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611.
为了促进LNG运输船主动力推进装置方面的研究,推动LNG运输船推进系统的转型,通过对LNG运输船几种推进方式特点的对比分析,为中小型LNG运输船主推进系统的选型提供参考。 相似文献
612.
目前,油位传感器普遍采用铍青铜电刷加厚膜电阻形式,作为一类技术成熟的油位传感器,有着无可比拟的价格和技术优势,虽在行业中占据主导地位,但这种传感器也有难以克服的缺陷,在正常通电状态下一般很难达到预期的设计寿命。随着油价上涨,劣质汽油流入市场,汽油中硫磷等腐蚀性物质对厚膜电阻腐蚀严重;耐乙醇汽油的丁晴橡胶浮子在生产过程中残留有硫元素,溶解在汽油中会腐蚀厚膜电阻,这两方面是导致油位传感器使用寿命降低的关键因素。 相似文献
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615.
汤璐诘 《城市轨道交通研究》2015,(Z2):50-52
车载信号设备中的速度传感器故障存在定位较难的问题。简要介绍了霍尔式速度传感器的工作原理和主要技术指标。描述了便携式速度传感器测试台的组成及工作原理,并介绍了便携式速度传感器测试台的操作方法和测试方式。便携式速度传感器具有便携,易操作且使用灵活等创新点,能有效减少试车时间,提升速度传感器故障的排故能力。 相似文献
616.
Juan Santos-Echeandía Ricardo Prego Antonio Cobelo-García 《Journal of Marine Systems》2008,72(1-4):350
The water column above the Prestige wreckage was sampled during two consecutive campaigns: Prestinaut (December 2002) two weeks after the tanker sunk and HidroPrestige0303 (March 2003) one month after the sealing of the main fuel leaks. Samples of the original cargo fuel and the emulsified fuel in the surface of the ocean were also collected. Analysis of the fuel indicated the release of 135 kg of Cu, 1700 kg of Ni and 5300 kg of V from the original fuel to the water column, remaining 35 kg of Cu, 3100 kg of Ni and 13,800 kg of V in the emulsified fuel. The metal partitioning between the water column and the emulsioned floating fuel, Cu > Ni ~ V, are in accordance with the stability index for the metal–nitrogen bond in metalloporphyrins. This release had an impact on dissolved trace metal concentrations in the water column. An increase on dissolved copper (2.8–4.7 nM) and nickel (2.2–8.0 nM) with respect to natural values (1–3 nM for Cu and 1.6–5 nM for Ni) was observed. Values for vanadium (28–35 nM) were in the range of pristine North Atlantic waters (30–36 nM). This contamination was especially observed in the upper water column (0–50 m), associated with the mixing of seawater with the fuel moving upwards, and in deep waters, where the residence time of fuel is higher. Future research in this field should focus on the environmental variables and the processes that control the release of contaminants from fuels for a better assessment of the contamination in oil-spill events. 相似文献
617.
Alessandra Cincinelli Tania Martellini Lucilla Bittoni Aniello Russo Andrea Gambaro Luciano Lepri 《Journal of Marine Systems》2008,73(1-2):208-220
In the framework of the Italian Research Programme in Antarctica (PNRA) an oceanographic cruise was carried out between December 2000 and February 2001 in the Western Ross Sea. n-Alkanes and PAHs concentrations were analysed in sea-water samples collected at different depths at four sites (D, B, CA2, and CA). Vertical profiles of pressure, temperature, salinity and fluorescence were also performed in order to distinguish the water masses present in the sampling areas. n-Alkanes concentrations were consistent with those found in the same area during previous expeditions and showed higher values in the particulate due to the low temperatures. n-Alkanes profiles exhibited different features in the dissolved and particulate phases. The dissolved phase was characterised by a bimodal distribution with two maxima at C16 and C24 and prevalent compounds in the range C15–C32 whereas particulate was strongly dominated by long chain n-alkanes C23–C34 with C24 (Site B, CA and CA2) or C32 (Site B) as Cmax. CPI values and Pr/Ph ratios suggested a prevalent biogenic origin for aliphatic hydrocarbons. n-Alkanes vertical distributions were affected by the dynamic of the pack-ice melting and phytoplankton activity as well by the chemical–physical properties of water masses. Higher n-alkanes values were found in the High Salinity Shelf Waters (HSSW), lower n-alkanes values were found in the Antarctic Surface Waters (AASW) and Modified Circumpolar Deep Water (MCDW).The low PAHs concentration levels confirmed the still pristine character of the Antarctic environment. Neither particular trend in total PAHs concentrations along the water column and nor correlations with the most characteristic water masses of the investigated area of the Ross Sea were observed, except that total PAH higher concentrations were generally observed in correspondence of HSSW. 相似文献
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619.
列车在运行时,对轨道和路基等的承载设施进行全面监测并将获取的信息实时传送给机车操控人员和列车运行监控记录装置具有重要的科研和实用意义。以此为背景,本文建立一种多网关移动条件下对线路进行实时监测的无线传感器网络模型,描述网络的结构、定义传感数据生成的服务等级划分规则和数据的传输流程。提出一种在网关运动条件下基于相对位置信息的网络功率控制方法并进行相应的通信协议设计。仿真结果表明,在选择合理的底层通信协议的条件下,该网络能够保证监测数据的可靠传输,并满足节能和实时性要求。 相似文献
620.
The red shrimp Aristeus antennatus is one of the target species of the bottom trawl fishery of the Balearic Islands. The objective of the present paper is to study the short spatial and temporal differences of this important economic resource between two different locations off Mallorca (Cabrera: CA; Sóller: SO), where a fleet mobility pattern has been detected, and to study the influence of environmental conditions on this species. Six simultaneous bottom-trawl and oceanographic surveys were carried out at these two locations in order to collect data from the demersal species, hydrography (temperature and salinity), trophic resources and sediment characteristics. The commercial fleet from both locations was monitored by monthly on-board sampling, log-books and daily landings obtained from sales slips. Additional data was obtained from other fishing surveys. Short spatial and temporal differences have been detected between both locations. The population at CA was more demographically homogeneous, while that at SO showed important variations, like high abundance of juveniles recruiting to fishing grounds in autumn–winter and high abundance of large females during summer. Several differences have also been found in the biology of the species between locations, such as males were more abundant in SO than in CA. Also, the reproductive period started sooner in SO than in CA, and the condition of pre-spawning females was better in SO. The percentage of total lipids in the hepatopancreas was minimal during the spawning period, showing their importance as a reserve of energy for the ovary ripening. Water masses could play an important role in these differences, the characteristics of water masses being more stable in CA than in SO. Red shrimp adult females seemed to be more correlated with the warmer and more saline Levantine Intermediate Waters, while juveniles (males and females) and adult males were more correlated with the colder Western Mediterranean Deep Waters, detected only in SO during autumn–winter. Two different hypothesis of mobility patterns for the species are discussed in relation to these observed differences. 相似文献