Electrocatalyst of RuO2 decorating TiO2 nanowire arrays for acidic oxygen evolution

Oxygen evolution reaction (OER) at the anode limits the efficiency of hydrogen production from water electrolysis substantially. A novel electrocatalyst of RuO₂ decorating TiO₂ nanowire arrays for OER was successfully prepared using a cyclic voltammetric method with electrodeposition of RuO₂ nanoparticles on the TiO₂ nanowire (TNW) arrays synthesized hydrothermally. Even though the electrodes with the composite electrocatalyst have a lower loading of RuO₂, they have higher electrocatalytic activity and stability for acidic oxygen evolution than the Ti/RuO₂ electrode prepared by conventional thermal decomposition method. The core-shell structure of the TNW@RuO₂ electrocatalyst not only increases the specific surface area of the electrodes, but also inhibits the adverse effect of the poor conductivity of TiO₂. This novel OER electrocatalyst can improve the efficiency and reduce the cost of hydrogen production from electrolytic water splitting.     

Integrating a Forward Feature Selection algorithm,Random Forest,and Cellular Automata to extrapolate urban growth in the Tehran-Karaj Region of Iran

This paper couples a Forward Feature Selection algorithm with Random Forest (FFS-RF) to create a transition index map, which then guides the spatial allocation for the extrapolation of urban growth using a Cellular Automata model. We used Landsat imagery to generate land cover maps at the years 1998, 2008, and 2018 for the Tehran-Karaj Region (TKR) in Iran. The FFS-RF considered the independent variables of slope, altitude, and distances from urban, crop, greenery, barren, and roads. The FFS-RF revealed temporal non-stationary of drivers from 1998–2008 to 2008–2018. The FFS-RF detected that altitude and distance from greenery were the most important drivers of urban growth during 1998–2008, then distances from crop and barren were the most important drivers during 2008–2018. We used the Total Operating Characteristic to evaluate the transition index maps. Validation during 2008–2018 showed that FFS-RF produced a transition index map that had predictive power no better than an allocation of urban growth near existing urban. Simulation to 2060 extrapolated that Tehran, Karaj, and their adjacent cities will interconnect spatially to form a gigantic city-region.     

Bearing capacity optimization of T-shaped soil-cement column-improved soft ground under soft fill

During dredging activities, a large amount of dredged clay slurry or lump is produced. A dumping site composed of soft clay near the water body is often used to deposit dredged soft fill. Soil-cement columns are commonly employed to treat the soft ground for this application. Under soft fill, failure of soft clay dominates the behaviour of composite ground. Hence, a soil-cement slab is needed to form a load transfer platform above the columns, which is costly. As an alternative, the use of T-shaped column with an enlarged column cap is proposed. In this study, the responses of composite ground with T-shaped column are measured experimentally, which are used to calibrate a numerical model. The results of numerical parametric analyses show that the implementation of T-shaped column under soft fill can change the governing failure mode into column failure, once the diameter of column cap exceeds a certain value, after which the improvement efficiency is the same between T-shaped column and column-slab system. The height of column cap results in negligible difference in bearing capacity, and a minimum value of 0.3 m is suggested for use in design to avoid punching failure.     

Efficient slope reliability analysis using adaptive classification-based sampling method

Slope reliability analysis can effectively account for uncertainties involved in a slope system. However, commonly used slope reliability analysis methods often require huge computational cost, especially in large-scale problems, which hinders its wide application to engineering practice. This paper proposes an efficient slope reliability analysis method based on the active learning support vector machine (SVM) and Monte Carlo simulation (MCS). The proposed method makes use of an active learning function and cross-validation techniques to select the most suitable training samples to update the SVM model. The selected training samples are associated with a small distance to the limit state surface of the slope stability model and a large local uncertainty, which are more informative to gradually tune the SVM model to approximate the actual slope performance function. As a result, the proposed method can estimate the slope reliability with a small number of evaluations of the slope performance function, thus improving the efficiency significantly. Four slope examples are employed to demonstrate the effectiveness of the proposed method. The presented approach is also compared with some other commonly used surrogate models in slope reliability analysis. It is shown that the proposed method performs better in terms of computational efficiency to obtain similar estimation accuracy of the failure probability for the investigated examples.

     

Substrate Recognition and Catalytic Mechanism of the Phosphate Acyltransferase PlsX from Bacillus subtilis

Phosphate: acyl-acyl carrier protein (ACP) acyltransferase PlsX is a peripheral enzyme catalysing acyl transfer to orthophosphate in phospholipid synthesis. Little is known about how it recognises substrates and catalyses the acyl transfer. Here we show that its active site includes many residues lining a long, narrow gorge at the dimeric interface, two positive residues forming a positive ACP docking pad next to the interfacial gorge, and a number of strictly conserved residues significantly contributing to the catalytic activity. These findings suggest a substrate recognition mode and a catalytic mechanism that are different from those of phosphotransacetylases catalysing a similar acyl transfer reaction. The catalytic mechanism involves substrate activation and transition-state stabilization by two strictly conserved residues, Lys184 and Asn229. Another noticeable feature of the catalysis is the release of the acyl phosphate product near the membrane, which might facilitate its membrane insertion.     

Modeling and energy reduction of multiple effect evaporator system with thermal vapor compression

A general and rigorous mathematical model is developed for a multiple effect evaporator system which includes various energy reduction schemes (ERSs). These ERSs are thermal vapor compression, vapor bleeding, condensate flashing and solution flashing. The model can achieve the function of pumping steam at any effect and can work as an effective screening tool for the selection of optimal feed flow sequence (OFFS). In order to solve the model, the iteration method combining with matrix methods is proposed. To study effect of different ERSs on steam consumption (SC), an example of the co-current quadruple effect evaporator system is considered. These schemes can reduce the SC up to 46.56% if the feed is heated up to 88 °C and ejection coefficient at 3rd effect is set to 0.3. The OFFS is forward sequence as long as preheating temperature is high enough when constraints of heat transfer driving force can be satisfied.     

柴达木盆地英西地区渐新统下干柴沟组上段储层微观孔隙结构特征

柴达木盆地英西地区渐新统下干柴沟组上段为“自生自储”型油气藏。利用X射线衍射全岩矿物含量分析、薄片鉴定、扫描电镜观察、二氧化碳吸附、氮气吸附/脱附、高压压汞、核磁共振、自发渗吸等实验手段,系统分析柴达木盆地英西地区渐新统下干柴沟组上段储层特征,精细表征了其微观孔隙结构特征。研究结果表明：(1)英西地区渐新统下干柴沟组上段储层为细粒沉积岩,其矿物成分主要为白云石和铁白云石等碳酸盐,含有长石、石英等陆源碎屑,伊蒙混层和伊利石等黏土矿物。(2)研究区储集岩整体较为致密,孔隙度为1.0%～14.5%,平均为4.0%,渗透率为0.011～6.146 mD,平均为0.125 mD,具有低孔特低渗特征。(3)研究区储集岩的孔隙类型以晶间孔、溶蚀孔、溶洞和裂缝为主,储层孔隙形态为平行狭缝型。(4)研究区微孔的质量体积平均为0.005 6 mL/g,占总孔的质量体积的34.70%;中孔的质量体积平均为0.006 6 mL/g,占总孔体积的40.84%,宏孔的质量体积相对较小,为0.003 9 mL/g,占总孔体积的24.46%,因此,对岩石储集性贡献最大的为中孔,其次是微孔。     

响应面法优化珍珠龙胆石斑鱼肉肽的酶法制备工艺及酶解产物的抗氧化活性

以珍珠龙胆石斑鱼肉为原料,利用蛋白酶酶解制备生物活性肽。以水解度和DPPH自由基清除率为指标,在单因素实验的基础上采用响应面分析法优化制备工艺。并采用超滤法对酶解产物进行分离纯化,同时进行抗氧化活性探究。结果表明:珍珠龙胆石斑鱼肉酶解工艺条件为:采用风味蛋白酶,酶添加量1050 U/g,在pH7.0、53℃、料水比1:3.5条件下酶解5.5 h,水解度为9.99%±0.39%。酶解产物与超滤组分均具有较强DPPH自由基清除能力,其IC₅₀值在0.63~0.88 mg/mL之间;EH-2(5~8 kDa)和EH-3(3~5 kDa)有较强的羟基自由基清除能力,其IC₅₀值分别为16.94和16.38 mg/mL;酶解产物与超滤组分均具有还原能力,且酶解产物还原能力最佳。优化的珍珠龙胆石斑鱼肉肽的酶法制备工艺合理且可行,其酶解产物与超滤组分具有较强的抗氧化性,可作为功能食品的基料应用。     

基于逆变器直流电压模式波能装置并网接入方法

针对采用蓄电池提供直流母线电压难于满足波能装置装机容量不断增长需求的问题,提出基于逆变器直流电压模式的多液压发电机组并网接入方法。逆变器为液压发电机组直接提供直流母线电压,组建成波能装置无蓄电池组支撑的直流纳电网。建立了逆变器直流电压模式电路拓扑和直流电压外环控制回路。通过多液压发电机组波能装置基于逆变器直流电压模式仿真试验,验证了无蓄电池组波能装置并网接入方法的可行性。该研究成果已应用到500 kW“长山号”波能装置中,为大功率波能装置并网系统研究奠定了基础。     

Integrating hydrology,hydraulics and ecological response into a flexible approach to the determination of environmental water requirements for rivers

There are many different approaches to environmental water requirement (EWR) determinations that have been reported in the international literature. Many of these focus on different aspects of the problem, while few of them consider all of the issues associated with the eventual implementation of EWR as part of integrated water management. It is also necessary to recognize that there is a wide range of different types and resolution of information available in different parts of the world. This paper presents an integrated framework that has been in use in South Africa for several years and which is based on integrating the impacts of changing flow regimes on different ecosystem response components through indices of ‘stress’ measured on a common scale (0–10). Software to support its implementation has been included as part of an existing hydrological modelling framework package that includes a GIS interface and database management procedures. The framework is flexible enough to be used with different approaches to analyzing ecosystem responses, ranging from complex hydraulic habitat assessments to the interpretation of expert opinion and therefore should be widely applicable. The framework can also be used to design a modified flow regime for a given set of ecological objectives, or it can be applied to assess scenarios of flow regimes based on a range of possible future water management options. The paper explains the approach, provides some illustrations of its application and discusses some of the issues associated with its more widespread use.