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Simulation of Propagating Acoustic Wavefronts with Random Sound Speed

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Communications in Computational Physics 2014年第9期16卷 1081-1101页

作者： Sheri L.Martinelli Undersea warfare weapons Vehiclesand Defensive Systems DepartmentNaval Undersea Warfare CenterNewportRhode Island 02841USA.

A method for simulating acoustic wavefronts propagating under random sound speed conditions is *** approach applies a level set method to solve the Eikonal equation of high frequency acoustics for surfaces of constant phase,instead of tracing *** Lagrangian nature often makes full-field ray solutions difficult to *** level set method captures multiple-valued solutions on a fixed *** is straightforward to represent other sources of uncertainty in the input data using this model,which has an advantage over Monte Carlo approaches in that it yields an expression for the solution as a function of random variables.

关键词： Level set method wavefront methods high-frequency acoustic propagation stochastic collocation.

A study of solid ramjet fuel containing boron–magnesium mixtures

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Propulsion and Power Research 2017年第4期6卷 243-252页

作者： Eric T.Sandall Joseph Kalman John N.Quigley Scott Munro Trevor D.Hedman College of Science and Engineering Southern Utah UniversityCedar CityUT 84720USA naval air warfare center weapons division 1 Administration CircleChina LakeCA 93555USA

Solid fuel ramjets (SFRJ) are known for their operational simplicity and high specific impulse. The performance of the SFRJ propulsion system is directly tied to the energy density and combustion behavior of the fuel. A typical solid fuel used in a ramjet application is a collection of metal particles suspended in a polymeric binder. Boron is the ubiquitous candidate when considering metal additives for fuels due to an impressive 122.5 kJ/cm3 energy density. However, boron requires long residence times in combustors due to its high melting and boiling points. Magnesium appears to be a natural complement to boron;while possessing a lower energy density (42.1 kJ/cm3), it burns with a high flame temperature and readily reacts in combustion with a low melting point. In this study, several HTPB–boron–magnesium fuels are studied on a small scale to evaluate performance for ramjet application. Holography experiments are conducted, as well as laser ignition tests, to study particle behavior just above the fuel surface. Small, center-perforated fuel grains are examined in a direct-connect SFRJ test stand configuration to measure ignition temperatures and performance parameters. Combustion efficiency of the HTPB–boron–magnesium fuel is found to significantly increase for one of the fuels studied.

关键词： Boron Magnesium Holography Solid fuel ramjet Hydroxyl terminated polybutadiene

An Application of the Level Set Method to Underwater Acoustic Propagation

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Communications in Computational Physics 2012年第10期12卷 1359-1391页

作者： Sheri L.Martinelli Torpedo Systems Department Naval Undersea Warfare Center1176 Howell StreetNewportRhode Island 02841USA division of Applied Mathematics Brown UniversityProvidenceRhode Island 02912USA

An algorithm for computing wavefronts,based on the high frequency approximation to the wave equation,is *** technique applies the level set method to underwater acoustic wavefront propagation in the time *** level set method allows for computation of the acoustic phase function using established numerical techniques to solve a first order transport equation to a desired order of *** methods for solving the eikonal equation directly on a fixed grid limit one to only the first arrivals,so these approaches are not useful when multi-path propagation is *** the level set model to the problem allows for the time domain computation of the phase function on a fixed grid,without having to restrict to first arrival *** implementation presented has no restrictions on range dependence or direction of travel,and offers improved efficiency over solving the full wave equation which under the high frequency assumption requires a large number of grid points to resolve the highly oscillatory *** conditions are discussed,and an approach is suggested for producing good results in the presence of boundary *** efficientmethod to compute the amplitude from the level set method solutions is also *** to analytical solutions are presented where available,and numerical results are validated by comparing results with exact solutions where available,a full wave equation solver,and with wavefronts extracted from ray tracing software.

关键词： Geometric acoustics level set method high-frequency acoustic propagation WENO method

Numerical Boundary Conditions for Specular Reflection in a Level-Sets-Based Wavefront Propagation Method

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Communications in Computational Physics 2013年第7期14卷 509-536页

We study the simulation of specular reflection in a level set method implementation for wavefront propagation in high frequency acoustics using WENO spatial *** implement WENO efficiently andmaintain convergence rate,a rectangular grid is used over the physical *** the physical domain does not conformto the rectangular grid,appropriate boundary conditions to represent reflection must be derived to apply at grid locations that are not coincident with the reflecting boundary.A related problem is the extraction of the normal vectors to the boundary,which are required to formulate the reflection condition.A separate level set method is applied to pre-compute the boundary normals which are then stored for use in the wavefront *** approaches to handling the reflection boundary condition are proposed and studied:one uses an approximation to the boundary location,and the other uses a local reflection *** second method is shown to produce superior results.

关键词： Boundary conditions reflection level setmethod wavefrontmethods high-frequency acoustic propagation WENO

Peridynamic Solutions for Timoshenko Beams

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Engineering（科研） 2014年第6期6卷 304-317页

作者： E. Thomas Moyer Michael J. Miraglia naval Surface warfare center/Carderock division W. Bethesda USA

Peridynamics is a recently developed formulation for continuum mechanics which describes material deformation using a nonlocal approach. Unlike Classical Continuum Mechanics (CCM) where the conservation equations are cast into partial differential equations, Peridynamics describes the deformation in terms of integro-differential equations. Additionally, peridynamics permits a natural length scale that is absent in CCM. This facilitates the modeling of complex material behavior and fracture which is not dependent on the numerical discretization length scale. In this paper, we develop a Peridynamic formulation for a Timoshenko beam. Full details and numerical examples are presented for both bending and axial behavior. While the development in this paper is limited to elastic, infinitesimal deformations, the approach can be extended to finite inelastic deformations.

关键词： Peridynamics Timoshenko Beam Beam Bending Dynamic Deformation

Electronic warfare in the optical band:Main features,examples and selected measurement data

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Defence Technology（防务技术） 2021年第5期17卷 1636-1649页

作者： Roman Ostrowski Artur Cywinski Marek Strzelec Polish naval Academy Navigation and Naval Weapons Faculty69Smidowicza Str.81-127GdyniaPoland Military University of Technology Institute of Optoelectronics2 Gen.S.Kaliskiego Str.00-908WarsawPoland

The paper presents the possibilities of,and methods for,acquiring,analysing and processing optical signals in order to recognise,identify and counteract threats on the contemporary *** main ways electronic warfare is waged in the optical band of the electromagnetic wave spectrum have been formulated,including the acquisition of optical emitter signatures,as well as ultraviolet(UV)and thermal(IR)*** physical parameters and values describing the emission of laser radiation are discussed,including their importance in terms of creating optical ***,it has been shown that in the transformation of optical signals into signatures,only their spectral and temporal parameters can be *** was confirmed in experimental part of the paper,which includes our own measurements of spectral and temporal emission characteristics for three types of binocular laser *** has been further shown that through simple registration and quick analysis involving comparison of emission time parameters in the case of UV signatures in“solar-blind”band,various events can be identified quickly and *** same is true for IR signatures,where the amplitudes of the recorded signal for several wavelengths are *** was confirmed experimentally for UV signatures by registering and then analyzing signals from several events during military exercises at a training ground,namely Rocket Propelled Grenade(RPG)launches and explosions after hitting targets,trinitrotoluene(TNT)explosions,firing armour-piercing,fin-stabilised,discarding sabots(APFSDS)or high explosive(HE)*** final section describes a proposed model database of emitters,created as a result of analysing and transforming the recorded signals into optical signatures.

关键词： Optoelectronics Electronic warfare Optical signature

RADIATED NOISE MEASUREMENTS FOR A NATIONAL OCEANOGRAPHIC ATMOSPHERIC ADMINISTRATION （NOAA） FISHERIES SURVEY VESSEL

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RADIATED NOISE MEASUREMENTS FOR A NATIONAL OCEANOGRAPHIC ATM...

Technology Integration On Cargo Handling Systems

The Second International Symposium on Advanced Technology of Vibration and Sound

作者： Kevin F.O’Neill Michael P.Schilt naval Surface warfare center Carderock division West Bethesda ONR

＜正＞This report contains the results of the December 2004 measurement of acoustic underwater radiated noise of the R/V OSCAR DYSON （R 224）.One-third octave band source levels are provided at a variety of ship speeds along with frequencies,levels,and sources of significant tones *** final radiated noise results are compared to and below the ICES specification.

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Technology Integration On Cargo Handling Systems

Numerical Prediction of Form Factor and Wave Interference of A Trimaran for Different Outrigger Positions

作者： Mark DiTroia Daniel Feeney Suzanne Kralle naval Surface warfare center Carderock DivisionShip SystemsEngineering Station(Code 9732)Philadelphia.PAUSA

naval cargo handling systems have traditionally been designed as two independent systems:the hardware itself and theinformation systems that control *** lack of integration often posed *** operator might not discover that alimit switch needed repair until performing the tedious process of routine maintenance,or when the system failed to operate and anextensive troubleshooting procedure *** today’s technology,however,that has all *** switches and *** maintenance devices,and programmable logic controllers are integrated via networks such as DeviceNet and Ethernet toform the new generation of cargo handling *** systems not only reduce workload and manning through more powerfultroubleshooting tools and semi-automation,but they also decrease system downtime and maintenance costs by being able to identifymaintenance concerns before they cause a *** of the integrated networks installed on vertical package conveyors aspart of the Smart Carrier Program will illustrate how new technology and integrated networks are currently being applied to navalcargo handling systems and how they might be used to further reduce shipboard workload,manning,and maintenance costs in theyears to come.

关键词： integrated networks cargo handling systems programmable logic controller

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China Ocean Engineering 2022年第2期36卷 279-288页

作者： Ali DOGRUL Burak YILDIZ Department of naval Architecture and Marine Engineering Turkish Naval AcademyNational Defense UniversityIstanbul 34940Turkey Department of Marine Engineering Operations Yildiz Technical UniversityIstanbul 34349Turkey

Trimaran hydrodynamics have been an important research topic in recent *** have even been chosen for naval surface *** this case,investigation of a trimaran with different outrigger positions is important and necessary for better hydrodynamic *** paper focuses on the numerical investigation of trimaran *** trimaran model used in this study is a 1/80 scale high-speed displacement frigate-type concept developed by the center for Innovation in Ship Design(CISD)at naval Surface warfare center,Carderock division(NSWCCD).The numerical simulations were conducted for different outrigger positions at low and moderate Froude numbers by using commercial CFD software solving URANS equations.A verification and validation study was carried out for the numerical method in one configuration and one ship *** existing experimental results for the trimaran resistance in the literature were used for *** different outrigger positions were analyzed and the form factor of each configuration was calculated by the Prohaska *** total resistance was decomposed to its components using the form *** interference factor was calculated for each configuration in terms of total resistance,residual resistance and wave ***,wave profiles using the longitudinal wave cuts in different locations were obtained both numerically and *** was concluded that the outrigger position had different effects on the interference,total resistance and wave profile at different Froude *** was also shown that the CFD results were in good agreement with the experimental data in all *** conclusion,this study presents the results of interference effects for different trimaran configurations in terms of wave resistance in addition to the total resistance and residual *** numerical method was validated not only with the total resistance test data but also the longitudinal wave profiles a

关键词： CFD form factor wave interference wave profile outrigger trimaran