钢筋混凝土多高层建筑结构在地震作用下的割线刚度分析法

基于性能/位移的抗震设计,采用振型分解反应谱法进行抗震分析,并根据钢筋混凝土框架及抗震墙模型的试验数据,确定各变形阶段框架及抗震墙的割线刚度,分析了多高层建筑结构侧移的成分,以及引起震害的侧移。将不同变形阶段框架及抗震墙的割线刚度、目标位移的控制值与引起震害的侧移值相联系,对钢筋混凝土多高层建筑结构进行分析。预估结构遭遇本地区多遇地震、设防烈度地震及罕遇地震时的弹塑性变形和弹塑性内力的重分布,以便了解和把握地震时结构的行为。为基于性能/位移的抗震设计方法,提供了新的分析途径。     

Further results on output feedback stabilization for stochastic high-order nonlinear systems with time-varying delay

This article further discusses the output feedback stabilization problem for stochastic high-order nonlinear systems with time-varying delay. Under the weaker conditions on nonlinearities in drift and diffusion vector fields, by using the idea of homogeneous domination approach, skillfully choosing an appropriate Lyapunov–Krasoviskii functional, and successfully solving several troublesome obstacles in the design and analysis procedure, an output feedback controller is constructed to render the closed-loop system globally asymptotically stable in probability.     

Construction business system in China: an institutional transformation perspective

During the transformational period from a planned economic system to a market-oriented one, China's construction business system is in an intermediate stage of development. The developing business system has played an increasingly important part in regulating the relations between various actors in the building sector, but the disordered situation in the construction market has fully revealed the shortcomings of the system. Using international experience and practice for reference, China is making efforts to promote the construction business system with Chinese characteristics. The institutional change involves reforms in legislation, property rights, price mechanism and the investment system. The crucial issue lies in deregulation, but this is difficult to realize for a government-led reform. Only if government's control and intervention are decreased enough can the construction market and related professional bodies play their proper roles so that the development platform of China's construction industry can be gradually perfected.     

Influence of Low Level Ag Additions on Mg‐Alloy AZ91

The influence of low‐level silver (Ag) additions (0.12 and 0.5 wt%) to magnesium alloy AZ91 were studied in terms of electrochemical response and hardness. These properties were reconciled with microstructural analyses, indicating that 0.12 wt% Ag was capable of imparting an increment in hardness, with no significant increase in electrochemical corrosion kinetics, whilst 0.5 wt% Ag resulted in formation of an Mg₄Ag phase which increased cathodic kinetics concomitant with lowered alloy hardness.     

偶氮氯膦PN(CPA-PN)光度法测定氧化铝废渣中的微量钪

采用偶氮氯膦PN(CPA-PN)显色,在低酸度介质用强酸型树脂Dowex50W-X8吸附钪与干扰元素分离,用2 mol/L HCL洗提干扰元素,用5 mol/L HCL洗脱钪,再用0.01 mol/L PMBP-苯萃取,用1%甲酸洗有机相出去稀土元素,用1 mol HCL反萃取钪。实验结果表明,钪含量在0~12μg/mL范围内符合比尔定律,络合物的最大吸收波长680 nm,表观摩尔吸光系数为9.00×10~2,钪校准曲线的R~2=0.9979。对于铝废渣试样进行分析,相对标准偏差2.3%,加标回收率为99%。     

恒温平滑肌槽在生理学、药理学实验教学中的应用

以生理学、药理学实验中的药物对离体小肠平滑肌收缩性的影响实验为例,介绍了HW-400E恒温平滑肌槽的功能特点、使用方法和注意事项,以供生理学、药理学实验教学和科研工作者参考。     

318R微量氧分析仪的应用

本文介绍了目前在国内各个化工企业广泛应用的318R氧分析仪在实际使用中遇到的一些问题及其解决对策。     

Effect of Heat Treatment on Morphology of Fe-Rich Intermetallics in Hypereutectic Al-Si-Cu-Ni Alloy with 1.26 pct Fe

Cobalt is generally considered as the element that can neutralize the negative effects of iron in Al alloys, such as inducing fracture and failure for stress concentration. Nevertheless, Fe-rich intermetallics would be inclined to form coarse plate-like δ-Al₄(Fe, Co, Ni)Si₂ particles when the content of Fe was high, which could also cause inferior mechanical properties. The dissolution and transformation of δ-Al₄(Fe, Co, Ni)Si₂ phase in solution heat-treated samples of Al-20Si-1.85Cu-1.05Ni-1.26Fe-1.35Co alloy were studied using optical microscopy, image analysis, and scanning electron microscopy. The effects of solution heat treatment time ranging from 0 to 9 hours at 783.15 K (510 °C) on mechanical properties were also investigated. The coarse plate-like δ-Al₄(Fe, Co, Ni)Si₂ particles varied slowly through concurrent dissolution along widths and at the plate tips as solution treatment time increased, which could be explained from diffusion-induced grain boundary migration. Solution heat treatment also has an important influence on mechanical properties. The maximum ultimate tensile strength and yield strength after T6 treatment were 258 and 132 MPa, respectively, while the maximum hardness was 131 HB. Compared with those of the samples in the as-cast state, they increased by 53, 42, and 28 pct, respectively. Moreover, δ-Al₄(Fe, Co, Ni)Si₂ phase, which appears as a coarse plate-like particle in two dimensions, is actually a cuboid in three dimensions. The length of this cuboid is close to the width, while the height is much smaller.