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131.
本文从水上漂流的属性入手,对目前水上漂流安全监管工作的重难点问题进行了剖析,并类比内河交通安全管理模式,提出对水上漂流活动监管的对策与建议。 相似文献
132.
邱翀 《武汉船舶职业技术学院学报》2006,5(5):44-46
本文从流态、河段地形、水位、航行现象等方面介绍浅水区的特点,阐述了船舶驶入浅水区时的现象,以供船舶驾驶员判断不适航浅水区位置的参考。 相似文献
133.
Application of a validated primary production model (BLOOM) as a screening tool for marine, coastal and transitional waters 总被引:3,自引:0,他引:3
In order to manage aquatic systems, it is necessary to apply methods relating the environmental variables and system-state parameters with external factors that affect the system. External factors can be natural (i.e. the movement of water) or partly-anthropogenic (i.e. nutrient loads). In addition to the national authorities, who have been implementing environmental policies for several decades, the EU is presently implementing the Water Framework Directive (WFD) aimed at establishing a new set of standards for the ecological and water quality of water systems. Among these are the phytoplankton biomass and composition. Phytoplankton affects turbidity, oxygen depletion, total productivity of the system and the occurrence of (harmful) algal blooms. A range of methods is available to relate phytoplankton to the controlling environmental conditions. Among these are statistical relations for instance of the Vollenweider type as well as deterministic simulation models. At the end of the 1970s, a generic deterministic phytoplankton module called BLOOM was developed, which has since been applied to a wide range of fresh water and marine systems. Here we test the applicability of this model as a screening tool for coastal waters. We conclude that the model is able to reproduce observed chlorophyll levels adequately under a wide range of conditions. Subsequently the model is applied to demonstrate the potential impacts of reductions in nitrogen, phosphorus or both nutrients simultaneously. Depending on which factors are initially controlling, the impacts of these reductions vary considerably both between locations and during the season. While this type of application lacks explicit relations between nutrient concentrations and external loadings, it does consider a number of relevant conditions in a consistent way and requires remarkably little data and effort. It is therefore a valuable screening tool. 相似文献
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136.
A large-scale model test of a free-hanging water intake riser (WIR) is performed in an ocean basin to investigate the riser responses under vessel motion. Top end of the WIR is forced to oscillate at given vessel motion trajectories. Fiber Brag Grating (FBG) strain sensors are used to measure the WIR dynamic responses. Experimental results firstly confirms that the free-hanging WIR would experience out-of-plane vortex-induced vibrations (VIVs) under pure vessel motion even for the case with a KC number as low as 5. Meanwhile, comparison between numerical results and experimental measurements suggests a significant drag amplification by out-of-plane vessel motion-induced VIV. What’s more, further study on WIR response frequencies and cross section trajectories reveals a strong correlation between vessel motion-induced VIV and local KC number distribution, owing to the small KC number effect. The presented work provides useful references for gaining a better understanding on VIV induced by vessel motion, and for the development of future prediction models. 相似文献
137.
一体化反应堆结构紧凑、安全性高,在中小型反应堆的发展中具有很大优势。一体化反应堆中通常采用套管式直流蒸汽发生器(OTSG),传热管是套管结构,采用双面传热,换热能力强,但套管内存在单相区,汽水两相区和过热区,传热情况复杂,在反应堆启动、停止或低功率运行时容易产生两相流动不稳定现象。文章采用RELAP5程序,针对某陆用反应堆套管式直流蒸汽发生器建立了集总参数分析的模型,研究了系统压力、入口过冷度、入口节流等参数对流动不稳定性的影响。计算结果表明:增大系统压力,提高入口过冷度,在一定条件下增加入口节流均有利于系统的稳定。文章是对一体化反应堆直流蒸汽发生器流动性研究,对船用反应堆的直流蒸汽发生器流动性研究同样具有参考意义。 相似文献
138.
LY温拌剂是一种使用多种废旧材料复合而成的温拌添加剂。通过对LY温拌沥青混合料和热拌沥青混合料的性能测试及比较,结果表明:添加该温拌剂对沥青混合料的性能提升效果明显,优于对应热拌沥青混合料。 相似文献
139.
O. V. Kopelevich S. V. Sheberstov O. Yunev O. Basturk Z. Z. Finenko S. Nikonov V. I. Vedernikov 《Journal of Marine Systems》2002,36(3-4)
Absolute values of chlorophyll a concentration and its spatial and seasonal variations in the Black Sea were assessed by using satellite CZCS and in situ data. Since the satellite CZCS had operated for the 1978–1986 period, CZCS data was used for assessing the past state of the Black Sea just before the onset of drastic changes observed in late 1980s. The approach used for the calculation of the absolute values of chlorophyll a concentration from CZCS data was based on the direct comparison of in situ chlorophyll a data and those of CZCS and by applying the algorithm developed for the transformation of CZCS data into chlorophyll a values. CZCS Level 2 data related with pigment concentration having a spatial resolution of 1 km at nadir were used. The daily Level 3 files were derived by binning Level 2 values into 4-km grid cells and the monthly and seasonal Level 3 files were created by averaging the daily Level 3 files over the corresponding period. In situ chlorophyll a data were obtained by spectrophotometric and fluorometric methods in 15 scientific cruises over the 1978–1986 period. Total number of ship-measured data used for the comparison with those CZCS values was 590.Chlorophyll a concentration (Chl) was derived from CZCS values (C) with regression equations Chl=kC; the coefficient of transformation k was calculated from six different data sets by taking into account distinctions between subregions and seasons. The reasons for difference in the k values have been analyzed.Statistical comparison of the chlorophyll a values measured in situ and those derived from CZCS data was based on log-transformed data and gave the following results: regression SLOPE=0.842, regression INTERCEPT=−0.081, coefficient of determination (R2)=0.806, root–mean–square ERROR=0.195. The mean monthly chlorophyll a distributions derived from CZCS data over 1978–1986 have been constructed and the mean seasonal chlorophyll a values in different regions have been calculated and analyzed. The significant difference in chlorophyll concentration between the western shelf regions and the open part of the Black Sea has been demonstrated, especially in warm season. At almost all seasons, the highest chlorophyll concentration is observed in the western interior shelf region which is under strong influence of Danube. The summer mean chlorophyll concentration in this region is 18 times higher than that in the open parts and about nine times higher than in the eastern shelf region. The greatest seasonal variations are observed in the open part of the Black Sea: chlorophyll concentration in cold season is four to six times higher than in summer and three to five times higher than in April and October. To the contrary, in the western interior shelf regions, the concentration is higher in May–October (about twice than that in November–March). Seasonal variations in the western outer shelf regions are smoothed out as compared with both the western interior shelf and the open regions. 相似文献
140.
运用战略经营和企业能力等经济学和管理学的基本理论,在对我国内河水运企业竞争环境分析的基础上,探讨中国内河水运企业根据竞争环境和自身条件,确定竞争定位与战略目标,选择相应的竞争战略,注重培育核心竞争力,以保持竞争优势地位。 相似文献