Suchergebnisse

ABSTRACTIn this paper, a multiple stage wastewater treatment system (WTS) is solved for the selection of technological options at each stage to minimize (economic cost, size, odour emissions) and to maximize (nutrient recovery, robustness, global desirability). Stages in the wastewater treatment system are the levels of treatment. There are 17 levels of treatment, where the first 11 levels are for the liquid treatment and the last 6 levels are for the solid treatment. This results in a 20‐dimensional, continuous‐state, 17‐stage, 6‐objective, stochastic optimization problem. The resulting multiple stage, multiple objective (MSMO) WTS is solved using the three‐phase methodology in conjunction with the multiple objective version of high‐dimensional, continuous‐state, stochastic dynamic programming (SDP). The three‐phase methodology comprises the input phase, the matrix generation phase and the weighting phase. The primary goal of three‐phase methodology is to obtain weight vectors at each stage of the WTS utilizing expert's opinions in the input phase, computing pairwise comparison matrices at each stage using the geometric mean‐based methods in the matrix generation phase, and then calculating weight vectors at each stage using the eigenvector method in the weighting phase. The weight vectors are then used to scalarize the vector optimization problem, which is solved using the high‐dimensional, continuous‐state SDP augmented for handling multiple objectives at each stage.The results obtained are practical as evidenced by the selection of new technologies in levels 1 and 5 thereby validating expert's decision to include them in the evaluation process. In addition to encouraging reviews from WTS experts, the implementation results satisfy a set of external constraints in the form of interstage dependencies between technological options in the WTS. Furthermore, the solution technique presented here utilizes expert's opinions in the solution development process, and is quite general in its application to a variety of large‐scale MSMO problems. Copyright © 2011 John Wiley & Sons, Ltd.

Abstract. Climate changes seriously affect people's daily life. Temperature and precipitation have been the focus of many studies dealing with regional climate changes in recent decades. In this study, the climatic trends in Xinjiang, northwest of China during 1961–2008 are analysed in detail on the basis of several parameters: annual and seasonal mean precipitation, and annual mean, minimum, and maximum temperatures. The results show a significant increasing trend of 7.40 mm decade−1 in the annual mean precipitation and a relatively minimal upward trend of 1.45 mm decade−1 in winter in Xinjiang. The annual mean temperature increases significantly in Xinjiang with an increasing trend of 0.30 °C decade−1. There is an increasing trend of 0.25 °C decade−1 in the annual maximum temperature and an increasing trend of 0.52 °C decade−1 in the annual minimum temperature.

Abstract. Extreme precipitation events are major causes of severe floods and droughts worldwide. Therefore, scientific understanding of changing properties of extreme precipitation events is of great scientific and practical merit in the development of human mitigation of natural hazards, such as floods and droughts. Wetness and dryness variations during 1961–2008 in Xinjiang, a region of northwest China characterised by an arid climate, are thoroughly investigated using two extreme precipitation indices. These are annual maximum consecutive dry days (CDD) and annual maximum consecutive wet days (CWD), based on a daily precipitation dataset extracted from 51 meteorological stations across Xinjiang. As a result, we present spatial distributions of mean annual CDD and mean annual CWD and their trends within the study period. The results indicate that: (1) CDD maximize in the Taklimakan and Turban basins of southeast Xinjiang, while minima are found in the Tianshan Mountains and the Ili river valley of northwest Xinjiang. On the contrary, the longest CWD are observed in northwest Xinjiang and the shortest in the southeast part of the region. (2) On an annual basis, CWD temporal variability shows statistically positive trends and a rate of increase of 0.1d/10a. CDD temporal variability shows statistically negative trends and a rate of decrease of 1.7d/10a. (3) Goodness-of-fit analysis for three candidate probability distribution functions, generalised Pareto distribution (GPD), generalised extreme value (GEV) and Gumbel, in terms of probability behaviours of CDD and CWD, indicates that the GEV can well depict changes of CDD and CWD. (4) The CDD and CWD better describe wet and dry conditions than precipitation in the Xinjiang. The results pave the way for scientific evaluation of dryness/wetness variability under the influence of changing climate over the Xinjiang region.

A photochemical trajectory model (PTM), coupled with the Master Chemical Mechanism (MCM) describing the degradation of 139 volatile organic compounds (VOCs) in the troposphere, was developed and used for the first time to simulate the formation of photochemical pollutants at Wangqingsha (WQS), Guangzhou during photochemical pollution episodes between 12 and 17 November, 2007. The simulated diurnal variations and mixing ratios of ozone were in good agreement with observed data (R2=0.80, P<0.05), indicating that the photochemical trajectory model - an integration of boundary layer trajectories, precursor emissions and chemical processing - provides a reasonable description of ozone formation in the Pearl River Delta (PRD) region. Calculated photochemical ozone creation potential (POCP) indices for the region indicated that alkanes and oxygenated organic compounds had relatively low reactivity, while alkenes and aromatics presented high reactivity, as seen in other airsheds in Europe. Analysis of the emission inventory found that the sum of 60 of the 139 VOC species accounted for 92% of the total POCP-weighted emission. The 60 VOC species include C2-C6 alkenes, C6-C8 aromatics, biogenic VOCs, and so on. The results indicated that regional scale ozone formation in the PRD region can be mainly attributed to a relatively small number of VOC species, namely isoprene, ethene, m-xylene, and toluene, etc. A further investigation of the relative contribution of the main emission source categories to ozone formation suggested that mobile sources were the largest contributor to regional O3 formation (40%), followed by biogenic sources (29%), VOC product-related sources (23%), industry (6%), biomass burning (1%), and power plants (1%). The findings obtained in this study would advance our knowledge of air quality in the PRD region, and provide useful information to local government on effective control of photochemical smog in the region. © 2010 Elsevier Ltd.

Anti-Retroviral Therapy (ART) is the recommended first line therapy for patients with HIV. Since 2004, Chinese government has provided free Chinese herbal medicine (CHM) for Chinese HIV/AIDS patients. Data of living patients with HIV from the NFTCMP database and Center for Disease Control (CDC) database during 2003-2016 in Guangxi province was obtained and compared. Patients were divided into 3 groups according to their recorded treatment regimens. A total of 2954 patients with their treatment recorded in the two databases were included for analysis, their median age was 46 years (IQR = 36-59), and 64.63% were male. CHM regimens users had baseline CD4 cell counts (380.11±240.59 cell/μL), approximately 100 cell/μL significantly higher than patients receiving CHM combined with ART regimens or only ART regimens. There was no significant difference in mortality among groups. All three regimens improved patients' CD4 cell counts. Compared to the sharp improvement in ART group during the first 6 months, CD4 cell counts of patients in CHM group and CHM combined with ART group showed a smooth and steady rise. CD4 counts of the combined group remained much lower than ART group in the first 3 years, but overtook ART group in the fourth year.