力学大师S.P.铁木辛柯

S.P.铁木辛柯,20世纪活跃在工程力学领域约60年,培养了几代优秀的工程师和力学家,取得了丰硕的研究成果,推动了工程力学的进展,人们尊之为力学大师.本文从学术生涯、研究成果、学术著作、学术贡献几方面简介铁木辛柯.     

Operating stresses on S. S. “Michigan” propeller

The failure at sea of a number of merchantship propeller blodes initiated a research program supported by the Maritime Administration, the American Bureau of Shipping, the American President Lines and the States Steamship Company. Although extensive theoretical work has been carried out in the past (predicting propeller operating stresses), very little full-scale experimental stress measurements have been obtained. Brewer Engineering Laboratories, Inc. was retained by the sponsors to attach and protect fifty strain gages on the test propeller at the locations chosen by Littleton Research and Engineering Corporation. The propeller strain gages were protected from the severe environment by means of synthetic rubber and metallic overlays. The gage wiring was led down each blade and into a specially machined, hollow tailshaft through a waterproof bulkhead. The S.S. “Michigan”, with the test group aboard, sailed from Long Beach, Calif., in April 1970. The ship called at the ports of San Francisco, Yokohama, Naha, Manila, Bogo and Hong Kong during the test period. Throughout the trip across the Pacific, the gaging and instrumentation functioned without degradation or evidence of distress after onemillion propeller shaft turns. At the end of five weeks at sea and two-million turns, all but eight gages exhibited low ground resistance. The S.S. “Michigan” went into dry dock at the Bethlehem Steel Shipyard at Terminal Island, Calif., on June 15, 1970. The propeller was removed and all strain gages checked for continuity and ground resistance. Forty-two of the original 50 strain gages were found to be intact. No sign of deterioration due to cavitation or electrolysis attack existed on the metallic overlays or spot welding. Wire chafing within the fairwater adapter cap accounted for the low ground resistance values observed at the end of the voyage to Hong Kong.     

Co-Movements and Asymmetric Volatility in the Portuguese and U.S. Stock Markets

It has been widely recognised by economists that economic relationships are typically non-linear. This is so that, for example, C. W. J. Granger and T. Ter?svirta [Modelling Nonlinear Economic Relationships, Oxford University Press, New York, 1993], inter alia, have dedicated a whole book to the subject of modelling non-linear economic relationships. Non-linear relationships are present in many aspects of the economic activity, and particularly so in the context of financial markets. Examples of this include the attitude of investors towards the risk and the process of generating financial variables such as stock returns, dividends, interest rates, and so on. On the other hand, the performance of an economy also presents strong signs of a non-linear behaviour: e.g. business cycles, production functions, growth rates, unemployment, etc. Although the shape of non-linearity in these relationships may be rather complex, there are cases where one may admit some sort of linear relationship between the relevant variables within certain regimes. This is the case when one aims to study the co-movements of stock returns volatility and some relevant macroeconomic factors. One obvious question that we may pose in this context is whether the magnitude of positive and negative responses differs for similar positive and negative variations in the predictors, in which case we can say that the underlying variables display asymmetric adjustment. Markets characterised by higher elasticity of supply are likely to show less asymmetry than their counterparts due to increased security of supply. Models of financial markets have incorporated asymmetry using GARCH-type methodologies. An alternative way to deal with these cases is to use threshold autoregressive (TAR) and momentum threshold autoregressive (M-TAR) models to address the problem of multivariate asymmetry. These methodologies are essential when the asymmetric variables are non-stationary (but not only), because of the low power of unit roots and cointegration tests in such cases. In a non-stationary framework, asymmetric cointegration tests were developed by [W. Enders, and P. Siklos, Journal of Business & Economic Statistics 19(2), 2001, 166–176] using a modified error correction model derived from the original EG testing procedure. We apply this methodology to the Portuguese and U.S. stock markets using monthly observations from January 1993 to December 2003.     

New solutions of the C.S.Y. equation reveal increases in freak wave occurrence

In this article we study the time evolution of broad banded, random inhomogeneous fields of deep water waves. Our study is based on solutions of the equation derived by Crawford, Saffman and Yuen in 1980, (Crawford et al., 1980). Our main result is that there is a significant increase in the probability of freak wave occurrence than that predicted from the Rayleigh distribution. This result follows from the investigation of three related aspects. First, we study the instability of JONSWAP spectra to inhomogeneous disturbances whereby establishing a wider instability region than that predicted by Alber’s equation. Second, we study the long time evolution of such instabilities. We observe that, during the evolution, the variance of the free surface elevation and thus, the energy in the wave field, localizes in regions of space and time. Last, we compute the probabilities of encountering freak waves and compare it with predictions obtained from Alber’s equation and the Rayleigh distribution.     

钱学森先生简介

今年１２月１１日是国际著名力学家,我国近代力学的奠基人,我国航天技术的开创者和系统工程科学家,中国力学学会和中国空气动力学学会的创始人,钱学森先生的９０华诞．中国力学学会和中国空气动力学学会等２１个单位举办“新世纪力学研讨会──钱学森技术科学思想的回顾与展望”会议,重温他发展力学的丰富思想,共同探讨我国新世纪力学的前进道路．本期刊出《钱学森先生简介》、郑哲敏院士的《祝贺钱学森院士９０寿辰》以及研讨会的３篇大会报告,以表示对钱学森先生９０华诞的祝贺。     

钱学森开创的物理力学

回顾物理力学的创立和半个世纪的发展,表明物理力学对工程 技术和力学基础研究的双重作用,以及钱学森对物理力学的创建和发 展的卓越贡献,并展望物理力学的未来,说明我们这代人负有主动促进 物理力学发展的历史责任.     

The S. P. Timoshenko Institute of Mechanics at the beginning of the third millennium

A brief historical review of the main scientific activities at the S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, is outlined. Current trends are examined, in the Institute as a whole and in particular departments. As a resource, reviews of the Institute's activity published between 1955 and 1999 in this journal and elsewhere are listed in a bibliography. S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev. Translated from Prikladnaya Mekhanika, Vol. 36, No. 1, pp. 6–24, January, 2000.     

On the Cover of this Issue: Reflected Near-Field Blast Pressure Measurements by S. E. Rigby,R. Knighton,S. D. Clarke,and A. Tyas

Experimental Mechanics -     

Presentation of the monographs of the S. P. Timoshenko Institute of Mechanics to the scientific community

This paper presents information on 220 monographs published by scientists of the S. P. Timoshenko Institute of Mechanics (National Academy of Sciences of Ukraine) and available in the Library of Congress (USA), and on ways (reading rooms and catalog numbers) of familiarizing oneself with them. The Library of Congress Online Catalog makes it possible to obtain information on these monographs via the Internet at any center of science in any country. This allows the scientific community to access the results presented in these monographs and resolves the problem of presenting them to the world’s scientific community __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 3, pp. 3–49, March 2006.