Environmental changes and the responses of the ecosystems of the Yellow Sea during 1976–2000

The changes in the environmental features of the Yellow Sea during the last 25 years of the 20th century were studied using a set of seasonally monitored data along a transect (at 36°N) maintained by the State Oceanic Administration of China. The data included the ocean temperature (T), salinity (S) and biogenic elements, such as dissolved oxygen (DO), phosphorus (PO₄-P), silicon (SiO₃-Si) and dissolved inorganic nitrogen (DIN).The seasonal (summer and winter) values and the annual mean of these elements showed significant changes during the monitored period. Time series of T, S, DIN and N:P ratios exhibited positive trends, while those of DO, P and Si exhibited negative trends. During this period, the annual mean of T and DIN in the Yellow Sea increased by 1.7 °C and 2.95 μmol L⁻¹, respectively, while those of DO, P and Si decreased by 59.1, 0.1 and 3.93 μmol L⁻¹, respectively. In the 1980s, particularly in between 1985 and 1989, concentrations of P and Si dropped to near the ecological threshold for growth of diatoms. The N:P ratio increased from 4 in 1984 to over 16 in 2000. The climate trend coefficients, R_xt, for these time series are all above 0.43 with significance levels of 95%, except for salinity. The increases in T were consistent with the recent climate warming in northern China and the adjacent seas, i.e. the Bohai Sea and the East China Sea. The reduction of DO was probably attributable to the increase in T and decrease in primary production in these regions. The positive trend of DIN was mainly attributable to precipitation and partly to Changjiang River discharge. The negative concentration trends of P and Si were due to the decreases in their concentrations in seawater that flowed to the Yellow Sea from the Bohai Sea. As a result, N:P ratios greatly increased in the seawater of the Yellow Sea.Moreover, some important responses of the Yellow Sea ecosystems to the changes in physical variables and chemical biogenic elements were obviously displayed. These responses include strengthening nutrient limitation, decreasing chlorophyll a, primary production and phytoplankton abundance, succession of dominant phytoplankton species from diatoms to non-diatoms, changes in fish community structure and species diversity.     

Technical Note: Force Control in Electrohydraulic Active Suspensions Revisited

The inner loop control for the actuator force can be quite simply compensated by means of a correction term to the desired force signal at the input. The correction requires only a measurement of the actuator piston velocity and is employed to cancel the loop disturbance caused by the oil flow to the actuator. Although an additional time constant is introduced by the integration in the inner loop force control, the overall performance is nevertheless quite close to that of an ideal optimal system.     

接触网支柱电蚀保护装置的改进

为了对接触网支柱进行防电蚀保护,长期以来采用各种保护装置.对防电蚀保护装置的主要性能要求为:当轨道电路中存在牵引电流的情况下,装置必须工作可靠;在接触网短路情况下,装置应能正常动作.     

How much disruption to activities could fuel shortages cause? – The British fuel crisis of September 2000

In September of 2000 the UK experienced a blockade of oil refineries in response to rising fuel prices. These protests resulted in severe fuel supply disruptions that intensified over the course of about one week. During the peak of the crisis, travel activity by car was curtailed. This paper analyzes survey data collected about two months after the crisis utilizing the recent memory of respondents as to how they would expect this sort of disruption to affect their participation in daily activities. Specifically, we focused on a variety of non-discretionary and discretionary activities and examined what factors are associated with respondents expecting disruption to those activities. Statistical models were developed to analyze how demographic factors, commute mode selection, vehicle characteristics, and various other factors can explain how individuals expect disruption to their activities. Results suggest that the majority of individuals do not expect major disruptions, although for more car-dependent individuals, disruption was expected to be substantial, especially for work-related trips. These results have implications for the potential success and benefits of an integrated transport policy.     

Technical Note: RMS Values for Control Force, Suspension Stroke and Tyre Deflection in an Active Suspension

Expressions are derived for the numerical computation of rms values for control force, suspension stroke and dynamic tyre deflection in a quarter-car vehicle model on a random road of given roughness. A quadratic performance index is employed and the effects of the assumed weighting factors on the rms values and overall static stiffness determined.     

The competitiveness of short sea shipping in multimodal logistics supply chains: service attributes

Much has been written and spoken about short sea shipping within the European Union (EU) as a means of shifting goods from road to sea and of achieving a sustainable economic development. However, this shift is far from being a general reality, despite the few individual, and success stories that have taken place and the EUROSTAT data suggest that the overall effort has contributed very little towards attaining this desired shift. In the light of this, research was conducted to discover how to put short sea shipping on a more competitive level within European multimodal logistics supply chains. This paper aims at identifying service attributes of short sea shipping operations within multimodal transport chains by means of a questionnaire and, for that, examines the short sea shipping environment and contemporary European logistics trends. The analysis is based on empirical research, involving logistics operators, shippers' associations and intermodal rail operators, and allows an evaluation (based on statistical techniques) of the short sea shipping industry and its competitors. It extends previous work by considering these short sea shipping attributes within a multimodal transport context.     

Seasonal productivity dynamics in the pelagic central Benguela System inferred from the flux of carbonate and silicate organisms

Flux of bulk components, carbonate- and silicate-bearing skeleton organisms, and the δ¹⁵N-isotopic signal were investigated on a 1-year time-series sediment trap deployed at the pelagic NU mooring site (Namibia Upwelling, ca. 29°S, 13°E) in the central Benguela System. The flux of bulk components mostly shows bimodal seasonality with major peaks in austral summer and winter, and moderate to low export in austral fall and spring. The calcium carbonate fraction dominates the export of particulates throughout the year, followed by lithogenic and biogenic opal. Planktonic foraminifera and coccolithophorids are major components of the carbonate fraction, while diatoms clearly dominate the biogenic opal fraction. Bulk δ¹⁵N isotopic composition of particulate matter is positively correlated with the total mass flux during summer and fall, while negatively correlated during winter and spring. Seasonal changes in the intensity of the main oceanographic processes affecting the NU site are inferred from variations in bulk component flux, and in the flux and diversity patterns of individual species or group of species. Influence from the Namaqua (Hondeklip) upwelling cell through offshore migration of chlorophyll filaments is stronger in summer, while the winter flux maximum seems to reflect mainly in situ production, with less influence from the coastal and shelf upwelling areas. On a yearly basis, dominant microorganisms correspond well with the flora and fauna of tropical/subtropical waters, with minor contribution of near-shore organisms. The simultaneous occurrence of species with different ecological affinities mirrors the fact that the mooring site was located in a transitional region with large hydrographic variability over short-time intervals.     

The Art of Successfully Applying Human Systems Integration

This paper reviews developments in human factors and then draws from a number of "best practice" cases in studying how best to apply behavioral science principles, knowledge, and analytical tools to the engineering design or improvement of systems. Government and other commercial experiences are examined with a focus on the Navy human system integration (HSI) process. Included are discussions facilitated at a workshop session sponsored by the Transportation Research Board of the National Academies. There is general consensus that in addition to using a well-designed or proven process and doing the right things, success is dependent upon attending to a prioritized short list of critical elements. Continued focus on these elements is necessary to successfully apply human behavioral sciences effectively during design, construction, and operation of systems to improve safety, reliability, effectiveness, efficiency, and quality of life.     

采用异步牵引传动的ЗT2A型电动车组

电动车组的故障中，40％是发生在牵引电动机和电气设备上。因此应采用更经济、更安全、对旅客和维护人员都更方便的新型电动车组代替已经老化的、使用寿命已到期的直流近郊列车。ЗT2A型就是新型电动车组之一。文章介绍了其技术参数，分析了其电路原理和技术特点。     

Modelling high frequency force behaviour of hydraulic automotive dampers

Little information on automotive damper performance above 30 Hz is found in the published literature. Design of vehicles for low levels of noise, vibration and harshness requires attention to higher frequencies. This paper describes research into modelling damper behaviour at frequencies up to 500 Hz. The performance of a monotube damper was measured and the empirical data were used to evaluate a recently published parametric model. Methods of assessing prediction accuracy using transfer and coherence functions, and a wavelet-based transfer function were introduced. Modifications to the model were then developed to improve the prediction of high-frequency behaviour.