影响土壤N_2O排放和CH_4吸收的主控因素的研究(英文)

本文于2000年7月,在实验室模拟条件下,以长白山阔叶红松林鲜土壤为对象,采用正交试验设计法对土壤进行培养实验,研究了影响土壤N2O排放和CH4吸收的主要因素。考察了温度、水分、pH值、NH4+及NO3-五因素对森林土壤N2O排放和CH4吸收的影响。实验结果显示:在本试验设计的因素、水平条件下,N2O排放速率、CH4吸收速率二者均与土壤pH值和温度这两个因素呈显著正相关。并且N2O排放速率与CH4吸收速率间呈显著线性正相关关。

分工式门限认证加密方案

(t,n)门限认证加密方案允许t个以上签名方产生指定接收方的认证加密签名,使得只有指定的接收方能够恢复消息和验证消息的完整性,而其他人却无法做到这一点.最近,在Tseng和Jan的认证加密方案的基础上,Chung等构造了一个(t,n)门限认证加密方案.该方案运用了分工式签名技术,有效地减轻了签名方的负担.然而,该文作者对该方案的安全性仅进行了解释性说明.目前,文献中没有对分工式门限认证加密的形式化刻画,没有出现可证安全分工式门限认证加密方案.事实上,Chung等的分工式门限认证加密方案存在设计上的缺陷.文中给出了分工式门限认证加密方案的形式化模型和安全模型,基于双线性映射构造了一个新的分工式门限认证加密方案.在随机预言机模型下,证明了该方案对于适应性选择密文攻击是语义安全的,该方案对于适应性选择消息攻击是存在性不可伪造的.方案的安全性可规约到计算性Diffie-Hellman(CDH)困难假设和决定性双线性Diffie-Hellman困难假设(DBDH).

一种资源敏感的Web应用性能诊断方法

提出一种资源敏感的性能诊断方法.对于Web应用事务,该方法利用资源服务时间对于不同负载特征相对稳定的特点建立性能特征链,并依据运行时资源服务时间异常实现性能异常的有效检测、定位和诊断.实验结果表明,该方法可适应系统负载特征变化,诊断各种资源使用相关的性能异常.

海洋渔业遥感地理信息系统应用服务技术和方法

全面概要地介绍具有自主知识产权、可业务化运行的海洋渔业遥感、地理信息系统技术应用服务系统的研制技术方法和功能特点

Synthesis and Characterization of Urea Bridged Hybrid Periodic Mesoporous Organosilica Materials

Urea bridged organic-inorganic hybrid mesoporous SiO2 materials (U-BSQMs) were synthesized through a sol-gel procedure by co-condensation of bis(triethoxysilyl propyl) urea (BSPU) under basic conditions using cetyltrimethylammonium bromide (CTAB) as organic template. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the mesoporous structure of the sample. Fourier-transform infrared spectroscopy (FT-IR), solid state CP-MAS NMR spectroscopy of Si-29 (Si-29, CP-MAS NMR) and C-13 (C-13 CP NMR) indicated that most of the Si-C bonds are unbroken during the synthesis process.

Effect of Y for enhanced age hardening response and mechanical properties of Mg-Ho-Y-Zr alloys

In this study, compositional dependence of age hardening characteristics and tensile properties were investigated for Mg-4Ho-xY-0.6Zr alloys (x = 0, 3 5, and 7 wt%). The result showed that with increasing Y content, the hardness of the alloys increased in the as-quenched and aged-peak conditions. Considerable age hardening response was recognized for the alloys. When the alloy containing 7% Y showed the most remarkable age hardening response at aging temperature of 250 degrees C.

毛细管电泳及液相色谱法研究黄连黄芩配伍过程化学成分的变化

对黄连与黄芩的不同比例配伍进行定量研究。黄连与黄芩按6∶1、6∶4、6∶7、6∶10、6∶13比例配伍,采用高效毛细管电泳法测定了黄连单煎液、黄连黄芩共煎液中生物碱的含量;采用高效液相色谱法测定了黄芩单煎液、黄连黄芩共煎液中黄酮的含量。结果显示,黄连黄芩共煎产生沉淀,使有效成分的含量降低。

Implantation of Nafion (R) ionomer into polyvinyl alcohol/chitosan composites to form novel proton-conducting membranes for direct methanol fuel cells

A series of cost-effective, proton-conducting composite membranes, comprising of Nafion (R) ionomer, chitosan (CS). and polyvinyl alcohol (PVA), is successfully prepared. By taking advantage of the strong electrostatic interactions between Nafion (R) ionomer and CS component, Nafion ionomer is effectively implanted into the PVA/CS composite membranes, and improves proton conductivity of the PVA/CS composite membranes. Furthermore, this effect dramatically depends on the composition ratio of PVA/CS, and the optimum conductivity is obtained at the PVA/CS ratio of 1:1. The developed composite membranes exhibit much lower methanol permeability compared with the widely used Nafion (R) membrane, indicating that these novel membranes have great potential for direct methanol fuel cells (DMFCs).

Highly conductive, methanol resistant fuel cell membranes fabricated by layer-by-layer self-assembly of inorganic heteropolyacid

Layer-by-layer (LBL) self-assembly is a simple and elegant method of constructing organic-inorganic composite thin films from environmentally benign aqueous solutions. In this paper, we utilize this method to develop proton-exchange membranes for fuel cells. The multilayer film is constructed onto the surface of sulfonated poly(arylene ether ketone) (SPAEK-COOH) membrane by LBL self-assembly of polycation chitosan (CTS) and negatively charged inorganic particle phosphotungstic acid (VIA). The highly conductive inorganic nanoparticles ensure SPAEK-COOH-(CTS/PTA)(n) membranes to maintain high proton conductivity values up to 0.086 S cm(-1) at 25 degrees C and 0.24S cm(-1) at 80 degrees C, which are superior than previous LBL assembled electrolyte systems.

Direct electrochemistry and electrocatalysis of glucose oxidase immobilized on glassy carbon electrode modified by Nafion and ordered mesoporous silica-SBA-15

In this paper, it was found that glucose oxidase (GOD) has been stably immobilized on glassy carbon electrode modified by ordered mesoporous silica-SBA-15 and Nafion. The sorption behavior of GOD immobilized on SBA-15 matrix was characterized by transmission electron microscopy (TEM), ultraviolet-visible (UV-vis), FTIR, respectively, which demonstrated that SBA-15 can facilitate the electron exchange between the electroactive center of GOD and electrode. The direct electrochemistry and electrocatalysis behavior of GOD on modified electrode were characterized by cyclic voltammogram (CV) which indicated that GOD immobilized on Nafion and SBA-15 matrices displays direct, nearly reversible and surface-controlled redox reaction with an enhanced electron transfer rate constant of 3.89 s(-1) in 0.1 M phosphate buffer solution (PBS) (pH 7.12).

First principles investigation on the structural, mechanical and electronic properties of OsC2

The structural, mechanical and electronic properties Of OsC2 were investigated by use of the density functional theory. Seven structures were considered, i.e., orthorhombic Cmca (No. 12, OsSi2), Pmmn (No. 59, 002) and Pnnm (No. 58, OsN2); tetragonal P4(2)/mnm (No. 136, OsO2) and 14/mmm (No. 139, CaC2); cubic Fm-3m (No. 225, CaF2) and Pa-3 (No. 205, PtN2). The results indicate that Cmca in OsSi2 type structure is energetically the most stable phase among the considered structures. It is also stable mechanically. OsC2 in Pmmn phase has the largest bulk modulus 319 GPa and shear modulus 194 GPa. The elastic anisotropy is discussed. (C) 2009 Elsevier B.V. All rights reserved.