均布荷载作用下文克勒无限长梁解析解的探讨

该文通过基本微分方程推导了在均布荷载下的文克勒无限长梁的解析解,并提出了荷载作用区地基承载分担比α的概念,最后通过算例分析验证了该解析解和荷载作用区地基承载分担比α.     

同步硝化反硝化的影响因素研究

为了深入研究同步硝化反硝化(SND)的影响因素,试验研究了SBR工艺中C/N、DO和pH对SND率的影响.试验结果表明,在DO=0.45 mg/L、C/N在3.33～8.32的情况下,SND率随着C/N的升高而线性升高.当C/N超过8.32时,SND率增速减缓.在C/N=8.32、DO 0.2～0.4 mg/L的情况下,SND率随DO的升高而升高,当DO超过0.4 mg/L时,SND率开始下降.在C/N=8.32、pH处于7.6～8.4的情况下,SND率随着pH的增加先升高后下降,当pH处于8时,SND率达到最高.     

Durability studies of unsupported Pt cathodic catalyst with working time of direct methanol fuel cells

Life tests of direct methanol fuel cells (DMFCs) were carried out with three individual single cells for three different times. X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS) were used to evaluate the cathodic Pt black catalysts prior to and after the life tests. XRD results showed that the particle sizes of cathodic catalysts increased from an original value of 7.3–8.3, 8.7, and 9.2 nm, whereas their lattice parameters first increased and then decreased from an original value of 3.9188–3.9210, 3.9197, and 3.9196 Å before and after 117, 210, and 312 working hours, respectively. XPS results indicated that the metal content gradually decreased with test time, but the contents of Pt oxides in cathodic catalysts increased. Hydrogen adsorption–desorption cyclic voltammetry were employed to test the performances of three individual fuel cells and the electrochemically active surface areas (S_EAS) of cathodic catalysts before and after the life tests. It is found that both S_EAS of cathodic catalysts and their utilization decreased markedly. This indicates that the change of S_EAS and utilization of cathodic catalysts are the main factors affecting the performance decay of DMFC. The dissolution/agglomeration of Pt metal from cathodic catalysts also plays an important role in the performance decay of DMFC. The sintering/degradations of cathodic Pt nanoparticles were accelerated due to crossover of methanol to form the mixed potentials. The agglomeration of cathodic Pt nanoparticles may be illustrated with dissolution/deposition mechanism.     

钎焊金刚石砂轮磨削工程陶瓷表面完整性试验研究

本文采用单层钎焊金刚石镶块式砂轮磨削氧化锆陶瓷,并对其表面完整性进行实验研究。包括：采用单因素实验法测定其表面粗糙度,并通过SEM对其表面／亚表面损伤进行观察,得出以下结论：（1）氧化锆陶瓷材料的去除方式以显微塑性去除为主,同时存在脆性去除。去除过程中产生大量由脆性断裂形成的凹坑及表面／亚表面微裂纹;（2）氧化锆陶瓷的表面粗糙度随砂轮速度增加呈下降趋势,随工件速度及磨削深度的加大呈上升趋势。本文试验加工所得氧化锆陶瓷材料的表面粗糙度范围为：0．12-0．5um。     

Fully Roll-to-Roll Processed Efficient Perovskite Solar Cells via Precise Control on the Morphology of PbI2∶CsI Layer

Perovskite solar cells(PSCs)have attracted tremendous attention as a promising alternative candidate for clean energy genera-tion.Many attempts have been made w...     

谈地面塌陷的影响因素及防治措施

结合金岭铁矿区矿山采掘现状的调查,就影响采空塌陷的采空区暴露面积、围岩岩性、地质构造、地下水等因素进行了分析,并提出了防治地面塌陷的措施。     

化学溶液沉积法制备的Bi_4Ti_3O_(12)铁电薄膜的电学性能研究

采用化学溶液沉积工艺在电阻率为 6～ 9Ω·cm的n -Si(10 0 )衬底上生长Bi4Ti3O1 2 铁电多晶膜 ,研究了薄膜的电学性能 ,结果表明在 6 50℃下退火 1h得到的Bi4Ti3O1 2 薄膜具有良好的介电和铁电性能 ,其介电常数ε =12 9,剩余极化Pr=5.1μC/cm2 ,矫顽电场Ec=96kV/cm。     

高硫高砷金精矿电化学氧化机理研究

通过对黄铁矿、毒砂、金精矿的电化学氧化极化曲线、由平衡状态下的电化学反应速度计算的电化学反应参数和电化学氧化产物的Ｘ射线衍射（ＸＲＤ）分析结果的分析、推理,得到金精矿的电化学氧化机理。     

尿素合成塔贴衬焊缝超声检测的方法研究

介绍利用优化出的探头对设计的多种试块进行试验研究,检测结果与设计缺陷种类和尺寸具有良好的一致性,总结出用此方法来对尿素合成塔贴衬焊缝进行实际检测是可靠的。     

Generalized multi-state k-out-of-n:G systems

In a binary k-out-of-n:G system, k is the minimum number of components that must work for the system to work. Let 1 represent the working state and 0 the failure state, k then indicates the minimum number of components that must be in state 1 for the system to be in state 1. This paper defines the multi-state k-out-of-n:G system: each component and the system can be in 1 of M+1 possible states: 0, 1, ..., M. In Case I, the system is in state ⩾j iff at least k_j components are in state ⩾j. The value of k_j I 1 can be different for different required minimum system-state level j. Examples illustrate applications of this definition. Algorithms for reliability evaluation of such systems are presented