HVDC to Grow Rapidly

In the late 1880s, the war of the currents was waged by Nikola Tesla, who promoted AC current, and Thomas Edison, who promoted DC current. Ultimately, transmitting power over long distances with AC became the norm. This development was due to the ability to step up and step down the voltage through power transformers, which yielded a much lower cost of operation of AC over DC and led to the widespread acceptance of AC power transmission over DC. This could have spelled the end of DC transmission, but in the 1930s, through the use of mercury arc valves, it was shown that AC voltage could be transformed to higher levels of DC voltage.     

The Foreclosure Crisis,Foreclosed Properties,and Federal Policy: Some Implications for Housing and Community Development Planning

Problem: Foreclosures surged during the 2007 to 2009 national foreclosure crisis and federal policymakers failed to respond quickly and forcefully to the problem. The large numbers and geographic concentration of foreclosed properties have posed a particular problem for many planners.

Purpose: I aim to describe the intrametropolitan distribution of foreclosed properties at the zip code level, the often anemic or delayed federal policy response to rising foreclosures, and the potential effects of likely changes in federal policy and housing finance for metropolitan housing, development patterns, and local housing and community development planning.

Methods: I used archival research and secondary and media resources to document the federal response to the foreclosure crisis. I analyzed a proprietary data set to describe the problem of the accumulation of foreclosed properties across and within metropolitan areas.

Results and conclusions: Foreclosed properties were already accumulating in metropolitan areas with weak housing markets by 2006, but formerly hot markets such as Riverside, CA, Las Vegas, NV, and Phoenix, AZ, had many more by mid-2008. Within metropolitan areas, foreclosed properties were disproportionately concentrated in central city neighborhoods, although suburban zip codes with long commute times also had relatively high levels. The federal response to rapidly worsening foreclosures was faltering and timid. More conservative finance following the crisis will put downward pressure on housing consumption, potentially shifting demand to smaller homes. However, financing may be difficult or expensive to obtain for condominium buildings, and lenders and investors may shy away from less conventional projects, due partly to higher risk premiums.

Takeaway for practice: In the short run, local governments must confront the problems of foreclosed properties, especially when they are highly concentrated in certain neighborhoods. More conservative mortgage markets are likely to persist for some time, with potential impacts on housing demand. Planners should strive to diversify tax bases by promoting more diverse land use and housing patterns to make their communities more resilient in future crises. Federal policymakers may move toward greater mortgage market regulation, but this will be vigorously debated. Policymakers will also consider the ongoing federal role in secondary markets, without which long term stability is unlikely. Finally, Congress may extend the Community Reinvestment Act to nonbank financial institutions given the federal support they have received during the crisis.

Research support: None.     

青岛白沙湾片区污水干管施工设计经验

滨海浅滩地区污水干管改建工程,面临着埋深大、地质条件差、现状管线复杂等不利因素,在对青岛白沙湾片区污水干管施工方案设计时,根据不同地质情况,采用明开挖和顶管相结合的施工方法,在保证工程质量的前提下,实现投资节省、环境友好的目的。重点对开挖施工的支护方案和顶管施工的难点设计进行了阐述,为相似工程提供参考。     

两江重庆段沉积物中腐殖酸特性及其对荧蒽的吸附

从长江、嘉陵江(简称两江)重庆段的5个表层沉积物样品(JL1、JL2、YZ1、YZ2、YZ3)中提取腐殖酸,对其进行了化学组成分析和结构特性表征.结果表明,各样点的腐殖酸中元素含量比值(H/C值、O/C值、C/N值等)存在一定的差异.JL1、YZ3和YZ1样品中的腐殖酸具有较高的O/C值和H/C值,呈现明显的脂肪特性,而YZ2样品的芳香性特征相对明显;各样点腐殖酸的C/N值＞10,表明受藻类污染的潜势较低.傅里叶红外图谱结果表明,各样点腐殖酸的官能团结构组成相似度较高,均含有羧基、羟基、羰基等活性官能团,但官能团的含量存在差异.借助荧光光谱分析,进行腐殖酸对荧蒽的吸附特性试验以及吸附等温线修正Freundlich模型模拟,修正吸附系数(Kf')的大小顺序为:YZ2＞ JL2＞ YZ1＞YZ3＞ JL1,且吸附能力与腐殖酸的极性强弱、元素含量、活性官能团特征等具有一定的相关性;在连续多步解吸附试验中,相对于加标荧蒽的吸附量,各样点的解吸率为40.3％ ～74.8％.     

杨房沟水电站地下厂房围岩稳定分析

杨房沟水电站地下厂房是典型的大跨度、高边墙地下洞室群,工程区地质条件较复杂,高边墙及洞室间岩柱的稳定性是洞室设计的关键。根据地应力测试数据,采用边界位移条件回归方法,构造出厂区初始地应力场。采用FLAC3D软件对洞室群围岩稳定进行计算分析,获得洞周围岩变形与应力特征、塑性区分布及支护结构的受力状态,对地下厂房洞室群围岩稳定性做出评价,为洞室设计提供了科学依据与技术指导。     

深圳社区规划师制度的模式研究

随着城市化进程中原农村社区力量的崛起,城市规划开始关注和吸纳社区诉求,同时由于规划编制对象从新增建设用地转向存量建设用地,规划师的角色从进行物质规划的主体转向利益调节的主体,由此带动社区规划师的产生。基于此,研究论述了深圳社区规划师制度的制定背景、主要模式、挑战和问题,认为随着深圳的政府、市场和社会的力量进一步均衡化,基于社区利益诉求的社区规划师制度和市场驱动型的社区规划师制度将快速发展,政府主导的社区规划师制度将逐渐退居其次。研究最后还提出国内其他城市的社区规划师制度将沿着这一趋势演变的观点。     

冬季内区利用新风供冷案例分析

本文以北京某采用风机盘管+新风的空调系统的办公楼建筑为例,介绍了冬季内区利用新风供冷的空调系统的计算方法,空调风系统、水系统和排风系统的设计思路,内区加湿方式的选择,以及设计中需注意的儿点问题.     

Risk assessment for gas pipelines using fuzzy sets

Most gas pipelines have been buried for many years and it is hard to assess their safety. In some locations, gas pipeline breaks have resulted in severe economic and social consequences. The severity of such consequences increases with the number of people exposed. For these reasons, risk assessment for gas pipeline systems should consider both the prediction of damage occurrence and the estimation of the economic and social impacts. In this paper, a new measure denoted H. Index is introduced to assess the magnitude of gas accidents. In order to examine the correlation between the magnitude of accidents and the pipeline attributes, including the environment, fuzzy component analysis is developed. This paper presents a procedure based on linguistic variables to evaluate the main characteristics for each accident. Actual accidents data in Japan are used to illustrate the approach.     

北魏洛阳佛寺园林艺术探析

阐释了北魏洛阳佛寺园林的起源与发展历程、社会功能、构成要素及其艺术文化特征,总结了北魏洛阳佛寺园林的艺术成就,指出佛寺园林是古典园林的一个分支,公共属性突出,园林形态丰富,不仅能体现中华民族的文明和智慧,对当代景观设计也有借鉴意义。     

城市综合客运枢纽交通组织研究

以长沙市汽车南站枢纽为例,针对城市综合客运枢纽交通组织进行了研究,分析了枢纽的交通组成特性,基于冲突分离、人车分流的思想,分别设计了行人流线、机动车流线,为长沙新汽车南站的高效运行提供了借鉴。