Removal of hexavalent chromium in aquatic solutions by pomelo peel

This study investigated the removal of hexavalent chromium(Cr(VI)) in aqueous solutions using pomelo peel(PP) and FeCl_3-modified pomelo peel(FPP) as novel biomass adsorbents.Batch adsorption experiments were performed to evaluate the effects of pH,time,temperature,initial concentration,and adsorbent dose on Cr(VI) removal by PP and FPP.The results show that the maximum adsorption capacity of Cr(VI)was 21.55 mg/g for FPP and 0.57 mg/g for PP at a pH of 2.0 and a temperature of 40℃.The surface shape,microstructure,and chemical composition of FPP were analyzed with scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR),and energy dispersive spectroscopy(EDS),and compared with those of PP.The results show that the adsorption performance of FPP was much better than that of PP,indicating that FPP can be an alternative high-efficiency adsorbent for Cr(VI) removal.     

我国银行信用信息共享内生性分析

信用体系建设应该选择何种模式是当前学术界讨论的热点。作为信用体系的重要组成部分,银行信用信息共享的重要性已经在相关文献中得到了论证,但对于应该采取何种方式实现银行间的信息共享,仍然存在争议。本文试图在现有研究的基础上,通过建立一个基本的概率模型来分析影响银行信用信息共享内生性的重要因素,并结合我国的实际情况进行讨论。我们的结论是现阶段我国银行间内生出一套信用信息共享机制较难实现,为正在建设中的公共征信系统提供了理论支撑及相应的政策建议。     

河南省利用外商直接投资获取技术溢出效应分析

<正>上世纪90年代中后期以来,以"三缺口"及"四缺口"理论为主导思想,引进先进技术和管理经验,促进整个产业的技术进步成为我国引资的主要目的。对发展中国家而言,许多技术单靠国内开发往往是不可行或是不经济的,而通过引资的方式利用跨国公司现有的先进技术,则可     

地震荷载作用下地下厂房围岩稳定的离散元计算方法研究

 对离散元动力计算方法的理论基础进行了探索,主要是离散元动力计算的实现过程,边界条件和动力荷载的输入问题。在此基础上以某大型水电工程的地下厂房为例,计算在静力和地震荷载作用下,围岩的变形破坏情况,并监测了岩体不同时间速度和位移的变化情况。计算方法与成果可以为地下厂房的抗震工程设计提供指导。     

Effect of EM Bokashi application on control of secondary soil salinization

In order to ameliorate saline-alkaline soil, EM Bokashi has been applied to rice production in conjunction with subdrainage in Ningxia Autonomous Region and Zhejiang Province. The preliminary results can be summarized as follows： EM Bokashi can increase soil organic matter content, improve soil porosity and permeability, and raise the soil＇s levels of available nutrients; and EM Bokashi combined with subdrainage treatment is more effective in controlling secondary soil salinization and raising the grain yield and quality than other treatments. The results suggest that EM Bokashi can reduce the necessary amount of chemical fertilizer application, thereby improving the agricultural environment, and that the introduction of EM Bokashi into systems of secondary soil salinization control systems has resulted in significant benefits.     

Influence of shrinkage-reducing admixture on drying shrinkage and mechanical properties of high-performance concrete

High-performance concrete （HPC） has specific performance advantages over conventional concrete in strength and durability. HPC mixtures are usually produced with water/binder mass ratios （mW/mB） in the range of 0.2-0.4, so volume changes of concrete as a result of drying, chemical reactions, and temperature change cannot be avoided. For these reasons, shrinkage and cracking are frequent phenomena. It is necessary to add some types of admixture for reduction of shrinkage and cracking of HPC. This study used a shrinkage-reducing admixture （SRA） for that purpose. Concrete was prepared with two different mW/mB （0.22 and 0.40） and four different mass fractions of SRA to binder （w（SRA） = 0%, 1%, 2%, and 4%）. The mineral admixtures used for concrete mixes were： 25% fly ash （FA） and 25% slag by mass of binder for the mixture with mW/mB = 0.40, and 15% silica fume （SF） and 25% FA for the mixture with mW/mB = 0.22. Tests were conducted on 24 prismatic specimens, and shrinkage strains were measured through 120 days of drying. Compressive strength, splitting strength, and static modulus of elasticity were also determined. The results show that the SRA effectively reduces some mechanical properties of HPC. The reductions in compressive strength, splitting tensile strength, and elastic modulus of the concrete were 7%-24%, 9%-19%, and 5%-12%, respectively, after 90 days, compared to concrete mixtures without SRA. SRA can also help reduce drying shrinkage of concrete. The shrinkage strains of HPC with SRA were only as high as 41% of the average free shrinkage of concrete without SRA after 120 days of drying.     

灌浆技术在构皮滩水电站防渗工程中的应用

构皮滩水电站上游围堰处,落渣层内块石较多,地层架空现象严重,局部地段表层基岩中存在溶蚀通道;施工期间上、下游有2～4 m的水位差,造成灌入的浆液随水流流失,处理难度大.根据这些情况确定采用高喷灌浆和塑性灌浆对围堰进行防渗处理,对落渣层架空地段和溶蚀通道采取了增加灌浆孔等处理措施,并对部分地段进行了补充灌浆处理.检查孔注水试验表明,这些处理措施是恰当、正确的,取得了较好的防渗效果.     

Evaluation of numerical wave model for typhoon wave simulation in South China Sea

The simulating waves nearshore (SWAN) model has typically been designed for wave simulations in near-shore regions. In this study, the model's applicability to the simulation of typhoon waves in the South China Sea (SCS) was evaluated. A blended wind field, consisting of an interior domain based on Fujita's model and an exterior domain based on Takahashi's model, was used as the driving wind field. The waves driven by Typhoon Kai-tak over the SCS that occurred in 2012 were selected for the numerical simulation research. Sensitivity analyses of time step, grid resolution, and angle resolution were performed in order to obtain optimal model settings. Through sensitivity analyses, it can be found that the time step has a large influence on the results, while grid resolution and angle resolution have a little effect on the results.     

西部地区农业高新科技示范项目的方向和重点

论述了西部地区建立农业综合开发高新科技示范项目的必要性;指出西北地区科技示范项目的主攻方向和节水农业高新科技示范,农作物和畜、禽、鱼、瓜果业的新品种示范等8项重点;提出进一步明确示范项目建设的指导思想与实施总体思路等8项对策。     

中国松嫩平原盐碱土固碳潜力过程及机理研究

目的 通过2019—2021年对松嫩平原盐碱地土壤呼吸的监测,探究盐碱土是否存在净碳吸收过程,明确盐碱土碳吸收在区域碳循环中的作用和地位。方法 文章基于纯盐碱地原位土壤呼吸的3年连续监测,探究盐碱地土壤CO₂通量动态变化及其环境响应。结果 （1）松嫩平原盐碱地除碳释放外存在阶段性碳吸收,不同年份盐碱土发生碳吸收的时间和强度不一致。（2）2019年和2021年土壤碳吸收主要发生在夜间,两次间歇性碳吸收分别发生于生长季初期和末期,其强度与土壤温、湿度显著相关,是由水分参与下的NaCO₃转化为NaHCO₃的化学性吸碳。（3）松嫩平原盐碱土在水淹期间存在连续性碳吸收,水淹状态下的吸碳来源于温度梯度驱动的大气CO₂形成水合二氧化碳的物理性吸碳。结论 （1）生长季的不同时期,松嫩平原盐碱土有着不同的碳吸收模式和强度。（2）土壤水分是影响盐碱土夜间间歇性吸碳的关键因素,温差是影响水淹吸碳的重要驱动力,随着温差加大,土壤碳吸收加强。（3）2019年和2021年夜间土壤碳吸收的最大值分别为-0.31 μmol CO₂ m^-2 s^-1和-0.75 μmol CO₂ m^-2 s^-1;2020年和2021年淹水期间碳吸收最大强度为-1.51 μmol CO₂ m^-2 s^-1和-1.27 μmol CO₂ m^-2 s^-1。（4）松嫩平原盐碱土的规律性固碳可为生态系统年净碳吸收贡献15%。不考虑土壤碳吸收的空间异质性,其每年的碳吸收潜力预计可达0.37 Tg C a^-1。