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171.

This paper analyzes Hungary's export linkages of the interwar and Cold War periods using gravity model and historical analyses. Hungary is a useful example of former Soviet satellites because it combines relative political stability (since 1956) and experimentation with the New Economic Mechanism (NEM) during the 1970s and 1980s. Historical analysis reveals seven events since World War I that changed Hungary's trade patterns. Gravity model analysis for 1955, 1965, 1975, and 1985 shows the dramatic cleavage of the “Iron Curtain,” the effect of the NEM, and particularly strong and weak linkages for Hungarian trade that may result from historical legacies, complementarity, or specific political contacts.  相似文献   
172.
Nutrient and Chlorophyll-a (Chl-a) concentrations were investigated monthly along three transects extending from a mariculture area to open waters around the Zhangzi Island area from July to December 2009. The objective of this study is to illustrate food availability to the bottom-sowed scallop Patinopecten yessoensis under the influences of the Yellow Sea Cold Water Mass (YSCWM), freshwater input and feedbacks of cultivated scallops. Significant thermal stratification was present in open waters from July to October, and salinity decreased in July and August in surface layers in the mariculture area. Nutrient concentrations increased with depth in both areas in summer, but were similar through water column in November and December. On average, nutrient increased from summer to autumn in all components except ammonia. Nutrient concentrations lower than the minimum thresholds for phytoplankton growth were present only in upper layers in summer, but stoichiometric nitrogen limitation existed in the entire investigation period. Column-averaged Chl-a concentration was lower in open waters than in mariculture area in all months. It increased significantly in mariculture area in August and October, and was less variable in open waters. Our results show that nutrients limitation to phytoplankton growth is present mainly in upper layer in association with stratification caused by YSCWM in summer. Freshwater input and upwelling of nutrients accumulated in YSCWM can stimulate phytoplankton production in mariculture area. Farming activities may change stoichiometric nutrient ratios but have less influence on Chl-a concentration.  相似文献   
173.
This study uses a 30-year time series of standardized bottom trawl survey data (1982–2011) from the eastern Bering Sea shelf to model patterns of summer spatial distribution for various bottom fishes and crabs in response to changes in the areal extent of the cold pool, time lag between surveys, and fluctuations in population abundance. This investigation is the first to include data for the 2006–2010 cold period and to use between-year comparisons of local and shelf-wide spatial indices to test specific responses to three different isothermal boundaries within the cold pool. Distributional shifts in population varied considerably among species and directional vectors for some species were greater in magnitude to the east or west than to the north or south; however, in general, eastern Bering Sea shelf populations shifted southward in response to the increasing cold pool size, and after accounting for differences in temperature and population abundance, there was still a temporal northward shift in populations over the last three decades despite the recent cooling trend. Model results for local and shelf-wide indices showed that survey time lag and cold pool extent had a greater effect on spatial distribution than population abundance, suggesting that density-independent mechanisms play a major role in shaping distribution patterns on the eastern Bering Sea shelf. The area enclosed by the 1 °C isotherm most commonly affects both local and shelf-wide spatial indices suggesting that 1 °C is a more important boundary for describing temperature preferences of eastern Bering Sea bottom fishes and crabs than is the 2 °C isotherm used for designating the physical boundary for the cold pool.  相似文献   
174.
一次东北冷涡暴雨的水汽输送特征和位涡分析   总被引:1,自引:0,他引:1  
通过对2010年7月27~29日吉林省一次较大范围的冷涡暴雨、大暴雨过程进行诊断分析,建立了此类暴雨的天气概念模型:200 hPa呈现“两脊一槽”型,高空急流呈辐散状位于吉林省上空,急流中心最大风速≥60 m/s;500 hPa东北冷涡强烈发展,鄂海阻高稳定维持是此次强降水发生的重要天气系统,中心最大风速≥20 m/s的偏西风急流带横穿吉林省中部;850 hPa风速≥12 m/s的3条急流带在吉林省中东部地区交汇,形成低层辐合、高层辐散的气旋性涡度柱,较强的垂直上升气柱一直向上伸展到500 hPa附近,极有利于对流的发展和强降水的维持。通过计算整层水汽通量与吉林省逐6 h平均降水量的相关矢量场,结果表明:偏西、偏南及偏北3条水汽通道在吉林省中南部汇集是此次强降水发生的重要条件,暴雨落区与整层水汽通量汇合区密切相关,水汽输送以经向(南北方)水汽流入为主。暴雨期间具有较好的动力、热力及能量条件,特别是湿对流有效位能明显偏强,强降水出现在对流有效位能 (CAPE)值由极大值开始下降的过程中。干侵入是激发冷涡发生、发展的动力条件之一,≥1 PVU(位涡单位)的高位涡舌在下降的过程中,同时南移,与中部地区强降水落区自北向南移动相吻合。  相似文献   
175.
利用NECP再分析资料、卫星云图资料、新一代天气雷达资料及实况观测资料对2010年4月12-13日一次东北低涡产生的黑龙江省暴雪天气过程进行分析,详细讨论了此次暴雪的发生机制及天气特点。此次降雪过程由地面气旋北上引发,高空低涡前部东风暖平流和槽后冷平流相遇形成暖锋锋生,低涡东北部产生暴雪。低空急流对水汽的输送作用和低层较强的辐合上升运动为此次降雪过程提供增强机制。云系的发展、移动与降雪有较好的对应关系,较大降雪出现在逗点云系顶部。  相似文献   
176.
李江海  洛怡  宋珏琛 《地质科学》2019,54(2):305-318
克拉通盆地是所有盆地类型中最稳定、最长寿的盆地,也是地壳和地幔长期垂向变形最重要的地质记录。地史上面积最大的克拉通盆地(超级克拉通盆地)原型面积常超过200×10^4 km^2,对探讨克拉通盆地成因演化具有重要的代表性意义。目前世界各地的研究可以识别出10余个不同时期的超级克拉通盆地。本文根据超级克拉通盆地基底性质、盆地发育的超大陆构造演化背景及其构造特征,将超级克拉通盆地划分为A型盆地和B型盆地两种类型,它们分别以西西伯利亚盆地和刚果盆地为代表。A型盆地形成于超大陆裂解之前至初始裂解的背景下,基底为前期造山带,为短波长盆地。盆地形态不规则性强,内部均一性相对较低,克拉通盆地边缘可能渐变为弧后盆地或前陆盆地。B型盆地形成于超大陆裂解末期(即下一个超大陆汇聚之初),基底为古克拉通陆块,为长波长盆地,盆地多呈对称的宽缓碟型。A型盆地处于短期活动的热地幔柱之上,伴随早期裂谷作用及其随后的热衰减成盆;B型盆地常处于热点和地貌高地之间的部位,盆地沉降长期受地幔持续缓慢下沉控制。  相似文献   
177.
The air pollutant emissions of the ships at port represent a small percentage of the overall emissions from shipping however they are concentrated in a small area. In Mytilene, Lesvos, the port is located within the city limits, resulting in air pollution, congestion and noise, especially during the tourist season. The aim of this study is to estimate the quantities of particulate matter and CO2 emitted by ships in the port of Mytilene and to explore the potential of shore side electricity to reduce the emissions. The emissions were estimated using the bottom–up methodology, based on the activity of the ships in the port (berthing, maneuvering). Simulation of renewable energy sources was made using Homer Energy microgrid simulation software. The results showed that between the 10th and 20th of August 2012, there were 40 calls of passenger ships, tankers and bulk carriers in the port of Mytilene, emitting 441 kg of PM10 and 282 metric tonnes of CO2. About 63% of PM10 and 77% of CO2 were emitted at the berthing phase and the remaining during the maneuvering. These emissions could be reduced by providing electricity to the ships from a hybrid renewable energy system with wind turbines and photovoltaics, connected to the grid. Simulations showed that the total energy requirements of the ships in the port of Mytilene could be covered by four 1.5 MW wind turbines combined with a 5 MW photovoltaics. With this configuration, renewable energy will exceed the ships' electricity needs for most of the time in order not to increase the power station's load. The excess energy could be fed to the islands' grid, so a costly battery storage system is not necessary to handle the variations of alternative energy. In this way, a considerable reduction of the CO2 and PM10 emissions by the ships in the port occurs, providing a viable solution for a cleaner and healthier environment.  相似文献   
178.
利用常规观测、自动站逐时降水量、乌鲁木齐市风廓线雷达及ECMWF1°×1°再分析等资料,对2018年10月17—18日乌鲁木齐雨夹雪转大暴雪过程进行分析。结果表明,大暴雪是在低空西北气流与中高层西南急流叠加并维持的有利环流背景下,由700~850 hPa风切变、风速辐合、地面冷锋及地形强迫抬升等多尺度系统共同作用造成的。强降雪时雷达探测高度维持较高达7500 m,随着降雪结束探测高度明显降低。水平风场表明低空西北急流与中高层偏南急流形成的垂直风切变廓线的维持,是强降雪持续的动力条件。大气折射率结构常数C_n~2、垂直速度的大小与雨雪的开始、结束时间有较好的对应关系,且低层较强偏北风与C_n~2大值区相对应,降雪时低层垂直速度为0.8~1.2 m·s~(-1),雨或雨夹雪时垂直速度为1.8~2.5 m·s~(-1)。因此,水平风向风速、C_n~2和垂直速度的垂直变化对暴雪短临预报有很好的参考价值。  相似文献   
179.
对广东目前推广的 4个香蕉良种以及粉蕉和大蕉进行切片显微观察 ,并结合低温处理的电导率测定 ,结果表明 ,香蕉叶片组织细胞结构紧密度 (CTR值 )与品种的耐寒性密切相关 ,且具有相对的稳定性 ,可作为香蕉耐寒性的鉴定指标。供试品种耐寒力强弱依次为粉蕉、大蕉、威廉斯 (8818)、“巴西”、“93- 1”、广东二号 (6 3- 1)。  相似文献   
180.
In this paper, data obtained from a 164 m and a195 m meteorological tower in the northern suburb ofNanjing have been used to estimate and analyzetime-space distributions for velocity spectra andscales of multi-scaling turbulence during thepassages of two cold fronts. Results show that anon-precipitating weak cold front and aprecipitating cold front were clearly revealed bytheir wind field structures. The frontal passageinfluenced all meteorological variables over aperiod of 18–24 hours for the former, and a longerperiod of 44–56 hours for the latter. During these periods there occurred gust surges and eddymotions of various meso- and micro-scales with periodsof 3–4 hours and 1–20 minutes respectively. In the inertialsubrange Kolmogorov's -2/3 power law for thevelocity spectrum is partly distorted and theturbulence in the atmospheric boundary layer is not isotropic.  相似文献   
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