Laboratory studies of properties of the stone masonry in the Old Aswan Dam

The paper describes the results of mechanical and physical tests carried out on the masonry of the Old Aswan Dam for later assessment of its seismic stability and structural integrity. Mechanical tests were performed on 150 mm diameter cores obtained from various stages of construction of the dam. Tests indicate that the masonry in the first heightening exhibits higher strength characteristics than the masonry in the rest of the dam. Noticeably lower strength properties of the masonry in the second heightening were due to a higher water/cement ratio. The weakest link in the masonry of all three stages of construction from the point of view of its mechanical performance was the granite-mortar interfacial region. Analyses of test results show that the modulus of elasticity and the splitting tensile strength of the masonry may be expressed as a function of the compressive strength using the power regression equation and the logarithmic regression equation, respectively. The split cylinder test provides a more reliable measure of the tensile strength of the stone masonry than the direct tension test. In general, a wide scatter of test results in relation to the mean value appeared to be an inherent characteristic of this type of masonry. Variations were more pronounced in the case of the Poisson’s ratio test and in all instances when fracture at the horizontal mortar-stone interface was a primary mode of failure.     

糯扎渡高心墙堆石坝坝料特性研究及填筑质量检测方法和实时监控关键技术

系统研究了糯扎渡水电站高心墙堆石坝坝料特性,提出了静动力本构模型修正方法和水力劈裂发生的物理机制;研究了掺砾土料的压实特性、压实标准及填筑质量的检测方法;采用PDA、GPS、GPRS技术,通过传输网络,实现大坝填筑碾压各项参数的全面、实时、在线、自动监控的新技术。     

Efficient stockpiling and shipping policies for humanitarian relief: UNHCR��s inventory challenge

The United Nations High Commissioner for Refugees (UNHCR) establishes and maintains refugee camps to meet the needs of 34.5 million people affected by disaster or war worldwide. Like other international humanitarian organizations, UNHCR maintains central stockpiles which supply these refugee operations. Management at UNHCR seeks to improve the timeliness and quality of its disaster response subject to its budget constraints. We develop an inventory model to analyze the interaction between a stockpile and a downstream refugee camp or relief operation. We consider two inventory decisions: first, how to partition a fixed budget between stockpiling and shipping costs in order to best meet the needs of beneficiaries; and second, given the shipping budget determined by the budget partition, how to ship relief items from the stockpile to a downstream relief operation in an efficient manner. We solve for the shipment policy using dynamic programming, then determine the optimal stockpile size given knowledge of the optimal shipment policy. The optimization balances a key tradeoff: a larger stockpile is costly to procure and maintain, but enhances a humanitarian organization’s ability to respond to relief operation demands. We provide insights into shipment strategies and stockpile size. We also develop a spreadsheet model to help humanitarian organizations in their operational decision-making, leading to improved response to beneficiaries. Humanitarian organizations must use their financial resources wisely to carry out their mandates, and models of this type can help them make the best use of their limited response resources.     

Optimal decision of an economic production quantity model for imperfect manufacturing under hybrid maintenance policy with shortages and partial backlogging

Considering the characteristics of the stochastic shift of the machine state and the uncertainty of the product quality of production, in this paper, we develop an optimisation decision of economic production quantity model for an imperfect manufacturing system under hybrid maintenance policy with shortages and partial backlogging. We assume that the production process is imperfect stemming from the machine reliability and the probability of out-of-control, a hybrid maintenance policy combined of emergency maintenance and preventive maintenance is executed during each production run. Three decision models based on the scenarios of machine breakdown and repair time are developed. The optimal production quantity and maintenance inspection number during each production run are solved with minimising the expected average cost of the system. Numerical examples are used to demonstrate the effectiveness and feasibility of the model. Sensitivity analysis is conducted to analyse the impacts of key parameters on the optimal decision. Some implications related to the effective and economical execution of maintenance policy for practitioners are derived.     

Optimal stocking strategies for inventory mechanism with a stochastic short-term price discount and partial backordering

Price discount is an important research topic in the field of inventory management. The existing research on this topic mainly considers fixed price discount, but ignores the situation in which stochastic short-term price discount may be involved. In this paper, we study an inventory problem considering stochastic short-term price discount and partial backordering. To address this problem, we propose an optimal replenishment and stocking model to maximise the retailers' profit. After that, a cost–benefit analysis-based heuristic method for solving the developed model is presented by considering two scenarios depending on whether a replenishment point belongs to a discount period or not. Furthermore, an algorithm is provided to elicit an optimal ordering policy from multiple solutions derived from the given heuristic solution method. Finally, a real case is offered to demonstrate the application of the proposed model, followed by a sensitivity analysis. The results indicate that a retailer can identify the optimal replenishment policy with the aim of achieving maximal profit in situations where stochastic short-term price discount and partial backordering are considered for certain inventory problems at hand. In addition, sensitivity analysis illustrates a fact that different values of the introduced parameters may influence the optimal replenishment policy.     

Experimental and numerical studies on orifice spillway aerator of Bunji Dam

ABSTRACT

In this study, hydraulic design of the aerators of steep slope orifice spillways (26°–32°) was evaluated using physical and numerical modeling techniques. The Bunji Dam spillway, which is proposed to be constructed on the Indus River in Pakistan, was selected for physical and numerical modeling of the aerators. Extensive experimentation was carried out on a physical model of the Bunji Dam spillway by changing the air vent size and ramp angle of the aerator. Three air vent sizes and five ramp angles were constructed to assess the hydraulic performance of the aerator. The numerical model was formulated using Computational Fluid Dynamics (CFD)—FLOW 3D. The air vent size showed a significant impact on the dimensionless performance indicators of the aerators. Empirical equations were developed based on the outputs of physical and numerical models of the aerator. It is believed that the proposed equations will be useful for the estimation of nondimensional cavity length and air entrainment coefficient of the orifice spillway aerators having a short horizontal stretch leading to a convex curvature with slope varied from 26° to 32°.     

Reliability Analysis and Condition‐based Maintenance for Failure Processes with Degradation‐dependent Hard Failure Threshold

In this study, we introduce reliability models for a device with two dependent failure processes: soft failure due to degradation and hard failure due to random shocks, by considering the declining hard failure threshold according to changes in degradation. Owing to the nature of degradation for complex devices such as microelectromechanical systems, a degraded system is more vulnerable to force and stress during operation. We address two different scenarios of the changing hard failure threshold due to changes in degradation. In Case 1, the initial hard failure threshold value reduces to a lower level as soon as the overall degradation reaches a critical value. In Case 2, the hard failure threshold decreases gradually and the amount of reduction is proportional to the change in degradation. A condition‐based maintenance model derived from a failure limit policy is presented to ensure that a device is functioning under a certain level of degradation. Finally, numerical examples are illustrated to explain the developed reliability and maintenance models, along with sensitivity analysis. Copyright © 2016 John Wiley & Sons, Ltd.     

OPTIMAL OPERATION OF MULTIQUALITY WATER SUPPLY SYSTEMS-III: THE Q-C-H MODEL

A new technique for optimal operation of multiquality water supply systems is proposed. The technique, which is known as a Q-C-H (flow-quality-head) model, combines previously developed Sow-quality (Q-C) and flow-head (Q-H) models for optimal operation of water supply systems. The decision variables in the model are the operation of treatment plants, pumps and valves. The model minimizes the cost of water at sources, treatment, energy, and loss of agricultural yield when water quality is low. The model uses an iterative modified projected gradient method combined with the Complex method. As in the Q-C and Q-H models, the solution method is based on decomposition, dis-aggregation/aggregation approach, involving internal and external optimization. The decision variables of the external model are the flows in the loops of the network and the removal ratios at the treatment plants. The operation of the pumps and valves are the decision variables of the internal model. The method is demonstrated by application to an example problem.     

THE HYSTERESIS LOOP 1. A STATISTICAL THEORY

Abstract— Starting from a knowledge of inhomogeneous dislocation structures observed in cyclically strained metals, a model for cyclic straining is developed. A distribution of volumes with different internal critical flow stresses is assumed characterized by a probability density function. A generalization which includes a thermally activated component of the flow stress is derived assuming that the saturated microscopic effective stress, μ_es, is equal in all volumes. The relations to obtain the probability density function from experimental data are derived. The theory yields the macroscopic internal stress, σ_e and the macroscopic effective stress, σ_e, along the hysteresis loop. Experimental observations on cyclically strained metals can be explained using this statistical theory.     

多体系统斜碰撞动力学中的结构柔性效应

本文针对重力场下作大范围回转运动的柔性梁与一固定斜面发生斜碰撞的情况,建立起系统含碰撞的一致线性化的动力学方程。根据Ｈｅｒｔｚ接触理论和线性切线接触刚度建立碰撞接触模型。针对结构不同刚度的情况进行了仿真计算,由仿真算例的计算结果可以看出,结构的柔性对碰撞过程中的微运动具有明显的作用,同时对降低由于碰撞而引起的能量损耗和减少碰撞作用力起到一定的效果。     

Complexity analysis of an operation in demand-based manufacturing

In demand-based production systems with stochastic demand arrival times, operations often take place in random and long-time intervals. Therefore, traditional learning curve models may not be a good fit for estimating the operation time (OT) in such production environments. Moreover, the complexity of an operation is another influential factor in OT that is not quantified. In this article, human cognitive and complexity factors in demand-based production systems with stochastic demand arrival time are studied. Performing statistical analysis, a double segment learning curve is developed that is a best fit for OT with breakpoint feature. The breakpoint indicates the required number of orders received to reach the mastery level of performing a certain operation. A comparative analysis among existing and the double segment learning curve models is performed and the operation complexity measure is derived from the model.     

The use of near-infrared spectroscopy for the quantitation of a drug in hot-melt extruded films

The objective of the study was to demonstrate the utility of near-infrared spectroscopy (NIRS) for quantitative analysis of a model drug in hot-melt extruded film formulations. Polyethylene oxide (PEO) films with clotrimazole (CT) as a model drug were prepared by hot-melt extrusion (HME) incorporating drug concentrations ranging from 0-20% and analyzed using a Fourier transform near-infrared (FT-NIR) spectrophotometer in the reflectance mode. High performance liquid chromatography (HPLC) was the reference method used for this study. The NIR calibration model derived for CT was composed of 21 frequency ranges that were correlated to the values quantified using the HPLC reference method. The NIR method developed resulted in an assayed CT amount in the film matrix to be within 3.5% of the quantity determined by the reference method. These studies clearly demonstrate that NIRS is a powerful method for the quantitation of active drug substances contained in films produced by HME and warrants further investigation.     

有色动态噪声下多变量自相关过程调整策略研究

针对生产阶段有限的多变量自相关生产制造过程,研究了过程动态噪声为有色噪声、调整花费成本为二次型函数情形下的过程调整策略问题.在建立过程状态空间方程的基础上,利用卡尔曼滤波方法在线估计过程的状态变量,根据随机二次型最优控制理论,得到了使过程质量损失最小的最优调整策略.通过算例解释了最优调整策略的实现方法,并进行了仿真验证.结果表明,提出的调整策略与过程噪声为白噪声时的调整策略相比,能更有效地减少过程的总体质量损失.     

塌陷作用下埋地悬空管道的力学响应分析

地面塌陷会使得管道弯曲发生下沉或悬空现象,进而埋地管道会发生局部应力集中现象,是威胁管道安全运行的重要因素。根据管道的受力特点,将管道分为埋地段和悬空段,分别简化为Vlasov弹性地基梁和简支梁模型进行分析。依据管道的变形协调条件,得到了管道的挠度和内力计算公式。结合管道的运行状态,利用解得的内力计算公式,对管道的应力状态进行了分析和计算,为理论模型合理的应用范围提供了判别依据。通过与数值模拟结果和Winkler模型计算结果的对比,采用Vlasov模型对该类问题进行分析是可行的,其计算结果优于Winkler模型的计算结果。分析了管道尺寸、管道埋深、塌陷区域尺寸、以及管道材料对塌陷作用下悬空管道的影响,并进行归一化分析,发现塌陷区域尺寸对管道安全运行的影响最大。     

Maintenance schedule optimisation for a railway power supply system

High reliability is the crucial requirement in railway operation and a power supply system is one of the key components of electrified railways. The cost-effectiveness of the maintenance works is also the concern of the railway operators while the time window on trackside maintenance is often limited. Maintenance scheduling is thus essential to uphold reliability and to reduce operation cost. It is however difficult to formulate the optimal schedule to meet both reliability and maintenance cost for a railway power supply system as a whole because of its functional complexity and demanding operation conditions. Maintenance scheduling models to achieve reliability and maintenance cost are proposed in this study. Optimisation algorithms are then developed to attain the solutions of the model. The applicability of the models and efficiency of the solution algorithms are demonstrated in an example. The proposed methods are vitally important for the railway engineers and operators to assure the service quality in the increasing demands of the modern electrified railways.     

A Comprehensive Evaluation of Policy Effectiveness for Energy Efficiency in Existing Buildings

The healthy and stable development of energy efficiencies in existing buildings cannot be separated from effective policy operation, and evaluating policy effectiveness contributes to scientifically-sound government decision-making. This paper creates an evaluation index system and a grey comprehensive evaluation model for policy effectiveness for energy efficiency in existing buildings using three dimensions: 1) the effect of the policy itself; 2) the administrative effect of the policy; and 3) policy implementation effects. It chooses the government’s subsidy policy and preferential tax policy at market cultivation stage for its empirical comparative evaluation. The evaluation indicates that the former is more effective. Finally, it puts forward policy development suggestions from the perspective of: 1) clarifying incentive object; 2) broadening incentive scope; 3) increasing incentive intensity; and 4) innovating incentive mode.     

Simultaneous determination of preventive maintenance and replacement policies in a queue-like production system with minimal repair

This paper addresses the joint effects of preventive maintenance and replacement policies on a queue-like production system with minimal repair at failures. We consider a policy which calls for a preventive maintenance operation whenever N parts have been processed. If a failure occurs and at least K preventive maintenance operations have been carried out, the system is replaced by a new one. Otherwise, a failure is handled by minimal repair. An analytical model is developed and the argument of renewal–reward theory is used to provide long-run expected profit per unit time for a given maintenance and replacement policy. Numerical examples are given to provide some managerial insights.     

Asymptotic failure rate of a continuously monitored system

This paper deals with a perfectly continuously monitored system which gradually and stochastically deteriorates. The system is renewed by a delayed maintenance operation, which is triggered when the measured deterioration level exceeds an alarm threshold. A mathematical model is developed to study the asymptotic behavior of the reliability function. A procedure is proposed which allows us to identify the asymptotic failure rate of the maintained system. Numerical experiments illustrate the efficiency of the proposed procedure and emphasize the relevance of the asymptotic failure rate as an interesting indicator for the evaluation of the control-limit preventive replacement policy.     

框架-剪力墙-薄壁筒斜交结构分析的状态空间法

采用沿高度方向连续化的方法,建立了框架-剪力墙-薄壁筒斜交结构协同分析的连续化计算模型.将沿结构高度方向的坐标模拟成时间坐标,导出了问题的状态空间表达式,用状态空间理论的方法求出了状态向量表达式,由结构的边界条件可求出初始状态向量,从而得到了结构各单元的侧移与内力.给出了数值算例,并与其他算法的结果进行了比较.这种结构计算方法计算量小,精度较高,便于应用,能方便地推广应用于变截面建筑结构.     

A STATISTICAL-ECONOMIC FRAMEWORK FOR EVALUATING THE EFFECT OF ROBOT REPEATABILITY ON PROFIT

This paper presents a statistical-economic model for evaluating robot precision as measured by its positional repeatability. The model formulated assumes that repeatability follows a Rayleigh distribution. An economic measure maximizing the expected profit per unit time is developed, leading to an optimal velocity solution for a given task. Additional properties of the solution and sensitivity analyses are also provided. Finally, the model is validated by an empirical study of a simulated multi-station assembly operation with a PUMA robot that meets a random set of task requirements.