Surface chlorophyll in the Black Sea over 1978–1986 derived from satellite and in situ data

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.     

谈锦朝高速公路的接地系统

本文针对高速公路的各种接地系统进行了探讨.     

The Dead Sea hydrography from 1992 to 2000

The modern hydrological regime of the Dead Sea is strongly affected by anthropogenic activity. The natural fresh water budget has changed mainly due to the drastic reduction of runoff. Since 1977, the surface level of the Dead Sea has been lowered by an average rate of about 60 cm/year and for the period from 1998 to 2000, the lowering rate has reached about 100 cm/year. As a result of the runoff reduction, the upper layer salinity of the Dead Sea has increased and the gravitational stability of the water body was diminished. Eventually, during the winter of 1978–1979, the lake waters overturned, bringing to an end the long-term stable meromictic¹ hydrological regime. The lake entered a new phase in which its hydrological regime switches between holomictic and meromictic regimes, depending on the size of the runoff into the lake (i.e. the amount of precipitation in the lake's watershed). The first holomictic period, 1979–1980, lasted for 2 months only. It was succeeded by a 4-year meromictic period (1980–1983). The second holomictic period lasted for 9 years (1983–1991). The rainy winter of 1991–1992 resulted in an almost 2-m sea level rise. The upper layer with a relatively low salinity was restored and a new meromictic period persisted for 4 years, until winter 1995–1996. During the last meromictic period, the hydrological regime of the Dead Sea was characterized by following long-term trends: the depth of the summer thermocline increased from 12–15 to 25–30 m; the quasi-salinity of the upper layer, initially of about 164 kg/m³, increased rapidly at a rate of about 16–18 kg/m³/year; the quasi-salinity of the deep water, initially of about 235 kg/m³, decreased slowly at a rate of about 0.08–0.10 kg/m³/year (for the sake of comparison, a quasi salinity of 235 kg/m³ is the equivalent of 280‰ “usual” salinity); and the winter minimal temperature of the upper layer, initially of about 16 °C, increased rapidly at a rate of about 2 °C/year. In November 1995, the latest meromictic period of the Dead Sea came to an end. During the present holomictic period, 1996–2000, the hydrological regime of the Dead Sea is also characterized by long-term trends: the quasi-salinity of the entire Dead Sea increased at a rate of about 0.5 kg/m³/year, with practically no decrease during the winters; the temperature of the deep water mass increased with a rate of about 0.25 °C/year; and the period of vertical convection of the entire water column, initially about 3 months, increased at a rate of about 1 week/year. Moreover, we observed that the temperature and salinity of the bottom layer in the deepest part of the Dead Sea raised by about 0.5–0.6 °C and 0.15–0.25 kg/m³ during each holomictic summer.     

关于防风制动器应用效能的探讨

介绍沈阳铁路局装卸系统门式起重机防风制动器调整标准的制定过程及制动力矩的计算,探讨了门式起重机滑行时迎风面积与自重对防风性能的影响。     

基于空间句法的城市道路网可达性分析

本文论述了分析道路可达性的两种不同方法,深入探讨了空间句法的原理、方法、软件和进一步应用的前景,对空间句法在城市道路网络规划方案评价等方面的应用进行了试验性的探讨。     

轨道交通对减少城市环境污染经济损失的作用

随着经济的发展，机动车尾气对于城市环境的危害已是公认的事实，但就对人类健康的具体影响少见阐述，其对环境危害究竞多大的定量分析并不清晰也不多见。此文试从环境工程学角度研究对此进行剖析。根据历年经济、交通数据，分析、预测中国城市经济和机动车交通发展的现状和趋势，发现中国城市机动车交通即将进入一个高速增长的爆发期，从而造成中国城市空气污染问题恶化，轨道交通的发展可以改善这一状况，减少因城市空气污染问题恶化而造成的巨大经济损失。     

板柱节点的抗冲切性能研究

在板柱结构体系中，由于楼板上没有梁的支撑，柱节点处只有板与柱连接，板的设计厚度又有局限性，因此板柱节点就成为板柱体系的薄弱环节，为有效提高板柱节点的抗冲切能力，采用SATWE和ANSYS两种有限元分析软件，分别对影响板柱节点抗冲切性能的几种因素进行了系统分析，得出了几种因素对板刚度影响的规律，依据这些规律，设计人员可以根据具体情况，采取合理的改进措施，避免由于措施不当，导致施工困难。     

地铁车辆运行平稳性测试

空气弹簧对地铁车辆运行平稳性影响较大，目前国内B型车部分采用国产部件，A型车主要采用进口的空气簧。文章介绍了国产与日本进口的空气簧，对车辆进行平稳性指标的影响及测试方法并对北京1号线地铁车辆运行平稳性进行了测试，分析了起动、中间运行和制动停车等不同运行阶段的平稳性情况，对比分析了装用2种空气弹簧车辆的运行平稳性结果，得出了2种空气弹簧具有相同减振效果均满足车辆运行平稳性要求的结论。     

关于交—直—交传动机车轮径偏差问题的探讨

本文主要探讨了交—直—交传动机车轮径偏差、异步牵引电动机转矩和电流偏差、轮周牵引力偏差以及电动机转差率之间的数量关系。给出的计算公式不要求知道牵引电动机的具体特性参数和供电电压及频率,适用于牵引电动机尚未设计出来前,对交—直—交传动机车的总体方案进行分析研究。文中还对上述偏差及牵引电动机转差率的数值提出了建议。     

论公元7世纪前华人向东南亚地区移动的特点

公元7世纪以前华人向东南亚地区的移动,虽然就单元行为而言是相当少的,不仅完全不能与同期中国国内人口的移动行为相比,也远远不能与7世纪后华人向东南亚地区移民(殖民)行为的情况相比,但由于我们划定的时间跨度较长,故而在数量总合上应该不会是太少的,应该是有一定的人口规模,并具有较广泛地域分布性的现象.在许多方面,这时期华人向东南亚地区的移动行为有着自己的历史特点.遗憾的是,目前确实少见有关的研究成果问世.我们不揣浅陋,以仅有的知识和粗浅的认识来尝试分析这个问题,不当之处,还请专家学者给予批评.