On the decoder error probability of block codes

By using coding and combinational techniques, an explicit formula is derived which enumerates the complete weight distribution of decodable words of block codes using partially known weight distributions. Also, an approximation formula for nonbinary block codes is obtained. These results give exact and approximate expressions for the decoder error probability P_E(u) of block codes     

基于变分模态分解和蝙蝠算法-相关向量机的短期风速区间预测

现有的风速预测方法大多是确定性的点预测,无法描述风速的随机性。针对该问题,建立基于变分模态分解(VMD)和蝙蝠算法-相关向量机(BA-RVM)的短期风速区间预测模型。对原始风速序列进行变分模态分解获得多个子序列;采用样本熵(SE)算法对子序列进行重组得到3类具有典型特性的分量;对各分量采用相关向量机算法分别建立预测模型。为进一步提高预测精度、缩小区间范围,引入蝙蝠算法(BA)对预测模型进行参数优化。将各分量的预测结果进行叠加求和得到一定置信水平下总体的区间预测结果。实际算例结果表明,与现有方法相比,所提区间预测方法的预测精度和区间覆盖率更高,区间宽度更窄。     

Evolution toward standardized market design

The evolution toward the standardized market design (SMD) is presented in this paper with references to the market developments in New Zealand, Australia, PJM, ISO-NE, and ERCOT. In the development of market designs, two main objectives-market liquidity facilitating bilateral trading and pricing efficiency facilitating congestion management, have been pursued. The efforts to balance the seemingly conflicting objectives led to most markets designed with a uniform or zonal pricing model. Introduction of locational marginal pricing and evolution of transmission rights from physical to financial form made it possible to harmonize the potentially conflicting goals in a market design. The close coupling between energy and ancillary services requires that markets for these commodities be carefully coordinated. Different operational practices and reliability standard requirements have led to major differences in ancillary service market designs.     

采用馈电线组法提高配电网安全性

介绍了配电网应用中的一种新方法——馈电线组法，讨论了其设计观念及其在馈电线利用、区域变电站间的负荷传输能力和安全性的提高等方面的主要特点；还提出了改进后的混合馈电线组的设计观念，该方法可缩短因电缆故障引起的电力供应中断时间。     

Dietary exposure of Hong Kong secondary school students to total mercury and methylmercury from fish intake

Fish is the main source of dietary exposure to methylmercury (MeHg), which is a public health concern owing to its potential neurotoxicity. To evaluate the public health risk, this study estimated the total mercury (tHg) and MeHg exposure from fish intake in Hong Kong secondary school students. Median tHg and MeHg concentrations of 280 samples purchased from different commercial outlets (covering 89 species of whole fish and three types of canned tuna), together with the local food consumption data of secondary school students obtained by semi-quantitative food frequency questionnaire in 2000, were used to estimate dietary exposure from fish intake for the average and high consumer (95th percentile exposure). For tHg, the median concentration was 63 µg kg^–1 (range 3–1370 µg kg^–1) and estimated exposures ranged 0.5–0.6 µg kg^–1 body weight (bw) week^–1 for an average consumer and 1.6–1.9 µg kg^–1 bw week^–1 for a high consumer. For MeHg, median concentration was 48 µg kg^–1 (range 3–1010 µg kg^–1) and estimated dietary exposures were 0.4–0.5 µg kg^–1 bw week^–1 for an average consumer and 1.2–1.4 µg kg^–1 bw week^–1 for a high consumer. These values are below the respective provisional tolerable weekly intake (PTWI) established by the Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives (JECFA). The health risk is greater for high consumers since MeHg exposures may approach or exceed the PTWI when other dietary sources are taken into account.     

Automated online solid-phase extraction of albendazole and its metabolites in Chinese mitten crabs followed by stable isotope dilution UPLC–MS/MS analysis

The determination of albendazole (ABZ) and its metabolites, albendazole sulfoxide, albendazole sulfone, and albendazole 2-aminosulfone in crab tissue is a complex analysis involving the extraction of trace levels of potentially unstable analytes from a solid matrix. Here, we report on an online solid-phase extraction (SPE) for automated trapping of ABZ and its metabolites in Chinese mitten crab, Eriocheir sinensis H. Milne Edwards (E. sinensis), followed by stable isotope dilution UPLC–MS/MS analysis. The performance of online SPE was fully validated. Good linearity was obtained with correlation coefficients >0.99. In the analytical range, the intra-day and inter-day precision and accuracies (RSD %) were 1.44–4.62 and 3.28–6.93 %, respectively. The mean recoveries were in the range of 78.2–109.3 %. All these demonstrated that the online SPE is an excellent technique for trapping and purification of ABZ and its metabolites in crab tissue samples. Finally, this online SPE–UPLC–MS/MS strategy was successfully applied to analyze the crude extracts from several crab tissue samples.     

Dietary exposure to antimony,lead and mercury of secondary school students in Hong Kong

The aim of this first study was to determine the dietary exposure of antimony, lead, mercury in foodstuffs consumed by secondary school students in Hong Kong. Around 100 composite food items were purchased and then cooked prior to analysis. Antimony was measured by hydrogen generation (HG)/inductively coupled plasma–mass spectrometry (ICP–MS), while lead was determined by ICP–MS. Total mercury was measured by cold vapour atomic absorption spectrometry. The detection limits for antimony, lead and total mercury were 1, 0.6 and 3 µg kg^?1, respectively. The dietary intake of antimony, lead and total mercury for an average secondary student were estimated to be 0.252, 1.98 and 0.92 µg (kg bw)^?1 week^?1, respectively. The dietary intake of antimony, lead and total mercury for high-consumer secondary student were estimated to be 0.567, 5.09 and 2.33 µg (kg bw)^?1 week^?1, respectively. The main contribution to antimony, lead and mercury were milk, vegetables and seafood, respectively. The Tolerable Daily Intake (TDI) of antimony, as recommended by WHO, is 6 µg (kg bw)^?1 week^?1, while the Provisional Tolerable Weekly Intakes (PTWI) of lead and mercury, as recommended by JECFA, are 25 and 5 µg (kg bw)^?1 week^?1, respectively. The estimated exposure values for secondary school students were compared to these safety reference values. For the relevant population, this study confirms the low probability of health risks from these metals via food consumption.     

The effect of self-determined motivation on household energy consumption behaviour in a metropolitan area in southern China

Promoting pro-environmental behaviour among individuals could help to mitigate climate change. In this research, we tested the effect of self-determined motivation on pro-environmental behaviours related to household energy consumption. A questionnaire survey was conducted in Hong Kong (n = 1004) to examine the importance of self-determined motivation on pro-environmental behaviours that promote climate change mitigation. Our results indicated that incorporating self-determined motivation into a model of goal-directed behaviour (MGB) improved its predictive power and that both the intrinsic and extrinsic motivations of an individual were important predictors of pro-environmental energy consumption behaviour. The empirical results suggest measures that can be used by the government to motivate residents’ pro-environmental energy consumption behaviours and to achieve the goal of reducing greenhouse gas emissions for a metropolitan area in southern China.     

Salmonella in food surveillance: PCR,immunoassays, and other rapid detection and quantification methods

Foodborne diseases caused by Salmonella have always been a significant health burden to many countries. Recent epidemiological data have indicated that Salmonella was the most common bacterial etiologic agent in food poisoning outbreaks both in the United States and in Asian regions like Hong Kong. In the past, labor-intensive traditional standard culture methods with long turnaround time have always been employed by many laboratories of public health services for the detection of Salmonella in Food Surveillance Programmes. To cope with the enormous volume of sample received for Salmonella detection, recent advances in nucleic acid- and immunoassay-based methods, and the subsequent commercialization and automation of the technologies have provided more rapid, specific, and productive alternatives for routine applications in testing laboratories. Fluorogenic or real-time PCR methods are able to generate results in a day, whereas immunoassay-based methods can produce negative results in 1–3 days. Some of these rapid methods have already been validated and accepted by international authorities as standard methods and have become increasingly popular among testing laboratories.