Simulation results are shown to verify the effectiveness of the proposed method.

Variation in harbour porpoise activity in response to seismic survey noise

PubMed Central

Pirotta, Enrico; Brookes, Kate L.; Graham, Isla M.; Thompson, Paul M.

2014-01-01

Animals exposed to anthropogenic disturbance make trade-offs between perceived risk and the cost of leaving disturbed areas. Impact assessments tend to focus on overt behavioural responses leading to displacement, but trade-offs may also impact individual energy budgets through reduced foraging performance. Previous studies found no evidence for broad-scale displacement of harbour porpoises exposed to impulse noise from a 10 day two-dimensional seismic survey. Here, we used an array of passive acoustic loggers coupled with calibrated noise measurements to test whether the seismic survey influenced the activity patterns of porpoises remaining in the area. We showed that the probability of recording a buzz declined by 15% in the ensonified area and was positively related to distance from the source vessel. We also estimated received levels at the hydrophones and characterized the noise response curve. Our results demonstrate how environmental impact assessments can be developed to assess more subtle effects of noise disturbance on activity patterns and foraging efficiency. PMID:24850891

Ultrasound phase contrast thermal imaging with reflex transmission imaging methods in tissue phantoms

PubMed Central

Farny, Caleb H.; Clement, Gregory T.

2009-01-01

Thermal imaging measurements using ultrasound phase contrast have been performed in tissue phantoms heated with a focused ultrasound source. Back projection and reflex transmission imaging principles were employed to detect sound speed-induced changes in the phase caused by an increase in the temperature. The temperature was determined from an empirical relationship for the temperature dependence on sound speed. The phase contrast was determined from changes in the sound field measured with a hydrophone scan conducted before and during applied heating. The lengthy scanning routine used to mimic a large two-dimensional array required a steady-state temperature distribution within the phantom. The temperature distribution in the phantom was validated with magnetic resonance (MR) thermal imaging measurements. The peak temperature was found to agree within 1°C with MR and good agreement was found between the temperature profiles. The spatial resolution was 0.3 × 0.3 × 0.3 mm, comparing favorably with the 0.625 × 0.625 × 1.5 mm MR spatial resolution. PMID:19683380

Source levels and call parameters of harbor seal breeding vocalizations near a terrestrial haulout site in Glacier Bay National Park and Preserve.

PubMed

Matthews, Leanna P; Parks, Susan E; Fournet, Michelle E H; Gabriele, Christine M; Womble, Jamie N; Klinck, Holger

2017-03-01

Source levels of harbor seal breeding vocalizations were estimated using a three-element planar hydrophone array near the Beardslee Islands in Glacier Bay National Park and Preserve, Alaska. The average source level for these calls was 144 dB RMS re 1 μPa at 1 m in the 40-500 Hz frequency band. Source level estimates ranged from 129 to 149 dB RMS re 1 μPa. Four call parameters, including minimum frequency, peak frequency, total duration, and pulse duration, were also measured. These measurements indicated that breeding vocalizations of harbor seals near the Beardslee Islands of Glacier Bay National Park are similar in duration (average total duration: 4.8 s, average pulse duration: 3.0 s) to previously reported values from other populations, but are 170-220 Hz lower in average minimum frequency (78 Hz).

Polarimetric Imaging System for Automatic Target Detection and Recognition

DTIC Science & Technology

2000-03-01

technique shown in Figure 4(b) can also be used to integrate polarizer arrays with other types of imaging sensors, such as LWIR cameras and uncooled...vertical stripe pattern in this φ image is caused by nonuniformities in the particular polarizer array used. 2. CIRCULAR POLARIZATION IMAGING USING

Short cavity DFB fiber laser based vector hydrophone for low frequency signal detection

NASA Astrophysics Data System (ADS)

Zhang, Xiaolei; Zhang, Faxiang; Jiang, Shaodong; Min, Li; Li, Ming; Peng, Gangding; Ni, Jiasheng; Wang, Chang

2017-12-01

A short cavity distributed feedback (DFB) fiber laser is used for low frequency acoustic signal detection. Three DFB fiber lasers with different central wavelengths are chained together to make three-element vector hydrophone with proper sensitivity enhancement design, which has extensive and significant applications to underwater acoustic monitoring for the national defense, oil, gas exploration, and so on. By wavelength-phase demodulation, the lasing wavelength changes under different frequency signals can be interpreted, and the sensitivity is tested about 33 dB re pm/g. The frequency response range is rather flat from 5 Hz to 300 Hz.

Underwater Ambient Noise. Proceedings of a Conference Held at SACLANTCEN on 11-14 May 1982. Volume 2. Unclassified Papers. Part 1

DTIC Science & Technology

1982-06-15

tiers d’octave, le nombre de mesures de bruit etait limite a trois . On a prefere etudier 1’influence de 1’immersion avec des hydrophones om...bateaux presents dans le secteur . Un minimum serait la reproduction d’un scope radar donnant le nombre et les positions des bruiteurs. Rien d’em...d’environnement pour la pluie, le vent, 1’interception radar (fig.2). 5.2. Ligne sous-marine (fig.3) . Les trois hydrophones et le reseau de

Range estimates of whale signals recorded by triplets of hydrophones.

NASA Astrophysics Data System (ADS)

Le Bras, R. J.; Nielsen, P.

2017-12-01

The International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty Organization includes a hydroacoustic network as one of the monitoring technologies. The underwater part of this network includes six stations and is now complete with the recent installation of the HA04 station located in the Southern Ocean island of Crozet (France). A large number of calls emanating from marine mammals are recorded by the hydrophones, and we present examples where the animals are sufficiently close that a range estimate can be attempted. We also present examples of scattered arrivals and related interpretations.

A multi-hypothesis tracker for clicking whales.

PubMed

Baggenstoss, Paul M

2015-05-01

This paper describes a tracker specially designed to track clicking beaked whales using widely spaced bottom-mounted hydrophones, although it can be adapted to different species and sensors. The input to the tracker is a sequence of static localization solutions obtained using time difference of arrival information at widely spaced hydrophones. To effectively handle input localizations with high ambiguity, the tracker is based on multi-hypothesis tracker concepts, so it considers all potential association hypotheses and keeps a large number of potential tracks in memory. The method is demonstrated on actual data and shown to successfully track multiple beaked whales at depth.

Producibility of Vertically Integrated Photodiode (VIP)tm scanning focal plane arrays

NASA Astrophysics Data System (ADS)

Turner, Arthur M.; Teherani, Towfik; Ehmke, John C.; Pettitt, Cindy; Conlon, Peggy; Beck, Jeffrey D.; McCormack, Kent; Colombo, Luigi; Lahutsky, Tom; Murphy, Terry; Williams, Robert L.

1994-07-01

Vertically integrated photodiode, VIPTM, technology is now being used to produce second generation infrared focal plane arrays with high yields and performance. The VIPTM process employs planar, ion implanted, n on p diodes in HgCdTe which is epoxy hybridized directly to the read out integrated circuits on 100 mm Si wafers. The process parameters that are critical for high performance and yield include: HgCdTe dislocation density and thickness, backside passivation, frontside passivation, and junction formation. Producibility of infrared focal plane arrays (IRFPAs) is also significantly enhanced by read out integrated circuits (ROICs) which have the ability to deselect defective pixels. Cold probe screening before lab dewar assembly reduces costs and improves cycle times. The 240 X 1 and 240 X 2 scanning array formats are used to demonstrate the effect of process optimization, deselect, and cold probe screening on yield and cycle time. The versatility of the VIPTM technology and its extension to large area arrays is demonstrated using 240/288 X 4 and 480 X 5 TDI formats. Finally, the high performance of VIPTM IRFPAs is demonstrated by comparing data from a 480 X 5 to the SADA-II specification.

Multiple-wavelength vertical cavity laser arrays with wide wavelength span and high uniformity

NASA Astrophysics Data System (ADS)

Yuen, Wupen; Li, Gabriel S.; Chang-Hasnain, Connie J.

1996-12-01

Vertical-cavity surface-emitting lasers (VCSELs) are promising for numerous applications. In particular, due to their inherent single Fabry-Perot mode operation, VCSELs can be very useful for wavelength division multiplexing (WDM) systems allowing high bandwidth and high functionalities.1, 2 Multiple wavelength VCSEL arrays with wide channel spacings (>10 nm) provide an inexpensive solution to increasing the capacity of local area networks without using active wavelength controls.1 The lasing wavelength of a VCSEL is determined by the equivalent laser cavity thickness which can be varied by changing the thickness of either the l-spacer or the distributed Bragg reflector (DBR) layers. To make monolithic multiple-wavelength VCSEL arrays, the lasing wavelength, and therefore the cavity thickness, has to be varied at reasonable physical distances. For all practical applications, it is imperative for the fabrication technology to be controllable, cost-effective, and wafer-scale. Recently, we demonstrated a patterned-substrate molecular beam epitaxy (MBE) growth technique with in-situ laser reflectometry monitoring for fabricating multiple wavelength VCSEL arrays.3, 4 With this method, VCSEL arrays with very large and highly controllable lasing wavelength spans and excellent lasing characteristics have been achieved.

The Development of High-Density Vertical Silicon Nanowires and Their Application in a Heterojunction Diode

PubMed Central

Chang, Wen-Chung; Su, Sheng-Chien; Wu, Chia-Ching

2016-01-01

Vertically aligned p-type silicon nanowire (SiNW) arrays were fabricated through metal-assisted chemical etching (MACE) of Si wafers. An indium tin oxide/indium zinc oxide/silicon nanowire (ITO/IZO/SiNW) heterojunction diode was formed by depositing ITO and IZO thin films on the vertically aligned SiNW arrays. The structural and electrical properties of the resulting ITO/IZO/SiNW heterojunction diode were characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and current−voltage (I−V) measurements. Nonlinear and rectifying I−V properties confirmed that a heterojunction diode was successfully formed in the ITO/IZO/SiNW structure. The diode had a well-defined rectifying behavior, with a rectification ratio of 550.7 at 3 V and a turn-on voltage of 2.53 V under dark conditions. PMID:28773656

In Situ Synthesis of Vertical Standing Nanosized NiO Encapsulated in Graphene as Electrodes for High-Performance Supercapacitors.

PubMed

Lin, Jinghuang; Jia, Henan; Liang, Haoyan; Chen, Shulin; Cai, Yifei; Qi, Junlei; Qu, Chaoqun; Cao, Jian; Fei, Weidong; Feng, Jicai

2018-03-01

NiO is a promising electrode material for supercapacitors. Herein, the novel vertically standing nanosized NiO encapsulated in graphene layers (G@NiO) are rationally designed and synthesized as nanosheet arrays. This unique vertical standing structure of G@NiO nanosheet arrays can enlarge the accessible surface area with electrolytes, and has the benefits of short ion diffusion path and good charge transport. Further, an interconnected graphene conductive network acts as binder to encapsulate the nanosized NiO particles as core-shell structure, which can promote the charge transport and maintain the structural stability. Consequently, the optimized G@NiO hybrid electrodes exhibit a remarkably enhanced specific capacity up to 1073 C g -1 and excellent cycling stability. This study provides a facial strategy to design and construct high-performance metal oxides for energy storage.

Vertical pillar-superlattice array and graphene hybrid light emitting diodes.

PubMed

Lee, Jung Min; Choung, Jae Woong; Yi, Jaeseok; Lee, Dong Hyun; Samal, Monica; Yi, Dong Kee; Lee, Chul-Ho; Yi, Gyu-Chul; Paik, Ungyu; Rogers, John A; Park, Won Il

2010-08-11

We report a type of device that combines vertical arrays of one-dimensional (1D) pillar-superlattice (PSL) structures with 2D graphene sheets to yield a class of light emitting diode (LED) with interesting mechanical, optical, and electrical characteristics. In this application, graphene sheets coated with very thin metal layers exhibit good mechanical and electrical properties and an ability to mount, in a freely suspended configuration, on the PSL arrays as a top window electrode. Optical characterization demonstrates that graphene exhibits excellent optical transparency even after deposition of the thin metal films. Thermal annealing of the graphene/metal (Gr/M) contact to the GaAs decreases the contact resistance, to provide enhanced carrier injection. The resulting PSL-Gr/M LEDs exhibit bright light emission over large areas. The result suggests the utility of graphene-based materials as electrodes in devices with unusual, nonplanar 3D architectures.

Digital solar edge tracker for the Halogen Occultation Experiment

NASA Technical Reports Server (NTRS)

Mauldin, L. E., III; Moore, A. S.; Stump, C. W.; Mayo, L. S.

1987-01-01

The optical and electronic design of the Halogen Occultation Experiment (Haloe) elevation sun sensor is described. The Haloe instrument is a gas-correlation radiometer now being developed at NASA Langley for the Upper Atmosphere Research Satellite. The system uses a Galilean telescope to form a solar image on a linear silicon photodiode array. The array is a self-scanned monolithic CCD. The addresses of both solar edges imaged on the array are used by the control/pointing system to scan the Haloe science instantaneous field of view (IFOV) across the vertical solar diameter during instrument calibration and then to maintain the science IFOV 4 arcmin below the top edge during the science data occultation event. Vertical resolution of 16 arcsec and a radiometric dynamic range of 100 are achieved at the 700-nm operating wavelength. The design provides for loss of individual photodiode elements without loss of angular tracking capability.

Transfer of vertically aligned carbon nanofibers to polydimethylsiloxane (PDMS) while maintaining their alignment and impalefection functionality.

PubMed

Pearce, Ryan C; Railsback, Justin G; Anderson, Bryan D; Sarac, Mehmet F; McKnight, Timothy E; Tracy, Joseph B; Melechko, Anatoli V

2013-02-01

Vertically aligned carbon nanofibers (VACNFs) are synthesized on Al 3003 alloy substrates by direct current plasma-enhanced chemical vapor deposition. Chemically synthesized Ni nanoparticles were used as the catalyst for growth. The Si-containing coating (SiN(x)) typically created when VACNFs are grown on silicon was produced by adding Si microparticles prior to growth. The fiber arrays were transferred to PDMS by spin coating a layer on the grown substrates, curing the PDMS, and etching away the Al in KOH. The fiber arrays contain many fibers over 15 μm (long enough to protrude from the PDMS film and penetrate cell membranes) and SiN(x) coatings as observed by SEM, EDX, and fluorescence microscopy. The free-standing array in PDMS was loaded with pVENUS-C1 plasmid and human brain microcapillary endothelial (HBMEC) cells and was successfully impalefected.

Ten Years of Observatory Science from Saanich Inlet on the VENUS Cabled Ocean Observatory

NASA Astrophysics Data System (ADS)

Dewey, R. K.; Tunnicliffe, V.; Macoun, P.; Round, A.

2016-02-01

The Saanich Inlet array of the VENUS cabled ocean observatory, maintained and operated by Ocean Networks Canada, was installed in February 2006, and in 2016 will have supported ten years of comprehensive interactive science. Representing the first in the present generation of cabled observing technologies, this coastal array has provided continuous high power and broadband communications to a variety of instrument platforms, hundreds of sensors, and enabled dozens of short, medium, and long-term studies. Saanich Inlet is a protected fjord with limited tidal action, resulting in an extremely productive environment, with strong seasonal chemical variations driven by episodic deep water renewal events and oxygen reduction processes. The breadth of the research has included microbial and benthic community dynamics, biogeochemical cycles, forensics, quantifying inter-annual variations, benthic-pelagic coupling, sensor testing, plankton dynamics, and bio-turbulence. Observatory measurements include core water properties (CTD & O2) and water-column echo-sounder records, as well as experiment-oriented deployments utilizing cameras, Gliders, Dopplers, hydrophones, and a variety of biogeochemical sensors. With a recently installed Buoy Profiler System for monitoring the entire water column, community plans continue with a dedicated Redox experiment through the 2016-17 seasons. Highlights from the dozens of research papers and theses will be presented to demonstrate the achievements enabled by a comprehensive coastal cabled observing system.

Sounds and source levels from bowhead whales off Pt. Barrow, Alaska.

PubMed

Cummings, W C; Holliday, D V

1987-09-01

Sounds were recorded from bowhead whales migrating past Pt. Barrow, AK, to the Canadian Beaufort Sea. They mainly consisted of various low-frequency (25- to 900-Hz) moans and well-defined sound sequences organized into "song" (20-5000 Hz) recorded with our 2.46-km hydrophone array suspended from the ice. Songs were composed of up to 20 repeated phrases (mean, 10) which lasted up to 146 s (mean, 66.3). Several bowhead whales often were within acoustic range of the array at once, but usually only one sang at a time. Vocalizations exhibited diurnal peaks of occurrence (0600-0800, 1600-1800 h). Sounds which were located in the horizontal plane had peak source spectrum levels as follows--44 moans: 129-178 dB re: 1 microPa, 1 m (median, 159); 3 garglelike utterances: 152, 155, and 169 dB; 33 songs: 158-189 dB (median, 177), all presumably from different whales. Based on ambient noise levels, measured total propagation loss, and whale sound source levels, our detection of whale sounds was theoretically noise-limited beyond 2.5 km (moans) and beyond 10.7 km (songs), a model supported by actual localizations. This study showed that over much of the shallow Arctic and sub-Arctic waters, underwater communications of the bowhead whale would be limited to much shorter ranges than for other large whales in lower latitude, deep-water regions.

Calibration and comparison of the acoustic location methods used during the spring migration of the bowhead whale, Balaena mysticetus, off Pt. Barrow, Alaska, 1984-1993.

PubMed

Clark, C W; Ellison, W T

2000-06-01

Between 1984 and 1993, visual and acoustic methods were combined to census the Bering-Chukchi-Beaufort bowhead whale, Balaena mysticetus, population. Passive acoustic location was based on arrival-time differences of transient bowhead sounds detected on sparse arrays of three to five hydrophones distributed over distances of 1.5-4.5 km along the ice edge. Arrival-time differences were calculated from either digital cross correlation of spectrograms (old method), or digital cross correlation of time waveforms (new method). Acoustic calibration was conducted in situ in 1985 at five sites with visual site position determined by triangulation using two theodolites. The discrepancy between visual and acoustic locations was <1%-5% of visual range and less than 0.7 degrees of visual bearing for either method. Comparison of calibration results indicates that the new method yielded slightly more precise and accurate positions than the old method. Comparison of 217 bowhead whale call locations from both acoustic methods showed that the new method was more precise, with location errors 3-4 times smaller than the old method. Overall, low-frequency bowhead transients were reliably located out to ranges of 3-4 times array size. At these ranges in shallow water, signal propagation appears to be dominated by the fundamental mode and is not corrupted by multipath.

Production of vertical arrays of small diameter single-walled carbon nanotubes

DOEpatents

Hauge, Robert H; Xu, Ya-Qiong

2013-08-13

A hot filament chemical vapor deposition method has been developed to grow at least one vertical single-walled carbon nanotube (SWNT). In general, various embodiments of the present invention disclose novel processes for growing and/or producing enhanced nanotube carpets with decreased diameters as compared to the prior art.

Natural convection and radiation heat transfer from an array of inclined pin fins

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

Alessio, M.E.; Kaminski, D.A.

1989-02-01

Natural convection and radiation from an air-cooled, highly populated pin-fin array were studied experimentally. the effects of pin density, pin length, and the angle of the pin to the horizontal were measured. Previous work by Sparrow and Vemuri treated the case of a vertical base plate with horizontal fins. recently, Sparrow and Vemuri (1986) extended their study to include results for vertical fins with a horizontal down-facing base plate, as well as vertical fins with a horizontal up-facing base plate. In this study, the base plate is maintained in a vertical position and the angle of the pins is variedmore » from the horizontal. The main intent of this study was to compare the performance of inclined pin fins with straight pin fins. In all cases studied, the straight, horizontal fins were superior to the inclined fins. It was possible to obtain a single general correlation of the test data. While this correlation is recommended within the range of parameters that were tested here, one significant parameter, the size of the base plate, was not varied.« less

Triple seismic source, double research ship, single ambitious goal: integrated imaging of young oceanic crust in the Panama Basin

NASA Astrophysics Data System (ADS)

Wilson, Dean; Peirce, Christine; Hobbs, Richard; Gregory, Emma

2016-04-01

Understanding geothermal heat and mass fluxes through the seafloor is fundamental to the study of the Earth's energy budget. Using geophysical, geological and physical oceanography data we are exploring the interaction between the young oceanic crust and the ocean in the Panama Basin. We acquired a unique geophysical dataset that will allow us to build a comprehensive model of young oceanic crust from the Costa Rica Ridge axis to ODP borehole 504B. Data were collected over two 35 x 35 km2 3D grid areas, one each at the ridge axis and the borehole, and along three 330 km long 2D profiles orientated in the spreading direction, connecting the two grids. In addition to the 4.5 km long multichannel streamer and 75 ocean-bottom seismographs (OBS), we also deployed 12 magnetotelluric (MT) stations and collected underway swath bathymetry, gravity and magnetic data. For the long 2D profiles we used two research vessels operating synchronously. The RRS James Cook towed a high frequency GI-gun array (120 Hz) to image the sediments, and a medium frequency Bolt-gun array (50 Hz) for shallow-to-mid-crustal imaging. The R/V Sonne followed the Cook, 9 km astern and towed a third seismic source; a low frequency, large volume G-gun array (30 Hz) for whole crustal and upper mantle imaging at large offsets. Two bespoke vertical hydrophone arrays recorded real far field signatures that have enabled us to develop inverse source filters and match filters. Here we present the seismic reflection image, forward and inverse velocity-depth models and a density model along the primary 330 km north-south profile, from ridge axis to 6 Ma crust. By incorporating wide-angle streamer data from our two-ship, synthetic aperture acquisition together with traditional wide-angle OBS data we are able to constrain the structure of the upper oceanic crust. The results show a long-wavelength trend of increasing seismic velocity and density with age, and a correlation between velocity structure and basement roughness. Increased basement roughness leads to a non-uniform distribution of sediments, which we hypothesise influences the pattern of hydrothermal circulation and ultimately the secondary alteration of the upper crust. A combination of the complimentary wide-angle and normal incidence datasets and their individual models act as a starting point for joint inversion of seismic, gravity and MT data. The joint inversion produces a fully integrated model, enabling us to better understand how the oceanic crust evolves as a result of hydrothermal fluid circulation and cooling, as it ages from zero-age at the ridge-axis to 6 Ma at borehole 504B. Ultimately, this model can be used to undertake full waveform inversion to produce a high-resolution velocity model of the oceanic crust in the Panama Basin. This research is part of a major, interdisciplinary NERC-funded research collaboration entitled: Oceanographic and Seismic Characterisation of heat dissipation and alteration by hydrothermal fluids at an Axial Ridge (OSCAR).

Establishing a Dynamic Database of Blue and Fin Whale Locations from Recordings at the IMS CTBTO hydro-acoustic network. The Baleakanta Project

NASA Astrophysics Data System (ADS)

Le Bras, R. J.; Kuzma, H.

2013-12-01

Falling as they do into the frequency range of continuously recording hydrophones (15-100Hz), blue and fin whale songs are a significant source of noise on the hydro-acoustic monitoring array of the International Monitoring System (IMS) of the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO). One researcher's noise, however, can be a very interesting signal in another field of study. The aim of the Baleakanta Project (www.baleakanta.org) is to flag and catalogue these songs, using the azimuth and slowness of the signal measured at multiple hydrophones to solve for the approximate location of singing whales. Applying techniques borrowed from human speaker identification, it may even be possible to recognize the songs of particular individuals. The result will be a dynamic database of whale locations and songs with known individuals noted. This database will be of great value to marine biologists studying cetaceans, as there is no existing dataset which spans the globe over many years (more than 15 years of data have been collected by the IMS). Current whale song datasets from other sources are limited to detections made on small, temporary listening devices. The IMS song catalogue will make it possible to study at least some aspects of the global migration patterns of whales, changes in their songs over time, and the habits of individuals. It is believed that about 10 blue whale 'cultures' exist with distinct vocal patterns; the IMS song catalogue will test that number. Results and a subset of the database (delayed in time to mitigate worries over whaling and harassment of the animals) will be released over the web. A traveling museum exhibit is planned which will not only educate the public about whale songs, but will also make the CTBTO and its achievements more widely known. As a testament to the public's enduring fascination with whales, initial funding for this project has been crowd-sourced through an internet campaign.

Multifunctional Woven Structure Operating as Triboelectric Energy Harvester, Capacitive Tactile Sensor Array, and Piezoresistive Strain Sensor Array

PubMed Central

Kim, Kihong; Song, Giyoung; Park, Cheolmin; Yun, Kwang-Seok

2017-01-01

This paper presents a power-generating sensor array in a flexible and stretchable form. The proposed device is composed of resistive strain sensors, capacitive tactile sensors, and a triboelectric energy harvester in a single platform. The device is implemented in a woven textile structure by using proposed functional threads. A single functional thread is composed of a flexible hollow tube coated with silver nanowires on the outer surface and a conductive silver thread inside the tube. The total size of the device is 60 × 60 mm2 having a 5 × 5 array of sensor cell. The touch force in the vertical direction can be sensed by measuring the capacitance between the warp and weft functional threads. In addition, because silver nanowire layers provide piezoresistivity, the strain applied in the lateral direction can be detected by measuring the resistance of each thread. Last, with regard to the energy harvester, the maximum power and power density were measured as 201 μW and 0.48 W/m2, respectively, when the device was pushed in the vertical direction. PMID:29120363

Optical properties of ordered vertical arrays of multi-walled carbon nanotubes from FDTD simulations.

PubMed

Bao, Hua; Ruan, Xiulin; Fisher, Timothy S

2010-03-15

A finite-difference time-domain (FDTD) method is used to model thermal radiative properties of vertical arrays of multi-walled carbon nanotubes (MWCNT). Individual CNTs are treated as solid circular cylinders with an effective dielectric tensor. Consistent with experiments, the results confirm that CNT arrays are highly absorptive. Compared with the commonly used Maxwell-Garnett theory, the FDTD calculations generally predict larger reflectance and absorbance, and smaller transmittance, which are attributed to the diffraction and scattering within the cylinder array structure. The effects of volume fraction, tube length, tube distance, and incident angle on radiative properties are investigated systematically. Low volume fraction and long tubes are more favorable to achieve low reflectance and high absorbance. For a fixed volume fraction and finite tube length, larger periodicity results in larger reflectance and absorbance. The angular dependence studies reveal an optimum incident angle at which the reflectance can be minimized. The results also suggest that an even darker material could be achieved by using CNTs with good alignment on the top surface.

Vertical integration of array-type miniature interferometers at wafer level by using multistack anodic bonding

NASA Astrophysics Data System (ADS)

Wang, Wei-Shan; Wiemer, Maik; Froemel, Joerg; Enderlein, Tom; Gessner, Thomas; Lullin, Justine; Bargiel, Sylwester; Passilly, Nicolas; Albero, Jorge; Gorecki, Christophe

2016-04-01

In this work, vertical integration of miniaturized array-type Mirau interferometers at wafer level by using multi-stack anodic bonding is presented. Mirau interferometer is suitable for MEMS metrology and for medical imaging according to its vertical-, lateral- resolutions and working distances. Miniaturized Mirau interferometer can be a promising candidate as a key component of an optical coherence tomography (OCT) system. The miniaturized array-type interferometer consists of a microlens doublet, a Si-based MEMS Z scanner, a spacer for focus-adjustment and a beam splitter. Therefore, bonding technologies which are suitable for heterogeneous substrates are of high interest and necessary for the integration of MEMS/MOEMS devices. Multi-stack anodic bonding, which meets the optical and mechanical requirements of the MOEMS device, is adopted to integrate the array-type interferometers. First, the spacer and the beam splitter are bonded, followed by bonding of the MEMS Z scanner. In the meanwhile, two microlenses, which are composed of Si and glass wafers, are anodically bonded to form a microlens doublet. Then, the microlens doublet is aligned and bonded with the scanner/spacer/beam splitter stack. The bonded array-type interferometer is a 7- wafer stack and the thickness is approximately 5mm. To separate such a thick wafer stack with various substrates, 2-step laser cutting is used to dice the bonded stack into Mirau chips. To simplify fabrication process of each component, electrical connections are created at the last step by mounting a Mirau chip onto a flip chip PCB instead of through wafer vias. Stability of Au/Ti films on the MEMS Z scanner after anodic bonding, laser cutting and flip chip bonding are discussed as well.

Up or down? Reading direction influences vertical counting direction in the horizontal plane - a cross-cultural comparison.

PubMed

Göbel, Silke M

2015-01-01

Most adults and children in cultures where reading text progresses from left to right also count objects from the left to the right side of space. The reverse is found in cultures with a right-to-left reading direction. The current set of experiments investigated whether vertical counting in the horizontal plane is also influenced by reading direction. Participants were either from a left-to-right reading culture (UK) or from a mixed (left-to-right and top-to-bottom) reading culture (Hong Kong). In Experiment 1, native English-speaking children and adults and native Cantonese-speaking children and adults performed three object counting tasks. Objects were presented flat on a table in a horizontal, vertical, and square display. Independent of culture, the horizontal array was mostly counted from left to right. While the majority of English-speaking children counted the vertical display from bottom to top, the majority of the Cantonese-speaking children as well as both Cantonese- and English-speaking adults counted the vertical display from top to bottom. This pattern was replicated in the counting pattern for squares: all groups except the English-speaking children started counting with the top left coin. In Experiment 2, Cantonese-speaking adults counted a square array of objects after they read a text presented to them either in left-to-right or in top-to-bottom reading direction. Most Cantonese-speaking adults started counting the array by moving horizontally from left to right. However, significantly more Cantonese-speaking adults started counting with a top-to-bottom movement after reading the text presented in a top-to-bottom reading direction than in a left-to-right reading direction. Our results show clearly that vertical counting in the horizontal plane is influenced by longstanding as well as more recent experience of reading direction.

High Aspect Ratio Semiconductor Heterojunction Solar Cells

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

Redwing, Joan; Mallouk, Tom; Mayer, Theresa

2013-05-17

The project focused on the development of high aspect ratio silicon heterojunction (HARSH) solar cells. The solar cells developed in this study consisted of high density vertical arrays of radial junction silicon microwires/pillars formed on Si substrates. Prior studies have demonstrated that vertical Si wire/pillar arrays enable reduced reflectivity and improved light trapping characteristics compared to planar solar cells. In addition, the radial junction structure offers the possibility of increased carrier collection in solar cells fabricated using material with short carrier diffusion lengths. However, the high junction and surface area of radial junction Si wire/pillar array devices can be problematicmore » and lead to increased diode leakage and enhanced surface recombination. This study investigated the use of amorphous hydrogenated Si in the form of a heterojunction-intrinsic-thin layer (HIT) structure as a junction formation method for these devices. The HIT layer structure has widely been employed to reduce surface recombination in planar crystalline Si solar cells. Consequently, it was anticipated that it would also provide significant benefits to the performance of radial junction Si wire/pillar array devices. The overall goals of the project were to demonstrate a HARSH cell with a HIT-type structure in the radial junction Si wire/pillar array configuration and to develop potentially low cost pathways to fabricate these devices. Our studies demonstrated that the HIT structure lead to significant improvements in the open circuit voltage (V oc>0.5) of radial junction Si pillar array devices compared to devices fabricated using junctions formed by thermal diffusion or low pressure chemical vapor deposition (LPCVD). In addition, our work experimentally demonstrated that the radial junction structure lead to improvements in efficiency compared to comparable planar devices for devices fabricated using heavily doped Si that had reduced carrier diffusion lengths. Furthermore, we made significant advances in employing the bottom-up vapor-liquid-solid (VLS) growth technique for the fabrication of the Si wire arrays. Our work elucidated the effects of growth conditions and substrate pattern geometry on the growth of large area Si microwire arrays grown with SiCl4. In addition, we also developed a process to grow p-type Si nanowire arrays using aluminum as the catalyst metal instead of gold. Finally, our work demonstrated the feasibility of growing vertical arrays of Si wires on non-crystalline glass substrates using polycrystalline Si template layers. The accomplishments demonstrated in this project will pave the way for future advances in radial junction wire array solar cells.« less

Density controlled carbon nanotube array electrodes

DOEpatents

Ren, Zhifeng F [Newton, MA; Tu, Yi [Belmont, MA

2008-12-16

CNT materials comprising aligned carbon nanotubes (CNTs) with pre-determined site densities, catalyst substrate materials for obtaining them and methods for forming aligned CNTs with controllable densities on such catalyst substrate materials are described. The fabrication of films comprising site-density controlled vertically aligned CNT arrays of the invention with variable field emission characteristics, whereby the field emission properties of the films are controlled by independently varying the length of CNTs in the aligned array within the film or by independently varying inter-tubule spacing of the CNTs within the array (site density) are disclosed. The fabrication of microelectrode arrays (MEAs) formed utilizing the carbon nanotube material of the invention is also described.

Thermal Conduction in Vertically Aligned Copper Nanowire Arrays and Composites.

PubMed

Barako, Michael T; Roy-Panzer, Shilpi; English, Timothy S; Kodama, Takashi; Asheghi, Mehdi; Kenny, Thomas W; Goodson, Kenneth E

2015-09-02

The ability to efficiently and reliably transfer heat between sources and sinks is often a bottleneck in the thermal management of modern energy conversion technologies ranging from microelectronics to thermoelectric power generation. These interfaces contribute parasitic thermal resistances that reduce device performance and are subjected to thermomechanical stresses that degrade device lifetime. Dense arrays of vertically aligned metal nanowires (NWs) offer the unique combination of thermal conductance from the constituent metal and mechanical compliance from the high aspect ratio geometry to increase interfacial heat transfer and device reliability. In the present work, we synthesize copper NW arrays directly onto substrates via templated electrodeposition and extend this technique through the use of a sacrificial overplating layer to achieve improved uniformity. Furthermore, we infiltrate the array with an organic phase change material and demonstrate the preservation of thermal properties. We use the 3ω method to measure the axial thermal conductivity of freestanding copper NW arrays to be as high as 70 W m(-1) K(-1), which is more than an order of magnitude larger than most commercial interface materials and enhanced-conductivity nanocomposites reported in the literature. These arrays are highly anisotropic, and the lateral thermal conductivity is found to be only 1-2 W m(-1) K(-1). We use these measured properties to elucidate the governing array-scale transport mechanisms, which include the effects of morphology and energy carrier scattering from size effects and grain boundaries.

Vertically aligned carbon nanotube arrays as thermal interface material for vibrational structure of piezoelectric transformer

NASA Astrophysics Data System (ADS)

Chen, Lie; Ju, Bin; Feng, Zhihua; Zhao, Yang

2018-07-01

The application and characterization of thermal interface material (TIM) for vibrational structures is investigated in this paper. The vibrating feature during the operation requires unique solution for its thermal management, since the connection between the device and heat dissipater should be able to conduct heat efficiently and impose minimum constraint onto the vibration simultaneously. As a typical vibrational device, piezoelectric transformers (PTs) are discussed in this paper. The PTs have urgent demands for thermal dissipation since their power conversion efficiency decrease rapidly with the rising temperature. A novel method by applying vertically aligned carbon nanotube (VACNT) arrays to the interface between PT and heat dissipater is presented to enhance the performance of piezoelectric transformers. VACNT arrays are one of the excellent TIMs. It can directly establish thermal contact between two surfaces by van der Waals’ forces. In addition, the unique anisotropic character of CNT arrays provides enough flexibility to accommodate the vibration during the operation. Different configurations of TIMs are compared with each other in this work, including CNT arrays, tape of polypropylene (PP) membrane and without heat transfer structure (HTS). The results indicate that the temperature rise is lowest and the efficiency is highest at the same power density while CNT arrays served as the TIM. Almost no significant fretting and wearing damage occurred on PT electrode surface with CNT arrays TIM even after working continuously for 120 days. Meanwhile, the thermo-physical properties of CNT arrays at contact interface are measured by optical transient thermo-reflectance technique.

Layered-metal-hydroxide nanosheet arrays with controlled nanostructures to assist direct electronic communication at biointerfaces.

PubMed

An, Zhe; Lu, Shan; Zhao, Liwei; He, Jing

2011-10-18

In this work, ordered vertical arrays of layered double hydroxide (LDH) nanosheets have been developed to achieve electron transfer (eT) at biointerfaces in electrochemical devices. It is found that tailoring the gap size of LDH nanosheet arrays could significantly promote the eT rate. This research has successfully extended nanomaterials for efficient modifications of electrode surfaces from nanoparticles, nanowires, nanorods, and nanotubes to nanosheets. © 2011 American Chemical Society

Challenges and regulatory considerations in the acoustic measurement of high-frequency (>20 MHz) ultrasound.

PubMed

Nagle, Samuel M; Sundar, Guru; Schafer, Mark E; Harris, Gerald R; Vaezy, Shahram; Gessert, James M; Howard, Samuel M; Moore, Mary K; Eaton, Richard M

2013-11-01

This article examines the challenges associated with making acoustic output measurements at high ultrasound frequencies (>20 MHz) in the context of regulatory considerations contained in the US Food and Drug Administration industry guidance document for diagnostic ultrasound devices. Error sources in the acoustic measurement, including hydrophone calibration and spatial averaging, nonlinear distortion, and mechanical alignment, are evaluated, and the limitations of currently available acoustic measurement instruments are discussed. An uncertainty analysis of acoustic intensity and power measurements is presented, and an example uncertainty calculation is done on a hypothetical 30-MHz high-frequency ultrasound system. This analysis concludes that the estimated measurement uncertainty of the acoustic intensity is +73%/-86%, and the uncertainty in the mechanical index is +37%/-43%. These values exceed the respective levels in the Food and Drug Administration guidance document of 30% and 15%, respectively, which are more representative of the measurement uncertainty associated with characterizing lower-frequency ultrasound systems. Recommendations made for minimizing the measurement uncertainty include implementing a mechanical positioning system that has sufficient repeatability and precision, reconstructing the time-pressure waveform via deconvolution using the hydrophone frequency response, and correcting for hydrophone spatial averaging.

Bowhead whale localization using asynchronous hydrophones in the Chukchi Sea.

PubMed

Warner, Graham A; Dosso, Stan E; Hannay, David E; Dettmer, Jan

2016-07-01

This paper estimates bowhead whale locations and uncertainties using non-linear Bayesian inversion of their modally-dispersed calls recorded on asynchronous recorders in the Chukchi Sea, Alaska. Bowhead calls were recorded on a cluster of 7 asynchronous ocean-bottom hydrophones that were separated by 0.5-9.2 km. A warping time-frequency analysis is used to extract relative mode arrival times as a function of frequency for nine frequency-modulated whale calls that dispersed in the shallow water environment. Each call was recorded on multiple hydrophones and the mode arrival times are inverted for: the whale location in the horizontal plane, source instantaneous frequency (IF), water sound-speed profile, seabed geoacoustic parameters, relative recorder clock drifts, and residual error standard deviations, all with estimated uncertainties. A simulation study shows that accurate prior environmental knowledge is not required for accurate localization as long as the inversion treats the environment as unknown. Joint inversion of multiple recorded calls is shown to substantially reduce uncertainties in location, source IF, and relative clock drift. Whale location uncertainties are estimated to be 30-160 m and relative clock drift uncertainties are 3-26 ms.

Acoustic Propagation Studies For Sperm Whale Phonation Analysis During LADC Experiments

NASA Astrophysics Data System (ADS)

Sidorovskaia, Natalia A.; Ioup, George E.; Ioup, Juliette W.; Caruthers, Jerald W.

2004-11-01

The Littoral Acoustic Demonstration Center (LADC) conducted a series of passive acoustic experiments in the Northern Gulf of Mexico and the Ligurian Sea in 2001 and 2002. Environmental and acoustic moorings were deployed in areas of large concentrations of marine mammals (mainly, sperm whales). Recordings and analysis of whale phonations are among the objectives of the project. Each mooring had a single autonomously recording hydrophone (Environmental Acoustic Recording System (EARS)) obtained from the U.S. Naval Oceanographic Office after modification to record signals up to 5,859 Hz in the Gulf of Mexico and up to 12,500 Hz in the Ligurian Sea. Self-recording environmental sensors, attached to the moorings, and concurrent environmental ship surveys provided the environmental data for the experiments. The results of acoustic simulations of long-range propagation of the broad-band (500-6,000 Hz) phonation pulses from a hypothetical whale location to the recording hydrophone in the experimental environments are presented. The utilization of the simulation results for an interpretation of the spectral features observed in whale clicks and for the development of tracking algorithms from single hydrophone recordings based on the identification of direct and surface and bottom reflected arrivals are discussed. [Research supported by ONR.

Measuring changes in ambient noise levels from the installation and operation of a surge wave energy converter in the coastal ocean

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

Haxel, Joe H; Henkel, Sarah K

Ecosystem impacts resulting from elevated underwater noise levels generated by anthropogenic activities in the coastal ocean are poorly understood and remain difficult to address as a result of a significant gap in knowledge for existing nearshore sound levels. Ambient noise is an important habitat component for marine mammals and fish that use sound for essential functions such as communication, navigation, and foraging. Questions surrounding the amplitudes, frequency distributions, and durations of noise emissions from renewable wave energy conversion (WEC) projects during their construction and operation present concerns for long-term consequences in marine habitats. Oregon’s dynamic nearshore environment presents significant challengesmore » for passive acoustic monitoring that include flow noise contamination from wave orbital motions, turbulence from breaking surf, equipment burial, and fishing pressure from sport and commercial crabbers. This project included 2 techniques for passive acoustic data collection: 1) campaign style deployments of fixed hydrophone lander stations to capture temporal variations in noise levels and 2) a drifting hydrophone system to record spatial variations within the project site. The hydrophone lander deployments were effective and economically feasible for enabling robust temporal measurements of ambient noise levels in a variety of sea state conditions. Limiting factors for the fixed stations included 1) a flow shield mitigation strategy failure in the first deployment resulting in significant wideband data contamination and 2) flow noise contamination of the unshielded sensors restricting valuable analysis to frequencies above 500 Hz for subsequent deployments. Drifting hydrophone measurements were also effective and economically feasible (although logistically challenging in the beginning of the project due to vessel time constraints) providing a spatial distribution of sound levels, comparisons of noise levels in varying levels of vessel traffic during similar sea states, and reducing the frequencies contaminated by flow noise to f < 50 Hz by an effective drifting hydrophone system design strategy. Results from this project can still assist regulatory agencies and WEC developers in permitting and licensing, reducing project costs overall and assisting the economic development of the WEC industry, thus furthering the MHK energy industry and easing the U.S. reliance on foreign oil for energy production. Additionally, results from this project can be used to help inform coastal resource managers and regulatory agencies on existing baseline noise level variability and ecosystem health.« less

An Update on Phased Array Results Obtained on the GE Counter-Rotating Open Rotor Model

NASA Technical Reports Server (NTRS)

Podboy, Gary; Horvath, Csaba; Envia, Edmane

2013-01-01

Beamform maps have been generated from 1) simulated data generated by the LINPROP code and 2) actual experimental phased array data obtained on the GE Counter-rotating open rotor model. The beamform maps show that many of the tones in the experimental data come from their corresponding Mach radius. If the phased array points to the Mach radius associated with a tone then it is likely that the tone is a result of the loading and thickness noise on the blades. In this case, the phased array correctly points to where the noise is coming from and indicates the axial location of the loudest source in the image but not necessarily the correct vertical location. If the phased array does not point to the Mach radius associated with a tone then some mechanism other than loading and thickness noise may control the amplitude of the tone. In this case, the phased array may or may not point to the actual source. If the source is not rotating it is likely that the phased array points to the source. If the source is rotating it is likely that the phased array indicates the axial location of the loudest source but not necessarily the correct vertical location. These results indicate that you have to be careful in how you interpret phased array data obtained on an open rotor since they may show the tones coming from a location other than the source location. With a subsonic tip speed open rotor the tones can come form locations outboard of the blade tips. This has implications regarding noise shielding.

Combined antenna and localized plasmon resonance in Raman scattering from random arrays of silver-coated, vertically aligned multiwalled carbon nanotubes.

PubMed

Dawson, P; Duenas, J A; Boyle, M G; Doherty, M D; Bell, S E J; Kern, A M; Martin, O J F; Teh, A-S; Teo, K B K; Milne, W I

2011-02-09

The electric field enhancement associated with detailed structure within novel optical antenna nanostructures is modeled using the surface integral equation technique in the context of surface-enhanced Raman scattering (SERS). The antennae comprise random arrays of vertically aligned, multiwalled carbon nanotubes dressed with highly granular Ag. Different types of "hot-spot" underpinning the SERS are identified, but contrasting characteristics are revealed. Those at the outer edges of the Ag grains are antenna driven with field enhancement amplified in antenna antinodes while intergrain hotspots are largely independent of antenna activity. Hot-spots between the tops of antennae leaning towards each other also appear to benefit from antenna amplification.

Vertically aligned multiwalled carbon nanotubes for pressure, tactile and vibration sensing.

PubMed

Yilmazoglu, O; Popp, A; Pavlidis, D; Schneider, J J; Garth, D; Schüttler, F; Battenberg, G

2012-03-02

We report a simple method for the micro-nano integration of flexible, vertically aligned multiwalled CNT arrays sandwiched between a top and bottom carbon layer via a porous alumina (Al(2)O(3)) template approach. The electromechanical properties of the flexible CNT arrays have been investigated under mechanical stress conditions. First experiments show highly sensitive piezoresistive sensors with a resistance decrease of up to ∼35% and a spatial resolution of <1 mm. The results indicate that these CNT structures can be utilized for tactile sensing components. They also confirm the feasibility of accessing and utilizing nanoscopic CNT bundles via lithographic processing. The method involves room-temperature processing steps and standard microfabrication techniques.

A top-down approach to fabrication of high quality vertical heterostructure nanowire arrays.

PubMed

Wang, Hua; Sun, Minghua; Ding, Kang; Hill, Martin T; Ning, Cun-Zheng

2011-04-13

We demonstrate a novel top-down approach for fabricating nanowires with unprecedented complexity and optical quality by taking advantage of a nanoscale self-masking effect. We realized vertical arrays of nanowires of 20-40 nm in diameter with 16 segments of complex longitudinal InGaAsP/InP structures. The unprecedented high quality of etched wires is evidenced by the narrowest photoluminescence linewidth ever produced in similar wavelengths, indistinguishable from that of the corresponding wafer. This top-down, mask-free, large scale approach is compatible with the established device fabrication processes and could serve as an important alternative to the bottom-up approach, significantly expanding ranges and varieties of applications of nanowire technology.

Spatiotemporal distribution of the seismicity along the Mid-Atlantic Ridge north of the Azores from hydroacoustic data: Insights into seismogenic processes in a ridge-hot spot context

NASA Astrophysics Data System (ADS)

Goslin, J.; Perrot, J.; Royer, J.-Y.; Martin, C.; LourençO, N.; Luis, J.; Dziak, R. P.; Matsumoto, H.; Haxel, J.; Fowler, M. J.; Fox, C. G.; Lau, A. T.-K.; Bazin, S.

2012-02-01

The seismicity of the North Atlantic was monitored from May 2002 to September 2003 by the `SIRENA array' of autonomous hydrophones. The hydroacoustic signals provide a unique data set documenting numerous low-magnitude earthquakes along the section of the Mid-Atlantic Ridge (MAR) located in a ridge-hot spot interaction context. During the experiment, 1696 events were detected along the MAR axis between 40°N and 51°N, with a magnitude of completeness level ofmb≈ 2.4. Inside the array, location errors are in the order of 2 km, and errors in the origin time are less than 1 s. From this catalog, 15 clusters were detected. The distribution of source level (SL) versus time within each cluster is used to discriminate clusters occurring in a tectonic context from those attributed to non-tectonic (i.e. volcanic or hydrothermal) processes. The location of tectonic and non-tectonic sequences correlates well with regions with positive and negative Mantle Bouguer Anomalies (MBAs), indicating the presence of thinner/colder and thicker/warmer crust respectively. At the scale of the entire array, both the complete and declustered catalogs derived from the hydroacoustic signals show an increase of the seismicity rate from the Azores up to 43°30'N suggesting a diminishing influence of the Azores hot spot on the ridge-axis temperature, and well correlated with a similar increase in the along-axis MBAs. The comparison of the MAR seismicity with the Residual MBA (RMBA) at different scales leads us to think that the low-magnitude seismicity rates are directly related to along-axis variations in lithosphere rheology and temperatures.

Echolocation signals of free-ranging killer whales (Orcinus orca) and modeling of foraging for chinook salmon (Oncorhynchus tshawytscha)

NASA Astrophysics Data System (ADS)

Au, Whitlow W. L.; Ford, John K. B.; Horne, John K.; Allman, Kelly A. Newman

2004-02-01

Fish-eating ``resident''-type killer whales (Orcinus orca) that frequent the coastal waters off northeastern Vancouver Island, Canada have a strong preference for chinook salmon (Oncorhynchus tshawytscha). The whales in this region often forage along steep cliffs that extend into the water, echolocating their prey. Echolocation signals of resident killer whales were measured with a four-hydrophone symmetrical star array and the signals were simultaneously digitized at a sample rate of 500 kHz using a lunch-box PC. A portable VCR recorded the images from an underwater camera located adjacent to the array center. Only signals emanating from close to the beam axis (1185 total) were chosen for a detailed analysis. Killer whales project very broadband echolocation signals (Q equal 0.9 to 1.4) that tend to have bimodal frequency structure. Ninety-seven percent of the signals had center frequencies between 45 and 80 kHz with bandwidths between 35 and 50 kHz. The peak-to-peak source level of the echolocation signals decreased as a function of the one-way transmission loss to the array. Source levels varied between 195 and 224 dB re:1 μPa. Using a model of target strength for chinook salmon, the echo levels from the echolocation signals are estimated for different horizontal ranges between a whale and a salmon. At a horizontal range of 100 m, the echo level should exceed an Orcinus hearing threshold at 50 kHz by over 29 dB and should be greater than sea state 4 noise by at least 9 dB. In moderately heavy rain conditions, the detection range will be reduced substantially and the echo level at a horizontal range of 40 m would be close to the level of the rain noise.

Echolocation signals of free-ranging killer whales (Orcinus orca) and modeling of foraging for chinook salmon (Oncorhynchus tshawytscha).

PubMed

Au, Whitlow W L; Ford, John K B; Horne, John K; Allman, Kelly A Newman

2004-02-01

Fish-eating "resident"-type killer whales (Orcinus orca) that frequent the coastal waters off northeastern Vancouver Island, Canada have a strong preference for chinook salmon (Oncorhynchus tshawytscha). The whales in this region often forage along steep cliffs that extend into the water, echolocating their prey. Echolocation signals of resident killer whales were measured with a four-hydrophone symmetrical star array and the signals were simultaneously digitized at a sample rate of 500 kHz using a lunch-box PC. A portable VCR recorded the images from an underwater camera located adjacent to the array center. Only signals emanating from close to the beam axis (1185 total) were chosen for a detailed analysis. Killer whales project very broadband echolocation signals (Q equal 0.9 to 1.4) that tend to have bimodal frequency structure. Ninety-seven percent of the signals had center frequencies between 45 and 80 kHz with bandwidths between 35 and 50 kHz. The peak-to-peak source level of the echolocation signals decreased as a function of the one-way transmission loss to the array. Source levels varied between 195 and 224 dB re: 1 microPa. Using a model of target strength for chinook salmon, the echo levels from the echolocation signals are estimated for different horizontal ranges between a whale and a salmon. At a horizontal range of 100 m, the echo level should exceed an Orcinus hearing threshold at 50 kHz by over 29 dB and should be greater than sea state 4 noise by at least 9 dB. In moderately heavy rain conditions, the detection range will be reduced substantially and the echo level at a horizontal range of 40 m would be close to the level of the rain noise.

Spatial and temporal distribution of the seismicity along two mid-oceanic ridges with contrasted spreading rates in the Indian Ocean

NASA Astrophysics Data System (ADS)

Tsang-Hin-Sun, E.; Perrot, J.; Royer, J. Y.

2015-12-01

The seismicity of the ultra-slow spreading Southwest (14 mm/y) and intermediate spreading Southeast (60 mm/y) Indian ridges was monitored from February 2012 to March 2013 by the OHASISBIO array of 7 autonomous hydrophones. A total of 1471 events were located with 4 instruments or more, inside the array, with a median location uncertainty < 5 km and a completeness magnitude of mb = 3. Both ridges display similar average rates of seismicity, suggesting that there is no systematic relationship between seismicity and spreading rates. Accretion modes do differ, however, by the along-axis distribution of the seismic events. Along the ultra-slow Southwest Indian Ridge, events are sparse but regularly spaced and scattered up to 50 km off-axis. Along the fast Southeast Indian Ridge, events are irregularly distributed, focusing in narrow regions near the ridge axis at segment ends and along transform faults, whereas ridge-segment centers generally appear as seismic gaps (at the level of completeness of the array). Only two clusters, 6 months apart, are identified in a segment-center at 29°S. From the temporal distribution of the clustered events and comparisons with observations in similar mid-oceanic ridge setting, both clusters seem to have a volcanic origin and to be related to a dike emplacement or a possible eruption on the seafloor. Their onset time and migration rate are comparable to volcanic swarms recorded along the Juan de Fuca Ridge. Overall, the rate of seismicity along the two Indian spreading ridges correlates with the large-scale variations in the bathymetry and shear-wave velocity anomaly in the upper mantle, suggesting that the distribution of the low-magnitude seismicity is mainly controlled by along-axis variations in the lithosphere rheology and temperature.

Vertical Seismic Profiling at riser drilling site in the rupture area of the 1944 Tonankai Earthquake, Japan (Invited)

NASA Astrophysics Data System (ADS)

Hino, R.; Kinoshita, M.; Araki, E.; Byrne, T. B.; McNeill, L. C.; Saffer, D. M.; Eguchi, N. O.; Takahashi, K.; Toczko, S.

2009-12-01

A series of scientific drilling expeditions is in operation in the Nankai Trough to reveal the faulting mechanism of the magathrust earthquakes, through clarifying composition, fine structure, mechanical behavior, and environmental variables of the seismogenic faults. In the studied area, extensive seismic surveys for site characterization have been made to image detailed geometry of the fault complex in the accretionary prism as well as Vp distribution around the faults. Although these previous surveys provided invaluable information for understanding seismotectonic processes in this subduction zone, more complete knowledge is needed to be acquired to predict dynamic behavior of the faults, such as geometrical irregularities in short wavelength, Vs and seismic attenuation which are sensitive to fluid distribution in and around fault zones. It is expected that estimation of these parameters would be improved considerably by a seismic exploration using a vertical array of seismographs installed in a deep borehole (VSP: vertical seismic profiling). In July 2009, we made a VSP at one of the drilling sites located just above the rupture area of the 1994 Tonankai Earthquake (M 8.1), during the IODP Exp.319. The well site of our VSP was made by the riser drilling of D/V Chikyu. The seismic array, lowered from Chikyu into the hole, was composed of a three-component accelerometer and vertical separation of the array elements was 15.12 m. The VSP was composed of offset VSP and zero-offset VSP. In the offset VSP, a tuned airgun array towed by R/V Kairei was shot along one straight line (walk-away VSP) and another circular line (walk-around VSP) and seismic signals were recorded by an array consisting of 16 elements installed from 907 to 1,135 m in depth from seafloor. The object of the walk-away VSP is to obtain fine image of the faults using reflection arrivals with less attenuation. It is also expected to obtain spatial variation of Vs from arrival time tomography of refracted S waves. For this purpose, we preferred extraordinarily longer (~ 30 km) offset shooting than usual industrial VSPs. Shot spacing was 60 m along the same line as the previous 3D reflection and OBS wide angle surveys. The radius of circle of the walk-around VSP was 3.5 km to detect azimuthal anisotropy of downgoing P and S waves, correlated to stress state around the site. In zero-offset VSP, shots just above the hole were recorded by the 8 element array moving from 0 to 1,135 mbsf along the hole so that seismic structure with comparable vertical resolution as core-log information would be obtained. In the records of the walk-away VSP, clear first arrivals as well as several evident later arrivals were clearly identified. The later phases contain the reflection from the megasplay fault and the refracted S wave through the accretional prism, on both of which we have significant interest. The walk-around VSP also provided us with high S/N records but detailed data reduction, such as velocity analysis using vertical array, are required to derive anisotropic nature of the formation around the hole.

Arrays of carbon nanofibers as a platform for biosensing at the molecular level and for tissue engineering and implantation.

PubMed

Koehne, Jessica E; Chen, Hua; Cassell, Alan; Liu, Gang-yu; Li, Jun; Meyyappan, M

2009-01-01

Arrays of Carbon nanofibers (CNFs) harness the advantages of individual CNF as well the collective property of assemblies, which made them promising materials in biosensing and tissue engineering or implantation. Here, we report two studies to explore the applications of vertically aligned CNFs. First, a nanoelectrode array (NEA) based on vertically aligned CNFs embedded in SiO(2) is used for ultrasensitive DNA detection. Oligonucleotide probes are selectively functionalized at the open ends of the CNFs and specifically hybridized with oligonucleotide targets. The guanine groups are employed as the signal moieties in the electrochemical measurements. Ru(bpy)(3)(2+) mediator is used to further amplify the guanine oxidation signal. The hybridization of less than approximately 1000 molecules of PCR amplified DNA targets are detected electrochemically by combining the CNF nanoelectrode array with the Ru(bpy)(3)(2+) amplification mechanism. Second, the SiO(2) matrix was etched back to produce needle-like protruding nanoelectrode arrays to be used as cell interfacing fibers for investigating gene transfection, electrical stimulation and detection of cellular processes. Our goal is to take advantage of the nanostructure of CNFs for unconventional biomolecular studies requiring ultrahigh sensitivity, high-degree of miniaturization and selective biofunctionalization.

Boron Nitride Coated Carbon Nanotube Arrays with Enhanced Compressive Mechanical Property

NASA Astrophysics Data System (ADS)

Jing, Lin; Tay, Roland Yingjie; Li, Hongling; Tsang, Siu Hon; Tan, Dunlin; Zhang, Bowei; Tok, Alfred Iing Yoong; Teo, Edwin Hang Tong

Vertically aligned carbon nanotube (CNT) array is one of the most promising energy dissipating materials due to its excellent temperature invariant mechanical property. However, the CNT arrays with desirable recoverability after compression is still a challenge. Here, we report on the mechanical enhancement of the CNT arrays reinforced by coating with boron nitride (BN) layers. These BN coated CNT (BN/CNT) arrays exhibit excellent compressive strength and recoverability as compared to those of the as-prepared CNT arrays which totally collapsed after compression. In addition, the BN coating also provides better resistance to oxidation due to its intrinsic thermal stability. This work presented here opens a new pathway towards tuning mechanical behavior of any arbitrary CNT arrays for promising potential such as damper, vibration isolator and shock absorber applications.

A New Concept in Helicopter Communications Antennas

NASA Technical Reports Server (NTRS)

Pogorzelski, R. J.

1995-01-01

We consider a five blade rotor and envision an array with one element mounted on each rotor blade. These elements may be dipoles or horizontal slots depending upon the desired polarization characteristics. For example, slots would provide vertical polarization on horizontal paths. The array is excited through a novel type of rotary joint located on the rotor shaft.

Energy-based adaptive focusing of waves: application to noninvasive aberration correction of ultrasonic wavefields

PubMed Central

Herbert, Eric; Pernot, Mathieu; Montaldo, Gabriel; Fink, Mathias; Tanter, Mickael

2009-01-01

An aberration correction method based on the maximization of the wave intensity at the focus of an emitting array is presented. The potential of this new adaptive focusing technique is investigated for ultrasonic focusing in biological tissues. The acoustic intensity is maximized non invasively through the direct measurement or indirect estimation of the beam energy at the focus for a series of spatially coded emissions. For ultrasonic waves, the acoustic energy at the desired focus can be indirectly estimated from the local displacements induced in tissues by the ultrasonic radiation force of the beam. Based on the measurement of these displacements, this method allows the precise estimation of the phase and amplitude aberrations and consequently the correction of aberrations along the beam travel path. The proof of concept is first performed experimentally using a large therapeutic array with strong electronic phase aberrations (up to 2π). Displacements induced by the ultrasonic radiation force at the desired focus are indirectly estimated using the time shift of backscattered echoes recorded on the array. The phase estimation is deduced accurately using a direct inversion algorithm which reduces the standard deviation of the phase distribution from σ = 1.89 before correction to σ = 0.53 following correction. The corrected beam focusing quality is verified using a needle hydrophone. The peak intensity obtained through the aberrator is found to be −7.69 dB below the reference intensity obtained without any aberration. Using the phase correction, a sharp focus is restored through the aberrator with a relative peak intensity of −0.89 dB. The technique is tested experimentally using a linear transmit/receive array through a real aberrating layer. The array is used to automatically correct its beam quality, as it both generates the radiation force with coded excitations and indirectly estimates the acoustic intensity at the focus with speckle tracking. This technique could have important implications in the field of High Intensity Focused Ultrasound even in complex configurations such as transcranial, transcostal or deep seated organs. PMID:19942526

Geometrical optics, electrostatics, and nanophotonic resonances in absorbing nanowire arrays.

PubMed

Anttu, Nicklas

2013-03-01

Semiconductor nanowire arrays have shown promise for next-generation photovoltaics and photodetection, but enhanced understanding of the light-nanowire interaction is still needed. Here, we study theoretically the absorption of light in an array of vertical InP nanowires by moving continuously, first from the electrostatic limit to the nanophotonic regime and then to the geometrical optics limit. We show how the absorption per volume of semiconductor material in the array can be varied by a factor of 200, ranging from 10 times weaker to 20 times stronger than in a bulk semiconductor sample.

Passive magnetic bearing for a horizontal shaft

DOEpatents

Post, Richard F.

2003-12-02

A passive magnetic bearing is composed of a levitation element and a restorative element. The levitation element is composed of a pair of stationary arcuate ferromagnetic segments located within an annular radial-field magnet array. The magnet array is attached to the inner circumference of a hollow shaft end. An attractive force between the arcuate segments and the magnet array acts vertically to levitate the shaft, and also in a horizontal transverse direction to center the shaft. The restorative element is comprised of an annular Halbach array of magnets and a stationary annular circuit array located within the Halbach array. The Halbach array is attached to the inner circumference of the hollow shaft end. A repulsive force between the Halbach array and the circuit array increases inversely to the radial space between them, and thus acts to restore the shaft to its equilibrium axis of rotation when it is displaced therefrom.

In situ SEM Observation of Column-like and Foam-like CNT Array Nanoindentation

DTIC Science & Technology

2011-03-02

frompyrolization of iron(II) phthalocyanine , producing vertically aligned CNTs with a nominal outer diameter of 50 nm.11,12 The array was indented using a 40 40 μm...www.acsami.org In situ SEM Observation of Column-like and Foam-like CNT Array Nanoindentation Matthew R. Maschmann,†,‡Qiuhong Zhang,†,§ Robert Wheeler...multiple length scales. Their behavior is expected to rely heavily on the properties of individual constituent CNTs , interactions and load distribution

Basic principles and recent observations of rotationally sampled wind

NASA Technical Reports Server (NTRS)

Connell, James R.

1995-01-01

The concept of rotationally sampled wind speed is described. The unusual wind characteristics that result from rotationally sampling the wind are shown first for early measurements made using an 8-point ring of anemometers on a vertical plane array of meteorological towers. Quantitative characterization of the rotationally sampled wind is made in terms of the power spectral density function of the wind speed. Verification of the importance of the new concept is demonstrated with spectral analyses of the response of the MOD-OA blade flapwise root bending moment and the corresponding rotational analysis of the wind measured immediately upwind of the MOD-OA using a 12-point ring of anemometers on a 7-tower vertical plane array. The Pacific Northwest Laboratory (PNL) theory of the rotationally sampled wind speed power spectral density function is tested successfully against the wind spectrum measured at the MOD-OA vertical plane array. A single-tower empirical model of the rotationally sampled wind speed is also successfully tested against the measurements from the full vertical plane array. Rotational measurements of the wind velocity with hotfilm anemometers attached to rotating blades are shown to be accurate and practical for research on winds at the blades of wind turbines. Some measurements at the rotor blade of a MOD-2 turbine using the hotfilm technique in a pilot research program are shown. They are compared and contrasted to the expectations based upon application of the PNL theory of rotationally sampled wind to the MOD-2 size and rotation rate but without teeter, blade bending, or rotor induction accounted for. Finally, the importance of temperature layering and of wind modifications due to flow over complex terrain is demonstrated by the use of hotfilm anemometer data, and meteorological tower and acoustic doppler sounder data from the MOD-2 site at Goodnoe Hills, Washington.

Does language shape thought? Mandarin and English speakers' conceptions of time.

PubMed

Boroditsky, L

2001-08-01

Does the language you speak affect how you think about the world? This question is taken up in three experiments. English and Mandarin talk about time differently--English predominantly talks about time as if it were horizontal, while Mandarin also commonly describes time as vertical. This difference between the two languages is reflected in the way their speakers think about time. In one study, Mandarin speakers tended to think about time vertically even when they were thinking for English (Mandarin speakers were faster to confirm that March comes earlier than April if they had just seen a vertical array of objects than if they had just seen a horizontal array, and the reverse was true for English speakers). Another study showed that the extent to which Mandarin-English bilinguals think about time vertically is related to how old they were when they first began to learn English. In another experiment native English speakers were taught to talk about time using vertical spatial terms in a way similar to Mandarin. On a subsequent test, this group of English speakers showed the same bias to think about time vertically as was observed with Mandarin speakers. It is concluded that (1) language is a powerful tool in shaping thought about abstract domains and (2) one's native language plays an important role in shaping habitual thought (e.g., how one tends to think about time) but does not entirely determine one's thinking in the strong Whorfian sense. Copyright 2001 Academic Press.

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

NASA Astrophysics Data System (ADS)

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

1991-06-01

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

Fabrication of Vertically Aligned Carbon Nanotube or Zinc Oxide Nanorod Arrays for Optical Diffraction Gratings.

PubMed

Kim, Jeong; Kim, Sun Il; Cho, Seong-Ho; Hwang, Sungwoo; Lee, Young Hee; Hur, Jaehyun

2015-11-01

We report on new fabrication methods for a transparent, hierarchical, and patterned electrode comprised of either carbon nanotubes or zinc oxide nanorods. Vertically aligned carbon nanotubes or zinc oxide nanorod arrays were fabricated by either chemical vapor deposition or hydrothermal growth, in combination with photolithography. A transparent conductive graphene layer or zinc oxide seed layer was employed as the transparent electrode. On the patterned surface defined using photoresist, the vertically grown carbon nanotubes or zinc oxides could produce a concentrated electric field under applied DC voltage. This periodic electric field was used to align liquid crystal molecules in localized areas within the optical cell, effectively modulating the refractive index. Depending on the material and morphology of these patterned electrodes, the diffraction efficiency presented different behavior. From this study, we established the relationship between the hierarchical structure of the different electrodes and their efficiency for modulating the refractive index. We believe that this study will pave a new path for future optoelectronic applications.

Vertically aligned N-doped CNTs growth using Taguchi experimental design

NASA Astrophysics Data System (ADS)

Silva, Ricardo M.; Fernandes, António J. S.; Ferro, Marta C.; Pinna, Nicola; Silva, Rui F.

2015-07-01

The Taguchi method with a parameter design L9 orthogonal array was implemented for optimizing the nitrogen incorporation in the structure of vertically aligned N-doped CNTs grown by thermal chemical deposition (TCVD). The maximization of the ID/IG ratio of the Raman spectra was selected as the target value. As a result, the optimal deposition configuration was NH3 = 90 sccm, growth temperature = 825 °C and catalyst pretreatment time of 2 min, the first parameter having the main effect on nitrogen incorporation. A confirmation experiment with these values was performed, ratifying the predicted ID/IG ratio of 1.42. Scanning electron microscopy (SEM) characterization revealed a uniform completely vertically aligned array of multiwalled CNTs which individually exhibit a bamboo-like structure, consisting of periodically curved graphitic layers, as depicted by high resolution transmission electron microscopy (HRTEM). The X-ray photoelectron spectroscopy (XPS) results indicated a 2.00 at.% of N incorporation in the CNTs in pyridine-like and graphite-like, as the predominant species.

Flexible symmetric supercapacitors based on vertical TiO2 and carbon nanotubes

NASA Astrophysics Data System (ADS)

Chien, C. J.; Chang, Pai-Chun; Lu, Jia G.

2010-03-01

Highly conducting and porous carbon nanotubes are widely used as electrodes in double-layer-effect supercapacitors. In this presentation, vertical TiO2 nanotube array is fabricated by anodization process and used as supercapacitor electrode utilizing its compact density, high surface area and porous structure. By spin coating carbon nanotube networks on vertical TiO2 nanotube array as electrodes with 1M H2SO4 electrolyte in between, the specific capacitance can be enhanced by 30% compared to using pure carbon nanotube network alone because of the combination of double layer effect and redox reaction from metal oxide materials. Based on cyclic voltammetry and galvanostatic charge-discharge measurements, this type of hybrid electrode has proven to be suitable for high performance supercapacitor application and maintain desirable cycling stability. The electrochemical impedance spectroscopy technique shows that the electrode has good electrical conductivity. Furthermore, we will discuss the prospect of extending this energy storage approach in flexible electronics.

A new seismic probe for coal seam hazard detection

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

Peters, W.R.; Owen, T.E.; Thill, R.E.

1985-01-01

An experimental hole-to-hole seismic probe system has been developed for use in coal measure geology as a means of determining the structural conditions of coal seams. The source probe produces a 500-joule electric arc discharge whose seismic wavelet has a spectrum in the 200 to 2,000 Hz frequency range. Low compliance hydrophones contained in the source probe as well as in a separate seismic detector probe are matched to the frequency range of the source. Both probes are constructed with 5.72 cm diameter housings. The transducers in the probes are equipped with fluid-inflatable boots to permit operation in either wetmore » or dry boreholes. Preliminary tests in vertical boreholes drilled 213 m apart in sedimentary rock formations show reliable operation and useful seismic propagation measurements along horizontal and oblique paths up to 232 m in length. Because the seismic wavelet has an accurately repeatable waveshape, multiple shots and signal averaging techniques can be used to enhance the signal-to-noise ratio and extend the transmission distances.« less

Femtosecond laser modification of an array of vertically aligned carbon nanotubes intercalated with Fe phase nanoparticles

PubMed Central

2013-01-01

Femtosecond lasers (FSL) are playing an increasingly important role in materials research, characterization, and modification. Due to an extremely short pulse width, interactions of FSL irradiation with solid surfaces attract special interest, and a number of unusual phenomena resulted in the formation of new materials are expected. Here, we report on a new nanostructure observed after the interaction of FSL irradiation with arrays of vertically aligned carbon nanotubes (CNTs) intercalated with iron phase catalyst nanoparticles. It was revealed that the FSL laser ablation transforms the topmost layer of CNT array into iron phase nanospheres (40 to 680 nm in diameter) located at the tip of the CNT bundles of conical shape. Besides, the smaller nanospheres (10 to 30 nm in diameter) are found to be beaded at the sides of these bundles. Some of the larger nanospheres are encapsulated into carbon shells, which sometime are found to contain CNTs. The mechanism of creation of such nanostructures is proposed. PMID:24004518

Rhesus monkeys (Macaca mulatta) map number onto space

PubMed Central

Drucker, Caroline B.; Brannon, Elizabeth M.

2014-01-01

Humans map number onto space. However, the origins of this association, and particularly the degree to which it depends upon cultural experience, are not fully understood. Here we provide the first demonstration of a number-space mapping in a non-human primate. We trained four adult male rhesus macaques (Macaca mulatta) to select the fourth position from the bottom of a five-element vertical array. Monkeys maintained a preference to choose the fourth position through changes in the appearance, location, and spacing of the vertical array. We next asked whether monkeys show a spatially-oriented number mapping by testing their responses to the same five-element stimulus array rotated ninety degrees into a horizontal line. In these horizontal probe trials, monkeys preferentially selected the fourth position from the left, but not the fourth position from the right. Our results indicate that rhesus macaques map number onto space, suggesting that the association between number and space in human cognition is not purely a result of cultural experience and instead has deep evolutionary roots. PMID:24762923

Femtosecond laser modification of an array of vertically aligned carbon nanotubes intercalated with Fe phase nanoparticles.

PubMed

Labunov, Vladimir; Prudnikava, Alena; Bushuk, Serguei; Filatov, Serguei; Shulitski, Boris; Tay, Beng Kang; Shaman, Yury; Basaev, Alexander

2013-09-03

Femtosecond lasers (FSL) are playing an increasingly important role in materials research, characterization, and modification. Due to an extremely short pulse width, interactions of FSL irradiation with solid surfaces attract special interest, and a number of unusual phenomena resulted in the formation of new materials are expected. Here, we report on a new nanostructure observed after the interaction of FSL irradiation with arrays of vertically aligned carbon nanotubes (CNTs) intercalated with iron phase catalyst nanoparticles. It was revealed that the FSL laser ablation transforms the topmost layer of CNT array into iron phase nanospheres (40 to 680 nm in diameter) located at the tip of the CNT bundles of conical shape. Besides, the smaller nanospheres (10 to 30 nm in diameter) are found to be beaded at the sides of these bundles. Some of the larger nanospheres are encapsulated into carbon shells, which sometime are found to contain CNTs. The mechanism of creation of such nanostructures is proposed.

Study of system-size effects on the emergent magnetic monopoles and Dirac strings in artificial kagome spin ice

NASA Astrophysics Data System (ADS)

Leon, Alejandro

2012-02-01

In this work we study the dynamical properties of a finite array of nanomagnets in artificial kagome spin ice at room temperature. The dynamic response of the array of nanomagnets is studied by implementing a ``frustrated celular aut'omata'' (FCA), based in the charge model. In this model, each dipole is replaced by a dumbbell of two opposite charges, which are situated at the neighbouring vertices of the honeycomb lattice. The FCA simulations, allow us to study in real-time and deterministic way, the dynamic of the system, with minimal computational resource. The update function is defined according to the coordination number of vertices in the system. Our results show that for a set geometric parameters of the array of nanomagnets, the system exhibits high density of Dirac strings and high density emergent magnetic monopoles. A study of the effect of disorder in the arrangement of nanomagnets is incorporated in this work.

Fish schooling as a basis for vertical axis wind turbine farm design.

PubMed

Whittlesey, Robert W; Liska, Sebastian; Dabiri, John O

2010-09-01

Most wind farms consist of horizontal axis wind turbines (HAWTs) due to the high power coefficient (mechanical power output divided by the power of the free-stream air through the turbine cross-sectional area) of an isolated turbine. However when in close proximity to neighboring turbines, HAWTs suffer from a reduced power coefficient. In contrast, previous research on vertical axis wind turbines (VAWTs) suggests that closely spaced VAWTs may experience only small decreases (or even increases) in an individual turbine's power coefficient when placed in close proximity to neighbors, thus yielding much higher power outputs for a given area of land. A potential flow model of inter-VAWT interactions is developed to investigate the effect of changes in VAWT spatial arrangement on the array performance coefficient, which compares the expected average power coefficient of turbines in an array to a spatially isolated turbine. A geometric arrangement based on the configuration of shed vortices in the wake of schooling fish is shown to significantly increase the array performance coefficient based upon an array of 16 x 16 wind turbines. The results suggest increases in power output of over one order of magnitude for a given area of land as compared to HAWTs.

Dye-sensitized solar cells with vertically aligned TiO2 nanowire arrays grown on carbon fibers.

PubMed

Cai, Xin; Wu, Hongwei; Hou, Shaocong; Peng, Ming; Yu, Xiao; Zou, Dechun

2014-02-01

One-dimensional semiconductor TiO2 nanowires (TNWs) have received widespread attention from solar cell and related optoelectronics scientists. The controllable synthesis of ordered TNW arrays on arbitrary substrates would benefit both fundamental research and practical applications. Herein, vertically aligned TNW arrays in situ grown on carbon fiber (CF) substrates through a facile, controllable, and seed-assisted thermal process is presented. Also, hierarchical TiO2 -nanoparticle/TNW arrays were prepared that favor both the dye loading and depressed charge recombination of the CF/TNW photoanode. An impressive conversion efficiency of 2.48 % (under air mass 1.5 global illumination) and an apparent efficiency of 4.18 % (with a diffuse board) due to the 3D light harvesting of the wire solar cell were achieved. Moreover, efficient and inexpensive wire solar cells made from all-CF electrodes and completely flexible CF-based wire solar cells were demonstrated, taking into account actual application requirements. This work may provide an intriguing avenue for the pursuit of lightweight, cost-effective, and high-performance flexible/wearable solar cells. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Plasmonic Biosensor Based on Vertical Arrays of Gold Nanoantennas.

PubMed

Klinghammer, Stephanie; Uhlig, Tino; Patrovsky, Fabian; Böhm, Matthias; Schütt, Julian; Pütz, Nils; Baraban, Larysa; Eng, Lukas M; Cuniberti, Gianaurelio

2018-06-25

Implementing large arrays of gold nanowires as functional elements of a plasmonic biosensor is an important task for future medical diagnostic applications. Here we present a microfluidic-channel-integrated sensor for the label-free detection of biomolecules, relying on localized surface plasmon resonances. Large arrays (∼1 cm 2 ) of vertically aligned and densely packed gold nanorods to receive, locally confine, and amplify the external optical signal are used to allow for reliable biosensing. We accomplish this by monitoring the change of the optical nanostructure resonance in the presence of biomolecules within the tight focus area above the nanoantennas, combined with a surface treatment of the nanowires for a specific binding of the target molecules. As a first application, we detect the binding kinetics of two distinct DNA strands as well as the following hybridization of two complementary strands (cDNA) with different lengths (25 and 100 bp). Upon immobilization, a redshift of 1 nm was detected; further backfilling and hybridization led to a peak shift of additional 2 and 5 nm for 25 and 100 bp, respectively. We believe that this work gives deeper insight into the functional understanding and technical implementation of a large array of gold nanowires for future medical applications.

Composite Li metal anode with vertical graphene host for high performance Li-S batteries

NASA Astrophysics Data System (ADS)

Zhang, Y. J.; Liu, S. F.; Wang, X. L.; Zhong, Y.; Xia, X. H.; Wu, J. B.; Tu, J. P.

2018-01-01

Efficient and stable operation of a lithium metal anode has become the enabling factor for next-generation high energy density storage system. Here, vertical graphene (VG) arrays are used as the scaffold structure for high performance Li metal batteries. The melt infusion method is employed to encapsulate Li inside the VG scaffold structure, and the lithiophilic Si layer is coated onto the array surface by magnetron sputtering to assist this melt-infusion process. The porous scaffold structure can control the volume expansion and inhibit the formation of dendritic lithium significantly, leading to the excellent electrochemical performance of the Li composite anode. In addition, the Li-S full batteries with the composite anode display enhanced cycling reversibility.

A grating coupler with a trapezoidal hole array for perfectly vertical light coupling between optical fibers and waveguides

NASA Astrophysics Data System (ADS)

Mizutani, Akio; Eto, Yohei; Kikuta, Hisao

2017-12-01

A grating coupler with a trapezoidal hole array was designed and fabricated for perfectly vertical light coupling between a single-mode optical fiber and a silicon waveguide on a silicon-on-insulator (SOI) substrate. The grating coupler with an efficiency of 53% was computationally designed at a 1.1-µm-thick buried oxide (BOX) layer. The grating coupler and silicon waveguide were fabricated on the SOI substrate with a 3.0-µm-thick BOX layer by a single full-etch process. The measured coupling efficiency was 24% for TE-polarized light at 1528 nm wavelength, which was 0.69 times of the calculated coupling efficiency for the 3.0-µm-thick BOX layer.

Vertically aligned carbon nanofiber electrode arrays for nucleic acid detection

NASA Astrophysics Data System (ADS)

Arumugam, Prabhu U.; Yu, Edmond; Riviere, Roger; Meyyappan, M.

2010-10-01

We present electrochemical detection of DNA targets that corresponds to Escherichia coli O157:H7 16S rRNA gene using a nanoelectrode array consisting of vertically aligned carbon nanofiber (VACNF) electrodes. Parylene C is used as gap filling 'matrix' material to avoid high temperature processing in electrode construction. This easy to deposit film of several micron heights provides a conformal coating between the high aspect ratio VACNFs with negligible pin-holes. The low background currents show the potential of this approach for ultra-sensitive detection. Consistent and reproducible electrochemical-signals are achieved using a simple electrode preparation. This simple, reliable and low-cost approach is a forward step in developing practical sensors for applications like pathogen detection, early cancer diagnosis and environmental monitoring.

Assembly of Nanowire Arrays: Exploring Interparticle Interactions, Particle Orientation, and Mixed Particle Arrays

NASA Astrophysics Data System (ADS)

Kirby, David J.

This dissertation explores the fundamental interparticle and particle-substrate forces that contribute to nanowire assembly. Nanowires have a large aspect ratio which has made them favorable materials for applications in energy and sensing technologies. However, this anisotropy means that nanowires must be positioned and oriented during an assembly process. Within this work, the roles of gravity, van der Waals (VDW) attractions, and electrostatic repulsions are explored when different nanowire assemblies are created. Particles were synthesized by the template electrodeposition process so that stripes of different materials and therefore different VDW interactions could be patterned along the particle length. Electrostatic repulsions were provided by a small molecule coating or a porous silica shell to prevent aggregation during the assembly process. Chapters 2, 3, 5, 6, and 8 all used particles whose asymmetry was further adjusted by removal of a sacrificial segment to leave a partially etched nanowire (PEN), a rigid silica shell partially filled with a metal core. For these particles, the role of gravity was amplified due to the drastic density differences between the two segments. Topographic and high VDW surface interactions were patterned onto assembly substrates using photolithographic processing. These forces served as a passive template to direct nanowire assembly. The segment anisotropy of PENs allowed gravity to drive their sedimentation with the long axis perpendicular to the surface. The density difference between the two ends allowed them to convert between the horizontal and vertical orientation as they diffused on the substrate. Vertical arrays formed as particle concentrations increased while VDW attractions from neighboring PENs or the physical barrier of a microwell wall supported this structure. While vertical arrays were typically PENs, microwell walls were also able to enforce a vertical orientation on solid Au nanowires. These particles typically formed horizontal arrays on planar surfaces, but careful design of the microwell and nanowire dimensions enabled these particles to take on the vertical orientation. Solid nanowires and PENs with greater segment symmetry aligned parallel to the surface as gravity did not allow a conversion to the vertical orientation. When concentrated, these particles formed smectic row arrangements which were previously shown to originate from a balance of VDW attractions and electrostatic repulsions. Within rows of segmented particles, a preference was observed for like orientation of nearest neighbor particles (Chapter 6). With the aid of Monte Carlo simulations, it was determined that this observation was the result of small differences in VDW attractions between the two nanowire ends. Differences in VDW attraction were also applied to patterned surfaces (Chapter 7). Stripes of high VDW material (Au) were placed on a silica surface (a low VDW material). When relatively low surface concentrations were used, the high VDW regions collected Au nanowires and organized them into rows that were reminiscent of those observed on un-patterned surfaces at high particle concentrations. VDW and the gravitational force were explored as they combined to influence array orientation in binary PEN mixtures. Depending on the geometries of the particles combined, the contributions of gravity and interparticle interactions exhibited different balance in creating the final array. VDW and gravitational forces could also act as a force for reconfigurable nanowire assembly. In chapter 8, fluid flow was used to concentrate PENs and force them into horizontal arrangements. When fluid flow was stopped, van der Waals forces and gravity were responsible for a reorientation of the assembled particles into a standing array. These studies represent early steps into the future of nanowire assembly methods. I conclude this dissertation by discussing the implications of my work and providing perspective on their importance to the scientific community. I also offer suggestions for future work in nanowire assembly. These areas focus on the development of assembled nanowire devices, mixed nanowire assembly techniques, and potential stimuli responsive reconfigurable assemblies.

Validation of finite element computations for the quantitative prediction of underwater noise from impact pile driving.

PubMed

Zampolli, Mario; Nijhof, Marten J J; de Jong, Christ A F; Ainslie, Michael A; Jansen, Erwin H W; Quesson, Benoit A J

2013-01-01

The acoustic radiation from a pile being driven into the sediment by a sequence of hammer strikes is studied with a linear, axisymmetric, structural acoustic frequency domain finite element model. Each hammer strike results in an impulsive sound that is emitted from the pile and then propagated in the shallow water waveguide. Measurements from accelerometers mounted on the head of a test pile and from hydrophones deployed in the water are used to validate the model results. Transfer functions between the force input at the top of the anvil and field quantities, such as acceleration components in the structure or pressure in the fluid, are computed with the model. These transfer functions are validated using accelerometer or hydrophone measurements to infer the structural forcing. A modeled hammer forcing pulse is used in the successive step to produce quantitative predictions of sound exposure at the hydrophones. The comparison between the model and the measurements shows that, although several simplifying assumptions were made, useful predictions of noise levels based on linear structural acoustic models are possible. In the final part of the paper, the model is used to characterize the pile as an acoustic radiator by analyzing the flow of acoustic energy.

Dolphin biosonar signals measured at extreme off-axis angles: insights to sound propagation in the head.

PubMed

Au, Whitlow W L; Branstetter, Brian; Moore, Patrick W; Finneran, James J

2012-08-01

Biosonar signals radiated along the beam axis of an Atlantic bottlenose dolphin resemble short transient oscillations. As the azimuth of the measuring hydrophones in the horizontal plane progressively increases with respect to the beam axis the signals become progressively distorted. At approximately ±45°, the signals begin to divide into two components with the time difference between the components increasing with increasing angles. At ±90° or normal to the longitudinal axis of the animal, the time difference between the two pulses measured by the hydrophone on the right side of the dolphin's head is, on average, ∼11.9 μs larger than the time differences observed by the hydrophone on the left side of the dolphin's head. The center frequency of the first pulse is generally lower, by 33-47 kHz, than the center frequency of the second pulse. When considering the relative locations of the two phonic lips, the data suggest that the signals are being produced by one of the phonic lips and the second pulse resulting from a reflection within the head of the animal. The generation of biosonar signals is a complex process and the propagation pathways through the dolphin's head are not well understood.

Bowhead whale localization using time-difference-of-arrival data from asynchronous recorders.

PubMed

Warner, Graham A; Dosso, Stan E; Hannay, David E

2017-03-01

This paper estimates bowhead whale locations and uncertainties using nonlinear Bayesian inversion of the time-difference-of-arrival (TDOA) of low-frequency whale calls recorded on onmi-directional asynchronous recorders in the shallow waters of the northeastern Chukchi Sea, Alaska. A Y-shaped cluster of seven autonomous ocean-bottom hydrophones, separated by 0.5-9.2 km, was deployed for several months over which time their clocks drifted out of synchronization. Hundreds of recorded whale calls are manually associated between recorders. The TDOA between hydrophone pairs are calculated from filtered waveform cross correlations and depend on the whale locations, hydrophone locations, relative recorder clock offsets, and effective waveguide sound speed. A nonlinear Bayesian inversion estimates all of these parameters and their uncertainties as well as data error statistics. The problem is highly nonlinear and a linearized inversion did not produce physically realistic results. Whale location uncertainties from nonlinear inversion can be low enough to allow accurate tracking of migrating whales that vocalize repeatedly over several minutes. Estimates of clock drift rates are obtained from inversions of TDOA data over two weeks and agree with corresponding estimates obtained from long-time averaged ambient noise cross correlations. The inversion is suitable for application to large data sets of manually or automatically detected whale calls.

Ultrahigh-Density Nanowire Arrays Grown in Self-Assembled Diblock Copolymer Templates

NASA Astrophysics Data System (ADS)

Thurn-Albrecht, T.; Schotter, J.; Kästle, G. A.; Emley, N.; Shibauchi, T.; Krusin-Elbaum, L.; Guarini, K.; Black, C. T.; Tuominen, M. T.; Russell, T. P.

2000-12-01

We show a simple, robust, chemical route to the fabrication of ultrahigh-density arrays of nanopores with high aspect ratios using the equilibrium self-assembled morphology of asymmetric diblock copolymers. The dimensions and lateral density of the array are determined by segmental interactions and the copolymer molecular weight. Through direct current electrodeposition, we fabricated vertical arrays of nanowires with densities in excess of 1.9 × 1011 wires per square centimeter. We found markedly enhanced coercivities with ferromagnetic cobalt nanowires that point toward a route to ultrahigh-density storage media. The copolymer approach described is practical, parallel, compatible with current lithographic processes, and amenable to multilayered device fabrication.

Focused ultrasound transducer spatial peak intensity estimation: a comparison of methods

NASA Astrophysics Data System (ADS)

Civale, John; Rivens, Ian; Shaw, Adam; ter Haar, Gail

2018-03-01

Characterisation of the spatial peak intensity at the focus of high intensity focused ultrasound transducers is difficult because of the risk of damage to hydrophone sensors at the high focal pressures generated. Hill et al (1994 Ultrasound Med. Biol. 20 259-69) provided a simple equation for estimating spatial-peak intensity for solid spherical bowl transducers using measured acoustic power and focal beamwidth. This paper demonstrates theoretically and experimentally that this expression is only strictly valid for spherical bowl transducers without a central (imaging) aperture. A hole in the centre of the transducer results in over-estimation of the peak intensity. Improved strategies for determining focal peak intensity from a measurement of total acoustic power are proposed. Four methods are compared: (i) a solid spherical bowl approximation (after Hill et al 1994 Ultrasound Med. Biol. 20 259-69), (ii) a numerical method derived from theory, (iii) a method using measured sidelobe to focal peak pressure ratio, and (iv) a method for measuring the focal power fraction (FPF) experimentally. Spatial-peak intensities were estimated for 8 transducers at three drive powers levels: low (approximately 1 W), moderate (~10 W) and high (20-70 W). The calculated intensities were compared with those derived from focal peak pressure measurements made using a calibrated hydrophone. The FPF measurement method was found to provide focal peak intensity estimates that agreed most closely (within 15%) with the hydrophone measurements, followed by the pressure ratio method (within 20%). The numerical method was found to consistently over-estimate focal peak intensity (+40% on average), however, for transducers with a central hole it was more accurate than using the solid bowl assumption (+70% over-estimation). In conclusion, the ability to make use of an automated beam plotting system, and a hydrophone with good spatial resolution, greatly facilitates characterisation of the FPF, and consequently gives improved confidence in estimating spatial peak intensity from measurement of acoustic power.

Lithospheric structure beneath the extinct ridge of South China Sea: Constraints from Rayleigh wave phase velocity tomography using OBS data

NASA Astrophysics Data System (ADS)

Yang, T.; Le, B. M.; passive-Source Seismic Team, S.

2016-12-01

What would happen when a mid-ocean-ridge stops spreading? Global occurrences of such ridges appear to indicate that magmatic activities had continued for million years after ridges were abandoned and often formed seamount chains over ridges. The extinct ridge and the seamount chain at the South China Sea represent one classic example of such ridges. To understand this unique process and the lithospheric and deep mantle structure, we carry out a Rayleigh wave phase velocity tomography using data from a passive-source OBS array experiment in South China Sea from 2012 to 2013. We correct OBS clock errors by using Scholte waves retrieved through cross-correlating hydrophone records of each OBS pair. 60 regional and teleseismic events with high quality Rayleigh waves are selected and their dispersion curves at the OBS array are used to inverse the phase velocities of periods from 15 s to 100 s. The shear wave velocity model derived from phase velocities of all periods shows a strong low-velocity zone situated beneath the seamounts starting at about 30 km depth. The lithosphere thickness of the extinct ridge inferred from this model provide insights on the cooling process and magmatism at this unique oceanic setting. In addition, our model images the tear of the subducting South China Sea plate beneath the Manila trench and Luzon island, which is clearly generated by the subduction of the extinct ridge and overriding seamounts.

Research on characteristics of radiated noise of large cargo ship in shallow water

NASA Astrophysics Data System (ADS)

Liu, Yongdong; Zhang, Liang

2017-01-01

With the rapid development of the shipping industry, the number of the world's ship is gradually increasing. The characteristics of the radiated noise of the ship are also of concern. Since the noise source characteristics of multichannel interference, the surface wave and the sea temperature microstructure and other reasons, the sound signal received in the time-frequency domain has varying characteristics. The signal of the radiated noise of the large cargo ship JOCHOH from horizontal hydrophone array in some shallow water of China is processed and analyzed in the summer of 2015, and the results show that a large cargo ship JOCHOH has a number of noise sources in the direction of the ship's bow and stern lines, such as host, auxiliary and propellers. The radiating sound waves generated by these sources do not meet the spherical wave law at lower frequency in the ocean, and its radiated noise has inherent spatial distribution, the variation characteristics of the radiated noise the large cargo ship in time and frequency domain are given. The research method and results are of particular importance.

Elastic parabolic equation solutions for oceanic T-wave generation and propagation from deep seismic sources.

PubMed

Frank, Scott D; Collis, Jon M; Odom, Robert I

2015-06-01

Oceanic T-waves are earthquake signals that originate when elastic waves interact with the fluid-elastic interface at the ocean bottom and are converted to acoustic waves in the ocean. These waves propagate long distances in the Sound Fixing and Ranging (SOFAR) channel and tend to be the largest observed arrivals from seismic events. Thus, an understanding of their generation is important for event detection, localization, and source-type discrimination. Recently benchmarked seismic self-starting fields are used to generate elastic parabolic equation solutions that demonstrate generation and propagation of oceanic T-waves in range-dependent underwater acoustic environments. Both downward sloping and abyssal ocean range-dependent environments are considered, and results demonstrate conversion of elastic waves into water-borne oceanic T-waves. Examples demonstrating long-range broadband T-wave propagation in range-dependent environments are shown. These results confirm that elastic parabolic equation solutions are valuable for characterization of the relationships between T-wave propagation and variations in range-dependent bathymetry or elastic material parameters, as well as for modeling T-wave receptions at hydrophone arrays or coastal receiving stations.

Spatial orientation of different frequencies within the echolocation beam of a Tursiops truncatus and Pseudorca crassidens.

PubMed

Ibsen, Stuart D; Nachtigall, Paul E; Krause-Nehring, Jacqueline; Kloepper, Laura; Breese, Marlee; Li, Songhai; Vlachos, Stephanie

2012-08-01

A two-dimensional array of 16 hydrophones was created to map the spatial distribution of different frequencies within the echolocation beam of a Tursiops truncatus and a Pseudorca crassidens. It was previously shown that both the Tursiops and Pseudorca only paid attention to frequencies between 29 and 42 kHz while echolocating. Both individuals tightly focused the 30 kHz frequency and the spatial location of the focus was consistently pointed toward the target. At 50 kHz the beam was less focused and less precisely pointed at the target. At 100 kHz the focus was often completely lost and was not pointed at the target. This indicates that these individuals actively focused the beam toward the target only in the frequency range they paid attention to. Frequencies outside this range were left unfocused and undirected. This focusing was probably achieved through sensorimotor control of the melon morphology and nasal air sacs. This indicates that both morphologically different species can control the spatial distribution of different frequency ranges within the echolocation beam to create consistent ensonation of desired targets.

Acoustic characteristics of biosonar sounds of free-ranging botos (Inia geoffrensis) and tucuxis (Sotalia fluviatilis) in the Negro River, Amazon, Brazil.

PubMed

Yamamoto, Yukiko; Akamatsu, Tomonari; da Silva, Vera M F; Yoshida, Yayoi; Kohshima, Shiro

2015-08-01

Odontoceti emit broadband high-frequency clicks on echolocation for orientation or prey detection. In the Amazon Basin, two odontoceti species, boto (Amazon River dolphin, Inia geoffrensis) and tucuxi (Sotalia fluviatilis), live sympatrically. The acoustic characteristics of the echolocation clicks of free-ranging botos and tucuxis were measured with a hydrophone array consisting of a full-band and an acoustic event recorder (A-tag). The clicks of the two species were short-duration broadband signals. The apparent source level was 201 dB 1 μPa peak-to-peak at 1 m in the botos and 181 dB 1 μPa peak-to-peak at 1 m in the tucuxis, and the centroid frequency was 82.3 kHz in the botos and 93.1 kHz in the tucuxis. The high apparent source level and low centroid frequency are possibly due to the difference in body size or sound production organs, especially the nasal structure, the sound source of clicks in odontoceti.

Stereotypical rapid source level regulation in the harbour porpoise biosonar

NASA Astrophysics Data System (ADS)

Linnenschmidt, Meike; Kloepper, Laura N.; Wahlberg, Magnus; Nachtigall, Paul E.

2012-09-01

Some odontocetes and bats vary both click intensity and receiver sensitivity during echolocation, depending on target range. It is not known how this so-called automatic gain control is regulated by the animal. The source level of consecutive echolocation clicks from a harbour porpoise was measured with a hydrophone array while the animal detected an aluminium cylinder at 2, 4 or 8 m distance in a go/no-go paradigm. On-axis clicks had source levels of 145-174 dB re 1 μPa peak-to-peak. During target-present trials the click trains reached comparable source levels independent of the range to the target after three clicks. After an additional click, the source level was reduced for the 2 and 4 m trials until it equalled the one-way transmission loss. During target-absent trials, the source level remained high throughout the entire click train. Given typical values of harbour porpoise inter-click intervals, the source level reduction commenced within a few 100 ms from the first click in the click train. This may indicate a sub-cortically regulated source level regulation in the harbour porpoise.

Single Carrier with Frequency Domain Equalization for Synthetic Aperture Underwater Acoustic Communications

PubMed Central

He, Chengbing; Xi, Rui; Wang, Han; Jing, Lianyou; Shi, Wentao; Zhang, Qunfei

2017-01-01

Phase-coherent underwater acoustic (UWA) communication systems typically employ multiple hydrophones in the receiver to achieve spatial diversity gain. However, small underwater platforms can only carry a single transducer which can not provide spatial diversity gain. In this paper, we propose single-carrier with frequency domain equalization (SC-FDE) for phase-coherent synthetic aperture acoustic communications in which a virtual array is generated by the relative motion between the transmitter and the receiver. This paper presents synthetic aperture acoustic communication results using SC-FDE through data collected during a lake experiment in January 2016. The performance of two receiver algorithms is analyzed and compared, including the frequency domain equalizer (FDE) and the hybrid time frequency domain equalizer (HTFDE). The distances between the transmitter and the receiver in the experiment were about 5 km. The bit error rate (BER) and output signal-to-noise ratio (SNR) performances with different receiver elements and transmission numbers were presented. After combining multiple transmissions, error-free reception using a convolution code with a data rate of 8 kbps was demonstrated. PMID:28684683

Modal processing for acoustic communications in shallow water experiment.

PubMed

Morozov, Andrey K; Preisig, James C; Papp, Joseph

2008-09-01

Acoustical array data from the Shallow Water Acoustics experiment was processed to show the feasibility of broadband mode decomposition as a preprocessing method to reduce the effective channel delay spread and concentrate received signal energy in a small number of independent channels. The data were collected by a vertical array designed at the Woods Hole Oceanographic Institution. Phase-shift Keying (PSK) m-sequence modulated signals with different carrier frequencies were transmitted at a distance 19.2 km from the array. Even during a strong internal waves activity a low bit error rate was achieved.

A functional hybrid memristor crossbar-array/CMOS system for data storage and neuromorphic applications.

PubMed

Kim, Kuk-Hwan; Gaba, Siddharth; Wheeler, Dana; Cruz-Albrecht, Jose M; Hussain, Tahir; Srinivasa, Narayan; Lu, Wei

2012-01-11

Crossbar arrays based on two-terminal resistive switches have been proposed as a leading candidate for future memory and logic applications. Here we demonstrate a high-density, fully operational hybrid crossbar/CMOS system composed of a transistor- and diode-less memristor crossbar array vertically integrated on top of a CMOS chip by taking advantage of the intrinsic nonlinear characteristics of the memristor element. The hybrid crossbar/CMOS system can reliably store complex binary and multilevel 1600 pixel bitmap images using a new programming scheme. © 2011 American Chemical Society

A vertically aligned carbon nanotube-based impedance sensing biosensor for rapid and high sensitive detection of cancer cells.

PubMed

Abdolahad, Mohammad; Taghinejad, Mohammad; Taghinejad, Hossein; Janmaleki, Mohsen; Mohajerzadeh, Shams

2012-03-21

A novel vertically aligned carbon nanotube based electrical cell impedance sensing biosensor (CNT-ECIS) was demonstrated for the first time as a more rapid, sensitive and specific device for the detection of cancer cells. This biosensor is based on the fast entrapment of cancer cells on vertically aligned carbon nanotube arrays and leads to mechanical and electrical interactions between CNT tips and entrapped cell membranes, changing the impedance of the biosensor. CNT-ECIS was fabricated through a photolithography process on Ni/SiO(2)/Si layers. Carbon nanotube arrays have been grown on 9 nm thick patterned Ni microelectrodes by DC-PECVD. SW48 colon cancer cells were passed over the surface of CNT covered electrodes to be specifically entrapped on elastic nanotube beams. CNT arrays act as both adhesive and conductive agents and impedance changes occurred as fast as 30 s (for whole entrapment and signaling processes). CNT-ECIS detected the cancer cells with the concentration as low as 4000 cells cm(-2) on its surface and a sensitivity of 1.7 × 10(-3)Ω cm(2). Time and cell efficiency factor (TEF and CEF) parameters were defined which describe the sensor's rapidness and resolution, respectively. TEF and CEF of CNT-ECIS were much higher than other cell based electrical biosensors which are compared in this paper.

Optical Phased Array Antennas using Coupled Vertical Cavity Surface Emitting Lasers

NASA Technical Reports Server (NTRS)

Mueller, Carl H.; Rojas, Roberto A.; Nessel, James A.; Miranda, Felix A.

2007-01-01

High data rate communication links are needed to meet the needs of NASA as well as other organizations to develop space-based optical communication systems. These systems must be robust to high radiation environments, reliable, and operate over a wide temperature range. Highly desirable features include beam steering capability, reconfigurability, low power consumption, and small aperture size. Optical communication links, using coupled vertical cavity surface emitting laser radiating elements are promising candidates for the transmit portion of these communication links. In this talk we describe a mission scenario, and how the antenna requirements are derived from the mission needs. We describe a potential architecture for this type of antenna, and outline the advantages and drawbacks of this approach relative to competing technologies. The technology we are proposing used coupled arrays of 1550 nm vertical cavity surface emitting lasers for transmission. The feasibility of coupling these arrays together, to form coherent high-power beams that can be modulated at data rates exceeding 1 Gbps, will be explored. We will propose an architecture that enables electronic beam steering, thus mitigating the need for ancillary acquisition, tracking and beam pointing equipment such as needed for current optical communicatin systems. The beam-steering capability we are proposing also opens the possibility of using this technology for inter-satellite communicatin links, and satellite-to-surface links.

Self-bridging of vertical silicon nanowires and a universal capacitive force model for spontaneous attraction in nanostructures.

PubMed

Sun, Zhelin; Wang, Deli; Xiang, Jie

2014-11-25

Spontaneous attractions between free-standing nanostructures have often caused adhesion or stiction that affects a wide range of nanoscale devices, particularly nano/microelectromechanical systems. Previous understandings of the attraction mechanisms have included capillary force, van der Waals/Casimir forces, and surface polar charges. However, none of these mechanisms universally applies to simple semiconductor structures such as silicon nanowire arrays that often exhibit bunching or adhesions. Here we propose a simple capacitive force model to quantitatively study the universal spontaneous attraction that often causes stiction among semiconductor or metallic nanostructures such as vertical nanowire arrays with inevitably nonuniform size variations due to fabrication. When nanostructures are uniform in size, they share the same substrate potential. The presence of slight size differences will break the symmetry in the capacitive network formed between the nanowires, substrate, and their environment, giving rise to electrostatic attraction forces due to the relative potential difference between neighboring wires. Our model is experimentally verified using arrays of vertical silicon nanowire pairs with varied spacing, diameter, and size differences. Threshold nanowire spacing, diameter, or size difference between the nearest neighbors has been identified beyond which the nanowires start to exhibit spontaneous attraction that leads to bridging when electrostatic forces overcome elastic restoration forces. This work illustrates a universal understanding of spontaneous attraction that will impact the design, fabrication, and reliable operation of nanoscale devices and systems.

Fractal-Based Lightning Channel Length Estimation from Convex-Hull Flash Areas for DC3 Lightning Mapping Array Data

NASA Technical Reports Server (NTRS)

Bruning, Eric C.; Thomas, Ronald J.; Krehbiel, Paul R.; Rison, William; Carey, Larry D.; Koshak, William; Peterson, Harold; MacGorman, Donald R.

2013-01-01

We will use VHF Lightning Mapping Array data to estimate NOx per flash and per unit channel length, including the vertical distribution of channel length. What s the best way to find channel length from VHF sources? This paper presents the rationale for the fractal method, which is closely related to the box-covering method.

Microtremor exploration for shallow S-wave velocity structure in Bandung Basin, Indonesia

NASA Astrophysics Data System (ADS)

Pramatadie, Andi Muhamad; Yamanaka, Hiroaki; Chimoto, Kosuke; Afnimar Collaboration; Koketsu, Kazuki; Sakaue, Minoru; Miyake, Hiroe; Sengara, I. Wayan; Sadisun, Imam A.

2017-05-01

We have conducted a microtremor survey for shallow S-wave velocity profiles to be used for seismic hazard evaluation in the Bandung Basin, Indonesia. In the survey, two arrays were deployed temporarily at each of 29 sites, by installing seven vertical sensors in triangular configurations with side lengths from 1 to 16 m. Records of vertical microtremors from each array were used to estimate Rayleigh wave phase velocity spectra using the spatial autocorrelation method, as well as the horizontal-to-vertical spectral ratio obtained at the centre of the arrays. Phase velocities at sites on the basin margin exhibit higher values than those obtained in the central part of the basin, in a frequency range of 7 to 30 Hz. The phase velocity data were used to deduce S-wave velocity profiles of shallow soil using a hybrid heuristic inversion method. We validated our inversion models by comparing observed horizontal-to-vertical spectral ratios with ellipticities of the fundamental mode of Rayleigh waves, calculated for the inversion models. The S-wave velocity profiles in the area can be characterised by two soft layers over a firm engineering basement that has an S-wave velocity of 500 m/s. The S-wave velocities of the two layers are 120 and 280 m/s on average. The distribution of the averaged S-wave velocity in the top 30 m clearly indicates low values in the eastern central part and high values in the edge of the basin. The amplification is large in the areas with low velocity layers. In addition, we have proposed an empirical relation between the amplification factor and the topographical slope in the area.

Design of diffractive microlens array integration with focal plane arrays

NASA Astrophysics Data System (ADS)

Chen, Sihai; Yi, Xinjian; Li, Yi; He, Miao; Chen, Sixiang; Kong, Lingbin

2000-10-01

The IR spectrum from 3 to 5micrometers has numerous applications in both military and civil industries. High performance at high operating temperature is often important in these applications. Conventional Focal Plane Arrays (FPAs) without integration with concentrator such as microlens have poor sensitivity and low signal-to-noise ratio because of their lower fill factor. The binary optics microlens arrays reported in this paper are designed for integration with FPAs. Thus, the FPAs' fill factor, sensitivity, and signal- to-noise ratio can be improved while retaining a given image resolution and optical collection area. In the paper, we discussed the 256(Horizontal)x290(Vertical) microlens arrays designed for a center wavelength of 4micrometers , with 50micrometers (Horizontalx33micrometers (Vertical) quadrate pixel dimension and a speed (F number) of F/1.96. PtSi FPAs were fabricated on the front side of a 400-micrometers -thick Si substrate. The designed diffractive microlens arrays will be etched on the back side of the same wafer in a register fashion and it will be reported in other paper. Considering the diffraction efficiency, 8-phase-level approximation is enough. For the diffraction efficiency of 8-phase-level diffractive microlens reaches 95%. The process only need three mask-level, so we designed and fabricated three masks with the same dimension 4'x4'. Also, a set of fine verniers was designed and fabricated on each mask to allow accurate alignment during the fabrication process. Through a computer simulation, the microlens arrays are nearly diffraction limited, with the diffraction efficiency of 93%, a bit lower than the theoretical value of 95%. Introduction of microlens arrays has the ability to increase the FPAs' fill factor to 100%, while it is only about 21.6% without microlens. To our knowledge, this is the first trial of integration large area microlens arrays with FPAs at home.

Optical Characteristics of Vertical Cavity Surface Emitting Lasers and Two Dimensional Coherently Coupled Arrays.

NASA Astrophysics Data System (ADS)

Catchmark, Jeffrey Michael

1995-01-01

The following describes extensive experimental and theoretical research concerning the optical, electrical and thermal characteristics of GaAs/AlGaAs vertical cavity surface emitting lasers (VCSELs) and coherently coupled two dimensional VCSEL arrays grown by molecular beam epitaxy. The temperature and wavelength performance of VCSELs containing various epitaxial designs is discussed in detail. By employing a high barrier confinement spacer region and by blue shifting the optical gain with respect to the Fabry Perot transmission wavelength, greater than 150^circ rm C continuous wave operation was obtained. This is accomplished while maintaining a variation in the threshold current of only +/-0.93mA over a temperature range of 150^circrm C. This exceptional performance is achieved while attaining a minimum threshold current of approximately 4.3mA at 75^circrm C. In addition, the optical characteristics of multi-transverse mode VCSEL arrays are examined experimentally. A total of nine transverse modes have been identified and are found to couple coherently into distinct array modes. While operating in higher order transverse modes, a record 1.4W (pulsed) of optical power is obtained from a 15 x 15 VCSEL array. Array mode formation in coherently coupled VCSEL arrays is also examined theoretically. A numerical model is developed to describe the formation of supermodes in reflectivity modulated VCSEL arrays. Using this model, the effects of depth of reflectivity modulation, cavity length, window size and grid size on mode formation are explored. The array modes predicted by this model are in agreement with those observed experimentally. Analytic models will also be presented describing the effects of thermally induced waveguiding on the optical characteristics of VCSELs operating in the fundamental transverse mode. A thermal waveguide is found to have a significant effect on the spot size and radius of curvature of the phase of the fundamental optical mode. In addition, an analytic model is developed to predict the higher order transverse modes of a VCSEL exhibiting a cruciform type geometry.

The NASA Inductrack Model Rocket Launcher at the Lawrence Livermore National Laboratory

NASA Technical Reports Server (NTRS)

Tung, L. S.; Post, R. F.; Cook, E.; Martinez-Frias, J.

2000-01-01

The Inductrack magnetic levitation system, developed at the Lawrence Livermore National Laboratory, is being studied for its possible use for launching rockets. Under NASA sponsorship, a small model system is being constructed at the Laboratory to pursue key technical aspects of this proposed application. The Inductrack is a passive magnetic levitation system employing special arrays of high-field permanent magnets (Halbach arrays) on the levitating carrier, moving above a "track" consisting of a close-packed array of shorted coils with which are interleaved with special drive coils. Halbach arrays produce a strong spatially periodic magnetic field on the front surface of the arrays, while canceling the field on their back surface. Relative motion between the Halbach arrays and the track coils induces currents in those coils. These currents levitate the carrier cart by interacting with the horizontal component of the magnetic field. Pulsed currents in the drive coils, synchronized with the motion of the carrier, interact with the vertical component of the magnetic field to provide acceleration forces. Motional stability, including resistance to both vertical and lateral aerodynamic forces, is provided by having Halbach arrays that interact with both the upper and the lower sides of the track coils. In its completed form the model system that is under construction will have a track approximately 100 meters in length along which the carrier cart will be propelled up to peak speeds of Mach 0.4 to 0.5 before being decelerated. Preliminary studies of the parameters of a full-scale system have also been made. These studies address the problems of scale-up, including means to simplify the track construction and to reduce the cost of the pulsed-power systems needed for propulsion.

Programmable Aperture with MEMS Microshutter Arrays

NASA Technical Reports Server (NTRS)

Moseley, Samuel; Li, Mary; Kutyrev, Alexander; Kletetschka, Gunther; Fettig, Rainer

2011-01-01

A microshutter array (MSA) has been developed for use as an aperture array for multi-object selections in James Webb Space Telescope (JWST) technology. Light shields, molybdenum nitride (MoN) coating on shutters, and aluminum/aluminum oxide coatings on interior walls are put on each shutter for light leak prevention, and to enhance optical contrast. Individual shutters are patterned with a torsion flexure that permits shutters to open 90 deg. with a minimized mechanical stress concentration. The shutters are actuated magnetically, latched, and addressed electrostatically. Also, micromechanical features are tailored onto individual shutters to prevent stiction. An individual shutter consists of a torsion hinge, a shutter blade, a front electrode that is coated on the shutter blade, a backside electrode that is coated on the interior walls, and a magnetic cobalt-iron coating. The magnetic coating is patterned into stripes on microshutters so that shutters can respond to an external magnetic field for the magnetic actuation. A set of column electrodes is placed on top of shutters, and a set of row electrodes on sidewalls is underneath the shutters so that they can be electrostatically latched open. A linear permanent magnet is aligned with the shutter rows and is positioned above a flipped upside-down array, and sweeps across the array in a direction parallel to shutter columns. As the magnet sweeps across the array, sequential rows of shutters are rotated from their natural horizontal orientation to a vertical open position, where they approach vertical electrodes on the sidewalls. When the electrodes are biased with a sufficient electrostatic force to overcome the mechanical restoring force of torsion bars, shutters remain latched to vertical electrodes in their open state. When the bias is removed, or is insufficient, the shutters return to their horizontal, closed positions. To release a shutter, both the electrode on the shutter and the one on the back wall where the shutter sits are grounded. The shutters with one or both ungrounded electrodes are held open. Sub-micron bumps underneath light shields and silicon ribs on back walls are the two features to prevent stiction. These features ensure that the microshutter array functions properly in mechanical motions. The MSA technology can be used primarily in multi-object imaging and spectroscopy, photomask generation, light switches, and in the stepper equipment used to make integrated circuits and MEMS (microelectromechanical systems) devices.

Rules to fly by: pigeons navigating horizontal obstacles limit steering by selecting gaps most aligned to their flight direction.

PubMed

Ros, Ivo G; Bhagavatula, Partha S; Lin, Huai-Ti; Biewener, Andrew A

2017-02-06

Flying animals must successfully contend with obstacles in their natural environments. Inspired by the robust manoeuvring abilities of flying animals, unmanned aerial systems are being developed and tested to improve flight control through cluttered environments. We previously examined steering strategies that pigeons adopt to fly through an array of vertical obstacles (VOs). Modelling VO flight guidance revealed that pigeons steer towards larger visual gaps when making fast steering decisions. In the present experiments, we recorded three-dimensional flight kinematics of pigeons as they flew through randomized arrays of horizontal obstacles (HOs). We found that pigeons still decelerated upon approach but flew faster through a denser array of HOs compared with the VO array previously tested. Pigeons exhibited limited steering and chose gaps between obstacles most aligned to their immediate flight direction, in contrast to VO navigation that favoured widest gap steering. In addition, pigeons navigated past the HOs with more variable and decreased wing stroke span and adjusted their wing stroke plane to reduce contact with the obstacles. Variability in wing extension, stroke plane and wing stroke path was greater during HO flight. Pigeons also exhibited pronounced head movements when negotiating HOs, which potentially serve a visual function. These head-bobbing-like movements were most pronounced in the horizontal (flight direction) and vertical directions, consistent with engaging motion vision mechanisms for obstacle detection. These results show that pigeons exhibit a keen kinesthetic sense of their body and wings in relation to obstacles. Together with aerodynamic flapping flight mechanics that favours vertical manoeuvring, pigeons are able to navigate HOs using simple rules, with remarkable success.

High fill-factor micromirror array using a self-aligned vertical comb drive actuator with two rotational axes

NASA Astrophysics Data System (ADS)

Kim, Minsoo; Park, Jae-Hyoung; Jeon, Jin-A.; Yoo, Byung-Wook; Park, I. H.; Kim, Yong-Kweon

2009-03-01

We present a two-axis micromirror array with high fill-factor, using a new fabrication procedure on the full wafer scale. The micromirror comprises a self-aligned vertical comb drive actuator with a mirror plate mounted on it and electrical lines on a bottom substrate. A high-aspect-ratio vertical comb drive was built using a bulk micromachining technique on a silicon-on-insulator (SOI) wafer. The thickness of the torsion spring was adjusted using multiple silicon etching steps to enhance the static angular deflection of the mirrors. To address the array, electrical lines were fabricated on a glass substrate and combined with the comb actuators using an anodic bonding process. The silicon mirror plate was fabricated together with the actuator using a wafer bonding process and segmented at the final release step. The actuator and addressing lines were hidden behind the mirror plate, resulting in a high fill-factor of 84% in an 8 × 8 array of micromirrors, each 340 µm × 340 µm. The fabricated mirror plate has a high-quality optical surface with an average surface roughness (Ra) of 4 nm and a curvature radius of 0.9 m. The static and dynamic responses of the micromirror were characterized by comparing the measured results with the calculated values. The maximum static optical deflection for the outer axis is 4.32° at 60 V, and the maximum inner axis tilting angle is 2.82° at 96 V bias. The torsion resonance frequencies along the outer and inner axes were 1.94 kHz and 0.95 kHz, respectively.

Rules to fly by: pigeons navigating horizontal obstacles limit steering by selecting gaps most aligned to their flight direction

PubMed Central

Ros, Ivo G.; Bhagavatula, Partha S.; Lin, Huai-Ti

2017-01-01

Flying animals must successfully contend with obstacles in their natural environments. Inspired by the robust manoeuvring abilities of flying animals, unmanned aerial systems are being developed and tested to improve flight control through cluttered environments. We previously examined steering strategies that pigeons adopt to fly through an array of vertical obstacles (VOs). Modelling VO flight guidance revealed that pigeons steer towards larger visual gaps when making fast steering decisions. In the present experiments, we recorded three-dimensional flight kinematics of pigeons as they flew through randomized arrays of horizontal obstacles (HOs). We found that pigeons still decelerated upon approach but flew faster through a denser array of HOs compared with the VO array previously tested. Pigeons exhibited limited steering and chose gaps between obstacles most aligned to their immediate flight direction, in contrast to VO navigation that favoured widest gap steering. In addition, pigeons navigated past the HOs with more variable and decreased wing stroke span and adjusted their wing stroke plane to reduce contact with the obstacles. Variability in wing extension, stroke plane and wing stroke path was greater during HO flight. Pigeons also exhibited pronounced head movements when negotiating HOs, which potentially serve a visual function. These head-bobbing-like movements were most pronounced in the horizontal (flight direction) and vertical directions, consistent with engaging motion vision mechanisms for obstacle detection. These results show that pigeons exhibit a keen kinesthetic sense of their body and wings in relation to obstacles. Together with aerodynamic flapping flight mechanics that favours vertical manoeuvring, pigeons are able to navigate HOs using simple rules, with remarkable success. PMID:28163883

Thermal wave interference with high-power VCSEL arrays for locating vertically oriented subsurface defects

NASA Astrophysics Data System (ADS)

Thiel, Erik; Kreutzbruck, Marc; Studemund, Taarna; Ziegler, Mathias

2018-04-01

Among the photothermal methods, full-field thermal imaging is used to characterize materials, to determine thicknesses of layers, or to find inhomogeneities such as voids or cracks. The use of classical light sources such as flash lamps (impulse heating) or halogen lamps (modulated heating) led to a variety of nondestructive testing methods, in particular, lock-in and flash-thermography. In vertical-cavity surface-emitting lasers (VCSELs), laser light is emitted perpendicularly to the surface with a symmetrical beam profile. Due to the vertical structure, they can be arranged in large arrays of many thousands of individual lasers, which allows power scaling into the kilowatt range. Recently, a high-power yet very compact version of such a VCSEL-array became available that offers both the fast timing behavior of a laser as well as the large illumination area of a lamp. Moreover, it allows a spatial and temporal control of the heating because individual parts of the array can be controlled arbitrarily in frequency, amplitude, and phase. In conjunction with a fast infrared camera, such structured heating opens up a field of novel thermal imaging and testing methods. As a first demonstration of this approach, we chose a testing problem very challenging to conventional thermal infrared testing: The detection of very thin subsurface defects perpendicularly oriented to the surface of metallic samples. First, we generate destructively interfering thermal wave fields, which are then affected by the presence of defects within their reach. It turned out that this technique allows highly sensitive detection of subsurface defects down to depths in excess of the usual thermographic rule of thumb, with no need for a reference or surface preparation.

A CWDM photoreceiver module for 10 Gb/s x 4ch interconnection based on a vertical-illumination-type Ge-on-Si photodetectors and a silica-based AWG

NASA Astrophysics Data System (ADS)

Jang, Ki-Seok; Joo, Jiho; Kim, Taeyong; Kim, Sanghoon; Oh, Jin Hyuk; Kim, In Gyoo; Kim, Sun Ae; Kim, Gyungock

2015-03-01

We report a 40 Gb/s photoreceiver based on vertical-illumination type Ge-on-Si photodetectors and a silica-based AWG demultiplexer by employing 4-channel CWDM. The 60um-diameter Ge-on-Si photodetector arrays, grown on a bulk silicon wafer by RPCVD and fabricated with CMOS-compatible process, have ~0.9 A/W responsivity with 13 GHz bandwidth at λ ~ 1330nm. Ge-on-Si photodetector arrays are hybrid-integrated with TIA/LAs and directly-coupled to the AWG. The low-cost FPCB-package based photoreceiver module shows 10.3 Gb/s × 4-channel interconnection with -11 ~ -12.2 dBm sensitivity at a BER = 10-12.

Near-field effect in the infrared range through periodic Germanium subwavelength arrays.

PubMed

Dong, Wei; Hirohata, Toru; Nakajima, Kazutoshi; Wang, Xiaoping

2013-11-04

Using finite-difference-time-domain simulation, we have studied the near-field effect of Germanium (Ge) subwavelength arrays designed in-plane with a normal incidence. Spectra of vertical electric field component normal to the surface show pronounced resonance peaks in an infrared range, which can be applied in a quantum well infrared photodetector. Unlike the near-field optics in metallic systems that are commonly related to surface plasmons, the intense vertical field along the surface of the Ge film can be interpreted as a combination of diffraction and waveguide theory. The existence of the enhanced field is confirmed by measuring the Fourier transform infrared spectra of fabricated samples. The positions of the resonant peaks obtained in experiment are in good agreement with our simulations.

Elastogranular Mechanics: Buckling, Jamming, and Structure Formation.

PubMed

Schunter, David J; Brandenbourger, Martin; Perriseau, Sophia; Holmes, Douglas P

2018-02-16

Confinement of a slender body into a granular array induces stress localization in the geometrically nonlinear structure, and jamming, reordering, and vertical dislodging of the surrounding granular medium. By varying the initial packing density of grains and the length of a confined elastica, we identify the critical length necessary to induce jamming, and demonstrate how folds couple with the granular medium to localize along grain boundaries. Above the jamming threshold, the characteristic length of elastica deformation is shown to diverge in a manner that is coupled with the motion and rearrangement of the grains, suggesting the ordering of the granular array governs the deformation of the slender structure. However, overconfinement of the elastica will vertically dislodge grains, a form of stress relaxation in the granular medium that illustrates the intricate coupling in elastogranular interactions.

Elastogranular Mechanics: Buckling, Jamming, and Structure Formation

NASA Astrophysics Data System (ADS)

Schunter, David J.; Brandenbourger, Martin; Perriseau, Sophia; Holmes, Douglas P.

2018-02-01

Confinement of a slender body into a granular array induces stress localization in the geometrically nonlinear structure, and jamming, reordering, and vertical dislodging of the surrounding granular medium. By varying the initial packing density of grains and the length of a confined elastica, we identify the critical length necessary to induce jamming, and demonstrate how folds couple with the granular medium to localize along grain boundaries. Above the jamming threshold, the characteristic length of elastica deformation is shown to diverge in a manner that is coupled with the motion and rearrangement of the grains, suggesting the ordering of the granular array governs the deformation of the slender structure. However, overconfinement of the elastica will vertically dislodge grains, a form of stress relaxation in the granular medium that illustrates the intricate coupling in elastogranular interactions.

The calibration of an HF radar used for ionospheric research

NASA Astrophysics Data System (ADS)

From, W. R.; Whitehead, J. D.

1984-02-01

The HF radar on Bribie Island, Australia, uses crossed-fan beams produced by crossed linear transmitter and receiver arrays of 10 elements each to simulate a pencil beam. The beam points vertically when all the array elements are in phase, and is steerable by up to 20 deg off vertical at the central one of the three operating frequencies. Phase and gain changes within the transmitters and receivers are compensated for by an automatic system of adjustment. The 10 transmitting antennas are, as nearly as possible, physically identical as are the 10 receiving antennas. Antenna calibration using high flying aircraft or satellites is not possible. A method is described for using the ionospheric reflections to measure the polar diagram and also to correct for errors in the direction of pointing.

Control of Heat and Charge Transport in Nanostructured Hybrid Materials

DTIC Science & Technology

2015-07-21

measurements in our groups have yielded device ZT values of 0.4 on thermoelectric modules consisting of vertically oriented silicon nanowires . This is... nanowires with aspect ratio’s exceeding 10,000. Temperature differences as high as 800 °C are achievable for both types. The bulk nanostructured...thermal conductivity of the silicon nanostructures. Specifically, experiments on an array of 20 nm diameter vertically oriented silicon nanowires have

Disposable sensor based on enzyme-free Ni nanowire array electrode to detect glutamate.

PubMed

Jamal, Mamun; Hasan, Maksudul; Mathewson, Alan; Razeeb, Kafil M

2013-02-15

Enzyme free electrochemical sensor platform based on a vertically aligned nickel nanowire array (NiNAE) and Pt coated nickel nanowire array (Pt/NiNAE) have been developed to detect glutamate. Morphological characterisation of Ni electrodes was carried out using scanning and transmission electron microscopy combined with energy dispersive X-ray (SEM-EDX), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Cyclic voltammetry (CV) and amperometry were used to evaluate the catalytic activity of the NiNAE and the Pt/NiNAE for glutamate. It has been found that both NiNAE and Pt/NiNAE electrodes showed remarkably enhanced electrocatalytic activity towards glutamate compared to planar Ni electrodes, and showed higher catalytic activity when compared to other metallic nanostructure electrodes such as gold nanowire array electrodes (AuNAE) and Pt coated gold nanowire array electrode (Pt/AuNAE). The sensitivity of NiNAE and Pt/NiNAE has been found to be 65 and 96 μA mM(-1) cm(-2), respectively, which is approximately 6 to 9 times higher than the state of the art glutamate sensor. Under optimal detection conditions, the as prepared sensors exhibited linear behaviour for glutamate detection in the concentration up to 8mM for both NiNAE and Pt/NiNAE with a limit of detection of 68 and 83 μM, respectively. Experimental results show that the vertically aligned ordered nickel nanowire array electrode (NiNAE) has significant promise for fabricating cost effective, enzyme-less, sensitive, stable and selective sensor platform. Copyright © 2012 Elsevier B.V. All rights reserved.

Electrical and optical properties of binary CNx nanocone arrays synthesized by plasma-assisted reaction deposition.

PubMed

Liu, Xujun; Guan, Leilei; Fu, Xiaoniu; Zhao, Yu; Wu, Jiada; Xu, Ning

2014-03-21

Light-absorbing and electrically conductive binary CNx nanocone (CNNC) arrays have been fabricated using a glow discharge plasma-assisted reaction deposition method. The intact CNNCs with amorphous structure and central nickel-filled pipelines could be vertically and neatly grown on nickel-covered substrates according to the catalyst-leading mode. The morphologies and composition of the as-grown CNNC arrays can be well controlled by regulating the methane/nitrogen mixture inlet ratio, and their optical absorption and resistivity strongly depend on their morphologies and composition. Beside large specific surface area, the as-grown CNNC arrays demonstrate high wideband absorption, good conduction, and nice wettability to polymer absorbers.

Ultrahigh-density nanowire arrays grown in self-assembled diblock copolymer templates.

PubMed

Thurn-Albrecht, T; Schotter, J; Kästle, G A; Emley, N; Shibauchi, T; Krusin-Elbaum, L; Guarini, K; Black, C T; Tuominen, M T; Russell, T P

2000-12-15

We show a simple, robust, chemical route to the fabrication of ultrahigh-density arrays of nanopores with high aspect ratios using the equilibrium self-assembled morphology of asymmetric diblock copolymers. The dimensions and lateral density of the array are determined by segmental interactions and the copolymer molecular weight. Through direct current electrodeposition, we fabricated vertical arrays of nanowires with densities in excess of 1.9 x 10(11) wires per square centimeter. We found markedly enhanced coercivities with ferromagnetic cobalt nanowires that point toward a route to ultrahigh-density storage media. The copolymer approach described is practical, parallel, compatible with current lithographic processes, and amenable to multilayered device fabrication.

Large-scale fabrication of vertically aligned ZnO nanowire arrays

DOEpatents

Wang, Zhong Lin; Hu, Youfan; Zhang, Yan; Xu, Chen; Zhu, Guang

2014-09-09

A generator includes a substrate, a first electrode layer, a dense plurality of vertically-aligned piezoelectric elongated nanostructures, an insulating layer and a second electrode layer. The substrate has a top surface and the first electrode layer is disposed on the top surface of the substrate. The dense plurality of vertically-aligned piezoelectric elongated nanostructures extends from the first electrode layer. Each of the nanostructures has a top end. The insulating layer is disposed on the top ends of the nanostructures. The second electrode layer is disposed on the non-conductive layer and is spaced apart from the nanostructures.