Assessment of the maximum possible liquid superheat during flashing leak flow

During the discharge of flashing liquids through leaks due to abrupt depressurization a transient thermodynamic non-equilibrium in the form of a boiling delay in the superheated liquid flow can occur. As a consequence the actual mass flow quality is smaller than calculated under the assumption of an immediate adjustment of the thermodynamic equilibrium between the phases. For the prediction of the leak mass flow for a given pressure difference the magnitude of this self-adjusting mass flow quality is needed.

Most of the models cited in the literature include only the equilibrium mass quality as limiting quantity and ignore further effects as that of the depressurization velocity or the mean nucleus distance. For the assessment of the maximum possible liquid superheat during flashing only the conduction heat transfer from a stagnant liquid to the bubble surface is used to describe the bubble growth.

The sub-model for the bubble growth due to expansion and mass transfer necessary for the global prediction of the transient thermodynamic non-equilibrium in flashing liquids was validated using bubble radii measured by Hooper et al. [Bubble growth and pressure relationship in the flashing of superheated water. Technical publication 6904, Mechanical Engineering Department, University of Toronto, 1969] for the case of a sudden depressurization of initially saturated water. On this basis the calculated time-dependent temperature field, the actual mass quality, the mean liquid temperature and, in comparison to the corresponding values based on the assumption of immediate thermodynamic equilibrium, the maximum possible liquid superheat are predicted.     

地震的社会经济影响

在查阅前人研究成果的基础上,分析了地震造成社会灾害严重、影响地区经济发展的现象,认为地震灾害对一个地区所造成的影响程度与该地区的承灾力有关,并影响地区经济的可持续发展.     

移栽期变化对黑龙江省水稻低温冷害的影响——以2002年为例

针对影响黑龙江省水稻生产的低温冷害问题,利用黑龙江省水稻主要种植区域10个农业气象观测站1999-2004年每年5-9月的水稻生长观测数据和逐日平均温度数据,运用统计方法建立了产量构成与温度指标的关系方程,并结合黑龙江省2002年逐日平均温度格点化数据,对3个不同移栽日期情况下低温冷害的发生情况进行了分析。结果显示:2002年的低温冷害在黑龙江中部最严重,东部次之,西部受害最轻;北部地区受害面积和冷害损失比南部地区更大;在3个移栽日期中,随着移栽日期的推后,水稻产量有5%～11%的不同程度的减少,冷害损失逐渐增大,即按时间5月中旬—5月下旬—6月初依次递增。     

中国环境质量拐点:基于EKC的实证判断

促进环境质量改善是"十三五"时期实现绿色发展和最终全面建成小康社会的重要目标和任务。随着经济进入新常态和环境治理政策的强势推进,中国环境质量是否已经跨越峰值和进入持续改善的通道?本文基于环境库兹涅茨曲线这一理论工具,依据环境统计数据和国际经验事实判断中国是否到达环境库兹涅茨曲线的拐点和具备促使环境质量持续改善的经济特征。首先,应用中国各省份1998—2013年的面板数据,对人均收入水平与主要大气污染物排放的关系进行回归拟合发现,人均烟粉尘排放自1998年以来持续下降,人均二氧化硫、氮氧化物排放均在"十二五"中前期到达峰值。大部分东部省份已经越过环境库兹涅茨曲线的拐点,但环境质量改善仍然缓慢。多数中部省份处于峰值阶段,而西部省份大都处于经济增长与环境质量恶化的矛盾阶段。其次,基于污染物排放的驱动因素框架,将中国当前的经济特征与美、日、韩三国跨越环境库兹涅茨曲线拐点的经验进行比较,结论表明中国目前已基本具备了跨越环境库兹涅茨曲线拐点的经济驱动条件,但是相对滞后的城镇化进程将会导致污染物排放峰值的扁平化和波动性。以主要污染物排放在2014年的基础上削减30%—40%作为环境质量全面改善的转折点判断,中国环境质量将在2025年左右趋于全面改善。最后,为了促进环境质量全面改善,认为应该根据各地区经济发展与环境污染形势的不同,实施差别化环境治理政策。同时积极防范新一轮城镇化过程中的环境风险,进一步强化区域环境污染的协同治理。     

Discussing why population growth is still ignored or denied

Due to a number of factors outlined in this article, the issue of population growth is excluded from the sustainability discussion. In this article, we explore some of the ethical presumptions that underlie the issues linking population growth and sustainability. Critics argue that action to address population creates social and economic segregation, and portray overpopulation concerns as being “anti-poor,” “anti-developing country,” or even “antihuman.” Yet, de-linking demographic factors from sustainability concerns ignores significant global realities and trends, such as the ecological limits of the Earth, the welfare and long-term livelihood of the most vulnerable groups, future prospects of humanity, as well as the ecosystems that support society.     

基于面板数据的研发投入对区域经济增长影响分析

利用长江经济带110个地市1990~2013年RD投入与经济增长水平的相关面板数据,通过单位根检验、协整性检验和面板数据模型,对RD经费投入和人员投入与区域经济增长的影响进行了分析。结果表明:1长江经济带各市的经济增长与RD投入存在长期稳定的关系,RD短期投入对区域经济增长的影响则存在着一定的滞后效应;2RD人员投入产出弹性高于RD经费投入,说明区域经济增长对RD人员的依赖性更大;3RD投入表现出东部地区高于中部地区,中部地区高于西部地区,但RD投入对区域经济增长的影响则表现出中西部大于东部的现象,造成这一现象的原因在于所处发展阶段的不同和东中西区域经济特征不同。最后,从加大RD经费投入强度、制定RD投入中长期计划等方面提出了促进区域经济增长的建议。     

鼠李糖脂洗脱氯丹和灭蚁灵污染场地土壤的工艺参数

优化了鼠李糖脂洗脱氯丹、灭蚁灵污染土壤的工艺条件,为开展有机氯农药污染场地土壤洗脱修复工程实践提供科学依据和技术参数。实验结果表明,随着洗脱剂———鼠李糖脂浓度的增加,氯丹和灭蚁灵的洗脱量呈现先增加后降低的趋势;洗脱时间和液固比对洗脱效果的影响趋势与浓度相同;在0~120 r/min范围内,氯丹和灭蚁灵洗脱量随着搅拌速度的增加而增大,80、120和200 r/min的洗脱量间差异不显著;单次洗脱量随洗脱次数的增加而降低,累计洗脱量则逐渐增大。综上所述,氯丹、灭蚁灵污染场地土壤鼠李糖脂洗脱的适宜工艺参数为鼠李糖浓度10 mmol/L,搅拌速度80 r/min,固液比1∶10,洗脱时间20 min,洗脱3次。     

The implementation of a measurement system for brushless DC motor parameters

Most of the energy conversion in industrial devices and equipment is completed by the motor. The acquirement of motor parameters becomes very important for designing the motor drives. The aim of this paper is to design and implement a motor measurement system. Through the processing of an Advanced RISC Machines (ARM) microcontroller, the various parameters of motors such as input voltage, input current, input power, motor speed, and motor torque can be obtained. Consequently, the torque constant, load torque, viscous friction, and the inertia of the motor are calculated and achieved. The motor parameters can be commanded and displayed in the designed human interface of a PC via USB communication. The hardware system designed in this system includes an ARM microcontroller, an inverter, a voltage sensor, a current sensor, a torque sensor, and power supply. The software programming is developed under the Visual Studio 2012 environment development platform using the C language. Finally, the prototype of the motor measurement system is completed and verified. The experimental results for the motor parameters and torque/speed characteristic are demonstrated and show the feasibility of the complete designed system.     

资源产业空间集聚与区域经济增长:“资源诅咒”效应实证

针对"资源诅咒"研究中自然资源度量指标选取存在的科学性问题,利用资源产业空间集聚代替自然资源丰裕度和资源产业依赖度作为自然资源丰裕程度的解释变量。首先,在Krugman空间基尼系数的基础上,构建适用于测度资源产业空间集聚的计算公式,基于我国30个省(区、市)层面的数据,量化1999—2013年间资源产业的空间集聚程度,分析其排名情况和分布格局。研究显示:我国有15个省(区、市)存在资源产业空间集聚现象,这些地区大多位于长江以北,且均为自然资源富集地区。其次,构建经济增长计量模型,选取存在资源产业空间集聚现象的省(区、市)作为样本空间,并采用多种计量分析和检验方法考察资源产业空间集聚度与区域经济增长之间的直接和间接关系,分析"资源诅咒"的传导机制。研究显示:1在模型整体估计中,资源产业空间集聚的系数符号均为负,且在5%的水平上显著,说明资源产业空间集聚与区域经济增长间的关系呈现负相关,符合"资源诅咒"的基本假设。2在模型分步估计中,人力资本投资、技术创新投入和制造业发展与区域经济增长正相关,符合经典经济增长理论的逻辑关系;物质资本投资与区域经济增长负相关,可能是由于当地经济主体的消费跨期替代弹性较小,导致物质资本投资对经济增长的直接增益效应小于其对社会人力资本积累的负向效应,进而阻碍区域经济增长;政府干涉程度越高越不利于经济增长。根据研究结果,建议应明确市场调节为主、政府调控为辅的导向机制,进一步提升资源产业空间集聚程度,强化行业人员素质与技术水平匹配,逐步提高自然资源生产和利用效率,从而实现加快地区经济转型,有效促进经济可持续发展的全面提升。     

Assessing local planning capacity to promote environmentally sustainable residential development

Smart growth and sustainability planning have, in recent years, become central issues in planning discourse. Scholars have argued that planning capacity at the local government level is critical for smart growth planning, and that planners have a fundamental role to play in advancing local and regional sustainability. In this paper, we investigate the extent to which local planning capacity enables communities to promote more sustainable, smart growth residential development. Based on a 2013 survey of 38 county and 53 municipal governments in the state of Wisconsin, USA, this study finds that the majority of the sample communities have permitted residential developments characterized as transit-oriented, New Urbanist, mixed use, infill developments, or conservation subdivisions as alternatives to low-density, automobile-dependent conventional developments. The study also finds that jurisdictions with higher planning capacities are more likely to overcome significant barriers to more sustainable residential development.