淹水土壤中Se(Ⅵ)还原反应的机理及条件

通过红黄泥和紫潮泥两种土壤淹水培养和硒的价态测定结果表明 :在 45 0mV培养下 ,外加Se(Ⅵ )第 1天有 5 7 2 %仍保持Se(Ⅵ ) ,2 3 4%还原为有机Se ,培养过程中Se(Ⅵ )呈稳定态 ,有机Se则氧化成Se(Ⅵ ) ,反应为准一级动力学方程 ;在 175mV培养下 ,外加Se(Ⅵ )第 1天有 81 8%还原为有机Se ,8 9%为Se(Ⅵ ) ,培养过程中有机Se呈稳定态 ,Se(Ⅵ )则还原为Se(Ⅳ ) ,反应符合动力学一级方程 .土壤中Se(Ⅵ ) Se(Ⅳ )体系氧化还原反应的临界电位为 71 4mV— 2 0 6 1mV(pH7 0 ) ,土壤pH上升 1个单位 ,电位相应降低 40 1mV .Se(Ⅵ ) Se(Ⅳ )体系在土壤氧化还原顺序中的反应次序居锰体系之后 。

衢州市家庭农场的发展机理与条件研究

本文基于制度变迁理论,立足浙江省衢州市现代农业发展实情,对衢州市大力发展家庭农场从发展机理和发展条件两方面进行了系统的梳理与分析,认为衢州市应充分利用独特的自然条件和良好的制度政策环境,结合全市"四化同步"发展的背景,大力开展家庭农场的发展。

技术进步影响农村劳动力转移的条件和机理

采用数理方法研究技术进步对劳动力转移就业的作用规律。研究认为,只有在完全竞争的市场条件下,企业在规模报酬递减阶段,采用资本节约型技术进步,生产较高需求弹性的产品,技术进步的就业补偿效应才能得以发挥。研究还表明,长期内,技术进步能够扩张劳动需求;技术进步对农村劳动力转移具有正向作用,而非农部门资本产出弹性对农村劳动力转移具有负向作用。

离子迁移的机理、危害和对策

概述了在印制板中"离子迁移"(CAF)漏电的机理、危害和对策.明确提出PCB走向高密度化和信号传输高频化的条件下,"离子迁移"漏电将走向严重化,要求进行CAF的测试与管控的重要性.

生态文明背景下基于绿色GDP角度的资源诅咒再验证

从绿色GDP角度对我国区域层面是否"资源诅咒"进行再验证,发现并不是所有的资源大省都存在资源诅咒现象,资源诅咒的存在具有一定的条件机理。以新疆和内蒙古地区为例,作比较性分析,结果表明在资源丰裕地区引发资源诅咒的原因主要包括,资源开发结构不合理,资源消耗和环境成本过高;产业结构不合理和产品初级化严重,粗放型模式诱发"荷兰病"现象,并造成一定的挤出效应;国家扶持力度不够,市场发育程度低,基础设施条件差,影响吸收外资能力;制度、法律法规的不完善导致产生寻租行为和投机主义。

Selective oxidation of glycerol in a base-free aqueous solution: A short review

Catalytic transformation of glycerol to value-added products has attracted the attention of scientists all over the world. Among various transformations, selective oxidation of glycerol with molecular oxygen to dihydroxyacetone, glyceric acid, glyceraldehydes, and tartronic acid is challenging both from the viewpoint of academic research and industrial application. Herein, we review the recent progresses in the selective oxidation of glycerol under base-free conditions. Those catalysts widely reported for the selective oxidation of the terminal hydroxyl and secondary hydroxyl groups in glycerol, such as monometallic Au, Pt, and Pd NPs, and bimetallic Au-Pt, Au-Pd, Pt-Bi, Pt-Sb, and Pt-Cu, were compared and discussed in detail. The reaction mechanism over Pt-based catalysts, possible catalyst deactivation, and the corresponding improvements are presented. Further, the recent progresses in the continuous oxidation of glycerol in fixed bed reactors and its excellent selectivity in the formation of dihydroxyacetone are highlighted.

Kinetics and Mechanism of Decomposition of Nano-sized Calcium Carbonate under Non-isothermal Condition

Experiments on thermal decomposition of nano-sized calcium carbonate were carried out in a thermo-gravimetric analyzer under non-isothermal condition of different heating rates (5 to 20K·min-1). The Coats and Redfern's equation was used to determine the apparent activation energy and the pre-exponential factors. The mechanism of thermal decomposition was evaluated using the master plots, Coats and Redfern's equation and the kinetic compensation law. It was found that the thermal decomposition property of nano-sized calcium carbonate was different from that of bulk calcite. Nano-sized calcium carbonate began to decompose at 640℃, which was 180℃lower than the reported value for calcite. The experimental results of kinetics were compatible with the mechanism of one-dimensional phase boundary movement. The apparent activation energy of nano-sized calcium carbonate was estimated to be 151kJ·mol-1 while the literature value for normal calcite was approximately 200kJ·mol-1. The order of magnitude of pre-exponential factors was estimated to be 10~9 s-1.

Adsorption of zinc onto anionic ion-exchange resin from cyanide barren solution

Removal of zinc from cyanide barren solution is obligatory for its reuse in leach process. Batch experiments were carried out to evaluate the adsorption capacity of resins under different experimental conditions, including con- centration, resin amount, initial pH, contact time and temperature. More than 99% of adsorption was achieved under the optimal condition. High adsorption rates on the resin were observed at the beginning and plateau values were obtained in 60 rain. The thermodynamic parameters （free energy change AG, enthalpy change AS and entropy change AH） for the adsorption were evaluated, The adsorption kinetic mechanism was studied with four models. The experimental results show that the adsorption follows the Langmuir isotherm and the kinetics follows the pseudo-second-order model.

Research on Preparation Method of Static Head Space for Volatile Organic Compounds in Drinking Water

[Objective] This research aimed to study the pre-treatment conditions of head space so as to establish a HS-GC determination method, which is suitable for China's conditions, for trace volatile organic compounds in drinking water. [Method]The preparation method of head space was adopted for the volatile organic compounds in drinking water. [Result] The 20 kinds of volatile organic compounds in drinking water all could be detected simultaneously by using HS-GC-FID method,and they all could be separated well. The HS-GC-FID method could analyze the detected substances qualitatively and quantitatively. In addition, this detection method was characterized by larger linear range of concentration, higher precision, higher detection limit and higher recovery rate. [Conclusion] Under certain conditions, HSGC can reduce the loss of volatile organic compound in drinking water and improve the sensitivity of detection. Moreover, the detection results meet the requirements by quality control.

Thermal Decomposition Kinetics of Abietic Acid in Static Air

The thermal decomposition of abietic acid in air was investigated under non-isothermal condition using thermogravimetric analysis-differential thermal analysis （TGA-DTA） technique with heating rates of 5, 10, 15 and 25 K.min-~. The non-isothermal kinetic parameters were obtained via the analysis of the thermogravimetric and differential thermogravimetric （TG-DTG） curves by using Flynn-Wall-Ozawa method and Kissinger method. The thermal decomposition mechanism of abietic acid was studied with four integral methods （Satava-Sestak, MacCallum-Tanner, ordinary integral and Agrawal）. The results show that the thermal decomposition mechanism is nu- cleation and growth, and the mechanism function is Avrami-Erofeev equation with n equates 1/2. The activation energy and the pre-exponential factor are 64.04 kJ.mol^-1 and 5.89×10^5 s^-1, respectively.

Growth, Survival and Physiological Condition of Cultured Marron, Cherax tenuimanus （Smith, 1912） Fed Different Levels of Organic Selenium

A 90-day feeding experiment was conducted to evaluate the effects of three levels of dietary supplementation of organic selenium （OS） on physiological and immunological responses of marron （Cherax tenuimanus）. Three levels viz. 0.1, 0.2 and 0.3 g kg^-1 of basal diet of Sel-Plex as a source of OS. were prepared and tested against the basal diet, which was used as a control. Each diet was fed to four replicated groups of marron, （initial mean weight of 39.43 ± 0.55 g）, at a rate of 3% body weight every second day. At the end of the feeding experiment, dietary inclusion of all Sel-Plex levels significantly improved specific growth rate （SGR） and survival of marron. Inclusion of Sel-Plex above 0.1 g kg^-1 resulted in significantly higher hepatopancreatic moisture level （HM） and wet hepatosomatic index （Hiw）, of marron than matron fed without Sel-Plex. Total Se level in the hepatopancreas was the highest （5.41 ± 0.28 μg g^-1） in the matron fed 0.2 g kg^-1 of Sel-Plex, whereas muscle accumulated significantly higher level of Se when man-on were fed 0.3 g kgl of dietary Sel-Plex. It is therefore suggested that the beneficial dietary supplementation levels of Sel-Plex in marron should range from 0.2 to 0.3 g kg^-1.

The degradation of organophosphorus pesticides by means of sodium percarbonate

The factors and mechanisms of oxidative degradation of three organophosphorus pesticides （dichlorvos, methamidophos and phoxim） were studied with sodium percarbonate （SPC） as a solid oxidant. The result showed that SPC has highly activity in degrading these organophosphous pesticides. The most efficient degradation of pesticides occurred under basic conditions and the degradation rates increased with time extension and high temperature. The degradation of organophosphorus pesticides was expected to get even better results at lower initial concentration. Furthermore, we analyzed the intermediate products by NMP, spectrometry. On the basis of the analytical result, the oxidative degradation mechanism was proposed for each organophosphous pesticide. It is significant to understand the environment chemistry of organophosphorus pesticides in environmental system.

Failure mechanism of pump chambers and their optimized design in deep mining at Qishan Coal Mine

Pump chambers, normally used as dominant structures in mining engineering to insure the safety and production of un-derground coal mines, become generally deformed under conditions of deep mining. Given the geology and engineering condition of Qishan Coal Mine in Xuzhou, the failure characteristics of pump chambers at the –1000 m level show that the main cause can be attributed to the spatial effect induced by intersectional chambers, where one pump is constructed per well. We developed an opti-mized design of the pump room, in which the pump wells in the traditional design are integrated into one compounding well. We suggest that the new design can limit the spatial effect of intersectional chambers during construction given our relevant numerical simulation. The new design is able to simplify the structure of the pump chamber and reduce the amount of excavation required. Based on a bolt-mesh-anchor with a rigid gap coupling supporting technology, the stability of pump chamber can be improved greatly.

敦化秋梨沟稀有矿泉水特征与开发利用战略

本文介绍了敦化稀有矿泉水出露的地质环境条件,矿泉水的赋存条件和形成机理,分析了矿泉水的动态特征与稀有化学元素的特征指标,对敦化秋梨沟稀有矿泉水水源地合理开发利用、保护及开发利用战略提出合理化建议。

Experimental research on variation of porosity in destruction process of cement stabilized soil

Based on the process of reinforcing soft soil using cement in laboratory, the porosity of test samples under different pressures conditions were determined through mercury intrusion porosimetry. The experiment was introduced and the law of porosity variation was summarized. The results show that when stress is between 0 and 0.15--0.2 qu, porosity decreases along with the pressure, then porosity has increased in the wake of the pressure until the sample damaged. It can provide an experimental basis for exploring the failure mechanism of cement stabilized soil from the microscopic view and the study to establish the microcosmic constitutive model of cement stabilized soil.

Reaction mechanism of molten Na OH decomposing Zn_2SiO_4 in willemite

Based on the existing form of Zn2 Si O4 in willemite, the chemical precipitation method was used to synthesize Zn2 Si O4.Through the orthogonal experimentation, the reaction conditions of melten Na OH decomposing Zn2 Si O4 were optimized, and the optimal experimental conditions include reaction temperature of 400 °C, reaction time of 4 h, and alkaline-to-ore molar ratio of 20:1.Based on the optimized experiment, on-line detection for the alkali leaching was made by using Raman spectroscopy; XRD was used to analyze the structure of water leaching residue, to explore the reaction mechanism of Na OH decomposing Zn2 Si O4. The results show that during the reaction process, the Si — O bond in Si O4 is destroyed, and the Na OH inserts itself into the silicate lattice,producing an immediate Na2 Zn Si O4 product. After the alkali leaching process, Zn2+ can be separated from the Si O4 array, which can be released out of the silicate in the form of ZnO.

Different Growth Characteristics of Grewia mollis, Grewia tenax and Grewia villosa Under Nursery and Field Conditions

This study was carried out to assess the growth characteristics of Grewia moll＆, Grewia tenax and Grewia villosa under the nursery and field conditions. Two experiments were conducted at the farm of the College of Natural Resources and Environmental Studies, University of Juba, Khartoum, Sudan. Randomized complete block design with three replications was used. Morphological and physiological factors were measured. Seedlings height, number of leaves, number of branches and sub-branches were different （P 〈 0.05） among the three species at the nursery stage and under field conditions. Collar diameter showed significant difference among the species under field conditions. Physiological factors exhibited more significant variations in the field than at the nursery stage. Variations in growth characteristics were attributed to genetics differences and different growth habit, while variations in physiological factors （photosynthesis and transpiration rate） were attributed to differences in leaf structure, size and number of stomatal pores.

Failure mechanism of full-size concrete filled steel circle and square tubes under uniaxial compression

In this paper, the failure mechanisms of full-size concrete filled steel tubes(CFST) under uniaxial compression were investigated with nonlinear finite element method. Existing experimental results were employed to verify the validity of the finite element models of CFST specimens. Then, the numerical analysis was further conducted to study the mechanical behaviors of full-size CFST columns with circular and square cross sections under uniaxial compression. The simulation results indicate that the distribution of the contact pressure between circular steel tube and core concrete is much more uniform than that between square steel tube and concrete, resulting in much higher confinement and more efficient interaction between steel tube and core concrete in circular CFST columns, as well as ultimate load capacity and ultimate displacement. Extensive parametric analysis was also conducted to examine the effect of various parameters on the uniaxial compression behaviors of circular and square CFST columns.

Effect of electromagnetic boundary condition on dynamo actions

In this paper, based on the mean field dynamo theory, the influence of the electromagnetic boundary condition on the dynamo actions driven by the small scale turbulent flows in a cylindrical vessel is investigated by the integral equation approach. The numerical results show that the increase of the electrical conductivity or magnetic permeability of the walls of the cylindrical vessel can reduce the critical magnetic Reynolds number. Furthermore, the critical magnetic Reynolds number is more sensi- tive to the varying electrical conductivity of the end wall or magnetic permeability of the side wall. For the anisotropic dynamo which is the mean field model of the Karlsruhe experiment, when the relative electrical conductivity of the side wall or the rel- ative magnetic permeability of the end wall is less than some critical value, the m=l （m is the azimuthal wave number） mag- netic mode is the dominant mode, otherwise the m=0 mode predominates the excited magnetic field. Therefore, by changing the material of the walls of the cylindrical vessel, one can select the magnetic mode excited by the anisotropic dynamo.

How can survival processing improve memory encoding?

We investigated the psychological mechanism of survival processing advantage from the perspective of false memory in two experiments.Using a DRM paradigm in combination with analysis based on signal detection theory,we were able to separately examine participants’utilization of verbatim representation and gist representation.Specifically,in Experiment 1,participants rated semantically related words in a survival scenario for a survival condition but rated pleasantness of words in the same DRM lists for a non-survival control condition.The results showed that participants demonstrated more gist processing in the survival condition than in the pleasantness condition;however,the degree of item-specific processing in the two encoding conditions did not significantly differ.In Experiment 2,the control task was changed to a category rating task,in which participants were asked to make category ratings of words in the category lists.We found that the survival condition involved more item-specific processing than did the category condition,but we found no significant difference between the two encoding conditions at the level of gist processing.Overall,our study demonstrates that survival processing can simultaneously promote gist and item-specific representations.When the control tasks only promoted either item-specific representation or gist representation,memory advantages of survival processing occurred.