Spatial Disparity of Slope Farmland and Food Security in Three Gorges Area

As an important measure of ecoenvironmental construction, the process of de-farming in slope farmland is being undertaken gradually in the whole China. Meanwhile, the problem of reducing in food yield in de-farming areas can not be neglected any more. It is especially the case in areas with concentrated slope farmland and inconvenient transportation. In this paper, we analyze the causes of hidden troubles in food security, and the spatial relationship between farmland and slope farmland in the reservoir area of Three Gorges, and unveil the spatial disparity of contradictions between food supply and demand. Finally, combining the accessibility of areas, three different spatial types of food security, food security area, food alert area, and food crisis area, are divided.     

建筑用途的城市职住空间组织特征研究

针对现有职住空间关系的研究难以在微观维度上有效促进大城市职住功能空间的均衡发展以及规划政策与现状发展存在的时序错位问题,该文以北京市为例,从房屋建筑使用用途的角度切入,运用空间自相关分析模型、热点分析模型和职住用地比三个评价方法,同时借用ArcGIS软件平台进行空间分析与可视化表达,探究北京职住空间在乡镇尺度下的组织特征。研究发现:北京市职住空间表现为聚类分布的空间格局特征,以首都功能核心区为中心,大致呈现出环状圈层分布,北京市职住空间的“热点区”在空间分布上存在差异,而“冷点区”在空间分布上基本相同,职住空间关系存在失衡,与规划目标存在一定的偏差。提出的研究方法从微观维度分析了城市职住空间的组织特征,促进了城市规划与发展时序的有效结合,可在特大城市的职住空间关系的研究中进行推广应用。     

Influence of dietary n-3 LC-PUFA on growth,nutritional composition and immune function in marine fish Sebastiscus marmoratus

A 60-day feeding experiment was conducted to investigate the influence of dietary omega-3 long-chain polyunsaturated fatty acids(n-3 LC-PUFA) on growth, nutritional composition and immune function of marine fish Sebastiscus marmoratus. Five diets containing 3.6, 10.2, 18.2, 26.5, or 37.0 g/kg n-3 LC-PUFA were prepared. The results reveal significant influences of dietary n-3 LC-PUFA on the final weight, weight gain, specific growth rate, feed conversion ratio, and condition factor. As dietary n-3 LCPUFA increased, weight gain and specific growth rate increased and were significantly higher in groups fed 18.2, 26.5 and 37.0 g/kg than in groups fed 3.6 and 10.2 g/kg( P 0.05); there was no significant difference between groups fed 18.2, 26.5, or 37.0 g/kg( P 0.05). With increasing dietary n-3 LC-PUFA, eicosapentaenoic acid and docosahexenoic acid content in muscle and liver increased significantly, immunoglobulin class M content gradually increased from 9.1 to 14.8 μg/L, and lysozyme activity content increased from 1355 to 2268 U/mL. Broken line model analysis according to weight gain indicated that a dietary n-3 LC-PUFA level of 18.2 g/kg is essential for normal growth at a fat level of 125 g/kg. Therefore, appropriate dietary n-3 LC-PUFA not only promote growth and improve the n-3 LC-PUFA content, but also enhance immune function in S. marmoratus.     

A Case Study of the November 2012 Mixed Rain-Snow Storm over North China

A mixed rain-snow storm associated with a strong burst of cold air and development of an extratropical cyclone occurred over North China from 3 to 5 November 2012.This early snowfall event was characterized by a dramatic drop in temperature,strong winds,high precipitation intensity,broad spatial extent,and coexistence of multi-phase precipitating hydrometeors.This study investigates the multi-scale interactions between the large-scale circulation background and the synoptic-scale weather systems associated with the storm.The results are as follows.（1） The Arctic Oscillation （AO） had been in its negative phase long before the event,leading to southward advection of cold air into North China in advance of the storm.（2）The large-scale atmospheric circulation experienced a decreased number of long waves upstream of North China prior to the storm,resulting in reduced wave velocity and an almost stagnant low pressure system （extratropical cyclone） over North China.（3） An Ω-shaped blocking high over East Asia and the western Pacific obstructed the eastward movement of an upstream trough,allowing the corresponding surface cyclone to stabilize and persist over Beijing and its neighboring areas.This blocking high was a major factor in making this event a historically most severe precipitation event in autumn in Beijing for the past 60 years.（4） Baroclinic instability at lower levels gave rise to rapid development of the cyclone under the classical ＂second type＂ development mechanism for extratropical cyclones.（5） Moisture originated from the Yellow Sea entered the slowly-moving cyclone in a steady stream,creating fairly favorable water vapor supply for the heavy rainfall-snowfall,especially during the later stage of the cyclone development.（6） Moisture transport and frontal lifting triggered low-level instability and updrafts.Intensification of the front enhanced the vertical wind shear,causing conditional symmetric instability （CSI） to expand upward within the unstable lower troposphere,and to eventually gear into the CSI region of the upper troposphere,which facilitated the upward development of low-level updrafts.     

近50年来乌兰乌苏多种天气事件变化特征研究

利用乌兰乌苏镇1964～2012年的气象资料,选取逐年平均气温、极端最高气温、极端最低气温、大风、雷暴、沙尘暴、沙尘天气及大雾、轻雾天气出现的天数作为分析对象,运用3年移动平均法、回归分析法、非参数检验方法的Mann-Kendall趋势检验和突变检验法以及小波分析法,进行了多种天气事件的年纪变化趋势分析.结果表明：（1）大雾天气的发生日数呈增加趋势,沙尘天气、沙尘暴天气、轻雾天气、大风天气和雷暴天气的发生日数都呈减少趋势,其中大风天气发生日数减少趋势最为明显.（2）平均气温、年极端最高气温、年极端最低气温、大雾天气、轻雾天气、沙尘暴天气、雷暴天气和沙尘天气在研究时段都出现了突变,且平均气温、轻雾天气、沙尘天气和雷暴天气在突变之后不久都达到了极显著的上升或者下降变化趋势.（3）平均气温、年极端最低气温、年极端最高气温、大雾天气、雷暴天气和大风天气有明显的周期性,但是不同的气象要素周期性长短是不同的,沙尘、沙尘暴和轻雾天气则没有明显的周期性.     

浅谈长跨度桥梁的雷电防护

介绍了现代化建设中长跨度桥梁直击雷和感应雷防护工程的设计技术和施工要素,重点说明了电源部分和信号部分防感应雷的实施方案,并提出了相应的施工要点和要求。     

1880-2006年中国夏季雨带类型的年代际变化特征

 利用1880-2006年中国东部地区夏季降水量及1951-2006年中国160个站夏季降水量和北半球大气环流资料,在夏季降水分型的基础上,研究了夏季雨型的年代际变化规律,分析了夏季各类雨型所对应的北半球500 hPa环流场的主要特征。结果表明：东部季风区和西部区存在着20～40 a左右的年代际振荡趋势,东北区则表现为明显的15 a左右的年代际变化特点;东部季风区四类雨型东亚大气环流差异显著,西部区二类雨型和东北区二类雨型欧亚大气环流的配置基本都相反。     

青海玛多7.4级地震极震区震灾调查及分析

2021年5月22日2时4分,青海省玛多县发生7.4级地震,距震中26 km的野马滩大桥及周边区域为此次地震极震区（地震烈度Ⅹ度,面积约69 km2）,受损尤为严重。桥梁表现为落梁式破坏,房屋不同程度受损。对极震区内野马滩大桥及周边房屋进行实地调查与震灾分析,并提出灾后重建及震灾防御相关建议,包括组织专业人员进行灾区房屋安全鉴定,建议牧民居住建筑采用轻钢式结构,建议原地重建野马滩大桥并增加限位装置及连梁装置。     

正断层的阶区构造及生长机制：以狼山山前断层带为例

正断层带在生长过程中内部发育有阶区构造,阶区在正断层的相互作用、连接过程中起重要控制作用,同时阶区还影响地表径流和沉积盆地的发展、流体的运移和圈闭的形成。位于内蒙古河套断陷西缘的狼山山前断裂是晚新生代以来持续活动的大型正断层系统,断层带内部发育有不同类型的阶区构造。识别出了两种类型阶区的连接方式,一种是两条平行断层之间的斜坡从"软连接"到"硬连接"的演化过程;另一种是楔状阶区通过一条断层向另一条断层扩展的方式连接产生。基岩中的先存构造要素控制并影响山前正断层的展布方位及阶区的形态:基底内部NNE向糜棱面理控制山前断层带的走向,早期向SE倾斜的逆冲断层面被正断层局部利用。沿断层倾向方向,山前正断层逐渐向盆地方向扩展,最新活动的断层位于盆地边缘甚至盆地内部;沿断层走向方向,狼山山前正断层逐渐向南西侧扩展。     

土地整治与乡村振兴——土地利用多功能性视角

长期以来乡村土地利用功能的供需不平衡是造成乡村问题的主要原因之一。论文基于土地利用多功能性视角,以“供给—需求”“要素—结构—功能”为主线,阐释了农村土地整治与乡村振兴的互馈关系,探讨了如何通过农村土地整治实现乡村土地利用功能的供需平衡,进而促进乡村振兴。研究结果如下：① 综合土地整治是一种多功能的土地利用方式,是当前解决乡村问题、促进乡村振兴的重要手段,其本质是从以经济效益为主的生产主义向兼顾社会、经济、环境等的非生产主义的转变。② 乡村土地利用具有生产、生活、生态、文化等4种主要功能,满足乡村振兴在经济、社会、环境、文化等方面的需求,其中生产功能分为农业、商业、工业生产功能,生活功能分为居住、就业和公共服务功能。③ 农村土地整治沿整合土地利用要素、重组土地利用结构、优化土地利用功能的路径,从供给侧因地制宜地平衡乡村发展对土地利用多功能的需求。④ 今后,农村土地整治与乡村振兴的研究应该考虑不同空间尺度下土地整治对于乡村振兴的作用机制与模式,定量分析土地整治影响下土地利用的多功能供给以及不同类型乡村发展对土地利用功能的需求,从而为土地利用和乡村振兴规划的制定和实施提供科学依据。