Solution method of overtopping risk model for earth dams

Hydrologic risk analysis relies on a series of probabilistic analyses, and it is a complex problem in estimating the probability distributions of multiple independent and random variables. The goal of this study is to presents the procedure and application of a probability-based risk analysis methodology to evaluate earth dam overtopping risk that induced by concurrent flood and wind. The uncertainty arising from initial water surface level, flood, wind velocity, and dam height are discussed in this research. The improved Monte Carlo simulation and mean-value first-order second-moment method are used to solve the proposed dam overtopping risk model, respectively. The nonparametric kernel density estimation method, which can better learn the complex multimodal characteristic of probability density function than that of traditional parametric estimation method, is employed to improve the probability density function of initial water surface level. The latin hypercube sampling is introduced to generate uniform random number, which improves the efficient and stability compared with simple random sampling. Afterward, an application to the Dongwushi Reservoir in China illustrates that the dam overtopping risk computed using the improved Monte Carlo simulation is lower than that using mean-value first-order second-moment method. Furthermore, the sensitivity analysis show that initial water surface level is more sensitive to overtopping risk than wind velocity.     

国际粮食贸易背景下的市场整合与虚拟资源流动——以中国巴基斯坦大米市场为例

贸易自由化和区域经济一体化不仅会通过比较优势整合市场、提升效率,还会带来农产品贸易中虚拟资源的流动。以中国—巴基斯坦大米贸易为研究对象,使用两国大米贸易数据,首先检验中巴粮食市场整合程度,其次分析中巴大米贸易带来的虚拟水和虚拟土地的流动。结果表明：（1）中巴之间大米市场已经高度整合,且价格存在长期均衡,但巴基斯坦大米价格比中国波动大,其对中国大米的价格弹性为1.097;“一带一路”倡议带来了巴方大米价格7.8%的下降,增加了穷人的福利。（2）贸易带来了虚拟水土资源的流动。中国累计从巴基斯坦净进口大米354万t,相当于净进口国内52万hm²、巴基斯坦96.4万hm²耕地,以及国内34.4亿t、巴基斯坦101.7亿t水资源。中国应加大技术支持和扩散的力度,具有促进粮食安全,节约全球资源的意义。     

Contamination of Clams with Human Norovirus and a Novel Hepatitis A Virus in Cameroon

Food and Environmental Virology - Shellfish constitute an important protein source but may be contaminated by viruses from various origins. A study performed on clams collected in Cameroon showed a...     

Diffusion effect and learning effect: an examination on MSW recycling

The increase in MSW (Municipal Solid Waste) recycling may attribute to two factors: one is diffusion effect through households' adoption of MSW recycling (an innovative service offered and provided by the government); the other is organizational learning effect due to the reformation of MSW management system (the MSW recycling service provider). The diffusion effect takes place across households through the exchange of information while learning effect occurs through employee's accumulated experience in MSW recycling and the consequent innovation in associated with institutional change within the service provider. In this paper, we develop three models, including (1) the diffusion effect model, (2) the organizational learning effect model, and (3) the interaction model to explain the performance of MSW recycling. Using Taiwan's recyclable waste collected, we show that (1) the diffusion effect and learning effect have significantly impacts on MSW recycling, (2) environmental policy has a significant impact on environmental diffusion and organizational learning, and leads to the accelerating performance of MSW recycling, (3) the interaction of diffusion and organizational learning have a positive impact on MSW recycling performance.     

Are politicians office or policy motivated? The case of U.S. governors' environmental policies

Are elected politicians primarily motivated by holding office, thus choosing environmental policies accordingly? Or are they motivated by the chance to implement their preferred environmental policies? Do governors have character, in the sense that they promise and implement environmental policies consistent with their own preferences? To answer these questions, we study the differences in environmental spending across both re-electable and lame duck governors from the two main political parties. In our empirical analysis, we make use of parametric and non-parametric regression-discontinuity approaches. While re-electable governors do not set significantly different policies, lame duck governors do. We argue that in the area of environmental policy governors appear to be primarily office motivated and lack character.     

水文地球化学热力学在山西省辛安泉氮污染预测中的运用

山西省辛安泉是长治地区的主要供水水源，目前它的部份泉城域已遭到了严重的氮污染，本文在环境水文地质地球化学调查的基础上，应用水文地球化学热力学理论，对氮化牧在岩溶水中转化方向，平衡组成进行了分析，并用稀释环境容量方法，作出了辛安泉氮污染预测初步评价。这表明在水文地质地球化学研究程度不足以建立溶质运移确定型模型时，水文地球化学方法是研究氮污染预测的一种有效的近似方法。