Pre-Holocene to Modern Evolution of the Lower Delaware Estuary: Constraints from High-Resolution Chirp Subbottom Profiles

NASA Astrophysics Data System (ADS)

Daw, Julianne

Throughout the Quaternary Period, the Delaware Estuary, which is located within the Mid-Atlantic region of the United States, has undergone substantial change as a result of sea-level fluctuations. To better understand the recent (late Pleistocene to Holocene) evolution of the region, chirp subbottom profiles were analyzed within Delaware Bay near the southern end of the Delaware River Navigation Channel including the adjacent shoals and sloughs, using RoxAnn bottom classification data and available vibracores to aid in interpreting sediment types and depositional environments within the study area. Using seismic processing software (SonarWiz6), chirp profiles were processed and reflection events were identified and their positions digitized. Major reflection events were analyzed using a seismic facies approach. The identified facies were each characterized as distinct units composed of reflections with unique elements, such as configuration, amplitude, and continuity. Five seismic facies were identified and their thicknesses determined. Depths to the major reflection events were correlated with sediment boundaries as observed in the available vibracores, allowing the seismic facies to be interpreted in terms of their associated sediment types and inferred environments of deposition. The distributions of surficial and subsurface seismic and sedimentological features were visualized using three-dimensional images. The interpretations of the identified facies are as follows: Facies I is a surficial unit of the modern Holocene estuarine deposits; Facies II is a beach-berm washover zone deposition; Facies III is a deposit of a lagoonal environment; Facies IV is a deposit of an open water environment; and Facies V is a marsh deposition. The chirp data, when integrated with available information from vibracores and RoxAnn bottom sediment classification, was also used to map the position of a former major river system (paleochannel). This paleochannel, trending generally northwest to southeast, can be correlated with the southern channel that was identified in previous work by Knebel and Circe (1988). In addition to the knowledge gained by studying the geological evolution of Delaware Bay, our data can be used by decision makers and stakeholders to inform future management of the Delaware Estuary in practical applications that range from planning for maintenance dredging of the navigation channel to determining locations and thicknesses of suitable sand resources for shoreline replenishment. The surficial layer that would be most affected by such applications is mostly composed of sand & muddy sand, but in the deeper portions and along the shoals, it is composed of mixed and coarse sediments and mud & sandy mud, respectively. Furthermore, the surficial unit is thickest (between 1.5 and 4 meters) in the central and eastern regions of the study area encompassing the deeper portions, and it is thinnest (up to 1 meter) along the western and northern regions that include the shoals.

Near-surface stratigraphy and morphology, Mississippi Inner Shelf, northern Gulf of Mexico

USGS Publications Warehouse

Flocks, James G.; Kindinger, Jack; Kelso, Kyle W.; Bernier, Julie C.; DeWitt, Nancy T.; FitzHarris, Michael

2015-01-01

In June 2013, as part of the MsCIP project, the USGS conducted a geophysical survey consisting of about 650 line-kilometers (km), encompassing an area of approximately 212 square kilometers (km2). The survey area extended from 1 to 13 km offshore of Petite Bois Island. The geophysical investigation included interferometric swath bathymetry, sidescan sonar, and chirp subbottom profiling. The intent of the survey was to provide geologic information that would assist the USACE in developing a sediment sampling strategy for identifying deposits suitable for shoreline restoration operations. The data from the geophysical survey would also further our understanding of the geologic framework along the inner shelf. Numerous seafloor and subbottom features were identified. At the surface, shoals and shelf sand sheets of various sizes and orientations are the predominant morphology. In the subsurface, Holocene- and Pleistocene-age features include marine transgressive deposits infilling older fluvia distributary systems. These interpretations from the geophysical research were integrated with sediment cores collected by the USGS and USACE to provide textural and volumetric information.

Geophysical Data from Offshore of the Chandeleur Islands, Eastern Mississippi Delta

USGS Publications Warehouse

Baldwin, Wayne E.; Pendleton, Elizabeth A.; Twichell, David C.

2009-01-01

This report contains the geophysical and geospatial data that were collected during two cruises on the R/V Acadiana along the eastern, offshore side of the Chandeleur Islands in 2006 and 2007. Data were acquired with the following equipment: a Systems Engineering and Assessment, Ltd., SwathPlus interferometric sonar; a Klein 3000 dual-frequency sidescan sonar; and an EdgeTech 512i chirp sub-bottom profiling system. The long-term goal of this mapping effort is to produce high-quality, high-resolution geologic maps and geophysical interpretations that can be utilized to investigate the impact of Hurricane Katrina, identify sand resources within the region, and make predictions regarding the future evolution of this coastal system.

High-resolution geophysical data from the inner continental shelf—Buzzards Bay, Massachusetts

USGS Publications Warehouse

Ackerman, Seth D.; Andrews, Brian D.; Foster, David S.; Baldwin, Wayne E.; Schwab, William C.

2012-01-01

The U.S. Geological Survey (USGS) and the Massachusetts Office of Coastal Zone Management (CZM) have cooperated to map approximately 410 square kilometers (km²) of the inner continental shelf in Buzzards Bay, Massachusetts. This report contains geophysical data collected by the USGS on three cruises conducted in 2009, 2010, and 2011, and additional bathymetry data collected by the National Oceanic and Atmospheric Administration in 2004. The geophysical data include (1) swath bathymetry using interferometric sonar and multibeam echosounder systems, (2) acoustic backscatter from sidescan sonar, and (3) seismic-reflection profiles from a chirp subbottom profiler. These spatial data support research on the Quaternary evolution of Buzzards Bay, the influence of sea-level change and sediment supply on coastal evolution, and efforts to understand the type, distribution, and quality of subtidal marine habitats in the coastal ocean of Massachusetts.

MBARI Mapping AUV: A High-Resolution Deep Ocean Seafloor Mapping Capability

NASA Astrophysics Data System (ADS)

Caress, D. W.; Kirkwood, W. J.; Thomas, H.; McEwen, R.; Henthorn, R.; McGill, P.; Thompson, D.; Sibenac, M.; Jensen, S.; Shane, F.; Hamilton, A.

2005-05-01

The Monterey Bay Aquarium Research Institute (MBARI) is developing an autonomous seafloor mapping capability for deep ocean science applications. The MBARI Mapping AUV is a 0.53 m (21 in) diameter, 5.1 m (16.7 ft) long, Dorado-class vehicle designed to carry four mapping sonars. The primary sensor is a 200 kHz multibeam sonar producing swath bathymetry and sidescan. In addition, the vehicle carries 100 kHz and 410 kHz chirp sidescan sonars, and a 2-16 kHz sweep chirp subbottom profiler. Navigation and attitude data are obtained from an inertial navigation system (INS) incorporating a ring laser gyro and a 300 kHz Doppler velocity log (DVL). The vehicle also includes acoustic modem, ultra-short baseline navigation, and long-baseline navigation systems. The Mapping AUV is powered by 6 kWhr of Li-polymer batteries, providing expected mission duration of 12 hours at a typical speed of 1.5 m/s. All components of the vehicle are rated to 6000 m depth, allowing MBARI to conduct high-resolution mapping of the deep-ocean seafloor. The sonar package is also be mountable on ROV Ventana, allowing surveys at altitudes less than 20 m at topographically challenging sites. The vehicle was assembled and extensively tested during 2004; this year we are commencing operations for MBARI science projects while continuing the process of testing and integrating the complete suite of sensors and systems. MBARI is beginning to use this capability to observe the changing morphology of dynamic systems such as submarine canyons and active slumps, to map deep-water benthic habitats at resolutions comparable to ROV and submersible observations, to provide basemaps for ROV dives, and to provide high resolution bathymetry and subbottom profiles as part of a variety of projects requiring knowledge of the seafloor. We will present initial results from surveys in and around Monterey Canyon, including high resolution repeat surveys of four sites along the canyon axis.

Pelagic erosion and sedimentation north of Carnegie Ridge, eastern equatorial Pacific

NASA Astrophysics Data System (ADS)

Brooks, C. K.; Lyle, M. W.; Marcantonio, F.; Lewis, D. M.; Paul, C.

2011-12-01

The Carnegie Ridge is one of three bathymetric highs bounding the Panama Basin and is known to exhibit erosion and redeposition of pelagic sediments. The extent of erosion and redeposition was studied during the R/V Melville cruise MV1014 in November 2010 to compare with geochemical estimates of sediment focusing. The MV1014 cruise acquired geochemical, geological and geophysical data using multichannel 2-D seismic and 3.5 kHz sub-bottom profiler, swathmap bathymetry, coring, and water casts. The seismic reflection, digital sub-bottom profiler and swathmap bathymetry data were used to investigate biogenic sedimentary deposition in the Panama Basin and erosion from Carnegie Ridge. We compare the new geophysical results with drilling on ODP Leg 202, the NEMO-03 site survey cruise for Leg 202, an early survey from 1969 and other data compiled by Ecuadorian surveys. Areas of non-deposition and/or erosion include the bathymetric highs along the ridge, seamounts, and an area of interest, a valley located on the northwestern flank of the ridge. The valley encompasses 183 km2 and exhibits large scale erosion, cutting down through sediments deposited over the 10-million year life of this segment of the Carnegie Ridge. All other valleys located within the Carnegie Ridge study area demonstrate ample deposition with sedimentary packages ranging from 200-800m with an average value trending around 400m. Higher sediment deposition is found in basins to the north of the erosional valley but similar sedimentation is also found even further north, beyond intervening high topography. The thickest sediment deposit near the Carnegie Ridge is actually found on the southern flank of the ridge, more than 100 km to the south of the survey area. Digital chirp sub-bottom profiler data combined with high-resolution seismic illustrate changes in sedimentation and erosion on the Carnegie Ridge, highlighting the dynamic sedimentary environment.

The glacimarine sediment budget of the Nares Strait-Petermann Fjord area since the Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Jakobsson, M.; Hogan, K.; Mayer, L. A.; Mix, A. C.; Nielsen, T.; Kamla, E.; Stranne, C.; Eriksson, B.; Jerram, K.

2016-12-01

During the Petermann 2015 Expedition of the Swedish icebreaker Oden more than 6500 line-km of high-resolution chirp sub-bottom profiles (2-7 kHz) were acquired in Petermann Fjord and Nares Strait in the area immediately outside of the fjord. The sub-bottom profiles reveal a highly-variable distribution of post-glacial sediment that appears to be largely controlled by the rugged relief of the underlying bedrock. Sediment thicknesses are between 0-60 m above bedrock and comprise predominantly acoustically-stratified, homogeneous to transparent acoustic facies. In Petermann Fjord itself unlithified sediment cover typically comprises two units: an underlying acoustically-transparent unit overlain by an acoustically-stratified unit. Both of these units are conformable over scoured and fairly flat bedrock terrain; small basins are present only locally. Outside of the fjord are a few local sedimentary basins containing up to 40 m of stratified basin-fill deposits, and several areas of stacked mass-flow deposits. Glacial lineations both in the fjord and Nares Strait are formed in an acoustically-homogenous unit that underlies stratified and transparent units. In addition to the sub-bottom profiles, approximately 780 line-km of 2D seismic reflection profiles were acquired using an airgun (210 cu in.) and a 300-m long streamer. These profiles have allowed us to map full unlithified sediment thicknesses down to basement in the area. Here we present the results of this mapping and we calculate the volumes of a prominent grounding-zone wedge at the mouth of Petermann Fjord, and smaller GZWs in Kennedy Channel. These features demarcate former still-stand positions of grounded ice retreating through this system, both towards the present-day grounding line of Petermann Glacier and southwards through Nares Strait. Post-glacial sediment volumes are also calculated and the sedimentary processes responsible for their distribution examined. These data, when combined with chronological information, will provide sediment fluxes through the Petermann system and help us to identify how the system has responded to a past global warming event, namely the last deglaciation. This is particularly important in light of the recent thinning and acceleration of NW Greenland's marine-terminating outlet glaciers at present.

2008 Joint United States-Canadian program to explore the limits of the Extended Continental Shelf aboard the U.S. Coast Guard cutter Healy--Cruise HLY0806

USGS Publications Warehouse

Childs, Jonathan R.; Triezenberg, Peter J.; Danforth, William W.

2012-01-01

In September 2008, the U.S. Geological Survey (USGS), in cooperation with Natural Resources Canada, Geological Survey of Canada (GSC), conducted bathymetric and geophysical surveys in the Arctic Beaufort Sea aboard the U.S. Coast Guard cutter USCGC Healy. The principal objective of this mission to the high Arctic was to acquire data in support of delineation of the outer limits of the U.S. and Canadian Extended Continental Shelf (ECS) in the Arctic Ocean in accordance with the provisions of Article 76 of the Law of the Sea Convention. The Healy was accompanied by the Canadian Coast Guard icebreaker Louis S. St- Laurent. The science parties on the two vessels consisted principally of staff from the USGS (Healy), and the GSC and the Canadian Hydrographic Service (Louis). The crew included marine mammal and Native-community observers, ice observers, and biologists conducting research of opportunity in the Arctic Ocean. The joint survey proved an unqualified success. The Healy collected 5,528 km of swath (multibeam) bathymetry (38,806 km2) and CHIRP subbottom profile data, with accompanying marine gravity measurements. The Louis acquired 2,817 km of multichannel seismic (airgun) deep-penetration reflection-profile data along 12 continuous lines, as well as 35 sonobuoy refraction stations and accompanying single-beam bathymetry. The coordinated efforts of the two vessels resulted in seismic-reflection profile data of much higher quality and continuity than if the data had been acquired with a single vessel alone. Equipment failure rate of the seismic equipment gear aboard the Louis was greatly improved with the advantage of having a leading icebreaker. When ice conditions proved too severe to deploy the seismic system, the Louis led the Healy, resulting in much improved quality of the swath bathymetry and CHIRP sub-bottom data in comparison with data collected by the Healy in the lead or working alone. Ancillary science objectives, including ice observations, deployment of ice-monitoring buoys and water-column sampling for biologic (phytoplankton) studies, were also successfully accomplished.

Geophysical data from offshore of the Gulf Islands National Seashore, Cat Island to Western Horn Island, Mississippi

USGS Publications Warehouse

Pendleton, E.A.; Baldwin, W.E.; Danforth, W.W.; DeWitt, N.T.; Forde, A.S.; Foster, D.S.; Kelso, K.W.; Pfeiffer, W.R.; Turecek, A.M.; Flocks, J.G.; Twichell, D.C.

2011-01-01

This report contains the geophysical and geospatial data that were collected along the western offshore side of the Gulf Islands of Mississippi on the research vessel Tommy Munro during two cruises in 2010. Geophysical data were collected by the U.S. Geological Survey in Woods Hole, Massachusetts, and St. Petersburg, Forida, in cooperation with the U.S. Army Corps of Engineers Mobile District. Bathymetric-sonar, sidescan-sonar, and Chirp seismic-reflection data were acquired with the following equipment, respectively: Systems Engineering and Assessment, Ltd., SwathPlus interferometric sonars; Klein 3000 and 3900 dual-frequency sidescan sonars; and an EdgeTech 512i Chirp sub-bottom profiling system. The long-term goals of this mapping effort are to produce high-quality, high-resolution geologic maps and interpretations that can be utilized to identify sand resources within the region, to better understand the Holocene evolution, and to anticipate future changes in this coastal system. Processed geospatial data files and the geophysical data provided in this report help attain these goals.

High resolution shallow imaging of the mega-splay fault in the central Nankai Trough off Kumano

NASA Astrophysics Data System (ADS)

Ashi, J.

2012-12-01

Steep slopes are continuously developed at water depths between 2200 to 2800 m at the Nankai accretionary prism off Kumano. These slopes are interpreted to be surface expressions caused by the megasplay fault on seismic reflection profiles. The fault plane has been drilled at multiple depths below seafloor by IODP NanTroSEIZE project. Mud breccias only recognized at the hanging wall of the fault (Site C0004) by Xray CT scanner are interpreted be formed by strong ground shaking and the age of the shallowest event of mud breccia layers suggests deformation in 1944 Tonankai earthquake (Sakaguchi et al., 2011). Detailed structures around the fault have been examined by seismic reflection profiles including 3D experiments. Although the fault plane deeper than 100 m is well imaged, the structure shallower than 100 m is characterized by obscure sediment veneer suggesting no recent fault activity. Investigation of shallow deformation structures is significant for understanding of recent tectonic activity. Therefore, we carried out deep towed subbottom profile survey by ROV NSS (Navigable Sampling System) during Hakuho-maru KH-11-9 cruise. We introduced a chirp subbottom profiling system of EdgeTech DW-106 for high resolution mapping of shallow structures. ROV NSS also has capability to take a long core with a pinpoint accuracy. The subbottom profiler crossing the megasplay fault near Site C0004 exhibits a landward dipping reflector suggesting the fault plane. The shallowest depth of the reflector is about 10 m below seafloor and the strata above it shows reflectors parallel to the seafloor without any topographic undulation. The fault must have displaced the shallow formation because intense deformation indicated by mud breccia was restricted to near fault zone. Slumping or sliding probably modified the shallow formation after the faulting. The shallow deformations near the megasplay fault were well imaged at the fault scarp 20 km southwest of Site C0004. Although the fault plane itself is not recognized, displacements of sedimentary layers are observed along the fault up to 30 meter below the seafloor. Landward dip of the fault is estimated to be 30 degrees. Displacements of strata are about 3 m near the surface and about 5 m at 7 m below the seafloor suggesting accumulation of fault displacement. The structure more than 30 m below the seafloor is obscure due to decrease of acoustic signal. Active cold seep is expected in this site by high heat flow (Yamano et al., 2012) and many trails of Calyptogena detected by seafloor observations. These results are consistent with the shallow structures reveled by our subbottom profiling survey. References Sakaguchi, A. et al., Geology 39, 919-922, 2011. Yamano, M. et al., JpGU Meeting abstract, SSS38-P23, 2012

CHIRP survey of the submerged harbors of King Herod's Caesarea, offshore Israel - looking for evidence of ancient disasters

NASA Astrophysics Data System (ADS)

Austin, J. A.; Goodman-Tchernov, B.

2012-12-01

Caesarea Maritima, located on the Israel coast south of Haifa, is an ancient city/harbor site built ~2,000 years ago that continues to produce important insights into both the maritime livelihoods of antiquity and natural/anthropogenic influences on coastal structures/processes. The grandiose, three-basin harbor complex was built by Herod the Great. Today, the inner harbor basin is terrestrial, while the majority of the intermediate/outer harbors lies 1-7 m beneath the sea surface. Explanations for the harbor's destruction have included earthquakes, liquefaction, deterioration from erosion, storm undercutting and tsunami damage. Recently, evidence for tsunami events has been discovered offshore during excavation and coring expeditions, specifically trench exposures and pneumatic hammer cores. Stratigraphic horizons containing tsunamite signatures suggest the occurrence of at least three tsunamis in the past ~3,500 yrs. One may correspond with the catastrophic eruption of Santorini ~1500 BC; another appears to have done significant damage to Caesarea ~115 AD, and a third occurred within the period 5th-7th centuries AD. Extant combined bathymetric/magnetic surveys offshore also show unusual, anomalous features. Excavations in 2003 suggest that these features may be part of an ancient designated anchoring station, and support the existence of underlying man-made terrestrial structures from an earlier period when sea-level was lower. The primary goal of the current survey was to correlate recognized/potential tsunamigenic sediment layers throughout the proximal shelf offshore Caesarea, using extremely high-resolution geophysical images. Such surficial sub-bottom profiling will allow archaeologists to proceed with investigations of recognized anthropogenically-influenced submerged coastal features. The field survey was conducted in August 2011. Seismic data were collected using UTIG's portable Knudsen 320BP CHIRP (2.5-5.5 kHz) profiler, affixed to a metal pole mounted on the starboard flank of a ~8 m-long catamaran. Data acquisition was generally conducted from dawn to mid-day, when wind/wave conditions were most favorable. A dense (5-10 m average profile spacing) grid of profiles, both along-strike (spanning the entire harbor complex) and across-strike (from intermediate harbor to ~10-15 m of water), was acquired. Total track length is ~126 line-km. In certain places, multiple sub-bottom horizons can be traced and mapped; sub-seafloor penetrations up to ~ 4-5 m were occasionally achieved, particularly in deeper water. However, sub-bottom penetration is spatially variable in sand-prone sediments. Correlation difficulties relate both to uneven acoustic penetration and to the presence offshore of "kurkar" ridges, calcareous sandstone ridges paralleling the modern shoreline that represent now-submerged Pleistocene dune complexes. These ancient dunes can produce physical barriers that both alter the depositional regime as well as complicate the acoustic mapping task. Mapped horizons within the survey area will be shown, along with preliminary correlations to the stratigraphy described from previously cored sediments (e.g., interpreted "tsunamites").

Transpressional Tectonics across the N. American-Caribbean Plate Boundary: Preliminary Results of a Multichannel Seismic Survey of Lake Azuei, Haiti.

NASA Astrophysics Data System (ADS)

Hearn, C. K.; Cormier, M. H.; Sloan, H.; Wattrus, N. J.; Boisson, D.; Brown, B.; Guerrier, K.; King, J. W.; Knotts, P.; Momplaisir, R.; Sorlien, C. C.; Stempel, R.; Symithe, S. J.; Ulysse, S. M. J.

2017-12-01

On January 12, 2010, a Mw 7.0 earthquake struck Haiti, killing over 200,000 people and devastating the Capital city of Port-au-Prince and the surrounding regions. It ruptured a previously unknown blind-thrust fault that abuts the Enriquillo Plantain Garden Fault (EPGF), one of two transform faults that define the North American-Caribbean plate boundary. That earthquake highlighted how transpression across this complex boundary is accommodated by slip partitioning into strike-slip and compressional structures. Because the seismic hazard is higher for a rupture on a reverse or oblique-slip fault than on a vertical strike-slip fault, the need to characterize the geometry of that fault system is clear. Lake Azuei overlies this plate boundary 60 km east of the 2010 epicenter. The lake's 23 km long axis trends NW-SE, parallel to the Haitian fold-and-thrust belt and oblique to the EPGF. This tectonic context makes it an ideal target for investigating the partitioning of plate motion between strike-slip and compressional structures. In January 2017, we acquired 222 km of multichannel seismic (MCS) profiles in the lake, largely concurrent with subbottom seismic (CHIRP) profiles. The MCS data were acquired using a high-frequency BubbleGun source and a 75 m-long, 24-channel streamer, achieving a 24 seismic fold with a penetration of 200 m below lakebed. With the goal of resolving tectonic structures in 3-D, survey lines were laid out in a grid with profiles spaced 1.2 km apart. Additional profiles were acquired at the SE end of the lake where most of the tectonic activity is presumably occurring. The co-located CHIRP and MCS profiles document the continuity of tectonic deformation between the surficial sediments and the deeper strata. Preliminary processing suggests that a SW-dipping blind thrust fault, expressed updip as a large monocline fold, may control the western edge of the lake. Gentle, young folds that protrude from the flat lakebed are also imaged with the CHIRP data. No obvious strike-slip faults are revealed in the MCS or CHIRP imagery. This result is consistent with a published analysis of GPS measurements that suggests oblique convergence on a south-dipping reverse fault along the southern shore of the lake.

A multi-frequency investigation of the influences of groundwater discharge on hydrocarbon emission and transport in the Baltic Sea

NASA Astrophysics Data System (ADS)

Weidner, E. F.; Jakobsson, M.; Nycander, J.; Mayer, L. A.

2017-12-01

In nearshore coastal regions submarine groundwater discharge is a major component of the hydro-geological cycle: transporting nutrients and pollutants to the ocean, producing up-welling currents through buoyancy effects, and acting as an erosional force at discharge sites. In nearshore regions where biogenic gas production is high, groundwater discharge could potentially act as a control on hydrocarbon emission and transport from the seafloor though the water-column. In the southern Stockholm Archipelago of the Baltic Sea, terraces and semi-circular depressions on shallow (<20 meters) seafloor have been linked to the discharge of ground water, traveling along the permeable layers in glacial clay deposits (Söderberg and Flodén 1995; Jakobsson et al., 2016). Sub-bottom profiles over the same region have identified widespread areas of subsurface blanking, commonly attributed to gas, as well as water-column seep features, both in spatial proximity to the groundwater discharge sites. High-resolution multibeam bathymetry and chirp sub-bottom profiles were combined with water-column data sets collected at multiple frequencies (300 kHz, 45-90 kHz, 160-260 kHz) to map the spatial distribution of seeps and investigate their relationship to localized groundwater discharge as determined by seafloor and subsurface morphology. The spatial extent of seep sites appears closely tied to regions of suspected groundwater discharge, suggesting direct or indirect controls on gas emission pathways. Additionally, seep morphology in the broadband data hints at the possibility of groundwater and gas flow mixing.

The University of Texas Institute for Geophysics Marine Geology and Geophysics Field Course

NASA Astrophysics Data System (ADS)

Davis, M. B.; Gulick, S. P.; Allison, M. A.; Goff, J. A.; Duncan, D. D.; Saustrup, S.

2010-12-01

During the spring-summer intersession, we annually offer an intensive three-week field course designed to provide hands-on instruction and training for graduate and upper-level undergraduate students in the acquisition, processing, interpretation, and visualization of marine geological and geophysical data. Now in year four, the course covers high-resolution air gun and streamer seismic reflection, CHIRP sub-bottom profiling, multibeam bathymetry, sidescan sonar, several types of sediment coring, grab sampling, and the sedimentology of resulting seabed samples (e.g., core description, grain size analysis, x-radiography, etc.). Students first participate in three days of classroom instruction designed to provide theoretical and technical background on each field method and impart geologic context of the study area. Students then travel to the Gulf Coast for a week of at-sea field work. In the field, students rotate between two small research vessels: one vessel, the 22’ aluminum-hulled R/V Lake Itasca, owned and operated by UTIG, is used for multibeam bathymetry, sidescan sonar, and sediment sampling; the other, NOAA’s R/V Manta or the R/V Acadiana, operated by the Louisiana Universities Marine Consortium, is used for high-resolution seismic reflection, CHIRP sub-bottom profiling, gravity coring, and vibracoring. Students assist with survey design, learn systems setup and acquisition parameters, and safe instrument deployment and retrieval techniques. Students also perform on-shore sedimentology lab work, data quality control, data processing and visualization using industry-standard software such as Focus, Landmark, Caris, and Fledermaus. During the course’s final week, students return to the classroom where, collaborating in teams of three, they integrate and interpret data in a final project which examines the geologic history and/or sedimentary processes as typified by the Gulf Coast continental shelf. The course culminates in a series of professional-level final presentations and discussions. Following the course, students report a greater understanding of marine geology and geophysics via the course’s intensive, hands-on, team approach, and low instructor to student ratio. This course satisfies field experience requirements for some degree programs and thus provides a unique alternative to land-based field courses.

Subbottom seismic profiling survey of Lake Azuei, Haiti: Seismic signature of paleo-shorelines in a transpressional environment and possible tectonic implications

NASA Astrophysics Data System (ADS)

Sloan, H.; Cormier, M. H.; Boisson, D.; Brown, B.; Guerrier, K.; Hearn, C. K.; Heil, C. W., Jr.; Hines, L.; Kelly, R. P.; King, J. W.; Knotts, P.; Lucier, O. F.; Momplaisir, R.; Stempel, R.; Symithe, S. J.; Ulysse, S. M. J.; Wattrus, N. J.

2017-12-01

The left-lateral Enriquillo-Plantain Garden Fault (EPGF) is one of two major transform faults that form the North American-Caribbean plate boundary. GPS measurements indicate that relative motion evolves from nearly pure strike-slip in western Haiti to highly transpressional near Lake Azuei in eastern Haiti, where the EPGF may terminate against a south-dipping oblique reverse fault. Lake Azuei, one of the largest lakes in the Caribbean region (10 km x 23 km), is surrounded by two high-elevation sierras (> 2,000 m). Because the lake has no outlet to the sea, its level is sensitive to variations in precipitation and is thought to have fluctuated by 10's of meters during the Holocene. A rise of 5 m over the past 10 years has had a devastating impact, submerging villages, farmland, and roads. A grid of high-resolution ( 10 cm) subbottom seismic (CHIRP) profiles acquired in January 2017 captures the subtle signature of the 5 m-deep shoreline and also images a prominent paleo-shoreline at 10 m water depth. This 10 m paleo-shoreline is well expressed in the CHIRP data suggesting it was occupied for a long period of time. It is buried beneath a thin (< 20 cm-thick) veneer of sediments, indicating that it was submerged centuries to millennia ago. This paleo-shoreline represents a key horizontal marker that may have been warped by local transpressional tectonics. We therefore catalogued its varying seismic signature with the goal of detecting any subtle but systematic depth variations of the associated shoreline angle around the periphery of the lake. Two sediment cores, collected in water depths of 14 m and 17 m, each bottomed 80-90 cm below the lakebed into a distinctively coarser bed. On-going radiometric dating is expected to constrain the age of this distinctive layer. Should this layer be tied to the perduring 10-m lowstand of the lake, determining its age could help quantify vertical deformation rates around Lake Azuei.

High-resolution sub-bottom seismic and sediment core records from the Chukchi Abyssal Plain reveal Quaternary glaciation impacts on the western Arctic Ocean

NASA Astrophysics Data System (ADS)

Joe, Y. J.; Seokhoon, Y.; Nam, S. I.; Polyak, L.; Niessen, F.

2017-12-01

For regional context of the Quaternary history of Arctic marine glaciations, such as glacial events in northern North America and on the Siberian and Chukchi margins, we used CHIRP sub-bottom profiles (SBP) along with sediment cores, including a 14-m long piston core ARA06-04JPC taken from the Chukchi abyssal plain during the RV Araon expedition in 2015. Based on core correlation with earlier developed Arctic Ocean stratigraphies using distribution of various sedimentary proxies, core 04JPC is estimated to extend to at least Marine Isotope Stage 13 (>0.5 Ma). The stratigraphy developed for SBP lines from the Chukchi abyssal plain to surrounding slopes can be divided into four major seismostratigraphic units (SSU 1-4). SBP records from the abyssal plain show well preserved stratification, whereas on the surrounding slopes this pattern is disrupted by lens-shaped, acoustically transparent sedimentary bodies interpreted as glaciogenic debris flow deposits. Based on the integration of sediment physical property and SBP data, we conclude that these debris flows were generated during several ice-sheet grounding events on the Chukchi and East Siberian margins, including adjacent ridges and plateaus, during the middle to late Quaternary.

Archive of digital Chirp subbottom profile data collected during USGS cruises 10CCT01, 10CCT02, and 10CCT03, Mississippi and Alabama Gulf Islands, March and April 2010

USGS Publications Warehouse

Forde, Arnell S.; Dadisman, Shawn V.; Flocks, James G.; Wiese, Dana S.; DeWitt, Nancy T.; Pfeiffer, William R.; Kelso, Kyle W.; Thompson, Phillip R.

2011-01-01

This Digital Versatile Disc (DVD) publication was prepared by an agency of the United States Government. Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made regarding the display or utility of the data on any other system, nor shall the act of distribution imply any such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and (or) contained herein. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof.

Archive of Digital Chirp Sub-bottom profile data collected during USGS cruise 09CCT01 offshore of Sabine Pass and Galveston, Texas, March 2009

USGS Publications Warehouse

Forde, Arnell S.; Dadisman, Shawn V.; Flocks, James G.; Dellapenna, Timothy M.; Sanford, Jordan M.; Wiese, Dana S.

2010-01-01

This Digital Versatile Disc (DVD) publication was prepared by an agency of the United States Government. Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made regarding the display or utility of the data on any other system, nor shall the act of distribution imply any such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and (or) contained herein. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof.

Seafloor geomorphic manifestations of gas venting and shallow subbottom gas hydrate occurrences

USGS Publications Warehouse

Paull, C K; Caress, D W; Thomas, Hans; Lundsten, Eve M.; Anderson, Kayce; Gwiazda, Roberto; Riedel, M; McGann, Mary; Herguera, J C

2015-01-01

High-resolution multibeam bathymetry data collected with an autonomous underwater vehicle (AUV) complemented by compressed high-intensity radar pulse (Chirp) profiles and remotely operated vehicle (ROV) observations and sediment sampling reveal a distinctive rough topography associated with seafloor gas venting and/or near-subsurface gas hydrate accumulations. The surveys provide 1 m bathymetric grids of deep-water gas venting sites along the best-known gas venting areas along the Pacific margin of North America, which is an unprecedented level of resolution. Patches of conspicuously rough seafloor that are tens of meters to hundreds of meters across and occur on larger seafloor topographic highs characterize seepage areas. Some patches are composed of multiple depressions that range from 1 to 100 m in diameter and are commonly up to 10 m deeper than the adjacent seafloor. Elevated mounds with relief of >10 m and fractured surfaces suggest that seafloor expansion also occurs. Ground truth observations show that these areas contain broken pavements of methane-derived authigenic carbonates with intervening topographic lows. Patterns seen in Chirp profiles, ROV observations, and core data suggest that the rough topography is produced by a combination of diagenetic alteration, focused erosion, and inflation of the seafloor. This characteristic texture allows previously unknown gas venting areas to be identified within these surveys. A conceptual model for the evolution of these features suggests that these morphologies develop slowly over protracted periods of slow seepage and shows the impact of gas venting and gas hydrate development on the seafloor morphology.

Megafloods in Marginal Basins: New Data from the Black Sea

NASA Astrophysics Data System (ADS)

Giosan, L.; Mart, Y.; McHugh, C. M.; Vachtman, D.; Cagatay, N. M.; Kadir, E. K.; Ryan, W. B.

2005-12-01

One of Jim Kennett's long-standing scientific interests has been the study of abrupt events ranging from destabilization of the gas hydrate reservoir, to volcanism, to megafloods. In appreciation to his contribution to the study of catastrophes in paleoceanography, we present new data on the Holocene reconnection of the Black Sea basin to the ocean, resulting from a July 2005 survey aboard the R/V Mediterranean Explorer of the EcoOcean Foundation. The survey included tightly-spaced Chirp subbottom profiling on the outer shelf northwest of the Bosporus outlet (Istanbul Bogazi), combined with precisely targeted gravity coring. Subbottom horizons are calibrated by radiocarbon and optical luminescence ages on cores. Chirp profiles reveal channels and ridges nearly transversal to the bathymetric contours. Ridges have grown on a seaward-dipping erosion surface that truncates the top of older prograding clinoforms. The ridges are up 12 m in height and have an asymmetrical cross-section, gentler on the west and steeper on the east. Sediment drifting is apparent on the gentler side. In the interiors of the ridges we found highly reflective mounds that are rooted directly on the erosion surface. The mounds organize in both elongated and circular to oval features. Shell-bearing marine mud drapes the mounds. Between the ridges and mounds the drape rests directly on the erosion surface that can be traced seaward to beyond -120 m. High abundance of exceptionally large shells of Mytilus sp. at the base of the drape suggests that bedforms were seeded by a colonization of mollusks building bioherms right on top of the erosion surface beginning at the time of the Mediterranean connection. The Black Sea lacustrine stage experienced an evaporative drawdown below its outlet and has only tracked the global sea level rise since 8.4 ky bp. The saltwater megaflood from the Mediterranean led to dramatic morphologic reorganization of the shelf sea-floor close to the Bosporus and exceptional preservation of shorelines and coastal bedforms elsewhere. The continued input of Mediterranean water has cut a network of channels through the ridges. Presumably the bioherm explosion was shut down by changes in salinity, nutrient budget, or nepheloid layer activity or it was soon terminated by anoxia. Sediment bodies formerly interpreted as lagoons are mud drifts in the lee of the bioherm ridges and mounds.

Last deglaciation of the Svalbard/Barents Sea Ice Sheet - a swath bathymetric and sub-bottom seismic study from the Kveithola Trough

NASA Astrophysics Data System (ADS)

Rebesco, Michele; Liu, Yanguang; Camerlenghi, Angelo; Winsborrow, Monica; Sverre Laberg, Jan; Caburlotto, Andrea; Diviacco, Paolo; Accettella, Daniela; Sauli, Chiara; Wardell, Nigel

2010-05-01

Kveithola Trough, an E-W trending cross-shelf glacial trough in the NW Barents Sea, was surveyed for the first time during the EGLACOM cruise between 8th July and 4th August 2008 on board R/V OGS-Explora. EGLACOM (Evolution of a GLacial Arctic COntinental Margin: the southern Svalbard ice stream-dominated sedimentary system) project is the Italian contribution to the International Polar Year (IPY) Activity 367 (Neogene ice streams and sedimentary processes on high- latitude continental margins - NICE STREAMS). Such IPY activity included as well the Spanish SVAIS 2008 cruise on board BIO Hesperides. EGLACOM data acquisition, focused on the Storfjorden Fan and Kveithola Trough, included a multi-channel seismic (MCS) reflection survey and the simultaneous collection of swath bathymetry and sub-bottom CHIRP profiles. Swath bathymetry in the Kveithola Trough shows that the seafloor is characterized by E-W trending mega-scale glacial lineations (MSGL). These include large-scale ridges about 2 km wide and 15 m high as well as smaller grooves about 100 m wide and a few metres deep. Such MSGL record the fast flow of an ice stream draining the Svalbard/Barents Sea Ice Sheet (SBSIS) during the Last Glacial Maximum (LGM). MSGL are overprinted by transverse sediment ridges about 15 km apart which give rise to a staircase long profile of the trough. Such transverse ridges are interpreted as grounding-zone wedges (GZW) formed by deposition of unconsolidated, saturated subglacial till during ice stream retreat. Sub-bottom (CHIRP) and multi-channel reflection seismic data show that the morphology is controlled by stacked sets of lensoidal transparent units (tills) overlain by a draping glaciomarine unit up to over 15 m thick. Formed during temporary stillstands in grounding-zone position before complete deglaciation, GZW ridges are diagnostic of episodic retreat. Our data allow the reconstruction of deglaciation in the Spitsbergen Bank area, with each stage during deglaciation recorded by deposition of a GZW. Three independent lines of reasoning suggest that an ice cap persisted on Spitsbergen Bank for some thousand years and lasted much longer than those that fed the adjacent glacial troughs: 1) the freshness of the morphology in Kveithola Trough compared to that of adjacent Storfjorden and Bear Island troughs; 2) the volume of sediment in the GZW ridges compared to the small catchment area; 3) preliminary assessment of the stratigraphic position of debris flow deposits on the continental slope. The 15 m of sedimentary drape deposited on top of GZW ridges contains a high-resolution palaeoclimatic record of the last thousand years, which accumulated at a very high average sedimentation rate. Sampling (through drilling) of the thin glaciomarine sediments between the till lenses of the successive GZW ridges may allow the dating of deglaciation phases in the Barents Sea.

Archive of digital Chirp sub-bottom profile data collected during USGS Cruise 07SCC01 offshore of the Chandeleur Islands, Louisiana, June 2007

USGS Publications Warehouse

Forde, Arnell S.; Dadisman, Shawn V.; Flocks, James G.; Wiese, Dana S.

2010-01-01

In June of 2007, the U.S. Geological Survey (USGS) conducted a geophysical survey offshore of the Chandeleur Islands, Louisiana, in cooperation with the Louisiana Department of Natural Resources (LDNR) as part of the USGS Barrier Island Comprehensive Monitoring (BICM) project. This project is part of a broader study focused on Subsidence and Coastal Change (SCC). The purpose of the study was to investigate the shallow geologic framework and monitor the enviromental impacts of Hurricane Katrina (Louisiana landfall was on August 29, 2005) on the Gulf Coast's barrier island chains. This report serves as an archive of unprocessed digital 512i and 424 Chirp sub-bottom profile data, trackline maps, navigation files, Geographic Information System (GIS) files, Field Activity Collection System (FACS) logs, observer's logbook, and formal Federal Geographic Data Committee (FGDC) metadata. Gained (a relative increase in signal amplitude) digital images of the seismic profiles are also provided. Refer to the Acronyms page for expansion of acronyms and abbreviations used in this report. The USGS St. Petersburg Coastal and Marine Science Center (SPCMSC) assigns a unique identifier to each cruise or field activity. For example, 07SCC01 tells us the data were collected in 2007 for the Subsidence and Coastal Change (SCC) study and the data were collected during the first field activity for that study in that calendar year. Refer to http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html for a detailed description of the method used to assign the field activity identification (ID). All Chirp systems use a signal of continuously varying frequency; the Chirp systems used during this survey produce high resolution, shallow penetration profile images beneath the seafloor. The towfish is a sound source and receiver, which is typically towed 1 - 2 m below the sea surface. The acoustic energy is reflected at density boundaries (such as the seafloor or sediment layers beneath the seafloor), detected by a receiver, and recorded by a PC-based seismic acquisition system. This process is repeated at timed intervals (for example, 0.125 s) and recorded for specific intervals of time (for example, 50 ms). In this way, a two-dimensional vertical image of the shallow geologic structure beneath the ship track is produced. Figure 1 displays the acquisition geometry. Refer to table 1 for a summary of acquisition parameters. See the digital FACS equipment log (11-KB PDF) for details about the acquisition equipment used. Table 2 lists trackline statistics. Scanned images of the handwritten FACS logs and handwritten science logbook (449-KB PDF) are also provided. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y rev 1 format (Norris and Faichney, 2002); ASCII character encoding is used for the first 3,200 bytes of the card image header instead of the SEG-Y rev 0 (Barry and others, 1975) EBCDIC format. The SEG-Y files may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU) (Cohen and Stockwell, 2010). See the How To Download SEG-Y Data page for download instructions. The web version of this archive does not contain the SEG-Y trace files. These files are very large and would require extremely long download times. To obtain the complete DVD archive, contact USGS Information at 1-888-ASK-USGS or infoservices@usgs.gov. The printable profiles provided here are GIF images that were processed and gained using SU software; refer to the Software page for links to example SU processing scripts and USGS software for viewing the SEG-Y files (Zihlman, 1992). The processed SEG-Y data were also exported to Chesapeake Technology, Inc. (CTI) SonarWeb software to produce an interactive version of the profile that allows the user to obtain a geographic location and depth from the profile for a given cursor position. This information is displayed in the status bar of the browser.

The University of Texas Institute for Geophysics Marine Geology and Geophysics Field Course

NASA Astrophysics Data System (ADS)

Davis, M. B.; Gulick, S. P.; Allison, M. A.; Goff, J. A.; Duncan, D. D.; Saustrup, S.

2011-12-01

The University of Texas Institute for Geophysics, part of the Jackson School of Geosciences, annually offers an intensive three-week marine geology and geophysics field course during the spring-summer intersession. Now in year five, the course provides hands-on instruction and training for graduate and upper-level undergraduate students in data acquisition, processing, interpretation, and visualization. Techniques covered include high-resolution seismic reflection, CHIRP sub-bottom profiling, multibeam bathymetry, sidescan sonar, several types of sediment coring, grab sampling, and the sedimentology of resulting seabed samples (e.g., core description, grain size analysis, x-radiography, etc.). Students seek to understand coastal and sedimentary processes of the Gulf Coast and continental shelf through application of these techniques in an exploratory mode. Students participate in an initial three days of classroom instruction designed to communicate geological context of the field area (which changes each year) along with theoretical and technical background on each field method. The class then travels to the Gulf Coast for a week of at-sea field work. In the field, students rotate between two small research vessels: one vessel, the 22' aluminum-hulled R/V Lake Itasca, owned and operated by UTIG, is used principally for multibeam bathymetry, sidescan sonar, and sediment sampling; the other, NOAA's R/V Manta or the R/V Acadiana, operated by the Louisiana Universities Marine Consortium, is used primarily for high-resolution seismic reflection, CHIRP sub-bottom profiling, multibeam bathymetry, gravity coring, and vibracoring. While at sea, students assist with survey design, learn instrumentation set up, acquisition parameters, data quality control, and safe instrument deployment and retrieval. In teams of three, students work in onshore field labs preparing sediment samples for particle size analysis and initial data processing. During the course's final week, teams return to the classroom where they integrate, interpret, and visualize data in a final project using industry-standard software such as Focus, Landmark, Caris, and Fledermaus. The course concludes with a series of professional-level final presentations and discussions in which students examine geologic history and/or sedimentary processes represented by the Gulf Coast continental shelf. With course completion, students report a greater understanding of marine geology and geophysics via the course's intensive, hands-on, team approach and low instructor to student ratio. This course satisfies field experience requirements for some degree programs and thus provides a unique alternative to land-based field courses.

Nearshore geophysical investigation of the underwater trace of the Enriquillo-Plantain Garden Fault following the 12 January 2010 Haiti earthquake

NASA Astrophysics Data System (ADS)

Johnson, H. E.; Hornbach, M.; Cormier, M.; McHugh, C. M.; Gulick, S. P.; Braudy, N.; Davis, M.; Dieudonne, N.; Diebold, J. B.; Douilly, R.; Mishkin, K.; Seeber, L.; Sorlien, C. C.; Steckler, M. S.; Symithe, S. J.; Templeton, J.

2010-12-01

In response to the January 12, 2010 earthquake in Haiti, we investigated offshore structures where aftershocks, lateral spreading, and a small tsunami suggested a coseismic underwater rupture. One aspect of that expedition involved mapping the trace of the Enriquillo-Plantain Garden fault (EPGF) very close to shore, in water as shallow as 2 m. For this, we deployed from the ship a small inflatable boat mounted with a sidescan sonar and a chirp subbottom profiler. These nearshore surveys focused on Grand Goave Bay and Petit Goave Bay, two areas 40-60 km west of Port-au-Prince where the EPGF briefly extends offshore. In Grand Goave Bay, the combination of shipboard multibeam bathymetric data and nearshore geophysical data highlights a series of en-echelon ridges striking about EW, sub-parallel to the expected fault trend. These rise 50-80 m above the surrounding seafloor and some slumps occur on their steep flanks. Although the sidescan imagery does not capture any well-defined seafloor offset or mole tracks that could be attributed to a 2010 earthquake rupture, the chirp profiles document faults that clearly affect the upper 20 m of sediments. The chirp also imaged an EW-striking ridge that appears to be fault-bounded on its north flank and is located about 1 km north of the onshore trace of the EPGF, suggesting that this fault system affects a relatively broad zone. In Petit Goave Bay, a series of textured, sub-circular mounds rising ~5 m above the sedimented bottom most likely indicate bioherms. These align roughly EW at the base of a 20-30 m-high ridge and may be forming at cold seeps associated with an active fault strand, as reported for other offshore transform fault systems. Lateral spreading and slumps fringe the southern shoreline of that bay. Based on the sharp resolution of the sidescan imagery over the slumps, detailing individual fissures and angular blocks, we interpret these to have been triggered by the 2010 earthquake, and that they therefore are likely to have enhanced tsunamigenesis in the area, as addressed in Hornbach et al. (Nature Geoscience, Accepted Sept. 2010).

Marine Geophysical Investigation of Selected Sites in Bridgeport Harbor, Connecticut, 2006

USGS Publications Warehouse

Johnson, Carole D.; White, Eric A.

2007-01-01

A marine geophysical investigation was conducted in 2006 to help characterize the bottom and subbottom materials and extent of bedrock in selected areas of Bridgeport Harbor, Connecticut. The data will be used by the U.S. Army Corps of Engineers in the design of confined aquatic disposal (CAD) cells within the harbor to facilitate dredging of the harbor. Three water-based geophysical methods were used to evaluate the geometry and composition of subsurface materials: (1) continuous seismic profiling (CSP) methods provide the depth to water bottom, and when sufficient signal penetration can be achieved, delineate the depth to bedrock and subbottom materials; (2) continuous resistivity profiling (CRP) methods were used to define the electrical properties of the shallow subbottom, and to possibly determine the distribution of conductive materials, such as clay, and resistive materials, such as sand and bedrock; (3) and magnetometer data were used to identify conductive anomalies of anthropogenic sources, such as cables and metallic debris. All data points were located using global positioning systems (GPS), and the GPS data were used for real-time navigation. The results of the CRP, CSP, and magnetometer data are consistent with the conceptual site model of a bedrock channel incised beneath the present day harbor. The channel appears to follow a north-northwest to south-southeast trend and is parallel to the Pequannock River. The seismic record and boring data indicate that under the channel, the depth to bedrock is as much as 42.7 meters (m) below mean low-low water (MLLW) in the dredged part of the harbor. The bedrock channel becomes shallower towards the shore, where bedrock outcrops have been mapped at land surface. CSP and CRP data were able to provide a discontinuous, but reasonable, trace from the channel toward the west under the proposed southwestern CAD cell. The data indicate a high amount of relief on the bedrock surface, as well as along the water bottom. Under the southwestern CAD cell, the sediments are only marginally thick enough for a CAD cell, at about 8 to 15 m in depth. Some of the profiles show small diffractions in the unconsolidated sediments, but no large-scale boulders or boulder fields were identified. No bedrock reflectors were imaged under the southeastern CAD cell, where core logs indicate the rock is as much as 30 m below MLLW. The chirp frequency, tuned transducer, and boomer-plate CSP surveys were adversely affected by a highly reflective water bottom causing strong multiples in the seismic record and very limited depths of penetration. These multiples are attributed to entrapped gas (methane) in the sediments or to very hard bottom conditions. In a limited number of places, the bedrock surface was observed in the CSP record, creating a discontinuous and sporadic image of the bedrock surface. These interpretations generally matched core data at FP-03-10 and FB-06-1. Use of two analog CSP systems, the boomer plate and tuned transducer, did not overcome the reflections off the water bottom and did not improve the depth of penetration. In general, the CRP profiles were used to corroborate the results of the CSP profiles. Relatively resistive zones associated with the locations of seismic reflections were interpreted as bedrock. The shape of the bedrock surface generally was similar in the CRP and CSP profiles. Evaluation of the CRP profiles indicated that the inversions were adversely affected where the depth and (or) ionic concentration of the water column varied. Consequently, the CRP profiles were broken into short intervals that extended just over the area of interest, where the depth to water bottom was fairly constant. Over these short profiles, efforts were made to evaluate the resistivity of the very shallow sediments to determine if there were any large contrasts in the resistivity of the sediments that might indicate differences in the shallow subbottom materials. No conclusions abo

Seismic profile analysis of sediment deposits in Brownlee and Hells Canyon Reservoirs near Cambridge, Idaho

USGS Publications Warehouse

Flocks, James; Kelso, Kyle; Fosness, Ryan; Welcker, Chris

2014-01-01

The U.S. Geological Survey (USGS) St. Petersburg Coastal and Marine Science Center, in cooperation with the USGS Idaho Water Science Center and the Idaho Power Company, collected high-resolution seismic reflection data in the Brownlee and Hells Canyon Reservoirs, in March of 2013.These reservoirs are located along the Snake River, and were constructed in 1958 (Brownlee) and 1967 (Hells Canyon). The purpose of the survey was to gain a better understanding of sediment accumulation within the reservoirs since their construction. The chirp system used in the survey was an EdgeTech Geo-Star Full Spectrum Sub-Bottom (FSSB) system coupled with an SB-424 towfish with a frequency range of 4 to 24 kHz. Approximately 325 kilometers of chirp data were collected, with water depths ranging from 0-90 meters. These reservoirs are characterized by very steep rock valley walls, very low flow rates, and minimal sediment input into the system. Sediments deposited in the reservoirs are characterized as highly fluid clays. Since the acoustic signal was not able to penetrate the rock substrate, only the thin veneer of these recent deposits were imaged. Results from the seismic survey indicate that throughout both of the Brownlee and Hells Canyon reservoirs the accumulation of sediments ranged from 0 to 2.5 m, with an average of 0.5 m. Areas of above average sediment accumulation may be related to lower slope, longer flooding history, and proximity to fluvial sources.

Submarine Neotectonic Investigations of the Bahia Soledad Fault, off Northern Baja California Near the US - Mexico Border

NASA Astrophysics Data System (ADS)

Anderson, K.; Lundsten, E. M.; Paull, C. K.; Caress, D. W.; Thomas, H. J.; Maier, K. L.; McGann, M.; Herguera, J. C.; Gwiazda, R.; Arregui, S.; Barrientos, L. A.

2015-12-01

The Monterey Bay Aquarium Research Institute (MBARI) conducted detailed surveys at selected sites on the seafloor along the Bahia Soledad Fault offshore of Northern Baja California, Mexico, during a two-ship expedition in the spring of 2015. The Bahia Soledad Fault is a NNW-trending strike-slip fault that is likely continuous with the San Diego Trough Fault offshore of San Diego, California. Constraining the style of deformation, continuity, and slip rate along this fault system is critical to characterizing the seismic hazards to the adjacent coastal areas extending from Los Angeles to Ensenada. Detailed morphologic surveys were conducted using an autonomous underwater vehicle (AUV) to provide ultra high-resolution multibeam bathymetry (vertical precision of 0.15 m and horizontal resolution of 1.0 m). The AUV also carried a 2-10 kHz chirp sub-bottom profiler and an Edgetech 110kHz and 410kHz sidescan. The two sites along the Bahia Soledad Fault each run ~6 km along the fault with ~1.8 km wide footprint. The resulting bathymetry shows these fault zones are marked with distinct lineations that are flanked by ~1 km long elongated ridges and depressions which are interpreted to be transpressional pop-up structures and transtensional pull-apart basins up to 100 m of relief. Offset seismic reflectors that extend to near the seafloor confirm that these lineations are fault scarps. The detailed bathymetric maps and sub-bottom profiles were used to locate key sites where deformed stratigraphic horizons along the fault are within 1.5 m of the seafloor. These areas were sampled using a remotely operated vehicle (ROV) equipped with a vibracoring system capable of collecting precisely located cores that are up to 1.5 m long. The coupled use of multibeam imagery and surgically-collected stratigraphic samples will enable to constrain the frequency and timing of recent movements on this fault which will be useful to incorporated into future seismic hazard assessment.

Archive of digital chirp subbottom profile data collected during USGS cruise 10BIM04 offshore Cat Island, Mississippi, September 2010

USGS Publications Warehouse

Forde, Arnell S.; Dadisman, Shawn V.; Kindinger, Jack G.; Miselis, Jennifer L.; Wiese, Dana S.; Buster, Noreen A.

2012-01-01

In September of 2010, the U.S. Geological Survey (USGS), in cooperation with the U.S. Army Corps of Engineers (USACE), conducted a geophysical survey to investigate the geologic controls on barrier island framework of Cat Island, Miss., as part of a broader USGS study on Barrier Island Mapping (BIM). These surveys were funded through the Mississippi Coastal Improvements Program (MsCIP) and the Northern Gulf of Mexico (NGOM) Ecosystem Change and Hazard Susceptibility Project as part of the Holocene Coastal Evolution of the Mississippi-Alabama Region Subtask. This report serves as an archive of unprocessed digital chirp subbottom data, trackline maps, navigation files, GIS files, Field Activity Collection System (FACS) logs, and formal FGDC metadata. Gained (showing a relative increase in signal amplitude) digital images of the seismic profiles are also provided. Refer to the Acronyms page for expansions of acronyms and abbreviations used in this report. The USGS Saint Petersburg Coastal and Marine Science Center (SPCMSC) assigns a unique identifier to each cruise or field activity. For example, 10BIM04 tells us the data were collected in 2010 during the fourth field activity for that project in that calendar year. Refer to http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html for a detailed description of the method used to assign the field activity identification (ID). All chirp systems use a signal of continuously varying frequency; the EdgeTech SB-512i system used during this survey produces high-resolution, shallow-penetration (typically less than 50 milliseconds (ms)) profile images of sub-seafloor stratigraphy. The towfish contains a transducer that transmits and receives acoustic energy; it was housed within a float system (built at the SPCMSC), which allows the towfish to be towed at a constant depth of 1.07 meters (m) below the sea surface. As transmitted acoustic energy intersects density boundaries, such as the seafloor or sub-surface sediment layers, some energy is reflected back toward the transducer, received, and recorded by a Personal Computer (PC)-based seismic acquisition system. This process is repeated at regular time intervals (for example, 0.125 seconds (s)), and returned energy is recorded for a specific duration (for example, 50 ms). In this way, a two-dimensional (2-D) vertical image of the shallow geologic structure beneath the ship track is produced. Figure 1 displays the acquisition geometry. Refer to table 1 for a summary of acquisition parameters and table 2 for trackline statistics. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG Y rev. 0 format (Barry and others, 1975); the first 3,200 bytes of the card image header are in American Standard Code for Information Interchange (ASCII) format instead of Extended Binary Coded Decimal Interchange Code (EBCDIC) format. The SEG Y files may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU) (Cohen and Stockwell, 2010). See the How To Download SEG Y Data page for download instructions. The printable profiles provided here are GIF images that were processed and gained using SU software, and they can be viewed from the Profiles page or from links located on the trackline maps; refer to the Software page for links to example SU processing scripts. The SEG Y files are available on the DVD version of this report or on the Web, downloadable via the USGS Coastal and Marine Geoscience Data System (http://cmgds.marine.usgs.gov). The data are also available for viewing using GeoMapApp (http://www.geomapapp.org) and Virtual Ocean (http://www.virtualocean.org) multi-platform open source software.

Application of Sub-Bottom Profiler to Study Riverbed Structure and Sediment Density

NASA Astrophysics Data System (ADS)

Rui, Wang; Changzheng, Li; Xiaofei, Yan

2018-03-01

In this pater, we present a study on the riverbed structure and sediment density in-situ test by using sub-bottom profiler. Compared with traditional direct observation methods, the sub-bottom profiler method based on sonar technology is non-contact, low-disturbance and high-efficient. We finish the investigation of several sections in Sanmenxia and Xiaolangdi reservoirs, which located on the main channel of lower reaches of Yellow River. Collected data show a detailed layered structure of the riverbed sediment which believed caused by sedimentary processes in different periods. Further more, we analyse the reflection coefficient of water-sediment interface and inverse the sediment density data from the raw wave record. The inversion method is based on the effective density fluid model and Kozeny-Carman formula. The comparison of the inversion results and sample tests shows that the in-situ test is reliable and useable.

Geophysical Surveys of the San Andreas and Crystal Springs Reservoir System Including Seismic-Reflection Profiles and Swath Bathymetry, San Mateo County, California

USGS Publications Warehouse

Finlayson, David P.; Triezenberg, Peter J.; Hart, Patrick E.

2010-01-01

This report describes geophysical data acquired by the U.S. Geological Survey (USGS) in San Andreas Reservoir and Upper and Lower Crystal Springs Reservoirs, San Mateo County, California, as part of an effort to refine knowledge of the location of traces of the San Andreas Fault within the reservoir system and to provide improved reservoir bathymetry for estimates of reservoir water volume. The surveys were conducted by the Western Coastal and Marine Geology (WCMG) Team of the USGS for the San Francisco Public Utilities Commission (SFPUC). The data were acquired in three separate surveys: (1) in June 2007, personnel from WCMG completed a three-day survey of San Andreas Reservoir, collecting approximately 50 km of high-resolution Chirp subbottom seismic-reflection data; (2) in November 2007, WCMG conducted a swath-bathymetry survey of San Andreas reservoir; and finally (3) in April 2008, WCMG conducted a swath-bathymetry survey of both the upper and lower Crystal Springs Reservoir system. Top of PageFor more information, contact David Finlayson.

Geophysical Data Collected off the South Shore of Martha's Vineyard, Massachusetts

USGS Publications Warehouse

Denny, J.F.; Danforth, W.W.; Foster, D.S.; Sherwood, C.R.

2010-01-01

The U.S. Geological Survey Woods Hole Science Center conducted a nearshore geophysical survey offshore of the southern coast of Martha's Vineyard, in the vicinity of the Martha's Vineyard Coastal Observatory in 2007. This mapping program was part of a larger research effort supporting the Office of Naval Research Ripples Directed-Research Initiative studies at Martha's Vineyard Coastal Observatory designed to improve our understanding of coastal sediment-transport processes. The survey was conducted aboard the Megan T. Miller August 9-13, 2007. The study area covers 35 square kilometers from about 0.2 kilometers to 5 kilometers offshore of the south shore of Martha's Vineyard, and ranges in depth from ~6 to 24 meters. The geophysical mapping utilized the following suite of high-resolution instrumentation to map the surficial sediment distribution, bathymetry, and sub-surface geology: a dual-frequency 100/500 kilohertz sidescan-sonar system, 234 kilohertz interferometric sonar, and 500 hertz -12 kilohertz chirp subbottom profiler. These geophysical data will be used to provide initial conditions for wave and circulation modeling within the study area.

Fine-scale relief related to late holocene channel shifting within the floor of the upper Redondo Fan, offshore Southern California

USGS Publications Warehouse

Normark, W.R.; Paull, C.K.; Caress, D.W.; Ussler, W.; Sliter, R.

2009-01-01

Erosional and depositional bedforms have been imaged at outcrop scale in the upper Redondo Fan, in the San Pedro Basin of offshore Southern California in ???600 m water depths, using an Autonomous Underwater Vehicle developed by the Monterey Bay Aquarium Research Institute. The Autonomous Underwater Vehicle is equipped with multibeam and chirp sub-bottom sonars. Sampling and photographic images using the Monterey Bay Aquarium Research Institute Remotely Operated Vehicle Tiburon provide groundtruth for the Autonomous Underwater Vehicle survey. The 0??3 m vertical and 1??5 m lateral bathymetric resolution and 0??1 m sub-bottom profile resolution provide unprecedented detail of bedform morphology and structure. Multiple channels within the Redondo Fan have been active at different times during the Late Holocene (0 to 3000 yr bp). The currently active channel extending from Redondo Canyon makes an abrupt 90?? turn at the canyon mouth before resuming a south-easterly course along the east side of the Redondo Fan. This channel is floored by sand and characterized by small steps generally <1 m in relief, spaced 10 to 80 m in the down-channel direction. A broader channel complex lies along the western side of the fan valley that was last active more than 850 years ago. Two distinct trains of large scours, with widths ranging from tens to a few hundred metres and depths of 20 m, occur on the floor of the western channel complex, which has a thin mud drape. If observed in cross-section only, these large scours would probably be misidentified as the thalweg of an active channel. ?? 2009 The Authors. Journal compilation ?? 2009 International Association of Sedimentologists.

Marine Geology and Geophysics Field Course Offered by The University of Texas Institute for Geophysics

NASA Astrophysics Data System (ADS)

Duncan, D.; Davis, M. B.; Allison, M. A.; Gulick, S. P.; Goff, J. A.; Saustrup, S.

2012-12-01

The University of Texas Institute for Geophysics, part of the Jackson School of Geosciences, annually offers an intensive three-week marine geology and geophysics field course during the spring-summer intersession. Now in year six, the course provides hands-on instruction and training for graduate and upper-level undergraduate students in data acquisition, processing, interpretation, and visualization. Techniques covered include high-resolution seismic reflection, CHIRP sub-bottom profiling, multibeam bathymetry, sidescan sonar, several types of sediment coring, grab sampling, and the sedimentology of resulting seabed samples (e.g., core description, grain size analysis, x-radiography, etc.). Students participate in an initial period of classroom instruction designed to communicate geological context of the field area (which changes each year) along with theoretical and technical background on each field method. The class then travels to the Gulf Coast for a week of at-sea field work. Our field sites at Port Aransas and Galveston, Texas, and Grand Isle, Louisiana, have provided ideal locations for students to investigate coastal and sedimentary processes of the Gulf Coast and continental shelf through application of geophysical techniques. In the field, students rotate between two research vessels: one vessel, the 22' aluminum-hulled R/V Lake Itasca, owned and operated by UTIG, is used principally for multibeam bathymetry, sidescan sonar, and sediment sampling; the other, NOAA's R/V Manta or the R/V Acadiana, operated by the Louisiana Universities Marine Consortium, and is used primarily for high-resolution seismic reflection, CHIRP sub-bottom profiling, multibeam bathymetry, gravity coring, and vibrocoring. While at sea, students assist with survey design, learn instrumentation set up, acquisition parameters, data quality control, and safe instrument deployment and retrieval. In teams of three, students work in onshore field labs preparing sediment samples for particle size analysis and initial post-processing of geophysical data. During the course's final week, teams return to the classroom where they integrate, interpret, and visualize data in a final project using industry-standard software such as Focus, Landmark, Caris, and Fledermaus. The course concludes with a series of professional-level final presentations and discussions with academic and industry supporters in which students examine the geologic history and sedimentary processes of the studied area of the Gulf Coast continental shelf. After completion, students report a greater understanding of marine geology and geophysics through the course's intensive, hands-on, team approach and low instructor to student ratio (12 students, three faculty, and three teaching assistants). This course satisfies field experience requirements for some degree programs and thus provides a unique alternative to land-based field courses.

Sensitive clay landslide detection and characterization in and around Lakelse Lake, British Columbia, Canada

NASA Astrophysics Data System (ADS)

Geertsema, Marten; Blais-Stevens, Andrée; Kwoll, Eva; Menounos, Brian; Venditti, Jeremy G.; Grenier, Alain; Wiebe, Kelsey

2018-02-01

The Lakelse Lake area in northwestern British Columbia, Canada, has a long history, and prehistory, of rapid sensitive clay landslides moving on very low gradients. However, until now, many landslides have gone undetected. We use an array of modern tools to identify hitherto unknown or poorly known landslide deposits, including acoustic subbottom profiles, multibeam sonar, and LiDAR. The combination of these methods reveals not only landslide deposits, but also geomorphic and sedimentologic structures that give clues about landslide type and mode of emplacement. LiDAR and bathymetric data reveal the areal extent of landslide deposits as well as the orientation of ridges that differentiate between spreading and flowing kinematics. The subbottom profiles show two-dimensional structures of disturbed landslide deposits, including horst and grabens indicative of landslides classified as spreads. A preliminary computer tomography (CT) scan of a sediment core confirms the structures of one subbottom profile. We also use archival data from the Ministry of Transportation and Infrastructure and resident interviews to better characterize historic landslides.

Near-shore Evaluation of Holocene Faulting and Earthquake Hazard in the New York City Metropolitan Region

NASA Astrophysics Data System (ADS)

Cormier, M. H.; King, J. W.; Seeber, L.; Heil, C. W., Jr.; Caccioppoli, B.

2016-12-01

During its relatively short historic period, the Atlantic Seaboard of North America has experienced a few M6+ earthquakes. These events raise the specter of a similar earthquake occurring anywhere along the eastern seaboard, including in the greater New York City (NYC) metropolitan area. Indeed, the NYC Seismic Zone is one of several concentrations of earthquake activity that stand out in the field of epicenters over eastern North America. Various lines of evidence point to a maximum magnitude in the M7 range for metropolitan NYC - a dramatic scenario that is counterbalanced by the low probability of such an event. Several faults mapped near NYC strike NW, sub-normal to the NE-striking structural trends of the Appalachians, and all earthquake sequences with well-established fault sources in the NYC seismic zone originate from NW-striking faults. With funding from the USGS Earthquake Hazard Program, we recently (July 2016) collected 85 km of high-resolution sub-bottom (CHIRP) profiles along the north shore of western Long Island Sound, immediately adjacent to metropolitan NYC. This survey area is characterized by a smooth, 15.5 kyr-old erosional surface and overlying strata with small original relief. CHIRP sonar profiles of these reflectors are expected to resolve fault or fold-related vertical relief (if present) greater than 50 cm. They would also resolve horizontal fault displacements with similar resolution, as may be expressed by offsets of either sedimentary or geomorphic features. No sedimentary cover on the land portion of the metro area offers such ideal reference surfaces, which are continuous in both time and space. Seismic profiles have a spacing of 200 m and have been acquired mostly perpendicular to the NW-striking faults mapped on land. These new data will be analyzed systematically for all resolvable features and then interpreted, distinguishing sedimentary, geomorphic, and tectonic features. The absence of evidence of post-glacial tectonic deformation would be a reliable negative result with implications regarding the lateral dimensions and southeastward continuity of the brittle faults mapped on land, and their potential for generation of large earthquakes with surface ruptures.

Archive of Digital Chirp Subbottom Profile Data Collected During USGS Cruise 14BIM05 Offshore of Breton Island, Louisiana, August 2014

USGS Publications Warehouse

Forde, Arnell S.; Flocks, James G.; Wiese, Dana S.; Fredericks, Jake J.

2016-03-29

The archived trace data are in standard SEG Y rev. 0 format (Barry and others, 1975); the first 3,200 bytes of the card image header are in American Standard Code for Information Interchange (ASCII) format instead of Extended Binary Coded Decimal Interchange Code (EBCDIC) format. The SEG Y files are available on the DVD version of this report or online, downloadable via the USGS Coastal and Marine Geoscience Data System (http://cmgds.marine.usgs.gov). The data are also available for viewing using GeoMapApp (http://www.geomapapp.org) and Virtual Ocean (http://www.virtualocean.org) multi-platform open source software. The Web version of this archive does not contain the SEG Y trace files. To obtain the complete DVD archive, contact USGS Information Services at 1-888-ASK-USGS or infoservices@usgs.gov. The SEG Y files may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU) (Cohen and Stockwell, 2010). See the How To Download SEG Y Data page for download instructions. The printable profiles are provided as Graphics Interchange Format (GIF) images processed and gained using SU software and can be viewed from theProfiles page or by using the links located on the trackline maps; refer to the Software page for links to example SU processing scripts.

Assessing subaqueous mudslide hazard on the Mississippi River delta front, Part 2: Insights revealed through high-resolution geophysical surveying

NASA Astrophysics Data System (ADS)

Obelcz, J.; Xu, K.; Bentley, S. J.; Georgiou, I. Y.; Maloney, J. M.; Miner, M. D.; Hanegan, K.; Keller, G.

2014-12-01

The northern Gulf of Mexico, including the subaqueous Mississippi River delta front (MRDF), has been productive for oil and gas development since the early 1900s. In 1969 cyclic seafloor wave loading associated with the passage of Hurricane Camille triggered subaqueous mudflows across the MRDF, destroying several offshore oil platforms. This incident spurred geophysical and geotechnical studies of the MRDF, which found that the delta front is prone to mass failures on gentle gradients (<0.5°) due to (1) high rates of fine-grained sedimentation and associated underconsolidation, (2) excess sediment pore pressure attributed to in-situ biogenic gas production, and (3) the frequent passage of tropical cyclones. In June 2014, a geophysical pilot study was conducted 8 km southwest of Southwest Pass, the distributary that currently receives the largest fraction of Mississippi River sediment supply. The resultant dataset encompasses 216 km of subbottom Chirp seismic profiles and a 60 km2 grid of bathymetry and sidescan data. Preliminary interpretation of these data shows the survey area can be classified into four primary sedimentary facies: mudflow gullies, mudflow lobes, undisturbed prodelta, and undisturbed delta front. Subbottom profiles reveal extensive biogenic gas from 20 to about 80 m water depths on the delta front; sidescan data show a variety of bottleneck slides, mudflow gullies and mudflow noses. Previous studies have attempted to constrain the periodicity and magnitude of subaqueous mudslides on the MRDF. However, large age gaps and varied resolution between datasets result in ambiguity regarding the cause and magnitude of observed bathymetric changes. We present high-temporal resolution MRDF bathymetric variations from 2005 (post Hurricane Katrina), 2009 (relatively quiescent storm period), and 2014 (post 2011 Mississippi River flood). These data yield better magnitude and timing estimates of mass movements. This exercise represents a first step towards (1) assembling a comprehensive geologic dataset upon which future MRDF geohazard assessments can be founded, and (2) understanding the dynamics of a massive passive margin deltaic lobe entering a phase of decline.

Geophysical exploration of an active pockmark field in the Bay of Concarneau, southern Brittany, and implications for resident suspension feeders

NASA Astrophysics Data System (ADS)

Baltzer, Agnès; Ehrhold, Axel; Rigolet, Carinne; Souron, Aurélie; Cordier, Céline; Clouet, Hélène; Dubois, Stanislas F.

2014-06-01

About a decade ago, a large field of pockmarks (individual features up to 30 m in diameter and <2 m deep) was discovered in water depths of 15-40 m in the Bay of Concarneau in southern Brittany along the French Atlantic coast, covering an overall area of 36 km2 and characterised by unusually high pockmark densities in places reaching 2,500 per square kilometre. As revealed by geophysical swath and subbottom profile data ground-truthed by sediment cores collected during two campaigns in 2005 and 2009, the confines of the pockmark field show a spectacular spatial association with those of a vast expanse of tube mats formed by a benthic community of the suspension-feeding amphipod Haploops nirae. The present study complements those findings with subbottom chirp profiles, seabed sonar imagery and ultrasonic backscatter data from the water column acquired in April 2011. Results show that pockmark distribution is influenced by the thickness of Holocene deposits covering an Oligocene palaeo-valley system. Two groups of pockmarks were identified: (1) a group of large (>10 m diameter), more widely scattered pockmarks deeply rooted (up to 8 ms two-way travel time, TWTT) in the Holocene palaeo-valley infills, and (2) a group of smaller, more densely spaced pockmarks shallowly rooted (up to 2 ms TWTT) in interfluve deposits. Pockmark pore water analyses revealed high methane concentrations peaking at ca. 400 μl/l at 22 and 30 cm core depth in silty sediments immediately above Haploops-bearing layers. Water column data indicate acoustic plumes above pockmarks, implying ongoing pockmark activity. Pockmark gas and/or fluid expulsion resulting in increased turbidity (resuspension of, amongst others, freshly settled phytoplankton) could at least partly account for the strong spatial association with the phytoplankton-feeding H. nirae in the Bay of Concarneau, exacerbating impacts of anthropogenically induced eutrophication and growing offshore trawling activities. Tidally driven hydraulic pumping in gas-charged pockmarks represents a good candidate as large-scale short-term triggering mechanism of pockmark activation, in addition to episodic regional seismic activity.

Experimental demonstration of a multi-wavelength distributed feedback semiconductor laser array with an equivalent chirped grating profile based on the equivalent chirp technology.

PubMed

Li, Wangzhe; Zhang, Xia; Yao, Jianping

2013-08-26

We report, to the best of our knowledge, the first realization of a multi-wavelength distributed feedback (DFB) semiconductor laser array with an equivalent chirped grating profile based on equivalent chirp technology. All the lasers in the laser array have an identical grating period with an equivalent chirped grating structure, which are realized by nonuniform sampling of the gratings. Different wavelengths are achieved by changing the sampling functions. A multi-wavelength DFB semiconductor laser array is fabricated and the lasing performance is evaluated. The results show that the equivalent chirp technology is an effective solution for monolithic integration of a multi-wavelength laser array with potential for large volume fabrication.

Archive of digital chirp subbottom profile data collected during USGS cruise 12BIM03 offshore of the Chandeleur Islands, Louisiana, July 2012

USGS Publications Warehouse

Forde, Arnell S.; Miselis, Jennifer L.; Wiese, Dana S.

2014-01-01

From July 23 - 31, 2012, the U.S. Geological Survey conducted geophysical surveys to investigate the geologic controls on barrier island framework and long-term sediment transport along the oil spill mitigation sand berm constructed at the north end and just offshore of the Chandeleur Islands, La. (figure 1). This effort is part of a broader USGS study, which seeks to better understand barrier island evolution over medium time scales (months to years). This report serves as an archive of unprocessed digital chirp subbottom data, trackline maps, navigation files, Geographic Information System (GIS) files, Field Activity Collection System (FACS) logs, and formal Federal Geographic Data Committee (FGDC) metadata. Gained (showing a relative increase in signal amplitude) digital images of the seismic profiles are also provided. Refer to the Abbreviations page for expansions of acronyms and abbreviations used in this report. The USGS St. Petersburg Coastal and Marine Science Center (SPCMSC) assigns a unique identifier to each cruise or field activity. For example, 12BIM03 tells us the data were collected in 2012 during the third field activity for that project in that calendar year and BIM is a generic code, which represents efforts related to Barrier Island Mapping. Refer to http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html for a detailed description of the method used to assign the field activity ID. All chirp systems use a signal of continuously varying frequency; the EdgeTech SB-424 system used during this survey produces high-resolution, shallow-penetration (typically less than 50 milliseconds (ms)) profile images of sub-seafloor stratigraphy. The towfish contains a transducer that transmits and receives acoustic energy and is typically towed 1 - 2 m below the sea surface. As transmitted acoustic energy intersects density boundaries, such as the seafloor or sub-surface sediment layers, energy is reflected back toward the transducer, received, and recorded by a PC-based seismic acquisition system. This process is repeated at regular time intervals (for example, 0.125 seconds (s)) and returned energy is recorded for a specific duration (for example, 50 ms). In this way, a two-dimensional (2-D) vertical image of the shallow geologic structure beneath the ship track is produced. Figure 2 displays the acquisition geometry. Refer to table 1 for a summary of acquisition parameters and table 2 for trackline statistics. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG Y rev. 0 format (Barry and others, 1975); the first 3,200 bytes of the card image header are in ASCII format instead of EBCDIC format. The SEG Y files may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU) (Cohen and Stockwell, 2010). See the How To Download SEG Y Data page for download instructions. The web version of this archive does not contain the SEG Y trace files. These files are very large and would require extremely long download times. To obtain the complete DVD archive, contact USGS Information Services at 1-888-ASK-USGS or infoservices@usgs.gov. The printable profiles provided here are GIF images that were processed and gained using SU software and can be viewed from the Profiles page or from links located on the trackline maps; refer to the Software page for links to example SU processing scripts. The SEG Y files are available on the DVD version of this report or on the Web, downloadable via the USGS Coastal and Marine Geoscience Data System (http://cmgds.marine.usgs.gov). The data are also available for viewing using GeoMapApp (http://www.geomapapp.org) and Virtual Ocean (http://www.virtualocean.org) multi-platform open source software. Detailed information about the navigation system used can be found in table 1 and the Field Activity Collection System (FACS) logs. To view the trackline maps and navigation files, and for more information about these items, see the Navigation page.

Multi-event behavior of El Golfo landslide (El Hierro Island, Canary Archipelago)

NASA Astrophysics Data System (ADS)

León, Ricardo; Biain, Ander; Urgeles, Roger; Somoza, Luis; Ferrer, Mercedes; García-Crespo, Jesús; Francisco Mediato, José; Galindo, Inés; Yepes, Jorge; Gimenez-Moreno, Julia

2017-04-01

Based on the re-interpretation of a vast onshore-offshore data set, a new morpho-structural characterization of the El Golfo giant landslide in the island of El Hierro (Canary Archipelago, Spain) is presented. Offshore multibeam echosounder data, chirp sub-bottom profiles, multichannel seismic reflection data and onshore information from water wells and galleries have been analyzed to determine the nature of the event. The subaerial headscarp shows a non-continuous arcuate profile formed by two nested semi-circular amphitheaters that extend offshore along a smooth chute, suggesting the occurrence of at least two large retrogressive events. Channels/gullies and escarpments developed along the submarine sector of the scar also indicate smaller-scale events and predominance of sediment bypass. At the base of submerged island, two subunits within the related submarine mass transport deposit (MTD) are identified on multichannel seismic reflection profiles confirming the multi-event nature of the landslide. The MTD, identified as a debris avalanche, has a total estimated volume of 318 km3: 84 km3 and 234 km3, for the lower and upper subunits respectively. Data from wells and galleries show abrasion platforms with beach deposits at sea-level (0 masl) formed after the landslide scar and buried by the El Golfo post-collapse infill lavas, suggesting an age at least older than 23.5-82.5 ka for the landslide. This work has been supported by the projects IGCP-640 S4SLIDE, High resolution seabed mapping EASME/EMFF/2016/005 and CTM2010-09496-E. Keywords: Submarine landslides, volcanic islands, debris avalanche, Canary Islands

Development of levees on deep-sea channels: Insights from high-resolution AUV exploration of the Lucia Chica system, offshore central California

NASA Astrophysics Data System (ADS)

Maier, K. L.; Fildani, A.; Romans, B.; Paull, C. K.; McHargue, T.; Graham, S. A.; Caress, D. W.

2010-12-01

The Lucia Chica, a tributary channel system of the Lucia Canyon, offshore central California, was imaged using the Monterey Bay Aquarium Research Institute’s (MBARI) Autonomous Underwater Vehicle (AUV) in order to investigate seafloor and subsurface morphologies associated with low-relief submarine channels. In larger, previously investigated seafloor channel-levee systems, initial deposits are either eroded, compacted, or below the resolution of available imaging. In this dataset from the Lucia Chica, the unprecedented high-resolution multibeam bathymetry (1 m lateral resolution) and chirp sub-bottom profiles (11 cm vertical resolution) reveal a highly irregular seafloor with scours, depressions, and discontinuous low-relief conduits over an area of ~70 km2. Sediment packages associated with channels, levees, and deposits related to less confined flows are correlated between chirp profiles and with the multibeam bathymetric image to determine the stratigraphic evolution of the Lucia Chica and the sequence of channel-levee development. In the Lucia Chica, channels appear to have initiated as trains of scours that eventually coalesced into continuous channel thalwegs carved by erosional turbidity currents. Channel incision and stepped lateral migration led to the development of terraces, complex levee stratigraphy, and distinct morphologies associated with inner and outer bends of sinuous channels. The inner bend levee stratigraphy indicates that the channel position migrated in discrete shifts, as opposed to continuous channel migration associated with lateral accretion. Discrete levee packages, formed from flow-stripped turbidity currents, later infilled abandoned portions of the channel and overbank areas. While processes of initial channel and levee development are well established in fluvial settings, detailed examples are lacking for deep-sea systems. These results highlight the differences in initiation between submarine channel systems, their fluvial counterparts, and larger submarine channel-levee systems imaged only with lower-resolution technologies. High-resolution imaging and detailed mapping made possible by cutting-edge oceanographic technology provide an unprecedented examination of deep-water channel-levee morphology and improve understanding of deep-water channel migration and levee development.

Interaction of free charged particles with a chirped electromagnetic pulse.

PubMed

Khachatryan, A G; van Goor, F A; Boller, K-J

2004-12-01

We study the effect of chirp on electromagnetic (EM) pulse interaction with a charged particle. Both the one-dimensional (1D) and 3D cases are considered. It is found that, in contrast to the case of a nonchirped pulse, the charged particle energy can be changed after the interaction with a 1D EM chirped pulse. Different types of chirp and pulse envelopes are considered. In the case of small chirp, an analytical expression is found for arbitrary temporal profiles of the chirp and the pulse envelope. In the 3D case, the interaction with a chirped pulse results in a polarization-dependent scattering of charged particles.

Optical signal splitting and chirping device modeling

NASA Astrophysics Data System (ADS)

Vinogradova, Irina L.; Andrianova, Anna V.; Meshkov, Ivan K.; Sultanov, Albert Kh.; Abdrakhmanova, Guzel I.; Grakhova, Elizaveta P.; Ishmyarov, Arsen A.; Yantilina, Liliya Z.; Kutlieva, Gulnaz R.

2017-04-01

This article examines the devices for optical signal splitting and chirping device modeling. Models with splitting and switching functions are taken into consideration. The described device for optical signal splitting and chirping represents interferential splitter with profiled mixer which provides allocation of correspondent spectral component from ultra wide band frequency diapason, and signal phase shift for aerial array (AA) directive diagram control. This paper proposes modeling for two types of devices for optical signal splitting and chirping: the interference-type optical signal splitting and chirping device and the long-distance-type optical signal splitting and chirping device.

Preliminary Results from Acoustic Survey Offshore Kefken, Southwestern Black Sea Margin

NASA Astrophysics Data System (ADS)

Dondurur, Derman; Karaca, Onur; Nasıf, Aslıhan

2017-04-01

In March 2016, different marine acoustic datasets were collected aboard of R/V K. Piri Reis research vessel of Dokuz Eylül University within the scope of Turkish Research Council (Tübitak) Project (115Y218) to reveal submarine morphology and seismo-acoustical structure of the continental shelf and upper slope of Şile-Kefken region in the southwest of the Black Sea. A total of 1564 km high resolution seismic, multibeam bathymetry and Chirp sub-bottom profiler data were collected. Seismic data was collected using a 1500 m long digital streamer with 240 active channels. Group and shot intervals were 6.25 m and 25 m, respectively. Collected data were analyzed by means of (i) stratigraphic and (ii) structural components, and (iii) the structure of upper slope and shelf break. The stratigraphic elements in the region indicate the existence of Eocene and younger units. A distinctive acoustical basement in the seismic data observed throughout the shelf which is interpreted as uplifted Cretaceous basement of the Black Sea, that is Akveren or Yemişliçay Formation. The basement also outcrops around the Kefken Island. Chirp data is used to map the shallow stratigraphy of the shelf including the Holocene sediment distribution which exists on a very restricted area on the shelf. To the east, there is a large outcrop zone offshore Kefken where no Holocene sediments are observed. Initial evaluation of the collected data indicates that there is no present day delta formation in the area due to a few weak streams observed in the study area. The penetration of Chirp data in the western and the southern parts of the shelf area is very limited while it increases towards to upper continental slope to the North, and east of Kefken Cape. The acoustic data suggests that the study area is under the influence of the Pontide overthrust. Possible existence of reverse faults of Pontide overthrust is evident on the seismic data from southwestern shelf. In addition to the reverse faults to the SW, the whole shelf is highly affected by a northwards trending strike slip fault system with a significant vertical slip. Canyon heads and shelf break is deformed by numerous near vertical normal faults. Multibeam bathymetric data indicate that the upper slope is formed by highly steep canyon heads with several small scale gullies connecting to the thalweg at low angles.

Developing Age Models to Utilize High Arctic Coastal Sediments for Paleoclimate Research: Results from the Colville Delta and Simpson Lagoon, Alaska

NASA Astrophysics Data System (ADS)

Miller, A. J.; Allison, M. A.; Bianchi, T. S.; Marcantonio, F.

2012-12-01

Sediment cores collected from Simpson Lagoon on the inner Beaufort Sea shelf adjacent to the Colville River delta, AK are being utilized to develop new, high-resolution (sub-decadal scale) archives of the 0-3,000 year Arctic paleoclimate record necessary to assess natural and anthropogenic climate variability. An imperative first step for developing a new paleoclimate archive is to establish methodologies for constraining the age-depth relationship. Naturally occurring and bomb-produced radioisotopes have been utilized in sediments to constrain downcore variability of accumulation rates on 100-103 y timescales, but this methodology is complicated by low activities of many of these tracers at high latitudes. The present study utilizes the combination of a (1) multi-tracer approach and a (2) tailored measurement strategy to overcome this limitation. 210Pb and 137Cs analyses were conducted on the fine (<32μm) sediment fraction to maximize measurable activity and to minimize radioisotope activity variability resulting from changes in grain size: 137Cs geochronologies proved more reliable in this setting and revealed mm/y sediment accumulation in the lagoon. To corroborate the 137Cs results, 239,240Pu activities were analyzed for selected sites using ICP-MS which has ultra-low detection limits, and yielded accumulation rates that matched the Cs geochronology. Age model development for the remainder of the core lengths (>~100 y in age) were completed using radiocarbon dating of benthic foraminifera tests, which proved the only datable in situ carbon available in this sediment archive. These dates have been used to constrain the ages of acoustic reflectors in CHIRP subbottom seismic records collected from the lagoon. Using this age control, spatial patterns of lagoonal sediment accumulation over the last ~3 ky were derived from the CHIRP data. Two depocenters are identified and validate combining age-dated coring with high-resolution seismic profiling to identify areas of the highest temporal resolution for Arctic paleoclimate research in coastal sediments.

Investigation of Submarine Groundwater Discharge and Preferential Groundwater Flow-paths in a Coastal Karst Area using towed Marine and Terrestrial Electrical Resistivity

NASA Astrophysics Data System (ADS)

O'connell, Y.; Daly, E.; Duffy, G.; Henry, T.

2012-12-01

Large volumes of groundwater, containing nutrients and contaminants enter the coastal waters of southern Galway Bay on the west coast of Ireland through submarine groundwater discharge (SGD). The SGD occurs through karstified Carboniferous limestone in a major karst region comprising the Burren and Gort Lowlands. The Carboniferous limestones have experienced extensive dissolution resulting in the development of an underground network of conduits and fissures that define a trimodal groundwater flow pattern across the region. Groundwater discharge to the sea in this area is exclusively intertidal and submarine. Storage in the karst is limited and typical winter rainfall conditions result in the karst system becoming saturated. Temporary lakes (turloughs) form in lowlying areas and act as large reservoirs which provide storage to enable the transmission of the large volumes of water in the system to the sea. Between 2010 and 2012, terrestrial and shallow marine geophysical surveying has been undertaken to investigate preferential groundwater flow-paths and SGD locations in order to quantify the groundwater-seawater interactions in this coastal karst system. A report into the groundwater system of this karst region following a major flood event proposed a conceptual conduit model defined by extensive water tracing, water level monitoring, hydrochemical sampling, geological mapping and drilling. Limited information about the dimensions of the conduits was known. Electrical resistivity tomography (ERT) profiling to depths of 100m below ground level, with multiple array configurations, has been carried out to investigate the modes of groundwater flow in to and out of both temporary and permanent freshwater lakes in the system. Towed dipole-dipole profiles have been recorded to investigate conduits beneath a permanent lake exhibiting a tidal influence despite its location 5.5 km from the seashore. The ERT data indicates significant variations in subsurface resistivities including very low resistivity features which have been modeled as large diameter conduits. Ongoing analysis of the data will allow more accurate conduit dimensions to be incorporated in to future groundwater flow models. In the shallow marine bays along the coast, towed ERT employing dipole-dipole and non-conventional modified Wenner arrays has been coupled with high-resolution digital chirp sub-bottom profiling. Combining the two techniques allows the determination of sediment, structural and lithological variations beneath the sea floor, delineating saturated sediment layers, till and bedrock horizons. Incorporation of the water column thickness and conductivity, recorded simultaneously with the ERT survey, constrains the inversion process. In addition, multiple layer boundaries interpreted from the sub-bottom profiling are incorporated in to the model, further constraining the inversion process. The combined inversion allows improved data interpretation to facilitate more accurate assessment of SGD locations.

Nearshore sediment thickness, Fire Island, New York

USGS Publications Warehouse

Locker, Stanley D.; Miselis, Jennifer L.; Buster, Noreen A.; Hapke, Cheryl J.; Wadman, Heidi M.; McNinch, Jesse E.; Forde, Arnell S.; Stalk, Chelsea A.

2017-04-03

Investigations of coastal change at Fire Island, New York (N.Y.), sought to characterize sediment budgets and determine geologic framework controls on coastal processes. Nearshore sediment thickness is critical for assessing coastal system sediment availability, but it is largely unquantified due to the difficulty of conducting geological or geophysical surveys across the nearshore. This study used an amphibious vessel to acquire chirp subbottom profiles. These profiles were used to characterize nearshore geology and provide an assessment of nearshore sediment volume. Two resulting sediment-thickness maps are provided: total Holocene sediment thickness and the thickness of the active shoreface. The Holocene sediment section represents deposition above the maximum flooding surface that is related to the most recent marine transgression. The active shoreface section is the uppermost Holocene sediment, which is interpreted to represent the portion of the shoreface thought to contribute to present and future coastal behavior. The sediment distribution patterns correspond to previously defined zones of erosion, accretion, and stability along the island, demonstrating the importance of sediment availability in the coastal response to storms and seasonal variability. The eastern zone has a thin nearshore sediment thickness, except for an ebb-tidal deposit at the wilderness breach caused by Hurricane Sandy. Thicker sediment is found along a central zone that includes shoreface-attached sand ridges, which is consistent with a stable or accretional coastline in this area. The thickest overall Holocene section is found in the western zone of the study, where a thicker lower section of Holocene sediment appears related to the westward migration of Fire Island Inlet over several hundred years.

Linear chirped slope profile for spatial calibration in slope measuring deflectometry

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

Siewert, F., E-mail: frank.siewert@helmholtz-berlin.de; Zeschke, T.; Arnold, T.

2016-05-15

Slope measuring deflectometry is commonly used by the X-ray optics community to measure the long-spatial-wavelength surface figure error of optical components dedicated to guide and focus X-rays under grazing incidence condition at synchrotron and free electron laser beamlines. The best performing instruments of this kind are capable of absolute accuracy on the level of 30-50 nrad. However, the exact bandwidth of the measurements, determined at the higher spatial frequencies by the instrument’s spatial resolution, or more generally by the instrument’s modulation transfer function (MTF) is hard to determine. An MTF calibration method based on application of a test surface withmore » a one-dimensional (1D) chirped height profile of constant amplitude was suggested in the past. In this work, we propose a new approach to designing the test surfaces with a 2D-chirped topography, specially optimized for MTF characterization of slope measuring instruments. The design of the developed MTF test samples based on the proposed linear chirped slope profiles (LCSPs) is free of the major drawback of the 1D chirped height profiles, where in the slope domain, the amplitude strongly increases with the local spatial frequency of the profile. We provide the details of fabrication of the LCSP samples. The results of first application of the developed test samples to measure the spatial resolution of the BESSY-NOM at different experimental arrangements are also presented and discussed.« less

Overview of SAX99: Environmental considerations

USGS Publications Warehouse

Richardson, M.D.; Briggs, K.B.; Bibee, L.D.; Jumars, P.A.; Sawyer, W.B.; Albert, D.B.; Bennett, R.H.; Berger, T.K.; Buckingham, M.J.; Chotiros, N.P.; Dahl, P.H.; DeWitt, N.T.; Fleischer, P.; Flood, R.; Greenlaw, C.F.; Holliday, D.V.; Hulbert, M.H.; Hutnak, M.P.; Jackson, P.D.; Jaffe, J.S.; Johnson, H. Paul; Lavoie, D.L.; Lyons, A.P.; Martens, C.S.; McGehee, D.E.; Moore, K.D.; Orsi, T.H.; Piper, J.N.; Ray, R.I.; Reed, A.H.; Self, R.F.L.; Schmidt, J.L.; Schock, S.G.; Simonet, F.; Stoll, R.D.; Tang, D.; Thistle, D.E.; Thorsos, E.I.; Walter, D.J.; Wheatcroft, R.A.

2001-01-01

A 1-km2 area located 2 km off the Florida Pan-handle (30??22.6???N; 86??38.7???W) was selected as the site to conduct high-frequency acoustic seafloor penetration, sediment propagation, and bottom scattering experiments [1]. Side scan, multibeam, and normal incidence chirp acoustic surveys as well as subsequent video surveys, diver observations, and vibra coring, indicate a uniform distribution of surficial and subbottom seafloor characteristics within the area. The site, in 18-19 m of water, is characterized by 1-2-m thick fine-to-medium clean sand and meets the logistic and scientific requirements specified for the acoustic experiments. This paper provides a preliminary summary of the meteorological, oceanographic, and seafloor conditions found during the experiments and describes the important physical and biological process that control the spatial distribution and temporal changes in these characteristics.

Compact fiber CPA system based on a CFBG stretcher and CVBG compressor with matched dispersion profile.

PubMed

Bartulevicius, Tadas; Frankinas, Saulius; Michailovas, Andrejus; Vasilyeu, Ruslan; Smirnov, Vadim; Trepanier, Francois; Rusteika, Nerijus

2017-08-21

In this work, a compact fiber chirped pulse amplification system exploiting a tandem of a chirped fiber Bragg grating stretcher and a chirped volume Bragg grating compressor with matched chromatic dispersion is presented. Chirped pulses of 230 ps duration were amplified in a Yb-doped fiber amplifier and re-compressed to 208 fs duration with good fidelity. The compressed pulse duration was fine-tuned by temperature gradient along the fiber Bragg grating stretcher.

Association among active seafloor deformation, mound formation, and gas hydrate growth and accumulation within the seafloor of the Santa Monica Basin, offshore California

USGS Publications Warehouse

Paull, C.K.; Normark, W.R.; Ussler, W.; Caress, D.W.; Keaten, R.

2008-01-01

Seafloor blister-like mounds, methane migration and gas hydrate formation were investigated through detailed seafloor surveys in Santa Monica Basin, offshore of Los Angeles, California. Two distinct deep-water (??? 800??m water depth) topographic mounds were surveyed using an autonomous underwater vehicle (carrying a multibeam sonar and a chirp sub-bottom profiler) and one of these was explored with the remotely operated vehicle Tiburon. The mounds are > 10??m high and > 100??m wide dome-shaped bathymetric features. These mounds protrude from crests of broad anticlines (~ 20??m high and 1 to 3??km long) formed within latest Quaternary-aged seafloor sediment associated with compression between lateral offsets in regional faults. No allochthonous sediments were observed on the mounds, except slumped material off the steep slopes of the mounds. Continuous streams of methane gas bubbles emanate from the crest of the northeastern mound, and extensive methane-derived authigenic carbonate pavements and chemosynthetic communities mantle the mound surface. The large local vertical displacements needed to produce these mounds suggests a corresponding net mass accumulation has occurred within the immediate subsurface. Formation and accumulation of pure gas hydrate lenses in the subsurface is proposed as a mechanism to blister the seafloor and form these mounds. ?? 2008 Elsevier B.V. All rights reserved.

Holocene Activity of the Enriquillo-Plantain Garden Fault in Lake Enriquillo Derived from Seismic Stratigraphy

NASA Astrophysics Data System (ADS)

Rios, J. K.; McHugh, C. M.; Hornbach, M. J.; Mann, P.; Wright, V. D.; Gurung, D.

2013-12-01

The Enriquillo-Plantain-Garden fault zone (EPGF) crosses Lake Enriquillo (LE) in the Dominican Republic and extends E-W across the southern peninsula of Haiti, south of the Baie de Port au Prince (BPP). Seismic stratigraphic studies of CHIRP high-resolution subbottom profiles calibrated to ages obtained from sediment cores and previous coral reef studies provide a Holocene record of relative sea level rise into the BPB and LE and a time frame for understanding tectonics of the EPGF. The BPP is 20 km wide, 20 km long, 150 m deep, and surrounded by coral reefs at water depths of 30 m. Three seismic units were identified: Unit 1: stepped terraces 5-10 m high. Laminated strata onlaps the terraces. This unit possibly represents Marine Isotope Stages 6 and 5, but has not been dated. Unit 2: laminated strata, thicker than 10 m and dated near its top at 22 ka BP. The microfossil assemblages reveal that during the latest Pleistocene sea level lowstand the BPP had a restricted connection with the global ocean. Few well-preserved marine microfossils are present and mostly are reworked. Geochemical analyses reveal that the laminated sediments were deposited during wet periods (>Si, Al wt %, Cu ppm) and dry periods (>Ca wt %). Unit 3: acoustically transparent, ~10 m thick, dated near its base and top at 14 ka BP and 2 ka BP, respectively. This unit represents the Holocene initiation of sea level rise and high stand containing well-preserved marine fossils. At ~9.5 ka BP planktonic foraminifers become abundant implying deepening of marine waters. Lake Enriquillo is 127 km east of the BPP. It is 15 km wide, 40 km long and 45 m deep. CHIRP subbottom profiles penetrated ~30 m below the lake floor. Four main acoustic units were identified: Unit 1: deformed basement with steeply dipping and folded beds. Based on land studies this unit is likely Plio-Pleistocene in age. Unit 2: laminated strata. Ages from coral reefs and deformed strata on land indicate this unit is likely pre-20 ka BP. Unit 3: acoustically transparent is 5-10 m thick. This unit shows top-lap terminations with the overlying strata and is interpreted as marine. Based on coral reef ages it was deposited during the Holocene 10 to 2 ka BP. Unit 4: laminated strata is ~ 5 m thick and downlaps offshore forming progradational packages. Pending Pb-210 ages from LE sediment cores a correlation between the two basins is proposed. During the latest Pleistocene sea level lowstand LE was separated from the BPP and the global ocean. The BPP was only partly connected to the sea. Sedimentation in both basins was dominated by wet and dry climate. The initial rise to high-stand of sea level into the BPP was at 14 ka BP. LE marine incursion was at 9.7 ka BP. At 2.8 ka BP LE became separated from the BPP possibly due to increased alluvial fan sedimentation. Evaporative conditions dominated the lake from 2.8 ka BP to the present and the lake waters lowered to ~43 m below sea level. We interpret the top laminated strata as deposited during the evaporative stage of the lake. Sediment progradation resulted from increased sedimentation due to lowering of base level. There is no evidence of tectonic activity in the BPP during the Holocene. In contrast, there are breaks in the Holocene strata in LE. So the EPGF is technically active across LE.

2010 Joint United States-Canadian Program to explore the limits of the Extended Continental Shelf aboard U.S. Coast Guard Cutter Healy--Cruise HLY1002

USGS Publications Warehouse

Edwards, Brian D.; Childs, Jonathan R.; Triezenberg, Peter J.; Danforth, William W.; Gibbons, Helen

2013-01-01

In August and September 2010, the U.S. Geological Survey, in cooperation with Natural Resources Canada, Geological Survey of Canada, conducted bathymetric and geophysical surveys in the Beaufort Sea and eastern Arctic Ocean aboard the U.S. Coast Guard Cutter Healy. The principal objective of this mission to the high Arctic was to acquire data in support of a delineation of the outer limits of the U.S. and Canadian Extended Continental Shelf in the Arctic Ocean, in accordance with the provisions of Article 76 of the United Nations Convention on the Law of the Sea. The Healy was accompanied by the Canadian Coast Guard icebreaker Louis S. St-Laurent. The scientific parties on board the two vessels consisted principally of staff from the U.S. Geological Survey (Healy), and the Geological Survey of Canada and the Canadian Hydrographic Service (Louis). The crew also included marine-mammal observers, Native-community observers, ice observers, and biologists conducting research of opportunity in the Arctic Ocean. Despite interruptions necessitated by three medical emergencies, the joint survey proved largely successful. The Healy collected 7,201 trackline-kilometers of swath (multibeam) bathymetry (47,663 square kilometers) and CHIRP subbottom data, with accompanying marine gravity measurements, and expendable bathythermograph data. The Louis acquired 3,673 trackline-kilometers of multichannel seismic (airgun) deep-penetration reflection data along 25 continuous profiles, as well as 34 sonobuoy refraction stations and 9,500 trackline-kilometers of single-beam bathymetry. The coordinated efforts of the two vessels resulted in seismic-reflection-profile data that were of much higher quality and continuity than if the data had been acquired with a single vessel alone. The equipment-failure rate of the seismic equipment aboard the Louis was greatly reduced when the Healy led as the ice breaker. When ice conditions proved too severe to deploy the seismic system, the Louis led the Healy, resulting in much improved quality of the swath bathymetric and CHIRP subbottom data in comparison with data collected either by the Healy in the lead or the Healy working alone. During periods when the Healy was operating alone (principally when the Louis was diverted for emergency medical evacuations or ship repairs), the Healy was able to deploy a piston-core-sampler (10 meters maximum potential recovery depending on configuration). The coring operations resulted in recovery of cores at five locations ranging from 2.4 to 5.7 meters in length from water depths ranging from 1,157 to 3,700 meters. One of these cores sited on the Alaskan margin recovered the first reported occurrence of methane hydrate from the Arctic Ocean. Ancillary science objectives, including ice observations and deployment of ice-monitoring buoys and water-column sampling to measure acidification of Arctic waters were successfully conducted. The water-column sampling included using 10 full-ocean-depth, water-sampling casts with accompanying conductivity-temperature-depth measurements. Except for the data deemed proprietary, data from the cruise have been archived and are available for download at the National Geophysical Data Center and at cooperating organizations. Outreach staff and guest teachers aboard the two vessels provided near-real-time connection between the research activities and the public through online blogs, web pages, and other media.

30 CFR 251.12 - Submission, inspection, and selection of geophysical data and information collected under a...

Code of Federal Regulations, 2011 CFR

2011-07-01

... Section 251.12 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, REGULATION, AND ENFORCEMENT..., shallow and deep subbottom profiles, bathymetry, sidescan sonar, gravity and magnetic surveys, and special...

Geomorphology of submerged river channels indicates Late Quaternary tectonic activity in the Gulf of Trieste, Northern Adriatic

NASA Astrophysics Data System (ADS)

Vrabec, M.; Slavec, P.; Poglajen, S.; Busetti, M.

2012-04-01

We use multibeam and parametric subbottom sonar data, complemented with multichannel and high-resolution single-channel seismic profiles, to investigate sea-bottom morphology and subbottom sediment structure in the south-eastern half of the Gulf of Trieste, northern Adriatic Sea. The study area comprises 180 km2 of predominantly flat seabed with the water depth from 20 to 25 m. Pre-Quaternary basement consists of Mesozoic-Paleogene carbonate platform unit, overlain by Eocene marls and sandstones, covered by up to 300 m thick Quaternary sediments of predominantly continental origin. The uppermost few meters of sediment consist of Holocene fine-grained marine deposits. Structurally, the investigated area belongs to the imbricated rim of the Adriatic microplate and is dissected by several NE-dipping low-angle thrusts with up to several kms of displacement. The thrusts are cut by younger NE-SW-trending steeply dipping faults with sinistral and/or normal offset, mapped onshore. The continuation of those faults into the offshore area is suggested by mismatch of thrust structures between parallel seismic profiles. Geodetic data on present-day tectonic activity is controversial. Whereas the Adriatic microplate is currently moving northwards towards Eurasia at the rate of 2-4 mm/yr, the GNSS data show no measurable deformation in the Gulf of Trieste. On the other hand, onshore precise-levelling data suggest localized vertical motions in the range of 1 mm/yr, interpreted as an indication of thrust activity. High-resolution swath bathymetry revealed several current-related erosional and depositional features such as gullies and megadunes with up to 5 m of relief. The most conspicuous seabed morphological features are pre-Holocene river channels preserved in low-erosion submarine environment, which make excellent markers for studying the long-term geomorphological evolution of the area. The WNW-ESE-trending paleo-Rižana river is characterized by highly sinuous meandering channels. Sequential profiles perpendicular to the river course suggest consistent ~NE-ward lateral shifting of channels, parallel with inclination of the present-day seabed and with the present-day lateral gradient in channel depth. A longitudinal profile of the Rižana river plain revealed downstream increase in elevation of the stream bed, visible both from seabed bathymetry and from vertical position of channel lag deposits in subbottom sonar profiles. These observations suggest post-depositional tectonic tilting of the fluvial sediments that could be related either to activation of NE-dipping thrusts in the pre-Quaternary basement, or to minor anticlinal folding associated with Quaternary transpressional faulting along NW-SE-trending zones, implied from seismic profiles NW-ward of our study area. An enigmatic low-sinuosity channel feature runs along the coastline in the NE-SW direction and crosses the paleo-Rižana channel. Subbottom sonar profiles show asymmetric channel geometry and strong reflectors (channel lag deposits?) at the channel bottom, typical of other documented river channels in the area. This feature is vertically offset by a NE-SW-trending linear morphological flexure that corresponds in location and orientation to the onshore Monte Spaccato fault. Subbottom profiling revealed in several places an abrupt truncation of horizontal reflectors that could be manifestation of faulting. These indications of Late Quaternary - Holocene tectonic activity may have important implications for seismic hazard in the heavily populated coastal area of the Gulf of Trieste.

High-Resolution Chirp and Mini-Sparker Seismic-Reflection Data From the Southern California Continental Shelf - Gaviota to Mugu Canyon

USGS Publications Warehouse

Sliter, Ray W.; Triezenberg, Peter J.; Hart, Patrick E.; Draut, Amy E.; Normark, William R.; Conrad, James E.

2008-01-01

The U.S. Geological Survey (USGS) collected high-resolution shallow seismic-reflection data in September, 2007, and June-July, 2008, from the continental shelf offshore of southern California between Gaviota and Mugu Canyon, in support of the California's State Waters Mapping Program. Data were acquired using SIG 2mille mini-sparker and Edgetech chirp 512 instruments aboard the R/V Zephyr (Sept. 2007) and R/V Parke Snavely (June-July 2008). The survey area spanned approximately 120 km of coastline, and included shore-perpendicular transects spaced 1.0-1.5 km apart that extended offshore to at least the 3-mile limit of State waters, in water depths ranging from 10 m near shore to 300 m near the offshore extent of Mugu and Hueneme submarine canyons. Subbottom acoustic penetration spanned tens to several hundred meters, variable by location. This report includes maps of the surveyed transects, linked to Google Earth software, as well as digital data files showing images of each transect in SEG-Y, JPEG, and TIFF formats. The images of sediment deposits, tectonic structure, and natural-gas seeps collected during this study provide geologic information that is essential to coastal zone and resource management at Federal, State and local levels, as well as to future research on the sedimentary, tectonic, and climatic record of southern California.

Latest Pleistocene to Holocene Evolution of the Baie de Port au Prince, Haiti

NASA Astrophysics Data System (ADS)

Rios, J. K.; McHugh, C. M.; Seeber, L.; Blair, S.; Sorlien, C. C.

2012-12-01

The Baie de Port au Prince (BPP) is adjacent a restraining segment of the sinistral Caribbean-North America plate boundary and is therefore situated between converging high-relief thrust systems, the Massif Selle (Peninsula Range) to the south and the Chaine de Matheux (Hispaniola highlands) to the north. To evaluate neotectonic deformation, seismic hazards and sedimentation patterns for the BPP, six gravity cores were studied within the framework of chirp profiles collected from the R/V Endeavor in 2010. The cores were recovered from 76 m to 148 m of water depth sampling sediment from the carbonate platform that rims the BPP and from the slope. We studied the biostratigraphy (foraminifers, nannoplankton), geochemical elemental composition and physical properties of the sediment. An age model from the last glacial to the present (~20 ka BP) was derived from radiocarbon. Nannoplankton biostratigraphy provide constraints on the late Pleistocene. The BPP is 150 m maximum water depth and is rimmed by an ~30 m deep carbonate platform that has undergone dissolution. Terraces characterize the sub-bottom topography to the NE. This topography was covered by sediment during at least one relative sea-level cycle. Sediment progradation and mass-wasting on the northern and southern flanks of the BPP respectively, occurred during the latest Pleistocene low stand (~20 ka BP). Increased sedimentation from 0.2 mm/year to 0.8 mm/year occurred from 14.2 ka BP to 9.5 ka BP. This period also corresponds with a global rapid rate in sea-level rise from -94 m to -37 m. A basin wide acoustically transparent layer of sediment ~10 m thick covered the BPP. Mass-wasting, microfaulting, fluidization and turbidites caused by erosion triggered by pre-historic earthquakes possibly associated with EPG transform fault are found in the cores. One such deposit is possibly associated to the 2010 earthquake and another to an unconformable surface that separates early- from late-Holocene sediment on the slope. The late Pleistocene sediment is laminated and microfossils assemblages reveal sediment reworking and shallow water depths. Normal marine sedimentation resumed from ~14 ka BP to the present. The climate was characterized by wet or high discharge intervals noted by an influx of wood fragments and sediment most likely derived from land (>Si weight %, Al%, Fe% and Cu ppm). Wet periods were less frequent in the Holocene. The late Holocene trend is to dryer climate consistent with previous studies of the region. Evaporation is manifested by an increase in subhedral gypsum coated in calcite. Limited chirp profiles across the BPP suggest subsidence to the south. Ages from the base of the cores will verify this possibility. Coseismic 2010 uplift was documented in the southwestern part of the Leogane delta, an area that has no evidence of long-term uplift. Chirp profiles and multibeam bathymetry close to this uplift, show a deepening of the sea-floor suggestive of ongoing subsidence. More studies are needed to better understand the long-term patterns of subsidence and uplift in this region.

30 CFR 282.5 - Disclosure of data and information to the public.

Code of Federal Regulations, 2010 CFR

2010-07-01

..., bathymetry, side-scan sonar, subbottom profiler, and magnetometer) in compliance with stipulations or orders concerning protection of environmental aspects of the lease may be made available to the public 60 days after...

Continuous resistivity profiling and seismic-reflection data collected in April 2010 from Indian River Bay, Delaware

USGS Publications Warehouse

Cross, V.A.; Bratton, J.F.; Michael, H.A.; Kroeger, K.D.; Green, Adrian; Bergeron, Emile M.

2014-01-01

A geophysical survey to delineate the fresh-saline groundwater interface and associated sub-bottom sedimentary structures beneath Indian River Bay, Delaware, was carried out in April 2010. This included surveying at higher spatial resolution in the vicinity of a study site at Holts Landing, where intensive onshore and offshore studies were subsequently completed. The total length of continuous resistivity profiling (CRP) survey lines was 145 kilometers (km), with 36 km of chirp seismic lines surveyed around the perimeter of the bay. Medium-resolution CRP surveying was performed using a 50-meter streamer in a baywide grid. Results of the surveying and data inversion showed the presence of many buried paleochannels beneath Indian River Bay that generally extended perpendicular from the shoreline in areas of modern tributaries, tidal creeks, and marshes. An especially wide and deep paleochannel system was imaged in the southeastern part of the bay near White Creek. Many paleochannels also had high-resistivity anomalies corresponding to low-salinity groundwater plumes associated with them, likely due to the presence of fine-grained estuarine mud and peats in the channel fills that act as submarine confining units. Where present, these units allow plumes of low-salinity groundwater that was recharged onshore to move beyond the shoreline, creating a complex fresh-saline groundwater interface in the subsurface. The properties of this interface are important considerations in construction of accurate coastal groundwater flow models. These models are required to help predict how nutrient-rich groundwater, recharged in agricultural watersheds such as this one, makes its way into coastal bays and impacts surface-water quality and estuarine ecosystems.

High-resolution Geophysical Constraints on Fault Structure and Morphology in the Catalina Basin, Southern California Inner Continental Borderland

NASA Astrophysics Data System (ADS)

Walton, M. A. L.; Roland, E. C.; Brothers, D. S.; Kluesner, J.; Maier, K. L.; Conrad, J. E.; Hart, P. E.; Balster-Gee, A. F.

2016-12-01

Southern California's Inner Continental Borderland, offshore of Los Angeles and San Diego, contains a complex arrangement of basins, ridges, and active faults that present seismic hazards to the region. In 2014 and 2016, the U.S. Geological Survey and University of Washington collected new geophysical data throughout the Catalina Basin (CB), including multibeam bathymetry, Chirp sub-bottom profiles, and more than 2000 line-km of high-resolution multi-channel seismic reflection profiles. These data provide the first detailed imaging of the San Clemente and Catalina faults, which border the CB. We now have improved constraints on the seabed morphology, fault structure, and deformation history along significant length of the San Clemente and Catalina fault systems, as well as insights into sediment deposition and basin development in the CB since the late Miocene. New multibeam data image the Catalina Fault as a continuous linear seafloor feature along the base of Catalina Island, and subsurface imaging indicates dominantly strike-slip motion. We also image the San Clemente Fault as a straight lineament along the seafloor downslope of San Clemente Island; the fault offsets several gullies and ridges, suggesting recent strike-slip motion. In the northwest region of the CB, the San Clemente Fault's main trace splits into several transpressional splays, as indicated by a series of uplifted, fault-bounded blocks. Growth strata throughout the CB suggest that oblique transform motion along the Catalina and San Clemente faults has affected regional sedimentation patterns and depocenters over time, providing a fundamental control on sediment distribution within the CB. Buried folds, faults, and unconformities within basin strata, including a prominent surface that is likely late Miocene based on regional geology, indicate multiple episodes of deformation throughout the CB's history.

3D AUV Microseismic Implementation for Deepwater Seabed Investigations

NASA Astrophysics Data System (ADS)

George, R.; Taylor, M. W.; Gravely, J. G.

2005-05-01

Autonomous Underwater Vehicle (AUV) technology, developed commercially over the past 5 years, allows for the geophysical investigation of the seabed on the deepwater continental slope at resolutions, data densities and timelines not previously attainable. High-resolution geophysical systems normally employed on deepwater survey AUVs consist of multibeam bathymetry, side scan sonar and subbottom profiler. Inertial navigation allows positioning accuracies on the order of plus or minus 3 meters in depths up to 2,000 meters. C & C Technologies, Inc. owns and operates the C-Surveyor I AUV, which has collected more than 40,000 km of geohazard survey data on the continental slopes of the Gulf of Mexico, Mediterranean Sea, Brazil and West Africa. The oil and gas industry routinely engineers deepwater platform-mooring systems and other bottom founded subsea systems for exploration and production developments. Resolute subbottom imaging of the foundation zone in order to identify the near-seafloor geologic conditions at these deepwater development sites is critical in order to maintain system integrity. The paper describes the methodology and post-processing techniques used to create a high-resolution (2-8 kHz) 3D seismic cube from subbottom profiler data collected from an AUV system. Data examples of the multibeam bathymetry, side scan sonar and 2D seismic profiles will be provided to complement the results of the 3D seismic cube processing. Examples of inlines, crosslines, arbitrary lines, seafloor amplitude extraction and time slices are presented for the 4-meter binned data set. Advantages, disadvantages and suggested improvements for the survey acquisition technique and post processing are discussed.

30 CFR 550.197 - Data and information to be made available to the public or for limited inspection.

Code of Federal Regulations, 2013 CFR

2013-07-01

.... (2) Data or information is collected with high-resolution systems (e.g., bathymetry, side-scan sonar, subbottom profiler, and magnetometer) to comply with safety or environmental protection requirements...

30 CFR 550.197 - Data and information to be made available to the public or for limited inspection.

Code of Federal Regulations, 2012 CFR

2012-07-01

.... (2) Data or information is collected with high-resolution systems (e.g., bathymetry, side-scan sonar, subbottom profiler, and magnetometer) to comply with safety or environmental protection requirements...

30 CFR 550.197 - Data and information to be made available to the public or for limited inspection.

Code of Federal Regulations, 2014 CFR

2014-07-01

.... (2) Data or information is collected with high-resolution systems (e.g., bathymetry, side-scan sonar, subbottom profiler, and magnetometer) to comply with safety or environmental protection requirements...

Development and applications of an acoustic package for deep-sea sub-bottom profiling and detailed seafloor imaging

NASA Astrophysics Data System (ADS)

Nishimura, Kiyokazu; Kisimoto, Kiyoyuki; Joshima, Masato; Arai, Kohsaku

In the deep-sea geological survey, good survey results are difficult to obtain by a conventional surface-towed acoustic survey system, because the horizontal resolution is limited due to the long distance between the sensor and the target (seafloor). In order to improve the horizontal resolution, a deep-tow system, which tows the sensor in the vicinity of seafloor, is most practical, and many such systems have been developed and used until today. It is not easy, however, to carry out a high-density survey in a small area by maneuvering the towing body altitude sufficiently close to the seafloor with rugged topography. A ROV (Remotely Operated Vehicle) can be used to solve this problem. The ROV makes a high-density 2D survey feasible because of its maneuverability, although a long-distance survey is difficult with it. Accordingly, we have developed an acoustic survey system installed on a ROV. The system named DAIPACK (Deep-sea Acoustic Imaging Package) consists of (1) a deep-sea sub-bottom profiler and (2) a deep-sea sidescan sonar. (1) Deep-sea sub-bottom profiler A light-weight and compact sub-bottom profiler for shallow water was chosen to improve and repackage for the deep sea usage. The system is composed of three units; a transducer, an electronic unit and a notebook computer for system control and data acquisition. The source frequency is 10kHz. To convert the system for the deep sea, the transducer was exchanged for the deep sea model, and the electronic unit was improved accordingly. The electronic unit and the notebook computer were installed in a spherical pressure vessel. (2) Deep-sea sidescan sonar We remodeled a compact shallow sea sidescan sonar(water depth limitation is 30m ) into a deep sea one. This sidescan sonar is composed of a sonar towfish (transducers and an electronic unit ), a cable and a notebook computer (data processor). To accommodate in the deep water, the transducers were remodeled into a high pressure resistance type, and the electronic unit and the computer unit were stored in a spherical pressure vessel. The frequency output of the sidescan sonar is 330kHz, and the ranging distance is variable from 15m to 120m (one side).

Effect of pulse profile and chirp on a laser wakefield generation

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

Zhang Xiaomei; Shen Baifei; Ji Liangliang

2012-05-15

A laser wakefield driven by an asymmetric laser pulse with/without chirp is investigated analytically and through two-dimensional particle-in-cell simulations. For a laser pulse with an appropriate pulse length compared with the plasma wavelength, the wakefield amplitude can be enhanced by using an asymmetric un-chirped laser pulse with a fast rise time; however, the growth is small. On the other hand, the wakefield can be greatly enhanced for both positively chirped laser pulse having a fast rise time and negatively chirped laser pulse having a slow rise time. Simulations show that at the early laser-plasma interaction stage, due to the influencemore » of the fast rise time the wakefield driven by the positively chirped laser pulse is more intense than that driven by the negatively chirped laser pulse, which is in good agreement with analytical results. At a later time, since the laser pulse with positive chirp exhibits opposite evolution to the one with negative chirp when propagating in plasma, the wakefield in the latter case grows more intensely. These effects should be useful in laser wakefield acceleration experiments operating at low plasma densities.« less

Control of Brillouin short-pulse seed amplification by chirping the pump pulse

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

Lehmann, G.; Spatschek, K. H.

Seed amplification via Brillouin backscattering of a long pump pulse is considered. Similar to Raman amplification, several obstructive effects may occur during short-pulse Brillouin amplification. One is the spontaneous Raman backscattering of the pump before interacting with the seed. Preforming the plasma and/or chirping the pump will reduce unwanted pump backscattering. Optimized regions for low-loss pump propagation were proposed already in conjunction with Raman seed amplification. Hence, the influence of the chirp of the pump during Brillouin interaction with the seed becomes important and will be considered here. Both, the linear as well as the nonlinear evolution phases of themore » seed caused by Brillouin amplification under the action of a chirped pump are investigated. The amplification rate as well as the seed profiles are presented as function of the chirping rate. Also the dependence of superradiant scaling rates on the chirp parameter is discussed.« less

Geomorphic characterization of four shelf-sourced submarine canyons along the U.S. Mid-Atlantic continental margin

USGS Publications Warehouse

Obelcz, Jeffrey; Brothers, Daniel S.; Chaytor, Jason D.; ten Brink, Uri S.; Ross, Steve W.; Brooke, Sandra

2013-01-01

Shelf-sourced submarine canyons are common features of continental margins and are fundamental to deep-sea sedimentary systems. Despite their geomorphic and geologic significance, relatively few passive margin shelf-breaching canyons worldwide have been mapped using modern geophysical methods. Between 2007 and 2012 a series of geophysical surveys was conducted across four major canyons of the US Mid-Atlantic margin: Wilmington, Baltimore, Washington, and Norfolk canyons. More than 5700 km2 of high-resolution multibeam bathymetry and 890 line-km of sub-bottom CHIRP profiles were collected along the outer shelf and uppermost slope (depths of 80-1200 m). The data allowed us to compare and contrast the fine-scale morphology of each canyon system. The canyons have marked differences in the morphology and orientation of canyon heads, steepness and density of sidewall gullies, and the character of the continental shelf surrounding canyon rims. Down-canyon axial profiles for Washington, Baltimore and Wilmington canyons have linear shapes, and each canyon thalweg exhibits morphological evidence for recent, relatively small-scale sediment transport. For example, Washington Canyon displays extremely steep wall gradients and contains ~100 m wide, 5–10 m deep, v-shaped incisions down the canyon axis, suggesting modern or recent sediment transport. In contrast, the convex axial thalweg profile, the absence of thalweg incision, and evidence for sediment infilling at the canyon head, suggest that depositional processes strongly influence Norfolk Canyon during the current sea-level high-stand. The north walls of Wilmington, Washington and Norfolk canyons are steeper than the south walls due to differential erosion, though the underlying cause for this asymmetry is not clear. Furthermore, we speculate that most of the geomorphic features observed within the canyons (e.g., terraces, tributary canyons, gullies, and hanging valleys) were formed during the Pleistocene, and show only subtle modification by Holocene processes active during the present sea-level high-stand.

Records of continental slope sediment flow morphodynamic responses to gradient and active faulting from integrated AUV and ROV data, offshore Palos Verdes, southern California Borderland

USGS Publications Warehouse

Maier, Katherine L.; Brothers, Daniel; Paull, Charles K.; McGann, Mary; Caress, David W.; Conrad, James E.

2016-01-01

Variations in seabed gradient are widely acknowledged to influence deep-water deposition, but are often difficult to measure in sufficient detail from both modern and ancient examples. On the continental slope offshore Los Angeles, California, autonomous underwater vehicle, remotely operated vehicle, and shipboard methods were used to collect a dense grid of high-resolution multibeam bathymetry, chirp sub-bottom profiles, and targeted sediment core samples that demonstrate the influence of seafloor gradient on sediment accumulation, depositional environment, grain size of deposits, and seafloor morphology. In this setting, restraining and releasing bends along the active right-lateral Palos Verdes Fault create and maintain variations in seafloor gradient. Holocene down-slope flows appear to have been generated by slope failure, primarily on the uppermost slope (~ 100–200 m water depth). Turbidity currents created a low relief (< 10 m) channel, up-slope migrating sediment waves (λ = ~ 100 m, h ≤ 2 m), and a series of depocenters that have accumulated up to 4 m of Holocene sediment. Sediment waves increase in wavelength and decrease in wave height with decreasing gradient. Integrated analysis of high-resolution datasets provides quantification of morphodynamic sensitivity to seafloor gradients acting throughout deep-water depositional systems. These results help to bridge gaps in scale between existing deep-sea and experimental datasets and may provide constraints for future numerical modeling studies.

Final Act of an Oceanic Detachment Fault Revealed by Submersible Dives at 13°48'N on the Mid-Atlantic Ridge

NASA Astrophysics Data System (ADS)

Parnell-Turner, R. E.; Mittelstaedt, E. L.; Kurz, M. D.; Klein, F.

2017-12-01

A large proportion of crustal accretion on the slow-spreading Mid-Atlantic Ridge occurs under the influence of slip on low-angle detachment faults. The final stages of activity on an individual detachment system remain poorly understood, since it is difficult to place age constraints on exposed fault surfaces or lava flows. We use data from a combination of manned (Alvin) and autonomous (Sentry) submersible dives on a detachment near 13°48'N, to infer the history of slip and volcanism on a detachment fault which has recently become extinct. The corrugated surface, near the toe of the detachment, is cross-cut by a volcanic ridge, where pillow lavas have been photographed and sampled. Sub-bottom (CHIRP) profiles acquired by Sentry provide estimates of sediment thickness, which we use as a proxy for seafloor age, thus providing a relative dating tool for the exposed detachment footwall and erupted lavas. Sediments covering the footwall are 2 m thinner than those on lavas which cut across the detachment, implying that slip continued for 150 ka after eruption (assuming a constant sedimentation rate of 7 ± 2 mm/yr). Alternatively, sediment on the footwall may have been mass-wasted, and volcanism could have been contemporaneous with detachment inactivity. These results demonstrate that detachment faults may be highly sensitive to local changes in magma supply, and that direct seafloor observations are crucial to understanding slow-spreading ridge mechanics.

Linearly chirped tapered fiber-Bragg-grating-based Fabry-Perot cavity and its application in simultaneous strain and temperature measurement.

PubMed

Markowski, Konrad; Jędrzejewski, Kazimierz; Marzęcki, Michał; Osuch, Tomasz

2017-04-01

A novel concept of a Fabry-Perot (F-P) cavity composed of two linearly chirped fiber Bragg gratings written in a thermally fused fiber taper is presented. Both chirped gratings are written in counter-directional chirp configuration, where chirps resulting from the optical fiber taper profile and linearly increasing grating periods cancel each other out, forming a high-quality F-P resonator. A new strain-sensing mechanism is proposed in the presented structure, which is based on strain-induced detuning of the F-P resonator. Due to the different strain and temperature responses of the cavity, the resonator can be used for the simultaneous measurement of these physical quantities, or it can be used as a temperature-independent strain sensor.

Site assessment using echo sounding, side scan sonar and sub-bottom profiling.

DOT National Transportation Integrated Search

2014-02-01

The primary objective of this research is to use multifaceted geophysical data techniques in order to better map karst terrain beneath : standing bodies of water. This study may help providing stronger mapping techniques for future bridge and dam con...

Amplification of a seed pumped by a chirped laser in the strong coupling Brillouin regime

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

Schluck, F.; Lehmann, G.; Spatschek, K. H.

Seed amplification via Brillouin backscattering of a long pump laser-pulse is considered. The interaction takes place in the so called strong coupling regime. Pump chirping is applied to mitigate spontaneous Raman backscattering of the pump before interacting with the seed. The strong coupling regime facilitates stronger exponential growth and narrower seeds compared to the so called weak coupling regime, although in the latter the scaling with pump amplitude is stronger. Strong coupling is achieved when the pump laser amplitude exceeds a certain threshold. It is shown how the chirp influences both the linear as well as the nonlinear amplification process.more » First, linear amplification as well as the seed profiles are determined in dependence of the chirping rate. In contrast to the weak coupling situation, the evolution is not symmetric with respect to the sign of the chirping rate. In the nonlinear stage of the amplification, we find an intrinsic chirp of the seed pulse even for an un-chirped pump. We show that chirping the pump may have a strong influence on the shape of the seed in the nonlinear amplification phase. Also, the influence of pump chirp on the efficiency of Brillouin seed amplification is discussed.« less

Numerical analysis of double chirp effect in tapered and linearly chirped fiber Bragg gratings.

PubMed

Markowski, Konrad; Jedrzejewski, Kazimierz; Osuch, Tomasz

2016-06-10

In this paper, a theoretical analysis of recently developed tapered chirped fiber Bragg gratings (TCFBG) written in co-directional and counter-directional configurations is presented. In particular, the effects of the synthesis of chirps resulting from both a fused taper profile and a linearly chirped fringe pattern of the induced refractive index changes within the fiber core are extensively examined. For this purpose, a numerical model based on the transfer matrix method (TMM) and the coupled mode theory (CMT) was developed for such a grating. The impact of TCFBG parameters, such as grating length and steepness of the taper transition, as well as the effect of the fringe pattern chirp rate on the spectral properties of the resulting gratings, are presented. Results show that, by using the appropriate design process, TCFBGs with reduced or enhanced resulting chirp, and thus with widely tailored spectral responses, can be easily achieved. In turn, it reveals a great potential application of such structures. The presented numerical approach provides an excellent tool for TCFBG design.

Changes in Depositional Setting Reflect Rising Sealevel in Latest Holocene Sediments of the Hudson River

NASA Astrophysics Data System (ADS)

Slagle, A.; Carbotte, S. M.; Ryan, W. B.; Bell, R.; Nitsche, F. O.; McHugh, C. M.

2002-12-01

An extensive database of geophysical and sampling data in the Hudson River has been obtained in ten study areas between the New York Harbor and the Troy Dam. These data include bathymetry, bank-to-bank coverage of side-looking sonar imagery, subbottom reflection profiles, sediment cores and grabs. Geophysical properties, including gamma density, magnetic susceptibility and P-wave velocity, have been measured in a 9.3 m Vibracore (SD-30) from the near-channel tidal flats of the Tappan Zee area. Three distinct sedimentary facies have been identified, based on changes in physical properties, lithology and seismic reflections. Facies 1 is an oyster-rich unit with unstratified sediments and high sound velocities, and is found in the upper 1.5 m of core SD-30. Chirp subbottom data, which provide reflectors down to approximately 4 m depth, show a distinct horizon at 1.5 m, supporting the change seen in physical property data and lithology at this depth. A unit characterized by laminated sediments, interbedded with homogeneous layers and coquina layers, is identified as Facies 2 and is found between 1.5 and 6.1 m. This facies has high magnetic susceptibility and the appearance of discrete density cycles. The oldest unit, Facies 3, extends from 6.1 m to the base of the core at 9.3 m. It is made up of oyster-rich, unbedded sediments and thick coquina layers, and is characterized by low magnetic susceptibility. Radiocarbon dating of oysters and bivalves indicates that the different facies in SD-30 correspond to different sedimentation rates, with highest values occurring during deposition of Facies 2. The facies changes and variations in sedimentation rates are attributed to an evolving depositional environment in the tidal flats of the Tappan Zee area due to rising sealevel. Extrapolating from nearby cores that penetrate deeper into the sedimentary record, Facies 3 sits above post-glacial fluvial sands and represents the transition from a fresh to more brackish environment, suitable for development of oyster beds. The laminated sediments of Facies 2 are attributed to infilling of the tidal flats during a rapid rise in sealevel. The lack of laminated sediments and low sedimentation rates of Facies 1 are attributed to the modern wave-base dominated depositional setting in the Tappan Zee area.

Deglaciation of the Western Margin of the Barents Sea Ice Sheet - a Swath Bathymetric and Sub-Bottom Seismic Study from Eglacom Nice-Streams Data in the Kveithola Trough

NASA Astrophysics Data System (ADS)

Rebesco, M.; Liu, Y.; Camerlenghi, A.; Winsborrow, M. C.; Laberg, J.; Caburlotto, A.; Diviacco, P.; Accettella, D.; Sauli, C.; Wardell, N.

2010-12-01

IPY Activity N. 367 focusing on Neogene ice streams and sedimentary processes on high- latitude continental margins (NICE-STREAMS) resulted in two coordinated cruises on the adjacent Storfjorden and Kveithola trough-mouth fans in the NW Barents Sea: SVAIS Cruise of BIO Hespérides, summer 2007, and EGLACOM Cruise of Cruise R/V OGS-Explora, summer 2008. The objectives were to acquire a high-resolution set of bathymetric, seismic and sediment core data in order to decipher the Neogene architectural development of the glacially-dominated NW Barents Sea continental margin in response to natural climate change. The paleo-ice streams drained ice from southern Spitsbergen, Spitsbergen Bank, and Bear Island. The short distance from the ice source to the calving front produced a short residence time of ice, and therefore a rapid response to climatic changes. We describe here the EGLACOM data collected within the Kveithola Trough, an E-W trending glacial trough in the NW Barents Sea, NW of the Bear Island. Swath bathymetry shows that the seafloor is characterised by E-W trending mega-scale glacial lineations (MSGL) that record a fast flowing ice stream draining the Svalbard/Barents Sea Ice Sheet (SBIS) during the Last Glacial Maximum (LGM). MSGL are overprinted by transverse sediment ridges about 15 km apart which give rise to a staircase axial profile of the trough. Such transverse ridges are interpreted as grounding-zone wedges (GZW) formed by deposition of unconsolidated, saturated subglacial till during episodic ice stream retreat. Sub-bottom (CHIRP) and multi-channel reflection seismic data show that present-day morphology is largely inherited from the palaeo-seafloor topography at the time of deposition of the transverse ridges, overlain by a draping glaciomarine unit up to over 15 m thick. Our data allow the reconstruction of depositional processes that accompanied the deglaciation of the Spitsbergen Bank area. The sedimentary drape deposited on top of the GZWs which accumulated at a very high rate in the order of 1-1.5 m ka-1 has a potential to preserve a high resolution palaeoclimatic record of the deglaciation and post-glacial condition in this sector of the Barents Sea.

Role of Frequency Chirp and Energy Flow Directionality in the Strong Coupling Regime of Brillouin-Based Plasma Amplification.

PubMed

Chiaramello, M; Amiranoff, F; Riconda, C; Weber, S

2016-12-02

A detailed analysis is presented of the various stages of strong coupling Brillouin plasma amplification, emphasizing the importance of the chirp which can be of threefold origin: the intrinsic one driven by the amplification process, the one originating from the chirped-pulse-generated laser pulses, and the one associated with the plasma profile. Control of the overall chirp can optimize or quench the energy transfer. The time-dependent phase relation explains the energy flow direction during amplification and is characteristic for this strong coupling process. The study is also of potential importance to understand and maybe control cross-beam-energy transfer in inertial confinement fusion.

System for generating pluralities of optical pulses with predetermined frequencies in a temporally and spatially overlapped relationship

DOEpatents

Meyerhofer, David D.; Schmid, Ansgar W.; Chuang, Yung-ho

1992-01-01

Ultra short (pico second and shorter) laser pulses having components of different frequency which are overlapped coherently in space and with a predetermined constant relationship in time, are generated and may be used in applications where plural spectrally separate, time-synchronized pulses are needed as in wave-length resolved spectroscopy and spectral pump probe measurements for characterization of materials. A Chirped Pulse Amplifier (CPA), such as a regenerative amplifier, which provides amplified, high intensity pulses at the output thereof which have the same spatial intensity profile, is used to process a series of chirped pulses, each with a different central frequency (the desired frequencies contained in the output pulses). Each series of chirped pulses is obtained from a single chirped pulse by spectral windowing with a mask in a dispersive expansion stage ahead of the laser amplifier. The laser amplifier amplifies the pulses and provides output pulses with like spatial and temporal profiles. A compression stage then compresses the amplified pulses. All the individual pulses of different frequency, which originated in each single chirped pulse, are compressed and thereby coherently overlapped in space and time. The compressed pulses may be used for the foregoing purposes and other purposes wherien pulses having a plurality of discrete frequency components are required.

System for generating pluralities of optical pulses with predetermined frequencies in a temporally and spatially overlapped relationship

DOEpatents

Meyerhofer, D.D.; Schmid, A.W.; Chuang, Y.

1992-03-10

Ultrashort (pico second and shorter) laser pulses having components of different frequency which are overlapped coherently in space and with a predetermined constant relationship in time, are generated and may be used in applications where plural spectrally separate, time-synchronized pulses are needed as in wave-length resolved spectroscopy and spectral pump probe measurements for characterization of materials. A Chirped Pulse Amplifier (CPA), such as a regenerative amplifier, which provides amplified, high intensity pulses at the output thereof which have the same spatial intensity profile, is used to process a series of chirped pulses, each with a different central frequency (the desired frequencies contained in the output pulses). Each series of chirped pulses is obtained from a single chirped pulse by spectral windowing with a mask in a dispersive expansion stage ahead of the laser amplifier. The laser amplifier amplifies the pulses and provides output pulses with like spatial and temporal profiles. A compression stage then compresses the amplified pulses. All the individual pulses of different frequency, which originated in each single chirped pulse, are compressed and thereby coherently overlapped in space and time. The compressed pulses may be used for the foregoing purposes and other purposes wherien pulses having a plurality of discrete frequency components are required. 4 figs.

Comparison and prediction of chirping in NSTX and DIII-D

NASA Astrophysics Data System (ADS)

Duarte, Vinicius; Berk, Herbert; Gorelenkov, Nikolai; Heidbrink, William; Kramer, Gerrit; Nazikian, Raffi; Pace, David; Podesta, Mario; van Zeeland, Michael

2016-10-01

We present an explanation of why frequency chirping of Alfven waves is ubiquitous in NSTX and rarely observed in DIII-D. A time-delayed cubic nonlinear equation is employed for the study of the onset of nonlinear phase-space structures. Its explosive solutions are chirping precursors. We employ NOVA and NOVA-K codes to provide consistent Alfvenic eigenmodes and weighted physical contributions from all regions of phase space. In addition, TRANSP is employed to determine the diffusivity needed to fulfill power balance. Though background micro-turbulence is usually unimportant in determining the energetic particle spatial profile, it may still be important with regard to whether chirping structures likely form. We show that the energetic particle micro-turbulent induced scattering often competes with collisional pitch-angle scattering. This competition explains the tendency for NSTX, where micro-turbulence is weak, to exhibit Alfvénic chirping, whereas in DIII-D turbulent diffusion usually dominates and chirping is not observed except when micro-turbulence markedly reduces.

Spectral effects in the propagation of chirped laser pulses in uniform underdense plasma

NASA Astrophysics Data System (ADS)

Pathak, Naveen; Zhidkov, Alexei; Hosokai, Tomonao; Kodama, Ryosuke

2018-01-01

Propagation of linearly chirped and linearly polarized, powerful laser pulses in uniform underdense plasma with their duration exceeding the plasma wave wavelength is examined via 3D fully relativistic particle-in-cell simulations. Spectral evolution of chirped laser pulses, determined by Raman scattering, essentially depends on the nonlinear electron evacuation from the first wake bucket via modulation of the known parameter /n e ( r ) ω0 2 γ . Conversely, the relative motion of different spectral components inside a pulse changes the evolution of the pulse length and, therefore, the ponderomotive forces at the pulse rear. Such longitudinal dynamics of the pulse length provoke a parametric resonance in the laser wake with continuous electron self-injection for any chirped pulses. However, the total charge of accelerated electrons and their energy distribution essentially depends on the chirp. Besides, negatively chirped laser pulses are shown to be useful for spatially resolved measurements of the plasma density profiles and for rough estimations of the laser pulse intensity evolution in underdense plasma.

Optical parametric amplifiers using chirped quasi-phase-matching gratings I: practical design formulas

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

Charbonneau-Lefort, Mathieu; Afeyan, Bedros; Fejer, M. M.

Optical parametric amplifiers using chirped quasi-phase-matching (QPM) gratings offer the possibility of engineering the gain and group delay spectra. We give practical formulas for the design of such amplifiers. We consider linearly chirped QPM gratings providing constant gain over a broad bandwidth, sinusoidally modulated profiles for selective frequency amplification and a pair of QPM gratings working in tandem to ensure constant gain and constant group delay at the same time across the spectrum. Finally, the analysis is carried out in the frequency domain using Wentzel–Kramers–Brillouin analysis.

Multi-angle backscatter classification and sub-bottom profiling for improved seafloor characterization

NASA Astrophysics Data System (ADS)

Alevizos, Evangelos; Snellen, Mirjam; Simons, Dick; Siemes, Kerstin; Greinert, Jens

2018-06-01

This study applies three classification methods exploiting the angular dependence of acoustic seafloor backscatter along with high resolution sub-bottom profiling for seafloor sediment characterization in the Eckernförde Bay, Baltic Sea Germany. This area is well suited for acoustic backscatter studies due to its shallowness, its smooth bathymetry and the presence of a wide range of sediment types. Backscatter data were acquired using a Seabeam1180 (180 kHz) multibeam echosounder and sub-bottom profiler data were recorded using a SES-2000 parametric sonar transmitting 6 and 12 kHz. The high density of seafloor soundings allowed extracting backscatter layers for five beam angles over a large part of the surveyed area. A Bayesian probability method was employed for sediment classification based on the backscatter variability at a single incidence angle, whereas Maximum Likelihood Classification (MLC) and Principal Components Analysis (PCA) were applied to the multi-angle layers. The Bayesian approach was used for identifying the optimum number of acoustic classes because cluster validation is carried out prior to class assignment and class outputs are ordinal categorical values. The method is based on the principle that backscatter values from a single incidence angle express a normal distribution for a particular sediment type. The resulting Bayesian classes were well correlated to median grain sizes and the percentage of coarse material. The MLC method uses angular response information from five layers of training areas extracted from the Bayesian classification map. The subsequent PCA analysis is based on the transformation of these five layers into two principal components that comprise most of the data variability. These principal components were clustered in five classes after running an external cluster validation test. In general both methods MLC and PCA, separated the various sediment types effectively, showing good agreement (kappa >0.7) with the Bayesian approach which also correlates well with ground truth data (r2 > 0.7). In addition, sub-bottom data were used in conjunction with the Bayesian classification results to characterize acoustic classes with respect to their geological and stratigraphic interpretation. The joined interpretation of seafloor and sub-seafloor data sets proved to be an efficient approach for a better understanding of seafloor backscatter patchiness and to discriminate acoustically similar classes in different geological/bathymetric settings.

36 CFR 2.1 - Preservation of natural, cultural and archeological resources.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 36 Parks, Forests, and Public Property 1 2012-07-01 2012-07-01 false Preservation of natural, cultural and archeological resources. 2.1 Section 2.1 Parks, Forests, and Public Property NATIONAL PARK... subbottom profilers used for authorized scientific, mining, or administrative activities. (b) The...

36 CFR 2.1 - Preservation of natural, cultural and archeological resources.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 36 Parks, Forests, and Public Property 1 2014-07-01 2014-07-01 false Preservation of natural, cultural and archeological resources. 2.1 Section 2.1 Parks, Forests, and Public Property NATIONAL PARK... subbottom profilers used for authorized scientific, mining, or administrative activities. (b) The...

30 CFR 282.5 - Disclosure of data and information to the public.

Code of Federal Regulations, 2014 CFR

2014-07-01

... public. 282.5 Section 282.5 Mineral Resources BUREAU OF SAFETY AND ENVIRONMENTAL ENFORCEMENT, DEPARTMENT... (including, but not limited to, bathymetry, side-scan sonar, subbottom profiler, and magnetometer) in compliance with stipulations or orders concerning protection of environmental aspects of the lease may be...

30 CFR 282.5 - Disclosure of data and information to the public.

Code of Federal Regulations, 2012 CFR

2012-07-01

... public. 282.5 Section 282.5 Mineral Resources BUREAU OF SAFETY AND ENVIRONMENTAL ENFORCEMENT, DEPARTMENT... (including, but not limited to, bathymetry, side-scan sonar, subbottom profiler, and magnetometer) in compliance with stipulations or orders concerning protection of environmental aspects of the lease may be...

30 CFR 282.5 - Disclosure of data and information to the public.

Code of Federal Regulations, 2013 CFR

2013-07-01

... public. 282.5 Section 282.5 Mineral Resources BUREAU OF SAFETY AND ENVIRONMENTAL ENFORCEMENT, DEPARTMENT... (including, but not limited to, bathymetry, side-scan sonar, subbottom profiler, and magnetometer) in compliance with stipulations or orders concerning protection of environmental aspects of the lease may be...

30 CFR 280.51 - What types of geophysical data and information must I submit to MMS?

Code of Federal Regulations, 2010 CFR

2010-07-01

..., shallow and deep subbottom profiles, bathymetry, sidescan sonar, gravity and magnetic surveys, and special... and of a quality suitable for processing; (c) Processed geophysical information derived from seismic... interpretive evaluation, reflecting state-of-the-art processing techniques; and (d) Other geophysical data...

Large Erosional Features on the Cascadia Accretionary Wedge Imaged with New High-Resolution Multibeam Bathymetry and Seismic Datasets

NASA Astrophysics Data System (ADS)

Beeson, J. W.; Goldfinger, C.

2013-12-01

Utilizing new high resolution multibeam bathymetric data along with chirp sub-bottom and multichannel seismic reflection (MCS) data, we identified remarkable erosional features on the toe of the Cascadia accretionary wedge near Willapa Canyon, offshore Washington, USA. Bathymetric data was compiled from the Cascadia Open-Access Seismic Transects (COAST) cruise and from the site survey cruise for the Cascadia Initiative. These features loosely resemble slope failures of the frontal thrust, but can be distinguished from such failures by several key features: They incise the crest of the frontal thrust and encompass the landward limb; They have floors below the level of the abyssal plain, similar to plunge pool morphology; They show no evidence of landslide blocks at the base of the slope indicative of block sliding. The features where likely formed during the latest Pleistocene based on post event deposition, cross-cutting relationships with Juan de Fuca Channel and the Willapa Channel levees and wave field, and post event slip on the frontal thrust of the Cascadia accretionary prism. The Holocene levees of both Willapa Channel and Juan de Fuca Channel overlap these older features, and clearly place an upper bound on the age of the erosional features in the latest Pleistocene. A lower bound is estimated from a sub-bottom profile that images ~30 meters of post scour sediment fill. Using existing literature of Holocene and Pleistocene sedimentation rates we estimate a lower age bound between ~23,000 - 56,000 y.b.p. We also map a fault scarp within the erosional feature, with ~60 m of vertical offset. Using multi-channel seismic reflection profiles from the COAST cruise we interpret this scarp as the surface expression of the landward vergent frontal thrust fault. The apparent short duration of the erosional event along the seaward margin of the accretionary wedge, coupled with the presence of the fresh fault scarp within the erosion zone, are indicative of a dormant feature with significant time required to develop the scarp after cessation of the causative process. Based on morphology, dissimilarity with other submarine features, and available age constraints, we infer that these features were most likely formed during the glacial lake outpouring in the Pacific Northwest known as the Missoula floods which occurred 13,000-19,500 y.b.p. The features themselves bear a strong resemblance to 'coulees' formed during the same glacial events onshore, and the outpourings through Willapa Channel are consistent with previous inferences of the deposition of Missoula Flood deposits in Escanaba Trough. If this timing is correct, the slip rate along the Cascadia frontal thrust can be estimated using fault geometry and scarp height as 2.8 - 4.1 mm/yr.

Atwater Valley Deep-Towed Sidescan Sonar Imagery and Bathymetric Survey

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

Joan M. Gardner; Mike Czarnecki; Rick Hagen

2005-11-22

The purpose of this project was to conduct detailed surface mapping of one of the areas drilled by the Joint Industry Project with ChevronTexaco to understand gas hydrates in the Gulf of Mexico. The gently sloping, mostly flat floor of the Mississippi Canyon is interrupted by mounds and depressions that presumably reflect the complex geology and geohydrology related to turbidite deposition and pervasive salt tectonism. The seafloor mounds we mapped in this study occur in approximately 1300 water depth along the floor of the Mississippi Canyon in lease block areas Atwater Valley 13 and 14. High resolution sidescan sonar (100more » kHz and 500 kHz) backscatter imagery, and chirp sub-bottom profiler data were collected using the DT1 deep-towed oceanographic mapping instrument, concentrating on the region directly adjacent to and surrounding two mounds identified as, mounds D and F, and in the region directly adjacent to and surrounding the mounds. The backscatter data have been mosaiced and normalized to provide information on the shape and extent of the mounds, the possible lateral extent of fauna, such as mussel and clam fields on the mounds, possible seep related flows and the occurrence of carbonate material. The extent of a mudflow can be mapped on the southeastern side of mound F. The backscatter data show extremely high-resolution detail about the shape, relief, and morphology of the mounds. This information, coupled with porewater chemistry , DTAGS and heatflow data form a coherent picture of possible mechanics for fluid venting and flora/fauna of the seeps in this region.« less

Late Holocene distal mud deposits off the Nakdong delta, SE Korea: evidence for shore-parallel sediment transport in a current-dominated setting

NASA Astrophysics Data System (ADS)

Chun, Jong-Hwa; Kim, Yuri; Bahk, Jang-Jun; Kim, Young Jun; Kang, Dong-Hyo; Kim, Yong Hoon; Kim, Gil Young; Ryu, Byong-Jae

2015-12-01

The distal mud deposits (DMDs) off the Nakdong delta represent a subaqueous delta on the inner continental shelf aligned parallel to the southeast coast of Korea and displaying a clinoform geometry. Hydrographically, the coast is characterized by a micro-tidal regime, the strong Korean Coastal Current (KCC) and the East Korean Warm Current (EKWC). Age models and sedimentary facies related to the clinoform geometries are based on high-resolution chirp subbottom profile data and have provided information on shore-parallel sediment transport and accumulation during the late Holocene sea-level highstand. The highest sedimentation rates (6.19-9.17 cm/year) produced steep foresets in the central DMDs at water depths of 35-50 m. Here, vertical burrows are repeatedly truncated by laminated mud packages displaying erosional surfaces. This region represents the main depocenter of the Nakdong subaqueous delta. The topset sediments of the southern DMD at ~40 m water depth closer to the river mouth show relatively low sedimentation rates (0.01-0.12 cm/year). Here, the muds have a predominantly mottled character. Similarly, the foreset sediments of the northern DMD at ~71-80 m water depth with sedimentation rates of 0.10-2.03 cm/year are also predominantly characterized by mottled muds. The spatial dispersal pattern of the DMDs is consistent with the coast-parallel front between the KCC and EKWC along the southeast Korean coast. In addition, the depocenter of the Nakdong subaqueous delta clinoform is affected by the near-bed turbulence generated by episodic storm events.

Reflectivity of linear and nonlinear gamma radiated apodized chirped Bragg grating under ocean

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

Hamdalla, Taymour A.; Faculty of Science, Tabuk University, Tabuk

In this paper, the effect Co{sup 60} gamma radiation is investigated on the effective refractive index of apodized chirped Bragg grating. Nine apodization profiles are considered. Comparison between the reflectivity of the gamma radiated and non radiated fiber Bragg grating has been carried out. The electric field of signals propagating through the apodized chirped fiber Bragg grating (ACFBG) is first calculated from which, new values for the refractive index are determined. The nonlinear effects appear on the ACFBG reflectivity. The effect of nonlinearity and undersea temperature and pressure on the grating is also studied.

Electromagnetic Surveying in the Mangrove Lakes Region of Everglades National Park

NASA Astrophysics Data System (ADS)

Whitman, D.; Price, R.; Frankovich, T.; Fourqurean, J.

2015-12-01

The Mangrove Lakes are an interconnected set of shallow (~ 1m), brackish lake and creek systems on the southern margin of the Everglades adjacent to Florida Bay. Current efforts associated with the Comprehensive Everglades Restoration Plan (CERP) aim to increase freshwater flow into this region. This study describes preliminary results of geophysical surveys in the lakes conducted to assess changes in the groundwater chemistry as part of a larger hydrologic and geochemical study in the Everglades Lakes region. Marine geophysical profiles were conducted in Alligator Creek (West Lake) and McCormick Creek systems in May, 2014. Data included marine electromagnetic (EM) profiles and soundings, water depth measurements, surface water conductivity and salinity measurements. A GSSI Profiler EMP-400 multi-frequency EM conductivity meter continuously recorded in-phase and quadrature field components at 1, 8, and 15 KHz. The system was deployed in a flat bottomed plastic kayak towed behind a motorized skiff. Lake water depths were continuously measured with a sounder/chart plotter which was calibrated with periodic sounding rod measurements. At periodic intervals during the survey, the profiling was stopped and surface water conductivity, temperature and salinity are recorded with a portable YSI probe on the tow boat. Over 40,000 discrete 3-frequency EM measurements were collected. The data were inverted to 2-layer models representing the water layer thickness and conductivity and the lake bottom conductivity. At spot locations, models were constrained with water depth soundings and surface water conductivity measurements. At other locations along the profiles, the water depth and conductivity were allowed to be free, but the free models were generally consistent with the constrained models. Multilayer sub-bottom models were also explored but were found to be poorly constrained. In West Lake, sub-bottom conductivities decreased from 400 mS/m in the west to 200 mS/m in the east indicating a general W to E decrease in groundwater salinity. In the McCormick Creek system, sub-bottom conductivities increased from 200 mS/m at the north end of Seven Palm Lake to over 650 mS/m at the southern end of Monroe Lake indicating a general N to S increase in ground water salinity. Additional profiles are planned in August, 2015.

Interpretation of echo sounding and sub-bottom profiling data : Mark Twain Bridge A-3798, MoDOT Route 107

DOT National Transportation Integrated Search

2008-02-01

The project consists of essentially doing what is outlined in the objective above. In addition, MoDOT will be responsible for choosing the 30 soils and 5 base materials to be tested, for doing initial property tests on them, and delivering them to UM...

Propagation properties of the chirped Airy beams through the gradient-index medium

NASA Astrophysics Data System (ADS)

Feng, Liyan; Zhang, Jianbin; Pang, Zihao; Wang, Linyi; Zhong, Tianfen; Yang, Xiangbo; Deng, Dongmei

2017-11-01

Through analytical derivation and numerical analysis, the propagation properties of the chirped Airy(CAi) beams in the gradient-index medium are investigated. The intensity and the phase distributions, the propagation trajectory and the Poynting vector of the CAi beams are demonstrated to investigate the propagation properties. Owing to the special and symmetrical refractive index profile of the gradient-index medium, the CAi beams propagate periodically. The effects of the distribution factor and the chirped parameter on the propagation of the CAi beams are analyzed. As the increasing of the distribution factor, the intensity distribution of the CAi beams is more scattering. However, with the chirped parameter increasing, the focusing property of the CAi beams strengthens. The variation of the chirped parameter can change the position of the peak intensity maximum, but it cannot alter the period of the peak intensity. The variations of the initial phase and the energy of the beams in the transverse plane expedite accordingly.

Geophysical Features and Inferred Triggering Factors of Submarine Landslides in the Western Continental Margin of the Ulleung Basin, East Sea of Korea

NASA Astrophysics Data System (ADS)

Cukur, D.; Kim, S. P.; Kong, G. S.; Yoon, Y.; Kim, J. K.; Choi, J. G.

2015-12-01

Submarine landslides form very complex features on the seafloor and the associated geological processes are yet to be known completely. Various researches are still undergoing not only for their profound academic significance but also for their hazardous impact potential to seafloor infrastructures and coastal areas. In order to investigate the morphology and cause of landslides along the western margin of the Ulleung Basin in the East Sea, we collected multiple geophysical datasets in the summer of 2015, including sparker, subbottom profiler, and multibeam echosounder. The preliminary analysis of the bathymetric data shows a number of U-shaped scarps that occur on a rather steep slope (up to 10°) in water depths of ~600 m. The scarps cover an area of ~100 km2 and have reliefs of up to 50 m. Seismic data clearly image erosional headwalls and the basal gliding plane which is characterized by a prominent high-amplitude reflector. Chaotic- to transparent-seismic facies, located immediately downslope of the headwall scarps, represent landslide deposits of about 20 m in thickness. At the base of slope, the slides form lens-shaped transparent bodies, resting on well-stratified turbidite deposits. Several V-shaped seafloor depressions near the head of these scarps are seen on the subbottom profiles. These depressions, which are ~5 m deep and ~150 m wide, are interpreted to be representing pockmarks, resulted from upward migration of gas in the sediment layers beneath. The presence of these pockmarks directly above the scars may suggest that the gases and/or gas fluids might be playing an important role for destabilizing slope sediments. Furthermore, subbottom profiles suggest the presence of numerous faults in close vicinity of headwall scarps; some are extending to the seafloor suggesting their recent activity. Earthquakes associated with tectonic activity are indicated to be the cause of these faults. Thus the fault-related earthquakes might be the final triggering mechanism of the landslides along the slopes.

Comparison with Offshore and Onshore Mud Volcanoes in the Southwestern Taiwan

NASA Astrophysics Data System (ADS)

Chen, Y. H.; Su, C. C.; Chen, T. T.; Liu, C. S.; Paull, C. K.; Caress, D. W.; Gwiazda, R.; Lundsten, E. M.; Hsu, H. H.

2017-12-01

The offshore area southwest (SW) of Taiwan is on the convergent boundary between the Eurasian and Philippine Sea plates. The plate convergence manifests in this unique geological setting as a fold-and-thrust-belt. Multi-channel seismic profiles, and bathymetry and gravity anomaly data collected from Taiwan offshore to the SW show the presence of a large amount of mud volcanoes and diapirs with NE-SW orientations. In the absence of comprehensive sampling and detailed geochemistry data from submarine mud volcanoes, the relation between onshore and offshore mud volcanoes remains ambiguous. During two MBARI and IONTU joint cruises conducted in 2017 we collected high-resolution multibeam bathymetry data (1-m-resolution) and chirp sub-bottom profiles with an autonomous underwater vehicle (AUV) from submarine Mud Volcano III (MV3), and obtained precisely located samples and video observations with a remotely operated vehicle (ROV). MV3 is an active submarine mud volcano at 465 m water depth offshore SW Taiwan. This cone-shape mud volcano is almost 780 m wide, 150 m high, with 8° slopes, and a 30 m wide mound on the top. Several linear features are observed in the southwest of the mound, and these features are interpreted as a series of marks caused by rolling rocks that erupted from the top of MV3. We collected three rocks and push cores from MV3 and its top with the ROV, in order to compare their chemical and mineralogical composition to that of samples collected from mud volcanoes along the Chishan fault. The surface and X-radiography imaging, 210Pb chronology, grain size and X-ray diffractometer analyses were conducted to compare geochemical and sedimentary properties of offshore and onshore mud volcanoes. The results indicate that the offshore and onshore mud volcanoes have similar characteristics. We suggest that offshore and onshore mud volcanoes of SW Taiwan are no different in the source of their materials and their mechanism of creation and evolution.

Manipulation of group-velocity-locked vector dissipative solitons and properties of the generated high-order vector soliton structure.

PubMed

Zhu, S N; Wu, Z C; Fu, S N; Zhao, L M

2018-03-20

Details of various composites of the projections originated from a fundamental group-velocity-locked vector dissipative soliton (GVLVDS) are both experimentally and numerically explored. By combining the projections from the orthogonal polarization components of the GVLVDS, a high-order vector soliton structure with a double-humped pulse profile along one polarization and a single-humped pulse profile along the orthogonal polarization can be observed. Moreover, by de-chirping the composite double-humped pulse, the time separation between the two humps is reduced from 15.36 ps to 1.28 ps, indicating that the frequency chirp of the GVLVDS contributes significantly to the shaping of the double-humped pulse profile.

30 CFR 580.51 - What types of geophysical data and information must I submit to BOEM?

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 2 2013-07-01 2013-07-01 false What types of geophysical data and information must I submit to BOEM? 580.51 Section 580.51 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT... not limited to, shallow and deep subbottom profiles, bathymetry, sidescan sonar, gravity and magnetic...

30 CFR 580.51 - What types of geophysical data and information must I submit to BOEM?

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 2 2012-07-01 2012-07-01 false What types of geophysical data and information must I submit to BOEM? 580.51 Section 580.51 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT... not limited to, shallow and deep subbottom profiles, bathymetry, sidescan sonar, gravity and magnetic...

30 CFR 580.51 - What types of geophysical data and information must I submit to BOEM?

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 2 2014-07-01 2014-07-01 false What types of geophysical data and information must I submit to BOEM? 580.51 Section 580.51 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT... not limited to, shallow and deep subbottom profiles, bathymetry, sidescan sonar, gravity and magnetic...

Archive of Digital boomer subbottom data collected during USGS cruises 99FGS01 and 99FGS02 offshore southeast and southwest Florida, July and November, 1999

USGS Publications Warehouse

Forde, Arnell S.; Dadisman, Shawn V.; Wiese, Dana S.; Phelps, Daniel C.

2013-01-01

In July (19 - 26) and November (17 - 18) of 1999, the USGS, in cooperation with the Florida Geological Survey (FGS), conducted two geophysical surveys in: (1) the Atlantic Ocean offshore of Florida's east coast from Orchid to Jupiter, FL, and (2) the Gulf of Mexico offshore of Venice, FL. This report serves as an archive of unprocessed digital boomer subbottom data, trackline maps, navigation files, GIS files, Field Activity Collection System (FACS) logs, and formal Federal Geographic Data Committee (FGDC) metadata. Filtered and gained (showing a relative increase in signal amplitude) digital images of the subbottom profiles are also provided. The USGS St. Petersburg Coastal and Marine Science Center (SPCMSC) assigns a unique identifier to each cruise or field activity. For example, identifiers 99FGS01 and 99FGS02 refer to field data collected in 1999 for cooperative work with the FGS. The numbers 01 and 02 indicate the data were collected during the first and second field activities for that project in that calendar year. Refer to http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html for a detailed description of the method used to assign the field activity identification (ID).

Elliptical-core two mode fiber sensors and devices incorporating photoinduced refractive index gratings

NASA Technical Reports Server (NTRS)

Greene, Jonathan A.; Miller, Mark S.; Starr, Suzanne E.; Fogg, Brian R.; Murphy, Kent A.; Claus, Richard O.; Vengsarkar, Ashish M.

1991-01-01

Results of experiments performed using germanium-doped, elliptical core, two-mode optical fibers whose sensitivity to strain was spatially varied through the use of chirped, refractive-index gratings permanently induced into the core using Argon-ion laser light are presented. This type of distributed sensor falls into the class of eighted-fiber sensors which, through a variety of means, weight the strain sensitivity of a fiber according to a specified spatial profile. We describe results of a weighted-fiber vibration mode filter which successfully enhances the particular vibration mode whose spatial profile corresponds to the profile of the grating chirp. We report on the high temperature survivability of such grating-based sensors and discuss the possibility of multiplexing more than one sensor within a single fiber.

Immersive, hands-on, team-based geophysical education at the University of Texas Marine Geology and Geophysics Field Course

NASA Astrophysics Data System (ADS)

Saustrup, S.; Gulick, S. P.; Goff, J. A.; Davis, M. B.; Duncan, D.; Reece, R.

2013-12-01

The University of Texas Institute for Geophysics (UTIG), part of the Jackson School of Geosciences, annually offers a unique and intensive three-week marine geology and geophysics field course during the spring/summer semester intersession. Now entering its seventh year, the course transitions students from a classroom environment through real-world, hands-on field acquisition, on to team-oriented data interpretation, culminating in a professional presentation before academic and industry employer representatives. The course is available to graduate students and select upper-division undergraduates, preparing them for direct entry into the geoscience workforce or for further academic study. Geophysical techniques used include high-resolution multichannel seismic reflection, CHIRP sub-bottom profiling, multibeam bathymetry, sidescan sonar, sediment coring, grab sampling, data processing, and laboratory analysis of sediments. Industry-standard equipment, methods, software packages, and visualization techniques are used throughout the course, putting students ahead of many of their peers in this respect. The course begins with a 3-day classroom introduction to the field area geology, geophysical methods, and computing resources used. The class then travels to the Gulf Coast for a week of hands-on field and lab work aboard two research vessels: UTIG's 22-foot, aluminum hulled Lake Itasca; and NOAA's 82-foot high-speed catamaran R/V Manta. The smaller vessel handles primarily shallow, inshore targets using multibeam bathymetry, sidescan sonar, and grab sampling. The larger vessel is used both inshore and offshore for multichannel seismic, CHIRP profiling, multibeam bathymetry, gravity coring, and vibracoring. Field areas to date have included Galveston and Port Aransas, Texas, and Grand Isle, Louisiana, with further work in Grand Isle scheduled for 2014. In the field, students work in teams of three, participating in survey design, instrument set-up, field deployment, data acquisition optimization, quality control, data archival, log-keeping, real-time data processing, laboratory sediment analysis, and even boat-handling. Teams are rotated through the two vessels and the onshore field laboratory to ensure that each student has hands-on experience with each aspect of the process. Although all students work on all data areas in the field, after returning from the field each team is assigned a particular region or geologic problem to interpret. Each team prepares and presents a formal presentation to UTIG researchers and industry representatives, explaining and defending their interpretations. This unique approach to hands-on field training, real-world science, and project-based teamwork helps prepare students for direct entry into the workforce, giving them a leg up on competitors for positions. This course has an impressive success ratio to show, with many students receiving job offers directly as a result of their participation in the course.

Electron heating enhancement by frequency-chirped laser pulses

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

Yazdani, E.; Afarideh, H., E-mail: hafarideh@aut.ac.ir; Sadighi-Bonabi, R., E-mail: Sadighi@sharif.ir

2014-09-14

Propagation of a chirped laser pulse with a circular polarization through an uprising plasma density profile is studied by using 1D-3V particle-in-cell simulation. The laser penetration depth is increased in an overdense plasma compared to an unchirped pulse. The induced transparency due to the laser frequency chirp results in an enhanced heating of hot electrons as well as increased maximum longitudinal electrostatic field at the back side of the solid target, which is very essential in target normal sheath acceleration regime of proton acceleration. For an applied chirp parameter between 0.008 and 0.01, the maximum amount of the electrostatic fieldmore » is improved by a factor of 2. Furthermore, it is noticed that for a chirped laser pulse with a₀=5, because of increasing the plasma transparency length, the laser pulse can penetrate up to about n{sub e}≈6n{sub c}, where n{sub c} is plasma critical density. It shows 63% increase in the effective critical density compared to the relativistic induced transparency regime for an unchirped condition.« less

Population transfer and rapid passage effects in a low pressure gas using a continuous wave quantum cascade laser.

PubMed

McCormack, E A; Lowth, H S; Bell, M T; Weidmann, D; Ritchie, G A D

2012-07-21

A continuous wave quantum cascade laser (cw-QCL) operating at 10 μm has been used to record absorption spectra of low pressure samples of OCS in an astigmatic Herriott cell. As a result of the frequency chirp of the laser, the spectra show clearly the effects of rapid passage on the absorption line shape. At the low chirp rates that can be obtained with the cw-QCL, population transfer between rovibrational quantum states is predicted to be much more efficient than in typical pulsed QCL experiments. This optical pumping is investigated by solving the Maxwell Bloch equations to simulate the propagation of the laser radiation through an inhomogeneously broadened two-level system. The calculated absorption profiles show good quantitative agreement with those measured experimentally over a range of chirp rates and optical thicknesses. It is predicted that at a low chirp rate of 0.13 MHz ns(-1), the population transfer between rovibrational quantum states is 12%, considerably more than that obtained at the higher chirp rates utilised in pulsed QCL experiments.

Sedimentary response to ice stream advance and retreat on the Storfjorden Trough Mouth Fan (NW Barents Sea), during Late Weichselian

NASA Astrophysics Data System (ADS)

Pedrosa, Mayte; Camerlengui, Angelo; de Mol, Ben; Lucchi, Renata. G.; Úrgeles, Roger; Rebesco, Michele; Winsborrow, Monica; Laberg, Jan. S.; Andreassen, Karin; Accettella, Daniela

2010-05-01

This seafloor morphological study of the Storfjorden Trough Mouth Fan (TMF) (offshore Svalbard, NW Barents Sea) is based on new multibeam bathymetry and chirp sub-bottom profiler data acquired in 2007 during the BIO Hespérides cruise SVAIS that provides an unprecedented image of the sedimentary processes that accompanied the last advance and retreat of the Storfjorden Ice Stream. Compared to other glacial-marine sedimentary systems (such as the adjacent Bjørnøyrenna TMF), the Storfjorden TMF system is small and associated to a relatively small terrestrial ice sheet, approximately 40.000 km2, with local provenance from Svalbard and the Spitsbergen Bank. Due to this short distance from the ice source to the calving areas and the resulting short residence time of ice in the ice sheet, therefore the glacio -marine system of the Storfjorden reacts rapidly to climatic changes. The Storfjorden continental slope is characterized by three depositional lobes, produced by focused sedimentation at the terminus of ice streams that have changed their location with time. The superficial morphology features associated to the two northernmost lobes are straight gullies in the upper slope, and debris lobes starting from the midslope onwards. The seafloor expression of the southernmost lobe, adjacent to the much smaller Kveithola TMF, demonstrate almost no gully incisions and is dominated by the widespread occurrence of small-scale submarine landslides. The subbottom profiles illustrate that sediment failures occurred throughout the Late Neogene evolution of the southern Storfjorden and Kveithola margin, including large-scale mass transport deposits of up to 200 m thick. Seismic facies of the Neogene sequence shows an alternation of glacigenic debris flows and laminated sediment drape inferred to be plumites. Gullies incising glacigenic debris flows at the surface and subsurface and are filled by an interglacial drape sequence. The gullies are formed during each deglaciation phase, most likely by the erosive action of short-lived high density currents originated by sediment-loaded subglacial melt water discharge.At the outer continental shelf of the southernmost lobe a striking fresh linear straight, which has a width of 1, 5 kilometres and cut the morainal deposits. These features are interpreted as mega-scale glacial lineations, which are tentatively attributed to mega-iceberg scours. These lineations are witness the latest advances of the Storfjorden ice streams before the final retreat which was located at the southernmost lobe. One of the main pre-conditioning factors to slope instability on the southern part of the Storfjorden TMF is identified as high sedimentation rate plumites deposited on the middle-upper continental slope by glacial melt water plumes. This study is part of the SVAIS project (funded by the Spanish IPY), that has a main objective to improve the understanding and the relationship between sedimentation and ice sheet dynamics under natural climatic changes.

Seismic stratigraphy of the Heuksan mud belt in the southeastern Yellow Sea, Korea

NASA Astrophysics Data System (ADS)

Lee, Gwang-Soo; Yoo, Dong Geun; Bae, Sung Ho; Min, Gun-Hong; Kim, Seong-Pil; Choi, Hunsoo

2015-12-01

To establish the seismic stratigraphy of the Heuksan mud belt (HMB) and reconstruct its depositional history, approximately 1,600 km of high-resolution seismic data were newly obtained using chirp acoustic sub-bottom profiler, sparker, and air-gun seismic systems. Based on seismic stratigraphic analysis, the HMB can be divided into three major seismic units (I, II, and III, from top to bottom) and four subunits (II-a, II-b, III-a, and III-b) overlying transgressive sands, pre-last glacial maximum (LGM) deposits, and the acoustic basement. Each unit and subunit show different seismic facies and geometry, being clearly separated from each other by bounding surfaces formed since the LGM. The spatial distribution, thicknesses and volumes of the seismic units were determined and plotted to document the sequential formation of the HMB. The correlation between deep drill core data (HMB-101, HMB-102, HMB-103, YSDP-101, and YSDP-102) and the seismic data suggests that subunits III-b and III-a were formed by the continuous accumulation of fine-grained sediment with partial sandy sediment in an estuarine/deltaic environment during the early to middle transgressive stage, accompanied by landward migration of the shoreline. Subunits II-b and II-a were probably formed by re-deposition of large volumes of sediment eroded from unit III during the middle transgressive to early highstand stage. Unit I is interpreted as the most recent mud deposit representing the highstand systems tract when sea-level rise terminated. The careful definition of seismic units and their interpretation proposed in this study, on the basis of the large and partly new seismic dataset covering the entire HMB together with deep drill core data, have been instrumental in reconstructing the depositional environment and formation mechanisms of the HMB.

High Resolution Seafloor Environmental Characterization of Methane Seeps in the Mississippi Canyon Near Atwater Valley 13/14, Gulf of Mexico.

NASA Astrophysics Data System (ADS)

Gardner, J. M.; Hagen, R.; Hart, P.; Czarnecki, M.; Nishimura, C.; Hutchinson, D. R.

2005-12-01

The purpose of this project was to conduct detailed surface mapping of one of the areas drilled by the Joint Industry Project with ChevronTexaco to understand gas hydrates in the Gulf of Mexico. The gently sloping, mostly flat floor of the Mississippi Canyon is interrupted by mounds and depressions that presumably reflect the complex geology and geohydrology related to turbidite deposition and pervasive salt tectonism. The seafloor mounds we mapped in this study occur in approximately 1300 water depth along the floor of the Mississippi Canyon in lease block areas Atwater Valley 13 and 14. High resolution sidescan sonar (100 kHz and 500 kHz) backscatter imagery, and chirp sub-bottom profiler data were collected using the DT1 deep-towed oceanographic mapping instrument, concentrating on the region directly adjacent to and surrounding two mounds identified as, mounds D and F, and in the region directly adjacent to and surrounding the mounds. The backscatter data have been mosaiced and normalized to provide information on the shape and extent of the mounds, the possible lateral extent of fauna, such as mussel and clam fields on the mounds, possible seep related flows and the occurrence of carbonate material. The extent of a mudflow can be mapped on the southeastern side of mound F. Previously collected bottom camera images have been used to ground-truth the backscatter information. Coincident with the collection of backscatter information was the collection of very high-resolution bathymetric data. Together, the backscatter and bathymetric data show extremely high-resolution detail about the shape, relief, and morphology of the mounds. This information, coupled with porewater chemistry and heatflow data form a coherent picture of possible mechanics for fluid venting and flora/fauna of the seeps in this region.

The method for scanning reshaping the spectrum of chirped laser pulse based on the quadratic electro-optic effects

NASA Astrophysics Data System (ADS)

Ye, Rong; Yin, Ming; Wu, Xianyun; Tan, Hang

2017-10-01

T A new method for scanning reshaping the spectrum of chirped laser pulse based on quadratic electro-optic effects is proposed. The scanning reshaping scheme with a two-beam interference system is designed and the spectrum reshaping properties are analyzed theoretically. For the Gaussian chirped laser pulse with central wavelength λ0=800nm, nearly flat-topped spectral profiles with wider bandwidth is obtained with the proposed scanning reshaping method, which is beneficial to compensate for the gain narrowing effect in CPA and OPCPA. Further numerical simulations show that the reshaped spectrum is sensitive to the time-delay and deviation of the voltage applied to the crystal. In order to avoid narrowing or distorting the reshaped spectrum pointing to target, it is necessary to reduce the unfavorable deviations. With the rapid and wide applications of ultra-short laser pulse supported by some latter research results including photo-associative formation of ultra-cold molecules from ultra-cold atoms[1-3], laser-induced communications[4], capsule implosions on the National Ignition Facility(NIF)[5-6], the control of the temporal and spectral profiles of laser pulse is very important and urgently need to be addressed. Generally, the control of the pulse profiles depends on practical applications, ranging from femtosecond and picosecond to nanosecond. For instance, the basic shaping setup is a Fourier transform system for ultra-short laser pulse. The most important element is a spatially patterned mask which modulates the phase or amplitude, or sometimes the polarization after the pulse is decomposed into its constituent spectral components by usually a grating and a lens[7]. One of the generation techniques of ultra-short laser pulse is the chirped pulse amplifications(CPA), which brings a new era of development for high energy and high peak intensity ultra-short laser pulse, proposed by D. Strcik and G. Mourou from the chirping radar technology in microwave region since 1985[8]. The other generation technique of ultra-short pulse is the optical parametric chirped pulse amplification(OPCPA) invented by Dubietis et al. in 1992, which combined the respective superiorities of CPA and optical parametric amplification(OPA). However, there are disadvantages for the both technologies such as gain narrowing, gain saturation effects, and even spectrum shift. The first one among the three is the most significant which narrows the spectrum after amplification so that it limits the minimum durations of ultra-short laser pulse. This paper proposed a approach for scanning reshaping the spectrum of chirped laser pulse to compensate for the gain narrowing effect, according to the characteristics of the chirped laser pulse, i.e. the frequency varies with time linearly. The spectral characteristics of the scanning reshaping was analyzed quantitatively. Furthermore, the influence of the time-delay and deviation of the controlling voltage employed on the electro-optic crystal on the reshaped spectrum was also been discussed in detail.

75 FR 49709 - Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-13

...]Pa rms. Due to its high frequency range, NMFS does not consider its acoustic energy would be strong... source levels of the sub-bottom profiler and the high-frequency nature of the multi-beam echo sounder...-frequency side scan sonar, (100-400 kHz or 300-600 kHz): Based on Shell's 2006 90-day report, the source...

Complete pulse characterization of quantum dot mode-locked lasers suitable for optical communication up to 160 Gbit/s.

PubMed

Schmeckebier, H; Fiol, G; Meuer, C; Arsenijević, D; Bimberg, D

2010-02-15

A complete characterization of pulse shape and phase of a 1.3 microm, monolithic-two-section, quantum-dot mode-locked laser (QD-MLL) at a repetition rate of 40 GHz is presented, based on frequency resolved optical gating. We show that the pulse broadening of the QD-MLL is caused by linear chirp for all values of current and voltage investigated here. The chirp increases with the current at the gain section, whereas larger bias at the absorber section leads to less chirp and therefore to shorter pulses. Pulse broadening is observed at very high bias, likely due to the quantum confined stark effect. Passive- and hybrid-QD-MLL pulses are directly compared. Improved pulse intensity profiles are found for hybrid mode locking. Via linear chirp compensation pulse widths down to 700 fs can be achieved independent of current and bias, resulting in a significantly increased overall mode-locking range of 101 MHz. The suitability of QD-MLL chirp compensated pulse combs for optical communication up to 160 Gbit/s using optical-time-division multiplexing are demonstrated by eye diagrams and autocorrelation measurements.

Role of misalignment-induced angular chirp in the electro-optic detection of THz waves.

PubMed

Walsh, D A; Cliffe, M J; Pan, R; Snedden, E W; Graham, D M; Gillespie, W A; Jamison, S P

2014-05-19

A general description of electro-optic detection including non-collinear phase matching and finite transverse beam profiles is presented. It is shown theoretically and experimentally that non-collinear phase matching in ZnTe (and similar materials) produces an angular chirp in the χ(2)-generated optical signal. Due to this, in non-collinear THz and probe arrangements such as single-shot THz measurements or through accidental misalignment, measurement of an undistorted THz signal is critically dependent on having sufficient angular acceptance in the optical probe path. The associated spatial walk-off can also preclude the phase retardation approximation used in THz-TDS. The rate of misalignment-induced chirping in commonly used ZnTe and GaP schemes is tabulated, allowing ready analysis of a detection system.

An Analysis of Wind Power Development in the Town of Hull, MA_Appendix 4_Geophysical Survey Report

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

Adams, Christopher

2013-06-30

CR Environmental, Inc. (CR) was contracted by GZA GeoEnvironmental, Inc. (GZA) to perform hydrographic and geophysical surveys of an approximately 3.35 square mile area off the eastern shore of Hull, Massachusetts. Survey components included: • Single-beam bathymetry; • 100-kHz and 500-kHz side scan sonar; • Magnetometry; and • Low to mid-frequency sub-bottom profiling.

Lake Mohave Geophysical Survey 2002: GIS Data Release

USGS Publications Warehouse

Cross, VeeAnn A.; Foster, David S.; Twichell, David C.

2005-01-01

This CD-ROM contains sidescan-sonar imagery, sub-bottom reflection profiles, and an interpretive map derived from these data. These data were collected in Lake Mohave, a reservoir behind the Davis Dam and below the Hoover Dam on the Colorado River. These data are veiwable within an Environmental system Research Institute, Inc. (ESRI) Geographic Information system (GIS) ArcView 3.2 project file stored on this CD-ROM

Late Glacial to Holocene evolution and sea-level history of Gulf of Gemlik, Sea of Marmara, Turkey

NASA Astrophysics Data System (ADS)

Sabuncu, Asen; Kadir Eriş, K.; Kaslilar, Ayse; Namık Çaǧatay, M.; Gasperini, Luca; Filikçi, Betül

2016-04-01

The Gulf of Gemlik is an E-W elongated trans-tensional basin with a maximum depth of 113 m, located on the middle strand of the North Anatolian Fault (NAF) in the south eastern part of the Sea of Marmara (SoM). While during the Holocene the sea level in the Gulf of Gemlik changed in tandem with the water level changes in the SoM, it may have been different in the late glacial when the Sea of Marmara was lacustrine. Beside the tectonic activity related to the NAFZ, eustatic sea level changes would have controlled the basin evolution and consequent sedimentary history during the different paleocanographic phases of the SoM. Considering the limited studies on the late glacial-Holocene stratigraph of the Gulf of Gemlik, this study aims to investigate the depositional units and their environments with respect to different allogenic and autogenic controls. For these purposes, we analyzed over 300 2 - 7 kHz bandwidth high-resolution gridded seismic sub-bottom CHIRP profiles together with 70 kHz high resolution multibeam bathymetry with backscatter data. Four seismic stratigraphic units were defined and correlated with chronstratigraphic units in five piston cores covering the last 15.8 ka BP according to radiocarbon ages (14C). The depth-scale accuracy of chronostratigraphic units in cores is of key importance for the precise calculation of sedimentation rates. Correlation between the seismic profiles and cores were made by matching Multi-Sensor Core-Logger (MSCL) data and seismic reflection coefficients and amplitudes for different stratigraphic units. The impedance data derived from the logger were used to generate a synthetic seismogram. We used an approach to display, estimate, and correct the depth-scale discrepancies due to oversampling affecting the upper part of sedimentary series during piston coring. The method is based on the resynchronization of synthetic seismograms computed from high-quality physical property logs to the corresponding CHIRP profiles. Each sequence boundary represented by different reflection coefficient and various amplitude values were mapped for the whole gulf area from the pseudo-3D seismic data. Isopach and isochron maps were generated using 2-D cubic B-spline interpolation method to reconstruct basin evolution models through late glacial to Holocene. Each map shows various depositional period with respect to water level changes that has been controlled by sea level fluctuations in the SoM. The seismic units labeled as Unit S1-S4 from top to bottom display different seismic facies and geometries. Unit S1 is a transgressive marine mud drape younger than 10.6 ka BP, which lacustrine sediments, Unit S2 is a parallel bedded mud drape in the basin and progradational clinoforms on the shelf edge. It is dated between 13.9-10.6 ka BP, Unit S3 is characterized by erosional gullies and a clinoform architecture indicating a deltaic system dated between 15.8-13.9 ka BP. Unit S4 represents mounded sediments that are truncated by erosional gullies and dated >15.8 ka BP. Key words: Gulf of Gemlik, Seismic Stratigraphy, Numerical Modelling, Late Pleistocene to Holocene

Repeat AUV Mapping and ROV Observations of Active Mud Volcanos on the Canadian Beaufort Sea Continental Slope

NASA Astrophysics Data System (ADS)

Caress, D. W.; Paull, C. K.; Dallimore, S.; Lundsten, E. M.; Anderson, K.; Gwiazda, R.; Melling, H.; Lundsten, L.; Graves, D.; Thomas, H. J.; Cote, M.

2017-12-01

Two active submarine mud volcano sites located at 420 and 740 m depths on the margin of the Canadian Beaufort Sea were mapped in 2013 and again in 2016 using the same survey line pattern allowing detection of change over three years. The surveys were conducted using MBARI's mapping AUVs which fields a 200 kHz or 400 kHz multibeam sonar, a 1-6 kHz chirp sub-bottom profiler, and a 110 kHz chirp sidescan from a 50 m altitude. The resulting bathymetry has 1 m lateral resolution and 0.1 m vertical precision and sidescan mosaics have 1 m lateral resolution. Vertical changes of ≥0.2 m are observable by differencing repeat surveys. These features were also visited with MBARI's miniROV, which was outfitted for these dives with a manipulator mounted temperature probe. The 420 m mud volcano is nearly circular, 1100 m across, flat-topped, and superimposed on the pre-existing smooth slope. The central plateau has low relief <3 m consisting of concentric rings and ovoid mounds that appear to reflect distinct eruptions at shifting locations. The 740 m site contains 3 mud volcanoes, most prominently a 630 m wide, 30 m high flat-topped plateau with about 4 m of relief similar to the 420 m feature plus a 5 m high cone on the southern rim. North of this plateau is a smooth-textured conically shaped feature also standing about 30 m above the floor of the subsidence structure. Sidescan mosaics reveal significant changes in backscatter patterns at both mud volcano sites between surveys. Comparison of bathymetry also reveals new flows of up to 1.8 m thickness at both sites, as well as subtle spreading of the flat plateaus rims. An active mudflow was encountered during a miniROV dive on a high backscatter target at the 740 m site. This tongue of mud was observed to be slowly flowing downslope. The ROV temperature probe inserted 2 cm into the flow measured 23°C, compared to ambient water (-0.4°C), indicating the rapid ascent of the mud from considerable subsurface depths. Bubbles (presumably methane) were escaping from the active mudflow. Combining seafloor mapping with ROV observations indicates that new sediment flows with entrained methane bubbles exhibit very high backscatter which rapidly changes to very low backscatter following degassing of the smooth, bare mud. To our knowledge this is the first time an eruption on a submarine mud volcano has been observed.

Advances in Shallow-Water, High-Resolution Seafloor Mapping: Integrating an Autonomous Surface Vessel (ASV) Into Nearshore Geophysical Studies

NASA Astrophysics Data System (ADS)

Denny, J. F.; O'Brien, T. F.; Bergeron, E.; Twichell, D.; Worley, C. R.; Danforth, W. W.; Andrews, B. A.; Irwin, B.

2006-12-01

The U.S. Geological Survey (USGS) has been heavily involved in geological mapping of the seafloor since the 1970s. Early mapping efforts such as GLORIA provided broad-scale imagery of deep waters (depths > 400 meters) within the Exclusive Economic Zone (EEZ). In the early 1990's, the USGS research emphasis shifted from deep- to shallow-water environments (inner continental shelf, nearshore, estuaries) to address pertinent coastal issues such as erosion, sediment availability, sediment transport, vulnerability of coastal areas to natural and anthropogenic hazards, and resource management. Geologic framework mapping in these shallow- water environments has provided valuable data used to 1) define modern sediment distribution and thickness, 2) determine underlying stratigraphic and structural controls on shoreline behavior, and 3) enable onshore-to- offshore geologic mapping within the coastal zone when coupled with subaerial techniques such as GPR and topographic LIDAR. Research in nearshore areas presents technological challenges due to the dynamics of the environment, high volume of data collected, and the geophysical limitations of operating in very shallow water. In 2004, the USGS, in collaboration with NOAA's Coastal Services Center, began a multi-year seafloor mapping effort to better define oyster habitats within Apalachicola Bay, Florida, a shallow water estuary along the northern Gulf of Mexico. The bay poses a technological challenge due to its shallow depths (< 4-m) and high turbidity that prohibits the use of bathymetric LIDAR. To address this extreme shallow water setting, the USGS incorporated an Autonomous Surface Vessel (ASV) into seafloor mapping operations, in June 2006. The ASV is configured with a chirp sub-bottom profiler (4 24 kHz), dual-frequency chirp sidescan-sonar (100/500 kHz), single-beam echosounder (235 kHz), and forward-looking digital camera, and will be used to delineate the distribution and thickness of surficial sediment, presence of oyster beds, and sea bed morphology in water depths less than 5-m. The ASV is a catamaran-based platform, 10 feet in length, 4 feet in width, and approximately 260 lbs in weight. The vehicle is operated remotely through a wireless modem network enabling real-time monitoring of data acquisition. The ASV is navigated using RTK, and heave, pitch and roll are recorded with onboard motion sensors. Additional sensors, such as ADCPs, can also be housed within the vehicle. The ASV is able to operate in previously inaccessible areas, and will not only augment existing shallow-water research capabilities, but will also improve our understanding of the geologic controls to modern beach behavior and coastal evolution.

High-Resolution Geophysical Constraints on Late Pleistocene-Present Deformation History, Seabed Morphology, and Slip-Rate along the Queen Charlotte-Fairweather Fault, Offshore Southeastern Alaska

NASA Astrophysics Data System (ADS)

Brothers, D. S.; Haeussler, P. J.; Dartnell, P.; Conrad, J. E.; Kluesner, J. W.; Hart, P. E.; Witter, R. C.; Balster-Gee, A. F.; Maier, K. L.; Watt, J. T.; East, A. E.

2015-12-01

The Queen Charlotte-Fairweather Fault (QCFF) of southeastern Alaska and British Columbia is the dominant fault along the 1200 km-long transform boundary between the Pacific and North American plates. More than 900 km of the QCFF lies offshore where the style and rates of deformation are poorly constrained due to a lack of high-resolution marine geophysical data. In May 2015, the USGS acquired ~900 km2 of high-resolution multibeam bathymetry data and >2000 line-km of high-resolution multichannel seismic reflection profiles between Cross Sound, Yakobi Sea Valley, and Icy Point (the northernmost offshore section of the QCFF) using a 24-ch streamer and 500 Joule minisparker source. During a second cruise in August 2015 we conducted targeted multichannel seismic and subbottom CHIRP profiling in the same region. The new data reveal a single trace of the QCFF expressed as a clear and remarkably straight seafloor lineation for >60 km. Subtle jogs in the fault (<3 degrees) are associated with pop-up structures and en echelon pull-apart basins. The near surface deformation along the fault never exceeds a width of 1.2 km. Northward, as the fault approaches Icy Point and a restraining bend, it splays into multiple strands and displays evidence for uplift and transpression. The fault appears to transition from almost purely strike-slip in the south to oblique-convergence as it steps onshore to the north. The QCFF cuts through the Yakobi Sea Valley and Cross Sound, two elongate bathymetric troughs that were filled with glaciers as recently as 17-19 ka. The southern wall of the Yakobi Sea Valley is offset 890±30 m by the QCFF, providing a late Pleistocene-present slip-rate estimate of 45-54 mm/yr. This suggests that nearly the entire plate boundary slip budget is confined to a single, narrow, strike-slip fault zone, which may have implications for models of plate boundary strain localization.

1-J white-light continuum from 100-TW laser pulses

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

Petit, Yannick; Henin, Stefano; Bejot, Pierre

2011-01-15

We experimentally measured the supercontinuum generation using 3-J, 30-fs laser pulses and measured white-light generation at the level of 1 J. Such high energy is allowed by a strong contribution to the continuum by the photon bath, as compared to the self-guided filaments. This contribution due to the recently observed congestion of the filament number density in the beam profile at very high intensity also results in a wider broadening for positively chirped pulses rather than for negatively chirped ones, similar to broadening in hollow-core fibers.

Temporal characterization of ultrashort linearly chirped electron bunches generated from a laser wakefield accelerator

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

Zhang, C. J.; Hua, J. F.; Wan, Y.

A new method for diagnosing the temporal characteristics of ultrashort electron bunches with linear energy chirp generated from a laser wakefield accelerator is described. When the ionization-injected bunch interacts with the back of the drive laser, it is deflected and stretched along the direction of the electric field of the laser. Upon exiting the plasma, if the bunch goes through a narrow slit in front of the dipole magnet that disperses the electrons in the plane of the laser polarization, it can form a series of bunchlets that have different energies but are separated by half a laser wavelength. Sincemore » only the electrons that are undeflected by the laser go through the slit, the energy spectrum of the bunch is modulated. By analyzing the modulated energy spectrum, the shots where the bunch has a linear energy chirp can be recognized. Consequently, the energy chirp and beam current profile of those bunches can be reconstructed. Lastly, this method is demonstrated through particle-in-cell simulations and experiment.« less

Shallow Water UXO Technology Demonstration Site, Scoring Record Number 2

DTIC Science & Technology

2006-09-01

The Sound Metrics Corporation High frequency Imaging Sonar ( HFIS ) (fig. 4) dual frequency imaging sonar operates at 1.1 and 1.8 MHz. For this...the HFIS unit was determined using a National Marine Electronics Association (NMEA) GPRMC string from a Leica GPS system antenna mounted directly...above the HFIS instrument. This permits the image data to be integrated with the Multiple Frequency Sub-Bottom Profiler (MFSBP) and MGS data during

Single-channel seismic-reflection profiles and sidescan sonar records collected during May 15-20, 1978, on the southern New England continental shelf

USGS Publications Warehouse

Twichell, David C.

1980-01-01

The U.S. Geological Survey completed a cruise aboard the R/V CAPE HENLOPEN during May 15-20, 1978, to map the surface character, thickness and extent of the fine-grained.sediment deposit that covers an area 100 x 200 km on the southern New England Continental Shelf. The study area lies between Great South Channel to the east and Black Channel to the west, and extends from the 50-m isobath to the shelf edge.Single-channel high-resolution seismic-reflection profiles and echo-sounding profiles were collected along 941 km of trackline, sidescan sonar records were collected along 673 km of trackline. The subbottom profiles were collected by using a Huntec*system that was towed at midwater depths. Filters were set at 1 to 7 kHz. Echo-sounding records were collected by using a 60 kHz EDO Western system. A Klein stdescan sonar, set to scan 100 m to either side of the towed fish, was used to collect the sonographs.Navigation during the survey was done by the scientific staff using Loran-C equipment. Fixes were recorded and logged at least every 15 minutes; after the cruise, they were digitized and stored on magnetic tape.The original records can be seen and studied at the U.S. Geological Survey Data Library at Woods Hole, MA 02543. Microfilm copies of the subbottom, echo­sounding, and sidescan sonar records collected during the cruise can be purchased from the National Geophysical and Solar-Terrestrial Data Center, NOAA (National Oceanic ancl Atmosphere Administration), Boulder, CO 80302.

Gas hydrate volume estimations on the South Shetland continental margin, Antarctic Peninsula

USGS Publications Warehouse

Jin, Y.K.; Lee, M.W.; Kim, Y.; Nam, S.H.; Kim, K.J.

2003-01-01

Multi-channel seismic data acquired on the South Shetland margin, northern Antarctic Peninsula, show that Bottom Simulating Reflectors (BSRs) are widespread in the area, implying large volumes of gas hydrates. In order to estimate the volume of gas hydrate in the area, interval velocities were determined using a 1-D velocity inversion method and porosities were deduced from their relationship with sub-bottom depth for terrigenous sediments. Because data such as well logs are not available, we made two baseline models for the velocities and porosities of non-gas hydrate-bearing sediments in the area, considering the velocity jump observed at the shallow sub-bottom depth due to joint contributions of gas hydrate and a shallow unconformity. The difference between the results of the two models is not significant. The parameters used to estimate the total volume of gas hydrate in the study area were 145 km of total length of BSRs identified on seismic profiles, 350 m thickness and 15 km width of gas hydrate-bearing sediments, and 6.3% of the average volume gas hydrate concentration (based on the second baseline model). Assuming that gas hydrates exist only where BSRs are observed, the total volume of gas hydrates along the seismic profiles in the area is about 4.8 ?? 1010 m3 (7.7 ?? 1012 m3 volume of methane at standard temperature and pressure).

High-resolution surveys for geohazards and shallow gas: NW Adriatic (Italy) and Iskenderun Bay (Turkey)

USGS Publications Warehouse

Orange, D.L.; Garcia-Garcia, Ana; McConnell, D.; Lorenson, T.; Fortier, G.; Trincardi, F.; Can, E.

2005-01-01

The need for quantifying and understanding the distribution of shallow gas is both of academic interest and of relevance to offshore facilities. The combination of seafloor mapping, subbottom profiling, and multi-channel seismic data can provide information on regions of possible shallow gas, where the gas impacts the acoustic properties of the host material and the seafloor. In this paper, we present two case studies - one academic and one industry - that evaluate the distribution of shallow gas in two field areas in the Mediterranean. In the first case study, geophysical data from Iskenderun Bay, southeastern Turkey, indicate the presence and distribution of shallow gas. Pockmarks on the seafloor are associated with acoustic wipeout in the shallow subbottom data. Although deeper seismic data do not show bright spots or other indicators of possible gas, instantaneous frequency analysis clearly shows laterally restricted anomalies indicating gas-rich zones. The interpretation of possible shallow gas resulted in moving a proposed drilling location to a nearby area characterized by fewer (but still present) shallow gas signatures. In the second case study, cores acquired in the Po Delta, Adriatic Sea, provide quantitative ground-truthing of shallow gas - as suggested by geophysical data - and provide minimum estimates of the percentage of gas in the subsurface. Cores targeted on anomalous subbottom data yielded up to 41,000 ppm methane; cores with anomalous gas content are associated with thick recent flood deposits which may effectively isolate reactive terrigenous organic matter from biologic and physical re-working. ?? Springer 2005.

Seismic-reflection and sidescan-sonar data collected on the Potomac River, Maryland and Virginia, during May 1979

USGS Publications Warehouse

Knebel, Harley J.

1981-01-01

The U.S. Geological Survey collected 2,170 line kilometers of single-channel seismic-reflection profiles and sidescan sonar records on the Potomac River during R/V NEECHO cruise NE-3-79 in May 1979. The purposes of the survey were to define: (1) areas of sediment accumulation and erosion; (2) the thickness of Holocene sediments; (3) the internal structure of the near-surface sediments; (4) the types of bottom topography; and (5) the general geologic framework of the tidal river and estuary.The survey utilized a variety of acoustic systems. Bottom data were obtained by using a Raytheon _1/ model DE-719 fathometer (200 kHz) and an EDO Western model 606 sidescan-sonar system (100 kHz). Subbottom data were collected with a 7-kHz Raytheon model PTR-106 system and a small airgun system (170-645 Hz band pass; l in3 chamber). An EDO Western sidescan fish (model 604-150) coupled with a 2.5-kHz seismic-reflection system also was used during the longitudinal run up the river. The totals for the ,various kinds of data collected were 481 line kilometers each of fathometer, sidescan sonar, 7-kHz, and airgun records, and 246 line kilometers of 2.5-kHz records. Positional control for all tracklines was provided by frequent radar fixes, by dead reckoning, and by sightings on buoys, landmarks, and other navigational aids.The quality of the acoustic records varied with location in the river. Good fathometer and sidescan-sonar records were collected along all tracklines. However, because of the nature of the sediments within some sections of the river, the degree of subbottom penetration in many places was limited. In general, the subbottom penetration and resolution were poor in the upper and middle reaches of the river, whereas the subbottom records from the lower reach usually were quite good.The original records may be examined at the U.S. Geological Survey, Woods Hole, MA 02543. Microfilm copies of the data are available for purchase from the National Geophysical and Solar-Terrestrial Data Center (NGSDC), Boulder, CO 80303.

Design and comparative performance analysis of different chirping profiles of tanh apodized fiber Bragg grating and comparison with the dispersion compensation fiber for long-haul transmission system

NASA Astrophysics Data System (ADS)

Dar, Aasif Bashir; Jha, Rakesh Kumar

2017-03-01

Various dispersion compensation units are presented and evaluated in this paper. These dispersion compensation units include dispersion compensation fiber (DCF), DCF merged with fiber Bragg grating (FBG) (joint technique), and linear, square root, and cube root chirped tanh apodized FBG. For the performance evaluation 10 Gb/s NRZ transmission system over 100-km-long single-mode fiber is used. The three chirped FBGs are optimized individually to yield pulse width reduction percentage (PWRP) of 86.66, 79.96, 62.42% for linear, square root, and cube root, respectively. The DCF and Joint technique both provide a remarkable PWRP of 94.45 and 96.96%, respectively. The performance of optimized linear chirped tanh apodized FBG and DCF is compared for long-haul transmission system on the basis of quality factor of received signal. For both the systems maximum transmission distance is calculated such that quality factor is ≥ 6 at the receiver and result shows that performance of FBG is comparable to that of DCF with advantages of very low cost, small size and reduced nonlinear effects.

Surficial geology mapping of the Arctic Ocean: using subbottom profiling and multibeam echosounding data sets to constrain the subsea north of 64° as a layer for the IBCAO

NASA Astrophysics Data System (ADS)

Mosher, D. C.; Baldwin, K.; Gebhardt, C.

2016-12-01

Barriers to data collection such as perennial ice cover, climate, and remoteness have contributed to a paucity of geologic data in the Arctic. The last decade, however, has seen a multi-national push to increase the quantity and extent of data available at high latitudes. With increased availability of geophysical and geological data holdings, we expand on previous mapping initiatives by creating a comprehensive surficial geology map as a layer to the International Bathymetric Chart of the Arctic Ocean (IBCAO), providing a way to collectively analyze physiography, morphology and geology. Acoustic facies derived from subbottom profiles, combined with morphology illuminated from IBCAO and multibeam bathymetric datasets, and ground truth data compiled from cores and samples are used to map surficial geology units. We identified over 25 seismo-acoustic facies leading to interpretation of 12 distinct geologic units for the Arctic Ocean. The largest variety of seismic facies occurs on the shelves, which demonstrate the complex ice-margin history (e.g. chaotic bottom echoes with amorphous subbottom reflections that imply ice scouring processes). Shelf-crossing troughs generally lead to trough mouth fans on the continental margin with characteristic glaciogenic debris flow deposits (acoustically transparent units) comprising the bulk of the sedimentary succession. Other areas of continental slopes show a variety of facies suggesting sediment mass failure and turbidite deposition. Vast areas of the deep water portion of the Arctic are dominated by parallel reflections, indicative of hemi-pelagic and turbidity current deposition. Some deep water parts of the basin, however, show evidence of current reworking (sigmoidal reflections within bedforms), and contain deep sea channels with thalwegs (bright reflections within channels) and levee deposits (reflection pinch-out). These results delineated in the surficial geology map provide a comprehensive database of regional geologic information of the Arctic Ocean that can be applied to a variety of disciplines, including the study of Arctic sedimentary processes, climatologic and oceanographic processes, environmental and geohazard risk assessment, resource management, and Extended Continental Shelf mapping.

Glacimarine sedimentation in Petermann Fjord and Nares Strait, NW Greenland

NASA Astrophysics Data System (ADS)

Hogan, Kelly; Jakobsson, Martin; Mayer, Larry; Mix, Alan; Nielsen, Tove; Kamla, Elina; Reilly, Brendan; Heirman, Katrina An; Stranne, Christian; Mohammed, Rezwan; Eriksson, Bjorn; Jerram, Kevin

2017-04-01

Here we build on preliminary results from 6500 line-km of high-resolution chirp sub-bottom profiles (2-7 kHz) acquired in Petermann Fjord and Nares Strait during the Petermann 2015 Expedition of the Swedish icebreaker Oden. We map the unlithified sediment cover in Peterman Fjord, which consists of up to 3 conformable "drape" units and calculate volumes of this assumed "post-glacial" fill. In Nares Strait we have mapped sediment volumes in local basins just beyond the sill at the Petermann Fjord-mouth: do these sediments represent material flushed out from the grounding zone of Petermann Glacier when it was grounded at the sill? In this vein, and interestingly, some of the thickest sediments that we observe are found close to a grounding-zone wedge (GZW) in Nares Strait that represents a former grounding zone of ice retreating southwards through the strait. We also map conformable units across Nares Strait and consider the similarities between these and the sediment units in the fjord. Do the strong reflections between the units represent the same climatic, oceanographic or process-shift both inside and outside the fjord? We also aim to tie our new acoustic stratigraphy to sediment-core data (lithofacies, dates) and, therefore, to comment on the age of the mapped sediment units and present ideas on the glacimarine flux of material to the Petermann-Nares system. Primary sediment delivery to the seafloor in this environment is thought to be predominantly through sedimentation from meltwater plumes but also of iceberg-rafted debris (IRD). However, sediment redeposition by slope failures on a variety of scales also occurs and has focussed sediments into discrete basins where the seafloor is rugged. This work - which aims to relate past sediment, meltwater and iceberg fluxes to changes in climate - will help us to identify how the system has responded to a past global warming event, namely the last deglaciation. This is particularly relevant in light of the recent thinning and acceleration of NW Greenland's marine-terminating outlet glaciers.

The Palos Verdes Fault offshore southern California: late Pleistocene to present tectonic geomorphology, seascape evolution and slip rate estimate based on AUV and ROV surveys

USGS Publications Warehouse

Brothers, Daniel S.; Conrad, James E.; Maier, Katherine L.; Paull, Charles K.; McGann, Mary L.; Caress, David W.

2015-01-01

The Palos Verdes Fault (PVF) is one of few active faults in Southern California that crosses the shoreline and can be studied using both terrestrial and subaqueous methodologies. To characterize the near-seafloor fault morphology, tectonic influences on continental slope sedimentary processes and late Pleistocene to present slip rate, a grid of high-resolution multibeam bathymetric data, and chirp subbottom profiles were acquired with an autonomous underwater vehicle (AUV) along the main trace of PVF in water depths between 250 and 600 m. Radiocarbon dates were obtained from vibracores collected using a remotely operated vehicle (ROV) and ship-based gravity cores. The PVF is expressed as a well-defined seafloor lineation marked by subtle along-strike bends. Right-stepping transtensional bends exert first-order control on sediment flow dynamics and the spatial distribution of Holocene depocenters; deformed strata within a small pull-apart basin record punctuated growth faulting associated with at least three Holocene surface ruptures. An upper (shallower) landslide scarp, a buried sedimentary mound, and a deeper scarp have been right-laterally offset across the PVF by 55 ± 5, 52 ± 4 , and 39 ± 8 m, respectively. The ages of the upper scarp and buried mound are approximately 31 ka; the age of the deeper scarp is bracketed to 17–24 ka. These three piercing points bracket the late Pleistocene to present slip rate to 1.3–2.8 mm/yr and provide a best estimate of 1.6–1.9 mm/yr. The deformation observed along the PVF is characteristic of strike-slip faulting and accounts for 20–30% of the total right-lateral slip budget accommodated offshore Southern California.

Windward Passage and Jamaica Channel: New Insights About two Tectonic Gateways of the Northern Caribbean

NASA Astrophysics Data System (ADS)

Cormier, M. H.; Blake, R. E.; Coleman, D. F.; Guerrier, K.; Raineault, N.; Saintilus, N.; Walker, S. L.; Auscavitch, S.; Wagner, J.

2014-12-01

This August 2014, a 14-day expedition of the E/V NAUTILUS of the OCEAN EXPLORATION TRUST will explore the region delimited by two deep straits of the northern Caribbean, the Windward passage and the Jamaica Channel. The morphology of these straits is controlled by two transform faults: The Septentrional fault, which stretches between Cuba and Haiti (slip rate: ~13 mm/yr), and the Enriquillo-Plantain Garden Fault (EPGF), which stretches between Jamaica and Haiti (slip rate: ~9 mm/yr). Together, these faults bound the Gonave microplate, an elongated platelet caught between the North America plate and Caribbean plates. The Septentrional fault ruptured in 1842, devastating the town of Cap Haitien. The EPGF ruptured catastrophically in 2010 near Port-au-Prince (death toll > 100,000). Tsunamis were associated with both earthquakes. Oblique slip on these two faults is presumably controlling the history of uplift and subsidence of the seafloor, and has therefore also been regulating the water exchanges between the north central Atlantic and the Caribbean Sea. New multibeam bathymetric and CHIRP sub-bottom profiling data will be acquired with the E/V NAUTILUS, while the ROV HERCULES will be used to collect video, water and rock samples, as well as water column physical properties. We anticipate that this survey will document the following: (1) The nature of drowned carbonate platforms, which in turn may provide useful markers to assess rates of vertical deformation along the two faults. (2) The extent of major landslides detected on the steep fore reefs from existing multibeam bathymetric data. (3) Whether fluids are actively seeping along the fault traces or in association with the landslides, as has been reported elsewhere around the World. (4) If cold seeps are indeed present, to what extent their associated ecosystems are affected by the bottom currents that flow through these gateways. Altogether, the new findings should contribute to a better understanding of the natural hazards associated with two major transform faults.

Hands-on Marine Geology and Geophysics Field Instruction at the University of Texas

NASA Astrophysics Data System (ADS)

Saustrup, S.; Gulick, S. P. S.; Goff, J. A.; Fernandez, R.; Davis, M. B.; Duncan, D.

2015-12-01

The University of Texas Institute for Geophysics, part of the Jackson School of Geosciences, annually offers an intensive three-week marine geology and geophysics field course during the spring-summer intersession. Now in its ninth year, the course provides instruction in survey design, data acquisition, processing, interpretation, and visualization. Methods covered include seismic reflection, multibeam bathymetry, sidescan sonar, and sediment sampling. The emphasis of the course is team-oriented, hands-on, field training in real-world situations. The course begins with classroom instruction covering the field area and field methods, followed by a week of at-sea field work in 4-student teams. The students then return to the classroom where they integrate, interpret, and visualize data using industry-standard software. The teams present results in a series of professional-level final presentations before academic and industry supporters. Our rotating field areas provide ideal locations for students to investigate coastal and sedimentary processes of the Gulf Coast and continental shelf . In the field, student teams rotate between two research vessels: the smaller vessel, the Jackson School's newly-commissioned R/V Scott Petty (26 feet LOA), is used principally for multibeam bathymetry, sidescan sonar, and sediment sampling; the other, NOAA's R/V Manta (82 feet LOA) is used for high-resolution seismic reflection, CHIRP sub-bottom profiling, multibeam bathymetry, gravity coring, and vibracoring. Teams also rotate through a field laboratory performing processing of geophysical data and sediment samples. This past year's course in Freeport, Texas proceeded unabated despite concurrent record-breaking rainfall and flooding, which offered students a unique opportunity to observe and image, in real time, flood-related bedform migration on a time scale of hours. The data also allowed an in-class opportunity to examine natural and anthropogenic processes recorded in the river and coastal morphology and stratigraphy. http://www.ig.utexas.edu/research/mgg/courses/geof348K/

Coastal bathymetry and backscatter data collected in 2012 from the Chandeleur Islands, Louisiana

USGS Publications Warehouse

DeWitt, Nancy T.; Bernier, Julie C.; Pfeiffer, William R.; Miselis, Jennifer L.; Reynolds, B.J.; Wiese, Dana S.; Kelso, Kyle W.

2014-01-01

As part of the Barrier Island Evolution Research Project, scientists from the U.S. Geological Survey St. Petersburg Coastal and Marine Science Center conducted nearshore geophysical surveys off the northern Chandeleur Islands, Louisiana, in July and August of 2012. The objective of the study is to better understand barrier island geomorphic evolution, particularly storm-related depositional and erosional processes that shape the islands over annual to interannual timescales (1-5 years). Collecting geophysical data will allow us to identify relationships between the geologic history of the island and its present day morphology and sediment distribution. This mapping effort was the second in a series of three planned surveys in this area. High resolution geophysical data collected in each of 3 consecutive years along this rapidly changing barrier island system will provide a unique time-series dataset that will significantly further the analyses and geomorphological interpretations of this and other coastal systems, improving our understanding of coastal response and evolution over short time scales (1-5 years). This Data Series report includes the geophysical data that were collected during two cruises (USGS Field Activity Numbers 12BIM03 and 12BIM04) aboard the RV Survey Cat and the RV Twin Vee along the northern portion of the Chandeleur Islands, Breton National Wildlife Refuge, Louisiana. Data were acquired with the following equipment: a Systems Engineering and Assessment, Ltd., SWATHplus interferometric sonar (468 kilohertz (kHz)), an EdgeTech 424 (4-24 kHz) chirp sub-bottom profiling system, and a Knudsen 320BP (210 kHz) echosounder. This report serves as an archive of processed interferometric swath and single-beam bathymetry data. Geographic information system data products include an interpolated digital elevation model, an acoustic backscatter mosaic, trackline maps, and point data files. Additional files include error analysis maps, Field Activity Collection System logs, and formal Federal Geographic Data Committee metadata. NOTE: These data are scientific in nature and are not to be used for navigation.

Bedforms, Channel Formation, and Flow Stripping in the Navy Fan, Offshore Baja California

NASA Astrophysics Data System (ADS)

Carvajal, C.; Paull, C. K.; Caress, D. W.; Fildani, A.; Lundsten, E. M.; Anderson, K.; Maier, K. L.; McGann, M.; Gwiazda, R.; Herguera, J. C.

2017-12-01

Deep-sea fans store some of the largest volumes of siliciclastic sediment in marine basins. These sandy accumulations record the history of sediment transfer from land to sea, serving as direct records of the geologic history of the continents. Despite their importance, deep-sea fans are difficult to study due to their remote locations in thousands of meters of water depth. In addition, deep-sea fans have a low relief, and geomorphological changes important for the evolution of the fan are often too subtle to be adequately resolved by 3D seismic data or surface-ship bathymetry. To improve our understanding of deep-sea fans, an autonomous underwater vehicle (AUV) was used to acquire high-resolution bathymetry and sub-bottom CHIRP profiles in the proximal sectors of the Navy Fan, offshore Baja California. A remotely operated vehicle was also used to acquire vibracores. The 1-m grid resolution bathymetry shows the seafloor geomorphology in extreme detail revealing different kinds of bedforms, which in combination with the vibracores help to interpret the sedimentary processes active during the Holocene. Morphological elements in the survey area include a main channel, numerous scours, an incipient channel, sediment waves, and a fault escarpment. Several of the scours are interpreted to result from flow stripping at a bend in the main channel. Along high gradient sectors (e.g. > 1o), the scours form bedforms with an erosionally truncated headwall immediately followed down-dip by an upflow accreting sedimentary bulge. These bedforms, the presence of clean sands in the scours and the high gradients suggest that these scours are net-erosional cyclic steps. Scours seem to coalesce along the sediment transport direction to form an incipient channel with abundant rip-up clast gravels. Elsewhere in the survey area, scours are elongated and intimately associated with sediment waves. The acquired dataset illustrates that deep-sea fans may show a variety of processes and geomorphologies, difficult to infer with the use of low-resolution data.

The Morpho-Acoustic Structure of Sakarya Canyon, Southwestern Black Sea

NASA Astrophysics Data System (ADS)

Nasıf, Aslıhan; Dondurur, Derman

2017-04-01

In this study, Black Sea outlet of Sakarya River in the western Black Sea continental margin is analyzed using a total of 1400 km multichannel seismics, Chirp sub-bottom profiler and multibeam bathymetric datasets. Three scientific cruises between 2012 and 2016 have been conducted in the area to map and reveal the morphological structure of the Sakarya Canyon along the southwestern Black Sea margin. The Western Black Sea Turkey coastal area is also home to many active canyons. These canyons extend from deep shallow shelf areas of about 100 m to deep water depths of 1800-2000 m. The largest and most active of the Western Black Sea canyons is the Sakarya Canyon, which is located at the exit of the Sakarya River. Research on submarine canyons are important for military submarine operations, positioning of marine engineering structures and understanding the sedimentology, ecological and oceanographic functions of canyons. The canyon systems observed on continental slopes lead to the most convenient sedimentary transportation from the shelf platform. The dataset from study area was analyzed to identify the acoustic structure of Sakarya Canyon, the morphology of which is not widely known. Bathymetric data shows that the canyon consists of two separate canyon heads in the shallow continental shelf to the south, both of which coalesce at 867 m water depth. This meandering canyon then deepens along the continental slope towards to north. Another wide canyon from west, named as Kefken Canyon, then conjoins this main canyon at approximately 1000 m water depths to form the deeper structure of the modern Sakarya Canyon. In the distal parts, canyon gets wider and wider, and its thalweg becomes significantly flat eroded by the present day activity of small scale turbidity channels. Multichannel seismic data indicate that the Sakarya Canyon was formed by the activity of hyperphycnal flows and also clearly show the extensive sediment erosion along the canyon.

The University of Texas Institute for Geophysics' Marine Geology and Geophysics Field Course: A Hand-On Education Approach to Applied Geophysics

NASA Astrophysics Data System (ADS)

Davis, M. B.; Goff, J.; Gulick, S. P. S.; Fernandez, R.; Duncan, D.; Saustrup, S.

2016-12-01

The University of Texas Institute for Geophysics, Jackson School of Geosciences, offers a 3-week marine geology and geophysics field course. The course provides hands-on instruction and training for graduate and upper-level undergraduate students in high-resolution seismic reflection, CHIRP sub-bottom profiling, multibeam bathymetry, sidescan sonar, and sediment sampling and analysis. Students first participate in 3 days of classroom instruction designed to communicate geological context of the field area along with theoretical and technical background on each field method. The class then travels to the Gulf Coast for a week of at-sea field work at locations that provide an opportunity to investigate coastal and continental shelf processes. Teams of students rotate between UTIG's 26' R/V Scott Petty and NOAA's 82' R/V Manta. They assist with survey design, instrumentation set up, and learn about acquisition, quality control, and safe instrument deployment. Teams also process data and analyze samples in onshore field labs. During the final week teams integrate, interpret, and visualize data in a final project using industry-standard software. The course concludes with team presentations on their interpretations with academic and industry supporters. Students report a greater understanding of marine geology and geophysics through the course's intensive, hands-on, team approach and high instructor/student ratio (sixteen students, three faculty, and three teaching assistants). Post-class, students may incorporate course data in senior honors or graduate thesis and are encouraged to publish and present results at national meetings. This course (to our knowledge) remains the only one of its kind, satisfies field experience requirements for some degree programs, and provides an alternative to land-based field courses. Alumni note the course's applicability to energy, environmental, and geotechnical industries as well as coastal restoration/management fields.

Sedimentary Framework of an Inner Continental Shelf Sand-Ridge System, West-Central Florida

NASA Astrophysics Data System (ADS)

Locker, S. D.; Hine, A. C.; Wright, A. K.; Duncan, D. S.

2002-12-01

The west-central Florida inner continental shelf is a dynamic environment subject to current flows on a variety of temporal and spatial scales. A site survey program, undertaken in support of the Office of Naval Research's Mine Burial prediction program, is focused on the sedimentary framework and sediment accumulation patterns in 10-18 meters water depth. Our specific goals are to image the shallow subsurface and to monitor changes in bedform distribution patterns that coincide with physical processes studies ongoing in the area. Methods of study include side-scan sonar imaging, boomer and chirp subbottom profiling, and sedimentary facies analysis using surface sediment sampling and vibracoring. A well-defined sand-ridge system was imaged, trending oblique to the west-Florida coastline. The side-scan clearly shows that there is extensive three-dimensional structure within these large-scale NW-SE trending sedimentary bedforms. The sand ridges commonly are approximately 1 km wide and 4-8 km in length. The characteristics of these ridges are distinctly different than the sand ridges in < 8 m water that we have previously studied. Ridges in the offshore area tend to be thicker, have a flatter morphology, and exhibit fewer smaller-scale sand waves. Sand-ridge thickness ranges 2-3 meters, and typically consists of fining upward medium to fine quartz sand facies with occasional centimeter-scale coarser-grained carbonate-rich intervals. Time series investigations tracking the shift in position of the sand ridge margins have found undetectable net annual movement. However significant resuspension and bedform development accompanies high-energy events such as winter cold front passage. Thus the large-scale bedforms (sand ridges) are in a state of dynamic equilibrium with the average annual hydrodynamic regime. Repeated field surveys will focus on monitoring small-scale sedimentological and stratal framework changes that will be integrated with the quantitative process studies.

Paleodrainage insights into the fluvial and glacial history of the western Chukchi margin, Arctic Alaska

NASA Astrophysics Data System (ADS)

Stockmaster, B. A.; Hill, J. C.; Klotsko, S.; Driscoll, N. W.

2016-12-01

CHIRP subbottom data collected from the Chukchi shelf offshore of northwest Alaska reveal extensive paleodrainage networks that incised the margin during sea level lowstands. These features are cut into folded Cretaceous bedrock strata and likely represent multiple sea level cycles. Several large incised valleys, 10s of km wide and up to 50m deep, as well as numerous smaller, individual channels have been identified. Possible sources of fluvial input include drainage from the Hope Valley to the south, as well as several smaller rivers on the northwest Alaskan coast such as the Utukok, Kokolik, Kukpowruk, and Kuk Rivers. Correlation of sediment infill patterns provides insight to paleochannels and paleovalleys as well as outlining potential drainage networks. This new data will be used to examine sediment infill and erosion patterns to assess whether some of the valleys were formed by non-fluvial (i.e. glacial) processes. Preliminary results indicate the presence of six paleodrainage networks across the eastern Chukchi shelf, based on shape, size and infill of the paleovalleys: Incised Valley, Middle Valley, Northern Valley, Borderlands Valley, the Hanna Bank Valley and the Barrow Valley. All of the paleodrainage valleys are oriented perpendicular to the coast except for Barrow Valley, which follows the northwest coastline, and the Hanna Bank Valley, which is oriented parallel. The Barrow Valley also displays several interesting features in the subsurface. In all of the profiles across this paleovalley, the fluvial infill is overlain by high amplitude, acoustically laminated reflectors that appear to represent hemipelagic marine sediment, indicating rapid sea level rise flooded the shelf. There also appears to be 1 m erosional relief on the transgressive surface, which suggests there may have been an additional source of erosion within the Barrow Valley during sea level rise, possibly from an ice shelf or other glacial features. The presence of ice could also possibly explain the occupation of Barrow Canyon that would have diverted the Barrow Valley drainage.

An Inverse Method for Obtaining the Attenuation Profile and Small Variations in the Sound Speed and Density Profiles of the Ocean Bottom.

DTIC Science & Technology

1985-05-01

Source level in decibels SBL Sub-bottom loss TL Transmission loss of signal going through the water/sediment interface -- 4 - • .’ I.. zL...explained in the legend to figure 3-1. ’-4 RLb - S-BL-2Oog2D-2aD (3.1) RL8b S- TLb- SBL -TLW-2az-2Olog(D+z)-2aD (3.2) jZ h𔃾 -57- OCEAN SURFACE...RLb -RLab= SBL + [TL,+TL,-BL-201og2D" + 2az + 20log(D+z). (3.3) Assuming that the term within the bracket remains constant for the entire wedge, we

Nondegenerate parametric generation of 2.2-mJ, few-cycle 2.05-μm pulses using a mixed phase matching scheme

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

Xu, Guibao; Wandel, Scott F.; Jovanovic, Igor, E-mail: ijovanovic@psu.edu

2014-02-15

We describe the production of 2.2-mJ, ∼6 optical-cycle-long mid-infrared laser pulses with a carrier wavelength of 2.05 μm in a two-stage β-BaB{sub 2}O{sub 4} nondegenerate optical parametric amplifier design with a mixed phase matching scheme, which is pumped by a standard Ti:sapphire chirped-pulse amplification system. It is demonstrated that relatively high pulse energies, short pulse durations, high stability, and excellent beam profiles can be obtained using this simple approach, even without the use of optical parametric chirped-pulse amplification.

Theory and Simulation of Gain-Guided Noncollinear Modes in Chirped Quasi-Phase-Matched Optical Parametric Amplifiers

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

Charbonneau-Lefort, Mathieu; Afeyan, Bedros; Fejer, Martin

Chirped quasi-phase-matched (QPM) gratings offer essentially constant gain over wide bandwidths, making them promising candidates for short-pulse optical parametric amplifiers. However, experiments have shown that high-gain non-collinear processes exist in spite of the dephasing caused by the non-uniformity of the QPM grating and compete with the desired collinear broadband gain of the amplifier. In this paper, these non-collinear gain-guided modes are investigated numerically and analytically in a model that includes longitudinal non-uniformity of the phase-matching profile, lateral localization of the pump beam and non-collinear propagation of the interacting waves.

K1-95-HW, cruise report 1995: preliminary results. Phase III: sediment chemistry and biological sampling survey

USGS Publications Warehouse

Torresan, M.E.; Hampton, M.A.; Barber, J.H.; Wong, F.L.

1995-01-01

Mamala Bay, off the south shore of the island of Oahu, has been used as a repository of dredged material primarily from Pearl and Honolulu Harbors for over a century. The U.S. Geological Survey, U.S. Army Corps of Engineers, and the U.S. Environmental Protection Agency are conducting an integrated study on the distribution and character of dredged materials as well as the effects of dredged material on the marine environment. A three phase study is providing information to evaluate the effects on seafloor substrate and the benthic fauna. The studies include geophysical profiling and imaging, bottom photography, sampling, chemical and physical analyses of sediment, and evaluations of the benthic population, population density, and adverse impacts to the benthic fauna. Phase 1, conducted in 1993, inventoried the seafloor via remote sensing. Sidescan sonar and subbottom profilers characterized the seafloor in and around the disposal sites, and the resulting products reveal the character and extent of the dredged material. These data were used to plan Phase 2 in 1994, a sampling program that employed subbottom profilers, video and still photography, and seafloor sampling to ground truth the sonar mosaic and identify the seafloor substrates responsible for the various acoustic signatures on the sonar images and subbottom profiles. Box coring provided the samples necessary to distinguish dredged material from native sediment, and for the chemical analyses used to determine contaminant concentrations. Phase 3 studies conducted in June of 1995 consisted of box core sampling for chemical and biological analyses. Specific studies include: infaunal taxonomy and population density, bioassay/bioaccumulation, sediment chemistry, and post-disposal resuspension and transport. The 1995 survey, conducted June 14 through 17, resulted in the collection of 39 box cores from 20 different stations. Multiple box cores were composited at 7 different locations occupied in 1994, to provide the material required for the 7 bioassay and bioaccumulation analyses currently underway (Figure 1). Seventeen of the 20 stations occupied provided the biological samples for the benthic infaunal identification and population density study conducted by Dr. Julie Brock of the University of Hawaii, and the sediment chemistry analyses conducted (and completed) by Quanterra Environmental Laboratories (Figure 1). Seven of the 20 stations occupied in 1995 were occupied in 1994, and provide the data for direct comparison of sediment chemistry at the same sites from two consecutive years. The sum total of the data collected from all three phases of the monitoring program will provide the U.S. Army Corps of Engineers and the U.S. Environmental Protection Agency with the information required to make informed decisions as to the management of the South Oahu disposal site in Mamala Bay.

Seismic-reflection and sidescan-sonar data collected off eastern Cape Cod, Massachusetts, during April 1979

USGS Publications Warehouse

Knebel, Harley J.

1981-01-01

The U.S. Geological Survey collected 98 line kilometers of single-channel seismic-reflection profiles and sidescan sonar records on the inner shelf of eastern Cape Cod, Massachusetts, during April 1979. The data were obtained during cruise NE-1-79 of the R/V NEECHO. The purposes of the survey were: (1) to study the development of barrier islands; (2) to document the frequency and rate of migration of inlets that breach barrier islands; and (3) to define the characteristics of shoreface ridges on a barrier island.he survey uti I ized two acoustic systems. Information about the bottom was obtained by using an EDO Western model 606 sidescan-sonar system (100 kHz). Profiles of the subbottom were collected by an EG&G Uni boom transducer (400-4,000 Hz) and a Del Norte streamer. Positional control for al I track! ines was provided by a shore-based Miniranger system and by LORAN-C.The quality of the records generally is very good. However, subbottom penetration did vary somewhat from place to place during the survey due to the nature of the bottom sediments and to the presence or absence of buried channels.The original records may be examined at the U.S. Geological Survey, Woods Hole, MA 02543. Microfilm copies of the data are avai I able for purchase from the National Geophysical pnd Solar-Terrestrial Data Center, NOAA/EDIS/NGSDC, Code D621, 325 Broadway, Boulder, CO 80303 (303-497-6338).

Impact of Hurricane Sandy on the Shoreface and Inner Shelf, Offshore Long Island: Evidence for Ravinement?

NASA Astrophysics Data System (ADS)

Goff, J. A.; Austin, J. A.; Flood, R. D.; Schwab, W. C.; Denny, J. F.; Christensen, B. A.; Browne, C. M.; Saustrup, S.

2013-12-01

In January 2013, approximately two months after Hurricane Sandy made landfall in the Mid-Atlantic Bight, a scientific team from the University of Texas Institute for Geophysics, partnering with colleagues at Adelphi and Stony Brook universities and the USGS, conducted marine geophysical and surficial sampling surveys both offshore and in the inshore bays of Long Island, NY. The primary scientific goal was to assess the impact of the storm on the shoreface and inner shelf. Sandy made landfall as a post-tropical cyclone near Brigantine, NJ, with 70-kt maximum sustained winds. However, its unusual trajectory and massive size created record storm surges along the heavily-populated NJ and NY coastlines. As a result, infrastructure in the NY metropolitan area was damaged, and the Long Island barrier island system was both breached in places and elsewhere seriously eroded. The surveys included ten days of operations aboard Stony Brook's R/V Seawolf, offshore of Long Beach and Fire Island, barrier islands south of Long Island, complementing ongoing land-based studies of Sandy's impact on the NY-NJ barrier island system. Data collection involved multibeam bathymetric swath mapping, CHIRP very high resolution acoustic subbottom profiling, and surface sediment (grab) sampling to provide ground truth for the geophysical data. We surveyed regions that had been previously surveyed, both by Stony Brook in 2001 and 2005 to support reef management, and by the USGS for coastal sedimentary research, most recently in 2011 offshore Fire Island. These areas include shoreface-attached sand ridges that may be exchanging sand with the barrier island shoreface. We focus on before-and-after data comparisons on the shoreface and inner shelf, searching in particular for evidence that the storm contributed significantly to ravinement, either by wave- or current-forced erosion along the shoreface or via migration of shoreface-attached or detached sand ridges on the inner shelf. The interpreted (Holocene) transgressive ravinement surface, which may have been modified in part by Sandy, is frequently well-imaged in CHIRP data on the inner- to outer shelf; it represents the physical contrast between Holocene sands above and either Holocene estuarine (often residing in buried river channels) or older (Pleistocene) material below, typically with coarser-grained lag material at the interface. However, the process of ravinement in response to shelf-wide base-level changes is not well understood, and is also difficult to observe because it presumably happens during the most inclement of conditions. Our study provides an opportunity to investigate the ravinement process directly in response to a specific event, to link that process to the stratigraphic record, and therefore to gauge one large storm's contribution to this important part of the sediment budget for inner shelf/beach barrier systems.

Acoustic profiles and images of the Palos Verdes Margin: Implications concerning deposition from the White's Point outfall

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

Hampton, M A.; Karl, H; Murray, Christopher J.

2001-12-01

Subbottom profiles and sidescan-sonar images collected on and around the Palos Verdes shelf show a surficial deposit interpreted to contain effluent from the White's Point diffusers, as well as showing several geologic features that affect the deposit's distribution. The effluent-affected deposit is visible in high-resolution subbottom profiles on the shelf and the adjacent San Pedro basin slope to water depths of 170 m. It has a maximum thickness of 75 cm and was mapped acoustically over an area of 10.8 km{sup 2}, which encompasses a volume of about 3.2 million m{sup 3}. The deposit's basal reflector is acoustically distinct overmore » most of the mapped area, implying that the deposit has not been extensively mixed across its base, perhaps being relatively free of reworking since its initial deposition. Nearshore, the basal reflector is weak and fades away toward land, which could result from syndepositional intermixing of coarse native sediment (particularly from the Portuguese Bend landslide) with effluent in the high-energy nearshore zone, or postdepositionally by physical (wave) or biological mixing across the interface. The geometry of the deposit implies that effluent is dispersed primarily in a northwesterly and seaward direction from the diffusers. Dispersal across the shelf break is in some places strongly affected by topography, particularly by submarine canyons. The deposit overlies stratified and unstratified Quaternary sediment, up to 30 m thick, that in turn overlies the irregular erosional surface of deformed Miocene bedrock that crops out in places on the shelf and upper basin slope. The effluent-affected deposit rests on potentially unstable landslide deposits on the San Pedro basin slope. The acoustic profiles and side-scan images show evidence for active and inactive vents, probably of hot water and gas, some of which are within the boundary of the effluent-affected sediment deposit and could disrupt it if seepage occurs.« less

3D Chirp Sonar Images on Fluid Migration Pathways and Their Implications on Seafloor Stability East of the Fangliao Submarine Canyon Offshore SW Taiwan

NASA Astrophysics Data System (ADS)

Lu, Y. W.; Liu, C. S.; Su, C. C.; Hsu, H. H.; Chen, Y. H.

2015-12-01

This study utilizes both chirp sonar images and coring results to investigate the unstable seafloor strata east of the Fangliao Submarine Canyon offshore southwestern Taiwan. We have constructed 3D chirp sonar images from a densely surveyed block to trace the attitude of an acoustic transparent layer and features caused by fluid activities. Based on the distribution of this transparent layer and fluid-related features, we suggest that this transparent layer forms a pathway for fluid migration which induces fluid-related characters such as acoustic blanking and fluid chimneys in the 3D chirp sonar images. Cored seafloor samples are used in this study to investigate the sediment compositions. The 210Pb activity profiles of the cores show oscillating and unsteady values at about 20~25 cm from core top. The bulk densities of the core samples in the same section (about 20~25 cm from core top) give values lower than those at deeper parts of the cores. These results indicate that the water content is much higher in the shallow sediments than in the deeper strata. From core sample analyses, we deduce that the local sediments are disturbed by liquefaction. From the analyses of 3D chirp sonar images and core data, we suggest that the seafloor east of the Fangliao Submarine Canyon is in an unstable condition, if disturbed by earthquakes, submarine landslides and gravity flows could be easily triggered and cause some geohazards, like breaking submarine cables during the 2006 Pingtung earthquake event.

Evidence from acoustic imaging for submarine volcanic activity in 2012 off the west coast of El Hierro (Canary Islands, Spain)

NASA Astrophysics Data System (ADS)

Pérez, Nemesio M.; Somoza, Luis; Hernández, Pedro A.; de Vallejo, Luis González; León, Ricardo; Sagiya, Takeshi; Biain, Ander; González, Francisco J.; Medialdea, Teresa; Barrancos, José; Ibáñez, Jesús; Sumino, Hirochika; Nogami, Kenji; Romero, Carmen

2014-12-01

We report precursory geophysical, geodetic, and geochemical signatures of a new submarine volcanic activity observed off the western coast of El Hierro, Canary Islands. Submarine manifestation of this activity has been revealed through acoustic imaging of submarine plumes detected on the 20-kHz chirp parasound subbottom profiler (TOPAS PS18) mounted aboard the Spanish RV Hespérides on June 28, 2012. Five distinct "filament-shaped" acoustic plumes emanating from the flanks of mounds have been recognized at water depth between 64 and 88 m on a submarine platform located NW El Hierro. These plumes were well imaged on TOPAS profiles as "flares" of high acoustic contrast of impedance within the water column. Moreover, visible plumes composed of white rafts floating on the sea surface and sourcing from the location of the submarine plumes were reported by aerial photographs on July 3, 2012, 5 days after acoustic plumes were recorded. In addition, several geophysical and geochemical data support the fact that these submarine vents were preceded by several precursory signatures: (i) a sharp increase of the seismic energy release and the number of daily earthquakes of magnitude ≥2.5 on June 25, 2012, (ii) significant vertical and horizontal displacements observed at the Canary Islands GPS network (Nagoya University-ITER-GRAFCAN) with uplifts up to 3 cm from June 25 to 26, 2012, (iii) an anomalous increase of the soil gas radon activity, from the end of April until the beginning of June reaching peak values of 2.7 kBq/m3 on June 3, 2012, and (iv) observed positive peak in the air-corrected value of 3He/4He ratio monitored in ground waters (8.5 atmospheric 3He/4He ratio ( R A)) at the northwestern El Hierro on June 16, 2012. Combining these submarine and subaerial information, we suggest these plumes are the consequence of submarine vents exhaling volcanic gas mixed with fine ash as consequence of an event of rapid rise of volatile-rich magma beneath the NW submarine ridge of El Hierro. These precursory signals have revealed important to improve and optimize the detection of early warning signals of volcanic unrest episodes at El Hierro.

Northern Cascadia Subduction Zone Earthquake Records from Onshore and Offshore Core Data

NASA Astrophysics Data System (ADS)

Hausmann, R. B.; Goldfinger, C.; Black, B.; Romsos, C. G.; Galer, S.; Collins, T.

2016-12-01

We are investigating the paleoseismic record at Bull Run Lake, at the latitude of Portland, Oregon, central Cascadia margin. Bull Run is a landslide dammed lake in a cirque basin on the western flanks of Mt. Hood, 65 km east of Portland, and is the City of Portland's primary water supply. We collected full coverage high-resolution multibeam and backscatter data, high resolution CHIRP sub-bottom profiles, and seven sediment cores which contain a correlative turbidite sequence of post Mazama beds. The continuity of the turbidite record shows little or no relationship to the minor stream inlets, suggesting the disturbance beds are not likely to be storm related. CT and physical property data were used to separate major visible beds and background sedimentation, which also contain thin laminae. The XRF element Compton scattering may show grading due to mineralogical variation and a change in wave profile, commonly found at bed boundaries. We have identified 27 post -Mazama event beds and 5 ashes in the lake, and constructed an OxCal age model anchored by radiocarbon ages, the Mazama ash, and the twin Timberline ash beds. The radiocarbon ages, age model results, as well as electron microprobe (EMP) data clearly identify the Mazama ash at the base of our cores. Two closely-spaced ash beds in our cores likely correlate to the Timberline eruptive period at 1.5ka. The number, timing and sequence of the event beds, and physical property log correlation, as well as key bed characteristics, closely matches offshore turbidite sequences off northern Oregon. For example, key regional bed T11, observed as a thick two-pulse bed in all offshore cores, also anchors the Bull Run sequence. One difference is that the twin Timberline ash occupies the stratigraphic position of regional offshore paleoseismic bed T4, which is also a two pulse event at this latitude. The cores also contain many faint laminae that may contain a storm record, however, the identification of small beds is complicated by the low sedimentation rate and low resolution of the Bull Run cores. The watershed and lake may also contain evidence of crustal faulting, though the event sequence appears to be primarily that of the Cascadia subduction zone earthquake sequence. See also Goldfinger et al. for investigation of slope stability and ground motions at Bull Run and other Cascadia lakes.

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

NASA Astrophysics Data System (ADS)

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

2016-12-01

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

Sediment dispersal patterns within the Nares Abyssal Plain: observations from GLORIA Sonographs

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

Shephard, L.E.; Tucholke, B.E.; Fry, V.A.

1985-01-01

Features evident on GLORIA sonographs from the Nares Abyssal Plain suggest a sediment dispersal pattern for turbidity currents that varies temporally and spatially, resulting in randomly distributed turbidite deposits in the distal abyssal plain east of 64/sup 0/W. Regional variations in backscatter intensities across the abyssal plain are related to the frequency and thickness of near-surface silt beds, basement highs disrupting the seafloor, and subtle changes in surface and sub-surface bedforms related to low-relief turbidite flow paths, biologic activity, and possibly erosion. High backscatter intensities, prevalent west of 64/sup 0/W, are generally associated with those areas containing thicker silt bedsmore » and very regular subbottom reflectors on 3.5 kHz profiles. Low backscatter intensities, prevalent east of 64/sup 0/W, are associated with those areas containing thin silt beds or stringers with a much higher percentage of pelagic clay. Seafloor lineaments occur throughout the survey area but decrease in abundance east of 64/sup 0/W. These features have no apparent relief when crossed by surface-towed seismic reflection profiles. In some instances the lineaments may correspond to low-relief turbidite flow paths that contain varying textural compositions resulting in increased backscatter. These features would be indicative of sediment transport directions. Other possible origins for the lineaments, that often appear trackline parallel, include near-surface morphology that is preferentially detected and aligned by GLORIA, or possibly the lineaments result from complex subbottom interference patterns that would not be readily apparent in areas with a more irregular seafloor.« less

Diversity in the structure of electrocommunication signals within a genus of electric fish, Apteronotus.

PubMed

Dunlap, K D; Larkins-Ford, J

2003-02-01

Some gymnotiform electric fish modulate their electric organ discharge for intraspecific communication. In Apteronotus leptorhynchus, chirps are usually rapid (10-30 ms) modulations that are activated through non- N-methyl- d-aspartate (non-NMDA) glutamate receptors in the hindbrain pacemaker nucleus. Males produce longer chirp types than females and chirp at higher rates. In Apteronotus albifrons, chirp rate is sexually monomorphic, but chirp structure (change in frequency and amplitude during a chirp) was unknown. To better understand the neural regulation and evolution of chirping behavior, we compared chirp structure in these two species under identical stimulus regimes. A. albifrons, like A. leptorhynchus, produced distinct types of chirps that varied, in part, by frequency excursion. However, unlike in A. leptorhynchus, chirp types in A. albifrons varied little in duration, and chirps were all longer (70-200 ms) than those of A. leptorhynchus. Chirp type production was not sexually dimorphic in A. albifrons, but within two chirp types males produced longer chirps than females. We suggest that species differences in chirp duration might be attributable to differences in the relative proportions of fast-acting (non-NMDA) and slow-acting (NMDA) glutamate receptors in the pacemaker. Additionally, we map species difference onto a phylogeny and hypothesize an evolutionary sequence for the diversification of chirp structure.

Digitally controlled chirped pulse laser for sub-terahertz-range fiber structure interrogation.

PubMed

Chen, Zhen; Hefferman, Gerald; Wei, Tao

2017-03-01

This Letter reports a sweep velocity-locked laser pulse generator controlled using a digital phase-locked loop (DPLL) circuit. This design is used for the interrogation of sub-terahertz-range fiber structures for sensing applications that require real-time data collection with millimeter-level spatial resolution. A distributed feedback laser was employed to generate chirped laser pulses via injection current modulation. A DPLL circuit was developed to lock the optical frequency sweep velocity. A high-quality linearly chirped laser pulse with a frequency excursion of 117.69 GHz at an optical communication band was demonstrated. The system was further adopted to interrogate a continuously distributed sub-terahertz-range fiber structure (sub-THz-fs) for sensing applications. A strain test was conducted in which the sub-THz-fs showed a linear response to longitudinal strain change with predicted sensitivity. Additionally, temperature testing was conducted in which a heat source was used to generate a temperature distribution along the fiber structure to demonstrate its distributed sensing capability. A Gaussian temperature profile was measured using the described system and tracked in real time, as the heat source was moved.

Archive of digital CHIRP seismic reflection data collected during USGS cruise 06FSH01 offshore of Siesta Key, Florida, May 2006

USGS Publications Warehouse

Harrison, Arnell S.; Dadisman, Shawn V.; Flocks, James G.; Wiese, Dana S.; Robbins, Lisa L.

2007-01-01

In May of 2006, the U.S. Geological Survey conducted geophysical surveys offshore of Siesta Key, Florida. This report serves as an archive of unprocessed digital chirp seismic reflection data, trackline maps, navigation files, GIS information, Field Activity Collection System (FACS) logs, observer's logbook, and formal FGDC metadata. Gained digital images of the seismic profiles are also provided. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Example SU processing scripts and USGS software for viewing the SEG-Y files (Zihlman, 1992) are also provided.

Archive of digital CHIRP seismic reflection data collected during USGS cruise 06SCC01 offshore of Isles Dernieres, Louisiana, June 2006

USGS Publications Warehouse

Harrison, Arnell S.; Dadisman, Shawn V.; Ferina, Nick F.; Wiese, Dana S.; Flocks, James G.

2007-01-01

In June of 2006, the U.S. Geological Survey conducted a geophysical survey offshore of Isles Dernieres, Louisiana. This report serves as an archive of unprocessed digital CHIRP seismic reflection data, trackline maps, navigation files, GIS information, Field Activity Collection System (FACS) logs, observer's logbook, and formal FGDC metadata. Gained digital images of the seismic profiles are also provided. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic UNIX (SU). Example SU processing scripts and USGS software for viewing the SEG-Y files (Zihlman, 1992) are also provided.

Generation of 3D ellipsoidal laser beams by means of a profiled volume chirped Bragg grating

NASA Astrophysics Data System (ADS)

Mironov, S. Yu; Poteomkin, A. K.; Gacheva, E. I.; Andrianov, A. V.; Zelenogorskii, V. V.; Vasiliev, R.; Smirnov, V.; Krasilnikov, M.; Stephan, F.; Khazanov, E. A.

2016-05-01

A method for shaping photocathode laser driver pulses into 3D ellipsoidal form has been proposed and implemented. The key idea of the method is to use a chirped Bragg grating recorded within the ellipsoid volume and absent outside it. If a beam with a constant (within the grating reflection band) spectral density and uniform (within the grating aperture) cross-section is incident on such a grating, the reflected beam will be a 3D ellipsoid in space and time. 3D ellipsoidal beams were obtained in experiment for the first time. It is expected that such laser beams will allow the electron bunch emittance to be reduced when applied at R± photo injectors.

Analysis of radial and longitudinal force of plasma wakefield generated by a chirped pulse laser

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

Ghasemi, Leila; Afhami, Saeedeh; Eslami, Esmaeil, E-mail: eeslami@iust.ac.ir

2015-08-15

In present paper, the chirp effect of an electromagnetic pulse via an analytical model of wakefield generation is studied. Different types of chirps are employed in this study. Our results show that by the use of nonlinear chirped pulse the longitudinal wakefield and focusing force is stronger than that of linear chirped pulse. It is indicated that quadratic nonlinear chirped pulses are globally much efficient than periodic nonlinear chirped pulses. Our calculations also predict that in nonlinear chirped pulse case, the overlap of focusing and accelerating regions is broader than that achieved in linear chirped pulse.

Diversity And Abundance Of Deep-Water Coral Mounds In The Straits Of Florida: A Result of Adaptability To Local Environments?

NASA Astrophysics Data System (ADS)

Correa, T. B.; Grasmueck, M.; Eberli, G.; Viggiano, D. A.; Rosenberg, A.; Reed, J. K.

2007-12-01

To improve the understanding of the Florida-Bahamas deep-water coral mound ecosystem, Autonomous Underwater Vehicle (AUV) surveys were conducted on five coral mound fields throughout the Straits of Florida (three sites at the base of slope of Great Bahama Bank (GBB), one in the middle of the Straits (MS) and one at the base of the Miami Terrace (MT)) in water depths of 590 to 860 m. The AUV provides high-resolution bathymetric maps, sub-bottom profiles and oceanographic data. The AUV survey sites were subsequently groundtruthed via sample collection and video transects, using the Johnson Sealink submersible. Contrary to previous surveys, we found a high diversity in coral mound morphology between sites separated by 15 to 80 km. The MT site is characterized by sinusoidal coral mound ridges, while the MS site contains densely clustered small coral mounds. Meanwhile, mounds of the GBB region are better developed, with some individual mounds reaching up to 90 m in height. Benthic coverage of live corals also differs between sites; the GBB sites are characterized by mounds densely covered by large thickets of live corals, while small thickets of mostly dead corals dominate the MT and MS sites. Several environmental factors may explain these differences. For example, bottom current patterns change between sites. The MT and the MS sites have a unidirectional regime (southward or northward flow, respectively), whereas the GBB sites have a tidal current regime. Sedimentation patterns as depicted by sub-bottom profiles also vary between the sites; coral mounds in the GBB area appear to receive higher sediment input, which can significantly enhance mound growth rates as the reef framework baffles and traps mobile sediments. However, coral mounds that cannot keep-up with the sedimentation rate are buried. Therefore, in the high sedimentation areas of GBB, flourishing live coral mounds are limited to elevated positions (i.e. plateaus, ridges crests) where sediment accumulation is lessened. Corals in these raised locations also benefit from increased exposure to nutrient-rich tidal currents, supporting a denser live coral coverage. Sub-bottom profiles of the MT site show undulating coral ridges developed on top of a relatively flat sub-surface, indicating that antecedent topography is not the only factor determining mound distribution. The integrated AUV data suggest that variable environmental factors, such as sedimentation and current patterns, contribute to the high diversity between coral mound sites of the Straits of Florida. Environmental conditions change over distances of only a few kilometers creating localized and diverse deep-water coral habitats. The deepwater fauna adapts to the local oceanographic and geological conditions. This results in an unexpectedly high abundance of deep-water coral communities with diverse expressions.

Co-adaptation of Electric Organ Discharges and Chirps in South American Ghost Knifefishes (Apteronotidae)

PubMed Central

Petzold, Jacquelyn M.; Marsat, Gary; Smith, G. Troy

2016-01-01

Animal communication signals that simultaneously share the same sensory channel are likely to coevolve to maximize the transmission of each signal component. Weakly electric fish continuously produce a weakly electric field that functions in communication. Fish modulate the electric organ discharge (EOD) on short timescales to produce context-specific signals called chirps. EODs and chirps are simultaneously detected by electroreceptors and processed in the electrosensory system. We analyzed these signals, first to explore whether EOD waveform is encoded in the signal received by electroreceptors and then to examine how EODs and chirps interact to influence conspicuousness. Our findings show that gross discrimination of sinusoidal from complex EOD waveforms is feasible for all species, but fine discrimination of waveform may be possible only for species with waveforms of intermediate complexity. The degree of chirp frequency modulation and chirp relative decay strongly influenced chirp conspicuousness, but other chirp parameters were less influential. The frequency difference between the interacting EODs also strongly impacted chirp conspicuousness. Finally, we developed a method for creating hybrid chirp/EOD combinations to independently analyze the impact of chirp species, EOD species, and EOD difference frequency on chirp conspicuousness. All three components and their interactions strongly influenced chirp conspicuousness, which suggests that evolutionary changes in parameters of either chirps or EODs are likely to influence chirp detection. Examining other environmental factors such as noise created by fish movement and species-typical patterns of sociality may enrich our understanding of how interacting EODs affect the detection and discrimination of chirps across species. PMID:27989653

Neonate Auditory Brainstem Responses to CE-Chirp and CE-Chirp Octave Band Stimuli I: Versus Click and Tone Burst Stimuli.

PubMed

Cobb, Kensi M; Stuart, Andrew

The purpose of the study was to generate normative auditory brainstem response (ABR) wave component peak latency and amplitude values for neonates with air- and bone-conducted CE-Chirps and air-conducted CE-Chirp octave band stimuli (i.e., 500, 1000, 2000, and 4000 Hz). A second objective was to compare neonate ABRs to CE-Chirp stimuli with ABR responses to traditional click and tone burst stimuli with the same stimulus parameters. Participants were 168 healthy neonates. ABRs were obtained to air- and bone-conducted CE-Chirp and click stimuli and air-conducted CE-Chirp octave band and tone burst stimuli. The effects of stimulus level, rate, and polarity were examined with air-conducted CE-Chirps and clicks. The effect of stimulus level was also examined with bone-conducted CE-Chirps and clicks and air-conducted CE-Chirp octave band stimuli. In general, ABR wave V amplitudes to air- and bone-conducted CE-Chirp stimuli were significantly larger (p < 0.05) than those evoked to traditional click and tone burst stimuli. Systematic statistically significant (p < 0.05) wave V latency differences existed between the air- and bone-conducted CE-Chirp and CE-Chirp octave band stimuli relative to traditional click and tone burst stimuli. ABRs to air- and bone-conducted CE-Chirps and CE-Chirp octave band stimuli may be valuable in the assessment of newborn infants. However, the prognostic value of such stimuli needs to be validated.

Direct and indirect evidence for earthquakes; an example from the Lake Tahoe Basin, California-Nevada

NASA Astrophysics Data System (ADS)

Maloney, J. M.; Noble, P. J.; Driscoll, N. W.; Kent, G.; Schmauder, G. C.

2012-12-01

High-resolution seismic CHIRP data can image direct evidence of earthquakes (i.e., offset strata) beneath lakes and the ocean. Nevertheless, direct evidence often is not imaged due to conditions such as gas in the sediments, or steep basement topography. In these cases, indirect evidence for earthquakes (i.e., debris flows) may provide insight into the paleoseismic record. The four sub-basins of the tectonically active Lake Tahoe Basin provide an ideal opportunity to image direct evidence for earthquake deformation and compare it to indirect earthquake proxies. We present results from high-resolution seismic CHIRP surveys in Emerald Bay, Fallen Leaf Lake, and Cascade Lake to constrain the recurrence interval on the West Tahoe Dollar Point Fault (WTDPF), which was previously identified as potentially the most hazardous fault in the Lake Tahoe Basin. Recently collected CHIRP profiles beneath Fallen Leaf Lake image slide deposits that appear synchronous with slides in other sub-basins. The temporal correlation of slides between multiple basins suggests triggering by events on the WTDPF. If correct, we postulate a recurrence interval for the WTDPF of ~3-4 k.y., indicating that the WTDPF is near its seismic recurrence cycle. In addition, CHIRP data beneath Cascade Lake image strands of the WTDPF that offset the lakefloor as much as ~7 m. The Cascade Lake data combined with onshore LiDAR allowed us to map the geometry of the WTDPF continuously across the southern Lake Tahoe Basin and yielded an improved geohazard assessment.

Calculation and manipulation of the chirp rates of high-order harmonics

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

Murakami, M.; Mauritsson, J.; Schafer, K.J.

2005-01-01

We calculate the linear chirp rates of high-order harmonics in argon, generated by intense, 810 nm laser pulses, and explore the dependence of the chirp rate on harmonic order, driving laser intensity, and pulse duration. By using a time-frequency representation of the harmonic fields we can identify several different linear chirp contributions to the plateau harmonics. Our results, which are based on numerical integration of the time-dependent Schroedinger equation, are in good agreement with the adiabatic predictions of the strong field approximation for the chirp rates. Extending the theoretical analysis in the recent paper by Mauritsson et al. [Phys. Rev.more » A 70, 021801(R) (2004)], we also manipulate the chirp rates of the harmonics by adding a chirp to the driving pulse. We show that the chirp rate for harmonic q is given by the sum of the intrinsic chirp rate, which is determined by the new duration and peak intensity of the chirped driving pulse, and q times the external chirp rate.« less

Investigation of Coastal Hydrogeology Utilizing Geophysical and Geochemical Tools along the Broward County Coast, Florida

USGS Publications Warehouse

Reich, Christopher D.; Swarzenski, Peter W.; Greenwood, W. Jason; Wiese, Dana S.

2008-01-01

Geophysical (CHIRP, boomer, and continuous direct-current resistivity) and geochemical tracer studies (continuous and time-series 222Radon) were conducted along the Broward County coast from Port Everglades to Hillsboro Inlet, Florida. Simultaneous seismic, direct-current resistivity, and radon surveys in the coastal waters provided information to characterize the geologic framework and identify potential groundwater-discharge sites. Time-series radon at the Nova Southeastern University National Coral Reef Institute (NSU/NCRI) seawall indicated a very strong tidally modulated discharge of ground water with 222Rn activities ranging from 4 to 10 disintegrations per minute per liter depending on tidal stage. CHIRP seismic data provided very detailed bottom profiles (i.e., bathymetry); however, acoustic penetration was poor and resulted in no observed subsurface geologic structure. Boomer data, on the other hand, showed features that are indicative of karst, antecedent topography (buried reefs), and sand-filled troughs. Continuous resistivity profiling (CRP) data showed slight variability in the subsurface along the coast. Subtle changes in subsurface resistivity between nearshore (higher values) and offshore (lower values) profiles may indicate either a freshening of subsurface water nearshore or a change in sediment porosity or lithology. Further lithologic and hydrologic controls from sediment or rock cores or well data are needed to constrain the variability in CRP data.

Archive of digital boomer and CHIRP seismic reflection data collected during USGS cruise 06FSH03 offshore of Fort Lauderdale, Florida, September 2006

USGS Publications Warehouse

Harrison, Arnell S.; Dadisman, Shawn V.; Reich, Christopher D.; Wiese, Dana S.; Greenwood, Jason W.; Swarzenski, Peter W.

2007-01-01

In September of 2006, the U.S. Geological Survey conducted geophysical surveys offshore of Fort Lauderdale, FL. This report serves as an archive of unprocessed digital boomer and CHIRP seismic reflection data, trackline maps, navigation files, GIS information, Field Activity Collection System (FACS) logs, observer's logbook, and formal FGDC metadata. Filtered and gained digital images of the seismic profiles are also provided. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Example SU processing scripts and USGS software for viewing the SEG-Y files (Zihlman, 1992) are also provided.

Ionization waves of arbitrary velocity driven by a flying focus

NASA Astrophysics Data System (ADS)

Palastro, J. P.; Turnbull, D.; Bahk, S.-W.; Follett, R. K.; Shaw, J. L.; Haberberger, D.; Bromage, J.; Froula, D. H.

2018-03-01

A chirped laser pulse focused by a chromatic lens exhibits a dynamic, or flying, focus in which the trajectory of the peak intensity decouples from the group velocity. In a medium, the flying focus can trigger an ionization front that follows this trajectory. By adjusting the chirp, the ionization front can be made to travel at an arbitrary velocity along the optical axis. We present analytical calculations and simulations describing the propagation of the flying focus pulse, the self-similar form of its intensity profile, and ionization wave formation. The ability to control the speed of the ionization wave and, in conjunction, mitigate plasma refraction has the potential to advance several laser-based applications, including Raman amplification, photon acceleration, high-order-harmonic generation, and THz generation.

Tectonics and Volcanism During the Cretaceous Normal Superchron Seafloor in the Western Pacific Ocean

NASA Astrophysics Data System (ADS)

O'Brien, E.

2017-12-01

We have conducted an integration study on the origin and evolution of the tectonics and volcanism of seafloor in the Western Pacific Ocean that took place during the Cretaceous Normal Superchron (CNS) where sparse data has so far precluded detailed investigation. We have compiled the latest satellite-based gravity, gravity gradient, and magnetic grids (EMAG2 v.3) for this region. These crustal-scale high-resolution grids suggest that the CNS seafloor contains fossilized lithospheric morphology possibly attributed to the interaction between Cretaceous supervolcanism activity and Mid-Cretaceous Pacific mid ocean ridge systems that have continuously expanded the Pacific Plate. We recognize previously identified fossilized microplates west of the Magellan Rise, short-lived abandoned propagating rifts and fracture zones, all of which show significant rotation of seafloor fabric. In addition to these large scale observations, we have also compiled marine geological information from previously drilled cores and new data from a Kongsberg Topas PS18 Parametric Sub-Bottom Profiler collected on a transect from Honolulu, Hawaii to Apra, Guam acquired during research cruise SKQ2014S2. In particular, the narrow beam and high bandwidth signal of the Topas PS18 sub-bottom profiler provides sonar data of the seabed with a resolution and depth penetration that is unprecedented compared with previously available surveys in the region. A preliminary assessment of this high resolution Topas data allows us to better characterize sub-seafloor sediment properties and identify features, including the Upper Transparent Layer with identifiable pelagic clay and porcelanite-chert reflectors as well as tectonic features such as the westernmost tip of the Waghenaer Fracture Zone.

Integration of NOAA Ship Okeanos Explorer Seafloor Mapping, Little Hercules ROV, and Sentry AUV Data into Ocean Exploration Operations and Public Data Holdings

NASA Astrophysics Data System (ADS)

Lobecker, E.; Malik, M.; Skarke, A. D.; VerPlanck, N.

2012-12-01

Within NOAA's Office of Ocean Exploration and Research, the Okeanos Explorer Program's main tools for preliminary ocean exploration include a Kongsberg EM 302 multibeam sonar (30 kHz), Kongsberg EK 60 singlebeam sonar (18 kHz), and Knudsen subbottom profiler (3.5 kHz chirp). The program devoted multiple expeditions in the Gulf of Mexico and U.S. Atlantic Margin during its 2012 Field Season to confirm and further develop the EM 302 multibeam sonar's water column backscatter data capability to detect gaseous seeps and vents. While mapping in the seafloor and water column in the vicinity of the salt domes of the Northern Gulf of Mexico, the EM 302 detected over two hundred distinct seeps in the water column. Several seeps have been explored in more detail using high definition cameras and lighting systems of the remotely operated vehicle Little Hercules and the camera platform Seirios. This included filming bubbles escaping from the seafloor at the locations determined by the EM 302 data to ground truth EM302 observations and deduce other properties of these gas seeps e.g. gas flux, and effect of these seeps on surrounding ecosystem. These seeps are now a major research focus area by scientists at the University of New Hampshire's Center for Coastal and Ocean Mapping and other academic institutions around the U.S., and the U.S. Bureau of Ocean Energy Management. . While mapping the Blake Ridge and Cape Fear Diapirs, seven distinct seeps were detected, each rising approximately 900 meters from the seafloor in water depths ranging from 2200 to 2500 meters. Several of these seeps were further explored with Woods Hole Oceanographic Institute's Sentry autonomous underwater vehicle, utilizing itsReson 7125 high resolution multibeam, photo imagery, sidescan, subbottom, and various in-situ sensors to characterize the local environment. It is to be noted that very few of these seeps were previously known. Following the Okeanos Explorer Program's paradigm of "Always Exploring", the mapping team collects data not only during focused mapping operations, but also during all transits. Okeanos Explorer data are collected with regard to the Integrated Ocean and Coastal Mapping Center's concept to "map once use many times", which aims to encourage and enable the multidisciplinary use of seafloor mapping data, including by the fields of marine archaeology, hydrographic mapping, extended continental shelf, biology, geology, geophysics, biopharmaceutical, ocean energy and resources, marine managed areas, fisheries, corals, oceanography, hazards modeling and assessments, education and outreach. To this end, all mapping, CTD and meteorology data sets collected by the NOAA Ship Okeanos Explorer are monitored and evaluated in the field for quality control purposes, and are made available through NOAA's public archives within 60 to 90 days of data collection, in useable formats and with associated metadata records. Additionally, all data sets collected by vehicles onboard the ship, including ROVs and AUVs, are made available directly following each cruise via NOAA's public archives.

High Resolution Quaternary Seismic Stratigraphy of the New York Bight Continental Shelf

USGS Publications Warehouse

Schwab, William C.; Denny, J.F.; Foster, D.S.; Lotto, L.L.; Allison, M.A.; Uchupi, E.; Swift, B.A.; Danforth, W.W.; Thieler, E.R.; Butman, Bradford

2003-01-01

A principal focus for the U.S. Geological Survey (USGS) Coastal and Marine Geology Program (marine.usgs.gov) is regional reconnaissance mapping of inner-continental shelf areas, with initial emphasis on heavily used areas of the sea floor near major population centers. The objectives are to develop a detailed regional synthesis of the sea-floor geology in order to provide information for a wide range of management decisions and to form a basis for further investigations of marine geological processes. In 1995, the USGS, in cooperation with the U.S. Army Corps of Engineers (USACOE), New York District, began to generate reconnaissance maps of the continental shelf seaward of the New York - New Jersey metropolitan area. This mapping encompassed the New York Bight inner-continental shelf, one of the most heavily trafficked and exploited coastal regions in the United States. Contiguous areas of the Hudson Shelf Valley, the largest physiographic feature on this segment of the continental shelf, also were mapped as part of a USGS study of contaminated sediments (Buchholtz ten Brink and others, 1994; 1996). The goal of the reconnaissance mapping was to provide a regional synthesis of the sea-floor geology in the New York Bight area, including: (a) a description of sea-floor morphology; (b) a map of sea-floor sedimentary lithotypes; (c) the geometry and structure of the Cretaceous strata and Quaternary deposits; and (d) the geologic history of the region. Pursuing the course of this mapping effort, we obtained sidescan-sonar images of 100 % of the sea floor in the study area. Initial interpretations of these sidescan data were presented by Schwab and others, (1997a, 1997b, 2000a). High-resolution seismic-reflection profiles collected along each sidescan-sonar line used multiple acoustic sources (e.g., watergun, CHIRP, Geopulse). Multibeam swath-bathymetry data also were obtained for a portion of the study area (Butman and others, 1998;). In this report, we present a series of structural and sediment isopach maps and interpretations of the Quaternary evolution of the inner-continental shelf off the New York - New Jersey metropolitan area based on subbottom, sidescan-sonar, and multibeam-bathymetric data.

Outer Continental Shelf Stratigraphic Development and Sand Resource Potential: Integration of New and Legacy Geologic Datasets

NASA Astrophysics Data System (ADS)

Hughes, M.; Harris, S.; Luciano, K. E.; Alexander, C. R., Jr.

2017-12-01

Following the impact of Hurricane Sandy on the U.S. Atlantic coast in 2012 the Bureau of Ocean Energy Management (BOEM), in cooperation with state partners, instituted several regional offshore resource studies for the near outer continental shelf (OCS) on the US East Coast. This study focuses on a portion of this region, offshore of South Carolina and Georgia, with a primary goal of identifying beach renourishment sands and wind-tower placement locations, and creating a conceptual model of the evolution of the shelf in these areas. New and previously collected data are being used to identify sediment distribution patterns, paleolandscapes, sand resources for beach renourishment projects, and feasible locations for offshore wind installations. New chirp subbottom profiler data ( 1000 km), sidescan sonar data ( 7900km2), magnetometer data ( 1700 km), and multibeam bathymetry data ( 430km2) have been processed and interpreted at the University of Charleston using SonarWiz7, QPS-Qimera and QPS-Fledermaus software suites. Areas of focus for the Atlantic Sand Assessment Program (ASAP) data collection along the SC and GA coast are located within the 3 to 8 nautical mile (nm) OCS offshore of (North to South) Little River, Cape Romain, Folly Beach, Hilton Head, Wassaw, Ossabaw, Jekyll, St. Simons, and Cumberland islands. Ravinement, pre-Holocene, and other seismic surfaces, along with internal geometries, were mapped in these distinctly different tidal and wave regimes. Holocene sediment thickness gradually increases to the south with several sediment wedges in excess of 40 meters thickness. Where mapped, subsurface paleochannels/valleys were identified and analyzed for their orientation and complexity, as well as their size and distribution. These paleochannels are more numerous and increasingly complex in the southern survey areas. The channels are possibly related to transgressive channeling, Pleistocene low-stand river channeling, and braided stream formation during glacial maxima and portions of the marine transgression. Further research will be conducted once the surveys are compiled and merged with previous data sets to build a more complete understanding of the paleolandscapes, shelf development, and sand resources in the South Carolina and Georgia OCS.

Coastal bathymetry data collected in 2013 from the Chandeleur Islands, Louisiana

USGS Publications Warehouse

DeWitt, Nancy T.; Miselis, Jennifer L.; Fredericks, Jake J.; Bernier, Julie C.; Reynolds, Billy J.; Kelso, Kyle W.; Thompson, David M.; Flocks, James G.; Wiese, Dana S.

2017-01-12

As part of the Barrier Island Evolution Research Project, scientists from the U.S. Geological Survey (USGS) St. Petersburg Coastal and Marine Science Center conducted nearshore geophysical surveys around the northern Chandeleur Islands, Louisiana, in July and August of 2013. The objective of the study is to better understand barrier-island geomorphic evolution, particularly storm-related depositional and erosional processes that shape the islands over annual to interannual timescales (1‒5 years). Collecting geophysical data will allow us to identify relationships between the geologic history of the island and its present day morphology and sediment distribution. This mapping effort was the third in a series of three planned surveys in this area. High resolution geophysical data collected in each of three consecutive years along this rapidly changing barrier island system will provide a unique time-series dataset that will significantly further the analyses and geomorphological interpretations of this and other coastal systems, improving our understanding of coastal response and evolution over short time scales (1‒5 years).This data series includes the geophysical data that were collected during two cruises (USGS Field Activity Numbers (FAN) 13BIM02, 13BIM03, and 13BIM04, in July 2013; and FANs 13BIM07 and 13BIM08 in August 2013) aboard the R/V Sallenger, the R/V Jabba Jaw, and the R/V Shark along the northern portion of the Chandeleur Islands, Breton National Wildlife Refuge, Louisiana. Primary data were acquired with the following equipment: (1) a Systems Engineering and Assessment, Ltd., SWATHplus interferometric sonar (468 kilohertz [kHz]), (2) an EdgeTech 424 (4‒24 kHz) chirp sub-bottom profiling system, and (3) two Odom Hydrographic Systems, Incorporated, Echotrach CV100 single beam echosounders.This data series report serves as an archive of processed interferometric swath and single-beam bathymetry data. Geographic information system data products include an interpolated digital elevation model, trackline maps, and point data files. Additional files include error analysis maps, Field Activity Collection System logs, and formal Federal Geographic Data Committee metadata.

Late-Quaternary glacial to postglacial sedimentation in three adjacent fjord-lakes of the Québec North Shore (eastern Canadian Shield)

NASA Astrophysics Data System (ADS)

Poiré, Antoine G.; Lajeunesse, Patrick; Normandeau, Alexandre; Francus, Pierre; St-Onge, Guillaume; Nzekwe, Obinna P.

2018-04-01

High-resolution swath bathymetry imagery allowed mapping in great detail the sublacustrine geomorphology of lakes Pentecôte, Walker and Pasteur, three deep adjacent fjord-lakes of the Québec North Shore (eastern Canada). These sedimentary basins have been glacio-isostatically uplifted to form deep steep-sided elongated lakes. Their key geographical position and limnogeological characteristics typical of fjords suggest exceptional potential for long-term high-resolution paleoenvironmental reconstitutions. Acoustic subbottom profiles acquired using a bi-frequency Chirp echosounder (3.5 & 12 kHz), together with cm- and m-long sediment core data, reveal the presence of four acoustic stratigraphic units. The acoustic basement (Unit 1) represents the structural bedrock and/or the ice-contact sediments of the Laurentide Ice Sheet and reveals V-shaped bedrock valleys at the bottom of the lakes occupied by ice-loaded sediments in a basin-fill geometry (Unit 2). Moraines observed at the bottom of lakes and in their structural valleys indicate a deglaciation punctuated by short-term ice margin stabilizations. Following ice retreat and their isolation, the fjord-lakes were filled by a thick draping sequence of rhythmically laminated silts and clays (Unit 3) deposited during glaciomarine and/or glaciolacustrine settings. These sediments were episodically disturbed by mass-movements during deglaciation due to glacial-isostatic rebound. AMS 14C dating reveal that the transition between deglaciation of the lakes Pentecôte and Walker watersheds and the development of para- and post-glacial conditions occurred around 8000 cal BP. The development of the lake-head river delta plain during the Holocene provided a constant source of fluvial sediment supply to the lakes and the formation of turbidity current bedforms on the sublacustrine delta slopes. The upper sediment succession (i.e., ∼4-∼6.5 m) consists of a continuous para-to post-glacial sediment drape (Unit 4) that contains laminated and massive sediment and series of Rapidly Deposited Layers. These results allow establishing a conceptual model of how a glaciated coastal fjord evolves during and after deglaciation in a context of rapid glacio-isostatically induced forced regression.

The University of Texas Institute for Geophysics Marine Geology and Geophysics Field Course

NASA Astrophysics Data System (ADS)

Duncan, D.; Davis, M. B.; Goff, J. A.; Gulick, S. P. S.; McIntosh, K. D.; Saustrup, S., Sr.

2014-12-01

The University of Texas Institute for Geophysics, part of the Jackson School of Geosciences, annually offers a three-week marine geology and geophysics field course during the spring-summer intersession. The course provides hands-on instruction and training for graduate and upper-level undergraduate students in high-resolution seismic reflection, CHIRP sub-bottom profiling, multibeam bathymetry, sidescan sonar, several types of sediment coring, grab sampling, and the sedimentology of resulting seabed samples. Students participate in an initial three days of classroom instruction designed to communicate geological context of the field area along with theoretical and technical background on each field method. The class then travels to the Gulf Coast for a week of at-sea field work. Our field sites at Port Aransas, and Galveston, TX, and Grand Isle, LA, provide ideal locations for students to investigate coastal processes of the Gulf Coast and continental shelf through application of geophysical techniques in an exploratory mode. At sea, students assist with survey design and instrumentation set up while learning about acquisition parameters, data quality control, trouble-shooting, and safe instrument deployment and retrieval. In teams of four, students work in onshore field labs preparing sediment samples for particle size analysis and data processing. During the course's final week, teams return to the classroom where they integrate, interpret, and visualize data in a final project using industry-standard software such as Echos, Landmark, Caris, and Fledermaus. The course concludes with a series of final presentations and discussions in which students examine geologic history and/or sedimentary processes represented by the Gulf Coast continental shelf with academic and industry supporters. Students report a greater understanding of marine geology and geophysics through the course's intensive, hands-on, team approach and low instructor to student ratio (sixteen students, three faculty, and three teaching assistants). This course (to our knowledge) remains the only one of its kind, satisfies field experience requirements for some degree programs, and provides an alternative to land-based field courses. www.ig.utexas.edu/research/mgg/courses/geof348K/

A Hands-on Approach to Teaching Geophysics through the University of Texas Institute for Geophysics Marine Geology and Geophysics Field Course in the Gulf of Mexico.

NASA Astrophysics Data System (ADS)

Duncan, D.; Davis, M. B.; Goff, J.; Gulick, S. P. S.; Fernandez-Vasquez, R. A.; Saustrup, S.

2017-12-01

The three week field course is offered to graduate and upper-level undergraduate students as hands-on instruction and training for marine geology and geophysics applications. Instructors provide theoretical and technical background of high-resolution seismic reflection, CHIRP sub-bottom profiling, multibeam bathymetry, sidescan sonar, sediment coring, grab sampling, and the sedimentology of resulting seabed samples in the initial phase of the course. The class then travels to the Gulf Coast for a week of at-sea field work. Over the last 10 years, field sites at Freeport, Port Aransas, and Galveston, TX, and Grand Isle, LA, have provided ideal locations for students to explore and investigate coastal and continental shelf processes through the application of geophysical techniques. Students with various backgrounds work in teams of four and rotate between two marine vessels: the R/V Scott Petty, a 26' vessel owned and operated by UTIG, and the R/V Manta, an 82' vessel owned and operated by NOAA. They assist with survey design, instrumentation setup and breakdown, data acquisition, trouble-shooting, data quality control, and safe instrumentation deployment and recovery. Teams also process data and sediment samples in an onshore field lab. During the final week, students visualize, integrate and interpret data for a final project using industry software. The course concludes with final presentations and discussions wherein students examine Gulf Coast geological history and sedimentary processes with academic and industry supporters. Students report a greater understanding of marine geology and geophysics through the course's intensive, hands-on, team approach and low instructor to student ratio (sixteen students, three faculty, and three teaching assistants). Post-class, students may incorporate course data in senior honors or graduate thesis and are encouraged to publish and present results at national meetings. This course satisfies field experience requirements for some degree programs, provides an alternative to land-based field courses and to our knowledge, remains the only class of its kind. Alumni note the course's applicability to energy, environmental, and geotechnical industries as well as coastal restoration/management fields.

A multi-factor approach for process-based seabed characterization: example from the northeastern continental margin of the Korean peninsula (East Sea)

NASA Astrophysics Data System (ADS)

Cukur, Deniz; Um, In-Kwon; Chun, Jong-Hwa; Kim, So-Ra; Lee, Gwang-Soo; Kim, Yuri; Kong, Gee-Soo; Horozal, Senay; Kim, Seong-Pil

2018-04-01

This study investigates sediment transport and depositional processes from a newly collected dataset comprising sub-bottom chirp profiles, multibeam bathymetry, and sediment cores from the northeastern continental margin of Korea in the East Sea (Japan Sea). Twelve echo-types and eleven sedimentary facies have been defined and interpreted as deposits formed by shallow-marine, hemipelagic sedimentation, bottom current, and mass-movement processes. Hemipelagic sedimentation, which is acoustically characterized by undisturbed layered sediments, appears to have been the primary sedimentary process throughout the study area. The inner and outer continental shelf (<150 m water depth) have been influenced by shallow-marine sedimentary processes. Two slope-parallel canyons, 0.2-2 km wide and up to 30 km long, appear to have acted as possible conduits for turbidity currents from the shallower shelf into the deep basins. Bottom current deposits, expressed as erosional moats immediately below topographic highs, are prevalent on the southern lower slope at water depths of 400-450 m. Mass-movements (i.e., slides/slumps, debris flow deposits) consisting of chaotic facies characterize the lower slope and represent one of the most important sedimentary processes in the study area. Piston cores confirm the presence of mass-transport deposits (MTDs) that are characterized by mud clasts of variable size, shape, and color. Multibeam bathymetry shows that large-scale MTDs are chiefly initiated on the lower slope (400-600 m) with gradients up to 3° and where they produce scarps on the order of 100 m in height. Sandy MTDs also occur on the upper continental slope adjacent to the seaward edge of the shelf terrace. Earthquakes associated with tectonic activity and the development of fluid overpressure is considered as the main conditioning factor for destabilizing the slope sediments. Overall, the sedimentary processes show typical characteristics of a fine-grained clastic slope apron and change down-slope and differ within each physiographic province. Furthermore, the influence of geological inheritance (i.e., structural folds and faults) on geomorphology and sediment facies development is an important additional factor on the lower slopes. Together, these factors provide a rational basis for continental margin seabed characterization.

The relative importance of different direct benefits in the mate choices of a field cricket.

PubMed

Wagner, William E; Basolo, Alexandra L

2007-03-01

Discussions about the evolution of female mating preferences have often suggested that females should express multiple strong preferences when different male traits are correlated with different mating benefits, yet few studies have directly tested this hypothesis by comparing the strength of female preferences for male traits known to be correlated with different benefits. In the variable field cricket, Gryllus lineaticeps, females receive fecundity and fertility benefits from mating with males with higher chirp rates and life-span benefits from mating with males with longer chirp durations. Although females prefer higher chirp rates and longer chirp durations when the other trait is held constant, it is possible that they give priority to one of these song traits when both vary. In this study, we examined the relative importance of chirp rate and chirp duration in female mate choice using single-stimulus presentations of songs that varied in both chirp rate and chirp duration. Females expressed both directional and stabilizing preferences based on chirp rate, responding most strongly to a chirp rate approximately one standard deviation above the population mean. Females did not express preferences based on chirp duration, and did not express correlational preferences. These results suggest that females may give priority to the reproductive benefits provided by males that produce higher chirp rates.

Archive of digital boomer subbottom data collected during USGS cruise 05FGS01 offshore east-central Florida, July 17-29, 2005

USGS Publications Warehouse

Forde, Arnell S.; Dadisman, Shawn V.; Wiese, Dana S.; Phelps, Daniel C.

2012-01-01

In July of 2005, the U.S. Geological Survey (USGS), in cooperation with the Florida Geological Survey (FGS), conducted a geophysical survey of the Atlantic Ocean offshore of Florida's east coast from Flagler Beach to Daytona Beach. This report serves as an archive of unprocessed digital boomer subbottom data, trackline maps, navigation files, Geographic Information System (GIS) files, Field Activity Collection System (FACS) logs and formal Federal Geographic Data Committee (FGDC) metadata. Filtered and gained (showing a relative increase in signal amplitude) digital images of the seismic profiles are also provided. Refer to the Acronyms page for expansions of acronyms and abbreviations used in this report. The USGS Saint Petersburg Coastal and Marine Science Center (SPCMSC) assigns a unique identifier to each cruise or field activity. For example, 05FGS01 tells us the data were collected in 2005 for cooperative work with the FGS and the data were collected during the first field activity for that project in that calendar year. Refer to http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html for a detailed description of the method used to assign the field activity ID. The boomer subbottom processing system consists of an acoustic energy source that is made up of capacitors charged to a high voltage and discharged through a transducer in the water. The transducer is towed on a sled floating on the water surface and when discharged emits a short acoustic pulse, or shot, which propagates through the water column and shallow stratrigraphy below. The acoustic energy is reflected at density boundaries (such as the seafloor or sediment layers beneath the seafloor), detected by the receiver (a hydrophone streamer), and recorded by a PC-based seismic acquisition system. This process is repeated at timed intervals (for example, 0.5 s) and recorded for specific intervals of time (for example, 100 ms). In this way, a two-dimensional (2-D) vertical image of the shallow geologic structure beneath the ship track is produced. Figure 1 displays the acquisition geometry. Refer to table 1 for a summary of acquisition parameters and table 2 for trackline statistics. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG Y format (Barry and others, 1975), except an ASCII format is used for the first 3,200 bytes of the card image header instead of the standard EBCDIC format. For a detailed description about the recorded trace headers, refer to the SEG Y Format page. The SEG Y files may be downloaded and processed with commercial or public domain software such as Seismic Unix (Cohen and Stockwell, 2005). See the How To Download SEG Y Data page for download instructions. The printable profiles provided here are GIF images that were processed and gained using SU software; refer to the Software page for links to example SU processing scripts. The processed SEG Y data were also exported to Chesapeake Technology, Inc. (CTI) SonarWeb software to produce a geospatially interactive version of the profile that allows the user to obtain a geographic location and depth from the profile for a given cursor position; this information is displayed in the status bar of the browser. Please note that clicking on the profile image switches it to "Expanded View" (a compressed image of the entire line) and cursor tracking is not available in this mode.

Multiplexed chirp waveform synthesizer

DOEpatents

Dudley, Peter A.; Tise, Bert L.

2003-09-02

A synthesizer for generating a desired chirp signal has M parallel channels, where M is an integer greater than 1, each channel including a chirp waveform synthesizer generating at an output a portion of a digital representation of the desired chirp signal; and a multiplexer for multiplexing the M outputs to create a digital representation of the desired chirp signal. Preferably, each channel receives input information that is a function of information representing the desired chirp signal.

Wavelength-spacing-tunable multichannel filter incorporating a sampled chirped fiber Bragg grating based on a symmetrical chirp-tuning technique without center wavelength shift

NASA Astrophysics Data System (ADS)

Han, Young-Geun; Dong, Xinyong; Lee, Ju Han; Lee, Sang Bae

2006-12-01

We propose and experimentally demonstrate a simple and flexible scheme for a wavelength-spacing-tunable multichannel filter exploiting a sampled chirped fiber Bragg grating based on a symmetrical modification of the chirp ratio. Symmetrical bending along a sampled chirped fiber Bragg grating attached to a flexible cantilever beam induces a variation of the chirp ratio and a reflection chirp bandwidth of the grating without a center wavelength shift. Accordingly, the wavelength spacing of a sampled chirped fiber Bragg grating is continuously controlled by the reflection chirp bandwidth variation of the grating corresponding to the bending direction, which allows for realization of an effective wavelength-spacing-tunable multichannel filter. Based on the proposed technique, we achieve the continuous tunability of the wavelength spacing in a range from 1.51 to 6.11 nm, depending on the bending direction of the cantilever beam.

Marine mammal audibility of selected shallow-water survey sources.

PubMed

MacGillivray, Alexander O; Racca, Roberto; Li, Zizheng

2014-01-01

Most attention about the acoustic effects of marine survey sound sources on marine mammals has focused on airgun arrays, with other common sources receiving less scrutiny. Sound levels above hearing threshold (sensation levels) were modeled for six marine mammal species and seven different survey sources in shallow water. The model indicated that odontocetes were most likely to hear sounds from mid-frequency sources (fishery, communication, and hydrographic systems), mysticetes from low-frequency sources (sub-bottom profiler and airguns), and pinnipeds from both mid- and low-frequency sources. High-frequency sources (side-scan and multibeam) generated the lowest estimated sensation levels for all marine mammal species groups.

Responses of neurons in cat primary auditory cortex to bird chirps: effects of temporal and spectral context.

PubMed

Bar-Yosef, Omer; Rotman, Yaron; Nelken, Israel

2002-10-01

The responses of neurons to natural sounds and simplified natural sounds were recorded in the primary auditory cortex (AI) of halothane-anesthetized cats. Bird chirps were used as the base natural stimuli. They were first presented within the original acoustic context (at least 250 msec of sounds before and after each chirp). The first simplification step consisted of extracting a short segment containing just the chirp from the longer segment. For the second step, the chirp was cleaned of its accompanying background noise. Finally, each chirp was replaced by an artificial version that had approximately the same frequency trajectory but with constant amplitude. Neurons had a wide range of different response patterns to these stimuli, and many neurons had late response components in addition, or instead of, their onset responses. In general, every simplification step had a substantial influence on the responses. Neither the extracted chirp nor the clean chirp evoked a similar response to the chirp presented within its acoustic context. The extracted chirp evoked different responses than its clean version. The artificial chirps evoked stronger responses with a shorter latency than the corresponding clean chirp because of envelope differences. These results illustrate the sensitivity of neurons in AI to small perturbations of their acoustic input. In particular, they pose a challenge to models based on linear summation of energy within a spectrotemporal receptive field.

Ionization waves of arbitrary velocity driven by a flying focus

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

Palastro, J. P.; Turnbull, D.; Bahk, S. -W.

A chirped laser pulse focused by a chromatic lens exhibits a dynamic, or flying, focus in which the trajectory of the peak intensity decouples from the group velocity. In a medium, the flying focus can trigger an ionization front that follows this trajectory. By adjusting the chirp, the ionization front can be made to travel at an arbitrary velocity along the optical axis. For this study, we present analytical calculations and simulations describing the propagation of the flying focus pulse, the self-similar form of its intensity profile, and ionization wave formation. The ability to control the speed of the ionizationmore » wave and, in conjunction, mitigate plasma refraction has the potential to advance several laser-based applications, including Raman amplification, photon acceleration, high-order-harmonic generation, and THz generation.« less

Ionization waves of arbitrary velocity driven by a flying focus

DOE PAGES

Palastro, J. P.; Turnbull, D.; Bahk, S. -W.; ...

2018-03-01

A chirped laser pulse focused by a chromatic lens exhibits a dynamic, or flying, focus in which the trajectory of the peak intensity decouples from the group velocity. In a medium, the flying focus can trigger an ionization front that follows this trajectory. By adjusting the chirp, the ionization front can be made to travel at an arbitrary velocity along the optical axis. For this study, we present analytical calculations and simulations describing the propagation of the flying focus pulse, the self-similar form of its intensity profile, and ionization wave formation. The ability to control the speed of the ionizationmore » wave and, in conjunction, mitigate plasma refraction has the potential to advance several laser-based applications, including Raman amplification, photon acceleration, high-order-harmonic generation, and THz generation.« less

Dual view FIDA measurements on MAST

NASA Astrophysics Data System (ADS)

Michael, C. A.; Conway, N.; Crowley, B.; Jones, O.; Heidbrink, W. W.; Pinches, S.; Braeken, E.; Akers, R.; Challis, C.; Turnyanskiy, M.; Patel, A.; Muir, D.; Gaffka, R.; Bailey, S.

2013-09-01

A fast-ion deuterium alpha (FIDA) spectrometer was installed on MAST to measure radially resolved information about the fast-ion density and its distribution in energy and pitch angle. Toroidally and vertically directed collection lenses are employed, to detect both passing and trapped particle dynamics, and reference views are installed to subtract the background. This background is found to contain a substantial amount of passive FIDA emission driven by edge neutrals, and to depend delicately on viewing geometry. Results are compared with theoretical expectations based on the codes NUBEAM (for fast-ion distributions) and FIDASIM. Calibrating via the measured beam emission peaks, the toroidal FIDA signal profile agrees with classical simulations in magnetohydrodynamic quiescent discharges where the neutron rate is also classical. Long-lived modes (LLMs) and chirping modes decrease the core FIDA signal significantly, and the profile can be matched closely to simulations using anomalous diffusive transport; a spatially uniform diffusion coefficient is sufficient for chirping modes, while a core localized diffusion is better for a LLM. Analysis of a discharge with chirping mode activity shows a dramatic drop in the core FIDA signal and rapid increase in the edge passive signal at the onset of the burst indicating a very rapid redistribution towards the edge. Vertical-viewing measurements show a discrepancy with simulations at higher Doppler shifts when the neutron rate is classical, which, combined with the fact that the toroidal signals agree, means that the difference must be occurring for pitch angles near the trapped-passing boundary, although uncertainties in the background subtraction, which are difficult to assess, may contribute to this. Further evidence of an anomalous transport mechanism for these particles is provided by the fact that an increase of beam power does not increase the higher energy vertical FIDA signals, while the toroidal signals do increase.

Shallow Investigations of the Deep Seafloor: Quantitative Morphology in the Levant Basin, Eastern Mediterranean

NASA Astrophysics Data System (ADS)

Kanari, M.; Ketter, T.; Tibor, G.; Schattner, U.

2017-12-01

We aim to characterize the seafloor morphology and its shallow sub-surface structures and deformations in the deep part of the Levant basin (eastern Mediterranean) using recently acquired high-resolution shallow seismic reflection data and multibeam bathymetry, which allow quantitative analysis of morphology and structure. The Levant basin at the eastern Mediterranean is considered a passive continental margin, where most of the recent geological processes were related in literature to salt tectonics rooted at the Messinian deposits from 6Ma. We analyzed two sets of recently acquired high-resolution data from multibeam bathymetry and 3.5 kHz Chirp sub-bottom seismic reflection in the deep basin of the continental shelf offshore Israel (water depths up to 2100 m). Semi-automatic mapping of seafloor features and seismic data interpretation resulted in quantitative morphological analysis of the seafloor and its underlying sediment with penetration depth up to 60 m. The quantitative analysis and its interpretation are still in progress. Preliminary results reveal distinct morphologies of four major elements: channels, faults, folds and sediment waves, validated by seismic data. From the spatial distribution and orientation analyses of these phenomena, we identify two primary process types which dominate the formation of the seafloor in the Levant basin: structural and sedimentary. Characterization of the geological and geomorphological processes forming the seafloor helps to better understand the transport mechanisms and the relations between sediment transport and deposition in deep water and the shallower parts of the shelf and slope.

Impact of initial pulse shape on the nonlinear spectral compression in optical fibre

NASA Astrophysics Data System (ADS)

Boscolo, Sonia; Chaussard, Frederic; Andresen, Esben; Rigneault, Hervé; Finot, Christophe

2018-02-01

We theoretically study the effects of the temporal intensity profile of the initial pulse on the nonlinear propagation spectral compression process arising from nonlinear propagation in an optical fibre. Various linearly chirped input pulse profiles are considered, and their dynamics is explained with the aid of time-frequency representations. While initially parabolic-shaped pulses show enhanced spectral compression compared to Gaussian pulses, no significant spectral narrowing occurs when initially super-Gaussian pulses are used. Triangular pulses lead to a spectral interference phenomenon similar to the Fresnel bi-prism experiment.

Comparison between ABR with click and narrow band chirp stimuli in children.

PubMed

Zirn, Stefan; Louza, Julia; Reiman, Viktor; Wittlinger, Natalie; Hempel, John-Martin; Schuster, Maria

2014-08-01

Click and chirp-evoked auditory brainstem responses (ABR) are applied for the estimation of hearing thresholds in children. The present study analyzes ABR thresholds across a large sample of children's ears obtained with both methods. The aim was to demonstrate the correlation between both methods using narrow band chirp and click stimuli. Click and chirp evoked ABRs were measured in 253 children aged from 0 to 18 years to determine their individual auditory threshold. The delay-compensated stimuli were narrow band CE chirps with either 2000 Hz or 4000 Hz center frequencies. Measurements were performed consecutively during natural sleep, and under sedation or general anesthesia. Threshold estimation was performed for each measurement by two experienced audiologists. Pearson-correlation analysis revealed highly significant correlations (r=0.94) between click and chirp derived thresholds for both 2 kHz and 4 kHz chirps. No considerable differences were observed either between different age ranges or gender. Comparing the thresholds estimated using ABR with click stimuli and chirp stimuli, only 0.8-2% for the 2000 Hz NB-chirp and 0.4-1.2% of the 4000 Hz NB-chirp measurements differed more than 15 dB for different degrees of hearing loss or normal hearing. The results suggest that either NB-chirp or click ABR is sufficient for threshold estimation. This holds for the chirp frequencies of 2000 Hz and 4000 Hz. The use of either click- or chirp-evoked ABR allows a reduction of recording time in young infants. Nevertheless, to cross-check the results of one of the methods, we recommend measurements with the other method as well. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Detection of thermal gradients through fiber-optic Chirped Fiber Bragg Grating (CFBG): Medical thermal ablation scenario

NASA Astrophysics Data System (ADS)

Korganbayev, Sanzhar; Orazayev, Yerzhan; Sovetov, Sultan; Bazyl, Ali; Schena, Emiliano; Massaroni, Carlo; Gassino, Riccardo; Vallan, Alberto; Perrone, Guido; Saccomandi, Paola; Arturo Caponero, Michele; Palumbo, Giovanna; Campopiano, Stefania; Iadicicco, Agostino; Tosi, Daniele

2018-03-01

In this paper, we describe a novel method for spatially distributed temperature measurement with Chirped Fiber Bragg Grating (CFBG) fiber-optic sensors. The proposed method determines the thermal profile in the CFBG region from demodulation of the CFBG optical spectrum. The method is based on an iterative optimization that aims at minimizing the mismatch between the measured CFBG spectrum and a CFBG model based on coupled-mode theory (CMT), perturbed by a temperature gradient. In the demodulation part, we simulate different temperature distribution patterns with Monte-Carlo approach on simulated CFBG spectra. Afterwards, we obtain cost function that minimizes difference between measured and simulated spectra, and results in final temperature profile. Experiments and simulations have been carried out first with a linear gradient, demonstrating a correct operation (error 2.9 °C); then, a setup has been arranged to measure the temperature pattern on a 5-cm long section exposed to medical laser thermal ablation. Overall, the proposed method can operate as a real-time detection technique for thermal gradients over 1.5-5 cm regions, and turns as a key asset for the estimation of thermal gradients at the micro-scale in biomedical applications.

Dynamic propagation of symmetric Airy pulses with initial chirps in an optical fiber

NASA Astrophysics Data System (ADS)

Shi, Xiaohui; Huang, Xianwei; Deng, Yangbao; Tan, Chao; Bai, Yanfeng; Fu, Xiquan

2017-09-01

We analytically and numerically investigate the propagation dynamics of initially chirped symmetric Airy pulses in an optical fiber. The results show that the positive chirps act to promote the interference in generating a focal point on the propagation axis, while the negative chirps tend to suppress the focusing effect, as compared to conventional unchirped symmetric Airy pulses. The numerical results demonstrate that the linear propagation of chirped symmetric Airy pulses depend considerably on the chirp parameter and the primary lobe position. In the anomalous dispersion region, positively chirped symmetric Airy pulses first undergo an initial compression, and reach a foci due to the opposite acceleration, and then experience a lossy inversion transformation, and come to the opposite facing focal position. The impact of truncation coefficient and Kerr nonlinearity on the chirped symmetric Airy pulses propagation is also disclosed separately.

pathChirp: Efficient Available Bandwidth Estimation for Network Paths

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

Cottrell, Les

2003-04-30

This paper presents pathChirp, a new active probing tool for estimating the available bandwidth on a communication network path. Based on the concept of ''self-induced congestion,'' pathChirp features an exponential flight pattern of probes we call a chirp. Packet chips offer several significant advantages over current probing schemes based on packet pairs or packet trains. By rapidly increasing the probing rate within each chirp, pathChirp obtains a rich set of information from which to dynamically estimate the available bandwidth. Since it uses only packet interarrival times for estimation, pathChirp does not require synchronous nor highly stable clocks at the sendermore » and receiver. We test pathChirp with simulations and Internet experiments and find that it provides good estimates of the available bandwidth while using only a fraction of the number of probe bytes that current state-of-the-art techniques use.« less

Nutritional effects on male calling behaviour in the variable field cricket.

PubMed

Wagner; Hoback

1999-01-01

In the variable field cricket, Gryllus lineaticeps, females prefer higher chirp rates and longer chirp durations in male calling song. Higher chirp rates are energetically more expensive to produce, but the energetic cost of calling does not vary with chirp duration. We tested the hypothesis that nutrition affects male chirp rate and chirp duration. Full-sibling brothers of similar age were placed on high- and low-nutrition feeding regimes. There was no effect of feeding regime on male weight; neither group showed a significant change in weight, and the two groups did not differ from each other in weight change. However, males on the high-nutrition feeding regime both called more frequently and called at higher chirp rates when they did call. The two groups did not differ in chirp duration, the duration of pulses within chirps or chirp dominant frequency. These results suggest that females select mates based on one nutrition-dependent call character (chirp rate) and one nutrition-independent call character (chirp duration). In addition, because males in the two groups did not show significant differences in weight change, and because males on the high-nutrition feeding regime engaged in energetically more expensive calling, these results suggest that males invest any excess energy above their basic maintenance requirements in the production of call types that increase their attractiveness to females. The absence of a relationship between body condition and calling song structure for males in the field may be a consequence of this pattern of energy allocation. Copyright 1999 The Association for the Study of Animal Behaviour.

A direct approach for the design of chirp stimuli used for the recording of auditory brainstem responses

PubMed Central

Elberling, Claus; Don, Manuel

2010-01-01

A recent study evaluates auditory brainstem responses (ABRs) evoked by chirps of different durations (sweeping rates) [Elberling et al. (2010). J. Acoust. Soc. Am. 128, 215–223]. The study demonstrates that shorter chirps are most efficient at higher levels of stimulation whereas longer chirps are most efficient at lower levels. Mechanisms other than the traveling wave delay, in particular, upward spread of excitation and changes in cochlear-neural delay with level, are suggested to be responsible for these findings. As a consequence, delay models based on estimates of the traveling wave delay are insufficient for the design of chirp stimuli, and another delay model based on a direct approach is therefore proposed. The direct approach uses ABR-latencies from normal-hearing subjects in response to octave-band chirps over a wide range of levels. The octave-band chirps are constructed by decomposing a broad-band chirp, and constitute a subset of the chirp. The delay compensations of the proposed model are similar to those found in the previous experimental study, which thus verifies the results of the proposed model. PMID:21110591

Hybrid simulations of Alfvén modes driven by energetic particles

NASA Astrophysics Data System (ADS)

Zhu, J.; Ma, Z. W.; Wang, S.

2016-12-01

A hybrid kinetic-magnetohydrodynamic code (CLT-K) is developed to study nonlinear dynamics of Alfvén modes driven by energetic particles (EP). A n = 2 toroidicity-induced discrete shear Alfvén eigenmode (TAE)-type energetic particle mode (EPM) with two dominant poloidal harmonics (m = 2 and 3) is first excited and its frequency remains unchanged in the early phase. Later, a new branch of the n = 2 frequency with a single dominant poloidal mode (m = 3) splits from the original TAE-type EPM. The new single m EPM (m = 3) slowly moves radially outward with the downward chirping of the frequency and the mode amplitude remains at a higher level. The original EPM remains at its original position without the frequency chirping, but its amplitude decays with time. Finally, the m = 3 EPM becomes dominant and the frequency falls into the β-induced gap of the Alfvén continuum. The redistribution of the δf in the phase space is consistent with the mode frequency downward chirping and the drifting direction of the resonance region is mainly due to the biased free energy profile. The transition from a TAE-type EPM to a single m EPM is mainly caused by extension of the p = 0 trapped particle resonance in the phase space.

Measurement and control of the frequency chirp rate of high-order harmonic pulses

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

Mauritsson, J.; Johnsson, P.; Lopez-Martens, R.

2004-08-01

We measure the chirp rate of harmonics 13 to 23 in argon by cross correlation with a 12 femtosecond probe pulse. Under low ionization conditions, we directly measure the negative chirp due to the atomic dipole phase, and show that an additional chirp on the pump pulse is transferred to the qth harmonic as q times the fundamental chirp. Our results are in accord with simulations using the experimentally measured 815 nm pump and probe pulses. The ability to measure and manipulate the harmonic chirp rate is essential for the characterization and optimization of attosecond pulse trains.

Callback response of dugongs to conspecific chirp playbacks.

PubMed

Ichikawa, Kotaro; Akamatsu, Tomonari; Shinke, Tomio; Adulyanukosol, Kanjana; Arai, Nobuaki

2011-06-01

Dugongs (Dugong dugon) produce bird-like calls such as chirps and trills. The vocal responses of dugongs to playbacks of several acoustic stimuli were investigated. Animals were exposed to four different playback stimuli: a recorded chirp from a wild dugong, a synthesized down-sweep sound, a synthesized constant-frequency sound, and silence. Wild dugongs vocalized more frequently after playback of broadcast chirps than that after constant-frequency sounds or silence. The down-sweep sound also elicited more vocal responses than did silence. No significant difference was found between the broadcast chirps and the down-sweep sound. The ratio of wild dugong chirps to all calls and the dominant frequencies of the wild dugong calls were significantly higher during playbacks of broadcast chirps, down-sweep sounds, and constant-frequency sounds than during those of silence. The source level and duration of dugong chirps increased significantly as signaling distance increased. No significant correlation was found between signaling distance and the source level of trills. These results show that dugongs vocalize to playbacks of frequency-modulated signals and suggest that the source level of dugong chirps may be manipulated to compensate for transmission loss between the source and receiver. This study provides the first behavioral observations revealing the function of dugong chirps. © 2011 Acoustical Society of America

Low sidelobe level and high time resolution for metallic ultrasonic testing with linear-chirp-Golay coded excitation

NASA Astrophysics Data System (ADS)

Zhang, Jiaying; Gang, Tie; Ye, Chaofeng; Cong, Sen

2018-04-01

Linear-chirp-Golay (LCG)-coded excitation combined with pulse compression is proposed in this paper to improve the time resolution and suppress sidelobe in ultrasonic testing. The LCG-coded excitation is binary complementary pair Golay signal with linear-chirp signal applied on every sub pulse. Compared with conventional excitation which is a common ultrasonic testing method using a brief narrow pulse as exciting signal, the performances of LCG-coded excitation, in terms of time resolution improvement and sidelobe suppression, are studied via numerical and experimental investigations. The numerical simulations are implemented using Matlab K-wave toolbox. It is seen from the simulation results that time resolution of LCG excitation is 35.5% higher and peak sidelobe level (PSL) is 57.6 dB lower than linear-chirp excitation with 2.4 MHz chirp bandwidth and 3 μs time duration. In the B-scan experiment, time resolution of LCG excitation is higher and PSL is lower than conventional brief pulse excitation and chirp excitation. In terms of time resolution, LCG-coded signal has better performance than chirp signal. Moreover, the impact of chirp bandwidth on LCG-coded signal is less than that on chirp signal. In addition, the sidelobe of LCG-coded signal is lower than that of chirp signal with pulse compression.

Role of third-order dispersion in chirped Airy pulse propagation in single-mode fibers

NASA Astrophysics Data System (ADS)

Cai, Wangyang; Wang, Lei; Wen, Shuangchun

2018-04-01

The dynamic propagation of the initial chirped Airy pulse in single-mode fibers is studied numerically, special attention being paid to the role of the third-order dispersion (TOD). It is shown that for the positive TOD, the Airy pulse experiences inversion irrespective of the sign of initial chirp. The role of TOD in the dynamic propagation of the initial chirped Airy pulse depends on the combined sign of the group-velocity dispersion (GVD) and the initial chirp. If the GVD and chirp have the opposite signs, the chirped Airy pulse compresses first and passes through a breakdown area, then reconstructs a new Airy pattern with opposite acceleration, with the breakdown area becoming small and the main peak of the new Airy pattern becoming asymmetric with an oscillatory structure due to the positive TOD. If the GVD and chirp have the same signs, the finite-energy Airy pulse compresses to a focal point and then inverses its acceleration, in the case of positive TOD, the distance to the focal point becoming smaller. At zero-dispersion point, the finite-energy Airy pulse inverses to the opposite acceleration at a focal point, with the tight-focusing effect being reduced by initial chirp. Under the effect of negative TOD, the initial chirped Airy pulse disperses and the lobes split. In addition, in the anomalous dispersion region, for strong nonlinearity, the initial chirped Airy pulse splits and enters a soliton shedding regime.

Chirping and Sudden Excitation of Energetic-Particle-Driven Geodesic Acoustic Modes in a Large Helical Device Experiment

NASA Astrophysics Data System (ADS)

Wang, Hao; Todo, Yasushi; Ido, Takeshi; Suzuki, Yasuhiro

2018-04-01

Energetic-particle-driven geodesic acoustic modes (EGAMs) observed in a Large Helical Device experiment are investigated using a hybrid simulation code for energetic particles interacting with a magnetohydrodynamic (MHD) fluid. The frequency chirping of the primary mode and the sudden excitation of the half-frequency secondary mode are reproduced for the first time with the hybrid simulation using the realistic physical condition and the three-dimensional equilibrium. Both EGAMs have global spatial profiles which are consistent with the experimental measurements. For the secondary mode, the bulk pressure perturbation and the energetic particle pressure perturbation cancel each other out, and thus the frequency is lower than the primary mode. It is found that the excitation of the secondary mode does not depend on the nonlinear MHD coupling. The secondary mode is excited by energetic particles that satisfy the linear and nonlinear resonance conditions, respectively, for the primary and secondary modes.

Chirping and Sudden Excitation of Energetic-Particle-Driven Geodesic Acoustic Modes in a Large Helical Device Experiment.

PubMed

Wang, Hao; Todo, Yasushi; Ido, Takeshi; Suzuki, Yasuhiro

2018-04-27

Energetic-particle-driven geodesic acoustic modes (EGAMs) observed in a Large Helical Device experiment are investigated using a hybrid simulation code for energetic particles interacting with a magnetohydrodynamic (MHD) fluid. The frequency chirping of the primary mode and the sudden excitation of the half-frequency secondary mode are reproduced for the first time with the hybrid simulation using the realistic physical condition and the three-dimensional equilibrium. Both EGAMs have global spatial profiles which are consistent with the experimental measurements. For the secondary mode, the bulk pressure perturbation and the energetic particle pressure perturbation cancel each other out, and thus the frequency is lower than the primary mode. It is found that the excitation of the secondary mode does not depend on the nonlinear MHD coupling. The secondary mode is excited by energetic particles that satisfy the linear and nonlinear resonance conditions, respectively, for the primary and secondary modes.

Neonate Auditory Brainstem Responses to CE-Chirp and CE-Chirp Octave Band Stimuli II: Versus Adult Auditory Brainstem Responses.

PubMed

Cobb, Kensi M; Stuart, Andrew

The purpose of the study was to examine the differences in auditory brainstem response (ABR) latency and amplitude indices to the CE-Chirp stimuli in neonates versus young adults as a function of stimulus level, rate, polarity, frequency and gender. Participants were 168 healthy neonates and 20 normal-hearing young adults. ABRs were obtained to air- and bone-conducted CE-Chirps and air-conducted CE-Chirp octave band stimuli. The effects of stimulus level, rate, and polarity were examined with air-conducted CE-Chirps. The effect of stimulus level was also examined with bone-conducted CE-Chirps and CE-Chirp octave band stimuli. The effect of gender was examined across all stimulus manipulations. In general, ABR wave V amplitudes were significantly larger (p < 0.0001) and latencies were significantly shorter (p < 0.0001) for adults versus neonates for all air-conducted CE-Chirp stimuli with all stimulus manipulations. For bone-conducted CE-Chirps, infants had significantly shorter wave V latencies than adults at 15 dB nHL and 45 dB nHL (p = 0.02). Adult wave V amplitude was significantly larger for bone-conducted CE-Chirps only at 30 dB nHL (p = 0.02). The effect of gender was not statistically significant across all measures (p > 0.05). Significant differences in ABR latencies and amplitudes exist between newborns and young adults using CE-Chirp stimuli. These differences are consistent with differences to traditional click and tone burst stimuli and reflect maturational differences as a function of age. These findings continue to emphasize the importance of interpreting ABR results using age-based normative data.

Band limited chirp stimulation in vestibular evoked myogenic potentials.

PubMed

Walther, Leif Erik; Cebulla, Mario

2016-10-01

Air conducted vestibular evoked myogenic potentials (VEMP) can be elicited by various low frequency and intense sound stimuli, mainly clicks or short tone bursts (STB). Chirp stimuli are increasingly used in diagnostic audiological evaluations as an effective means to obtain acoustically evoked responses in narrowed or extended frequency ranges. We hypothesized in this study that band limited chirp stimulation, which covers the main sensitivity range of sound sensitive otolithic afferents (around 500 Hz), might be useful for application in cervical and ocular VEMP to air conduction. For this purpose we designed a chirp stimulus ranging 250-1000 Hz (up chirp). The chirp stimulus was delivered with a stimulus intensity of 100 dB nHL in normal subjects (n = 10) and patients with otolith involvement (vestibular neuritis) (n = 6). Amplitudes of the designed chirp ("CW-VEMP-chirp, 250-1000 Hz") were compared with amplitudes of VEMPs evoked by click stimuli (0.1 ms) and a short tone burst (STB, 1-2-1, 8 ms, 500 Hz). CVEMPs and oVEMPs were detectable in 9 of 10 normal individuals. Statistical evaluation in healthy patients revealed significantly larger cVEMP and oVEMP amplitudes for CW-VEMP-chirp (250-1000 Hz) stimuli. CVEMP amplitudes evoked by CW-VEMP-chirp (250-1000 Hz) showed a high stability in comparison with click and STB stimulation. CW-VEMP-chirp (250-1000 Hz) showed abnormal cVEMP and oVEMP amplitudes in patients with vestibular neuritis, with the same properties as click and STB stimulated VEMPs. We conclude that the designed CW-VEMP-chirp (250-1000 Hz) is an effective stimulus which can be further used in VEMP diagnostic. Since a chirp stimulus can be easily varied in its properties, in particular with regard to frequency, this might be a promising tool for further investigations.

Chirped femtosecond pulse scattering by spherical particles

NASA Astrophysics Data System (ADS)

Kim, Dal-Woo; Xiao, Gang-Yao; Lee, Tong-Nyong

1996-05-01

Generalized Lorentz-Mie formulas are used to study the scattering characteristics when a chirped femtosecond pulse illuminates a spherical particle. For a linear chirped Gaussian pulse with the envelope function g( tau ) = exp[- pi (1 + ib) tau 2], dimensionless parameter b is defined as a chirp. The calculation illustrated that even for pulses with a constant carrier wavelength ( lambda 0 = 0.5 mu m) and pulse-filling coefficient (l0 = 1.98), the efficiencies for extinction and scattering differ very much between the carrier wave and the different chirped pulses. The slowly varying background of the extinction and the scattering curves is damped by the chirp. When the pulse is deeply chirped, the maxima and minima of the background curves reduce to the point where they disappear, and the efficiency curves illustrate a steplike dependence on the sphere size. Another feature is that the only on the amount of chirp (|b|), regardless of upchirp (b greater than 0) or downchirp (b less than 0).

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.

Test-retest reliability of auditory brainstem responses to chirp stimuli in newborns.

PubMed

Cobb, Kensi M; Stuart, Andrew

2014-11-01

The purpose of this study was to examine the test-retest reliability of auditory brainstem responses (ABRs) to air- and bone-conducted chirp stimuli in newborns as a function of intensity. A repeated measures quasi-experimental design was employed. Thirty healthy newborns participated. ABRs were evoked using 60, 45, and 30 dB nHL air-conducted CE-Chirps and 45, 30, and 15 dB nHL bone-conducted CE-Chirps at a rate of 57.7/s. Measures were repeated by a second tester. Statistically significant correlations (p <.0001) and predictive linear relations (p <.0001) were found between testers for wave V latencies and amplitudes to air- and bone-conducted CE-Chirps. There were also no statistically significant differences between testers with wave V latencies and amplitudes to air- and bone-conducted CE-Chirps (p >.05). As expected, significant differences in wave V latencies and amplitudes were seen as a function of stimulus intensity for air- and bone-conducted CE-Chirps (p <.0001). These results suggest that ABRs to air- and bone-conducted CE-Chirps can be reliably repeated in newborns with different testers. The CE-Chirp may be valuable for both screening and diagnostic audiologic assessments of newborns.

Propagation and Signal Modeling

NASA Astrophysics Data System (ADS)

Jensen, Finn B.

The use of sound in the sea is ubiquitous: Apart from the military aspect of trying to detect an adversary’s mines and submarines, ship-mounted sonars measure water depth, ship speed, and the presence of fish shoals. Side-scan systems are used for mapping the bottom topography, sub-bottom profilers for getting information about the deeper layering, and other sonar systems for locating pipelines and cables on the seafloor. Sound is also used for navigating submerged vehicles, for underwater communications and for tracking marine mammals. Finally, in the realm of ‘acoustical oceanography’ and ‘ocean acoustic tomography,’ sound is used for measuring physical parameters of the ocean environment and for monitoring oceanic processes [1-6].

Optimizing chirped laser pulse parameters for electron acceleration in vacuum

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

Akhyani, Mina; Jahangiri, Fazel; Niknam, Ali Reza

2015-11-14

Electron dynamics in the field of a chirped linearly polarized laser pulse is investigated. Variations of electron energy gain versus chirp parameter, time duration, and initial phase of laser pulse are studied. Based on maximizing laser pulse asymmetry, a numerical optimization procedure is presented, which leads to the elimination of rapid fluctuations of gain versus the chirp parameter. Instead, a smooth variation is observed that considerably reduces the accuracy required for experimentally adjusting the chirp parameter.

Orthogonal Chirp-Based Ultrasonic Positioning

PubMed Central

Khyam, Mohammad Omar; Ge, Shuzhi Sam; Li, Xinde; Pickering, Mark

2017-01-01

This paper presents a chirp based ultrasonic positioning system (UPS) using orthogonal chirp waveforms. In the proposed method, multiple transmitters can simultaneously transmit chirp signals, as a result, it can efficiently utilize the entire available frequency spectrum. The fundamental idea behind the proposed multiple access scheme is to utilize the oversampling methodology of orthogonal frequency-division multiplexing (OFDM) modulation and orthogonality of the discrete frequency components of a chirp waveform. In addition, the proposed orthogonal chirp waveforms also have all the advantages of a classical chirp waveform. Firstly, the performance of the waveforms is investigated through correlation analysis and then, in an indoor environment, evaluated through simulations and experiments for ultrasonic (US) positioning. For an operational range of approximately 1000 mm, the positioning root-mean-square-errors (RMSEs) &90% error were 4.54 mm and 6.68 mm respectively. PMID:28448454

Orthogonal Chirp-Based Ultrasonic Positioning.

PubMed

Khyam, Mohammad Omar; Ge, Shuzhi Sam; Li, Xinde; Pickering, Mark

2017-04-27

This paper presents a chirp based ultrasonic positioning system (UPS) using orthogonal chirp waveforms. In the proposed method, multiple transmitters can simultaneously transmit chirp signals, as a result, it can efficiently utilize the entire available frequency spectrum. The fundamental idea behind the proposed multiple access scheme is to utilize the oversampling methodology of orthogonal frequency-division multiplexing (OFDM) modulation and orthogonality of the discrete frequency components of a chirp waveform. In addition, the proposed orthogonal chirp waveforms also have all the advantages of a classical chirp waveform. Firstly, the performance of the waveforms is investigated through correlation analysis and then, in an indoor environment, evaluated through simulations and experiments for ultrasonic (US) positioning. For an operational range of approximately 1000 mm, the positioning root-mean-square-errors (RMSEs) &90% error were 4.54 mm and 6.68 mm respectively.

The effect of difference frequency on electrocommunication: chirp production and encoding in a species of weakly electric fish, Apteronotus leptorhynchus.

PubMed

Hupé, Ginette J; Lewis, John E; Benda, Jan

2008-01-01

The brown ghost knifefish, Apteronotus leptorhynchus, is a model wave-type gymnotiform used extensively in neuroethological studies. As all weakly electric fish, they produce an electric field (electric organ discharge, EOD) and can detect electric signals in their environments using electroreceptors. During social interactions, A. leptorhynchus produce communication signals by modulating the frequency and amplitude of their EOD. The Type 2 chirp, a transient increase in EOD frequency, is the most common modulation type. We will first present a description of A. leptorhynchus chirp production from a behavioural perspective, followed by a discussion of the mechanisms by which chirps are encoded by electroreceptor afferents (P-units). Both the production and encoding of chirps are influenced by the difference in EOD frequency between interacting fish, the so-called beat or difference frequency (Df). Chirps are produced most often when the Df is small, whereas attacks are more common when Dfs are large. Correlation analysis has shown that chirp production induces an echo response in interacting conspecifics and that chirps are produced when attack rates are low. Here we show that both of these relationships are strongest when Dfs are large. Electrophysiological recordings from electroreceptor afferents (P-units) have suggested that small, Type 2 chirps are encoded by increases in electroreceptor synchrony at low Dfs only. How Type 2 chirps are encoded at higher Dfs, where the signals seem to exert the greatest behavioural influence, was unknown. Here, we provide evidence that at higher Dfs, chirps could be encoded by a desynchronization of the P-unit population activity.

Chirping response of weakly electric knife fish (Apteronotus leptorhynchus) to low-frequency electric signals and to heterospecific electric fish.

PubMed

Dunlap, K D; DiBenedictis, B T; Banever, S R

2010-07-01

Brown ghost knife fish (Apteronotus leptorhynchus) can briefly increase their electric organ discharge (EOD) frequency to produce electrocommunication signals termed chirps. The chirp rate increases when fish are presented with conspecific fish or high-frequency (700-1100 Hz) electric signals that mimic conspecific fish. We examined whether A. leptorhynchus also chirps in response to artificial low-frequency electric signals and to heterospecific electric fish whose EOD contains low-frequency components. Fish chirped at rates above background when presented with low-frequency (10-300 Hz) sine-wave stimuli; at 30 and 150 Hz, the threshold amplitude for response was 1 mV cm(-1). Low-frequency (30 Hz) stimuli also potentiated the chirp response to high-frequency ( approximately 900 Hz) stimuli. Fish increased their chirp rate when presented with two heterospecific electric fish, Sternopygus macrurus and Brachyhypopomus gauderio, but did not respond to the presence of the non-electric fish Carassius auratus. Fish chirped to low-frequency (150 Hz) signals that mimic those of S. macrurus and to EOD playbacks of B. gauderio. The response to the B. gauderio playback was reduced when the low-frequency component (<150 Hz) was experimentally filtered out. Thus, A. leptorhynchus appears to chirp specifically to the electric signals of heterospecific electric fish, and the low-frequency components of heterospecific EODs significantly influence chirp rate. These results raise the possibility that chirps function to communicate to conspecifics about the presence of a heterospecific fish or to communicate directly to heterospecific fish.

Chirp Scaling Algorithms for SAR Processing

NASA Technical Reports Server (NTRS)

Jin, M.; Cheng, T.; Chen, M.

1993-01-01

The chirp scaling SAR processing algorithm is both accurate and efficient. Successful implementation requires proper selection of the interval of output samples, which is a function of the chirp interval, signal sampling rate, and signal bandwidth. Analysis indicates that for both airborne and spaceborne SAR applications in the slant range domain a linear chirp scaling is sufficient. To perform nonlinear interpolation process such as to output ground range SAR images, one can use a nonlinear chirp scaling interpolator presented in this paper.

Accuracy of active chirp linearization for broadband frequency modulated continuous wave ladar.

PubMed

Barber, Zeb W; Babbitt, Wm Randall; Kaylor, Brant; Reibel, Randy R; Roos, Peter A

2010-01-10

As the bandwidth and linearity of frequency modulated continuous wave chirp ladar increase, the resulting range resolution, precisions, and accuracy are improved correspondingly. An analysis of a very broadband (several THz) and linear (<1 ppm) chirped ladar system based on active chirp linearization is presented. Residual chirp nonlinearity and material dispersion are analyzed as to their effect on the dynamic range, precision, and accuracy of the system. Measurement precision and accuracy approaching the part per billion level is predicted.

Generation of multi-millijoule red-shifted pulses for seeding stimulated Raman backscattering amplifiers.

PubMed

Landgraf, Björn; Hoffmann, Andreas; Kartashov, Daniil; Gärtner, Felix; Samsonova, Zhanna; Polynkin, Pavel; Jacoby, Joachim; Kühl, Thomas; Spielmann, Christian

2015-03-23

The efficient generation of redshifted pulses from chirped femtosecond joule level Bessel beam pulses in gases is studied. The redshift spans from a few 100 cm⁻¹ to several 1000 cm⁻¹ corresponding to a shift of 50-500 nm for Nd:glass laser systems. The generated pulses have an almost perfect Gaussian beam profile insensitive of the pump beam profile, and are much shorter than the pump pulses. The highest measured energy is as high as 30 mJ, which is significantly higher than possible with solid state nonlinear frequency shifters.

Archive of Digital Boomer and CHIRP Seismic Reflection Data Collected During USGS Field Activity 08LCA03 in Lake Panasoffkee, Florida, May 2008

USGS Publications Warehouse

Harrison, Arnell S.; Dadisman, Shawn V.; McBride, W. Scott; Flocks, James G.; Wiese, Dana S.

2009-01-01

In May of 2008, the U.S. Geological Survey (USGS) conducted geophysical surveys in Lake Panasoffkee, located in central Florida, as part of the USGS Lakes and Coastal Aquifers (LCA) study. This report serves as an archive of unprocessed digital boomer and Compressed High Intensity Radar Pulse (CHIRP)* seismic reflection data, trackline maps, navigation files, Field Activity Collection System (FACS) logs, Geographic Information System (GIS) files, and formal Federal Geographic Data Committee (FGDC) metadata. Filtered and gained (a relative increase in signal amplitude) digital images of the seismic profiles and geospatially corrected interactive profiles are also provided. Refer to the Acronyms page for expansions of acronyms and abbreviations used in this report. *Due to poor data acquisition conditions associated with the lake bottom sediments, only two CHIRP tracklines were collected during this field activity. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Example SU processing scripts and USGS software for viewing the SEG-Y files (Zihlman, 1992) are provided. The USGS Florida Integrated Science Center (FISC) - St. Petersburg assigns a unique identifier to each cruise or field activity. For example, 08LCA03 tells us the data were collected in 2008 for the Lakes and Coastal Aquifers (LCA) study and the data were collected during the third field activity for that study in that calendar year. Refer to http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html for a detailed description of the method used to assign the field activity ID. The naming convention used for each seismic line is as follows: yye##a, where 'yy' are the last two digits of the year in which the data were collected, 'e' is a 1-letter abbreviation for the equipment type (for example, b for boomer and c for CHIRP), '##' is a 2-digit number representing a specific track, and 'a' is a letter representing the section of a line if recording was prematurely terminated or rerun for quality or acquisition problems. The boomer plate is an acoustic energy source that consists of capacitors charged to a high voltage and discharged through a transducer in the water. The transducer is towed on a sled floating on the water surface and, when discharged, emits a short acoustic pulse, or shot, which propagates through the water, sediment column, or rock beneath. The acoustic energy is reflected at density boundaries (such as the seafloor, sediment, or rock layers beneath the seafloor), detected by the receiver, and recorded by a PC-based seismic acquisition system. This process is repeated at timed intervals (for example, 0.5 s) and recorded for specific intervals of time (for example, 100 ms). In this way, a two-dimensional (2-D) vertical profile of the shallow geologic structure beneath the ship track is produced. Figure 1 displays the boomer acquisition geometry. The EdgeTech SB-424 CHIRP system used for this survey has a vertical resolution of 4 - 8 cm, a penetration depth that is usually less than 2 m beneath the seafloor, and uses a signal of continuously varying frequency. The towfish is a sound source and receiver, which is typically towed 2 - 5 m above the seafloor. The acoustic energy is reflected at density boundaries (such as the seafloor or sediment layers beneath the seafloor), detected by a receiver, and recorded by a PC-based seismic acquisition system. This process is repeated at timed intervals (for example, 0.125 s) and recorded for specific intervals of time (for example, 50 ms); the resulting profile is a two-dimensional vertical image of the shallow geologic structure beneath the ship track. Figure 2 displays the acquisition geometry for the CHIRP system. Refer to table 1 for a summary of acquisition parameters and table 2 for trackline statistics.

Characterization and compensation of the residual chirp in a Mach-Zehnder-type electro-optical intensity modulator.

PubMed

Rogers, C E; Carini, J L; Pechkis, J A; Gould, P L

2010-01-18

We utilize various techniques to characterize the residual phase modulation of a waveguide-based Mach-Zehnder electro-optical intensity modulator. A heterodyne technique is used to directly measure the phase change due to a given change in intensity, thereby determining the chirp parameter of the device. This chirp parameter is also measured by examining the ratio of sidebands for sinusoidal amplitude modulation. Finally, the frequency chirp caused by an intensity pulse on the nanosecond time scale is measured via the heterodyne signal. We show that this chirp can be largely compensated with a separate phase modulator. The various measurements of the chirp parameter are in reasonable agreement.

Frequency-chirp rates of harmonics driven by a few-cycle pulse

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

Murakami, M.; Mauritsson, J.; Gaarde, M.B.

2005-08-15

We present numerical calculations of the time-frequency characteristics of cutoff harmonics generated by few-cycle laser pulses. We find that for driving pulses as short as three optical cycles, the adiabatic prediction for the harmonic chirp rate is very accurate. This negative chirp is so large that the resulting bandwidth causes substantial overlap between neighboring harmonics, and the harmonic phase therefore appears to not vary in time or frequency. By adding a compensating positive chirp to the driving pulse, which reduces the harmonic bandwidth and allows for the appearance of the negative chirp, we can measure the harmonic chirp rates. Wemore » also find that the positive chirp on the driving pulse causes the harmonics to shift down in frequency. We show that this counterintuitive result is caused by the change in the strong field continuum dynamics introduced by the variation of the driving frequency with time.« less

Extension of harmonic cutoff in a multicycle chirped pulse combined with a chirp-free pulse

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

Xu Junjie; Zeng Bin; Yu Yongli

2010-11-15

We demonstrate high-order harmonic generation in a wave form synthesized by a multicycle 800-nm chirped laser pulse and a chirp-free laser pulse. Compared with the case of using only a chirped pulse, both the harmonic cutoff and the extreme ultraviolet supercontinuum can be extended when a weak chirp-free pulse is combined with the chirped pulse. When chirp-free pulse intensity grows, the cutoff energy and bandwidth of the supercontinuum grow as well. It is found that the broad supercontinuum can be achieved for a driving pulse with long duration even though the driving pulse reaches 10 optical cycles. An isolated attosecondmore » pulse with duration of about 59 as is obtained, and after appropriate phase compensation with a duration of about 11 as. In addition, by performing time-frequency analyses and the classical trajectory simulation, the difference in supercontinuum generation between the preceding wave form and a similar wave form synthesized by an 800-nm fundamental pulse and a 1600-nm subharmonic pulse is investigated.« less

Chirp-modulated visual evoked potential as a generalization of steady state visual evoked potential

NASA Astrophysics Data System (ADS)

Tu, Tao; Xin, Yi; Gao, Xiaorong; Gao, Shangkai

2012-02-01

Visual evoked potentials (VEPs) are of great concern in cognitive and clinical neuroscience as well as in the recent research field of brain-computer interfaces (BCIs). In this study, a chirp-modulated stimulation was employed to serve as a novel type of visual stimulus. Based on our empirical study, the chirp stimuli visual evoked potential (Chirp-VEP) preserved frequency features of the chirp stimulus analogous to the steady state evoked potential (SSVEP), and therefore it can be regarded as a generalization of SSVEP. Specifically, we first investigated the characteristics of the Chirp-VEP in the time-frequency domain and the fractional domain via fractional Fourier transform. We also proposed a group delay technique to derive the apparent latency from Chirp-VEP. Results on EEG data showed that our approach outperformed the traditional SSVEP-based method in efficiency and ease of apparent latency estimation. For the recruited six subjects, the average apparent latencies ranged from 100 to 130 ms. Finally, we implemented a BCI system with six targets to validate the feasibility of Chirp-VEP as a potential candidate in the field of BCIs.

Holocene evolution of the Tonle Sap Lake: valley network infill and rates of sedimentation in Cambodia's Great Lake

NASA Astrophysics Data System (ADS)

Best, J.; Darby, S. E.; Langdon, P. G.; Hackney, C. R.; Leyland, J.; Parsons, D. R.; Aalto, R. E.; Marti, M.

2017-12-01

Tonle Sap Lake, the largest freshwater lake in SE Asia (c. 120km long and 35 km wide), is a vital ecosystem that provides 40-60% of the protein for the population of Cambodia. The lake is fed by flow from the Mekong River that causes the lake rise in level by c. 8m during monsoonal and cyclone-related floods, with drainage of the lake following the monsoon. Hydropower dam construction on the Mekong River has raised concerns as to the fragility of the Tonle Sap habitat due to any changing water levels and sedimentation rates within the lake. This paper details results of sub-bottom profiling surveys of Tonle Sap Lake in October 2014 that detailed the stratigraphy of the lake and assessed rates of infill. An Innomar Parametric Echo Sounder (PES) was used to obtain c. 250 km of sub-bottom profiles, with penetration up to 15m below the lake bed at a vertical resolution of c. 0.20m. These PES profiles were linked to cores from the north of the lake and previous literature. The PES profiles reveal a network of valleys, likely LGM, with relief up to c. 15-20m, that have been infilled by a suite of Holocene sediments. The valley surface is picked out as a strong reflector throughout the lake, and displays a series of valleys that are up to c. 15m deep and commonly 50-200m wide, although some of the largest valleys are 1.2km in width. Modelling of channel network incision during LGM conditions generates landscapes consistent with our field observations. The Tonle Sap valley network is infilled by sediments that show firstly fluvial and/or subaerial slope sedimentation, and then by extensive, parallel-bedded, lacustrine sedimentation. Lastly, the top c. 1m of sedimentation is marked by a distinct basal erosional surface that can be traced over much of the Tonle Sap Lake, and that is overlain by a series of parallel PES reflections. This upper sediment layer is interpreted to represent sedimentation in the Tonle Sap lake due to sediment suspension settling but after a period of widespread erosion that generated the extensive erosion surface. This paper will detail the characteristics and interpretation of the PES facies, their correlation to cores and estimates of sedimentation rates. Dating and PES profiles indicate that infill of the lake was complete by c. 6ka and that minimal sedimentation has occurred since then, likely due to reworking by wave resuspension.

Phase-locking and coherent power combining of broadband linearly chirped optical waves.

PubMed

Satyan, Naresh; Vasilyev, Arseny; Rakuljic, George; White, Jeffrey O; Yariv, Amnon

2012-11-05

We propose, analyze and demonstrate the optoelectronic phase-locking of optical waves whose frequencies are chirped continuously and rapidly with time. The optical waves are derived from a common optoelectronic swept-frequency laser based on a semiconductor laser in a negative feedback loop, with a precisely linear frequency chirp of 400 GHz in 2 ms. In contrast to monochromatic waves, a differential delay between two linearly chirped optical waves results in a mutual frequency difference, and an acoustooptic frequency shifter is therefore used to phase-lock the two waves. We demonstrate and characterize homodyne and heterodyne optical phase-locked loops with rapidly chirped waves, and show the ability to precisely control the phase of the chirped optical waveform using a digital electronic oscillator. A loop bandwidth of ~ 60 kHz, and a residual phase error variance of < 0.01 rad(2) between the chirped waves is obtained. Further, we demonstrate the simultaneous phase-locking of two optical paths to a common master waveform, and the ability to electronically control the resultant two-element optical phased array. The results of this work enable coherent power combining of high-power fiber amplifiers-where a rapidly chirping seed laser reduces stimulated Brillouin scattering-and electronic beam steering of chirped optical waves.

A Study of Mexican Free-Tailed Bat Chirp Syllables: Bayesian Functional Mixed Models for Nonstationary Acoustic Time Series.

PubMed

Martinez, Josue G; Bohn, Kirsten M; Carroll, Raymond J; Morris, Jeffrey S

2013-06-01

We describe a new approach to analyze chirp syllables of free-tailed bats from two regions of Texas in which they are predominant: Austin and College Station. Our goal is to characterize any systematic regional differences in the mating chirps and assess whether individual bats have signature chirps. The data are analyzed by modeling spectrograms of the chirps as responses in a Bayesian functional mixed model. Given the variable chirp lengths, we compute the spectrograms on a relative time scale interpretable as the relative chirp position, using a variable window overlap based on chirp length. We use 2D wavelet transforms to capture correlation within the spectrogram in our modeling and obtain adaptive regularization of the estimates and inference for the regions-specific spectrograms. Our model includes random effect spectrograms at the bat level to account for correlation among chirps from the same bat, and to assess relative variability in chirp spectrograms within and between bats. The modeling of spectrograms using functional mixed models is a general approach for the analysis of replicated nonstationary time series, such as our acoustical signals, to relate aspects of the signals to various predictors, while accounting for between-signal structure. This can be done on raw spectrograms when all signals are of the same length, and can be done using spectrograms defined on a relative time scale for signals of variable length in settings where the idea of defining correspondence across signals based on relative position is sensible.

2014/2015 Investigations of the Ontong Java and Kerguelen Plateaus

NASA Astrophysics Data System (ADS)

Coffin, M. F.; Whittaker, J. M.

2013-12-01

The two largest oceanic plateaus, Ontong Java in the western Pacific, and Kerguelen in the southern Indian Ocean, will be the focus of scheduled multidisciplinary/interdisciplinary shipboard expeditions in 2014 and 2015. In mid-2014, scientists aboard the Schmidt Ocean Institute's RV Falkor will investigate the origin and evolution of two large atolls, Ontong Java and Nukumanu, surmounting the ca 122 Ma Ontong Java Plateau, as well how Kroenke Canyon, which deeply incises the plateau, formed and evolved. First-ever multibeam bathymetry and sub-bottom profiling data from the atolls and canyon will reveal their submarine and shallow sub-seafloor morphology, and, if combined with geochemical and geochronological analyses of potential igneous basement samples, will yield important information on their origin and evolution. The primary goals of this atoll and canyon project are: to test potential genetic relationships between a) the atolls and the OJP, and b) the atolls and Kroenke Canyon; to understand and model how atolls and canyons form and evolve on oceanic plateaus, isolated from terrestrial influences and subject to sea level fluctuations; and to contribute to understanding tsunami risk on low-lying atolls. In late 2014 and early 2015, researchers aboard Australia's new Marine National Facility, RV Investigator, will investigate active submarine hotspot volcanism on the Kerguelen Plateau and its consequences. The project's overall aim is to test the hypothesis that hydrothermal activity driven by active submarine magmatism fertilizes surface waters with iron that enhances primary biological productivity. Surmounting the Cretaceous plateau, Heard and McDonald Islands are among the world's most active hotspot volcanoes, and new multibeam bathymetry and sub-bottom profiling data will enable identification of candidate active submarine volcanoes, which we will sample. In the overlying water column, we will collect samples to test for the presence or absence of associated hydrothermalism as well as iron and other elemental enrichment. If present, we will compare our data to satellite images of primary biological productivity (eg, chlorophyll) to test for temporal and spatial correlations.

Holocene lake level changes at a lowland lake in northeastern Germany inferred from acoustic sub-bottom profiling and a transect of sediment cores

NASA Astrophysics Data System (ADS)

Dietze, Elisabeth; Zawiska, Izabela; Słowiński, Michał; Brauer, Achim

2015-04-01

Holocene lake level changes were studied at Lake Fürstenseer See, a typical lake with complex basin morphology in northeastern German sandur area. An acoustic sub-bottom profile and a transect of four long sediment cores in the deepest lake sub-basin were analyzed. The cores were dated with AMS-14C and correlated with multiple proxies (sediment facies, μ-XRF, macrofossils, subfossil Cladocera, carbonate isotopes). At sites in 10 and 15 m water depth, shifts in the sand-mud boundary, i.e. sediment limit sensu Digerfeldt (1986), allowed quantitative estimates of the absolute amplitude of lake level changes. At sites in 20 and 23 m water depth, the negative correlation of Ca and Ti reflect lake level changes qualitatively. During high lake stands massive organic muds were deposited. Lower lake levels isolated the lake sub-basins which reduced the overall water circulation and lead to the deposition of Ti-poor carbonate muds. Furthermore, macrofossil and subfossil Cladocera analyses were used as proxies for the intense reworking at the slope and for the trophic state of the lake, respectively. Lake levels were up to 4 m higher, e.g. around 5000 cal. yrs BP and during the Medieval time period (see also Kaiser et al., 2014). During the early to mid-Holocene (between 9400 and 6400 cal. yrs BP), Lake Fürstenseer See fluctuated at an at least 3-m lower level. Further water level changes can be related to known climatic events and regional human impact. Digerfeldt, G., 1986. Studies on past lake-level fluctuations. In Berglund, B. (ed.), Handbook of Holocene Palaeoecology and Palaeohydrology: 127-144. John Wiley & Sons, New York. Kaiser, K., Küster, M., Fülling, A., Theuerkauf, M., Dietze, E., Graventein, H., Koch, P.J., Bens, O., Brauer, A., 2014. Littoral landforms and pedosedimentary sequences indicating late Holocene lake-level changes in northern central Europe ' A case study from northeastern Germany. Geomorphology 216, 58-78.

Analysis of intrapulse chirp in CO2 oscillators

NASA Technical Reports Server (NTRS)

Moody, Stephen E.; Berger, Russell G.; Thayer, William J., III

1987-01-01

Pulsed single-frequency CO2 laser oscillators are often used as transmitters for coherent lidar applications. These oscillators suffer from intrapulse chirp, or dynamic frequency shifting. If excessive, such chirp can limit the signal-to-noise ratio of the lidar (by generating excess bandwidth), or limit the velocity resolution if the lidar is of the Doppler type. This paper describes a detailed numerical model that considers all known sources of intrapulse chirp. Some typical predictions of the model are shown, and simple design rules to minimize chirp are proposed.

Laser chirp effect on femtosecond laser filamentation generated for pulse compression.

PubMed

Park, Juyun; Lee, Jae-Hwan; Nam, Chang H

2008-03-31

The influence of laser chirp on the formation of femtosecond laser filamentation in Ar was investigated for the generation of few-cycle high-power laser pulses. The condition for the formation of a single filament has been carefully examined using 28-fs laser pulses with energy over 3 mJ. The filament formation and output spectrum changed very sensitively to the initial laser chirp and gas pressure. Much larger spectral broadening was obtained with positively chirped pulses, compared to the case of negatively chirped pulses that generated much longer filament, and compressed pulses of 5.5 fs with energy of 0.5 mJ were obtained from the filamentation of positively chirped 30-fs laser pulses in a single Ar cell.

Chirp of the single attosecond pulse generated by a polarization gating

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

Chang Zenghu

2005-02-01

The chirp of the xuv supercontinuum generated by a polarization gating is investigated by comparing three-dimensional nonadiabatic numerical simulations with classical calculations. The origin of the chirp is the dependence of the energy gain by an electron on the return time. The chirp is positive and its value is almost the same as that when a linearly polarized laser is used. Although the 250-eV-wide supercontinuum corresponds to a single attosecond pulse, the shortest duration of the pulse is limited by the chirp. By compensating the positive chirp with the negative group velocity dispersion of a Sn filter, it is predictedmore » that a single 58-as pulse can be generated.« less

Properties of Chirped Grating Lenses in Optical Waveguides.

DTIC Science & Technology

1984-10-01

the design, the materials and the fabrication q process. In this report, we will summarize the research results obtained at UCSD on the fundamental...limitations of their performance in efficiency, angular field of view and F-number caused by diffraction, materials properties and fabrication techniques... material index, the grating groove pattern in both the transverse and the longitudinal direction and the profile of the grooves can all be varied, while in

A Study of Mexican Free-Tailed Bat Chirp Syllables: Bayesian Functional Mixed Models for Nonstationary Acoustic Time Series

PubMed Central

MARTINEZ, Josue G.; BOHN, Kirsten M.; CARROLL, Raymond J.

2013-01-01

We describe a new approach to analyze chirp syllables of free-tailed bats from two regions of Texas in which they are predominant: Austin and College Station. Our goal is to characterize any systematic regional differences in the mating chirps and assess whether individual bats have signature chirps. The data are analyzed by modeling spectrograms of the chirps as responses in a Bayesian functional mixed model. Given the variable chirp lengths, we compute the spectrograms on a relative time scale interpretable as the relative chirp position, using a variable window overlap based on chirp length. We use 2D wavelet transforms to capture correlation within the spectrogram in our modeling and obtain adaptive regularization of the estimates and inference for the regions-specific spectrograms. Our model includes random effect spectrograms at the bat level to account for correlation among chirps from the same bat, and to assess relative variability in chirp spectrograms within and between bats. The modeling of spectrograms using functional mixed models is a general approach for the analysis of replicated nonstationary time series, such as our acoustical signals, to relate aspects of the signals to various predictors, while accounting for between-signal structure. This can be done on raw spectrograms when all signals are of the same length, and can be done using spectrograms defined on a relative time scale for signals of variable length in settings where the idea of defining correspondence across signals based on relative position is sensible. PMID:23997376

Click- and chirp-evoked human compound action potentials

PubMed Central

Chertoff, Mark; Lichtenhan, Jeffery; Willis, Marie

2010-01-01

In the experiments reported here, the amplitude and the latency of human compound action potentials (CAPs) evoked from a chirp stimulus are compared to those evoked from a traditional click stimulus. The chirp stimulus was created with a frequency sweep to compensate for basilar membrane traveling wave delay using the O-Chirp equations from Fobel and Dau [(2004). J. Acoust. Soc. Am. 116, 2213–2222] derived from otoacoustic emission data. Human cochlear traveling wave delay estimates were obtained from derived compound band action potentials provided by Eggermont [(1979). J. Acoust. Soc. Am. 65, 463–470]. CAPs were recorded from an electrode placed on the tympanic membrane (TM), and the acoustic signals were monitored with a probe tube microphone attached to the TM electrode. Results showed that the amplitude and latency of chirp-evoked N1 of the CAP differed from click-evoked CAPs in several regards. For the chirp-evoked CAP, the N1 amplitude was significantly larger than the click-evoked N1s. The latency-intensity function was significantly shallower for chirp-evoked CAPs as compared to click-evoked CAPs. This suggests that auditory nerve fibers respond with more unison to a chirp stimulus than to a click stimulus. PMID:21117748

Comparisons of transient evoked otoacoustic emissions using chirp and click stimuli

PubMed Central

Keefe, Douglas H.; Feeney, M. Patrick; Hunter, Lisa L.; Fitzpatrick, Denis F.

2016-01-01

Transient-evoked otoacoustic emission (TEOAE) responses (0.7–8 kHz) were measured in normal-hearing adult ears using click stimuli and chirps whose local frequency increased or decreased linearly with time over the stimulus duration. Chirp stimuli were created by allpass filtering a click with relatively constant incident pressure level over frequency. Chirp TEOAEs were analyzed as a nonlinear residual signal by inverse allpass filtering each chirp response into an equivalent click response. Multi-window spectral and temporal averaging reduced noise levels compared to a single-window average. Mean TEOAE levels using click and chirp stimuli were similar with respect to their standard errors in adult ears. TEOAE group delay, group spread, instantaneous frequency, and instantaneous bandwidth were similar overall for chirp and click conditions, except for small differences showing nonlinear interactions differing across stimulus conditions. These results support the theory of a similar generation mechanism on the basilar membrane for both click and chirp conditions based on coherent reflection within the tonotopic region. TEOAE temporal fine structure was invariant across changes in stimulus level, which is analogous to the intensity invariance of click-evoked basilar-membrane displacement data. PMID:27914441

Mechanisms for synchrony and alternation in song interactions of the bushcricket Mecopoda elongata (Tettigoniidae: Orthoptera)

PubMed Central

Hartbauer, Manfred; Kratzer, Silvia; Steiner, Klaus; Römer, Heiner

2014-01-01

Males of the bushcricket Mecopoda elongata synchronise or alternate their chirps with their neighbours in an aggregation. Since synchrony is imperfect, leader and follower chirps are established in song interactions; females prefer leader chirps in phonotactic trials. Using playback experiments and simulations of song oscillator interactions, we investigate the mechanisms that result in synchrony and alternation, and the probability for the leader role in synchrony. A major predictor for the leader role of a male is its intrinsic chirp period, which varies in a population from 1.6 to 2.3 s. Faster singing males establish the leader role more often than males with longer chirp periods. The phase-response curve (PRC) of the song oscillators differs to other rhythmically calling or flashing insects, in that only the disturbed cycle is influenced in duration by a stimulus. This results in sustained leader or follower chirps of one male, when the intrinsic chirp periods of two males differ by 150 ms or more. By contrast, the individual shape of the male’s PRC has only little influence on the outcome of chirp interactions. The consequences of these findings for the evolution of synchrony in this species are discussed. PMID:15614532

Comparisons of transient evoked otoacoustic emissions using chirp and click stimuli.

PubMed

Keefe, Douglas H; Feeney, M Patrick; Hunter, Lisa L; Fitzpatrick, Denis F

2016-09-01

Transient-evoked otoacoustic emission (TEOAE) responses (0.7-8 kHz) were measured in normal-hearing adult ears using click stimuli and chirps whose local frequency increased or decreased linearly with time over the stimulus duration. Chirp stimuli were created by allpass filtering a click with relatively constant incident pressure level over frequency. Chirp TEOAEs were analyzed as a nonlinear residual signal by inverse allpass filtering each chirp response into an equivalent click response. Multi-window spectral and temporal averaging reduced noise levels compared to a single-window average. Mean TEOAE levels using click and chirp stimuli were similar with respect to their standard errors in adult ears. TEOAE group delay, group spread, instantaneous frequency, and instantaneous bandwidth were similar overall for chirp and click conditions, except for small differences showing nonlinear interactions differing across stimulus conditions. These results support the theory of a similar generation mechanism on the basilar membrane for both click and chirp conditions based on coherent reflection within the tonotopic region. TEOAE temporal fine structure was invariant across changes in stimulus level, which is analogous to the intensity invariance of click-evoked basilar-membrane displacement data.

Evolution of the frequency chirp of Gaussian pulses and beams when passing through a pulse compressor.

PubMed

Li, Derong; Lv, Xiaohua; Bowlan, Pamela; Du, Rui; Zeng, Shaoqun; Luo, Qingming

2009-09-14

The evolution of the frequency chirp of a laser pulse inside a classical pulse compressor is very different for plane waves and Gaussian beams, although after propagating through the last (4th) dispersive element, the two models give the same results. In this paper, we have analyzed the evolution of the frequency chirp of Gaussian pulses and beams using a method which directly obtains the spectral phase acquired by the compressor. We found the spatiotemporal couplings in the phase to be the fundamental reason for the difference in the frequency chirp acquired by a Gaussian beam and a plane wave. When the Gaussian beam propagates, an additional frequency chirp will be introduced if any spatiotemporal couplings (i.e. angular dispersion, spatial chirp or pulse front tilt) are present. However, if there are no couplings present, the chirp of the Gaussian beam is the same as that of a plane wave. When the Gaussian beam is well collimated, the introduced frequency chirp predicted by the plane wave and Gaussian beam models are in closer agreement. This work improves our understanding of pulse compressors and should be helpful for optimizing dispersion compensation schemes in many applications of femtosecond laser pulses.

High-resolution seismic-reflection and marine-magnetic data from offshore central California--San Gregorio to Point Sur

USGS Publications Warehouse

Sliter, Ray W.; Johnson, Samuel Y.; Watt, Janet T.; Scheirer, Daniel S.; Allwardt, Parker; Triezenberg, Peter J.

2013-01-01

The U.S. Geological Survey collected high-resolution seismic-reflection data on four surveys (S-N1-09-MB, S-15-10-NC, S-06-11-MB, and S-04-12-MB) and marine-magnetic data on one survey (S-06-11-MB) between 2009 and 2012, offshore of central California between San Gregorio and Point Sur. This work was supported in part by the California Seafloor Mapping Program. The survey areas span about 120 km of California's coast (including Monterey Bay). Most data were collected aboard the U.S. Geological Survey R/V Parke Snavely. Cumulatively, approximately 1,410 km of single-channel seismic-reflection data were acquired, mainly using a SIG 2mille minisparker. About 44 km of data were collected simultaneously using an EdgeTech Chirp 512. Subbottom acoustic penetration spanned tens to several hundreds of meters, variable by location. Marine magnetic data were collected on approximately 460 km of track lines (mainly in southern Monterey Bay) using a Geometrics G882 cesium-vapor marine magnetometer. This report includes maps and navigation files of the surveyed transects, linked to Google Earth™ software, as well as digital data files showing images of each transect in SEG-Y and JPEG formats. The images of bedrock, sediment deposits, and tectonic structure provide geologic information that is essential to hazard assessment, regional sediment management, and coastal and marine spatial planning at Federal, State and local levels, as well as to future research on the geomorphic, sedimentary, tectonic, and climatic record of central California.

Geologic control on the evolution of the inner shelf morphology offshore of the Mississippi barrier islands, northern Gulf of Mexico, USA

USGS Publications Warehouse

Flocks, James G.; Kindinger, Jack G.; Kelso, Kyle W.

2015-01-01

Between 2008 and 2013, high-resolution geophysical surveys were conducted around the Mississippi barrier islands and offshore. The sonar surveys included swath and single-beam bathymetry, sidescan, and chirp subbottom data collection. The geophysical data were groundtruthed using vibracore sediment collection. The results provide insight into the evolution of the inner shelf and the relationship between the near surface geologic framework and the morphology of the coastal zone. This study focuses on the buried Pleistocene fluvial deposits and late Holocene shore-oblique sand ridges offshore of Petit Bois Island and Petit Bois Pass. Prior to this study, the physical characteristics, evolution, and interrelationship of the ridges between both the shelf geology and the adjacent barrier island platform had not been evaluated. Numerous studies elsewhere along the coastal margin attribute shoal origin and sand-ridge evolution to hydrodynamic processes in shallow water (<20 m). Here we characterize the correlation between the geologic framework and surface morphology and demonstrate that the underlying stratigraphy must also be considered when developing an evolutionary conceptual model. It is important to understand this near surface, nearshore dynamic in order to understand how the stratigraphy influences the long-term response of the coastal zone to sea-level rise. The study also contributes to a growing body of work characterizing shore-oblique sand ridges which, along with the related geology, are recognized as increasingly important components to a nearshore framework whose origins and evolution must be understood and inventoried to effectively manage the coastal zone.

Geologic control on the evolution of the inner shelf morphology offshore of the Mississippi barrier islands, northern Gulf of Mexico, USA

NASA Astrophysics Data System (ADS)

Flocks, James G.; Kindinger, Jack L.; Kelso, Kyle W.

2015-06-01

Between 2008 and 2013, high-resolution geophysical surveys were conducted around the Mississippi barrier islands and offshore. The sonar surveys included swath and single-beam bathymetry, sidescan, and chirp subbottom data collection. The geophysical data were groundtruthed using vibracore sediment collection. The results provide insight into the evolution of the inner shelf and the relationship between the near surface geologic framework and the morphology of the coastal zone. This study focuses on the buried Pleistocene fluvial deposits and late Holocene shore-oblique sand ridges offshore of Petit Bois Island and Petit Bois Pass. Prior to this study, the physical characteristics, evolution, and interrelationship of the ridges between both the shelf geology and the adjacent barrier island platform had not been evaluated. Numerous studies elsewhere along the coastal margin attribute shoal origin and sand-ridge evolution to hydrodynamic processes in shallow water (<20 m). Here we characterize the correlation between the geologic framework and surface morphology and demonstrate that the underlying stratigraphy must also be considered when developing an evolutionary conceptual model. It is important to understand this near surface, nearshore dynamic in order to understand how the stratigraphy influences the long-term response of the coastal zone to sea-level rise. The study also contributes to a growing body of work characterizing shore-oblique sand ridges which, along with the related geology, are recognized as increasingly important components to a nearshore framework whose origins and evolution must be understood and inventoried to effectively manage the coastal zone.

A modified adaptive algorithm of dealing with the high chirp when chirped pulses propagating in optical fiber

NASA Astrophysics Data System (ADS)

Wu, Lianglong; Fu, Xiquan; Guo, Xing

2013-03-01

In this paper, we propose a modified adaptive algorithm (MAA) of dealing with the high chirp to efficiently simulate the propagation of chirped pulses along an optical fiber for the propagation distance shorter than the "temporal focal length". The basis of the MAA is that the chirp term of initial pulse is treated as the rapidly varying part by means of the idea of the slowly varying envelope approximation (SVEA). Numerical simulations show that the performance of the MAA is validated, and that the proposed method can decrease the number of sampling points by orders of magnitude. In addition, the computational efficiency of the MAA compared with the time-domain beam propagation method (BPM) can be enhanced with the increase of the chirp of initial pulse.

Submarine mass wasting on the Ionian Calabrian margin

NASA Astrophysics Data System (ADS)

Ceramicola, S.; Forlin, E.; Coste, M.; Cova, A.; Praeg, D.; Fanucci, F.; Critelli, S.

2010-12-01

Mass wasting processes on continental margins have strong relevance both for geohazards of coastal areas and for the emplacement and monitoring of offshore infrastructures. The seabed dynamics of the Ionian Calabrian Margin (ICM) are currently being examined in the context of the project MAGIC (Marine Geohazard along the Italian Coasts). The objective of this project is the definition of elements that may constitute geological risk for coastal areas. The ICM is a tectonically-active margin, the structures of which reflect two main processes: frontal compression and fore-arc extension during the SE advance of the Calabrian accretionary prism since the late Miocene; and a rapid uplift (up to 1mm/yr) of onshore and shallow shelf areas since the mid-Pleistocene. These processes are reflected in different tectonic settings at seabed, which is characterized by a narrow continental shelf above a slope of irregular morphology in water depths of 150-2000 m. In the north, a broad slope is dominated by ridges and intervening basins that are the morphological expression of the southern Apennine fold-and-thrust belt; in the south, the continental slope descends steeply towards the deep-water Crotone and Spartivento fore-arc basins. The overall objective of this study is to map major features of mass wasting on the slopes of the ICM, investigate possible triggering mechanisms and consider the geohazards these features may represent for coastal areas. The study is based on an integrated analysis of multibeam morpho-bathymetric data and subbottom profiles, which together allow the recognition of four main types of mass wasting phenomena along the slopes of the ICM: 1) mass transport complexes (MTCs) within intra-slope basins - these are identified in the northern area, within the piggy-back basins: seabed imagery show the slopes of all the seabed ridges to be marked by headwall scarps recording widespread failure, while Chirp profiles show the adjacent basins to contain unstratified bodies indicative of debris flows buried beneath stratified sediments; multiple debris flows in several basins indicate one or more past episodes of failure that may be linked to activity on the faults bounding the structural highs. 2) slope slide scars - these are identified in two locations along the relatively steep southern Calabrian slope; the slide scars record several episodes of failure, linked to deposits within the deep-water basins that are yet to be identified. 3) possible gravity sliding - in one area of the southern Calabrian slope, elongate seabed features oriented subparallel to contours are observed, associated with diapiric structures that have been linked to Messinian salt observed on seismic profiles (Rossi & Sartori 1981); we suggest that the elongate seabed features may record a form of downslope sediment sliding above salt, resulting in features analogous to the cobblestone topography of the outer Calabrian Arc; 4) canyon headwalls - in the upper parts of all canyons, numerous headwall scarps are consistent with retrogressive activity of the canyons.

The Climate Hazards group InfraRed Precipitation (CHIRP) with Stations (CHIRPS): Development and Validation

NASA Astrophysics Data System (ADS)

Peterson, P.; Funk, C. C.; Husak, G. J.; Pedreros, D. H.; Landsfeld, M.; Verdin, J. P.; Shukla, S.

2013-12-01

CHIRP and CHIRPS are new quasi-global precipitation products with daily to seasonal time scales, a 0.05° resolution, and a 1981 to near real-time period of record. Developed by the Climate Hazards Group at UCSB and scientists at the U.S. Geological Survey Earth Resources Observation and Science Center specifically for drought early warning and environmental monitoring, CHIRPS provides moderate latency precipitation estimates that place observed hydrologic extremes in their historic context. Three main types of information are used in the CHIRPS: (1) global 0.05° precipitation climatologies, (2) time-varying grids of satellite-based precipitation estimates, and (3) in situ precipitation observations. CHIRP: The global grids of long-term (1980-2009) average precipitation were estimated for each month based on station data, averaged satellite observations, and physiographic parameters. 1981-present time-varying grids of satellite precipitation were derived from spatially varying regression models based on pentadal cold cloud duration (CCD) values and TRMM V7 training data. The CCD time-series were derived from the CPC and NOAA B1 datasets. Pentadal CCD-percent anomaly values were multiplied by pentadal climatology fields to produce low bias pentadal precipitation estimates. CHIRPS: The CHG station blending procedure uses the satellite-observed spatial covariance structure to assign relative weights to neighboring stations and the CHIRP values. The CHIRPS blending procedure is based on the expected correlation between precipitation at a given target location and precipitation at the locations of the neighboring observation stations. These correlations are estimated using the CHIRP fields. The CHG has developed an extensive archive of in situ daily, pentadal and monthly precipitation totals. The CHG database has over half a billion daily rainfall observations since 1980 and another half billion before 1980. Most of these observations come from four sets of global climate observations: the monthly Global Historical Climate Network version 2 archive, the daily Global Historical Climate Network archive, the Global Summary of the Day dataset (GSOD), and the daily Global Telecommunication System (GTS) archive provided by NOAA's Climate Prediction Center (CPC). A screening procedure was developed to flag and remove potential false zeros from the daily data, since these potentially spurious data can artificially suppress rainfall totals. Validation: Our validation focused on precipitation products with global coverage, long periods of record and near real-time availability: CHIRP, CHIRPS, CPC-Unified, CFS Reanalysis and ECMWF datasets were compared to GPCC and high quality datasets from Uganda, Colombia and the Sahel. The CHIRP and CHIRPS are shown to have low systematic errors (bias) and low mean absolute errors. Analyses in Uganda, Colombia and the Sahel indicate that the ECMWF, CPC-Unified and CFS-Reanalysis have large inhomogeneities, making them unsuitable for drought monitoring. The CHIRPS performance appears quite similar to research quality products like the GPCC and GPCP, but with higher resolution and lower latency.

Active stabilization of a rapidly chirped laser by an optoelectronic digital servo-loop control.

PubMed

Gorju, G; Jucha, A; Jain, A; Crozatier, V; Lorgeré, I; Le Gouët, J-L; Bretenaker, F; Colice, M

2007-03-01

We propose and demonstrate a novel active stabilization scheme for wide and fast frequency chirps. The system measures the laser instantaneous frequency deviation from a perfectly linear chirp, thanks to a digital phase detection process, and provides an error signal that is used to servo-loop control the chirped laser. This way, the frequency errors affecting a laser scan over 10 GHz on the millisecond timescale are drastically reduced below 100 kHz. This active optoelectronic digital servo-loop control opens new and interesting perspectives in fields where rapidly chirped lasers are crucial.

Investigation of Non-linear Chirp Coding for Improved Second Harmonic Pulse Compression.

PubMed

Arif, Muhammad; Ali, Muhammad Asim; Shaikh, Muhammad Mujtaba; Freear, Steven

2017-08-01

Non-linear frequency-modulated (NLFM) chirp coding was investigated to improve the pulse compression of the second harmonic chirp signal by reducing the range side lobe level. The problem of spectral overlap between the fundamental component and second harmonic component (SHC) was also investigated. Therefore, two methods were proposed: method I for the non-overlap condition and method II with the pulse inversion technique for the overlap harmonic condition. In both methods, the performance of the NLFM chirp was compared with that of the reference LFM chirp signals. Experiments were performed using a 2.25 MHz transducer mounted coaxially at a distance of 5 cm with a 1 mm hydrophone in a water tank, and the peak negative pressure of 300 kPa was set at the receiver. Both simulations and experimental results revealed that the peak side lobe level (PSL) of the compressed SHC of the NLFM chirp was improved by at least 13 dB in method I and 5 dB in method II when compared with the PSL of LFM chirps. Similarly, the integrated side lobe level (ISL) of the compressed SHC of the NLFM chirp was improved by at least 8 dB when compared with the ISL of LFM chirps. In both methods, the axial main lobe width of the compressed NLFM chirp was comparable to that of the LFM signals. The signal-to-noise ratio of the SHC of NLFM was improved by as much as 0.8 dB, when compared with the SHC of the LFM signal having the same energy level. The results also revealed the robustness of the NLFM chirp under a frequency-dependent attenuation of 0.5 dB/cm·MHz up to a penetration depth of 5 cm and a Doppler shift up to 12 kHz. Copyright © 2017 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Influence of cochlear traveling wave and neural adaptation on auditory brainstem responses.

PubMed

Junius, Dirk; Dau, Torsten

2005-07-01

The present study investigates the relationship between evoked responses to transient broadband chirps and responses to the same chirps when embedded in longer-duration stimuli. It examines to what extent the responses to the composite stimuli can be explained by a linear superposition of the responses to the single components, as a function of stimulus level. In the first experiment, a single rising chirp was temporally and spectrally embedded in two steady-state tones. In the second experiment, the stimulus consisted of a continuous alternating train of chirps: each rising chirp was followed by the temporally reversed (falling) chirp. In both experiments, the transitions between stimulus components were continuous. For stimulation levels up to approximately 70 dB SPL, the responses to the embedded chirp corresponded to the responses to the single chirp. At high stimulus levels (80-100 dB SPL), disparities occurred between the responses, reflecting a nonlinearity in the processing when neural activity is integrated across frequency. In the third experiment, the effect of within-train rate on wave-V response was investigated. The response to the chirp presented at a within-train rate of 95 Hz exhibited the same amplitude as that to the chirp presented in the traditional single-stimulus paradigm at a rate of 13 Hz. For a corresponding experiment with bandlimited chirps of 4 ms duration, where the within-train rate was 250 Hz, a clear reduction of the response amplitude was observed. This nonlinearity in terms of temporal processing most likely reflects effects of short-term adaptation. Overall, the results of the present study further demonstrate the importance of cochlear processing for the formation of brainstem potentials. The data may provide constraints on future models of peripheral processing in the human auditory system. The findings might also be useful for the development of effective stimulation paradigms in clinical applications.

Relationship Between Subduction Erosion, Seamount Subduction, Fluid Venting and Mound Formation on the Slope of the Costa Rican Continental Margin

NASA Astrophysics Data System (ADS)

Petersen, C.; Klaucke, I.; Weinrebe, W.

2006-12-01

The oceanic crust off central Costa Rica northwest of the Cocos Ridge is dominated by chains of seamounts rising 1-2 km above the seafloor with diameters of up to 20 km. The subduction of these seamounts leads to strong indentations, scars and slides on the continental margin. A smoother segment of about 80 km width is located offshore Nicoya peninsula. The segment ends at a fracture zone which marks the transition of oceanic crust created at the Cocos-Nazca spreading center (CNS) and at the East Pacific Rise (EPR). Offshore Nicaragua the incoming EPR crust is dominated by bending related faults. To investigate the relationship between subduction erosion, fluid venting and mound formation, multibeam bathymetry and high-resolution deep-tow sidescan sonar and sediment echosounder data were acquired during R/V Sonne cruises SO163 and SO173 (2002/2003). The deep-tow system consisted of a dual-frequency 75/410 kHz sidescan sonar and a 2-12 kHz chirp sub-bottom profiler. The connection of the observed seafloor features to deeper subduction related processes is obtained by analysis of multi-channel streamer (MCS) data acquired during cruises SO81 (1992) and BGR99 (1999). Data examples and interpretations for different settings along the margin are presented. Near the Fisher seamount the large Nicoya slump failed over the flank of a huge subducted seamount. The sidescan and echosounder data permit a detailed characterization of fault patterns and fluid escape structures around the headwall of the slump. Where the fracture zone separating CNS and EPR crust subducts, the Hongo mound field was mapped in detail. Several mounds of up to 100 m height are located in line with a scar possibly created by a subducting ridge of the fracture zone. MCS data image a topographic high on the subducting oceanic crust beneath the mound field which lead to uplift and possibly enabled ascent of fluids from the subducting plate. The combined analysis of geoacoustic and seismic MCS data confirms that fracturing of the continental slope by subducting oceanic relief is a major mechanism which causes the opening of pathways for fluids to migrate upwards.

Distinctive Geomorphology of Gas Venting and Near Seafloor Gas Hydrate-Bearing sites

NASA Astrophysics Data System (ADS)

Paull, C. K.; Caress, D. W.; Lundsten, E.; Anderson, K.; Gwiazda, R.; McGann, M. L.; Edwards, B. D.; Riedel, M.; Herguera, J.

2012-12-01

High-resolution multibeam bathymetry and chirp seismic-reflection profiles collected with an Autonomous Underwater Vehicle (AUV) complimented by Remotely Operated Vehicle (ROV) observations and sampling reveal the fine scale geomorphology associated with gas venting and/or near subsurface gas hydrate accumulations along the Pacific North American continental margin (Santa Monica Basin, Hydrate Ridge, Eel River, Barkley Canyon, and Bullseye Vent) and along the transform faults in the Gulf of California. At the 1 m multibeam grid resolution of the new data, distinctive features and textures that are undetectable at lower resolution, show the impact of gas venting, gas hydrate development, and related phenomena on the seafloor morphology. Together a suite of geomorphic characteristics illustrates different stages in the development of seafloor gas venting systems. The more mature and/or impacted areas are associated with widespread exposures of methane-derived carbonates, which form broken and irregular seafloor pavements with karst-like voids in between the cemented blocks. These mature areas also contain elevated features >10 m high and circular seafloor craters with diameters of 3-50 m that appear to be associated with missing sections of the original seafloor. Smaller mound-like features (<10 m in diameter and 1-3 m higher than the surrounding seafloor) occur at multiple sites. Solid lenses of gas hydrate are occasionally exposed along fractures on the sides of these mounds and suggest that these are push-up features associated with gas hydrate growth within the near seafloor sediments. The youngest appearing features are associated with more-subtle (<3 m in diameter and ~0.5 m high) seafloor mounds, the crests of which are crossed with small cracks lined with white bacterial mats. ROV-collected (<1.5 m long) cores obtained from these subtle mounds encountered a hard layer at 30-60 cm sub-bottom. When this layer was penetrated, methane bubbles gushed out and continued to flow out for over an hour. These observations indicate that these small mounds are young features that trap considerable volumes of gas near the seafloor. Together these observations reveal the integrated effect that gas and/or gas hydrate occurrences can have on the seafloor. The existence of gaseous methane within ~1 m of the seafloor has intriguing implications as to the geo-hazard potential of such sites.

The history of retreat dynamics of Petermann Glacier inferred from submarine glacial landforms

NASA Astrophysics Data System (ADS)

Jakobsson, M.; Hogan, K.; Mayer, L. A.; Mix, A. C.; Jerram, K.; Mohammad, R.; Stranne, C.; Eriksson, B.

2016-12-01

Preserved submarine glacial landforms produced at the base and margin of ice sheets and outlet glaciers comprise records of past ice dynamics complementary to modern glaciological process studies. The Petermann 2015 Expedition on the Swedish icebreaker Oden systematically mapped approximately 3100 km2 of the seafloor in Petermann Fjord and the adjacent Hall Basin of Nares Strait, northwest Greenland, with an EM122 (12 kHz) multibeam and SBP120 (2-7 kHz) chirp sub-bottom profiler. Complete, overlapping mapping coverage permitted compilation of a high-quality (15x15m) digital terrain model (DTM). In addition, the seafloor at the margin of one of the smaller outlet glaciers draining into the Petermann Fjord and selected shallow areas along the coast were mapped using a small survey boat (RV Skidbladner), equipped with an EM2040 (200-300 kHz) multibeam. High-resolution (2 x 2 m) DTMs were compiled from the RV Skidbladner surveys. The seafloor morphology of Petermann Fjord and adjacent Hall Basin is dominated by a stunning glacial landform record comprising the imprints of Petermann Glacier's retreat dynamics since the Last Glacial Maximum (LGM). The entrance to Petermann Fjord consists of a prominent bathymetric sill formed by a large well-develop grounding zone wedge that undoubtedly represents a stability point during the glacier's retreat history. The deepest entrance to the fjord is 443 m and located on the southern side of this grounding zone wedge. Outside of this grounding zone wedge in Hall Basin, less well developed grounding zones appears to be present. The landform assemblage in between the grounding zones, in particular the lack of retreat ridges, may signify a leap-frog behavior of the glacier's retreat; rapid break-up and disintegration of the outlet glacier causing retreat back to the next stability point dictated by the local bedrock geology. While numerous classical glacial landforms characteristic for fast flowing ice streams are identified, the multibeam bathymetry also reveals an enigmatic, toilet bowl-shaped features whose origin is still unclear. The collected data during the Petermann 2015 Expedition will among other things provide new insights into ice shelf-ocean interactions, essential to projecting future climate impacts on Greenland and global sea level changes.

Tectonic activity and stratigraphic history over the last 130-540 ka on the Southern Shelf of the Sea of Marmara, western North Anatolian Fault, Turkey

NASA Astrophysics Data System (ADS)

Smith, W. H.; Grall, C.; Sorlien, C. C.; Steckler, M. S.; Okay, S.; Cormier, M. H.; Seeber, L.; Cifci, G.; Dondurur, D.

2016-12-01

The submerged section of the North Anatolian Fault in the Sea of Marmara, which corresponds to the dextral plate boundary between Eurasia and Anatolia, poses strong hazard for earthquakes and subsequent submarine landslides and tsunamis in the vicinity of the highly populated region of Istanbul. Most of the right-lateral slip is accommodated by the Northern Branch of the North Anatolian Fault (NAF-N), which crosses the central part of the Sea of Marmara and is capable of an earthquake with a magnitude greater than 7. However, both the geology and the geodesy suggest that the NAF-N accommodates only 3/4 of the total slip between the plates. The deformation mechanisms for the rest of the strain (slip distributed on secondary faults, strain partitioning, and diffuse deformation) remains unexplained. Other fault systems, primarily south of the NAF-N, are shown to be important regarding the tectonic evolution of the Sea of Marmara. However, the activity of these peripheral fault systems as well as their relationships with the NAF-N need to be further constrained. For this purpose, a dense dataset of 2D geophysical images (high-resolution seismic reflection data, sparker reflection, CHIRP sub-bottom profiling), as well as multibeam bathymetry, have been acquired in 2008, 2010, 2013 and 2014 during TAMAM and SOMAR cruises, primarily in the southern shelf of the Sea of Marmara. The 15-20 km-wide southern shelf ledge is relatively flat and mostly shallower than 90 m. In this shallow marine region, we have been able to image the detailed stratigraphic record associated with the 125 ka and younger glacio-eustatic cycles and, notably, to identify paleo-shorelines at water depths shallower than 100 m. Several erosional unconformities, laterally correlative to low-stand deltas have been regionally linked to the stratigraphic boundaries previously defined for the last 130-540 ka. While the present-day shelf is relatively flat, a shallow ridge separates the inner and outer parts of the shelf. This ridge exhibits erosional unconformities, and a set of transtensive faults are mapped along its length. We show that parts of these faults were active during the last 540 ka. By estimating fault slip and folding rates along these structures, we estimate the deformation that they accommodated over this time-frame.

Habituation analysis of chirp vs. tone evoked auditory late responses.

PubMed

Kern, Kevin; Royter, Vladislav; Corona-Strauss, Farah I; Mariam, Mai; Strauss, Daniel J

2010-01-01

We have recently shown that tone evoked auditory late responses are able to proof that habituation is occurring [1], [2]. The sweep to sweep analysis using time scale coherence method from [1] is used. Where clear results using tone evoked ALRs were obtained. Now it is of interest how does the results behave using chirp evoked ALRs compared to tone evoked ALRs so that basilar membrane dispersion is compensated. We presented three different tone bursts and three different band limited chirps to 10 subjects using two different loudness levels which the subjects determined themselves before as medium and uncomfortably loud. The 3 chirps are band limited within 3 different ranges, the chirp with the lowest center frequency has the smallest range (according to octave-band). Chirps and tone bursts are using the same center frequencies.

Suppression of stimulated Brillouin scattering in optical fibers using a linearly chirped diode laser.

PubMed

White, J O; Vasilyev, A; Cahill, J P; Satyan, N; Okusaga, O; Rakuljic, G; Mungan, C E; Yariv, A

2012-07-02

The output of high power fiber amplifiers is typically limited by stimulated Brillouin scattering (SBS). An analysis of SBS with a chirped pump laser indicates that a chirp of 2.5 × 10(15) Hz/s could raise, by an order of magnitude, the SBS threshold of a 20-m fiber. A diode laser with a constant output power and a linear chirp of 5 × 10(15) Hz/s has been previously demonstrated. In a low-power proof-of-concept experiment, the threshold for SBS in a 6-km fiber is increased by a factor of 100 with a chirp of 5 × 10(14) Hz/s. A linear chirp will enable straightforward coherent combination of multiple fiber amplifiers, with electronic compensation of path length differences on the order of 0.2 m.

Perturbation-theory analysis of ionization by a chirped few-cycle attosecond pulse

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

Pronin, E. A.; Starace, Anthony F.; Peng Liangyou

2011-07-15

The angular distribution of electrons ionized from an atom by a chirped few-cycle attosecond pulse is analyzed using perturbation theory (PT), keeping terms in the transition amplitude up to second order in the pulse electric field. The dependence of the asymmetry in the ionized electron distributions on both the chirp and the carrier-envelope phase (CEP) of the pulse are explained using a simple analytical formula that approximates the exact PT result. This approximate formula (in which the chirp dependence is explicit) reproduces reasonably well the chirp-dependent oscillations of the electron angular distribution asymmetries found numerically by Peng et al. [Phys.more » Rev. A 80, 013407 (2009)]. It can also be used to determine the chirp rate of the attosecond pulse from the measured electron angular distribution asymmetry.« less

Comparison of ABR response amplitude, test time, and estimation of hearing threshold using frequency specific chirp and tone pip stimuli in newborns.

PubMed

Ferm, Inga; Lightfoot, Guy; Stevens, John

2013-06-01

To evaluate the auditory brainstem response (ABR) amplitudes evoked by tone pip and narrowband chirp (NB CE-Chirp) stimuli when testing post-screening newborns and to determine the difference in estimated hearing level correction values. Tests were performed with tone pips and NB CE-Chirps at 4 kHz or 1 kHz. The response amplitude, response quality (Fmp), and residual noise were compared for both stimuli. Thirty babies (42 ears) who passed our ABR discharge criterion at 4 kHz following referral from their newborn hearing screen. Overall, NB CE-Chirp responses were 64% larger than the tone pip responses, closer to those evoked by clicks. Fmp was significantly higher for NB CE-Chirps. It is anticipated that there could be significant reductions in test time for the same signal to noise ratio by using NB CE-Chirps when testing newborns. This effect may vary in practice and is likely to be most beneficial for babies with low amplitude ABR responses. We propose that the ABR nHL threshold to eHL correction for NB CE-Chirps should be approximately 5 dB less than the corrections for tone pips at 4 and 1 kHz.

Quadratic Frequency Modulation Signals Parameter Estimation Based on Two-Dimensional Product Modified Parameterized Chirp Rate-Quadratic Chirp Rate Distribution.

PubMed

Qu, Zhiyu; Qu, Fuxin; Hou, Changbo; Jing, Fulong

2018-05-19

In an inverse synthetic aperture radar (ISAR) imaging system for targets with complex motion, the azimuth echo signals of the target are always modeled as multicomponent quadratic frequency modulation (QFM) signals. The chirp rate (CR) and quadratic chirp rate (QCR) estimation of QFM signals is very important to solve the ISAR image defocus problem. For multicomponent QFM (multi-QFM) signals, the conventional QR and QCR estimation algorithms suffer from the cross-term and poor anti-noise ability. This paper proposes a novel estimation algorithm called a two-dimensional product modified parameterized chirp rate-quadratic chirp rate distribution (2D-PMPCRD) for QFM signals parameter estimation. The 2D-PMPCRD employs a multi-scale parametric symmetric self-correlation function and modified nonuniform fast Fourier transform-Fast Fourier transform to transform the signals into the chirp rate-quadratic chirp rate (CR-QCR) domains. It can greatly suppress the cross-terms while strengthening the auto-terms by multiplying different CR-QCR domains with different scale factors. Compared with high order ambiguity function-integrated cubic phase function and modified Lv's distribution, the simulation results verify that the 2D-PMPCRD acquires higher anti-noise performance and obtains better cross-terms suppression performance for multi-QFM signals with reasonable computation cost.

Design of bent waveguide semiconductor lasers using nonlinear equivalent chirp

NASA Astrophysics Data System (ADS)

Li, Lianyan; Shi, Yuechun; Zhang, Yunshan; Chen, Xiangfei

2018-01-01

Reconstruction equivalent chirp (REC) technique is widely used in the design and fabrication of semiconductor laser arrays and tunable lasers with low cost and high wavelength accuracy. Bent waveguide is a promising method to suppress the zeroth order resonance, which is an intrinsic problem in REC technique. However, it may introduce basic grating chirp and deteriorate the single longitudinal mode (SLM) property of the laser. A nonlinear equivalent chirp pattern is proposed in this paper to compensate the grating chirp and improve the SLM property. It will benefit the realization of low-cost Distributed feedback (DFB) semiconductor laser arrays with accurate lasing wavelength.

Structure of the southern Juan de Fuca Ridge from seismic reflection records

USGS Publications Warehouse

Morton, Janet L.; Sleep, Norman H.; Normark, William R.; Tompkins, Donald H.

1987-01-01

Twenty-four-channel seismic reflection records were obtained from the axial region of the southern Juan de Fuca Ridge. Two profiles are normal to the strike of the spreading center and intersect the ridge at latitude 44°40′N and 45°05′N; a third profile extends south along the ridge axis from latitude 45°20′N and crosses the Blanco Fracture Zone. Processing of the axial portions of the cross-strike lines resolved a weak reflection centered beneath the axis. The reflector is at a depth similar to seismically detected magma chambers on the East Pacific Rise and a Lau Basin spreading center; we suggest that the reflector represents the top of an axial magma chamber. In the migrated sections the top of the probable magma chamber is relatively flat and 1–2 km wide, and the subbottom depth of the chamber is greater where the depth to the ridge axis is greater.

Radar echo processing with partitioned de-ramp

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

Dubbert, Dale F.; Tise, Bertice L.

2013-03-19

The spurious-free dynamic range of a wideband radar system is increased by apportioning de-ramp processing across analog and digital processing domains. A chirp rate offset is applied between the received waveform and the reference waveform that is used for downconversion to the intermediate frequency (IF) range. The chirp rate offset results in a residual chirp in the IF signal prior to digitization. After digitization, the residual IF chirp is removed with digital signal processing.

Chirped Peregrine solitons in a class of cubic-quintic nonlinear Schrödinger equations.

PubMed

Chen, Shihua; Baronio, Fabio; Soto-Crespo, Jose M; Liu, Yi; Grelu, Philippe

2016-06-01

We shed light on the fundamental form of the Peregrine soliton as well as on its frequency chirping property by virtue of a pertinent cubic-quintic nonlinear Schrödinger equation. An exact generic Peregrine soliton solution is obtained via a simple gauge transformation, which unifies the recently-most-studied fundamental rogue-wave species. We discover that this type of Peregrine soliton, viable for both the focusing and defocusing Kerr nonlinearities, could exhibit an extra doubly localized chirp while keeping the characteristic intensity features of the original Peregrine soliton, hence the term chirped Peregrine soliton. The existence of chirped Peregrine solitons in a self-defocusing nonlinear medium may be attributed to the presence of self-steepening effect when the latter is not balanced out by the third-order dispersion. We numerically confirm the robustness of such chirped Peregrine solitons in spite of the onset of modulation instability.

Extension of supercontinuum spectrum, generated in polarization-maintaining photonic crystal fiber, using chirped femtosecond pulses

NASA Astrophysics Data System (ADS)

Vengelis, Julius; Jarutis, Vygandas; Sirutkaitis, Valdas

2018-01-01

We present results of experimental and numerical investigation of supercontinuum (SC) generation in polarization-maintaining photonic crystal fiber (PCF) using chirped femtosecond pulses. The initial unchirped pump pulse source was a mode-locked Yb:KGW laser generating 52-nJ energy, 110-fs duration pulses at 1030 nm with a 76-MHz repetition rate. The nonlinear medium was a 32-cm-long polarization-maintaining PCF manufactured by NKT Photonics A/S. We demonstrated the influence of pump pulse chirp on spectral characteristics of a SC. We showed that by chirping pump pulses positively or negatively one can obtain a broader SC spectrum than in the case of unchirped pump pulses at the same peak power. Moreover, the extension can be controlled by changing the amount of pump pulse chirp. Numerical simulation results also indicated that pump pulse chirp yields an extension of SC spectrum.

Automatic Parametrization of Somatosensory Evoked Potentials With Chirp Modeling.

PubMed

Vayrynen, Eero; Noponen, Kai; Vipin, Ashwati; Thow, X Y; Al-Nashash, Hasan; Kortelainen, Jukka; All, Angelo

2016-09-01

In this paper, an approach using polynomial phase chirp signals to model somatosensory evoked potentials (SEPs) is proposed. SEP waveforms are assumed as impulses undergoing group velocity dispersion while propagating along a multipath neural connection. Mathematical analysis of pulse dispersion resulting in chirp signals is performed. An automatic parameterization of SEPs is proposed using chirp models. A Particle Swarm Optimization algorithm is used to optimize the model parameters. Features describing the latencies and amplitudes of SEPs are automatically derived. A rat model is then used to evaluate the automatic parameterization of SEPs in two experimental cases, i.e., anesthesia level and spinal cord injury (SCI). Experimental results show that chirp-based model parameters and the derived SEP features are significant in describing both anesthesia level and SCI changes. The proposed automatic optimization based approach for extracting chirp parameters offers potential for detailed SEP analysis in future studies. The method implementation in Matlab technical computing language is provided online.

Generation of an isolated sub-40-as pulse using two-color laser pulses: Combined chirp effects

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

Feng, Liqiang; Chu, Tianshu; Institute for Computational Sciences and Engineering, Laboratory of New Fiber Materials and Modern Textile, the Growing Base for State Key Laboratory, Qingdao University, Qingdao, 266071

2011-11-15

In this paper, we theoretically discuss the combined chirp effects on the isolated attosecond generation when a model Ar is exposed to an intense 5-fs, 800-nm fundamental chirped pulse combined with a weak 10-fs, 1200-nm controlling chirped pulse. It shows that for the case of the chirp parameters {beta}{sub 1} = 6.1 (corresponding to the 800-nm field) and {beta}{sub 2} = 4.0 (corresponding to the 1200-nm field), both the harmonic cutoff energy and the supercontinuum can be remarkably extended resulting in a 663-eV bandwidth. Moreover, due to the introduction of the chirps, the short quantum path is selected to contributemore » to the harmonic spectrum. Finally, by superposing a properly selected harmonic spectrum in the supercontinuum region, an isolated pulse as short as 31 as (5 as) is generated without (with) phase compensation.« less

The Climate Hazards group InfraRed Precipitation with Stations (CHIRPS) dataset and its applications in drought risk management

NASA Astrophysics Data System (ADS)

Shukla, Shraddhanand; Funk, Chris; Peterson, Pete; McNally, Amy; Dinku, Tufa; Barbosa, Humberto; Paredes-Trejo, Franklin; Pedreros, Diego; Husak, Greg

2017-04-01

A high quality, long-term, high-resolution precipitation dataset is key for supporting drought-related risk management and food security early warning. Here, we present the Climate Hazards group InfraRed Precipitation with Stations (CHIRPS) v2.0, developed by scientists at the University of California, Santa Barbara and the U.S. Geological Survey Earth Resources Observation and Science Center under the direction of Famine Early Warning Systems Network (FEWS NET). CHIRPS is a quasi-global precipitation product and is made available at daily to seasonal time scales with a spatial resolution of 0.05° and a 1981 to near real-time period of record. We begin by describing the three main components of CHIRPS - a high-resolution climatology, time-varying cold cloud duration precipitation estimates, and in situ precipitation estimates, and how they are combined. We then present a validation of this dataset and describe how CHIRPS is being disseminated and used in different applications, such as large-scale hydrologic models and crop water balance models. Validation of CHIRPS has focused on comparisons with precipitation products with global coverage, long periods of record and near real-time availability such as CPC-Unified, CFS Reanalysis and ECMWF datasets and datasets such GPCC and GPCP that incorporate high quality in situ datasets from places such as Uganda, Colombia, and the Sahel. The CHIRPS is shown to have low systematic errors (bias) and low mean absolute errors. We find that CHIRPS performance appears quite similar to research quality products like the GPCC and GPCP, but with higher resolution and lower latency. We also present results from independent validation studies focused on South America and East Africa. CHIRPS is currently being used to drive FEWS NET Land Data Assimilation System (FLDAS), that incorporates multiple hydrologic models, and Water Requirement Satisfaction Index (WRSI), which is a widely used crop water balance model. The outputs (such as soil moisture and runoff) from these models are being used for real-time drought monitoring in Africa. Under support from the USAID FEWS NET, CHG/USGS has developed a two way strategy for dissemination of CHIRPS and related products (e.g. FLDAS, WRSI) and incorporate contributed station data. For example, we are currently working with partners in Mexico (Conagua), Southern Africa (SASSCAL), Colombia (IDEAM), Nigeria (Kukua), Somalia (SWALIM) and Ethiopia (NMA). These institutions provide in situ observations which enhance the CHIRPS and CHIRPS provides feedback on data quality. The CHIRPS is then placed in a web accessible geospatial database. Partners in these countries can then access CHIRPS and other outputs, and display this information using web-based mapping tools. This provides a win-win collaboration, leading to improved globally accessible precipitation estimates and improved climate services in developing nations.

Latest Holocene evolution and human disturbance of a channel segment in the Hudson River Estuary

USGS Publications Warehouse

Klingbeil, A.D.; Sommerfield, C.K.

2005-01-01

The latest Holocene sedimentary record of a cohesive channel and subtidal shoal in the lower Hudson River Estuary was examined to elucidate natural (sea-level rise, sediment transport) and anthropogenic (bulkheading, dredging) influences on the recent morphodynamic evolution of the system. To characterize the seafloor and shallow subbottom, ??? 100 km of high-resolution seismic reflection profiles (chirp) were collected within a 20-km reach of the estuary and correlated with sediment lithologies provided by eight vibracores recovered along seismic lines. Sediment geochronology with 137Cs and 14C was used to estimate intermediate and long-term sedimentation rates, respectively, and historical bathymetric data were analyzed to identify regional patterns of accretion and erosion, and to quantify changes in channel geometry and sediment volume. The shoal lithosome originated around 4 ka presumably with decelerating eustatic sea level rise during the latest Holocene. Long-term sedimentation rates on the shoal (2.3-2.6 mm/yr) are higher than in the channel (2 mm/yr) owing to hydrodynamic conditions that preferentially sequester suspended sediment on the western side of the estuary. As a result, the shoal accretes oblique to the principal axis of tidal transport, and more rapidly than the channel to produce an asymmetric cross-section. Shoal deposits consist of tidally bedded muds and are stratified by minor erosion surfaces that seismic profiles reveal to extend for 10s of meters to kilometers. The frequency and continuity of these surfaces suggest that the surficial shoal is catastrophically stripped on decadal-centennial time scales by elevated tidal flows; tidal erosion maintains the shoal at a uniform depth below sea level and prevents it from transitioning to an intertidal environment. Consequently, the long-term sedimentation rate approximates the rate of sea-level rise in the lower estuary (1-3 mm/yr). After the mid 1800s, the natural geometry of the lower Hudson River Estuary changed rapidly in response to engineering works that forced the channel to self-deepen. Analysis of historical bathymetric data indicates that the channel lost an estimated 3 ?? 106 tons of sediment between ca. 1939 and 2002 (50,000 tons/yr average) by subaqueous erosion, increasing in depth by as much as 4 m in places. Erosion appears to have been concurrent with systematic bulkheading of the shoreline after ca. 1865, which decreased the estuary surface area by ??? 19% overall. Evidently, self-deepening of the channel is a morphodynamic adjustment to reestablish equilibrium cross-sectional area, yet the state of this change locally and elsewhere in the estuary is unknown. Subaqueous erosion documented in this study is a significant source of sediment with implications to the sediment budget and environmental quality of the Hudson River Estuary. ?? 2005 Elsevier B.V. All rights reserved.

Phylogenetic comparative analysis of electric communication signals in ghost knifefishes (Gymnotiformes: Apteronotidae).

PubMed

Turner, Cameron R; Derylo, Maksymilian; de Santana, C David; Alves-Gomes, José A; Smith, G Troy

2007-12-01

Electrocommunication signals in electric fish are diverse, easily recorded and have well-characterized neural control. Two signal features, the frequency and waveform of the electric organ discharge (EOD), vary widely across species. Modulations of the EOD (i.e. chirps and gradual frequency rises) also function as active communication signals during social interactions, but they have been studied in relatively few species. We compared the electrocommunication signals of 13 species in the largest gymnotiform family, Apteronotidae. Playback stimuli were used to elicit chirps and rises. We analyzed EOD frequency and waveform and the production and structure of chirps and rises. Species diversity in these signals was characterized with discriminant function analyses, and correlations between signal parameters were tested with phylogenetic comparative methods. Signals varied markedly across species and even between congeners and populations of the same species. Chirps and EODs were particularly evolutionarily labile, whereas rises differed little across species. Although all chirp parameters contributed to species differences in these signals, chirp amplitude modulation, frequency modulation (FM) and duration were particularly diverse. Within this diversity, however, interspecific correlations between chirp parameters suggest that mechanistic trade-offs may shape some aspects of signal evolution. In particular, a consistent trade-off between FM and EOD amplitude during chirps is likely to have influenced the evolution of chirp structure. These patterns suggest that functional or mechanistic linkages between signal parameters (e.g. the inability of electromotor neurons increase their firing rates without a loss of synchrony or amplitude of action potentials) constrain the evolution of signal structure.

Competing collinear and noncollinear interactions in chirped quasi-phase-matched optical parametric amplifiers

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

Charbonneau-Lefort, Mathieu; Afeyan, Bedros; Fejer, M. M.

Chirped quasi-phase-matched optical parametric amplifiers (chirped QPM OPAs) are investigated experimentally. The measured collinear gain is constant over a broad bandwidth, which makes these devices attractive candidates for use in femtosecond amplifier systems. The experiment also shows that chirped QPM OPAs support noncollinear gain-guided modes. These modes can dominate the desired collinear gain and generate intense parametric fluorescence. Finally, design guidelines to mitigate these parasitic processes are discussed.

Auditory Brainstem Response Thresholds to Air- and Bone-Conducted CE-Chirps in Neonates and Adults.

PubMed

Cobb, Kensi M; Stuart, Andrew

2016-08-01

The purpose of this study was to compare auditory brainstem response (ABR) thresholds to air- and bone-conducted CE-Chirps in neonates and adults. Thirty-two neonates with no physical or neurologic challenges and 20 adults with normal hearing participated. ABRs were acquired with a starting intensity of 30 dB normal hearing level (nHL). The lowest stimulus intensity level at which a wave V was identifiable and replicable was considered the ABR threshold. ABR thresholds to air-conducted CE-Chirps were 9.8 dB nHL for neonates and adults. ABR thresholds to bone-conducted CE-Chirps were 3.8 and 13.8 dB nHL for neonates and adults, respectively. The difference in ABR thresholds to bone-conducted CE-Chirps was significantly different (p < .0001, ηp2 = .45). Adults had significantly larger wave V amplitudes to air- (p < .0001, ηp2 = .50) and bone-conducted (p = .013, ηp2 = .15) CE-Chirps at a stimulus intensity of 30 dB nHL. At the same intensity, adults evidenced significantly shorter wave V latencies (p < .0001, ηp2 = .49) only with air-conducted CE-chirps. The difference in ABR thresholds and wave V latencies to air- and bone-conducted CE-Chirps between neonates and adults may be attributed to a disparity in effective signal delivery to the cochlea.

Validation of the CHIRPS Satellite Rainfall Estimates over Eastern of Africa

NASA Astrophysics Data System (ADS)

Dinku, T.; Funk, C. C.; Tadesse, T.; Ceccato, P.

2017-12-01

Long and temporally consistent rainfall time series are essential in climate analyses and applications. Rainfall data from station observations are inadequate over many parts of the world due to sparse or non-existent observation networks, or limited reporting of gauge observations. As a result, satellite rainfall estimates have been used as an alternative or as a supplement to station observations. However, many satellite-based rainfall products with long time series suffer from coarse spatial and temporal resolutions and inhomogeneities caused by variations in satellite inputs. There are some satellite rainfall products with reasonably consistent time series, but they are often limited to specific geographic areas. The Climate Hazards Group Infrared Precipitation (CHIRP) and CHIRP combined with station observations (CHIRPS) are recently produced satellite-based rainfall products with relatively high spatial and temporal resolutions and quasi-global coverage. In this study, CHIRP and CHIRPS were evaluated over East Africa at daily, dekadal (10-day) and monthly time scales. The evaluation was done by comparing the satellite products with rain gauge data from about 1200 stations. The is unprecedented number of validation stations for this region covering. The results provide a unique region-wide understanding of how satellite products perform over different climatic/geographic (low lands, mountainous regions, and coastal) regions. The CHIRP and CHIRPS products were also compared with two similar satellite rainfall products: the African Rainfall Climatology version 2 (ARC2) and the latest release of the Tropical Applications of Meteorology using Satellite data (TAMSAT). The results show that both CHIRP and CHIRPS products are significantly better than ARC2 with higher skill and low or no bias. These products were also found to be slightly better than the latest version of the TAMSAT product. A comparison was also done between the latest release of the TAMSAT product (TAMSAT3) and the earlier version(TAMSAT2), which has shown that the latest version is a substantial improvement over the previous one, particularly with regards to the bias statistics.

Validation of automated supervised segmentation of multibeam backscatter data from the Chatham Rise, New Zealand

NASA Astrophysics Data System (ADS)

Hillman, Jess I. T.; Lamarche, Geoffroy; Pallentin, Arne; Pecher, Ingo A.; Gorman, Andrew R.; Schneider von Deimling, Jens

2018-06-01

Using automated supervised segmentation of multibeam backscatter data to delineate seafloor substrates is a relatively novel technique. Low-frequency multibeam echosounders (MBES), such as the 12-kHz EM120, present particular difficulties since the signal can penetrate several metres into the seafloor, depending on substrate type. We present a case study illustrating how a non-targeted dataset may be used to derive information from multibeam backscatter data regarding distribution of substrate types. The results allow us to assess limitations associated with low frequency MBES where sub-bottom layering is present, and test the accuracy of automated supervised segmentation performed using SonarScope® software. This is done through comparison of predicted and observed substrate from backscatter facies-derived classes and substrate data, reinforced using quantitative statistical analysis based on a confusion matrix. We use sediment samples, video transects and sub-bottom profiles acquired on the Chatham Rise, east of New Zealand. Inferences on the substrate types are made using the Generic Seafloor Acoustic Backscatter (GSAB) model, and the extents of the backscatter classes are delineated by automated supervised segmentation. Correlating substrate data to backscatter classes revealed that backscatter amplitude may correspond to lithologies up to 4 m below the seafloor. Our results emphasise several issues related to substrate characterisation using backscatter classification, primarily because the GSAB model does not only relate to grain size and roughness properties of substrate, but also accounts for other parameters that influence backscatter. Better understanding these limitations allows us to derive first-order interpretations of sediment properties from automated supervised segmentation.

Effect of chromatic-dispersion-induced chirp on the temporal coherence properties of individual beams from spontaneous four-wave mixing

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

Ma Xiaoxin; Li Xiaoying; Cui Liang

2011-08-15

Temporal coherence of individual signal or idler beam, determined by the spectral correlation property of photon pairs, is important for realizing quantum interference among independent sources. Based on spontaneous four-wave mixing in optical fibers, we study the effect of chirp on the temporal coherence property by introducing a different amount of chirp into either the pulsed pump or individual signal (idler) beam. The investigation shows that the pump chirp induces additional frequency correlation into photon pairs; the mutual spectral correlation of photon pairs and the coherence of individual beam can be characterized by measuring the intensity correlation function g{sup (2)}more » of the individual beam. To improve the coherence degree, the pump chirp should be minimized. Moreover, a Hong-Ou-Mandel-type two-photon interference experiment with the signal beams generated in two different fibers illustrates that the chirp of the individual signal (idler) beam does not change the temporal coherence degree, but affects the temporal mode matching. To achieve high visibility among multiple sources, apart from improving the coherence degree, mode matching should be optimized by managing the chirps of individual beams.« less

Simulation of Chirping Avalanche in Neighborhood of TAE gap

NASA Astrophysics Data System (ADS)

Berk, Herb; Breizman, Boris; Wang, Ge; Zheng, Linjin

2016-10-01

A new kinetic code, CHIRP, focuses on the nonlinear response of resonant energetic particles (EPs) that destabilize Alfven waves which then can produce hole and clump phase space chirping structures, while the background plasma currents are assumed to respond linearly to the generated fields. EP currents are due to the motion arising from the perturbed field that is time averaged over an equilibrium orbit. A moderate EP source produces TAE chirping structures that have a limited range of chirping that do not reach the continuum. When the source is sufficiently strong, an EPM is excited in the lower continuum and it chirps rapidly downward as its amplitude rapidly grows in time. This response resembles the experimental observation of an avalanche, which occurs after a series of successive chirping events with a modest frequency shift, and then suddenly a rapid large amplitude and rapid frequency burst to low frequency with the loss of EPs. From these simulation observations we propose that in the experiment the EP population is slowly increasing to the point where the EPM is eventually excited. Supported by SCIDAC Center for Nonlinear Simulation of Energetic Particles Burning Plasmas (CSEP).

Control of femtosecond laser driven retro-Diels-Alder-like reaction of dicyclopentadiene

PubMed Central

Das, Dipak Kumar; Goswami, Tapas; Goswami, Debabrata

2013-01-01

Using femtosecond time resolved degenerate pump-probe mass spectrometry coupled with simple linearly chirped frequency modulated pulse, we elucidate that the dynamics of retro-Diels-Alder-like reaction of diclopentadiene (DCPD) to cyclopentadiene (CPD) in supersonic molecular beam occurs in ultrafast time scale. Negatively chirped pulse enhances the ion yield of CPD, as compared to positively chirped pulse. This indicates that by changing the frequency (chirp) of the laser pulse we can control the ion yield of a chemical reaction. PMID:23814449

Ultralow chirp photonic crystal fiber Mach-Zehnder interferometer.

PubMed

Carvalho, William O F; Spadoti, Danilo H; Silvestre, Enrique; Beltran-Mejia, Felipe

2018-05-20

A photonic crystal fiber Mach-Zehnder interferometer design was optimized to obtain high performance and ultralow chirp. Two long-period gratings were used to excite the cladding modes, and the rich structure of the cladding was tailored to obtain a slightly chirped free spectral range, as required by the Telecommunication Standardization Sector of the International Telecommunication Union (ITU-T) Norm G.694.1. Finally, a fabrication tolerance analysis was performed. The advantages of the proposed device are an ultralow chirp, high bandwidth, and fabrication robustness tolerance.

Dynamic Chirp Control and Pulse Compression for Attosecond High-Order Harmonic Emission

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

Zheng Yinghui; Zeng Zhinan; Zou Pu

2009-07-24

We propose a scheme to compensate dynamically the intrinsic chirp of the attosecond harmonic pulses. By adding a weak second harmonic laser field to the driving laser field, the chirp compensation can be varied from the negative to the positive continuously by simply adjusting the relative time delay between the two-color pulses. Using this technique, the compensation of the negative chirp in harmonic emission is demonstrated experimentally for the first time and the nearly transform-limited attosecond pulse trains are obtained.

Auditory brainstem responses to broad-band chirps: amplitude growth functions in sedated and anaesthetised infants.

PubMed

Mühler, Roland; Rahne, Torsten; Verhey, Jesko L

2013-01-01

Recently an optimized broad-band chirp stimulus has been proposed for the objective estimation of hearing thresholds with auditory brainstem responses (ABRs). Several studies have demonstrated that this stimulus, compensating for the travelling wave delay of the frequency components of a click stimulus at the basilar membrane, evokes larger ABR amplitudes in adults. This study analyses the amplitude of chirp-evoked ABRs recorded in infants below 48 month of age under clinical conditions and compares these results with literature data. Chirp-evoked ABR recordings in 46 infants under chloral hydrate sedation or general anaesthesia were analysed retrospectively. The amplitude of the wave V was measured as a function of the stimulus intensity. To compare ABR amplitudes across infants with different hearing losses, the stimulus intensity was readjusted to the subjects' individual physiological threshold in dB SL (sensation level). Individual wave V amplitudes were plotted against stimulus intensity and individual amplitude growth functions were calculated. To investigate the maturation of chirp-evoked ABR, data from infants below and above 18 months of age were analysed separately. Chirp-evoked ABR amplitudes in both age groups were larger than the click-evoked ABR amplitudes in young infants from the literature. Amplitudes of chirp-evoked ABR in infants above 18 months of age were not substantially smaller than those reported for normal hearing adults. Amplitudes recorded in infants below 18 months were significantly smaller than those in infants above 18 months. A significant difference between chirp-evoked ABR amplitudes recorded in sedation or under general anaesthesia was not found. The higher amplitudes of ABR elicited by a broadband chirp stimulus allow for a reduction of the recording time in young infants. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Chirped self-similar optical pulses in tapered centrosymmetric nonlinear waveguides doped with resonant impurities

NASA Astrophysics Data System (ADS)

He, J. R.; Xu, S. L.; Xue, L.

2017-11-01

Exact chirped self-similar optical pulses propagating in tapered centrosymmetric nonlinear waveguides doped with resonant impurities are reported. The propagation behaviors of the pulses are studied by tailoring of the tapering function. Numerical simulations and stability analysis reveal that the tapering can be used to postpone the wave dispersion and the addition of a small cubic self-focusing term to the governing equation could stabilize the chirped bright pulses. An example of possible experimental protocol that may generate the pulses in realistic waveguides is given. The obtained chirped self-similar optical pulses are particularly useful in the design of amplifying or attenuating pulse compressors for chirped solitary waves in tapered centrosymmetric nonlinear waveguides doped with resonant impurities.

Chirped-pulse coherent-OTDR with predistortion

NASA Astrophysics Data System (ADS)

Xiong, Ji; Jiang, Jialin; Wu, Yue; Chen, Yongxiang; Xie, Lianlian; Fu, Yun; Wang, Zinan

2018-03-01

In this paper, a novel method for generating high-quality chirped pulses with IQ modulator is studied theoretically and experimentally, which is a crucial building block for high-performance coherent optical time-domain reflectometry (COTDR). In order to compensate the nonlinearity of the modulator transfer function, we present a predistortion technique for chirped-pulse coherent optical time-domain reflectometry (CP-COTDR), the arcsin predistortion method and the single sideband with a suppressed carrier analog modulation used to generate the high quality chirped optical pulse. The high order sidebands, due to the large amplitude of the modulation signal and the nonlinear transfer function of the IQ modulator, can be relieved by the predistortion process, which means the power and the quality of the generated chirped pulse has been improved. In the experiment, this method increases the peak power of the chirped pulse by 4.2 dB compared to the case without predistortion process, as for the CP-COTDR system, this method increases the signal-to-noise ratio of the demodulated phase variation by 6.3 dB.

FD-CHIRP: hosted payload system engineering lessons

NASA Astrophysics Data System (ADS)

Schueler, Carl F.

2012-10-01

The Commercially Hosted Infrared Payload (CHIRP) Flight Demonstration (FD-CHIRP) launched 21 Sept 2011 was designated a "resounding success" as the first Wide Field-of-View (WFOV) staring infrared (IR) sensor flown in geostationary earth orbit (GEO) with a primary mission of Missile Warning (MW). FD-CHIRP was an Air Force research and development project initiated in July 2008 via an unsolicited industry proposal aimed to mature and reduce the risk of WFOV sensors and ground processing technologies. Unlike the Defense Support Program (DSP) and the Space Based Infrared System (SBIRS) which were acquired via traditional integrated sensor and satellite design, FDCHIRP was developed using the "commercially hosted" approach. The FD-CHIRP host spacecraft and sensor were independently designed, creating significant development risk to the industry proposer, especially under a Firm Fixed Price contract. Yet, within 39 months of contract initiation, FD-CHIRP was launched and successfully operated in GEO to 30 June 2012 at a total cost of 111M including the 82.9M CHIRP commercial-hosting contract and a $28M sensor upgrade. The commercial-hosting contract included sensor and spacecraft modifications, integration and test, design and development of secure Mission Operations and Analysis Centers, launch, and nearly a year of GEO operations with 70 Mbps secure data acquisition. The Air Force extended the contract for six months to continue operations through the end of calendar 2012. This paper outlines system engineering challenges FD-CHIRP overcame and key lessons to smooth development of future commercially hosted missions.

The origin and distribution of subbottom sediments in southern Lake Champlain.

USGS Publications Warehouse

Freeman-Lynde, R. P.; Hutchinson, D.R.; Folger, D.W.; Wiley, B.H.; Hewett, M.J.

1980-01-01

3 units, correlatable with recent Lake Champlain, late-glacial marine Champlain Sea, and proglacial Lake Vermont sediments, have been identified from seismic reflection profiles and 8 piston cores. Lake Vermont deposits are nonfossiliferous and range from thin to absent nearshore and on bedrock highs to more than 126 m thick near Split Rock Point. Champlain Sea sediments contain marine foraminifers and ostracodes and are fairly uniform in thickness (20-30 m). Recent Lake Champlain sediments range in thickness from 0 to 25 m. Average sedimentation rates for Lake Vermont are considerably higher (4-8 cm/yr) than those for the Champlain Sea (0.8-1.2 cm/yr) and Lake Champlain (0.14-0.15 cm/yr). Bedrock, till, and deltaic and alluvial deposits were also identified.- from Authors

Quantum dynamics of a two-state system induced by a chirped zero-area pulse

NASA Astrophysics Data System (ADS)

Lee, Han-gyeol; Song, Yunheung; Kim, Hyosub; Jo, Hanlae; Ahn, Jaewook

2016-02-01

It is well known that area pulses make Rabi oscillation and chirped pulses in the adiabatic interaction regime induce complete population inversion of a two-state system. Here we show that chirped zero-area pulses could engineer an interplay between the adiabatic evolution and Rabi-like rotations. In a proof-of-principle experiment utilizing spectral chirping of femtosecond laser pulses with a resonant spectral hole, we demonstrate that the chirped zero-area pulses could induce, for example, complete population inversion and return of the cold rubidium atom two-state system. Experimental result agrees well with the theoretically considered overall dynamics, which could be approximately modeled to a Ramsey-like three-pulse interaction, where the x and z rotations are driven by the hole and the main pulse, respectively.

Effects of chirp on two-dimensional Fourier transform electronic spectra.

PubMed

Tekavec, Patrick F; Myers, Jeffrey A; Lewis, Kristin L M; Fuller, Franklin D; Ogilvie, Jennifer P

2010-05-24

We examine the effect that pulse chirp has on the shape of two- dimensional electronic spectra through calculations and experiments. For the calculations we use a model two electronic level system with a solvent interaction represented by a simple Gaussian correlation function and compare the resulting spectra to experiments carried out on an organic dye molecule (Rhodamine 800). Both calculations and experiments show that distortions due to chirp are most significant when the pulses used in the experiment have different amounts of chirp, introducing peak shape asymmetry that could be interpreted as spectrally dependent relaxation. When all pulses have similar chirp the distortions are reduced but still affect the anti-diagonal symmetry of the peak shapes and introduce negative features that could be interpreted as excited state absorption.

Generation and parametric amplification of broadband chirped pulses in the near-infrared

NASA Astrophysics Data System (ADS)

Marcinkevičiūtė, A.; Michailovas, K.; Butkus, R.

2018-05-01

We demonstrate generation and optical parametric amplification of broadband chirped pulses in the range of 1.8- 2 . 5 μm. The setup is built around Ti:sapphire oscillator as a seed source and 1 kHz Nd:YAG laser system as a pump source. Visible broadband seed pulses are temporally stretched and amplified in a non-collinear optical parametric amplifier before being mixed with fundamental harmonic of the pump laser. Difference frequency generation between positively-chirped broadband pulses centered at 0 . 7 μm and non-chirped narrowband pulses at 1064 nm produces negatively-chirped wide spectral bandwidth pulses in the infrared. After subsequent parametric amplification, pulses with more than 0.5 mJ energy were obtained with spectral bandwidth supporting transform-limited pulse durations as short as 23 fs.

Chirped femtosecond pulses in the higher-order nonlinear Schrödinger equation with non-Kerr nonlinear terms and cubic-quintic-septic nonlinearities

NASA Astrophysics Data System (ADS)

Triki, Houria; Biswas, Anjan; Milović, Daniela; Belić, Milivoj

2016-05-01

We consider a high-order nonlinear Schrödinger equation with competing cubic-quintic-septic nonlinearities, non-Kerr quintic nonlinearity, self-steepening, and self-frequency shift. The model describes the propagation of ultrashort (femtosecond) optical pulses in highly nonlinear optical fibers. A new ansatz is adopted to obtain nonlinear chirp associated with the propagating femtosecond soliton pulses. It is shown that the resultant elliptic equation of the problem is of high order, contains several new terms and is more general than the earlier reported results, thus providing a systematic way to find exact chirped soliton solutions of the septic model. Novel soliton solutions, including chirped bright, dark, kink and fractional-transform soliton solutions are obtained for special choices of parameters. Furthermore, we present the parameter domains in which these optical solitons exist. The nonlinear chirp associated with each of the solitonic solutions is also determined. It is shown that the chirping is proportional to the intensity of the wave and depends on higher-order nonlinearities. Of special interest is the soliton solution of the bright and dark type, determined for the general case when all coefficients in the equation have nonzero values. These results can be useful for possible chirped-soliton-based applications of highly nonlinear optical fiber systems.

The response of phospholipid-encapsulated microbubbles to chirp-coded excitation: Implications for high-frequency nonlinear imaging

PubMed Central

Shekhar, Himanshu; Doyley, Marvin M.

2013-01-01

The current excitation strategy for harmonic and subharmonic imaging (HI and SHI) uses short sine-bursts. However, alternate pulsing strategies may be useful for enhancing nonlinear emissions from ultrasound contrast agents. The goal of this study was to corroborate the hypothesis that chirp-coded excitation can improve the performance of high-frequency HI and SHI. A secondary goal was to understand the mechanisms that govern the response of ultrasound contrast agents to chirp-coded and sine-burst excitation schemes. Numerical simulations and acoustic measurements were conducted to evaluate the response of a commercial contrast agent (Targestar-P®) to chirp-coded and sine-burst excitation (10 MHz frequency, peak pressures 290 kPa). The results of the acoustic measurements revealed an improvement in signal-to-noise ratio by 4 to 14 dB, and a two- to threefold reduction in the subharmonic threshold with chirp-coded excitation. Simulations conducted with the Marmottant model suggest that an increase in expansion-dominated radial excursion of microbubbles was the mechanism responsible for the stronger nonlinear response. Additionally, chirp-coded excitation detected the nonlinear response for a wider range of agent concentrations than sine-bursts. Therefore, chirp-coded excitation could be a viable approach for enhancing the performance of HI and SHI. PMID:23654417

The response of phospholipid-encapsulated microbubbles to chirp-coded excitation: implications for high-frequency nonlinear imaging.

PubMed

Shekhar, Himanshu; Doyley, Marvin M

2013-05-01

The current excitation strategy for harmonic and subharmonic imaging (HI and SHI) uses short sine-bursts. However, alternate pulsing strategies may be useful for enhancing nonlinear emissions from ultrasound contrast agents. The goal of this study was to corroborate the hypothesis that chirp-coded excitation can improve the performance of high-frequency HI and SHI. A secondary goal was to understand the mechanisms that govern the response of ultrasound contrast agents to chirp-coded and sine-burst excitation schemes. Numerical simulations and acoustic measurements were conducted to evaluate the response of a commercial contrast agent (Targestar-P(®)) to chirp-coded and sine-burst excitation (10 MHz frequency, peak pressures 290 kPa). The results of the acoustic measurements revealed an improvement in signal-to-noise ratio by 4 to 14 dB, and a two- to threefold reduction in the subharmonic threshold with chirp-coded excitation. Simulations conducted with the Marmottant model suggest that an increase in expansion-dominated radial excursion of microbubbles was the mechanism responsible for the stronger nonlinear response. Additionally, chirp-coded excitation detected the nonlinear response for a wider range of agent concentrations than sine-bursts. Therefore, chirp-coded excitation could be a viable approach for enhancing the performance of HI and SHI.

Broadband spectroscopy of dynamic impedances with short chirp pulses.

PubMed

Min, M; Land, R; Paavle, T; Parve, T; Annus, P; Trebbels, D

2011-07-01

An impedance spectrum of dynamic systems is time dependent. Fast impedance changes take place, for example, in high throughput microfluidic devices and in operating cardiovascular systems. Measurements must be as short as possible to avoid significant impedance changes during the spectrum analysis, and as long as possible for enlarging the excitation energy and obtaining a better signal-to-noise ratio (SNR). The authors propose to use specific short chirp pulses for excitation. Thanks to the specific properties of the chirp function, it is possible to meet the needs for a spectrum bandwidth, measurement time and SNR so that the most accurate impedance spectrogram can be obtained. The chirp wave excitation can include thousands of cycles when the impedance changes slowly, but in the case of very high speed changes it can be shorter than a single cycle, preserving the same excitation bandwidth. For example, a 100 kHz bandwidth can be covered by the chirp pulse with durations from 10 µs to 1 s; only its excitation energy differs also 10(5) times. After discussing theoretical short chirp properties in detail, the authors show how to generate short chirps in the microsecond range with a bandwidth up to a few MHz by using digital synthesis architectures developed inside a low-cost standard field programmable gate array.

Notched-noise embedded frequency specific chirps for objective audiometry using auditory brainstem responses

PubMed Central

Corona-Strauss, Farah I.; Schick, Bernhard; Delb, Wolfgang; Strauss, Daniel J.

2012-01-01

It has been shown recently that chirp-evoked auditory brainstem responses (ABRs) show better performance than click stimulations, especially at low intensity levels. In this paper we present the development, test, and evaluation of a series of notched-noise embedded frequency specific chirps. ABRs were collected in healthy young control subjects using the developed stimuli. Results of the analysis of the corresponding ABRs using a time-scale phase synchronization stability (PSS) measure are also reported. The resultant wave V amplitude and latency measures showed a similar behavior as for values reported in literature. The PSS of frequency specific chirp-evoked ABRs reflected the presence of the wave V for all stimulation intensities. The scales that resulted in higher PSS are in line with previous findings, where ABRs evoked by broadband chirps were analyzed, and which stated that low frequency channels are better for the recognition and analysis of chirp-evoked ABRs. We conclude that the development and test of the series of notched-noise embedded frequency specific chirps allowed the assessment of frequency specific ABRs, showing an identifiable wave V for different intensity levels. Future work may include the development of a faster automatic recognition scheme for these frequency specific ABRs. PMID:26557336

Study on control of defect mode in hybrid mirror chirped porous silicon photonic crystal

NASA Astrophysics Data System (ADS)

Chen, Ying; Luo, Pei; Han, Yangyang; Cui, Xingning; He, Lei

2018-03-01

Based on the optical resonance principle and the tight-binding theory, a hybrid mirror chirped porous silicon photonic crystal is proposed. The control of the defect mode in hybrid mirror chirped porous silicon photonic crystal is studied. Through the numerical simulation, the control regulations of the defect modes resulted by the number of the periodical layers for the fundamental unit and the cascading number of the chirped structures are analyzed, and the split and the degeneration of the defect modes resulted by the change of the relative location between the mirror structures and the quasi-mirror structures are discussed. The simulation results show that the band gap would be broadened with the increase of the chirp quantity and the layer number of unilateral chirp. Adjusting the structural parameters of the hybrid mirror structure, the multimode characteristics will occur in the band gap. The more the cascading number of the chirped units, the more the number of the filtering channels will be. In addition, with the increase of the relative location between the mirror structures and the quasi-mirror structures, the degeneration of the defect modes will occur and can obtain high Q value. The structure can provide effective theoretical references for the design the multi-channel filters and high Q value sensors.

Short-time fractional Fourier methods for the time-frequency representation of chirp signals.

PubMed

Capus, Chris; Brown, Keith

2003-06-01

The fractional Fourier transform (FrFT) provides a valuable tool for the analysis of linear chirp signals. This paper develops two short-time FrFT variants which are suited to the analysis of multicomponent and nonlinear chirp signals. Outputs have similar properties to the short-time Fourier transform (STFT) but show improved time-frequency resolution. The FrFT is a parameterized transform with parameter, a, related to chirp rate. The two short-time implementations differ in how the value of a is chosen. In the first, a global optimization procedure selects one value of a with reference to the entire signal. In the second, a values are selected independently for each windowed section. Comparative variance measures based on the Gaussian function are given and are shown to be consistent with the uncertainty principle in fractional domains. For appropriately chosen FrFT orders, the derived fractional domain uncertainty relationship is minimized for Gaussian windowed linear chirp signals. The two short-time FrFT algorithms have complementary strengths demonstrated by time-frequency representations for a multicomponent bat chirp, a highly nonlinear quadratic chirp, and an output pulse from a finite-difference sonar model with dispersive change. These representations illustrate the improvements obtained in using FrFT based algorithms compared to the STFT.

Combining harmonic generation and laser chirping to achieve high spectral density in Compton sources

DOE PAGES

Terzić, Balša; Reeves, Cody; Krafft, Geoffrey A.

2016-04-25

Recently various laser-chirping schemes have been investigated with the goal of reducing or eliminating ponderomotive line broadening in Compton or Thomson scattering occurring at high laser intensities. Moreover, as a next level of detail in the spectrum calculations, we have calculated the line smoothing and broadening expected due to incident beam energy spread within a one-dimensional plane wave model for the incident laser pulse, both for compensated (chirped) and unchirped cases. The scattered compensated distributions are treatable analytically within three models for the envelope of the incident laser pulses: Gaussian, Lorentzian, or hyperbolic secant. We use the new results tomore » demonstrate that the laser chirping in Compton sources at high laser intensities: (i) enables the use of higher order harmonics, thereby reducing the required electron beam energies; and (ii) increases the photon yield in a small frequency band beyond that possible with the fundamental without chirping. We found that this combination of chirping and higher harmonics can lead to substantial savings in the design, construction and operational costs of the new Compton sources. This is of particular importance to the widely popular laser-plasma accelerator based Compton sources, as the improvement in their beam quality enters the regime where chirping is most effective.« less

Observations of the R Reflector and Sediment Interface Reflection at the Shallow Water 󈧊 Central Site

DTIC Science & Technology

2008-08-28

line array position of Woods Hole Oceanographic Institution (WHOI) during the SWARM experiment by 26 km, and southeast of the AMCOR borehole No. 6010...guided by the stratigraphic constraints provided by closely spaced 50 m chirp seismic reflection profiles that provide pseudo three-dimensional... array is at the center of set of stations at location M. c Geometry showing source position R/V KNORR with respect to the receiving array and the

Assessing the deep drilling potential of Lago de Tota, Colombia, with a seismic survey

NASA Astrophysics Data System (ADS)

Bird, B. W.; Wattrus, N. J.; Fonseca, H.; Velasco, F.; Escobar, J.

2015-12-01

Reconciling orbital-scale patterns of inter-hemispheric South American climate during the Quaternary requires continuous, high-resolution paleoclimate records that span multiple glacial cycles from both hemispheres. Southern Andean Quaternary climates are represented by multi-proxy results from Lake Titicaca (Peru-Bolivia) spanning the last 400 ka and by pending results from the Lago Junin Drilling Project (Peru). Although Northern Andean sediment records spanning the last few million years have been retrieved from the Bogota and Fúquene Basins in the Eastern Cordillera of the Colombian Andes, climatic reconstructions based on these cores have thus far been limited to pollen-based investigations. When viewed together with the Southern Hemisphere results, these records suggest an anti-phased hemispheric climatic response during glacial cycles. In order to better assess orbital-scale climate responses, however, independent temperature and hydroclimate proxies from the Northern Hemisphere are needed in addition to vegetation histories. As part of this objective, an effort is underway to develop a paleoclimate record from Lago de Tota (3030 m asl), the largest lake in Colombia and the third largest lake in the Andes. One of 17 highland tectonic basins in Eastern Cordillera, Lago de Tota formed during Tertiary uplift that deformed pre-foreland megasequences, synrift and back-arc megasequences. The precise age and thickness of sediments in the Lago de Tota basin has not previously been established. Here, we present results from a recent single-channel seismic reflection survey collected with a small (5 cubic inch) air gun and high-resolution CHIRP sub-bottom data. With these data, we examine the depositional history and sequence stratigraphy of Lago de Tota and assess its potential as a deep drilling target.

Relationship of Hotspots to the Distribution of Surficial Surf-Zone Sediments along the Outer Banks of North Carolina

NASA Astrophysics Data System (ADS)

Schupp, C. A.; McNinch, J. E.; List, J. H.; Farris, A. S.

2002-12-01

The formation and behavior of hotspots, or sections of the beach that exhibit markedly higher shoreline change rates than adjacent regions, are poorly understood. Several hotspots have been identified on the Outer Banks, a developed barrier island in North Carolina. To better understand hotspot dynamics and the potential relationship to the geologic framework in which they occur, the surf zone between Duck and Bodie Island was surveyed in June 2002 as part of a research effort supported by the U.S. Geological Survey and U.S. Army Corps of Engineers. Swath bathymetry, sidescan sonar, and chirp seismic were used to characterize a region 40 km long and1 km wide. Hotspot locations were pinpointed using standard deviation values for shoreline position as determined by monthly SWASH buggy surveys of the mean high water contour between October 1999 and September 2002. Observational data and sidescan images were mapped to delineate regions of surficial sediment distributions, and regions of interest were ground-truthed via grab samples or visual inspection. General kilometer-scale correlation between acoustic backscatter and high shoreline standard deviation is evident. Acoustic returns are uniform in a region of Duck where standard deviation is low, but backscatter is patchy around the Kitty Hawk hotspot, where standard deviation is higher. Based on ground-truthing of an area further north, these patches are believed to be an older ravinement surface of fine sediment. More detailed analyses of the correlation between acoustic data, standard deviation, and hotspot locations will be presented. Future work will include integration of seismic, bathymetric, and sidescan data to better understand the links between sub-bottom geology, temporal changes in surficial sediments, surf-zone sediment budgets, and short-term changes in shoreline position and morphology.

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

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

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

2009-02-23

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

Fluctuations of Broadband Acoustic Signals in Shallow Water

DTIC Science & Technology

2015-09-30

ships, strumming noise at 5 and 20 Hz, etc. In the Fig. 11, chirp signals from R/V Sharp were recorded. Whistles and clicks by dolphin are also observed...Fig 10. Low frequency ambient noise measurements. click chirp unknown Fig 11. Ambient noise measurements up to 9 kHz. Chirp signals and dolphin

Real-time chirp-coded imaging with a programmable ultrasound biomicroscope.

PubMed

Bosisio, Mattéo R; Hasquenoph, Jean-Michel; Sandrin, Laurent; Laugier, Pascal; Bridal, S Lori; Yon, Sylvain

2010-03-01

Ultrasound biomicroscopy (UBM) of mice can provide a testing ground for new imaging strategies. The UBM system presented in this paper facilitates the development of imaging and measurement methods with programmable design, arbitrary waveform coding, broad bandwidth (2-80 MHz), digital filtering, programmable processing, RF data acquisition, multithread/multicore real-time display, and rapid mechanical scanning (

Design and performance evaluation of a dispersion compensation unit using several chirping functions in a tanh apodized FBG and comparison with dispersion compensation fiber.

PubMed

Mohammed, Nazmi A; Solaiman, Mohammad; Aly, Moustafa H

2014-10-10

In this work, various dispersion compensation methods are designed and evaluated to search for a cost-effective technique with remarkable dispersion compensation and a good pulse shape. The techniques consist of different chirp functions applied to a tanh fiber Bragg grating (FBG), a dispersion compensation fiber (DCF), and a DCF merged with an optimized linearly chirped tanh FBG (joint technique). The techniques are evaluated using a standard 10 Gb/s optical link over a 100 km long haul. The linear chirp function is the most appropriate choice of chirping function, with a pulse width reduction percentage (PWRP) of 75.15%, lower price, and poor pulse shape. The DCF yields an enhanced PWRP of 93.34% with a better pulse quality; however, it is the most costly of the evaluated techniques. Finally, the joint technique achieved the optimum PWRP (96.36%) among all the evaluated techniques and exhibited a remarkable pulse shape; it is less costly than the DCF, but more expensive than the chirped tanh FBG.

Simulation and theory of spontaneous TAE frequency sweeping

NASA Astrophysics Data System (ADS)

Wang, Ge; Berk, H. L.

2012-09-01

A simulation model, based on the linear tip model of Rosenbluth, Berk and Van Dam (RBV), is developed to study frequency sweeping of toroidal Alfvén eigenmodes (TAEs). The time response of the background wave in the RBV model is given by a Volterra integral equation. This model captures the properties of TAE waves both in the gap and in the continuum. The simulation shows that phase space structures form spontaneously at frequencies close to the linearly predicted frequency, due to resonant particle-wave interactions and background dissipation. The frequency sweeping signals are found to chirp towards the upper and lower continua. However, the chirping signals penetrate only the lower continuum, whereupon the frequency chirps and mode amplitude increases in synchronism to produce an explosive solution. An adiabatic theory describing the evolution of a chirping signal is developed which replicates the chirping dynamics of the simulation in the lower continuum. This theory predicts that a decaying chirping signal will terminate at the upper continuum though in the numerical simulation the hole disintegrates before the upper continuum is reached.

A theoretical investigation of chirp insonification of ultrasound contrast agents.

PubMed

Barlow, Euan; Mulholland, Anthony J; Gachagan, Anthony; Nordon, Alison

2011-08-01

A theoretical investigation of second harmonic imaging of an Ultrasound Contrast Agent (UCA) under chirp insonification is considered. By solving the UCA's dynamical equation analytically, the effect that the chirp signal parameters and the UCA shell parameters have on the amplitude of the second harmonic frequency are examined. This allows optimal parameter values to be identified which maximise the UCA's second harmonic response. A relationship is found for the chirp parameters which ensures that a signal can be designed to resonate a UCA for a given set of shell parameters. It is also shown that the shell thickness, shell viscosity and shell elasticity parameter should be as small as realistically possible in order to maximise the second harmonic amplitude. Keller-Herring, Second Harmonic, Chirp, Ultrasound Contrast Agent. Copyright © 2011 Elsevier B.V. All rights reserved.

The optimal input optical pulse shape for the self-phase modulation based chirp generator

NASA Astrophysics Data System (ADS)

Zachinyaev, Yuriy; Rumyantsev, Konstantin

2018-04-01

The work is aimed to obtain the optimal shape of the input optical pulse for the proper functioning of the self-phase modulation based chirp generator allowing to achieve high values of chirp frequency deviation. During the research, the structure of the device based on self-phase modulation effect using has been analyzed. The influence of the input optical pulse shape of the transmitting optical module on the chirp frequency deviation has been studied. The relationship between the frequency deviation of the generated chirp and frequency linearity for the three options for implementation of the pulse shape has been also estimated. The results of research are related to the development of the theory of radio processors based on fiber-optic structures and can be used in radars, secure communications, geolocation and tomography.

Seafloor morphology of the continental slope in front the Petacalco Bay and its tsunamigenic relationship at the Mexican sector of the Middle American subduction zone

NASA Astrophysics Data System (ADS)

Mortera-Gutierrez, C. A.; Bandy, W. L.; Millan-Motolinia, C.; Ponce-Nuñez, F.; Ortega-Ramirez, J.

2014-12-01

The recent occurrence of offshore, large, earthquake ruptures in the western limit of the Guerrero Seismic Gap and the scattered data of seafloor morphology of the continental slope along this sector at the Mexican Mid American subduction zone have encouraged the UNAM marine geophysical group to initiate a mapping program at the Guerrero margin, from the shelf break to the Middle American Trench. The main objective of this initiative is to have a complete cover of the seafloor morphology of the Guerrero slope as the background data for comparative studies of the seafloor deformation in case of future offshore earthquake ruptures in this region. At he first stage of this initiative, we have mapped the continental slope in front the Petacalco Bay, west of the Guerrero Seismic Gap, where three important large earthquakes occurred and caused great damages in Mexico City: Petatlán earthquake (Mw=7.6) at 1979, Michoacán earthquake (Mw=8.1) and its aftershock (Mw=7.9) at 1985. Geophysical results of two campaigns carry in 2012 (MAMRIV12) and 2013 (BABPET13) on board the BO EL PUMA are presented which include multibeam data and subbottom profiles. These data sets cover an area between 101°W and 103°W, and from the shelf-slope break to the trench. The multibeam chart shows details of the hydrological erosion induced by many submarine cannons at the upper slope, whereas the seafloor relief in the lower slope is dominated by tectonic structures. The subbottom profiles and the seafloor morphology evidence zones of big slumps and faults. For first time the Rio Balsas submarine cannon is completed chart, reaching the trench basin. The river course is deflected, possibly by shear faulting. There are slump sites near the trench that probably one is associated to the 1925 tsunami at Zihuatanejo, Guerrero. The 1985 Michoacán aftershock was accompany by a small Tsunami. At that time, the lack of morphology data in this slope inhibited further studies of seafloor-deformation and its tsunamigenic relationship. Funding providing by UNAM-DGAPA-PAPIIT grants: IN115613 and IN115513

Recent Sedimentary Processes Along the Western Continental Margin of the South Korea Plateau, East Sea of Korea

NASA Astrophysics Data System (ADS)

Cukur, D.; Um, I. K.; Bahk, J. J.; Chun, J. H.; Lee, G. S.; Soo, K. G.; Horozal, S.; Kim, S. P.

2017-12-01

The continental margins of the marginal seas is largely shaped by a complex interplay of sediment transport processes directed both downslope and along-slope. Factors influence the sediment transport from shelf to the deep basin include: (i) seabed morphology, (ii) climate, (iii) sea level changes, (iv) slope stability, (v) oceanographic regime, and (vi) sediment sources. In order to understand the recent sedimentary processes along the western margin of the South Korea Plateau in the East Sea, we collected multiple geophysical datasets including the subbottom profiler and multibeam echosounder as well as geological sampling. Twelve echo types have been defined and interpreted as deposits formed by shallow marine, hemipelagic sedimentation, bottom currents, combined- (mass-movement/hemipelagic and hemipelagic/turbidites) and mass-movement-processes. Hemipelagic sedimentation, which is reflected as undisturbed layered sediments, appears to have been the primary sedimentary process throughout the study area. Two major slope-parallel channels appear to have acted as major conduits for turbidity currents from shallower shelf into the deep basins. Bottom current deposits, which is expressed as undulating seafloor morphology, are prevalent in the southern mid-slope at water depths between 250 to 450 m. Mass-transport deposits, consisting of chaotic seismic facies, occur in the upper and lower parts of the continental slope. Piston cores confirm the presence of MTDs that are characterized by mud clasts of variable size and shape. Multibeam bathymetry data show that these MTDs chiefly initiate on lower-slopes (400-600 m) where the gradient is up to 3°. In addition, subbottom profiles suggest the presence of numerous faults in close vicinity of headwall scarps; some are extending to the seafloor suggesting their recent activity. Earthquakes associated with tectonic activity are considered as the main triggering mechanism for these MTDs. Overall, the acoustic facies distribution shows that the sedimentary processes change downslope and differ within each physiographic province. In particular, the role of geological inheritance (i.e., structural folds and faults) on the geomorphology and sediment facies on the lower slopes appears to be quite important.

All-Fiber, Directly Chirped Laser Source for Chirped-Pulse-Amplification

NASA Astrophysics Data System (ADS)

Xin, Ran

Chirped-pulse-amplification (CPA) technology is widely used to produce ultra-short optical pulses (sub picosecond to femtoseconds) with high pulse energy. A chirped pulse laser source with flexible dispersion control is highly desirable as a CPA seed. This thesis presents an all-fiber, directly chirped laser source (DCLS) that produces nanosecond, linearly-chirped laser pulses at 1053 nm for seeding high energy CPA systems. DCLS produces a frequency chirp on an optical pulse through direct temporal phase modulation. DCLS provides programmable control for the temporal phase of the pulse, high pulse energy and diffraction-limited beam performance, which are beneficial for CPA systems. The DCLS concept is first described. Its key enabling technologies are identified and their experimental demonstration is presented. These include high-precision temporal phase control using an arbitrary waveform generator, multi-pass phase modulation to achieve high modulation depth, regenerative amplification in a fiber ring cavity and a negative feedback system that controls the amplifier cavity dynamics. A few technical challenges that arise from the multi-pass architecture are described and their solutions are presented, such as polarization management and gain-spectrum engineering in the DCLS fiber cavity. A DCLS has been built and its integration into a high energy OPCPA system is demonstrated. DCLS produces a 1-ns chirped pulse with a 3-nm bandwidth. The temporal phase and group delay dispersion on the DCLS output pulse is measured using temporal interferometry. The measured temporal phase has an ˜1000 rad amplitude and is close to a quadratic shape. The chirped pulse is amplified from 0.9 nJ to 76 mJ in an OPCPA system. The amplified pulse is compressed to close to its Fourier transform limit, producing an intensity autocorrelation trace with a 1.5-ps width. Direct compressed-pulse duration control by adjusting the phase modulation drive amplitude is demonstrated. Limitation to pulse compression is investigated using numerical simulation.

Modeling Two-Stage Bunch Compression With Wakefields: Macroscopic Properties And Microbunching Instability

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

Bosch, R.A.; Kleman, K.J.; /Wisconsin U., SRC

2011-09-08

In a two-stage compression and acceleration system, where each stage compresses a chirped bunch in a magnetic chicane, wakefields affect high-current bunches. The longitudinal wakes affect the macroscopic energy and current profiles of the compressed bunch and cause microbunching at short wavelengths. For macroscopic wavelengths, impedance formulas and tracking simulations show that the wakefields can be dominated by the resistive impedance of coherent edge radiation. For this case, we calculate the minimum initial bunch length that can be compressed without producing an upright tail in phase space and associated current spike. Formulas are also obtained for the jitter in themore » bunch arrival time downstream of the compressors that results from the bunch-to-bunch variation of current, energy, and chirp. Microbunching may occur at short wavelengths where the longitudinal space-charge wakes dominate or at longer wavelengths dominated by edge radiation. We model this range of wavelengths with frequency-dependent impedance before and after each stage of compression. The growth of current and energy modulations is described by analytic gain formulas that agree with simulations.« less

Archive of Boomer and Chirp Seismic Reflection Data Collected During USGS Cruise 01RCE02, Southern Louisiana, April and May 2001

USGS Publications Warehouse

Calderon, Karynna; Dadisman, Shawn V.; Flocks, James G.; Wiese, Dana S.

2003-01-01

In April and May of 2001, the U.S. Geological Survey conducted a geophysical study of the Mississippi River Delta, Atchafalaya River Delta, and Shell Island Pass in southern Louisiana. This study was part of a larger USGS River Contaminant Evaluation (RCE) Project. This disc serves as an archive of unprocessed digital seismic reflection data, trackline navigation files, shotpoint navigation maps, observers' logbooks, GIS information, and formal Federal Geographic Data Committee (FGDC) metadata. In addition, a filtered and gained digital GIF-formatted image of each seismic profile is provided. For your convenience, a list of acronyms and abbreviations frequently used in this report has also been provided. This DVD (Digital Versatile Disc) document is readable on any computing platform that has standard DVD driver software installed. Documentation on this DVD was produced using Hyper Text Markup Language (HTML) utilized by the World Wide Web (WWW) and allows the user to access the information by using a web browser (i.e. Netscape or Internet Explorer). To access the information contained on this disc, open the file 'index.htm' located at the top level of the disc using your web browser. This report also contains WWW links to USGS collaborators and other agencies. These links are only accessible if access to the internet is available while viewing the DVD. The archived boomer and chirp seismic reflection data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry et al., 1975) and may be downloaded for processing with public domain software such as Seismic Unix (SU), currently located at http://www.cwp.mines.edu/cwpcodes. Examples of SU processing scripts are provided in the boom.tar and chirp.tar files located in the SU subfolder of the SOFTWARE folder located at the top level of this DVD. In-house (USGS) DOS and Microsoft Windows compatible software for viewing SEG-Y headers - DUMPSEGY.EXE (Zilhman, 1992) - is provided in the USGS subfolder of the SOFTWARE folder. Processed profile images, shotpoint navigation maps, logbooks, and formal metadata may be viewed with your web browser.

Influence of long-term social interaction on chirping behavior, steroid levels and neurogenesis in weakly electric fish.

PubMed

Dunlap, Kent D; Chung, Michael; Castellano, James F

2013-07-01

Social interactions dramatically affect the brain and behavior of animals. Studies in birds and mammals indicate that socially induced changes in adult neurogenesis participate in the regulation of social behavior, but little is known about this relationship in fish. Here, we review studies in electric fish (Apteronotus leptorhychus) that link social stimulation, changes in electrocommunication behavior and adult neurogenesis in brain regions associated with electrocommunication. Compared with isolated fish, fish living in pairs have greater production of chirps, an electrocommunication signal, during dyadic interactions and in response to standardized artificial social stimuli. Social interaction also promotes neurogenesis in the periventricular zone, which contributes born cells to the prepacemaker nucleus, the brain region that regulates chirping. Both long-term chirp rate and periventricular cell addition depend on the signal dynamics (amplitude and waveform variation), modulations (chirps) and novelty of the stimuli from the partner fish. Socially elevated cortisol levels and cortisol binding to glucocorticoid receptors mediate, at least in part, the effect of social interaction on chirping behavior and brain cell addition. In a closely related electric fish (Brachyhypopomus gauderio), social interaction enhances cell proliferation specifically in brain regions for electrocommunication and only during the breeding season, when social signaling is most elaborate. Together, these studies demonstrate a consistent correlation between brain cell addition and environmentally regulated chirping behavior across many social and steroidal treatments and suggest a causal relationship.

Frequency chirping for resonance-enhanced electron energy during laser acceleration

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

Gupta, D.N.; Suk, H.

2006-04-15

The model given by Singh-Tripathi [Phys. Plasmas 11, 743 (2004)] for laser electron acceleration in a magnetic wiggler is revisited by including the effect of laser frequency chirping. Laser frequency chirp helps to maintain the resonance condition longer, which increases the electron energy gain. A significant enhancement in electron energy gain during laser acceleration is observed.

Chirp effects on impulsive vibrational spectroscopy: a multimode perspective.

PubMed

Wand, Amir; Kallush, Shimshon; Shoshanim, Ofir; Bismuth, Oshrat; Kosloff, Ronnie; Ruhman, Sanford

2010-03-07

The well-documented propensity of negatively-chirped pulses to enhance resonant impulsive Raman scattering has been rationalized in terms of a one pulse pump-dump sequence which "follows" the evolution of the excited molecules and dumps them back at highly displaced configurations. The aim of this study was to extend the understanding of this effect to molecules with many displaced vibrational modes in the presence of condensed surroundings. In particular, to define an optimally chirped pulse, to investigate what exactly it "follows" and to discover how this depends on the molecule under study. To this end, linear chirp effects on vibrational coherences in poly-atomics are investigated experimentally and theoretically. Chirped pump-impulsive probe experiments are reported for Sulforhodamine-B ("Kiton Red"), Betaine-30 and Oxazine-1 in ethanol solutions with <10 fs resolution. Numerical simulations, including numerous displaced modes and electronic dephasing, are conducted to reproduce experimental results. Through semi-quantitative reproduction of experimental results in all three systems we show that the effect of group velocity dispersion (GVD) on the buildup of ground state wave-packets depends on the pulse spectrum, on the displacements of vibrational modes upon excitation, on the detuning of the excitation pulses from resonance, and on electronic dephasing rates. Akin to scenarios described for frequency-domain resonance Raman, within the small-displacement regime each mode responds to excitation chirp independently and the optimal GVD is mode-specific. Highly-displaced modes entangle the dynamics of excitation in different modes, requiring a multi-dimensional description of the response. Rapid photochemistry and ultrafast electronic dephasing narrow the window of opportunity for coherent manipulations, leading to a reduced and similar optimal chirp for different modes. Finally, non-intuitive coherent aspects of chirp "following" are predicted in the small-displacement and slow-dephasing regime, which remain to be observed in experiment.

Research on Debonding Defects in Thermal Barrier Coatings Structure by Thermal-Wave Radar Imaging (TWRI)

NASA Astrophysics Data System (ADS)

Wang, Fei; Liu, Junyan; Mohummad, Oliullah; Wang, Yang

2018-06-01

In this paper, thermal-wave radar imaging (TWRI) is introduced to detect debonding defects in SiC-coated Ni-based superalloy plates. Linear frequency modulation signal (chirp) is used as the excitation signal which has a large time-bandwidth product. Artificial debonding defects in SiC coating are excited by the laser beam with the light intensity modulated by a chirp signal. Cross-correlation algorithm and chirp lock-in algorithm are introduced to extract the thermal-wave signal characteristic. The comparative experiment between TWRI reflection mode and transmission mode was carried out. Experiments are conducted to investigate the influence of laser power density, chirp period, and excitation frequency. Experimental results illustrate that chirp lock-in phase has a better detection capability than other characteristic parameters. TWRI can effectively detect simulated debonding defects of SiC-coated Ni-based superalloy plates.

Few-cycle attosecond pulse chirp effects on asymmetries in ionized electron momentum distributions

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

Peng Liangyou; Tan Fang; Gong Qihuang

2009-07-15

The momentum distributions of electrons ionized from H atoms by chirped few-cycle attosecond pulses are investigated by numerically solving the time-dependent Schroedinger equation. The central carrier frequency of the pulse is chosen to be 25 eV, which is well above the ionization threshold. The asymmetry (or difference) in the yield of electrons ionized along and opposite to the direction of linear laser polarization is found to be very sensitive to the pulse chirp (for pulses with fixed carrier-envelope phase), both for a fixed electron energy and for the energy-integrated yield. In particular, the larger the pulse chirp, the larger themore » number of times the asymmetry changes sign as a function of ionized electron energy. For a fixed chirp, the ionized electron asymmetry is found to be sensitive also to the carrier-envelope phase of the few-cycle pulse.« less

Phase control in coherent population distribution in molecules

NASA Astrophysics Data System (ADS)

Datta, Avijit

2018-06-01

A chirped laser pulse transfers population from one level to another level accessible by one photon dipole transition. We have used a pair of phase-locked chirped pulses of same frequency instead of a single chirped pulse to achieve phase control over the population transfer and thus creating coherent population distribution in hydrogen molecule. Simultaneous actions of the phase controlled interference and rapid adiabatic passages due to chirped pulses lead to the control in population transfer from the ground X(v = 0, j = 0) level to the C(v = 2, j = 1) level. We have extended this two-level system to a three-level 1 + 1 ladder system for population transfer from the X level to the J(v = 2, j = 2) level via the C intermediate level using two pairs of phase-locked laser chirped pulses and have achieved laudable control over the coherent population distribution.

Gain-phase modulation in chirped-pulse amplification

NASA Astrophysics Data System (ADS)

Shen, Yijie; Gao, Gan; Meng, Yuan; Fu, Xing; Gong, Mali

2017-10-01

The cross-modulation between the gain and chirped phase in chirped-pulse amplification (CPA) is theoretically and experimentally demonstrated. We propose a gain-phase coupled nonlinear Schrödinger equation (GPC-NLSE) for solving chirped-pulse propagation in a nonlinear gain medium involved in the gain-phase modulation (GPM) process. With the GPC-NLSE, the space-time-frequency-dependent gain, chirped phase, pulse, and spectrum evolutions can be precisely calculated. Moreover, a short-length high-gain Yb-doped fiber CPA experiment is presented in which a self-steepening distortion of the seed pulse is automatically compensated after amplification. This phenomenon can be explained by the GPM theory whereas conventional models cannot. The experimental results for the temporal and spectral intensities show excellent agreement with our theory. Our GPM theory paves the way for further investigations of the finer structures of the pulse and spectrum in CPA systems.

Photonic generation of phase-stable and wideband chirped microwave signals based on phase-locked dual optical frequency combs.

PubMed

Tong, Yitian; Zhou, Qian; Han, Daming; Li, Baiyu; Xie, Weilin; Liu, Zhangweiyi; Qin, Jie; Wang, Xiaocheng; Dong, Yi; Hu, Weisheng

2016-08-15

A photonics-based scheme is presented for generating wideband and phase-stable chirped microwave signals based on two phase-locked combs with fixed and agile repetition rates. By tuning the difference of the two combs' repetition rates and extracting different order comb tones, a wideband linearly frequency-chirped microwave signal with flexible carrier frequency and chirped range is obtained. Owing to the scheme of dual-heterodyne phase transfer and phase-locked loop, extrinsic phase drift and noise induced by the separated optical paths is detected and suppressed efficiently. Linearly frequency-chirped microwave signals from 5 to 15 GHz and 237 to 247 GHz with 30 ms duration are achieved, respectively, contributing to the time-bandwidth product of 3×10⁸. And less than 1.3×10^-5 linearity errors (RMS) are also obtained.

Bias correction of daily satellite precipitation data using genetic algorithm

NASA Astrophysics Data System (ADS)

Pratama, A. W.; Buono, A.; Hidayat, R.; Harsa, H.

2018-05-01

Climate Hazards Group InfraRed Precipitation with Stations (CHIRPS) was producted by blending Satellite-only Climate Hazards Group InfraRed Precipitation (CHIRP) with Stasion observations data. The blending process was aimed to reduce bias of CHIRP. However, Biases of CHIRPS on statistical moment and quantil values were high during wet season over Java Island. This paper presented a bias correction scheme to adjust statistical moment of CHIRP using observation precipitation data. The scheme combined Genetic Algorithm and Nonlinear Power Transformation, the results was evaluated based on different season and different elevation level. The experiment results revealed that the scheme robustly reduced bias on variance around 100% reduction and leaded to reduction of first, and second quantile biases. However, bias on third quantile only reduced during dry months. Based on different level of elevation, the performance of bias correction process is only significantly different on skewness indicators.

Bubble-based acoustic radiation force using chirp insonation to reduce standing wave effects.

PubMed

Erpelding, Todd N; Hollman, Kyle W; O'Donnell, Matthew

2007-02-01

Bubble-based acoustic radiation force can measure local viscoelastic properties of tissue. High intensity acoustic waves applied to laser-generated bubbles induce displacements inversely proportional to local Young's modulus. In certain instances, long pulse durations are desirable but are susceptible to standing wave artifacts, which corrupt displacement measurements. Chirp pulse acoustic radiation force was investigated as a method to reduce standing wave artifacts. Chirp pulses with linear frequency sweep magnitudes of 100, 200 and 300 kHz centered around 1.5 MHz were applied to glass beads within gelatin phantoms and laser-generated bubbles within porcine lenses. The ultrasound transducer was translated axially to vary standing wave conditions, while comparing displacements using chirp pulses and 1.5 MHz tone burst pulses of the same duration and peak rarefactional pressure. Results demonstrated significant reduction in standing wave effects using chirp pulses, with displacement proportional to acoustic intensity and bubble size.

Bubble-Based Acoustic Radiation Force Using Chirp Insonation to Reduce Standing Wave Effects

PubMed Central

Erpelding, Todd N.; Hollman, Kyle W.; O’Donnell, Matthew

2007-01-01

Bubble-based acoustic radiation force can measure local viscoelastic properties of tissue. High intensity acoustic waves applied to laser-generated bubbles induce displacements inversely proportional to local Young’s modulus. In certain instances, long pulse durations are desirable but are susceptible to standing wave artifacts, which corrupt displacement measurements. Chirp pulse acoustic radiation force was investigated as a method to reduce standing wave artifacts. Chirp pulses with linear frequency sweep magnitudes of 100, 200, and 300 kHz centered around 1.5 MHz were applied to glass beads within gelatin phantoms and laser-generated bubbles within porcine lenses. The ultrasound transducer was translated axially to vary standing wave conditions, while comparing displacements using chirp pulses and 1.5 MHz tone burst pulses of the same duration and peak rarefactional pressure. Results demonstrated significant reduction in standing wave effects using chirp pulses, with displacement proportional to acoustic intensity and bubble size. PMID:17306697

Gas hydrates (clathrates) causing pore-water freshening and oxygen isotope fractionation in deep-water sedimentary sections of terrigenous continental margins

USGS Publications Warehouse

Hesse, R.; Harrison, W.E.

1981-01-01

The occurrence of gas hydrates in deep-water sections of the continental margins predicted from anomalous acoustic reflectors on seismic profiles has been confirmed by recent deep-sea drilling results. On the Pacific continental slope off Guatemala gas hydrates were brought up for the first time from two holes (497, 498A) drilled during Leg 67 of the DSDP in water depths of 2360 and 5500 m, respectively. The hydrates occur in organic matter-rich Pleistocene to Miocene terrigenous sediments. In the hydrate-bearing zone a marked decrease in interstitial water chlorinities was observed starting at about 10-20 m subbottom depth. Pore waters at the bottom of the holes (near 400 m subbottom) have as little as half the chlorinity of seawater (i.e. 9???). Similar, but less pronounced, trends were observed during previous legs of the DSDP in other hydrate-prone segments of the continental margins where recharge of fresh water from the continent can be excluded (e.g. Leg 11). The crystallization of hydrates, like ice, excludes salt ions from the crystal structure. During burial the dissolved salts are separated from the solids. Subsidence results in a downward motion of the solids (including hydrates) relative to the pore fluids. Thawing of hydrates during recovery releases fresh water which is remixed with the pore fluid not involved in hydrate formation. The volume of the latter decreases downhole thus causing downward decreasing salinity (chlorinity). Hydrate formation is responsible for oxygen isotope fractionation with 18O-enrichment in the hydrate explaining increasingly more positive ??18O values in the pore fluids recovered (after hydrate dissociation) with depth. ?? 1981.

Tunable Infrared Semiconductor Lasers

DTIC Science & Technology

2013-12-20

stripe to different positions of an addressable chirped, location-dependent period grating to select the different lasing wavelengths. Interferometric...grating or vernier effects. Our tuning mechanism is to shift the pump stripe to different positions of an addressable chirped, location-dependent period... stripe is applied and the lateral direction is the perpendicular direction across the pump stripe and parallel to the grating lines.  The chirped

Controlling nanoscale acoustic strains in silicon using chirped femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Tzianaki, E.; Bakarezos, M.; Tsibidis, G. D.; Petrakis, S.; Loukakos, P. A.; Kosmidis, C.; Tatarakis, M.; Papadogiannis, N. A.

2016-06-01

The influence of femtosecond laser pulse chirp on laser-generated longitudinal acoustic strains in Si (100) monocrystal substrates is studied. Degenerate femtosecond pump-probe transient reflectivity measurements are performed using a layered structure of thin Ti transducer film on an Si substrate. Experimental results show that acoustic strains, manifested as strong Brillouin oscillations, are more effectively induced when negatively chirped femtosecond laser pulses pump the transducer. These results are theoretically supported by a modified thermo-mechanical model based on the combination of a revised two-temperature model and elasticity theory that takes into account the instantaneous frequency of the chirped femtosecond laser pump pulses.

Tunable reflecting terahertz filter based on chirped metamaterial structure

PubMed Central

Yang, Jing; Gong, Cheng; Sun, Lu; Chen, Ping; Lin, Lie; Liu, Weiwei

2016-01-01

Tunable reflecting terahertz bandstop filter based on chirped metamaterial structure is demonstrated by numerical simulation. In the metamaterial, the metal bars are concatenated to silicon bars with different lengths. By varying the conductivity of the silicon bars, the reflectivity, central frequency and bandwidth of the metamaterial could be tuned. Light illumination could be introduced to change the conductivity of the silicon bars. Numerical simulations also show that the chirped metamaterial structure is insensitive to the incident angle and polarization-dependent. The proposed chirped metamaterial structure can be operated as a tunable bandstop filter whose modulation depth, bandwidth, shape factor and center frequency can be controlled by light pumping. PMID:27941833

Effects of chirp of pump pulses on broadband terahertz pulse spectra generated by optical rectification

NASA Astrophysics Data System (ADS)

Hamazaki, Junichi; Furusawa, Kentaro; Sekine, Norihiko; Kasamatsu, Akifumi; Hosako, Iwao

2016-11-01

The effects of the chirp of the pump pulse in broadband terahertz (THz) pulse generation by optical rectification (OR) in GaP were systematically investigated. It was found that the pre-compensation for the dispersion of GaP is important for obtaining smooth and single-peaked THz spectra as well as high power-conversion efficiency. It was also found that an excessive amount of chirp leads to distortions in THz spectra, which can be quantitatively analyzed by using a simple model. Our results highlight the importance of accurate control over the chirp of the pump pulse for generating broadband THz pulses by OR.

Influence of laser frequency chirp on deuteron energy from laser-driven deuterated methane cluster expansion

NASA Astrophysics Data System (ADS)

Li, H. Y.; Liu, J. S.

2010-06-01

The simulations of three-dimensional particle dynamics are carried out to investigate the Coulomb explosion dynamics of deuterated methane clusters under the irradiation of an ultrashort intense laser pulse. The final kinetic energy of deuterons produced from the cluster explosion is calculated as a function of the pulse width, the laser intensity and the pulse chirp. It is found that the deuteron energy obtained in an intense laser pulse with negative chirp is higher than that with positive chirp, which agrees qualitatively with the experimental results reported by Fukuda et al. [Y. Fukuda et al., Phys. Rev. A 67, 061201 (2003)].

Input and output compensation for the cochlear traveling wave delay in wide-band ABR recordings: implications for small acoustic tumor detection.

PubMed

Don, Manuel; Elberling, Claus; Maloff, Erin

2009-02-01

The Stacked ABR (auditory brainstem response) attempts at the output of the auditory periphery to compensate for the temporal dispersion of neural activation caused by the cochlear traveling wave in response to click stimulation. Compensation can also be made at the input by using a chirp stimulus. It has been demonstrated that the Stacked ABR is sensitive to small tumors that are often missed by standard ABR latency measures. Because a chirp stimulus requires only a single data acquisition run whereas the Stacked ABR requires six, we try to evaluate some indirect evidence justifying the use of a chirp for small tumor detection. We compared the sensitivity and specificity of different Stacked ABRs formed by aligning the derived-band ABRs according to (1) the individual's peak latencies, (2) the group mean latencies, and (3) the modeled latencies used to develop a chirp. For tumor detection with a chosen sensitivity of 95%, a relatively high specificity of 85% may be achieved with a chirp. It appears worthwhile to explore the actual use of a chirp because significantly shorter test and analysis times might be possible.

On the single sweep processing of auditory brainstem responses: click vs. chirp stimulations and active vs. passive electrodes.

PubMed

Corona-Strauss, Farah I; Delb, Wolfgang; Bloching, Marc; Strauss, Daniel J

2008-01-01

We have recently shown that click evoked auditory brainstem responses (ABRs) single sweeps can efficiently be processed by a hybrid novelty detection system. This approach allowed for the objective detection of hearing thresholds in a fraction of time of conventional schemes, making it appropriate for the efficient implementation of newborn hearing screening procedures. It is the objective of this study to evaluate whether this approach might further be improved by different stimulation paradigms and electrode settings. In particular, we evaluate chirp stimulations which compensate the basilar-membrane dispersion and active electrodes which are less sensitive to movements. This is the first study which is directed to a single sweep processing of chirp evoked ABRs. By concentrating on transparent features and a minimum number of adjustable parameters, we present an objective comparison of click vs.chirp stimulations and active vs. passive electrodes in the ultrafast ABR detection. We show that chirp evoked brainstem responses and active electrodes might improve the single sweeps analysis of ABRs.Consequently, we conclude that a single sweep processing of ABRs for the objective determination of hearing thresholds can further be improved by the use of optimized chirp stimulations and active electrodes.

Detecting the spatial chirp signals by fractional Fourier lens with transformation materials

NASA Astrophysics Data System (ADS)

Chen, J.; Hu, J.

2018-02-01

Fractional Fourier transform (FrFT) is the general form of the Fourier transform and is an important tool in signal processing. As one typical application of FrFT, detecting the chirp rate (CR, or known as the rate of frequency change) of a chirp signal is important in many optical measurements. The optical FrFT that based on graded index lens fails to detect the high CR chirp because the short wave propagation distance of the impulse in the lens will weaken the paraxial approximation condition. With the help of transformation optics, the improved FrFT lens is proposed to adjust the high CR as well as the impulse location of the given input chirp signal. The designed transformation materials can implement the effect of space compression, making the input chirp signal is equivalent to have lower CR, therefore the system can satisfy the paraxial approximation better. As a result, this lens can improve the detection precision for the high CR. The numerical simulations verified the design. The proposed device may have both theoretical and practical values, and the design demonstrates the ability and flexibility of TO in spatial signal processing.

Influence of long-term social interaction on chirping behavior, steroid levels and neurogenesis in weakly electric fish

PubMed Central

Dunlap, Kent D.; Chung, Michael; Castellano, James F.

2013-01-01

Summary Social interactions dramatically affect the brain and behavior of animals. Studies in birds and mammals indicate that socially induced changes in adult neurogenesis participate in the regulation of social behavior, but little is known about this relationship in fish. Here, we review studies in electric fish (Apteronotus leptorhychus) that link social stimulation, changes in electrocommunication behavior and adult neurogenesis in brain regions associated with electrocommunication. Compared with isolated fish, fish living in pairs have greater production of chirps, an electrocommunication signal, during dyadic interactions and in response to standardized artificial social stimuli. Social interaction also promotes neurogenesis in the periventricular zone, which contributes born cells to the prepacemaker nucleus, the brain region that regulates chirping. Both long-term chirp rate and periventricular cell addition depend on the signal dynamics (amplitude and waveform variation), modulations (chirps) and novelty of the stimuli from the partner fish. Socially elevated cortisol levels and cortisol binding to glucocorticoid receptors mediate, at least in part, the effect of social interaction on chirping behavior and brain cell addition. In a closely related electric fish (Brachyhypopomus gauderio), social interaction enhances cell proliferation specifically in brain regions for electrocommunication and only during the breeding season, when social signaling is most elaborate. Together, these studies demonstrate a consistent correlation between brain cell addition and environmentally regulated chirping behavior across many social and steroidal treatments and suggest a causal relationship. PMID:23761468

Improving the sensitivity of high-frequency subharmonic imaging with coded excitation: A feasibility study

PubMed Central

Shekhar, Himanshu; Doyley, Marvin M.

2012-01-01

Purpose: Subharmonic intravascular ultrasound imaging (S-IVUS) could visualize the adventitial vasa vasorum, but the high pressure threshold required to incite subharmonic behavior in an ultrasound contrast agent will compromise sensitivity—a trait that has hampered the clinical use of S-IVUS. The purpose of this study was to assess the feasibility of using coded-chirp excitations to improve the sensitivity and axial resolution of S-IVUS. Methods: The subharmonic response of Targestar-pTM, a commercial microbubble ultrasound contrast agent (UCA), to coded-chirp (5%–20% fractional bandwidth) pulses and narrowband sine-burst (4% fractional bandwidth) pulses was assessed, first using computer simulations and then experimentally. Rectangular windowed excitation pulses with pulse durations ranging from 0.25 to 3 μs were used in all studies. All experimental studies were performed with a pair of transducers (20 MHz/10 MHz), both with diameter of 6.35 mm and focal length of 50 mm. The size distribution of the UCA was measured with a CasyTM Cell counter. Results: The simulation predicted a pressure threshold that was an order of magnitude higher than that determined experimentally. However, all other predictions were consistent with the experimental observations. It was predicted that: (1) exciting the agent with chirps would produce stronger subharmonic response relative to those produced by sine-bursts; (2) increasing the fractional bandwidth of coded-chirp excitation would increase the sensitivity of subharmonic imaging; and (3) coded-chirp would increase axial resolution. The experimental results revealed that subharmonic-to-fundamental ratios obtained with chirps were 5.7 dB higher than those produced with sine-bursts of similar duration. The axial resolution achieved with 20% fractional bandwidth chirps was approximately twice that achieved with 4% fractional bandwidth sine-bursts. Conclusions: The coded-chirp method is a suitable excitation strategy for subharmonic IVUS imaging. At the 20 MHz transmission frequency and 20% fractional bandwidth, coded-chirp excitation appears to represent the ideal tradeoff between subharmonic strength and axial resolution. PMID:22482626

Quantum-optical coherence tomography with classical light.

PubMed

Lavoie, J; Kaltenbaek, R; Resch, K J

2009-03-02

Quantum-optical coherence tomography (Q-OCT) is an interferometric technique for axial imaging offering several advantages over conventional methods. Chirped-pulse interferometry (CPI) was recently demonstrated to exhibit all of the benefits of the quantum interferometer upon which Q-OCT is based. Here we use CPI to measure axial interferograms to profile a sample accruing the important benefits of Q-OCT, including automatic dispersion cancellation, but with 10 million times higher signal. Our technique solves the artifact problem in Q-OCT and highlights the power of classical correlation in optical imaging.

Transient snakes in an ohmic plasma associated with a minor disruption in the HT-7 tokamak

NASA Astrophysics Data System (ADS)

Mao, Songtao; Xu, Liqing; Hu, Liqun; Chen, Kaiyun

2014-05-01

A transient burst (ms, an order of the fast-particle slowdown timescale) of a spontaneous snake is observed for the first time in a HT-7 heavy impurity ohmic plasma. The features of the low-Z impurity snake are presented. The flatten electron profile due to the heavy impurity reveals the formation of a large magnetic island. The foot of the impurity accumulation is consistent with the location of the transient snake. The strong frequency-chirping behaviors and the spatial structures of the snake are also presented.

Broadband interferometric characterization of divergence and spatial chirp.

PubMed

Meier, Amanda K; Iliev, Marin; Squier, Jeff A; Durfee, Charles G

2015-09-01

We demonstrate a spectral interferometric method to characterize lateral and angular spatial chirp to optimize intensity localization in spatio-temporally focused ultrafast beams. Interference between two spatially sheared beams in an interferometer will lead to straight fringes if the wavefronts are curved. To produce reference fringes, we delay one arm relative to another in order to measure fringe rotation in the spatially resolved spectral interferogram. With Fourier analysis, we can obtain frequency-resolved divergence. In another arrangement, we spatially flip one beam relative to the other, which allows the frequency-dependent beamlet direction (angular spatial chirp) to be measured. Blocking one beam shows the spatial variation of the beamlet position with frequency (i.e., the lateral spatial chirp).

Pre-chirp managed nonlinear amplification in fibers delivering 100  W, 60  fs pulses.

PubMed

Liu, Wei; Schimpf, Damian N; Eidam, Tino; Limpert, Jens; Tünnermann, Andreas; Kärtner, Franz X; Chang, Guoqing

2015-01-15

We demonstrate a pre-chirp managed Yb-doped fiber laser system that outputs 75 MHz, 130 W spectrally broadened pulses, which are compressed by a diffraction-grating pair to 60 fs with average powers as high as 100 W. Fine tuning the pulse chirp prior to amplification leads to high-quality compressed pulses. Detailed experiments and numerical simulation reveal that the optimum pre-chirp group-delay dispersion increases from negative to positive with increasing output power for rod-type high-power fiber amplifiers. The resulting laser parameters are suitable for extreme nonlinear optics applications such as frequency conversion in femtosecond enhancement cavities.

Chirped-cavity dispersion-compensation filter design.

PubMed

Li, Ya-Ping; Chen, Sheng-Hui; Lee, Cheng-Chung

2006-03-01

A new basic structure of a dispersive-compensation filter, called a chirped-cavity dispersion-compensator (CCDC) filter, was designed to offer the advantages of small ripples in both reflectance and group-delay dispersion (GDD). This filter provides a high dispersion compensation, like the Gires-Tournois interferometer (GTI) filter, and a wide working bandwidth, like the chirped mirror (CM). The structure of the CCDC is a cavity-type Fabry-Perot filter with a spacer layer (2 mH or 2 mL) and a chirped high reflector. The CCDC filter can provide a negative GDD of -50 fs2 over a bandwidth of 56 THz with half the optical thickness of the CM or the GTI.

Chirped-cavity dispersion-compensation filter design

NASA Astrophysics Data System (ADS)

Li, Ya-Ping; Chen, Sheng-Hui; Lee, Cheng-Chung

2006-03-01

A new basic structure of a dispersive-compensation filter, called a chirped-cavity dispersion-compensator (CCDC) filter, was designed to offer the advantages of small ripples in both reflectance and group-delay dispersion (GDD). This filter provides a high dispersion compensation, like the Gires-Tournois interferometer (GTI) filter, and a wide working bandwidth, like the chirped mirror (CM). The structure of the CCDC is a cavity-type Fabry-Perot filter with a spacer layer (2 mH or 2 mL) and a chirped high reflector. The CCDC filter can provide a negative GDD of -50 fs2 over a bandwidth of 56 THz with half the optical thickness of the CM or the GTI.

Individual acoustic variation in Belding's ground squirrel alarm chirps in the High Sierra Nevada

NASA Astrophysics Data System (ADS)

McCowan, Brenda; Hooper, Stacie L.

2002-03-01

The acoustic structure of calls within call types can vary as function of individual identity, sex, and social group membership and is important in kin and social group recognition. Belding's ground squirrels (Spermophilus beldingi) produce alarm chirps that function in predator avoidance but little is known about the acoustic variability of these alarm chirps. The purpose of this preliminary study was to analyze the acoustic structure of alarm chirps with respect to individual differences (e.g., signature information) from eight Belding's ground squirrels from four different lakes in the High Sierra Nevada. Results demonstrate that alarm chirps are individually distinctive, and that acoustic similarity among individuals may correspond to genetic similarity and thus dispersal patterns in this species. These data suggest, on a preliminary basis, that the acoustic structure of calls might be used as a bioacoustic tool for tracking individuals, dispersal, and other population dynamics in Belding's ground squirrels, and perhaps other vocal species.

Effects of auditory selective attention on chirp evoked auditory steady state responses.

PubMed

Bohr, Andreas; Bernarding, Corinna; Strauss, Daniel J; Corona-Strauss, Farah I

2011-01-01

Auditory steady state responses (ASSRs) are frequently used to assess auditory function. Recently, the interest in effects of attention on ASSRs has increased. In this paper, we investigated for the first time possible effects of attention on AS-SRs evoked by amplitude modulated and frequency modulated chirps paradigms. Different paradigms were designed using chirps with low and high frequency content, and the stimulation was presented in a monaural and dichotic modality. A total of 10 young subjects participated in the study, they were instructed to ignore the stimuli and after a second repetition they had to detect a deviant stimulus. In the time domain analysis, we found enhanced amplitudes for the attended conditions. Furthermore, we noticed higher amplitudes values for the condition using frequency modulated low frequency chirps evoked by a monaural stimulation. The most difference between attended and unattended modality was exhibited at the dichotic case of the amplitude modulated condition using chirps with low frequency content.

Mother-offspring recognition in the domestic cat: Kittens recognize their own mother's call.

PubMed

Szenczi, Péter; Bánszegi, Oxána; Urrutia, Andrea; Faragó, Tamás; Hudson, Robyn

2016-07-01

Acoustic communication can play an important part in mother-young recognition in many mammals. This, however, has still only been investigated in a small range mainly of herd- or colony-living species. Here we report on the behavioral response of kittens of the domestic cat, a typically solitary carnivore, to playbacks of "greeting chirps" and "meows" from their own versus alien mothers. We found significantly stronger responses to the chirps from kittens' own mother than to her meows or to the chirps or meows of alien mothers. Acoustic analysis revealed greater variation between vocalizations from different mothers than for vocalizations from the same mother. We conclude that chirps emitted by mother cats at the nest represent a specific form of vocal communication with their young, and that kittens learn and respond positively to these and distinguish them from chirps of other mothers and from other cat vocalizations while still in the nest. © 2016 Wiley Periodicals, Inc. Dev Psychobiol 58: 568-577, 2016. © 2016 Wiley Periodicals, Inc.

Two-photon absorption spectroscopy using intense phase-chirped entangled beams

NASA Astrophysics Data System (ADS)

Svozilík, Jiří; Peřina, Jan; León-Montiel, Roberto de J.

2018-06-01

We numerically analyze the use of intense entangled twin beams for ultra-sensitive spectroscopic measurements in chemical and biological systems. The examined scheme makes use of intense frequency-modulated (chirped) entangled beams to successfully extract information about the intermediate material states that contribute to the two-photon excitation of an absorbing medium. Robustness of the presented method is examined with respect to the applied intervals of the frequency chirp.

Project REPONS: Offshore Faults, Tectonic Deformation and Turbidite Record in Response to the January 12 2010 Earthquake, Haiti

NASA Astrophysics Data System (ADS)

McHugh, C. M.; Gulick, S. P.; Cormier, M.; Dieudonne, N.; Diebold, J. B.; Douilly, R.; Hornbach, M.; Johnson, H. E.; Mishkin, K.; Seeber, L.; Sorlien, C. C.; Steckler, M. S.; Symithe, S. J.

2010-12-01

As part of an NSF RAPID response to the January 12, 2010 earthquake, we mapped the underwater continuation of the Enriquillo-Plantain Garden fault zone (EPGF) west of Léogâne. Multibeam bathymetry, sidescan sonar, chirp subbottom profiler, sediment sampling and CTD measurements were conducted in water depths of 2 m to 1750 m from the R/V Endeavor and from a small inflatable boat. The offshore segment of the EPGF is manifested by two steep, 50-80 m high linear ridges and at least two subsurface faults. The submarine EPGF is part of a transition from releasing to restraining segment. To the east, it joins its onshore trace in a releasing bend and continues to the west in a restraining bend that perhaps caused the Tapion ridge. Within the Baies de Petit and Grand Goâve, river outlets are correlated with lateral spreading and/or subsidence where we observed increased local damage to structures. Lateral spreading and/or subsidence appears to have increased tsunami effects locally. Coral uplift NE and SW of offshore fault traces offer evidence of the January 12, 2010 surface deformation. While a seafloor rupture is not evident from the data collected we do image deformation within the upper 20 m in both bays. Mass wasting and gravity flow deposits from the last and older earthquakes were tracked from the Léogâne delta and along the coast to the deepest depocenter. Th-234 and Be-7 with half-lives of 24 and 53 days, respectively verified the January 12 turbidite and indicated an influx of terrigenous sediment mixed with marine sources. Coral debris was sampled in the shelf and upper slope (100-300 m) near the EPGF; basalt sand derived from the highlands and wood fragments at intermediate water depths (1000-1100 m); lastly an ~0.03 km3 and >1 m thick turbidite was deposited over 50 km2 in the Canal du Sud depocenter (1750 m). The sandy parts of all cores recovered from Canal du Sud depocenter have alternate episodes of traction deposition and erosion that reflect pulses of increased energy fluctuations consistent with long waves. These currents are generated by seiches and tsunamis. In the deepest waters of Canal du Sud at 1750 m, we observed a 600 m thick layer of sediment that was still in suspension almost two months after the earthquake. Deep marginal basins adjacent to strike slip margins are important for tracking paleoseismic records that are critical for understanding the rupture history of these faults.

Approaching the potential seismogenic source of the 8 September 1905 earthquake: New geophysical, geological and biochemical data from the S. Eufemia Gulf (S Italy)

NASA Astrophysics Data System (ADS)

Loreto, Maria Filomena; Fracassi, Umberto; Franzo, Annalisa; Del Negro, Paola; Zgur, Fabrizio; Facchin, Lorenzo

2013-04-01

The earthquake that occurred on 8 September 1905 is one of the strongest events that ever affected western Calabria. This event caused 557 casualties, more than 2000 injured, and left about 300,000 people homeless. The mainshock was followed by a feeble tsunami and hundreds of aftershocks. During the last 15 years, various authors proposed hypotheses for a seismogenic source causative of the 1905 earthquake, apparently diverse and without an unequivocal solution. To study the active tectonics of the region and to gain insight into a potential seismogenic source responsible for the 1905 event, we carried out a well-targeted multidisciplinary survey within the Gulf of S. Eufemia (summer 2010) in the frame of the ISTEGE project, using the R/V OGS-Explora. The acquired dataset consists of geophysical data, oceanographical measurements, and biological, chemical and sedimentary samples. The analysis of the geophysical data (330 km of MultiChannel Seismic, 2223 km of sub-bottom Chirp profiles, and 2231 km2 of high resolution morpho-bathymetric data) allowed the identification of some main morpho-structural features characterizing the sedimentary basin hosted within the S. Eufemia Gulf. The three main tectonic structures shaping the basin and its sedimentary bodies are: 1) an E-dipping large normal fault, N31° oriented; 2) a WNW-trending polyphased fault system; and 3) a likely E-W trending fault with dip-slip motion. Among these, the large normal fault shows evidence of activity, as witnessed by the deformed recent sediments, and by the lineament due to consistent seabed rupture observed on the seafloor along which, locally, fluids leakage occurs. Finally, evidence of probable geothermal activity is reflected by the anomalous distribution of prokaryotic abundance and biopolymeric C content, whereas no such evidence comes from water temperature analysis (CTD measurements). The various seismogenic sources proposed in the literature make up a composite framework of this sector of western Calabria, and can be reviewed a) in the light of the geological evidence arising from the newly acquired multidisciplinary dataset and b) against regional seismotectonic models - with surprising results. Re-appraising such a major historical earthquakes as the 1905 one located within poorly explored submarine areas, promisingly enhances the seismotectonic picture of western Calabria. A comprehensive understanding of the region and robust constraining of the seismogenic source of the 1905 earthquake may arise from an integrated interpretation of our data together with a) on-land field evidence and b) seismological modeling.

Geologic framework of the northern North Carolina, USA inner continental shelf and its influence on coastal evolution

USGS Publications Warehouse

Thieler, E. Robert; Foster, David S.; Himmelstoss, Emily A.; Mallinson, David J.

2013-01-01

The inner continental shelf off the northern Outer Banks of North Carolina was mapped using sidescan sonar, interferometric swath bathymetry, and high-resolution chirp and boomer subbottom profiling systems. We use this information to describe the shallow stratigraphy, reinterpret formation mechanisms of some shoal features, evaluate local relative sea-levels during the Late Pleistocene, and provide new constraints, via recent bedform evolution, on regional sediment transport patterns. The study area is approximately 290 km long by 11 km wide, extending from False Cape, Virginia to Cape Lookout, North Carolina, in water depths ranging from 6 to 34 m. Late Pleistocene sedimentary units comprise the shallow geologic framework of this region and determine both the morphology of the inner shelf and the distribution of sediment sources and sinks. We identify Pleistocene sedimentary units beneath Diamond Shoals that may have provided a geologic template for the location of modern Cape Hatteras and earlier paleo-capes during the Late Pleistocene. These units indicate shallow marine deposition 15–25 m below present sea-level. The uppermost Pleistocene unit may have been deposited as recently as Marine Isotope Stage 3, although some apparent ages for this timing may be suspect. Paleofluvial valleys incised during the Last Glacial Maximum traverse the inner shelf throughout the study area and dissect the Late Pleistocene units. Sediments deposited in the valleys record the Holocene transgression and provide insight into the evolutionary history of the barrier-estuary system in this region. The relationship between these valleys and adjacent shoal complexes suggests that the paleo-Roanoke River did not form the Albemarle Shelf Valley complex as previously proposed; a major fluvial system is absent and thus makes the formation of this feature enigmatic. Major shoal features in the study area show mobility at decadal to centennial timescales, including nearly a kilometer of shoal migration over the past 134 yr. Sorted bedforms occupy ~ 1000 km2 of seafloor in Raleigh Bay, and indicate regional sediment transport patterns between Capes Hatteras and Lookout that help explain long-term sediment accumulation and morphologic development. Portions of the inner continental shelf with relatively high sediment abundance are characterized by shoals and shoreface-attached ridges, and where sediment is less abundant, the seafloor is dominated by sorted bedforms. These relationships are also observed in other passive margin settings, suggesting a continuum of shelf morphology that may have broad application for interpreting inner shelf sedimentation patterns.

Auditory Brainstem Responses for Click and CE-chirp Stimuli in Individuals with and without Occupational Noise Exposure

PubMed Central

Pushpalatha, Zeena Venkatacheluvaiah; Konadath, Sreeraj

2016-01-01

Introduction: Encoding of CE-chirp and click stimuli in auditory system was studied using auditory brainstem responses (ABRs) among individuals with and without noise exposure. Materials and Methods: The study consisted of two groups. Group 1 (experimental group) consisted of 20 (40 ears) individuals exposed to occupational noise with hearing thresholds within 25 dB HL. They were further divided into three subgroups based on duration of noise exposure (0–5 years of exposure-T1, 5–10 years of exposure-T2, and >10 years of exposure-T3). Group 2 (control group) consisted of 20 individuals (40 ears). Absolute latency and amplitude of waves I, III, and V were compared between the two groups for both click and CE-chirp stimuli. T1, T2, and T3 groups were compared for the same parameters to see the effect of noise exposure duration on CE-chirp and click ABR. Result: In Click ABR, while both the parameters for wave III were significantly poorer for the experimental group, wave V showed a significant decline in terms of amplitude only. There was no significant difference obtained for any of the parameters for wave I. In CE-Chirp ABR, the latencies for all three waves were significantly prolonged in the experimental group. However, there was a significant decrease in terms of amplitude in only wave V for the same group. Discussion: Compared to click evoked ABR, CE-Chirp ABR was found to be more sensitive in comparison of latency parameters in individuals with occupational noise exposure. Monitoring of early pathological changes at the brainstem level can be studied effectively by using CE-Chirp stimulus in comparison to click stimulus. Conclusion: This study indicates that ABR's obtained with CE-chirp stimuli serves as an effective tool to identify the early pathological changes due to occupational noise exposure when compared to click evoked ABR. PMID:27762255

The Steppengrille (Gryllus spec./assimilis): Selective Filters and Signal Mismatch on Two Time Scales

PubMed Central

Rothbart, Matti Michael; Hennig, Ralf Matthias

2012-01-01

In Europe, several species of crickets are available commercially as pet food. Here we investigated the calling song and phonotactic selectivity for sound patterns on the short and long time scales for one such a cricket, Gryllus spec., available as “Gryllus assimilis”, the Steppengrille, originally from Ecuador. The calling song consisted of short chirps (2–3 pulses, carrier frequency: 5.0 kHz) emitted with a pulse period of 30.2 ms and chirp rate of 0.43 per second. Females exhibited high selectivity on both time scales. The preference for pulse period peaked at 33 ms which was higher then the pulse period produced by males. Two consecutive pulses per chirp at the correct pulse period were already sufficient for positive phonotaxis. The preference for the chirp pattern was limited by selectivity for small chirp duty cycles and for chirp periods between 200 ms and 500 ms. The long chirp period of the songs of males was unattractive to females. On both time scales a mismatch between the song signal of the males and the preference of females was observed. The variability of song parameters as quantified by the coefficient of variation was below 50% for all temporal measures. Hence, there was not a strong indication for directional selection on song parameters by females which could account for the observed mismatch. The divergence of the chirp period and female preference may originate from a founder effect, when the Steppengrille was cultured. Alternatively the mismatch was a result of selection pressures exerted by commercial breeders on low singing activity, to satisfy customers with softly singing crickets. In the latter case the prominent divergence between male song and female preference was the result of domestication and may serve as an example of rapid evolution of song traits in acoustic communication systems. PMID:22970154

Combined chirp coded tissue harmonic and fundamental ultrasound imaging for intravascular ultrasound: 20–60 MHz phantom and ex vivo results

PubMed Central

Park, Jinhyoung; Li, Xiang; Zhou, Qifa; Shung, K. Kirk

2013-01-01

The application of chirp coded excitation to pulse inversion tissue harmonic imaging can increase signal to noise ratio. On the other hand, the elevation of range side lobe level, caused by leakages of the fundamental signal, has been problematic in mechanical scanners which are still the most prevalent in high frequency intravascular ultrasound imaging. Fundamental chirp coded excitation imaging can achieve range side lobe levels lower than –60 dB with Hanning window, but it yields higher side lobes level than pulse inversion chirp coded tissue harmonic imaging (PI-CTHI). Therefore, in this paper a combined pulse inversion chirp coded tissue harmonic and fundamental imaging mode (CPI-CTHI) is proposed to retain the advantages of both chirp coded harmonic and fundamental imaging modes by demonstrating 20–60 MHz phantom and ex vivo results. A simulation study shows that the range side lobe level of CPI-CTHI is 16 dB lower than PI-CTHI, assuming that the transducer translates incident positions by 50 μm when two beamlines of pulse inversion pair are acquired. CPI-CTHI is implemented for a proto-typed intravascular ultrasound scanner capable of combined data acquisition in real-time. A wire phantom study shows that CPI-CTHI has a 12 dB lower range side lobe level and a 7 dB higher echo signal to noise ratio than PI-CTHI, while the lateral resolution and side lobe level are 50 μm finer and –3 dB less than fundamental chirp coded excitation imaging respectively. Ex vivo scanning of a rabbit trachea demonstrates that CPI-CTHI is capable of visualizing blood vessels as small as 200 μm in diameter with 6 dB better tissue contrast than either PI-CTHI or fundamental chirp coded excitation imaging. These results clearly indicate that CPI-CTHI may enhance tissue contrast with less range side lobe level than PI-CTHI. PMID:22871273

Chirping for efficiency enhancement of the free-electron laser

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

Moore, G.T.; Goldstein, J.C.

1988-01-01

One-dimensional numerical studies have been made of free-electron laser oscillators in which the incident electron energy varies (chirps) as a function of time over each micropulse. Optical radiation resonant with such micropulses is chirped in frequency. Highest calculated efficiency (up to 8.1% for wavelengths near 10 ..mu..m) has been obtained in cases where the optical pulse at saturation is short compared to the slippage. 8 refs., 7 figs., 1 tab.

Frequency chirped light at large detuning with an injection-locked diode laser

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

Teng, K.; Disla, M.; Dellatto, J.

2015-04-15

We have developed a laser system to generate frequency-chirped light at rapid modulation speeds (∼100 MHz) with a large frequency offset. Light from an external cavity diode laser with its frequency locked to an atomic resonance is passed through a lithium niobate electro-optical phase modulator. The phase modulator is driven by a ∼6 GHz signal whose frequency is itself modulated with a RF MHz signal (<200 MHz). A second injection locked diode laser is used to filter out all of the light except the frequency-chirped ±1 order by more than 30 dB. Using this system, it is possible to generatemore » a 1 GHz frequency chirp in 5 ns.« less

Photonic chirped radio-frequency generator with ultra-fast sweeping rate and ultra-wide sweeping range.

PubMed

Wun, Jhih-Min; Wei, Chia-Chien; Chen, Jyehong; Goh, Chee Seong; Set, S Y; Shi, Jin-Wei

2013-05-06

A high-performance photonic sweeping-frequency (chirped) radio-frequency (RF) generator has been demonstrated. By use of a novel wavelength sweeping distributed-feedback (DFB) laser, which is operated based on the linewidth enhancement effect, a fixed wavelength narrow-linewidth DFB laser, and a wideband (dc to 50 GHz) photodiode module for the hetero-dyne beating RF signal generation, a very clear chirped RF waveform can be captured by a fast real-time scope. A very-high frequency sweeping rate (10.3 GHz/μs) with an ultra-wide RF frequency sweeping range (~40 GHz) have been demonstrated. The high-repeatability (~97%) in sweeping frequency has been verified by analyzing tens of repetitive chirped waveforms.

Phase-locking transition in a chirped superconducting Josephson resonator.

PubMed

Naaman, O; Aumentado, J; Friedland, L; Wurtele, J S; Siddiqi, I

2008-09-12

We observe a sharp threshold for dynamic phase locking in a high-Q transmission line resonator embedded with a Josephson tunnel junction, and driven with a purely ac, chirped microwave signal. When the drive amplitude is below a critical value, which depends on the chirp rate and is sensitive to the junction critical current I0, the resonator is only excited near its linear resonance frequency. For a larger amplitude, the resonator phase locks to the chirped drive and its amplitude grows until a deterministic maximum is reached. Near threshold, the oscillator evolves smoothly in one of two diverging trajectories, providing a way to discriminate small changes in I0 with a nonswitching detector, with potential applications in quantum state measurement.

A fractional Fourier transform analysis of the scattering of ultrasonic waves.

PubMed

Tant, Katherine M M; Mulholland, Anthony J; Langer, Matthias; Gachagan, Anthony

2015-03-08

Many safety critical structures, such as those found in nuclear plants, oil pipelines and in the aerospace industry, rely on key components that are constructed from heterogeneous materials. Ultrasonic non-destructive testing (NDT) uses high-frequency mechanical waves to inspect these parts, ensuring they operate reliably without compromising their integrity. It is possible to employ mathematical models to develop a deeper understanding of the acquired ultrasonic data and enhance defect imaging algorithms. In this paper, a model for the scattering of ultrasonic waves by a crack is derived in the time-frequency domain. The fractional Fourier transform (FrFT) is applied to an inhomogeneous wave equation where the forcing function is prescribed as a linear chirp, modulated by a Gaussian envelope. The homogeneous solution is found via the Born approximation which encapsulates information regarding the flaw geometry. The inhomogeneous solution is obtained via the inverse Fourier transform of a Gaussian-windowed linear chirp excitation. It is observed that, although the scattering profile of the flaw does not change, it is amplified. Thus, the theory demonstrates the enhanced signal-to-noise ratio permitted by the use of coded excitation, as well as establishing a time-frequency domain framework to assist in flaw identification and classification.

Numerical investigation of output beam quality in efficient broadband optical parametric chirped pulse amplification

NASA Astrophysics Data System (ADS)

Liu, Xiao-Di; Xu, Lu; Liang, Xiao-Yan

2017-01-01

We theoretically analyzed output beam quality of broad bandwidth non-collinear optical parametric chirped pulse amplification (NOPCPA) in LiB3O5 (LBO) centered at 800 nm. With a three-dimensional numerical model, the influence of the pump intensity, pump and signal spatial modulations, and the walk-off effect on the OPCPA output beam quality are presented, together with conversion efficiency and the gain spectrum. The pump modulation is a dominant factor that affects the output beam quality. Comparatively, the influence of signal modulation is insignificant. For a low-energy system with small beam sizes, walk-off effect has to be considered. Pump modulation and walk-off effect lead to asymmetric output beam profile with increased modulation. A special pump modulation type is found to optimize output beam quality and efficiency. For a high-energy system with large beam sizes, the walk-off effect can be neglected, certain back conversion is beneficial to reduce the output modulation. A trade-off must be made between the output beam quality and the conversion efficiency, especially when the pump modulation is large since. A relatively high conversion efficiency and a low output modulation are both achievable by controlling the pump modulation and intensity.

Ultrasound Elasticity Imaging System with Chirp-Coded Excitation for Assessing Biomechanical Properties of Elasticity Phantom

PubMed Central

Chun, Guan-Chun; Chiang, Hsing-Jung; Lin, Kuan-Hung; Li, Chien-Ming; Chen, Pei-Jarn; Chen, Tainsong

2015-01-01

The biomechanical properties of soft tissues vary with pathological phenomenon. Ultrasound elasticity imaging is a noninvasive method used to analyze the local biomechanical properties of soft tissues in clinical diagnosis. However, the echo signal-to-noise ratio (eSNR) is diminished because of the attenuation of ultrasonic energy by soft tissues. Therefore, to improve the quality of elastography, the eSNR and depth of ultrasound penetration must be increased using chirp-coded excitation. Moreover, the low axial resolution of ultrasound images generated by a chirp-coded pulse must be increased using an appropriate compression filter. The main aim of this study is to develop an ultrasound elasticity imaging system with chirp-coded excitation using a Tukey window for assessing the biomechanical properties of soft tissues. In this study, we propose an ultrasound elasticity imaging system equipped with a 7.5-MHz single-element transducer and polymethylpentene compression plate to measure strains in soft tissues. Soft tissue strains were analyzed using cross correlation (CC) and absolution difference (AD) algorithms. The optimal parameters of CC and AD algorithms used for the ultrasound elasticity imaging system with chirp-coded excitation were determined by measuring the elastographic signal-to-noise ratio (SNRe) of a homogeneous phantom. Moreover, chirp-coded excitation and short pulse excitation were used to measure the elasticity properties of the phantom. The elastographic qualities of the tissue-mimicking phantom were assessed in terms of Young’s modulus and elastographic contrast-to-noise ratio (CNRe). The results show that the developed ultrasound elasticity imaging system with chirp-coded excitation modulated by a Tukey window can acquire accurate, high-quality elastography images. PMID:28793718

Contralateral Inhibition of Click- and Chirp-Evoked Human Compound Action Potentials

PubMed Central

Smith, Spencer B.; Lichtenhan, Jeffery T.; Cone, Barbara K.

2017-01-01

Cochlear outer hair cells (OHC) receive direct efferent feedback from the caudal auditory brainstem via the medial olivocochlear (MOC) bundle. This circuit provides the neural substrate for the MOC reflex, which inhibits cochlear amplifier gain and is believed to play a role in listening in noise and protection from acoustic overexposure. The human MOC reflex has been studied extensively using otoacoustic emissions (OAE) paradigms; however, these measurements are insensitive to subsequent “downstream” efferent effects on the neural ensembles that mediate hearing. In this experiment, click- and chirp-evoked auditory nerve compound action potential (CAP) amplitudes were measured electrocochleographically from the human eardrum without and with MOC reflex activation elicited by contralateral broadband noise. We hypothesized that the chirp would be a more optimal stimulus for measuring neural MOC effects because it synchronizes excitation along the entire length of the basilar membrane and thus evokes a more robust CAP than a click at low to moderate stimulus levels. Chirps produced larger CAPs than clicks at all stimulus intensities (50–80 dB ppeSPL). MOC reflex inhibition of CAPs was larger for chirps than clicks at low stimulus levels when quantified both in terms of amplitude reduction and effective attenuation. Effective attenuation was larger for chirp- and click-evoked CAPs than for click-evoked OAEs measured from the same subjects. Our results suggest that the chirp is an optimal stimulus for evoking CAPs at low stimulus intensities and for assessing MOC reflex effects on the auditory nerve. Further, our work supports previous findings that MOC reflex effects at the level of the auditory nerve are underestimated by measures of OAE inhibition. PMID:28420960

Best chirplet chain: Near-optimal detection of gravitational wave chirps

NASA Astrophysics Data System (ADS)

Chassande-Mottin, Éric; Pai, Archana

2006-02-01

The list of putative sources of gravitational waves possibly detected by the ongoing worldwide network of large scale interferometers has been continuously growing in the last years. For some of them, the detection is made difficult by the lack of a complete information about the expected signal. We concentrate on the case where the expected gravitational wave (GW) is a quasiperiodic frequency modulated signal i.e., a chirp. In this article, we address the question of detecting an a priori unknown GW chirp. We introduce a general chirp model and claim that it includes all physically realistic GW chirps. We produce a finite grid of template waveforms which samples the resulting set of possible chirps. If we follow the classical approach (used for the detection of inspiralling binary chirps, for instance), we would build a bank of quadrature matched filters comparing the data to each of the templates of this grid. The detection would then be achieved by thresholding the output, the maximum giving the individual which best fits the data. In the present case, this exhaustive search is not tractable because of the very large number of templates in the grid. We show that the exhaustive search can be reformulated (using approximations) as a pattern search in the time-frequency plane. This motivates an approximate but feasible alternative solution which is clearly linked to the optimal one. The time-frequency representation and pattern search algorithm are fully determined by the reformulation. This contrasts with the other time-frequency based methods presented in the literature for the same problem, where these choices are justified by “ad hoc” arguments. In particular, the time-frequency representation has to be unitary. Finally, we assess the performance, robustness and computational cost of the proposed method with several benchmarks using simulated data.

Cascaded chirped photon acceleration for efficient frequency conversion

NASA Astrophysics Data System (ADS)

Edwards, Matthew R.; Qu, Kenan; Jia, Qing; Mikhailova, Julia M.; Fisch, Nathaniel J.

2018-05-01

A cascaded sequence of photon acceleration stages using the instantaneous creation of a plasma density gradient by flash ionization allows the generation of coherent and chirped ultraviolet and x-ray pulses with independently tunable frequency and bandwidth. The efficiency of the cascaded process scales with 1/ω in energy, and multiple stages produce significant frequency up-conversion with gas-density plasmas. Chirping permits subsequent pulse compression to few-cycle durations, and output frequencies are not limited to integer harmonics.

Chirp-enhanced fast light in semiconductor optical amplifiers.

PubMed

Sedgwick, F G; Pesala, Bala; Uskov, Alexander V; Chang-Hasnain, C J

2007-12-24

We present a novel scheme to increase the THz-bandwidth fast light effect in semiconductor optical amplifiers and increase the number of advanced pulses. By introducing a linear chirp to the input pulses before the SOA and recompressing at the output with an opposite chirp, the advance-bandwidth product reached 3.5 at room temperature, 1.55 microm wavelength. This is the largest number reported, to the best of our knowledge, for a semiconductor slow/fast light device.

Influence of two-electrode montages on the level-specific (LS) CE-Chirp auditory brainstem response (ABR) at multiple intensity levels.

PubMed

Dzulkarnain, Ahmad Aidil Arafat; Noor Ibrahim, Siti Hajra Mu'minah; Anuar, Nur Farah Aida; Abdullah, Siti Aisyah; Tengku Zam Zam, Tengku Zulaila Hasma; Rahmat, Sarah; Mohd Ruzai, Muhammad Amar

2017-10-01

To investigate the influence of two different electrode montages (ipsilateral: reference to mastoid and vertical: reference to nape of neck) to the ABR results recorded using a level-specific (LS)-CE-Chirp® in normally hearing subjects at multiple intensities levels. Quasi-experimental and repeated measure study designs were applied in this study. Two different stopping criteria were used, (1) a fixed-signal averaging 4000 sweeps and, (2) a minimum quality indicator of Fmp = 3.1 with a minimum of 800 sweeps. Twenty-nine normally hearing adults (18 females, 11 male) participated. Wave V amplitudes were significantly larger in the LS CE-Chirp® recorded from the vertical montage than the ipsilateral montage. Waves I and III amplitudes were significantly larger from the ipsilateral LS CE-Chirp® than from the other montages and stimulus combinations. The differences in the quality of the ABR recording between the vertical and ipsilateral montages were marginal. Overall, the result suggested that the vertical LS CE-Chirp® ABR had a high potential for a threshold-seeking application, because it produced a higher wave V amplitude. The Ipsilateral LS CE-Chirp® ABR, on the other hand, might also have a high potential for the site of lesion application, because it produced larger waves I and III amplitudes.

Characteristics of nonlinear imaging of broadband laser stacked by chirped pulses

NASA Astrophysics Data System (ADS)

Wang, Youwen; You, Kaiming; Chen, Liezun; Lu, Shizhuan; Dai, Zhiping; Ling, Xiaohui

2014-11-01

Nanosecond-level pulses of specific shape is usually generated by stacking chirped pulses for high-power inertial confinement fusion driver, in which nonlinear imaging of scatterers may damage precious optical elements. We present a numerical study of the characteristics of nonlinear imaging of scatterers in broadband laser stacked by chirped pulses to disclose the dependence of location and intensity of images on the parameters of the stacked pulse. It is shown that, for sub-nanosecond long sub-pulses with chirp or transform-limited sub-pulses, the time-mean intensity and location of images through normally dispersive and anomalously dispersive self-focusing medium slab are almost identical; While for picosecond-level short sub-pulses with chirp, the time-mean intensity of images for weak normal dispersion is slightly higher than that for weak anomalous dispersion through a thin nonlinear slab; the result is opposite to that for strong dispersion in a thick nonlinear slab; Furthermore, for given time delay between neighboring sub-pulses, the time-mean intensity of images varies periodically with chirp of the sub-pulse increasing; for a given pulse width of sub-pulse, the time-mean intensity of images decreases with the time delay between neighboring sub-pulses increasing; additionally, there is a little difference in the time-mean intensity of images of the laser stacked by different numbers of sub-pulses. Finally, the obtained results are also given physical explanations.

Rational harmonic mode-locking pulse quality of the dark-optical-comb injected semiconductor optical amplifier fiber ring laser.

PubMed

Lin, Gong-Ru; Lee, Chao-Kuei; Kang, Jung-Jui

2008-06-09

We study the rational harmonic mode-locking (RHML) order dependent pulse shortening force and dynamic chirp characteristics of a gain-saturated semiconductor optical amplifier fiber laser (SOAFL) under dark-optical-comb injection, and discuss the competition between mode-locking mechanisms in the SOAFL at high-gain and strong optical injection condition at higher RHML orders. The evolutions of spectra, mode-locking and continuous lasing powers by measuring the ratio of DC/pulse amplitude and the pulse shortening force (I(pulse)/P(avg)(2) ) are performed to determine the RHML capability of SOAFL. As the rational harmonic order increases up to 20, the spectral linewidth shrinks from 12 to 3 nm, the ratio of DC/pulse amplitude enlarges from 0.025 to 2.4, and the pulse-shortening force reduces from 0.9 to 0.05. At fundamental and highest RHML condition, we characterize the frequency detuning range to realize the mode-locking quality, and measure the dynamic frequency chirp of the RHML-SOAFL to distinguish the linear and nonlinear chirp after dispersion compensation. With increasing RHML order, the pulsewidth is broadened from 4.2 to 26.4 ps with corresponding chirp reducing from 0.7 to 0.2 GHz and linear/nonlinear chirp ratio changes from 4.3 to 1.3, which interprets the high-order chirp becomes dominates at higher RHML orders.

Exploring Agro-Climatic Trends in Ethiopia Using CHIRPS

NASA Astrophysics Data System (ADS)

Pedreros, D. H.; Funk, C. C.; Brown, M. E.; Korecha, D.; Seid, Y. M.

2015-12-01

The Famine Early Warning Systems Network (FEWS NET) uses the Climate Hazards Group Infrared Precipitation with Stations (CHIRPS) to monitor agricultural food production in different regions of the world. CHIRPS is a 1981-present, 5 day, approximately 5km resolution, rainfall product based on a combination of geostationary satellite observations, a high resolution climatology and in situ station observations. Furthermore, FEWS NET has developed a gridded implementation of the Water Requirement Satisfaction Index (WRSI), a water balance measurement indicator of crop performance. This study takes advantage of the CHIRPS' long term period of record and high spatial and temporal resolution to examine agro-climatic trends in Ethiopia. We use the CHIRPS rainfall dataset to calculate the WRSI for the boreal spring and summer crop seasons, as well as for spring-summer rangelands conditions. We find substantial long term rainfall declines in the spring and summer seasons across southeastern and northeastern Ethiopia. Crop Model results indicate that rainfall declines in the cropped regions have been associated with water deficits during the critical grain filling periods in well populated and/or highly vulnerable parts of eastern Ethiopia. WRSI results in the pastoral areas indicate substantial reductions in rangeland health during the later part of the growing seasons. These health declines correspond to the regions of Somaliland and Afar that have experienced chronic severe food insecurity since 2010. Key words: CHIRPS, satellite estimated rainfall, agricultural production

Digital simulation of scalar optical diffraction: revisiting chirp function sampling criteria and consequences.

PubMed

Voelz, David G; Roggemann, Michael C

2009-11-10

Accurate simulation of scalar optical diffraction requires consideration of the sampling requirement for the phase chirp function that appears in the Fresnel diffraction expression. We describe three sampling regimes for FFT-based propagation approaches: ideally sampled, oversampled, and undersampled. Ideal sampling, where the chirp and its FFT both have values that match analytic chirp expressions, usually provides the most accurate results but can be difficult to realize in practical simulations. Under- or oversampling leads to a reduction in the available source plane support size, the available source bandwidth, or the available observation support size, depending on the approach and simulation scenario. We discuss three Fresnel propagation approaches: the impulse response/transfer function (angular spectrum) method, the single FFT (direct) method, and the two-step method. With illustrations and simulation examples we show the form of the sampled chirp functions and their discrete transforms, common relationships between the three methods under ideal sampling conditions, and define conditions and consequences to be considered when using nonideal sampling. The analysis is extended to describe the sampling limitations for the more exact Rayleigh-Sommerfeld diffraction solution.

Likelihood of Alfvénic instability bifurcation in experiments

NASA Astrophysics Data System (ADS)

Duarte, Vinicius; Gorelenkov, Nikolai; Schneller, Mirjam; Fredrickson, Eric; Berk, Herbert; Canal, Gustavo; Heidbrink, William; Kaye, Stanley; Podesta, Mario; van Zeeland, Michael; Wang, Weixing

2017-10-01

We apply a criterion for the likely nature of fast ion redistribution in tokamaks to be in the convective or diffusive nonlinear regimes. The criterion, which is shown to be rather sensitive to the relative strength of collisional or micro-turbulent scattering and drag processes, ultimately translates into a condition for the applicability of reduced quasilinear modeling for realistic tokamak eigenmodes scenarios. The criterion is tested and validated against different machines, where the chirping mode behavior is shown to be in accord with the model. It has been found that the anomalous fast ion transport is a likely mediator of the bifurcation between the fixed-frequency mode behavior and rapid chirping in tokamaks. In addition, micro-turbulence appears to resolve the disparity with respect to the ubiquitous chirping observation in spherical tokamaks and its rarer occurrence in conventional tokamaks. In NSTX, the tendency for chirping is further studied in terms of the beam beta and the plasma rotation shear. For more accurate quantitative assessment, numerical simulations of the effects of electrostatic ion temperature gradient turbulence on chirping are presently being pursued using the GTS code.

Female giant panda (Ailuropoda melanoleuca) chirps advertise the caller's fertile phase

PubMed Central

Charlton, Benjamin D.; Keating, Jennifer L.; Rengui, Li; Huang, Yan; Swaisgood, Ronald R.

2010-01-01

Although female mammal vocal behaviour is known to advertise fertility, to date, no non-human mammal study has shown that the acoustic structure of female calls varies significantly around their fertile period. Here, we used a combination of hormone measurements and acoustic analyses to determine whether female giant panda chirps have the potential to signal the caller's precise oestrous stage (fertile versus pre-fertile). We then used playback experiments to examine the response of male giant pandas to female chirps produced during fertile versus pre-fertile phases of the caller's reproductive cycle. Our results show that the acoustic structure of female giant panda chirps differs between fertile and pre-fertile callers and that male giant pandas can perceive differences in female chirps that allow them to determine the exact timing of the female's fertile phase. These findings indicate that male giant pandas could use vocal cues to preferentially associate and copulate with females at the optimum time for insemination and reveal the likely importance of female vocal signals for coordinating reproductive efforts in this critically endangered species. PMID:19955154

Method for shaping and aiming narrow beams. [sonar mapping and target identification

NASA Technical Reports Server (NTRS)

Heyser, R. C. (Inventor)

1981-01-01

A sonar method and apparatus is discribed which utilizes a linear frequency chirp in a transmitter/receiver having a correlator to synthesize a narrow beamwidth pattern from otherwise broadbeam transducers when there is relative velocity between the transmitter/receiver and the target. The chirp is so produced in a generator in bandwidth, B, and time, T, as to produce a time bandwidth product, TB, that is increased for a narrower angle. A replica of the chirp produced in a generator is time delayed and Doppler shifted for use as a reference in the receiver for correlation of received chirps from targets. This reference is Doppler shifted to select targets preferentially, thereby to not only synthesize a narrow beam but also aim the beam in azimuth and elevation.

Estimation of multiple accelerated motions using chirp-Fourier transform and clustering.

PubMed

Alexiadis, Dimitrios S; Sergiadis, George D

2007-01-01

Motion estimation in the spatiotemporal domain has been extensively studied and many methodologies have been proposed, which, however, cannot handle both time-varying and multiple motions. Extending previously published ideas, we present an efficient method for estimating multiple, linearly time-varying motions. It is shown that the estimation of accelerated motions is equivalent to the parameter estimation of superpositioned chirp signals. From this viewpoint, one can exploit established signal processing tools such as the chirp-Fourier transform. It is shown that accelerated motion results in energy concentration along planes in the 4-D space: spatial frequencies-temporal frequency-chirp rate. Using fuzzy c-planes clustering, we estimate the plane/motion parameters. The effectiveness of our method is verified on both synthetic as well as real sequences and its advantages are highlighted.

Enhancement of ultracold molecule formation by local control in the nanosecond regime

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

Carini, J. L.; Kallush, S.; Kosloff, R.

2015-02-01

We describe quantum simulations of ultracold 87Rb 2 molecule formation using photoassociation (PA) with nanosecond-time-scale pulses of frequency chirped light. In particular, we compare the case of a linear chirp to one where the frequency evolution is optimized by local control (LC) of the phase, and find that LC can provide a significant enhancement. The resulting optimal frequency evolution corresponds to a rapid jump from the PA absorption resonance to a downward transition to a bound level of the lowest triplet state. We also consider the case of two frequencies and investigate interference effects. The assumed chirp parameters should bemore » achievable with nanosecond pulse shaping techniques and are predicted to provide a significant enhancement over recent experiments with linear chirps.« less

Isolated few-cycle radiation from chirped-pulse compression of a superradiant free-electron laser

DOE PAGES

Huang, Yen -Chieh; Zhang, Zhen; Chen, Chia -Hsiang; ...

2015-08-31

When a short electron bunch traverses an undulator to radiate a wavelength longer than the bunch length, intense superradiance from the electron bunch can quickly deplete the electron’s kinetic energy and lead to generation of an isolated chirped radiation pulse. Here, we develop a theory to describe this novel chirped pulse radiation in a superradiant free-electron laser and show the opportunity to generate isolated few-cycle high-power radiation through chirped-pulse compression after the undulator. The theory is completely characterized by how fast the electron energy is depleted for a given length of an undulator. We further present two design examples atmore » the THz and extreme-ultraviolet wavelengths and numerically generate isolated three- and nine-cycle radiation pulses, respectively.« less

Thomson scattering in high-intensity chirped laser pulses

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

Holkundkar, Amol R., E-mail: amol.holkundkar@pilani.bits-pilani.ac.in; Harvey, Chris, E-mail: christopher.harvey@chalmers.se; Marklund, Mattias, E-mail: mattias.marklund@chalmers.se

2015-10-15

We consider the Thomson scattering of an electron in an ultra-intense laser pulse. It is well known that at high laser intensities, the frequency and brilliance of the emitted radiation will be greatly reduced due to the electron losing energy before it reaches the peak field. In this work, we investigate the use of a small frequency chirp in the laser pulse in order to mitigate this effect of radiation reaction. It is found that the introduction of a negative chirp means the electron enters a high frequency region of the field while it still has a large proportion ofmore » its original energy. This results in a significant enhancement of the frequency and intensity of the emitted radiation as compared to the case without chirping.« less

Note: Directly measuring the direct digital synthesizer frequency chirp-rate for an atom interferometer

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

Tao, Juan-Juan; Zhou, Min-Kang, E-mail: zkhu@hust.edu.cn, E-mail: zmk@hust.edu.cn; Zhang, Qiao-Zhen

2015-09-15

During gravity measurements with Raman type atom interferometry, the frequency of the laser used to drive Raman transition is scanned by chirping the frequency of a direct digital synthesizer (DDS), and the local gravity is determined by precisely measuring the chip rate α of DDS. We present an effective method that can directly evaluate the frequency chirp rate stability of our DDS. By mixing a pair of synchronous linear sweeping signals, the chirp rate fluctuation is precisely measured with a frequency counter. The measurement result shows that the relative α instability can reach 5.7 × 10{sup −11} in 1 s,more » which is neglectable in a 10{sup −9} g level atom interferometry gravimeter.« less

Chirped pulse inverse free-electron laser vacuum accelerator

DOEpatents

Hartemann, Frederic V.; Baldis, Hector A.; Landahl, Eric C.

2002-01-01

A chirped pulse inverse free-electron laser (IFEL) vacuum accelerator for high gradient laser acceleration in vacuum. By the use of an ultrashort (femtosecond), ultrahigh intensity chirped laser pulse both the IFEL interaction bandwidth and accelerating gradient are increased, thus yielding large gains in a compact system. In addition, the IFEL resonance condition can be maintained throughout the interaction region by using a chirped drive laser wave. In addition, diffraction can be alleviated by taking advantage of the laser optical bandwidth with negative dispersion focusing optics to produce a chromatic line focus. The combination of these features results in a compact, efficient vacuum laser accelerator which finds many applications including high energy physics, compact table-top laser accelerator for medical imaging and therapy, material science, and basic physics.

Chirped-Pulse Millimeter-Wave Spectroscopy of Rydberg-Rydberg Transitions

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

Prozument, Kirill; Colombo, Anthony P.; Zhou Yan

2011-09-30

Transitions between Rydberg states of Ca atoms, in a pulsed, supersonic atomic beam, are directly detected by chirped-pulse millimeter-wave spectroscopy. Broadband, high-resolution spectra with accurate relative intensities are recorded instantly. Free induction decay (FID) of atoms, polarized by the chirped pulse, at their Rydberg-Rydberg transition frequencies, is heterodyne detected, averaged in the time domain, and Fourier transformed into the frequency domain. Millimeter-wave transient nutations are observed, and the possibility of FID evolving to superradiance is discussed.

Imaging Through Random Discrete-Scatterer Dispersive Media

DTIC Science & Technology

2015-08-27

to that of a conventional, continuous, linear - frequency-modulated chirped signal [3]. Chirped train signals are a particular realization of a class of...continuous chirp signals, characterized by linear frequency modulation [3], we assume the time instances tn to be given by 1 tn = τg ( 1− βg n 2Ng ) n...kernel Dn(z) [9] by sincN (z) = (N + 1)−1DN/2(2πz/N). DISTRIBUTION A: Distribution approved for public release. 4 We use the elementary identity5 π sin

Are chirps better than clicks and tonebursts for evoking middle latency responses?

PubMed

Atcherson, Samuel R; Moore, Page C

2014-06-01

The middle latency response (MLR) is considered a valid clinical tool for assessing the integrity of cortical and subcortical structures. Several investigators have demonstrated that a rising frequency chirp stimulus is capable of eliciting not only larger wave V amplitudes but larger MLR components as well. However, the chirp has never been specifically examined in a hemispheric electrode montage setup that is typical for neurodiagnostic application and site-of-lesion testing. The purpose of this study was to examine the effect of chirp, click, and toneburst stimuli on MLR waveform peak latency and peak-to-peak amplitude in a hemispheric electrode montage setup. This study used a repeated-measures design. A total of 10 young adult participants (3 males, 7 females) with normal hearing were recruited and had negative histories of audiologic, otologic, and neurologic involvement, and no reported language or learning difficulties. MLR latencies (Na, Pa, Nb, and Pb) and peak-to-peak amplitudes (Na-Pa, Pa-Nb, and Nb-Pb) were measured for all conditions and were statistically evaluated for left hemisphere-right ear (C3-A2) and right hemisphere-left ear (C4-A1) recordings. Statistical analyses revealed no significant difference between C3-A2 and C4-A1 peak-to-peak amplitudes; therefore, data were collapsed. Stimulus comparisons revealed that Na evoked by tonebursts were statistically prolonged compared with both chirp and click, and that both Na-Pa and Pa-Nb peak-to-peak amplitudes were statistically larger for chirps compared with both clicks and tonebursts, and for clicks compared with tonebursts. The results of this study support the hypothesis that a chirp would offer a clinical advantage to the click and toneburst in overall peak-to-peak amplitude. As expected, normal-hearing participants did not exhibit hemispheric differences when comparing C3-A2 and C4-A1 peak-to-peak amplitudes demonstrating symmetric auditory brain function. However, chirp-evoked MLRs will require further study to determine its usefulness in clinical practice. American Academy of Audiology.

Cortical origin of the 2007 Mw = 6.2 Aysén earthquake: surface rupture evidence and paleoseismological assessment

NASA Astrophysics Data System (ADS)

Villalobos, A.

2015-12-01

On 2007 April 21, a Mw = 6.2 earthquake hit the Aysén region, an area of low seismicity in southern Chile. This event corresponds to the main shock of a sequence of earthquakes that were felt from January 10, with a small earthquake of magnitude ML <3, to February 2008 as recurrent aftershocks. This area is characterized by the presence of the Liquiñe-Ofqui Fault System (LOFS), which corresponds to neotectonic feature and the main seismotectonic southern Chile. In this research we use improved sub-aqueous paleoseismological techniques with geomorphological evidence to constrain the seismogenic source of this event as cortical origin. It is established that the Punta Cola Fault, a dextral-reverse structure which exhibits in seismic profiles a complex fault zone with distinguished positive flower geometry, is responsible for the main shock. This fault caused vertical offsets that reached the seafloor generating fault scarps in a mass movement deposit triggered by the same earthquake. Following this idea, a model of surface rupture is proposed for this structure. Further evidence that this cortical phenomenon is not an isolated event in time is presented by paleoseismological trench-like mappings in sub-bottom profiles.

Asymptotically exact parabolic solutions of the generalized nonlinear Schrödinger equation with varying parameters

NASA Astrophysics Data System (ADS)

Kruglov, Vladimir I.; Harvey, John D.

2006-12-01

We present exact asymptotic similariton solutions of the generalized nonlinear Schrödinger equation (NLSE) with gain or loss terms for a normal-dispersion fiber amplifier with dispersion, nonlinearity, and gain profiles that depend on the propagation distance. Our treatment is based on the mapping of the NLSE with varying parameters to the NLSE with constant dispersion and nonlinearity coefficients and an arbitrary varying gain function. We formulate an effective procedure that leads directly, under appropriate conditions, to a wide range of exact asymptotic similariton solutions of NLSE demonstrating self-similar propagating regimes with linear chirp.

Deep sea sedimentation processes and geomorphology: Northwest Atlantic continental margin

NASA Astrophysics Data System (ADS)

Mosher, David; Campbell, Calvin; Gardner, Jim; Chaytor, Jason; Piper, David; Rebesco, Michele

2017-04-01

Deep-sea sedimentation processes impart a fundamental control on the morphology of the western North Atlantic continental margin from Blake Spur to Hudson Strait. This fact is illustrated by the variable patterns of cross-margin gradients that are based on extensive new multibeam echo-sounder data informed by subbottom profiler and seismic reflection data. Erosion by off-shelf sediment transport in turbidity currents creates gullies, canyons and channels and a steep upper slope. Amalgamation of these conduits produces singular channels and turbidite fan complexes on the lower slope, flattening slope-profile gradients. The effect is an exponentially decaying "graded" slope profile. Comparatively, sediment mass failure produces steeper upper slopes due to head scarp development and a wedging architecture to the lower slope as deposits thin in the downslope direction. This process results in either a "stepped" slope, and/or a significant downslope gradient change where MTDs pinch out. Large drift deposits created by geostrophic currents are developed all along the margin. Blake Ridge, Sackville Spur, and Hamilton Spur are large detached drifts on disparate parts of the margin. They form a linear "above grade" profile along their crests from the shelf to abyssal plain. Deeper portions of the US continental margin are dominated by the Chesapeake Drift and Hatteras Outer Ridge; both plastered elongate mounded drifts. Farther north, particularly on the Grand Banks margin, are plastered and separated drifts. These drifts form "stepped" slope profiles, where they onlap the margin. Trough-mouth fan complexes become more common along the margin with increasing latitude. Sediment deposition and retention, particularly those dominated by glacigenic debris flows, characterize these segments producing an "above grade" slope profile. Understanding these geomorphological consequences of deep sea sedimentation processes is important to extended continental shelf mapping in which gradients and gradient change is a critical metric.

Enhancing high-order harmonic generation by sculpting waveforms with chirp

NASA Astrophysics Data System (ADS)

Peng, Dian; Frolov, M. V.; Pi, Liang-Wen; Starace, Anthony F.

2018-05-01

We present a theoretical analysis showing how chirp can be used to sculpt two-color driving laser field waveforms in order to enhance high-order harmonic generation (HHG) and/or extend HHG cutoff energies. Specifically, we consider driving laser field waveforms composed of two ultrashort pulses having different carrier frequencies in each of which a linear chirp is introduced. Two pairs of carrier frequencies of the component pulses are considered: (ω , 2 ω ) and (ω , 3 ω ). Our results show how changing the signs of the chirps in each of the two component pulses leads to drastic changes in the HHG spectra. Our theoretical analysis is based on numerical solutions of the time-dependent Schrödinger equation and on a semiclassical analytical approach that affords a clear physical interpretation of how our optimized waveforms lead to enhanced HHG spectra.

Photonic generation of low phase noise arbitrary chirped microwave waveforms with large time-bandwidth product.

PubMed

Xie, Weilin; Xia, Zongyang; Zhou, Qian; Shi, Hongxiao; Dong, Yi; Hu, Weisheng

2015-07-13

We present a photonic approach for generating low phase noise, arbitrary chirped microwave waveforms based on heterodyne beating between high order correlated comb lines extracted from frequency-agile optical frequency comb. Using the dual heterodyne phase transfer scheme, extrinsic phase noises induced by the separate optical paths are efficiently suppressed by 42-dB at 1-Hz offset frequency. Linearly chirped microwave waveforms are achieved within 30-ms temporal duration, contributing to a large time-bandwidth product. The linearity measurement leads to less than 90 kHz RMS frequency error during the entire chirp duration, exhibiting excellent linearity for the microwave and sub-THz waveforms. The capability of generating arbitrary waveforms up to sub-THz band with flexible temporal duration, long repetition period, broad bandwidth, and large time-bandwidth product is investigated and discussed.

Preparing isolated vibrational wave packets with light-induced molecular potentials by chirped laser pulses

NASA Astrophysics Data System (ADS)

Vatasescu, Mihaela

2012-05-01

We consider a specific wave packet preparation arising from the control of tunneling in the 0g-(6s,6p3/2) double well potential of a Cs2 cold molecule with chirped laser pulses. Such a possibility to manipulate the population dynamics in the 0g-(6s,6p3/2) potential appears in a pump-dump scheme designed to form cold molecules by photoassociation of two cold cesium atoms. The initial population in the 0g-(6s,6p3/2) double well is a wave packet prepared in the outer well at large interatomic distances (94 a0) by a photoassociation step with a first chirped pulse, being a superposition of several vibrational states whose energies surround the energy of a tunneling resonance. Our present work is focused on a second delayed chirped pulse, coupling the 0g-(6s,6p3/2) surface with the a3Σu+(6s,6s) one in the zone of the double well barrier (15 a0) and creating deeply bound cold molecules in the a3Σu+(6s,6s) state. We explore the parameters choice (intensity, duration, chirp rate and sign) for this second pulse, showing that picoseconds pulses with a negative chirp can lead to trapping of population in the inner well in strongly bound vibrational states, out of the resonant tunneling able to transfer it back to the outer well.

Photoacoustic simulation study of chirp excitation response from different size absorbers

NASA Astrophysics Data System (ADS)

Jnawali, K.; Chinni, B.; Dogra, V.; Rao, N.

2017-03-01

Photoacoustic (PA) imaging is a hybrid imaging modality that integrates the strength of optical and ultrasound imaging. Nanosecond (ns) pulsed lasers used in current PA imaging systems are expensive, bulky and they often waste energy. We propose and evaluate, through simulations, the use of a continuous wave (CW) laser whose amplitude is linear frequency modulated (chirp) for PA imaging. The chirp signal provides signal-to-side-lobe ratio (SSR) improvement potential and full control over PA signal frequencies excited in the sample. The PA signal spectrum is a function of absorber size and the time frequencies present in the chirp. A mismatch between the input chirp spectrum and the output PA signal spectrum can affect the compressed pulse that is recovered from cross-correlating the two. We have quantitatively characterized this effect. The k-wave Matlab tool box was used to simulate PA signals in three dimensions for absorbers ranging in size from 0.1 mm to 0.6 mm, in response to laser excitation amplitude that is linearly swept from 0.5 MHz to 4 MHz. This sweep frequency range was chosen based on the spectrum analysis of a PA signal generated from ex-vivo human prostate tissue samples. In comparison, the energy wastage by a ns laser pulse was also estimated. For the chirp methodology, the compressed pulse peak amplitude, pulse width and side lobe structure parameters were extracted for different size absorbers. While the SSR increased 6 fold with absorber size, the pulse width decreased by 25%.

Structural Constraints and Earthquake Recurrence Estimates for the West Tahoe-Dollar Point Fault, Lake Tahoe Basin, California

NASA Astrophysics Data System (ADS)

Maloney, J. M.; Driscoll, N. W.; Kent, G.; Brothers, D. S.; Baskin, R. L.; Babcock, J. M.; Noble, P. J.; Karlin, R. E.

2011-12-01

Previous work in the Lake Tahoe Basin (LTB), California, identified the West Tahoe-Dollar Point Fault (WTDPF) as the most hazardous fault in the region. Onshore and offshore geophysical mapping delineated three segments of the WTDPF extending along the western margin of the LTB. The rupture patterns between the three WTDPF segments remain poorly understood. Fallen Leaf Lake (FLL), Cascade Lake, and Emerald Bay are three sub-basins of the LTB, located south of Lake Tahoe, that provide an opportunity to image primary earthquake deformation along the WTDPF and associated landslide deposits. We present results from recent (June 2011) high-resolution seismic CHIRP surveys in FLL and Cascade Lake, as well as complete multibeam swath bathymetry coverage of FLL. Radiocarbon dates obtained from the new piston cores acquired in FLL provide age constraints on the older FLL slide deposits and build on and complement previous work that dated the most recent event (MRE) in Fallen Leaf Lake at ~4.1-4.5 k.y. BP. The CHIRP data beneath FLL image slide deposits that appear to correlate with contemporaneous slide deposits in Emerald Bay and Lake Tahoe. A major slide imaged in FLL CHIRP data is slightly younger than the Tsoyowata ash (7950-7730 cal yrs BP) identified in sediment cores and appears synchronous with a major Lake Tahoe slide deposit (7890-7190 cal yrs BP). The equivalent age of these slides suggests the penultimate earthquake on the WTDPF may have triggered them. If correct, we postulate a recurrence interval of ~3-4 k.y. These results suggest the FLL segment of the WTDPF is near its seismic recurrence cycle. Additionally, CHIRP profiles acquired in Cascade Lake image the WTDPF for the first time in this sub-basin, which is located near the transition zone between the FLL and Rubicon Point Sections of the WTDPF. We observe two fault-strands trending N45°W across southern Cascade Lake for ~450 m. The strands produce scarps of ~5 m and ~2.7 m, respectively, on the lake floor, but offset increases down-section to ~14 m and ~8 m at the acoustic basement. Studying the style and timing of earthquake deformation in Fallen Leaf Lake, Cascade Lake, Emerald Bay and Lake Tahoe will help us to understand how strain is partitioned between adjacent segments and the potential rupture magnitude.

Validation of new satellite rainfall products over the Upper Blue Nile Basin, Ethiopia

NASA Astrophysics Data System (ADS)

Tesfaye Ayehu, Getachew; Tadesse, Tsegaye; Gessesse, Berhan; Dinku, Tufa

2018-04-01

Accurate measurement of rainfall is vital to analyze the spatial and temporal patterns of precipitation at various scales. However, the conventional rain gauge observations in many parts of the world such as Ethiopia are sparse and unevenly distributed. An alternative to traditional rain gauge observations could be satellite-based rainfall estimates. Satellite rainfall estimates could be used as a sole product (e.g., in areas with no (or poor) ground observations) or through integrating with rain gauge measurements. In this study, the potential of a newly available Climate Hazards Group Infrared Precipitation with Stations (CHIRPS) rainfall product has been evaluated in comparison to rain gauge data over the Upper Blue Nile basin in Ethiopia for the period of 2000 to 2015. In addition, the Tropical Applications of Meteorology using SATellite and ground-based observations (TAMSAT 3) and the African Rainfall Climatology (ARC 2) products have been used as a benchmark and compared with CHIRPS. From the overall analysis at dekadal (10 days) and monthly temporal scale, CHIRPS exhibited better performance in comparison to TAMSAT 3 and ARC 2 products. An evaluation based on categorical/volumetric and continuous statistics indicated that CHIRPS has the greatest skills in detecting rainfall events (POD = 0.99, 1.00) and measure of volumetric rainfall (VHI = 1.00, 1.00), the highest correlation coefficients (r = 0.81, 0.88), better bias values (0.96, 0.96), and the lowest RMSE (28.45 mm dekad-1, 59.03 mm month-1) than TAMSAT 3 and ARC 2 products at dekadal and monthly analysis, respectively. CHIRPS overestimates the frequency of rainfall occurrence (up to 31 % at dekadal scale), although the volume of rainfall recorded during those events was very small. Indeed, TAMSAT 3 has shown a comparable performance with that of the CHIRPS product, mainly with regard to bias. The ARC 2 product was found to have the weakest performance underestimating rain gauge observed rainfall by about 24 %. In addition, the skill of CHIRPS is less affected by variation in elevation in comparison to TAMSAT 3 and ARC 2 products. CHIRPS resulted in average biases of 1.11, 0.99, and 1.00 at lower (< 1000 m a.s.l.), medium (1000 to 2000 m a.s.l.), and higher elevation (> 2000 m a.s.l.), respectively. Overall, the finding of this validation study shows the potentials of the CHIRPS product to be used for various operational applications such as rainfall pattern and variability study in the Upper Blue Nile basin in Ethiopia.

Range side lobe inversion for chirp-encoded dual-band tissue harmonic imaging.

PubMed

Shen, Che-Chou; Peng, Jun-Kai; Wu, Chi

2014-02-01

Dual-band (DB) harmonic imaging is performed by transmitting and receiving at both fundamental band (f0) and second-harmonic band (2f0). In our previous work, particular chirp excitation has been developed to increase the signal- to-noise ratio in DB harmonic imaging. However, spectral overlap between the second-order DB harmonic signals results in range side lobes in the pulse compression. In this study, a novel range side lobe inversion (RSI) method is developed to alleviate the level of range side lobes from spectral overlap. The method is implemented by firing an auxiliary chirp to change the polarity of the range side lobes so that the range side lobes can be suppressed in the combination of the original chirp and the auxiliary chirp. Hydrophone measurements show that the RSI method reduces the range side lobe level (RSLL) and thus increases the quality of pulse compression in DB harmonic imaging. With the signal bandwidth of 60%, the RSLL decreases from -23 dB to -36 dB and the corresponding compression quality improves from 78% to 94%. B-mode images also indicate that the magnitude of range side lobe is suppressed by 7 dB when the RSI method is applied.

Model for spontaneous frequency sweeping of an Alfvén wave in a toroidal plasma

NASA Astrophysics Data System (ADS)

Wang, Ge; Berk, H. L.

2012-05-01

We study the frequency chirping signals arising from spontaneously excited toroidial Alfvén eigenmode (TAE) waves that are being driven by an inverted energetic particle distribution whose free energy is tapped from the generic particle/wave resonance interaction. Initially a wave is excited inside the Alfvén gap with a frequency determined from the linear tip model of Rosenbluth, Berk and Van dam (RBV) [1]. Hole/clumps structures are formed and are observed to chirp towards lower energy states. We find that the chirping signals from clump enter the Alfvén continuum which eventually produce more rapid chirping signals. The accuracy of the adiabatic approximation for the mode evolution is tested and verified by demonstrating that a WKB-like decomposition of the time response for the field phase and amplitude agree with the data. Plots of the phase space structure correlate well with the chirping dependent shape of the separatrix structure. A novel aspect of the simulation is that it performed close to the wave frame of the phase space structure, which enables the numerical time step to remain the same during the simulation, independent of the rest frame frequency.

Numerical and analytic models of spontaneous frequency sweeping for energetic particle-driven Alfven eigenmodes

NASA Astrophysics Data System (ADS)

Wang, Ge; Berk, H. L.

2011-10-01

The frequency chirping signal arising from spontaneous a toroidial Alfven eigenmode (TAE) excited by energetic particles is studied for both numerical and analytic models. The time-dependent numerical model is based on the 1D Vlasov equation. We use a sophisticated tracking method to lock onto the resonant structure to enable the chirping frequency to be nearly constant in the calculation frame. The accuracy of the adiabatic approximation is tested during the simulation which justifies the appropriateness of our analytic model. The analytic model uses the adiabatic approximation which allows us to solve the wave evolution equation in frequency space. Then, the resonant interactions between energetic particles and TAE yield predictions for the chirping rate, wave frequency and amplitudes vs. time. Here, an adiabatic invariant J is defined on the separatrix of a chirping mode to determine the region of confinement of the wave trapped distribution function. We examine the asymptotic behavior of the chirping signal for its long time evolution and find agreement in essential features with the results of the simulation. Work supported by Department of Energy contract DE-FC02-08ER54988.

Frequency chirpings in Alfven continuum

NASA Astrophysics Data System (ADS)

Wang, Ge; Berk, Herb; Breizman, Boris; Zheng, Linjin

2017-10-01

We have used a self-consistent mapping technique to describe both the nonlinear wave-energetic particle resonant interaction and its spatial mode structure that depends upon the resonant energetic particle pressure. At the threshold for the onset of the energetic particle mode (EPM), strong chirping emerges in the lower continuum close to the TAE gap and then, driven by strong continuum damping, chirps rapidly to lower frequencies in the Alfven continuum. An adiabatic theory was developed that accurately replicated the results from the simulation where the nonlinearity was only due to the EPM resonant particles. The results show that the EPM-trapped particles have their action conserved during the time of rapid chirping. This adiabaticity enabled wave trapped particles to be confined within their separatrix, and produce even larger resonant structures, that can produce a large amplitude mode far from linearly predicted frequencies. In the present work we describe the effect of additional MHD nonlinearity to this calculation. We studied how the zonal flow component and its nonlinear feedback to the fundamental frequency and found that the MHD nonlinearity doesn't significantly alter the frequency chirping response that is predicted by the calculation that neglects the MHD nonlinearity.

Optical chirped beam amplification and propagation

DOEpatents

Barty, Christopher P.

2004-10-12

A short pulse laser system uses dispersive optics in a chirped-beam amplification architecture to produce high peak power pulses and high peak intensities without the potential for intensity dependent damage to downstream optical components after amplification.

Ultrashort pulse chirp measurement via transverse second-harmonic generation in strontium barium niobate crystal

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

Trull, J.; Wang, B.; Parra, A.

2015-06-01

Pulse compression in dispersive strontium barium niobate crystal with a random size and distribution of the anti-parallel orientated nonlinear domains is observed via transverse second harmonic generation. The dependence of the transverse width of the second harmonic trace along the propagation direction allows for the determination of the initial chirp and duration of pulses in the femtosecond regime. This technique permits a real-time analysis of the pulse evolution and facilitates fast in-situ correction of pulse chirp acquired in the propagation through an optical system.

Volterra equalization of complex modulation utilizing frequency chirp in directly modulated lasers

NASA Astrophysics Data System (ADS)

Hu, Shaohua; Yi, Xingwen; Zhang, Jing; Song, Yang; Zhu, Mingyue; Qiu, Kun

2018-02-01

We apply Volterra-based equalization for complex modulated optical signals utilizing the frequency chirp in DMLs. We experimentally demonstrate that the higher order Volterra filter is necessary in the higher speed transmissions. For further study, we isolate the adiabatic chirp by injection locking and realize the optical PM transmission. We make a comparison among IM, FM and PM with Volterra equalization, finding that PM and FM are more power insensitive and suitable for high speed, power limited fiber transmission. The performance can be further improved by exploiting the diversity gain.

All-fiber highly chirped dissipative soliton generation in the telecom range.

PubMed

Kharenko, Denis S; Zhdanov, Innokentiy S; Bednyakova, Anastasia E; Podivilov, Evgeniy V; Fedoruk, Mikhail P; Apolonski, Alexander; Turitsyn, Sergei K; Babin, Sergey A

2017-08-15

A high-energy (0.93 nJ) all-fiber erbium femtosecond oscillator operating in the telecom spectral range is proposed and realized. The laser cavity, built of commercially available fibers and components, combines polarization maintaining (PM) and non-PM parts providing stable generation of highly chirped (chirp parameter 40) pulses compressed in an output piece of standard PM fiber to 165 fs. The results of the numerical simulation agree well with the experiment. The analyzed intracavity pulse dynamics enables the classification of the generated pulses as dissipative solitons.

Observation of contrast agent response to chirp insonation with a simultaneous optical-acoustical system.

PubMed

Sun, Yang; Zhao, Shukui; Dayton, Paul A; Ferrara, Katherine W

2006-06-01

Rayleigh-Plesset analysis, ultra-high speed photography, and single bubble acoustical recordings previously were applied independently to characterize the radial oscillation and resulting echoes from a microbubble in response to an ultrasonic pulse. In addition, high-speed photography has shown that microbubbles are destroyed over a single pulse or pulse train by diffusion and fragmentation. In order to develop a single model to characterize microbubble echoes based on oscillatory and destructive characteristics, an optical-acoustical system was developed to simultaneously record the optical image and backscattered echo from each microbubble. Combined observation provides the opportunity to compare predictions for oscillation and echoes with experimental results and identify discrepancies due to diffusion or fragmentation. Optimization of agents and insonating pulse parameters may be facilitated with this system. The mean correlation of the predicted and experimental radius-time curves and echoes exceeds 0.7 for the parameters studied here. An important application of this new system is to record and analyze microbubble response to a long pulse in which diffusion is shown to occur over the pulse duration. The microbubble response to an increasing or decreasing chirp is evaluated using this new tool. For chirp insonation beginning with the lower center frequency, low-frequency modulation of the oscillation envelope was obvious. However, low-frequency modulation was not observed in the radial oscillation produced by decreasing chirp insonation. Comparison of the echoes from similar sized microbubbles following increasing and decreasing chirp insonation demonstrated that the echoes were not time-reversed replicas. Using a transmission pressure of 620 kPa, the -6 dB echo length was 0.9 and 1.1 micros for increasing and decreasing chirp insonation, respectively (P = 0.02). The mean power in the low-frequency portion of the echoes was 8 (mV)2 and 13 (mV)2 for increasing and decreasing chirp insonation, respectively (P = 0.01).

Chirp- and random-based coded ultrasonic excitation for localized blood-brain barrier opening

PubMed Central

Kamimura, HAS; Wang, S; Wu, S-Y; Karakatsani, ME; Acosta, C; Carneiro, AAO; Konofagou, EE

2015-01-01

Chirp- and random-based coded excitation methods have been proposed to reduce standing wave formation and improve focusing of transcranial ultrasound. However, no clear evidence has been shown to support the benefits of these ultrasonic excitation sequences in vivo. This study evaluates the chirp and periodic selection of random frequency (PSRF) coded-excitation methods for opening the blood-brain barrier (BBB) in mice. Three groups of mice (n=15) were injected with polydisperse microbubbles and sonicated in the caudate putamen using the chirp/PSRF coded (bandwidth: 1.5-1.9 MHz, peak negative pressure: 0.52 MPa, duration: 30 s) or standard ultrasound (frequency: 1.5 MHz, pressure: 0.52 MPa, burst duration: 20 ms, duration: 5 min) sequences. T1-weighted contrast-enhanced MRI scans were performed to quantitatively analyze focused ultrasound induced BBB opening. The mean opening volumes evaluated from the MRI were 9.38±5.71 mm3, 8.91±3.91 mm3 and 35.47 ± 5.10 mm3 for the chirp, random and regular sonications, respectively. The mean cavitation levels were 55.40±28.43 V.s, 63.87±29.97 V.s and 356.52±257.15 V.s for the chirp, random and regular sonications, respectively. The chirp and PSRF coded pulsing sequences improved the BBB opening localization by inducing lower cavitation levels and smaller opening volumes compared to results of the regular sonication technique. Larger bandwidths were associated with more focused targeting but were limited by the frequency response of the transducer, the skull attenuation and the microbubbles optimal frequency range. The coded methods could therefore facilitate highly localized drug delivery as well as benefit other transcranial ultrasound techniques that use higher pressure levels and higher precision to induce the necessary bioeffects in a brain region while avoiding damage to the surrounding healthy tissue. PMID:26394091

Observation of contrast agent response to chirp insonation with a simultaneous optical-acoustical system

PubMed Central

Sun, Yang; Zhao, Shukui; Dayton, Paul A.; Ferrara, Katherine W.

2006-01-01

Rayleigh-Plesset analysis, ultra-high speed photography, and single bubble acoustical recordings have previously been applied independently to characterize the radial oscillation and resulting echoes from a microbubble in response to an ultrasonic pulse. In addition, high speed photography has shown that microbubbles are destroyed over a single pulse or pulse train by diffusion and fragmentation. In order to develop a single model to characterize microbubble echoes based on oscillatory and destructive characteristics, an optical-acoustical system was developed to simultaneously record the optical image and backscattered echo from each microbubble. Combined observation provides the opportunity to compare predictions for oscillation and echoes with experimental results and identify discrepancies due to diffusion or fragmentation. Optimization of agents and insonating pulse parameters may be facilitated with this system. The mean correlation of the predicted and experimental radius-time curves and echoes exceeds 0.7 for the parameters studied here. An important application of this new system is to record and analyze microbubble response to a long pulse where diffusion is shown to occur over the pulse duration. The microbubble response to an increasing or decreasing chirp is evaluated using this new tool. For chirp insonation beginning with the lower center frequency, low frequency modulation of the oscillation envelope was obvious. However, low frequency modulation was not observed in the radial oscillation produced by decreasing chirp insonation. Comparison of the echoes from similar sized microbubbles following increasing and decreasing chirp insonation demonstrated that the echoes were not time-reversed replicas. Using a transmission pressure of 620 kPa, the −6 dB echo length was 0.9 and 1.1 μs for increasing and decreasing chirp insonation, respectively (P = 0.02). The mean power in the low frequency portion of the echoes was 8 (mV)2 and 13 (mV)2 for increasing and decreasing chirp insonation, respectively, (P = 0.01). PMID:16846145

Extinction-ratio-independent electrical method for measuring chirp parameters of Mach-Zehnder modulators using frequency-shifted heterodyne.

PubMed

Zhang, Shangjian; Wang, Heng; Zou, Xinhai; Zhang, Yali; Lu, Rongguo; Liu, Yong

2015-06-15

An extinction-ratio-independent electrical method is proposed for measuring chirp parameters of Mach-Zehnder electric-optic intensity modulators based on frequency-shifted optical heterodyne. The method utilizes the electrical spectrum analysis of the heterodyne products between the intensity modulated optical signal and the frequency-shifted optical carrier, and achieves the intrinsic chirp parameters measurement at microwave region with high-frequency resolution and wide-frequency range for the Mach-Zehnder modulator with a finite extinction ratio. Moreover, the proposed method avoids calibrating the responsivity fluctuation of the photodiode in spite of the involved photodetection. Chirp parameters as a function of modulation frequency are experimentally measured and compared to those with the conventional optical spectrum analysis method. Our method enables an extinction-ratio-independent and calibration-free electrical measurement of Mach-Zehnder intensity modulators by using the high-resolution frequency-shifted heterodyne technique.

Chirp and error rate analyses of an optical-injection gain-switching VCSEL based all-optical NRZ-to-PRZ converter.

PubMed

Lin, Chia-Chi; Kuo, Hao-Chung; Peng, Peng-Chun; Lin, Gong-Ru

2008-03-31

Optically injection-locked single-wavelength gain-switching VCSEL based all-optical converter is demonstrated to generate RZ data at 2.5 Gbit/s with bit-error-rate of 10(-9) under receiving power of -29.3 dBm. A modified rate equation model is established to elucidate the optical injection induced gain-switching and NRZ-to-RZ data conversion in the VCSEL. The peak-to-peak frequency chirp of the VCSEL based NRZ-to-RZ is 4.5 GHz associated with a reduced frequency chirp rate of 178 MHz/ps at input optical NRZ power of -21 dBm, which is almost decreasing by a factor of 1/3 comparing with chirp on the SOA based NRZ-to-RZ converter reported previously. The power penalty of the BER measured back-to-back is about 2 dB from 1 Gbit/s to 2.5 Gbit/s.

THz field engineering in two-color femtosecond filaments using chirped and delayed laser pulses

NASA Astrophysics Data System (ADS)

Nguyen, A.; González de Alaiza Martínez, P.; Thiele, I.; Skupin, S.; Bergé, L.

2018-03-01

We numerically study the influence of chirping and delaying several ionizing two-color light pulses in order to engineer terahertz (THz) wave generation in air. By means of comprehensive 3D simulations, it is shown that two chirped pulses can increase the THz yield when they are separated by a suitable time delay for the same laser energy in focused propagation geometry. To interpret these results, the local current theory is revisited and we propose an easy, accessible all-optical criterion that predicts the laser-to-THz conversion efficiencies given any input laser spectrum. In the filamentation regime, numerical simulations display evidence that a chirped pulse is able to produce more THz radiation due to propagation effects, which maintain the two colors of the laser field more efficiently coupled over long distances. A large delay between two pulses promotes multi-peaked THz spectra as well as conversion efficiencies above 10‑4.

Duobinary pulse shaping for frequency chirp enabled complex modulation.

PubMed

Che, Di; Yuan, Feng; Khodakarami, Hamid; Shieh, William

2016-09-01

The frequency chirp of optical direct modulation (DM) used to be a performance barrier of optical transmission system, because it broadens the signal optical spectrum, which becomes more susceptible to chromatic dispersion induced inter-symbol interference (ISI). However, by considering the chirp as frequency modulation, the single DM simultaneously generates a 2-D signal containing the intensity and phase (namely, the time integral of frequency). This complex modulation concept significantly increases the optical signal to noise ratio (OSNR) sensitivity of DM systems. This Letter studies the duobinary pulse shaping (DB-PS) for chirp enabled DM and its impact on the optical bandwidth and system OSNR sensitivity. DB-PS relieves the bandwidth requirement, at the sacrifice of system OSNR sensitivity. As DB-PS induces a controlled ISI, the receiver requires one more tap for maximum likelihood sequence estimation (MLSE). We verify this modified MLSE with a 10-Gbaud duobinary PAM-4 transmission experiment.

Song pattern recognition in crickets based on a delay-line and coincidence-detector mechanism

PubMed Central

Sarmiento-Ponce, Edith Julieta

2017-01-01

Acoustic communication requires filter mechanisms to process and recognize key features of the perceived signals. We analysed such a filter mechanism in field crickets (Gryllus bimaculatus), which communicate with species-specific repetitive patterns of sound pulses and chirps. A delay-line and coincidence-detection mechanism, in which each sound pulse has an impact on the processing of the following pulse, is implicated to underlie the recognition of the species-specific pulse pattern. Based on this concept, we hypothesized that altering the duration of a single pulse or inter-pulse interval in three-pulse chirps will lead to different behavioural responses. Phonotaxis was tested in female crickets walking on a trackball exposed to different sound paradigms. Changing the duration of either the first, second or third pulse of the chirps led to three different characteristic tuning curves. Long first pulses decreased the phonotactic response whereas phonotaxis remained strong when the third pulse was long. Chirps with three pulses of increasing duration of 5, 20 and 50 ms elicited phonotaxis, but the chirps were not attractive when played in reverse order. This demonstrates specific, pulse duration-dependent effects while sequences of pulses are processed. The data are in agreement with a mechanism in which processing of a sound pulse has an effect on the processing of the subsequent pulse, as outlined in the flow of activity in a delay-line and coincidence-detector circuit. Additionally our data reveal a substantial increase in the gain of phonotaxis, when the number of pulses of a chirp is increased from two to three. PMID:28539524

High-Frequency Chirp Ultrasound Imaging with an Annular-array for Ophthalmologic and Small-Animal Imaging

PubMed Central

Mamou, Jonathan; Aristizábal, Orlando; Silverman, Ronald H.; Ketterling, Jeffrey A.; Turnbull, Daniel H.

2009-01-01

High-frequency ultrasound (HFU, > 20 MHz) is an attractive means of obtaining fine-resolution images of biological tissues for ophthalmologic, dermatological, and small-animal imaging applications. Even with current improvements in circuit designs and high-frequency equipment, HFU suffers from two inherent limitations. First, HFU images have a limited depth of field (DOF) because of the short wavelength and the low fixed F-number of conventional HFU transducers. Second, HFU is usually limited to shallow imaging because of the significant attenuation in most tissues. In a previous study, a five-element annular array with a 17-MHz center frequency was excited using chirp-coded signals, and a synthetic-focusing algorithm was used to extend the DOF and increase penetration depth. In the present study, a similar approach with two different five-element annular arrays operating near a center frequency of 35-MHz is implemented and validated. Following validation studies, the chirp-imaging methods were applied to imaging vitreous-hemorrhage mimicking phantoms and mouse embryos. Images of the vitreous phantom showed increased sensitivity using the chirp method compared to a standard monocycle imaging method, and blood droplets could be visualized 4 mm deeper into the phantom. Three-dimensional datasets of 12.5-day-old, mouse-embryo heads were acquired in utero using chirp and conventional excitations. Images were formed and brains ventricles were segmented and reconstructed in three dimensions. The brain-ventricle volumes for the monocycle excitation exhibited artifacts that were not apparent on the chirp-based dataset reconstruction. PMID:19394754

Song pattern recognition in crickets based on a delay-line and coincidence-detector mechanism.

PubMed

Hedwig, Berthold; Sarmiento-Ponce, Edith Julieta

2017-05-31

Acoustic communication requires filter mechanisms to process and recognize key features of the perceived signals. We analysed such a filter mechanism in field crickets ( Gryllus bimaculatus ), which communicate with species-specific repetitive patterns of sound pulses and chirps. A delay-line and coincidence-detection mechanism, in which each sound pulse has an impact on the processing of the following pulse, is implicated to underlie the recognition of the species-specific pulse pattern. Based on this concept, we hypothesized that altering the duration of a single pulse or inter-pulse interval in three-pulse chirps will lead to different behavioural responses. Phonotaxis was tested in female crickets walking on a trackball exposed to different sound paradigms. Changing the duration of either the first, second or third pulse of the chirps led to three different characteristic tuning curves. Long first pulses decreased the phonotactic response whereas phonotaxis remained strong when the third pulse was long. Chirps with three pulses of increasing duration of 5, 20 and 50 ms elicited phonotaxis, but the chirps were not attractive when played in reverse order. This demonstrates specific, pulse duration-dependent effects while sequences of pulses are processed. The data are in agreement with a mechanism in which processing of a sound pulse has an effect on the processing of the subsequent pulse, as outlined in the flow of activity in a delay-line and coincidence-detector circuit. Additionally our data reveal a substantial increase in the gain of phonotaxis, when the number of pulses of a chirp is increased from two to three. © 2017 The Authors.

Multibeam bathymetric survey of the Ipala Submarine Canyon, Jalisco, Mexico (20°N): The southern boundary of the Banderas Forearc Block?

NASA Astrophysics Data System (ADS)

Urías Espinosa, J.; Bandy, W. L.; Mortera Gutiérrez, C. A.; Núñez Cornú, Fco. J.; Mitchell, N. C.

2016-03-01

The Middle America Trench bends sharply northward at 20°N. This, along with the close proximity of the Rivera-North America Euler pole to the northern end of this trench, sharply increases the obliquity of subduction at 20°N. By analogy with other subduction zones with similar sharply changing obliquity, significant trench parallel extension is expected to exist in the forearc region near the bend. To evaluate this possibility, multibeam bathymetric, seafloor backscatter and sub-bottom seismic reflection data were collected in this area during the MORTIC08 campaign of the B.O. El Puma. These data image in detail a large submarine canyon (the Ipala Canyon) extending from the coast at 20°05‧N to the Middle America Trench at 19°50‧N. This canyon is 114 km long and is fed by sediments originating from two, possibly three, small rivers: the Ipala, Tecolotlán and Maria Garza. This canyon deeply incises (up to 600 m) the entire continental slope and at least the outer part of the shelf. Within the canyon, we observe meanders and narrow channels produced by turbidity flows indicating that the canyon is active. In the marginal areas of the canyon slumps, rills, and uplifts suggest that mass movements and fluid flow have had a major impact on the seafloor morphology. The seafloor bathymetry, backscatter images and sub-bottom reflection profiles evidence the tectonic processes occurring in this area. Of particular interest, the canyon is deflected by almost 90° at three locations, the deflections all having a similar azimuth of between 125° and 130°. Given the prominence and geometry of this canyon, along with its tectonic setting, we propose that the presence of the canyon is related to extension produced by the sharp change in the plate convergence. If so, the canyon may lie along the southeast boundary of a major forearc block (the Banderas Forearc Block).

Application of a new genetic classification and semi-automated geomorphic mapping approach in the Perth submarine canyon, Australia

NASA Astrophysics Data System (ADS)

Picard, K.; Nanson, R.; Huang, Z.; Nichol, S.; McCulloch, M.

2017-12-01

The acquisition of high resolution marine geophysical data has intensified in recent years (e.g. multibeam echo-sounding, sub-bottom profiling). This progress provides the opportunity to classify and map the seafloor in greater detail, using new methods that preserve the links between processes and morphology. Geoscience Australia has developed a new genetic classification approach, nested within the Harris et al (2014) global seafloor mapping framework. The approach divides parent units into sub-features based on established classification schemes and feature descriptors defined by Bradwell et al. (2016: http://nora.nerc.ac.uk/), the International Hydrographic Organization (https://www.iho.int) and the Coastal Marine and Ecological Classification Standard (https://www.cmecscatalog.org). Owing to the ecological significance of submarine canyon systems in particular, much recent attention has focused on defining their variation in form and process, whereby they can be classified using a range of topographic metrics, fluvial dis/connection and shelf-incising status. The Perth Canyon is incised into the continental slope and shelf of southwest Australia, covering an area of >1500 km2 and extending from 4700 m water depth to the shelf break in 170 m. The canyon sits within a Marine Protected Area, incorporating a Marine National Park and Habitat Protection Zone in recognition of its benthic and pelagic biodiversity values. However, detailed information of the spatial patterns of the seabed habitats that influence this biodiversity is lacking. Here we use 20 m resolution bathymetry and acoustic backscatter data acquired in 2015 by the Schmidt Ocean Institute plus sub-bottom datasets and sediment samples collected Geoscience Australia in 2005 to apply the new geomorphic classification system to the Perth Canyon. This presentation will show the results of the geomorphic feature mapping of the canyon and its application to better defining potential benthic habitats.

National Scale Marine Geophysical Data Portal for the Israel EEZ with Public Access Web-GIS Platform

NASA Astrophysics Data System (ADS)

Ketter, T.; Kanari, M.; Tibor, G.

2017-12-01

Recent offshore discoveries and regulation in the Israel Exclusive Economic Zone (EEZ) are the driving forces behind increasing marine research and development initiatives such as infrastructure development, environmental protection and decision making among many others. All marine operations rely on existing seabed information, while some also generate new data. We aim to create a single platform knowledge-base to enable access to existing information, in a comprehensive, publicly accessible web-based interface. The Israel EEZ covers approx. 26,000 sqkm and has been surveyed continuously with various geophysical instruments over the past decades, including 10,000 km of multibeam survey lines, 8,000 km of sub-bottom seismic lines, and hundreds of sediment sampling stations. Our database consists of vector and raster datasets from multiple sources compiled into a repository of geophysical data and metadata, acquired nation-wide by several research institutes and universities. The repository will enable public access via a web portal based on a GIS platform, including datasets from multibeam, sub-bottom profiling, single- and multi-channel seismic surveys and sediment sampling analysis. Respective data products will also be available e.g. bathymetry, substrate type, granulometry, geological structure etc. Operating a web-GIS based repository allows retrieval of pre-existing data for potential users to facilitate planning of future activities e.g. conducting marine surveys, construction of marine infrastructure and other private or public projects. User interface is based on map oriented spatial selection, which will reveal any relevant data for designated areas of interest. Querying the database will allow the user to obtain information about the data owner and to address them for data retrieval as required. Wide and free public access to existing data and metadata can save time and funds for academia, government and commercial sectors, while aiding in cooperation and data sharing among the various stakeholders.

Multiple expressions of plume-ridge interaction in the Galápagos: Volcanic lineaments and ridge jumps

NASA Astrophysics Data System (ADS)

Mittelstaedt, E.; Soule, S.; Harpp, K.; Fornari, D.; McKee, C.; Tivey, M.; Geist, D.; Kurz, M. D.; Sinton, C.; Mello, C.

2012-05-01

Anomalous volcanism and tectonics between near-ridge mantle plumes and mid-ocean ridges provide important insights into the mechanics of plume-lithosphere interaction. We present new observations and analysis of multibeam, side scan sonar, sub-bottom chirp, and total magnetic field data collected during the R/V Melville FLAMINGO cruise (MV1007; May-June, 2010) to the Northern Galápagos Volcanic Province (NGVP), the region between the Galápagos Archipelago and the Galápagos Spreading Center (GSC) on the Nazca Plate, and to the region east of the Galápagos Transform Fault (GTF) on the Cocos Plate. The NGVP exhibits pervasive off-axis volcanism related to the nearby Galápagos hot spot, which has dominated the tectonic evolution of the region. Observations indicate that ˜94% of the excess volcanism in our survey area occurs on the Nazca Plate in three volcanic lineaments. Identified faults in the NGVP are consistent with normal ridge spreading except for those within a ˜60 km wide swath of transform-oblique faults centered on the GTF. These transform-oblique faults are sub-parallel to the elongation direction of larger lineament volcanoes, suggesting that lineament formation is influenced by the lithospheric stress field. We evaluate current models for lineament formation using existing and new observations as well as numerical models of mantle upwelling and melting. The data support a model where the lithospheric stress field controls the location of volcanism along the lineaments while several processes likely supply melt to these eruptions. Synthetic magnetic models and an inversion for crustal magnetization are used to determine the tectonic history of the study area. Results are consistent with creation of the GTF by two southward ridge jumps, part of a series of jumps that have maintained a plume-ridge separation distance of 145 km to 215 km since ˜5 Ma.

Geophysical Mapping of the South Carolina Offshore for Wind Energy Development

NASA Astrophysics Data System (ADS)

Brantley, D.; Knapp, C. C.; Battista, B.; Stone, J.

2017-12-01

The Bureau of Ocean Energy Management (BOEM) has identified potential Wind Energy Areas (WEA's) on the continental shelf of South Carolina characterized by good wind resource potential and minimal environmental and societal use conflicts based on existing regional data sets. A multi-sensor geophysical survey has been initiated to provide a more thorough determination of the shallow geologic framework and bottom habitat and cultural resources potential to further refine future wind farm siting. The most recent phase of deposition (Pleistocene; <1.8 Mya) took place during repeated, large-scale (120 m) sea-level changes which resulted in extensive exposure and inundation of the shelf. The shallow subsurface of the near-shore environment under consideration for wind energy development requires thorough analysis of seabed bottom type, seafloor roughness and geomorphology, potential sites of cultural resources and features such as active and inactive faults, filled channels, and potential slope instabilities which would have a considerable potential impact on sitting installations for wind energy. The study is focused on the inner shelf from 18 to 26 km offshore of North Myrtle Beach, SC. The collaborative effort is generating multibeam, and side scan sonar, CHIRP sub-bottom and magnetometer data. Across the region a thin veneer of sediments overlies indurated Tertiary deposits. The Tertiary geologic section is locally scoured and influenced small channels and probable karstification and enduring fluid exchange across the sea floor which has been previously identified in the region. The sea floor exhibits large-scale (100s of meters) low relief shore-perpendicular bedforms similar to those found within the shoreface and innermost shelf though the SC Coastal Erosion Study. Post-processed bathymetry shows a radial distribution of coast-perpendicular features that transition between two coastal processes: 1) there is the sediment distribution caused by the longshore currents and wave energy, and 2) there are areas related to the coastal inlets that disrupt the primary sedimentation patterns and impose patterns of terrestrial sedimentation such as those from rivers, deltas and estuaries.

A fractional Fourier transform analysis of the scattering of ultrasonic waves

PubMed Central

Tant, Katherine M.M.; Mulholland, Anthony J.; Langer, Matthias; Gachagan, Anthony

2015-01-01

Many safety critical structures, such as those found in nuclear plants, oil pipelines and in the aerospace industry, rely on key components that are constructed from heterogeneous materials. Ultrasonic non-destructive testing (NDT) uses high-frequency mechanical waves to inspect these parts, ensuring they operate reliably without compromising their integrity. It is possible to employ mathematical models to develop a deeper understanding of the acquired ultrasonic data and enhance defect imaging algorithms. In this paper, a model for the scattering of ultrasonic waves by a crack is derived in the time–frequency domain. The fractional Fourier transform (FrFT) is applied to an inhomogeneous wave equation where the forcing function is prescribed as a linear chirp, modulated by a Gaussian envelope. The homogeneous solution is found via the Born approximation which encapsulates information regarding the flaw geometry. The inhomogeneous solution is obtained via the inverse Fourier transform of a Gaussian-windowed linear chirp excitation. It is observed that, although the scattering profile of the flaw does not change, it is amplified. Thus, the theory demonstrates the enhanced signal-to-noise ratio permitted by the use of coded excitation, as well as establishing a time–frequency domain framework to assist in flaw identification and classification. PMID:25792967

Nonlinear fishbone dynamics in spherical tokamaks

DOE Data Explorer

Wang, Feng [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Dalian Univ Technol, Sch Phys & Optoelect Technol, Minist Educ, Key Lab Mat Modificat Laser Ion & Electron Beams, Dalian 116024, Peoples R China.; Fu, G.Y. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Institute for Fusion Theory and Simulation and Department of Physics Hangzhou, Zhejiang University, Hangzhou, 310027, People's Republic of China; Shen, Wei [Institute of Plasma Physics, Chinese Academy of Science, Hefei 230031, People's Republic of China

2017-01-01

Linear and nonlinear kinetic-MHD hybrid simulations have been carried out to investigate linear stability and nonlinear dynamics of beam-driven fishbone instability in spherical tokamak plasmas. Realistic NSTX parameters with finite toroidal rotation were used. The results show that the fishbone is driven by both trapped and passing particles. The instability drive of passing particles is comparable to that of trapped particles in the linear regime. The effects of rotation are destabilizing and a new region of instability appears at higher q min (>1.5) values, q min being the minimum of safety factor profile. In the nonlinear regime, the mode saturates due to flattening of beam ion distribution, and this persists after initial saturation while mode frequency chirps down in such a way that the resonant trapped particles move out radially and keep in resonance with the mode. Correspondingly, the flattening region of beam ion distribution expands radially outward. A substantial fraction of initially non-resonant trapped particles become resonant around the time of mode saturation and keep in resonance with the mode as frequency chirps down. On the other hand, the fraction of resonant passing particles is significantly smaller than that of trapped particles. Our analysis shows that trapped particles provide the main drive to the mode in the nonlinear regime.

Nonlinear fishbone dynamics in spherical tokamaks

DOE PAGES

Wang, Feng; Fu, G. Y.; Shen, Wei

2016-11-22

Linear and nonlinear kinetic-MHD hybrid simulations have been carried out to investigate linear stability and nonlinear dynamics of beam-driven fishbone instability in spherical tokamak plasmas. Realistic NSTX parameters with finite toroidal rotation were used. Our results show that the fishbone is driven by both trapped and passing particles. The instability drive of passing particles is comparable to that of trapped particles in the linear regime. The effects of rotation are destabilizing and a new region of instability appears at higher q min (>1.5) values, q min being the minimum of safety factor profile. In the nonlinear regime, the mode saturatesmore » due to flattening of beam ion distribution, and this persists after initial saturation while mode frequency chirps down in such a way that the resonant trapped particles move out radially and keep in resonance with the mode. Correspondingly, the flattening region of beam ion distribution expands radially outward. Furthermore, a substantial fraction of initially non-resonant trapped particles become resonant around the time of mode saturation and keep in resonance with the mode as frequency chirps down. On the other hand, the fraction of resonant passing particles is significantly smaller than that of trapped particles. Finally, our analysis shows that trapped particles provide the main drive to the mode in the nonlinear regime.« less

Sonotropic effects of commercial air transport sound on birds.

DOT National Transportation Integrated Search

1962-03-01

The Electra sound spectrum contains an audible chirp which appears identical in frequency and wave form to the chirp of field crickets. Field observations strongly indicate the sound of the taxiing Electra exerts an attraction for starlings, and poss...

a Low-Cost Chirped-Pulse Fourier Transform Microwave Spectrometer for Undergraduate Physical Chemistry Lab

NASA Astrophysics Data System (ADS)

Carroll, Brandon; Finneran, Ian; Blake, Geoffrey

2014-06-01

We present the design and construction of a simple and low-cost waveguide chirped pulse Fourier transform microwave (CP-FTMW) spectrometer suitable for gas-phase rotational spectroscopy experiments in undergraduate physical chemistry labs as well as graduate level research. The spectrometer operates with modest bandwidth, using phased locked loop (PLL) microwave sources and a direct digital synthesis (DDS) chirp source, making it an affordable for undergraduate labs. The performance of the instrument is benchmarked by acquiring the pure rotational spectrum of the J = 1 - 0 transition OCS and its isotopologues from 11-12.5 GHz.

160-Gb/s all-optical phase-transparent wavelength conversion through cascaded SFG-DFG in a broadband linear-chirped PPLN waveguide.

PubMed

Lu, Guo-Wei; Shinada, Satoshi; Furukawa, Hideaki; Wada, Naoya; Miyazaki, Tetsuya; Ito, Hiromasa

2010-03-15

We experimentally demonstrated ultra-fast phase-transparent wavelength conversion using cascaded sum- and difference-frequency generation (cSFG-DFG) in linear-chirped periodically poled lithium niobate (PPLN). Error-free wavelength conversion of a 160-Gb/s return-to-zero differential phase-shift keying (RZ-DPSK) signal was successfully achieved. Thanks to the enhanced conversion bandwidth in the PPLN with linear-chirped periods, no optical equalizer was required to compensate the spectrum distortion after conversion, unlike a previous demonstration of 160-Gb/s RZ on-off keying (OOK) using fixed-period PPLN.

Controlling the femtosecond laser-driven transformation of dicyclopentadiene into cyclopentadiene

PubMed Central

Goswami, Tapas; Das, Dipak K.; Goswami, Debabrata

2013-01-01

Dynamics of the chemical transformation of dicyclopentadiene into cyclopentadiene in a supersonic molecular beam is elucidated using femtosecond time-resolved degenerate pump–probe mass spectrometry. Control of this ultrafast chemical reaction is achieved by using linearly chirped frequency modulated pulses. We show that negatively chirped femtosecond laser pulses enhance the cyclopentadiene photoproduct yield by an order of magnitude as compared to that of the unmodulated or the positively chirped pulses. This demonstrates that the phase structure of femtosecond laser pulse plays an important role in determining the outcome of a chemical reaction. PMID:24098059

Prediction of nonlinear evolution character of energetic-particle-driven instabilities

DOE PAGES

Duarte, Vinicius N.; Berk, H. L.; Gorelenkov, N. N.; ...

2017-03-17

A general criterion is proposed and found to successfully predict the emergence of chirping oscillations of unstable Alfvénic eigenmodes in tokamak plasma experiments. The model includes realistic eigenfunction structure, detailed phase-space dependences of the instability drive, stochastic scattering and the Coulomb drag. The stochastic scattering combines the effects of collisional pitch angle scattering and micro-turbulence spatial diffusion. Furthermore, the latter mechanism is essential to accurately identify the transition between the fixed-frequency mode behavior and rapid chirping in tokamaks and to resolve the disparity with respect to chirping observation in spherical and conventional tokamaks.

Chirped self-similar waves for quadratic-cubic nonlinear Schrödinger equation

NASA Astrophysics Data System (ADS)

Pal, Ritu; Loomba, Shally; Kumar, C. N.

2017-12-01

We have constructed analytical self-similar wave solutions for quadratic-cubic Nonlinear Schrödinger equation (QC-NLSE) by means of similarity transformation method. Then, we have investigated the role of chirping on these self-similar waves as they propagate through the tapered graded index waveguide. We have revealed that the chirping leads to interesting features and allows us to control the propagation of self-similar waves. This has been demonstrated for two cases (i) periodically distributed system and (ii) constant choice of system parameters. We expect our results to be useful in designing high performance optical devices.

Chirped pulse digital holography for measuring the sequence of ultrafast optical wavefronts

NASA Astrophysics Data System (ADS)

Karasawa, Naoki

2018-04-01

Optical setups for measuring the sequence of ultrafast optical wavefronts using a chirped pulse as a reference wave in digital holography are proposed and analyzed. In this method, multiple ultrafast object pulses are used to probe the temporal evolution of ultrafast phenomena and they are interfered with a chirped reference wave to record a digital hologram. Wavefronts at different times can be reconstructed separately from the recorded hologram when the reference pulse can be treated as a quasi-monochromatic wave during the pulse width of each object pulse. The feasibility of this method is demonstrated by numerical simulation.

Efficient terahertz wave generation from GaP crystals pumped by chirp-controlled pulses from femtosecond photonic crystal fiber amplifier

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

Li, Jiang; Shi, Junkai; Xu, Baozhong

2014-01-20

A chirp-tunable femtosecond 10 W, 42 MHz photonic-crystal-fiber oscillator-amplifier system that is capable of delivering sub-60 fs light pulses at 1040 nm is used to demonstrate high-efficiency terahertz radiation generation via optical rectification in GaP crystals only a few millimeters in length. The optimization of the chirp of the fiber-laser pulses is shown to radically enhance the terahertz output, indicating one possible way to more efficiently use these extended nonlinear crystals in compact fiber-pumped terahertz radiation sources.

Synchronous, Alternating, and Phase-Locked Stridulation by a Tropical Katydid

NASA Astrophysics Data System (ADS)

Sismondo, Enrico

1990-07-01

In the field the chirps of neighboring Mecopoda sp. (Orthoptera, Tettigoniidae, and Mecopodinae) males are normally synchronized, but between more distant individuals the chirps are either synchronous or regularly alternating. The phase response to single-stimulus chirps depends on both the phase and the intensity of the stimulus. Iteration of the Poincare map of the phase response predicts a variety of phase-locked synchronization regimes, including period-doubling bifurcations, in close agreement with experimental observations. The versatile acoustic behavior of Mecopoda encompasses most of the phenomena found in other synchronizing insects and thus provides a general model of insect synchronization behavior.

Prediction of nonlinear evolution character of energetic-particle-driven instabilities

NASA Astrophysics Data System (ADS)

Duarte, V. N.; Berk, H. L.; Gorelenkov, N. N.; Heidbrink, W. W.; Kramer, G. J.; Nazikian, R.; Pace, D. C.; Podestà, M.; Tobias, B. J.; Van Zeeland, M. A.

2017-05-01

A general criterion is proposed and found to successfully predict the emergence of chirping oscillations of unstable Alfvénic eigenmodes in tokamak plasma experiments. The model includes realistic eigenfunction structure, detailed phase-space dependences of the instability drive, stochastic scattering and the Coulomb drag. The stochastic scattering combines the effects of collisional pitch angle scattering and micro-turbulence spatial diffusion. The latter mechanism is essential to accurately identify the transition between the fixed-frequency mode behavior and rapid chirping in tokamaks and to resolve the disparity with respect to chirping observation in spherical and conventional tokamaks.

Dispersion management for a sub-10-fs, 10 TW optical parametric chirped-pulse amplifier.

PubMed

Tavella, Franz; Nomura, Yutaka; Veisz, Laszlo; Pervak, Vladimir; Marcinkevicius, Andrius; Krausz, Ferenc

2007-08-01

We report the amplification of three-cycle, 8.5 fs optical pulses in a near-infrared noncollinear optical parametric chirped-pulse amplifier (OPCPA) up to energies of 80 mJ. Improved dispersion management in the amplifier by means of a combination of reflection grisms and a chirped-mirror stretcher allowed us to recompress the amplified pulses to within 6% of their Fourier limit. The novel ultrabroad, ultraprecise dispersion control technology presented in this work opens the way to scaling multiterawatt technology to even shorter pulses by optimizing the OPCPA bandwidth.

Wavelength-tunable, passively mode-locked fiber laser based on graphene and chirped fiber Bragg grating.

PubMed

He, Xiaoying; Liu, Zhi-bo; Wang, D N

2012-06-15

We demonstrate a wavelength-tunable, passively mode-locked erbium-doped fiber laser based on graphene and chirped fiber Bragg grating. The saturable absorber used to enable passive mode-locking in the fiber laser is a section of microfiber covered by graphene film, which allows light-graphene interaction via the evanescent field of the microfiber. The wavelength of the laser can be continuously tuned by adjusting the chirped fiber Bragg grating, while maintaining mode-locking stability. Such a system has high potential in tuning the mode-locked laser pulses across a wide wavelength range.

Flattop wideband wavelength converters based on cascaded sum and difference-frequency generation using step-chirped gratings

NASA Astrophysics Data System (ADS)

Tehranchi, Amirhossein; Kashyap, Raman

2011-03-01

We investigate the role of step-chirped gratings (SCG) for flattening of conversion efficiency response and enhancing the pump bandwidth in cascaded sum and difference frequency generation (SFG + DFG) with a large pump wavelength difference. To obtain a flat response with maximum efficiency, using SCG instead of uniform grating with the same length, the appropriate critical period shifts are presented for the reasonable number of sections and chirp steps feasible for fabrication. Furthermore, it is shown that adding the section numbers for SCG structure increases the pump bandwidth.

Study of spread spectrum multiple access systems for satellite communications with overlay on current services

NASA Technical Reports Server (NTRS)

Ha, Tri T.; Pratt, Timothy

1989-01-01

The feasibility of using spread spectrum techniques to provide a low-cost multiple access system for a very large number of low data terminals was investigated. Two applications of spread spectrum technology to very small aperture terminal (VSAT) satellite communication networks are presented. Two spread spectrum multiple access systems which use a form of noncoherent M-ary FSK (MFSK) as the primary modulation are described and the throughput analyzed. The analysis considers such factors as satellite power constraints and adjacent satellite interference. Also considered is the effect of on-board processing on the multiple access efficiency and the feasibility of overlaying low data rate spread spectrum signals on existing satellite traffic as a form of frequency reuse is investigated. The use of chirp is examined for spread spectrum communications. In a chirp communication system, each data bit is converted into one or more up or down sweeps of frequency, which spread the RF energy across a broad range of frequencies. Several different forms of chirp communication systems are considered, and a multiple-chirp coded system is proposed for overlay service. The mutual interference problem is examined in detail and a performance analysis undertaken for the case of a chirp data channel overlaid on a video channel.

Paraxial propagation of the first-order chirped Airy vortex beams in a chiral medium.

PubMed

Xie, Jintao; Zhang, Jianbin; Ye, Junran; Liu, Haowei; Liang, Zhuoying; Long, Shangjie; Zhou, Kangzhu; Deng, Dongmei

2018-03-05

We introduce the propagation of the first-order chirped Airy vortex beams (FCAiV) in a chiral medium analytically. Results show that the FCAiV beams split into the left circularly polarized vortex (LCPV) beams and the right circularly polarized vortex (RCPV) beams, which have totally different propagation trajectories in the chiral medium. In this paper, we investigate the effects of the first-order chirped parameter β, the chiral parameter γ and the optical vortex on the propagation process of the FCAiV beams. It is shown that the propagation trajectory of the FCAiV beams declines with the chirped parameter increasing. Besides, the increase of the chiral parameter acting on the LCPV beams makes the relative position between the main lobe and the optical vortex further while the effect on the RCPV beams is the opposite. Furthermore, the relative position between the main lobe and the optical vortex contributes to the position of the intensity focusing. Meanwhile, with the chiral parameter increasing, the maximum gradient and scattering forces of the LCPV beams decrease but those of the RCPV beams will increase during the propagation. It is significant that we can control the propagation trajectory, the intensity focusing position and the radiation forces of the FCAiV beams by varying the chirped parameter and the chiral parameter.

Electron acceleration from rest to GeV energy by chirped axicon Gaussian laser pulse in vacuum in the presence of wiggler magnetic field

NASA Astrophysics Data System (ADS)

Kant, Niti; Rajput, Jyoti; Singh, Arvinder

2018-03-01

This paper presents a scheme of electron energy enhancement by employing frequency - chirped lowest order axicon focussed radially polarised (RP) laser pulse in vacuum under the influence of wiggler magnetic field. Terawatt RP laser can be focussed down to ∼5μm by an axicon optical element, which produces an intense longitudinal electric field. This unique property of axicon focused Gaussian RP laser pulse is employed for direct electron acceleration in vacuum. A linear frequency chirp increases the time duration of laser-electron interaction, whereas, the applied magnetic wiggler helps in improving the strength of ponderomotive force v→ ×B→ and periodically deflects electron in order to keep it traversing in the accelerating phase up to longer distance. Numerical simulations have been carried out to investigate the influence of laser, frequency chirp and magnetic field parameters on electron energy enhancement. It is noticed that an electron from rest can be accelerated up to GeV energy under optimized laser and magnetic field parameters. Significant enhancement in the electron energy gain of the order of 11.2 GeV is observed with intense chirped laser pulse in the presence of wiggler magnetic field of strength 96.2 kG.

Encoding of social signals in all three electrosensory pathways of Eigenmannia virescens.

PubMed

Stöckl, Anna; Sinz, Fabian; Benda, Jan; Grewe, Jan

2014-11-01

Extracting complementary features in parallel pathways is a widely used strategy for a robust representation of sensory signals. Weakly electric fish offer the rare opportunity to study complementary encoding of social signals in all of its electrosensory pathways. Electrosensory information is conveyed in three parallel pathways: two receptor types of the tuberous (active) system and one receptor type of the ampullary (passive) system. Modulations of the fish's own electric field are sensed by these receptors and used in navigation, prey detection, and communication. We studied the neuronal representation of electric communication signals (called chirps) in the ampullary and the two tuberous pathways of Eigenmannia virescens. We first characterized different kinds of chirps observed in behavioral experiments. Since Eigenmannia chirps simultaneously drive all three types of receptors, we studied their responses in in vivo electrophysiological recordings. Our results demonstrate that different electroreceptor types encode different aspects of the stimuli and each appears best suited to convey information about a certain chirp type. A decoding analysis of single neurons and small populations shows that this specialization leads to a complementary representation of information in the tuberous and ampullary receptors. This suggests that a potential readout mechanism should combine information provided by the parallel processing streams to improve chirp detectability. Copyright © 2014 the American Physiological Society.

Improvement of SPM nonlinear limit by chirped duobinary PolSK transmission

NASA Astrophysics Data System (ADS)

Yang, Lixiu; Fan, Jiayu; Wang, Lutang; Huang, Zhaoming

2005-02-01

In today's terrestrial long-haul optical fiber communication systems, high channel powers are required to obtain a large transmission distance with reasonable optical amplifier spacing. In such systems, however, the presence of nonlinear effects such as the self-phase modulation (SPM) and the fiber dispersion as well as their combined effects, called SPM-induced nonlinear limitation or SPM limit, will seriously degrade the system performances in respect of the effective transmission distance and ultimately become a limiting factor in high-speed, long-haul optical fiber transmission.In this paper, a new transmission format: chirped duobinary PolSK transmission, has been proposed to generate a pre-chirped duobianry signal with fixed polarity (either positive or negative), which is modulated by a PolSK modulator. This format is based on a transmitter setup consisting of a duobinary PolSK Modulation transmitter followed by an additional phase modulator. The chirped duobinary PolSK transmission reduces the signal degradation and spectral broadening in the nonlinear regime significantly. Thus it shifts this SPM nonlinear limit to enable more relaxed dispersion compensation at high optical power compared to the conventional duobinary schemes.The simulation results show chirped duobinary PolSK transmission enlarges the dispersion limited transmission distance, increases the dispersion tolerance and overcome the SPM nonlinear limit.

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

Candy, J. V.

Chirp signals have evolved primarily from radar/sonar signal processing applications specifically attempting to estimate the location of a target in surveillance/tracking volume. The chirp, which is essentially a sinusoidal signal whose phase changes instantaneously at each time sample, has an interesting property in that its correlation approximates an impulse function. It is well-known that a matched-filter detector in radar/sonar estimates the target range by cross-correlating a replicant of the transmitted chirp with the measurement data reflected from the target back to the radar/sonar receiver yielding a maximum peak corresponding to the echo time and therefore enabling the desired range estimate.more » In this application, we perform the same operation as a radar or sonar system, that is, we transmit a “chirp-like pulse” into the target medium and attempt to first detect its presence and second estimate its location or range. Our problem is complicated by the presence of disturbance signals from surrounding broadcast stations as well as extraneous sources of interference in our frequency bands and of course the ever present random noise from instrumentation. First, we discuss the chirp signal itself and illustrate its inherent properties and then develop a model-based processing scheme enabling both the detection and estimation of the signal from noisy measurement data.« less

High-resolution seismic-reflection profiles collected by the R/V Columbus Iselin, cruise CI 7807-1, in the Baltimore Canyon outer continental shelf area, offshore New Jersey

USGS Publications Warehouse

Robb, James M.

1980-01-01

High-resolution seismic-reflection profiles were collected by the U.S. Geological Survey (USGS) aboard R/V COLUMBUS ISELIN, cruise 7807-1, from 18 August to 4 September 1978 over the Continental Slope of the Eastern United States between Wilmington and Hudson Canyons. These data were acquired as part of a study to determine potential geologic hazards to petroleum development of the Baltimore Canyon trough area. On this cruise, the Continental Slope between Lindenkohl and Carteret Canyons was surveyed along lines spaced one-half nautical mile apart to study the size and distribution of mass-wasting features as a guide to assess the importance of mass wasting processes on the Continental Slope. The seismic-reflection profiles were placed to complement other data gathered previously by the USGS.Track-line distances totaled 2,050 km of 40-in3 air-gun (with wave shaper) profiles, 2,100 km of 800-J sparker data, and 2,100 km of 3 .5-kHz data. The air-gun and sparker profiles are of high quality, but the 3.5-kHz system did not function well and achieved no subbottom penetration. The side-scan sonar system was operated along the uppermost Continental Slope to investigate its potential for use in this environment. Data were acquired over 22 km of ship's track.Navigation was by Loran-C (5-minute fix interval).The original records can be examined at the U.S. Geological Survey offices in Woods Hole, Massachusetts 02543. Microfilm copies of the data are available for purchase from the National Geophysical and Solar-Terrestrial Data Center (NGSDC), Boulder, Colorado 80303.

Geophysical Investigation Along the Great Miami River From New Miami to Charles M. Bolton Well Field, Cincinnati, Ohio

USGS Publications Warehouse

Sheets, R.A.; Dumouchelle, D.H.

2009-01-01

Three geophysical profiling methods were tested to help characterize subsurface materials at selected transects along the Great Miami River, in southwestern Ohio. The profiling methods used were continuous seismic profiling (CSP), continuous resistivity profiling (CRP), and continuous electromagnetic profiling (CEP). Data were collected with global positioning systems to spatially locate the data along the river. The depth and flow conditions of the Great Miami River limited the amount and quality of data that could be collected with the CSP and CRP methods. Data from the CSP were generally poor because shallow reflections (less than 5 meters) were mostly obscured by strong multiple reflections and deep reflections (greater than 5 meters) were sparse. However, modeling of CRP data indicated broad changes in subbottom geology, primarily below about 3 to 5 meters. Details for shallow electrical conductivity (resistivity) (less than 3 meters) were limited because of the 5-meter electrode spacing used for the surveys. For future studies of this type, a cable with 3-meter electrode spacing (or perhaps even 1-meter spacing) might best be used in similar environments to determine shallow electrical properties of the stream-bottom materials. CEP data were collected along the entire reach of the Great Miami River. The CRP and CEP data did not correlate well, but the CRP electrode spacing probably limited the correlation. Middle-frequency (3,510 hertz) and high-frequency (15,030 hertz) CEP data were correlated to water depth. Low-frequency (750 hertz) CEP data indicate shallow (less than 5-meter) changes in electrical conductivity. Given the variability in depth and flow conditions on a river such as the Great Miami, the CEP method worked better than either the CSP or CRP methods.

Farbrication of diffractive optical elements on a Si chip by an imprint lithography using nonsymmetrical silicon mold

NASA Astrophysics Data System (ADS)

Hirai, Yoshihiko; Okano, Masato; Okuno, Takayuki; Toyota, Hiroshi; Yotsuya, Tsutomu; Kikuta, Hisao; Tanaka, Yoshio

2001-11-01

Fabrication of a fine diffractive optical element on a Si chip is demonstrated using imprint lithography. A chirped diffraction grating, which has modulated pitched pattern with curved cross section is fabricated by an electron beam lithography, where the exposure dose profile is automatically optimized by computer aided system. Using the resist pattern as an etching mask, anisotropic dry etching is performed to transfer the resist pattern profile to the Si chip. The etched Si substrate is used as a mold in the imprint lithography. The Si mold is pressed to a thin polymer (poly methyl methacrylate) on a Si chip. After releasing the mold, a fine diffractive optical pattern is successfully transferred to the thin polymer. This method is exceedingly useful for fabrication of integrated diffractive optical elements with electric circuits on a Si chip.

Archive of chirp seismic reflection data collected during USGS cruises 00SCC02 and 00SCC04, Barataria Basin, Louisiana, May 12-31 and June 17-July 2, 2000

USGS Publications Warehouse

Calderon, Karynna; Dadisman, S.V.; Kindinger, J.L.; Flocks, J.G.; Wiese, D.S.; Kulp, Mark; Penland, Shea; Britsch, L.D.; Brooks, G.R.

2003-01-01

This archive consists of two-dimensional marine seismic reflection profile data collected in the Barataria Basin of southern Louisiana. These data were acquired in May, June, and July of 2000 aboard the R/V G.K. Gilbert. Included here are data in a variety of formats including binary, American Standard Code for Information Interchange (ASCII), Hyper-Text Markup Language (HTML), shapefiles, and Graphics Interchange Format (GIF) and Joint Photographic Experts Group (JPEG) images. Binary data are in Society of Exploration Geophysicists (SEG) SEG-Y format and may be downloaded for further processing or display. Reference maps and GIF images of the profiles may be viewed with a web browser. The Geographic Information Systems (GIS) information provided here is compatible with Environmental Systems Research Institute (ESRI) GIS software.

Pulse compression of harmonic chirp signals using the fractional fourier transform.

PubMed

Arif, M; Cowell, D M J; Freear, S

2010-06-01

In ultrasound harmonic imaging with chirp-coded excitation, a harmonic matched filter (HMF) is typically used on the received signal to perform pulse compression of the second harmonic component (SHC) to recover signal axial resolution. Designing the HMF for the compression of the SHC is a problematic issue because it requires optimal window selection. In the compressed second harmonic signal, the sidelobe level may increase and the mainlobe width (MLW) widen under a mismatched condition, resulting in loss of axial resolution. We propose the use of the fractional Fourier transform (FrFT) as an alternative tool to perform compression of the chirp-coded SHC generated as a result of the nonlinear propagation of an ultrasound signal. Two methods are used to experimentally assess the performance benefits of the FrFT technique over the HMF techniques. The first method uses chirp excitation with central frequency of 2.25 MHz and bandwidth of 1 MHz. The second method uses chirp excitation with pulse inversion to increase the bandwidth to 2 MHz. In this study, experiments were performed in a water tank with a single-element transducer mounted coaxially with a hydrophone in a pitch-catch configuration. Results are presented that indicate that the FrFT can perform pulse compression of the second harmonic chirp component, with a 14% reduction in the MLW of the compressed signal when compared with the HMF. Also, the FrFT provides at least 23% reduction in the MLW of the compressed signal when compared with the harmonic mismatched filter (HMMF). The FrFT maintains comparable peak and integrated sidelobe levels when compared with the HMF and HMMF techniques. Copyright 2010 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Advanced satellite communication system

NASA Technical Reports Server (NTRS)

Staples, Edward J.; Lie, Sen

1992-01-01

The objective of this research program was to develop an innovative advanced satellite receiver/demodulator utilizing surface acoustic wave (SAW) chirp transform processor and coherent BPSK demodulation. The algorithm of this SAW chirp Fourier transformer is of the Convolve - Multiply - Convolve (CMC) type, utilizing off-the-shelf reflective array compressor (RAC) chirp filters. This satellite receiver, if fully developed, was intended to be used as an on-board multichannel communications repeater. The Advanced Communications Receiver consists of four units: (1) CMC processor, (2) single sideband modulator, (3) demodulator, and (4) chirp waveform generator and individual channel processors. The input signal is composed of multiple user transmission frequencies operating independently from remotely located ground terminals. This signal is Fourier transformed by the CMC Processor into a unique time slot for each user frequency. The CMC processor is driven by a waveform generator through a single sideband (SSB) modulator. The output of the coherent demodulator is composed of positive and negative pulses, which are the envelopes of the chirp transform processor output. These pulses correspond to the data symbols. Following the demodulator, a logic circuit reconstructs the pulses into data, which are subsequently differentially decoded to form the transmitted data. The coherent demodulation and detection of BPSK signals derived from a CMC chirp transform processor were experimentally demonstrated and bit error rate (BER) testing was performed. To assess the feasibility of such advanced receiver, the results were compared with the theoretical analysis and plotted for an average BER as a function of signal-to-noise ratio. Another goal of this SBIR program was the development of a commercial product. The commercial product developed was an arbitrary waveform generator. The successful sales have begun with the delivery of the first arbitrary waveform generator.

Study of the Q branch structure of the 14N and 15N isotopologues of the ν4 band of ammonia using frequency chirped quantum cascade lasers.

PubMed

Duxbury, Geoffrey; Wilson, David; Hay, Kenneth; Langford, Nigel

2013-10-03

Intrapulse quantum cascade (QC) laser spectrometers are able to produce both saturation and molecular alignment of a gas sample owing to the rapid sweep of the radiation through the absorption features. In the QC lasers used to study the (14)N and (15)N isotopologues of the ν4 band of ammonia centered near 1625 cm(-1), the variation of the chirp rate during the scan is very large, from ca. 85 to ca. 15 MHz ns(-1). In the rapid chirp zone the collisional interaction time of the laser radiation with the gas molecules is short, and large rapid passage effects are seen, whereas at the slow chirp end the line shape resembles that of a Doppler broadened line. The total scan range of the QC laser of ca. 10 cm(-1) is sufficient to allow the spectra of both isotopologues to be recorded and the rapid and slow interactions with the laser radiation to be seen. The rapid passage effects are enhanced by the use of an off axis Herriott cell with an effective path length of 62 m, which allows a buildup of polarization to occur. The effective resolution of the chirped QC laser is ca. 0.012 cm(-1) full width at half-maximum in the 1625 cm(-1) region. The results of these experiments are compared with those of other studies of the ν4 band of ammonia carried out using Fourier transform and Laser Stark spectroscopy. They also demonstrate the versatility of the down chirped QC laser for investigating collisional effects in low pressure gases using long absorbing path lengths.

Intensity noise reduction of a high-power nonlinear femtosecond fiber amplifier based on spectral-breathing self-similar parabolic pulse evolution

NASA Astrophysics Data System (ADS)

Wang, Sijia; Liu, Bowen; Song, Youjian; Hu, Minglie

2016-04-01

We report on a simple passive scheme to reduce the intensity noise of high-power nonlinear fiber amplifiers by use of the spectral-breathing parabolic evolution of the pulse amplification with an optimized negative initial chirp. In this way, the influences of amplified spontaneous emission (ASE) on the amplifier intensity noise can be efficiently suppressed, owing to the lower overall pulse chirp, shorter spectral broadening distance, as well as the asymptotic attractive nature of self-similar pulse amplification. Systematic characterizations of the relative intensity noise (RIN) of a free-running nonlinear Yb-doped fiber amplifier are performed over a series of initial pulse parameters. Experiments show that the measured amplifier RIN increases respect to the decreased input pulse energy, due to the increased amount of ASE noise. For pulse amplification with a proper negative initial chirp, the increase of RIN is found to be smaller than with a positive initial chirp, confirming the ASE noise tolerance of the proposed spectral-breathing parabolic amplification scheme. At the maximum output average power of 27W (25-dB amplification gain), the incorporation of an optimum negative initial chirp (-0.84 chirp parameter) leads to a considerable amplifier root-mean-square (rms) RIN reduction of ~20.5% (integrated from 10 Hz to 10 MHz Fourier frequency). The minimum amplifier rms RIN of 0.025% (integrated from 1 kHz to 5 MHz Fourier frequency) is obtained along with the transform-limited compressed pulse duration of 55fs. To our knowledge, the demonstrated intensity noise performance is the lowest RIN level measured from highpower free-running femtosecond fiber amplifiers.

Dynamic chirp control of all-optical format-converted pulsed data from a multi-wavelength inverse-optical-comb injected semiconductor optical amplifier.

PubMed

Lin, Gong-Ru; Pan, Ci-Ling; Yu, Kun-Chieh

2007-10-01

By spectrally and temporally reshaping the gain-window of a traveling-wave semiconductor optical amplifier (TWSOA) with a backward injected multi- or single-wavelength inverse-optical-comb, we theoretically and experimentally investigate the dynamic frequency chirp of the all-optical 10GBit/s Return-to-Zero (RZ) data-stream format-converted from the TWSOA under strong cross-gain depletion scheme. The multi-wavelength inverse-optical-comb injection effectively depletes the TWSOA gain spectrally and temporally, remaining a narrow gain-window and a reduced spectral linewidth and provide a converted RZ data with a smaller peak-to-peak frequency chirp of 6.7 GHz. Even at high inverse-optical-comb injection power and highly biased current condition for improving the operational bit-rate, the chirp of the multi-wavelength-injection converted RZ pulse is still 2.1-GHz smaller than that obtained by using single-wavelength injection at a cost of slight pulse-width broadening by 1 ps.

[Study on Differential Optical Absorption Spectroscopy Data Processing Based on Chirp-Z Transformation].

PubMed

Zheng, Hai-ming; Li, Guang-jie; Wu, Hao

2015-06-01

Differential optical absorption spectroscopy (DOAS) is a commonly used atmospheric pollution monitoring method. Denoising of monitoring spectral data will improve the inversion accuracy. Fourier transform filtering method is effectively capable of filtering out the noise in the spectral data. But the algorithm itself can introduce errors. In this paper, a chirp-z transform method is put forward. By means of the local thinning of Fourier transform spectrum, it can retain the denoising effect of Fourier transform and compensate the error of the algorithm, which will further improve the inversion accuracy. The paper study on the concentration retrieving of SO2 and NO2. The results show that simple division causes bigger error and is not very stable. Chirp-z transform is proved to be more accurate than Fourier transform. Results of the frequency spectrum analysis show that Fourier transform cannot solve the distortion and weakening problems of characteristic absorption spectrum. Chirp-z transform shows ability in fine refactoring of specific frequency spectrum.

Chirped bright and dark solitons of (3 + 1)-dimensional coupled nonlinear Schrödinger equations in negative-index metamaterials with both electric and magnetic nonlinearity of Kerr type

NASA Astrophysics Data System (ADS)

Dai, Chao-Qing; Fan, Yan; Wang, Yue-Yue; Zheng, Jun

2018-02-01

The (3 + 1)-dimensional generalized coupled nonlinear Schrödinger equation with electric and magnetic nonlinearities of Kerr type and self-steepening effects is studied, and bright and dark soliton solutions are derived. Based on these analytical solutions, dynamical behaviors of bright and dark solitons are discussed. The amplitudes, widths and velocities of bright and dark solitons are all constants determined by the self-steepening effect parameters SE, SH. The phase chirp of a bright soliton diminishes in the pulse front of y-direction, however, it increases in the pulse back edge of y-direction. On the contrary, the phase chirp of a dark soliton increases in the pulse front of y-direction, however, it diminishes in the pulse back edge of y-direction. The phase chirps of a bright and dark soliton both shift along positive y -axis as time goes on. Moreover, the stability of the solutions is discussed.

Chirped pulse Raman amplification in warm plasma: towards controlling saturation

PubMed Central

Yang, X.; Vieux, G.; Brunetti, E.; Ersfeld, B.; Farmer, J. P.; Hur, M. S.; Issac, R. C.; Raj, G.; Wiggins, S. M.; Welsh, G. H.; Yoffe, S. R.; Jaroszynski, D. A.

2015-01-01

Stimulated Raman backscattering in plasma is potentially an efficient method of amplifying laser pulses to reach exawatt powers because plasma is fully broken down and withstands extremely high electric fields. Plasma also has unique nonlinear optical properties that allow simultaneous compression of optical pulses to ultra-short durations. However, current measured efficiencies are limited to several percent. Here we investigate Raman amplification of short duration seed pulses with different chirp rates using a chirped pump pulse in a preformed plasma waveguide. We identify electron trapping and wavebreaking as the main saturation mechanisms, which lead to spectral broadening and gain saturation when the seed reaches several millijoules for durations of 10’s – 100’s fs for 250 ps, 800 nm chirped pump pulses. We show that this prevents access to the nonlinear regime and limits the efficiency, and interpret the experimental results using slowly-varying-amplitude, current-averaged particle-in-cell simulations. We also propose methods for achieving higher efficiencies. PMID:26290153

Overview of Spontaneous Frequency Chirping in Confined Plasmas

NASA Astrophysics Data System (ADS)

Berk, Herbert

2012-10-01

Spontaneous rapid frequency chirping is now a commonly observed phenomenon in plasmas with an energetic particle component. These particles typically induce so called weak instabilities, where they excite background waves that the plasma can support such as shear Alfven waves. The explanation for this phenomenon attributes the frequency chirping to the formation of phase space structures in the form of holes and clumps. Normally a saturated mode, in the presence of background dissipation, would be expected decay after saturation as the background plasma absorbs the energy of the excited wave. However the phase space structures take an alternate route, and move to a regions of phase space that are lower energy states of the energetic particle distribution. Through the wave-resonant particle interaction, this movement is locked to the frequency observed by the wave. This phenomenon implies that alternate mechanisms for plasma relaxation need to be considered for plasma states new marginal stability. It is also possible that these chirping mechanisms can be used to advantage to externally control states of plasma.

Influence of chirp on laser-pulse amplification in Brillouin backscattering schemes

NASA Astrophysics Data System (ADS)

Lehmann, Goetz; Schluck, Friedrich; Spatschek, Karl-Heinz

2015-11-01

Plasma-based amplification of laser pulses is currently discussed as a key component for the next generation of high-intensity laser systems, possibly enabling the generation of ultra-short pulses in the exawatt-zetawatt regime. In these scenarios the energy of a long pump pulse (several ps to ns of duration) is transferred to a short seed pulse via a plasma oscillation. Weakly- and strongly-coupled (sc) Brillouin backscattering have been identified as potential candidates for robust amplification scenarios. With the help of three-wave interaction models, we investigate the influence of a chirp of the pump beam on the seed amplification. We show that chirp can mitigate deleterious spontaneous Raman backscattering of the pump off noise and that at the same time the amplification dynamics due to Brillouin scattering is still intact. For the experimentally very interesting case of sc-Brillouin we find a dependence of the efficiency on the sign of the chirp. Funding provided by project B10 of SFB TR18 of the Deutsche Forschungsgemeinschaft (DFG).

Non-stationary component extraction in noisy multicomponent signal using polynomial chirping Fourier transform.

PubMed

Lu, Wenlong; Xie, Junwei; Wang, Heming; Sheng, Chuan

2016-01-01

Inspired by track-before-detection technology in radar, a novel time-frequency transform, namely polynomial chirping Fourier transform (PCFT), is exploited to extract components from noisy multicomponent signal. The PCFT combines advantages of Fourier transform and polynomial chirplet transform to accumulate component energy along a polynomial chirping curve in the time-frequency plane. The particle swarm optimization algorithm is employed to search optimal polynomial parameters with which the PCFT will achieve a most concentrated energy ridge in the time-frequency plane for the target component. The component can be well separated in the polynomial chirping Fourier domain with a narrow-band filter and then reconstructed by inverse PCFT. Furthermore, an iterative procedure, involving parameter estimation, PCFT, filtering and recovery, is introduced to extract components from a noisy multicomponent signal successively. The Simulations and experiments show that the proposed method has better performance in component extraction from noisy multicomponent signal as well as provides more time-frequency details about the analyzed signal than conventional methods.

Effects of a chirped bias voltage on ion energy distributions in inductively coupled plasma reactors

NASA Astrophysics Data System (ADS)

Lanham, Steven J.; Kushner, Mark J.

2017-08-01

The metrics for controlling reactive fluxes to wafers for microelectronics processing are becoming more stringent as feature sizes continue to shrink. Recent strategies for controlling ion energy distributions to the wafer involve using several different frequencies and/or pulsed powers. Although effective, these strategies are often costly or present challenges in impedance matching. With the advent of matching schemes for wide band amplifiers, other strategies to customize ion energy distributions become available. In this paper, we discuss results from a computational investigation of biasing substrates using chirped frequencies in high density, electronegative inductively coupled plasmas. Depending on the frequency range and chirp duration, the resulting ion energy distributions exhibit components sampled from the entire frequency range. However, the chirping process also produces transient shifts in the self-generated dc bias due to the reapportionment of displacement and conduction with frequency to balance the current in the system. The dynamics of the dc bias can also be leveraged towards customizing ion energy distributions.

Progress Towards Chirped-Pulse Fourier Transform Thz Spectroscopy

NASA Astrophysics Data System (ADS)

Douglass, Kevin O.; Plusquellic, David F.; Gerecht, Eyal

2010-06-01

New opportunities are provided by the development of higher power THz frequency multiplier sources, the development of a broadband Chirped-Pulse FTMW spectroscopy technique at microwave and mm Wave frequencies, and recently demonstrated heterodyne hot electron bolometer detection technology in the THz frequency region with near quantum noise-limited performance and high spectral resolution. Combining these three technologies and extending the chirped-pulse technique to 0.85 THz enables a host of new applications. NIST is currently pursing applications as a point sensor for greenhouse gases, volatile organic compounds, and potentially human breath. The generation and detection of phase stable chirped pulses at 850 GHz will be demonstrated. A description of the experimental setup and preliminary data will be presented for nitrous oxide. G.G. Brown, B.C. Dian, K.O. Douglass, S.M. Geyer, S. Shipman and B.H. Pate, Rev.Sci.Instrum. 79 (2008) 053103. E. Gerecht, D. Gu, L. You, K.S. Yngvesson, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES. 56, (2008) 1083.

Shear wave speed and dispersion measurements using crawling wave chirps.

PubMed

Hah, Zaegyoo; Partin, Alexander; Parker, Kevin J

2014-10-01

This article demonstrates the measurement of shear wave speed and shear speed dispersion of biomaterials using a chirp signal that launches waves over a range of frequencies. A biomaterial is vibrated by two vibration sources that generate shear waves inside the medium, which is scanned by an ultrasound imaging system. Doppler processing of the acquired signal produces an image of the square of vibration amplitude that shows repetitive constructive and destructive interference patterns called "crawling waves." With a chirp vibration signal, successive Doppler frames are generated from different source frequencies. Collected frames generate a distinctive pattern which is used to calculate the shear speed and shear speed dispersion. A special reciprocal chirp is designed such that the equi-phase lines of a motion slice image are straight lines. Detailed analysis is provided to generate a closed-form solution for calculating the shear wave speed and the dispersion. Also several phantoms and an ex vivo human liver sample are scanned and the estimation results are presented. © The Author(s) 2014.

Breaking the limitation of mode building time in an optoelectronic oscillator.

PubMed

Hao, Tengfei; Cen, Qizhuang; Dai, Yitang; Tang, Jian; Li, Wei; Yao, Jianping; Zhu, Ninghua; Li, Ming

2018-05-09

An optoelectronic oscillator (OEO) is a microwave photonic system with a positive feedback loop used to create microwave oscillation with ultra-low phase noise thanks to the employment of a high-quality-factor energy storage element, such as a fiber delay line. For many applications, a frequency-tunable microwave signal or waveform, such as a linearly chirped microwave waveform (LCMW), is also needed. Due to the long characteristic time constant required for building up stable oscillation at an oscillation mode, it is impossible to generate an LCMW with a large chirp rate using a conventional frequency-tunable OEO. In this study, we propose and demonstrate a new scheme to generate a large chirp-rate LCMW based on Fourier domain mode locking technique to break the limitation of mode building time in an OEO. An LCMW with a high chirp rate of 0.34 GHz/μs and a large time-bandwidth product of 166,650 is demonstrated.

Real-time ultrawide-band group delay profile monitoring through low-noise incoherent temporal interferometry.

PubMed

Park, Yongwoo; Malacarne, Antonio; Azaña, José

2011-02-28

A simple, highly accurate measurement technique for real-time monitoring of the group delay (GD) profiles of photonic dispersive devices over ultra-broad spectral bandwidths (e.g. an entire communication wavelength band) is demonstrated. The technique is based on time-domain self-interference of an incoherent light pulse after linear propagation through the device under test, providing a measurement wavelength range as wide as the source spectral bandwidth. Significant enhancement in the signal-to-noise ratio of the self-interference signal has been observed by use of a relatively low-noise incoherent light source as compared with the theoretical estimate for a white-noise light source. This fact combined with the use of balanced photo-detection has allowed us to significantly reduce the number of profiles that need to be averaged to reach a targeted GD measurement accuracy, thus achieving reconstruction of the device GD profile in real time. We report highly-accurate monitoring of (i) the group-delay ripple (GDR) profile of a 10-m long chirped fiber Bragg grating over the full C band (~42 nm), and (ii) the group velocity dispersion (GVD) and dispersion slope (DS) profiles of a ~2-km long dispersion compensating fiber module over an ~72-nm wavelength range, both captured at a 15 frames/s video rate update, with demonstrated standard deviations in the captured GD profiles as low as ~1.6 ps.

Highly chirped single-bandpass microwave photonic filter with reconfiguration capabilities.

PubMed

Bolea, Mario; Mora, José; Ortega, Beatriz; Capmany, José

2011-02-28

We propose a novel photonic structure to implement a chirped single-bandpass microwave photonic filter based on the amplitude modulation of a broadband optical signal transmitted by a non-linear dispersive element and an interferometric system prior to balanced photodetection. A full reconfigurability of the filter is achieved since amplitude and phase responses can be independently controlled. We have experimentally demonstrated chirp values up to tens of ns/GHz, which is, as far as we know, one order of magnitude better than others achieved by electrical approaches and furthermore, without restrictions in terms of frequency tuning since a frequency operation range up to 40 GHz has been experimentally demonstrated.

Joint Estimation of Time-Frequency Signature and DOA Based on STFD for Multicomponent Chirp Signals

PubMed Central

Zhao, Ziyue; Liu, Congfeng

2014-01-01

In the study of the joint estimation of time-frequency signature and direction of arrival (DOA) for multicomponent chirp signals, an estimation method based on spatial time-frequency distributions (STFDs) is proposed in this paper. Firstly, array signal model for multicomponent chirp signals is presented and then array processing is applied in time-frequency analysis to mitigate cross-terms. According to the results of the array processing, Hough transform is performed and the estimation of time-frequency signature is obtained. Subsequently, subspace method for DOA estimation based on STFD matrix is achieved. Simulation results demonstrate the validity of the proposed method. PMID:27382610

[Analysis of scatterer microstructure feature based on Chirp-Z transform cepstrum].

PubMed

Guo, Jianzhong; Lin, Shuyu

2007-12-01

The fundamental research field of medical ultrasound has been the characterization of tissue scatterers. The signal processing method is widely used in this research field. A new method of Chirp-Z Transform Cepstrum for mean spacing estimation of tissue scatterers using ultrasonic scattered signals has been developed. By using this method together with conventional AR cepstrum method, we processed the backscattered signals of mimic tissue and pig liver in vitro. The results illustrated that the Chirp-Z Transform Cepstrum method is effective for signal analysis of ultrasonic scattering and characterization of tissue scatterers, and it can improve the resolution for mean spacing estimation of tissue scatterers.

Joint Estimation of Time-Frequency Signature and DOA Based on STFD for Multicomponent Chirp Signals.

PubMed

Zhao, Ziyue; Liu, Congfeng

2014-01-01

In the study of the joint estimation of time-frequency signature and direction of arrival (DOA) for multicomponent chirp signals, an estimation method based on spatial time-frequency distributions (STFDs) is proposed in this paper. Firstly, array signal model for multicomponent chirp signals is presented and then array processing is applied in time-frequency analysis to mitigate cross-terms. According to the results of the array processing, Hough transform is performed and the estimation of time-frequency signature is obtained. Subsequently, subspace method for DOA estimation based on STFD matrix is achieved. Simulation results demonstrate the validity of the proposed method.

Hybrid chirped pulse amplification system

DOEpatents

Barty, Christopher P.; Jovanovic, Igor

2005-03-29

A hybrid chirped pulse amplification system wherein a short-pulse oscillator generates an oscillator pulse. The oscillator pulse is stretched to produce a stretched oscillator seed pulse. A pump laser generates a pump laser pulse. The stretched oscillator seed pulse and the pump laser pulse are directed into an optical parametric amplifier producing an optical parametric amplifier output amplified signal pulse and an optical parametric amplifier output unconverted pump pulse. The optical parametric amplifier output amplified signal pulse and the optical parametric amplifier output laser pulse are directed into a laser amplifier producing a laser amplifier output pulse. The laser amplifier output pulse is compressed to produce a recompressed hybrid chirped pulse amplification pulse.

Broadband continuous-variable entanglement source using a chirped poling nonlinear crystal

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

Zhao, J. S.; Sun, L.; Yu, X. Q.

2010-01-15

Aperiodically poled nonlinear crystal can be used as a broadband continuous-variable entanglement source and has strong stability under perturbations. We study the conversion dynamics of the sum-frequency generation and the quantum correlation of the two pump fields in a chirped-structure nonlinear crystal using the quantum stochastic method. The results show that there exists a frequency window for the pumps where two optical fields can perform efficient upconversion. The two pump fields are demonstrated to be entangled in the window and the chirped-structure crystal can be used as a continuous-variable entanglement source with a broad response bandwidth.

Application of nonlinear pulse shaping of femtosecond pulse generation in a fiber amplifier at 500 MHz repetition rate

NASA Astrophysics Data System (ADS)

Liu, Yang; Luo, Daping; Wang, Chao; Zhu, Zhiwei; Li, Wenxue

2018-03-01

We numerically and experimentally demonstrate that a nonlinear pulse shaping technique based on pre-chirping management in a short gain fiber can be exploited to improve the quality of a compressed pulse. With prior tuning of the pulse chirp, the amplified pulse express different nonlinear propagating processes. A spectrum with s flat top and more smooth wings, showing a similariton feature, generates with the optimal initial pulse chirp, and the shortest pulses with minimal pulse pedestals are obtained. Experimental results show the ability of nonlinear pulse shaping to enhance the quality of compressed pulses, as theoretically expected.

Archive of Chirp Seismic Reflection Data Collected During USGS Cruises 01SCC01 and 01SCC02, Timbalier Bay and Offshore East Timbalier Island, Louisiana, June 30 - July 9 and August 1 - 12, 2001

USGS Publications Warehouse

Calderon, Karynna; Dadisman, Shawn V.; Flocks, James G.; Wiese, Dana S.; Kindinger, Jack G.

2003-01-01

In June, July, and August of 2001, the U.S. Geological Survey (USGS), in cooperation with the University of New Orleans, the U.S. Army Corps of Engineers, and the Louisiana Department of Natural Resources, conducted a shallow geophysical and sediment core survey of Timbalier Bay and the Gulf of Mexico offshore East Timbalier Island, Louisiana. This report serves as an archive of unprocessed digital seismic reflection data, trackline navigation files, trackline navigation maps, observers' logbooks, Geographic Information Systems (GIS) information, and formal Federal Geographic Data Committee (FGDC) metadata. In addition, a gained digital Graphics Interchange Format (GIF) image of each seismic profile is provided. Please see Kulp and others (2002), Flocks and others (2003), and Kulp and others (in prep.) for further information about the sediment cores collected and the geophysical results. For convenience, a list of acronyms and abbreviations frequently used in this report is also included. This Digital Versatile Disc (DVD) document is readable on any computing platform that has standard DVD driver software installed. Documentation on this DVD was produced using Hyper Text Markup Language (HTML) utilized by the World Wide Web (WWW) and allows the user to access the information using a web browser (i.e. Netscape, Internet Explorer). To access the information contained on these discs, open the file 'index.htm' located at the top level of each disc using a web browser. This report also contains WWW links to USGS collaborators and other agencies. These links are only accessible if access to the internet is available while viewing these DVDs. The archived chirp seismic reflection data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry et al., 1975) and may be downloaded for processing with public domain software such as Seismic Unix (SU), currently located at http://www.cwp.mines.edu/cwpcodes/index.html. Examples of SU processing scripts are provided in the CHIRP.tar file located in the SU subfolder of the SOFTWARE folder located at the top level of each disc. In-house (USGS) DOS and Microsoft Windows compatible software for viewing SEG-Y headers - DUMPSEGY.EXE (Zihlman, 1992) - is provided in the USGS subfolder of the SOFTWARE folder. Processed profile images, trackline navigation maps, logbooks, and formal metadata may be viewed with a web browser.

Reassessment of seismically induced, tsunamigenic submarine slope failures in Port Valdez, Alaska, USA

USGS Publications Warehouse

Lee, H.J.; Haeussler, P.J.; Kayen, R.E.; Hampton, M.A.; Locat, Jacques; Suleimani, E.; Alexander, C.R.

2007-01-01

The M9.2 Alaska earthquake of 1964 caused major damage to the port facilities and town of Valdez, most of it the result of submarine landslide and the consequent tsunamis. Recent bathymetric multibeam surveys, high-resolution subbottom profiles, and dated sediment cores in Port Valdez supply new information about the morphology and character of the landslide deposits. A comparison of pre- and post-earthquake bathymetry provides an estimate of the net volume of landslide debris deposited in the basin and the volume of sediment removed from the source region. Landslide features include (1) large blocks (up to 40-m high) near the location of the greatest tsunamiwave runup (~50 m), (2) two debris lobes associated with the blocks, (3) a series of gullies, channels and talus, near the fjord-head delta and badly damaged old town of Valdez, and (4) the front of a debris lobe that flowed half-way down the fjord from the east end.

Application of parasound data for sediment study on methane seep site at Simeulue basin

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

Wiguna, Taufan, E-mail: taufan.wiguna@bppt.go.id; Ardhyastuti, Sri

2015-09-30

The Parasound data presents sea depth and sub-bottom profiler. In terms of geological terminology, parasound data represents significant recent surface sedimentary structures that valuable for the selection of subsequent sampling site such as sampling at methane seep site. Therefore, Parasound is used to detailing methane seep at surface sediment following seismic data interpretation. In this study, parasound is used to focus observe area especially for sediment study on methane seep site. The Parasound systems works both as narrow beam sounder use high frequency and as sediment echosounder use low frequency. Parasound acquisition applies parametric effect. It produces additional frequency bymore » nonlinear acoustic interaction of finite amplitude waves. Parasound transducers have 128 elements on 1 m2 and need transmission power up to 70 kW. The results of this study are discovered large seep carbonate with porous surface which means there are gas expulsions passing through that rock.« less

The Mentawai forearc sliver off Sumatra: A model for a strike-slip duplex at a regional scale

NASA Astrophysics Data System (ADS)

Berglar, Kai; Gaedicke, Christoph; Ladage, Stefan; Thöle, Hauke

2017-07-01

At the Sumatran oblique convergent margin the Mentawai Fault and Sumatran Fault zones accommodate most of the trench parallel component of strain. These faults bound the Mentawai forearc sliver that extends from the Sunda Strait to the Nicobar Islands. Based on multi-channel reflection seismic data, swath bathymetry and high resolution sub-bottom profiling we identified a set of wrench faults obliquely connecting the two major fault zones. These wrench faults separate at least four horses of a regional strike-slip duplex forming the forearc sliver. Each horse comprises an individual basin of the forearc with differing subsidence and sedimentary history. Duplex formation started in Mid/Late Miocene southwest of the Sunda Strait. Initiation of new horses propagated northwards along the Sumatran margin over 2000 km until Early Pliocene. These results directly link strike-slip tectonics to forearc evolution and may serve as a model for basin evolution in other oblique subduction settings.

High-resolution seismic stratigraphy of an Holocene lacustrine delta in western Lake Geneva (Switzerland)

USGS Publications Warehouse

Baster, I.; Girardclos, S.; Pugin, A.; Wildi, W.

2003-01-01

A high-resolution seismic survey was conducted in western Lake Geneva on a small delta formed by the Promenthouse, the Asse and the Boiron rivers. This dataset provides information on changes in the geometry and sedimentation patterns of this delta from Late-glacial to Present. The geometry of the deposits of the lacustrine delta has been mapped using 300-m spaced grid lines acquired with a 12 kHz Echosounder subbottom profiler. A complete three dimensional image of the sediment architecture was reconstructed through seismic stratigraphic analysis. Six different delta lobes have been recognized in the prodelta area. Depositional centers and lateral extension of the delta have changed through time, indicating migration and fluctuation of river input as well as changes in lake currents and wind regime from the time of glacier retreat to the Present. The delta slope is characterized by a high instability causing stumps developing and by the accumulation of biogenic gas that prevents seismic penetration.

Morphologic Response and Sediment Redistribution of the Beach and Nearshore Sand Bars due to Extratropical and Tropical Storm Forcing: a Spatial and Temporal Analysis

NASA Astrophysics Data System (ADS)

Miselis, J. L.; McNinch, J. E.

2005-05-01

Shore-oblique bars and associated exposures of an underlying geologic stratum in the nearshore have been documented along the US East Coast and have been linked to shoreline erosional hotspots. While earlier studies acknowledged that the bedforms responded to extratropical and tropical storms, neither quantified the extent of sediment redistribution after the events. An approach that encompasses actual volume measurements across the nearshore-beach down to a non-sandy stratum and quantifies the response of the beach and the nearshore to the same hydrodynamic forcing will enable a better understanding of the exchange of sediment between the two regions. Total nearshore sediment volume has been shown to be a first-order contributor to the behavior of the shoreline. This volumetric approach is employed in the analysis of morphological changes and the redistribution of sediment in the nearshore and beach following storms. A regional survey from 2002 provides the initial, fair-weather morphologic state of the nearshore (1.5-15m water depth) spanning 40 km of the North Carolina Outer Banks. Four small-scale surveys were conducted in subsequent years, focusing on four 1-km2 regions within the initial 2002 survey area. The smaller regions were selected on the basis of the morphological state observed during the 2002 survey and historical shoreline behavior. Data were collected in March 2003 following a Northeaster; in May 2003 following an extended period of fair weather conditions; in November 2003 following Hurricane Isabel; and finally, in June 2004 after another period of fair weather. A swath bathymetry system was used to collect bathymetry and side scan sonar (acoustic backscatter) and a high-resolution chirp sub-bottom profiler imaged the shallow sub-surface geology of the nearshore. In addition, RTK-GPS was used to map the sub-aerial beach at each 1-km2 site from the toe of the dune to the water line for the May 2003, November 2003, and June 2004 sampling periods. This sampling regime and data set offers a unique opportunity 1) to compare the simultaneous response of the beach and the nearshore to storms and 2) to investigate how the response of the beach and the nearshore varies depending on sandbar morphology and differences in the geologic framework. Three-dimensional maps of the beach and nearshore, from the toe of the dune to the 15m isobath, are used to demonstrate changes in total shoreface volume after storms and during recovery. Understanding the redistribution of sediment in the context of volumetric change enables the quantification of the exchange of sediment between the beach and the nearshore during large-scale forcing events.

High-resolution geophysical data collected within Red Brook Harbor, Buzzards Bay, Massachusetts, in 2009

USGS Publications Warehouse

Turecek, Aaron M.; Danforth, William W.; Baldwin, Wayne E.; Barnhardt, Walter A.

2012-01-01

The U.S. Geological Survey conducted a high-resolution geophysical survey within Red Brook Harbor, Massachusetts, from September 28 through November 17, 2009. Red Brook Harbor is located on the eastern edge of Buzzards Bay, south of the Cape Cod Canal. The survey area was approximately 7 square kilometers, with depths ranging from 0 to approximately 10 meters. Data were collected aboard the U.S. Geological Survey Research Vessel Rafael. The research vessel was equipped with a 234-kilohertz interferometric sonar system to collect bathymetry and backscatter data, a dual frequency (3.5- and 200-kilohertz) compression high-intensity radar pulse seismic reflection profiler to collect subbottom data, a sound velocity profiler to acquire speed of sound within the water column, and a sea floor sampling device to collect sediment samples, video, and photographs. The survey was part of an ongoing cooperative effort between the U.S. Geological Survey and the Massachusetts Office of Coastal Zone Management to map the geology of the Massachusetts inner continental shelf. In addition to inclusion within the cooperative geologic mapping effort, these data will be used to assess the shallow-water mapping capability of the geophysical systems deployed for this project, with an emphasis on identifying resolution benchmarks for the interferometric sonar system.

Holocene glacier fluctuations inferred from lacustrine sediment, Emerald Lake, Kenai Peninsula, Alaska

NASA Astrophysics Data System (ADS)

LaBrecque, Taylor S.; Kaufman, Darrell S.

2016-01-01

Physical and biological characteristics of lacustrine sediment from Emerald Lake were used to reconstruct the Holocene glacier history of Grewingk Glacier, southern Alaska. Emerald Lake is an ice-marginal threshold lake, receiving glaciofluvial sediment when Grewingk Glacier overtops the topographic divide that separates it from the lake. Sub-bottom acoustical profiles were used to locate core sites to maximize both the length and resolution of the sedimentary sequence recovered in the 4-m-long cores. The age model for the composite sequence is based on 13 14C ages and a 210Pb profile. A sharp transition from the basal inorganic mud to organic-rich mud at 11.4 ± 0.2 ka marks the initial retreat of Grewingk Glacier below the divide of Emerald Lake. The overlaying organic-rich mud is interrupted by stony mud that records a re-advance between 10.7 ± 0.2 and 9.8 ± 0.2 ka. The glacier did not spill meltwater into the lake again until the Little Ice Age, consistent with previously documented Little Ice Ages advances on the Kenai Peninsula. The retreat of Grewingk Glacier at 11.4 ka took place as temperature increased following the Younger Dryas, and the subsequent re-advance corresponds with a climate reversal beginning around 11 ka across southern Alaska.

20 mJ, 1 ps Yb:YAG Thin-disk Regenerative Amplifier

PubMed Central

Alismail, Ayman; Wang, Haochuan; Brons, Jonathan; Fattahi, Hanieh

2017-01-01

This is a report on a 100 W, 20 mJ, 1 ps Yb:YAG thin-disk regenerative amplifier. A homemade Yb:YAG thin-disk, Kerr-lens mode-locked oscillator with turn-key performance and microjoule-level pulse energy is used to seed the regenerative chirped-pulse amplifier. The amplifier is placed in airtight housing. It operates at room temperature and exhibits stable operation at a 5 kHz repetition rate, with a pulse-to-pulse stability less than 1%. By employing a 1.5 mm-thick beta barium borate crystal, the frequency of the laser output is doubled to 515 nm, with an average power of 70 W, which corresponds to an optical-to-optical efficiency of 70%. This superior performance makes the system an attractive pump source for optical parametric chirped-pulse amplifiers in the near-infrared and mid-infrared spectral range. Combining the turn-key performance and the superior stability of the regenerative amplifier, the system facilitates the generation of a broadband, CEP-stable seed. Providing the seed and pump of the optical parametric chirped-pulse amplification (OPCPA) from one laser source eliminates the demand of active temporal synchronization between these pulses. This work presents a detailed guide to set up and operate a Yb:YAG thin-disk regenerative amplifier, based on chirped-pulse amplification (CPA), as a pump source for an optical parametric chirped-pulse amplifier. PMID:28745636

Fast direct fourier reconstruction of radial and PROPELLER MRI data using the chirp transform algorithm on graphics hardware.

PubMed

Feng, Yanqiu; Song, Yanli; Wang, Cong; Xin, Xuegang; Feng, Qianjin; Chen, Wufan

2013-10-01

To develop and test a new algorithm for fast direct Fourier transform (DrFT) reconstruction of MR data on non-Cartesian trajectories composed of lines with equally spaced points. The DrFT, which is normally used as a reference in evaluating the accuracy of other reconstruction methods, can reconstruct images directly from non-Cartesian MR data without interpolation. However, DrFT reconstruction involves substantially intensive computation, which makes the DrFT impractical for clinical routine applications. In this article, the Chirp transform algorithm was introduced to accelerate the DrFT reconstruction of radial and Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction (PROPELLER) MRI data located on the trajectories that are composed of lines with equally spaced points. The performance of the proposed Chirp transform algorithm-DrFT algorithm was evaluated by using simulation and in vivo MRI data. After implementing the algorithm on a graphics processing unit, the proposed Chirp transform algorithm-DrFT algorithm achieved an acceleration of approximately one order of magnitude, and the speed-up factor was further increased to approximately three orders of magnitude compared with the traditional single-thread DrFT reconstruction. Implementation the Chirp transform algorithm-DrFT algorithm on the graphics processing unit can efficiently calculate the DrFT reconstruction of the radial and PROPELLER MRI data. Copyright © 2012 Wiley Periodicals, Inc.

Monolithic polarization maintaining fiber chirped pulse amplification (CPA) system for high energy femtosecond pulse generation at 1.03 µm.

PubMed

Kim, Kyungbum; Peng, Xiang; Lee, Wangkuen; Gee, Sangyoun; Mielke, Michael; Luo, Tao; Pan, Lei; Wang, Qing; Jiang, Shibin

2015-02-23

A monolithic polarization maintaining fiber chirped pulse amplification system with 25 cm Yb(3+)-doped high efficiency media fiber that generates 62 µJ sub-400 fs pulses with 25 W at 1.03 µm has recently been demonstrated.

Experimental determination of frequency response function estimates for flexible joint industrial manipulators with serial kinematics

NASA Astrophysics Data System (ADS)

Saupe, Florian; Knoblach, Andreas

2015-02-01

Two different approaches for the determination of frequency response functions (FRFs) are used for the non-parametric closed loop identification of a flexible joint industrial manipulator with serial kinematics. The two applied experiment designs are based on low power multisine and high power chirp excitations. The main challenge is to eliminate disturbances of the FRF estimates caused by the numerous nonlinearities of the robot. For the experiment design based on chirp excitations, a simple iterative procedure is proposed which allows exploiting the good crest factor of chirp signals in a closed loop setup. An interesting synergy of the two approaches, beyond validation purposes, is pointed out.

Complete chirp analysis of a gain-switched pulse using an interferometric two-photon absorption autocorrelation.

PubMed

Chin, Sang Hoon; Kim, Young Jae; Song, Ho Seong; Kim, Dug Young

2006-10-10

We propose a simple but powerful scheme for the complete analysis of the frequency chirp of a gain-switched optical pulse using a fringe-resolved interferometric two-photon absorption autocorrelator. A frequency chirp imposed on the gain-switched pulse from a laser diode was retrieved from both the intensity autocorrelation trace and the envelope of the second-harmonic interference fringe pattern. To verify the accuracy of the proposed phase retrieval method, we have performed an optical pulse compression experiment by using dispersion-compensating fibers with different lengths. We have obtained close agreement by less than a 1% error between the compressed pulse widths and numerically calculated pulse widths.

Chirp and temperature effects in parametric down conversion from crystals pumped at 800 nm

NASA Astrophysics Data System (ADS)

Sánchez-Lozano, X.; Wiechers, C.; Lucio, J. L.

2018-04-01

We consider spontaneous parametric down conversion from aperiodic poled crystals pumped at 800 nm. Our analyses account the effect of internal and external parameters, where, in the former, we include the crystal chirp and length, while in the latter temperature, also the pump chirp and other beam properties. The typical distribution produced is a pop-tab like structure in frequency-momentum space, and our results show that this system is a versatile light source, appropriated to manipulate the frequency and transverse momentum properties of the light produced. We briefly comment on the potential usefulness of the types of telecom wavelength light produced, in particular for quantum information applications.

Spectrum bandwidth narrowing of Thomson scattering X-rays with energy chirped electron beams from laser wakefield acceleration

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

Xu, Tong; Chen, Min, E-mail: minchen@sjtu.edu.cn; Li, Fei-Yu

2014-01-06

We study incoherent Thomson scattering between an ultrashort laser pulse and an electron beam accelerated from a laser wakefield. The energy chirp effects of the accelerated electron beam on the final radiation spectrum bandwidth are investigated. It is found that the scattered X-ray radiation has the minimum spectrum width and highest intensity as electrons are accelerated up to around the dephasing point. Furthermore, it is proposed that the electron acceleration process inside the wakefield can be studied by use of 90° Thomson scattering. The dephasing position and beam energy chirp can be deduced from the intensity and bandwidth of themore » scattered radiation.« less

Acoustic Retrieval of Seafloor Geotechnics.

DTIC Science & Technology

1977-12-01

from the seafloor and subbottom layer interfaces (e.g., Hastrup , 1969; Mackenzie , 1960; Bell and Porter , 1974). It is known that the physical...L. Inderbitzen , New York , Plenum Press, 1974 , pp 1-44. Hastrup , Ole (1969) “Digital analysis of acoustic reflectivity in the Tyrrhenia n A byssal

Forty Gb/s hybrid silicon Mach-Zehnder modulator with low chirp.

PubMed

Chen, Hui-Wen; Peters, Jonathan D; Bowers, John E

2011-01-17

We demonstrate a hybrid silicon modulator operating up to 40 Gb/s with 11.4 dB extinction ratio. The modulator has voltage-length product of 2.4 V-mm and chirp of -0.75 over the entire bias range. As a switch, it has a switching time less than 20 ps.

Generating nonlinear FM chirp radar signals by multiple integrations

DOEpatents

Doerry, Armin W [Albuquerque, NM

2011-02-01

A phase component of a nonlinear frequency modulated (NLFM) chirp radar pulse can be produced by performing digital integration operations over a time interval defined by the pulse width. Each digital integration operation includes applying to a respectively corresponding input parameter value a respectively corresponding number of instances of digital integration.

Phase-Locking and Coherent Power Combining of Broadband Linearly Chirped Optical Waves

DTIC Science & Technology

2012-11-05

ensure path-length matching, and we estimate an accuracy of ±2 cm. Fiber-coupled acoustooptic modulators ( Brimrose Corporation) with a nominal...was performed using the VCSEL-based SFL with a chirp rate of ±2×1014 Hz/s, polarization maintaining fiber-optic components, and an AOFS ( Brimrose

The climate hazards infrared precipitation with stations—a new environmental record for monitoring extremes

USGS Publications Warehouse

Funk, Chris; Peterson, Pete; Landsfeld, Martin; Pedreros, Diego; Verdin, James; Shukla, Shraddhanand; Husak, Gregory; Rowland, James; Harrison, Laura; Hoell, Andrew; Michaelsen, Joel

2015-01-01

The Climate Hazards group Infrared Precipitation with Stations (CHIRPS) dataset builds on previous approaches to ‘smart’ interpolation techniques and high resolution, long period of record precipitation estimates based on infrared Cold Cloud Duration (CCD) observations. The algorithm i) is built around a 0.05° climatology that incorporates satellite information to represent sparsely gauged locations, ii) incorporates daily, pentadal, and monthly 1981-present 0.05° CCD-based precipitation estimates, iii) blends station data to produce a preliminary information product with a latency of about 2 days and a final product with an average latency of about 3 weeks, and iv) uses a novel blending procedure incorporating the spatial correlation structure of CCD-estimates to assign interpolation weights. We present the CHIRPS algorithm, global and regional validation results, and show how CHIRPS can be used to quantify the hydrologic impacts of decreasing precipitation and rising air temperatures in the Greater Horn of Africa. Using the Variable Infiltration Capacity model, we show that CHIRPS can support effective hydrologic forecasts and trend analyses in southeastern Ethiopia.

Analysis and iterative equalization of transient and adiabatic chirp effects in DML-based OFDM transmission systems.

PubMed

Wei, Chia-Chien

2012-11-05

This work theoretically studies the transmission performance of a DML-based OFDM system by small-signal approximation, and the model considers both the transient and adiabatic chirps. The dispersion-induced distortion is modeled as subcarrier-to-subcarrier intermixing interference (SSII), and the theoretical SSII agrees with the distortion obtained from large-signal simulation statistically and deterministically. The analysis shows that the presence of the adiabatic chirp will ease power fading or even provide gain, but will increase the SSII to deteriorate OFDM signals after dispersive transmission. Furthermore, this work also proposes a novel iterative equalization to eliminate the SSII. From the simulation, the distortion could be effectively mitigated by the proposed equalization such that the maximum transmission distance of the DML-based OFDM signal is significantly improved. For instance, the transmission distance of a 30-Gbps DML-based OFDM signal can be extended from 10 km to more than 100 km. Besides, since the dispersion-induced distortion could be effectively mitigated by the equalization, negative power penalties are observed at some distances due to chirp-induced power gain.

Concurrent validation of CHIRP, a new instrument for measuring healthcare student attitudes towards interdisciplinary teamwork.

PubMed

Hollar, David; Hobgood, Cherri; Foster, Beverly; Aleman, Marco; Sawning, Susan

2012-01-01

Positive attitudes towards teamwork among health care professionals are critical to patient safety. The purpose of this study is to describe the development and concurrent validation of a new instrument to measure attitudes towards healthcare teamwork that is generalizable across various populations of healthcare students. The Collaborative Healthcare Interdisciplinary Planning (CHIRP) scale was validated against the Readiness for Inter-Professional Learning Scale (RIPLS). Analyses included student (n = 266) demographics, ANOVA, internal consistency, factor analysis, and Rasch analysis. The two instruments correlated at r = .582. The CHIRP showed a multifactorial structure having excellent internal consistency (alpha = .850), with 25 of the 36 scale items loading onto a single Teamwork Attitudes factor. The RIPLS likewise had strong internal consistency (alpha = .796) and a three-factor structure, supporting previous studies of the instrument. However, Rasch analyses showed 14 (38.9%) of the 36 CHIRP items, but only four (21.1%) of the 19 RIPLS items remaining within the satisfactory standardized OUTFIT zone of 2.0 standard deviation units. We propose the 14 fitting items as a new, validated teamwork attitudes scale.

Broadband turbulent spectra in gamma-ray burst light curves

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

Van Putten, Maurice H. P. M.; Guidorzi, Cristiano; Frontera, Filippo, E-mail: mvp@sejong.ac.kr

2014-05-10

Broadband power density spectra offer a window to understanding turbulent behavior in the emission mechanism and, at the highest frequencies, in the putative inner engines powering long gamma-ray bursts (GRBs). We describe a chirp search method alongside Fourier analysis for signal detection in the Poisson noise-dominated, 2 kHz sampled, BeppoSAX light curves. An efficient numerical implementation is described in O(Nnlog n) operations, where N is the number of chirp templates and n is the length of the light-curve time series, suited for embarrassingly parallel processing. For the detection of individual chirps over a 1 s duration, the method is onemore » order of magnitude more sensitive in signal-to-noise ratio than Fourier analysis. The Fourier-chirp spectra of GRB 010408 and GRB 970816 show a continuation of the spectral slope with up to 1 kHz of turbulence identified in low-frequency Fourier analysis. The same continuation is observed in an average spectrum of 42 bright, long GRBs. An outlook on a similar analysis of upcoming gravitational wave data is included.« less

The effects of five-order nonlinear on the dynamics of dark solitons in optical fiber.

PubMed

He, Feng-Tao; Wang, Xiao-Lin; Duan, Zuo-Liang

2013-01-01

We study the influence of five-order nonlinear on the dynamic of dark soliton. Starting from the cubic-quintic nonlinear Schrodinger equation with the quadratic phase chirp term, by using a similarity transformation technique, we give the exact solution of dark soliton and calculate the precise expressions of dark soliton's width, amplitude, wave central position, and wave velocity which can describe the dynamic behavior of soliton's evolution. From two different kinds of quadratic phase chirps, we mainly analyze the effect on dark soliton's dynamics which different fiver-order nonlinear term generates. The results show the following two points with quintic nonlinearities coefficient increasing: (1) if the coefficients of the quadratic phase chirp term relate to the propagation distance, the solitary wave displays a periodic change and the soliton's width increases, while its amplitude and wave velocity reduce. (2) If the coefficients of the quadratic phase chirp term do not depend on propagation distance, the wave function only emerges in a fixed area. The soliton's width increases, while its amplitude and the wave velocity reduce.

The Effects of Five-Order Nonlinear on the Dynamics of Dark Solitons in Optical Fiber

PubMed Central

Wang, Xiao-Lin; Duan, Zuo-Liang

2013-01-01

We study the influence of five-order nonlinear on the dynamic of dark soliton. Starting from the cubic-quintic nonlinear Schrodinger equation with the quadratic phase chirp term, by using a similarity transformation technique, we give the exact solution of dark soliton and calculate the precise expressions of dark soliton's width, amplitude, wave central position, and wave velocity which can describe the dynamic behavior of soliton's evolution. From two different kinds of quadratic phase chirps, we mainly analyze the effect on dark soliton's dynamics which different fiver-order nonlinear term generates. The results show the following two points with quintic nonlinearities coefficient increasing: (1) if the coefficients of the quadratic phase chirp term relate to the propagation distance, the solitary wave displays a periodic change and the soliton's width increases, while its amplitude and wave velocity reduce. (2) If the coefficients of the quadratic phase chirp term do not depend on propagation distance, the wave function only emerges in a fixed area. The soliton's width increases, while its amplitude and the wave velocity reduce. PMID:23818814

Packet personal radiation monitor

DOEpatents

Phelps, J.E.

1988-03-31

A personal radiation monitor of the chirper type is provided for detecting ionizing radiation. A battery powered high voltage power supply is used to generate and apply a high voltage bias to a G-M tube radiation sensor. The high voltage is monitored by a low-loss sensing network which generates a feedback signal to control the high voltage power supply such that the high voltage bias is recharged to +500 VDC when the current pulses of the sensor, generated by the detection of ionizing radiatonevents, discharges the high voltage bias to +450 VDC. During the high voltage recharge period an audio transducer is activated to produce an audible ''chirp''. The rate of the ''chirps'' is controlled by the rate at which the high voltage bias is recharged, which is proportional to the radiation field intensity to which the sensor is exposed. The chirp rate sensitivity is set to be approximately 1.5 (chirps/min/MR/hr.). The G-M tube sensor is used in a current sensing mode so that the device does not paralyze in a high radiation field. 2 figs.

The climate hazards infrared precipitation with stations—a new environmental record for monitoring extremes

PubMed Central

Funk, Chris; Peterson, Pete; Landsfeld, Martin; Pedreros, Diego; Verdin, James; Shukla, Shraddhanand; Husak, Gregory; Rowland, James; Harrison, Laura; Hoell, Andrew; Michaelsen, Joel

2015-01-01

The Climate Hazards group Infrared Precipitation with Stations (CHIRPS) dataset builds on previous approaches to ‘smart’ interpolation techniques and high resolution, long period of record precipitation estimates based on infrared Cold Cloud Duration (CCD) observations. The algorithm i) is built around a 0.05° climatology that incorporates satellite information to represent sparsely gauged locations, ii) incorporates daily, pentadal, and monthly 1981-present 0.05° CCD-based precipitation estimates, iii) blends station data to produce a preliminary information product with a latency of about 2 days and a final product with an average latency of about 3 weeks, and iv) uses a novel blending procedure incorporating the spatial correlation structure of CCD-estimates to assign interpolation weights. We present the CHIRPS algorithm, global and regional validation results, and show how CHIRPS can be used to quantify the hydrologic impacts of decreasing precipitation and rising air temperatures in the Greater Horn of Africa. Using the Variable Infiltration Capacity model, we show that CHIRPS can support effective hydrologic forecasts and trend analyses in southeastern Ethiopia. PMID:26646728

Packet personal radiation monitor

DOEpatents

Phelps, James E.

1989-01-01

A personal radiation monitor of the chirper type is provided for detecting ionizing radiation. A battery powered high voltage power supply is used to generate and apply a high voltage bias to a G-M tube radiation sensor. The high voltage is monitored by a low-loss sensing network which generates a feedback signal to control the high voltage power supply such that the high voltage bias is recharged to +500 VDC when the current pulses of the sensor, generated by the detection of ionizing radiation events, discharges the high voltage bias to +450 VDC. During the high voltage recharge period an audio transducer is activated to produce an audible "chirp". The rate of the "chirps" is controlled by the rate at which the high voltage bias is recharged, which is proportional to the radiation field intensity to which the sensor is exposed. The chirp rate sensitivity is set to be approximately 1.5 (chirps/min/MR/hr.). The G-M tube sensor is used in a current sensing mode so that the device does not paralyze in a high radiation field.

Mapping Rotational Wavepacket Dynamics with Chirped Probe Pulses

NASA Astrophysics Data System (ADS)

Romanov, Dmitri; Odhner, Johanan; Levis, Robert

2014-05-01

We develop an analytical model description of the strong-field pump-probe polarization spectroscopy of rotational transients in molecular gases in a situation when the probe pulse is considerably chirped: the frequency modulation over the pulse duration is comparable with the carrier frequency. In this scenario, a femtosecond pump laser pulse prepares a rotational wavepacket in a gas-phase sample at room temperature. The rotational revivals of the wavepacket are then mapped onto a chirped broadband probe pulse derived from a laser filament. The slow-varying envelope approximation being inapplicable, an alternative approach is proposed which is capable of incorporating the substantial chirp and the related temporal dispersion of refractive indices. Analytical expressions are obtained for the probe signal modulation over the interaction region and for the resulting heterodyned transient birefringence spectra. Dependencies of the outputs on the probe pulse parameters reveal the trade-offs and the ways to optimize the temporal-spectral imaging. The results are in good agreement with the experiments on snapshot imaging of rotational revival patterns in nitrogen gas. We gratefully acknowledge financial support through AFOSR MURI Grant No. FA9550-10-1-0561.

Review on Photonic Generation of Chirp Arbitrary Microwave Waveforms for Remote Sensing Application

NASA Astrophysics Data System (ADS)

Raghuwanshi, Sanjeev Kumar; Srivastav, Akash; Athokpam, Bidhanshel Singh

2017-12-01

A novel technique to generate an arbitrary chirped waveform by harnessing features of lithium niobate (LiNb O_3) Mach-Zehnder modulator is proposed and demonstrated. The most important application of chirped microwave waveform is that, it improves the range resolution of radar. Microwave photonics system provides high bandwidth capabilities of fiber-optic systems and also contains the ability to provide interconnect transmission properties, which are virtually independent of length. The low-loss wide bandwidth capability of optoelectronic systems makes them attractive for the transmission and processing of microwave signals, while the development of high-capacity optical communication systems has required the use of microwave techniques in optical transmitters and receivers. These two strands have led to the development of the research area of microwave photonics. So, it should be consider that microwave photonics as the field that studies the interaction between microwave and optical waves for applications such as communications, radars, sensors and instrumentations. In this paper, we have thoroughly reviewed the arbitrary chirped microwave generation techniques by using photonics technology.

Tidal Deformability from GW170817 as a Direct Probe of the Neutron Star Radius

NASA Astrophysics Data System (ADS)

Raithel, Carolyn A.; Özel, Feryal; Psaltis, Dimitrios

2018-04-01

Gravitational waves from the coalescence of two neutron stars were recently detected for the first time by the LIGO–Virgo Collaboration, in event GW170817. This detection placed an upper limit on the effective tidal deformability of the two neutron stars and tightly constrained the chirp mass of the system. We report here on a new simplification that arises in the effective tidal deformability of the binary, when the chirp mass is specified. We find that, in this case, the effective tidal deformability of the binary is surprisingly independent of the component masses of the individual neutron stars, and instead depends primarily on the ratio of the chirp mass to the neutron star radius. Thus, a measurement of the effective tidal deformability can be used to directly measure the neutron star radius. We find that the upper limit on the effective tidal deformability from GW170817 implies that the radius cannot be larger than ∼13 km, at the 90% level, independent of the assumed masses for the component stars. The result can be applied generally, to probe the stellar radii in any neutron star–neutron star merger with a measured chirp mass. The approximate mass independence disappears for neutron star–black hole mergers. Finally, we discuss a Bayesian inference of the equation of state that uses the measured chirp mass and tidal deformability from GW170817 combined with nuclear and astrophysical priors and discuss possible statistical biases in this inference.

Towards Terawatt Sub-Cycle Long-Wave Infrared Pulses via Chirped Optical Parametric Amplification and Indirect Pulse Shaping

PubMed Central

Yin, Yanchun; Chew, Andrew; Ren, Xiaoming; Li, Jie; Wang, Yang; Wu, Yi; Chang, Zenghu

2017-01-01

We present an approach for both efficient generation and amplification of 4–12 μm pulses by tailoring the phase matching of the nonlinear crystal Zinc Germanium Phosphide (ZGP) in a narrowband-pumped optical parametric chirped pulse amplifier (OPCPA) and a broadband-pumped dual-chirped optical parametric amplifier (DC-OPA), respectively. Preliminary experimental results are obtained for generating 1.8–4.2 μm super broadband spectra, which can be used to seed both the signal of the OPCPA and the pump of the DC-OPA. The theoretical pump-to-idler conversion efficiency reaches 27% in the DC-OPA pumped by a chirped broadband Cr2+:ZnSe/ZnS laser, enabling the generation of  Terawatt-level 4–12 μm pulses with an available large-aperture ZGP. Furthermore, the 4–12 μm idler pulses can be compressed to sub-cycle pulses by compensating the tailored positive chirp of the idler pulses using the bulk compressor NaCl, and by indirectly controlling the higher-order idler phase through tuning the signal (2.4–4.0 μm) phase with a commercially available acousto-optic programmable dispersive filter (AOPDF). A similar approach is also described for generating high-energy 4–12 μm sub-cycle pulses via OPCPA pumped by a 2 μm Ho:YLF laser. PMID:28367966