Characterization and exposure assessment of household fine particulate matter pollution in China

Household fine particulate matter (PM_2.5) pollution greatly impacts residents' health. To explore the current national situation of household PM_2.5 pollution in China, a study was conducted based on literature published from 1998 to 2018. After extracting data from the literature in conformity with the requirements, the nationwide household-weighted mean concentration of household PM_2.5 (HPL) was calculated. Subgroup analyses of spatial, geographic, and temporal differences were also done. The estimated overall HPL in China was 132.2 ± 117.7 μg/m³. HPL in the rural area (164.3 ± 104.5 μg/m³) was higher than that in the urban area (123.9 ± 122.3 μg/m³). For HPLs of indoor sampling sites, the kitchen was the highest, followed by the bedroom and living room. There were significant differences of geographic distributions. The HPLs in the South were higher than the North in four seasons. The inhaled dose of household PM_2.5 among school-age children differed from provinces with the highest dose up to 5.9 μg/(kg·d). Countermeasures should be carried out to reduce indoor pollution and safeguard health urgently.     

多维不确定性影响下的水期权交易最优策略研究

为解决来水预测不确定性和水价不确定性给用水户带来的风险对冲问题,引入对冲性的水期权交易模式,建立了以用水户期望收益最大为目标的水期权交易模型,得到了最优的期权交易策略应满足的条件,并利用二分法计算得到了最优的期权交易策略,探究了来水不确定性与水价不确定性对期权交易策略的影响。结果表明,来水预测误差和水价的波动越大,用水户的期望收益越大,最优的期权交易策略能有效降低来水预测不确定性和水价不确定性带来的风险。     

Reliability of design approaches for axially loaded offshore piles and its consequences with respect to the North Sea

In the near future, several offshore wind farms are planned to be built in the North Sea. Therefore, jacket and tripod constructions with mainly axially loaded piles are suitable as support structures. The current design of axial bearing resistance of these piles leads to deviant results regarding the pile resistance when different design methods are adopted. Hence, a strong deviation regarding the required pile length must be addressed. The reliability of a design method can be evaluated based on a model error which describes the quality of the considered design method by comparing measured and predicted pile bearing resistances. However, only few pile load tests are reported with regard to the boundary conditions in the North Sea. This paper presents 6 large-scale axial pile load tests which were incorporated within a new model error approach for the current design methods used for the axial bearing resistance, namely API Main Text method and cone penetration test (CPT)-based design methods, such as simplified ICP-05, offshore UWA-05, Fugro-05 and NGI-05 methods. Based on these new model errors, a reliability-based study towards the safety was conducted by performing a Monte-Carlo simulation. In addition, consequences regarding the deterministic pile design in terms of quality factors were evaluated. It is shown that the current global safety factor (GSF) prescribed and the partial safety factors are only valid for the API Main Text and the offshore UWA-05 design methods; whereas for the simplified ICP-05, Fugro-05 and NGI-05 design methods, an increase in the required embedded pile length and thus in the GSF up to 2.69, 2.95 and 3.27, respectively, should be considered to satisfy the desired safety level according to DIN EN 1990 of β = 3.8. Further, quality factors for each design method on the basis of all reliability-based design results were derived. Hence, evaluation of each design method regarding the reliability of the pile capacity prediction is possible.     

Data‐driven model for river flood forecasting based on a Bayesian network approach

Uncertainty analysis of hydrological models often requires a large number of model runs, which can be time consuming and computationally intensive. In order to reduce the number of runs required for uncertainty prediction, Bayesian networks (BNs) are used to graphically represent conditional probability dependence between the set of variables characterizing a flood event. Bayesian networks (BNs) are relevant due to their capacity to handle uncertainty, combine statistical data and expertise and introduce evidences in real‐time flood forecasting. In the present study, a runoff–runoff model is considered. The discharge at a gauging station located is estimated at the outlet of a basin catchment based on discharge measurements at the gauging stations upstream. The BN model shows good performances in estimating the discharges at the basin outlet. Another application of the BN model is to be used as a reverse method. Knowing discharges values at the outlet of the basin, we can propagate back these values through the model to estimate discharges at upstream stations. This turns out to be a practical method to fill the missing data in streamflow records which are critical to the sustainable management of water and the development of hydrological models.     

基于峰谷分时电价的虚拟电厂日前申报及运行优化

鉴于分布式能源的出力性质为间歇性和波动性,影响电网安全高效运行,而虚拟电厂可解决此问题。对虚拟电厂进行申报-调度两阶段建模,以包含分布式电源(光电、风电和燃气轮机)和储能系统(储能电池)两大类分布式能源的虚拟电厂为例,基于光照强度及风速等不确定因素,研究峰谷分时电价下日前市场虚拟电厂的出力申报和运行调度策略并利用风险价值模型进行风险管理。结果表明,申报出力时,当电价激励足够高时储能电池方会参与出力,成功起到削峰填谷的作用;运行调度时,平衡出力偏差方面,储能电池发挥主要作用,且虚拟电厂运行调度策略具有一定的经济效益。     

三元层状固体润滑Ti3SiC2复合材料的制备与摩擦学研究进展

Ti_3SiC_2作为一种新型的陶瓷材料,兼具金属和陶瓷的双重性能,同时也由于具有良好的导电导热性、低密度、机械可加工性、优异的抗热震性能、高熔点、高热稳定性、耐高温氧化、耐腐蚀性能,近年来受到了越来越多研究者的关注。首先介绍了Ti_3SiC_2内部晶体学结构,指出其与二元碳化物Ti C有着紧密的晶体学关系,接着详细叙述了各种Ti_3SiC_2制备工艺及其复合材料的研究现状,阐述了化学气相沉积(CVD)、磁控溅射(MS)、脉冲激光沉积(PLD)、自蔓延高温合成(SHS)、热等静压(HIP)、热压烧结(HP)、火花等离子烧结(SPS)等技术在制备Ti_3SiC_2及其复合材料方面的优点和不足。随后重点分析了温度、滑动速度、载荷、添加组分含量、对偶材料种类和润滑环境等因素对Ti_3SiC_2及其复合材料摩擦学性能的影响。最后总结了在Ti_3SiC_2及其复合材料研究中存在的一些问题,并指出进一步提高摩擦磨损性能,添加多元增强相,改进现有技术以及采取新型制备工艺,是未来发展的重要方向。     

紫外分光光度法测定核酸含量的影响因素分析

选择寡聚核苷酸、鲑鱼精单链DNA、小牛胸腺双链DNA标准物质为样本,系统研究了溶液pH、苯酚、丙酮、蛋白质、多糖等对紫外分光光度法测量结果的影响情况,另外考察了核糖核酸(RNA)和脱氧核糖核酸(DNA)的相互影响情况。研究发现基于分光光度法的核酸定量分析,易受溶液pH、苯酚、丙酮、蛋白质、多糖等的影响,另外,DNA和RNA之间也会相互干扰。因此,紫外分光光度法测定核酸含量时,特别是该方法用于核酸标准物质特性量值确定时,需要样品高度纯化,pH确定的条件下才能保证测量结果的准确可靠。     

油田注水管道的腐蚀因素及防腐措施

随着时代以及经济的不断发展,因为油田的注水管道系统运行的好坏会直接关系到油田开发的程度,所以油田注水系统受到了油田工作者的极大重视。但是由于一些地理因素或者是天气的原因,油田注水管道的腐蚀问题依然十分严重,接下来,本文将结合油田注水管道的腐蚀因素,探讨加强油田主水管道防腐工作的方法和措施。     

Partial safety factors for laminated glass

Glass plies can be bonded together by polymeric interlayers to form laminated glass. Thanks to the capacity in finding alternative stress paths after partial breakage, it is commonly accepted that the more the layers are, the higher the safety level is. However, a negative aspect is that the tensile strength of glass carries a size effect in terms of surface area, which increases with lamination. Here we evaluate these competing factors by calibrating the partial safety factors to be used in semi-probabilistic (level-I) design, through comparison with probabilistic (level-III) methods in paradigmatic case-studies under wind, snow, and dead weight. Starting from a two-parameter Weibull distribution for glass strength, the “failure modes” approach determines the statistical distribution of strength for a multi-laminate as a function of the number of plies, which interferes with the statistics for actions. As a function of the target probability of failure for the assigned class of consequence, we introduce a new coefficient in the verification formula of level-I, to account for the effects of lamination with dependence upon the number of plies. We find that there is strong gain when passing from a monolith to a two-ply laminate, but the advantage fades by increasing the number of layers. Verification formulas of this type could avoid overconservative design.