Human spaceflight in the UK: the cost of non-participation     

Kevin Fong 《Earth, Moon, and Planets》2004,94(3-4):169-176

Human space exploration is not considered a strategic priority in the United Kingdom at present. However the UK would benefit from participating in human spaceflight, for both scientific and social reasons. From the point of view of medical science there are many parallels between the physiology of spaceflight and terrestrial disease processes, and studies of the response of astronauts to long-duration spaceflight can therefore help in the development of therapeutic strategies on Earth. On the social side, human spaceflight is an attractive vehicle for stimulating the interest of young people in science and engineering, something that must be of value for an aspiring ‘knowledge-based’ economy.  相似文献   

The trouble with nature: Ambivalence in the lives of urban Australian environmentalists   总被引：1，自引：0，他引：1  

Aidan Davison   《Geoforum》2008,39(3):1284-1295

The number and range of contests over the social production of nature is growing. Much environmentalist discourse, however, continues to appeal for unequivocal scientific support on clearly demarcated issues of pure, a-social nature. This paper explores the question of how participants in environmental movements view this demarcation in the context of their own lives. After introducing scholarly critique of dualistic ideas of nature and the ambivalence characteristic of environmentalist conceptions of nature, the paper draws upon a qualitative study with environmentalists in the Australian cities of Melbourne, Perth and Hobart. Inquiring into the interplay of discourse of nature and everyday worlds, interviews revealed a complex interdependence of dualistic and non-dualistic understandings of nature. This ecology of ideas was especially evident in spatial imaginaries of nature. Scientific terminology, social disaffection and pessimism were associated with abstract and mutually exclusive conceptions of society and nature. Reflections on personal experience, however, indicated more flexible and hopeful negotiations in everyday liminal spaces offering ‘the best of both worlds’. It is concluded that environmentalist resistance to dismantling of conceptual boundaries between society and nature may often stem not from failure to appreciate socionatural complexity, but from a strongly felt sense that the self can only truly be found in nature.  相似文献   

‘We are managing!’ Uncertain paths to respectable adulthoods in Accra, Ghana     

Thilde Langevang 《Geoforum》2008,39(6):2039-2047

Studies have shown that the life experiences and future prospects of young people in many parts of the world today are more complex and less predictable than those of past generations. This has led to a recognition of the need to reconsider the conceptual frameworks applied in youth studies. Thus far, research within geography has mainly focused on young people’s paths to adulthood in the Global North or on particularly vulnerable children’s lives in the Global South. In this paper an approach based on the ‘social navigation’ of ‘vital conjunctures’ is adopted to explore the complex ways in which young people in Ghana navigate their way through life in a city marked by economic hardship and neo-liberal reform. The stories of three young people are presented to show the variety of life conditions, the complex social positions they occupy and their various and shifting future imaginations. The actions of these young people are steered by prevailing cultural ideals and social expectations of what a desirable and respectable future entails and by the actual space of possibility in the urban space they move through. It is argued that achieving respectable adulthoods in present-day Accra is a complicated and convoluted journey involving the careful management of social relationships.  相似文献   

Tantulocarida (Crustacea: Maxillopoda): A New Taxon from the Temporary Meiobenthos1     

Rony Huys 《Marine Ecology》1991,12(1):1-34

Abstract. Two new genera of Tantulocarida are described from the Ligurian deep sea (Western Mediterranean) off Corsica. Xenalytus scotophilia is referred to the Microdajidae and differs from Microdajus GREVE in thoracopodal segmentation as well as in the presence of coupling spines on thoracopod 6 and longitudinal lamellae on the cephalic shield. Aphotocentor styx is placed in the Deoterthridae and holds an intermediate position between Deoterthron BRADFORD & HEWITT and Boreotantulus HI/YS & BOXSHALL. Some aspects of cephalon internal structure are described for the first time and give a possible explanation for the mechanism of stylet protrusion. The external structures of the oral disc are described using SEM. The discovery of well-developed muscles in the trunk and thoracopods is discussed in the light of the benthic phase the tantulus passes through. The boundary between the thorax and abdomen in the tantulus is reinterpreted, corroborating the 5–7-5 bodyplan of the hypothetical urmaxillopodan as found in the Upper Cambrian Skaracarida and possibly also Dala peilertae MOLLER. Some aspects related to dispersal, infection, and feeding are reinterpreted or approached from a different perspective. SEM of Microdajus langi GREVE gives evidence that the tantuli hatch via a conspicuous slit located at the posterior end of the female trunk sac. A worldwide key to the tantulocaridan families and genera is given, and distributional records are compiled. It is suggested that Tantulocarida might be common representatives of the temporary meiobenthos and that their present species number represents only the tip of the iceberg.  相似文献   

Reliability-Based Optimal Design for Very Large Floating Structure     

张淑华 《中国海洋工程》2003,17(1)

1 .ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅａｐｐｒａｉｓａｌｏｆａｇｏｏｄｄｅｓｉｇｎｆｏｒａｖｅｒｙｌａｒｇｅｆｌｏａｔｉｎｇｓｔｒｕｃｔｕｒｅ(ＶＬＦＳ)ｔｈａｔｗｉｌｌｓｅｒｖｅｉｎａｓｐｅｃｉ ｆｉｅｄｏｃｅａｎａｒｅａｒｅｑｕｉｒｅｓｔｈａｔｔｈｅｓｔｒｕｃｔｕｒａｌｓｙｓｔｅｍｂｅｅｃｏｎｏｍｉｃａｌｌｙｄｅｓｉｇｎｅｄ ,ｔｈｅｒｅｑｕｉｒｅｍｅｎｔｓｆｏｒｉｔｓｆｕｎｃｔｉｏｎｂｅｓａｔｉｓｆｉｅｄａｎｄｔｈｅｓｔｒｕｃｔｕｒｅｋｅｅｐｓｓｔａｂｌｅｉｎｉｔｓｗｈｏｌｅｓｅｒｖｉｃｅｐｅｒｉｏ…  相似文献   

0421号热带风暴"海马"登陆前后环境场对其移向和强度影响的分析     

赵凯  濮梅娟 《台湾海峡》2005,24(3):370-376

0421号热带风暴“海马(Haima)”于2004年9月13日12:00在浙江省温州市沿海登陆,登陆后迅速减弱为热带低压,20:00在浙江境内消失.本研究采用物理量诊断分析法,探讨该热带风暴登陆前后涡度场、湿焓场变化对其移向和强度的影响.结果表明,该热带风暴登陆后,涡度(ξ)明显减弱.涡度局地变化(ξ/t)值分布显示,风暴移动方向的后方,涡度减弱的趋势比前方涡度增大的趋势更剧烈;风暴有向其外围(ξ/t)正值中心(即涡度增幅最大)移动的趋势.该热带风暴登陆前、后,湿焓都增大,但登陆后湿焓增大趋势已大大减弱;风暴有向湿焓局地变化(E/t)正值中心移动的趋势,即向能量增强最大的方向移动.  相似文献   

Robust adaptive control of underactuated ships on a linear course with comfort     

K. D. Do  J. Pan  Z. P. Jiang   《Ocean Engineering》2003,30(17):2201-2225

This paper addresses an important problem in ship control application—the robust stabilization of underactuated ships on a linear course with comfort. Specifically, we develop a multivariable controller to stabilize ocean surface ships without a sway actuator on a linear course and to reduce roll and pitch simultaneously. The controller adapts to unknown parameters of the ship and constant environmental disturbances induced by wave, ocean current and wind. It is also robust to time-varying environmental disturbances, time-varying change in ship parameters and other motions of the ship such as surge and heave. The roll and pitch can be made arbitrarily small while the heading angle and sway are kept to be in reasonably small bounds. The controller development is based on Lyapunov’s direct method and backstepping technique. A Lipschitz continuous projection algorithm is used to update the estimate of the unknown parameters to avoid the parameters’ drift due to time-varying environmental disturbances. Simulations on a full-scale catamaran illustrate the effectiveness of our proposed controller.  相似文献   

Fatigue Behavior of Plain Concrete Under Biaxial Compression: Experiments and Theoretical Model     

ZHU  Jin-song 《中国海洋工程》2003,17(4):617-630

The effects of different lateral confinement stress on the fatigue behavior of and cumulative damage to plain concrete are investigated experimentally. Eighty 100 mm x 100 mm x 100 mm specimens of ordinary strength concrete are tested under constant- or variable-amplitude fatigue loading and lateral confinement pressure in two orthogonal directions. A fatigue equation is developed by modifying the classical Aas-Jakobsen S-N equation for taking into account the effect of the confined stress on fatigue strength of plain concrete. The results of variable-amplitude fatigue tests indicate that the linear damage theory proposed by Palmgren and Miner is unreasonable in the biaxial stress state. A nonlinear cumulative damage model that could model the effects of the magnitude and sequence of variable-amplitude fatigue loading and lateral confinement pressure is proposed on the basis of the evolution laws of the residual strains in the longitudinal direction during fatigue tests. The residual fatigue life predic  相似文献   

日照近海金乌贼生物学的初步研究   总被引：7，自引：0，他引：7  

韦柳枝  高天翔  韩志强  柳志强  王云中 《中国海洋大学学报(自然科学版)》2005,35(6):923-928

为给金乌贼渔业的可持续发展提供依据,通过形态学观察及生物学测定,初步研究了山东日照岚山头近海金乌贼Sepia esculentaHoyle,1885的外部形态特征和生物学特性(胴长与体重组成、生长参数相关关系等),并结合相关资料,对其生活史进行了讨论。研究结果表明:金乌贼胴长(ML)与体重(TW)之间的关系为:TW幼体=6.0×10-4ML2.762 6,TW♀=6.0×10-4ML2.767 1,TW♂=12.0×10-4ML2.585 6;金乌贼为异速生长型,其生长迅速、个体生长差异较大;5~6月为金乌贼繁殖季节,成体交配产卵后死亡,属1年生头足类。  相似文献   

The seasonal dynamics of six species of Dorvilleidae (Polychaeta) in the harbour of La Spezia (Italy)   总被引：1，自引：0，他引：1  

D. Prevedelli  G. Massamba N'Siala  & R. Simonini 《Marine Ecology》2005,26(3-4):286-293

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