Effects of ship-induced waves on aquatic ecosystems.

PubMed

Gabel, Friederike; Lorenz, Stefan; Stoll, Stefan

2017-12-01

Most larger water bodies worldwide are used for navigation, and the intensity of commercial and recreational navigation is expected to further increase. Navigation profoundly affects aquatic ecosystems. To facilitate navigation, rivers are trained and developed, and the direct effects of navigation include chemical and biological impacts (e.g., inputs of toxic substances and dispersal of non-native species, respectively). Furthermore, propagating ships create hydrodynamic alterations, often simply summarized as waves. Although ship-induced waves are recognized as influential stressors, knowledge on their effects is poorly synthesized. We present here a review on the effects of ship-induced waves on the structure, function and services of aquatic ecosystems based on more than 200 peer reviewed publications and technical reports. Ship-induced waves act at multiple organizational levels and different spatial and temporal scales. All the abiotic and biotic components of aquatic ecosystems are affected, from the sediment and nutrient budget to the planktonic, benthic and fish communities. We highlight how the effects of ship-induced waves cascade through ecosystems and how different effects interact and feed back into the ecosystem finally leading to altered ecosystem services and human health effects. Based on this synthesis of wave effects, we discuss strategies for mitigation. This may help to develop scientifically based and target-oriented management plans for navigational waters that optimize abiotic and biotic integrity and their ecosystem services and uses. Copyright © 2017 Elsevier B.V. All rights reserved.

Numerical study on wave loads and motions of two ships advancing in waves by using three-dimensional translating-pulsating source

NASA Astrophysics Data System (ADS)

Xu, Yong; Dong, Wen-Cai

2013-08-01

A frequency domain analysis method based on the three-dimensional translating-pulsating (3DTP) source Green function is developed to investigate wave loads and free motions of two ships advancing on parallel course in waves. Two experiments are carried out respectively to measure the wave loads and the freemotions for a pair of side-byside arranged ship models advancing with an identical speed in head regular waves. For comparison, each model is also tested alone. Predictions obtained by the present solution are found in favorable agreement with the model tests and are more accurate than the traditional method based on the three dimensional pulsating (3DP) source Green function. Numerical resonances and peak shift can be found in the 3DP predictions, which result from the wave energy trapped in the gap between two ships and the extremely inhomogeneous wave load distribution on each hull. However, they can be eliminated by 3DTP, in which the speed affects the free surface and most of the wave energy can be escaped from the gap. Both the experiment and the present prediction show that hydrodynamic interaction effects on wave loads and free motions are significant. The present solver may serve as a validated tool to predict wave loads and motions of two vessels under replenishment at sea, and may help to evaluate the hydrodynamic interaction effects on the ships safety in replenishment operation.

Ship Shoal as a prospective borrow site for barrier island restoration, coastal south-central Louisiana, Usa: Numerical wave modeling and field measurements of hydrodynamics and sediment transport

USGS Publications Warehouse

Stone, G.W.; Pepper, D.A.; Xu, Jie; Zhang, X.

2004-01-01

Ship Shoal, a transgressive sand body located at the 10 m isobath off south-central Louisiana, is deemed a potential sand source for restoration along the rapidly eroding Isles Dernieres barrier chain and possibly other sites in Louisiana. Through numerical wave modeling we evaluate the potential response of mining Ship Shoal on the wave field. During severe and strong storms, waves break seaward of the western flank of Ship Shoal. Therefore, removal of Ship Shoal (approximately 1.1 billion m3) causes a maximum increase of the significant wave height by 90%-100% and 40%-50% over the shoal and directly adjacent to the lee of the complex for two strong storm scenarios. During weak storms and fair weather conditions, waves do not break over Ship Shoal. The degree of increase in significant wave height due to shoal removal is considerably smaller, only 10%-20% on the west part of the shoal. Within the context of increasing nearshore wave energy levels, removal of the shoal is not significant enough to cause increased erosion along the Isles Dernieres. Wave approach direction exerts significant control on the wave climate leeward of Ship Shoal for stronger storms, but not weak storms or fairweather. Instrumentation deployed at the shoal allowed comparison of measured wave heights with numerically derived wave heights using STWAVE. Correlation coefficients are high in virtually all comparisons indicating the capability of the model to simulate wave behavior satisfactorily at the shoal. Directional waves, currents and sediment transport were measured during winter storms associated with frontal passages using three bottom-mounted arrays deployed on the seaward and landward sides of Ship Shoal (November, 1998-January, 1999). Episodic increases in wave height, mean and oscillatory current speed, shear velocity, and sediment transport rates, associated with recurrent cold front passages, were measured. Dissipation mechanisms included both breaking and bottom friction due to variable depths across the shoal crest and variable wave amplitudes during storms and fair-weather. Arctic surge fronts were associated with southerly storm waves, and southwesterly to westerly currents and sediment transport. Migrating cyclonic fronts generated northerly swell that transformed into southerly sea, and currents and sediment transport that were southeasterly overall. Waves were 36% higher and 9% longer on the seaward side of the shoal, whereas mean currents were 10% stronger landward, where they were directed onshore, in contrast to the offshore site, where seaward currents predominated. Sediment transport initiated by cold fronts was generally directed southeasterly to southwesterly at the offshore site, and southerly to westerly at the nearshore site. The data suggest that both cold fronts and the shoal, exert significant influences on regional hydrodynamics and sediment transport.

46 CFR 160.156-11 - Fabrication of prototype rescue boats and fast rescue boats for approval.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 6 2012-10-01 2012-10-01 false Fabrication of prototype rescue boats and fast rescue boats for approval. 160.156-11 Section 160.156-11 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY... Boats and Fast Rescue Boats (SOLAS) § 160.156-11 Fabrication of prototype rescue boats and fast rescue...

46 CFR 160.156-11 - Fabrication of prototype rescue boats and fast rescue boats for approval.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 6 2014-10-01 2014-10-01 false Fabrication of prototype rescue boats and fast rescue boats for approval. 160.156-11 Section 160.156-11 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY... Boats and Fast Rescue Boats (SOLAS) § 160.156-11 Fabrication of prototype rescue boats and fast rescue...

46 CFR 160.156-11 - Fabrication of prototype rescue boats and fast rescue boats for approval.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 6 2013-10-01 2013-10-01 false Fabrication of prototype rescue boats and fast rescue boats for approval. 160.156-11 Section 160.156-11 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY... Boats and Fast Rescue Boats (SOLAS) § 160.156-11 Fabrication of prototype rescue boats and fast rescue...

Nonlinear dead water resistance at subcritical speed

NASA Astrophysics Data System (ADS)

Grue, John

2015-08-01

The dead water resistance F 1 = /1 2 C d w ρ S U 2 (ρ fluid density, U ship speed, S wetted body surface, Cdw resistance coefficient) on a ship moving at subcritical speed along the upper layer of a two-layer fluid is calculated by a strongly nonlinear method assuming potential flow in each layer. The ship dimensions correspond to those of the Polar ship Fram. The ship draught, b0, is varied in the range 0.25h0-0.9h0 (h0 the upper layer depth). The calculations show that Cdw/(b0/h0)2 depends on the Froude number only, in the range close to critical speed, Fr = U/c0 ˜ 0.875-1.125 (c0 the linear internal long wave speed), irrespective of the ship draught. The function Cdw/(b0/h0)2 attains a maximum at subcritical Froude number depending on the draught. Maximum Cdw/(b0/h0)2 becomes 0.15 for Fr = 0.76, b0/h0 = 0.9, and 0.16 for Fr = 0.74, b0/h0 = 1, where the latter extrapolated value of the dead water resistance coefficient is about 60 times higher than the frictional drag coefficient and relevant for the historical dead water observations. The nonlinear Cdw significantly exceeds linear theory (Fr < 0.85). The ship generated waves have a wave height comparable to the upper layer depth. Calculations of three-dimensional wave patterns at critical speed compare well to available laboratory experiments. Upstream solitary waves are generated in a wave tank of finite width, when the layer depths differ, causing an oscillation of the force. In a wide ocean, a very wide wave system develops at critical speed. The force approaches a constant value for increasing time.

Adaptability of solar energy conversion systems on ships

NASA Astrophysics Data System (ADS)

Visa, I.; Cotorcea, A.; Neagoe, M.; Moldovan, M.

2016-08-01

International trade of goods largely uses maritime/transoceanic ships driven by engines using fossil fuels. This two centuries tradition is technologically mature but significantly adds to the CO2 emissions; therefore, recent trends focus on on-board implementation of systems converting the solar energy into power (photovoltaic systems) or heat (solar-thermal systems). These systems are carbon-emissions free but are still under research and plenty of effort is devoted to fast reach maturity and feasibility. Unlike the systems implemented in a specific continental location, the design of solar energy conversion systems installed on shipboard has to face the problem generated by the system base motion along with the ship travelling on routes at different latitudes: the navigation direction and sense and roll-pitch combined motion with reduced amplitude, but with relatively high frequency. These raise highly interesting challenges in the design and development of mechanical systems that support the maximal output in terms of electricity or heat. The paper addresses the modelling of the relative position of a solar energy conversion surface installed on a ship according to the current position of the sun; the model is based on the navigation trajectory/route, ship motion generated by waves and the relative sun-earth motion. The model describes the incidence angle of the sunray on the conversion surface through five characteristic angles: three used to define the ship orientation and two for the solar angles; based on, their influence on the efficiency in solar energy collection is analyzed by numerical simulations and appropriate recommendations are formulated for increasing the solar energy conversion systems adaptability on ships.

Research on characteristics of radiated noise of large cargo ship in shallow water

NASA Astrophysics Data System (ADS)

Liu, Yongdong; Zhang, Liang

2017-01-01

With the rapid development of the shipping industry, the number of the world's ship is gradually increasing. The characteristics of the radiated noise of the ship are also of concern. Since the noise source characteristics of multichannel interference, the surface wave and the sea temperature microstructure and other reasons, the sound signal received in the time-frequency domain has varying characteristics. The signal of the radiated noise of the large cargo ship JOCHOH from horizontal hydrophone array in some shallow water of China is processed and analyzed in the summer of 2015, and the results show that a large cargo ship JOCHOH has a number of noise sources in the direction of the ship's bow and stern lines, such as host, auxiliary and propellers. The radiating sound waves generated by these sources do not meet the spherical wave law at lower frequency in the ocean, and its radiated noise has inherent spatial distribution, the variation characteristics of the radiated noise the large cargo ship in time and frequency domain are given. The research method and results are of particular importance.

Fast iterative censoring CFAR algorithm for ship detection from SAR images

NASA Astrophysics Data System (ADS)

Gu, Dandan; Yue, Hui; Zhang, Yuan; Gao, Pengcheng

2017-11-01

Ship detection is one of the essential techniques for ship recognition from synthetic aperture radar (SAR) images. This paper presents a fast iterative detection procedure to eliminate the influence of target returns on the estimation of local sea clutter distributions for constant false alarm rate (CFAR) detectors. A fast block detector is first employed to extract potential target sub-images; and then, an iterative censoring CFAR algorithm is used to detect ship candidates from each target blocks adaptively and efficiently, where parallel detection is available, and statistical parameters of G0 distribution fitting local sea clutter well can be quickly estimated based on an integral image operator. Experimental results of TerraSAR-X images demonstrate the effectiveness of the proposed technique.

The choice of speed and clearance for RAS on 3D method

NASA Astrophysics Data System (ADS)

Wang, Jian-Fang; Li, Ji-De; Cai, Xin-Gong

2003-12-01

In this paper, a 3D source distribution technique is used to calculate the coupled motions between two ships which advance in the wave with the same speed. The numerical results of coupled motions for a frigate and a supply ship have a good agreement with the experimental results. Based on the 3D coupled motions of two ships, a spectral analysis is employed to clearly observe the effect of speed, clearance and wave heading on the significant relative motion amplitude (SRMA) of two ships. The method presented in this paper will be helpful to select suitable clearance, speed and wave heading for underway replenishment at sea(RAS).

Fast Sealift and Maritime Prepositioning Options for Improving Sealift Capabilities

DTIC Science & Technology

1991-01-01

cargo ships with speeds of 22 to 25 knots as fas* The eight existing T- AKRs , which have a speed of 30... cargo than in the case of no ship attrition. 2.0 ---- Without -- attrition --- • attrition 0- 1.0- High -capacity Low-cost Improved MPS( A ) SES T- AKR ...fast sealift and maritime prepositioning ships and evaluates their performance in terms of speed and the ability to make cumulative cargo deliveries

The Effects of Wave Escape on Fast Magnetosonic Wave Turbulence in Solar Flares

NASA Technical Reports Server (NTRS)

Pongkitiwanichakul, Peera; Chandran, Benjamin D. G.; Karpen, Judith T.; DeVore, C. Richard

2012-01-01

One of the leading models for electron acceleration in solar flares is stochastic acceleration by weakly turbulent fast magnetosonic waves ("fast waves"). In this model, large-scale flows triggered by magnetic reconnection excite large-wavelength fast waves, and fast-wave energy then cascades from large wavelengths to small wavelengths. Electron acceleration by large-wavelength fast-waves is weak, and so the model relies on the small-wavelength waves produced by the turbulent cascade. In order for the model to work, the energy cascade time for large-wavelength fast waves must be shorter than the time required for the waves to propagate out of the solar-flare acceleration region. To investigate the effects of wave escape, we solve the wave kinetic equation for fast waves in weak turbulence theory, supplemented with a homogeneous wave-loss term.We find that the amplitude of large-wavelength fast waves must exceed a minimum threshold in order for a significant fraction of the wave energy to cascade to small wavelengths before the waves leave the acceleration region.We evaluate this threshold as a function of the dominant wavelength of the fast waves that are initially excited by reconnection outflows.

Ship Wakes Generated in a Diffuse Internal Layer

DTIC Science & Technology

2015-01-01

can enhance wake detectability by increasing the surface flows. One example is the reflection of natural waves from a ship hull. A wave carries...be observed using satellite borne optical sensors and high resolution radar. Their existence implies the presence of significant internal layers. The...The principal factors associated with the ship appear to be its principal dimensions (length, beam and draft), its block coefficient and its speed

Sea loads on ships and offshore structures

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

Faltinsen, O.

1990-01-01

The book introduces the theory of the structural loading on ships and offshore structures caused by wind, waves and currents, and goes on to describe the applications of this theory in terms of real structures. The main topics described are linear-wave induced motions, loads on floating structures, numerical methods for ascertaining wave induced motions and loads, viscous wave loads and damping, stationkeeping and water impact and entry. The applications of the theoretical principles are introduced with extensive use of exercises and examples. Applications covered include conventional ships, barges, high speed marine vehicles, semisubmersibles, tension leg platforms, moored or dynamic positionedmore » ships, risers, buoys, fishing nets, jacket structures and gravity platforms. One aim of the book is to provide a physical understanding through simplified mathematical models. In this way one can develop analytical tools to evaluate results from test models, full scale trials or computer simulation, and learns which parameters represent the major contributions and influences on sea loads.« less

46 CFR 160.156-19 - Operating instructions and information for the ship's training manual.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 6 2014-10-01 2014-10-01 false Operating instructions and information for the ship's... Boats and Fast Rescue Boats (SOLAS) § 160.156-19 Operating instructions and information for the ship's training manual. (a) Each rescue boat must have instructions and information for the ship's training manual...

46 CFR 160.156-19 - Operating instructions and information for the ship's training manual.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 6 2012-10-01 2012-10-01 false Operating instructions and information for the ship's... Boats and Fast Rescue Boats (SOLAS) § 160.156-19 Operating instructions and information for the ship's training manual. (a) Each rescue boat must have instructions and information for the ship's training manual...

Counter Piracy Off Somalia; A Case for Applying the Comprehensive Approach Strategy

DTIC Science & Technology

2011-01-03

operations conducted by HDMS ABSALON 15 comprise the threat of being captured , trialed and jailed for many years in another country. Finally a pirate...The first wave secured the open deck of the ship and the second wave breached into the bridge and took over control of the ship manoeuvres. In the...at this stage not able to take command of his own ship. The chock and stress he had been through had obviously had an impact on him. But after a

Development and testing of instrumentation for ship-based UAV measurements of ocean surface processes and the marine atmospheric boundary layer

NASA Astrophysics Data System (ADS)

Reineman, B. D.; Lenain, L.; Statom, N.; Melville, W. K.

2012-12-01

We have developed instrumentation packages for unmanned aerial vehicles (UAVs) to measure ocean surface processes along with momentum fluxes and latent, sensible, and radiative heat fluxes in the marine atmospheric boundary layer (MABL). The packages have been flown over land on BAE Manta C1s and over water on Boeing-Insitu ScanEagles. The low altitude required for accurate surface flux measurements (< 30 m) is below the typical safety limit of manned research aircraft; however, with advances in laser altimeters, small-aircraft flight control, and real-time kinematic differential GPS, low-altitude flight is now within the capability of small UAV platforms. Fast-response turbulence, hygrometer, and temperature probes permit turbulent flux measurements, and short- and long-wave radiometers allow the determination of net radiation, surface temperature, and albedo. Onboard laser altimetry and high-resolution visible and infrared video permit observations of surface waves and fine-scale (O(10) cm) ocean surface temperature structure. Flight tests of payloads aboard ScanEagle UAVs were conducted in April 2012 at the Naval Surface Warfare Center Dahlgren Division (Dahlgren, VA), where measurements of water vapor, heat, and momentum fluxes were made from low-altitude (31-m) UAV flights over water (Potomac River). ScanEagles are capable of ship-based launch and recovery, which can extend the reach of research vessels and enable scientific measurements out to ranges of O(10-100) km and altitudes up to 5 km. UAV-based atmospheric and surface observations can complement observations of surface and subsurface phenomena made from a research vessel and avoid the well-known problems of vessel interference in MABL measurements. We present a description of the instrumentation, summarize results from flight tests, and discuss potential applications of these UAVs for ship-based MABL studies.

Quick realization of a ship steering training simulation system by virtual reality

NASA Astrophysics Data System (ADS)

Sun, Jifeng; Zhi, Pinghua; Nie, Weiguo

2003-09-01

This paper addresses two problems of a ship handling simulator. Firstly, 360 scene generation, especially 3D dynamic sea wave modeling, is described. Secondly, a multi-computer complementation of ship handling simulator. This paper also gives the experimental results of the proposed ship handling simulator.

Rogue waves: from nonlinear Schrödinger breather solutions to sea-keeping test.

PubMed

Onorato, Miguel; Proment, Davide; Clauss, Günther; Klein, Marco

2013-01-01

Under suitable assumptions, the nonlinear dynamics of surface gravity waves can be modeled by the one-dimensional nonlinear Schrödinger equation. Besides traveling wave solutions like solitons, this model admits also breather solutions that are now considered as prototypes of rogue waves in ocean. We propose a novel technique to study the interaction between waves and ships/structures during extreme ocean conditions using such breather solutions. In particular, we discuss a state of the art sea-keeping test in a 90-meter long wave tank by creating a Peregrine breather solution hitting a scaled chemical tanker and we discuss its potential devastating effects on the ship.

Rogue Waves: From Nonlinear Schrödinger Breather Solutions to Sea-Keeping Test

PubMed Central

Onorato, Miguel; Proment, Davide; Clauss, Günther; Klein, Marco

2013-01-01

Under suitable assumptions, the nonlinear dynamics of surface gravity waves can be modeled by the one-dimensional nonlinear Schrödinger equation. Besides traveling wave solutions like solitons, this model admits also breather solutions that are now considered as prototypes of rogue waves in ocean. We propose a novel technique to study the interaction between waves and ships/structures during extreme ocean conditions using such breather solutions. In particular, we discuss a state of the art sea-keeping test in a 90-meter long wave tank by creating a Peregrine breather solution hitting a scaled chemical tanker and we discuss its potential devastating effects on the ship. PMID:23405086

Investigation of hydroelastic ship responses of an ULOC in head seas

NASA Astrophysics Data System (ADS)

Wang, Xue-liang; Temarel, Pandeli; Hu, Jia-jun; Gu, Xue-kang

2016-10-01

Investigation of hydroelastic ship responses has been brought to the attention of the scientific and engineering world for several decades. There are two kinds of high-frequency vibrations in general ship responses to a large ocean-going ship in its shipping line, so-called springing and whipping, which are important for the determination of design wave load and fatigue damage as well. Because of the huge scale of an ultra large ore carrier (ULOC), it will suffer seldom slamming events in the ocean. The resonance vibration with high frequency is springing, which is caused by continuous wave excitation. In this paper, the wave-induced vibrations of the ULOC are addressed by experimental and numerical methods according to 2D and 3D hydroelasticity theories and an elastic model under full-load and ballast conditions. The influence of loading conditions on high-frequency vibration is studied both by numerical and experimental results. Wave-induced vibrations are higher under ballast condition including the wave frequency part, the multiple frequencies part, the 2-node and the 3-node vertical bending parts of the hydroelastic responses. The predicted results from the 2D method have less accuracy than the 3D method especially under ballast condition because of the slender-body assumption in the former method. The applicability of the 2D method and the further development of nonlinear effects to 3D method in the prediction of hydroelastic responses of the ULOC are discussed.

Construction strength analysis of landing craft tank conversion to passenger ship using finite element method

NASA Astrophysics Data System (ADS)

Nurul Misbah, Mohammad; Setyawan, Dony; Murti Dananjaya, Wisnu

2018-03-01

This research aims to determine the longitudinal strength of passenger ship which was converted from Landing Craft Tank with 54 m of length as stated by BKI (Biro Klasifikasi Indonesia / Indonesian Classification Bureau). Verification of strength value is done to 4 (four) loading conditions which are (1) empty load condition during sagging wave, (2) empty load condition during hogging wave, (3) full load condition during sagging wave and (4) full load condition during hogging wave. Analysis is done using Finite Element Analysis (FEA) software by modeling the entire part of passenger ship and its loading condition. The back and upfront part of ship centerline were used as the boundary condition. From that analysis it can be concluded that the maximum stress for load condition (1) is 72,393 MPa, 74,792 MPa for load condition (2), 129,92 MPa for load condition (3), and 132,4 MPa for load condition (4). Longitudinal strength of passenger ship fulfilled the criteria of empty load condition having smaller stress value than allowable stress which is 90 MPa, and during full load condition with smaller stress value than allowable stress which is 150 MPa. Analysis on longitudinal strength comparison with entire ship plate thickness variation of ± 2 mm from initial plate was also done during this research. From this research it can be concluded that plate thickness reduction causes the value of longitudinal strength to decrease, while plate thickness addition causes the value of longitudinal strength to increase.

Benchmarking Naval Shipbuilding with 3D Laser Scanning, Additive Manufacturing, and Collaborative Product Lifecycle Management

DTIC Science & Technology

2015-09-20

battle force ships . The changes affect a small number of ship classes designated as (very) small combatants or logistics and support ships . Specifically...accurate, and fast method of helping shipbuilders and manufacturers design , redesign, modify, and salvage ships . However, only a handful of several... ship construction to become a fleet of 306 battle force ships over the next 30 years. It is critical that the Navy capture the full benefits of new

Hydrodynamic Interactions during Launch and Recovery of a Small Boat from a Ship in a Seaway

DTIC Science & Technology

2014-11-28

during launch and recovery. The RHIB is based on a Zodiac H935, with properties given in Table 1 when loaded with 12 person- nel. Figure 1 shows the hull...and recovery of a small craft from a larger ship, wave-induced motions of the larger ship will influence dy- namic loads on the crane. The motions of... the small craft will be a major determinant of the safety of onboard personnel. This paper exam- ines wave-induced motions during launch and recovery

Research on theoretical optimization and experimental verification of minimum resistance hull form based on Rankine source method

NASA Astrophysics Data System (ADS)

Zhang, Bao-Ji; Zhang, Zhu-Xin

2015-09-01

To obtain low resistance and high efficiency energy-saving ship, minimum total resistance hull form design method is studied based on potential flow theory of wave-making resistance and considering the effects of tail viscous separation. With the sum of wave resistance and viscous resistance as objective functions and the parameters of B-Spline function as design variables, mathematical models are built using Nonlinear Programming Method (NLP) ensuring the basic limit of displacement and considering rear viscous separation. We develop ship lines optimization procedures with intellectual property rights. Series60 is used as parent ship in optimization design to obtain improved ship (Series60-1) theoretically. Then drag tests for the improved ship (Series60-1) is made to get the actual minimum total resistance hull form.

The destructive impact of the rogue waves

NASA Astrophysics Data System (ADS)

Shamin, Roman

2013-04-01

In our talk rogue waves at the ocean will be considered. By means of numerical modeling dangerous impact of rogue waves on the ships and oil rigs is calculated. Cases when these waves can bring in accident are considered. Using statistics of emergence of waves (see [1]-[2]), it is possible to estimate risks in each case. These results can be used for safety of the ships and oil rigs from rogue waves. References [1] V.E. Zakharov, A.I. Dyachenko, R.V. Shamin. How probability for freak wave formation can be found // THE EUROPEAN PHYSICAL JOURNAL - SPECIAL TOPICS Volume 185, Number 1, 113-124, DOI: 10.1140/epjst/e2010-01242-y [2] V.E. Zakharov, R.V. Shamin. Statistics of rogue waves in computer experiments // JETP Letters, 2012, V. 96, Issue 1, pp 66-69.

Numerical evaluation of longitudinal motions of Wigley hulls advancing in waves by using Bessho form translating-pulsating source Green'S function

NASA Astrophysics Data System (ADS)

Xiao, Wenbin; Dong, Wencai

2016-06-01

In the framework of 3D potential flow theory, Bessho form translating-pulsating source Green's function in frequency domain is chosen as the integral kernel in this study and hybrid source-and-dipole distribution model of the boundary element method is applied to directly solve the velocity potential for advancing ship in regular waves. Numerical characteristics of the Green function show that the contribution of local-flow components to velocity potential is concentrated at the nearby source point area and the wave component dominates the magnitude of velocity potential in the far field. Two kinds of mathematical models, with or without local-flow components taken into account, are adopted to numerically calculate the longitudinal motions of Wigley hulls, which demonstrates the applicability of translating-pulsating source Green's function method for various ship forms. In addition, the mesh analysis of discrete surface is carried out from the perspective of ship-form characteristics. The study shows that the longitudinal motion results by the simplified model are somewhat greater than the experimental data in the resonant zone, and the model can be used as an effective tool to predict ship seakeeping properties. However, translating-pulsating source Green function method is only appropriate for the qualitative analysis of motion response in waves if the ship geometrical shape fails to satisfy the slender-body assumption.

Time-domain separation of interfering waves in cancellous bone using bandlimited deconvolution: simulation and phantom study.

PubMed

Wear, Keith A

2014-04-01

In through-transmission interrogation of cancellous bone, two longitudinal pulses ("fast" and "slow" waves) may be generated. Fast and slow wave properties convey information about material and micro-architectural characteristics of bone. However, these properties can be difficult to assess when fast and slow wave pulses overlap in time and frequency domains. In this paper, two methods are applied to decompose signals into fast and slow waves: bandlimited deconvolution and modified least-squares Prony's method with curve-fitting (MLSP + CF). The methods were tested in plastic and Zerdine(®) samples that provided fast and slow wave velocities commensurate with velocities for cancellous bone. Phase velocity estimates were accurate to within 6 m/s (0.4%) (slow wave with both methods and fast wave with MLSP + CF) and 26 m/s (1.2%) (fast wave with bandlimited deconvolution). Midband signal loss estimates were accurate to within 0.2 dB (1.7%) (fast wave with both methods), and 1.0 dB (3.7%) (slow wave with both methods). Similar accuracies were found for simulations based on fast and slow wave parameter values published for cancellous bone. These methods provide sufficient accuracy and precision for many applications in cancellous bone such that experimental error is likely to be a greater limiting factor than estimation error.

Tether Deployer And Brake

NASA Technical Reports Server (NTRS)

Carroll, Joseph A.; Alexander, Charles M.

1993-01-01

Design concept promises speed, control, and reliability. Scheme for deploying tether provides for fast, free, and snagless payout and fast, dependable braking. Developed for small, expendable tethers in outer space, scheme also useful in laying transoceanic cables, deploying guidance wires to torpedoes and missiles, paying out rescue lines from ship to ship via rockets, deploying antenna wires, releasing communication and power cables to sonobuoys and expendable bathythermographs, and in reeling out lines from fishing rods.

Development of a Shipboard Remote Control and Telemetry Experimental System for Large-Scale Model’s Motions and Loads Measurement in Realistic Sea Waves

PubMed Central

Jiao, Jialong; Ren, Huilong; Adenya, Christiaan Adika; Chen, Chaohe

2017-01-01

Wave-induced motion and load responses are important criteria for ship performance evaluation. Physical experiments have long been an indispensable tool in the predictions of ship’s navigation state, speed, motions, accelerations, sectional loads and wave impact pressure. Currently, majority of the experiments are conducted in laboratory tank environment, where the wave environments are different from the realistic sea waves. In this paper, a laboratory tank testing system for ship motions and loads measurement is reviewed and reported first. Then, a novel large-scale model measurement technique is developed based on the laboratory testing foundations to obtain accurate motion and load responses of ships in realistic sea conditions. For this purpose, a suite of advanced remote control and telemetry experimental system was developed in-house to allow for the implementation of large-scale model seakeeping measurement at sea. The experimental system includes a series of technique sensors, e.g., the Global Position System/Inertial Navigation System (GPS/INS) module, course top, optical fiber sensors, strain gauges, pressure sensors and accelerometers. The developed measurement system was tested by field experiments in coastal seas, which indicates that the proposed large-scale model testing scheme is capable and feasible. Meaningful data including ocean environment parameters, ship navigation state, motions and loads were obtained through the sea trial campaign. PMID:29109379

Two-wave propagation in in vitro swine distal ulna

NASA Astrophysics Data System (ADS)

Mano, Isao; Horii, Kaoru; Matsukawa, Mami; Otani, Takahiko

2015-07-01

Ultrasonic transmitted waves were obtained in an in vitro swine distal ulna specimen, which mimics a human distal radius, that consists of interconnected cortical bone and cancellous bone. The transmitted waveforms appeared similar to the fast waves, slow waves, and overlapping fast and slow waves measured in the specimen after removing the surface cortical bone (only cancellous bone). In addition, the circumferential waves in the cortical bone and water did not affect the fast and slow waves. This suggests that the fast-and-slow-wave phenomenon can be observed in an in vivo human distal radius.

46 CFR 160.156-19 - Operating instructions and information for the ship's training manual.

Code of Federal Regulations, 2013 CFR

2013-10-01

... Boats and Fast Rescue Boats (SOLAS) § 160.156-19 Operating instructions and information for the ship's training manual. (a) Each rescue boat must have instructions and information for the ship's training manual... subpart) to describe the location and operation of the rescue boat. (b) The instructions and information...

Department of Defense Dictionary of Military and Associated Terms

DTIC Science & Technology

2008-05-30

cargo on board a ship for the purpose of accomplishing en route maintenance and security. supersonic — Of or pertaining to speed ...information systems TAK cargo ship T- AKR fast logistics ship TALCE tanker airlift control element Appendix A As Amended Through 30 May 2008...priorities committee — (*) A committee set up to determine the priorities of passengers and cargo . air raid reporting control ship — (*) A

Excitation of ship waves by a submerged object: New solution to the classical problem

NASA Astrophysics Data System (ADS)

Arzhannikov, A. V.; Kotelnikov, I. A.

2016-08-01

We have proposed a new method for solving the problem of ship waves excited on the surface of a nonviscous liquid by a submerged object that moves at a variable speed. As a first application of this method, we have obtained a new solution to the classic problem of ship waves generated by a submerged ball that moves rectilinearly with constant velocity parallel to the equilibrium surface of the liquid. For this example, we have derived asymptotic expressions describing the vertical displacement of the liquid surface in the limit of small and large values of the Froude number. The exact solution is presented in the form of two terms, each of which is reduced to one-dimensional integrals. One term describes the "Bernoulli hump" and another term the "Kelvin wedge." As a second example, we considered vertical oscillation of the submerged ball. In this case, the solution leads to the calculation of one-dimensional integral and describes surface waves propagating from the epicenter above the ball.

Excitation of ship waves by a submerged object: New solution to the classical problem.

PubMed

Arzhannikov, A V; Kotelnikov, I A

2016-08-01

We have proposed a new method for solving the problem of ship waves excited on the surface of a nonviscous liquid by a submerged object that moves at a variable speed. As a first application of this method, we have obtained a new solution to the classic problem of ship waves generated by a submerged ball that moves rectilinearly with constant velocity parallel to the equilibrium surface of the liquid. For this example, we have derived asymptotic expressions describing the vertical displacement of the liquid surface in the limit of small and large values of the Froude number. The exact solution is presented in the form of two terms, each of which is reduced to one-dimensional integrals. One term describes the "Bernoulli hump" and another term the "Kelvin wedge." As a second example, we considered vertical oscillation of the submerged ball. In this case, the solution leads to the calculation of one-dimensional integral and describes surface waves propagating from the epicenter above the ball.

Numerical and experimental study on the wave attenuation in bone--FDTD simulation of ultrasound propagation in cancellous bone.

PubMed

Nagatani, Yoshiki; Mizuno, Katsunori; Saeki, Takashi; Matsukawa, Mami; Sakaguchi, Takefumi; Hosoi, Hiroshi

2008-11-01

In cancellous bone, longitudinal waves often separate into fast and slow waves depending on the alignment of bone trabeculae in the propagation path. This interesting phenomenon becomes an effective tool for the diagnosis of osteoporosis because wave propagation behavior depends on the bone structure. Since the fast wave mainly propagates in trabeculae, this wave is considered to reflect the structure of trabeculae. For a new diagnosis method using the information of this fast wave, therefore, it is necessary to understand the generation mechanism and propagation behavior precisely. In this study, the generation process of fast wave was examined by numerical simulations using elastic finite-difference time-domain (FDTD) method and experimental measurements. As simulation models, three-dimensional X-ray computer tomography (CT) data of actual bone samples were used. Simulation and experimental results showed that the attenuation of fast wave was always higher in the early state of propagation, and they gradually decreased as the wave propagated in bone. This phenomenon is supposed to come from the complicated propagating paths of fast waves in cancellous bone.

Econometric analysis of the changing effects in wind strength and significant wave height on the probability of casualty in shipping.

PubMed

Knapp, Sabine; Kumar, Shashi; Sakurada, Yuri; Shen, Jiajun

2011-05-01

This study uses econometric models to measure the effect of significant wave height and wind strength on the probability of casualty and tests whether these effects changed. While both effects are in particular relevant for stability and strength calculations of vessels, it is also helpful for the development of ship construction standards in general to counteract increased risk resulting from changing oceanographic conditions. The authors analyzed a unique dataset of 3.2 million observations from 20,729 individual vessels in the North Atlantic and Arctic regions gathered during the period 1979-2007. The results show that although there is a seasonal pattern in the probability of casualty especially during the winter months, the effect of wind strength and significant wave height do not follow the same seasonal pattern. Additionally, over time, significant wave height shows an increasing effect in January, March, May and October while wind strength shows a decreasing effect, especially in January, March and May. The models can be used to simulate relationships and help understand the relationships. This is of particular interest to naval architects and ship designers as well as multilateral agencies such as the International Maritime Organization (IMO) that establish global standards in ship design and construction. Copyright © 2011 Elsevier Ltd. All rights reserved.

ShipMo3D Version 3.0 User Manual for Computing Ship Motions in the Time and Frequency Domains

DTIC Science & Technology

2012-01-01

permettent de modéliser un navire en manœuvre libre et en eau calme ou dans les vagues. SM3DBuildSeaway construit des modèles de voie maritime à trajet...manœuvrant libre - ment en eau calme ou dans une voie maritime modélisée. Plusieurs applications du logiciel ShipMo3D font des prévisions des mouvements de...can be produced. For a random seaway, the range of wave frequencies should be sufficient to encompass almost all energy within the wave spectrum. For

A Novel Approach to Resonant Absorption of the Fast Magnetohydrodynamic Eigenmodes of a Coronal Arcade

NASA Astrophysics Data System (ADS)

Hindman, Bradley W.; Jain, Rekha

2018-05-01

The arched field lines forming coronal arcades are often observed to undulate as magnetohydrodynamic waves propagate both across and along the magnetic field. These waves are most likely a combination of resonantly coupled fast magnetoacoustic waves and Alfvén waves. The coupling results in resonant absorption of the fast waves, converting fast wave energy into Alfvén waves. The fast eigenmodes of the arcade have proven difficult to compute or derive analytically, largely because of the mathematical complexity that the coupling introduces. When a traditional spectral decomposition is employed, the discrete spectrum associated with the fast eigenmodes is often subsumed into the continuous Alfvén spectrum. Thus fast eigenmodes become collective modes or quasi-modes. Here we present a spectral decomposition that treats the eigenmodes as having real frequencies but complex wavenumbers. Using this procedure we derive dispersion relations, spatial damping rates, and eigenfunctions for the resonant, fast eigenmodes of the arcade. We demonstrate that resonant absorption introduces a fast mode that would not exist otherwise. This new mode is heavily damped by resonant absorption, travelling only a few wavelengths before losing most of its energy.

VISIR-I: small vessels, least-time nautical routes using wave forecasts

NASA Astrophysics Data System (ADS)

Mannarini, G.; Pinardi, N.; Coppini, G.; Oddo, P.; Iafrati, A.

2015-09-01

A new numerical model for the on-demand computation of optimal ship routes based on sea-state forecasts has been developed. The model, named VISIR (discoVerIng Safe and effIcient Routes) is designed to support decision-makers when planning a marine voyage. The first version of the system, VISIR-I, considers medium and small motor vessels with lengths of up to a few tens of meters and a displacement hull. The model is made up of three components: the route optimization algorithm, the mechanical model of the ship, and the environmental fields. The optimization algorithm is based on a graph-search method with time-dependent edge weights. The algorithm is also able to compute a voluntary ship speed reduction. The ship model accounts for calm water and added wave resistance by making use of just the principal particulars of the vessel as input parameters. The system also checks the optimal route for parametric roll, pure loss of stability, and surfriding/broaching-to hazard conditions. Significant wave height, wave spectrum peak period, and wave direction forecast fields are employed as an input. Examples of VISIR-I routes in the Mediterranean Sea are provided. The optimal route may be longer in terms of miles sailed and yet it is faster and safer than the geodetic route between the same departure and arrival locations. Route diversions result from the safety constraints and the fact that the algorithm takes into account the full temporal evolution and spatial variability of the environmental fields.

Flow measurement around a model ship with propeller and rudder

NASA Astrophysics Data System (ADS)

van, S. H.; Kim, W. J.; Yoon, H. S.; Lee, Y. Y.; Park, I. R.

2006-04-01

For the design of hull forms with better resistance and propulsive performance, it is essential to understand flow characteristics, such as wave and wake development, around a ship. Experimental data detailing the local flow characteristics are invaluable for the validation of the physical and numerical modeling of computational fluid dynamics (CFD) codes, which are recently gaining attention as efficient tools for hull form evaluation. This paper describes velocity and wave profiles measured in the towing tank for the KRISO 138,000 m3 LNG carrier model with propeller and rudder. The effects of propeller and rudder on the wake and wave profiles in the stern region are clearly identified. The results contained in this paper can provide an opportunity to explore integrated flow phenomena around a model ship in the self-propelled condition, and can be added to the International Towing Tank Conference benchmark data for CFD validation as the previous KCS and KVLCC cases.

HF Surface Wave Radar Tests at the Eastern China Sea

NASA Astrophysics Data System (ADS)

Wu, Xiong Bin; Cheng, Feng; Wu, Shi Cai; Yang, Zi Jie; Wen, Biyang; Shi, Zhen Hua; Tian, Jiansheng; Ke, Hengyu; Gao, Huotao

2005-01-01

The HF surface wave radar system OSMAR2000 adopts Frequency Modulated Interrupted Continuous Waveform (FMICW) and its 120m-antenna array is transmitting/receiving co-used. MUSIC and MVM are applied to obtain sea echo's direction of arrival (DOA) when extracting currents information. Verification tests of OSMAR2000 ocean surface dynamics detection against in-situ measurements had been accomplished on Oct. 23~29, 2000. Ship detection test was carried out on Dec.24, 2001. It shows that OSMAR2000 is capable of detecting 1000 tons ships with a wide beam out to 70 km. This paper introduces the radar system and the applied DOA estimation methods in the first, and then presents ship detection results and some sea state measurement results of surface currents and waves. The results indicate the validity of the developed radar system and the effectiveness of the applied signal processing methods.

Domain decomposition and matching for time-domain analysis of motions of ships advancing in head sea

NASA Astrophysics Data System (ADS)

Tang, Kai; Zhu, Ren-chuan; Miao, Guo-ping; Fan, Ju

2014-08-01

A domain decomposition and matching method in the time-domain is outlined for simulating the motions of ships advancing in waves. The flow field is decomposed into inner and outer domains by an imaginary control surface, and the Rankine source method is applied to the inner domain while the transient Green function method is used in the outer domain. Two initial boundary value problems are matched on the control surface. The corresponding numerical codes are developed, and the added masses, wave exciting forces and ship motions advancing in head sea for Series 60 ship and S175 containership, are presented and verified. A good agreement has been obtained when the numerical results are compared with the experimental data and other references. It shows that the present method is more efficient because of the panel discretization only in the inner domain during the numerical calculation, and good numerical stability is proved to avoid divergence problem regarding ships with flare.

Navy Littoral Combat Ship (LCS) Program: Oversight Issues and Options for Congress

DTIC Science & Technology

2007-07-18

including unmanned vehicles (UVs). The basic version of the LCS, without any mission packages, is referred to as the LCS sea frame. The first LCS was...Littoral Combat Ship (LCS). The LCS is a small, fast ship that uses modular “plug-and- fight” mission packages, including unmanned vehicles (UVs). The...fight” mission packages, including unmanned vehicles (UVs). Rather than being a multimission ship like the Navy’s current large surface combatants

Development of ship structure health monitoring system based on IOT technology

NASA Astrophysics Data System (ADS)

Yang, Sujun; Shi, Lei; Chen, Demin; Dong, Yuqing; Hu, Zhenyi

2017-06-01

It is very important to monitor the ship structure, because ships are affected by all kinds of wind wave and current environment factor. At the same time, internet of things (IOT) technology plays more and more important role of in the development of industrial process. In the paper, real-time online monitoring of the ship can be realized by means of IOT technology. Ship stress, vibration and dynamic parameters are measured. Meanwhile, data is transmitted to remote monitoring system through intelligent data gateway. Timely remote support can be realized for dangerous stage of ship. Safe navigation of ships is guaranteed through application of the system.

Association of plasma aldosterone with the metabolic syndrome in two German populations.

PubMed

Hannemann, Anke; Meisinger, Christa; Bidlingmaier, Martin; Döring, Angela; Thorand, Barbara; Heier, Margit; Belcredi, Petra; Ladwig, Karl-Heinz; Wallaschofski, Henri; Friedrich, Nele; Schipf, Sabine; Lüdemann, Jan; Rettig, Rainer; Peters, Jörg; Völzke, Henry; Seissler, Jochen; Beuschlein, Felix; Nauck, Matthias; Reincke, Martin

2011-05-01

The aim of this study was to analyze the potential association of the plasma aldosterone concentration (PAC) with the metabolic syndrome (MetS) and its components in two German population-based studies. We selected 2830 and 2901 participants (31-80 years) from the follow-ups of the Study of Health in Pomerania (SHIP)-1 and the Cooperative Health Research in the Region of Augsburg (KORA) F4 respectively. MetS was defined as the presence of at least three out of the following five criteria: waist circumference ≥94 cm (men (m)) and ≥80 cm (women (w)); high-density lipoprotein (HDL) cholesterol <1.0 mmol/l (m) and <1.3 mmol/l (w); blood pressure ≥130/85 mmHg or antihypertensive treatment; non-fasting glucose (SHIP-1) ≥8 mmol/l, fasting glucose (KORA F4) ≥5.55 mmol/l or antidiabetic treatment; non-fasting triglycerides (SHIP-1) ≥2.3 mmol/l, fasting triglycerides (KORA F4) ≥1.7 mmol/l, or lipid-lowering treatment. We calculated logistic regression models by comparing the highest study- and sex-specific PAC quintiles versus all lower quintiles. MetS was common with 48.1% (m) and 34.8% (w) in SHIP-1 and 42.7% (m) and 27.5% (w) in KORA F4. Our logistic regression models revealed associations of PAC with MetS, elevated triglycerides, and decreased HDL cholesterol in SHIP-1 and KORA F4. Our findings add to the increasing evidence supporting a relation between aldosterone and MetS and suggest that aldosterone may be involved in the pathophysiology of MetS and lipid metabolism disorders.

46 CFR 12.10-9 - Endorsement for proficiency in fast rescue boats.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 1 2011-10-01 2011-10-01 false Endorsement for proficiency in fast rescue boats. 12.10... SEAMEN REQUIREMENTS FOR RATING ENDORSEMENTS Lifeboatman § 12.10-9 Endorsement for proficiency in fast rescue boats. (a) Each person engaged or employed as a lifeboatman proficient in fast rescue boats must...

46 CFR 12.10-9 - Endorsement for proficiency in fast rescue boats.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 1 2013-10-01 2013-10-01 false Endorsement for proficiency in fast rescue boats. 12.10... SEAMEN REQUIREMENTS FOR RATING ENDORSEMENTS Lifeboatman § 12.10-9 Endorsement for proficiency in fast rescue boats. (a) Each person engaged or employed as a lifeboatman proficient in fast rescue boats must...

75 FR 17196 - Self-Regulatory Organizations; The Depository Trust Company; Order Granting Approval of a...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-05

... Part of the Fast Automated Transfer Program March 30, 2010. I. Introduction On January 19, 2010, The... made unsponsored ADRs eligible for DTC's Fast Automated Securities Transfer Program (``FAST'').\\4\\ \\3... associated with safekeeping, transfer, shipping and insurance costs. \\4\\ FAST was designed to eliminate some...

46 CFR 12.10-9 - Endorsement for proficiency in fast rescue boats.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 1 2010-10-01 2010-10-01 false Endorsement for proficiency in fast rescue boats. 12.10... SEAMEN REQUIREMENTS FOR RATING ENDORSEMENTS Lifeboatman § 12.10-9 Endorsement for proficiency in fast rescue boats. (a) Each person engaged or employed as a lifeboatman proficient in fast rescue boats must...

46 CFR 12.10-9 - Endorsement for proficiency in fast rescue boats.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 1 2012-10-01 2012-10-01 false Endorsement for proficiency in fast rescue boats. 12.10... SEAMEN REQUIREMENTS FOR RATING ENDORSEMENTS Lifeboatman § 12.10-9 Endorsement for proficiency in fast rescue boats. (a) Each person engaged or employed as a lifeboatman proficient in fast rescue boats must...

FAST MAGNETOACOUSTIC WAVE TRAINS OF SAUSAGE SYMMETRY IN CYLINDRICAL WAVEGUIDES OF THE SOLAR CORONA

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

Shestov, S.; Kuzin, S.; Nakariakov, V. M., E-mail: sshestov@gmail.com

2015-12-01

Fast magnetoacoustic waves guided along the magnetic field by plasma non-uniformities, in particular coronal loops, fibrils, and plumes, are known to be highly dispersive, which lead to the formation of quasi-periodic wave trains excited by a broadband impulsive driver, e.g., a solar flare. We investigated the effects of cylindrical geometry on the fast sausage wave train formation. We performed magnetohydrodynamic numerical simulations of fast magnetoacoustic perturbations of a sausage symmetry, propagating from a localized impulsive source along a field-aligned plasma cylinder with a smooth radial profile of the fast speed. The wave trains are found to have pronounced period modulation,more » with the longer instant period seen in the beginning of the wave train. The wave trains also have a pronounced amplitude modulation. Wavelet spectra of the wave trains have characteristic tadpole features, with the broadband large-amplitude heads preceding low-amplitude quasi-monochromatic tails. The mean period of the wave train is about the transverse fast magnetoacoustic transit time across the cylinder. The mean parallel wavelength is about the diameter of the wave-guiding plasma cylinder. Instant periods are longer than the sausage wave cutoff period. The wave train characteristics depend on the fast magnetoacoustic speed in both the internal and external media, the smoothness of the transverse profile of the equilibrium quantities, and also the spatial size of the initial perturbation. If the initial perturbation is localized at the axis of the cylinder, the wave trains contain higher radial harmonics that have shorter periods.« less

Current drive with combined electron cyclotron wave and high harmonic fast wave in tokamak plasmas

NASA Astrophysics Data System (ADS)

Li, J. C.; Gong, X. Y.; Dong, J. Q.; Wang, J.; Zhang, N.; Zheng, P. W.; Yin, C. Y.

2016-12-01

The current driven by combined electron cyclotron wave (ECW) and high harmonic fast wave is investigated using the GENRAY/CQL3D package. It is shown that no significant synergetic current is found in a range of cases with a combined ECW and fast wave (FW). This result is consistent with a previous study [Harvey et al., in Proceedings of IAEA TCM on Fast Wave Current Drive in Reactor Scale Tokamaks (Synergy and Complimentarily with LHCD and ECRH), Arles, France, IAEA, Vienna, 1991]. However, a positive synergy effect does appear with the FW in the lower hybrid range of frequencies. This positive synergy effect can be explained using a picture of the electron distribution function induced by the ECW and a very high harmonic fast wave (helicon). The dependence of the synergy effect on the radial position of the power deposition, the wave power, the wave frequency, and the parallel refractive index is also analyzed, both numerically and physically.

The observation of ocean surface phenomena using imagery from the SEASAT synthetic aperture radar: An assessment

NASA Astrophysics Data System (ADS)

Vesecky, John F.; Stewart, Robert H.

1982-04-01

Over the period July 4 to October 10, 1978, the SEASAT synthetic aperture radar (SAR) gathered 23 cm wavelength radar images of some 108 km2 of the earth's surface, mainly of ocean areas, at 25-40 m resolution. Our assessment is in terms of oceanographic and ocean monitoring objectives and is directed toward discovering the proper role of SAR imagery in these areas of interest. In general, SAR appears to have two major and somewhat overlapping roles: first, quantitative measurement of ocean phenomena, like long gravity waves and wind fields, as well as measurement of ships; second, exploratory observations of large-scale ocean phenomena, such as the Gulf Stream and its eddies, internal waves, and ocean fronts. These roles are greatly enhanced by the ability of 23 cm SAR to operate day or night and through clouds. To begin we review some basics of synthetic aperture radar and its implementation on the SEASAT spacecraft. SEASAT SAR imagery of the ocean is fundamentally a map of the radar scattering characteristics of ˜30 cm wavelength ocean waves, distorted in some cases by ocean surface motion. We discuss how wind stress, surface currents, long gravity waves, and surface films modulate the scattering properties of these resonant waves with particular emphasis on the mechanisms that could produce images of long gravity waves. Doppler effects by ocean motion are also briefly described. Measurements of long (wavelength ≳100 m) gravity waves, using SEASAT SAR imagery, are compared with surface measurements during several experiments. Combining these results we find that dominant wavelength and direction are measured by SEASAT SAR within ±12% and ±15°, respectively. However, we note that ocean waves are not always visible in SAR images and discuss detection criteria in terms of wave height, length, and direction. SAR estimates of omnidirectional wave height spectra made by assuming that SAR image intensity is proportional to surface height fluctuations are more similar to corresponding surface measurements of wave height spectra than to wave slope spectra. Because SEASAT SAR images show the radar cross section σ° of ˜30 cm waves (neglecting doppler effects), and because these waves are raised by wind stress on the ocean surface, wind measurements are possible. Comparison between wind speeds estimated from SEASAT SAR imagery and from the SEASAT satellite scatterometer (SASS) agreed to within ±0.7 m s- over a 350-km comparison track and for wind speeds from 2 to 15 m s-. The great potential of SAR wind measurements lies in studying the spatial structure of the wind field over a range of spatial scales of from ≲1 km to ≳100 km. At present, the spatial and temporal structure of ocean wind fields is largely unknown. Because SAR responds to short waves whose energy density is a function of wind stress at the surface rather than wind speed at some distance above the surface, variations in image intensity may also reflect changes in air-sea temperature difference (thus complicating wind measurements by SAR). Because SAR images show the effects of surface current shear, air-sea temperature difference, and surface films through their modulation of the ˜30 cm waves, SEASAT images can be used to locate and study the Gulf Stream and related warm water rings, tidal flows at inlets, internal waves, and slicks resulting from surface films. In many of these applications, SAR provides a remote sensing capability that is complementary to infrared imagery because the two techniques sense largely different properties, namely, surface roughness and temperature. Both stationary ships and moving ships with their attendant wakes are often seen in SAR images. Ship images can be used to estimate ship size, heading, and speed. However, ships known to be in areas imaged by SAR are not always detectable. Clearly, a variety of factors, such as image resolution, ship size, sea state, and winds could affect ship detection. Overall, the role of SAR imagery in oceanography is definitely evolving at this time, but its ultimate role is unclear. We have assessed the ability of SEASAT SAR to measure a variety of ocean phenomena and have commented briefly on applications. In the end, oceanographers and others will have to judge from these capabilities the proper place for SAR in oceanography and remote sensing of the ocean.

48 CFR 13.403 - Preparation and execution of orders.

Code of Federal Regulations, 2012 CFR

2012-10-01

... REGULATION CONTRACTING METHODS AND CONTRACT TYPES SIMPLIFIED ACQUISITION PROCEDURES Fast Payment Procedure 13... the fast payment procedure shall include the following: (a) A requirement that the supplies be shipped...

48 CFR 13.403 - Preparation and execution of orders.

Code of Federal Regulations, 2011 CFR

2011-10-01

... REGULATION CONTRACTING METHODS AND CONTRACT TYPES SIMPLIFIED ACQUISITION PROCEDURES Fast Payment Procedure 13... the fast payment procedure shall include the following: (a) A requirement that the supplies be shipped...

48 CFR 13.403 - Preparation and execution of orders.

Code of Federal Regulations, 2014 CFR

2014-10-01

... REGULATION CONTRACTING METHODS AND CONTRACT TYPES SIMPLIFIED ACQUISITION PROCEDURES Fast Payment Procedure 13... the fast payment procedure shall include the following: (a) A requirement that the supplies be shipped...

48 CFR 13.403 - Preparation and execution of orders.

Code of Federal Regulations, 2010 CFR

2010-10-01

... REGULATION CONTRACTING METHODS AND CONTRACT TYPES SIMPLIFIED ACQUISITION PROCEDURES Fast Payment Procedure 13... the fast payment procedure shall include the following: (a) A requirement that the supplies be shipped...

48 CFR 13.403 - Preparation and execution of orders.

Code of Federal Regulations, 2013 CFR

2013-10-01

... REGULATION CONTRACTING METHODS AND CONTRACT TYPES SIMPLIFIED ACQUISITION PROCEDURES Fast Payment Procedure 13... the fast payment procedure shall include the following: (a) A requirement that the supplies be shipped...

Optimum Vessel Performance in Evolving Nonlinear Wave Fields

DTIC Science & Technology

2012-11-01

TEMPEST , the new, nonlinear, time-domain ship motion code being developed by the Navy. Table of Contents Executive Summary i List of Figures iii...domain ship motion code TEMPEST . The radiation and diffraction forces in the level 3.0 version of TEMPEST will be computed by the body-exact strip theory...nonlinear responses of a ship to a seaway are being incorporated into version 3 of TEMPEST , the new, nonlinear, time-domain ship motion code that

Modeling Water Waves with Smoothed Particle Hydrodynamics

DTIC Science & Technology

2013-09-30

SPH Model for Water Waves and Other Free Surface Flows ...Lagrangian nature of SPH allows the modeling of wave breaking, surf zones, ship waves, and wave-structure interaction, where the free surface becomes...proving to be a competent modeling scheme for free surface flows in three dimensions including the complex flows of the surf zone. As the GPU

a Novel Ship Detection Method for Large-Scale Optical Satellite Images Based on Visual Lbp Feature and Visual Attention Model

NASA Astrophysics Data System (ADS)

Haigang, Sui; Zhina, Song

2016-06-01

Reliably ship detection in optical satellite images has a wide application in both military and civil fields. However, this problem is very difficult in complex backgrounds, such as waves, clouds, and small islands. Aiming at these issues, this paper explores an automatic and robust model for ship detection in large-scale optical satellite images, which relies on detecting statistical signatures of ship targets, in terms of biologically-inspired visual features. This model first selects salient candidate regions across large-scale images by using a mechanism based on biologically-inspired visual features, combined with visual attention model with local binary pattern (CVLBP). Different from traditional studies, the proposed algorithm is high-speed and helpful to focus on the suspected ship areas avoiding the separation step of land and sea. Largearea images are cut into small image chips and analyzed in two complementary ways: Sparse saliency using visual attention model and detail signatures using LBP features, thus accordant with sparseness of ship distribution on images. Then these features are employed to classify each chip as containing ship targets or not, using a support vector machine (SVM). After getting the suspicious areas, there are still some false alarms such as microwaves and small ribbon clouds, thus simple shape and texture analysis are adopted to distinguish between ships and nonships in suspicious areas. Experimental results show the proposed method is insensitive to waves, clouds, illumination and ship size.

Motion-Correlated Flow Distortion and Wave-Induced Biases in Air-Sea Flux Measurements From Ships

NASA Astrophysics Data System (ADS)

Prytherch, J.; Yelland, M. J.; Brooks, I. M.; Tupman, D. J.; Pascal, R. W.; Moat, B. I.; Norris, S. J.

2016-02-01

Direct measurements of the turbulent air-sea fluxes of momentum, heat, moisture and gases are often made using sensors mounted on ships. Ship-based turbulent wind measurements are corrected for platform motion using well established techniques, but biases at scales associated with wave and platform motion are often still apparent in the flux measurements. It has been uncertain whether this signal is due to time-varying distortion of the air flow over the platform, or to wind-wave interactions impacting the turbulence. Methods for removing such motion-scale biases from scalar measurements have previously been published but their application to momentum flux measurements remains controversial. Here we use eddy covariance momentum flux measurements obtained onboard RRS James Clark Ross as part of the Waves, Aerosol and Gas Exchange Study (WAGES), a programme of near-continuous measurements using the autonomous AutoFlux system (Yelland et al., 2009). Measurements were made in 2013 in locations throughout the North and South Atlantic, the Southern Ocean and the Arctic Ocean, at latitudes ranging from 62°S to 75°N. We show that the measured motion-scale bias has a dependence on the horizontal ship velocity, and that a correction for it reduces the dependence of the measured momentum flux on the orientation of the ship to the wind. We conclude that the bias is due to experimental error, and that time-varying motion-dependent flow distortion is the likely source. Yelland, M., Pascal, R., Taylor, P. and Moat, B.: AutoFlux: an autonomous system for the direct measurement of the air-sea fluxes of CO2, heat and momentum. J. Operation. Oceanogr., 15-23, doi:10.1080/1755876X.2009.11020105, 2009.

Littoral Combat Ship: Knowledge of Survivability and Lethality Capabilities Needed Prior to Making Major Funding Decisions

DTIC Science & Technology

2015-12-01

USS Port Royal hit a coral reef in order to provide an independent review of the damage the ship sustained. Our classified report discussed...explosion. Underwater explosions create a shock wave and a highly compressed gas bubble that expands and contracts. This can cause a type of vertical or...conditions also remains unknown. Due to the dynamic nature of waves , the Navy cannot rely on modeling and simulation alone to provide an accurate

Calculation of Viscous Effects on Ship Wave Resistance Using Axisymmetric Boundary Layer Approaches

DTIC Science & Technology

1985-05-13

Layers in Pressure Gradients," NSRDC Report 3308, April 1970. 38. Garcia, J.M. and Zazurca, J.A.A., " Calculo de la Resistencia Viscosa de un Buque a...none USERS 21 ABSTRACT SECURITY CLASSIFICATION UNCLASSIFIED 22a NAME OF RESPONSIBLE INDIVIDUAL Henry T. Wang 22b TELEPHONE (Include Area Code...theory. Since then, calculation of the resistance due to the waves generated by a surface ship advancing at constant forward speed has been an area of

Determining attenuation properties of interfering fast and slow ultrasonic waves in cancellous bone.

PubMed

Nelson, Amber M; Hoffman, Joseph J; Anderson, Christian C; Holland, Mark R; Nagatani, Yoshiki; Mizuno, Katsunori; Matsukawa, Mami; Miller, James G

2011-10-01

Previous studies have shown that interference between fast waves and slow waves can lead to observed negative dispersion in cancellous bone. In this study, the effects of overlapping fast and slow waves on measurements of the apparent attenuation as a function of propagation distance are investigated along with methods of analysis used to determine the attenuation properties. Two methods are applied to simulated data that were generated based on experimentally acquired signals taken from a bovine specimen. The first method uses a time-domain approach that was dictated by constraints imposed by the partial overlap of fast and slow waves. The second method uses a frequency-domain log-spectral subtraction technique on the separated fast and slow waves. Applying the time-domain analysis to the broadband data yields apparent attenuation behavior that is larger in the early stages of propagation and decreases as the wave travels deeper. In contrast, performing frequency-domain analysis on the separated fast waves and slow waves results in attenuation coefficients that are independent of propagation distance. Results suggest that features arising from the analysis of overlapping two-mode data may represent an alternate explanation for the previously reported apparent dependence on propagation distance of the attenuation coefficient of cancellous bone. © 2011 Acoustical Society of America

Determining attenuation properties of interfering fast and slow ultrasonic waves in cancellous bone

PubMed Central

Nelson, Amber M.; Hoffman, Joseph J.; Anderson, Christian C.; Holland, Mark R.; Nagatani, Yoshiki; Mizuno, Katsunori; Matsukawa, Mami; Miller, James G.

2011-01-01

Previous studies have shown that interference between fast waves and slow waves can lead to observed negative dispersion in cancellous bone. In this study, the effects of overlapping fast and slow waves on measurements of the apparent attenuation as a function of propagation distance are investigated along with methods of analysis used to determine the attenuation properties. Two methods are applied to simulated data that were generated based on experimentally acquired signals taken from a bovine specimen. The first method uses a time-domain approach that was dictated by constraints imposed by the partial overlap of fast and slow waves. The second method uses a frequency-domain log-spectral subtraction technique on the separated fast and slow waves. Applying the time-domain analysis to the broadband data yields apparent attenuation behavior that is larger in the early stages of propagation and decreases as the wave travels deeper. In contrast, performing frequency-domain analysis on the separated fast waves and slow waves results in attenuation coefficients that are independent of propagation distance. Results suggest that features arising from the analysis of overlapping two-mode data may represent an alternate explanation for the previously reported apparent dependence on propagation distance of the attenuation coefficient of cancellous bone. PMID:21973378

STEREO OBSERVATIONS OF FAST MAGNETOSONIC WAVES IN THE EXTENDED SOLAR CORONA ASSOCIATED WITH EIT/EUV WAVES

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

Kwon, Ryun-Young; Ofman, Leon; Kramar, Maxim

2013-03-20

We report white-light observations of a fast magnetosonic wave associated with a coronal mass ejection observed by STEREO/SECCHI/COR1 inner coronagraphs on 2011 August 4. The wave front is observed in the form of density compression passing through various coronal regions such as quiet/active corona, coronal holes, and streamers. Together with measured electron densities determined with STEREO COR1 and Extreme UltraViolet Imager (EUVI) data, we use our kinematic measurements of the wave front to calculate coronal magnetic fields and find that the measured speeds are consistent with characteristic fast magnetosonic speeds in the corona. In addition, the wave front turns outmore » to be the upper coronal counterpart of the EIT wave observed by STEREO EUVI traveling against the solar coronal disk; moreover, stationary fronts of the EIT wave are found to be located at the footpoints of deflected streamers and boundaries of coronal holes, after the wave front in the upper solar corona passes through open magnetic field lines in the streamers. Our findings suggest that the observed EIT wave should be in fact a fast magnetosonic shock/wave traveling in the inhomogeneous solar corona, as part of the fast magnetosonic wave propagating in the extended solar corona.« less

29 CFR 1915.165 - Ship's deck machinery.

Code of Federal Regulations, 2010 CFR

2010-07-01

... Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) OCCUPATIONAL SAFETY AND HEALTH STANDARDS FOR SHIPYARD EMPLOYMENT Ship's Machinery and Piping... claws (also known as chain stoppers) shall be made fast to the anchor chains. (2) The riding pawls shall...

46 CFR 160.156-21 - Operation and maintenance instructions.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 6 2012-10-01 2012-10-01 false Operation and maintenance instructions. 160.156-21 Section 160.156-21 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Rescue Boats and Fast Rescue...

46 CFR 160.156-3 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 6 2012-10-01 2012-10-01 false Definitions. 160.156-3 Section 160.156-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Rescue Boats and Fast Rescue Boats (SOLAS) § 160.156-3...

46 CFR 160.156-21 - Operation and maintenance instructions.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 6 2014-10-01 2014-10-01 false Operation and maintenance instructions. 160.156-21 Section 160.156-21 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Rescue Boats and Fast Rescue...

46 CFR 160.156-3 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 6 2014-10-01 2014-10-01 false Definitions. 160.156-3 Section 160.156-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Rescue Boats and Fast Rescue Boats (SOLAS) § 160.156-3...

46 CFR 160.156-3 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 6 2013-10-01 2013-10-01 false Definitions. 160.156-3 Section 160.156-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Rescue Boats and Fast Rescue Boats (SOLAS) § 160.156-3...

46 CFR 160.156-21 - Operation and maintenance instructions.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 6 2013-10-01 2013-10-01 false Operation and maintenance instructions. 160.156-21 Section 160.156-21 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Rescue Boats and Fast Rescue...

46 CFR 160.156-13 - Approval inspections and tests for prototype rescue boats and fast rescue boats.

Code of Federal Regulations, 2013 CFR

2013-10-01

... boats and fast rescue boats. 160.156-13 Section 160.156-13 Shipping COAST GUARD, DEPARTMENT OF HOMELAND... EQUIPMENT Rescue Boats and Fast Rescue Boats (SOLAS) § 160.156-13 Approval inspections and tests for prototype rescue boats and fast rescue boats. (a) After the Commandant notifies the manufacturer that the...

46 CFR 160.156-13 - Approval inspections and tests for prototype rescue boats and fast rescue boats.

Code of Federal Regulations, 2012 CFR

2012-10-01

... boats and fast rescue boats. 160.156-13 Section 160.156-13 Shipping COAST GUARD, DEPARTMENT OF HOMELAND... EQUIPMENT Rescue Boats and Fast Rescue Boats (SOLAS) § 160.156-13 Approval inspections and tests for prototype rescue boats and fast rescue boats. (a) After the Commandant notifies the manufacturer that the...

46 CFR 160.156-13 - Approval inspections and tests for prototype rescue boats and fast rescue boats.

Code of Federal Regulations, 2014 CFR

2014-10-01

... boats and fast rescue boats. 160.156-13 Section 160.156-13 Shipping COAST GUARD, DEPARTMENT OF HOMELAND... EQUIPMENT Rescue Boats and Fast Rescue Boats (SOLAS) § 160.156-13 Approval inspections and tests for prototype rescue boats and fast rescue boats. (a) After the Commandant notifies the manufacturer that the...

46 CFR 12.617 - Requirements to qualify for an STCW endorsement in proficiency in fast rescue boats.

Code of Federal Regulations, 2014 CFR

2014-10-01

... proficiency in fast rescue boats. 12.617 Section 12.617 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY... Endorsements § 12.617 Requirements to qualify for an STCW endorsement in proficiency in fast rescue boats. (a) To qualify for an STCW endorsement in proficiency in fast rescue boats, an applicant must— (1) Be not...

Staphylococcal food poisoning on a cruise ship.

PubMed Central

Waterman, S. H.; Demarcus, T. A.; Wells, J. G.; Blake, P. A.

1987-01-01

Two waves of vomiting and/or diarrhoea affected approximately 215 of the 715 passengers on a Caribbean cruise ship. The outbreak was independently associated with eating cream-filled pastries at two separate meals. Staphylococcus aureus phage type 85/+ was isolated from cases and pastry cooks, but not from controls. This is the first well-documented outbreak of staphylococcal food poisoning on a cruise ship. PMID:3678396

Study on process design of partially-balanced, hydraulically lifting vertical ship lift

NASA Astrophysics Data System (ADS)

Xin, Shen; Xiaofeng, Xu; Lu, Zhang; Bing, Zhu; Fei, Li

2017-11-01

The hub ship lift in Panjin is the first navigation structure in China for the link between the inland and open seas, which adopts a novel partially-balanced, hydraulically lifting ship lift; it can meet such requirements as fast and sharp water level change in open sea, large draft of a yacht, and launching of a ship reception chamber; its balancing weight system can effectively reduce the load of the primary lifting cylinder, and optimize the force distribution of the ship reception chamber. The paper provides an introduction to main equipment, basic principles, main features and system composition of a ship lift. The unique power system and balancing system of the completed ship lift has offered some experience for the construction of the tourism-type ship lifts with a lower lifting height.

Conventional, Bayesian, and Modified Prony's methods for characterizing fast and slow waves in equine cancellous bone

PubMed Central

Groopman, Amber M.; Katz, Jonathan I.; Holland, Mark R.; Fujita, Fuminori; Matsukawa, Mami; Mizuno, Katsunori; Wear, Keith A.; Miller, James G.

2015-01-01

Conventional, Bayesian, and the modified least-squares Prony's plus curve-fitting (MLSP + CF) methods were applied to data acquired using 1 MHz center frequency, broadband transducers on a single equine cancellous bone specimen that was systematically shortened from 11.8 mm down to 0.5 mm for a total of 24 sample thicknesses. Due to overlapping fast and slow waves, conventional analysis methods were restricted to data from sample thicknesses ranging from 11.8 mm to 6.0 mm. In contrast, Bayesian and MLSP + CF methods successfully separated fast and slow waves and provided reliable estimates of the ultrasonic properties of fast and slow waves for sample thicknesses ranging from 11.8 mm down to 3.5 mm. Comparisons of the three methods were carried out for phase velocity at the center frequency and the slope of the attenuation coefficient for the fast and slow waves. Good agreement among the three methods was also observed for average signal loss at the center frequency. The Bayesian and MLSP + CF approaches were able to separate the fast and slow waves and provide good estimates of the fast and slow wave properties even when the two wave modes overlapped in both time and frequency domains making conventional analysis methods unreliable. PMID:26328678

Mathematical model of snake-type multi-directional wave generation

NASA Astrophysics Data System (ADS)

Muarif; Halfiani, Vera; Rusdiana, Siti; Munzir, Said; Ramli, Marwan

2018-01-01

Research on extreme wave generation is one intensive research on water wave study because the fact that the occurrence of this wave in the ocean can cause serious damage to the ships and offshore structures. One method to be used to generate the wave is self-correcting. This method controls the signal on the wavemakers in a wave tank. Some studies also consider the nonlinear wave generation in a wave tank by using numerical approach. Study on wave generation is essential in the effectiveness and efficiency of offshore structure model testing before it can be operated in the ocean. Generally, there are two types of wavemakers implemented in the hydrodynamic laboratory, piston-type and flap-type. The flap-type is preferred to conduct a testing to a ship in deep water. Single flap wavemaker has been explained in many studies yet snake-type wavemaker (has more than one flap) is still a case needed to be examined. Hence, the formulation in controlling the wavemaker need to be precisely analyzed such that the given input can generate the desired wave in the space-limited wave tank. By applying the same analogy and methodhology as the previous study, this article represents multi-directional wave generation by implementing snake-type wavemakers.

Wave-particle interactions on the FAST satellite

NASA Technical Reports Server (NTRS)

Temerin, M. A.; Carlson, C. W.; Cattell, C. A.; Ergun, R. E.; Mcfadden, J. P.

1990-01-01

NASA's Fast Auroral Snapshot, or 'FAST' satellite, scheduled for launch in 1993, will investigate the plasma physics of the low altitude auroral zone from a 3500-km apogee polar orbit. FAST will give attention to wave, double-layer, and soliton production processes due to electrons and ions, as well as to wave-wave interactions, and the acceleration of electrons and ions by waves and electric fields. FAST will employ an intelligent data-handling system capacle of data acquisition at rates of up to 1 Mb/sec, in addition to a 1-Gbit solid-state memory. The data need be gathered for only a few minutes during passes through the auroral zone, since the most interesting auroral phenomena occur in such narrow regions as auroral arcs, electrostatic shocks, and superthermal electron bursts.

On the nature of fast sausage waves in coronal loops

NASA Astrophysics Data System (ADS)

Bahari, Karam

2018-05-01

The effect of the parameters of coronal loops on the nature of fast sausage waves are investigated. To do this three models of the coronal loop considered, a simple loop model, a current-carrying loop model and a model with radially structured density called "Inner μ" profile. For all the models the Magnetohydrodynamic (MHD) equations solved analytically in the linear approximation and the restoring forces of oscillations obtained. The ratio of the magnetic tension force to the pressure gradient force obtained as a function of the distance from the axis of the loop. In the simple loop model for all values of the loop parameters the fast sausages wave have a mixed nature of Alfvénic and fast MHD waves, in the current-carrying loop model with thick annulus and low density contrast the fast sausage waves can be considered as purely Alfvénic wave in the core region of the loop, and in the "Inner μ" profile for each set of the parameters of the loop the wave can be considered as a purely Alfvénic wave in some regions of the loop.

Modification of wave propagation and wave travel-time by the presence of magnetic fields in the solar network atmosphere

NASA Astrophysics Data System (ADS)

Nutto, C.; Steiner, O.; Schaffenberger, W.; Roth, M.

2012-02-01

Context. Observations of waves at frequencies above the acoustic cut-off frequency have revealed vanishing wave travel-times in the vicinity of strong magnetic fields. This detection of apparently evanescent waves, instead of the expected propagating waves, has remained a riddle. Aims: We investigate the influence of a strong magnetic field on the propagation of magneto-acoustic waves in the atmosphere of the solar network. We test whether mode conversion effects can account for the shortening in wave travel-times between different heights in the solar atmosphere. Methods: We carry out numerical simulations of the complex magneto-atmosphere representing the solar magnetic network. In the simulation domain, we artificially excite high frequency waves whose wave travel-times between different height levels we then analyze. Results: The simulations demonstrate that the wave travel-time in the solar magneto-atmosphere is strongly influenced by mode conversion. In a layer enclosing the surface sheet defined by the set of points where the Alfvén speed and the sound speed are equal, called the equipartition level, energy is partially transferred from the fast acoustic mode to the fast magnetic mode. Above the equipartition level, the fast magnetic mode is refracted due to the large gradient of the Alfvén speed. The refractive wave path and the increasing phase speed of the fast mode inside the magnetic canopy significantly reduce the wave travel-time, provided that both observing levels are above the equipartition level. Conclusions: Mode conversion and the resulting excitation and propagation of fast magneto-acoustic waves is responsible for the observation of vanishing wave travel-times in the vicinity of strong magnetic fields. In particular, the wave propagation behavior of the fast mode above the equipartition level may mimic evanescent behavior. The present wave propagation experiments provide an explanation of vanishing wave travel-times as observed with multi-line high-cadence instruments. Movies are available in electronic form at http://www.aanda.org

Options for the Navy’s Future Fleet

DTIC Science & Technology

2006-05-01

capability than most of those options by other than for inflation, how big and how capable can the most measures of capability. But even under the Navy’s...The most prominent of those vessels are fast combat support ships, which operate with carrier strike groups to resupply them with fuel, dry Supply...categories of ships-submarines and large surface Similarly, the ship construction schedule for large surface combatants-are responsible for most of the

Fast decomposition of two ultrasound longitudinal waves in cancellous bone using a phase rotation parameter for bone quality assessment: Simulation study.

PubMed

Taki, Hirofumi; Nagatani, Yoshiki; Matsukawa, Mami; Kanai, Hiroshi; Izumi, Shin-Ichi

2017-10-01

Ultrasound signals that pass through cancellous bone may be considered to consist of two longitudinal waves, which are called fast and slow waves. Accurate decomposition of these fast and slow waves is considered to be highly beneficial in determination of the characteristics of cancellous bone. In the present study, a fast decomposition method using a wave transfer function with a phase rotation parameter was applied to received signals that have passed through bovine bone specimens with various bone volume to total volume (BV/TV) ratios in a simulation study, where the elastic finite-difference time-domain method is used and the ultrasound wave propagated parallel to the bone axes. The proposed method succeeded to decompose both fast and slow waves accurately; the normalized residual intensity was less than -19.5 dB when the specimen thickness ranged from 4 to 7 mm and the BV/TV value ranged from 0.144 to 0.226. There was a strong relationship between the phase rotation value and the BV/TV value. The ratio of the peak envelope amplitude of the decomposed fast wave to that of the slow wave increased monotonically with increasing BV/TV ratio, indicating the high performance of the proposed method in estimation of the BV/TV value in cancellous bone.

Simultaneous realization of slow and fast acoustic waves using a fractal structure of Koch curve.

PubMed

Ding, Jin; Fan, Li; Zhang, Shu-Yi; Zhang, Hui; Yu, Wei-Wei

2018-01-24

An acoustic metamaterial based on a fractal structure, the Koch curve, is designed to simultaneously realize slow and fast acoustic waves. Owing to the multiple transmitting paths in the structure resembling the Koch curve, the acoustic waves travelling along different paths interfere with each other. Therefore, slow waves are created on the basis of the resonance of a Koch-curve-shaped loop, and meanwhile, fast waves even with negative group velocities are obtained due to the destructive interference of two acoustic waves with opposite phases. Thus, the transmission of acoustic wave can be freely manipulated with the Koch-curve shaped structure.

46 CFR 151.45-9 - Signals.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 5 2014-10-01 2014-10-01 false Signals. 151.45-9 Section 151.45-9 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES BARGES CARRYING BULK LIQUID HAZARDOUS MATERIAL CARGOES Operations § 151.45-9 Signals. While fast to a dock, a vessel during transfer of...

46 CFR 151.45-9 - Signals.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 5 2013-10-01 2013-10-01 false Signals. 151.45-9 Section 151.45-9 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES BARGES CARRYING BULK LIQUID HAZARDOUS MATERIAL CARGOES Operations § 151.45-9 Signals. While fast to a dock, a vessel during transfer of...

46 CFR 160.156-17 - Marking and labeling.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 6 2013-10-01 2013-10-01 false Marking and labeling. 160.156-17 Section 160.156-17 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Rescue Boats and Fast Rescue Boats (SOLAS) § 160.156-17 Marking...

46 CFR 151.45-9 - Signals.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 5 2011-10-01 2011-10-01 false Signals. 151.45-9 Section 151.45-9 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES BARGES CARRYING BULK LIQUID HAZARDOUS MATERIAL CARGOES Operations § 151.45-9 Signals. While fast to a dock, a vessel during transfer of...

46 CFR 160.156-17 - Marking and labeling.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 6 2014-10-01 2014-10-01 false Marking and labeling. 160.156-17 Section 160.156-17 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Rescue Boats and Fast Rescue Boats (SOLAS) § 160.156-17 Marking...

46 CFR 160.156-17 - Marking and labeling.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 6 2012-10-01 2012-10-01 false Marking and labeling. 160.156-17 Section 160.156-17 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Rescue Boats and Fast Rescue Boats (SOLAS) § 160.156-17 Marking...

46 CFR 151.45-9 - Signals.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 5 2012-10-01 2012-10-01 false Signals. 151.45-9 Section 151.45-9 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES BARGES CARRYING BULK LIQUID HAZARDOUS MATERIAL CARGOES Operations § 151.45-9 Signals. While fast to a dock, a vessel during transfer of...

Estimation of fast and slow wave properties in cancellous bone using Prony's method and curve fitting.

PubMed

Wear, Keith A

2013-04-01

The presence of two longitudinal waves in poroelastic media is predicted by Biot's theory and has been confirmed experimentally in through-transmission measurements in cancellous bone. Estimation of attenuation coefficients and velocities of the two waves is challenging when the two waves overlap in time. The modified least squares Prony's (MLSP) method in conjuction with curve-fitting (MLSP + CF) is tested using simulations based on published values for fast and slow wave attenuation coefficients and velocities in cancellous bone from several studies in bovine femur, human femur, and human calcaneus. The search algorithm is accelerated by exploiting correlations among search parameters. The performance of the algorithm is evaluated as a function of signal-to-noise ratio (SNR). For a typical experimental SNR (40 dB), the root-mean-square errors (RMSEs) for one example (human femur) with fast and slow waves separated by approximately half of a pulse duration were 1 m/s (slow wave velocity), 4 m/s (fast wave velocity), 0.4 dB/cm MHz (slow wave attenuation slope), and 1.7 dB/cm MHz (fast wave attenuation slope). The MLSP + CF method is fast (requiring less than 2 s at SNR = 40 dB on a consumer-grade notebook computer) and is flexible with respect to the functional form of the parametric model for the transmission coefficient. The MLSP + CF method provides sufficient accuracy and precision for many applications such that experimental error is a greater limiting factor than estimation error.

Ship-wave-shaped wave clouds induced by the Crozet Islands, south Indian Ocean

NASA Image and Video Library

2017-12-08

There are special places on Earth that sometimes write their personal signature in the clouds. The Crozet Islands are one such place, thanks to the tall volcanic peaks that grace the islands. When air flows around these tall peaks, it gets pushed around the islands as well as up and over the peak. The net effect of the flowing air flowing around the solid, tall peaks is much like the solid bow of a ship cutting through standing water. In each case v-shaped waves are formed behind the motion. In liquid, this is called a wake; in the atmosphere, when clouds are present or created, they are known as ship-wave-shaped clouds. The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra satellite captured this true-color image as it passed over the Crozet Islands on November 26, 2014. Three distinct waves are seen behind the three largest islands. From west to east these are Pig Island, Possession Island and East Island. Credit: NASA/GSFC/Jeff Schmaltz/MODIS Land Rapid Response Team NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Using dynamic interferometric synthetic aperature radar (InSAR) to image fast-moving surface waves

DOEpatents

Vincent, Paul

2005-06-28

A new differential technique and system for imaging dynamic (fast moving) surface waves using Dynamic Interferometric Synthetic Aperture Radar (InSAR) is introduced. This differential technique and system can sample the fast-moving surface displacement waves from a plurality of moving platform positions in either a repeat-pass single-antenna or a single-pass mode having a single-antenna dual-phase receiver or having dual physically separate antennas, and reconstruct a plurality of phase differentials from a plurality of platform positions to produce a series of desired interferometric images of the fast moving waves.

A Study of Stranding of Juvenile Salmon by Ship Wakes Along the Lower Columbia River Using a Before-and-After Design: Before-Phase Results

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

Pearson, Walter H.; Skalski, J R.; Sobocinski, Kathryn L.

2006-02-01

Ship wakes produced by deep-draft vessels transiting the lower Columbia River have been observed to cause stranding of juvenile salmon. Proposed deepening of the Columbia River navigation channel has raised concerns about the potential impact of the deepening project on juvenile salmon stranding. The Portland District of the U.S. Army Corps of Engineers requested that the Pacific Northwest National Laboratory design and conduct a study to assess stranding impacts that may be associated with channel deepening. The basic study design was a multivariate analysis of covariance of field observations and measurements under a statistical design for a before and aftermore » impact comparison. We have summarized field activities and statistical analyses for the ?before? component of the study here. Stranding occurred at all three sampling sites and during all three sampling seasons (Summer 2004, Winter 2005, and Spring 2005), for a total of 46 stranding events during 126 observed vessel passages. The highest occurrence of stranding occurred at Barlow Point, WA, where 53% of the observed events resulted in stranding. Other sites included Sauvie Island, OR (37%) and County Line Park, WA (15%). To develop an appropriate impact assessment model that accounted for relevant covariates, regression analyses were conducted to determine the relationships between stranding probability and other factors. Nineteen independent variables were considered as potential factors affecting the incidence of juvenile salmon stranding, including tidal stage, tidal height, river flow, current velocity, ship type, ship direction, ship condition (loaded/unloaded), ship speed, ship size, and a proxy variable for ship kinetic energy. In addition to the ambient and ship characteristics listed above, site, season, and fish density were also considered. Although no single factor appears as the primary factor for stranding, statistical analyses of the covariates resulted in the following equations: (1) Stranding Probability {approx} Location + Kinetic Energy Proxy + Tidal Height + Salmonid Density + Kinetic energy proxy ? Tidal Height + Tidal Height x Salmonid Density. (2) Stranding Probability {approx} Location + Total Wave Distance + Salmonid Density Index. (3) Log(Total Wave Height) {approx} Ship Block + Tidal Height + Location + Ship Speed. (4) Log(Total Wave Excursion Across the Beach) {approx} Location + Kinetic Energy Proxy + Tidal Height The above equations form the basis for a conceptual model of the factors leading to salmon stranding. The equations also form the basis for an approach for assessing impacts of dredging under the before/after study design.« less

A FAST PROPAGATING EXTREME-ULTRAVIOLET WAVE ASSOCIATED WITH A MINI-FILAMENT ERUPTION

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

Zheng Ruisheng; Jiang Yunchun; Yang Jiayan

The fast extreme-ultraviolet (EUV) waves (>1000 km s{sup -1}) in the solar corona were very rare in the past. Taking advantage of the high temporal and spatial resolution of the Solar Dynamics Observatory observations, we present a fast EUV wave associated with a mini-filament eruption, a C1.0 flare, and a coronal mass ejection (CME) on 2011 September 30. The event took place at the periphery between two active regions (ARs). The mini-filament rapidly erupted as a blowout jet associated with a flare and a CME. The CME front was likely developed from the large-scale overlying loops. The wave onset wasmore » nearly simultaneous with the start of the jet and the flare. The wave departed far from the flare center and showed a close location relative to the rapid jet. The wave had an initial speed of about 1100 km s{sup -1} and a slight deceleration in the last phase, and the velocity decreased to about 500 km s{sup -1}. The wave propagated in a narrow angle extent, likely to avoid the ARs on both sides. All the results provide evidence that the fast EUV wave was a fast-mode MHD wave. The wave resisted being driven by the CME, because it opened up the large-scale loops and its front likely formed later than the wave. The wave was most likely triggered by the jet, due to their close timing and location relations.« less

A review of potential tsunami impacts to the Suez Canal

NASA Astrophysics Data System (ADS)

Finkl, C.; Pelinovsky, E.

2012-04-01

Destructive tsunamis in the eastern Mediterranean and Red seas, induced by earthquakes and/or volcanic activity, pose potential hazards to docked seaport shipping and fixed harbor infrastructure as well as to in-transit international shipping within the Suez Canal. Potential vulnerabilities of the Suez Canal to possible tsunami impacts are reviewed by reference to geological, historical, archaeoseismological, and anecdotal data. Tsunami catalogues and databases compiled by earlier researchers are perused to estimate potential return periods for tsunami events that could affect directly the Suez Canal and its closely associated operational infrastructures. Analysis of these various records indicates a centurial return period, or multiples thereof, for long-wave repetition that could generally affect the Nile Delta. It is estimated that tsunami waves 2 m high would have a breaking length about 5 km down Canal whereas a 10 m wave break would occur about 1 km into the Canal. Should a tsunami strike the eastern flanks of the Nile Delta, it would damage Egypt's maritime infrastructure and multi-national commercial vessels and military ships then using the Canal.

Millimeter Wave Radar for Atmospheric Turbulence Characterization and Wind Profiling for Improved Naval Operations

DTIC Science & Technology

2016-12-29

airflows surrounding ships can be used to determine operational envelopes, more efficiently space incoming aircraft, and can be used in conjunction with...aircraft, and can be used in conjunction with simulations to inform and influence ship design. Another application is for high-energy laser propagation

46 CFR 45.187 - Weather limitations.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 2 2010-10-01 2010-10-01 false Weather limitations. 45.187 Section 45.187 Shipping... River Barges on Lake Michigan Routes § 45.187 Weather limitations. (a) Tows on the Burns Harbor route must operate during fair weather conditions only. (b) The weather limits (ice conditions, wave height...

46 CFR 45.187 - Weather limitations.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 2 2012-10-01 2012-10-01 false Weather limitations. 45.187 Section 45.187 Shipping... River Barges on Lake Michigan Routes § 45.187 Weather limitations. (a) Tows on the Burns Harbor route must operate during fair weather conditions only. (b) The weather limits (ice conditions, wave height...

46 CFR 45.187 - Weather limitations.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 2 2014-10-01 2014-10-01 false Weather limitations. 45.187 Section 45.187 Shipping... River Barges on Lake Michigan Routes § 45.187 Weather limitations. (a) Tows on the Burns Harbor route must operate during fair weather conditions only. (b) The weather limits (ice conditions, wave height...

46 CFR 45.187 - Weather limitations.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 2 2011-10-01 2011-10-01 false Weather limitations. 45.187 Section 45.187 Shipping... River Barges on Lake Michigan Routes § 45.187 Weather limitations. (a) Tows on the Burns Harbor route must operate during fair weather conditions only. (b) The weather limits (ice conditions, wave height...

46 CFR 45.187 - Weather limitations.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 2 2013-10-01 2013-10-01 false Weather limitations. 45.187 Section 45.187 Shipping... River Barges on Lake Michigan Routes § 45.187 Weather limitations. (a) Tows on the Burns Harbor route must operate during fair weather conditions only. (b) The weather limits (ice conditions, wave height...

Avoiding the parametric roll

NASA Astrophysics Data System (ADS)

Acomi, Nicoleta; Ancuţa, Cristian; Andrei, Cristian; Boştinǎ, Alina; Boştinǎ, Aurel

2016-12-01

Ships are mainly built to sail and transport cargo at sea. Environmental conditions and state of the sea are communicated to vessels through periodic weather forecasts. Despite officers being aware of the sea state, their sea time experience is a decisive factor when the vessel encounters severe environmental conditions. Another important factor is the loading condition of the vessel, which triggers different behaviour in similar marine environmental conditions. This paper aims to analyse the behaviour of a port container vessel in severe environmental conditions and to estimate the potential conditions of parametric roll resonance. Octopus software simulation is employed to simulate vessel motions under certain conditions of the sea, with possibility to analyse the behaviour of ships and the impact of high waves on ships due to specific wave encounter situations. The study should be regarded as a supporting tool during the decision making process.

Structural analysis of a ship on global aspect using ANSYS

NASA Astrophysics Data System (ADS)

Rahman, M. Muzibur; Kamol, Rajia Sultana; Islam, Reyana

2017-12-01

Ship is a complex geometry which undergoes a combination of loadings such as hydrostatic, hydrodynamic, wind, wave etc. at sea and thus adequate strength in a ship has always been one of the most challenging tasks for the ship designers. International Maritime Organization (IMO) and classification societies are providing the standards to ensure the adequacy of strength for the ship against all demands throughout its service life. Thus, structural analysis is needed to assess the overall strength of hull, and the means in this regard are based on finite element method which may be applied either local or global aspect of the ship. This paper is an attempt to carry out the structural analysis of a ship in global aspect using ANSYS software to locate the most stress concentration and deformed area, which will have ultimate effect on fatigue fracture.

Fast Ion and Thermal Plasma Transport in Turbulent Waves in the Large Plasma Device (LAPD)

NASA Astrophysics Data System (ADS)

Zhou, Shu

2011-10-01

The transport of fast ions and thermal plasmas in electrostatic microturbulence is studied. Strong density and potential fluctuations (δn / n ~ δϕ / kTe ~ 0 . 5 , f ~5-50 kHz) are observed in the LAPD in density gradient regions produced by obstacles with slab or cylindrical geometry. Wave characteristics and the associated plasma transport are modified by driving sheared E ×B drift through biasing the obstacle, and by modification of the axial magnetic fields (Bz) and the plasma species. Cross-field plasma transport is suppressed with small bias and large Bz, and is enhanced with large bias and small Bz. Suppressed cross-field thermal transport coincides with a 180° phase shift between the density and potential fluctuations in the radial direction, while the enhanced thermal transport is associated with modes having low mode number (m = 1) and long radial correlation length. Large gyroradius lithium ions (ρfast /ρs ~ 10) orbit through the turbulent region. Scans with a collimated analyzer and with Langmuir probes give detailed profiles of the fast ion spatial-temporal distribution and of the fluctuating fields. Fast-ion transport decreases rapidly with increasing fast-ion gyroradius. Background waves with different scale lengths also alter the fast ion transport: Beam diffusion is smaller in waves with smaller structures (higher mode number); also, coherent waves with long correlation length cause less beam diffusion than turbulent waves. Experimental results agree well with gyro-averaging theory. When the fast ion interacts with the wave for most of a wave period, a transition from super-diffusive to sub-diffusive transport is observed, as predicted by diffusion theory. A Monte Carlo trajectory-following code simulates the interaction of the fast ions with the measured turbulent fields. Good agreement between observation and modeling is observed. Work funded by DOE and NSF and performed at the Basic Plasma Science Facility.

STS-54 Earth observation of a ship wake in the Bay of Bengal

NASA Image and Video Library

1993-01-19

STS054-72-056 (13-19 Jan 1993) --- A ship wake in the Bay of Bengal is noticeable in this 70mm frame. The sun glint pattern on the ocean reveals many patterns of sea surface roughness related to currents, waves, wind roughening, and biology that and are not apparent when the ocean is viewed away from the Sun's reflection. In this view of the Bay of Bengal, southeast of Madras, India, sun glint highlights convergence zones between ocean currents (bright, linear features), a eddy, and the wake of a ship. In several locations where the ship has passed areas of current shear, the ship wake is distorted, indicating the relative current direction.

STS-54 Earth observation of a ship wake in the Bay of Bengal

NASA Technical Reports Server (NTRS)

1993-01-01

STS-54 Earth observation taken aboard Endeavour, Orbiter Vehicle (OV) 105, is of a ship wake in the Bay of Bengal. The sun glint pattern on the ocean reveals many patterns of sea surface roughness related to currents, waves, wind roughening, and biology that and are not apparent when the ocean is viewed away from the sun's reflection. In this view of the Bay of Bengal, southeast of Madras, India, sun glint highlights convergence zones between ocean currents (bright, linear features), a eddy, and the wake of a ship. In several locations where the ship has passed areas of current shear, the ship wake is distorted, indicating the relative current direction.

User Manual for Program SCOMOT Second Part of U.S.C.G. Ship Motion Program.

DTIC Science & Technology

1981-02-01

wave angle, etc. - 52 - Entry 8 - Jl - First Index Number First index for motion calculation using coordinate points or moment and force calculations using...162.4 .6500 .5434 .2942 179.8 .6786 170.0 1.0258 161.8 1.4070 144.3 .7000 .4686 .1774 179.6 .5946 167.1 1.0292 154.8 1.2598 110.5 .7500 .4082 . 0786 ...SHIP MOTION PROGRAM 77.1 02/24/81 05.49.12 PAGE 52 SL-7 - NORMAL FULL LOAD DEPARTURE SPEED = 25.000 KNOTS REGULAR WAVE LATERAL BENDING MOMENT AT STATION

Lamb wave detection of limpet mines on ship hulls.

PubMed

Bingham, Jill; Hinders, Mark; Friedman, Adam

2009-12-01

This paper describes the use of ultrasonic guided waves for identifying the mass loading due to underwater limpet mines on ship hulls. The Dynamic Wavelet Fingerprint Technique (DFWT) is used to render the guided wave mode information in two-dimensional binary images because the waveform features of interest are too subtle to identify in time domain. The use of wavelets allows both time and scale features from the original signals to be retained, and image processing can be used to automatically extract features that correspond to the arrival times of the guided wave modes. For further understanding of how the guided wave modes propagate through the real structures, a parallel processing, 3D elastic wave simulation is developed using the finite integration technique (EFIT). This full field, technique models situations that are too complex for analytical solutions, such as built up 3D structures. The simulations have produced informative visualizations of the guided wave modes in the structures as well as mimicking directly the output from sensors placed in the simulation space for direct comparison to experiments. Results from both drydock and in-water experiments with dummy mines are also shown.

Helioseismic Implications of Mode Conversion

NASA Astrophysics Data System (ADS)

Moradi, H.; Cally, P. S.

2013-12-01

The Sun leaks waves through its active regions. The leakage of acoustic waves into the atmosphere through these ‘magnetoacoustic portals’ is well known, but magnetic (fast) waves also enter the atmosphere there. Fast waves ultimately reflect because of the increase in Alfvén speed with height, but when they do so they can partially convert to Alfvén waves. The weakened fast waves then re-enter the interior, to rejoin the seismic p-mode field. But how has the Alfvénic loss they suffered affected the seismology? We present results from simulations that compare Alfvénic losses with travel-time shifts, and draw general conclusions about the role of active region atmospheres in local helioseismology.

Fast-to-Alfvén Mode Conversion in the Presence of Ambipolar Diffusion

NASA Astrophysics Data System (ADS)

Cally, Paul S.; Khomenko, Elena

2018-03-01

It is known that fast magnetohydrodynamic waves partially convert to upward and/or downward propagating Alfvén waves in a stratified atmosphere where Alfvén speed increases with height. This happens around the fast wave reflection height, where the fast wave’s horizontal phase speed equals the Alfvén speed (in a low-β plasma). Typically, this takes place in the mid to upper solar chromosphere for low-frequency waves in the few-millihertz band. However, this region is weakly ionized and thus susceptible to nonideal MHD processes. In this article, we explore how ambipolar diffusion in a zero-β plasma affects fast waves injected from below. Classical ambipolar diffusion is far too weak to have any significant influence at these low frequencies, but if enhanced by turbulence (in the quiet-Sun chromosphere but not in sunspot umbrae) or the production of sufficiently small-scale structure, can substantially absorb waves for turbulent ambipolar Reynolds numbers of around 20 or less. In that case, it is found that the mode conversion process is not qualitatively altered from the ideal case, though conversion to Alfvén waves is reduced because the fast wave flux reaching the conversion region is degraded. It is also found that any upward propagating Alfvén waves generated in this process are almost immune to further ambipolar attenuation, thereby reducing local ambipolar heating compared to cases without mode conversion. In that sense, mode conversion provides a form of “Alfvén cooling.”

46 CFR 160.156-23 - Procedure for approval of design, material, or construction change.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 6 2013-10-01 2013-10-01 false Procedure for approval of design, material, or construction change. 160.156-23 Section 160.156-23 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Rescue Boats and Fast Rescue Boats (SOLAS) § 160.156...

46 CFR 160.156-23 - Procedure for approval of design, material, or construction change.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 6 2014-10-01 2014-10-01 false Procedure for approval of design, material, or construction change. 160.156-23 Section 160.156-23 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Rescue Boats and Fast Rescue Boats (SOLAS) § 160.156...

Modeling of Synergy Between 4th and 6th Harmonic Absorptions of Fast Waves on Injected Beams in DIII-D Tokamak

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

Choi, M.; Pinsker, R. I.; Chan, V. S.

2011-12-23

In recent moderate to high harmonic fast wave heating and current drive experiments in DIII-D, a synergy effect was observed when the 6{sup th} harmonic 90 MHz fast wave power is applied to the plasma preheated by neutral beams and the 4{sup th} harmonic 60 MHz fast wave. In this paper, we investigate how the synergy can occur using ORBIT-RF coupled with AORSA. Preliminary simulations suggest that damping of 4{sup th} harmonic FW on beam ions accelerates them above the injection energy, which may allow significant damping of 6{sup th} harmonic FW on beam ion tails to produce synergy.

Edge loss of high-harmonic fast-wave heating power in NSTX: a cylindrical model

DOE PAGES

Perkins, R. J.; Hosea, J. C.; Bertelli, N.; ...

2017-09-04

Efficient high-harmonic fast-wave (HHFW) heating in the National Spherical Torus Experiment Upgrade (NSTX-U) would facilitate experiments in turbulence, transport, fast-ion studies, and more. However, previous HHFW operation in NSTX exhibited a large loss of fast-wave power to the divertor along the scrape-off layer field lines for edge densities above the fast-wave cutoff. It was postulated that the wave amplitude is enhanced in the scrapeoff layer due to cavity-like modes, and that these enhanced fields drive sheath losses through RF rectification. As part of ongoing work to confirm this hypothesis, we have developed a cylindrical cold-plasma model to identify and understandmore » scenarios where a substantial fraction of wave power is confined to the plasma periphery. We previously identified a peculiar class of modes, named annulus resonances, that conduct approximately half of their wave power in the periphery and can also account for a significant fraction of the total wave power. Here, we study the influence of annulus resonances on wave field reconstructions and find instances where annulus-resonant modes dominate the spectrum and trap over half of the total wave power at the edge. The work is part of an ongoing effort to determine the mechanism underlying these scrape-off layer losses in NSTX, identify optimal conditions for operation in NSTX-U, and predict whether similar losses occur for the ion-cyclotron minority heating scheme for both current experiments and future devices such as ITER.« less

Edge loss of high-harmonic fast-wave heating power in NSTX: a cylindrical model

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

Perkins, R. J.; Hosea, J. C.; Bertelli, N.

Efficient high-harmonic fast-wave (HHFW) heating in the National Spherical Torus Experiment Upgrade (NSTX-U) would facilitate experiments in turbulence, transport, fast-ion studies, and more. However, previous HHFW operation in NSTX exhibited a large loss of fast-wave power to the divertor along the scrape-off layer field lines for edge densities above the fast-wave cutoff. It was postulated that the wave amplitude is enhanced in the scrapeoff layer due to cavity-like modes, and that these enhanced fields drive sheath losses through RF rectification. As part of ongoing work to confirm this hypothesis, we have developed a cylindrical cold-plasma model to identify and understandmore » scenarios where a substantial fraction of wave power is confined to the plasma periphery. We previously identified a peculiar class of modes, named annulus resonances, that conduct approximately half of their wave power in the periphery and can also account for a significant fraction of the total wave power. Here, we study the influence of annulus resonances on wave field reconstructions and find instances where annulus-resonant modes dominate the spectrum and trap over half of the total wave power at the edge. The work is part of an ongoing effort to determine the mechanism underlying these scrape-off layer losses in NSTX, identify optimal conditions for operation in NSTX-U, and predict whether similar losses occur for the ion-cyclotron minority heating scheme for both current experiments and future devices such as ITER.« less

VISIR-I: small vessels - least-time nautical routes using wave forecasts

NASA Astrophysics Data System (ADS)

Mannarini, Gianandrea; Pinardi, Nadia; Coppini, Giovanni; Oddo, Paolo; Iafrati, Alessandro

2016-05-01

A new numerical model for the on-demand computation of optimal ship routes based on sea-state forecasts has been developed. The model, named VISIR (discoVerIng Safe and effIcient Routes) is designed to support decision-makers when planning a marine voyage. The first version of the system, VISIR-I, considers medium and small motor vessels with lengths of up to a few tens of metres and a displacement hull. The model is comprised of three components: a route optimization algorithm, a mechanical model of the ship, and a processor of the environmental fields. The optimization algorithm is based on a graph-search method with time-dependent edge weights. The algorithm is also able to compute a voluntary ship speed reduction. The ship model accounts for calm water and added wave resistance by making use of just the principal particulars of the vessel as input parameters. It also checks the optimal route for parametric roll, pure loss of stability, and surfriding/broaching-to hazard conditions. The processor of the environmental fields employs significant wave height, wave spectrum peak period, and wave direction forecast fields as input. The topological issues of coastal navigation (islands, peninsulas, narrow passages) are addressed. Examples of VISIR-I routes in the Mediterranean Sea are provided. The optimal route may be longer in terms of miles sailed and yet it is faster and safer than the geodetic route between the same departure and arrival locations. Time savings up to 2.7 % and route lengthening up to 3.2 % are found for the case studies analysed. However, there is no upper bound for the magnitude of the changes of such route metrics, which especially in case of extreme sea states can be much greater. Route diversions result from the safety constraints and the fact that the algorithm takes into account the full temporal evolution and spatial variability of the environmental fields.

Nonlinear excitation of fast magnetosonic waves via quasi-electrostatic whistler wave mixing

NASA Astrophysics Data System (ADS)

Zechar, Nathan; Sotnikov, Vladimir; Caplinger, James; Chu, Arthur

2017-10-01

We report on experiments of nonlinear simultaneous generation of low frequency fast magnetosonic waves and electromagnetic whistler waves using two loop antennas in the afterglow of a cold magnetized helium plasma. The exciting antennas each have a frequency that is below half the electron cyclotron frequency, and the difference between the two is just below the lower hybrid frequency. They both directly excite whistler waves, however their nonlinear interaction excite the low frequency fast magnetosonic waves at the frequency given by their difference. Plasma is generated using a helicon plasma source in a one meter length cylindrical chamber. The spatial and temporal data of the electromagnetic and electrostatic components of the plasma waves are then captured with developed diagnostic techniques. Wave spectra, general structure and time domain frequencies observed will be reported.

Heating a plasma by a broadband stream of fast electrons: Fast ignition, shock ignition, and Gbar shock wave applications

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

Gus’kov, S. Yu., E-mail: guskov@sci.lebedev.ru; Nicolai, Ph.; Ribeyre, X.

2015-09-15

An exact analytic solution is found for the steady-state distribution function of fast electrons with an arbitrary initial spectrum irradiating a planar low-Z plasma with an arbitrary density distribution. The solution is applied to study the heating of a material by fast electrons of different spectra such as a monoenergetic spectrum, a step-like distribution in a given energy range, and a Maxwellian spectrum, which is inherent in laser-produced fast electrons. The heating of shock- and fast-ignited precompressed inertial confinement fusion (ICF) targets as well as the heating of a target designed to generate a Gbar shock wave for equation ofmore » state (EOS) experiments by laser-produced fast electrons with a Maxwellian spectrum is investigated. A relation is established between the energies of two groups of Maxwellian fast electrons, which are responsible for generation of a shock wave and heating the upstream material (preheating). The minimum energy of the fast and shock igniting beams as well as of the beam for a Gbar shock wave generation increases with the spectral width of the electron distribution.« less

Modeling Water Waves with Smoothed Particle Hydrodynamics

DTIC Science & Technology

2011-09-30

Lagrangian nature of SPH allows the modeling of wave breaking, surf zones, ship waves, and wave-structure interaction, where the free surface becomes...particle detection--To study free surface flows and analyze their complex deformations, we need to know which particles are located on the free surface ...Hydrodynamics is proving to be a competent modeling scheme for free surface flows in two and three dimensions. As the GPU hardware improves, it is

Spatial patterns of fasting and fed antropyloric pressure waves in humans.

PubMed Central

Sun, W M; Hebbard, G S; Malbert, C H; Jones, K L; Doran, S; Horowitz, M; Dent, J

1997-01-01

1. Gastric mechanics were investigated by categorizing the temporal and spatial patterning of pressure waves associated with individual gastric contractions. 2. In twelve healthy volunteers, intraluminal pressures were monitored from nine side hole recording points spaced at 1.5 cm intervals along the antrum, pylorus and duodenum. 3. Pressure wave sequences that occurred during phase II fasting contractions (n = 221) and after food (n = 778) were evaluated. 4. The most common pattern of pressure wave onset along the antrum was a variable combination of antegrade, synchronous and retrograde propagation between side hole pairs. This variable pattern accounted for 42% of sequences after food, and 34% during fasting (P < 0.05). Other common pressure wave sequence patterns were: purely antegrade-29% after food and 42% during fasting (P < 0.05); purely synchronous-23% fed and 17% fasting; and purely retrograde-6% fed and 8% fasting. The length of sequences was shorter after food (P < 0.05). Some sequences 'skipped' individual recording points. 5. The spatial patterning of gastric pressure wave sequences is diverse, and may explain the differing mechanical outcomes among individual gastric contractions. 6. Better understanding of gastric mechanics may be gained from temporally precise correlations of luminal flows and pressures and gastric wall motion during individual gastric contraction sequences. PMID:9306286

Observational and Dynamical Wave Climatologies. VOS vs Satellite Data

NASA Astrophysics Data System (ADS)

Grigorieva, Victoria; Badulin, Sergei; Chernyshova, Anna

2013-04-01

The understanding physics of wind-driven waves is crucially important for fundamental science and practical applications. This is why experimental efforts are targeted at both getting reliable information on sea state and elaborating effective tools of the sea wave forecasting. The global Visual Wave Observations and satellite data from the GLOBWAVE project of the European Space Agency are analyzed in the context of these two viewpoints. Within the first "observational" aspect we re-analyze conventional climatologies of all basic wave parameters for the last decades [5]. An alternative "dynamical" climatology is introduced as a tool of prediction of dynamical features of sea waves on global scales. The features of wave dynamics are studied in terms of one-parametric dependencies of wave heights on wave periods following the theoretical concept of self-similar wind-driven seas [3, 1, 4] and recently proposed approach to analysis of Voluntary Observing Ship (VOS) data [2]. Traditional "observational" climatologies based on VOS and satellite data collections demonstrate extremely consistent pictures for significant wave heights and dominant periods. On the other hand, collocated satellite and VOS data show significant differences in wave heights, wind speeds and, especially, in wave periods. Uncertainties of visual wave observations can explain these differences only partially. We see the key reason of this inconsistency in the methods of satellite data processing which are based on formal application of data interpolation methods rather than on up-to-date physics of wind-driven waves. The problem is considered within the alternative climatology approach where dynamical criteria of wave height-to-period linkage are used for retrieving wave periods and constructing physically consistent dynamical climatology. The key dynamical parameter - exponent R of one-parametric dependence Hs ~ TR shows dramatically less pronounced latitudinal dependence as compared to observed Hs and T of conventional climatology in both satellite and VOS data collections. It can be treated as an effect of interaction of wind-driven seas and swell on global scales as it was stated in [2]. Further study combining the alternative and conventional climatologies can help to detail this important dynamical effect of global wave dynamics. The progress in satellite data processing and their physical interpretation is of great value for such study. The work was supported by Russian Foundation for Basic Research grant 11-05-01114-a and the Russian government contracts No.11.G34.31.0035, No.11.G34.31.0078. References [1] S. I. Badulin, A. V. Babanin, D. Resio, and V. Zakharov. Weakly turbulent laws of wind-wave growth. J. Fluid Mech., 591:339-378, 2007. [2] S. I. Badulin and Grigorieva V. G. On discriminating swell and wind-driven seas in voluntary observing ship data. J. Geophys. Res., 117(C00J29), 2012. [3] S. I. Badulin, A. N. Pushkarev, D. Resio, and V. E. Zakharov. Self-similarity of wind-driven seas. Nonl. Proc. Geophys., 12:891-946, 2005. [4] E. Gagnaire-Renou, M. Benoit, and S. I. Badulin. On weakly turbulent scaling of wind sea in simulations of fetch-limited growth. J. Fluid Mech., 669:178-213, 2011. [5] S. K. Gulev, V. Grigorieva, A. Sterl, and D. Woolf. Assessment for the reliability of wave observations from voluntary observing ships: insights from the validation of a global wind wave climatology based on voluntary observing ship data. J. Geophys. Res. - Oceans, 108(C7):3236, doi:10,1029/2002JC001437, 2003.

Waves and Water Beetles

ERIC Educational Resources Information Center

Tucker, Vance A.

1971-01-01

Capillary and gravity water waves are related to the position, wavelength, and velocity of an object in flowing water. Water patterns are presented for ships and the whirling beetle with an explanation of how the design affects the objects velocity and the observed water wavelengths. (DS)

A Fully Nonlinear, Dynamically Consistent Numerical Model for Solid-Body Ship Motion. I. Ship Motion with Fixed Heading

NASA Technical Reports Server (NTRS)

Lin, Ray-Quing; Kuang, Weijia

2011-01-01

In this paper, we describe the details of our numerical model for simulating ship solidbody motion in a given environment. In this model, the fully nonlinear dynamical equations governing the time-varying solid-body ship motion under the forces arising from ship wave interactions are solved with given initial conditions. The net force and moment (torque) on the ship body are directly calculated via integration of the hydrodynamic pressure over the wetted surface and the buoyancy effect from the underwater volume of the actual ship hull with a hybrid finite-difference/finite-element method. Neither empirical nor free parametrization is introduced in this model, i.e. no a priori experimental data are needed for modelling. This model is benchmarked with many experiments of various ship hulls for heave, roll and pitch motion. In addition to the benchmark cases, numerical experiments are also carried out for strongly nonlinear ship motion with a fixed heading. These new cases demonstrate clearly the importance of nonlinearities in ship motion modelling.

An Adaptive Ship Detection Scheme for Spaceborne SAR Imagery

PubMed Central

Leng, Xiangguang; Ji, Kefeng; Zhou, Shilin; Xing, Xiangwei; Zou, Huanxin

2016-01-01

With the rapid development of spaceborne synthetic aperture radar (SAR) and the increasing need of ship detection, research on adaptive ship detection in spaceborne SAR imagery is of great importance. Focusing on practical problems of ship detection, this paper presents a highly adaptive ship detection scheme for spaceborne SAR imagery. It is able to process a wide range of sensors, imaging modes and resolutions. Two main stages are identified in this paper, namely: ship candidate detection and ship discrimination. Firstly, this paper proposes an adaptive land masking method using ship size and pixel size. Secondly, taking into account the imaging mode, incidence angle, and polarization channel of SAR imagery, it implements adaptive ship candidate detection in spaceborne SAR imagery by applying different strategies to different resolution SAR images. Finally, aiming at different types of typical false alarms, this paper proposes a comprehensive ship discrimination method in spaceborne SAR imagery based on confidence level and complexity analysis. Experimental results based on RADARSAT-1, RADARSAT-2, TerraSAR-X, RS-1, and RS-3 images demonstrate that the adaptive scheme proposed in this paper is able to detect ship targets in a fast, efficient and robust way. PMID:27563902

Sensitivity of wave propagation in the LHRF to initial poloidal position in finite-aspect-ratio toroidal plasmas

NASA Astrophysics Data System (ADS)

Larson, J. J.; Pinsker, R. I.; Bonoli, P. T.; Porkolab, M.

2017-10-01

The important effect of varying the initial poloidal wave-launching location to the core accessibility of lower hybrid slow waves in a torus of finite aspect ratio has been understood for many years. Since the qualitative properties of the wave propagation of the other branch in this regime, known as the `whistler', `helicon' or simply the `fast wave', are similar in some ways to those of the slow wave, we expect a dependence on launch position for this wave also. We study this problem for both slow and fast waves, first with simplified analytic models and then using the ray-tracing code GENRAY for realistic plasma equilibria. We assess the prospects of inside, top, bottom or conventional outside launch of waves on each of the two branches. Although the slow wave has been the focus of research for LHRF heating and current drive in the past, the fast wave will play a major role in burning plasmas beyond ITER where Te(0) = 10-20 keV. The stronger electron Landau damping of the slow wave will restrict the power deposition to the outer third of the plasma, while the fast wave's weaker damping allows the wave to penetrate to the hot plasma core before depositing its power. Work supported in part by US DoE under the Science Undergraduate Laboratory Internship (SULI) program and under DE-FC02-04ER54698 and DE-FG02-91-ER54109.

Fast flows, ULF waves, firehose instability and their association in the Earth's mid-tail current sheet

NASA Astrophysics Data System (ADS)

Wang, C. P.; Xing, X.

2017-12-01

Ultra-Low Frequency (ULF) plasma waves with frequency range between 1 mHz to 10 Hz are widely observed in the Earth's magnetosphere and on the ground. In particular, Pi2 and Pc4 waves have been found to be closely related to many important dynamic processes in the magnetotail, e.g., fast flows (V > 300 km/s). Observations have shown Pi2 waves in association with fast flows in the near-Earth plasma sheet (X>-30 RE). However, in the mid-tail region, where fast flows are more frequently observed than those in the near-Earth magnetotail, this association has not been evaluated. Our preliminary study using ARTEMIS probes in the mid-tail region (X -60 RE) shows close association between Pi2 and Pc4 waves with the presence of fast flows. Strong connection between mid-tail Pi2 pulsations and high-latitude ground Pi2 signatures are also observed. Among many proposed theories for Pi2 wave, ballooning and firehose instabilities are plausible mechanisms in leading to the generation of plasma waves around Pi2 frequency band. Ballooning instability is widely admitted for fast flow associated Pi2 pulsations in the near-Earth region. However, firehose instability is expected to occur more easily in mid-tail and beyond due to the specific pressure anisotropy in that region. We examined the pressure anisotropy conditions and evaluated firehose instability condition for both Pi2 and Pc4 events in mid-tail. It is found that the plasma is unstable against firehose instability in association with the initiation of Pi2 and Pc4 waves. These may suggest that firehose instability can be a wave generation mechanism in the mid-tail region.

EVOLUTION OF FAST MAGNETOACOUSTIC PULSES IN RANDOMLY STRUCTURED CORONAL PLASMAS

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

Yuan, D.; Li, B.; Pascoe, D. J.

2015-02-01

We investigate the evolution of fast magnetoacoustic pulses in randomly structured plasmas, in the context of large-scale propagating waves in the solar atmosphere. We perform one-dimensional numerical simulations of fast wave pulses propagating perpendicular to a constant magnetic field in a low-β plasma with a random density profile across the field. Both linear and nonlinear regimes are considered. We study how the evolution of the pulse amplitude and width depends on their initial values and the parameters of the random structuring. Acting as a dispersive medium, a randomly structured plasma causes amplitude attenuation and width broadening of the fast wavemore » pulses. After the passage of the main pulse, secondary propagating and standing fast waves appear. Width evolution of both linear and nonlinear pulses can be well approximated by linear functions; however, narrow pulses may have zero or negative broadening. This arises because narrow pulses are prone to splitting, while broad pulses usually deviate less from their initial Gaussian shape and form ripple structures on top of the main pulse. Linear pulses decay at an almost constant rate, while nonlinear pulses decay exponentially. A pulse interacts most efficiently with a random medium with a correlation length of about half of the initial pulse width. This detailed model of fast wave pulses propagating in highly structured media substantiates the interpretation of EIT waves as fast magnetoacoustic waves. Evolution of a fast pulse provides us with a novel method to diagnose the sub-resolution filamentation of the solar atmosphere.« less

Bayesian hierarchical modelling of North Atlantic windiness

NASA Astrophysics Data System (ADS)

Vanem, E.; Breivik, O. N.

2013-03-01

Extreme weather conditions represent serious natural hazards to ship operations and may be the direct cause or contributing factor to maritime accidents. Such severe environmental conditions can be taken into account in ship design and operational windows can be defined that limits hazardous operations to less extreme conditions. Nevertheless, possible changes in the statistics of extreme weather conditions, possibly due to anthropogenic climate change, represent an additional hazard to ship operations that is less straightforward to account for in a consistent way. Obviously, there are large uncertainties as to how future climate change will affect the extreme weather conditions at sea and there is a need for stochastic models that can describe the variability in both space and time at various scales of the environmental conditions. Previously, Bayesian hierarchical space-time models have been developed to describe the variability and complex dependence structures of significant wave height in space and time. These models were found to perform reasonably well and provided some interesting results, in particular, pertaining to long-term trends in the wave climate. In this paper, a similar framework is applied to oceanic windiness and the spatial and temporal variability of the 10-m wind speed over an area in the North Atlantic ocean is investigated. When the results from the model for North Atlantic windiness is compared to the results for significant wave height over the same area, it is interesting to observe that whereas an increasing trend in significant wave height was identified, no statistically significant long-term trend was estimated in windiness. This may indicate that the increase in significant wave height is not due to an increase in locally generated wind waves, but rather to increased swell. This observation is also consistent with studies that have suggested a poleward shift of the main storm tracks.

Interaction between high harmonic fast waves and fast ions in NSTX/NSTX-U plasmas

NASA Astrophysics Data System (ADS)

Bertelli, N.; Valeo, E. J.; Gorelenkova, M.; Green, D. L.; RF SciDAC Team

2016-10-01

Fast wave (FW) heating in the ion cyclotron range of frequency (ICRF) has been successfully used to sustain and control the fusion plasma performance, and it will likely play an important role in the ITER experiment. As demonstrated in the NSTX and DIII-D experiments the interactions between fast waves and fast ions can be so strong to significantly modify the fast ion population from neutral beam injection. In fact, it has been recently found in NSTX that FWs can modify and, under certain conditions, even suppress the energetic particle driven instabilities, such as toroidal Alfvén eigenmodes and global Alfvén eigenmodes and fishbones. This paper examines such interactions in NSTX/NSTX-U plasmas by using the recent extension of the RF full-wave code TORIC to include non-Maxwellian ions distribution functions. Particular attention is given to the evolution of the fast ions distribution function w/ and w/o RF. Tests on the RF kick-operator implemented in the Monte-Carlo particle code NUBEAM is also discussed in order to move towards a self consistent evaluation of the RF wave-field and the ion distribution functions in the TRANSP code. Work supported by US DOE Contract DE-AC02-09CH11466.

Examples of, reasons for, and consequences of the poor quality of wind data from ships for the marine boundary layer: Implications for remote sensing

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

Pierson, W.J. Jr.

1990-08-15

Wind reports by data buoys are used to demonstrate that these reports have in the past provided useful values for the synoptic scale winds and that at present these reports provide very reliable values for the synoptic scale winds. Past studies of wind reports by ships have revealed that the data are of poor quality, but the causes for this poor quality are not identified. Examples of the poor quality of wind data from ships are obtained by comparing ship reports with buoy reports and comparing reports of different kinds of ships with each other. These comparisons identify many differentmore » reasons for the poor quality of wind data from ships. Suggestions are made for improving the quality of ship data. The consequences of the poor quality of ship winds are described in terms of the effects on weather and wave forecasts. The implications for remotely sensed winds are discussed.« less

The Origin of Compressible Magnetic Turbulence in the Very Local Interstellar Medium

NASA Astrophysics Data System (ADS)

Zank, G. P.; Du, S.; Hunana, P.

2017-06-01

Voyager 1 observed compressible magnetic turbulence in the very local interstellar medium (VLISM). We show that inner heliosheath (IHS) fast- and slow-mode waves incident on the heliopause (HP) generate VLISM fast-mode waves only that propagate into the VLISM. We suggest that this is the origin of compressible turbulence in the VLISM. We show that fast- and slow-mode waves transmitted across a tangential discontinuity such as the HP are strongly refracted on crossing the HP and subsequently propagate at highly oblique angles to the VLISM magnetic field. Thus, fast-mode waves in the VLISM contribute primarily to the compressible and not the transverse components of the VLISM fluctuating magnetic field variance < δ {\\hat{B}}2> since < δ {\\hat{B}}{fz}2> \

ICRF fast wave current drive and mode conversion current drive in EAST tokamak

NASA Astrophysics Data System (ADS)

Yin, L.; Yang, C.; Gong, X. Y.; Lu, X. Q.; Du, D.; Chen, Y.

2017-10-01

Fast wave in the ion-cyclotron resonance frequency (ICRF) range is a promising candidate for non-inductive current drive (CD), which is essential for long pulse and high performance operation of tokamaks. A numerical study on the ICRF fast wave current drive (FWCD) and mode-conversion current drive (MCCD) in the Experimental Advanced Superconducting Tokamak (EAST) is carried out by means of the coupled full wave and Ehst-Karney parameterization methods. The results show that FWCD efficiency is notable in two frequency regimes, i.e., f ≥ 85 MHz and f = 50-65 MHz, where ion cyclotron absorption is effectively avoided, and the maximum on-axis driven current per unit power can reach 120 kA/MW. The sensitivity of the CD efficiency to the minority ion concentration is confirmed, owing to fast wave mode conversion, and the peak MCCD efficiency is reached for 22% minority-ion concentration. The effects of the wave-launch position and the toroidal wavenumber on the efficiency of current drive are also investigated.

U.S. Navy Shipboard Damage Control: Innovation and Implementation During the Interwar Period

DTIC Science & Technology

2014-12-12

commander of the Emden put his ship at a coral reef under full steam, and yet the inner structure stood firm. It was astounding what out ships could...The Turbulent then disappeared under the waves . At 3:55 Admiral Hipper announced that the Derfflinger and the Von der Tann could not fire except with...

Thermal plasma and fast ion transport in electrostatic turbulence in the large plasma devicea)

NASA Astrophysics Data System (ADS)

Zhou, Shu; Heidbrink, W. W.; Boehmer, H.; McWilliams, R.; Carter, T. A.; Vincena, S.; Tripathi, S. K. P.; Van Compernolle, B.

2012-05-01

The transport of thermal plasma and fast ions in electrostatic microturbulence is studied. Strong density and potential fluctuations (δn /n˜δφ/kTe ˜ 0.5, f ˜ 5-50 kHz) are observed in the large plasma device (LAPD) [W. Gekelman, H. Pfister, Z. Lucky et al., Rev. Sci. Instrum. 62, 2875 (1991)] in density gradient regions produced by obstacles with slab or cylindrical geometry. Wave characteristics and the associated plasma transport are modified by driving sheared E × B drift through biasing the obstacle and by modification of the axial magnetic fields (Bz) and the plasma species. Cross-field plasma transport is suppressed with small bias and large Bz and is enhanced with large bias and small Bz. The transition in thermal plasma confinement is well explained by the cross-phase between density and potential fluctuations. Large gyroradius lithium fast ion beam (ρfast/ρs ˜ 10) orbits through the turbulent region. Scans with a collimated analyzer give detailed profiles of the fast ion spatial-temporal distribution. Fast-ion transport decreases rapidly with increasing fast-ion energy and gyroradius. Background waves with different scale lengths also alter the fast ion transport. Experimental results agree well with gyro-averaging theory. When the fast ion interacts with the wave for most of a wave period, a transition from super-diffusive to sub-diffusive transport is observed, as predicted by diffusion theory. Besides turbulent-wave-induced fast-ion transport, the static radial electric field (Er) from biasing the obstacle leads to drift of the fast-ion beam centroid. The drift and broadening of the beam due to static Er are evaluated both analytically and numerically. Simulation results indicate that the Er induced transport is predominately convective.

Changes in the Arctic: Background and Issues for Congress

DTIC Science & Technology

2014-03-28

within the population more suited to the changed environment) may not be able to occur fast enough, leaving migration and death as the only options...species in an ecosystem (e.g., host plants might not move north (or up) as fast as their moth herbivores, nor as fast as the birds that depend on the...services in the resource-rich region that is opening up fast to shipping, energy and mining companies, Canadian experts said on Monday [May 13].... “It

Fast Shear Compounding Using Robust Two-dimensional Shear Wave Speed Calculation and Multi-directional Filtering

PubMed Central

Song, Pengfei; Manduca, Armando; Zhao, Heng; Urban, Matthew W.; Greenleaf, James F.; Chen, Shigao

2014-01-01

A fast shear compounding method was developed in this study using only one shear wave push-detect cycle, such that the shear wave imaging frame rate is preserved and motion artifacts are minimized. The proposed method is composed of the following steps: 1. applying a comb-push to produce multiple differently angled shear waves at different spatial locations simultaneously; 2. decomposing the complex shear wave field into individual shear wave fields with differently oriented shear waves using a multi-directional filter; 3. using a robust two-dimensional (2D) shear wave speed calculation to reconstruct 2D shear elasticity maps from each filter direction; 4. compounding these 2D maps from different directions into a final map. An inclusion phantom study showed that the fast shear compounding method could achieve comparable performance to conventional shear compounding without sacrificing the imaging frame rate. A multi-inclusion phantom experiment showed that the fast shear compounding method could provide a full field-of-view (FOV), 2D, and compounded shear elasticity map with three types of inclusions clearly resolved and stiffness measurements showing excellent agreement to the nominal values. PMID:24613636

Two dimensional cylindrical fast magnetoacoustic solitary waves in a dust plasma

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

Liu Haifeng; Wang Shiqing; Engineering and Technical College of Chengdu University of Technology, Leshan 614000

2011-04-15

The nonlinear fast magnetoacoustic solitary waves in a dust plasma with the combined effects of bounded cylindrical geometry and transverse perturbation are investigated in a new equation. In this regard, cylindrical Kadomtsev-Petviashvili (CKP) equation is derived using the small amplitude perturbation expansion method. Under a suitable coordinate transformation, the CKP equation can be solved analytically. It is shown that the dust cylindrical fast magnetoacoustic solitary waves can exist in the CKP equation. The present investigation may have relevance in the study of nonlinear electromagnetic soliton waves both in laboratory and astrophysical plasmas.

Cancellous bone analysis with modified least squares Prony's method and chirp filter: phantom experiments and simulation.

PubMed

Wear, Keith A

2010-10-01

The presence of two longitudinal waves in porous media is predicted by Biot's theory and has been confirmed experimentally in cancellous bone. When cancellous bone samples are interrogated in through-transmission, these two waves can overlap in time. Previously, the Modified Least-Squares Prony's (MLSP) method was validated for estimation of amplitudes, attenuation coefficients, and phase velocities of fast and slow waves, but tended to overestimate phase velocities by up to about 5%. In the present paper, a pre-processing chirp filter to mitigate the phase velocity bias is derived. The MLSP/chirp filter (MLSPCF) method was tested for decomposition of a 500 kHz-center-frequency signal containing two overlapping components: one passing through a low-density-polyethylene plate (fast wave) and another passing through a cancellous-bone-mimicking phantom material (slow wave). The chirp filter reduced phase velocity bias from 100 m/s (5.1%) to 69 m/s (3.5%) (fast wave) and from 29 m/s (1.9%) to 10 m/s (0.7%) (slow wave). Similar improvements were found for 1) measurements in polycarbonate (fast wave) and a cancellous-bone-mimicking phantom (slow wave), and 2) a simulation based on parameters mimicking bovine cancellous bone. The MLSPCF method did not offer consistent improvement in estimates of attenuation coefficient or amplitude.

Seagoing Box Scores and Seakeeping Criteria for Monohull, SWATH, Planing, Hydrofoil, Surface Effect Ships, and Air Cushion Vehicles

DTIC Science & Technology

1979-03-01

g DAVID W. TAYLOR NAVAL SHIP SRESEARCH AND DEVELOPMENT CENTERIBethesda, Md. 20064 S C SEAGOING BOX SCORES AND SEAKEEPING CRITERIA FOR MONOHULL, SWATH...Iteria for SWATIH for the Trans it Alone or the ’ratwiit I’ltu Sonai Search Fti’lux. on . . . 5.1 A,.3 - Govorit nR Cr ier ia for Monolu I Is fti the...L V NOTATION A Nondimensional coefficients a Regular wave amplitude B Ship beam e Exponential e - 2.7183 g Gravity acceleration Hz Hertz, unit of

SDO/AIA Observations of Quasi-periodic Fast (~1000 km/s) Propagating (QFP) Waves as Evidence of Fast-mode Magnetosonic Waves in the Low Corona: Statistics and Implications

NASA Astrophysics Data System (ADS)

Liu, W.; Ofman, L.; Title, A. M.; Zhao, J.; Aschwanden, M. J.

2011-12-01

Recent EUV imaging observations from SDO/AIA led to the discovery of quasi-periodic fast (~2000 km/s) propagating (QFP) waves in active regions (Liu et al. 2011). They were interpreted as fast-mode magnetosonic waves and reproduced in 3D MHD simulations (Ofman et al. 2011). Since then, we have extended our study to a sample of more than a dozen such waves observed during the SDO mission (2010/04-now). We will present the statistical properties of these waves including: (1) Their projected speeds measured in the plane of the sky are about 400-2200 km/s, which, as the lower limits of their true speeds in 3D space, fall in the expected range of coronal Alfven or fast-mode speeds. (2) They usually originate near flare kernels, often in the wake of a coronal mass ejection, and propagate in narrow funnels of coronal loops that serve as waveguides. (3) These waves are launched repeatedly with quasi-periodicities in the 30-200 seconds range, often lasting for more than one hour; some frequencies coincide with those of the quasi-periodic pulsations (QPPs) in the accompanying flare, suggestive a common excitation mechanism. We obtained the k-omega diagrams and dispersion relations of these waves using Fourier analysis. We estimate their energy fluxes and discuss their contribution to coronal heating as well as their diagnostic potential for coronal seismology.

Measuring SO2 ship emissions with an ultraviolet imaging camera

NASA Astrophysics Data System (ADS)

Prata, A. J.

2014-05-01

Over the last few years fast-sampling ultraviolet (UV) imaging cameras have been developed for use in measuring SO2 emissions from industrial sources (e.g. power plants; typical emission rates ~ 1-10 kg s-1) and natural sources (e.g. volcanoes; typical emission rates ~ 10-100 kg s-1). Generally, measurements have been made from sources rich in SO2 with high concentrations and emission rates. In this work, for the first time, a UV camera has been used to measure the much lower concentrations and emission rates of SO2 (typical emission rates ~ 0.01-0.1 kg s-1) in the plumes from moving and stationary ships. Some innovations and trade-offs have been made so that estimates of the emission rates and path concentrations can be retrieved in real time. Field experiments were conducted at Kongsfjord in Ny Ålesund, Svalbard, where SO2 emissions from cruise ships were made, and at the port of Rotterdam, Netherlands, measuring emissions from more than 10 different container and cargo ships. In all cases SO2 path concentrations could be estimated and emission rates determined by measuring ship plume speeds simultaneously using the camera, or by using surface wind speed data from an independent source. Accuracies were compromised in some cases because of the presence of particulates in some ship emissions and the restriction of single-filter UV imagery, a requirement for fast-sampling (> 10 Hz) from a single camera. Despite the ease of use and ability to determine SO2 emission rates from the UV camera system, the limitation in accuracy and precision suggest that the system may only be used under rather ideal circumstances and that currently the technology needs further development to serve as a method to monitor ship emissions for regulatory purposes. A dual-camera system or a single, dual-filter camera is required in order to properly correct for the effects of particulates in ship plumes.

Acceleration of the Fast Solar Wind by Solitary Waves in Coronal Holes

NASA Technical Reports Server (NTRS)

Ofman, Leon

2001-01-01

The purpose of this investigation is to develop a new model for the acceleration of the fast solar wind by nonlinear. time-dependent multidimensional MHD simulations of waves in solar coronal holes. Preliminary computational studies indicate that nonlinear waves are generated in coronal holes by torsional Alfv\\'{e}n waves. These waves in addition to thermal conduction may contribute considerably to the accelerate the solar wind. Specific goals of this proposal are to investigate the generation of nonlinear solitary-like waves and their effect on solar wind acceleration by numerical 2.5D MHD simulation of coronal holes with a broad range of plasma and wave parameters; to study the effect of random disturbances at the base of a solar coronal hole on the fast solar wind acceleration with a more advanced 2.5D MHD model and to compare the results with the available observations; to extend the study to a full 3D MHD simulation of fast solar wind acceleration with a more realistic model of a coronal hole and solar boundary conditions. The ultimate goal of the three year study is to model the, fast solar wind in a coronal hole, based on realistic boundary conditions in a coronal hole near the Sun, and the coronal hole structure (i.e., density, temperature. and magnetic field geometry,) that will become available from the recently launched SOHO spacecraft.

Acceleration of the Fast Solar Wind by Solitary Waves in Coronal Holes

NASA Technical Reports Server (NTRS)

Ofman, Leon

2000-01-01

The purpose of this investigation is to develop a new model for the acceleration of the fast solar wind by nonlinear, time-dependent multidimensional MHD simulations of waves in solar coronal holes. Preliminary computational studies indicate that solitary-like waves are generated in coronal holes nonlinearly by torsional Alfven waves. These waves in addition to thermal conduction may contribute considerably to the accelerate the solar wind. Specific goals of this proposal are to investigate the generation of nonlinear solitary-like waves and their effect on solar wind acceleration by numerical 2.5D MHD simulation of coronal holes with a broad range of plasma and wave parameters; to study the effect of random disturbances at the base of a solar coronal hole on the fast solar wind acceleration with a more advanced 2.5D MHD model and to compare the results with the available observations; to extend the study to a full 3D MHD simulation of fast solar wind acceleration with a more realistic model of a coronal hole and solar boundary conditions. The ultimate goal of the three year study is to model the fast solar wind in a coronal hole, based on realistic boundary conditions in a coronal hole near the Sun, and the coronal hole structure (i.e., density, temperature, and magnetic field geometry) that will become available from the recently launched SOHO spacecraft.

CONTRIBUTION OF VELOCITY VORTICES AND FAST SHOCK REFLECTION AND REFRACTION TO THE FORMATION OF EUV WAVES IN SOLAR ERUPTIONS

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

Wang, Hongjuan; Liu, Siqing; Gong, Jiancun

2015-06-01

We numerically study the detailed evolutionary features of the wave-like disturbance and its propagation in the eruption. This work is a follow-up to Wang et al., using significantly upgraded new simulations. We focus on the contribution of the velocity vortices and the fast shock reflection and refraction in the solar corona to the formation of the EUV waves. Following the loss of equilibrium in the coronal magnetic structure, the flux rope exhibits rapid motions and invokes the fast-mode shock at the front of the rope, which then produces a type II radio burst. The expansion of the fast shock, whichmore » is associated with outward motion, takes place in various directions, and the downward expansion shows the reflection and the refraction as a result of the non-uniform background plasma. The reflected component of the fast shock propagates upward and the refracted component propagates downward. As the refracted component reaches the boundary surface, a weak echo is excited. The Moreton wave is invoked as the fast shock touches the bottom boundary, so the Moreton wave lags the type II burst. A secondary echo occurs in the area where reflection of the fast shock encounters the slow-mode shock, and the nearby magnetic field lines are further distorted because of the interaction between the secondary echo and the velocity vortices. Our results indicate that the EUV wave may arise from various processes that are revealed in the new simulations.« less

Quasi-periodic Fast-mode Wave Trains Within a Global EUV Wave and Sequential Transverse Oscillations Detected by SDO-AIA

NASA Technical Reports Server (NTRS)

Liu, Wei; Ofman, Leon; Nitta, Nariaki; Aschwanden, Markus J.; Schrijver, Carolus J.; Title, Alan M.; Tarbell, Theodore D.

2012-01-01

We present the first unambiguous detection of quasi-periodic wave trains within the broad pulse of a global EUV wave (so-called EIT wave) occurring on the limb. These wave trains, running ahead of the lateral coronal mass ejection (CME) front of 2-4 times slower, coherently travel to distances greater than approximately solar radius/2 along the solar surface, with initial velocities up to 1400 kilometers per second decelerating to approximately 650 kilometers per second. The rapid expansion of the CME initiated at an elevated height of 110 Mm produces a strong downward and lateral compression, which may play an important role in driving the primary EUV wave and shaping its front forwardly inclined toward the solar surface. The wave trains have a dominant 2 minute periodicity that matches the X-ray flare pulsations, suggesting a causal connection. The arrival of the leading EUV wave front at increasing distances produces an uninterrupted chain sequence of deflections and/or transverse (likely fast kink mode) oscillations of local structures, including a flux-rope coronal cavity and its embedded filament with delayed onsets consistent with the wave travel time at an elevated (by approximately 50%) velocity within it. This suggests that the EUV wave penetrates through a topological separatrix surface into the cavity, unexpected from CME-caused magnetic reconfiguration. These observations, when taken together, provide compelling evidence of the fast-mode MHD wave nature of the primary (outer) fast component of a global EUV wave, running ahead of the secondary (inner) slow component of CME-caused restructuring.

Reliability of Hull Girder Ultimate Strength of Steel Ships

NASA Astrophysics Data System (ADS)

Da-wei, Gao; Gui-jie, Shi

2018-03-01

Hull girder ultimate strength is an evaluation index reflecting the true safety margin or structural redundancy about container ships. Especially, after the hull girder fracture accident of the MOL COMFORT, the 8,000TEU class large container ship, on June 17 2013, larger container ship safety has been paid on much more attention. In this paper, different methods of calculating hull girder ultimate strength are firstly discussed and compared with. The bending ultimate strength can be analyzed by nonlinear finite element method (NFEM) and increment-iterative method, and also the shear ultimate strength can be analyzed by NFEM and simple equations. Then, the probability distribution of hull girder wave loads and still water loads of container ship are summarized. At last, the reliability of hull girder ultimate strength under bending moment and shear forces for three container ships is analyzed by using a first order method. The conclusions can be applied to give guidance for ship design and safety evaluation.

Understanding the Physical Nature of Coronal "EIT Waves"

NASA Astrophysics Data System (ADS)

Long, D. M.; Bloomfield, D. S.; Chen, P.-F.; Downs, C.; Gallagher, P. T.; Kwon, R.-Y.; Vanninathan, K.; Veronig, A.; Vourlidas, A.; Vrsnak, B.; Warmuth, A.; Zic, T.

2016-10-01

For almost 20 years the physical nature of globally-propagating waves in the solar corona (commonly called "EIT waves") has been controversial and subject to debate. Additional theories have been proposed throughout the years to explain observations that did not fit with the originally proposed fast-mode wave interpretation. However, the incompatibility of observations made using the Extreme-ultraviolet Imaging Telescope (EIT) on the Solar and Heliospheric Observatory with the fast-mode wave interpretation have been challenged by differing viewpoints from the Solar Terrestrial Relations Observatory spacecraft and higher spatial/temporal resolution data from the Solar Dynamics Observatory. In this paper, we reexamine the theories proposed to explain "EIT waves" to identify measurable properties and behaviours that can be compared to current and future observations. Most of us conclude that "EIT waves" are best described as fast-mode large-amplitude waves/shocks, which are initially driven by the impulsive expansion of an erupting coronal mass ejection in the low corona.

Understanding the Physical Nature of Coronal "EIT Waves".

PubMed

Long, D M; Bloomfield, D S; Chen, P F; Downs, C; Gallagher, P T; Kwon, R-Y; Vanninathan, K; Veronig, A M; Vourlidas, A; Vršnak, B; Warmuth, A; Žic, T

2017-01-01

For almost 20 years the physical nature of globally propagating waves in the solar corona (commonly called "EIT waves") has been controversial and subject to debate. Additional theories have been proposed over the years to explain observations that did not agree with the originally proposed fast-mode wave interpretation. However, the incompatibility of observations made using the Extreme-ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory with the fast-mode wave interpretation was challenged by differing viewpoints from the twin Solar Terrestrial Relations Observatory spacecraft and data with higher spatial and temporal resolution from the Solar Dynamics Observatory . In this article, we reexamine the theories proposed to explain EIT waves to identify measurable properties and behaviours that can be compared to current and future observations. Most of us conclude that the so-called EIT waves are best described as fast-mode large-amplitude waves or shocks that are initially driven by the impulsive expansion of an erupting coronal mass ejection in the low corona.

High-harmonic fast magnetosonic wave coupling, propagation, and heating in a spherical torus plasma

NASA Astrophysics Data System (ADS)

Menard, J.; Majeski, R.; Kaita, R.; Ono, M.; Munsat, T.; Stutman, D.; Finkenthal, M.

1999-05-01

A novel rotatable two-strap antenna has been installed in the current drive experiment upgrade (CDX-U) [T. Jones, Ph.D. thesis, Princeton University (1995)] in order to investigate high-harmonic fast wave coupling, propagation, and electron heating as a function of strap angle and strap phasing in a spherical torus plasma. Radio-frequency-driven sheath effects are found to fit antenna loading trends at very low power and become negligible above a few kilowatts. At sufficiently high power, the measured coupling efficiency as a function of strap angle is found to agree favorably with cold plasma wave theory. Far-forward microwave scattering from wave-induced density fluctuations in the plasma core tracks the predicted fast wave loading as the antenna is rotated. Signs of electron heating during rf power injection have been observed in CDX-U with central Thomson scattering, impurity ion spectroscopy, and Langmuir probes. While these initial results appear promising, damping of the fast wave on thermal ions at high ion-cyclotron-harmonic number may compete with electron damping at sufficiently high ion β—possibly resulting in a significantly reduced current drive efficiency and production of a fast ion population. Preliminary results from ray-tracing calculations which include these ion damping effects are presented.

Pulse propagation in discrete excitatory networks of integrate-and-fire neurons.

PubMed

Badel, Laurent; Tonnelier, Arnaud

2004-07-01

We study the propagation of solitary waves in a discrete excitatory network of integrate-and-fire neurons. We show the existence and the stability of a fast wave and a family of slow waves. Fast waves are similar to those already described in continuum networks. Stable slow waves have not been previously reported in purely excitatory networks and their propagation is particular to the discrete nature of the network. The robustness of our results is studied in the presence of noise.

Experiment to investigate current drive by fast Alfven waves in a small tokamak

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

Gahl, J.; Ishihara, O.; Wong, K.

1985-07-01

An experiment has been carried out to study current generation by Doppler shifted cyclotron resonance heating of minority ions with a unidirectional wave in the small tokamak at Texas Tech University. One of the objectives of the experiment is to understand in detail the wave-particle interactions through which fast (compressional) Alfven waves in the ion cyclotron range of frequencies drive currents in toroidal devices.

Low-Frequency Waves in Cold Three-Component Plasmas

NASA Astrophysics Data System (ADS)

Fu, Qiang; Tang, Ying; Zhao, Jinsong; Lu, Jianyong

2016-09-01

The dispersion relation and electromagnetic polarization of the plasma waves are comprehensively studied in cold electron, proton, and heavy charged particle plasmas. Three modes are classified as the fast, intermediate, and slow mode waves according to different phase velocities. When plasmas contain positively-charged particles, the fast and intermediate modes can interact at the small propagating angles, whereas the two modes are separate at the large propagating angles. The near-parallel intermediate and slow waves experience the linear polarization, circular polarization, and linear polarization again, with the increasing wave number. The wave number regime corresponding to the above circular polarization shrinks as the propagating angle increases. Moreover, the fast and intermediate modes cause the reverse change of the electromagnetic polarization at the special wave number. While the heavy particles carry the negative charges, the dispersion relations of the fast and intermediate modes are always separate, being independent of the propagating angles. Furthermore, this study gives new expressions of the three resonance frequencies corresponding to the highly-oblique propagation waves in the general three-component plasmas, and shows the dependence of the resonance frequencies on the propagating angle, the concentration of the heavy particle, and the mass ratio among different kinds of particles. supported by National Natural Science Foundation of China (Nos. 11303099, 41531071 and 41574158), and the Youth Innovation Promotion Association CAS

Fast shear compounding using robust 2-D shear wave speed calculation and multi-directional filtering.

PubMed

Song, Pengfei; Manduca, Armando; Zhao, Heng; Urban, Matthew W; Greenleaf, James F; Chen, Shigao

2014-06-01

A fast shear compounding method was developed in this study using only one shear wave push-detect cycle, such that the shear wave imaging frame rate is preserved and motion artifacts are minimized. The proposed method is composed of the following steps: 1. Applying a comb-push to produce multiple differently angled shear waves at different spatial locations simultaneously; 2. Decomposing the complex shear wave field into individual shear wave fields with differently oriented shear waves using a multi-directional filter; 3. Using a robust 2-D shear wave speed calculation to reconstruct 2-D shear elasticity maps from each filter direction; and 4. Compounding these 2-D maps from different directions into a final map. An inclusion phantom study showed that the fast shear compounding method could achieve comparable performance to conventional shear compounding without sacrificing the imaging frame rate. A multi-inclusion phantom experiment showed that the fast shear compounding method could provide a full field-of-view, 2-D and compounded shear elasticity map with three types of inclusions clearly resolved and stiffness measurements showing excellent agreement to the nominal values. Copyright © 2014 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

International Conference on Numerical Ship Hydrodynamics (2nd) Held in Berkeley, California on 19-21 September 1977

DTIC Science & Technology

1977-09-01

ORDERING INFORMATION Sec d Internat nal Contere ce on Nu erical Ship ydro nermics ay be order by mallin a req~uest the folio ng ad ess: Firt ilererin I...f(x)dx - 0 (f ’ J d Gd(x’,X 3) dx’ -D0 (jx) 0 d.’ d’U is a closed subspacs of aUoxV ’XT,. hence I O Gde Loach space. d o l , Aw D(4 (x U ’!’ ) Proofs...crest of unbro- domain as an initial-value problem advancing in Ken waves. The inception of wave breaking is time until a steady-state condition has

Air blast injuries killed the crew of the submarine H.L. Hunley.

PubMed

Lance, Rachel M; Stalcup, Lucas; Wojtylak, Brad; Bass, Cameron R

2017-01-01

The submarine H.L. Hunley was the first submarine to sink an enemy ship during combat; however, the cause of its sinking has been a mystery for over 150 years. The Hunley set off a 61.2 kg (135 lb) black powder torpedo at a distance less than 5 m (16 ft) off its bow. Scaled experiments were performed that measured black powder and shock tube explosions underwater and propagation of blasts through a model ship hull. This propagation data was used in combination with archival experimental data to evaluate the risk to the crew from their own torpedo. The blast produced likely caused flexion of the ship hull to transmit the blast wave; the secondary wave transmitted inside the crew compartment was of sufficient magnitude that the calculated chances of survival were less than 16% for each crew member. The submarine drifted to its resting place after the crew died of air blast trauma within the hull.

On singular and highly oscillatory properties of the Green function for ship motions

NASA Astrophysics Data System (ADS)

Chen, Xiao-Bo; Xiong Wu, Guo

2001-10-01

The Green function used for analysing ship motions in waves is the velocity potential due to a point source pulsating and advancing at a uniform forward speed. The behaviour of this function is investigated, in particular for the case when the source is located at or close to the free surface. In the far field, the Green function is represented by a single integral along one closed dispersion curve and two open dispersion curves. The single integral along the open dispersion curves is analysed based on the asymptotic expansion of a complex error function. The singular and highly oscillatory behaviour of the Green function is captured, which shows that the Green function oscillates with indefinitely increasing amplitude and indefinitely decreasing wavelength, when a field point approaches the track of the source point at the free surface. This sheds some light on the nature of the difficulties in the numerical methods used for predicting the motion of a ship advancing in waves.

Air blast injuries killed the crew of the submarine H.L. Hunley

PubMed Central

Stalcup, Lucas; Wojtylak, Brad; Bass, Cameron R.

2017-01-01

The submarine H.L. Hunley was the first submarine to sink an enemy ship during combat; however, the cause of its sinking has been a mystery for over 150 years. The Hunley set off a 61.2 kg (135 lb) black powder torpedo at a distance less than 5 m (16 ft) off its bow. Scaled experiments were performed that measured black powder and shock tube explosions underwater and propagation of blasts through a model ship hull. This propagation data was used in combination with archival experimental data to evaluate the risk to the crew from their own torpedo. The blast produced likely caused flexion of the ship hull to transmit the blast wave; the secondary wave transmitted inside the crew compartment was of sufficient magnitude that the calculated chances of survival were less than 16% for each crew member. The submarine drifted to its resting place after the crew died of air blast trauma within the hull. PMID:28832592

Mode Conversion of a Solar Extreme-ultraviolet Wave over a Coronal Cavity

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

Zong, Weiguo; Dai, Yu, E-mail: ydai@nju.edu.cn

2017-01-10

We report on observations of an extreme-ultraviolet (EUV) wave event in the Sun on 2011 January 13 by Solar Terrestrial Relations Observatory and Solar Dynamics Observatory in quadrature. Both the trailing edge and the leading edge of the EUV wave front in the north direction are reliably traced, revealing generally compatible propagation velocities in both perspectives and a velocity ratio of about 1/3. When the wave front encounters a coronal cavity near the northern polar coronal hole, the trailing edge of the front stops while its leading edge just shows a small gap and extends over the cavity, meanwhile gettingmore » significantly decelerated but intensified. We propose that the trailing edge and the leading edge of the northward propagating wave front correspond to a non-wave coronal mass ejection component and a fast-mode magnetohydrodynamic wave component, respectively. The interaction of the fast-mode wave and the coronal cavity may involve a mode conversion process, through which part of the fast-mode wave is converted to a slow-mode wave that is trapped along the magnetic field lines. This scenario can reasonably account for the unusual behavior of the wave front over the coronal cavity.« less

Present-day and future global bottom-up ship emission inventories including polar routes.

PubMed

Paxian, Andreas; Eyring, Veronika; Beer, Winfried; Sausen, Robert; Wright, Claire

2010-02-15

We present a global bottom-up ship emission algorithm that calculates fuel consumption, emissions, and vessel traffic densities for present-day (2006) and two future scenarios (2050) considering the opening of Arctic polar routes due to projected sea ice decline. Ship movements and actual ship engine power per individual ship from Lloyd's Marine Intelligence Unit (LMIU) ship statistics for six months in 2006 and further mean engine data from literature serve as input. The developed SeaKLIM algorithm automatically finds the most probable shipping route for each combination of start and destination port of a certain ship movement by calculating the shortest path on a predefined model grid while considering land masses, sea ice, shipping canal sizes, and climatological mean wave heights. The resulting present-day ship activity agrees well with observations. The global fuel consumption of 221 Mt in 2006 lies in the range of previously published inventories when undercounting of ship numbers in the LMIU movement database (40,055 vessels) is considered. Extrapolated to 2007 and ship numbers per ship type of the recent International Maritime Organization (IMO) estimate (100,214 vessels), a fuel consumption of 349 Mt is calculated which is in good agreement with the IMO total of 333 Mt. The future scenarios show Arctic polar routes with regional fuel consumption on the Northeast and Northwest Passage increasing by factors of up to 9 and 13 until 2050, respectively.

Marine natural hazards in coastal zone: observations, analysis and modelling (Plinius Medal Lecture)

NASA Astrophysics Data System (ADS)

Didenkulova, Ira

2010-05-01

Giant surface waves approaching the coast frequently cause extensive coastal flooding, destruction of coastal constructions and loss of lives. Such waves can be generated by various phenomena: strong storms and cyclones, underwater earthquakes, high-speed ferries, aerial and submarine landslides. The most famous examples of such events are the catastrophic tsunami in the Indian Ocean, which occurred on 26 December 2004 and hurricane Katrina (28 August 2005) in the Atlantic Ocean. The huge storm in the Baltic Sea on 9 January 2005, which produced unexpectedly long waves in many areas of the Baltic Sea and the influence of unusually high surge created by long waves from high-speed ferries, should also be mentioned as examples of regional marine natural hazards connected with extensive runup of certain types of waves. The processes of wave shoaling and runup for all these different marine natural hazards (tsunami, coastal freak waves, ship waves) are studied based on rigorous solutions of nonlinear shallow-water theory. The key and novel results presented here are: i) parameterization of basic formulas for extreme runup characteristics for bell-shape waves, showing that they weakly depend on the initial wave shape, which is usually unknown in real sea conditions; ii) runup analysis of periodic asymmetric waves with a steep front, as such waves are penetrating inland over large distances and with larger velocities than symmetric waves; iii) statistical analysis of irregular wave runup demonstrating that wave nonlinearity nearshore does not influence on the probability distribution of the velocity of the moving shoreline and its moments, and influences on the vertical displacement of the moving shoreline (runup). Wave runup on convex beaches and in narrow bays, which allow abnormal wave amplification is also discussed. Described analytical results are used for explanation of observed extreme runup of tsunami, freak (sneaker) waves and ship waves on different coasts along different bottom profiles.

A Baseline Analysis of Combat Logistics Force Scheduling Efficiency

DTIC Science & Technology

2016-06-01

from the data were mostly inconclusive, however; as a result, this paper recommends expanding the research years for further data analysis to include...the warship in the Fifth Fleet area of responsibility. The trends from the data were mostly inconclusive, however; as a result, this paper recommends...Commander, Naval Surface Forces T-AKE dry cargo ammunition ship T-AO fleet replenishment oiler T-AOE fast combat support ship THRSG Theodore

An Improved Shock Model for Bare and Covered Explosives

NASA Astrophysics Data System (ADS)

Scholtes, Gert; Bouma, Richard

2017-06-01

TNO developed a toolbox to estimate the probability of a violent event on a ship or other platform, when the munition bunker is hit by e.g. a bullet or fragment from a missile attack. To obtain the proper statistical output, several millions of calculations are needed to obtain a reliable estimate. Because millions of different scenarios have to be calculated, hydrocode calculations cannot be used for this type of application, but a fast and good engineering solutions is needed. At this moment the Haskins and Cook-model is used for this purpose. To obtain a better estimate for covered explosives and munitions, TNO has developed a new model which is a combination of the shock wave model at high pressure, as described by Haskins and Cook, in combination with the expanding shock wave model of Green. This combined model gives a better fit with the experimental values for explosives response calculations, using the same critical energy fluence values for covered as well as for bare explosives. In this paper the theory is explained and results of the calculations for several bare and covered explosives will be presented. To show this, the results will be compared with the experimental values from literature for composition B, Composition B-3 and PBX-9404.

High power fast wave experiments in LAPD: interaction with density fluctuations and status/plans for ICRH

NASA Astrophysics Data System (ADS)

Carter, Troy; Martin, Michael; van Compernolle, Bart; Gekelman, Walter; Pribyl, Pat; Vincena, Stephen; Tripathi, Shreekrishna; van Eester, Dirk; Crombe, Kristel

2016-10-01

The LArge Plasma Device (LAPD) at UCLA is a 17 m long, up to 60 cm diameter magnetized plasma column with typical plasma parameters ne 1012 -1013 cm-3, Te 1 - 10 eV, and B 1 kG. A new high-power ( 200 kW) RF system and antenna has been developed for LAPD, enabling the generation of large amplitude fast waves in LAPD. Interaction between the fast waves and density fluctuations is observed, resulting in modulation of the coupled RF power. Two classes of RF-induced density fluctuations are observed. First, a coherent (10 kHz) oscillation is observed spatially near the antenna in response to the initial RF turn-on transient. Second, broadband density fluctuations are enhanced when the RF power is above a threshold a threshold. Strong modulation of the fast wave magnetic fluctuations is observed along with broadening of the primary RF spectral line. Ultimately, high power fast waves will be used for ion heating in LAPD through minority species fundamental heating or second harmonic minority or majority heating. Initial experimental results from heating experiments will be presented along with a discussion of future plans. BaPSF supported by NSF and DOE.

Review of ship slamming loads and responses

NASA Astrophysics Data System (ADS)

Wang, Shan; Guedes Soares, C.

2017-12-01

The paper presents an overview of studies of slamming on ship structures. This work focuses on the hull slamming, which is one of the most important types of slamming problems to be considered in the ship design process and the assessment of the ship safety. There are three main research aspects related to the hull slamming phenomenon, a) where and how often a slamming event occurs, b) slamming load prediction and c) structural response due to slamming loads. The approaches used in each aspect are reviewed and commented, together with the presentation of some typical results. The methodology, which combines the seakeeping analysis and slamming load prediction, is discussed for the global analysis of the hull slamming of a ship in waves. Some physical phenomena during the slamming event are discussed also. Recommendations for the future research and developments are made.

Hydrodynamic Drag Reduction

DTIC Science & Technology

2015-04-01

Computational Engineering unstructured RANS/LES/DES solver , Tenasi, was used to predict drag and simulate the free surface flow around the ACV over a...using a second-order accurate Roe approximate Riemann scheme, while viscous fluxes are evaluated using a second-order directional derivative approach...Predictions of rigid body ship motions for the SI75 container ship in incident waves and methodology for a one-way coupling of the Tenasi flow solver

Analysis of Spontaneous and Nerve-Evoked Calcium Transients in Intact Extraocular Muscles in Vitro

PubMed Central

Feng, Cheng-Yuan; Hennig, Grant W.; Corrigan, Robert D.; Smith, Terence K.; von Bartheld, Christopher S.

2012-01-01

Extraocular muscles (EOMs) have unique calcium handling properties, yet little is known about the dynamics of calcium events underlying ultrafast and tonic contractions in myofibers of intact EOMs. Superior oblique EOMs of juvenile chickens were dissected with their nerve attached, maintained in oxygenated Krebs buffer, and loaded with fluo-4. Spontaneous and nerve stimulation-evoked calcium transients were recorded and, following calcium imaging, some EOMs were double-labeled with rhodamine-conjugated alpha-bungarotoxin (rhBTX) to identify EOM myofiber types. EOMs showed two main types of spontaneous calcium transients, one slow type (calcium waves with 1/2max duration of 2–12 s, velocity of 25–50 μm/s) and two fast “flash-like” types (Type 1, 30–90 ms; Type 2, 90–150 ms 1/2max duration). Single pulse nerve stimulation evoked fast calcium transients identical to the fast (Type 1) calcium transients. Calcium waves were accompanied by a local myofiber contraction that followed the calcium transient wavefront. The magnitude of calcium-wave induced myofiber contraction far exceeded those of movement induced by nerve stimulation and associated fast calcium transients. Tetrodotoxin eliminated nerve-evoked transients, but not spontaneous transients. Alpha-bungarotoxin eliminated both spontaneous and nerve-evoked fast calcium transients, but not calcium waves, and caffeine increased wave activity. Calcium waves were observed in myofibers lacking spontaneous or evoked fast transients, suggestive of multiply-innervated myofibers, and this was confirmed by double-labeling with rhBTX. We propose that the abundant spontaneous calcium transients and calcium waves with localized contractions that do not depend on innervation may contribute to intrinsic generation of tonic functions of EOMs. PMID:22579493

Evaluation of the wave measurement in a stormy sea by the Along-Track interferometry SAR

NASA Astrophysics Data System (ADS)

Kojima, S.

2015-12-01

NICT developed the along-track interferometry SAR (AT-InSAR) system to detect the running cars and ships and measure sea surface velocity in 2011. The preliminary experiments for the running truck and ship were performed and it confirmed that the system performance was satisfactory to its specifications. In addition, a method to estimate the wave height from the sea surface velocity measured by the AT-InSAR was developed. The preliminary wave height observation was performed in a calm sea, and it was confirmed that the wave height could be estimated from the measured sea surface velocity. The purpose of this study is to check the capability of the ocean waves observation in a stormy sea by the AT-InSAR. Therefore, the ocean wave observation was performed under the low atmospheric pressure. The observation area is the sea surface at 10 km off the coast of Kushiro, south-east to Hokaido, JAPAN on the 4th of March 2015. The wind speed was 8〜10m/s during the observation, and the significant wave height and period were 1.5m and 6.0s. The observation was performed in 2 directions and the accuracy of the estimation results were checked. The significant wave height and period measured by the AT-InSAR agreed with it measured by the wave gage located close to this observation area. In addition, it was confirmed that there were no irregular wave heights in the distribution of the estimated wave height. As a result, it became clear that the AT-InSAR could observe the wave height in a stormy sea.

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

NASA Astrophysics Data System (ADS)

Hachiken, Takuma; Nakanishi, Shoko; Matsukawa, Mami

2016-07-01

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

DETECTION OF FAST-MOVING WAVES PROPAGATING OUTWARD ALONG SUNSPOTS’ RADIAL DIRECTION IN THE PHOTOSPHERE

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

Zhao, Junwei; Chen, Ruizhu; Hartlep, Thomas

2015-08-10

Helioseismic and magnetohydrodynamic waves are abundant in and above sunspots. Through cross-correlating oscillation signals in the photosphere observed by the Solar Dynamics Observatory/Helioseismic and Magnetic Imager, we reconstruct how waves propagate away from virtual wave sources located inside a sunspot. In addition to the usual helioseismic wave, a fast-moving wave is detected traveling along the sunspot’s radial direction from the umbra to about 15 Mm beyond the sunspot boundary. The wave has a frequency range of 2.5–4.0 mHz with a phase velocity of 45.3 km s{sup −1}, substantially faster than the typical speeds of Alfvén and magnetoacoustic waves in themore » photosphere. The observed phenomenon is consistent with a scenario of that a magnetoacoustic wave is excited at approximately 5 Mm beneath the sunspot. Its wavefront travels to and sweeps across the photosphere with a speed higher than the local magnetoacoustic speed. The fast-moving wave, if truly excited beneath the sunspot’s surface, will help open a new window for studying the internal structure and dynamics of sunspots.« less

Measurement of flows around modern commercial ship models

NASA Astrophysics Data System (ADS)

Kim, W. J.; Van, S. H.; Kim, D. H.

To document the details of flow characteristics around modern commercial ships, global force, wave pattern, and local mean velocity components were measured in the towing tank. Three modern commercial hull models of a container ship (KRISO container ship = KCS) and of two very large crude-oil carriers (VLCCs) with the same forebody and slightly different afterbody (KVLCC and KVLCC2) having bow and stern bulbs were selected for the test. Uncertainty analysis was performed for the measured data using the procedure recommended by the ITTC. Obtained experimental data will provide a good opportunity to explore integrated flow phenomena around practical hull forms of today. Those can be also used as the validation data for the computational fluid dynamics (CFD) code of both inviscid and viscous flow calculations.

Detonation models of fast combustion waves in nanoscale Al-MoO3 bulk powder media

NASA Astrophysics Data System (ADS)

Shaw, Benjamin D.; Pantoya, Michelle L.; Dikici, Birce

2013-02-01

The combustion of nanometric aluminum (Al) powder with an oxidiser such as molybdenum trioxide (MoO3) is studied analytically. This study focuses on detonation wave models and a Chapman-Jouget detonation model provides reasonable agreement with experimentally-observed wave speeds provided that multiphase equilibrium sound speeds are applied at the downstream edge of the detonation wave. The results indicate that equilibrium sound speeds of multiphase mixtures can play a critical role in determining speeds of fast combustion waves in nanoscale Al-MoO3 powder mixtures.

Motion and Seasickness of Fast Warships

DTIC Science & Technology

2004-10-01

Motion and Seasickness of Fast Warships Riola J.M. (1), Esteban S. (2), Giron-Sierra J.M. (2) & Aranda J. (3) (1) Canal de Experiencias ...5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Canal de Experiencias Hidrodinámicas de ...Bretschneider Sp bability Density of Waves /λ, with H being the wave height (twice the wave a in a seakeeping basin Canal de Experiencias Hid r waves with

Teleseismic surface wave study of S-wave velocity structure in Southern California

NASA Astrophysics Data System (ADS)

Prindle-Sheldrake, K. L.; Tanimoto, T.

2002-12-01

We report on a 3D S-wave velocity structure derived from teleseismic Rayleigh and Love waves using TriNet broadband seismic data. Phase velocity maps, constructed between 20 and 55 mHz for Rayleigh waves and between 25 and 45 mHz for Love waves, were inverted for S-wave velocity structure at depth. Our starting model is SCEC 2.2, which has detailed crustal structure, but laterally homogeneous upper mantle structure. Depth resolution from the data set is good from the surface to approximately 100 km, but deteriorates rapidly beyond this depth. Our analysis indicates that, while Rayleigh wave data are mostly sensitive to mantle structure, Love wave data require some modifications of crustal structure from SCEC 2.2 model. Various regions in Southern California have different seismic-velocity signatures in terms of fast and slow S-wave velocities: In the Southern Sierra, both the crust and mantle are slow. In the Mojave desert, mid-crustal depths tend to show slow velocities, which are already built into SCEC 2.2. In the Transverse Ranges, the lower crust and mantle are both fast. Our Love wave results require much faster crustal velocity than those in SCEC 2.2 in this region. In the Peninsular ranges, both the crust and mantle are fast with mantle fast velocity extending to about 70 km. This is slightly more shallow than the depth extent under the Transverse Ranges, yet it is surprisingly deep. Under the Salton Sea, the upper crust is very slow and the upper mantle is also slow. However, these two slow velocity layers are separated by faster velocity lower crust which creates a distinct contrast with respect to the adjacent slow velocity regions. Existence of such a relatively fast layer, sandwiched by slow velocities, are related to features in phase velocity maps, especially in the low frequency Love wave phase velocity map (25 mHz) and the high frequency Rayleigh wave phase velocity maps (above 40 mHz). Such a feature may be related to partial melting processes under the Salton Sea.

A study of Equartorial wave characteristics using rockets, balloons, lidar and radar

NASA Astrophysics Data System (ADS)

Sasi, M.; Krishna Murthy, B.; Ramkumar, G.; Satheesan, K.; Parameswaran, K.; Rajeev, K.; Sunilkumar, S.; Nair, P.; Krishna Murthy, K.; Bhavanikumar, Y.; Raghunath, K.; Jain, A.; Rao, P.; Krishnaiah, M.; Nayar, S.; Revathy, K.

Dynamics of low latitude middle atmosphere is dominated by the zonal wind quasi- biennial oscillation (QBO) in the lower stratosphere and zonl wind semiannual oscillation (SAO) in the stratopause and mesopause regions. Equatorial waves play a significant role in the evolution of QBO and SAO through wave- mean flow interactions resulting in momentum transfer from the waves to the mean flow in the equatorial middle atmosphere. With the objective of characterising the equatorial wave characteristics and momentum fluxes associated with them a campaign experiment was conducted in 2000 using RH-200 rockets, balloons, Raleigh lidar and MST radar. Winds and temperatures in the troposphere, stratosphere and mesosphere over two low latitude stations Gadanki (13.5°N, 79.2°E) and SHAR (13.7°N, 80.2°E) were measured, using MST Radar, Rayleigh Lidar, balloons and RH-200 rockets, for 40 consecutive days from 21 February to 01 April 2000 and were used for the study of equatorial waves and their interactions with the background mean flow in various atmospheric regions. The study shows the occurrence of a strong stratospheric cooling (~25 K) anomaly along with a zonal wind anomaly and this low-latitude event appears to be linked to high-latitude stratospheric warming event and leads to subsequent generation of short period (~5 days) oscillations lasting for a few cycles in the stratosphere. A slow Kelvin wave (~18 day period), fast Kelvin wave (~8 days) and ultra fast Kelvin wave (~3.3 day period) and RG wave (~4.8 day period) have been identified. There are indications of slow and ultra fast Kelvin waves, in addition to fast Kelvin waves, contributing to the evolution of the westerly phase of the stratopause SAO.

Searching for Fast Radio Bursts with the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO)

NASA Astrophysics Data System (ADS)

Fisher, Ryan Patrick; Hughey, Brennan; Howell, Eric; LIGO Collaboration

2018-01-01

Although Fast Radio Bursts (FRB) are being detected with increasing frequency, their progenitor systems are still mostly a mystery. We present the plan to conduct targeted searches for gravitational-wave counterparts to these FRB events in the data from the first and second observing runs of the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO).

A current drive by using the fast wave in frequency range higher than two timeslower hybrid resonance frequency on tokamaks

NASA Astrophysics Data System (ADS)

Kim, Sun Ho; Hwang, Yong Seok; Jeong, Seung Ho; Wang, Son Jong; Kwak, Jong Gu

2017-10-01

An efficient current drive scheme in central or off-axis region is required for the steady state operation of tokamak fusion reactors. The current drive by using the fast wave in frequency range higher than two times lower hybrid resonance (w>2wlh) could be such a scheme in high density, high temperature reactor-grade tokamak plasmas. First, it has relatively higher parallel electric field to the magnetic field favorable to the current generation, compared to fast waves in other frequency range. Second, it can deeply penetrate into high density plasmas compared to the slow wave in the same frequency range. Third, parasitic coupling to the slow wave can contribute also to the current drive avoiding parametric instability, thermal mode conversion and ion heating occured in the frequency range w<2wlh. In this study, the propagation boundary, accessibility, and the energy flow of the fast wave are given via cold dispersion relation and group velocity. The power absorption and current drive efficiency are discussed qualitatively through the hot dispersion relation and the polarization. Finally, those characteristics are confirmed with ray tracing code GENRAY for the KSTAR plasmas.

Measuring SO2 ship emissions with an ultra-violet imaging camera

NASA Astrophysics Data System (ADS)

Prata, A. J.

2013-11-01

Over the last few years fast-sampling ultra-violet (UV) imaging cameras have been developed for use in measuring SO2 emissions from industrial sources (e.g. power plants; typical fluxes ~1-10 kg s-1) and natural sources (e.g. volcanoes; typical fluxes ~10-100 kg s-1). Generally, measurements have been made from sources rich in SO2 with high concentrations and fluxes. In this work, for the first time, a UV camera has been used to measure the much lower concentrations and fluxes of SO2 (typical fluxes ~0.01-0.1 kg s-1) in the plumes from moving and stationary ships. Some innovations and trade-offs have been made so that estimates of the fluxes and path concentrations can be retrieved in real-time. Field experiments were conducted at Kongsfjord in Ny Ålesund, Svalbard, where emissions from cruise ships were made, and at the port of Rotterdam, Netherlands, measuring emissions from more than 10 different container and cargo ships. In all cases SO2 path concentrations could be estimated and fluxes determined by measuring ship plume speeds simultaneously using the camera, or by using surface wind speed data from an independent source. Accuracies were compromised in some cases because of the presence of particulates in some ship emissions and the restriction of single-filter UV imagery, a requirement for fast-sampling (>10 Hz) from a single camera. Typical accuracies ranged from 10-30% in path concentration and 10-40% in flux estimation. Despite the ease of use and ability to determine SO2 fluxes from the UV camera system, the limitation in accuracy and precision suggest that the system may only be used under rather ideal circumstances and that currently the technology needs further development to serve as a method to monitor ship emissions for regulatory purposes.

Intermodal Transportation: Current Fast Ship Designs Specify Propulsion Systems that Are about 20 Knots Faster than Ships in the Current Fleet

ERIC Educational Resources Information Center

Childress, Vincent W.

2005-01-01

Intermodal transportation is the moving of people or cargo using more than one mode of transportation. When a person drives to the airport, stands on a conveyor to move through the terminal, and flies to another city, then he or she is using intermodal transportation. Moving cargo in the first half of the twentieth century was a time-consuming and…

Securing the High Seas: America’s Global Maritime Constabulatory Power

DTIC Science & Technology

2008-03-12

at www.heritage.org/ Research/HomelandSecurity/bg1950.cfm. 29. Construcciones Aeronáuticas, SA. 16 Securing the High Seas: America’s Global Maritime...Coast Guard ships (National Security Cutter, Off-Shore Patrol Cutter, and Fast Response Cutter) and many Navy ships currently in design or construction ...forge complementary maritime strategies. Only by developing common doctrine, creating greater synergy in the construction of core assets, and forging a

The Littoral Combat Ship: How We Got Here, and Why

DTIC Science & Technology

2014-01-01

Burke DDG, equating to a threshold (minimally acceptable) target cost of 7 $ 400 million per ship.36 However, in February 2003, with the program still...expected to provide the ship’s “Sunday punch.” As these simple calculations suggest, building a missionized LCS for $ 400 million would be challenging...was a family of fast, stealthy, 400 to 1,200-ton littoral combatants called Streetfighters which would operate in distributed groups. While the

Ship Vibration Design Guide

DTIC Science & Technology

1989-07-01

for further development are indicated. This guide addresses the major components over which we have the ability to excercise control in the design...this same period, very fast electronic analyzers also became available at a reasonable cost. Known as Fast Fourier Transform (FFT), these analyzers...An oscilloscope is desirable anyway to judge whether the signals look reasonable or not. Usually intermittent connections, 60 Hz noise, or other

46 CFR 160.156-15 - Production inspections, tests, quality control, and conformance of rescue boats and fast rescue...

Code of Federal Regulations, 2012 CFR

2012-10-01

... materials are as per the plans approved under § 160.156-13(h) of this subpart. (2) Post assembly tests and... 46 Shipping 6 2012-10-01 2012-10-01 false Production inspections, tests, quality control, and... inspections, tests, quality control, and conformance of rescue boats and fast rescue boats. (a) Unless the...

46 CFR 160.156-15 - Production inspections, tests, quality control, and conformance of rescue boats and fast rescue...

Code of Federal Regulations, 2013 CFR

2013-10-01

... materials are as per the plans approved under § 160.156-13(h) of this subpart. (2) Post assembly tests and... 46 Shipping 6 2013-10-01 2013-10-01 false Production inspections, tests, quality control, and... inspections, tests, quality control, and conformance of rescue boats and fast rescue boats. (a) Unless the...

Associations between major chain fast-food outlet availability and change in body mass index: a longitudinal observational study of women from Victoria, Australia

PubMed Central

Thornton, Lukar E; Olstad, Dana Lee; Cerin, Ester; Ball, Kylie

2017-01-01

Objectives The residential neighbourhood fast-food environment has the potential to lead to increased levels of obesity by providing opportunities for residents to consume energy-dense products. This longitudinal study aimed to examine whether change in body mass index (BMI) differed dependent on major chain fast-food outlet availability among women residing in disadvantaged neighbourhoods. Setting Eighty disadvantaged neighbourhoods in Victoria, Australia. Participants Sample of 882 women aged 18–46 years at baseline (wave I: 2007/2008) who remained at the same residential location at all three waves (wave II: 2010/2011; wave III: 2012/2013) of the Resilience for Eating and Activity Despite Inequality study. Primary outcome BMI based on self-reported height and weight at each wave. Results There was no evidence of an interaction between time and the number of major chain fast-food outlets within 2 (p=0.88), 3 (p=0.66) or 5 km (p=0.24) in the multilevel models of BMI. Furthermore, there was no evidence of an interaction between time and change in availability at any distance and BMI. Conclusions Change in BMI was not found to differ by residential major chain fast-food outlet availability among Victorian women residing in disadvantaged neighbourhoods. It may be that exposure to fast-food outlets around other locations regularly visited influence change in BMI. Future research needs to consider what environments are the key sources for accessing and consuming fast food and how these relate to BMI and obesity risk. PMID:29042381

Directional wave navigation radar measurements compared with pitch-roll buoy data

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

A.-Munoyerro, M.A.; Borge, J.C.N.

1997-02-01

The knowledge of the spectral behavior of a specific sea region is complete when one knows surface elevations and directional wave movements. Usually, sea directional descriptions have been made using pitch-roll buoys, which can provide one with several wave characteristic time series. Alternatively, there are other measure systems, which belong to remote sensing technics, such as shipboard navigation radars. The aim of the present work is to compare results obtained from pitch-roll data and ship radar wave measurements obtained during a campaign in the Cantabric Sea.

Nonlinear Waves.

DTIC Science & Technology

1988-02-01

in Multi- dimensions II, P.M. Santini and A.S. Fokas, preprint INS#67, 1986. The Recursion Operator of the Kadomtsev - Petviashvili Equation and the...solitons, multidimensional inverse problems, Painleve equations , direct linearizations of certain nonlinear wave equations , DBAR problems, Riemann...the Navy is (a) the recent discovery that many of the equations describing ship hydrodynamics in channels of finite depth obey nonlinear equations

[Psychopathology service on ships].

PubMed

Nowosielski, Radosław; Mazurek, Tomasz; Florkowski, Antoni

2010-06-01

The aim of this study was to describe the specific engineering services and suitability of candidates for the psychophysical performance. Navy ships are equipped with equipment and weapons are controlled by electronic devices ship and crew. Advanced technology puts high demands on operator. For the ship's staff are recruited soldiers of the psychophysical characteristics predisposing to this kind of action. The paper uses personal experience to work in military units of the Navy, and data from the literature. Terms of sailing ships off the summer season are defined as difficult. The crew during a combat mission felt the risks associated with movements of the ship in difficult meteorological conditions, and associated with the implementation of the task. The development of ship's technical equipment, working in isolated groups, functioning within a limited space, noise, vibration, electromagnetic waves heighten the emotional burden on crew members. Military service on Navy ships require high psycho-physical predisposition, resistance to stress. The crucial factor is proper selection among the candidates based on psychiatric and psychological counseling for military and medical jurisprudence. Also plays a significant role for training doctors and specialists in psychoprophylaxy of military units in the field of mental hygiene.

Prospects for gravitational wave astronomy with next generation large-scale pulsar timing arrays

NASA Astrophysics Data System (ADS)

Wang, Yan; Mohanty, Soumya D.

2018-02-01

Next generation radio telescopes, namely the Five-hundred-meter Aperture Spherical Telescope (FAST) and the Square Kilometer Array (SKA), will revolutionize the pulsar timing arrays (PTAs) based gravitational wave (GW) searches. We review some of the characteristics of FAST and SKA, and the resulting PTAs, that are pertinent to the detection of gravitational wave signals from individual supermassive black hole binaries.

Mesoscale wake clouds in Skylab pictures.

NASA Technical Reports Server (NTRS)

Fujita, T. T.; Tecson, J. J.

1974-01-01

The recognition of cloud patterns formed in the wake of orographic obstacles was investigated using pictures from Skylab, for the purpose of estimating atmospheric motions. The existence of ship-wake-type wave clouds in contrast to vortex sheets were revealed during examination of the pictures, and an attempt was made to characterize the pattern of waves as well as the transition between waves and vortices. Examples of mesoscale cloud patterns which were analyzed photogrammetrically and meteorologically are presented.

Observed ocean waves by tropical cyclones

NASA Astrophysics Data System (ADS)

Zhang, Lin; Oey, Leo

2017-04-01

Ocean waves produced by tropical cyclones (TC) modify air-sea fluxes which in turn are crucial to the storms' intensity and development, yet they are poorly understood. Here we use 24 years (1992-2015) of observed waves, winds and TC-track information to stratify storm-centered composite maps of waves and winds according to TC intensities and translation speeds (Uh). While the wind field is rightward-asymmetric independent of Uh, the wave field is rightward-symmetric in concert with the wind for slow-translating TCs (Uh ≤ 3 m s-1), but right-rear asymmetric with strongest waves in the 4th quadrant for medium to fast-translating TCs (3 < Uh ≤ 7 m s-1), especially for the very fast storms (Uh > 7 m s-1), all independent of TC-intensity. The dominance of the right-rear asymmetry for fast-translating TCs appears to be related to the development of cross swells as the storms move faster, but further research using models are needed to understand the physical mechanisms.

A new equation in two dimensional fast magnetoacoustic shock waves in electron-positron-ion plasmas

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

Masood, W.; Jehan, Nusrat; Mirza, Arshad M.

2010-03-15

Nonlinear properties of the two dimensional fast magnetoacoustic waves are studied in a three-component plasma comprising of electrons, positrons, and ions. In this regard, Kadomtsev-Petviashvili-Burger (KPB) equation is derived using the small amplitude perturbation expansion method. Under the condition that the electron and positron inertia are ignored, Burger-Kadomtsev-Petviashvili (Burger-KP) for a fast magnetoacoustic wave is derived for the first time, to the best of author's knowledge. The solutions of both KPB and Burger-KP equations are obtained using the tangent hyperbolic method. The effects of positron concentration, kinematic viscosity, and plasma beta are explored both for the KPB and the Burger-KPmore » shock waves and the differences between the two are highlighted. The present investigation may have relevance in the study of nonlinear electromagnetic shock waves both in laboratory and astrophysical plasmas.« less

Calibration and validation of a spar-type floating offshore wind turbine model using the FAST dynamic simulation tool

DOE PAGES

Browning, J. R.; Jonkman, J.; Robertson, A.; ...

2014-12-16

In this study, high-quality computer simulations are required when designing floating wind turbines because of the complex dynamic responses that are inherent with a high number of degrees of freedom and variable metocean conditions. In 2007, the FAST wind turbine simulation tool, developed and maintained by the U.S. Department of Energy's (DOE's) National Renewable Energy Laboratory (NREL), was expanded to include capabilities that are suitable for modeling floating offshore wind turbines. In an effort to validate FAST and other offshore wind energy modeling tools, DOE funded the DeepCwind project that tested three prototype floating wind turbines at 1/50 th scalemore » in a wave basin, including a semisubmersible, a tension-leg platform, and a spar buoy. This paper describes the use of the results of the spar wave basin tests to calibrate and validate the FAST offshore floating simulation tool, and presents some initial results of simulated dynamic responses of the spar to several combinations of wind and sea states. Wave basin tests with the spar attached to a scale model of the NREL 5-megawatt reference wind turbine were performed at the Maritime Research Institute Netherlands under the DeepCwind project. This project included free-decay tests, tests with steady or turbulent wind and still water (both periodic and irregular waves with no wind), and combined wind/wave tests. The resulting data from the 1/50th model was scaled using Froude scaling to full size and used to calibrate and validate a full-size simulated model in FAST. Results of the model calibration and validation include successes, subtleties, and limitations of both wave basin testing and FAST modeling capabilities.« less

Electrostatic waves driven by electron beam in lunar wake plasma

NASA Astrophysics Data System (ADS)

Sreeraj, T.; Singh, S. V.; Lakhina, G. S.

2018-05-01

A linear analysis of electrostatic waves propagating parallel to the ambient field in a four component homogeneous, collisionless, magnetised plasma comprising fluid protons, fluid He++, electron beam, and suprathermal electrons following kappa distribution is presented. In the absence of electron beam streaming, numerical analysis of the dispersion relation shows six modes: two electron acoustic modes (modes 1 and 6), two fast ion acoustic modes (modes 2 and 5), and two slow ion acoustic modes (modes 3 and 4). The modes 1, 2 and 3 and modes 4, 5, and 6 have positive and negative phase speeds, respectively. With an increase in electron beam speed, the mode 6 gets affected the most and the phase speed turns positive from negative. The mode 6 thus starts to merge with modes 2 and 3 and generates the electron beam driven fast and slow ion acoustic waves unstable with a finite growth. The electron beam driven slow ion-acoustic waves occur at lower wavenumbers, whereas fast ion-acoustic waves occur at a large value of wavenumbers. The effect of various other parameters has also been studied. We have applied this analysis to the electrostatic waves observed in lunar wake during the first flyby of the ARTEMIS mission. The analysis shows that the low (high) frequency waves observed in the lunar wake could be the electron beam driven slow (fast) ion-acoustic modes.

Alfvén wave dynamics at the neighborhood of a 2.5D magnetic null-point

NASA Astrophysics Data System (ADS)

Sabri, S.; Vasheghani Farahani, S.; Ebadi, H.; Hosseinpour, M.; Fazel, Z.

2018-05-01

The aim of the present study is to highlight the energy transfer via the interaction of magnetohydrodynamic waves with a 2.5D magnetic null-point in a finite plasma-β regime of the solar corona. An initially symmetric Alfvén pulse at a specific distance from a magnetic null-point is kicked towards the isothermal null-point. A shock-capturing Godunov-type PLUTO code is used to solve the ideal magnetohydrodynamic set equations in the context of wave-plasma energy transfer. As the Alfvén wave propagates towards the magnetic null-point it experiences speed lowering which ends up in releasing energy along the separatrices. In this line owing to the Alfvén wave, a series of events take place that contribute towards coronal heating. Nonlinear induced waves are by products of the torsional Alfvén interaction with magnetic null-points. The energy of these induced waves which are fast magnetoacoustic (transverse) and slow magnetoacoustic (longitudinal) waves are supplied by the Alfvén wave. The nonlinearly induced density perturbations are proportional to the Alfvén wave energy loss. This supplies energy for the propagation of fast and slow magnetoacoustic waves, where in contrast to the fast wave the slow wave experiences a continuous energy increase. As such, the slow wave may transfer its energy to the medium at later times, maintaining a continuous heating mechanism at the neighborhood of a magnetic null-point.

Numerical Simulation of Bow Waves and Transom-Stern Flows

NASA Astrophysics Data System (ADS)

Dommermuth, Douglas G.; Schlageter, Eric A.; Talcott, John C.; Wyatt, Donald C.; Novikov, Evgeny A.

1997-11-01

A stratified-flow formulation is used to model the breaking bow wave and the separated transom-stern flow that are generated by a ship moving with forward speed. The interface of the air with the water is identified as the zero level-set of a three-dimensional function. The ship is modeled using a body-force technique on a cartesian grid. The three-dimensional body-force is generated using a surface panelization of the entire ship, including the above-water geometry up to and including the deck. The effects of surface tension are modeled as a source term that is concentrated at the air-water interface. The effects of gravity are modeled as a volumetric force. The three-dimensional, unsteady, Navier-Stokes equations are expressed in primitive-variable form. A LES formulation with a Smagorinsky sub-grid-scale model is used to model turbulence. Numerical convergence is demonstrated using 128x64x65, 256x128x129, and 512x256x257 grid points. The numerical results compare well to whisker-probe measurements of the free-surface elevation generated by a naval combatant.

Effects of wind waves versus ship waves on tidal marsh plants: a flume study on different life stages of Scirpus maritimus.

PubMed

Silinski, Alexandra; Heuner, Maike; Schoelynck, Jonas; Puijalon, Sara; Schröder, Uwe; Fuchs, Elmar; Troch, Peter; Bouma, Tjeerd J; Meire, Patrick; Temmerman, Stijn

2015-01-01

Recent research indicates that many ecosystems, including intertidal marshes, follow the alternative stable states theory. This theory implies that thresholds of environmental factors can mark a limit between two opposing stable ecosystem states, e.g. vegetated marshes and bare mudflats. While elevation relative to mean sea level is considered as the overall threshold condition for colonization of mudflats by vegetation, little is known about the individual driving mechanisms, in particular the impact of waves, and more specifically of wave period. We studied the impact of different wave regimes on plants in a full scale flume experiment. Seedlings and adult shoots of the pioneer Scirpus maritimus were subjected to two wave periods at two water levels. Drag forces acting on, and sediment scouring occurring around the plants were quantified, as these are the two main mechanisms determining plant establishment and survival. Depending on life stage, two distinct survival strategies emerge: seedlings present a stress avoidance strategy by being extremely flexible, thus limiting the drag forces and thereby the risk of breaking. Adult shoots present a stress tolerance strategy by having stiffer stems, which gives them a higher resistance to breaking. These strategies work well under natural, short period wind wave conditions. For long period waves, however, caused e.g. by ships, these survival strategies have a high chance to fail as the flexibility of seedlings and stiffness of adults lead to plant tissue failure and extreme drag forces respectively. This results in both cases in strongly bent plant stems, potentially limiting their survival.

Effects of Wind Waves versus Ship Waves on Tidal Marsh Plants: A Flume Study on Different Life Stages of Scirpus maritimus

PubMed Central

Schoelynck, Jonas; Puijalon, Sara; Schröder, Uwe; Fuchs, Elmar; Troch, Peter; Bouma, Tjeerd J.; Meire, Patrick; Temmerman, Stijn

2015-01-01

Recent research indicates that many ecosystems, including intertidal marshes, follow the alternative stable states theory. This theory implies that thresholds of environmental factors can mark a limit between two opposing stable ecosystem states, e.g. vegetated marshes and bare mudflats. While elevation relative to mean sea level is considered as the overall threshold condition for colonization of mudflats by vegetation, little is known about the individual driving mechanisms, in particular the impact of waves, and more specifically of wave period. We studied the impact of different wave regimes on plants in a full scale flume experiment. Seedlings and adult shoots of the pioneer Scirpus maritimus were subjected to two wave periods at two water levels. Drag forces acting on, and sediment scouring occurring around the plants were quantified, as these are the two main mechanisms determining plant establishment and survival. Depending on life stage, two distinct survival strategies emerge: seedlings present a stress avoidance strategy by being extremely flexible, thus limiting the drag forces and thereby the risk of breaking. Adult shoots present a stress tolerance strategy by having stiffer stems, which gives them a higher resistance to breaking. These strategies work well under natural, short period wind wave conditions. For long period waves, however, caused e.g. by ships, these survival strategies have a high chance to fail as the flexibility of seedlings and stiffness of adults lead to plant tissue failure and extreme drag forces respectively. This results in both cases in strongly bent plant stems, potentially limiting their survival. PMID:25799017

Fast Magnetosonic Waves Observed by Van Allen Probes: Testing Local Wave Excitation Mechanism

NASA Astrophysics Data System (ADS)

Min, Kyungguk; Liu, Kaijun; Wang, Xueyi; Chen, Lunjin; Denton, Richard E.

2018-01-01

Linear Vlasov theory and particle-in-cell (PIC) simulations for electromagnetic fluctuations in a homogeneous, magnetized, and collisionless plasma are used to investigate a fast magnetosonic wave event observed by the Van Allen Probes. The fluctuating magnetic field observed exhibits a series of spectral peaks at harmonics of the proton cyclotron frequency Ωp and has a dominant compressional component, which can be classified as fast magnetosonic waves. Furthermore, the simultaneously observed proton phase space density exhibits positive slopes in the perpendicular velocity space, ∂fp/∂v⊥>0, which can be a source for these waves. Linear theory analyses and PIC simulations use plasma and field parameters measured in situ except that the modeled proton distribution is modified to have larger ∂fp/∂v⊥ under the assumption that the observed distribution corresponds to a marginally stable state when the distribution has already been scattered by the excited waves. The results show that the positive slope is the source of the proton cyclotron harmonic waves at propagation quasi-perpendicular to the background magnetic field, and as a result of interactions with the excited waves the evolving proton distribution progresses approximately toward the observed distribution.

Partial Reflection and Trapping of a Fast-mode Wave in Solar Coronal Arcade Loops

NASA Astrophysics Data System (ADS)

Kumar, Pankaj; Innes, D. E.

2015-04-01

We report on the first direct observation of a fast-mode wave propagating along and perpendicular to cool (171 Å) arcade loops observed by the Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA). The wave was associated with an impulsive/compact flare near the edge of a sunspot. The EUV wavefront expanded radially outward from the flare center and decelerated in the corona from 1060 to 760 km s-1 within ˜3-4 minutes. Part of the EUV wave propagated along a large-scale arcade of cool loops and was partially reflected back to the flare site. The phase speed of the wave was about 1450 km s-1, which is interpreted as a fast-mode wave. A second overlying loop arcade, orientated perpendicular to the cool arcade, is heated and becomes visible in the AIA hot channels. These hot loops sway in time with the EUV wave, as it propagated to and fro along the lower loop arcade. We suggest that an impulsive energy release at one of the footpoints of the arcade loops causes the onset of an EUV shock wave that propagates along and perpendicular to the magnetic field.

Large-amplitude hydromagnetic waves in collisionless relativistic plasma - Exact solution for the fast-mode magnetoacoustic wave

NASA Technical Reports Server (NTRS)

Barnes, A.

1983-01-01

An exact nonlinear solution is found to the relativistic kinetic and electrodynamic equations (in their hydromagnetic limit) that describes the large-amplitude fast-mode magnetoacoustic wave propagating normal to the magnetic field in a collisionless, previously uniform plasma. It is pointed out that a wave of this kind will be generated by transverse compression of any collisionless plasma. The solution is in essence independent of the detailed form of the particle momentum distribution functions. The solution is obtained, in part, through the method of characteristics; the wave exhibits the familiar properties of steepening and shock formation. A detailed analysis is given of the ultrarelativistic limit of this wave.

An Extreme-ultraviolet Wave Generating Upward Secondary Waves in a Streamer-like Solar Structure

NASA Astrophysics Data System (ADS)

Zheng, Ruisheng; Chen, Yao; Feng, Shiwei; Wang, Bing; Song, Hongqiang

2018-05-01

Extreme-ultraviolet (EUV) waves, spectacular horizontally propagating disturbances in the low solar corona, always trigger horizontal secondary waves (SWs) when they encounter the ambient coronal structure. We present the first example of upward SWs in a streamer-like structure after the passing of an EUV wave. This event occurred on 2017 June 1. The EUV wave happened during a typical solar eruption including a filament eruption, a coronal mass ejection (CME), and a C6.6 flare. The EUV wave was associated with quasi-periodic fast propagating (QFP) wave trains and a type II radio burst that represented the existence of a coronal shock. The EUV wave had a fast initial velocity of ∼1000 km s‑1, comparable to high speeds of the shock and the QFP wave trains. Intriguingly, upward SWs rose slowly (∼80 km s‑1) in the streamer-like structure after the sweeping of the EUV wave. The upward SWs seemed to originate from limb brightenings that were caused by the EUV wave. All of the results show that the EUV wave is a fast-mode magnetohydrodynamic (MHD) shock wave, likely triggered by the flare impulses. We suggest that part of the EUV wave was probably trapped in the closed magnetic fields of the streamer-like structure, and upward SWs possibly resulted from the release of slow-mode trapped waves. It is believed that the interplay of the strong compression of the coronal shock and the configuration of the streamer-like structure is crucial for the formation of upward SWs.

Associations between major chain fast-food outlet availability and change in body mass index: a longitudinal observational study of women from Victoria, Australia.

PubMed

Lamb, Karen E; Thornton, Lukar E; Olstad, Dana Lee; Cerin, Ester; Ball, Kylie

2017-10-16

The residential neighbourhood fast-food environment has the potential to lead to increased levels of obesity by providing opportunities for residents to consume energy-dense products. This longitudinal study aimed to examine whether change in body mass index (BMI) differed dependent on major chain fast-food outlet availability among women residing in disadvantaged neighbourhoods. Eighty disadvantaged neighbourhoods in Victoria, Australia. Sample of 882 women aged 18-46 years at baseline (wave I: 2007/2008) who remained at the same residential location at all three waves (wave II: 2010/2011; wave III: 2012/2013) of the Resilience for Eating and Activity Despite Inequality study. BMI based on self-reported height and weight at each wave. There was no evidence of an interaction between time and the number of major chain fast-food outlets within 2 (p=0.88), 3 (p=0.66) or 5 km (p=0.24) in the multilevel models of BMI. Furthermore, there was no evidence of an interaction between time and change in availability at any distance and BMI. Change in BMI was not found to differ by residential major chain fast-food outlet availability among Victorian women residing in disadvantaged neighbourhoods. It may be that exposure to fast-food outlets around other locations regularly visited influence change in BMI. Future research needs to consider what environments are the key sources for accessing and consuming fast food and how these relate to BMI and obesity risk. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Reflection of Fast Magnetosonic Waves near a Magnetic Reconnection Region

NASA Astrophysics Data System (ADS)

Provornikova, E.; Laming, J. M.; Lukin, V. S.

2018-06-01

Magnetic reconnection in the solar corona is thought to be unstable with the formation of multiple interacting plasmoids, and previous studies have shown that plasmoid dynamics can trigger MHD waves of different modes propagating outward from the reconnection site. However, variations in plasma parameters and magnetic field strength in the vicinity of a coronal reconnection site may lead to wave reflection and mode conversion. In this paper we investigate the reflection and refraction of fast magnetoacoustic waves near a reconnection site. Under a justified assumption of an analytically specified Alfvén speed profile, we derive and solve analytically the full wave equation governing the propagation of fast-mode waves in a non-uniform background plasma without recourse to the small wavelength approximation. We show that the waves undergo reflection near the reconnection current sheet due to the Alfvén speed gradient and that the reflection efficiency depends on the plasma-β parameter, as well as on the wave frequency. In particular, we find that waves are reflected more efficiently near reconnection sites in a low-β plasma, which is typical under solar coronal conditions. Also, the reflection is larger for lower-frequency waves while high-frequency waves propagate outward from the reconnection region almost without the reflection. We discuss the implications of efficient wave reflection near magnetic reconnection sites in strongly magnetized coronal plasma for particle acceleration, and also the effect this might have on first ionization potential (FIP) fractionation by the ponderomotive force of these waves in the chromosphere.

Seismic seiches

USGS Publications Warehouse

McGarr, Arthur; Gupta, Harsh K.

2011-01-01

Seismic seiche is a term first used by Kvale (1955) to discuss oscillations of lake levels in Norway and England caused by the Assam earthquake of August 15, 1950. This definition has since been generalized to apply to standing waves set up in closed, or partially closed, bodies of water including rivers, shipping channels, lakes, swimming pools and tanks due to the passage of seismic waves from an earthquake.

Vertical Ship Motion Study for Ambrose Entrance Channel, New York

DTIC Science & Technology

2014-05-01

channels, PIANC Bulletin 1971, Vol. 1, No. 7, 17-20. Hardy, T. A. 1993. The attenuation of spectral transformation of wind waves on a coral reef ...A80(12): 95 p. Hearn, C. J. 1999. Wave -breaking hydrodynamics within coral reef systems and the effect of changing relative sea level, Journal of...Values of cf applied for coral reefs range from 0.05 to 0.40 (Hardy 1993; Hearn 1999 and Lowe et al. 2005). CMS- Wave uses a default value of cf

U.S. Southern Command Official Website

Science.gov Websites

an estimated $180 million. The drugs represent six separate drug interdictions since February. Group -ship firefighting to extinguish a fire aboard a low-profile go-fast drug vessel. Colombian President

Preliminary study of slow and fast ultrasonic waves using MR images of trabecular bone phantom

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

Solis-Najera, S. E., E-mail: solisnajera@ciencias.unam.mx, E-mail: angel.perez@ciencias.unam.mx, E-mail: lucia.medina@ciencias.unam.mx; Neria-Pérez, J. A., E-mail: solisnajera@ciencias.unam.mx, E-mail: angel.perez@ciencias.unam.mx, E-mail: lucia.medina@ciencias.unam.mx; Medina, L., E-mail: solisnajera@ciencias.unam.mx, E-mail: angel.perez@ciencias.unam.mx, E-mail: lucia.medina@ciencias.unam.mx

Cancellous bone is a complex tissue that performs physiological and biomechanical functions in all vertebrates. It is made up of trabeculae that, from a simplified structural viewpoint, can be considered as plates and beams in a hyperstatic structure that change with time leading to osteoporosis. Several methods has been developed to study the trabecular bone microstructure among them is the Biot’s model which predicts the existence of two longitudinal waves in porous media; the slow and the fast waves, that can be related to porosity of the media. This paper is focused on the experimental detection of the two Biot’smore » waves of a trabecular bone phantom, consisting of a trabecular network of inorganic hydroxyapatite. Experimental measurements of both waves were performed using through transmission ultrasound. Results had shown clearly that the propagation of two waves propagation is transversal to the trabecular alignment. Otherwise the waves are overlapped and a single wave seems to be propagated. To validate these results, magnetic resonance images were acquired to assess the trabecular direction, and to assure that the pulses correspond to the slow and fast waves. This approach offers a methodology for non-invasive studies of trabecular bones.« less

Seafloor Geodesy usi­ng Wave Gliders to study Earthquake and Tsunami Hazards at Subduction Zones

NASA Astrophysics Data System (ADS)

Sathiakumar, S.; Barbot, S.; Hill, E.; Peng, D.; Zerucha, J.; Suhaimee, S.; Chia, G.; Salamena, G. G.; Syahailatua, A.

2016-12-01

Land-based GNSS networks are now in place to monitor most subduction zones of the world. These provide valuable information about the amount of­ geodetic strain accumulated in the region, which in turn gives insight into the seismic potential. However, it is usually impossible to resolve activity on the megathrust near the trench using land-based GNSS data alone, given typical signal-to-noise ratios. Ship-based seafloor geodesy is being used today to fill this observation gap. However, surveys using ships are very expensive, tedious and impractical due to the large areas to be covered. Instead of discrete missions using ships, continuous monitoring of the seafloor using autonomous marine robots would aid in understanding the tectonic setting of the seafloor better at a potentially lower cost, as well as help in designing better warning systems. Thus, we are developing seafloor geodesy capabilities using Wave Gliders, a new class of wave-propelled, persistent marine autonomous vehicle using a combination of acoustic and GNSS technologies. We use GNSS/INS to position the platform, and acoustic ranging to locate the seafloor. The GNSS/INS system to be integrated with the Wave Gliders has stringent requirements of low power, light weight, and high accuracy. All these factors are equally important due to limited power and space in the Wave Gliders and the need for highly accurate and precise measurements. With this hardware setup, a limiting factor is the accuracy of measurement of the sound velocity in the water column. We plan to obtain precise positioning of seafloor by exploring a measurement setup that minimizes uncertainties in sound velocity. This will be achieved by making fine-resolution measurements of the two-way travel time of the acoustic waves underwater using the Wave Gliders, and performing statistical signal processing on this data to obtain more reliable sound velocity measurement. This enhanced seafloor geodetic technique using Wave Gliders should enable us to measure deformation of the seafloor over annual and decadal time scales. Combination of seafloor data with land based GPS networks would allow us to study processes from the deep-ocean trench to the coast in a better way, and thereby give a more complete picture of the subduction process.

Ion absorption of the high harmonic fast wave in the National Spherical Torus Experiment

NASA Astrophysics Data System (ADS)

Rosenberg, Adam Lewis

Ion absorption of the high harmonic fast wave in a spherical torus is of critical importance to assessing the viability of the wave as a means of heating and driving current. Analysis of recent NSTX shots has revealed that under some conditions when neutral beam and RF power are injected into the plasma simultaneously, a fast ion population with energy above the beam injection energy is sustained by the wave. In agreement with modeling, these experiments find the RF-induced fast ion tail strength and neutron rate at lower B-fields to be less enhanced, likely due to a larger β profile, which promotes greater off-axis absorption where the fast ion population is small. Ion loss codes find the increased loss fraction with decreased B insufficient to account for the changes in tail strength, providing further evidence that this is an RF interaction effect. Though greater ion absorption is predicted with lower k∥, surprisingly little variation in the tail was observed, along with a neutron rate enhancement with higher k∥. Data from the neutral particle analyzer, neutron detectors, x-ray crystal spectrometer, and Thomson scattering is presented, along with results from the TRANSP transport analysis code, ray-tracing codes HPRT and CURRAY, full-wave code and AORSA, quasilinear code CQL3D, and ion loss codes EIGOL and CONBEAM.

Numerical Simulation of Coronal Waves Interacting with Coronal Holes. III. Dependence on Initial Amplitude of the Incoming Wave

NASA Astrophysics Data System (ADS)

Piantschitsch, Isabell; Vršnak, Bojan; Hanslmeier, Arnold; Lemmerer, Birgit; Veronig, Astrid; Hernandez-Perez, Aaron; Čalogović, Jaša

2018-06-01

We performed 2.5D magnetohydrodynamic (MHD) simulations showing the propagation of fast-mode MHD waves of different initial amplitudes and their interaction with a coronal hole (CH), using our newly developed numerical code. We find that this interaction results in, first, the formation of reflected, traversing, and transmitted waves (collectively, secondary waves) and, second, in the appearance of stationary features at the CH boundary. Moreover, we observe a density depletion that is moving in the opposite direction of the incoming wave. We find a correlation between the initial amplitude of the incoming wave and the amplitudes of the secondary waves as well as the peak values of the stationary features. Additionally, we compare the phase speed of the secondary waves and the lifetime of the stationary features to observations. Both effects obtained in the simulation, the evolution of secondary waves, as well as the formation of stationary fronts at the CH boundary, strongly support the theory that coronal waves are fast-mode MHD waves.

Ship-wave-shaped wave clouds induced by Kuril Islands

NASA Image and Video Library

2015-06-09

The Kuril Islands are a string of volcanically-formed islands that stretch between Russia and Japan, separating the North Pacific Ocean from the Sea of Okhotsk. Subject to the cold, moist breezes from the North Atlantic, and the frigid air from Siberia, the climate is severe, with frequent storms, and ever-present winds, which often reach hurricane strength. Cloudy, windy conditions are common. On June 1, 2015 the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Aqua satellite captured this true-color image as it passed over the Kuril Islands. Clouds curl into the center of a storm system, bringing strong winds to the region. As the winds scrape over the tall volcanic peaks of the Kuril Islands, they become turbulent air behind the islands. The turbulence disturbs the cloudbank, etching its passage into a striking pattern that can be seen from space. This particular pattern is called “ship-waved-shaped wave clouds”, because the pattern can be likened to that formed behind a ship cutting through a smooth ocean. On the windward side of the Kuril Islands, the cloud bank is generally smooth, with streaks that are lined up parallel to the movement of the wind, blowing from the west and towards the east. Behind the tall volcanic peaks of the islands, V’s fan out on the leeward side, illustrating the flow of the turbulent air. Image Credit: Jeff Schmaltz, MODIS Land Rapid Response Team, NASA GSFC NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Projections of wind-waves in South China Sea for the 21st century

NASA Astrophysics Data System (ADS)

Mohammed, Aboobacker; Dykyi, Pavlo; Zheleznyak, Mark; Tkalich, Pavel

2013-04-01

IPCC-coordinated work has been completed within Fourth Assessment Report (AR4) to project climate and ocean variables for the 21st century using coupled atmospheric-ocean General Circulation Models (GCMs). GCMs are not having a wind-wave variable due to a poor grid resolution; therefore, dynamical downscaling of wind-waves to the regional scale is advisable using well established models, such as Wave Watch III (WWIII) and SWAN. Rectilinear-coordinates WWIII model is adapted for the far field comprising the part of Pacific and Indian Oceans centered at the South China Sea and Sunda Shelf (90 °E-130 °E, 10 °S - 26.83 °N) with a resolution of 10' (about 18 km). Near-field unstructured-mesh SWAN model covers Sunda Shelf and centered on Singapore Strait, while reading lateral boundary values from WWIII model. The unstructured grid has the coarsest resolution in the South China Sea (6 to 10 km), medium resolution in the Malacca Strait (1 to 2 km), and the finest resolution in the Singapore Strait (400 m) and along the Singapore coastline (up to 100 m). Following IPCC methodology, the model chain is validated climatologically for the past period 1961-1990 against Voluntary Observing Ship (VOS) data; additionally, the models are validated using recent high-resolution satellite data. The calibrated model chain is used to project waves to 21st century using WRF-downscaled wind speed output of CCSM GCM run for A1FI climate change scenario. To comply with IPCC methodology the entire modeling period is split into three 30-years periods for which statistical parameters are computed individually. Time series of significant wave height at key points near Singapore and on ship sea routes in the SCS are statistically analysed to get probability distribution functions (PDFs) of extreme values. Climatological maps of mean and maximum significant wave height (SWH) values, and mean wave period are built for Singapore region for each 30-yrs period. Linear trends of mean SWH values for northeast (NE) and southwest (SW) monsoons have been derived. The maximum values of predicted 100 year return period (YRP) SWH are obtained for the 1st 30-yrs period (2011-2040). In the deep eastern part of the Singapore, 100yrp SWH are 2.4 - 2.8 m, whereas those at the shallow nearshore areas are 1.7-2.3 m. On the ship routes at Sunda Shelf the 100 YRP SWHs are 1.1 - 3.2 m, and those at the SCS routes are 3.6 - 10.4 m. The biggest changes in future against hindcasted SWH is in first 30-yrs, where extreme 100 YRP SWH will grow up in the range from 36%-120% at points near Singapore and to 39%-108% at ship sea routes.

Passive bottom reflection-loss estimation using ship noise and a vertical line array.

PubMed

Muzi, Lanfranco; Siderius, Martin; Verlinden, Christopher M

2017-06-01

An existing technique for passive bottom-loss estimation from natural marine surface noise (generated by waves and wind) is adapted to use noise generated by ships. The original approach-based on beamforming of the noise field recorded by a vertical line array of hydrophones-is retained; however, additional processing is needed in order for the field generated by a passing ship to show features that are similar to those of the natural surface-noise field. A necessary requisite is that the ship position, relative to the array, varies over as wide a range of steering angles as possible, ideally passing directly over the array to ensure coverage of the steepest angles. The methodology is illustrated through simulation and applied to data from a field experiment conducted offshore of San Diego, CA in 2009.

Quasi-periodic Counter-propagating Fast Magnetosonic Wave Trains from Neighboring Flares: SDO/AIA Observations and 3D MHD Modeling

NASA Astrophysics Data System (ADS)

Ofman, Leon; Liu, Wei

2018-06-01

Since their discovery by the Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA) in the extreme ultraviolet, rapid (phase speeds of ∼1000 km s‑1), quasi-periodic, fast-mode propagating (QFP) wave trains have been observed accompanying many solar flares. They typically propagate in funnel-like structures associated with the expanding magnetic field topology of the active regions (ARs). The waves provide information on the associated flare pulsations and the magnetic structure through coronal seismology (CS). The reported waves usually originate from a single localized source associated with the flare. Here we report the first detection of counter-propagating QFPs associated with two neighboring flares on 2013 May 22, apparently connected by large-scale, trans-equatorial coronal loops. We present the first results of a 3D MHD model of counter-propagating QFPs in an idealized bipolar AR. We investigate the excitation, propagation, nonlinearity, and interaction of the counter-propagating waves for a range of key model parameters, such as the properties of the sources and the background magnetic structure. In addition to QFPs, we also find evidence of trapped fast- (kink) and slow-mode waves associated with the event. We apply CS to determine the magnetic field strength in an oscillating loop during the event. Our model results are in qualitative agreement with the AIA-observed counter-propagating waves and used to identify the various MHD wave modes associated with the observed event, providing insights into their linear and nonlinear interactions. Our observations provide the first direct evidence of counter-propagating fast magnetosonic waves that can potentially lead to turbulent cascade and carry significant energy flux for coronal heating in low-corona magnetic structures.

An FMM-FFT Accelerated SIE Simulator for Analyzing EM Wave Propagation in Mine Environments Loaded With Conductors

PubMed Central

Sheng, Weitian; Zhou, Chenming; Liu, Yang; Bagci, Hakan; Michielssen, Eric

2018-01-01

A fast and memory efficient three-dimensional full-wave simulator for analyzing electromagnetic (EM) wave propagation in electrically large and realistic mine tunnels/galleries loaded with conductors is proposed. The simulator relies on Muller and combined field surface integral equations (SIEs) to account for scattering from mine walls and conductors, respectively. During the iterative solution of the system of SIEs, the simulator uses a fast multipole method-fast Fourier transform (FMM-FFT) scheme to reduce CPU and memory requirements. The memory requirement is further reduced by compressing large data structures via singular value and Tucker decompositions. The efficiency, accuracy, and real-world applicability of the simulator are demonstrated through characterization of EM wave propagation in electrically large mine tunnels/galleries loaded with conducting cables and mine carts. PMID:29726545

Multi-frequency ICRF diagnostic of Tokamak plasmas

NASA Astrophysics Data System (ADS)

Lafonteese, David James

This thesis explores the diagnostic possibilities of a fast wave-based method for measuring the ion density and temperature profiles of tokamak plasmas. In these studies fast waves are coupled to the plasma at frequencies at the second harmonic of the ion gyrofrequency, at which wave energy is absorbed by the finite-temperature ions. As the ion gyrofrequency is dependent upon the local magnetic field, which varies as l/R in a tokamak, this power absorption is radially localized. The simultaneous launching of multiple frequencies, all resonating at different plasma positions, allows local measurements of the ion density and temperature. To investigate the profile applications of wave damping measurements in a simulated tokamak, an inhouse slab-model ICRF code is developed. A variety of analysis methods are presented, and ion density and temperature profiles are reconstructed for hydrogen plasmas for the Electric Tokamak (ET) and ITER parameter spaces. These methods achieve promising results in simulated plasmas featuring bulk ion heating, off-axis RF heating, and density ramps. The experimental results of similar studies on the Electric Tokamak, a high aspect ratio (R/a = 5), low toroidal field (2.2 kG) device are then presented. In these studies, six fast wave frequencies were coupled using a single-strap, low-field-side antenna to ET plasmas. The frequencies were variable, and could be tuned to resonate at different radii for different experiments. Four magnetic pickup loops were used to measure of the toroidal component of the wave magnetic field. The expected greater eigenmode damping of center-resonant frequencies versus edge-resonant frequencies is consistently observed. Comparison of measured aspects of fast wave behavior in ET is made with the slab code predictions, which validate the code simulations under weakly-damped conditions. A density profile is measured for an ET discharge through analysis of the fast wave measurements, and is compared to an electron density profile derived from Thomson scattering data. The methodology behind a similar measurement of the ion temperature profile is also presented.

Feasibility of UltraFast Doppler in Post-operative Evaluation of Hepatic Artery in Recipients following Liver Transplantation.

PubMed

Kim, Se-Young; Kim, Kyoung Won; Choi, Sang Hyun; Kwon, Jae Hyun; Song, Gi-Won; Kwon, Heon-Ju; Yun, Young Ju; Lee, Jeongjin; Lee, Sung-Gyu

2017-11-01

To determine the feasibility of using UltraFast Doppler in post-operative evaluation of the hepatic artery (HA) after liver transplantation (LT), we evaluated 283 simultaneous conventional and UltraFast Doppler sessions in 126 recipients over a 2-mo period after LT, using an Aixplorer scanner The Doppler indexes of the HA (peak systolic velocity [PSV], end-diastolic velocity [EDV], resistive index [RI] and systolic acceleration time [SAT]) by retrospective analysis of retrieved waves from UltraFast Doppler clips were compared with those obtained by conventional spectral Doppler. Correlation, performance in diagnosing the pathologic wave, examination time and reproducibility were evaluated. The PSV, EDV, RI and SAT of spectral and UltraFast Doppler measurements exhibited excellent correlation with favorable diagnostic performance. During the bedside examination, the mean time spent for UltraFast clip storing was significantly shorter than that for conventional Doppler US measurements. Both conventional and UltraFast Doppler exhibited good to excellent inter-analysis consistency. In conclusion, compared with conventional spectral Doppler, UltraFast Doppler values correlated excellently and yielded acceptable pathologic wave diagnostic performance with reduced examination time at the bedside and excellent reproducibility. Copyright © 2017 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Waves and Tsunami Project

ERIC Educational Resources Information Center

Frashure, K. M.; Chen, R. F.; Stephen, R. A.; Bolmer, T.; Lavin, M.; Strohschneider, D.; Maichle, R.; Micozzi, N.; Cramer, C.

2007-01-01

Demonstrating wave processes quantitatively in the classroom using standard classroom tools (such as Slinkys and wave tanks) can be difficult. For example, waves often travel too fast for students to actually measure amplitude or wavelength. Also, when teaching propagating waves, reflections from the ends set up standing waves, which can confuse…

Ship wakes and spectrograms: mathematical modelling and experimental data for finite-depth flows

NASA Astrophysics Data System (ADS)

McCue, Scott; Pethiyagoda, Ravindra; Moroney, Timothy; Macfarlane, Gregor; Binns, Jonathan

2017-11-01

We are concerned with how properties of a ship wake can be extracted from surface height data collected at a single point as the ship travels past. The tool we use is a spectrogram, which is a heat map that visualises the time-dependent frequency spectrum of the surface height signal. In this talk, the focus will be on presenting the theoretical framework which involves an idealised mathematical model with a pressure distribution applied to the surface. A geometric argument based on linear water wave theory provides encouraging results for both subcritical and supercritical flow regimes. We then summarise some recent findings obtained by comparing our analysis to experimental data collected at the Australian Maritime College for various sailing speeds and hull shapes*. Our work has the potential to inform ship design, the detection of irregular vessels, and how coastal damage is attributed to specific vessels in shipping channels. We acknowledge support of the Australian Research Council via the Discovery Project DP140100933.

Ship Detection Based on Multiple Features in Random Forest Model for Hyperspectral Images

NASA Astrophysics Data System (ADS)

Li, N.; Ding, L.; Zhao, H.; Shi, J.; Wang, D.; Gong, X.

2018-04-01

A novel method for detecting ships which aim to make full use of both the spatial and spectral information from hyperspectral images is proposed. Firstly, the band which is high signal-noise ratio in the range of near infrared or short-wave infrared spectrum, is used to segment land and sea on Otsu threshold segmentation method. Secondly, multiple features that include spectral and texture features are extracted from hyperspectral images. Principal components analysis (PCA) is used to extract spectral features, the Grey Level Co-occurrence Matrix (GLCM) is used to extract texture features. Finally, Random Forest (RF) model is introduced to detect ships based on the extracted features. To illustrate the effectiveness of the method, we carry out experiments over the EO-1 data by comparing single feature and different multiple features. Compared with the traditional single feature method and Support Vector Machine (SVM) model, the proposed method can stably achieve the target detection of ships under complex background and can effectively improve the detection accuracy of ships.

Marine traffic model based on cellular automaton: Considering the change of the ship's velocity under the influence of the weather and sea

NASA Astrophysics Data System (ADS)

Qi, Le; Zheng, Zhongyi; Gang, Longhui

2017-10-01

It was found that the ships' velocity change, which is impacted by the weather and sea, e.g., wind, sea wave, sea current, tide, etc., is significant and must be considered in the marine traffic model. Therefore, a new marine traffic model based on cellular automaton (CA) was proposed in this paper. The characteristics of the ship's velocity change are taken into account in the model. First, the acceleration of a ship was divided into two components: regular component and random component. Second, the mathematical functions and statistical distribution parameters of the two components were confirmed by spectral analysis, curve fitting and auto-correlation analysis methods. Third, by combining the two components, the acceleration was regenerated in the update rules for ships' movement. To test the performance of the model, the ship traffic flows in the Dover Strait, the Changshan Channel and the Qiongzhou Strait were studied and simulated. The results show that the characteristics of ships' velocities in the simulations are consistent with the measured data by Automatic Identification System (AIS). Although the characteristics of the traffic flow in different areas are different, the velocities of ships can be simulated correctly. It proves that the velocities of ships under the influence of weather and sea can be simulated successfully using the proposed model.

Coronal magnetohydrodynamic waves and oscillations: observations and quests.

PubMed

Aschwanden, Markus J

2006-02-15

Coronal seismology, a new field of solar physics that emerged over the last 5 years, provides unique information on basic physical properties of the solar corona. The inhomogeneous coronal plasma supports a variety of magnetohydrodynamics (MHD) wave modes, which manifest themselves as standing waves (MHD oscillations) and propagating waves. Here, we briefly review the physical properties of observed MHD oscillations and waves, including fast kink modes, fast sausage modes, slow (acoustic) modes, torsional modes, their diagnostics of the coronal magnetic field, and their physical damping mechanisms. We discuss the excitation mechanisms of coronal MHD oscillations and waves: the origin of the exciter, exciter propagation, and excitation in magnetic reconnection outflow regions. Finally, we consider the role of coronal MHD oscillations and waves for coronal heating, the detectability of various MHD wave types, and we estimate the energies carried in the observed MHD waves and oscillations: Alfvénic MHD waves could potentially provide sufficient energy to sustain coronal heating, while acoustic MHD waves fall far short of the required coronal heating rates.

Strain in shore fast ice due to incoming ocean waves and swell

NASA Astrophysics Data System (ADS)

Fox, Colin; Squire, Vernon A.

1991-03-01

Using a development from the theoretical model presented by Fox and Squire (1990), this paper investigates the strain field generated in shore fast ice by normally incident ocean waves and swell. After a brief description of the model and its convergence, normalized absolute strain (relative to a 1-m incident wave) is found as a function of distance from the ice edge for various wave periods, ice thicknesses, and water depths. The squared transfer function, giving the relative ability of incident waves of different periods to generate strain in the ice, is calculated, and its consequences are discussed. The ice is then forced with a Pierson-Moskowitz spectrum, and the consequent strain spectra are plotted as a function of penetration into the ice sheet. Finally, rms strain, computed as the incoherent sum of the strains resulting from energy in the open water spectrum, is found. The results have implications to the breakup of shore fast ice and hence to the floe size distribution of the marginal ice zone.

Influence of viscoelastic property on laser-generated surface acoustic waves in coating-substrate systems

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

Sun Hongxiang; Faculty of Science, Jiangsu University, Zhenjiang 212013; Zhang Shuyi

2011-04-01

Taking account of the viscoelasticity of materials, the pulsed laser generation of surface acoustic waves in coating-substrate systems has been investigated quantitatively by using the finite element method. The displacement spectra of the surface acoustic waves have been calculated in frequency domain for different coating-substrate systems, in which the viscoelastic properties of the coatings and substrates are considered separately. Meanwhile, the temporal displacement waveforms have been obtained by applying inverse fast Fourier transforms. The numerical results of the normal surface displacements are presented for different configurations: a single plate, a slow coating on a fast substrate, and a fast coatingmore » on a slow substrate. The influences of the viscoelastic properties of the coating and the substrate on the attenuation of the surface acoustic waves have been studied. In addition, the influence of the coating thickness on the attenuation of the surface acoustic waves has been also investigated in detail.« less

Interaction of solitons for obliquely propagating magnetoacoustic waves in stellar atmosphere

NASA Astrophysics Data System (ADS)

Jahangir, R.; Masood, W.; Siddiq, M.; Batool, Nazia

2016-12-01

We study here the nonlinear oblique propagation of magnetoacoustic waves in dense plasmas with degenerate electrons by deriving Kadomtsev-Petviashvili (KP) equation for small but finite amplitude perturbations. The two soliton interaction has been studied by finding the solution of the KP equation using the Hirota bilinear formalism. For illustrative purposes, we have used the plasma parameters typically found in white dwarf stars for both the fast and slow modes of magnetoacoustic waves. It has been observed that the soliton interaction in the fast and slow modes is strongly influenced by the predominant and weak dispersive coefficients of the KP equation. The single soliton behavior has also been explained for the fast and slow magnetoacoustic modes.

High-harmonic fast-wave power flow along magnetic field lines in the scrape-off layer of NSTX.

PubMed

Perkins, R J; Hosea, J C; Kramer, G J; Ahn, J-W; Bell, R E; Diallo, A; Gerhardt, S; Gray, T K; Green, D L; Jaeger, E F; Jaworski, M A; LeBlanc, B P; McLean, A; Maingi, R; Phillips, C K; Roquemore, L; Ryan, P M; Sabbagh, S; Taylor, G; Wilson, J R

2012-07-27

A significant fraction of high-harmonic fast-wave (HHFW) power applied to NSTX can be lost to the scrape-off layer (SOL) and deposited in bright and hot spirals on the divertor rather than in the core plasma. We show that the HHFW power flows to these spirals along magnetic field lines passing through the SOL in front of the antenna, implying that the HHFW power couples across the entire width of the SOL rather than mostly at the antenna face. This result will help guide future efforts to understand and minimize these edge losses in order to maximize fast-wave heating and current drive.

Formulation of the rotational transformation of wave fields and their application to digital holography.

PubMed

Matsushima, Kyoji

2008-07-01

Rotational transformation based on coordinate rotation in Fourier space is a useful technique for simulating wave field propagation between nonparallel planes. This technique is characterized by fast computation because the transformation only requires executing a fast Fourier transform twice and a single interpolation. It is proved that the formula of the rotational transformation mathematically satisfies the Helmholtz equation. Moreover, to verify the formulation and its usefulness in wave optics, it is also demonstrated that the transformation makes it possible to reconstruct an image on arbitrarily tilted planes from a wave field captured experimentally by using digital holography.

Preliminary assessment of landslide-induced wave hazards, Tidal Inlet, Glacier Bay National Park, Alaska

USGS Publications Warehouse

Wieczorek, Gerald F.; Jakob, Matthias; Motyka, Roman J.; Zirnheld, Sandra L.; Craw, Patricia

2003-01-01

A large potential rock avalanche above the northern shore of Tidal Inlet, Glacier Bay National Park, Alaska, was investigated to determine hazards and risks of landslide-induced waves to cruise ships and other park visitors. Field and photographic examination revealed that the 5 to 10 million cubic meter landslide moved between AD 1892 and 1919 after the retreat of Little Ice Age glaciers from Tidal Inlet by AD 1890. The timing of landslide movement and the glacial history suggest that glacial debuttressing caused weakening of the slope and that the landslide could have been triggered by large earthquakes of 1899-1900 in Yakutat Bay. Evidence of recent movement includes fresh scarps, back-rotated blocks, and smaller secondary landslide movements. However, until there is evidence of current movement, the mass is classified as a dormant rock slump. An earthquake on the nearby active Fairweather fault system could reactivate the landslide and trigger a massive rock slump and debris avalanche into Tidal Inlet. Preliminary analyses show that waves induced by such a landslide could travel at speeds of 45 to 50 m/s and reach heights up to 76 m with wave runups of 200 m on the opposite shore of Tidal Inlet. Such waves would not only threaten vessels in Tidal Inlet, but would also travel into the western arm of Glacier Bay endangering large cruise ships and their passengers.

Lower solar chromosphere-corona transition region. II - Wave pressure effects for a specific form of the heating function

NASA Technical Reports Server (NTRS)

Woods, D. Tod; Holzer, Thomas E.; Macgregor, Keith B.

1990-01-01

Lower transition region models with a balance between mechanical heating and radiative losses are expanded to include wave pressure effects. The models are used to study the simple damping length form of the heating function. The results are compared to the results obtained by Woods et al. (1990) for solutions in the lower transition region. The results suggest that a mixture of fast-mode and slow-mode waves may provide the appropriate heating mechanism in the lower transition region, with the decline in effective vertical wave speed caused by the refraction and eventual total reflection of the fast-mode wave resulting from the decreasing atmospheric density.

A fast automatic target detection method for detecting ships in infrared scenes

NASA Astrophysics Data System (ADS)

Özertem, Kemal Arda

2016-05-01

Automatic target detection in infrared scenes is a vital task for many application areas like defense, security and border surveillance. For anti-ship missiles, having a fast and robust ship detection algorithm is crucial for overall system performance. In this paper, a straight-forward yet effective ship detection method for infrared scenes is introduced. First, morphological grayscale reconstruction is applied to the input image, followed by an automatic thresholding onto the suppressed image. For the segmentation step, connected component analysis is employed to obtain target candidate regions. At this point, it can be realized that the detection is defenseless to outliers like small objects with relatively high intensity values or the clouds. To deal with this drawback, a post-processing stage is introduced. For the post-processing stage, two different methods are used. First, noisy detection results are rejected with respect to target size. Second, the waterline is detected by using Hough transform and the detection results that are located above the waterline with a small margin are rejected. After post-processing stage, there are still undesired holes remaining, which cause to detect one object as multi objects or not to detect an object as a whole. To improve the detection performance, another automatic thresholding is implemented only to target candidate regions. Finally, two detection results are fused and post-processing stage is repeated to obtain final detection result. The performance of overall methodology is tested with real world infrared test data.

Global Hybrid Simulation of Alfvenic Waves Associated with Magnetotail Reconnection and Fast Flows

NASA Astrophysics Data System (ADS)

Cheng, L.; Lin, Y.; Wang, X.; Perez, J. D.

2017-12-01

Alfvenic fluctuations have been observed near the magnetotail plasma sheet boundary layer associated with fast flows. In this presentation, we use the Auburn 3-D Global Hybrid code (ANGIE3D) to investigate the generation and propagation of Alfvenic waves in the magnetotail. Shear Alfven waves and kinetic Alfven waves (KAWs) are found to be generated in magnetic reconnection in the plasma sheet as well as in the dipole-like field region of the magnetosphere, carrying Poynting flux along magnetic field lines toward the ionosphere, and the wave structure is strongly altered by the flow braking in the tail. The 3-D structure of the wave electromagnetic field and the associated parallel currents in reconnection and the dipole-like field region is presented. The Alfvenic waves exhibit a turbulence spectrum. The roles of these Alfvenic waves in ion heating is discussed.

Naval War College Review. Volume 61, Number 2, Spring 2008

DTIC Science & Technology

2008-01-01

However, for ships operating in the tramp trade in search of cargo on the spot market, transparency is problematic. Vessel position is a source of...commercial High Speed Vehicles. We have tried out the HSVs in a variety of exercises and real operations. Their wave-piercing catamaran hulls have helped to... a datum that independent shipping in World War II moved 250 nautical miles a day or more.11 On land an army maneuvering at operational speed against

An Application of Cartesian-Grid and Volume-of-Fluid Methods to Numerical Ship Hydrodynamics

DTIC Science & Technology

2007-10-01

water-particle ve- locity is discontinuous across the air-water interface, and where CiEA is the Levi - Civita function. rj is the moment the vertical...methods and volume-of- immersed- body and volume-of-fluid (VOF) methods. fluid methods is used to simulate breaking waves around The governing equations are...of a ship hull is used as input to automat- body -fitted grids. The sole geometric input into NFA ically generate an immersed-boundary representation of

User’s Guide for SHIPINT - A Computer Program to Compute Two Ship Interaction in Waves

DTIC Science & Technology

1996-08-01

P500693.PDF [Page: 1 of 84] Image Cover Sheet CLASSIFICATION SYSTEM NUMBER 500693 UNCLASSIFIED I llllll 111111111111111111111111111111111 TITLE...Halifax, Nova Scotia, Canada B3J 2X4 1 ---------· CONTRACTOR REPORT I I I I I iii;,"’: · 1 Defence Research Establishment Atlantic Canada...SUMMARY 1 Introduction 2 Coordinate Systems and Two Ship Motions 3 Flow Chart 4 Input Data File Description 4.1 shipint.in ........ . 4.2 paneLa.in

Defense Against Ship as a Weapon

DTIC Science & Technology

2011-12-01

wave height of no more than 0.5 meters [6]. The mean surface wind speed can reach up to 2.5 m/s and the average non-tidal streams are about 0.5 m/s...example, terrorists who are trained in seamanship may use this skill to ram a SAW to its target. In the SAW case, the perpetrators are thus the...vessels • Ship-launched missiles • Harbor mines • Underwater swimmers • Unmanned submarine bombs • Exploding fuel tankers • Explosives in cargo

Observation of a high-quality quasi-periodic rapidly propagating wave train using SDO/AIA

NASA Astrophysics Data System (ADS)

Nisticò, G.; Pascoe, D. J.; Nakariakov, V. M.

2014-09-01

Context. We present a new event of quasi-periodic wave trains observed in EUV wavebands that rapidly propagate away from an active region after a flare. Aims: We measured the parameters of a wave train observed on 7 December 2013 after an M1.2 flare, such as the phase speeds, periods and wavelengths, in relationship to the local coronal environment and the energy sources. Methods: We compared our observations with a numerical simulation of fast magnetoacoustic waves that undergo dispersive evolution and leakage in a coronal loop embedded in a potential magnetic field. Results: The wave train is observed to propagate as several arc-shaped intensity disturbances for almost half an hour, with a speed greater than 1000 km s-1 and a period of about 1 min. The wave train followed two different patterns of propagation, in accordance with the magnetic structure of the active region. The oscillatory signal is found to be of high-quality, i.e. there is a large number (10 or more) of subsequent wave fronts observed. The observations are found to be consistent with the numerical simulation of a fast wave train generated by a localised impulsive energy release. Conclusions: Transverse structuring in the corona can efficiently create and guide high-quality quasi-periodic propagating fast wave trains. The movies are available in electronic form at http://www.aanda.org

Physics of ultrasonic wave propagation in bone and heart characterized using Bayesian parameter estimation

NASA Astrophysics Data System (ADS)

Anderson, Christian Carl

This Dissertation explores the physics underlying the propagation of ultrasonic waves in bone and in heart tissue through the use of Bayesian probability theory. Quantitative ultrasound is a noninvasive modality used for clinical detection, characterization, and evaluation of bone quality and cardiovascular disease. Approaches that extend the state of knowledge of the physics underpinning the interaction of ultrasound with inherently inhomogeneous and isotropic tissue have the potential to enhance its clinical utility. Simulations of fast and slow compressional wave propagation in cancellous bone were carried out to demonstrate the plausibility of a proposed explanation for the widely reported anomalous negative dispersion in cancellous bone. The results showed that negative dispersion could arise from analysis that proceeded under the assumption that the data consist of only a single ultrasonic wave, when in fact two overlapping and interfering waves are present. The confounding effect of overlapping fast and slow waves was addressed by applying Bayesian parameter estimation to simulated data, to experimental data acquired on bone-mimicking phantoms, and to data acquired in vitro on cancellous bone. The Bayesian approach successfully estimated the properties of the individual fast and slow waves even when they strongly overlapped in the acquired data. The Bayesian parameter estimation technique was further applied to an investigation of the anisotropy of ultrasonic properties in cancellous bone. The degree to which fast and slow waves overlap is partially determined by the angle of insonation of ultrasound relative to the predominant direction of trabecular orientation. In the past, studies of anisotropy have been limited by interference between fast and slow waves over a portion of the range of insonation angles. Bayesian analysis estimated attenuation, velocity, and amplitude parameters over the entire range of insonation angles, allowing a more complete characterization of anisotropy. A novel piecewise linear model for the cyclic variation of ultrasonic backscatter from myocardium was proposed. Models of cyclic variation for 100 type 2 diabetes patients and 43 normal control subjects were constructed using Bayesian parameter estimation. Parameters determined from the model, specifically rise time and slew rate, were found to be more reliable in differentiating between subject groups than the previously employed magnitude parameter.

Time-domain hybrid method for simulating large amplitude motions of ships advancing in waves

NASA Astrophysics Data System (ADS)

Liu, Shukui; Papanikolaou, Apostolos D.

2011-03-01

Typical results obtained by a newly developed, nonlinear time domain hybrid method for simulating large amplitude motions of ships advancing with constant forward speed in waves are presented. The method is hybrid in the way of combining a time-domain transient Green function method and a Rankine source method. The present approach employs a simple double integration algorithm with respect to time to simulate the free-surface boundary condition. During the simulation, the diffraction and radiation forces are computed by pressure integration over the mean wetted surface, whereas the incident wave and hydrostatic restoring forces/moments are calculated on the instantaneously wetted surface of the hull. Typical numerical results of application of the method to the seakeeping performance of a standard containership, namely the ITTC S175, are herein presented. Comparisons have been made between the results from the present method, the frequency domain 3D panel method (NEWDRIFT) of NTUA-SDL and available experimental data and good agreement has been observed for all studied cases between the results of the present method and comparable other data.

Time-Dependent Simulations of Fast-Wave Heated High-Non-Inductive-Fraction H-Mode Plasmas in the National Spherical Torus Experiment Upgrade

NASA Astrophysics Data System (ADS)

Taylor, Gary; Bertelli, Nicola; Gerhardt, Stefan P.; Hosea, Joel C.; Mueller, Dennis; Perkins, Rory J.; Poli, Francesca M.; Wilson, James R.; Raman, Roger

2017-10-01

30 MHz fast-wave heating may be an effective tool for non-inductively ramping low-current plasmas to a level suitable for initiating up to 12 MW of neutral beam injection on the National Spherical Tokamak Experiment Upgrade (NSTX-U). Previously on NSTX 30 MHz fast wave heating was shown to efficiently and rapidly heat electrons; at the NSTX maximum axial toroidal magnetic field (BT(0)) of 0.55 T, 1.4 MW of 30 MHz heating increased the central electron temperature from 0.2 to 2 keV in 30 ms and generated an H-mode plasma with a non-inductive fraction (fNI) ˜ 0.7 at a plasma current (Ip) of 300 kA. NSTX-U will operate at BT(0) up to 1 T, with up to 4 MW of 30 MHz power (Prf). Predictive TRANSP free boundary transport simulations, using the TORIC full wave spectral code to calculate the fast-wave heating and current drive, have been run for NSTX-U Ip = 300 kA H-mode plasmas. Favorable scaling of fNI with 30 MHz heating power is predicted, with fNI ≥ 1 for Prf ≥ 2 MW.

Fluid Dynamics for Physicists

NASA Astrophysics Data System (ADS)

Faber, T. E.

1995-08-01

This textbook provides an accessible and comprehensive account of fluid dynamics that emphasizes fundamental physical principles and stresses connections with other branches of physics. Beginning with a basic introduction, the book goes on to cover many topics not typically treated in texts, such as compressible flow and shock waves, sound attenuation and bulk viscosity, solitary waves and ship waves, thermal convection, instabilities, turbulence, and the behavior of anisotropic, non-Newtonian and quantum fluids. Undergraduate or graduate students in physics or engineering who are taking courses in fluid dynamics will find this book invaluable.

The Smallest R/V: A Small-scale Ocean Exploration Demonstration of Real-time Bathymetric Measurements

NASA Astrophysics Data System (ADS)

Howell, S. M.; Boston, B.; Maher, S. M.; Sleeper, J. D.; Togia, H.; Tree, J. P.

2014-12-01

In October 2013, graduate student members of the University of Hawaii Geophysical Society designed a small-scale model research vessel (R/V) that uses sonar to create 3D maps of a model seafloor in real-time. This pilot project was presented to the public at the School of Ocean and Earth Science and Technology's (SOEST) Biennial Open House weekend. An estimated 7,600 people attended the two-day event, including children and teachers from Hawaii's schools, home school students, community groups, families, and science enthusiasts. Our exhibit demonstrated real-time sonar mapping of a cardboard volcano using a toy size research vessel on a fixed 2D model ship track suspended above a model seafloor. Sound wave travel times were recorded using an unltrasonic emitter/receiver attached to an Arduino microcontroller platform, while the same system measured displacement along the ship track. This data was streamed through a USB connection to a PC running MatLab, where a 3D model was updated as the ship collected data. Our exhibit demonstrates the practical use of complicated concepts, like wave physics and data processing, in a way that even the youngest elementary students are able to understand. It provides an accessible avenue to learn about sonar mapping, and could easily be adapted to talk about bat and marine mammal echolocation by replacing the model ship and volcano. The exhibit received an overwhelmingly positive response from attendees, and has inspired the group to develop a more interactive model for future exhibitions, using multiple objects to be mapped that participants could arrange, and a more robust ship movement system that participants could operate.

Observations of shallow water marine ambient sound: the low frequency underwater soundscape of the central Oregon coast.

PubMed

Haxel, Joseph H; Dziak, Robert P; Matsumoto, Haru

2013-05-01

A year-long experiment (March 2010 to April 2011) measuring ambient sound at a shallow water site (50 m) on the central OR coast near the Port of Newport provides important baseline information for comparisons with future measurements associated with resource development along the inner continental shelf of the Pacific Northwest. Ambient levels in frequencies affected by surf-generated noise (f < 100 Hz) characterize the site as a high-energy end member within the spectrum of shallow water coastal areas influenced by breaking waves. Dominant sound sources include locally generated ship noise (66% of total hours contain local ship noise), breaking surf, wind induced wave breaking and baleen whale vocalizations. Additionally, an increase in spectral levels for frequencies ranging from 35 to 100 Hz is attributed to noise radiated from distant commercial ship commerce. One-second root mean square (rms) sound pressure level (SPLrms) estimates calculated across the 10-840 Hz frequency band for the entire year long deployment show minimum, mean, and maximum values of 84 dB, 101 dB, and 152 dB re 1 μPa.

VTOL controls for shipboard landing. M.S.Thesis

NASA Technical Reports Server (NTRS)

Mcmuldroch, C. G.

1979-01-01

The problem of landing a VTOL aircraft on a small ship in rough seas using an automatic controller is examined. The controller design uses the linear quadratic Gaussian results of modern control theory. Linear time invariant dynamic models are developed for the aircraft, ship, and wave motions. A hover controller commands the aircraft to track position and orientation of the ship deck using only low levels of control power. Commands for this task are generated by the solution of the steady state linear quadratic gaussian regulator problem. Analytical performance and control requirement tradeoffs are obtained. A landing controller commands the aircraft from stationary hover along a smooth, low control effort trajectory, to a touchdown on a predicted crest of ship motion. The design problem is formulated and solved as an approximate finite-time linear quadratic stochastic regulator. Performance and control results are found by Monte Carlo simulations.

Application of oil-water discrimination technology in fractured reservoirs using the differences between fast and slow shear-waves

NASA Astrophysics Data System (ADS)

Luo, Cong; Li, Xiangyang; Huang, Guangtan

2017-08-01

Oil-water discrimination is of great significance in the design and adjustment of development projects in oil fields. For fractured reservoirs, based on anisotropic S-wave splitting information, it becomes possible to effectively solve such problems which are difficult to deal with in traditional longitudinal wave exploration, due to the similar bulk modulus and density of these two fluids. In this paper, by analyzing the anisotropic character of the Chapman model (2009 Geophysics 74 97-103), the velocity and reflection coefficient differences between the fast and slow S-wave caused by fluid substitution have been verified. Then, through a wave field response analysis of the theoretical model, we found that water saturation causes a longer time delay, a larger time delay gradient and a lower amplitude difference between the fast and slow S-wave, while the oil case corresponds to a lower time delay, a lower gradient and a higher amplitude difference. Therefore, a new class attribute has been proposed regarding the amplitude energy of the fast and slow shear wave, used for oil-water distinction. This new attribute, as well as that of the time delay gradient, were both applied to the 3D3C seismic data of carbonate fractured reservoirs in the Luojia area of the Shengli oil field in China. The results show that the predictions of the energy attributes are more consistent with the well information than the time delay gradient attribute, hence demonstrating the great advantages and potential of this new attribute in oil-water recognition.

Combined free-stream disturbance measurements and receptivity studies in hypersonic wind tunnels by means of a slender wedge probe and direct numerical simulation

NASA Astrophysics Data System (ADS)

Wagner, Alexander; Schülein, Erich; Petervari, René; Hannemann, Klaus; Ali, Syed R. C.; Cerminara, Adriano; Sandham, Neil D.

2018-05-01

Combined free-stream disturbance measurements and receptivity studies in hypersonic wind tunnels were conducted by means of a slender wedge probe and direct numerical simulation. The study comprises comparative tunnel noise measurements at Mach 3, 6 and 7.4 in two Ludwieg tube facilities and a shock tunnel. Surface pressure fluctuations were measured over a wide range of frequencies and test conditions including harsh test environments not accessible to measurement techniques such as pitot probes and hot-wire anemometry. Quantitative results of the tunnel noise are provided in frequency ranges relevant for hypersonic boundary layer transition. In combination with the experimental studies, direct numerical simulations of the leading-edge receptivity to fast and slow acoustic waves were performed for the slender wedge probe at conditions corresponding to the experimental free-stream conditions. The receptivity to fast acoustic waves was found to be characterized by an early amplification of the induced fast mode. For slow acoustic waves an initial decay was found close to the leading edge. At all Mach numbers, and for all considered frequencies, the leading-edge receptivity to fast acoustic waves was found to be higher than the receptivity to slow acoustic waves. Further, the effect of inclination angles of the acoustic wave with respect to the flow direction was investigated. The combined numerical and experimental approach in the present study confirmed the previous suggestion that the slow acoustic wave is the dominant acoustic mode in noisy hypersonic wind tunnels.

Propagation Characteristics Of Weakly Guiding Optical Fibers

NASA Technical Reports Server (NTRS)

Manshadi, Farzin

1992-01-01

Report discusses electromagnetic propagation characteristics of weakly guiding optical-fiber structures having complicated shapes with cross-sectional dimensions of order of wavelength. Coupling, power-dividing, and transition dielectric-waveguide structures analyzed. Basic data computed by scalar-wave, fast-Fourier-transform (SW-FFT) technique, based on numerical solution of scalar version of wave equation by forward-marching fast-Fourier-transform method.

Mica-dominated seismic properties of mid-crust beneath west Yunnan (China) and geodynamic implications

NASA Astrophysics Data System (ADS)

Shao, Tongbin; Ji, Shaocheng; Oya, Shoma; Michibayashi, Katsuyoshi; Wang, Qian

2016-05-01

Measurements of crystallographic preferred orientations (CPO) and calculations of P- and S-wave velocities (Vp and Vs) and anisotropy were conducted on three quartz-mica schists and one felsic mylonite, which are representative of typical metamorphic rocks deformed in the middle crust beneath the southeastern Tibetan plateau. Results show that the schists have Vp anisotropy (AVp) ranging from 16.4% to 25.5% and maximum Vs anisotropy [AVs(max)] between 21.6% and 37.8%. The mylonite has lower AVp and AVs(max) but slightly higher foliation anisotropy, which are 13.2%, 18.5%, and 3.07%, respectively, due to the lower content and CPO strength of mica. With increasing mica content, the deformed rocks tend to form transverse isotropy (TI) with fast velocities in the foliation plane and slow velocities normal to the foliation. However, the presence of prismatic minerals (e.g., amphibole and sillimanite) forces the overall symmetry to deviate from TI. An increase in feldspar content reduces the bulk anisotropy caused by mica or quartz because the fast-axis of feldspar aligns parallel to the slow-axis of mica and/or quartz. The effect of quartz on seismic properties of mica-bearing rocks is complex, depending on its content and prevailing slip system. The greatest shear-wave splitting and fastest Vp both occur for propagation directions within the foliation plane, consistent with the fast Pms (S-wave converted from P-wave at the Moho) polarization directions in the west Yunnan where mica/amphibole-bearing rocks have developed pervasive subvertical foliation and subhorizontal lineation. The fast Pms directions are perpendicular to the approximately E-W orienting fast SKS (S-wave traversing the core as P-wave) directions, indicating a decoupling at the Moho interface between the crust and mantle beneath the region. The seismic data are inconsistent with the model of crustal channel flow as the latter should produce a subhorizontal foliation where vertically incident shear waves suffer little splitting.

Receptivity of Hypersonic Boundary Layers to Distributed Roughness and Acoustic Disturbances

NASA Technical Reports Server (NTRS)

Balakumar, P.

2013-01-01

Boundary-layer receptivity and stability of Mach 6 flows over smooth and rough seven-degree half-angle sharp-tipped cones are numerically investigated. The receptivity of the boundary layer to slow acoustic disturbances, fast acoustic disturbances, and vortical disturbances is considered. The effects of three-dimensional isolated roughness on the receptivity and stability are also simulated. The results for the smooth cone show that the instability waves are generated in the leading edge region and that the boundary layer is much more receptive to slow acoustic waves than to the fast acoustic waves. Vortical disturbances also generate unstable second modes, however the receptivity coefficients are smaller than that of the slow acoustic wave. Distributed roughness elements located near the nose region decreased the receptivity of the second mode generated by the slow acoustic wave by a small amount. Roughness elements distributed across the continuous spectrum increased the receptivity of the second mode generated by the slow and fast acoustic waves and the vorticity wave. The largest increase occurred for the vorticity wave. Roughness elements distributed across the synchronization point did not change the receptivity of the second modes generated by the acoustic waves. The receptivity of the second mode generated by the vorticity wave increased in this case, but the increase is lower than that occurred with the roughness elements located across the continuous spectrum. The simulations with an isolated roughness element showed that the second mode waves generated by the acoustic disturbances are not influenced by the small roughness element. Due to the interaction, a three-dimensional wave is generated. However, the amplitude is orders of magnitude smaller than the two-dimensional wave.

The picosecond structure of ultra-fast rogue waves

NASA Astrophysics Data System (ADS)

Klein, Avi; Shahal, Shir; Masri, Gilad; Duadi, Hamootal; Sulimani, Kfir; Lib, Ohad; Steinberg, Hadar; Kolpakov, Stanislav A.; Fridman, Moti

2018-02-01

We investigated ultrafast rogue waves in fiber lasers and found three different patterns of rogue waves: single- peaks, twin-peaks, and triple-peaks. The statistics of the different patterns as a function of the pump power of the laser reveals that the probability for all rogue waves patterns increase close to the laser threshold. We developed a numerical model which prove that the ultrafast rogue waves patterns result from both the polarization mode dispersion in the fiber and the non-instantaneous nature of the saturable absorber. This discovery reveals that there are three different types of rogue waves in fiber lasers: slow, fast, and ultrafast, which relate to three different time-scales and are governed by three different sets of equations: the laser rate equations, the nonlinear Schrodinger equation, and the saturable absorber equations, accordingly. This discovery is highly important for analyzing rogue waves and other extreme events in fiber lasers and can lead to realizing types of rogue waves which were not possible so far such as triangular rogue waves.

Self-Consistent and Time-Dependent Solar Wind Models

NASA Technical Reports Server (NTRS)

Ong, K. K.; Musielak, Z. E.; Rosner, R.; Suess, S. T.; Sulkanen, M. E.

1997-01-01

We describe the first results from a self-consistent study of Alfven waves for the time-dependent, single-fluid magnetohydrodynamic (MHD) solar wind equations, using a modified version of the ZEUS MHD code. The wind models we examine are radially symmetrical and magnetized; the initial outflow is described by the standard Parker wind solution. Our study focuses on the effects of Alfven waves on the outflow and is based on solving the full set of the ideal nonlinear MHD equations. In contrast to previous studies, no assumptions regarding wave linearity, wave damping, and wave-flow interaction are made; thus, the models naturally account for the back-reaction of the wind on the waves, as well as for the nonlinear interaction between different types of MHD waves. Our results clearly demonstrate when momentum deposition by Alfven waves in the solar wind can be sufficient to explain the origin of fast streams in solar coronal holes; we discuss the range of wave amplitudes required to obtained such fast stream solutions.

Effect of Stress and Saturation on Shear Wave Anisotropy: Laboratory Observations Using Laser Doppler Interferometry

NASA Astrophysics Data System (ADS)

Lebedev, M.; Collet, O.; Bona, A.; Gurevich, B.

2015-12-01

Estimations of hydrocarbon and water resources as well as reservoir management during production are the main challenges facing the resource recovery industry nowadays. The recently discovered reservoirs are not only deep but they are also located in complicated geological formations. Hence, the effect of anisotropy on reservoir imaging becomes significant. Shear wave (S-wave) splitting has been observed in the field and laboratory experiments for decades. Despite the fact that S-wave splitting is widely used for evaluation of subsurface anisotropy, the effects of stresses as well fluid saturation on anisotropy have not been understood in detail. In this paper we present the laboratory study of the effect of stress and saturation on S-wave splitting for a Bentheim sandstone sample. The cubic sample (50mm3), porosity 22%, density 1890kg/m3) was placed into a true-triaxial cell. The sample was subjected to several combinations of stresses varying from 0 to 10MPa and applied to the sample in two directions (X and Y), while no stress was applied to the sample in the Z-direction. The sample's bedding was nearly oriented parallel to Y-Z plane. The ultrasonic S-waves were exited at a frequency of 0.5MHz by a piezoelectric transducer and were propagating in the Z-direction. Upon wave arrival onto the free surface the displacement of the surface was monitored by a Laser Doppler interferometer. Hodograms of the central point of the dry sample (Fig. 1) demonstrate how S-wave polarizations for both "fast" and "slow" S-waves change when increasing the stress in the X direction, while the stress in direction Y is kept constant at 3 MPa. Polarization of the fast S wave is shifted towards the X-axis (axis of the maximum stress). While both S-wave velocities increase with stress, the anisotropy level remains the same. No shift of polarization of fast wave was observed when the stress along the Y-axis was kept at 3 MPa, while the stress along the X-axis was increasing. However, in that case, S-wave splitting is more prominent. The fast S-wave velocity is increasing with the stress increase while the slow S-wave velocity starts decreasing after 5MPa, indicating possible cracks opening in the Y-direction. Interestingly no change in anisotropy was observed for the water-saturated sample.

Application of very high harmonic fast waves for off-axis current drive in the DIII-D and FNSF-AT tokamaks

DOE PAGES

Prater, Ronald; Moeller, Charles P.; Pinsker, Robert I.; ...

2014-06-26

Fast waves at frequencies far above the ion cyclotron frequency and approaching the lower hybrid frequency (also called “helicons” or “whistlers”) have application to off-axis current drive in tokamaks with high electron beta. The high frequency causes the whistler-like behavior of the wave power nearly following field lines, but with a small radial component, so the waves spiral slowly toward the plasma center. The high frequency also contributes to strong damping. Modeling predicts robust off-axis current drive with good efficiency compared to alternatives in high performance discharges in DIII-D and Fusion Nuclear Science Facility (FNSF) when the electron beta ismore » above about 1.8%. Detailed analysis of ray behavior shows that ray trajectories and damping are deterministic (that is, not strongly affected by plasma profiles or initial ray conditions), unlike the chaotic ray behavior in lower frequency fast wave experiments. Current drive was found to not be sensitive to the launched value of the parallel index of refraction n||, so wave accessibility issues can be reduced. Finally, use of a traveling wave antenna provides a very narrow n|| spectrum, which also helps avoid accessibility problems.« less

Classification and determination of cerebral biovailability of psychotropic drugs by quantitative "pharmaco-EEG" and psychometric investigations (studies with AX-A411-BS).

PubMed

Saletu, B; Grünberger, J; Linzmayer, L

1977-10-01

Utilizing computerized quantitative analysis of the human scalp recorded electroencephalogram (EEG), it is possible to classify psychotropic drugs. While neuroleptic compounds produce an increase of slow and decrease of fast activities, anxiolytic substances induce an augmentation of fast waves, decrease of alpha waves and--according to the sedative properties of the drug--an increase or decrease of slow waves. Antidepressants produce a concomitant augmentation of slow and fast activities as well as an attenuation of alpha waves. Nootropic substances attenuate slow activities, augment alpha and slow beta waves and decrease fast beta waves. The latter alterations are quite opposite to age-related changes. Since the main psychopharmacological classes seem to have characteristic pharmaco-EEG profiles, the method proved to be useful for determination of psychoactivity and cerebral bioavailability of newly developed substances as for instance AX-A411-BS, a new benzodiazepine. The latter substance was found to be CNS-active and was classified as anxiolytic. It induced dosedependent changes, which were barely visible in the 2nd hour post-drug, became quite obvious in the 4th hour and increased until the 8th hour after oral administration of one single dose. In the higher dosage range, slow activities came to the fore, indicating aoditional sedative properties. Psychometric tests measuring attention, psychomotor activity. mood, vigilance, extroversion, concentration aith a long-lasting effect. The implications of these methods are discussed.

Power selective optical filter devices and optical systems using same

DOEpatents

Koplow, Jeffrey P

2014-10-07

In an embodiment, a power selective optical filter device includes an input polarizer for selectively transmitting an input signal. The device includes a wave-plate structure positioned to receive the input signal, which includes at least one substantially zero-order, zero-wave plate. The zero-order, zero-wave plate is configured to alter a polarization state of the input signal passing in a manner that depends on the power of the input signal. The zero-order, zero-wave plate includes an entry and exit wave plate each having a fast axis, with the fast axes oriented substantially perpendicular to each other. Each entry wave plate is oriented relative to a transmission axis of the input polarizer at a respective angle. An output polarizer is positioned to receive a signal output from the wave-plate structure and selectively transmits the signal based on the polarization state.

Dynamic perception of dynamic affordances: walking on a ship at sea.

PubMed

Walter, Hannah; Wagman, Jeffrey B; Stergiou, Nick; Erkmen, Nurtekin; Stoffregen, Thomas A

2017-02-01

Motion of the surface of the sea (waves, and swell) causes oscillatory motion of ships at sea. Generally, ships are longer than they are wide. One consequence of this structural difference is that oscillatory ship motion typically will be greater in roll (i.e., the ship rolling from side to side) than in pitch (i.e., the bow and stern rising and falling). For persons on ships at sea, affordances for walking on the open deck should be differentially influenced by ship motion in roll and pitch. Specifically, the minimum width of a walkable path should be greater when walking along the ship's short, or athwart axis than when walking along its long, or fore-aft axis. On a ship at sea, we evaluated the effects of walking in different directions (fore-aft vs. athwart) on actual walking performance. We did this by laying out narrow paths on the deck and asking participants (experienced maritime crewmembers) to walk as far as they could while remaining within the lateral path boundaries. As predicted, participants walked farther along the athwart path than along the fore-aft path. Before actual walking, we evaluated participants' judgments of their walking ability in the fore-aft and athwart directions. These judgments mirrored the observed differences in walking performance, and the accuracy of judgments did not differ between the two directions. We conclude that experienced maritime crewmembers were sensitive to affordances for walking in which the relevant properties of the environment were exclusively dynamic.

Real time estimation of the heaving and pitching motions of a ship, using a Kalman filter

NASA Technical Reports Server (NTRS)

Triantafyllou, M.; Athans, M.

1981-01-01

In the present study the estimation of the heave and pitch motion of a ship is considered, using Kalman filtering techniques. A significant part of the study is devoted to constructing appropriate models for the sea and the ship. The governing equations are obtained from hydrodynamic considerations in the form of linear differential equations with frequency dependent coefficients. In addition, nonminimum phase characteristics are obtained due to the spatial integration of the water wave forces. The resulting transfer matrix function is irrational and nonminimum phase. The conditions for a finite-dimensional approximation are considered and the impact of the various parameters is assessed. A numerical application is considered for a DD-963 destroyer.

Classification of homoclinic rogue wave solutions of the nonlinear Schrödinger equation

NASA Astrophysics Data System (ADS)

Osborne, A. R.

2014-01-01

Certain homoclinic solutions of the nonlinear Schrödinger (NLS) equation, with spatially periodic boundary conditions, are the most common unstable wave packets associated with the phenomenon of oceanic rogue waves. Indeed the homoclinic solutions due to Akhmediev, Peregrine and Kuznetsov-Ma are almost exclusively used in scientific and engineering applications. Herein I investigate an infinite number of other homoclinic solutions of NLS and show that they reduce to the above three classical homoclinic solutions for particular spectral values in the periodic inverse scattering transform. Furthermore, I discuss another infinity of solutions to the NLS equation that are not classifiable as homoclinic solutions. These latter are the genus-2N theta function solutions of the NLS equation: they are the most general unstable spectral solutions for periodic boundary conditions. I further describe how the homoclinic solutions of the NLS equation, for N = 1, can be derived directly from the theta functions in a particular limit. The solutions I address herein are actual spectral components in the nonlinear Fourier transform theory for the NLS equation: The periodic inverse scattering transform. The main purpose of this paper is to discuss a broader class of rogue wave packets1 for ship design, as defined in the Extreme Seas program. The spirit of this research came from D. Faulkner (2000) who many years ago suggested that ship design procedures, in order to take rogue waves into account, should progress beyond the use of simple sine waves. 1An overview of other work in the field of rogue waves is given elsewhere: Osborne 2010, 2012 and 2013. See the books by Olagnon and colleagues 2000, 2004 and 2008 for the Brest meetings. The books by Kharif et al. (2008) and Pelinovsky et al. (2010) are excellent references.

Preliminary hydrodynamic analysis of landslide-generated waves in Tidal Inlet, Glacier Bay National Park, Alaska

USGS Publications Warehouse

Geist, Eric L.; Jakob, Matthias; Wieczoreck, Gerald F.; Dartnell, Peter

2003-01-01

A landslide block perched on the northern wall of Tidal Inlet, Glacier Bay National Park (Figure 1), has the potential to generate large waves in Tidal Inlet and the western arm of Glacier Bay if it were to fail catastrophically. Landslide-generated waves are a particular concern for cruise ships transiting through Glacier Bay on a daily basis during the summer months. The objective of this study is to estimate the range of wave amplitudes and periods in the western arm of Glacier Bay from a catastrophic landslide in Tidal Inlet. This study draws upon preliminary findings of a field survey by Wieczorek et al. (2003), and evaluates the effects of variations in landslide source parameters on the wave characteristics.

Equatorial Magnetohydrodynamic Shallow Water Waves in the Solar Tachocline

NASA Astrophysics Data System (ADS)

Zaqarashvili, Teimuraz

2018-03-01

The influence of a toroidal magnetic field on the dynamics of shallow water waves in the solar tachocline is studied. A sub-adiabatic temperature gradient in the upper overshoot layer of the tachocline causes significant reduction of surface gravity speed, which leads to trapping of the waves near the equator and to an increase of the Rossby wave period up to the timescale of solar cycles. Dispersion relations of all equatorial magnetohydrodynamic (MHD) shallow water waves are obtained in the upper tachocline conditions and solved analytically and numerically. It is found that the toroidal magnetic field splits equatorial Rossby and Rossby-gravity waves into fast and slow modes. For a reasonable value of reduced gravity, global equatorial fast magneto-Rossby waves (with the spatial scale of equatorial extent) have a periodicity of 11 years, matching the timescale of activity cycles. The solutions are confined around the equator between latitudes ±20°–40°, coinciding with sunspot activity belts. Equatorial slow magneto-Rossby waves have a periodicity of 90–100 yr, resembling the observed long-term modulation of cycle strength, i.e., the Gleissberg cycle. Equatorial magneto-Kelvin and slow magneto-Rossby-gravity waves have the periodicity of 1–2 years and may correspond to observed annual and quasi-biennial oscillations. Equatorial fast magneto-Rossby-gravity and magneto-inertia-gravity waves have periods of hundreds of days and might be responsible for observed Rieger-type periodicity. Consequently, the equatorial MHD shallow water waves in the upper overshoot tachocline may capture all timescales of observed variations in solar activity, but detailed analytical and numerical studies are necessary to make a firm conclusion toward the connection of the waves to the solar dynamo.

Optimization of 200 MWth and 250 MWt Ship Based Small Long Life NPP

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

Fitriyani, Dian; Su'ud, Zaki

2010-06-22

Design optimization of ship-based 200 MWth and 250 MWt nuclear power reactors have been performed. The neutronic and thermo-hydraulic programs of the three-dimensional X-Y-Z geometry have been developed for the analysis of ship-based nuclear power plant. Quasi-static approach is adopted to treat seawater effect. The reactor are loop type lead bismuth cooled fast reactor with nitride fuel and with relatively large coolant pipe above reactor core, the heat from primary coolant system is directly transferred to watersteam loop through steam generators. Square core type are selected and optimized. As the optimization result, the core outlet temperature distribution is changing withmore » the elevation angle of the reactor system and the characteristics are discussed.« less

The preplasma effect on the properties of the shock wave driven by a fast electron beam

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

Llor Aisa, E.; Ribeyre, X.; Tikhonchuk, V. T.

2016-08-15

Strong shock wave generation by a mono-energetic fast electron beam in a plasma with an increasing density profile is studied theoretically. The proposed analytical model describes the shock wave characteristics for a homogeneous plasma preceded by a low density precursor. The shock pressure and the time of shock formation depend on the ratio of the electron stopping length to the preplasma areal density and on the initial energy of injected electrons. The conclusions of theoretical model are confirmed in numerical simulations.

Novel Optical Processor for Phased Array Antenna.

DTIC Science & Technology

1992-10-20

parallel glass slide into the signal beam optical loop. The parallel glass acts like a variable phase shifter to the signal beam simulating phase drift...A list of possible designs are given as follows , _ _ Velocity fa (100dB/cm) Lumit Wavelength I M2I1 TeO2 Longi 4.2 /m/ns about 3 GHz 1.4 4m 34 Fast...subject to achievable acoustic frequency, the preferred materials are the slow shear wave in TeO2 , the fast shear wave in TeO2 or the shear waves in

Ship Detection from Ocean SAR Image Based on Local Contrast Variance Weighted Information Entropy

PubMed Central

Huang, Yulin; Pei, Jifang; Zhang, Qian; Gu, Qin; Yang, Jianyu

2018-01-01

Ship detection from synthetic aperture radar (SAR) images is one of the crucial issues in maritime surveillance. However, due to the varying ocean waves and the strong echo of the sea surface, it is very difficult to detect ships from heterogeneous and strong clutter backgrounds. In this paper, an innovative ship detection method is proposed to effectively distinguish the vessels from complex backgrounds from a SAR image. First, the input SAR image is pre-screened by the maximally-stable extremal region (MSER) method, which can obtain the ship candidate regions with low computational complexity. Then, the proposed local contrast variance weighted information entropy (LCVWIE) is adopted to evaluate the complexity of those candidate regions and the dissimilarity between the candidate regions with their neighborhoods. Finally, the LCVWIE values of the candidate regions are compared with an adaptive threshold to obtain the final detection result. Experimental results based on measured ocean SAR images have shown that the proposed method can obtain stable detection performance both in strong clutter and heterogeneous backgrounds. Meanwhile, it has a low computational complexity compared with some existing detection methods. PMID:29652863

The Development of Instrumentation and Methods for Measurement of Air-Sea Interaction and Coastal Processes from Manned and Unmanned Aircraft

NASA Astrophysics Data System (ADS)

Reineman, Benjamin D.

I present the development of instrumentation and methods for the measurement of coastal processes, ocean surface phenomena, and air-sea interaction in two parts. In the first, I discuss the development of a portable scanning lidar (light detection and ranging) system for manned aircraft and demonstrate its functionality for oceanographic and coastal measurements. Measurements of the Southern California coastline and nearshore surface wave fields from seventeen research flights between August 2007 and December 2008 are analyzed and discussed. The October 2007 landslide on Mt. Soledad in La Jolla, California was documented by two of the flights. The topography, lagoon, reef, and surrounding wave field of Lady Elliot Island in Australia's Great Barrier Reef were measured with the airborne scanning lidar system on eight research flights in April 2008. Applications of the system, including coastal topographic surveys, wave measurements, ship wake studies, and coral reef research, are presented and discussed. In the second part, I detail the development of instrumentation packages for small (18 -- 28 kg) unmanned aerial vehicles (UAVs) to measure momentum fluxes and latent, sensible, and radiative heat fluxes in the atmospheric boundary layer (ABL), and the surface topography. Fast-response turbulence, hygrometer, and temperature probes permit turbulent momentum and heat flux measurements, and short- and long-wave radiometers allow the determination of net radiation, surface temperature, and albedo. Careful design and testing of an accurate turbulence probe, as demonstrated in this thesis, are essential for the ability to measure momentum and scalar fluxes. The low altitude required for accurate flux measurements (typically assumed to be 30 m) is below the typical safety limit of manned research aircraft; however, it is now within the capability of small UAV platforms. Flight tests of two instrumented BAE Manta UAVs over land were conducted in January 2011 at McMillan Airfield (Camp Roberts, CA), and flight tests of similarly instrumented Boeing-Insitu ScanEagle UAVs were conducted in April 2012 at the Naval Surface Warfare Center, Dahlgren Division (Dahlgren, VA), where the first known direct flux measurements were made from low-altitude (down to 30 m) UAV flights over water (Potomac River). During the October 2012 Equatorial Mixing Experiment in the central Pacific aboard the R/V Roger Revelle, ship-launched and recovered ScanEagles were deployed in an effort to characterize the marine atmospheric boundary layer structure and dynamics. I present a description of the instrumentation, summarize results from flight tests, present preliminary analysis from UAV flights off of the Revelle, and discuss potential applications of these UAVs for marine atmospheric boundary layer studies.

Wave-plate structures, power selective optical filter devices, and optical systems using same

DOEpatents

Koplow, Jeffrey P [San Ramon, CA

2012-07-03

In an embodiment, an optical filter device includes an input polarizer for selectively transmitting an input signal. The device includes a wave-plate structure positioned to receive the input signal, which includes first and second substantially zero-order, zero-wave plates arranged in series with and oriented at an angle relative to each other. The first and second zero-wave plates are configured to alter a polarization state of the input signal passing in a manner that depends on the power of the input signal. Each zero-wave plate includes an entry and exit wave plate each having a fast axis, with the fast axes oriented substantially perpendicular to each other. Each entry wave plate is oriented relative to a transmission axis of the input polarizer at a respective angle. An output polarizer is positioned to receive a signal output from the wave-plate structure and selectively transmits the signal based on the polarization state.

Fast and precise technique for magnet lattice correction via sine-wave excitation of fast correctors

DOE PAGES

Yang, X.; Smaluk, V.; Yu, L. H.; ...

2017-05-02

A novel technique has been developed to improve the precision and shorten the measurement time of the LOCO (linear optics from closed orbits) method. This technique, named AC LOCO, is based on sine-wave (ac) beam excitation via fast correctors. Such fast correctors are typically installed at synchrotron light sources for the fast orbit feedback. The beam oscillations are measured by beam position monitors. The narrow band used for the beam excitation and measurement not only allows us to suppress effectively the beam position noise but also opens the opportunity for simultaneously exciting multiple correctors at different frequencies (multifrequency mode). Wemore » demonstrated at NSLS-II that AC LOCO provides better lattice corrections and works much faster than the traditional LOCO method.« less

Synthetic aperture radar images of ocean waves, theories of imaging physics and experimental tests

NASA Technical Reports Server (NTRS)

Vesecky, J. F.; Durden, S. L.; Smith, M. P.; Napolitano, D. A.

1984-01-01

The physical mechanism for the synthetic Aperture Radar (SAR) imaging of ocean waves is investigated through the use of analytical models. The models are tested by comparison with data sets from the SEASAT mission and airborne SAR's. Dominant ocean wavelengths from SAR estimates are biased towards longer wavelengths. The quasispecular scattering mechanism agrees with experimental data. The Doppler shift for ship wakes is that of the mean sea surface.

Turbulent Transport of Fast Ions in the Large Plasma Device (LAPD)

NASA Astrophysics Data System (ADS)

Zhou, Shu; Heidbrink, William; McWilliams, Roger; Boehmer, Heinrich; Carter, Troy; Popovich, Pavel; Tripathi, Shreekrishna; Vincena, Steve; Jenko, Frank

2010-11-01

Due to gyroradius averaging and drift-orbit averaging, the transport of fast ions by microturbulence is often smaller than for thermal ions. In this experiment, Strong drift wave turbulence is observed in LAPD on gradients produced by a plate obstacle. Energetic lithium ions orbit through the turbulent region. Scans with a collimated analyzer and with probes give detailed profiles of the fast ion spatial distribution and of the fluctuating fields. The fast-ion transport decreases rapidly with increasing fast-ion gyroradius. Unlike the diffusive transport caused by Coulomb collisions, in this case the turbulent transport is non-diffusive. Analysis and simulation suggest that the fast ions interact ballistically with stationary two-dimensional electrostatic turbulence. The energy dependence of the transport is well explained by gyro-averaging theory. In new experiments, different sources and obstacles alter the drift-wave turbulence to modify the nature of the transport.

15 CFR 1.2 - Description and design.

Code of Federal Regulations, 2010 CFR

2010-01-01

... fesse azure and or, a ship in full sail on waves of the sea, in chief proper; and in base a lighthouse... issued with the President's approval of the seal, made necessary by changes in the functions of the...

High-energy terahertz wave parametric oscillator with a surface-emitted ring-cavity configuration.

PubMed

Yang, Zhen; Wang, Yuye; Xu, Degang; Xu, Wentao; Duan, Pan; Yan, Chao; Tang, Longhuang; Yao, Jianquan

2016-05-15

A surface-emitted ring-cavity terahertz (THz) wave parametric oscillator has been demonstrated for high-energy THz output and fast frequency tuning in a wide frequency range. Through the special optical design with a galvano-optical scanner and four-mirror ring-cavity structure, the maximum THz wave output energy of 12.9 μJ/pulse is achieved at 1.359 THz under the pump energy of 172.8 mJ. The fast THz frequency tuning in the range of 0.7-2.8 THz can be accessed with the step response of 600 μs. Moreover, the maximum THz wave output energy from this configuration is 3.29 times as large as that obtained from the conventional surface-emitted THz wave parametric oscillator with the same experimental conditions.

Comparison of CFD simulations with experimental data for a tanker model advancing in waves

NASA Astrophysics Data System (ADS)

Orihara, Hideo

2011-03-01

In this paper, CFD simulation results for a tanker model are compared with experimental data over a range of wave conditions to verify a capability to predict the sea-keeping performance of practical hull forms. CFD simulations are conducted using WISDAM-X code which is capable of unsteady RANS calculations in arbitrary wave conditions. Comparisons are made of unsteady surface pressures, added resistance and ship motions in regular waves for cases of fully-loaded and ballast conditions of a large tanker model. It is shown that the simulation results agree fairly well with the experimental data, and that WISDAM-X code can predict sea-keeping performance of practical hull forms.

Mechanisms for Selective Single-Cell Reactivation during Offline Sharp-Wave Ripples and Their Distortion by Fast Ripples.

PubMed

Valero, Manuel; Averkin, Robert G; Fernandez-Lamo, Ivan; Aguilar, Juan; Lopez-Pigozzi, Diego; Brotons-Mas, Jorge R; Cid, Elena; Tamas, Gabor; Menendez de la Prida, Liset

2017-06-21

Memory traces are reactivated selectively during sharp-wave ripples. The mechanisms of selective reactivation, and how degraded reactivation affects memory, are poorly understood. We evaluated hippocampal single-cell activity during physiological and pathological sharp-wave ripples using juxtacellular and intracellular recordings in normal and epileptic rats with different memory abilities. CA1 pyramidal cells participate selectively during physiological events but fired together during epileptic fast ripples. We found that firing selectivity was dominated by an event- and cell-specific synaptic drive, modulated in single cells by changes in the excitatory/inhibitory ratio measured intracellularly. This mechanism collapses during pathological fast ripples to exacerbate and randomize neuronal firing. Acute administration of a use- and cell-type-dependent sodium channel blocker reduced neuronal collapse and randomness and improved recall in epileptic rats. We propose that cell-specific synaptic inputs govern firing selectivity of CA1 pyramidal cells during sharp-wave ripples. Copyright © 2017 Elsevier Inc. All rights reserved.

Underwater Sound Levels at a Wave Energy Device Testing Facility in Falmouth Bay, UK.

PubMed

Garrett, Joanne K; Witt, Matthew J; Johanning, Lars

2016-01-01

Passive acoustic monitoring devices were deployed at FaBTest in Falmouth Bay, UK, a marine renewable energy device testing facility during trials of a wave energy device. The area supports considerable commercial shipping and recreational boating along with diverse marine fauna. Noise monitoring occurred during (1) a baseline period, (2) installation activity, (3) the device in situ with inactive power status, and (4) the device in situ with active power status. This paper discusses the preliminary findings of the sound recording at FabTest during these different activity periods of a wave energy device trial.

Effects of contrasting wave conditions on scour and drag on pioneer tidal marsh plants

NASA Astrophysics Data System (ADS)

Silinski, Alexandra; Heuner, Maike; Troch, Peter; Puijalon, Sara; Bouma, Tjeerd J.; Schoelynck, Jonas; Schröder, Uwe; Fuchs, Elmar; Meire, Patrick; Temmerman, Stijn

2016-02-01

Tidal marshes are increasingly valued for protecting shorelines against wave impact, but waves in turn may limit the initial establishment of tidal marsh pioneer plants. In estuaries, the shorelines typically experience a wide range of wave periods, varying from short period wind waves (usually of around 1-2 s in fair weather conditions) to long ship-generated waves, with secondary waves in the order of 2-7 s and primary waves with periods that can exceed 1 min. Waves are known to create sediment scour around, as well as to exert drag forces on obstacles such as seedlings and adults of establishing pioneer plant species. In intertidal systems, these two mechanisms have been identified as main causes for limiting potential colonization of bare tidal flats. In this paper, we want to assess to which extent common quantitative formulae for predicting local scour and drag forces on rigid cylindrical obstacles are valid for the estimation of scour and drag on slightly flexible plants with contrasting morphology, and hence applicable to predict plant establishment and survival under contrasting wave conditions. This has been tested in a full-scale wave flume experiment on two pioneer species (Scirpus maritimus and Scirpus tabernaemontani) and two life stages (seedlings and adults of S. maritimus) as well as on cylindrical reference sticks, which we have put under a range of wave periods (2-10 s), intended to mimic natural wind waves (short period waves) and ship-induced waves (artificial long period waves), at three water levels (5, 20, 35 cm). Our findings suggest that at very shallow water depths (5 cm) particular hydrodynamic conditions are created that lead to drag and scour that deviate from predictions. For higher water levels (20, 35 cm) scour can be well predicted for all wave conditions by an established formula for wave-induced scour around rigid cylinders. Drag forces can be relatively well predicted after introducing experimentally derived drag coefficients that are specific for the different plant morphologies. Best predictions were found for plants with a simple near-cylindrical morphology such as S. tabernaemontani, but are less accurate for plants of more complex structure such as S. maritimus, particularly for long period waves. In conclusion, our study offers valuable insights towards predicting/modelling the conditions under which seedlings and shoots of pioneer species can establish, and elucidates that long waves are more likely to counteract successful plant establishment than natural short waves.

Linear Water Waves

NASA Astrophysics Data System (ADS)

Kuznetsov, N.; Maz'ya, V.; Vainberg, B.

2002-08-01

This book gives a self-contained and up-to-date account of mathematical results in the linear theory of water waves. The study of waves has many applications, including the prediction of behavior of floating bodies (ships, submarines, tension-leg platforms etc.), the calculation of wave-making resistance in naval architecture, and the description of wave patterns over bottom topography in geophysical hydrodynamics. The first section deals with time-harmonic waves. Three linear boundary value problems serve as the approximate mathematical models for these types of water waves. The next section uses a plethora of mathematical techniques in the investigation of these three problems. The techniques used in the book include integral equations based on Green's functions, various inequalities between the kinetic and potential energy and integral identities which are indispensable for proving the uniqueness theorems. The so-called inverse procedure is applied to constructing examples of non-uniqueness, usually referred to as 'trapped nodes.'

The variety of MHD shock waves interactions in the solar wind flow

NASA Technical Reports Server (NTRS)

Grib, S. A.

1995-01-01

Different types of nonlinear shock wave interactions in some regions of the solar wind flow are considered. It is shown, that the solar flare or nonflare CME fast shock wave may disappear as the result of the collision with the rotational discontinuity. By the way the appearance of the slow shock waves as the consequence of the collision with other directional discontinuity namely tangential is indicated. Thus the nonlinear oblique and normal MHD shock waves interactions with different solar wind discontinuities (tangential, rotational, contact, shock and plasmoidal) both in the free flow and close to the gradient regions like the terrestrial magnetopause and the heliopause are described. The change of the plasma pressure across the solar wind fast shock waves is also evaluated. The sketch of the classification of the MHD discontinuities interactions, connected with the solar wind evolution is given.

Full wave simulations of fast wave efficiency and power losses in the scrape-off layer of tokamak plasmas in mid/high harmonic and minority heating regimes

DOE PAGES

Bertelli, N.; Jaeger, E. F.; Hosea, J. C.; ...

2015-12-17

Here, several experiments on different machines and in different fast wave (FW) heating regimes, such as hydrogen minority heating and high harmonic fast waves (HHFW), have found strong interaction between radio-frequency (RF) waves and the scrape-off layer (SOL) region. This paper examines the propagation and the power loss in the SOL by using the full wave code AORSA, in which the edge plasma beyond the last closed flux surface (LCFS) is included in the solution domain and a collisional damping parameter is used as a proxy to represent the real, and most likely nonlinear, damping processes. 2D and 3D AORSAmore » results for the National Spherical Torus eXperiment (NSTX) have shown a strong transition to higher SOL power losses (driven by the RF field) when the FW cut-off is removed from in front of the antenna by increasing the edge density. Here, full wave simulations have been extended for 'conventional' tokamaks with higher aspect ratios, such as the DIII-D, Alcator C-Mod, and EAST devices. DIII-D results in HHFW regime show similar behavior found in NSTX and NSTX-U, consistent with previous DIII-D experimental observations. In contrast, a different behavior has been found for C-Mod and EAST, which operate in the minority heating regime.« less

The Future of U.S. Sea Power

DTIC Science & Technology

1993-05-01

significant as changes which occurred a century ago with the Teddy Roosevelt-sponsored Mahanian revolution. Indeed, one critic 3 . hinks this "hurtful...crucial areas as well as jobs seem to be at play. He has endorsed development of the V-22 Osprey for the Marines and improvement in fast sealift...total) 450 340 290 Carriers 13 12 8 SSNs 80 40 40 Assault Ships 50 50 50 Marine Corps Active Divisions 21/3 2 2 Reserve Divisions 1 1 1 Sealift Fast

Helicopter/Ship Qualification Testing (Les essais de qualification helicoptere/navire)

DTIC Science & Technology

2003-02-01

maximum all-up masses of the helicopter; • wind limitations. The data are presented as a polar diagramme , the radius representing the wind speed and the...Systems CAD Cartridge Actuated Device CG Center of Gravity DI Dynamic Interface EFP Elevated Fixed Platform FA Fore Aft FFG Guided Missile Fast Frigate...not be able to complete all the planned data points. The nature of DI testing results in a fast paced test program once flight testing begins. It is

Slow Magnetosonic Waves and Fast Flows in Active Region Loops

NASA Technical Reports Server (NTRS)

Ofman, L.; Wang, T. J.; Davila, J. M.

2012-01-01

Recent extreme ultraviolet spectroscopic observations indicate that slow magnetosonic waves are present in active region (AR) loops. Some of the spectral data were also interpreted as evidence of fast (approx 100-300 km/s) quasiperiodic flows. We have performed three-dimensional magnetohydrodynamic (3D MHD) modeling of a bipolar AR that contains impulsively generated waves and flows in coronal loops. The model AR is initiated with a dipole magnetic field and gravitationally stratified density, with an upflow-driven steadily or periodically in localized regions at the footpoints of magnetic loops. The resulting flows along the magnetic field lines of the AR produce higher density loops compared to the surrounding plasma by injection of material into the flux tubes and the establishment of siphon flow.We find that the impulsive onset of flows with subsonic speeds result in the excitation of damped slow magnetosonic waves that propagate along the loops and coupled nonlinearly driven fast-mode waves. The phase speed of the slow magnetosonic waves is close to the coronal sound speed. When the amplitude of the driving pulses is increased we find that slow shock-like wave trains are produced. When the upflows are driven periodically, undamped oscillations are produced with periods determined by the periodicity of the upflows. Based on the results of the 3D MHD model we suggest that the observed slow magnetosonic waves and persistent upflows may be produced by the same impulsive events at the bases of ARs.

Dynamic perception of dynamic affordances: walking on a ship at sea

PubMed Central

Walter, Hannah; Wagman, Jeffrey B.; Stergiou, Nick; Erkmen, Nurtekin

2017-01-01

Motion of the surface of the sea (waves, and swell) causes oscillatory motion of ships at sea. Generally, ships are longer than they are wide. One consequence of this structural difference is that oscillatory ship motion typically will be greater in roll (i.e., the ship rolling from side to side) than in pitch (i.e., the bow and stern rising and falling). For persons on ships at sea, affordances for walking on the open deck should be differentially influenced by ship motion in roll and pitch. Specifically, the minimum width of a walkable path should be greater when walking along the ship’s short, or athwart axis than when walking along its long, or fore-aft axis. On a ship at sea, we evaluated the effects of walking in different directions (fore-aft vs. athwart) on actual walking performance. We did this by laying out narrow paths on the deck and asking participants (experienced maritime crewmembers) to walk as far as they could while remaining within the lateral path boundaries. As predicted, participants walked farther along the athwart path than along the fore-aft path. Before actual walking, we evaluated participants’ judgments of their walking ability in the fore-aft and athwart directions. These judgments mirrored the observed differences in walking performance, and the accuracy of judgments did not differ between the two directions. We conclude that experienced maritime crewmembers were sensitive to affordances for walking in which the relevant properties of the environment were exclusively dynamic. PMID:27787584

Global Observation of Planetary-Scale Waves in UARS HRDI and WINDII MLT Winds

NASA Technical Reports Server (NTRS)

Lieberman, Ruth

1999-01-01

The purpose of this study is to use examine planetary-scale motions in the UARS mesosphere and lower thermospheric data. The actual study was confined to HRDI winds and temperatures, since these observations were more continuous, and spanned the 60-120 km range. Three classes of waves were studied: fast equatorial Kelvin waves, nonmigrating tides, and the midlatitude 2-day wave. The purpose of the Kelvin wave and the 2-day wave studies was to test whether the waves significantly affect the mean flow. Such studies require high-quality spectral definitions in order to derive the wave heat and momentum flux divergence which can act in comination to drive the mean flow. Accordingly, HRDI winds from several special observing campaigns were used for analyses of fast (periods under 5 days) waves. The campaigns are characterized by continuous viewing by HRDI in 2 viewing directions, for periods of 10-12 days. Data sampled in this manner lend themselves quite well to "asynoptic spectral analysis", from which motions with periods as low as one day can be retrieved with relatively minimal aliasing.

Monte-Carlo Orbit/Full Wave Simulation of Fast Alfvén Wave (FW) Damping on Resonant Ions in Tokamaks

NASA Astrophysics Data System (ADS)

Choi, M.; Chan, V. S.; Tang, V.; Bonoli, P.; Pinsker, R. I.; Wright, J.

2005-09-01

To simulate the resonant interaction of fast Alfvén wave (FW) heating and Coulomb collisions on energetic ions, including finite orbit effects, a Monte-Carlo code ORBIT-RF has been coupled with a 2D full wave code TORIC4. ORBIT-RF solves Hamiltonian guiding center drift equations to follow trajectories of test ions in 2D axisymmetric numerical magnetic equilibrium under Coulomb collisions and ion cyclotron radio frequency quasi-linear heating. Monte-Carlo operators for pitch-angle scattering and drag calculate the changes of test ions in velocity and pitch angle due to Coulomb collisions. A rf-induced random walk model describing fast ion stochastic interaction with FW reproduces quasi-linear diffusion in velocity space. FW fields and its wave numbers from TORIC are passed on to ORBIT-RF to calculate perpendicular rf kicks of resonant ions valid for arbitrary cyclotron harmonics. ORBIT-RF coupled with TORIC using a single dominant toroidal and poloidal wave number has demonstrated consistency of simulations with recent DIII-D FW experimental results for interaction between injected neutral-beam ions and FW, including measured neutron enhancement and enhanced high energy tail. Comparison with C-Mod fundamental heating discharges also yielded reasonable agreement.

a Floating Mobile Quay for Super Container Ships in a Hub Port

NASA Astrophysics Data System (ADS)

Chae, Jang-Won; Park, Woo-Sun

A floating mobile quay (FMQ), which is an innovative berth system, has functions of not only both side loading/unloading but also direct transshipment to feeder ships in a hub port. Applying the FMQ to a hub port such as the west terminal of Busan New Port of Korea, it is shown from a physical modeling and field model test that the quay is dynamically stable and workable in the prevailing wave condition and also safe in a design storm condition, respectively. The terminal productivity is increased by 30% comparing with the present land based berth. The B/C ratio of the new berth system is evaluated as 1.13 considering super-large container ships. It appears that the FMQ is a technically and economically feasible system in the hub port.

A Robust Self-Alignment Method for Ship's Strapdown INS Under Mooring Conditions

PubMed Central

Sun, Feng; Lan, Haiyu; Yu, Chunyang; El-Sheimy, Naser; Zhou, Guangtao; Cao, Tong; Liu, Hang

2013-01-01

Strapdown inertial navigation systems (INS) need an alignment process to determine the initial attitude matrix between the body frame and the navigation frame. The conventional alignment process is to compute the initial attitude matrix using the gravity and Earth rotational rate measurements. However, under mooring conditions, the inertial measurement unit (IMU) employed in a ship's strapdown INS often suffers from both the intrinsic sensor noise components and the external disturbance components caused by the motions of the sea waves and wind waves, so a rapid and precise alignment of a ship's strapdown INS without any auxiliary information is hard to achieve. A robust solution is given in this paper to solve this problem. The inertial frame based alignment method is utilized to adapt the mooring condition, most of the periodical low-frequency external disturbance components could be removed by the mathematical integration and averaging characteristic of this method. A novel prefilter named hidden Markov model based Kalman filter (HMM-KF) is proposed to remove the relatively high-frequency error components. Different from the digital filters, the HMM-KF barely cause time-delay problem. The turntable, mooring and sea experiments favorably validate the rapidness and accuracy of the proposed self-alignment method and the good de-noising performance of HMM-KF. PMID:23799492

SLOW PATCHY EXTREME-ULTRAVIOLET PROPAGATING FRONTS ASSOCIATED WITH FAST CORONAL MAGNETO-ACOUSTIC WAVES IN SOLAR ERUPTIONS

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

Guo, Y.; Ding, M. D.; Chen, P. F., E-mail: guoyang@nju.edu.cn

2015-08-15

Using the high spatiotemporal resolution extreme ultraviolet (EUV) observations of the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, we conduct a statistical study of the observational properties of the coronal EUV propagating fronts. We find that it might be a universal phenomenon for two types of fronts to coexist in a large solar eruptive event. It is consistent with the hybrid model of EUV propagating fronts, which predicts that coronal EUV propagating fronts consist of both a fast magneto-acoustic wave and a nonwave component. We find that the morphologies, propagation behaviors, and kinematic features of the two EUVmore » propagating fronts are completely different from each other. The fast magneto-acoustic wave fronts are almost isotropic. They travel continuously from the flaring region across multiple magnetic polarities to global distances. On the other hand, the slow nonwave fronts appear as anisotropic and sequential patches of EUV brightening. Each patch propagates locally in the magnetic domains where the magnetic field lines connect to the bottom boundary and stops at the magnetic domain boundaries. Within each magnetic domain, the velocities of the slow patchy nonwave component are an order of magnitude lower than that of the fast-wave component. However, the patches of the slow EUV propagating front can jump from one magnetic domain to a remote one. The velocities of such a transit between different magnetic domains are about one-third to one-half of those of the fast-wave component. The results show that the velocities of the nonwave component, both within one magnetic domain and between different magnetic domains, are highly nonuniform due to the inhomogeneity of the magnetic field in the lower atmosphere.« less

ITER Plasma at Ion Cyclotron Frequency Domain: The Fusion Alpha Particles Diagnostics Based on the Stimulated Raman Scattering of Fast Magnetosonic Wave off High Harmonic Ion Bernstein Modes

NASA Astrophysics Data System (ADS)

Stefan, V. Alexander

2014-10-01

A novel method for alpha particle diagnostics is proposed. The theory of stimulated Raman scattering, SRS, of the fast wave and ion Bernstein mode, IBM, turbulence in multi-ion species plasmas, (Stefan University Press, La Jolla, CA, 2008). is utilized for the diagnostics of fast ions, (4)He (+2), in ITER plasmas. Nonlinear Landau damping of the IBM on fast ions near the plasma edge leads to the space-time changes in the turbulence level, (inverse alpha particle channeling). The space-time monitoring of the IBM turbulence via the SRS techniques may prove efficient for the real time study of the fast ion velocity distribution function, spatial distribution, and transport. Supported by Nikola Tesla Labs., La Jolla, CA 92037.

An Improved Spectral Analysis Method for Fatigue Damage Assessment of Details in Liquid Cargo Tanks

NASA Astrophysics Data System (ADS)

Zhao, Peng-yuan; Huang, Xiao-ping

2018-03-01

Errors will be caused in calculating the fatigue damages of details in liquid cargo tanks by using the traditional spectral analysis method which is based on linear system, for the nonlinear relationship between the dynamic stress and the ship acceleration. An improved spectral analysis method for the assessment of the fatigue damage in detail of a liquid cargo tank is proposed in this paper. Based on assumptions that the wave process can be simulated by summing the sinusoidal waves in different frequencies and the stress process can be simulated by summing the stress processes induced by these sinusoidal waves, the stress power spectral density (PSD) is calculated by expanding the stress processes induced by the sinusoidal waves into Fourier series and adding the amplitudes of each harmonic component with the same frequency. This analysis method can take the nonlinear relationship into consideration and the fatigue damage is then calculated based on the PSD of stress. Take an independent tank in an LNG carrier for example, the accuracy of the improved spectral analysis method is proved much better than that of the traditional spectral analysis method by comparing the calculated damage results with the results calculated by the time domain method. The proposed spectral analysis method is more accurate in calculating the fatigue damages in detail of ship liquid cargo tanks.

Thalamic reticular nucleus induces fast and local modulation of arousal state

PubMed Central

Lewis, Laura D; Voigts, Jakob; Flores, Francisco J; Schmitt, L Ian; Wilson, Matthew A

2015-01-01

During low arousal states such as drowsiness and sleep, cortical neurons exhibit rhythmic slow wave activity associated with periods of neuronal silence. Slow waves are locally regulated, and local slow wave dynamics are important for memory, cognition, and behaviour. While several brainstem structures for controlling global sleep states have now been well characterized, a mechanism underlying fast and local modulation of cortical slow waves has not been identified. Here, using optogenetics and whole cortex electrophysiology, we show that local tonic activation of thalamic reticular nucleus (TRN) rapidly induces slow wave activity in a spatially restricted region of cortex. These slow waves resemble those seen in sleep, as cortical units undergo periods of silence phase-locked to the slow wave. Furthermore, animals exhibit behavioural changes consistent with a decrease in arousal state during TRN stimulation. We conclude that TRN can induce rapid modulation of local cortical state. DOI: http://dx.doi.org/10.7554/eLife.08760.001 PMID:26460547

Whistler Mode Based Explanation for the Fast Reconnection Rate Measured in the MIT Versatile Toroidal Facility

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

Singh, Nagendra

2011-12-09

Despite the widely discussed role of whistler waves in mediating magnetic reconnection (MR), the direct connection between such waves and the MR has not been demonstrated by comparing the characteristic temporal and spatial features of the waves and the MR process. Using the whistler wave dispersion relation, we theoretically predict the experimentally measured rise time ({tau}{sub rise}) of a few microseconds for the fast rising MR rate in the Versatile Toroidal Facility at MIT. The rise time is closely given by the inverse of the frequency bandwidth of the whistler waves generated in the evolving current sheet. The wave frequenciesmore » lie much above the ion cyclotron frequency, but they are limited to less than 0.1% of the electron cyclotron frequency in the argon plasma. The maximum normalized MR rate R=0.35 measured experimentally is precisely predicted by the angular dispersion of the whistler waves.« less

Generation of Pc 1 waves by the ion temperature anisotropy associated with fast shocks caused by sudden impulses

NASA Technical Reports Server (NTRS)

Mandt, M. E.; Lee, L. C.

1991-01-01

The high correlation of Pc 1 events with magnetospheric compressions is known. A mechanism is proposed which leads to the generation of Pc 1 waves. The interaction of a dynamic pressure pulse with the earth's bow shock leads to the formation of a weak fast-mode shock propagating into the magnetoshealth. The shock wave can pass right through a tangential discontinuity (magnetopause) and into the magnetosphere, without disturbing either of the structures. In a quasiperpendicular geometry, the shock wave exhibits anisotropic heating. This anisotropy drives unstable ion-cyclotron waves which can contribute to the generation of the Pc 1 waves which are detected. The viability of the mechanism is demonstrated with simulations. This mechanism could explain the peak in the occurrence of observed Pc 1 waves in the postnoon sector where a field-aligned discontinuity in the solar wind would most often be parallel to the magnetopause surface due to the average Parker-spiral magnetic-field configuration.

Isochoric heating and strong blast wave formation driven by fast electrons in solid-density targets

NASA Astrophysics Data System (ADS)

Santos, J. J.; Vauzour, B.; Touati, M.; Gremillet, L.; Feugeas, J.-L.; Ceccotti, T.; Bouillaud, R.; Deneuville, F.; Floquet, V.; Fourment, C.; Hadj-Bachir, M.; Hulin, S.; Morace, A.; Nicolaï, Ph; d'Oliveira, P.; Reau, F.; Samaké, A.; Tcherbakoff, O.; Tikhonchuk, V. T.; Veltcheva, M.; Batani, D.

2017-10-01

We experimentally investigate the fast (< 1 {ps}) isochoric heating of multi-layer metallic foils and subsequent high-pressure hydrodynamics induced by energetic electrons driven by high-intensity, high-contrast laser pulses. The early-time temperature profile inside the target is measured from the streaked optical pyrometry of the target rear side. This is further characterized from benchmarked simulations of the laser-target interaction and the fast electron transport. Despite a modest laser energy (< 1 {{J}}), the early-time high pressures and associated gradients launch inwards a strong compression wave developing over ≳ 10 ps into a ≈ 140 {Mbar} blast wave, according to hydrodynamic simulations, consistent with our measurements. These experimental and numerical findings pave the way to a short-pulse-laser-based platform dedicated to high-energy-density physics studies.

Enhanced situational technologies applied to ship channels

NASA Astrophysics Data System (ADS)

Helgeson, Michael A.; Wacker, Roger A.

1997-06-01

The Houston Ship Channel ranks as America's number one port in foreign tonnage by welcoming more than 50,000 cargo ships and barges annually. Locally 196,000 jobs, 5.5 billion dollars in business revenue and 213 million dollars in taxes are generated. Unfortunately, 32 days of each year vessel traffic stops for hours due to fog causing an estimated 40- 100 million dollars loss as ships idly wait in the channel for weather to clear. In addition, poor visibility has contributed to past vessel collisions which have resulted in channel closure, and associated damage to property and the environment. Today's imaging technology for synthetic vision systems and enhanced situational awareness systems offers a new solution to this problem. Whereas, typically these systems have been targeted at aircraft landing systems the channel navigation application provides a peripheral ground based market. This paper describes two imaging solutions to the problem. One using an active 35 GHz scanning radar and the other using a 94 GHz passive millimeter wave camera.

The ISPM unified radio and plasma wave experiment

NASA Technical Reports Server (NTRS)

Stone, R. G.; Caldwell, J.; Deconchy, Y.; Deschanciaux, C.; Ebbett, R.; Epstein, G.; Groetz, K.; Harvey, C. C.; Hoang, S.; Howard, R.

1983-01-01

Hardware for the International Solar Polar Mission (ISPM) Unified Radio and Plasma (URAP) wave experiment is presented. The URAP determines direction and polarization of distant radio sources for remote sensing of the heliosphere, and studies local wave phenomena which determine the transport coefficients of the ambient plasma. Electric and magnetic field antennas and preamplifiers; the electromagnetic compatibility plan and grounding; radio astronomy and plasma frequency receivers; a fast Fourier transformation data processing unit waveform analyzer; dc voltage measurements; a fast envelope sampler for the solar wind, and plasmas near Jupiter; a sounder; and a power converter are described.

[EFFECTS OF ELECTRICAL STIMULATION OF NUCLEUS RETICULARIS PONTIS ORALIS ON THE SLEEP-WAKING STATES IN KRUSHINSKII-MOLODKINA STRAIN RATS].

PubMed

Vataev, S I; Malgina, N A; Oganesyan, G A

2015-07-01

The effects of electrical stimulation of nucleus reticularis pontis oralis on the behavior and brain electrical activity during all phases of the sleep-waking cycle was studied in Krushinskii-Molodkina strain rats, which have an inherited predisposition to audiogenic seizures. Electrical stimulation with 7 Hz frequency in the deep stage of slow-wave sleep cause appearance the fast-wave sleep. Similar stimulation during fast-wave sleep periods did not effects on the electrographic patterns and EEG spectral characteristics of hippocampus, visual, auditory and somatocnen nrnrenc nf the cnrtey ThPe sfimul1stinns did nnt break a fast-wave sleenhut increased almost twice due the duration of these sleep episodes. After electrical stimulation by same frequency during the wakeftlness and superficial slow-wave sleep states, the patterns and spectral characteristics of brain electrical activity in rats showed no significant changes as compared with controls. The results of this study indicate that the state of the animals sleep-waking cycle at the time of stimulation is a critical variable that influences the responses which are induced by electrical stimulation of the nucleus reticularis pontis oralis.

Preferential Heating of Oxygen 5+ Ions by Finite-Amplitude Oblique Alfven Waves

NASA Technical Reports Server (NTRS)

Maneva, Yana G.; Vinas, Adolfo; Araneda, Jamie; Poedts, Stefaan

2016-01-01

Minor ions in the fast solar wind are known to have higher temperatures and to flow faster than protons in the interplanetary space. In this study we combine previous research on parametric instability theory and 2.5D hybrid simulations to study the onset of preferential heating of Oxygen 5+ ions by large-scale finite-amplitude Alfven waves in the collisionless fast solar wind. We consider initially non-drifting isotropic multi-species plasma, consisting of isothermal massless fluid electrons, kinetic protons and kinetic Oxygen 5+ ions. The external energy source for the plasma heating and energization are oblique monochromatic Alfven-cyclotron waves. The waves have been created by rotating the direction of initial parallel pump, which is a solution of the multi-fluid plasma dispersion relation. We consider propagation angles theta less than or equal to 30 deg. The obliquely propagating Alfven pump waves lead to strong diffusion in the ion phase space, resulting in highly anisotropic heavy ion velocity distribution functions and proton beams. We discuss the application of the model to the problems of preferential heating of minor ions in the solar corona and the fast solar wind.

Numerical study of a permanent magnet linear generator for ship motion energy conversion

NASA Astrophysics Data System (ADS)

Mahmuddin, Faisal; Gunadin, Indar Chaerah; Akhir, Anshar Yaumil

2017-02-01

In order to harvest kinetic energy of a ship moving in waves, a permanent magnet linear generator is designed and simulated in the present study. For the sake of simplicity, only heave motion which will be considered in this preliminary study. The dimension of the generator is designed based on the dimension of the ship. Moreover, in order to designed an optimal design of rotor and stator, the average vertical displacement of heave motion is needed. For this purpose, a numerical method called New Strip Method (NSM) is employed to compute the motions of the ship. With NSM, the ship hull is divided into several strips and the hydrodynamics forces are computed on each strip. Moreover, because the ship is assumed to be slender, the total forces are obtained by integrating the force on each strip. After the motions can be determined, the optimal design of the generator is designed and simulated. The performance of the generator in terms of force, magnetic flux, losses, current and induced voltage which are the primary parameters of the linear generator performance, are evaluated using a finite element analysis software named Maxwell. From the study, a linear generator for converting heave motions is designed so that the produced power from the designed generator can be determined.

Teleseismic P-wave polarization analysis at the Gräfenberg array

NASA Astrophysics Data System (ADS)

Cristiano, L.; Meier, T.; Krüger, F.; Keers, H.; Weidle, C.

2016-12-01

P-wave polarization at the Gräfenberg array (GRF) in southern Germany is analysed in terms of azimuthal deviations and deviations in the vertical polarization using 20 yr of broad-band recordings. An automated procedure for estimating P-wave polarization parameters is suggested, based on the definition of a characteristic function, which evaluates the polarization angles and their time variability as well as the amplitude, linearity and the signal-to-noise ratio of the P wave. P-wave polarization at the GRF array is shown to depend mainly on frequency and backazimuth and only slightly on epicentral distance indicating depth-dependent local anisotropy and lateral heterogeneity. A harmonic analysis is applied to the azimuthal anomalies to analyse their periodicity as a function of backazimuth. The dominant periods are 180° and 360°. At low frequencies, between 0.03 and 0.1 Hz, the observed fast directions of azimuthal anisotropy inferred from the 180° periodicity are similar across the array. The average fast direction of azimuthal anisotropy at these frequencies is N20°E with an uncertainty of about 8° and is consistent with fast directions of Pn-wave propagation. Lateral velocity gradients determined for the low-frequency band are compatible with the Moho topography of the area. A more complex pattern in the horizontal fast axis orientation beneath the GRF array is observed in the high-frequency band between 0.1 and 0.5 Hz, and is attributed to anisotropy in the upper crust. A remarkable rotation of the horizontal fast axis orientation across the suture between the geological units Moldanubicum and Saxothuringicum is observed. In contrast, the 360° periodicity at high frequencies is rather consistent across the array and may either point to lower velocities in the upper crust towards the Bohemian Massif and/or to anisotropy dipping predominantly in the NE-SW direction. Altogether, P-wave polarization analysis indicates the presence of layered lithospheric anisotropy in the area of the GRF array. Seismic anisotropy is more variable in the brittle upper crust compared to lower crustal and subcrustal depths.

Conversion of Radio-Frequency Pulses to Continuous-Wave Sinusoids by Fast Switching and Narrowband Filtering

DTIC Science & Technology

2016-09-01

Switching and Narrowband Filtering by Gregory J Mazzaro, Andrew J Sherbondy, Kenneth I Ranney, and Kelly D Sherbondy...Switching and Narrowband Filtering by Gregory J Mazzaro, Andrew J Sherbondy, Kenneth I Ranney, and Kelly D Sherbondy Sensors and Electron Devices...08/2016 4. TITLE AND SUBTITLE Conversion of Radio-Frequency Pulses to Continuous-Wave Sinusoids by Fast Switching and Narrowband Filtering 5a

Fast wave experiments in LAPD: RF sheaths, convective cells and density modifications

NASA Astrophysics Data System (ADS)

Carter, T. A.; van Compernolle, B.; Martin, M.; Gekelman, W.; Pribyl, P.; van Eester, D.; Crombe, K.; Perkins, R.; Lau, C.; Martin, E.; Caughman, J.; Tripathi, S. K. P.; Vincena, S.

2017-10-01

An overview is presented of recent work on ICRF physics at the Large Plasma Device (LAPD) at UCLA. The LAPD has typical plasma parameters ne 1012 -1013 cm-3, Te 1 - 10 eV and B 1000 G. A new high-power ( 150 kW) RF system and fast wave antenna have been developed for LAPD. The source runs at a frequency of 2.4 MHz, corresponding to 1 - 7fci , depending on plasma parameters. Evidence of rectified RF sheaths is seen in large increases ( 10Te) in the plasma potential on field lines connected to the antenna. The rectified potential scales linearly with antenna current. The rectified RF sheaths set up convective cells of local E × B flows, measured indirectly by potential measurements, and measured directly with Mach probes. At high antenna powers substantial modifications of the density profile were observed. The plasma density profile initially exhibits transient low frequency oscillations (10 kHz). The amplitude of the fast wave fields in the core plasma is modulated at the same low frequency, suggesting fast wave coupling is affected by the density rearrangement. Work performed at the Basic Plasma Science Facility, supported jointly by the National Science Foundation and the Department of Energy.

Magnetic swirls and associated fast magnetoacoustic kink waves in a solar chromospheric flux tube

NASA Astrophysics Data System (ADS)

Murawski, K.; Kayshap, P.; Srivastava, A. K.; Pascoe, D. J.; Jelínek, P.; Kuźma, B.; Fedun, V.

2018-02-01

We perform numerical simulations of impulsively generated magnetic swirls in an isolated flux tube that is rooted in the solar photosphere. These swirls are triggered by an initial pulse in a horizontal component of the velocity. The initial pulse is launched either (a) centrally, within the localized magnetic flux tube or (b) off-central, in the ambient medium. The evolution and dynamics of the flux tube are described by three-dimensional, ideal magnetohydrodynamic equations. These equations are numerically solved to reveal that in case (a) dipole-like swirls associated with the fast magnetoacoustic kink and m = 1 Alfvén waves are generated. In case (b), the fast magnetoacoustic kink and m = 0 Alfvén modes are excited. In both these cases, the excited fast magnetoacoustic kink and Alfvén waves consist of a similar flow pattern and magnetic shells are also generated with clockwise and counter-clockwise rotating plasma within them, which can be the proxy of dipole-shaped chromospheric swirls. The complex dynamics of vortices and wave perturbations reveals the channelling of sufficient amount of energy to fulfil energy losses in the chromosphere (˜104 W m-1) and in the corona (˜102 W m-1). Some of these numerical findings are reminiscent of signatures in recent observational data.

Cylindrical fast magnetosonic solitary waves in quantum degenerate electron-positron-ion plasma

NASA Astrophysics Data System (ADS)

Abdikian, A.

2018-02-01

The nonlinear properties of fast magnetosonic solitary waves in a quantum degenerate electron-positron (e-p) plasma in the presence of stationary ions for neutralizing the plasma background of bounded cylindrical geometry were studied. By employing the standard reductive perturbation technique and the quantum hydrodynamic model for the e-p fluid, the cylindrical Kadomtsev-Petviashvili (CKP) equation was derived for small, but finite, amplitude waves and was given the solitary wave solution for the parameters relevant to dense astrophysical objects such as white dwarf stars. By a suitable coordinate transformation, the CKP equation can be solved analytically. An analytical solution for magnetosonic solitons and periodic waves is presented. The numerical results reveal that the Bohm potential has a main effect on the periodic and solitary wave structures. By increasing the values of the plasma parameters, the amplitude of the solitary wave will be increased. The present study may be helpful in the understanding of nonlinear electromagnetic soliton waves propagating in both laboratory and astrophysical plasmas, and can help in providing good agreement between theoretical results and laboratory plasma experiments.

Crustal anisotropy in the forearc of the Northern Cascadia Subduction Zone, British Columbia

NASA Astrophysics Data System (ADS)

Balfour, N. J.; Cassidy, J. F.; Dosso, S. E.

2012-01-01

This paper aims to identify sources and variations of crustal anisotropy from shear-wave splitting measurements in the forearc of the Northern Cascadia Subduction Zone of southwest British Columbia. Over 20 permanent stations and 15 temporary stations were available for shear-wave splitting analysis on ˜4500 event-station pairs for local crustal earthquakes. Results from 1100 useable shear-wave splitting measurements show spatial variations in fast directions, with margin-parallel fast directions at most stations and margin-perpendicular fast directions at stations in the northeast of the region. Crustal anisotropy is often attributed to stress and has been interpreted as the fast direction being related to the orientation of the maximum horizontal compressive stress. However, studies have also shown anisotropy can be complicated by crustal structure. Southwest British Columbia is a complex region of crustal deformation and some of the stations are located near large ancient faults. To use seismic anisotropy as a stress indicator requires identifying which stations are influenced by stress and which by structure. We determine the source of anisotropy at each station by comparing fast directions from shear-wave splitting results to the maximum horizontal compressive stress orientation determined from earthquake focal mechanism inversion. Most stations show agreement between the fast direction and the maximum horizontal compressive stress. This suggests that anisotropy is related to stress-aligned fluid-filled microcracks based on extensive dilatancy anisotropy. These stations are further analysed for temporal variations to lay groundwork for monitoring temporal changes in the stress over extended time periods. Determining the sources of variability in anisotropy can lead to a better understanding of the crustal structure and stress, and in the future may be used as a monitoring and mapping tool.

Wave envelope technique for multimode wave guide problems

NASA Technical Reports Server (NTRS)

Hariharan, S. I.; Sudharsanan, S. I.

1986-01-01

A fast method for solving wave guide problems is proposed. In particular, the guide is considered to be inhomogeneous allowing propagation of waves of higher order modes. Such problems have been handled successfully for acoustic wave propagation problems with single mode and finite length. This paper extends this concept to electromagnetic wave guides with several modes and infinite length. The method is described and results of computations are presented.

[Fibrinolysis and acute stroke in maritime search and rescue medical evacuation].

PubMed

Lambert, R; Cabardis, S; Valance, J; Borge, E; Ducassé, J-L; Arzalier, J-J

2008-03-01

Medical management of a female passenger with acute stroke aboard a cruise ship at the sea allowed a fast evacuation towards a stroke unit by an helicopter staffed with an emergency medical doctor. Fibrinolysis begun in a short delay after magnetic resonance imaging.

Quasi-periodic Radio Bursts Associated with Fast-mode Waves near a Magnetic Null Point

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

Kumar, Pankaj; Nakariakov, Valery M.; Cho, Kyung-Suk, E-mail: pankaj.kumar@nasa.gov

This paper presents an observation of quasi-periodic rapidly propagating waves observed in the Atmospheric Image Assembly (AIA) 171/193 Å channels during the impulsive phase of an M1.9 flare that occurred on 2012 May 7. The instant period was found to decrease from 240 to 120 s, and the speed of the wavefronts was in the range of ∼664–1416 km s{sup −1}. Almost simultaneously, quasi-periodic bursts with similar instant periods, ∼70 and ∼140 s, occur in the microwave emission and in decimetric type IV and type III radio bursts, and in the soft X-ray emission. The magnetic field configuration of themore » flare site was consistent with a breakout topology, i.e., a quadrupolar field along with a magnetic null point. The quasi-periodic rapidly propagating wavefronts of the EUV emission are interpreted as a fast magnetoacoustic wave train. The observations suggest that the fast-mode waves are generated during the quasi-periodic magnetic reconnection in the cusp region above the flare arcade loops. For the first time, we provide evidence of a tadpole wavelet signature at about 70–140 s in decimetric (245/610 MHz) radio bursts, along with the direct observation of a coronal fast-mode wave train in EUV. In addition, at AIA 131/193 Å we observed quasi-periodic EUV disturbances with periods of 95 and 240 s propagating downward at apparent speeds of 172–273 km s{sup −1}. The nature of these downward propagating disturbances is not revealed, but they could be connected to magnetoacoustic waves or periodically shrinking loops.« less

Propagating Neural Source Revealed by Doppler Shift of Population Spiking Frequency

PubMed Central

Zhang, Mingming; Shivacharan, Rajat S.; Chiang, Chia-Chu; Gonzalez-Reyes, Luis E.

2016-01-01

Electrical activity in the brain during normal and abnormal function is associated with propagating waves of various speeds and directions. It is unclear how both fast and slow traveling waves with sometime opposite directions can coexist in the same neural tissue. By recording population spikes simultaneously throughout the unfolded rodent hippocampus with a penetrating microelectrode array, we have shown that fast and slow waves are causally related, so a slowly moving neural source generates fast-propagating waves at ∼0.12 m/s. The source of the fast population spikes is limited in space and moving at ∼0.016 m/s based on both direct and Doppler measurements among 36 different spiking trains among eight different hippocampi. The fact that the source is itself moving can account for the surprising direction reversal of the wave. Therefore, these results indicate that a small neural focus can move and that this phenomenon could explain the apparent wave reflection at tissue edges or multiple foci observed at different locations in neural tissue. SIGNIFICANCE STATEMENT The use of novel techniques with an unfolded hippocampus and penetrating microelectrode array to record and analyze neural activity has revealed the existence of a source of neural signals that propagates throughout the hippocampus. The source itself is electrically silent, but its location can be inferred by building isochrone maps of population spikes that the source generates. The movement of the source can also be tracked by observing the Doppler frequency shift of these spikes. These results have general implications for how neural signals are generated and propagated in the hippocampus; moreover, they have important implications for the understanding of seizure generation and foci localization. PMID:27013678

Anisotropy of the innermost inner core from body wave and normal mode observations

NASA Astrophysics Data System (ADS)

Deuss, A. F.; Smink, M.; Bouwman, D.; Ploegstra, J.; van Tent, R.

2016-12-01

It has been known for a long time that the Earth's inner core is cylindrically anisotropic, with waves that travel in the direction of the Earth's rotation axis arriving several seconds before waves travelling in the equatorial direction. Recently, several studies have suggested that the Earth's rotation axis may not be the fast anisotropy direction in the innermost inner core. Beghein and Trampert (2003) found that the Earth's rotation axis is slow, with the equatorial plane being fast. Wang et al (2015) found instead that the fast symmetry axis is in the equatorial plane. Here, we use both body wave and normal mode observations to test these two different hypotheses. Similar to Wang, we correct body wave PKIKP data for anisotropy in the upper inner core, and investigate if there is any anisotropy remaining in the innermost inner core. We find that the results strongly depend on the very limited number of polar direction waves with angle less than 25 degrees. With the limited data it is difficult to distinguish between the two different hypotheses, and if any tilted anisotropy is required at all. Normal modes see inner core anisotropy with north-south symmetry axis as anomalous zonal coefficients. We will show theoretically that if the anisotropy symmetry axis is tilted, non-zonal coefficients will also become anomalous. We search consistent anomalous non-zonal coefficients for modes sensitive to the innermost inner core. If the symmetry axis is still north south, but this is now the slow direction and the equatorial plane fast, then we predict negative zonal coefficients. This is observed for some normal modes, explaining why Beghein and Trampert (2003) found this type of anisotropy in the innermost inner core.

Fast shoreline erosion induced by ship wakes in a coastal lagoon: Field evidence and remote sensing analysis.

PubMed

Zaggia, Luca; Lorenzetti, Giuliano; Manfé, Giorgia; Scarpa, Gian Marco; Molinaroli, Emanuela; Parnell, Kevin Ellis; Rapaglia, John Paul; Gionta, Maria; Soomere, Tarmo

2017-01-01

An investigation based on in-situ surveys combined with remote sensing and GIS analysis revealed fast shoreline retreat on the side of a major waterway, the Malamocco Marghera Channel, in the Lagoon of Venice, Italy. Monthly and long-term regression rates caused by ship wakes in a reclaimed industrial area were considered. The short-term analysis, based on field surveys carried out between April 2014 and January 2015, revealed that the speed of shoreline regression was insignificantly dependent on the distance from the navigation channel, but was not constant through time. Periods of high water levels due to tidal forcing or storm surges, more common in the winter season, are characterized by faster regression rates. The retreat is a discontinuous process in time and space depending on the morpho-stratigraphy and the vegetation cover of the artificial deposits. A GIS analysis performed with the available imagery shows an average retreat of 3-4 m/yr in the period between 1974 and 2015. Digitization of historical maps and bathymetric surveys made in April 2015 enabled the construction of two digital terrain models for both past and present situations. The two models have been used to calculate the total volume of sediment lost during the period 1968-2015 (1.19×106 m3). The results show that in the presence of heavy ship traffic, ship-channel interactions can dominate the morphodynamics of a waterway and its margins. The analysis enables a better understanding of how shallow-water systems react to the human activities in the post-industrial period. An adequate evaluation of the temporal and spatial variation of shoreline position is also crucial for the development of future scenarios and for the sustainable management port traffic worldwide.

Fast shoreline erosion induced by ship wakes in a coastal lagoon: Field evidence and remote sensing analysis

PubMed Central

Lorenzetti, Giuliano; Manfé, Giorgia; Scarpa, Gian Marco; Molinaroli, Emanuela; Parnell, Kevin Ellis; Rapaglia, John Paul; Gionta, Maria; Soomere, Tarmo

2017-01-01

An investigation based on in-situ surveys combined with remote sensing and GIS analysis revealed fast shoreline retreat on the side of a major waterway, the Malamocco Marghera Channel, in the Lagoon of Venice, Italy. Monthly and long-term regression rates caused by ship wakes in a reclaimed industrial area were considered. The short-term analysis, based on field surveys carried out between April 2014 and January 2015, revealed that the speed of shoreline regression was insignificantly dependent on the distance from the navigation channel, but was not constant through time. Periods of high water levels due to tidal forcing or storm surges, more common in the winter season, are characterized by faster regression rates. The retreat is a discontinuous process in time and space depending on the morpho-stratigraphy and the vegetation cover of the artificial deposits. A GIS analysis performed with the available imagery shows an average retreat of 3˗4 m/yr in the period between 1974 and 2015. Digitization of historical maps and bathymetric surveys made in April 2015 enabled the construction of two digital terrain models for both past and present situations. The two models have been used to calculate the total volume of sediment lost during the period 1968˗2015 (1.19×106 m3). The results show that in the presence of heavy ship traffic, ship-channel interactions can dominate the morphodynamics of a waterway and its margins. The analysis enables a better understanding of how shallow-water systems react to the human activities in the post-industrial period. An adequate evaluation of the temporal and spatial variation of shoreline position is also crucial for the development of future scenarios and for the sustainable management port traffic worldwide. PMID:29088244

Investigating the Wave Nature of the Outer Envelope of Halo Coronal Mass Ejections

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

Kwon, Ryun-Young; Vourlidas, Angelos, E-mail: rkwon@gmu.edu

We investigate the nature of the outer envelope of halo coronal mass ejections (H-CMEs) using multi-viewpoint observations from the Solar Terrestrial Relations Observatory-A , -B , and SOlar and Heliospheric Observatory coronagraphs. The 3D structure and kinematics of the halo envelopes and the driving CMEs are derived separately using a forward modeling method. We analyze three H-CMEs with peak speeds from 1355 to 2157 km s{sup −1}; sufficiently fast to drive shocks in the corona. We find that the angular widths of the halos range from 192° to 252°, while those of the flux ropes range between only 58° andmore » 91°, indicating that the halos are waves propagating away from the CMEs. The halo widths are in agreement with widths of Extreme Ultraviolet (EUV) waves in the low corona further demonstrating the common origin of these structures. To further investigate the wave nature of the halos, we model their 3D kinematic properties with a linear fast magnetosonic wave model. The model is able to reproduce the position of the halo flanks with realistic coronal medium assumptions but fails closer to the CME nose. The CME halo envelope seems to arise from a driven wave (or shock) close to the CME nose, but it is gradually becoming a freely propagating fast magnetosonic wave at the flanks. This interpretation provides a simple unifying picture for CME halos, EUV waves, and the large longitudinal spread of solar energetic particles.« less

Geomorphologic Evolution of Barrier Islands along the Northern U.S. Gulf of Mexico and Implications for Engineering Design in Barrier Restoration

DTIC Science & Technology

2009-01-01

Chandeleur Is- lands). Finally, Stage 3 occurs when erosion and subsidence reduce the barrier island to a subaqueous inner shelf shoal (e.g., Ship Shoal...exception is the western- most island, Cat Island, which is primarily protected from offshore waves from the incident wave sheltering of the Chandeleur and...KAHN and ROBERTS (1982) discussed the morpho- logic response of the Chandeleur barrier islands to Hurricane Frederic, a powerful storm that made

Sea King SHOL Support for Post-HCM/FELEX HALIFAX Class Ships

DTIC Science & Technology

2014-05-01

correct this, a Network Time Protocol (NTP) time server was installed on two Raspberry - Pi computers3 (one used as a backup). Time was set to GPS time...data is needed, a wave buoy would be deployed for direct measurement. However, the launch & recovery of a 3The Raspberry Pi is an inexpensive credit...card-sized single-board computer developed in the UK by the Raspberry Pi Foundation. DRDC-RDDC-2014-R18 15 wave buoy was not practical in conjunction

Investigation of Response Amplitude Operators for Floating Offshore Wind Turbines: Preprint

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

Ramachandran, G. K. V.; Robertson, A.; Jonkman, J. M.

This paper examines the consistency between response amplitude operators (RAOs) computed from WAMIT, a linear frequency-domain tool, to RAOs derived from time-domain computations based on white-noise wave excitation using FAST, a nonlinear aero-hydro-servo-elastic tool. The RAO comparison is first made for a rigid floating wind turbine without wind excitation. The investigation is further extended to examine how these RAOs change for a flexible and operational wind turbine. The RAOs are computed for below-rated, rated, and above-rated wind conditions. The method is applied to a floating wind system composed of the OC3-Hywind spar buoy and NREL 5-MW wind turbine. The responsesmore » are compared between FAST and WAMIT to verify the FAST model and to understand the influence of structural flexibility, aerodynamic damping, control actions, and waves on the system responses. The results show that based on the RAO computation procedure implemented, the WAMIT- and FAST-computed RAOs are similar (as expected) for a rigid turbine subjected to waves only. However, WAMIT is unable to model the excitation from a flexible turbine. Further, the presence of aerodynamic damping decreased the platform surge and pitch responses, as computed by both WAMIT and FAST when wind was included. Additionally, the influence of gyroscopic excitation increased the yaw response, which was captured by both WAMIT and FAST.« less

A wideband fast multipole boundary element method for half-space/plane-symmetric acoustic wave problems

NASA Astrophysics Data System (ADS)

Zheng, Chang-Jun; Chen, Hai-Bo; Chen, Lei-Lei

2013-04-01

This paper presents a novel wideband fast multipole boundary element approach to 3D half-space/plane-symmetric acoustic wave problems. The half-space fundamental solution is employed in the boundary integral equations so that the tree structure required in the fast multipole algorithm is constructed for the boundary elements in the real domain only. Moreover, a set of symmetric relations between the multipole expansion coefficients of the real and image domains are derived, and the half-space fundamental solution is modified for the purpose of applying such relations to avoid calculating, translating and saving the multipole/local expansion coefficients of the image domain. The wideband adaptive multilevel fast multipole algorithm associated with the iterative solver GMRES is employed so that the present method is accurate and efficient for both lowand high-frequency acoustic wave problems. As for exterior acoustic problems, the Burton-Miller method is adopted to tackle the fictitious eigenfrequency problem involved in the conventional boundary integral equation method. Details on the implementation of the present method are described, and numerical examples are given to demonstrate its accuracy and efficiency.

Lateral heterogeneity and azimuthal anistropy of the upper mantle: Love and Rayleigh waves 100-250 sec

NASA Technical Reports Server (NTRS)

Tanimoto, T.; Anderson, D. L.

1983-01-01

The lateral heterogeneity and apparent anisotropy of the upper mantle are studied by measuring Rayleigh and Love wave phase velocities in the period range 100-250 sec. Spherical harmonic descriptions of the lateral heterogeneity are obtained for order and degree up to 1=m=10. Slow regions are evident at the East Pacific rise, northeast Africa, Tibet, Tasman sea, southwestern North America and triple junctions in the Northern Atlantic and Indian oceans. Fast regions occur in Australia, western Pacific and the eastern Atlantic. Details which are not evident in previous studies include two fast regions in the central Pacific and the subduction zone in the Scotia Arc region. Inversion for azimuthal dependence showed (1) little correlation between the fast phase velocity directions and the plate motion vector in plate interiors, but (2) correlation of the fast direction with the perpendicular direction to trenches and ridges. Phase velocity is high when waves propagate perpendicular to these structures. Severe tradeoffs exist between heterogeneity and azimuthal dependence because of the yet unsatisfactory path coverage.

Lateral heterogeneity and azimuthal anisotropy of the upper mantle - Love and Rayleigh waves 100-250 sec

NASA Technical Reports Server (NTRS)

Tanimoto, T.; Anderson, D. L.

1985-01-01

The lateral heterogeneity and apparent anisotropy of the upper mantle are studied by measuring Rayleigh and Love wave phase velocities in the period range 100-250 sec. Spherical harmonic descriptions of the lateral heterogeneity are obtained for order and degree up to 1=m=10. Slow regions are evident at the East Pacific rise, northeast Africa, Tibet, Tasman sea, southwestern North America and triple junctions in the Northern Atlantic and Indian oceans. Fast regions occur in Australia, western Pacific and the eastern Atlantic. Details which are not evident in previous studies include two fast regions in the central Pacific and the subduction zone in the Scotia Arc region. Inversion for azimuthal dependence showed (1) little correlation between the fast phase velocity directions and the plate motion vector in plate interiors, but (2) correlation of the fast direction with the perpendicular direction to trenches and ridges. Phase velocity is high when waves propagate perpendicular to these structures. Severe tradeoffs exist between heterogeneity and azimuthal dependence because of the yet unsatisfactory path coverage.

Fast solution of elliptic partial differential equations using linear combinations of plane waves.

PubMed

Pérez-Jordá, José M

2016-02-01

Given an arbitrary elliptic partial differential equation (PDE), a procedure for obtaining its solution is proposed based on the method of Ritz: the solution is written as a linear combination of plane waves and the coefficients are obtained by variational minimization. The PDE to be solved is cast as a system of linear equations Ax=b, where the matrix A is not sparse, which prevents the straightforward application of standard iterative methods in order to solve it. This sparseness problem can be circumvented by means of a recursive bisection approach based on the fast Fourier transform, which makes it possible to implement fast versions of some stationary iterative methods (such as Gauss-Seidel) consuming O(NlogN) memory and executing an iteration in O(Nlog(2)N) time, N being the number of plane waves used. In a similar way, fast versions of Krylov subspace methods and multigrid methods can also be implemented. These procedures are tested on Poisson's equation expressed in adaptive coordinates. It is found that the best results are obtained with the GMRES method using a multigrid preconditioner with Gauss-Seidel relaxation steps.

LETTER: Investigation of the effect of Alfven resonance mode conversion on fast wave current drive in ITER

NASA Astrophysics Data System (ADS)

Alava, M. J.; Heikkinen, J. A.; Hellsten, T.

1995-07-01

In order to reduce or to avoid ion cyclotron damping, the use of frequencies below the ion cyclotron frequency of minority ion species or the second harmonic of majority ion species has been proposed for fast wave current drive based on direct electron absorption. For these scenarios, the Alfven or ion-ion hybrid resonance can appear on the high field side of a tokamak. The presence of these resonances causes parasitic absorption, competing with the electron Landau damping and transit time magnetic pumping responsible for the fast wave current drive. In the present study, neglecting effects from toroidicity, the mode conversion at the Alfven resonance is shown to be of the order of 5 to 10% in the current drive scenarios for the planned ITER experiment. If the single pass absorption in the centre can be made sufficiently high, the conversion at the Alfven resonance becomes negligible

Investigation of the effect of Alfven resonance absorption on fast wave current drive in ITER

NASA Astrophysics Data System (ADS)

Alava, M. J.; Heikkinen, J. A.; Hellsten, T.

The use of frequencies below the ion cyclotron frequency of minority ion species or second harmonic of majority species has been proposed for fast wave current drive in order to reduce or to avoid ion cyclotron damping. For these scenarios, the Alfven resonance can appear on the high field side of a tokamak. The presence of this resonance causes parasitic absorption competing with the electron Landau damping and transit time magnetic pumping responsible for the fast wave current drive. In the present study, the mode conversion at the Alfven resonance is shown to be of the order of 5 to 10 percent in the current drive scenarios for the planned International Thermonuclear Experimental Reactor (ITER) experiment. However, if the single pass absorption in the center can be made sufficiently high, the conversion at the Alfven resonance becomes negligible.

Detection of Propagating Fast Sausage Waves through Detailed Analysis of a Zebra-pattern Fine Structure in a Solar Radio Burst

NASA Astrophysics Data System (ADS)

Kaneda, K.; Misawa, H.; Iwai, K.; Masuda, S.; Tsuchiya, F.; Katoh, Y.; Obara, T.

2018-03-01

Various magnetohydrodynamic (MHD) waves have recently been detected in the solar corona and investigated intensively in the context of coronal heating and coronal seismology. In this Letter, we report the first detection of short-period propagating fast sausage mode waves in a metric radio spectral fine structure observed with the Assembly of Metric-band Aperture Telescope and Real-time Analysis System. Analysis of Zebra patterns (ZPs) in a type-IV burst revealed a quasi-periodic modulation in the frequency separation between the adjacent stripes of the ZPs (Δf ). The observed quasi-periodic modulation had a period of 1–2 s and exhibited a characteristic negative frequency drift with a rate of 3–8 MHz s‑1. Based on the double plasma resonance model, the most accepted generation model of ZPs, the observed quasi-periodic modulation of the ZP can be interpreted in terms of fast sausage mode waves propagating upward at phase speeds of 3000–8000 km s‑1. These results provide us with new insights for probing the fine structure of coronal loops.

An evaluation of Seasat-A data in relation to optimum track ship weather routing and site specific forecasting for the offshore oil industry

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

Daley, C.; Johnson, R.G.; Thomson, J.C.

1981-07-01

The usefulness of Seasat-A SASS and altimeter measurements is reviewed. Five oceanic areas were selected: the Gulf of Alaska, central and western north Atlantic, eastern north Pacific, southern Indian Ocean, and the North Sea. Both Seasat-aided and conventional analyses were used in offshore hindcast and optimum ship routing situations. Where conventional observations are relatively dense, Seasat wind and wave data have greater impact in determining the shape of major map features than in positioning the features. In data sparse areas, Seasat data permit greater definition of surface features as well as their precise location. The use of Seasat data inmore » optimum ship routing is quantified by means of comparative studies in the Gulf of Alaska.« less

Airborne Monitoring of Pollution from Individual Ships in the Framework of the IGPS Project

NASA Astrophysics Data System (ADS)

Beecken, Jörg; Mellqvist, Johan; Salo, Kent; Ekholm, Johan

2013-04-01

The environmental impact of maritime transport has been recognized by the International Maritime Organization (IMO) which sets limits on fuel quality and emission characteristics of ships. The IGPS project (Identification of Gross-Polluting Ships) is a Swedish project aimed at developing a surveillance system for measuring emissions of SO2, NOx and particulate matter from individual vessels at sea as well as at harbors. Equipped on aircrafts, this system can be used for efficient compliance monitoring of ships at open sea. Additionally plumes can be sampled several times to increase the measurement quality. This operation environment also sets special demands on the instrumentation such as fast response times for example. The presented results cover the measurements of four airborne campaigns which were conducted during 2011 and 2012, covering the western Baltic Sea between Denmark, Sweden and Germany as well as the German Bight and the English Channel regions of the North Sea. As platforms, two different airplanes and a helicopter were used respectively. Emission data of more than 150 different vessels was obtained. From the measured emissions the sulfur content in the fuel and the emitted NOx per main engine speed as reference characteristics were determined for the individual ships. Additionally, measurements on the particle size distributions of ship plumes were studied. Furthermore the conducted measurements also showed that the system is flight functional and works fine independent from the type of aircraft.

Excitation of slow waves in front of an ICRF antenna in a basic plasma experiment

NASA Astrophysics Data System (ADS)

Soni, Kunal; van Compernolle, Bart; Crombe, Kristel; van Eester, Dirk

2017-10-01

Recent results of ICRF experiments at the Large Plasma Device (LAPD) indicate parasitic coupling to the slow wave by the fast wave antenna. Plasma parameters in LAPD are similar to the scrape-off layer of current fusion devices. The machine has a 17 m long, 60 cm diameter magnetized plasma column with typical plasma parameters ne 1012 -1013 cm-3, Te 1 - 10 eV and B0 1000 G. It was found that coupling to the slow mode occurs when the plasma density in front of the antenna is low enough such that the lower hybrid resonance is present in the plasma. The radial density profile is tailored to allow for fast mode propagation in the high density core and slow mode propagation in the low density edge region. Measurements of the wave fields clearly show two distinct modes, one long wavelength m=1 fast wave mode in the core and a short wavelength backward propagating mode in the edge. Perpendicular wave numbers compare favorably to the predicted values. The experiment was done for varying frequencies, ω /Ωi = 25 , 6 and 1.5. Future experiments will investigate the dependence on antenna tilt angle with respect to the magnetic field, with and without Faraday screen. This work is performed at the Basic Plasma Science Facility, sponsored jointly by DOE and NSF.

Calculating qP-wave traveltimes in 2-D TTI media by high-order fast sweeping methods with a numerical quartic equation solver

NASA Astrophysics Data System (ADS)

Han, Song; Zhang, Wei; Zhang, Jie

2017-09-01

A fast sweeping method (FSM) determines the first arrival traveltimes of seismic waves by sweeping the velocity model in different directions meanwhile applying a local solver. It is an efficient way to numerically solve Hamilton-Jacobi equations for traveltime calculations. In this study, we develop an improved FSM to calculate the first arrival traveltimes of quasi-P (qP) waves in 2-D tilted transversely isotropic (TTI) media. A local solver utilizes the coupled slowness surface of qP and quasi-SV (qSV) waves to form a quartic equation, and solve it numerically to obtain possible traveltimes of qP-wave. The proposed quartic solver utilizes Fermat's principle to limit the range of the possible solution, then uses the bisection procedure to efficiently determine the real roots. With causality enforced during sweepings, our FSM converges fast in a few iterations, and the exact number depending on the complexity of the velocity model. To improve the accuracy, we employ high-order finite difference schemes and derive the second-order formulae. There is no weak anisotropy assumption, and no approximation is made to the complex slowness surface of qP-wave. In comparison to the traveltimes calculated by a horizontal slowness shooting method, the validity and accuracy of our FSM is demonstrated.

Acoustic Receptivity of Mach 4.5 Boundary Layer with Leading- Edge Bluntness

NASA Technical Reports Server (NTRS)

Malik, Mujeeb R.; Balakumar, Ponnampalam

2007-01-01

Boundary layer receptivity to two-dimensional slow and fast acoustic waves is investigated by solving Navier-Stokes equations for Mach 4.5 flow over a flat plate with a finite-thickness leading edge. Higher order spatial and temporal schemes are employed to obtain the solution whereby the flat-plate leading edge region is resolved by providing a sufficiently refined grid. The results show that the instability waves are generated in the leading edge region and that the boundary-layer is much more receptive to slow acoustic waves (by almost a factor of 20) as compared to the fast waves. Hence, this leading-edge receptivity mechanism is expected to be more relevant in the transition process for high Mach number flows where second mode instability is dominant. Computations are performed to investigate the effect of leading-edge thickness and it is found that bluntness tends to stabilize the boundary layer. Furthermore, the relative significance of fast acoustic waves is enhanced in the presence of bluntness. The effect of acoustic wave incidence angle is also studied and it is found that the receptivity of the boundary layer on the windward side (with respect to the acoustic forcing) decreases by more than a factor of 4 when the incidence angle is increased from 0 to 45 deg. However, the receptivity coefficient for the leeward side is found to vary relatively weakly with the incidence angle.

Advanced computational simulations of water waves interacting with wave energy converters

NASA Astrophysics Data System (ADS)

Pathak, Ashish; Freniere, Cole; Raessi, Mehdi

2017-03-01

Wave energy converter (WEC) devices harness the renewable ocean wave energy and convert it into useful forms of energy, e.g. mechanical or electrical. This paper presents an advanced 3D computational framework to study the interaction between water waves and WEC devices. The computational tool solves the full Navier-Stokes equations and considers all important effects impacting the device performance. To enable large-scale simulations in fast turnaround times, the computational solver was developed in an MPI parallel framework. A fast multigrid preconditioned solver is introduced to solve the computationally expensive pressure Poisson equation. The computational solver was applied to two surface-piercing WEC geometries: bottom-hinged cylinder and flap. Their numerically simulated response was validated against experimental data. Additional simulations were conducted to investigate the applicability of Froude scaling in predicting full-scale WEC response from the model experiments.

Vorticity equation for MHD fast waves in geospace environment

NASA Technical Reports Server (NTRS)

Yamauchi, M.; Lundin, R.; Lui, A. T. Y.

1993-01-01

The MHD vorticity equation is modified in order to apply it to nonlinear MHD fast waves or shocks when their extent along the magnetic field is limited. Field-aligned current (FAC) generation is also discussed on the basis of this modified vorticity equation. When the wave normal is not aligned to the finite velocity convection and the source region is spatially limited, a longitudinal polarization causes a pair of plus and minus charges inside the compressional plane waves or shocks, generating a pair of FACs. This polarization is not related to the separation between the electrons and ions caused by their difference in mass, a separation which is inherent to compressional waves. The resultant double field-aligned current structure exists both with and without the contributions from curvature drift, which is questionable in terms of its contribution to vorticity change from the viewpoint of single-particle motion.

Evaluation of Composite-Hull Ships Operating in Arctic Ice

DTIC Science & Technology

2016-06-01

controller. During the time of thesis submission, public works closed the NPS tow tank spaces for environmental characterization of asbestos , as shown...environmental characterization of asbestos shut down the Halligan Hall tow tank spaces. This prevented the researcher to fully assemble the wave generating

Characteristics of a Power Line Used as a VLF Antenna.

DTIC Science & Technology

1982-05-01

were glass melamine . Assemblies of 12 layers were fabricated at El Segundo, CA and shipped by air to Tromso, Norway for final assembly of the full 120...sciences, applied electronics, semiconductor crystal and device physics, radiometric Imaging; millimeter-wave and microwave technology. Information

Capability of geometric features to classify ships in SAR imagery

NASA Astrophysics Data System (ADS)

Lang, Haitao; Wu, Siwen; Lai, Quan; Ma, Li

2016-10-01

Ship classification in synthetic aperture radar (SAR) imagery has become a new hotspot in remote sensing community for its valuable potential in many maritime applications. Several kinds of ship features, such as geometric features, polarimetric features, and scattering features have been widely applied on ship classification tasks. Compared with polarimetric features and scattering features, which are subject to SAR parameters (e.g., sensor type, incidence angle, polarization, etc.) and environment factors (e.g., sea state, wind, wave, current, etc.), geometric features are relatively independent of SAR and environment factors, and easy to be extracted stably from SAR imagery. In this paper, the capability of geometric features to classify ships in SAR imagery with various resolution has been investigated. Firstly, the relationship between the geometric feature extraction accuracy and the SAR imagery resolution is analyzed. It shows that the minimum bounding rectangle (MBR) of ship can be extracted exactly in terms of absolute precision by the proposed automatic ship-sea segmentation method. Next, six simple but effective geometric features are extracted to build a ship representation for the subsequent classification task. These six geometric features are composed of length (f1), width (f2), area (f3), perimeter (f4), elongatedness (f5) and compactness (f6). Among them, two basic features, length (f1) and width (f2), are directly extracted based on the MBR of ship, the other four are derived from those two basic features. The capability of the utilized geometric features to classify ships are validated on two data set with different image resolutions. The results show that the performance of ship classification solely by geometric features is close to that obtained by the state-of-the-art methods, which obtained by a combination of multiple kinds of features, including scattering features and geometric features after a complex feature selection process.

Producing Global Science Products for the Moderate Resolution Imaging Spectroradiometer (MODIS) in MODAPS

NASA Technical Reports Server (NTRS)

Masuoka, Edward J.; Tilmes, Curt A.; Ye, Gang; Devine, Neal; Smith, David E. (Technical Monitor)

2000-01-01

The MODerate resolution Imaging Spectroradiometer (MODIS) was launched on NASA's EOS-Terra spacecraft December 1999. With 36 spectral bands covering the visible, near wave and short wave infrared. MODIS produces over 40 global science data products, including sea surface temperature, ocean color, cloud properties, vegetation indices land surface temperature and land cover change. The MODIS Data Processing System (MODAPS) produces 400 GB/day of global MODIS science products from calibrated radiances generated in the Earth Observing System Data and Information System (EOSDIS). The science products are shipped to the EOSDIS for archiving and distribution to the public. An additional 200 GB of products are shipped each day to MODIS team members for quality assurance and validation of their products. In the sections that follow, we will describe the architecture of the MODAPS, identify processing bottlenecks encountered in scaling MODAPS from 50 GB/day backup system to a 400 GB/day production system and discuss how these were handled.

Non-linear wave-particle interactions and fast ion loss induced by multiple Alfvén eigenmodes in the DIII-D tokamak

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

Chen, Xi; Kramer, Gerrit J.; Heidbrink, William W.

2014-05-21

A new non-linear feature has been observed in fast-ion loss from tokamak plasmas in the form of oscillations at the sum, difference and second harmonic frequencies of two independent Alfvén eigenmodes (AEs). Full orbit calculations and analytic theory indicate this non-linearity is due to coupling of fast-ion orbital response as it passes through each AE — a change in wave-particle phase k • r by one mode alters the force exerted by the next. Furthermore, the loss measurement is of barely confined, non-resonant particles, while similar non-linear interactions can occur between well-confined particles and multiple AEs leading to enhanced fast-ionmore » transport.« less

Dispersive Evolution of Nonlinear Fast Magnetoacoustic Wave Trains

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

Pascoe, D. J.; Goddard, C. R.; Nakariakov, V. M., E-mail: D.J.Pascoe@warwick.ac.uk

2017-10-01

Quasi-periodic rapidly propagating wave trains are frequently observed in extreme ultraviolet observations of the solar corona, or are inferred by the quasi-periodic modulation of radio emission. The dispersive nature of fast magnetohydrodynamic waves in coronal structures provides a robust mechanism to explain the detected quasi-periodic patterns. We perform 2D numerical simulations of impulsively generated wave trains in coronal plasma slabs and investigate how the behavior of the trapped and leaky components depend on the properties of the initial perturbation. For large amplitude compressive perturbations, the geometrical dispersion associated with the waveguide suppresses the nonlinear steepening for the trapped wave train.more » The wave train formed by the leaky components does not experience dispersion once it leaves the waveguide and so can steepen and form shocks. The mechanism we consider can lead to the formation of multiple shock fronts by a single, large amplitude, impulsive event and so can account for quasi-periodic features observed in radio spectra.« less

Nonlinear effects associated with fast magnetosonic waves and turbulent magnetic amplification in laboratory and astrophysical plasmas

NASA Astrophysics Data System (ADS)

Tiwary, PremPyari; Sharma, Swati; Sharma, Prachi; Singh, Ram Kishor; Uma, R.; Sharma, R. P.

2016-12-01

This paper presents the spatio-temporal evolution of magnetic field due to the nonlinear coupling between fast magnetosonic wave (FMSW) and low frequency slow Alfvén wave (SAW). The dynamical equations of finite frequency FMSW and SAW in the presence of ponderomotive force of FMSW (pump wave) has been presented. Numerical simulation has been carried out for the nonlinear coupled equations of finite frequency FMSW and SAW. A systematic scan of the nonlinear behavior/evolution of the pump FMSW has been done for one of the set of parameters chosen in this paper, using the coupled dynamical equations. Filamentation of fast magnetosonic wave has been considered to be responsible for the magnetic turbulence during the laser plasma interaction. The results show that the formation and growth of localized structures depend on the background magnetic field but the order of amplification does not get affected by the magnitude of the background magnetic field. In this paper, we have shown the relevance of our model for two different parameters used in laboratory and astrophysical phenomenon. We have used one set of parameters pertaining to experimental observations in the study of fast ignition of laser fusion and hence studied the turbulent structures in stellar environment. The other set corresponds to the study of magnetic field amplification in the clumpy medium surrounding the supernova remnant Cassiopeia A. The results indicate considerable randomness in the spatial structure of the magnetic field profile in both the cases and gives a sufficient indication of turbulence. The turbulent spectra have been studied and the break point has been found around k which is consistent with the observations in both the cases. The nonlinear wave-wave interaction presented in this paper may be important in understanding the turbulence in the laboratory as well as the astrophysical phenomenon.

Rogue waves in the ocean - review and progress

NASA Astrophysics Data System (ADS)

Pelinovsky, Efim; Kharif, Christian; Slunyaev, Alexey

2010-05-01

Rogue waves in the ocean and physical mechanisms of their appearance are discussed. Theyse waves are among waves naturally observed by people on the sea surface that represent inseparable feature of the Ocean. Rogue waves appear from nowhere, cause danger and disappear at once. They may occur at the surface of a relatively calm sea, reach not very high amplitudes, but be fatal for ships and crew due to their unexpectedness and abnormal features. The billows appear suddenly exceeding the surrounding waves twice and more, and obtained many names: abnormal, exceptional, extreme, giant, huge, sudden, episodic, freak, monster, rogue, vicious, killer, mad- or rabid-dog waves; cape rollers, holes in the sea, walls of water, three sisters… Freak monsters, though living for seconds, were able to arouse superstitious fear of the crew, cause damage, death of heedless sailors or the whole ship. All these epithets are full of human fear and feebleness. The serious studies of the phenomenon started about 20-30 years ago and have been intensified during the recent decade. The research is being conducted in different fields: in physics (search of physical mechanisms and adequate models of wave enhancement and statistics), in geoscience (determining the regions and weather conditions when rogue waves are most probable), and in ocean and coastal engineering (estimations of the wave loads on fixed and drifting floating structures). Thus, scientists and engineers specializing in different subject areas are involved in the solution of the problem. The state-of-art of the rogue wave study is summarized in our book [Kharif, Ch., Pelinovsky, E., and Slunyaev, A. Rogue Waves in the Ocean. Springer, 2009] and presented in given review. Firstly, we start with a brief introduction to the problem of freak waves aiming at formulating what is understood as rogue or freak waves, what consequences their existence imply in our life, why people are so worried about them. Then we discuss existing observations and measurements of freak waves. Two approaches to the rogue wave description (deterministic and statistical) are presented. Briefly, the physical mechanisms that have been already suggested as possible explanations of the freak wave phenomenon are: i) wave-current interaction; ii) geometrical (spatial) focusing; iii) focusing due to dispersion (spatio-temporal focusing); iv) focusing due to modulational instability; v) soliton collision; vi) atmospheric action. In conclusion we emphasize that most of the developed theories are applicable to other physical phenomena starting from ocean waves of different nature and ending with nonlinear optics (for instance optical rogue waves in fibers) and astrophysical plasma processes. The recent trends in study of the oceanic rogue waves are discussed as well.

Broadband Geoelectrical Signatures of Water and Ethanol Solutions in Ottawa Sand

EPA Science Inventory

Ethanol is fast becoming the most widely used and distributed biofuel since its introduction as a fuel oxygenate to replace MTBE in gasoline and the rise in use of “Flex Fuel” vehicles. Distilleries create and store vast quantities of ethanol, which is then shipped in large quant...

Effects of Simulated Surface Effect Ship Motions on Crew Habitability. Phase II. Volume 2. Facility, Test conditions, and Schedules

DTIC Science & Technology

1977-05-01

fast acceleration response over the frequency range from 0.2 to 5 Hz, being characterized by a flat amplitude and a 0.02-0.03 sec effective delay...the hot reservoir oil through three fan-cooled radiators. The c••ling syst~m operates intermit - tently (controlled by a thermostat) to keep the oil...a very fast and puowerful hydrau- lic position servo, having its own 1000 psi power supply and very tight position control loop. It can position the 4

Continuous monitoring of noise levels in the Gulf of Catania (Ionian Sea). Study of correlation with ship traffic.

PubMed

Viola, S; Grammauta, R; Sciacca, V; Bellia, G; Beranzoli, L; Buscaino, G; Caruso, F; Chierici, F; Cuttone, G; D'Amico, A; De Luca, V; Embriaco, D; Favali, P; Giovanetti, G; Marinaro, G; Mazzola, S; Filiciotto, F; Pavan, G; Pellegrino, C; Pulvirenti, S; Simeone, F; Speziale, F; Riccobene, G

2017-08-15

Acoustic noise levels were measured in the Gulf of Catania (Ionian Sea) from July 2012 to May 2013 by a low frequency (<1000Hz) hydrophone, installed on board the NEMO-SN1 multidisciplinary observatory. NEMO-SN1 is a cabled node of EMSO-ERIC, which was deployed at a water depth of 2100m, 25km off Catania. The study area is characterized by the proximity of mid-size harbors and shipping lanes. Measured noise levels were correlated with the passage of ships tracked with a dedicated AIS antenna. Noise power was measured in the frequency range between 10Hz and 1000Hz. Experimental data were compared with the results of a fast numerical model based on AIS data to evaluate the contribution of shipping noise in six consecutive 1/3 octave frequency bands, including the 1/3 octave frequency bands centered at 63Hz and 125Hz, indicated by the Marine Strategy Framework Directive (2008/56/EC). Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

GPS-Acoustic Seafloor Geodesy using a Wave Glider

NASA Astrophysics Data System (ADS)

Chadwell, C. D.

2013-12-01

The conventional approach to implement the GPS-Acoustic technique uses a ship or buoy for the interface between GPS and Acoustics. The high cost and limited availability of ships restricts occupations to infrequent campaign-style measurements. A new approach to address this problem uses a remote controlled, wave-powered sea surface vehicle, the Wave Glider. The Wave Glider uses sea-surface wave action for forward propulsion with both upward and downward motions producing forward thrust. It uses solar energy for power with solar panels charging the onboard 660 W-h battery for near continuous operation. It uses Iridium for communication providing command and control from shore plus status and user data via the satellite link. Given both the sea-surface wave action and solar energy are renewable, the vehicle can operate for extended periods (months) remotely. The vehicle can be launched from a small boat and can travel at ~ 1 kt to locations offshore. We have adapted a Wave Glider for seafloor geodesy by adding a dual frequency GPS receiver embedded in an Inertial Navigation Unit, a second GPS antenna/receiver to align the INU, and a high precision acoustic ranging system. We will report results of initial testing of the system conducted at SIO. In 2014, the new approach will be used for seafloor geodetic measurements of plate motion in the Cascadia Subduction Zone. The project is for a three-year effort to measure plate motion at three sites along an East-West profile at latitude 44.6 N, offshore Newport Oregon. One site will be located on the incoming plate to measure the present day convergence between the Juan de Fuca and North American plates and two additional sites will be located on the continental slope of NA to measure the elastic deformation due to stick-slip behavior on the mega-thrust fault. These new seafloor data will constrain existing models of slip behavior that presently are poorly constrained by land geodetic data 100 km from the deformation front.

Dispersively formed quasi-periodic fast magnetosonic wavefronts due to the eruption of a nearby mini-filament

NASA Astrophysics Data System (ADS)

Shen, Yuandeng; Song, Tengfei; Liu, Yu

2018-06-01

Observational analysis is performed to study the excitation mechanism and propagation properties of a quasi-periodic fast-propagating (QFP) magnetosonic wave. The QFP wave was associated with the eruption of a nearby mini-filament and a small B4 Geostationary Operational Environmental Satellite (GOES) flare, which may indicate that the generation of a QFP wave does not require much flare energy. The propagation of the QFP wave was along a bundle of funnel-shaped open loops with a speed of about 1100 ± 78 km s-1 and an acceleration of -2.2 ± 1.1 km s-2. Periodicity analysis indicates that the periods of the QFP wave are 43 ± 6 and 79 ± 18 s. For the first time, we find that the periods of the QFP wave and the accompanying flare are inconsistent, which is different from the findings reported in previous studies. We propose that the present QFP wave was possibly caused by the mechanism of dispersive evolution of the initially broad-band disturbance resulting from the nearby mini-filament eruption.

Analytical study of body waves in orthorhombic media and comparison with SKS-phase observations from selected stations

NASA Astrophysics Data System (ADS)

Löberich, Eric; Bokelmann, Götz

2016-04-01

Anisotropic effects of wave propagation, observed in the Earth, provide interesting applications in basic research and practice, e.g., in reservoir geophysics and other fields. Teleseismic waves often evidence upper mantle anisotropy, as created by aligned olivine grains. While each grain is associated with orthorhombic symmetry, the preferred alignment may lead to a transversely isotropic characteristic. Considering body waves passing through an anisotropic medium, a splitting of shear waves can usually be observed, since their transverse polarization leads to a separation of the two quasi-shear waves. The associated splitting-delay is generated if the related fast and slow seismic velocities differ. Most of the previous shear-wave splitting investigations were based on the common assumption of near-vertical incidence. However, the influence of increasing incidence angles, which may lead to angular dependent splitting-delay and fast polarization orientation, has been pointed out by Davis (2003). Our study investigates the occurrence of these postulated dependences on azimuth and incidence angle (distance), examining splitting observations in SKS-recordings at selected broadband stations (e.g., Djibouti and Red Lake, Ontario).

Extreme Wave-Induced Oscillation in Paradip Port Under the Resonance Conditions

NASA Astrophysics Data System (ADS)

Kumar, Prashant; Gulshan

2017-12-01

A mathematical model is constructed to analyze the long wave-induced oscillation in Paradip Port, Odisha, India under the resonance conditions to avert any extreme wave hazards. Boundary element method (BEM) with corner contribution is utilized to solve the Helmholtz equation under the partial reflection boundary conditions. Furthermore, convergence analysis is also performed for the boundary element scheme with uniform and non-uniform discretization of the boundary. The numerical scheme is also validated with analytic approximation and existing studies based on harbor resonance. Then, the amplification factor is estimated at six key record stations in the Paradip Port with multidirectional incident waves and resonance modes are also estimated at the boundary of the port. Ocean surface wave field is predicted in the interior of Paradip Port for the different directional incident wave at various resonance modes. Moreover, the safe locations in the port have been identified for loading and unloading of moored ship with different resonance modes and directional incident waves.

Rogue Waves in the Ocean

NASA Astrophysics Data System (ADS)

Waseda, Takuji

2010-03-01

Giant episodic ocean waves that suddenly soar like a wall of water out of an otherwise calm sea are not just a legend. Such waves—which in the past have been called “abnormal,” “exceptional,” “extreme,” and even “vicious killer” waves—are now commonly known as “rogue waves” or “freak waves.” These waves have sunk or severely damaged 22 supercarriers in the world and caused the loss of more than 500 lives in the past 40 years. The largest wave registered by reliable instruments reached 30 meters in height, and the largest wave recorded by visual observation reached about 34 meters, equivalent to the height of an eight-story building. Tales of seafarers from Christopher Columbus to the passengers of luxury cruise ships had long been undervalued by scientists, but in the past 10 or so years, those historical notes and modern testimonies have been scientifically dissected to reveal the nature of these monster waves.

Ship wakes and their manifestations on the sea surface

NASA Astrophysics Data System (ADS)

Ermakov, Stanislav; Kapustin, Ivan; Kalimulin, Rashid

2013-04-01

Spatial/temporal evolution of turbulence generated by surface ships and the effect of the wake on short wind waves has been studied on the Black Sea and on the Gorky Water Reservoir. Measurements of currents in ship wakes were conducted using an Acoustic Doppler Current Profiler deployed from a motor boat. It was obtained that the temporal/spatial evolution of the wake width could be described approximately by a 0.4-power dependence, and the wake depth remained nearly constant at its initial stage. This allowed one to consider the wake widening as a one-dimensional process. We have developed a simple one-dimensional model of ship wake evolution using a semi-empirical theory of turbulence, and the initial stage of the wake widening (when neglecting dissipation) was described by the equation of turbulent energy balance with the pulse initial condition. Mean circulating currents in the wake zone resulting in the wind wave intensification ("suloi" areas) at the boundaries of the wake were detected in experiment. The asymmetry of the "suloi" bands was observed when the wind was blowing nearly perpendicular to the wake axis. It was shown that the later stage of the wake evolution is characterized by the formation of slick bands at the edges of the wake. The slick bands is a result of the transport of surfactants to the water surface by air bubbles in the wake and their compression due to the mean circulating currents. The work was supported by RFBR (projects 12-05-31237, 11-05-00295), the Program RAN Radiophysics, and by the Russian Government (Grants No. 11.G34.31.0048 and 11.G34.31.0078).

Effects of smoking on arterial distensibility, central aortic pressures and left ventricular mass.

PubMed

Markus, Marcello Ricardo Paulista; Stritzke, Jan; Baumeister, Sebastian Edgar; Siewert, Ulrike; Baulmann, Johannes; Hannemann, Anke; Schipf, Sabine; Meisinger, Christa; Dörr, Marcus; Felix, Stephan Burkhart; Keil, Ulrich; Völzke, Henry; Hense, Hans-Werner; Schunkert, Heribert

2013-10-03

The effects of smoking on central aortic pressures and the age-related increase in left ventricular mass (LVM) are largely unknown. We studied the relationship between smoking, arterial distensibility, central aortic pressures and left ventricular mass in two population-based studies. Data was obtained from two German population-based studies (KORA and SHIP, participants' ages 25-84 years). We identified 114 normotensive current smokers and 185 normotensive all-time non-smokers in KORA as well as 400 and 588 such individuals in SHIP. Echocardiographic LVM was obtained at baseline (T0) and follow-up after ten years (T1) in KORA and at follow-up (T1) in SHIP. Additionally, pulse-wave analysis-based central aortic pressure and augmentation index (AIx) were measured at T1 in KORA. Cross-sectional analysis, using KORA T0 and SHIP T1, revealed in both studies a higher covariate-adjusted LVM and left ventricular mass index (LVMI) in smokers as compared with non-smokers. Moreover, in the KORA T1 examination, the smokers demonstrated a more pronounced increase, relative to baseline, of LVM (+13.5%) and LVMI (+13.4%) compared to non-smokers (+8.59% and +8.65%; p=0.036 and 0.042, respectively). Additionally, at KORA T1 smokers had a higher central systolic blood pressure and higher AIx than non-smokers (p=0.012 and p=0.001, respectively). The difference in central aortic pressure due to enhanced and more prolonged wave reflection may explain our finding of a further pronounced increase in left ventricular wall thickness and mass over time in smokers. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

A miniature research vessel: A small-scale ocean-exploration demonstration of geophysical methods

NASA Astrophysics Data System (ADS)

Howell, S. M.; Boston, B.; Sleeper, J. D.; Cameron, M. E.; Togia, H.; Anderson, A.; Sigurdardottir, T. D.; Tree, J. P.

2015-12-01

Graduate student members of the University of Hawaii Geophysical Society have designed a small-scale model research vessel (R/V) that uses sonar to create 3D maps of a model seafloor in real-time. A pilot project was presented to the public at the School of Ocean and Earth Science and Technology's (SOEST) Biennial Open House weekend in 2013 and, with financial support from the Society of Exploration Geophysicists and National Science Foundation, was developed into a full exhibit for the same event in 2015. Nearly 8,000 people attended the two-day event, including children and teachers from Hawaii's schools, home school students, community groups, families, and science enthusiasts. Our exhibit demonstrates real-time sonar mapping of a cardboard volcano using a toy size research vessel on a programmable 2-dimensional model ship track suspended above a model seafloor. Ship waypoints were wirelessly sent from a Windows Surface tablet to a large-touchscreen PC that controlled the exhibit. Sound wave travel times were recorded using an ultrasonic emitter/receiver attached to an Arduino microcontroller platform and streamed through a USB connection to the control PC running MatLab, where a 3D model was updated as the ship collected data. Our exhibit demonstrates the practical use of complicated concepts, like wave physics, survey design, and data processing in a way that the youngest elementary students are able to understand. It provides an accessible avenue to learn about sonar mapping, and could easily be adapted to talk about bat and marine mammal echolocation by replacing the model ship and volcano. The exhibit received an overwhelmingly positive response from attendees and incited discussions that covered a broad range of earth science topics.

Experimental Studies of Radial Wave Thermoacoustic Engines. Navy Environmentally Safe Ships Program.

DTIC Science & Technology

1995-07-15

4 B. Pressure and specific acoustic impedance differer.: hd equation. .... ................ 6...the engine, Arf Sr) the resonator cross-see:iona! area at r. Ap(r) the cross-sectional area of" a porn at r, V; >h :c .... ,Ar tk. resonator at r

Traveling waves in the discrete fast buffered bistable system.

PubMed

Tsai, Je-Chiang; Sneyd, James

2007-11-01

We study the existence and uniqueness of traveling wave solutions of the discrete buffered bistable equation. Buffered excitable systems are used to model, among other things, the propagation of waves of increased calcium concentration, and discrete models are often used to describe the propagation of such waves across multiple cells. We derive necessary conditions for the existence of waves, and, under some restrictive technical assumptions, we derive sufficient conditions. When the wave exists it is unique and stable.

Rotating magnetic shallow water waves and instabilities in a sphere

NASA Astrophysics Data System (ADS)

Márquez-Artavia, X.; Jones, C. A.; Tobias, S. M.

2017-07-01

Waves in a thin layer on a rotating sphere are studied. The effect of a toroidal magnetic field is considered, using the shallow water ideal MHD equations. The work is motivated by suggestions that there is a stably stratified layer below the Earth's core mantle boundary, and the existence of stable layers in stellar tachoclines. With an azimuthal background field known as the Malkus field, ?, ? being the co-latitude, a non-diffusive instability is found with azimuthal wavenumber ?. A necessary condition for instability is that the Alfvén speed exceeds ? where ? is the rotation rate and ? the sphere radius. Magneto-inertial gravity waves propagating westward and eastward occur, and become equatorially trapped when the field is strong. Magneto-Kelvin waves propagate eastward at low field strength, but a new westward propagating Kelvin wave is found when the field is strong. Fast magnetic Rossby waves travel westward, whilst the slow magnetic Rossby waves generally travel eastward, except for some ? modes at large field strength. An exceptional very slow westward ? magnetic Rossby wave mode occurs at all field strengths. The current-driven instability occurs for ? when the slow and fast magnetic Rossby waves interact. With strong field the magnetic Rossby waves become trapped at the pole. An asymptotic analysis giving the wave speed and wave form in terms of elementary functions is possible both in polar trapped and equatorially trapped cases.

Relativistic electron scattering by magnetosonic waves: Effects of discrete wave emission and high wave amplitudes

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

Artemyev, A. V., E-mail: ante0226@gmail.com; Mourenas, D.; Krasnoselskikh, V. V.

2015-06-15

In this paper, we study relativistic electron scattering by fast magnetosonic waves. We compare results of test particle simulations and the quasi-linear theory for different spectra of waves to investigate how a fine structure of the wave emission can influence electron resonant scattering. We show that for a realistically wide distribution of wave normal angles θ (i.e., when the dispersion δθ≥0.5{sup °}), relativistic electron scattering is similar for a wide wave spectrum and for a spectrum consisting in well-separated ion cyclotron harmonics. Comparisons of test particle simulations with quasi-linear theory show that for δθ>0.5{sup °}, the quasi-linear approximation describes resonantmore » scattering correctly for a large enough plasma frequency. For a very narrow θ distribution (when δθ∼0.05{sup °}), however, the effect of a fine structure in the wave spectrum becomes important. In this case, quasi-linear theory clearly fails in describing accurately electron scattering by fast magnetosonic waves. We also study the effect of high wave amplitudes on relativistic electron scattering. For typical conditions in the earth's radiation belts, the quasi-linear approximation cannot accurately describe electron scattering for waves with averaged amplitudes >300 pT. We discuss various applications of the obtained results for modeling electron dynamics in the radiation belts and in the Earth's magnetotail.« less

History of Hubble Space Telescope (HST)

NASA Image and Video Library

1995-02-01

The nearby intense star-forming region known as the Great Nebula in the Orion constellation reveals a bow shock around a very young star as seen by NASA's Hubble Space Telescope (HST). Named for the crescent-shaped wave made by a ship as it moves through the water, a bow shock can be created in space where two streams of gas collide. LL Ori emits a vigorous solar wind, a stream of charged particles moving rapidly outward from the star. Our own sun has a less energetic version of this wind. The material in the fast wind from LL Ori collides with slow moving gas evaporating away form the center of the Orion Nebula, which is located in the lower right of this image, producing the crescent shaped bow shock seen in the image. Astronomers have identified numerous shock fronts in this complex star-forming region and are using this data to understand the many complex phenomena associated with the birth of stars. A close visitor in our Milky Way Galaxy, the nebula is only 1,500 light years away from Earth. The filters used in this color composite represent oxygen, nitrogen, and hydrogen emissions.

The Effect of Saturation on Shear Wave Anisotropy in a Transversely Isotropic Medium

NASA Astrophysics Data System (ADS)

Li, W.; Pyrak-Nolte, L. J.

2010-12-01

Seismic monitoring of fluid distributions in the subsurface requires an understanding of the effect of fluid saturation on the anisotropic properties of layered media. Austin Chalk is a carbonate rock composed mainly of calcite (99.9%) with fine bedding caused by a weakly-directed fabric. In this paper, we assess the shear-wave anisotropy of Austin Chalk and the effect of saturation on interpreting anisotropy based on shear wave velocity, attenuation and spectral content as a function of saturation. In the laboratory, we performed full shear-waveform measurements on several dry cubic samples of Austin Chalk with dimensions 50mm x 50mm x 50mm. Two shear-wave contact transducers (central Frequency 1 MHz) were use to send and receive signals. Data was collected for three orthogonal orientations of the sample and as a function of shear wave polarization relative to the layers in the sample. For the waves propagated parallel to the layers, both fast and slow shear waves were observed with velocities of 3444 m/s and 3193 m/s, respectively. It was noted that the minimum and maximum shear wave velocities did not occur when the shear wave polarization were perpendicular or parallel to the layering in the sample but occurred at an orientation of ~25 degrees from the normal to the layers. The sample was then vacuum saturated with water for approximately ~15 hours. The same measurements were performed on the saturated sample as those on the dry sample. Both shear wave velocities observed decreased upon water-saturation with corresponding velocities of 3155 m/s and 2939 m/s, respectively. In the dry condition the difference between the fast and slow shear wave velocities was 250 m/s. This difference decreased to 215 m/s after fluid saturation. In both the dry and saturated condition, the shear wave velocity for waves propagated perpendicularly to the layers was independent of polarization and had the same magnitude as that of the slow shear wave. A wavelet analysis was performed to determine changes in the spectral content of the signals upon saturation as well velocity dispersion. We found that (1) low frequency components exhibit a larger difference in time delay between the fast and slow shear waves for the water-saturated condition than for the dry condition; (2) that high frequency components have relatively small differences in time delay between the dry and saturated conditions; and (3) the dominant frequency shifted to lower frequencies for the fast shear wave upon saturation while no change in dominant frequency was observed for the slow shear wave upon saturation. Thus, fluid saturation affects shear velocity as well as the spectral content of the signal. Acknowledgments: The authors wish to acknowledge support of this work by the Geosciences Research Program, Office of Basic Energy Sciences US Department of Energy (DE-FG02-09ER16022), by Exxon Mobil Upstream Research Company and the GeoMathematical Imaging Group at Purdue University.

Airborne emission measurements of SO2, NOx and particles from individual ships using sniffer technique

NASA Astrophysics Data System (ADS)

Beecken, J.; Mellqvist, J.; Salo, K.; Ekholm, J.; Jalkanen, J.-P.

2013-12-01

A dedicated system for airborne ship emission measurements of SO2, NOx and particles has been developed and used from several small aircrafts. The system has been adapted for fast response measurements at 1 Hz and the use of several of the instruments is unique. The uncertainty of the given data is about 20.3% for SO2 and 23.8% for NOx emission factors. Multiple measurements of 158 ships measured from the air on the Baltic and North Sea during 2011 and 2012 show emission factors of 18.8 ± 6.5 g kgfuel-1, 66.6 ± 23.4 g kgfuel-1, and 1.8 ± 1.3 × 1016 particles kgfuel-1 for SO2, NOx and particle number respectively. The particle size distributions were measured for particle diameters between 15 and 560 nm. The mean sizes of the particles are between 50 and 62 nm dependent on the distance to the source and the number size distribution is mono-modal. Concerning the sulfur fuel content 85% of the ships comply with the IMO limits. The sulfur emission has decreased compared to earlier measurements from 2007 to 2009. The presented method can be implemented for regular ship compliance monitoring.

Shock and Rarefaction Waves in a Heterogeneous Mantle

NASA Astrophysics Data System (ADS)

Jordan, J.; Hesse, M. A.

2012-12-01

We explore the effect of heterogeneities on partial melting and melt migration during active upwelling in the Earth's mantle. We have constructed simple, explicit nonlinear models in one dimension to examine heterogeneity and its dynamic affects on porosity, temperature and the magnesium number in a partially molten, porous medium comprised of olivine. The composition of the melt and solid are defined by a closed, binary phase diagram for a simplified, two-component olivine system. The two-component solid solution is represented by a phase loop where concentrations 0 and 1 to correspond to fayalite and forsterite, respectively. For analysis, we examine an advective system with a Riemann initial condition. Chromatographic tools and theory have primarily been used to track large, rare earth elements as tracers. In our case, we employ these theoretical tools to highlight the importance of the magnesium number, enthalpy and overall heterogeneity in the dynamics of melt migration. We calculate the eigenvectors and eigenvalues in the concentration-enthalpy space in order to glean the characteristics of the waves emerging the Riemann step. Analysis on Riemann problems of this nature shows us that the composition-enthalpy waves can be represented by self-similar solutions. The eigenvalues of the composition-enthalpy system represent the characteristic wave propagation speeds of the compositions and enthalpy through the domain. Furthermore, the corresponding eigenvectors are the directions of variation, or ``pathways," in concentration-enthalpy space that the characteristic waves follow. In the two-component system, the Riemann problem yields two waves connected by an intermediate concentration-enthalpy state determined by the intersections of the integral curves of the eigenvectors emanating from both the initial and boundary states. The first wave, ``slow path," and second wave, ``fast path," follow the aformentioned pathways set by the eigenvectors. The slow path wave has a zero eigenvalue, corresponding to a wave speed of zero, which preserves a residual imprint of the initial condition. Freezing fronts textemdash those that result in a negative change in porositytextemdash feature fast path waves that travel as shocks, whereas the fast path waves of melting fronts travel as spreading, rarefaction waves.

Seismic anisotropy and its precursory change before eruptions at Piton de la Fournaise volcano, La Réunion

NASA Astrophysics Data System (ADS)

Savage, M. K.; Ferrazzini, V.; Peltier, A.; Rivemale, E.; Mayor, J.; Schmid, A.; Brenguier, F.; Massin, F.; Got, J.-L.; Battaglia, J.; DiMuro, A.; Staudacher, T.; Rivet, D.; Taisne, B.; Shelley, A.

2015-05-01

The Piton de la Fournaise volcano exhibits frequent eruptions preceded by seismic swarms and is a good target to test hypotheses about magmatically induced variations in seismic wave properties. We use a permanent station network and a portable broadband network to compare seismic anisotropy measured via shear wave splitting with geodetic displacements, ratios of compressional to shear velocity (Vp/Vs), earthquake focal mechanisms, and ambient noise correlation analysis of surface wave velocities and to examine velocity and stress changes from 2000 through 2012. Fast directions align radially to the central cone and parallel to surface cracks and fissures, suggesting stress-controlled cracks. High Vp/Vs ratios under the summit compared with low ratios under the flank suggest spatial variations in the proportion of fluid-filled versus gas-filled cracks. Secular variations of fast directions (ϕ) and delay times (dt) between split shear waves are interpreted to sense changing crack densities and pressure. Delay times tend to increase while surface wave velocity decreases before eruptions. Rotations of ϕ may be caused by changes in either stress direction or fluid pressure. These changes usually correlate with GPS baseline changes. Changes in shear wave splitting measurements made on multiplets yield several populations with characteristic delay times, measured incoming polarizations, and fast directions, which change their proportion as a function of time. An eruption sequence on 14 October 2010 yielded over 2000 shear wave splitting measurements in a 14 h period, allowing high time resolution measurements to characterize the sequence. Stress directions from a propagating dike model qualitatively fit the temporal change in splitting.

Observation of quasi-periodic solar radio bursts associated with propagating fast-mode waves

NASA Astrophysics Data System (ADS)

Goddard, C. R.; Nisticò, G.; Nakariakov, V. M.; Zimovets, I. V.; White, S. M.

2016-10-01

Aims: Radio emission observations from the Learmonth and Bruny Island radio spectrographs are analysed to determine the nature of a train of discrete, periodic radio "sparks" (finite-bandwidth, short-duration isolated radio features) which precede a type II burst. We analyse extreme ultraviolet (EUV) imaging from SDO/AIA at multiple wavelengths and identify a series of quasi-periodic rapidly-propagating enhancements, which we interpret as a fast wave train, and link these to the detected radio features. Methods: The speeds and positions of the periodic rapidly propagating fast waves and the coronal mass ejection (CME) were recorded using running-difference images and time-distance analysis. From the frequency of the radio sparks the local electron density at the emission location was estimated for each. Using an empirical model for the scaling of density in the corona, the calculated electron density was used to obtain the height above the surface at which the emission occurs, and the propagation velocity of the emission location. Results: The period of the radio sparks, δtr = 1.78 ± 0.04 min, matches the period of the fast wave train observed at 171 Å, δtEUV = 1.7 ± 0.2 min. The inferred speed of the emission location of the radio sparks, 630 km s-1, is comparable to the measured speed of the CME leading edge, 500 km s-1, and the speeds derived from the drifting of the type II lanes. The calculated height of the radio emission (obtained from the density) matches the observed location of the CME leading edge. From the above evidence we propose that the radio sparks are caused by the quasi-periodic fast waves, and the emission is generated as they catch up and interact with the leading edge of the CME. The movie associated to Fig. 2 is available at http://www.aanda.org

A scheme for recording a fast process at nanosecond scale by using digital holographic interferometry with continuous wave laser

NASA Astrophysics Data System (ADS)

Wang, Jun; Zhao, Jianlin; Di, Jianglei; Jiang, Biqiang

2015-04-01

A scheme for recording fast process at nanosecond scale by using digital holographic interferometry with continuous wave (CW) laser is described and demonstrated experimentally, which employs delayed-time fibers and angular multiplexing technique and can realize the variable temporal resolution at nanosecond scale and different measured depths of object field at certain temporal resolution. The actual delay-time is controlled by two delayed-time fibers with different lengths. The object field information in two different states can be simultaneously recorded in a composite hologram. This scheme is also suitable for recording fast process at picosecond scale, by using an electro-optic modulator.

Observation of extremely strong shock waves in solids launched by petawatt laser heating

DOE PAGES

Lancaster, K. L.; Robinson, A. P. L.; Pasley, J.; ...

2017-08-25

Understanding hydrodynamic phenomena driven by fast electron heating is important for a range of applications including fast electron collimation schemes for fast ignition and the production and study of hot, dense matter. In this work, detailed numerical simulations modelling the heating, hydrodynamic evolution, and extreme ultra-violet (XUV) emission in combination with experimental XUV images indicate shock waves of exceptional strength (200 Mbar) launched due to rapid heating of materials via a petawatt laser. In conclusion, we discuss in detail the production of synthetic XUV images and how they assist us in interpreting experimental XUV images captured at 256 eV usingmore » a multi-layer spherical mirror.« less

Cavitation studies in microgravity

NASA Astrophysics Data System (ADS)

Kobel, Philippe; Obreschkow, Danail; Farhat, Mohamed; Dorsaz, Nicolas; de Bosset, Aurele

The hydrodynamic cavitation phenomenon is a major source of erosion for many industrial systems such as cryogenic pumps for rocket propulsion, fast ship propellers, hydraulic pipelines and turbines. Erosive processes are associated with liquid jets and shockwaves emission fol-lowing the cavity collapse. Yet, fundamental understanding of these processes requires further cavitation studies inside various geometries of liquid volumes, as the bubble dynamics strongly depends the surrounding pressure field. To this end, microgravity represents a unique platform to produce spherical fluid geometries and remove the hydrostatic pressure gradient induced by gravity. The goal of our first experiment (flown on ESA's parabolic flight campaigns 2005 and 2006) was to study single bubble dynamics inside large spherical water drops (having a radius between 8 and 13 mm) produced in microgravity. The water drops were created by a micro-pump that smoothly expelled the liquid through a custom-designed injector tube. Then, the cavitation bubble was generated through a fast electrical discharge between two electrodes immersed in the liquid from above. High-speed imaging allowed to analyze the implications of isolated finite volumes and spherical free surfaces on bubble evolution, liquid jets formation and shock wave dynamics. Of particular interest are the following results: (A) Bubble lifetimes are shorter than in extended liquid volumes, which could be explain by deriving novel corrective terms to the Rayleigh-Plesset equation. (B) Transient crowds of micro-bubbles (smaller than 1mm) appeared at the instants of shockwaves emission. A comparison between high-speed visualizations and 3D N-particle simulations of a shock front inside a liquid sphere reveals that focus zones within the drop lead to a significantly increased density of induced cavitation. Considering shock wave crossing and focusing may hence prove crucially useful to understand the important process of cavitation erosion. The aim of our future microgravity experiment is to assess the direct effects of gravity on cavitation bubble collapse through a comparison of single cavitation bubbles collapsing in mi-crogravity, normal gravity, and hypergravity. In particular, we shall investigate the shape of the bubble in its final collapse stage and the amount of energy dissipated in the dominant collapse channels, such as liquid jet, shock wave, and rebound bubble. The highly spherical bubbles will be produced via a point-like plasma generated by a high power laser beam. One major hypothesis that we will test is an increase in shock wave energy with decreasing gravity as a consequence of the higher final sphericity and suppression of liquid jets. To support this, we introduce an analytical model for the gravity-perturbed asymmetric collapse of spherical bubbles, and demonstrate that all initially spherical bubbles develop a gravity-related vertical jet along their collapse.

NASA's Ship-Aircraft Bio-Optical Research (SABOR)

NASA Image and Video Library

2017-12-08

Storm in the Sargasso Sea Scientist aboard the R/V Endeavor in the Sargasso Sea put their research on hold on July 28, 2014, as a storm system brought high waves crashing onto the deck. NASA's Ship-Aircraft Bio-Optical Research (SABOR) experiment is a coordinated ship and aircraft observation campaign off the Atlantic coast of the United States, an effort to advance space-based capabilities for monitoring microscopic plants that form the base of the marine food chain. Read more: 1.usa.gov/WWRVzj Credit: NASA/SABOR/Chris Armanetti, University of Rhode Island .NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Reverberant Microwave Propagation

DTIC Science & Technology

2008-10-01

HERO Hazards of Electromagnetic Radiation to Ordnance HP Hewlett Packard HWD Half-Wave Dipole IEC International Electrotechnical Commission IEE...composite panels used in new ship design; Hazards of Electromagnetic Radiation to Ordnance ( HERO ) analyses; and digital wireless system performance...Electro-Explosive Device EMC Electromagnetic Compatibility ft Foot (feet) GHz Gigahertz HERO Hazards of Electromagnetic

Investigations of Pressure Distribution on Fast Flying Bodies

NASA Technical Reports Server (NTRS)

Stamm, G.

1946-01-01

The question to be treated is: how high is the pressure in the bow wave caused by a body flying at supersonic speed, and how far reaching are the destructive effects of that wave? The pressure distribution on an s.S. and an S. projectile of normal speed has been ascertained already by the methods of measurement used at the Ballistic Institute of the Technical Academy of the German Air Forces. Now similar investigations of the conditions on especially fast-flying bodies were carried out.

Extremely Fast Numerical Integration of Ocean Surface Wave Dynamics

DTIC Science & Technology

2007-09-30

sub-processor must be added as shown in the blue box of Fig. 1. We first consider the Kadomtsev - Petviashvili (KP) equation ηt + coηx +αηηx + βη ...analytic integration of the so-called “soliton equations ,” I have discovered how the GFT can be used to solved higher order equations for which study...analytical study and extremely fast numerical integration of the extended nonlinear Schroedinger equation for fully three dimensional wave motion

Helicon normal modes in Proto-MPEX

NASA Astrophysics Data System (ADS)

Piotrowicz, P. A.; Caneses, J. F.; Green, D. L.; Goulding, R. H.; Lau, C.; Caughman, J. B. O.; Rapp, J.; Ruzic, D. N.

2018-05-01

The Proto-MPEX helicon source has been operating in a high electron density ‘helicon-mode’. Establishing plasma densities and magnetic field strengths under the antenna that allow for the formation of normal modes of the fast-wave are believed to be responsible for the ‘helicon-mode’. A 2D finite-element full-wave model of the helicon antenna on Proto-MPEX is used to identify the fast-wave normal modes responsible for the steady-state electron density profile produced by the source. We also show through the simulation that in the regions of operation in which core power deposition is maximum the slow-wave does not deposit significant power besides directly under the antenna. In the case of a simulation where a normal mode is not excited significant edge power is deposited in the mirror region. ).

Helicon normal modes in Proto-MPEX

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

Piotrowicz, Pawel A.; Caneses, Juan F.; Green, David L.

Here, the Proto-MPEX helicon source has been operating in a high electron density 'helicon-mode'. Establishing plasma densities and magnetic field strengths under the antenna that allow for the formation of normal modes of the fast-wave are believed to be responsible for the 'helicon-mode'. A 2D finite-element full-wave model of the helicon antenna on Proto-MPEX is used to identify the fast-wave normal modes responsible for the steady-state electron density profile produced by the source. We also show through the simulation that in the regions of operation in which core power deposition is maximum the slow-wave does not deposit significant power besidesmore » directly under the antenna. In the case of a simulation where a normal mode is not excited significant edge power is deposited in the mirror region.« less

Helicon normal modes in Proto-MPEX

DOE PAGES

Piotrowicz, Pawel A.; Caneses, Juan F.; Green, David L.; ...

2018-05-22

Here, the Proto-MPEX helicon source has been operating in a high electron density 'helicon-mode'. Establishing plasma densities and magnetic field strengths under the antenna that allow for the formation of normal modes of the fast-wave are believed to be responsible for the 'helicon-mode'. A 2D finite-element full-wave model of the helicon antenna on Proto-MPEX is used to identify the fast-wave normal modes responsible for the steady-state electron density profile produced by the source. We also show through the simulation that in the regions of operation in which core power deposition is maximum the slow-wave does not deposit significant power besidesmore » directly under the antenna. In the case of a simulation where a normal mode is not excited significant edge power is deposited in the mirror region.« less

Analysis of ship maneuvering data from simulators

NASA Astrophysics Data System (ADS)

Frette, V.; Kleppe, G.; Christensen, K.

2011-03-01

We analyze complex manuevering histories of ships obtained from training sessions on bridge simulators. Advanced ships are used in fields like offshore oil exploration: dive support vessels, supply vessels, anchor handling vessels, tugs, cable layers, and multi-purpose vessels. Due to high demands from the operations carried out, these ships need to have very high maneuverability. This is achieved through a propulsion system with several thrusters, water jets, and rudders in addition to standard propellers. For some operations, like subsea maintenance, it is crucial that the ship accurately keeps a fixed position. Therefore, bridge systems usually incorporate equipment for Dynamic Positioning (DP). DP is a method to keep ships and semi submersible rigs in a fixed position using the propulsion systems instead of anchors. It may also be used for sailing a vessel from one position to another along a predefined route. Like an autopilot on an airplane, DP may operate without human involvement. The method relies on accurate determination of position from external reference systems like GPS, as well as a continuously adjusted mathematical model of the ship and external forces from wind, waves and currents. In a specific simulator exercise for offshore crews, a ship is to be taken up to an installation consisting of three nearby oil platforms connected by bridges (Frigg field, North Sea), where a subsea inspection is to be carried out. Due to the many degrees of freedom during maneuvering, including partly or full use of DP, the chosen routes vary significantly. In this poster we report preliminary results on representations of the complex maneuvering histories; representations that allow comparison between crew groups, and, possibly, sorting of the different strategic choices behind.

Bootstrap and fast wave current drive for tokamak reactors

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

Ehst, D.A.

1991-09-01

Using the multi-species neoclassical treatment of Hirshman and Sigmar we study steady state bootstrap equilibria with seed currents provided by low frequency (ICRF) fast waves and with additional surface current density driven by lower hybrid waves. This study applies to reactor plasmas of arbitrary aspect ratio. IN one limit the bootstrap component can supply nearly the total equilibrium current with minimal driving power (< 20 MW). However, for larger total currents considerable driving power is required (for ITER: I{sub o} = 18 MA needs P{sub FW} = 15 MW, P{sub LH} = 75 MW). A computational survey of bootstrap fractionmore » and current drive efficiency is presented. 11 refs., 8 figs.« less

Wave Energy Prize - 1/50th Testing - Float Inc

DOE Data Explorer

Wesley Scharmen

2016-01-15

This submission of data includes all the 1/50th scale testing data completed on the Wave Energy Prize for Float Inc. During the testing of its 1/50th-scale device, Float Inc. Berger ABAM was deemed ineligible due to the fact that they brought a device with them to test and did not ship the device by the deadline stipulated in the Wave Energy Prize Rules. Because of this, analysis, results, and judging were not completed for this team/device. This submission included files such as: 1/50th test data (raw & processed) 1/50th test data video and pictures 1/50th Test plans and testing documents

Application of Research-Informed Teaching in the Taught-Postgraduate Education of Maritime Law

ERIC Educational Resources Information Center

Zhu, Ling; Pan, Wei

2017-01-01

Despite numerous studies of the research-teaching nexus, applying research-informed teaching (RiT) to taught-postgraduate education has been largely overlooked. This knowledge gap is particularly significant in the maritime law discipline given the fast-growing business of international shipping and logistics. This paper aims to examine the impact…

Easy-To-Use Connector

NASA Technical Reports Server (NTRS)

Wightman, William D.; Gernhardt, Michael

1993-01-01

Quick-connect/disconnect mechanism consists of two mating assemblies put together easily, even when initially misaligned by fairly large amounts. Used as electrical- or fluid-connection interface. Operated by humans or robots when fast connections must be made without precise positioning, -- for example, on offshore oil rigs, ship-to-dock links, nuclear facilities, and aircraft at loading gates.

The Impact Analysis of a Mixed Squadron, Containing LCS and Multi-Mission Surface Platforms, on Blue Force Casualties and Mission Effectiveness

DTIC Science & Technology

2008-09-01

Littoral Combat Ships OTH Over-The-Horizon Pd Probability of Detection PGGF Fast Attack Craft – Missile PIM Plan of Intended Movement Pk...Lucas Naval Postgraduate School Monterey, California 2. Dudley Knox Library Naval Postgraduate School Monterey, California 3. CAPT Doug Otte

Modeling and Theory of RF Antenna Systems on Proto-MPEX

NASA Astrophysics Data System (ADS)

Piotrowicz, P. A.; Caneses, J. F.; Goulding, R. H.; Green, D.; Caughman, J. B. O.; Ruzic, D. N.; Proto-MPEX Team

2017-10-01

The RF wave coupling of the helicon and ICH antennas installed on the Prototype Material Plasma Exposure eXperiment (MPEX) has been explored theoretically and via a full wave model implemented in COMSOL Multiphysics. The high-density mode in Proto-MPEX has been shown to occur when exciting radial eigenmodes of the plasma column which coincides with entering a Trivelpiece Gould (TG) anti-resonant regime, therefore suppressing edge heating in favor of core power deposition. The fast wave launched by the helicon antenna has a large wavelength and travels at a steep group velocity angle with the background magnetic field; for this reason the fast wave launched by the helicon antenna efficiently couples power to the core plasma. However, the ICH heating scheme relies on a small wavelength slow wave to couple power to the core of the plasma column. Coupling slow wave power to the core of the plasma column is sensitive to the location of the Alfven resonance. The wave-vector and group velocity vector of the slow wave in this parameter regime undergoes a drastic change in behavior when approaching the Alfven resonance. Full wave simulation results and dispersion analysis will be presented with suggestions to guide experimental progress. This work was supported by the US. D.O.E. contract DE-AC05-00OR22725.

Reduced spike-timing reliability correlates with the emergence of fast ripples in the rat epileptic hippocampus.

PubMed

Foffani, Guglielmo; Uzcategui, Yoryani G; Gal, Beatriz; Menendez de la Prida, Liset

2007-09-20

Ripples are sharp-wave-associated field oscillations (100-300 Hz) recorded in the hippocampus during behavioral immobility and slow-wave sleep. In epileptic rats and humans, a different and faster oscillation (200-600 Hz), termed fast ripples, has been described. However, the basic mechanisms are unknown. Here, we propose that fast ripples emerge from a disorganized ripple pattern caused by unreliable firing in the epileptic hippocampus. Enhanced synaptic activity is responsible for the irregular bursting of CA3 pyramidal cells due to large membrane potential fluctuations. Lower field interactions and a reduced spike-timing reliability concur with decreased spatial synchronization and the emergence of fast ripples. Reducing synaptically driven membrane potential fluctuations improves both spike-timing reliability and spatial synchronization and restores ripples in the epileptic hippocampus. Conversely, a lower spike-timing reliability, with reduced potassium currents, is associated with ripple shuffling in normal hippocampus. Therefore, fast ripples may reflect a pathological desynchronization of the normal ripple pattern.

A fast wind-farm boundary-layer model to investigate gravity wave effects and upstream flow deceleration

NASA Astrophysics Data System (ADS)

Allaerts, Dries; Meyers, Johan

2017-11-01

Wind farm design and control often relies on fast analytical wake models to predict turbine wake interactions and associated power losses. Essential input to these models are the inflow velocity and turbulent intensity at hub height, which come from prior measurement campaigns or wind-atlas data. Recent LES studies showed that in some situations large wind farms excite atmospheric gravity waves, which in turn affect the upstream wind conditions. In the current study, we develop a fast boundary-layer model that computes the excitation of gravity waves and the perturbation of the boundary-layer flow in response to an applied force. The core of the model is constituted by height-averaged, linearised Navier-Stokes equations for the inner and outer layer, and the effect of atmospheric gravity waves (excited by the boundary-layer displacement) is included via the pressure gradient. Coupling with analytical wake models allows us to study wind-farm wakes and upstream flow deceleration in various atmospheric conditions. Comparison with wind-farm LES results shows excellent agreement in terms of pressure and boundary-layer displacement levels. The authors acknowledge support from the European Research Council (FP7-Ideas, Grant No. 306471).

Fast Solitons on Star Graphs

NASA Astrophysics Data System (ADS)

Adami, Riccardo; Cacciapuoti, Claudio; Finco, Domenico; Noja, Diego

We define the Schrödinger equation with focusing, cubic nonlinearity on one-vertex graphs. We prove global well-posedness in the energy domain and conservation laws for some self-adjoint boundary conditions at the vertex, i.e. Kirchhoff boundary condition and the so-called δ and δ‧ boundary conditions. Moreover, in the same setting, we study the collision of a fast solitary wave with the vertex and we show that it splits in reflected and transmitted components. The outgoing waves preserve a soliton character over a time which depends on the logarithm of the velocity of the ingoing solitary wave. Over the same timescale, the reflection and transmission coefficients of the outgoing waves coincide with the corresponding coefficients of the linear problem. In the analysis of the problem, we follow ideas borrowed from the seminal paper [17] about scattering of fast solitons by a delta interaction on the line, by Holmer, Marzuola and Zworski. The present paper represents an extension of their work to the case of graphs and, as a byproduct, it shows how to extend the analysis of soliton scattering by other point interactions on the line, interpreted as a degenerate graph.

Millimeter-Wave Generation Via Plasma Three-Wave Mixing

DTIC Science & Technology

1988-06-01

are coupled to a third space -charge wave with dispersion 2w W k -k k . (16) A plasma-loaded-waveguide mode is excited at the intersection of this...DISPERSION "FAST" W PLASMA WAVE Wc PLASMA WAVE A-lA oppositely directed EPWs with different phase velocities (wp/k., and wO/k. 2) are coupled to a third ... space -charge wave with dispersion 2w I- k k .(16) e 2 A plaama-loaded-waveguide mode is excited at the intersection of this coupled space-charge wave

Breakthroughs in Low-Profile Leaky-Wave HPM Antennas

DTIC Science & Technology

2015-03-18

presentation of our work at the 17th annual DEPS conference. 15. SUBJECT TERMS Leaky-wave Antennas. High Power Microwaves (HPM) Antennas. Low-profile...the performance, behavior, and design of innovative High Power Microwave (HPM, GW-class) antennas of the forward-traveling, fast-wave, leaky-wave...Conformal Antennas. 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME OF RESPONSIBLE PERSON (Monitor

DIFFRACTION, REFRACTION, AND REFLECTION OF AN EXTREME-ULTRAVIOLET WAVE OBSERVED DURING ITS INTERACTIONS WITH REMOTE ACTIVE REGIONS

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

Shen Yuandeng; Liu Yu; Zhao Ruijuan

2013-08-20

We present observations of the diffraction, refraction, and reflection of a global extreme-ultraviolet (EUV) wave propagating in the solar corona. These intriguing phenomena are observed when the wave interacts with two remote active regions, and together they exhibit properties of an EUV wave. When the wave approached AR11465, it became weaker and finally disappeared in the active region, but a few minutes later a new wavefront appeared behind the active region, and it was not concentric with the incoming wave. In addition, a reflected wave was also simultaneously observed on the wave incoming side. When the wave approached AR11459, itmore » transmitted through the active region directly and without reflection. The formation of the new wavefront and the transmission could be explained with diffraction and refraction effects, respectively. We propose that the different behaviors observed during the interactions may be caused by different speed gradients at the boundaries of the two active regions. We find that the EUV wave formed ahead of a group of expanding loops a few minutes after the start of the loops' expansion, which represents the initiation of the associated coronal mass ejection (CME). Based on these results, we conclude that the EUV wave should be a nonlinear magnetosonic wave or shock driven by the associated CME, which propagated faster than the ambient fast mode speed and gradually slowed down to an ordinary linear wave. Our observations support the hybrid model that includes both fast wave and slow non-wave components.« less

FAST Model Calibration and Validation of the OC5-DeepCwind Floating Offshore Wind System Against Wave Tank Test Data

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

Wendt, Fabian F; Robertson, Amy N; Jonkman, Jason

During the course of the Offshore Code Comparison Collaboration, Continued, with Correlation (OC5) project, which focused on the validation of numerical methods through comparison against tank test data, the authors created a numerical FAST model of the 1:50-scale DeepCwind semisubmersible system that was tested at the Maritime Research Institute Netherlands ocean basin in 2013. This paper discusses several model calibration studies that were conducted to identify model adjustments that improve the agreement between the numerical simulations and the experimental test data. These calibration studies cover wind-field-specific parameters (coherence, turbulence), hydrodynamic and aerodynamic modeling approaches, as well as rotor model (blade-pitchmore » and blade-mass imbalances) and tower model (structural tower damping coefficient) adjustments. These calibration studies were conducted based on relatively simple calibration load cases (wave only/wind only). The agreement between the final FAST model and experimental measurements is then assessed based on more-complex combined wind and wave validation cases.« less

Anisotropic Rayleigh-wave phase velocities beneath northern Vietnam

NASA Astrophysics Data System (ADS)

Legendre, Cédric P.; Zhao, Li; Huang, Win-Gee; Huang, Bor-Shouh

2015-02-01

We explore the Rayleigh-wave phase-velocity structure beneath northern Vietnam over a broad period range of 5 to 250 s. We use the two-stations technique to derive the dispersion curves from the waveforms of 798 teleseismic events recoded by a set of 23 broadband seismic stations deployed in northern Vietnam. These dispersion curves are then inverted for both isotropic and azimuthally anisotropic Rayleigh-wave phase-velocity maps in the frequency range of 10 to 50 s. Main findings include a crustal expression of the Red River Shear Zone and the Song Ma Fault. Northern Vietnam displays a northeast/southwest dichotomy in the lithosphere with fast velocities beneath the South China Block and slow velocities beneath the Simao Block and between the Red River Fault and the Song Da Fault. The anisotropy in the region is relatively simple, with a high amplitude and fast directions parallel to the Red River Shear Zone in the western part. In the eastern part, the amplitudes are generally smaller and the fast axis displays more variations with periods.

Weak rotating flow disturbances in a centrifugal compressor with a vaneless diffuser

NASA Technical Reports Server (NTRS)

Moore, F. K.

1988-01-01

A theory is presented to predict the occurrence of weak rotating waves in a centrifugal compression system with a vaneless diffuser. As in a previous study of axial systems, an undisturbed performance characteristic is assumed known. Following an inviscid analysis of the diffuser flow, conditions for a neutral rotating disturbance are found. The solution is shown to have two branches; one with fast rotation, the other with very slow rotation. The slow branch includes a dense set of resonant solutions. The resonance is a feature of the diffuser flow, and therefore such disturbances must be expected at the various resonant flow coefficients regardless of the compressor characteristic. Slow solutions seem limited to flow coefficients less than about 0.3, where third and fourth harmonics appear. Fast waves seem limited to a first harmonic. These fast and slow waves are described, and effects of diffuser-wall convergence, backward blade angles, and partial recovery of exit velocity head are assessed.

A study on crustal shear wave splitting in the western part of the Banda arc-continent collision

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

Syuhada, E-mail: hadda9@gmail.com; Research Centre for Physics - Indonesian Institute of Sciences; Hananto, Nugroho D.

2016-03-11

We analyzed shear wave splitting parameters from local shallow (< 30 km) earthquakes recorded at six seismic stations in the western part of the Banda arc-continent collision. We determined fast polarization and delay time for 195 event-stations pairs calculated from good signal-to-noise ratio waveforms. We observed that there is evidence for shear wave splitting at all stations with dominant fast polarization directions oriented about NE-SW, which are parallel to the collision direction of the Australian plate. However, minor fast polarization directions are oriented around NW-SE being perpendicular to the strike of Timor through. Furthermore, the changes in fast azimuths with themore » earthquake-station back azimuth suggest that the crustal anisotropy in the study area is not uniform. Splitting delay times are within the range of 0.05 s to 0.8 s, with a mean value of 0.29±0.18 s. Major seismic stations exhibit a weak tendency increasing of delay times with increasing hypocentral distance suggesting the main anisotropy contribution of the shallow crust. In addition, these variations in fast azimuths and delay times indicate that the crustal anisotropy in this region might not only be caused by extensive dilatancy anisotropy (EDA), but also by heterogeneity shallow structure such as the presence of foliations in the rock fabric and the fracture zones associated with active faults.« less

Just How Does Sound Wave?

ERIC Educational Resources Information Center

Shipman, Bob

2006-01-01

When children first hear the term "sound wave" perhaps they might associate it with the way a hand waves or perhaps the squiggly line image on a television monitor when sound recordings are being made. Research suggests that children tend to think sound somehow travels as a discrete package, a fast-moving invisible thing, and not something that…

Study on unsteady hydrodynamic performance of propeller in waves

NASA Astrophysics Data System (ADS)

Zhao, Qingxin; Guo, Chunyu; Su, Yumin; Liu, Tian; Meng, Xiangyin

2017-09-01

The speed of a ship sailing in waves always slows down due to the decrease in efficiency of the propeller. So it is necessary and essential to analyze the unsteady hydrodynamic performance of propeller in waves. This paper is based on the numerical simulation and experimental research of hydrodynamics performance when the propeller is under wave conditions. Open-water propeller performance in calm water is calculated by commercial codes and the results are compared to experimental values to evaluate the accuracy of the numerical simulation method. The first-order Volume of Fluid (VOF) wave method in STAR CCM+ is utilized to simulate the three-dimensional numerical wave. According to the above prerequisite, the numerical calculation of hydrodynamic performance of the propeller under wave conditions is conducted, and the results reveal that both thrust and torque of the propeller under wave conditions reveal intense unsteady behavior. With the periodic variation of waves, ventilation, and even an effluent phenomenon appears on the propeller. Calculation results indicate, when ventilation or effluent appears, the numerical calculation model can capture the dynamic characteristics of the propeller accurately, thus providing a significant theory foundation for further studying the hydrodynamic performance of a propeller in waves.

Spectral Anisotropy of Magnetic Field Fluctuations around Ion Scales in the Fast Solar Wind

NASA Astrophysics Data System (ADS)

Wang, X.; Tu, C.; He, J.; Marsch, E.; Wang, L.

2016-12-01

The power spectra of magnetic field at ion scales are significantly influenced by waves and structures. In this work, we study the ΘRB angle dependence of the contribution of waves on the spectral index of the magnetic field. Wavelet technique is applied to the high time-resolution magnetic field data from WIND spacecraft measurements in the fast solar wind. It is found that around ion scales, the parallel spectrum has a slope of -4.6±0.1 originally. When we remove the waves, which correspond to the data points with relatively larger value of magnetic helicity, the parallel spectrum gets shallower gradually to -3.2±0.2. However, the perpendicular spectrum does not change significantly during the wave-removal process, and its slope remains -3.1±0.1. It means that when the waves are removed from the original data, the spectral anisotropy gets weaker. This result may help us understand the physical nature of the spectral anisotropy around the ion scales.

Coastal Change on Gulf Islands National Seashore during Hurricane Gustav: West Ship, East Ship, Horn, and Petit Bois Islands

USGS Publications Warehouse

Stockdon, Hilary F.; Doran, Kara S.; Serafin, Katherine A.

2010-01-01

INTRODUCTION Hurricane Gustav made landfall on September 1, 2008, near Cocodrie, Louisiana, as a category 2 storm, with maximum sustained winds near 170 km/hr. Hurricane-force winds, with speeds in excess of 119 km/hr, extended along 270 km of the Louisiana coastline, from Marsh Island to the central barrier islands. Tropical-storm-force winds (speeds > 63 km/hr) were felt across the coasts of Mississippi and Alabama. Within this area of high wind and associated storm surge and waves lie the Mississippi barrier islands of West Ship, East Ship, Horn, and Petit Bois, part of the National Park Service (NPS) Gulf Islands National Seashore (GUIS). These east-west trending islands form a barrier between the Mississippi Sound to the north and the Gulf of Mexico to the south. The islands are generally less than 1 km wide with dune elevations ranging generally between 2 and 3 m, but reaching 6 m on Horn Island. The interaction of waves and currents with the low, sandy beaches forces a range of dynamic responses, such as dune erosion, overwash deposition, spit elongation, and island breaching. The passage of strong hurricanes (such as Camille in 1969 and Katrina in 2005), combined with a background signal of long-term shoreline retreat, has caused significant coastal changes on the Mississippi barrier islands, presenting management challenges for State and Federal officials, including NPS resource managers. At the request of the NPS, the U.S. Geological Survey (USGS) has processed, analyzed, and interpreted pre- and post-Hurricane-Gustav lidar topographic data for West Ship, East Ship, Horn, and Petit Bois. These data and analyses can be used to better assess the storm vulnerability of portions of GUIS by characterizing the magnitude and spatial variability of hurricane-induced coastal changes, such as shoreline retreat, dune erosion, and beach volume change. This information will provide park managers with a greater understanding of the long-term evolution of these islands, which are frequently impacted by coastal storms. The purpose of this report is to summarize the methods used and observations made during a study of the effects of Hurricane Gustav on the coastal morphology of four island in GUIS.

An accurate, fast, and scalable solver for high-frequency wave propagation

NASA Astrophysics Data System (ADS)

Zepeda-Núñez, L.; Taus, M.; Hewett, R.; Demanet, L.

2017-12-01

In many science and engineering applications, solving time-harmonic high-frequency wave propagation problems quickly and accurately is of paramount importance. For example, in geophysics, particularly in oil exploration, such problems can be the forward problem in an iterative process for solving the inverse problem of subsurface inversion. It is important to solve these wave propagation problems accurately in order to efficiently obtain meaningful solutions of the inverse problems: low order forward modeling can hinder convergence. Additionally, due to the volume of data and the iterative nature of most optimization algorithms, the forward problem must be solved many times. Therefore, a fast solver is necessary to make solving the inverse problem feasible. For time-harmonic high-frequency wave propagation, obtaining both speed and accuracy is historically challenging. Recently, there have been many advances in the development of fast solvers for such problems, including methods which have linear complexity with respect to the number of degrees of freedom. While most methods scale optimally only in the context of low-order discretizations and smooth wave speed distributions, the method of polarized traces has been shown to retain optimal scaling for high-order discretizations, such as hybridizable discontinuous Galerkin methods and for highly heterogeneous (and even discontinuous) wave speeds. The resulting fast and accurate solver is consequently highly attractive for geophysical applications. To date, this method relies on a layered domain decomposition together with a preconditioner applied in a sweeping fashion, which has limited straight-forward parallelization. In this work, we introduce a new version of the method of polarized traces which reveals more parallel structure than previous versions while preserving all of its other advantages. We achieve this by further decomposing each layer and applying the preconditioner to these new components separately and in parallel. We demonstrate that this produces an even more effective and parallelizable preconditioner for a single right-hand side. As before, additional speed can be gained by pipelining several right-hand-sides.

Supershear Rayleigh Waves at a Soft Interface

NASA Astrophysics Data System (ADS)

Le Goff, Anne; Cobelli, Pablo; Lagubeau, Guillaume

2013-06-01

We report on the experimental observation of waves at a liquid foam surface propagating faster than the bulk shear waves. The existence of such waves has long been debated, but the recent observation of supershear events in a geophysical context has inspired us to search for their existence in a model viscoelastic system. An optimized fast profilometry technique allows us to observe on a liquid foam surface the waves triggered by the impact of a projectile. At high impact velocity, we show that the expected subshear Rayleigh waves are accompanied by faster surface waves that can be identified as supershear Rayleigh waves.

The Consequences of Alfven Waves and Parallel Potential Drops in the Auroral Zone

NASA Technical Reports Server (NTRS)

Schriver, David

2003-01-01

The goal of this research is to examine the causes of field-aligned plasma acceleration in the auroral zone using satellite data and numerical simulations. A primary question to be addressed is what causes the field-aligned acceleration of electrons (leading to precipitation) and ions (leading to upwelling ions) in the auroral zone. Data from the Fast Auroral SnapshoT (FAST) and Polar satellites is used when the two satellites are in approximate magnetic conjunction and are in the auroral region. FAST is at relatively low altitudes and samples plasma in the midst of the auroral acceleration region while Polar is at much higher altitudes and can measure plasmas and waves propagating towards the Earth. Polar can determine the sources of energy streaming earthward from the magnetotail, either in the form of field-aligned currents, electromagnetic waves or kinetic particle energy, that ultimately leads to the acceleration of plasma in the auroral zone. After identifying and examining several events, numerical simulations are run that bridges the spatial region between the two satellites. The code is a one-dimensional, long system length particle in cell simulation that has been developed to model the auroral region. A main goal of this research project is to include Alfven waves in the simulation to examine how these waves can accelerate plasma in the auroral zone.

Strong fast long-period waves in the Efpalio 2010 earthquake records: explanation in terms of leaking modes

NASA Astrophysics Data System (ADS)

Vackář, Jiří; Zahradník, Jiří; Sokos, Efthimios

2014-01-01

The January 18, 2010, shallow earthquake in the Corinth Gulf, Greece ( M w 5.3) generated unusually strong long-period waves (periods 4-8 s) between the P and S wave arrival. These periods, being significantly longer than the source duration, indicated a structural effect. The waves were observed in epicentral distances 40-250 km and were significant on radial and vertical component. None of existing velocity models of the studied region provided explanation of the waves. By inverting complete waveforms, we obtained an 1-D crustal model explaining the observation. The most significant feature of the best-fitting model (as well as the whole suite of models almost equally well fitting the waveforms) is a strong velocity step at depth about 4 km. In the obtained velocity model, the fast long-period wave was modeled by modal summation and identified as a superposition of several leaking modes. In this sense, the wave is qualitatively similar to P long or Pnl waves, which however are usually reported in larger epicentral distances. The main innovation of this paper is emphasis to smaller epicentral distances. We studied properties of the wave using synthetic seismograms. The wave has a normal dispersion. Azimuthal and distance dependence of the wave partially explains its presence at 46 stations of 70 examined. Depth dependence shows that the studied earthquake was very efficient in the excitation of these waves just due to its shallow centroid depth (4.5 km).

Control of ULF Wave Accessibility to the Inner Magnetosphere by the Convection of Plasma Density

NASA Astrophysics Data System (ADS)

Degeling, A. W.; Rae, I. J.; Watt, C. E. J.; Shi, Q. Q.; Rankin, R.; Zong, Q.-G.

2018-02-01

During periods of storm activity and enhanced convection, the plasma density in the afternoon sector of the magnetosphere is highly dynamic due to the development of plasmaspheric drainage plume (PDP) structure. This significantly affects the local Alfvén speed and alters the propagation of ULF waves launched from the magnetopause. Therefore, it can be expected that the accessibility of ULF wave power for radiation belt energization is sensitively dependent on the recent history of magnetospheric convection and the stage of development of the PDP. This is investigated using a 3-D model for ULF waves within the magnetosphere in which the plasma density distribution is evolved using an advection model for cold plasma, driven by a (VollandStern) convection electrostatic field (resulting in PDP structure). The wave model includes magnetic field day/night asymmetry and extends to a paraboloid dayside magnetopause, from which ULF waves are launched at various stages during the PDP development. We find that the plume structure significantly alters the field line resonance location, and the turning point for MHD fast waves, introducing strong asymmetry in the ULF wave distribution across the noon meridian. Moreover, the density enhancement within the PDP creates a waveguide or local cavity for MHD fast waves, such that eigenmodes formed allow the penetration of ULF wave power to much lower L within the plume than outside, providing an avenue for electron energization.

Exploration of high harmonic fast wave heating on the National Spherical Torus Experiment

NASA Astrophysics Data System (ADS)

Wilson, J. R.; Bell, R. E.; Bernabei, S.; Bitter, M.; Bonoli, P.; Gates, D.; Hosea, J.; LeBlanc, B.; Mau, T. K.; Medley, S.; Menard, J.; Mueller, D.; Ono, M.; Phillips, C. K.; Pinsker, R. I.; Raman, R.; Rosenberg, A.; Ryan, P.; Sabbagh, S.; Stutman, D.; Swain, D.; Takase, Y.; Wilgen, J.

2003-05-01

High harmonic fast wave (HHFW) heating has been proposed as a particularly attractive means for plasma heating and current drive in the high beta plasmas that are achievable in spherical torus (ST) devices. The National Spherical Torus Experiment (NSTX) [M. Ono, S. M. Kaye, S. Neumeyer et al., in Proceedings of the 18th IEEE/NPSS Symposium on Fusion Engineering, Albuquerque, 1999 (IEEE, Piscataway, NJ, 1999), p. 53] is such a device. An rf heating system has been installed on the NSTX to explore the physics of HHFW heating, current drive via rf waves and for use as a tool to demonstrate the attractiveness of the ST concept as a fusion device. To date, experiments have demonstrated many of the theoretical predictions for HHFW. In particular, strong wave absorption on electrons over a wide range of plasma parameters and wave parallel phase velocities, wave acceleration of energetic ions, and indications of current drive for directed wave spectra have been observed. In addition HHFW heating has been used to explore the energy transport properties of NSTX plasmas, to create H-mode discharges with a large fraction of bootstrap current and to control the plasma current profile during the early stages of the discharge.

Manned mission to Mars with periodic refueling from electrically propelled tankers

NASA Technical Reports Server (NTRS)

Gogan, Laura; Melko, Joseph; Wang, Fritz; Lourme, Daniel; Moha, Sophie Ben; Lardon, Christele; Richard, Muriel

1992-01-01

In a joint study by students from the Ecole Polytechnique Feminine, France, and the University of California, Los Angeles, a mission concept that had the objective of evaluating the feasibility of a non-nuclear, yet fast, manned mission to Mars was considered. Ion-engine propelled tankers are postulated that would provide mid-coarse refueling of LOX and LH2 to the manned ship. The scenario is therefore one of a 'split mission', yet with the added feature that the cargo ships include tankers for mid-course refueling. The present study is a continuation of one first conducted last year. Emphasis this year was on the design of the tanker fleet.

Transition region, coronal heating and the fast solar wind

NASA Astrophysics Data System (ADS)

Li, Xing

2003-07-01

It is assumed that magnetic flux tubes are strongly concentrated at the boundaries of supergranule convection cells. A power law spectrum of high frequency Alfvén waves with a spectral index -1 originating from the sun is assumed to supply all the energy needed to energize the plasma flowing in such magnetic flux tubes. At the high frequency end, the waves are eroded by ions due to ion cyclotron resonance. The magnetic flux concentration is essential since it allows a sufficiently strong energy flux to be carried by high frequency ion cyclotron waves and these waves can be readily released at the coronal base by cyclotron resonance. The main results are: 1. The waves are capable of creating a steep transition region, a hot corona and a fast solar wind if both the wave frequency is high enough and the magnetic flux concentration is sufficiently strong in the boundaries of the supergranule convection zone. 2. By primarily heating alpha particles only, it is possible to produce a steep transition region, a hot corona and a fast solar wind. Coulomb coupling plays a key role in transferring the thermal energy of alpha particles to protons and electrons at the corona base. The electron thermal conduction then does the remaining job to create a sharp transition region. 3. Plasma species (even ions) may already partially lose thermal equilibrium in the transition region, and minor ions may already be faster than protons at the very base of the corona. 4. The model predicts high temperature alpha particles (Talpha ~ 2 x 107 K) and low proton temperatures (Tp < 106 K) between 2 and 4 solar radii, suggesting that hydrogen Lyman lines observed by UVCS above coronal holes may be primarily broadened by Alfvén waves in this range.

Investigation of mantle kinematics beneath the Hellenic-subduction zone with teleseismic direct shear waves

NASA Astrophysics Data System (ADS)

Confal, Judith M.; Eken, Tuna; Tilmann, Frederik; Yolsal-Çevikbilen, Seda; Çubuk-Sabuncu, Yeşim; Saygin, Erdinc; Taymaz, Tuncay

2016-12-01

The subduction and roll-back of the African plate beneath the Eurasian plate along the arcuate Hellenic trench is the dominant geodynamic process in the Aegean and western Anatolia. Mantle flow and lithospheric kinematics in this region can potentially be understood better by mapping seismic anisotropy. This study uses direct shear-wave splitting measurements based on the Reference Station Technique in the southern Aegean Sea to reveal seismic anisotropy in the mantle. The technique overcomes possible contamination from source-side anisotropy on direct S-wave signals recorded at a station pair by maximizing the correlation between the seismic traces at reference and target stations after correcting the reference stations for known receiver-side anisotropy and the target stations for arbitrary splitting parameters probed via a grid search. We obtained splitting parameters at 35 stations with good-quality S-wave signals extracted from 81 teleseismic events. Employing direct S-waves enabled more stable and reliable splitting measurements than previously possible, based on sparse SKS data at temporary stations, with one to five events for local SKS studies, compared with an average of 12 events for each station in this study. The fast polarization directions mostly show NNE-SSW orientation with splitting time delays between 1.15 s and 1.62 s. Two stations in the west close to the Hellenic Trench and one in the east show N-S oriented fast polarizations. In the back-arc region three stations exhibit NE-SW orientation. The overall fast polarization variations tend to be similar to those obtained from previous SKS splitting studies in the region but indicate a more consistent pattern, most likely due to the usage of a larger number of individual observations in direct S-wave derived splitting measurements. Splitting analysis on direct shear waves typically resulted in larger split time delays compared to previous studies, possibly because S-waves travel along a longer path in the same anisotropic structure. Considering the S-derived splitting measurements of this study together with earlier SKS and Rayleigh wave anisotropy modelling results we suggest that the very consistent direct S-derived fast shear wave directions can be explained by the lattice-preferred orientation of olivine in the asthenospheric mantle due to mantle flow induced by the roll-back of the slab. It is possible that a small contribution originated in the lower crust beneath the study region where anisotropic fabric might have formed in response to extension in the Miocene.

Fast Wave Transmission Measurements on Alcator C-Mod

NASA Astrophysics Data System (ADS)

Reardon, J.; Bonoli, P. T.; Porkolab, M.; Takase, Y.; Wukitch, S. J.

1997-11-01

Data are presented from an array of single-turn loop probes newly installed on the inner wall of C-Mod, directly opposite one of the two fast-wave antennas. The 8-loop array extends 32^circ in the toroidal direction at the midplane and can distinguish electromagnetic from electrostatic modes. Data are acquired by 1GHz digitizer, spectrum analyzer, and RF detector circuit. Phase measurements during different heating scenarios show evidence of both standing and travelling waves. The measurement of toroidal mode number N_tor (conserved under the assumption of axisymmetry) is used to guide the toroidal full-wave code TORIC(Brambilla, M., IPP Report 5/66, February 1996). Amplitude measurements show modulation both by Type III ELMs and sawteeth; the observed sawtooth modulation may be interpreted as due to changes in central absorption. The amplitude of tildeB_tor measured at the inner wall is compared to the prediction of TORIC.

Depth-variant azimuthal anisotropy in Tibet revealed by surface wave tomography

NASA Astrophysics Data System (ADS)

Pandey, Shantanu; Yuan, Xiaohui; Debayle, Eric; Tilmann, Frederik; Priestley, Keith; Li, Xueqing

2015-06-01

Azimuthal anisotropy derived from multimode Rayleigh wave tomography in China exhibits depth-dependent variations in Tibet, which can be explained as induced by the Cenozoic India-Eurasian collision. In west Tibet, the E-W fast polarization direction at depths <100 km is consistent with the accumulated shear strain in the Tibetan lithosphere, whereas the N-S fast direction at greater depths is aligned with Indian Plate motion. In northeast Tibet, depth-consistent NW-SE directions imply coupled deformation throughout the whole lithosphere, possibly also involving the underlying asthenosphere. Significant anisotropy at depths of 225 km in southeast Tibet reflects sublithospheric deformation induced by northward and eastward lithospheric subduction beneath the Himalaya and Burma, respectively. The multilayer anisotropic surface wave model can explain some features of SKS splitting measurements in Tibet, with differences probably attributable to the limited back azimuthal coverage of most SKS studies in Tibet and the limited horizontal resolution of the surface wave results.

An integrated sea monitoring system based on a X-band wave radar to support the removal activities of the Costa Concordia wreck.

NASA Astrophysics Data System (ADS)

Gozzini, Bernardo; Serafino, Francesco; Lugni, Claudio; Antonini, Andrea; Costanza, Letizia; Orlandi, Andrea; Arturi, Daniele; Ludeno, Giovanni; Natale, Antonio; Soldovieri, Francesco; Ortolani, Alberto; Brandini, Carlo

2013-04-01

The planning and management of different types of operations at sea requires a number of sea state data as much in real-time as possible, for rapid and effective response to different situations. This need is particularly strong in emergency management practices, in accidents due to man-made or natural causes, that require the planning of civil protection activities (such as search-and-rescue, cleaning of pollution, ship recovery), transport planning etc. The use of X-band radar technology nowadays provides great advantages over traditional in-situ and satellite-based techniques for sea state measuring, to update information on waves and currents over a sea area with high spatial and temporal resolution. Other advantages include a good spatial coverage around the area of interest, the flexibility of use, the capacity to provide, on-demand and when necessary, complementary information (possible oil spills detection, integration with VTS, etc.). X-band coastal radars (so-called "wave-radars") are widely used in the monitoring of large marine areas, in integration with in-situ measurements, satellites and other radar types (HF), as a key element of the observational component of present operational oceanography systems. Outside of these systems, the use of this technology to support emergency management practices is very promising for both the quality and quantity of available parameters, and for an easy integration with all other available monitoring and forecasting tools. A case study particularly relevant is offered by the presence of the Costa Concordia ship near the Giglio Island. The management of this disaster has requested at an early stage a large number of data to support the monitoring of marine environment around the ship, e.g. to optimally plan water samples. In the next and present phase, to support the highly risky and costly activities linked to the wreck removal, which are extremely sea-state dependent, the installation of a wave-radar allows to detect, in real-time and with high revisiting time, waves and currents in the area surrounding the wreck. In addition wave spectra measures allow to check the reliability of present wave forecasting models, which are unlikely to represent the local and coastal scales of interest and therefore require a continuous process of verification, calibration and quality control. Similar considerations can be made for the reconstruction of marine currents at a local scale, whose uncertainty is inherently greater. The integration of X-band radar data with in-situ data has allowed to optimally calibrate the data itself (especially for what concerns the significant wave height) and to provide a local scale observation system which proved to be fundamental to support the work of continuous sea state monitoring and forecasting around the area of the disaster. The observation system at Giglio is a kind of laboratory unique in its kind, to test the reliability of the wave and hydrodynamic models at a local scale, to assess our present ability to use X-band radars for emergency management activities, and to evaluate the response capacity of such practices to the actual needs of involved stakeholders and private users.

Spontaneous emergence of rogue waves in partially coherent waves: A quantitative experimental comparison between hydrodynamics and optics

NASA Astrophysics Data System (ADS)

El Koussaifi, R.; Tikan, A.; Toffoli, A.; Randoux, S.; Suret, P.; Onorato, M.

2018-01-01

Rogue waves are extreme and rare fluctuations of the wave field that have been discussed in many physical systems. Their presence substantially influences the statistical properties of a partially coherent wave field, i.e., a wave field characterized by a finite band spectrum with random Fourier phases. Their understanding is fundamental for the design of ships and offshore platforms. In many meteorological conditions waves in the ocean are characterized by the so-called Joint North Sea Wave Project (JONSWAP) spectrum. Here we compare two unique experimental results: the first one has been performed in a 270 m wave tank and the other in optical fibers. In both cases, waves characterized by a JONSWAP spectrum and random Fourier phases have been launched at the input of the experimental device. The quantitative comparison, based on an appropriate scaling of the two experiments, shows a very good agreement between the statistics in hydrodynamics and optics. Spontaneous emergence of heavy tails in the probability density function of the wave amplitude is observed in both systems. The results demonstrate the universal features of rogue waves and provide a fundamental and explicit bridge between two important fields of research. Numerical simulations are also compared with experimental results.

Spontaneous emergence of rogue waves in partially coherent waves: A quantitative experimental comparison between hydrodynamics and optics.

PubMed

El Koussaifi, R; Tikan, A; Toffoli, A; Randoux, S; Suret, P; Onorato, M

2018-01-01

Rogue waves are extreme and rare fluctuations of the wave field that have been discussed in many physical systems. Their presence substantially influences the statistical properties of a partially coherent wave field, i.e., a wave field characterized by a finite band spectrum with random Fourier phases. Their understanding is fundamental for the design of ships and offshore platforms. In many meteorological conditions waves in the ocean are characterized by the so-called Joint North Sea Wave Project (JONSWAP) spectrum. Here we compare two unique experimental results: the first one has been performed in a 270 m wave tank and the other in optical fibers. In both cases, waves characterized by a JONSWAP spectrum and random Fourier phases have been launched at the input of the experimental device. The quantitative comparison, based on an appropriate scaling of the two experiments, shows a very good agreement between the statistics in hydrodynamics and optics. Spontaneous emergence of heavy tails in the probability density function of the wave amplitude is observed in both systems. The results demonstrate the universal features of rogue waves and provide a fundamental and explicit bridge between two important fields of research. Numerical simulations are also compared with experimental results.

Breakthroughs in Low-Profile Leaky-Wave HPM Antennas

DTIC Science & Technology

2016-09-21

information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and... traveling , fast-wave, leaky-wave class. 1.1. Overview of Previous Activities (1st thru 11th Quarter) During the first quarter, we prepared and...theory to guide the design of high-gain configurations (again, limited to 2D, H-plane representations) for linear, forward traveling -wave, leaky

Alfven resonance mode conversion in the Phaedrus-T current drive experiments: Modelling and density fluctuations measurements

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

Vukovic, M.; Harper, M.; Breun, R.

1995-12-31

Current drive experiments on the Phaedrus-T tokamak performed with a low field side two-strap fast wave antenna at frequencies below {omega}{sub cH} show loop volt drops of up to 30% with strap phasing (0, {pi}/2). RF induced density fluctuations in the plasma core have also been observed with a microwave reflectometer. It is believed that they are caused by kinetic Alfven waves generated by mode conversion of fast waves at the Alfven resonance. Correlation of the observed density fluctuations with the magnitude of the {Delta}V{sub loop} suggest that the {Delta}V{sub loop} is attributable to current drive/heating due to mode convertedmore » kinetic Alfven waves. The toroidal cold plasma wave code LION is used to model the Alfven resonance mode conversion surfaces in the experiments while the cylindrical hot plasma kinetic wave code ISMENE is used to model the behavior of kinetic Alfven waves at the Alfven resonance location. Initial results obtained from limited density, magnetic field, antenna phase, and impurity scans show good agreement between the RF induced density fluctuations and the predicted behavior of the kinetic Alfven waves. Detailed comparisons between the density fluctuations and the code predictions are presented.« less

Basilar-membrane interference patterns from multiple internal reflection of cochlear traveling waves.

PubMed

Shera, Christopher A; Cooper, Nigel P

2013-04-01

At low stimulus levels, basilar-membrane (BM) mechanical transfer functions in sensitive cochleae manifest a quasiperiodic rippling pattern in both amplitude and phase. Analysis of the responses of active cochlear models suggests that the rippling is a mechanical interference pattern created by multiple internal reflection within the cochlea. In models, the interference arises when reverse-traveling waves responsible for stimulus-frequency otoacoustic emissions (SFOAEs) reflect off the stapes on their way to the ear canal, launching a secondary forward-traveling wave that combines with the primary wave produced by the stimulus. Frequency-dependent phase differences between the two waves then create the rippling pattern measurable on the BM. Measurements of BM ripples and SFOAEs in individual chinchilla ears demonstrate that the ripples are strongly correlated with the acoustic interference pattern measured in ear-canal pressure, consistent with a common origin involving the generation of SFOAEs. In BM responses to clicks, the ripples appear as temporal fine structure in the response envelope (multiple lobes, waxing and waning). Analysis of the ripple spacing and response phase gradients provides a test for the role of fast- and slow-wave modes of reverse energy propagation within the cochlea. The data indicate that SFOAE delays are consistent with reverse slow-wave propagation but much too long to be explained by fast waves.

Reliability of pulse waveform separation analysis: effects of posture and fasting.

PubMed

Stoner, Lee; Credeur, Daniel; Fryer, Simon; Faulkner, James; Lambrick, Danielle; Gibbs, Bethany Barone

2017-03-01

Oscillometric pulse wave analysis devices enable, with relative simplicity and objectivity, the measurement of central hemodynamic parameters. The important parameters are central blood pressures and indices of arterial wave reflection, including wave separation analysis (backward pressure component Pb and reflection magnitude). This study sought to determine whether the measurement precision (between-day reliability) of Pb and reflection magnitude: exceeds the criterion for acceptable reliability; and is affected by posture (supine, seated) and fasting state. Twenty healthy adults (50% female, 27.9 years, 24.2 kg/m) were tested on six different mornings: 3 days fasted, 3 days nonfasted condition. On each occasion, participants were tested in supine and seated postures. Oscillometric pressure waveforms were recorded on the left upper arm. The criterion intra-class correlation coefficient value of 0.75 was exceeded for Pb (0.76) and reflection magnitude (0.77) when participants were assessed under the combined supine-fasted condition. The intra-class correlation coefficient was lowest for Pb in seated-nonfasted condition (0.57), and lowest for reflection magnitude in the seated-fasted condition (0.56). For Pb, the smallest detectible change that must be exceeded in order for a significant change to occur in an individual was 2.5 mmHg, and for reflection magnitude, the smallest detectable change was 8.5%. Assessments of Pb and reflection magnitude are as follows: exceed the criterion for acceptable reliability; and are most reliable when participants are fasted in a supine position. The demonstrated reliability suggests sufficient precision to detect clinically meaningful changes in reflection magnitude and Pb.

Radar: Human Safety Net

ERIC Educational Resources Information Center

Ritz, John M.

2016-01-01

Radar is a technology that can be used to detect distant objects not visible to the human eye. A predecessor of radar, called the telemobiloscope, was first used to detect ships in the fog in 1904 off the German coast. Many scientists have worked on the development and refinement of radar (Hertz with electromagnetic waves; Popov with determining…

Effect of ship hull form on the resistance penalty from biofouling.

PubMed

Oliveira, Dinis; Larsson, Ann I; Granhag, Lena

2018-03-01

Hull biofouling is a well-known problem for the shipping industry, leading to increased resistance and fuel consumption. Considering that the effects of hull form on resistance are known to be higher for a less slender hull, it is hypothesised in this paper that the effect of biofouling roughness on resistance is also dependent on the hull form. To test this hypothesis, previously reported full-scale numerical results on a containership are re-analysed. Form effects on roughness penalties, corresponding to K ΔCT  = 0.058 ± 0.025, are observed at a low speed (19 knots, Re s  = 2.29 × 10 9 ), which are however cancelled out by traditionally neglected roughness effects on wave-making resistance at a higher speed (24 knots, Re s  = 2.89 × 10 9 ). It is concluded that hull form effects on biofouling penalties can be significant at low speeds, though not generalisable for higher speeds, namely when wave-making resistance corresponds to ≥ 29% of total resistance.

Rogue run-up events at the North Sea coast

NASA Astrophysics Data System (ADS)

Didenkulova, Ira; Blossier, Brice; Daly, Christopher; Herbst, Gabriel; Senichev, Dmitry; Winter, Christian

2015-04-01

On the 1st of January, 1995, the Statoil-operated "Draupner" platform located in the North Sea recorded the so-called "New Year wave". Since then, rogue waves have been the topic of active scientific discussions and investigations. Waves of extreme height appearing randomly at the sea surface have been measured in both deep and shallow waters and have been involved in a number of ship accidents. Nowadays rogue waves are frequently recorded all over the world with several different instruments (range finders installed on offshore platforms, deployed buoys, radars including SAR, etc.). Rogue wave also occur at the coast, where they appear as either sudden flooding of coastal areas or high splashes over steep banks or sea walls. These waves are especially dangerous for beach users and lead regularly to human injuries and fatalities. Despite numerous reports of human accidents, coastal rogue waves have not yet been recorded experimentally. In this paper we discuss the recording of rogue wave events at German North Sea coasts by using high-resolution beach cameras. The recorded rogue waves are observed during different tide levels and different weather conditions. Possible mechanisms of their generation are discussed.

46 CFR 105.45-20 - Warning sign at gangway.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 4 2011-10-01 2011-10-01 false Warning sign at gangway. 105.45-20 Section 105.45-20... COMMERCIAL FISHING VESSELS DISPENSING PETROLEUM PRODUCTS Special Operating Requirements § 105.45-20 Warning sign at gangway. (a) Warning placards shall be kept at hand for display while a vessel is fast to a...

46 CFR 153.955 - Warning signs during cargo transfer.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 5 2011-10-01 2011-10-01 false Warning signs during cargo transfer. 153.955 Section 153... Transfer Procedures § 153.955 Warning signs during cargo transfer. (a) When transferring cargo while fast to a dock or at anchor in port, the master shall ensure that the tankship displays a warning sign at...

46 CFR 105.45-20 - Warning sign at gangway.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 4 2014-10-01 2014-10-01 false Warning sign at gangway. 105.45-20 Section 105.45-20... COMMERCIAL FISHING VESSELS DISPENSING PETROLEUM PRODUCTS Special Operating Requirements § 105.45-20 Warning sign at gangway. (a) Warning placards shall be kept at hand for display while a vessel is fast to a...

46 CFR 105.45-20 - Warning sign at gangway.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 4 2012-10-01 2012-10-01 false Warning sign at gangway. 105.45-20 Section 105.45-20... COMMERCIAL FISHING VESSELS DISPENSING PETROLEUM PRODUCTS Special Operating Requirements § 105.45-20 Warning sign at gangway. (a) Warning placards shall be kept at hand for display while a vessel is fast to a...

46 CFR 153.955 - Warning signs during cargo transfer.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 5 2012-10-01 2012-10-01 false Warning signs during cargo transfer. 153.955 Section 153... Transfer Procedures § 153.955 Warning signs during cargo transfer. (a) When transferring cargo while fast to a dock or at anchor in port, the master shall ensure that the tankship displays a warning sign at...

46 CFR 153.955 - Warning signs during cargo transfer.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 5 2010-10-01 2010-10-01 false Warning signs during cargo transfer. 153.955 Section 153... Transfer Procedures § 153.955 Warning signs during cargo transfer. (a) When transferring cargo while fast to a dock or at anchor in port, the master shall ensure that the tankship displays a warning sign at...

46 CFR 105.45-20 - Warning sign at gangway.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 4 2013-10-01 2013-10-01 false Warning sign at gangway. 105.45-20 Section 105.45-20... COMMERCIAL FISHING VESSELS DISPENSING PETROLEUM PRODUCTS Special Operating Requirements § 105.45-20 Warning sign at gangway. (a) Warning placards shall be kept at hand for display while a vessel is fast to a...

46 CFR 105.45-20 - Warning sign at gangway.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 4 2010-10-01 2010-10-01 false Warning sign at gangway. 105.45-20 Section 105.45-20... COMMERCIAL FISHING VESSELS DISPENSING PETROLEUM PRODUCTS Special Operating Requirements § 105.45-20 Warning sign at gangway. (a) Warning placards shall be kept at hand for display while a vessel is fast to a...

46 CFR 153.955 - Warning signs during cargo transfer.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 5 2014-10-01 2014-10-01 false Warning signs during cargo transfer. 153.955 Section 153... Transfer Procedures § 153.955 Warning signs during cargo transfer. (a) When transferring cargo while fast to a dock or at anchor in port, the master shall ensure that the tankship displays a warning sign at...

46 CFR 153.955 - Warning signs during cargo transfer.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 5 2013-10-01 2013-10-01 false Warning signs during cargo transfer. 153.955 Section 153... Transfer Procedures § 153.955 Warning signs during cargo transfer. (a) When transferring cargo while fast to a dock or at anchor in port, the master shall ensure that the tankship displays a warning sign at...

Electromagnetic Cyclotron Waves in the Solar Wind: Wind Observation and Wave Dispersion Analysis

NASA Technical Reports Server (NTRS)

Jian, L. K.; Moya, P. S.; Vinas, A. F.; Stevens, M.

2016-01-01

Wind observed long-lasting electromagnetic cyclotron waves near the proton cyclotron frequency on 11 March 2005, in the descending part of a fast wind stream. Bi-Maxwellian velocity distributions are fitted for core protons, beam protons, and alpha-particles. Using the fitted plasma parameters we conduct kinetic linear dispersion analysis and find ion cyclotron and/or firehose instabilities grow in six of 10 wave intervals. After Doppler shift, some of the waves have frequency and polarization consistent with observation, thus may be correspondence to the cyclotron waves observed.

Electromagnetic cyclotron waves in the solar wind: Wind observation and wave dispersion analysis

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

Jian, L. K., E-mail: lan.jian@nasa.gov; Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771; Moya, P. S.

2016-03-25

Wind observed long-lasting electromagnetic cyclotron waves near the proton cyclotron frequency on 11 March 2005, in the descending part of a fast wind stream. Bi-Maxwellian velocity distributions are fitted for core protons, beam protons, and α-particles. Using the fitted plasma parameters we conduct kinetic linear dispersion analysis and find ion cyclotron and/or firehose instabilities grow in six of 10 wave intervals. After Doppler shift, some of the waves have frequency and polarization consistent with observation, thus may be correspondence to the cyclotron waves observed.

Corrosion monitoring using high-frequency guided waves

NASA Astrophysics Data System (ADS)

Fromme, P.

2016-04-01

Corrosion can develop due to adverse environmental conditions during the life cycle of a range of industrial structures, e.g., offshore oil platforms, ships, and desalination plants. Generalized corrosion leading to wall thickness loss can cause the reduction of the strength and thus degradation of the structural integrity. The monitoring of corrosion damage in difficult to access areas can be achieved using high frequency guided waves propagating along the structure from accessible areas. Using standard ultrasonic wedge transducers with single sided access to the structure, guided wave modes were selectively generated that penetrate through the complete thickness of the structure. The wave propagation and interference of the different guided wave modes depends on the thickness of the structure. Laboratory experiments were conducted for wall thickness reduction due to milling of the steel structure. From the measured signal changes due to the wave mode interference the reduced wall thickness was monitored. Good agreement with theoretical predictions was achieved. The high frequency guided waves have the potential for corrosion damage monitoring at critical and difficult to access locations from a stand-off distance.

Corrosion monitoring using high-frequency guided ultrasonic waves

NASA Astrophysics Data System (ADS)

Fromme, Paul

2014-02-01

Corrosion develops due to adverse environmental conditions during the life cycle of a range of industrial structures, e.g., offshore oil platforms, ships, and desalination plants. Both pitting corrosion and generalized corrosion leading to wall thickness loss can cause the degradation of the structural integrity. The nondestructive detection and monitoring of corrosion damage in difficult to access areas can be achieved using high frequency guided waves propagating along the structure from accessible areas. Using standard ultrasonic transducers with single sided access to the structure, guided wave modes were generated that penetrate through the complete thickness of the structure. The wave propagation and interference of the different guided wave modes depends on the thickness of the structure. Laboratory experiments were conducted and the wall thickness reduced by consecutive milling of the steel structure. Further measurements were conducted using accelerated corrosion in a salt water bath and the damage severity monitored. From the measured signal change due to the wave mode interference the wall thickness reduction was monitored. The high frequency guided waves have the potential for corrosion damage monitoring at critical and difficult to access locations from a stand-off distance.

Recent Developments in Gravity-Wave Effects in Climate Models and the Global Distribution of Gravity-Wave Momentum Flux from Observations and Models

DTIC Science & Technology

2010-07-01

by changes in wind and stability to a vertical wavelength lying outside the observable range. Gravity-wave parametrizations also represent intermit ...tropopause variability. J. Atmos. Sci. 65: 1817–1837. Salby ML. 1982. Sampling theory for asynoptic satellite observations. Part II: Fast Fourier synoptic

A Local Probe for Universal Non-equilibrium Dynamics

DTIC Science & Technology

2015-06-01

left in the ground 1T. E. Drake, Y . Sagi, R. Paudel, J. T. Stewart, J. P . Gaebler, and D. S. Jin, “ Direct observation of the fermi surface in an...bottom) allow to switch the laser fast and fine-tune the frequency. “λ/2” refers to half-wave plates, “λ/4” refers to quarter-wave plates, and all cubes...the beat note signal on a fast photodiode. state (|F = 9/2,mF = −7/2〉), any place where excitation light exists. Imaging atoms occurs on a cycling

Inverse multipath fingerprinting for millimeter wave V2I beam alignment.

DOT National Transportation Integrated Search

2017-05-01

Efficient beam alignment is a crucial component in millimeter wave systems with analog beamforming, especially in fast-changing vehicular settings. This paper uses the vehicles position (e.g., available via GPS) to query the multipath fingerprint ...

Upper Mantle Responses to India-Eurasia Collision in Indochina, Malaysia, and the South China Sea

NASA Astrophysics Data System (ADS)

Hongsresawat, S.; Russo, R. M.

2016-12-01

We present new shear wave splitting and splitting intensity measurements from SK(K)S phases recorded at seismic stations of the Malaysian National Seismic Network. These results, in conjunction with results from Tibet and Yunnan provide a basis for testing the degree to which Indochina and South China Sea upper mantle fabrics are responses to India-Eurasia collision. Upper mantle fabrics derived from shear wave splitting measurements in Yunnan and eastern Tibet parallel geodetic surface motions north of 26°N, requiring transmission of tractions from upper mantle depths to surface, or consistent deformation boundary conditions throughout the upper 200 km of crust and mantle. Shear wave splitting fast trends and surface velocities diverge in eastern Yunnan and south of 26°N, indicating development of an asthenospheric layer that decouples crust and upper mantle, or corner flow above the subducted Indo-Burma slab. E-W fast shear wave splitting trends southwest of 26°N/104°E indicate strong gradients in any asthenospheric infiltration. Possible upper mantle flow regimes beneath Indochina include development of olivine b-axis anisotropic symmetry due to high strain and hydrous conditions in the syntaxis/Indo-Burma mantle wedge (i.e., southward flow), development of strong upper mantle corner flow in the Indo-Burma wedge with olivine a-axis anisotropic symmetry (i.e., westward flow), and simple asthenospheric flow due to eastward motion of Sundaland shearing underlying asthenosphere. Further south, shear-wave splitting delay times at Malaysian stations vary from 0.5 seconds on the Malay Peninsula to over 2 seconds at stations on Borneo. Splitting fast trends at Borneo stations and Singapore trend NE-SW, but in northern Peninsular Malaysia, the splitting fast polarization direction is NW-SE, parallel to the trend of the Peninsula. Thus, there is a sharp transition from low delay time and NW-SE fast polarization to high delay times and fast polarization directions that parallel the strike of the now-inoperative spreading center in the South China Sea. This transition appears to occur in the central portion of Peninsular Malaysia and may mark the boundary between Tethyan upper mantle extruded from the India-Asia collision zone and supra-subduction upper mantle of the Indonesian arc.

Wave and tidal level analysis, maritime climate change, navigation's strategy and impact on the costal defences - Study case of São Paulo State Coastline Harbour Areas (Brazil)

NASA Astrophysics Data System (ADS)

Alfredini, P.; Pezzoli, A.; Cristofori, E. I.; Dovetta, A.; Arasaki, E.

2012-04-01

São Paulo State Coastline Harbour Area concentrates around of 40% of Brazilian GNP, Santos Harbour is the America South Atlantic Hub Port and São Sebastião Oil Maritime Terminal is the most important oil and gas facility of PETROBRAS, the Brazilian National Petroleum Company. Santos Harbour had in the last decade increased rapidly the container handling rate, being the first in Latin America. In the last decade important oil and gas reserves were discovered in the Santos Oceanic Basin and São Paulo Coastline received a big demand for supplier ships harbours for the petroleum industry. Santos Metropolitan Region is one of the most important of Brazilian Coastline, also considering the turism. For that great economic growth scenario it is very important to have the main maritime hydrodynamics forcing processes, wave climate and tidal levels, well known, considering the sea hazards influence in ship operations. Since the hindcast just represents the deep water wave climate, to make time-series of the waves parameters in coastal waters, for evaluation of sea hazards and ship operations, it is necessary to take into acount the variations of those parameters in shallow waters with coastal instrumental data. Analysis of long term wave data-base (1957-2002) generated by a comparison between wave's data modeled by a "deep water model" (ERA40-ECMWF) and measured wave's data in the years 1982-1984 by a coastal buoy in Santos littoral (São Paulo State, Brazil) was made. Calibration coefficients according to angular sectors of wave's direction were obtained by the comparison of the instrument data with the modeled ones, and applied to the original scenarios. Validation checking procedures with instrumental measurements of storm surges made in other years than 1982-1984 shows high level of confidence. The analysis of the wave climate change on the extreme storm surge wave's conditions, selecting cases of Hs > 3,0 m, using that virtual data-base shows an increase in the Hs and Tp figures and also in the frequency of storm surge events in the last decades. According to that trend, the 50 year return period Hs and Tp were forecasted for the next 50 years, comparing the figures obtained from the 1957-2006 and 2007-2056 periods, from the point of view of the harbour and coastal structures purposes of navigation and coastal defences. Another set of sea state long term data was added to that analysis, is the tidal level variability (high tide, mean sea level and low tide). Considering the CDS (Santos Dock Company) datum, extreme LLW level, tidal variability for the last six decades (1944 - 2007) shows a consistent linear response in cm/century: 1. Overall period: rising rates for MSL (23.2), HHW (36.5) and LLW (41.8); 2. Period before 1969: 1.1, - 7.3 and 54.3; 3. Period after 1975: 40.9, 44.9 and 75.4. Considering the increasing sea hazards demonstrated, the high values of the facilities and infrastructures, it is necessary to evaluate the harbour and coastal defences to mitigate the risks of natural disasters. Some of them are highlighted as guidelines strategies suggested.

A proposed new generation of intact stability criteria for assessment of ship stability in longitudinal waves

NASA Astrophysics Data System (ADS)

Andrei, C.

2017-08-01

Intact ship stability assessment to prevent stability failure in heavy weather conditions is of paramount importance on board vessel. The possibility of assessment the causes that can lead to loss of ship’s stability as well as the assessment of intact stability in heavy seas is a important problem and has attracted a huge interest of the national and international regulatory authorities. Despite the regulations in force, referring to intact ship stability, many ships continued to lose the stability and or capsize due to failure modes that presently are not covered by such regulations. Based on this aspect has been identified the necessity of modelling an updated criteria for assessment of ship’s stability taking into consideration actual possible situations for loss of stability in heavy seas as a measure of increasing she safety of ships. In this respect, the goal of this paper is to illustrate a possible criteria for assessment ship’s stability in heavy seas through a method of determination the possible problems in a form of dynamic stability criteria. A new intact stability criteria is proposed and developed based on separate levels for assessment of vulnerability and susceptibility of ships in situations of parametric rolling and pure loss of stability encountered in extreme sea conditions. Mathematical models correlated with ship’s construction particulars and weather conditions were developed for every separate level in order to assess the ship’s stability. The objective of the proposed criteria is to bring to officers on board ships the possibility of assessment the ship’s intact stability, as a measure of prevention and improvement of safety during the voyage.

On fast reconnection in pair plasmas

NASA Astrophysics Data System (ADS)

Zocco, A.; Chacon, L.; Simakov, A.; Lukin, V.

2008-11-01

The relevance of two-fluid effects to fast magnetic reconnection in standard electron-proton plasmas is well-known. The currently accepted view is that such fast reconnection is enabled by fast dispersive waves, which originate in the ion-electron mass difference. However, electron-positron (pair) plasmas do not feature such mass difference, and thus do not support fast dispersive waves. Nevertheless, recent kinetic and fluid pair-plasmas simulations have demonstrated that fast magnetic reconnection is indeed possible, thus casting doubt on the accepted view. In this study, we develop an analytical fluid model for 2D reconnection in non-relativistic, large-guide-field, low-β pair plasmas, including inertia, resistivity, and parallel viscosity.^4 We conclude that fast reconnection is possible in the collisionless (viscosity-dominated) regime, but not in the collisional (resistivity-dominated) one. J. Birn et al., J. Geophys. Res. 106 (A3), pp. 3715--3719 (2001) M. A. Shay et al., Geophys. Res. Lett. 26, 2163 (1999); B. N. Rogers et al., Phys. Rev. Lett. 87, 195004 (2001) See e.g. S. Zenitani and M. Hoshino, Astrophys. J. 562, L63 (2001); N. Bessho and A. Bhattacharjee, Phys. Rev. Lett. 95, 245001 (2005); W. Daughton and H. Karimabadi, Phys. Plasmas 14, 72303 (2007). L. Chac'on, A. N. Simakov, V. S. Lukin, A. Zocco, Phys. Rev. Lett., 025003 (2008)

A novel multi-segment path analysis based on a heterogeneous velocity model for the localization of acoustic emission sources in complex propagation media.

PubMed

Gollob, Stephan; Kocur, Georg Karl; Schumacher, Thomas; Mhamdi, Lassaad; Vogel, Thomas

2017-02-01

In acoustic emission analysis, common source location algorithms assume, independently of the nature of the propagation medium, a straight (shortest) wave path between the source and the sensors. For heterogeneous media such as concrete, the wave travels in complex paths due to the interaction with the dissimilar material contents and with the possible geometrical and material irregularities present in these media. For instance, cracks and large air voids present in concrete influence significantly the way the wave travels, by causing wave path deviations. Neglecting these deviations by assuming straight paths can introduce significant errors to the source location results. In this paper, a novel source localization method called FastWay is proposed. It accounts, contrary to most available shortest path-based methods, for the different effects of material discontinuities (cracks and voids). FastWay, based on a heterogeneous velocity model, uses the fastest rather than the shortest travel paths between the source and each sensor. The method was evaluated both numerically and experimentally and the results from both evaluation tests show that, in general, FastWay was able to locate sources of acoustic emissions more accurately and reliably than the traditional source localization methods. Copyright © 2016 Elsevier B.V. All rights reserved.

Shear wave splitting and crustal anisotropy at the Mid-Atlantic Ridge, 35°N

NASA Astrophysics Data System (ADS)

Barclay, Andrew H.; Toomey, Douglas R.

2003-08-01

Shear wave splitting observed in microearthquake data at the axis of the Mid-Atlantic Ridge near 35°N has a fast polarization direction that is parallel to the trend of the axial valley. The time delays between fast and slow S wave arrivals range from 35 to 180 ms, with an average of 90 ms, and show no relationship with ray path length, source-to-receiver azimuth, or receiver location. The anisotropy is attributed to a shallow distribution of vertical, fluid-filled cracks, aligned parallel to the trend of the axial valley. Joint modeling of the shear wave anisotropy and coincident P wave anisotropy results, using recent theoretical models for the elasticity of a porous medium with aligned cracks, suggests that the crack distribution that causes the observed P wave anisotropy can account for at most 10 ms of the shear wave delay. Most of the shear wave delay thus likely accrues within the shallowmost 500 m (seismic layer 2A), and the percent S wave anisotropy within this highly fissured layer is 8-30%. Isolated, fluid-filled cracks at 500 m to 3 km depth that are too thin or too shallow to be detected by the P wave experiment may also contribute to the shear wave delays. The joint analysis of P and S wave anisotropy is an important approach for constraining the crack distributions in the upper oceanic crust and is especially suited for seismically active hydrothermal systems at slow and intermediate spreading mid-ocean ridges.

Shear wave velocity and radial anisotropy beneath the Wyoming craton: craton destruction and lithospheric layering

NASA Astrophysics Data System (ADS)

Dave, R.; Li, A.

2016-12-01

The Wyoming craton has evolved under an intriguing geological history with suture zones, accreted margins, flat-slab subduction, orogeny and an encroaching hotspot. Whether and how the cratonic root has been widely destroyed by the series of tectonic events remain controversial. Aiming to address these questions using a craton-wide model, we have analyzed Rayleigh and Love wave data from 75 earthquakes recorded by 103 USArray TA stations in the Wyoming craton. 2-D phase velocity maps are constructed for 18 periods from 20 s to 166 s using the two-plane-wave tomography. The Yellowstone hotspot and the Cheyenne belt are characterized by low velocity anomalies at all periods in both Rayleigh and Love wave models. The northern craton in Montana is broadly fast at periods < 70 s and is relatively slow at longer periods, suggesting a shallower lithosphere. The fast anomaly in Wyoming has a NE-SW trend and extends to more than 200 km in the VSV model. However, such a fast anomaly is largely absent in the Love wave images at long periods. The association of VSV>VSH with this deep fast anomaly indicates mantle downwelling beneath south-central Wyoming. Mantle upwelling likely happens in slow regions at the hotspot, the Cheyenne belt, and the northeastern craton. The overall pattern of velocity anomaly and radial anisotropy suggests that small-scale mantle convection is vigorously acting beneath the Wyoming craton and continuously destructing the cratonic lithosphere. In addition, the average VSV and VSH models show a strong positive radial anisotropy of 5% (VSH>VSV) above 100 km and a weak negative anisotropy (VSV>VSH) below 120 km. Such a significant change in radial anisotropy could contribute to the observed mid-lithosphere discontinuity (MLD) from receiver functions. Both VSV and VSH reveal a fast lid above 100 km and a large velocity reduction at the depths of 115-190 km, corresponding with a lithosphere-asthenosphere boundary (LAB) at 150 km. These observations suggest different origins of the MLD and the LAB.

Simultaneous Observations of a Large-scale Wave Event in the Solar Atmosphere: From Photosphere to Corona

NASA Astrophysics Data System (ADS)

Shen, Yuandeng; Liu, Yu

2012-06-01

For the first time, we report a large-scale wave that was observed simultaneously in the photosphere, chromosphere, transition region, and low corona layers of the solar atmosphere. Using the high temporal and high spatial resolution observations taken by the Solar Magnetic Activity Research Telescope at Hida Observatory and the Atmospheric Imaging Assembly (AIA) on board Solar Dynamic Observatory, we find that the wave evolved synchronously at different heights of the solar atmosphere, and it propagated at a speed of 605 km s-1 and showed a significant deceleration (-424 m s-2) in the extreme-ultraviolet (EUV) observations. During the initial stage, the wave speed in the EUV observations was 1000 km s-1, similar to those measured from the AIA 1700 Å (967 km s-1) and 1600 Å (893 km s-1) observations. The wave was reflected by a remote region with open fields, and a slower wave-like feature at a speed of 220 km s-1 was also identified following the primary fast wave. In addition, a type-II radio burst was observed to be associated with the wave. We conclude that this wave should be a fast magnetosonic shock wave, which was first driven by the associated coronal mass ejection and then propagated freely in the corona. As the shock wave propagated, its legs swept the solar surface and thereby resulted in the wave signatures observed in the lower layers of the solar atmosphere. The slower wave-like structure following the primary wave was probably caused by the reconfiguration of the low coronal magnetic fields, as predicted in the field-line stretching model.

Alfven Eigenmode Control in DIII-D

NASA Astrophysics Data System (ADS)

Hu, W.; Olofsson, E.; Welander, A.; van Zeeland, M.; Collins, C.; Heidbrink, W.

2017-10-01

Alfven eigenmodes (AE) driven by fast ions from neutral beam and ion cyclotron heating are common in present day tokamak plasmas and are expected to be destabilized by alpha particles in future burning plasma experiments. Because these waves have been shown to cause loss and redistribution of fast ions which can impact plasma performance and potentially device integrity, developing control techniques for AEs is of paramount importance. In the DIII-D plasma control system, spectral analysis of real-time ECE data is used as a monitor of AE amplitude, frequency, and location. These values are then used for feedback control of the neutral beam power to control Alfven waves and reduce fast ion loss. This work describes tests of AE control experiments in the current ramp up phase, during which multiple Alfven eigenmodes are typically unstable and fast ion confinement is degraded significantly. Comparisons of neutron emission and confined fast ion profiles with and without active AE control will be made. Work supported by the U.S. Dept. of Energy under Award Number DE-FC02-04ER54698.

Crustal origin of trench-parallel shear-wave fast polarizations in the Central Andes

NASA Astrophysics Data System (ADS)

Wölbern, I.; Löbl, U.; Rümpker, G.

2014-04-01

In this study, SKS and local S phases are analyzed to investigate variations of shear-wave splitting parameters along two dense seismic profiles across the central Andean Altiplano and Puna plateaus. In contrast to previous observations, the vast majority of the measurements reveal fast polarizations sub-parallel to the subduction direction of the Nazca plate with delay times between 0.3 and 1.2 s. Local phases show larger variations of fast polarizations and exhibit delay times ranging between 0.1 and 1.1 s. Two 70 km and 100 km wide sections along the Altiplano profile exhibit larger delay times and are characterized by fast polarizations oriented sub-parallel to major fault zones. Based on finite-difference wavefield calculations for anisotropic subduction zone models we demonstrate that the observations are best explained by fossil slab anisotropy with fast symmetry axes oriented sub-parallel to the slab movement in combination with a significant component of crustal anisotropy of nearly trench-parallel fast-axis orientation. From the modeling we exclude a sub-lithospheric origin of the observed strong anomalies due to the short-scale variations of the fast polarizations. Instead, our results indicate that anisotropy in the Central Andes generally reflects the direction of plate motion while the observed trench-parallel fast polarizations likely originate in the continental crust above the subducting slab.

Lithospheric deformation in the Canadian Appalachians: evidence from shear wave splitting

NASA Astrophysics Data System (ADS)

Bastow, I. D.; Gilligan, A.; Watson, E.; Darbyshire, F. A.; Levin, V. L.; Menke, W. H.; Lane, V.; Boyce, A.; Liddell, M. V.; Petrescu, L.; Hawthorn, D.

2016-12-01

Plate-scale deformation is expected to impart seismic anisotropic fabrics on the lithosphere. Determination of the fast shear wave orientation (φ ) and the delay time between the fast and slow split shear waves (δt ) via SKS splitting can help place spatial and temporal constraints on lithospheric deformation. The Canadian Appalachians experienced multiple episodes of deformation during the Phanerozoic: accretionary collisions during the Palaeozoic prior to the collision between Laurentia and Gondwana, and rifting related to the Mesozoic opening of the North Atlantic. However, the extent to which extensional events have overprinted older orogenic trends is uncertain. We address this issue through measurements of seismic anisotropy beneath the Canadian Appalachians, computing shear wave splitting parameters (φ , δt ) for new and existing seismic stations in Nova Scotia and New Brunswick. Average δt values of 1.2 s, relatively short length scale (≥ 100 km) splitting parameter variations, and a lack of correlation with absolute plate motion direction and mantle flow models, demonstrate that fossil lithospheric anisotropic fabrics dominate our results. Most fast directions parallel Appalachian orogenic trends observed at the surface, while δt values point towards coherent deformation of the crust and mantle lithosphere. Mesozoic rifting had minimal impact on our study area, except locally within the Bay of Fundy and in southern Nova Scotia, where fast directions are subparallel to the opening direction of Mesozoic rifting; associated δt values of > 1 s require an anisotropic layer that spans both the crust and mantle, meaning the formation of the Bay of Fundy was not merely a thin-skinned tectonic event.

Lithospheric deformation in the Canadian Appalachians: evidence from shear wave splitting

NASA Astrophysics Data System (ADS)

Gilligan, Amy; Bastow, Ian D.; Watson, Emma; Darbyshire, Fiona A.; Levin, Vadim; Menke, William; Lane, Victoria; Hawthorn, David; Boyce, Alistair; Liddell, Mitchell V.; Petrescu, Laura

2016-08-01

Plate-scale deformation is expected to impart seismic anisotropic fabrics on the lithosphere. Determination of the fast shear wave orientation (ϕ) and the delay time between the fast and slow split shear waves (δt) via SKS splitting can help place spatial and temporal constraints on lithospheric deformation. The Canadian Appalachians experienced multiple episodes of deformation during the Phanerozoic: accretionary collisions during the Palaeozoic prior to the collision between Laurentia and Gondwana, and rifting related to the Mesozoic opening of the North Atlantic. However, the extent to which extensional events have overprinted older orogenic trends is uncertain. We address this issue through measurements of seismic anisotropy beneath the Canadian Appalachians, computing shear wave splitting parameters (ϕ, δt) for new and existing seismic stations in Nova Scotia and New Brunswick. Average δt values of 1.2 s, relatively short length scale (≥100 km) splitting parameter variations, and a lack of correlation with absolute plate motion direction and mantle flow models, demonstrate that fossil lithospheric anisotropic fabrics dominate our results. Most fast directions parallel Appalachian orogenic trends observed at the surface, while δt values point towards coherent deformation of the crust and mantle lithosphere. Mesozoic rifting had minimal impact on our study area, except locally within the Bay of Fundy and in southern Nova Scotia, where fast directions are subparallel to the opening direction of Mesozoic rifting; associated δt values of >1 s require an anisotropic layer that spans both the crust and mantle, meaning the formation of the Bay of Fundy was not merely a thin-skinned tectonic event.

A test of the Hall-MHD model: Application to low-frequency upstream waves at Venus

NASA Technical Reports Server (NTRS)

Orlowski, D. S.; Russell, C. T.; Krauss-Varban, D.; Omidi, N.

1994-01-01

Early studies suggested that in the range of parameter space where the wave angular frequency is less than the proton gyrofrequency and the plasma beta, the ratio of the thermal to magnetic pressure, is less than 1 magnetohydrodynamics provides an adequate description of the propagating modes in a plasma. However, recently, Lacombe et al. (1992) have reported significant differences between basic wave characteristics of the specific propagation modes derived from linear Vlasov and Hall-magnetohydrodynamic (MHD) theories even when the waves are only weakly damped. In this paper we compare the magnetic polarization and normalization magnetic compression ratio of ultra low frequency (ULF) upstream waves at Venus with magnetic polarization and normalized magnetic compression ratio derived from both theories. We find that while the 'kinetic' approach gives magnetic polarization and normalized magnetic compression ratio consistent with the data in the analyzed range of beta (0.5 less than beta less than 5) for the fast magnetosonic mode, the same wave characteristics derived from the Hall-MHD model strongly depend on beta and are consistent with the data only at low beta for the fast mode and at high beta for the intermediate mode.

Integrating field research, modeling and remote sensing to quantify morphodynamics in a high-energy coastal setting, ocean beach, San Francisco, California

USGS Publications Warehouse

Barnard, P.L.; Hanes, D.M.

2006-01-01

Wave and coastal circulation modeling are combined with multibeam bathymetry, high-resolution beach surveys, cross-shore Personal Water Craft surveys, digital bed sediment camera surveys, and real-time video monitoring to quantify morphological change and nearshore processes at Ocean Beach, San Francisco. Initial SWAN (Simulating Waves Nearshore) wave modeling results show a focusing of wave energy at the location of an erosion hot spot on the southern end of Ocean Beach during prevailing northwest swell conditions. During El Nin??o winters, swell out of the west and southwest dominates the region, and although the wave energy is focused further to the north on Ocean Beach, the oblique wave approach sets up a strong northerly littoral drift, thereby starving the southern end of sediment, leaving it increasingly vulnerable to wave attack when the persistent northwest swell returns. An accurate assessment of the interaction between wave and tidal processes is crucial for evaluating coastal management options in an area that includes the annual dredging and disposal of ship channel sediment and an erosion hot spot that is posing a threat to local infrastructure. Copyright ASCE 2006.

Exploration of High Harmonic Fast Wave Heating on the National Spherical Torus Experiment

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

J.R. Wilson; R.E. Bell; S. Bernabei

2003-02-11

High Harmonic Fast Wave (HHFW) heating has been proposed as a particularly attractive means for plasma heating and current drive in the high-beta plasmas that are achievable in spherical torus (ST) devices. The National Spherical Torus Experiment (NSTX) [Ono, M., Kaye, S.M., Neumeyer, S., et al., Proceedings, 18th IEEE/NPSS Symposium on Fusion Engineering, Albuquerque, 1999, (IEEE, Piscataway, NJ (1999), p. 53.)] is such a device. An radio-frequency (rf) heating system has been installed on NSTX to explore the physics of HHFW heating, current drive via rf waves and for use as a tool to demonstrate the attractiveness of the STmore » concept as a fusion device. To date, experiments have demonstrated many of the theoretical predictions for HHFW. In particular, strong wave absorption on electrons over a wide range of plasma parameters and wave parallel phase velocities, wave acceleration of energetic ions, and indications of current drive for directed wave spectra have been observed. In addition HHFW heating has been used to explore the energy transport properties of NSTX plasmas, to create H-mode (high-confinement mode) discharges with a large fraction of bootstrap current and to control the plasma current profile during the early stages of the discharge.« less

Eruption of a plasma blob, associated M-class flare, and large-scale extreme-ultraviolet wave observed by SDO

NASA Astrophysics Data System (ADS)

Kumar, P.; Manoharan, P. K.

2013-05-01

We present a multiwavelength study of the formation and ejection of a plasma blob and associated extreme ultraviolet (EUV) waves in active region (AR) NOAA 11176, observed by SDO/AIA and STEREO on 25 March 2011. The EUV images observed with the AIA instrument clearly show the formation and ejection of a plasma blob from the lower atmosphere of the Sun at ~9 min prior to the onset of the M1.0 flare. This onset of the M-class flare happened at the site of the blob formation, while the blob was rising in a parabolic path with an average speed of ~300 km s. The blob also showed twisting and de-twisting motion in the lower corona, and the blob speed varied from ~10-540 km s. The faster and slower EUV wavefronts were observed in front of the plasma blob during its impulsive acceleration phase. The faster EUV wave propagated with a speed of ~785 to 1020 km s, whereas the slower wavefront speed varied in between ~245 and 465 km s. The timing and speed of the faster wave match the shock speed estimated from the drift rate of the associated type II radio burst. The faster wave experiences a reflection by the nearby AR NOAA 11177. In addition, secondary waves were observed (only in the 171 Å channel), when the primary fast wave and plasma blob impacted the funnel-shaped coronal loops. The Helioseismic Magnetic Imager (HMI) magnetograms revealed the continuous emergence of new magnetic flux along with shear flows at the site of the blob formation. It is inferred that the emergence of twisted magnetic fields in the form of arch-filaments/"anemone-type" loops is the likely cause for the plasma blob formation and associated eruption along with the triggering of M-class flare. Furthermore, the faster EUV wave formed ahead of the blob shows the signature of fast-mode MHD wave, whereas the slower wave seems to be generated by the field line compression by the plasma blob. The secondary wave trains originated from the funnel-shaped loops are probably the fast magnetoacoustic waves. Three movies are available in electronic form at http://www.aanda.org

A Survey of WEC Reliability, Survival and Design Practices

DOE PAGES

Coe, Ryan G.; Yu, Yi-Hsiang; van Rij, Jennifer

2017-12-21

A wave energy converter must be designed to survive and function efficiently, often in highly energetic ocean environments. This represents a challenging engineering problem, comprising systematic failure mode analysis, environmental characterization, modeling, experimental testing, fatigue and extreme response analysis. While, when compared with other ocean systems such as ships and offshore platforms, there is relatively little experience in wave energy converter design, a great deal of recent work has been done within these various areas. Here, this article summarizes the general stages and workflow for wave energy converter design, relying on supporting articles to provide insight. By surveying published workmore » on wave energy converter survival and design response analyses, this paper seeks to provide the reader with an understanding of the different components of this process and the range of methodologies that can be brought to bear. In this way, the reader is provided with a large set of tools to perform design response analyses on wave energy converters.« less

A Survey of WEC Reliability, Survival and Design Practices

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

Coe, Ryan G.; Yu, Yi-Hsiang; van Rij, Jennifer

A wave energy converter must be designed to survive and function efficiently, often in highly energetic ocean environments. This represents a challenging engineering problem, comprising systematic failure mode analysis, environmental characterization, modeling, experimental testing, fatigue and extreme response analysis. While, when compared with other ocean systems such as ships and offshore platforms, there is relatively little experience in wave energy converter design, a great deal of recent work has been done within these various areas. Here, this article summarizes the general stages and workflow for wave energy converter design, relying on supporting articles to provide insight. By surveying published workmore » on wave energy converter survival and design response analyses, this paper seeks to provide the reader with an understanding of the different components of this process and the range of methodologies that can be brought to bear. In this way, the reader is provided with a large set of tools to perform design response analyses on wave energy converters.« less

The return of the bow shock

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

Scherer, K.; Fichtner, H., E-mail: kls@tp4.rub.de, E-mail: hf@tp4.rub.de

2014-02-10

Recently, whether a bow shock ahead of the heliospheric stagnation region exists or not has been a topic of discussion. This was triggered by measurements indicating that the Alfvén speed and the speed of fast magnetosonic waves are higher than the flow speed of the local interstellar medium (LISM) relative to the heliosphere and resulted in the conclusion that either a bow wave or a slow magnetosonic shock might exist. We demonstrate here that including the He{sup +} component of the LISM yields both an Alfvén and fast magnetosonic wave speed lower than the LISM flow speed. Consequently, the scenariomore » of a bow shock in front of the heliosphere, as modeled in numerous simulations of the interaction of the solar wind with the LISM, remains valid.« less

Stress wave calculations in composite plates using the fast Fourier transform.

NASA Technical Reports Server (NTRS)

Moon, F. C.

1973-01-01

The protection of composite turbine fan blades against impact forces has prompted the study of dynamic stresses in composites due to transient loads. The mathematical model treats the laminated plate as an equivalent anisotropic material. The use of Mindlin's approximate theory of crystal plates results in five two-dimensional stress waves. Three of the waves are flexural and two involve in-plane extensional strains. The initial value problem due to a transient distributed transverse force on the plate is solved using Laplace and Fourier transforms. A fast computer program for inverting the two-dimensional Fourier transform is used. Stress contours for various stresses and times after application of load are obtained for a graphite fiber-epoxy matrix composite plate. Results indicate that the points of maximum stress travel along the fiber directions.

Effect of strain wave shape on low-cycle fatigue crack propagation of SUS 304 stainless steel at elevated temperatures

NASA Astrophysics Data System (ADS)

Okazaki, Masakazu; Hattori, Ichiro; Shiraiwa, Fujio; Koizumi, Takashi

1983-08-01

Effect of strain wave shape on strain-controlled low-cycle fatigue crack propagation of SUS 304 stainless steel was investigated at 600 and 700 °C. It was found that the rate of crack propagation in a cycle-dependent region was successfully correlated with the range of cyclic J-integral, Δ Jf, regardless of the strain wave shape, frequency, and test temperature. It was also shown that the rate of crack propagation gradually increased from cycle-dependent curve to time-dependent one with decreasing frequency and slow-fast strain wave shape, and that one of the factors governing the rate of crack propagation in such a region was the ratio of the range of creep J-integral to that of total J-integral, Δ J c/Δ JT. Based on the results thus obtained, an interaction damage rule proposed semi-empirically was interpreted, with regard to crack propagation. Furthermore, fatigue crack initiation mechanism in slow-fast strain wave shape was studied, and it was shown that grain boundary sliding took an important role in it.

Analysis of wave motion in one-dimensional structures through fast-Fourier-transform-based wavelet finite element method

NASA Astrophysics Data System (ADS)

Shen, Wei; Li, Dongsheng; Zhang, Shuaifang; Ou, Jinping

2017-07-01

This paper presents a hybrid method that combines the B-spline wavelet on the interval (BSWI) finite element method and spectral analysis based on fast Fourier transform (FFT) to study wave propagation in One-Dimensional (1D) structures. BSWI scaling functions are utilized to approximate the theoretical wave solution in the spatial domain and construct a high-accuracy dynamic stiffness matrix. Dynamic reduction on element level is applied to eliminate the interior degrees of freedom of BSWI elements and substantially reduce the size of the system matrix. The dynamic equations of the system are then transformed and solved in the frequency domain through FFT-based spectral analysis which is especially suitable for parallel computation. A comparative analysis of four different finite element methods is conducted to demonstrate the validity and efficiency of the proposed method when utilized in high-frequency wave problems. Other numerical examples are utilized to simulate the influence of crack and delamination on wave propagation in 1D rods and beams. Finally, the errors caused by FFT and their corresponding solutions are presented.

Receptivity of Hypersonic Boundary Layers to Acoustic and Vortical Disturbances

NASA Technical Reports Server (NTRS)

Balakamar, P.; Kegerise, Michael A.

2011-01-01

Boundary layer receptivity to two-dimensional acoustic disturbances at different incidence angles and to vortical disturbances is investigated by solving the Navier-Stokes equations for Mach 6 flow over a 7deg half-angle sharp-tipped wedge and a cone. Higher order spatial and temporal schemes are employed to obtain the solution. The results show that the instability waves are generated in the leading edge region and that the boundary layer is much more receptive to slow acoustic waves as compared to the fast waves. It is found that the receptivity of the boundary layer on the windward side (with respect to the acoustic forcing) decreases when the incidence angle is increased from 0 to 30 degrees. However, the receptivity coefficient for the leeward side is found to vary relatively weakly with the incidence angle. The maximum receptivity is obtained when the wave incident angle is about 20 degrees. Vortical disturbances also generate unstable second modes, however the receptivity coefficients are smaller than that for the acoustic waves. Vortical disturbances first generate the fast acoustic modes and they switch to the slow mode near the continuous spectrum.

FAST Model Calibration and Validation of the OC5- DeepCwind Floating Offshore Wind System Against Wave Tank Test Data: Preprint

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

Wendt, Fabian F; Robertson, Amy N; Jonkman, Jason

During the course of the Offshore Code Comparison Collaboration, Continued, with Correlation (OC5) project, which focused on the validation of numerical methods through comparison against tank test data, the authors created a numerical FAST model of the 1:50-scale DeepCwind semisubmersible system that was tested at the Maritime Research Institute Netherlands ocean basin in 2013. This paper discusses several model calibration studies that were conducted to identify model adjustments that improve the agreement between the numerical simulations and the experimental test data. These calibration studies cover wind-field-specific parameters (coherence, turbulence), hydrodynamic and aerodynamic modeling approaches, as well as rotor model (blade-pitchmore » and blade-mass imbalances) and tower model (structural tower damping coefficient) adjustments. These calibration studies were conducted based on relatively simple calibration load cases (wave only/wind only). The agreement between the final FAST model and experimental measurements is then assessed based on more-complex combined wind and wave validation cases.« less

High Harmonic Fast Wave Damping on an Ion Beam: NSTX and DIII-D Regimes Compared

NASA Astrophysics Data System (ADS)

Pinsker, R. I.; Choi, C. C.; Petty, C. C.; Porkolab, M.; Wilson, J. R.; Murakami, M.; Harvey, R. W.

2004-11-01

Both NSTX and DIII-D use the combination of fast Alfven waves (FW) and neutral beam injection (NBI) for central electron heating and current drive. Damping of the fast wave on the beam ions at moderate to high harmonics (4th--20th) of the beam ion cyclotron frequency represents a loss process. In DIII-D current drive experiments at low density in which 4th and 8th harmonics were compared, damping at the 8th harmonic damping was much weaker than at the 4th [1]. However, recent simulations have predicted that in higher density and higher beam power regimes (of interest to the Advanced Tokamak program) the beam ion absorption will transition to the unmagnetized ion regime, where the damping is significant and essentially independent of harmonic number. In the present work, the transition from magnetized to unmagnetized ion regimes for the NSTX and DIII-D HHFW experiments is studied theoretically, with a combination of simple semi-analytic models and numerical models. \\vspace0.25 em [1] C.C. Petty, et al., Plasma Phys. and Contr. Fusion 43, 1747 (2001).

A Cut in the Clouds

NASA Image and Video Library

2017-12-08

Like a ship carving its way through the sea, the South Georgia and South Sandwich Islands parted the clouds. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite acquired this natural-color image on February 2, 2017. The ripples in the clouds are known as gravity waves. NASA image by Jeff Schmaltz, LANCE/EOSDIS Rapid Response #nasagoddard

Relativistic electromagnetic ion cyclotron instabilities

NASA Astrophysics Data System (ADS)

Chen, K. R.; Huang, R. D.; Wang, J. C.; Chen, Y. Y.

2005-03-01

The relativistic instabilities of electromagnetic ion cyclotron waves driven by MeV ions are analytically and numerically studied. As caused by wave magnetic field and in sharp contrast to the electrostatic case, interesting characteristics such as Alfvénic behavior and instability transition are discovered and illuminated in detail. The instabilities are reactive and are raised from the coupling of slow ions’ first-order resonance and fast ions’ second-order resonance, that is an essential extra mechanism due to relativistic effect. Because of the wave magnetic field, the nonresonant plasma dielectric is usually negative and large, that affects the instability conditions and scaling laws. A negative harmonic cyclotron frequency mismatch between the fast and slow ions is required for driving a cubic (and a coupled quadratic) instability; the cubic (square) root scaling of the peak growth rate makes the relativistic effect more important than classical mechanism, especially for low fast ion density and Lorentz factor being close to unity. For the cubic instability, there is a threshold (ceiling) on the slow ion temperature and density (the external magnetic field and the fast ion energy); the Alfvén velocity is required to be low. This Alfvénic behavior is interesting in physics and important for its applications. The case of fast protons in thermal deuterons is numerically studied and compared with the analytical results. When the slow ion temperature or density (the external magnetic field or the fast ion energy) is increased (reduced) to about twice (half) the threshold (ceiling), the same growth rate peak transits from the cubic instability to the coupled quadratic instability and a different cubic instability branch appears. The instability transition is an interesting new phenomenon for instability.

The Chinese Navy: Expanding Capabilities, Evolving Roles

DTIC Science & Technology

2011-01-01

AIRCRAFT 149 possible that the greater resources required to produce nuclear -powered boats might result in a reduction in the overall submarine...rines (two of which are nuclear powered), and other force enhancements such as three types of capable maritime interdiction aircraft, fast missile... disaster -relief operations, amphibious operations on disputed maritime territories, escorting merchant shipping, or (in the case of submarines and

Ship Motions and Capsizing in Astern Seas

DTIC Science & Technology

1974-12-01

result of these experiments and concurrent analytical work,a great deal has been learned about the mechanism of capsizing. This...computer time. It does not appear economically feasible using present-generation machines to numerically simulate a complete experimental...a Fast Cargo Liner in San Francisco Bay." Dept. of Naval Archi- tecture, University of Calif., Berkeley. January 1972. (Dept. of Transp

Southern hardwood growth-use gap closing fast as inventories peak

Treesearch

William A. Bechtold

1989-01-01

The use of hardwood for pulp and paper furnish and other fiber products is steadily increasing in the U.S. Pulpwood now accounts for half of all hardwood roundwood currently harvested for industrial timber products in the Southeast. In addition to domestic consumption, hardwood exports to Europe and Asia are also expanding, and good portion of these are shipped from...

Mobility and Cloud: Operating in Intermittent, Austere Network Conditions

DTIC Science & Technology

2014-09-01

consume information, and are connected to cloud-based servers over wired or wireless network connections. For mobile clients, this connection, by...near future. In addition to intermittent connectivity issues, many wireless networks introduce additional delay due to excessive buffering. This can...requirements, commercial cloud applications have grown at a fast rate. Similar to other mobile systems, navy ships connected over wireless networks

Fast Vessel Detection in Gaofen-3 SAR Images with Ultrafine Strip-Map Mode

PubMed Central

Liu, Lei; Qiu, Xiaolan; Lei, Bin

2017-01-01

This study aims to detect vessels with lengths ranging from about 70 to 300 m, in Gaofen-3 (GF-3) SAR images with ultrafine strip-map (UFS) mode as fast as possible. Based on the analysis of the characteristics of vessels in GF-3 SAR imagery, an effective vessel detection method is proposed in this paper. Firstly, the iterative constant false alarm rate (CFAR) method is employed to detect the potential ship pixels. Secondly, the mean-shift operation is applied on each potential ship pixel to identify the candidate target region. During the mean-shift process, we maintain a selection matrix recording which pixels can be taken, and these pixels are called as the valid points of the candidate target. The l1 norm regression is used to extract the principal axis and detect the valid points. Finally, two kinds of false alarms, the bright line and the azimuth ambiguity, are removed by comparing the valid area of the candidate target with a pre-defined value and computing the displacement between the true target and the corresponding replicas respectively. Experimental results on three GF-3 SAR images with UFS mode demonstrate the effectiveness and efficiency of the proposed method. PMID:28678197

Acoustic Wave Propagation in Snow Based on a Biot-Type Porous Model

NASA Astrophysics Data System (ADS)

Sidler, R.

2014-12-01

Despite the fact that acoustic methods are inexpensive, robust and simple, the application of seismic waves to snow has been sparse. This might be due to the strong attenuation inherent to snow that prevents large scale seismic applications or due to the somewhat counterintuitive acoustic behavior of snow as a porous material. Such materials support a second kind of compressional wave that can be measured in fresh snow and which has a decreasing wave velocity with increasing density of snow. To investigate wave propagation in snow we construct a Biot-type porous model of snow as a function of porosity based on the assumptions that the solid frame is build of ice, the pore space is filled with a mix of air, or air and water, and empirical relationships for the tortuosity, the permeability, the bulk, and the shear modulus.We use this reduced model to investigate compressional and shear wave velocities of snow as a function of porosity and to asses the consequences of liquid water in the snowpack on acoustic wave propagation by solving Biot's differential equations with plain wave solutions. We find that the fast compressional wave velocity increases significantly with increasing density, but also that the fast compressional wave velocity might be even lower than the slow compressional wave velocity for very light snow. By using compressional and shear strength criteria and solving Biot's differential equations with a pseudo-spectral approach we evaluate snow failure due to acoustic waves in a heterogeneous snowpack, which we think is an important mechanism in triggering avalanches by explosives as well as by skiers. Finally, we developed a low cost seismic acquisition device to assess the theoretically obtained wave velocities in the field and to explore the possibility of an inexpensive tool to remotely gather snow water equivalent.

Differential die-away analysis system response modeling and detector design

NASA Astrophysics Data System (ADS)

Jordan, K. A.; Gozani, T.; Vujic, J.

2008-05-01

Differential die-away-analysis (DDAA) is a sensitive technique to detect presence of fissile materials such as 235U and 239Pu. DDAA uses a high-energy (14 MeV) pulsed neutron generator to interrogate a shipping container. The signature is a fast neutron signal hundreds of microseconds after the cessation of the neutron pulse. This fast neutron signal has decay time identical to the thermal neutron diffusion decay time of the inspected cargo. The theoretical aspects of a cargo inspection system based on the differential die-away technique are explored. A detailed mathematical model of the system is developed, and experimental results validating this model are presented.

Fast T Wave Detection Calibrated by Clinical Knowledge with Annotation of P and T Waves.

PubMed

Elgendi, Mohamed; Eskofier, Bjoern; Abbott, Derek

2015-07-21

There are limited studies on the automatic detection of T waves in arrhythmic electrocardiogram (ECG) signals. This is perhaps because there is no available arrhythmia dataset with annotated T waves. There is a growing need to develop numerically-efficient algorithms that can accommodate the new trend of battery-driven ECG devices. Moreover, there is also a need to analyze long-term recorded signals in a reliable and time-efficient manner, therefore improving the diagnostic ability of mobile devices and point-of-care technologies. Here, the T wave annotation of the well-known MIT-BIH arrhythmia database is discussed and provided. Moreover, a simple fast method for detecting T waves is introduced. A typical T wave detection method has been reduced to a basic approach consisting of two moving averages and dynamic thresholds. The dynamic thresholds were calibrated using four clinically known types of sinus node response to atrial premature depolarization (compensation, reset, interpolation, and reentry). The determination of T wave peaks is performed and the proposed algorithm is evaluated on two well-known databases, the QT and MIT-BIH Arrhythmia databases. The detector obtained a sensitivity of 97.14% and a positive predictivity of 99.29% over the first lead of the validation databases (total of 221,186 beats). We present a simple yet very reliable T wave detection algorithm that can be potentially implemented on mobile battery-driven devices. In contrast to complex methods, it can be easily implemented in a digital filter design.

MMW radar enhanced vision systems: the Helicopter Autonomous Landing System (HALS) and Radar-Enhanced Vision System (REVS) are rotary and fixed wing enhanced flight vision systems that enable safe flight operations in degraded visual environments

NASA Astrophysics Data System (ADS)

Cross, Jack; Schneider, John; Cariani, Pete

2013-05-01

Sierra Nevada Corporation (SNC) has developed rotary and fixed wing millimeter wave radar enhanced vision systems. The Helicopter Autonomous Landing System (HALS) is a rotary-wing enhanced vision system that enables multi-ship landing, takeoff, and enroute flight in Degraded Visual Environments (DVE). HALS has been successfully flight tested in a variety of scenarios, from brown-out DVE landings, to enroute flight over mountainous terrain, to wire/cable detection during low-level flight. The Radar Enhanced Vision Systems (REVS) is a fixed-wing Enhanced Flight Vision System (EFVS) undergoing prototype development testing. Both systems are based on a fast-scanning, threedimensional 94 GHz radar that produces real-time terrain and obstacle imagery. The radar imagery is fused with synthetic imagery of the surrounding terrain to form a long-range, wide field-of-view display. A symbology overlay is added to provide aircraft state information and, for HALS, approach and landing command guidance cuing. The combination of see-through imagery and symbology provides the key information a pilot needs to perform safe flight operations in DVE conditions. This paper discusses the HALS and REVS systems and technology, presents imagery, and summarizes the recent flight test results.

Analysis of Maneuvering Targets with Complex Motions by Two-Dimensional Product Modified Lv's Distribution for Quadratic Frequency Modulation Signals.

PubMed

Jing, Fulong; Jiao, Shuhong; Hou, Changbo; Si, Weijian; Wang, Yu

2017-06-21

For targets with complex motion, such as ships fluctuating with oceanic waves and high maneuvering airplanes, azimuth echo signals can be modeled as multicomponent quadratic frequency modulation (QFM) signals after migration compensation and phase adjustment. For the QFM signal model, the chirp rate (CR) and the quadratic chirp rate (QCR) are two important physical quantities, which need to be estimated. For multicomponent QFM signals, the cross terms create a challenge for detection, which needs to be addressed. In this paper, by employing a novel multi-scale parametric symmetric self-correlation function (PSSF) and modified scaled Fourier transform (mSFT), an effective parameter estimation algorithm is proposed-referred to as the Two-Dimensional product modified Lv's distribution (2D-PMLVD)-for QFM signals. The 2D-PMLVD is simple and can be easily implemented by using fast Fourier transform (FFT) and complex multiplication. These measures are analyzed in the paper, including the principle, the cross term, anti-noise performance, and computational complexity. Compared to the other three representative methods, the 2D-PMLVD can achieve better anti-noise performance. The 2D-PMLVD, which is free of searching and has no identifiability problems, is more suitable for multicomponent situations. Through several simulations and analyses, the effectiveness of the proposed estimation algorithm is verified.

Tracking and Monitoring Oil Slicks Using remote Sensing

NASA Astrophysics Data System (ADS)

Klemas, V. V.

2011-12-01

Tracking and Monitoring Oil Slicks Using Remote Sensing Victor Klemas, Ph.D. , College of Earth, Ocean and Environment, University of Delaware, Newark, DE 19716 Abstract Oil spills can harm marine life in the ocean, estuaries and wetlands. To limit the damage by a spill and facilitate cleanup efforts, emergency managers need information on spill location, size and extent, direction and speed of oil movement, wind, current, and wave information for predicting oil drift and dispersion. The main operational data requirements are fast turn-around time and frequent imaging to monitor the dynamics of the spill. Radar and multispectral remote sensors on satellites and aircraft meet most of these requirements by tracking the spilled oil at various resolutions, over wide areas and at frequent intervals. They also provide key inputs to drift prediction models and facilitate targeting of skimming and booming efforts. Satellite data are frequently supplemented by information provided by aircraft, ships and remotely controlled underwater robots. The Sea Princess tanker grounding off the coast of Wales and the explosion on the Deepwater Horizon rig in the Gulf of Mexico provide two representative, yet different, scenarios for evaluating the effectiveness of remote sensors during oil spill emergencies. Session NH17: Remote Sensing of Natural Hazards Session Chair: Ramesh P. Singh Sponsor: Natural Hazards (NH)

Shear-wave polarization anisotropy in the mantle wedge beneath the southern part of Tohoku, Japan

NASA Astrophysics Data System (ADS)

Shimizu, J.; Nakajima, J.; Hasegawa, A.

2003-12-01

We investigated shear-wave polarization anisotropy in the mantle wedge beneath the southern part of Tohoku, Japan, by using waveform data of intermediate depth earthquakes with M>2.5 recorded by the seismic networks of Tohoku University and Japan Meteorological Agency (JMA). We selected waveform data with ray paths whose incident angles to the surface are 35 degrees or less to avoid contamination of particle motions by converted phases. All the seismograms thus selected were filtered with bandpassed ranges of 2-8 Hz. Cross-correlation method [Ando et al., 1983] was used for determining delay time between the leading and following shear-waves (delay time) and the leading shear-wave polarization direction (fast direction). Two horizontal components of observed seismograms were rotated with the direction from 0 to 180 degrees with an interval of 5 degrees, and shifted one horizontal component by a time lag. The time lag varied from 0 to 1 s with an interval of 0.01 s. The length of time window used to calculate correlation coefficient was set to be nearly equal to one cycle of the shear-wave. We do not use the data whose maximum correlation coefficient is less than 0.8. Obtained results show that most of the fast directions at stations in the back-arc side are nearly E-W, whereas those at stations in the fore-arc side are N-S. We infer that the anisotropy caused by lattice-preferred orientation of olivine, which is probably produced by flow in the mantle wedge, is a likely candidate for the observed shear-wave splitting with E-W trend fast directions in the back-arc side. Although it is not certain what causes the N-S trend fast directions in the for-arc side, the same trend is seen in the previous studies of other areas in Tohoku [Okada et al.,1995; Nakajima, 2002]. Observed delay times are mostly 0.1-0.3 s, which is consistent with the results of Okada et al. [1995] and Nakajima [2002]. Acknowledgments: We are grateful to the staff of the JMA for allowing us to use their data.

Detection of Propagating Fast Sausage Waves through a Detailed Analysis of a Zebra Pattern Fine Structure in a Solar Radio Burst

NASA Astrophysics Data System (ADS)

Kaneda, K.; Misawa, H.; Iwai, K.; Masuda, S.; Tsuchiya, F.; Katoh, Y.; Obara, T.

2017-12-01

Recent observations have revealed that various modes of magnetohydrodynamic (MHD) waves are ubiquitous in the corona. In imaging observations in EUV, propagating fast magnetoacoustic waves are difficult to observe due to the lack of time resolution. Quasi-periodic modulation of radio fine structures is an important source of information on these MHD waves. Zebra patterns (ZPs) are one of such fine structures in type IV bursts, which consist of several parallel stripes superimposed on the background continuum. Although the generation mechanism of ZPs has been discussed still, the most favorable model of ZPs is so-called double plasma resonance (DPR) model. In the DPR model, the frequency separation between the adjacent stripes (Δf) is determined by the plasma density and magnetic field in their source. Hence, the variation of Δf in time and frequency represents the disturbance in their source region in the corona. We report the detection of propagating fast sausage waves through the analysis of a ZP event on 2011 June 21. The variation of Δf in time and frequency was obtained using highly resolved spectral data from the Assembly of Metric-band Aperture Telescope and Real-time Analysis System (AMATERAS). We found that Δf increases with the increase of emission frequency as a whole, which is consistent with the DPR model. Furthermore, we also found that irregularities in Δf are repetitively drifting from the high frequency side to the low frequency side. Their frequency drift rate was 3 - 8 MHz/s and the repetitive frequency was several seconds. Assuming the ZP generation by the DPR model, the drifting irregularities in Δf correspond to propagating disturbances in plasma density and magnetic field with speeds of 3000 - 8000 km/s. Taking account of these facts, the observed modulations in Δf can be explained by fast sausage waves propagating through the corona. We will also discuss the plasma conditions in the corona estimated from the observational results.

Seismic anisotropies of the Songshugou peridotites (Qinling orogen, central China) and their seismic implications

NASA Astrophysics Data System (ADS)

Cao, Yi; Jung, Haemyeong; Song, Shuguang

2018-01-01

Though extensively studied, the roles of olivine crystal preferred orientations (CPOs or fabrics) in affecting the seismic anisotropies in the Earth's upper mantle are rather complicated and still not fully known. In this study, we attempted to address this issue by analyzing the seismic anisotropies [e.g., P-wave anisotropy (AVp), S-wave polarization anisotropy (AVs), radial anisotropy (ξ), and Rayleigh wave anisotropy (G)] of the Songshugou peridotites (dunite dominated) in the Qinling orogen in central China, based on our previously reported olivine CPOs. The seismic anisotropy patterns of olivine aggregates in our studied samples are well consistent with the prediction for their olivine CPO types; and the magnitude of seismic anisotropies shows a striking positive correlation with equilibrium pressure and temperature (P-T) conditions. Significant reductions of seismic anisotropies (AVp, max. AVs, and G) are observed in porphyroclastic dunite compared to coarse- and fine-grained dunites, as the results of olivine CPO transition (from A-/D-type in coarse-grained dunite, through AG-type-like in porphyroclastic dunite, to B-type-like in fine-grained dunite) and strength variation (weakening: A-/D-type → AG-type-like; strengthening: AG-type-like → B-type-like) during dynamic recrystallization. The transition of olivine CPOs from A-/D-type to B-/AG-type-like in the forearc mantle may weaken the seismic anisotropies and deviate the fast velocity direction and the fast S-wave polarization direction from trench-perpendicular to trench-oblique direction with the cooling and aging of forearc mantle. Depending on the size and distribution of the peridotite body such as the Songshugou peridotites, B- and AG-type-like olivine CPOs can be an additional (despite minor) local contributor to the orogen-parallel fast velocity direction and fast shear-wave polarization direction in the orogenic crust such as in the Songshugou area in Qinling orogen.

Substantial Fast-Wave Power Flux in the SOL of a Cylindrical Model; Comparison with Coaxial Modes

NASA Astrophysics Data System (ADS)

Perkins, R. J.; Bertelli, N.; Hosea, J. C.; Phillips, C. K.; Taylor, G.; Wilson, J. R.

2015-11-01

The NSTX high-harmonic fast-wave (HHFW) heating system can lose a significant amount of power along magnetic fields lines in the SOL to the divertor regions under certain conditions. A cylindrical cold-plasma model, with parameters resembling those of NSTX, shows the existence of modes with relatively large RF field amplitudes in the low-density annulus, similar to recent results found with the full-wave simulation AORSA. Here, we compare and contrast these modes against ``coaxial modes,'' modes that resemble TEM modes found in coaxial cables. We also compute the 3D Poynting flux as a function of length along the cylinder for comparison to NSTX. Such work is part of an effort to include the proper edge damping into full-wave codes so that they can reproduce the losses observed in NSTX and predict their importance for ITER. This work was supported by DOE Contract No. DE-AC02-09CH11466.

P-wave velocity structure beneath the northern Antarctic Peninsula

NASA Astrophysics Data System (ADS)

Park, Y.; Kim, K.; Jin, Y.

2010-12-01

We have imaged tomographically the tree-dimensional velocity structure of the upper mantle beneath the northern Antarctic Peninsula using teleseismic P waves. The data came from the seven land stations of the Seismic Experiment in Patagonia and Antarctica (SEPA) campaigned during 1997-1999, a permanent IRIS/GSN station (PMSA), and 3 seismic stations installed at scientific bases, Esperanza (ESPZ), Jubany (JUBA), and King Sejong (KSJ), in South Shetland Islands. All of the seismic stations are located in coast area, and the signal to noise ratios (SNR) are very low. The P-wave model was inverted from 95 earthquakes resulting in 347 ray paths with P- and PKP-wave arrivals. The inverted model shows a strong low velocity anmaly beneath the Bransfield Strait, and a fast anomaly beneath the South Shetland Islands. The low velocity anomaly beneath the Bransfield might be due to a back arc extension, and the fast velocity anomaly beneath the South Shetland Islands could indicates the cold subducted slab.

Measurements of the power spectrum and dispersion relation of self-excited dust acoustic waves

NASA Astrophysics Data System (ADS)

Nosenko, V.; Zhdanov, S. K.; Kim, S.-H.; Heinrich, J.; Merlino, R. L.; Morfill, G. E.

2009-12-01

The spectrum of spontaneously excited dust acoustic waves was measured. The waves were observed with high temporal resolution using a fast video camera operating at 1000 frames per second. The experimental system was a suspension of micron-size kaolin particles in the anode region of a dc discharge in argon. Wave activity was found at frequencies as high as 450 Hz. At high wave numbers, the wave dispersion relation was acoustic-like (frequency proportional to wave number). At low wave numbers, the wave frequency did not tend to zero, but reached a cutoff frequency instead. The cutoff value declined with distance from the anode. We ascribe the observed cutoff to the particle confinement in this region.

Model-Data Assimilation of Internal Waves during ASIAEX-2001

NASA Technical Reports Server (NTRS)

Liu, Antony; Zhao, Yun-He; Tang, T. Y.; Ramp, Steven R.

2003-01-01

In recent Asian Seas International Acoustics Experiment (ASIAEX), extensive moorings have been deployed around the continental shelf break area in the northeast of South China Sea in May 2001. Simultaneous RADARSAT SAR images have been collected during the field test to integrate with the in-situ measurements from moorings, ship-board sensors, and CTD casts. Besides it provides synoptic information, satellite imagery is very useful for tracking the internal waves, and locating surface fronts and mesoscale features. During ASIAEX in May 2001, many large internal waves were observed at the test area and were the major oceanic features for acoustic volume interaction. Based on the internal wave distribution maps compiled from satellite data, the wave crest can be as long as 200 km with amplitude of 100 m. Environmental parameters have been calculated based on extensive CTD casts data near the ASIAEX area. Nonlinear internal wave models have been applied to integrate and assimilate both SAR and mooring data. Using SAR data in deep water as an initial condition, numerical simulations produce the wave evolution on the continental shelf and compared reasonably well with the mooring measurements at the downstream station. The shoaling, turning, and dissipation of large internal waves on the shelf break, elevation solitons, and wave-wave interaction have been studied and are very important issues for acoustic propagation. The internal wave effects on acoustic modal coupling has been implicated and discussed.