Laboratory scale analysis of the influence of different heat transfer mechanisms on liquid nitrogen vaporization rate

The prediction of the potential hazards associated to accidental liquefied natural gas (LNG) spills has motivated a number of different studies including experimental and numerical approaches. Most of these studies focus on dispersion predictions, however there is limited information regarding source term of it: liquid spill and vaporization. There is a need of further improvements on the understanding of these phenomena and the quantification of the most important parameters that can affect them.The vaporization of cryogenic liquids is governed by the heat transfer phenomena including conduction, convection and thermal radiation mechanisms. The present work investigates the contribution of each of these heat transfer modes to the vaporization rate of cryogenic liquid nitrogen (LN₂) contained in a Dewar flask using well controlled and instrumented laboratory scale experiments. LN₂ vaporization rate was measured with individually controllable contributions from convective (generated by an electric fan) and thermal radiative (generated by light bulb) heat transfer in the presence of a baseline conductive heat transfer rate.In both cases of convection and radiation analysis the experimental study showed that they can play a significant role in the vaporization rate of LN₂. It was observed that the radiative heat absorbed by the LN₂ during the vaporization experiment represents only 50%–65% of the incident radiation that would reach the LN₂ pool surface if no vapour was present. Convective heat transfer generated by the fan was shown to have had the most significant contribution to the total heat transfer. As expected, this contribution was significantly higher than the one from bulb radiation. The experimental data also showed that the liquid level in the Dewar play a key role in the resulting amount of convective heat transfer. This could be attributed to the fact that lower liquid level the side walls of the Dewar were high enough to hold a layer of vapour and limit air motion directly above the liquid surface, thus limiting the heat transfer by convection.     

Assessment of Residential Rain Barrel Water Quality and Use in Cincinnati,Ohio1

The collection, storage, and reuse of rainwater collected in rain barrels from urban rooftop areas assists municipalities in achieving stormwater management objectives and in some areas also serves as an adjunct resource for domestic water supplies. In this study, rainwater reuse and levels of select microbial indicators were monitored for six residential rain barrels located in the Shepherd Creek watershed of Cincinnati, Ohio. Water from rain barrels typically had poor microbial quality and was used for watering indoor and outdoor plants. Rain barrel water chemistry was slightly acidic, exhibited wide ranges in conductivity, turbidity, and total organic carbon (TOC) concentrations and gave no evidence of the presence of cyanobacterial microcystin toxins. Selected microbial water‐quality indicators indicated that counts of total coliform and enterococci were consistently above U.S. Environmental Protection Agency standards for secondary recreational contact water‐quality standards. Residential rain barrels can provide water appropriate for low‐contact reuses (such as plant watering), although there may be transient periods of high levels of indicator bacteria in the collected water.     

Using Collaborative Technology in Environmental Strategy Development

This viewpoint explores, through a case study in Malawi, the application of collaborative technology tools to support National Environmental Strategy Development initiatives with the public and private sectors in Africa. A particular type of groupware, Group Support Systems, is introduced as a technology and approach that enables large groups of stakeholders to be involved in efficient and effective decision making. It helped the different ministries, community leaders, the private sector, NGOs, and different donors to find new and challenging opportunities for collaboration. The results of the case study show how an environmental strategy, including a prioritised plan of action, was developed and presented to the Ministry within three days. The most important lessons are identified. Participants to the presentation of the paper will be given hands-on experience using these tools.     

长株潭一体化中行政区划手段和非行政区划手段研究

长株潭地区是湖南省内以长沙为核心包括株洲、湘潭的一个典型的城市群，它在区域经济协调发展的取得了一系列重大成绩，但矛盾和问题也有不少。究其原因，主要是在“行政区经济”运行下区域发展所暴露出来的问题。本文在行政区经济还将长期存在的基本事实的基础上。从发挥其正面效应．削弱其负面效应着手．针对长株潭一体化中存在的主要问题。提出用行政区划手段和非行政区划手段来进行协调。并提出一系列解决问题措施和设想。     

Foraging guilds of North American birds

We propose a foraging guild classification for North American inland, coastal, and pelagic birds. This classification uses a three-part identification for each guild—major food, feeding substrate, and foraging technique—to classify 672 species of birds in both the breeding and nonbreeding seasons. We have attempted to group species that use similar resources in similar ways. Researchers have identified foraging guilds generally by examining species distributions along one or more defined environmental axes. Such studies frequently result in species with several guild designations. While the continuance of these studies is important, to accurately describe species' functional roles, managers need methods to consider many species simultaneously when trying to determine the impacts of habitat alteration. Thus, we present an avian foraging classification as a starting point for further discussion to aid those faced with the task of describing community effects of habitat change.     

The Precautionary Principle for Environmental Management: A Defensive-expenditure Application

The Precautionary Principle has emerged in response to the need for an effective method for dealing with risks and uncertainties in environmental management. In essence, the Principle requires action to prevent serious and irreversible damage even before harm can be scientifically demonstrated or economically assessed. Proponents argue that the Principle should be applied in situations where both the probability and value of irreversible damage are unknown. The lack of these particular data prevent a full cost–benefit analysis, but permit application of the Principle through the defensive-expenditure approach. How much would the community be required to pay to fund alternatives to maintain the environment and so defend existing levels of utility? Through the application of risk analysis and the stochastic dominance technique, a range of options and outcomes can be examined incorporating the using available information within a framework consistent with economic rationality. An extended risk simulation is applied to an environmental issue where there is a risk of serious and irreversible damage to the environment, namely, protection of the Barmah-Millewa forest-wetland in Australia.     

GIS技术在土地资源估价中的应用分析

本文主要分析了GIS技术的功能、概念、发展及基于该技术的土地估价信息系统的组成、功能和优越性。为土地估价提供了强有力的技术支持和科学依据