Dynamic mode I perturbation solution for a moving crack unsteadily

Rice et al. (Jounal of Mechanics and Physics of Solids 42, 813-843) analyze the propagation of a planar crack with a nominally straight front in a model elastic solid with a single displacement component. Using the form of Willis er al. (Journal of the Mechanics and Physics of Solids 43, 319-341), of dynamic mode I weight functions for a moving crack, we address that problem solved by Rice ei al. in the 3D context of elastodynamic theory. Oscillatory crack tip motion results from constructive-destructive interference of stress intensity waves. Those waves, including system of the dilatational, shear and Rayleigh waves, interact on each other and with moving edge of crack, can lead to continuing fluctuations of the crack front and propagation velocity. (C) 1997 Elsevier Science Ltd.

Comparative observation of Ar, Ar-H-2 and Ar-N-2 DC arc plasma jets and their arc root behaviour at reduced pressure

Results observed experimentally are presented, about the DC arc plasma jets and their arc-root behaviour generated at reduced gas pressure without or with an applied magnetic field. Pure argon, argon-hydrogen or argon- nitrogen mixture was used as the plasma-forming gas. A specially designed copper mirror was used for a better observation of the arc-root behaviour on the anode surface of the DC non-transferred arc plasma torch. It was found that in the cases without an applied magnetic field, the laminar plasma jets were stable and approximately axisymmetrical. The arc-root attachment on the anode surface was completely diffusive when argon was used as the plasma-forming gas, while the arc-root attachment often became constrictive when hydrogen or nitrogen was added into the argon. As an external magnetic field was applied, the arc root tended to rotate along the anode surface of the non-transferred arc plasma torch.

Relationship between strain localization and catastrophic rupture

In order to explore a prior warning to catastrophic rupture of heterogeneous media, like rocks, the present study investigates the relationship between surface strain localization and catastrophic rupture. Instrumented observations on the evolution of surface strain field and the catastrophic rupture of a rock under uniaxial compression were carried out. It is found that the evolution of surface strain field displays two phases: at the early stage, the strain field keeps nearly uniform with weak fluctuations increasing slowly; but at the stage prior to catastrophic rupture, a certain accelerating localization develops and a localized zone emerges. Based on the measurements, an analysis was performed with local mean-field approximation. More importantly, it is found that the scale of localized zone is closely related to the catastrophic rupture strain and the rupture strain can be calculated in accord with the local-mean-field model satisfactorily. This provides a possible clue to the forecast of catastrophic rupture. (c) 2007 Elsevier Ltd. All rights reserved.

Study of the shock motion in a hypersonic shock system turbulent boundary-layer interaction

Wall pressure fluctuations and surface heat transfer signals have been measured in the hypersonic turbulent boundary layer over a number of compression-corner models. The distributions of the separation shock oscillation frequencies and periods have been calculated using a conditional sampling algorithm. In all cases the oscillation frequency distributions are of broad band, but the most probable frequencies are low. The VITA method is used for deducing large scale disturbances at the wall in the incoming boundary layer and the separated flow region. The results at present showed the existence of coherent structures in the two regions. The zero-cross frequencies of the large scale structures in the two regions are of the same order as that of the separation shock oscillation. The average amplitude of the large scale structures in the separated region is much higher than that in the incoming boundary layer. The length scale of the separation shock motion region is found to increase with the disturbance strength. The results show that the shock oscillation is of inherent nature in the shock wave/turbulent boundary layer interaction with separation. The shock oscillation is considered to be the consequence of the coherent structures in the separated region.

Effects of high-frequency vibration on critical marangoni number

The influence of vibration on thermocapillary convection and critical Marangoni number in liquid bridge of half floating zone was discussed for the low frequency range 0.4-1.5 Hz and the intermediate frequency range 2.5-15 Hz in our previous papers. This paper extends the study to high frequency range 15-100Hz. This ground based experiment was completed on the deck of an electromagnetic vibration machine. The results of our experiment shows when the frequency of the applied acceleration is high enough, the amplitude of the time varying part of the temperature response is disappear and the shape of the free surface of the liquid bridge exhibits no fluctuations due to inertia. The critical Marangoni number which is defined to describe the transitions from a peroidical convection in response to vibration to an oscillatory convection due to internal instability is nearly the same as the critical Marangoni number for oscillatory flow in the absence of vibration.

G-jitter effects on half floating-zone convection in intermediate-frequency range

The g-jitter influence on thermocapillary convection and critical Marangoni number in a liquid bridge of half-floating rone was discussed in the low frequency range of 0.4 to 1.5 Hz in a previous paper. This paper extended the experiments to the intermediate frequency range of 2 to 18 Hz, which htrs often been recorded as vibration environment of spacecrafts. The experiment was completed on the deck of a vibration machine, which gave a periodical applied acceleration to simulate the effects of g-jitter. The experimental results in the intermediate frequency range are different from that in the low frequency range. The velocity field and the shape of the free surface have periodical fluctuations in response to g-jitter. The amplitude of the periodical varying part of the temperature response decreases obviously with increasing frequency of g-jitter and vanishes almost when the frequency of g-jitter is high enough. The critical Marangoni number is defined to describe the transition from a periodical convection in response to g-jitter to an oscillatory convection due to internal instability, and will increase with increasing g-jitter frequency. According to the spectral analysis, it can be found that the oscillatory part of temperature is a superposition of two harmonic waves if the Marangoni number is larger than a critical value.

Theoretical interpretation on ion heating experiments in reverse field pinch devices

A new set of equations for the energies of the mean magnetic field and the mean plasma velocity is derived taking the dynamo effects into account, by which the anomalous phenomenon, T(i) > T(e), observed in some reversed field pinches (RFP's) is successfully explained.

Upwind compact scheme with dispersion control for aerodynamic equations

A compact upwind scheme with dispersion control is developed using a dissipation analogy of the dispersion term. The term is important in reducing the unphysical fluctuations in numerical solutions. The scheme depends on three free parameters that may be used to regulate the size of dissipation as well as the size and direction of dispersion. A coefficient to coordinate the dispersion is given. The scheme has high accuracy, the method is simple, and the amount of computation is small. It also has a good capability of capturing shock waves. Numerical experiments are carried out with two-dimensional shock wave reflections and the results are very satisfactory.

太阳风动量涨落激发磁层亚暴的机制

本文将太阳风涨落传输能量产生磁层亚暴的机制推广到无碰撞等离子体过程。太阳风的涨落在磁层顶激发压缩阿尔文波,并在磁尾的无碰撞等离子体中传播。尾瓣中满足条件β<<1,而等离子体片中β≥1,其中β为等离子体压力与磁压之比。这样,快磁声波在尾瓣中几乎不衰减,而在等离子体片中很快衰减,将波动能量耗散在等离子体片中使等离子体加热或者粒子加速。这种机制还表明,磁尾等离子体片中的高能粒子可以由太阳风涨落动能耗散而被加速,不一定是直接源于太阳。

Asset pricing and systematic liquidity risk: an empirical investigation of the Spanish stock market

Systematic liquidity shocks should affect the optimal behavior of agents in financial markets. Indeed, fluctuations in various measures of liquidity are significantly correlated across common stocks. Accordingly, this paper empirically analyzes whether Spanish average returns vary cross-sectionally with betas estimated relative to two competing liquidity risk factors. The first one, proposed by Pastor and Stambaugh (2002), is associated with the strength of volume-related return reversals. Our marketwide liquidity factor is defined as the difference between returns highly sensitive to changes in the relative bid-ask spread and returns with low sensitivities to those changes. Our empirical results show that neither of these proxies for systematic liquidity risk seems to be priced in the Spanish stock market. Further international evidence is deserved.

PICES Press, Vol. 14, No. 1, January 2006

The state of PICES science - 2005 (pdf, 0.2 Mb) 2005 Wooster Award (pdf, 0.4 Mb) Korea and U.S. federate metadata collection (pdf, 0.3 Mb) PICES Interns (pdf, 0.3 Mb) Studies on long-term variation of ocean ecosystem / climate interactions based on the Odate collection (pdf, 0.2 Mb) Hokkaido University Fisheries & Oceanographic Database CD-ROM (pdf, 0.2 Mb) Workshop on sardine and anchovy fluctuations (pdf, 0.1 Mb) Photo highlights of PICES XIV (pdf, 0.4 Mb) Workshop on SEEDS-II (pdf, 0.2 Mb) NPAFC-PICES joint symposium "The status of Pacific salmon and their role in North Pacific marine ecosystems" (pdf, 0.2 Mb) PICES Calendar (pdf, 0.2 Mb) New Chairman of the PICES Fishery Science Committee (pdf, 0.1 Mb) The state of the western North Pacific in the first half of 2005 (pdf, 0.4 Mb) Latest and upcoming PICES publications (pdf, 0.4 Mb) Recent trends in waters of the subarctic NE Pacific (pdf, 0.2 Mb) The Bering Sea: Current status and recent events (pdf, 0.1 Mb) PICES and GLOBEC to sponsor workshop on sub-arctic seas (pdf, 0.1 Mb) Professor Mikhail N. Koshlyakov - 75 (pdf, 0.1 Mb) Obituary - Dr. Al Tyler (pdf, 0.1 Mb)

PICES Press, Vol. 5, No. 2, July 1997

WG 10 Fukuoka Workshop Pacific salmon:climate-linked long-term stock fluctuations The state of the eastern North Pacific in the second half of 1996 The state of the western North Pacific in the second half of 1996 The status of the Bering Sea in the second half of 1996 Yutaka Nagata Eulogy A brief look at mechanisms for support of oceanographic research in the United States Research interests and the funding system for the new Ministry of Maritime Affairs and Fisheries of the Republic of Korea PICES and electronic communication Japan Meteorological Agency: oceanographic activities

Water levels in artesian and nonartesian aquifers of Florida, 1971-72

The Department of Natural Resources, Bureau of Geology, is publishing as its Information Circular No. 85 the report entitled, "Water Levels in Artesian and Non-Artesian Aquifers of Florida, 1971-72," by Henry G. Healy, of the U. S. Geological Survey. In order to prevent future shortages developing from increasing demands, the present supplies of ground water must be properly appraised before they can be effectively utilized. Records of trends and fluctuations of ground water have long formed a basis for such an appraisal. (105 page document)

PICES-GLOBEC International Program on Climate Change and Carrying Capacity: Report of 2001 BASS/MODEL, MONITOR and REX Workshops, and the 2002 MODEL/REX Workshop

Table of Contents [pdf, 0.22 Mb] Executive Summary [pdf, 0.31 Mb] Report of the 2001 BASS/MODEL Workshop [pdf, 0.65 Mb] To review ecosystem models for the subarctic gyres Report of the 2001 MONITOR Workshop [pdf, 0.7 Mb] To review ecosystem models for the subarctic gyres Workshop presentations: Sonia D. Batten PICES Continuous Plankton Recorder pilot project Phillip R. Mundy GEM (Exxon Valdez Oil Spill Trustee Council`s "Gulf Ecosystem Monitoring" initiative) and U.S. GOOS plans in the North Pacific Ron McLaren and Brian O`Donnell A proposal for a North Pacific Action group of the international Data Buoy Cooperation Panel Gilberto Gaxiola-Castrol and Sila Najera-Martinez The Mexican oceanographic North Pacific program: IMECOCAL Sydney Levitus Building global ocean profile and plankton databases for scientific research Report of the 2001 REX Workshop [pdf, 1.73 Mb] On temporal variations in size-at-age for fish species in coastal areas around the Pacific Rim Workshop presentations: Brian J. Pyper, Randall M. Peterman, Michael F. Lapointe and Carl J. Walters [pdf, 0.33 Mb] Spatial patterns of covariation in size-at-age of British Columbia and Alaska sockeye salmon stocks and effects of abundance and ocean temperature R. Bruce MacFarlane, Steven Ralston, Chantell Royer and Elizabeth C. Norton [pdf, 0.4 Mb] Influences of the 1997-1998 El Niño and 1999 La Niña on juvenile Chinook salmon in the Gulf of the Farallones Olga S. Temnykh and Sergey L. Marchenko [pdf, 0.5 Mb] Variability of the pink salmon sizes in relation with abundance of Okhotsk Sea stocks Ludmila A. Chernoivanova, Alexander N. Vdoven and D.V. Antonenko [pdf, 0.3 Mb] The characteristic growth rate of herring in Peter the Great Bay (Japan/East Sea) Nikolay I. Naumenko [pdf, 0.5 Mb] Temporal variations in size-at-age of the western Bering Sea herring Evelyn D. Brown [pdf, 0.45 Mb] Effects of climate on Pacific herring, Clupea pallasii, in the northern Gulf of Alaska and Prince William Sound, Alaska Jake Schweigert, Fritz Funk, Ken Oda and Tom Moore [pdf, 0.6 Mb] Herring size-at-age variation in the North Pacific Ron W. Tanasichuk [pdf, 0.3 Mb] Implications of variation in euphausiid productivity for the growth, production and resilience of Pacific herring (Clupea pallasi) from the southwest coast of Vancouver Island Chikako Watanabe, Ahihiko Yatsu and Yoshiro Watanabe [pdf, 0.3 Mb] Changes in growth with fluctuation of chub mackerel abundance in the Pacific waters off central Japan from 1970 to 1997 Yoshiro Watanabe, Yoshiaki Hiyama, Chikako Watanabe and Shiro Takayana [pdf, 0.35 Mb] Inter-decadal fluctuations in length-at-age of Hokkaido-Sakhalin herring and Japanese sardine in the Sea of Japan Pavel A. Balykin and Alexander V. Buslov [pdf, 0.4 Mb] Long-term variability in length of walley pollock in the western Bering Sea and east Kamchtka Alexander A. Bonk [pdf, 0.4 Mb] Effect of population abundance increase on herring distribution in the western Bering Sea Sergey N. Tarasyuk [pdf, 0.4 Mb] Survival of yellowfin sole (Limanda aspera Pallas) in the northern part of the Tatar Strait (Sea of Japan) during the second half of the 20th century Report of the 2002 MODEL/REX Workshop [pdf, 1.2 Mb] To develop a marine ecosystem model of the North Pacific Ocean including pelagic fishes Summary and Overview [pdf, 0.4 Mb] Workshop presentations: Bernard A. Megrey, Kenny Rose, Francisco E. Werner, Robert A. Klumb and Douglas E. Hay [pdf, 0.47 Mb] A generalized fish bioenergetics/biomass model with an application to Pacific herring Robert A. Klumb [pdf, 0.34 Mb] Review of Clupeid biology with emphasis on energetics Douglas E. Hay [pdf, 0.47 Mb] Reflections of factors affecting size-at-age and strong year classes of herring in the North Pacific Shin-ichi Ito, Yutaka Kurita, Yoshioki Oozeki, Satoshi Suyama, Hiroya Sugisaki and Yongjin Tian [pdf, 0.34 Mb] Review for Pacific saury (Cololabis saira) study under the VENFISH project lexander V. Leonov and Gennady A. Kantakov [pdf, 0.34 Mb] Formalization of interactions between chemical and biological compartments in the mathematical model describing the transformation of nitrogen, phosphorus, silicon and carbon compounds Herring group report and model results [pdf, 0.34 Mb] Saury group report and model results [pdf, 0.46 Mb] Model experiments and hypotheses Recommendations [pdf, 0.4 Mb] Achievements and future steps Acknowledgements [pdf, 0.29 Mb] References [pdf, 0.32 Mb] Appendix 1. List of Participants [pdf, 0.32 Mb] Appendices 2-5. FORTRAN codes [pdf, 0.4 Mb] (Document pdf contains 182 pages)

近壁湍流脉动的概率分布函数

采用大涡模拟方法，模拟槽道湍流，获得了不同雷诺数情形下的槽道流大涡模拟数据库．在此基础上，获得了流向和垂向脉动速度的概率分布函数，并运用假设检验，分析了其与正态分布的定量差别．进一步计算了流向和垂向脉动速度的偏斜度、平坦度，讨论了二者在粘性子层、过渡区和对数律区的变化．同时，讨论了粘性子层、过渡区和对数律区流向和垂向脉动速度概率分布函数的特点及其与湍流猝发的高速流下扫和低速流喷发事件的关系．最后，分析了雷诺数对流向、垂向脉动速度分布的影响。