生物基可降解聚乳酸(PLA)沙障对沙丘表层沉积物粒度特征的影响

以吉兰泰盐湖北部流沙区铺设8 a的不同规格聚乳酸（PLA）沙障内沉积物为研究对象,利用激光衍射技术分析了沙丘表层0~3 cm沉积物粒度组成,计算并分析平均粒径、标准偏差等粒度参数,探讨了影响障内沉积物相对粗细的关键组分,分析PLA沙障的防沙效益。结果表明：PLA沙障内沉积物以细沙、中沙、极细沙为主。中沙、极细沙、细沙是障内沉积物的关键组分。PLA沙障的阻滞作用使得中沙、粗沙含量百分比升高,细颗粒含量百分比降低,障内沙粒分选性逐渐变差,峰态偏离正态分布,向负偏方向发展,频率分布曲线分布范围变宽,累积频率曲线变缓,表层颗粒组成趋于粗化。1 m×1 m规格PLA沙障内均以积沙为主;沙丘迎风坡和背风坡的2 m×2 m、3 m×3 m沙障内均为积沙状态,丘顶则为风蚀状态。综合考虑沙障铺设成本和防护效果,得出研究区域内2 m×2 m规格PLA沙障整体防沙效益最佳。     

Food gardens as important elements of urban agriculture: Spatio-developmental trends and future prospects for urban gardening in Czechia

The main research goals of the article are to explain the historical context of urban food gardens in Czechia, to describe the current spatial pattern of allotment gardens, and to introduce and analyse recent trends in urban gardening. The main method for achieving the first goal was a literature study. For the second goal, geographical mapping and analysis of data relating to the spatial distribution of allotment gardens were used. For the third goal, mapping together with analysis of semi-structured interviews carried out in community gardens in Prague were used. The analysis showed a strong tradition of urban agriculture and urban food gardening activities in Czechia. Both allotment gardens and newly emerged community gardens were concentrated mainly in the biggest cities and in areas with a rich industrial and mining tradition. This finding supports the significance of gardening as an important element of urban agriculture. However, uncertainty regarding land tenure and long-term sustainability were among the greatest obstacles for the future of allotment and community gardens. The authors’ main recommendations are that urban agriculture should be included as primary land use in sustainable planning and there should be broader community involvement in planning and decision-making processes.     

Immigrant groups and the local environment: socio-spatial differentiation in Czech metropolitan areas

The spatial distribution of immigrant groups is a more relevant topic now than ever before. While the study of this topic has a long tradition in the “traditional” immigration countries, it is rare in the very different context of Central and Eastern Europe, especially at the level of metropolitan areas. This study aims to address this gap by providing an analysis of the spatial distribution of various immigrant groups (defined by country of citizenship) in 17 Czech metropolitan areas, and its determinants. First, we characterize the specific situation of the Czech immigration system. Then we use cluster analysis to create a typology of neighbourhoods and compare the distribution of immigrant groups in each type of neighbourhood. Finally, we use regression analysis to examine which characteristics of the local environment are connected to concentrations of different immigrant groups. We show that the presence of foreigners remains associated with core urban areas. Some predominantly Western citizens act as gentrifiers, being associated with spacious pre-war apartments in prestigious inner-city areas, but there are also signs of suburbanization among more well-off immigrants to Czech metropolitan areas. We identify little evidence of ghettoization of immigrants into socially excluded areas.     

Changes in production potentials of rapeseed in the Yangtze River Basin of China under climate change: A multi-model ensemble approach

Rapeseed is one of the major oil crops in China and it is very sensitive to climate change. The Yangtze River Basin is the main rapeseed production area in China. Therefore, a better understanding of the impact of climate change on rapeseed production in the basin is of both scientific and practical importance to Chinese oil industry and food security. In this study, based on climate data from 5 General Circulation Models (GCMs) with 4 representative concentration pathways (RCPs) in 2011–2040 (2020s), 2041–2070 (2050s) and 2071–2100 (2080s), we assessed the changes in rapeseed production potential between the baseline climatology of 1981–2010 and the future climatology of the 2020s, 2050s, and 2080s, respectively. The key modelling tool – the AEZ model – was updated and validated based on the observation records of 10 representative sites in the basin. Our simulations revealed that: (1) the uncertainty of the impact of climate change on rapeseed production increases with time; (2) in the middle of this century (2050s), total rapeseed production would increase significantly; (3) the average production potential increase in the 2050s for the upper, middle and lower reaches of the Yangtze River Basin is 0.939, 1.639 and 0.339 million tons respectively; (4) areas showing most significant increases in production include southern Shaanxi, central and eastern Hubei, northern Hunan, central Anhui and eastern Jiangsu.     

大气环流客观分型在渤海海峡大风气候特征分析中的应用

应用Lamb-Jenkinson大气环流分型法对渤海海峡1979—2013年逐日海平面气压场进行大气环流客观分型,分析了渤海海峡大风天气与大气环流型的关系;以长岛气象站在渤海海峡大风天气中的指示作用为基础,分析了主要环流型下大风天气的气候特征。结果表明：渤海海峡大风天气以平直环流型为主,偏北型明显多于偏南型;春（夏）季是发生大风天气最多（少）的季节,以西南（SW）型出现频率最高,秋、冬季大风天气的环流型频率分布基本相同,均以偏北型为主;不同环流型下出现大风天气的概率及大风天气的气候特征也有明显不同。     

雷暴大风过程中对流层中低层动量通量和动能通量输送特征研究

2014年5月31日北京发生一次雷暴大风过程。以雷达资料同化结果为初始场,对此次过程进行高分辨率数值模拟。采用非静力平衡和非地转平衡的经向动量方程和质量权重动能方程,利用模拟资料,对雷暴大风过程中经向动量和质量权重动能进行收支分析,以此来研究雷暴过程中对流层中低层动量通量和动能通量输送特征,讨论地面大风的可能成因。分析结果表明,在对流层中低层,经向动量通量散度是影响经向动量局地变化的主要强迫项。雷暴系统后部的入流把中低层的经向动量倾斜向下输送,系统前部对流云区中低层的下沉气流也向下输送经向动量。这两支下传动量通量先后与近地面经向动量的水平通量汇合,向系统前沿输送经向动量。在北京西北部地形阻挡作用下,经向动量通量在系统前端近地面辐合,促进那里的经向动量局地增长,有利于增强那里的南风。质量动能收支的特征与经向动量收支类似,在近地面层质量动能的局地变化主要是由质量动能通量散度引起的。系统后部入流把中层质量动能向下传输到近地面层,然后与近地面质量动能的水平通量汇合,向系统前沿输送质量动能。相对来说,近地面层经向动量和质量动能的水平通量比下传通量更重要,这主要与低层较强的东南急流有关。     

基于GIS的沪汉蓉高铁线路暴雨灾害风险区划

通过收集整理沪汉蓉高铁沿线近13 a相关资料,采用层次分析法、专家打分法和加权综合评价法,通过暴雨灾害的危险性、孕灾环境的敏感性、承载体的易损性和防灾减灾能力等4类因子构建了沪汉蓉高铁线路暴雨灾害风险区划模型,绘制了沪汉蓉高铁线路暴雨灾害风险区划图。结果表明,沪汉蓉高铁线路暴雨灾害风险呈现西部高于东部特征,4个高风险区主要集中在武汉以西,分别为湖北天门—潜江段、宜昌西部—恩施东部、重庆东部、四川内江—资阳段,高风险区段与高铁沿线主要暴雨多发区中心位置基本一致,研究成果对沪汉蓉高铁沿线市县开展暴雨灾害防御工作具有较好的决策参考作用。     

“雪龙”号科考船在冰区航行的船体振动测量研究

船舶在冰区航行时,船体会受到多种类型激振力的作用而产生不同程度的结构振动。船体振动会对船体结构安全以及船上人员的正常工作产生不利影响。船体结构振动的现场测量可较为准确地分析船体振动的基本特性,确定船体振动与外界荷载因素的对应关系。在2015—2016年中国第32次南极科学考察过程中,对"雪龙"号极地科学考察船的冰激振动开展了现场测量。本研究对比了船体在无冰区和冰区航行过程中的船体振动变化,分析了船体在不同航速、冰厚以及不同破冰航行方式下的振动规律。测量结果表明:船体冰激振动随着航速和冰厚的增加而显著增大;在船体采用冲撞式破冰时横向振动最为明显,而在连续式破冰时,垂向振动最为明显。以上研究可为冰区航行中船体振动的现场监测技术提供有益参考,并有助于分析海冰对船体振动规律的影响。     

CIMISS中气象观测资料处理入库效率优化方法

气象资料种类多、海量、格式多样复杂,造成综合气象信息共享系统(CIMISS)巨大的处理压力。以高空L波段数据作为个例,进行详细的分析,在数据库表设计上,通过"键-要素"的拆分方式减少数据库冗余,建立合理的索引和分区提高数据表访问效率。在处理流程方面,通过简约化流程减少系统间消息交互和IO,从而优化系统的存储效率。同时简约流程中对比PRO*C和OCI两种入库方式,PRO*C简单高效便于开发,而OCI功能全面但相对复杂,通过比较两种入库方式的效率,系统采用PRO*C方式。高空L波段数据实际运行效果表明,平均28s完成一份数据的处理。对比高空探测数据的处理,简约流程比原流程入库更快。     

中国雷达强天气预警信息质量控制与集成应用

冰雹和龙卷等强对流天气容易产生严重气象灾害,而雷达可以为强对流天气提供高时效的监测信息。针对当前雷达业务系统仅提供单站预警,且强天气识别算法缺乏本地优化等问题,研究了全国雷达预警信息组网集成技术,为大范围监测中小尺度强对流天气提供及时高效的参考信息;通过对全国高空站3年0℃层高度资料的统计分析表明,雷达监测冰雹等算法的0℃层高度应在3~6km范围动态调整,提出了雷达强天气预警动态本地化等综合质量控制方法。通过质控前后统计分析表明,质量控制可以有效降低雷达预警的虚警率,虚警剔除率可达到95%以上;与雷电观测资料的检验结果显示,质控后的雷达预警信息与雷电分布具有较好的契合度。将基于上述组网集成与质量控制的综合技术应用于2016年6月23日盐城龙卷强天气监测,取得了较好的应用效果。