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21.
D. W. Shuttlewood D. A. Crolla R. S. Sharp I. L. Crawford 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1993,22(5):383-396
The development of a mathematical model of a limited bandwidth hydro-pneumatic suspension that is incorporated into a vehicle handling model is described. The combined model is used to evaluate a suitable control strategy for eliminating body roll during a cornering manoeuvre. The philosophy behind the roll control strategy has been to use feedback measurements of the body motions which do not compromise the ride control. A study of the influence of the position of the body motion feedback transducer on the effectiveness of the system to reduce the body roll is presented. Non-linear modelling of the suspension components for a 0.8g cornering manoeuvre has revealed performance limitations. Conclusions are drawn as to the effectiveness of the control scheme. 相似文献
22.
Benthic community patterns reflect water column processes in the Northeast Water polynya (Greenland)
Dieter Piepenburg William G. Ambrose Jr. Angelika Brandt Paul E. Renaud Michael J. Ahrens Preben Jensen 《Journal of Marine Systems》1997,10(1-4)
Benthic community patterns were investigated in the Northeast Water polynya (Greenland) during the summers of 1992 and 1993 to elucidate to what extent the bottom fauna is influenced by the dynamics of the overlying water. Five different fractions of the benthos (foraminiferans, nematodes, polychaetes, peracarid crustaceans, and epibenthic megafauna), ranging in average adult body size over 6 orders of magnitude (from about 100 μm to about 10 cm), were sampled quantitatively at 69 stations in water depths from 40 to 515 m. Total abundances of nematodes, polychaetes and peracarid crustaceans were found to be primarily correlated with parameters characterizing the potential benthic food supply (water column pigment and nitrate concentrations, sediment bound pigments and sediment biological activity), whereas abundances of foraminiferans and megabenthos were largely associated with seabed properties. Four benthic zones were distinguished by separately analyzing the faunistic composition and distribution of the five community fractions for Ob Bank, Western Westwind Trough, Eastern Westwind Trough, and Belgica Trough. This pattern was shown principally to reflect pelagic regimes differing in surface water hydrography, ice cover and euphotic productivity. This is the first time that a synoptic study of several benthic community portions spanning such a range in sizes and life styles has been performed in a polar shelf ecosystem. Our results indicate that abundances as well as composition of Arctic benthos are largely influenced by mesoscale pelagic processes, and thus provide further evidence for the importance of the benthic-pelagic coupling in high latitude seas. 相似文献
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The aim of this paper is to investigate the behaviour of water transportation company stock returns in the U.S. stock exchanges from 1985 to 1994 in order to determine whether the systematic risk of this industry is different from that of the 'average' company in the market, whether it has changed over the ten year period, over bull and bear market conditions, and whether there is a firm 'size' effect in the industry. In the context of the Capital Asset Pricing Model (Capm), we find that the systematic risk of the shipping industry return is not different from that of the 'average' company. It is also found that the covariance of water transportation companies with respect to the overall stock market return did not change over the ten year period although it appears that it has changed over normal upward/downward market movements. There is also reasonable evidence that the intercept of the equation might have changed over normal upward/downward market movements. Finally, we document contradictory evidence regarding the size effect; during the period 1985-1989 we find small companies to have significantly higher returns and risk while during the period 1990-1994 medium size companies tend to have higher risk than small and large firms, which is not however compensated by higher returns. 相似文献
25.
To identify the potential relationship between Pheaocystis globosa bloom conditions and seawater properties, a hydrobiological survey was performed in the inshore waters of the Eastern English Channel over the course of the phytoplankton spring bloom. Chlorophyll concentration, auto- and hetero/mixotrophic composition of protists and standing stock, and seawater viscosity were measured weekly from March to June 2004. The decline of the bloom is characterized by a massive foam formation in the turbulent surf zone. Before foam formation, seawater viscosity significantly increased, showing a significant positive correlation with chlorophyll concentration. In contrast, after foam formation this correlation was negative, seawater viscosity kept increasing despite a sharp decrease in chlorophyll concentrations. No significant correlation has been found between seawater viscosity and the composition of the phytoplankton assemblages observed during the survey. However, significant positive correlations have been found between seawater viscosity and both the size and the abundance of P. globosa colonies. From the correlation patterns observed between chlorophyll concentration and seawater viscosity, we suggest that the rheological properties of seawater are mainly driven by extracellular materials associated with colony formation and maintenance rather than by cell composition and standing stock. 相似文献
26.
武汉至广州客运专线项目 总被引:1,自引:0,他引:1
铁道部发展计划司合资处 《中国铁路》2005,(11):68-69
1项目概况 1.1项目建设必要性 武广铁路客运专线位于湖北、湖南、广东三省境内,是规划中的京广客运专线的重要组成部分.目前,京广铁路是我国铁路网中最繁忙的铁路干线之一,2002年以占全路约3.3%的营业公里完成了全路客、货运输周转量的16.8%和9%.其中,武汉-广州段尤为紧张,运输能力处于超饱和状态,严重制约了区域经济的发展.与此同时,国民经济和社会发展还将对京广通道客货运输能力和质量提出更高要求.利用既有线扩能,新建货运双线或其他线路改建分流等方式,均不能彻底解决运输能力和运输质量的问题.因此,迫切需要修建客运专线. 相似文献
27.
着重介绍《MARPOL 73/78》附则VI的起源和发达国家船舶柴油机氮氧化物(NOx)的排放控制技术发展状况,随着《MARPOL 73/78》附则VI的正式实施和今后国际海事组织(IMO)对《MARPOL 73/78》附则VI的进一步修订,船舶柴油机NOx的排放控制及其相关技术会受到包括轮机管理在内的相关人员越来越多的关注。 相似文献
28.
This paper presents a procedure for the estimation of origin‐destination (O‐D) matrices for a multimodal public transit network. The system consists of a number of favored public transit modes that are obtained from a modal split process in a traditional four‐step transportation model. The demand of each favored mode is assigned to the multimodal network, which is comprised of a set of connected links of different public transit modes. An entropy maximization procedure is proposed to simultaneously estimate the O‐D demand matrices of all favored modes, which are consistent with target data sets such as the boarding counts and line segment flows that are observed directly in the network. A case study of the Hong Kong multimodal transit network is used to demonstrate the effectiveness of the proposed methodology. 相似文献
29.
This paper presents an off‐line forecasting system for short‐term travel time forecasting. These forecasts are based on the historical traffic count data provided by detectors installed on Annual Traffic Census (ATC) stations in Hong Kong. A traffic flow simulator (TFS) is developed for short‐term travel time forecasting (in terms of offline forecasting), in which the variation of perceived travel time error and the fluctuations of origin‐destination (O‐D) demand are considered explicitly. On the basis of prior O‐D demand and partial updated detector data, the TFS can estimate the link travel times and flows for the whole network together with their variances and covariances. The short‐term travel time forecasting by O‐D pair can also be assessed and the O‐D matrix can be updated simultaneously. The application of the proposed off‐line forecasting system is illustrated by a numerical example in Hong Kong. 相似文献
30.