An improved partheno genetic algorithm for multi-objective economic dispatch in cascaded hydropower systems

The multi-objective economic dispatch (MOED) problem in cascaded hydropower systems is a complicated nonlinear optimization problem with a group of complex constraints. In this paper, an improved partheno genetic algorithm (IPGA) for resolving the MOED problem in hydropower energy systems based on the non-uniform mutation operator is proposed. In the new algorithm, the crossover operator is removed and only mutation operation is made, which makes it simpler than GA in the genetic operations and not generate invalid offspring during evolution. With the help of incorporating greedy selection idea into the non-uniform mutation operator, IPGA searches the solution space uniformly at the early stage and very locally at the later stage, which makes it avoid the random blind jumping and stay at the promising solution areas. Finally, the proposed algorithm is applied to a realistic hydropower energy system with two giant scale cascaded hydropower plants in China. Compared with other algorithms, the results obtained using IPGA verify its superiority in both efficiency and precision.     

Influence of accelerated curing on the compressive strength of polymer-modified concrete

In recent building practice, rapid construction is one of the principal requisites. Furthermore, in designing concrete structures, compressive strength is the most significant of all parameters. While 3-d and 7-d compressive strength reflects the strengths at early phases, the ultimate strength is paramount. An effort has been made in this study to develop mathematical models for predicting compressive strength of concrete incorporating ethylene vinyl acetate (EVA) at the later phases. Kolmogorov-Smirnov (KS) goodness-of-fit test was used to examine distribution of the data. The compressive strength of EVA-modified concrete was studied by incorporating various concentrations of EVA as an admixture and by testing at ages of 28, 56, 90, 120, 210, and 365 d. An accelerated compressive strength at 3.5 hours was considered as a reference strength on the basis of which all the specified strengths were predicted by means of linear regression fit. Based on the results of KS goodness-of-fit test, it was concluded that KS test statistics value (D) in each case was lower than the critical value 0.521 for a significance level of 0.05, which demonstrated that the data was normally distributed. Based on the results of compressive strength test, it was concluded that the strength of EVA-modified specimens increased at all ages and the optimum dosage of EVA was achieved at 16% concentration. Furthermore, it was concluded that predicted compressive strength values lies within a 6% difference from the actual strength values for all the mixes, which indicates the practicability of the regression equations. This research work may help in understanding the role of EVA as a viable material in polymer-based cement composites.     

长江流域上游干旱特征分析

为分析长江流域上游干旱特征,利用1961年1月至2012年12月长江上游共69个气象站的气象数据资料,以帕尔默干旱指数(PDSI)为主要指标对长江上游流域的干旱强度、干旱持续时间、干旱频率等干旱特征进行比较分析。结果表明,长江上游区域PDSI的月际变化较大,旱涝期交替出现,同时年代干旱最强值呈现先减弱后增强的趋势,并在2006年达到干旱强度最强值;干旱持续时间较长的干旱事件主要发生在1960、1970年代,平均干旱持续月数为4.2个月;上游干旱频率主要以初始干旱为主,其中年际干旱集中在1960年代末期至1970年代初期和2000年代后期两个阶段,季节干旱主要发生在冬季。研究成果可为长江流域上游的干旱治理提供参考。     

多级堆排尾矿沉积固结特性实验研究

基于多级堆排尾矿浆体沉积柱一维沉积固结实验,近似模拟一级尾矿子坝内堆排尾矿的沉积固结过程,针对不同排水控制条件下实验尾矿的沉积固结结果进行比较分析,探讨多级堆排尾矿的沉积固结规律。结果表明:尾矿浆体的沉积固结过程明显分为沉积和固结二个阶段;超静孔隙水压力前期消散迅速,后期消散缓慢;排水实验每日平均渗透系数前期逐日下降,后期小幅上升;不同排水控制条件下,固结完成尾矿的干密度及相对密实度均随深度的增加而增大,二者在排水实验各深度处均大于不排水实验。     

Controlling Corrosion Resistance of a Biodegradable Mg–Y–Zn Alloy with LPSO Phases via Multi-pass ECAP Process

Mg-RE(rear earth) alloys with long period stacking(LPSO) structures have great potential in biomedical applications. The present work focused on the microstructure and corrosion behaviors of Mg 98.5 Y_1 Zn_(0.5) alloys with 18 R LPSO structure after equal channel angular pressing(ECAP). The results showed that the ECAP process changed the grain size and the distribution of LPSO particles thus controlled the total corrosion rates of Mg 98.5 Y_1 Zn_(0.5) alloys. During the ECAP process from 0 p to 12 p, the grain size reduced from 160–180 μm(as-cast) to 6–8 μm(12 p). The LPSO structures became kinked(4 p), then started to be broken into smaller pieces(8 p), and at last comminuted to fine particles and redistributed uniformly inside the matrix(12 p). The improvement in the corrosion resistance for ECAP samples was obtained from 0 p to 8 p, with the corrosion rate reduced from 3.24 mm/year(0 p) to 2.35 mm/year(8 p) in simulated body fluid, and the 12 p ECAP alloy exhibited the highest corrosion rate of 4.54 mm/year.     

桩土复合路基静载试验改进方法研究

静载试验作为复合路基的一种重要检测手段而广泛应用,然而,在工程质量检测中,常出现检测结果与实际情况不符的情况,除人为操作因素外,垫层模拟过于简单是主要原因。借助引入弹性垫层,提出一种桩土复合路基静载试验改进方法。首先,基于数值模拟计算,建立复合路基桩土应力比n和桩土相对位移Δs、弹性垫层厚度h和弹性垫层模量E的函数关系;其次,通过模拟结果和路堤荷载结果对比,确定不同桩型复合路基静载试验中弹性垫层参数选择范围,最后,利用现场对比试验和实测结果,论证桩土复合路基静载试验改进方法的正确性和可靠性。     

强风化砂岩边坡锚筋桩布置方式及支护作用研究

强风化顺层砂岩边坡具有节理裂隙发育、强度低的特征,导致开挖过程中出现边坡稳定问题。单纯的锚杆锚索支护无法满足边坡稳定性需求,在现场抗滑桩施工困难的情况下,选用经济、高效、施工便利的锚筋桩结合锚杆锚索对强风化顺层砂岩边坡进行支护。针对强风化砂岩破碎且强度低的特性,考虑高压注浆的劈裂作用,通过FLAC 3D数值模拟进行方案比选,得到适用于强风化砂岩边坡的锚筋桩多角度交叉布置方案。根据试验段边坡锚筋桩监测数据,分析强风化顺层砂岩边坡锚筋桩作用机理,验证了多角度交叉布置锚筋桩对强风化顺层砂岩边坡的加固效果。     

Materials resistance to corrosion by I2–HI–H2O mixtures for the realization of a sulfur-iodine plant

The substances involved in the sulfur-iodine (SI) thermochemical cycle to produce H₂ by water splitting are very corrosive and may attack reactors, pumps, catalysts supports, and whatever part of the plant. This paper investigates the corrosion exerted by HI solutions in liquid, boiling, and gaseous phase at different temperatures. It shows the broadest overview of the behavior of different materials, ranging from pure metals to metallic alloys, from carbon materials to organic polymers, from ceramic materials to composite ones. Commercial nickel alloys and the effect of a specific element in their composition have here considerable attention. Regarding the composites materials, the impact of the substrate as well as the coating nature and thickness is studied, also through SEM-EDS (Scan Electron Microscope Energy Dispersive Spectroscopy) investigations.Carbon materials performed well, while most of the analyzed materials showed intergranular corrosion, pitting phenomena, and sometimes, carbide precipitation in the higher energy zones.     

河流护岸多孔生态材料对水体中硝态氮去除试验

为进一步提升护岸材料对面源污染物的净化能力,采用骨料交联法制备了具有较高透水率的多孔生态砌块,研究骨料粒径与砌块透水率的关系,并采用动水挂膜法对不同透水率的生态砌块进行反硝化细菌表面负载,在此基础上,研究所制备的不同骨料粒径的生态砌块的透水率、比表面积等对水体中硝态氮去除率的耦合效应。结果表明:在相同孔隙率条件下生态砌块的透水率随比表面积的增加而降低,且随着骨料粒径的增大而提高;生态砌块对水体中硝态氮的去除率随透水率的增加呈现先增大再减小的趋势,其中骨料粒径为7~11 mm,透水率为6.6 m L/(s.cm~2)的多孔生态砌块对硝态氮的去除率可达90.3%。     

Toxic response of aquatic organisms to guide application of artemisinin sustained-release granule algaecide

In our previous study, we prepared the granules by embedding artemisinin into alginate-chitosan using microcapsule technology. Thesgranules can release artemisinin sustainably and have a strong inhibitory effect on the growth of both single Microcystis aeruginosa and mixealgae. To safely and effectively use artemisinin sustained-release granules to control algal blooms, the ecotoxicity was studied by assessing theacute and chronic toxicity to Daphnia magna(D. magna) and Danio rerio(D. rerio), along with their antioxidant activities. The results showethat the 48-h median effective concentration(EC50) of pure artemisinin to D. magna was 24.54 mg/L and the 96-h median lethal concentratio(LC50) of pure artemisinin to D. rerio was 68.08 mg/L. Both values were classified as intermediate toxicity according to the Organization foEconomic Co-operation and Development(OECD). The optimal algae inhibitory concentration of artemisinin sustained-release granules(1 g/Lhad low acute toxicity to both D. magna and D. rerio. The sustained-release granules had higher chronic toxicity to D. magna than to D. reriPartial indices of D. magna were inhibited by granules when the concentrations were larger than 0.1 g/L. Low granule concentration had ainductive effect on antioxidant enzyme activities in D. magna and D. rerio. With the increase of the exposure concentration and time, the enzymactivity presented a trend of first increasing and then decreasing, and the overall changes were significant. The change trend and range of enzymactivity indicated that the granules could cause serious oxidative stress to D. magna and D. rerio, and the changes were consistent with the resultof toxicity experimentation.