Colliding Blast Waves Driven by the Interaction of a Short-Pulse Laser with a Gas of Atomic Clusters     

Roland A. Smith  James Lazarus  Matthias Hohenberger  Alastair S. Moore  Joseph S. Robinson  Edward T. Gumbrell  Mike Dunne 《Astrophysics and Space Science》2007,307(1-3):131-137

Collisions between shocks are commonly found in many astrophysical objects, however robust numerical models or laboratory analogues of these complex systems remain challenging to implement. We report on the development of scaled laboratory experiments which employ new techniques for launching and diagnosing colliding shocks and high Mach number blast waves, scalable to a limited subset of astrophysically-relevant regimes. Use of an extended medium of atomic clusters enables efficient (>80%) coupling of 700 fs, 1 J, 1054 nm laser pulses to a “cluster” gas with an average density of ≈10¹⁹ particles cm⁻³, producing an initial energy density >10⁵ J cm⁻³, equivalent to ≈5×10⁹ J/g. Multiple laser foci are used to tailor the spatial profile of energy deposition, or to launch pairs of counter-propagating cylindrical shocks which then collide. By probing the collision interferometrically at multiple view angles in 5^{^} increments and applying an inverse Radon transform to the resulting phase projections we have been able to tomographicall reconstruct the full three-dimensional, time-framed electron density profile of the system.  相似文献   

Hydrodynamics and petroleum migration in the Upper Ordovician Red River Formation of the Williston Basin   总被引：1，自引：0，他引：1  

D.K. Khan  B.J. Rostron  Z. Margitai  D. Carruthers 《Journal of Geochemical Exploration》2006,89(1-3):179

Simulations of petroleum migration within the Red River petroleum system of the Williston Basin show that petroleum generation and secondary migration preceded the onset of an active hydrodynamic regime that persists to the present day. Furthermore: (1) a better understanding of the eastern limit of the mature source rock area, which is largely facies controlled, is required to reduce exploration risk east of the Nesson Anticline, (2) the Red River play types that have been prosperous in southeastern Saskatchewan should extend considerable distances to the north, as well as throughout central Saskatchewan and western Manitoba, Canada, and (3) accumulations that may have developed in the southwest of the basin have likely been flushed and redistributed subsequent to the onset of hydrodynamics.  相似文献   

A note on the hydrodynamics of a tail tube buoy     

Umesh A. Korde   《Ocean Engineering》2000,27(12)

This note presents some analytical results for a tail–tube buoy configuration frequently used in wave energy conversion. The overall approach is based on Falnes and McIver's (Falnes, J., McIver, P., 1985. Surface wave interactions with systems of oscillating bodies and pressure distributions. Applied Ocean Research 7 (4), 225–234) extension to floating oscillating water columns of Evans' (Evans, D.V., 1982. Wave power absorbtion by systems of oscillating surface pressure distributions. Journal of Fluid Mechanics 114, 481–499) theory of oscillating pressure distributions. The diffraction air-flow flux through the tube and the diffraction wave force on the flotation collar are obtained using the formulation of Garrett (1970, 1971) (Garrett, C.J.R., 1970. Bottomless harbours. Journal of Fluid Mechanics 43 (3), 433–449. Garrett, C.J.R., 1971. Wave forces on a circular dock. Journal of Fluid Mechanics 46 (1), 129–139). Results can be used in sizing the tube and collar for efficient energy conversion.  相似文献   

中国第21次南极考察雪龙船实时航迹图   总被引：7，自引：0，他引：7       下载免费PDF全文

郝晓光  朱建钢  薛怀平  徐汉卿  刘根友  廖小韵 《极地研究》2005,17(2):134-138

采用新编《系列世界地图》成果,与GIS和计算机网络技术相结合,于2004年11月首次实现了我国南极考察雪龙船航迹的实时跟踪服务,并由“中国南北极信息网”向全社会实时发布。“实时航迹图”使我国南极考察与社会公众的沟通能力得到提高,并为进一步建立“中国历次极地考察航线显示系统”做好了技术准备。  相似文献   

Legal regulation of the shipbreaking industry in Bangladesh: The international regulatory framework and domestic implementation challenges     

《Marine Policy》2014

Shipbreaking is the process of dismantling an obsolete vessel for scrapping or disposal. This activity was not officially declared an industry in Bangladesh until 2006, even though the country is one of the biggest ship-breakers in the world. This industry has dramatically expanded in Bangladesh, at the cost of environmental degradation and severe labour exploitation. Despite environmental and human rights violations, the shipbreaking industry represents a vital source of income for the country and a livelihood for a significant portion of its population. Shipbreaking activities in Bangladesh present both opportunities and challenges for Bangladesh. This article examines the extent to which the existing regulatory framework for dealing with these issues in Bangladesh is congruent with international instruments. This article also examines relevant international instruments which prescribe the core principles for regulating the ship breaking industry and evaluates the legal regulation of the Bangladesh ship breaking industry against these international instruments. The underlying objective of this evaluation is to demonstrate that Bangladeshi instruments could incorporate the core of the international instruments to minimise the environmental damage caused by this industry. This article concludes that Bangladesh should either amend its laws or enact a new legislative scheme that is based on the core values of the Basel Convention. This change is vital if Bangladesh wants to ensure a long lasting industry that could serve its need for iron ore and engage its abundant labour force, without the cost of destroying its coastal line which is one of its most valuable natural assets.  相似文献   

A Comparison of Conventional and Shear-Rate Dependent Mohr-Coulomb Models for Simulating Landslides   总被引：1，自引：0，他引：1  

LIANG Dong-fang  HE Xu-zhen 《山地科学学报》2014,(6):1478-1490

Landslides may cause many fatalities and heavy economic losses,so it is vital to understand their mechanics so as to take appropriate measures to mitigate their risk.Phenomenally,the loose soil behaves like frictional material in most circumstances,so Mohr-Coulomb type equations are often used to describe their movement.However,these models generally do not consider the influence of the shearrate on the Mohr-Coulomb friction angle,so the shear-rate dependence effect on the soil flow and landslide runout is not well understood.This paper reports on an application of the incompressible Smoothed Particle Hydrodynamics（SPH） method to the dynamics of dry granular assemblies.The traditional model with a constant friction angle is compared with the modified Mohr-Coulomb model with a variable friction angle related to the shear-rate.It is found that the shear-rate dependence effect is negligible for shallow granular flows along mild slopes.With steeper slopes of the ground and larger aspect ratios of the initial soil column,the rate-dependence effect becomes more important.  相似文献   

Document based knowledge base engineering method for ship basic design     

Ying-Han Wu  Heiu-Jou Shaw 《Ocean Engineering》2011,38(13):1508-1521

We propose a basic ship design knowledge-model for information storage and retrieval using a knowledge-based engineering (KBE) system and develop a semantic inquiry function that allows users to use the retrieved information immediately. Our aim is to merge the repetitive access and calculating tasks and data such as the principal dimensions required during the basic ship design process into a single database, so that this information remains available for future construction projects. However, the concept of linking a design knowledge base and inference engine requires the combining of ship design information with the KBE system. This research enhances the flexibility, extension, and operation of the inference mechanism of the KBE design methodology through the establishment of a user interface, knowledge base, and inference engine. The design information is managed a document-based approach, which requires the conversion of the original documents into the XML (eXtensible Markup Language) format, and compiles rules for the basic design process. This system uses the KBE method attempts to reduce the double workload of design and modeling at the commencement of a new project with the document-generating integration work.  相似文献   

Numerical investigation of the seakeeping behavior of a catamaran advancing in regular head waves   总被引：3，自引：0，他引：3  

Teresa Castiglione  Frederick Stern  Manivannan Kandasamy 《Ocean Engineering》2011,38(16):1806-1822

A numerical study was undertaken in order to assess the capability of an unsteady RANS code to predict the seakeeping characteristics of a high-speed multi-hull vessel in high sea states. Numerical analysis includes evaluation of ship motions, effects of wave steepness on ship response, catamaran natural frequency and added resistance in waves. Computations were performed for the DELFT 372 catamaran by the URANS solver CFDSHIP-Iowa V.4. The code was validated with encouraging results for high ship speeds (0.3≤Fn≤0.75) and high wave amplitudes (0.025≤Ak≤0.1). Comparison with strip theory solutions shows that the RANS method predicts ship motions with higher accuracy and allows the detection of nonlinear effects. Current computations evidence that heave peaks occur at resonance for all Fn, and reach the absolute maximum at Fn=0.75. Maximum pitch occurs at frequencies lower than resonance, for each speed, and absolute maximum occurs at medium Fn=0.6. Maximum added resistance, R_aw, was computed at Fn=0.45, which, interestingly, is near the catamaran Fn_coincidence. Overall, we found similar results as Simonsen et al. (2008) for KCS containership, though, herein, a multi-hull geometry and higher speeds were tested. Also, our results are useful to further evaluate the exciting forces and their correlation with f_e and λ/L_pp.  相似文献   

The effect of star formation on the evolution of Blue Compact Dwarf galaxies     

Simone Recchi  Francesca Matteucci  Annibale D'Ercole  Monica Tosi 《Astrophysics and Space Science》2003,284(2):623-626

We study the effect of different star formation regimes on the dynamical and chemical evolution of Blue Compact Dwarf galaxies. To do that, we adopt a 2-D hydrocode coupled with detailed chemical yields originating from SNeII, SNeIa and from intermediate-mass stars. We apply this kind of simulation to a model of galaxy resembling IZw18. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Numerical Simulation of Small Perturbation on an Accretion Disk Due to the Collision of a Star with the Disk Near the Black Hole     

Orhan Dönmez 《Astrophysics and Space Science》2006,305(2):187-196

In this paper, perturbations of an accretion disk by a star orbiting around a black hole are studied. We report on a numerical experiment, which has been carried out by using a parallel-machine code originally developed by Dönmez (2004). An initially steady state accretion disk near a non-rotating (Schwarzschild) black hole interacts with a “star”, modeled as an initially circular region of increased density. Part of the disk is affected by the interaction. In some cases, a gap develops and shock wave propagates through the disk. We follow the evolution for order of one dynamical period and we show how the non-axisymetric density perturbation further evolves and moves downwards where the material of the disk and the star become eventually accreted onto the central body. When the star perturbs the steady state accretion disk, the disk around the black hole is destroyed by the effect of perturbation. The perturbed accretion disk creates a shock wave during the evolution and it loses angular momentum when the gas hits on the shock waves. Colliding gas with the shock wave is the one of the basic mechanism of emitting the X-rays in the accretion disk. The series of supernovae occurring in the inner disk could entirely destroy the disk in that region which leaves a more massive black hole behind, at the center of galaxies.  相似文献