Impact performances of steel tube-confined recycled aggregate concrete (STCRAC) after exposure to elevated temperatures

The impact behaviours of steel tube-confined recycled aggregate concrete (STCRAC) following exposure to elevated temperatures of 20 °C, 200 °C, 500 °C and 700 °C were experimentally investigated using a 100 mm-diameter split Hopkinson pressure bar (SHPB). The recycled coarse aggregate (RCA) replacement ratios were set as 0, 50% and 100%. The effect of RCA replacement ratio and exposure temperature on the impact properties of STCRAC were analysed in terms of failure modes, stress-strain time history curve and dynamic increase factor (DIF). The results show that the fire-damaged STCRAC can maintain its integrity during impact load. However, there were evident degradations in the dynamic behaviour of STCRAC after exposure to high temperatures of 500 °C and 700 °C. The ultimate impact strength, impact secant modulus and residual impact strength of STCRAC obviously decreased because of the damage due to high temperature exposure. But the degradations of both the ultimate impact strength and impact secant modulus of STCRAC under impact loading were less severe than those under quasi-static loading. The remaining strength factor and the DIF tended to increase with the raise of the elevated temperatures. Overall, during the impact loading, the fire-deteriorated STCRAC exhibited excellent impact behaviour.     

Prediction of the dynamic response of composite sandwich beams under shock loading

Finite element calculations are reported for the dynamic shock response of fully clamped monolithic and sandwich beams, with elastic face sheets and a compressible elastic–plastic core. Predictions of the peak mid-span deflections and deflected shapes of the beams are compared with the previously reported measured response of end-clamped sandwich beams, made from face sheets of glass fibre reinforced vinyl ester and a core of PVC foam or balsa wood [1]. Good agreement is observed, and the maximum sustainable impulse is also predicted adequately upon assuming a tensile failure criterion for the face sheets. The finite element calculations can also be used to bound the response by considering the extremes of a fully intact core and a fully damaged core. It is concluded that the shock resistance of a composite sandwich beam is maximised by selecting a composite with fibres of high failure strain.     

Influence of wavelength-to-excavation span ratio on ground motion around deep underground excavations

Accurate estimation of ground motion around excavations is important for dynamic rock support design in deep civil tunnels and underground mines. Among the influencing factors, the wavelength-to-excavation span ratio (λ/D) has a large effect on ground motion. Using an advanced wave propagation simulation tool, we performed two series numerical experiments to study the effect of the λ/D ratio on ground motion near excavation boundaries. The modeling results reveal that the wave field becomes more complex as the λ/D ratio decreases. The absolute PPV (Peak Particle Velocity) values around an excavation are closely related to the intensity of the seismic source but the relative PPV value depends on the λ/D ratio. Amplification factors, defined as the PPV in the excavation model to the PPV in the background model without any excavation, are calculated for each case. The amplification factor around the excavation increases significantly as the λ/D ratio decreases. When the λ/D ratio is greater than 30, the wave amplitudes are less affected by the excavation and a seismic wave loading can be considered as “quasi-static.” When the λ/D ratio is less than 20, significant wave interaction occurs and the wave loading needs to be considered as “dynamic.” The numerical results provide additional insights into the ground motion behavior around excavations under both “quasi-static” and “dynamic” loading conditions.     

Online decision making and automatic decision model adaptation

The paper investigates an online version of the vehicle routing problem with time windows, in which additionally arriving requests cause the revision of so far followed routes and schedules. An extended online optimization framework is proposed, which automatically adapts to problem variations and enables the explicit consideration of up-to-date knowledge about the current performance of the controlled system. Actually, we use the mean punctuality observed in the transportation system to adjust the objective function utilized for solving the next decision problem instance. The search is guided toward least cost solutions coming along with high punctuality. We prove the applicability of this approach within comprehensive numerical experiments.     

基于逻辑的乳腺癌诊断与治疗专家系统

本系统收集了天津市领域专家的经验,由编译性人工智能语言TurboProlog实现,共由七个模块-知识率、推理机构、解释机构、半自动人工知识获取、知识库管理、动态数据库和人机接口组成。本系统利用产生式规则表达知识,知识库中有多达1242条规则。在推理机构中,采用两类策略:启发式正向和反向推理方法,并利用黑板结构作为公共动态数据区。。提供了半自动人工知识获取以能获取新知识、丰富和更新知识库。在黑板上保留的推理进程是解释机构的素材。总系统共占用118KB内存,在IBM PC AT微机上运行正常,起到了总结和推广领域专家诊断与治疗乳腺癌经验的作用。     

继电器的动态接触特性研究

本文主要研究触点带低电平负载时,继电器的动态接触特性。为此,在不同的环境应力下,对继电器的动态接触电阻及其弹跳情况进行了数据采集及处理,得到了一些新的试验结果。     

钢铁工业发展战略的定量研究

利用系统动力学方法建立了我国钢铁工业发展动态仿真模型,研究了到本世纪末我国钢材需求供给规模及科技进步贡献等问题,提出了钢铁工业发展的政策及战略设想,为钢铁工业“八五”计划和十年规划的制订提供了依据。     

水电站实时优化调度模型及其应用

本文将随机动态规划（ＳＤＰ）与逐次优化算法（ＰＯＡ）结合起来，提出了水电站水库实时优化调度模型。该模型既能考虑水库调度的长期效益，又可根据实时水情变化及时调整调度决策，做到实时优化调度，克服了长、短期优化调度模型与实际水库调度工作不符，难以应用的缺点。     

面向对象方法在MIS中的应用研究

本文介绍了面向对象设计方法的概念和特点，并通过对传统的ＭＩＳ系统分析和面向对象的系统分析方法的比较，论述了面向对象方法在ＭＩＳ中的应用，体现了面向对象方法在移植性、复用性、可靠性、可扩充性及兼容性等方面的优势。文中在给出实例后，提出了面向对象方法在ＭＩＳ中应用的结论性意见。     

Dynamic Load Flow Used for Electric Power System State and Tendency Analysis

Dynamic load flow technology can simulate actual frequency and load flow change when a load naturally varies and generator units adjust their power output by an adjustment system during a certain time. Dynamic load flow is a basic part of power system state and tendency analysis. In this paper, a dynamic load flow model and its solution method are first presented and discussed. Then, the application of dynamic load flow to a real power system is given as a demonstration.