FLEXPERT: facility layout expert system using fuzzy linguistic relationship codes

Linguistic variables, fuzzy statements and fuzzy algorithms, from the theory of fuzzy sets, provide suitable tools to solve ill-defined problems. Unlike conventional techniques that deal only with discrete conditions, like 'on' and 'off', and precise numerical values, fuzzy logic offers an alternate technique that deals with non-discrete conditions, such as 'absolutely important', 'quite important' and 'less important'. This paper presents a new approach, based on the theory of fuzzy logic, to solve the facility layout problem. The proposed approach considers the multicriteria nature of the layout problem and the fuzziness of the input data through the integration of an expert system and a fuzzy algorithm with a facility layout program. The system generates the best layout that satisfies die qualitative as well as the quantitative constraints on the layout problem. This facilitates the incorporation of the knowledge of facility layout experts. A knowledge-based system, named FLEXPERT, has been developed to implement the new approach.     

Travel time prediction under heterogeneous traffic conditions using global positioning system data from buses

Travel time information is a vital component of many intelligent transportation systems (ITS) applications. In recent years, the number of vehicles in India has increased tremendously, leading to severe traffic congestion and pollution in urban areas, particularly during peak periods. A desirable strategy to deal with such issues is to shift more people from personal vehicles to public transport by providing better service (comfort, convenience and so on). In this context, advanced public transportation systems (APTS) are one of the most important ITS applications, which can significantly improve the traffic situation in India. One such application will be to provide accurate information about bus arrivals to passengers, leading to reduced waiting times at bus stops. This needs a real-time data collection technique, a quick and reliable prediction technique to calculate the expected travel time based on real-time data and informing the passengers regarding the same. The scope of this study is to use global positioning system data collected from public transportation buses plying on urban roadways in the city of Chennai, India, to predict travel times under heterogeneous traffic conditions using an algorithm based on the Kalman filtering technique. The performance of the proposed algorithm is found to be promising and expected to be valuable in the development of APTS in India. The work presented here is one of the first attempts at real-time short-term prediction of travel time for ITS applications in Indian traffic conditions.     

A fuzzy expert system approach using multiple experts for dynamic follow-up of endemic diseases

In this paper, an architecture oflepdiag — a knowledge-based system for on-line diagnosis and for monitoring prognosis of leprosy is presented. The important features oflepdiag that have been detailed are a multiple expert environment, a homeostatic expert containing the model of immune reaction, a performance evaluator that can compare the observed signs and symptoms with those predicted by the homeostatic expert and a prognostic expert which optimizes the management schedule for the patients. The entire systems is built around a fuzzy expert-system building toolfext to deal with the imprecise knowledge. A glossary of medical terms used is provided at the end of the paper     

Flow curve prediction of an Al-MMC under hot working conditions using neural networks

The plastic flow behaviour of a particle-reinforced aluminium alloy matrix composite (AA2618 + Al₂O_3p) was studied by analysing the results of hot compression tests carried out in extended ranges of temperature and strain rate, typical of hot working operations. In general, for a given temperature and strain rate, the flow curves exhibit a peak, at relatively low strains, followed by flow softening; for a constant strain, the flow stress increases with increasing strain rate and decreasing temperature. The experimental data were used as an input for training artificial neural networks in order to predict the flow curves of the composite investigated. The comparison of the predicted stress–strain curves with the ones obtained by experimental testing, under conditions different from those used for the training stage, has proven the prediction generalisation capability of the artificial neural network-based models.     

基于模糊神经网络的智能故障诊断专家系统

发动机是车辆的核心部件,及时有效地发现并排除故障,对降低维修费用,减少经济损失,增加发动机工作时的可靠性,避免事故发生具有重大的意义。以某型号发动机为研究对象,运用测试技术、信号处理、小波分析、神经网络和模糊控制理论,提出了基于模糊神经网络的智能故障诊断系统。建立了发动机故障信号采集试验台,在试验台上人工模拟3种转速下6种工况,通过加速度传感器采集正常工况和异常工况的振动信号,之后利用小波包技术进行消噪处理,并提取出故障信号的特征值,作为网络训练和测试的样本数据。用样本数据训练和检测自适应模糊神经网络,完成对信号的离线模式识别,之后以测试样本数据实现在线故障诊断,通过仿真分析,取得了很好的诊断效果。与传统的BP神经网络故障诊断方法进行对比,无论在诊断精度上还是学习速度上,模糊神经网络在故障诊断中更具有优势。同时,在专家系统的理论基础上,将模糊神经网络与专家系统进行信息融合,实现数据接口通信,利用网络的自学习能力建立智能故障诊断数据库和诊断规则库,通过程序语言快速高效的设计出智能诊断系统。最后,通过发动机故障诊断实例仿真分析,验证了基于模糊神经网络的智能故障诊断专家系统的可行性。     

Robust power system stabiliser design under multi-operating conditions using differential evolution

A power system stabiliser (PSS) design method, which aims at enhancing the damping of multiple electromechanical modes in a multi-machine system over a large and pre-specified set of operating conditions, is introduced. With the assumption of normal distribution, the statistical nature of the eigenvalues corresponding to different operating conditions is described by their expectations and variances. A probabilistic eigenvalue-based optimisation problem used for determining PSS parameters is then formulated. Differential evolution (DE) is applied for solving this highly nonlinear optimisation problem. Different strategies for control parameter settings of DE have been studied to verify the robustness of DE in PSS optimisation problems. The performance of the proposed PSS, with a conventional lead/lag structure, has been demonstrated based on two test systems by probabilistic eigenvalue analysis and nonlinear simulation.     

The stability behaviour of a Cu-stabilized NbTi-multifilamentary conductor under different cooling conditions

The investigations show that the recovery behaviour can be understood generally on the basis of a simplified equation of heat conduction with respect to the expansion and shrinkage of a normal conducting zone after a heat pulse. Under stationary cooling conditions, a lower threshold recovery current exists independent of the amount of local heat disturbance. It is characterized by an extended normal conducting zone and a slow recovery process. With decreasing disturbance energy the normal conducting zone remains localized, the recovery process becomes faster and the upper limit of the recovery current is shifter nearly up to critical current. If the spectrum of disturbances is not known, the safe limit of operational current is the lower threshold recovery current.The various cooling conditions considered show the at least in high fields with small critical temperatures nucleate boiling at the bare surface gives the most effective cooling power intensified by a natural convective flow. All other cooling modes, where the temperature difference between conductor and coolant is an essential parameter, have poor cooling capacity in the high field regime and become advantageous only in fields below 5 T due to the possible high temperature differences.The highest degree in electrical stability of a superconductor can be met obviously by nucleate boiling with an excited natural convection flow.     

Bayesian system reliability assessment under fuzzy environments

The Bayesian system reliability assessment under fuzzy environments is proposed in this paper. In order to apply the Bayesian approach, the fuzzy parameters are assumed as fuzzy random variables with fuzzy prior distributions. The (conventional) Bayes estimation method will be used to create the fuzzy Bayes point estimator of system reliability by invoking the well-known theorem called ‘Resolution Identity’ in fuzzy sets theory. On the other hand, we also provide the computational procedures to evaluate the membership degree of any given Bayes point estimate of system reliability. In order to achieve this purpose, we transform the original problem into a nonlinear programming problem. This nonlinear programming problem is then divided into four subproblems for the purpose of simplifying computation. Finally, the subproblems can be solved by using any commercial optimizers, e.g. GAMS or LINGO.     

Prototype and model masonry behaviour under different loading conditions

The aim of this paper is to systematically determine the effect of scale on masonry structural behaviour under various loading conditions. Small scale models have been employed to understand masonry structural behaviour over the years, because testing prototype masonry structures is both costly and challenging to undertake in a controlled laboratory environment. A programme of tests have been carried out at four scales namely prototype, half, fourth and sixth scale under five different loading conditions; compression, shear, diagonal tension, flexure and bond tension, with a view to understanding how each of these conditions affects masonry structural behaviour over the range of scales enumerated. The results show that scale or size effect is mostly pronounced in the masonry compressive strength.     

Modelling the flow behaviour of steel under non-isothermal conditions

Abstract

A mathematical model is proposed for evaluating flow behaviour under hot deformation conditions. The effects of dynamic recovery and recrystallisation as well as temperature and strain rate variations are considered in the model by means of Bergstrom's approach and the additivity rule for strain. To verify the model, hot compression tests for three grades of steel together with upsetting experiments are carried out. Comparison between experimental and theoretical results confirms the reliability of the model.     

Mechanical behaviour of Textile Concrete under accelerated ageing conditions

The mechanisms of ageing and environmental degradation involving exposure to cyclic hot/cold temperatures, wetting/drying movements as well as exposure to a carbon dioxide (CO₂)-rich environment, have different effects on the microstructure of interfaces within cementitious composites. This paper presents results of an investigation into changes occurring in fibre pull-out and composite tensile behaviour in Textile Concrete (TC) after exposure to accelerated ageing conditions. The microstructure of the matrix at the fibre/matrix interface, and fibre properties, were found directly to affect the mechanical behaviour at the macro-level. The study illustrated that exposure of TC to a CO₂-rich environment improves the fibre/matrix bond significantly; no major changes were observed in the mechanical behaviour of the composites after exposure to hot/cold and wetting/drying environments.     

Experimental investigations of a direction-finding system under urban conditions

The results of natural tests of the direction-finding locator of active radio beacons under urban conditions are presented.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 54–55, April, 1994.     

模糊随机桁架结构在模糊随机激励下的动力响应

研究了模糊随机参数桁架结构在模糊随机荷载激励下的复合模糊随机振动动力响应的问题。同时考虑结构的物理参数、几何尺寸和外载荷幅值的模糊随机性,从Duham e l积分式出发,利用振型迭加法求出了结构动力响应模糊随机变量的表达式;再由随机函数的矩法推导出结构模糊随机动力响应的模糊数字特征。最后,通过算例考察了结构参数和作用荷载的模糊随机性对结构动力响应的影响,并用M on te C arlo数值法对算例进行模拟,验证了文中模型和分析方法是可行有效的。     

Deformation behaviour of elastomeric matrix composites under static loading conditions

Damage mechanisms of elastomeric matrix composites (EMCs), propose a complex interplay between material properties and service conditions. The occurrence of defects such as the cavitations in EMCs specimens in using conditions is an important problem. This situation requires the well understanding of the damage mechanisms of EMCs used in automotive and aeronautical fields.Elastomeric matrix composites subjected to static and fluctuating loads basically fail due to the initiation and growth of defects (cracks, cavities, etc.). In fact, high hydrostatic pressures influence mechanical behaviours of EMCs. This paper reviews the damage mechanism of EMCs under static loading. In order to evaluate mechanical properties and fracture behaviour of EMCs, in situ observations were made by using X-rays computed tomography (CT). Two types of specimens are investigated in this work; Natural rubber, NR vulcanised and reinforced by carbon black, and synthetic rubber (styrene-butadiene-rubber), SBR. A detailed study was carried out by scanning electron microscopy (SEM) for a better understanding the damage mechanisms and confirming the CT results.     

Experimental study of the behaviour of leather under vacuum conditions

A characterization of the device-pumping behaviour of our vacuum reactor for plasma treatment of materials at low pressure is presented. The analysis of the pumpdown curves measured both in the viscous and in the molecular regimes was made to study the outgassing flowrates of several leather materials. Estimates of the relevant flowrates in different pressure ranges and measurements of the flow composition have been obtained. Such data can be interpreted in the framework of simplified desorption models and could be used in order to design the pumping system needed for vacuum treatment of such materials. We have also measured other related quantities such as the moisture uptake and the weight loss.     

Cooperative SLAM using fuzzy Kalman filtering for a collaborative air-ground robotic system

ABSTRACT

This paper presents a three-dimensional (3D) cooperative simultaneous location and mapping (SLAM) method for a collaborative air-ground robotic system, designed to manage an indoor quadrotor flying done together with a Mecanum-wheeled omnidirectional robot (MWOR) in indoor unknown and no GPS environments. An ORB (Oriented Fast and Rotated BRIEF)-SLAM 2.0 (ORB- SLAM 2.0) approach is used to produce a 3D map and discover the position of the indoor quadrotor simultaneously, and a particle-filter SLAM (FastSLAM 2.0) approach is employed to build the 2D map of the global environment for the MWOR. A more accurate 3D quadrotor position estimation (QPE) method for the quadrotor is proposed with the assistance of the MWOR. A cooperative SLAM using fuzzy Kalman filtering is proposed to fuse the outputs of the ORB-SLAM 2.0, FastSLAM 2.0, and QPE approaches, in order to localize the quadrotor more accurately. Both SLAM approaches, quadrotor position estimation method and cooperative SLAM have been implemented in the robotic operation system (ROS) environment. Moreover, the cooperative SLAM method is exploited to achieve landing of the quadrotor atop the MWOR. Five experiments are conducted to show the effectiveness and superiority of the proposed cooperative SLAM method.     

Decision support system for rapid prototyping process selection through integration of fuzzy synthetic evaluation and an expert system

A new method is proposed for selecting the most appropriate rapid prototyping process according to user's specific requirements by using the expert system and fuzzy synthetic evaluation. The selection process is divided into two stages. First, it is necessary to generate feasible alternatives, which are executed under the expert system environment. Second, given those feasible alternatives, the fuzzy synthetic evaluation approach is employed to produce a ranking order of the alternatives and to finalize the most suirapid prototyping system. One distinctive characteristic of this method is that quantitative as well as qualitative measures are employed, providing more accurate results. The decision system developed based on the proposed method is composed of four modules: a database to store the specifications of various rapid prototyping processes; a knowledge-based expert system for determining the feasible alternatives; a fuzzy synthetic evaluation model to select the most suitable rapid prototyping process; and a user interface and an expert interface to interact with the system. The fuzzy synthetic evaluation approach used in the system is illustrated in detail by a numerical example. Furthermore, a Java-enabled solution, together with web techniques, is employed for developing such a networked decision support system. Finally, two examples of rapid prototyping process selection are designed to demonstrate the application of the system. The system has been implemented and can run at a rapid prototyping and manufacturing networked service platform that the authors have developed.     

Stresses in a layer of a high-concentration disperse system under drying conditions

A mathematical model of the stress-strain state of a high-concentration disperse system in drying is proposed. The rheological behavior of the system in the saturation region is evaluated in terms of the micromechanics of approach of particles with account for viscous fluid flow in interparticle gaps and surface forces.Research Institute of Mathematics and Mechanics at Kazan University. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 67, Nos. 5–6, pp. 467–474, November–December, 1994.     

Fatigue behaviour of fine-grained alumina hip-joint heads under normal walking conditions

In prosthetic applications, the reliability of implant materials over a period of thirty years is absolutely essential. Calculation of the lifetimes of alumina ceramic heads is generally made on the basis of experimental fatigue and slow crack growth tests using finite element analysis. This investigation is aimed at understanding the fatigue behaviour of fine-grained alumina heads of hip joints. The service conditions of cyclic stress experienced by hip joints during walking are used in evaluating the fatigue behaviour of alumina femoral heads. These femoral heads have successfully withstood 10⁷ cycles at a maximum walking stress of 17.2 kN, which is equivalent to a body weight of 400 kg. The femoral heads did not exhibit any sub-critical crack growth at the maximum walking load of 10kN, indicating the quasi-infinite performance life in patients up to a body weight of 250 kg. The details of proof testing designed for evaluating the performance of femoral heads over 40 years are also presented.