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A flexible manufacturing system (FMS) due to its ability of being flexible in nature is concerned with automatic production of different parts in medium range. In short, it can be regarded as an automated manufacturing system. In this paper, an insight on previous work in the area of FMS modelling has been provided with an overview of research and development for better understanding of FMS. It serves as a medium for investigation of work that are accomplished by using different modelling techniques in FMS like mathematical, artificial intelligence, hierarchical, multi criteria decision-making method, Petri Nets and simulation. This paper will help researchers who are keen to do research in the area of FMS modelling, by highlighting contribution of available techniques in the field of FMS. It will also help them in deciding which modelling techniques can be used for a given problem. At last, comparison of different parameters considered in the recent papers of modelling FMS has been provided in the form of Table, along with a clear vision related to those works that still need to be investigated. [ABSTRACT FROM AUTHOR]

This is a very interesting paper that develops nonparametric identification results and and semiparametric estimators for a nonparametric and semiparametric nonclassical measurement error model using a combination of a primary data set and an auxiliary data set. Their estimator not only achieves the semiparametric efficiency bound when the conditional regression model is correctly specified parametrically, but also performs well in finite sample simulation designs. In their paper, an application of their method to studying the relation between the amount of beta-carotene from food and the latent true daily long-term intake of beta-carotene using two data sets from the Eating at America's Table Study (EATS) and the Observing Protein and Energy Nutrition study shows that ignoring measurement errors in the EATS data set leads to substantial attenuation bias in the regression coefficient. [ABSTRACT FROM AUTHOR]

In this paper, we seek robust policies for a multi-stage production/inventory problem to minimise total costs, including switching, production, inventory or shortage costs. While minimising switching costs often leads to non-convexity in the model, 0-1 variables are introduced to linearise the objective function. Considering the impossibility of obtaining the exact distribution of uncertain demand, we study the production/inventory problem under worst cases to resist uncertainty. In contrast to traditional inventory problems, unexpected yields in production are considered. Robust support vector regression is developed to approximate the yields of each unit.Amixed-integer linear programming is proposed, employing the duality theory to address the min--max model. A practical case study from cold rolling is considered. Experiments on the actual steel production data are reported to illustrate the validity of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper attempts to apply both global and local sensitivity analyses (SA) to fully test the integrated activity-based model (ABM) within several experiments based on a Chinese medium-sized city, Baoding. MATSim (Multi-agent Transport Simulation) that is a typical integrated ABM is used as an example for the SA. The global SA, which is based on the elementary effect method, is firstly applied to identify the influential parameters. Then the once-at-a-time (OAT)-based Local SA is employed to further reveal the relationship between the influential parameters and the outputs of interest, such as traffic flow. The SA results show the extent to which and how three influential MATSim parameters (population scaling factor, the number of iterations and time step size) influence the outputs of interest. In addition, the SA results of MATSim suggest that the parameters of time mutation rate and performing utility can heavily influence the outputs of interest and properly setting them can optimize the daily plans of agents. Finally, this paper concludes with suggestions on how to wisely use the SA findings for both MATSim and other ABM users. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to develop and test intelligible heuristics for the scheduling of production orders that can easily be used in practice. Grounded in a case study, this paper examines the combined effects of assignment and sequencing heuristics on commonly used performance indicators. Discrete event simulation is used in the analysis to adequately capture the complexity found in the case study: production orders differing in many aspects, two unrelated parallel machines with varying and product-specific speed, and set-up times that depend on the (dis)similarity of successive orders. Evaluating 108 strategy–scenario combinations including the base case derived from the case study, it is found that a loading heuristic based on order quantity and scheduled capacity in combination with the shortest set-up heuristic performs best. When compared to the heuristic approach used by the case company, this strategy saves about 13.9% of total machine busy time and increases service level by 10.2%. In addition, using a reduced set of 40 production orders we are able to demonstrate that the best heuristic strategies comes close to results generated in a two-stage optimisation. The gap to optimality is only 3.1% in total busy time on average over all scenarios. [ABSTRACT FROM PUBLISHER]

A paper published by Anagnostopoulos et al. in volume 55 of the Hydrological Sciences Journal (HSJ) concludes that climate models are poor based on temporal correlation between observations and individual simulations. This interpretation hinges on a common misconception, that climate models predict natural climate variability. This discussion underlines fundamental differences between hydrological and climatological models, and hopes to clear misunderstandings regarding the proper use of climate simulations. Citation Huard, D. (2011) A black eye for the Hydrological Sciences Journal. Discussion of ‘A comparison of local and aggregated climate model outputs with observed data’ by G.G. Anagnostopoulos et al. (2010, Hydrol. Sci. J. 55 (7), 1094–1110). Hydrol. Sci. J. 56(7), 1330–1333. [ABSTRACT FROM PUBLISHER]

M-ary baseband FSK modulated signals, which utilize M-set different frequencies, can be modelled as a set of complex rotating phasors. The received modulated signals can be detected by counting the speed and the direction of the complex phasor rotation. Conventional methods such as zero-crossing detection used this baseband FSK signal property. The detection approach presented in this paper is to count the number of quadrant crossing instead of zero crossing in a symbol period to demodulate FSK signals. Counting quadrant crossings acts as a noise filtering and improves the detection performance. The performance is improved further by using decision rules at fuzzy boundary and soft decision detection. The system modelling and simulation methods are illustrated in the paper. The performance comparison and improvement are shown by a 4-ary FSK signal example on wireless Rayleigh fading channels. [ABSTRACT FROM AUTHOR]

The tubeless vortex reducer was used to reduce the pressure drop in a cavity with radial inflow. In previous studies, the mechanism of vortex breakdown in tubeless vortex reducers was not clear, and there was a lack of direct guidance for engineering design. In this paper, we studied the vortex and pressure in the cavity in detail by large-eddy simulation (LES) and experiments. A mathematical model, which has high applicability and compatibility, was established to guide the pre-design of tubeless vortex reducers. The LES results showed that the high-speed and large-scale vortices broke rapidly at the nozzle inlet and reached the minimum size at the nozzle outlet. Furthermore, the enhancement of vortex in the downstream cavity was restrained. When the rotating speed was relatively low, strong negative vortices formed and the pressure drop increased in the downstream cavity. The experiments showed that the nozzle performance directly affected the flow characteristics and pressure drop in the cavity. Compared with the simple cavity, the tubeless vortex reducer generated lower pressure drop. The average relative error between the mathematical model and the experimental results was only 9.3%. [ABSTRACT FROM AUTHOR]

Simple moving average (SMA) is a well-known forecasting method. It is easy to understand and interpret and easy to use, but it does not have an appropriate length selection mechanism and does not have an underlying statistical model. In this paper, we show two statistical models underlying SMA and demonstrate that the automatic selection of the optimal length of the model can easily be done using this finding. We then evaluate the proposed model on a real data-set and compare its performance with other popular simple forecasting methods. We find that SMA performs better both in terms of point forecasts and prediction intervals in cases of normal and cumulative values. [ABSTRACT FROM AUTHOR]

The aim of this work is to introduce a new concept for a hydraulic semi-active yaw damper (SAYD) for the improvement of the stability of a high-speed rail vehicle. This concept represents a further elaboration of Secondary Yaw Control but envisages the use of semi-active hydraulic dampers instead of full-active electromechanical dampers, simplifying the design of the system and facilitating the design of a safe and fault tolerant device. Two control algorithms are proposed for the semi-active damper: maximum power point tracking and skyhook with Karnopp approximation. A multi-physics model of the SAYD is introduced and used in co-simulation with a multi-body model of a high-speed vehicle. Using these models, numerical simulations are performed to assess the behaviour of the semi-active damper in terms of improving the running stability of the rail vehicle at very high speed, showing that the use of the SAYD in combination with any of the two control strategies considered allows to improve substantially the stability of the vehicle. The results of experimental investigations performed in the project will be reported in a companion paper. [ABSTRACT FROM AUTHOR]

Design and control aspects of cellular manufacturing systems (CMSs) have been studied extensively and several robust procedures have been proposed to deal with cell formation and cell scheduling problems, separately. However, less attention has been paid to the interaction between the design and control aspects in the presence of uncertainty. In this paper, stochastic cell formation and cell scheduling problems are jointly studied where product demand and processing times are assumed as probabilistic. First, stochastic CMS design phase is handled and then stochastic cellular control phase is studied. Two stochastic non-linear mathematical models are developed to solve cell formation and cell scheduling problems consecutively. Later, Monte Carlo simulation is utilised to analyse the impact of uncertainty in design phase on the control phase. Various design risk and control risk scenarios are experimented with the proposed hierarchical approach to evaluate the chain impact of the risk taken during the cell formation (design risk) and the risk taken during the cell scheduling (control risk) on the scheduling performance: the number of tardy jobs (nT). A total of 3 cell formation and 300 cell scheduling scenarios are solved and results are summarised by design, control and integration subjects. Results indicate that higher design risk results in more pressure on control, which pushes scheduler to take lower risks during the cellular control. However, when lower design risk is taken, greater control risks can be taken, which provides more flexibility to scheduler. All in all, this paper presents a handy framework to practitioners to deal with modelling the uncertainty prior to design and during the control of CMS and deal with such short- and long-term decisions. [ABSTRACT FROM PUBLISHER]

Fixture errors are one of the error sources in machining operations. The fixture errors consist of positioning inaccuracies and errors due to workpiece and fixture deformations. Fixture locators’ height error causes incorrect positioning of the workpiece in the fixture and inaccuracy in machined surfaces which can be much more than the locators’ height error. For machining precise workpieces, it is necessary to eliminate these errors. This paper presents a method for modelling and compensating the fixture locators’ height error effect on workpiece machined surfaces. In this method, the planes of workpiece actual coordinate system (ACS) are mathematically modelled in the workpiece theoretical coordinate system (TCS). Using the model, required homogenous transformation matrix for coinciding ACS with TCS and modifying machining toolpath for compensating the errors is generated. The presented model is used to develop a post-processing fixture locator error compensation module, which can modify CNC machining codes to eliminate the effect of fixture locators’ height error on the workpiece machined surfaces. For verifying the presented method, machining simulations and cutting experiments have been performed in this work. The results show that the method can eliminate the effect of fixture locators’ height error on the workpiece machined surfaces considerably. [ABSTRACT FROM PUBLISHER]

This paper proposes the design of an approximated fractional-order low-pass Bessel filter using various optimisation techniques. Simulated annealing (SA), nonlinear least square (NLS), and firefly (FF) optimisation methods are applied for the designing of (1 + α) order low-pass Bessel filter. Stability analysis has been attempted for the proposed fractional-order Bessel filter in W-plane for α ranging from 0.1 to 0.9 in the interval of 0.1. The best optimisation technique in terms of error in gain, cut-off frequency, and stopband attenuation is validated on Biquad. Further, KHN Biquad has been simulated using SPICE to validate 1.2, 1.5, and 1.8 order Bessel filters. MATLAB and SPICE simulated results of gain, cut-off frequency, and stopband attenuation have been compared for the proposed Bessel filter. MATLAB simulated magnitude response shows a great extent of closeness with SPICE simulated magnitude response. Monte Carlo analysis has also been done in the SPICE environment. [ABSTRACT FROM AUTHOR]

Stochasticity in assembly processes is often associated with the processing time and availability of machinery, tools and manpower, however in this paper it is determined by probability of an assembly task successful completion which here is referred to as task reliability. We present a mathematical model for optimising the expected assembly cost, and consider two scenarios: the first a situation where a failure of one assembly task requires rework of that task alone; second a situation in which a failure in the midst of the process requires resumption of previously completed tasks. In the worst case scenario the assembly process must restart from the beginning. We show that the first scenario is insensitive to sequencing unless there are set-up costs. In the second scenario the process is sensitive to tasks' sequence. We present a heuristic that argues for accomplishing more uncertain tasks (with less reliability) earlier in the process to decrease the expected cost of assembly, and show that in a mutually dependent assembly process, when tasks' reliabilities are similar, the cheaper tasks should be executed earlier in the process. [ABSTRACT FROM AUTHOR]

Today, many companies use job production to produce small batches of work output according to customised specifications required by customers. With job production, the quantity of parts to be produced is finite and can be limited to a few thousands or hundreds (low-volume production). Usually, job production requires high-quality standards. When 100% sampling is not possible, online monitoring is a viable solution to immediately start process quality control. However, knowledge about the process distribution is frequently unavailable. Recently, it has been shown that the distribution-free Shewhart sign control chart is an efficient means to monitor processes performing high-volume production within a finite production horizon. In this paper, we reconsider the definition of the Shewhart sign chart statistic when the population size is small and we propose an approach that extends its implementation to finite batch sizes of work to be produced. Tables presenting the statistical properties of the Shewhart sign control chart for low-volume production are shown and commented. An illustrative example is discussed on a simulated data-set. [ABSTRACT FROM PUBLISHER]

Modelling the human cardiorespiratory system using computer simulation tools can serve to help physicians to comprehend the causes and development of cardiorespiratory diseases. The objective of this paper is to develop an integrated model of the cardiovascular and respiratory systems, along with their intrinsic control mechanisms, by combining analogous hydraulic-electric and diffusion-electric circuits, respectively. This modelling task is performed in object-oriented language in SIMSCAPE using the physical interconnected components to define the underlying dynamic equations. Simulation steady state results under rest and under variable physical exercise conditions, as well as under limiting conditions show a high qualitative agreement with clinical observations reported in literature. This object-oriented modelling approach, based on the combined use of electrical analogies, proves to be avaluable tool as a test bench for different strategies aimed to qualitative prediction of the effects of cardiorespiratory interactions during exercise, thus avoiding the formulation of complex mathematical models. [ABSTRACT FROM AUTHOR]

A defender defends and an attacker attacks each of n interdependent targets which can operate or fail and be in 2n possible states. Interdependence is modelled from each target to each other target. Despite such systems usually being analysed numerically, this paper succeeds in determining analytical solutions, accounting for unit effort costs, target values, and contest intensities. Increasing interdependence from some targets to some other targets induce both players to exert higher efforts into the former targets. For 100% interdependent targets, the attacker encounters a substitution effect. In contrast, for independent targets the defender encounters a substitution effect, defending the essential targets. For similarly advantaged players, increased target contest intensities cause higher efforts and lower expected utilities. Both players may withdraw in both 100% interdependent and independent systems. Applying the model to the US economy, we illustrate how interdependence between petroleum refineries, oil and gas extraction and air transportation impact defence, attack and expected utilities. [ABSTRACT FROM AUTHOR]

This paper discusses the problem of delay-dependent robust filtering design for polytopic systems with a time-varying delay. A new model transformation is firstly applied by employing a three-term approximation for the delayed state, which leads to a smaller approximation error than the two-term approximation. Then, based on the scaled small-gain Theorem combined with an appropriate Lyapunov-Krasovskii Functional, the performance analysis of the filtering error system is examined and then the full- and reduced-order filters are designed in terms of linear matrix inequalities via a simple linearisation technique. Before the end, a sufficient condition is presented to solve the problem of filtering design for a time-delay system without polytopic uncertainties. Finally, illustrative examples are presented to demonstrate the validity of the proposed methods. [ABSTRACT FROM AUTHOR]

The large thin-walled components in aerospace industry, such as wing panels of aircraft, are usually shaped with peen forming process by blasting numerous shots on the component to introduce compressive residual stresses in the surface layer. To obtain an objective shape, peening parameters are designed to introduce reasonable peening stresses, which are determined with physical trial and error traditionally. In this paper, an automatic numerical approach based on ABAQUS software is proposed to determine the peening stresses inversely from the objective shape. The approach consists of representation of peening stress field, monitoring of simulating shape, and performance of automatic calculation. With the approach, peening stresses in strip peened plates are inversely determined from measured bending curvatures. The variations of the peening stress field with peening parameters are obtained. The obtained peening stresses are compared with the results of regularly impacting simulations. The comparison shows an acceptable agreement and indicates the potential of the approach to determine the needed peening stresses for forming the aerospace components. [ABSTRACT FROM AUTHOR]

Recent successes in the design and implementation of expert systems in non-managerial problem domains has spurred interest in the proposition that expert systems may be viable in managerial problem domains as well. Continuing research in the design, implementation, and testing of a prototype managerial expert system is described in this paper. [ABSTRACT FROM AUTHOR]

In a number of recent papers, it has been argued that the use of ex post data can distort the picture when trying to analyse monetary policy reaction functions. This paper aims to establish whether the Taylor rule has been a reasonable representation of US monetary policy using both ex post and real-time output gap data. Results show that real-time data generate only minor differences to ex post data and, more interestingly, that the Taylor rule appears to be a questionable tool for evaluation of the Federal Reserve during the investigated samples. [ABSTRACT FROM AUTHOR]

Model predictive control in combination with discrete time non-linear observer theory is studied in this paper. Model predictive control, generally based on state space models, needs the complete state for feedback. In this paper the complete state is assumed not to be known and only outputs and inputs of the system are measured. To obtain knowledge of the full state an observer is used to obtain an estimate of the state. An extended non-linear observer is used for this purpose and potentially allows for successful output-based model predictive controllers. [ABSTRACT FROM AUTHOR]

A virtual enterprise (VE) is a temporary organisation that pools the core competencies of its member enterprises in order to exploit fast-changing market opportunities. Making successful collaborative partnerships is, in this context, a major challenge in today’s competitive business environments. The success of such a ‘virtual’ organisation is strongly dependent on its composition, and the selection of partners becomes therefore a crucial issue. This problem is particularly difficult because of the uncertainties related to information, market dynamics, customer expectations and technology speed-up, with a strongly stochastic decision-making context. In this paper, a chance-constrained approach to rank alternative VE configurations in business environments with uncertainty, and vague and random information, is proposed. This approach is based on a two-stage model: a chance-constraint multi-objective directional Tabu Search metaheuristic, complemented by a 2-tuple fuzzy linguistic representation model. Preliminary computational results clearly demonstrate the potential of the approach for practical application. [ABSTRACT FROM AUTHOR]

This paper presents a generic discrete model for the moving, intelligent target problem. Our objective is to maximise the probability of detection of the moving target with respect to target and searcher’s constraints. The solution method proposed here is composed on two stages. The first one aims at providing a large-scale strategy by solving an Integer Linear Program approach. As a direct solution of this problem is not practically possible, we use a decomposition of the problem into a searcher’s strategy on one side, and the target’s strategy on the other side. A good strategy for the searcher is determined using a sliding window procedure. Concerning the target, our approach consists in simulating some of the target’s possible strategies and considering each of these possibilities as an independent and deterministic entity. The second stage is dedicated to adjusting the large-scale strategy provided by stage 1. Finally, numerical results are presented so as to assess the impact of our approach. [ABSTRACT FROM PUBLISHER]

The purpose of this paper is to propose a revision of the well-known Campbellian system for causal research. The revised system, termed the COPS model, applies to both applied and basic research. Five validities are included, where two validities are adopted from the Campbellian system, and the validities are partly hierarchically ordered. Important similarities and differences between the Campbellian system and the COPS model are discussed. [ABSTRACT FROM AUTHOR]

Robustness analysis is a fundamental problem in the area of formal method, systems theory and performance evaluation. This paper investigates the global robustness of max-plus linear systems, which requires all state variables are entirely unaffected by the bounded parameter perturbations. The variable element is introduced to describe the global robustness. The relationship between solvable entries and solutions of systems of max-plus linear equations is further studied to find the variable elements of max-plus linear systems. It is pointed out that any non-solvable entry is a variable element. At the same time, the global robustness is used to analyse the stability of gene regulatory networks in biology systems and the time invariance of production processes in flexible manufacturing systems. Some numerical examples are given to illustrate the results. [ABSTRACT FROM AUTHOR]

This paper deals with the problem of query optimization in relational distributed database systems. It concentrates on the development of heuristic procedures that attempt to minimize the communication costs incurred by the distributed processing of queries. In particular, the paper deals with a class of heuristics that use a semi-join strategy as the mechanism for communication cost reduction. These heuristics are classified into two types — local and global heuristics. The global heuristic proposed in this paper is based on an optimal solution to a mathematical model of a simplified version of the problem. It is shown that the global heuristic can generate beneficial semi-join operations not included in local heuristic solutions. [ABSTRACT FROM AUTHOR]

Suspension components play key roles in the running behaviour of rail vehicles, and therefore, mathematical models of suspension components are essential ingredients of railway vehicle multi-body models. The aims of this paper are to review existing models for railway vehicle suspension components and their use for railway vehicle dynamics multi-body simulations, to describe how model parameters can be defined and to discuss the required level of detail of component models in view of the accuracy expected from the overall simulation model. This paper also addresses track models in use for railway vehicle dynamics simulations, recognising their relevance as an indispensable component of the system simulation model. Finally, this paper reviews methods presently in use for the checking and validation of the simulation model. [ABSTRACT FROM PUBLISHER]

This paper deals with durability design and comments on the assessment of reinforced concrete (RC) structures in relation to existing codes. Enhancement is provided by advanced approaches incorporating probabilistic simulations, mathematical models of the carbonation process in concretes made from CEM I through to CEM V, and the reliability issue. This paper presents practical software tools used for service life prediction, concrete cover evaluation and assessment of relevant reliability levels. A partial verification using test results is also presented. [ABSTRACT FROM AUTHOR]

This paper presents the dynamic formulation and performance evaluation of the 6-d.o.f. parallel structure seismic simulator. By means of the principle of virtual work and the concept of link Jacobian matrices, the inverse dynamic model of the seismic simulator is set up. Then, a series of new dynamic performance indices with obvious physical meanings have been proposed. The dynamic performance index combining the acceleration, velocity and gravity terms of the dynamic equations has been achieved by decoupling the inverse dynamics in an exhaustive way. By using the index, it is possible for us to evaluate the performance in different directions. The index has been applied to the dynamic characteristic evaluation of the 6-d.o.f. parallel structure seismic simulator in the numerical simulation. Conclusions and results are provided at the end of the paper. [ABSTRACT FROM AUTHOR]

This paper presents a novel idea on how to design an active suspension system to improve vehicle ride comfort and to actively tilt the vehicle inwards when it is subject to steering manoeuvres. Firstly, the motivations for active vehicle tilting via active suspensions are identified. Secondly, the mathematical models for the vehicle with active suspensions are built up and the link between active suspensions and vehicle roll characteristics is analysed. Thirdly, the control objectives of vehicle ride comfort and active tilting are incorporated into a standard robust-control framework and an H-infinity controller satisfying both objectives is designed. Finally, the integrated suspension control system is evaluated by computer simulations, in comparison to a passive suspension system and a traditional active one. The integrated control strategy not only improve vehicle ride comfort, but also actively tilt the vehicle inwards to act against vehicle steering manoeuvres. The active tilting reduces lateral acceleration experienced by passengers and reduces the possibility of vehicle rollover. [ABSTRACT FROM AUTHOR]

Thermal design of MEMS/NEMS packages is drawing more attention from both industrial and academic communities. When the system becomes extremely small, the atomistic effects have to be taken into account correctly. The finite element method is not capable of accurately capturing all the information, especially when it is applied to the small dimensions. In order to study failure behavior, precise modeling of interfacial thermal conductance is essential. In this paper, a multi-scale model is proposed to research interfacial thermal resistance in MEMS/NEMS packaging. The model combines a molecular dynamics simulation for the critical regions within the system with a FE method for a continuum description of the remainder of the system. For non-equilibrium simulations, the establishment of the proper boundary condition is very difficult. In this coupled model, the continuum subdomain serves primarily as a boundary model that provides the low frequency impedance and a sink for the energy associated with outgoing waves of the molecular dynamics model. The simulations results show that the temperature distribution is non-uniform along the interface, and the interface tends to accumulate much heat when the temperature of heat source changed. At the primary stage, the interfacial thermal resistance is unstable and will become very large at certain time steps. At the last stage, the change of interfacial thermal resistance tends to be stable. There are few direct experimental measurements of the interfacial thermal resistance between dissimilar materials, while the similar experimental results support the conclusions in this paper. [ABSTRACT FROM AUTHOR]

A hybrid distributed parameter model of a heating system for domestic hot water is presented in this paper. This heating system comprises a condensing boiler (burner), a counter current heat exchanger, and a so-called stratified storage tank which is the state of the art domestic hot water storage unit. The paper presents the model for the different operational modes of the plant which are described by a finite state automaton representing the discrete-event dynamics and driving the underlying continuous-time dynamics of the storage tank, the heat exchanger, and the burner. These interconnected components are modelled by a system of six coupled, quasi-linear partial differential equations (PDEs) comprising diffusion-, convection-, and source terms. In order to perform numerical simulations, the set of PDEs is spatially discretized using the method of lines. Thereby, the influence of various discretization schemes on the temporal evolution of the traveling temperature profiles in the single components is investigated. A high resolution slope limiter scheme for the stratified storage tank and a higher order up-/downwind scheme for the heat exchanger and the burner are found to be an appropriate choice for the spatial discretization of the model equations in order to adequately cover the plant dynamics. Simulation results fortify the effectiveness of the chosen discretization schemes and show the excellent performance of the suggested model representing the measurement data. [ABSTRACT FROM AUTHOR]

Ecological risk regionalisation is a process for determining the distribution of eco-risk, The basis of ecological risk regionalisation is regional ecological risk assessment. Existing procedures for ecological risk assessment often aim at natural ecosystems and are used mainly for retrospective evaluation of risks. This paper presents a tiered ecological risk assessment procedure (TERAP) for complex ecosystems. The approach is not only for current evaluation, but also for retrospective and future evaluations. Based on the TERAP, a regional ecological risk assessment model was constructed. The TERAP has three tiers: the first is demarcation of the area affected by a particular stressor; the second is a semi-quantitative assessment of the risk index and which is gained from the vulnerability index and integrated into the hazard index; the third is quantitative loss evaluation under the risk index. The main factors in the ecological risk assessment model are ecosystem attributes and socio-economy status. According to the main factors in the model, the change in the ecosystem into the future is simulated and the socioeconomic mathematical model is constructed. In this paper, taking Chongming Island as an example, the approach taken for simulation of the future ecosystem is analysis with the CLUE-S model. The end purpose of current and future ecological risk regionalisation is to direct region programming and risk management. [ABSTRACT FROM AUTHOR]

A dielectric half space model is introduced into the simulation of the scattering from ships on sea surface, which is excited by a plane wave. With the acceleration of Generalized Forward-Backward (GFB) method, the electromagnetic (EM) scattering can be simulated quickly in high precision. A High Resolution Range Profile (HRRP) is formed with the results computed in half space model, and the HRRP of ship on ocean in different aspects are discussed. As showed in the simulation, the model predicted in the paper is proved more valid and accurate than free space model. [ABSTRACT FROM AUTHOR]

This paper develops a simple mechanics-based model of snowplowing resistance for use in vehicle dynamic modeling for snowplowing operations. The mechanics-based model developed provides the basis for design of an advanced driver assistance system for snow removal operations. The control volume approach from continuum mechanics is used to develop a rather simple model that can estimate forces acting on the plow during steady state snow removal operation. Plow sliding resistance, plow air resistance, and friction force between the plow and the snow being deflected from the plow are all taken into account. The model is shown to closely match some of the existing experimental data on snow removal operations and can be incorporated easily into any vehicle dynamic model. [ABSTRACT FROM AUTHOR]

Environmental modelling languages provide the possibility to construct models in two or three spatial dimensions. These models can be static models, without a time component, or dynamic models. Dynamic models are simulations run forward in time, where the state of the model at time t is defined as a function of its state in a period or time step preceding t . Since inputs and parameters of environmental models are associated with errors, environmental modelling languages need to provide techniques to calculate how these errors propagate to the output(s) of the model. Since these techniques are not yet available, the paper describes concepts for extending an environmental-modelling language with functionality for error-propagation modelling. The approach models errors in inputs and parameters as stochastic variables, while the error in the model outputs is approximated with a Monte Carlo simulation. A modelling language is proposed which combines standard functions in a structured script (program) for building environmental models, and calculation of error propagation in these models. A prototype implementation of the language is used in three example models to illustrate the concepts. [ABSTRACT FROM AUTHOR]

In a simulation-based planning and control framework, timely monitoring, analysis, and control is important not to disrupt a dynamically changing system. To meet this temporal requirement, a dynamic-data-driven adaptive multi-scale simulation (DDDAMS) paradigm was proposed earlier, where the fidelity of a complex simulation model adapts to available computational resources by incorporating dynamic data into the executing model, which then steers the measurement process for selective data update. In this work, a sequential Monte Carlo method (sequential Bayesian inference technique) is proposed and embedded into the simulation to enable its ideal fidelity selection given massive datasets under the DDDAMS framework. As dynamic information becomes available, the proposed method makes efficient inferences to determine the sources of abnormality in the system (a shop floor in this paper). A parallelisation framework is also discussed to further reduce the number of data accesses while maintaining the accuracy of parameter estimates. A prototype DDDAMS involving the proposed algorithm has been implemented successfully for preventive maintenance scheduling and part routing scheduling in a semiconductor manufacturing supply chain, reducing the average waiting time of batches and increasing the machine utilisation significantly. [ABSTRACT FROM AUTHOR]

There is no general exact analysis for the class of generalized mixed models, and asymptotic procedures are widely used. Importantly, under small sample conditions equivalent asymptotic procedures can yield conflicting inference when applied to the same data set [Aubin, E. C. Q., Cordeiro, G. M. (2000). Bartlett-corrected tests for normal linear models when the covariance matrix is nonscalar. Commun. Statist.—Theory Methods 29:2405–2426]. For the classical likelihood ratio test (LRT), Bartlett’s [Bartlett, M. S. (1937). Properties of sufficiency and statistical tests. Proc. R. Soc. London. Ser. A, Math. Phys. Sci. 160(901):268–282] correction may be used to yield improved small sample performance. Zucker et al. [Zucker, D. M., Lieberman, O., Manor, O. (2000). Improved small sample inference in the mixed linear model: Bartlett correction and adjusted likelihood. J. R. Statist. Soc., Ser. B 62:827–838] proposed and investigated methods for improved small sample inference in the mixed linear model using refined LRTs. The refinements included the use of a Bartlett correction and the Cox–Reid adjusted likelihood [Cox, D. R., Reid, N. (1987). Approximations to noncentral distributions. Can. J. Statist. 15(2):105–114], which using simulation studies (under a random-line model, and a two-period, four-treatment crossover design) were shown to yield Type I error rates very close to the nominal level. An alternative approach which has also been shown [Kowalchuk, R., Keselman, H. (2001). The analysis of repeated measurements with mixed-model Kenward Roger's adjusted F-tests. Paper presented at the Annual Meeting of the American Educational Research Association, Seattle, Washington] to have improved performance characteristics is a procedure involving t and F statistics for tests of fixed effects with modified degrees of freedom calculations detailed by Kenward and Roger [Kenward, M. G., Roger, J. H. (1997). Small sample inference for fixed effects from restricted maximum likelihood. Biometrics 53:983–997]. However, to date there has been no direct comparison of the Bartlett modified likelihood ratio and Kenward Roger procedures. This paper provides the results from a Monte Carlo simulation study examining the Type I error control and power profiles of modified likelihood ratio procedures including those described in Zucker et al. and proposed by Kenward and Roger for tests of fixed effect parameters in mixed linear models with data simulated from small sample unbalanced repeated measures designs, followed by results from a real data example. [ABSTRACT FROM AUTHOR]

The paper deals with mathematical modelling and simulation of collisions in robot soccer representing ideal playground for studying multi-agent mobile systems. It involves robot and ball dynamic behaviour and focuses mainly on their collisions study and their realization. Some vital parts of the simulator are explained and modelled in more detail, beginning with the simple model of ball and robot motion and continuing with more complex collision models. Special consideration is given to collision between robots. The design of such model takes two steps. In the first, information about possible collision is obtained. The second step realizes collision by determining appropriate force impulse. The results from model verification are presented. It is shown that the developed model represents a good basis for realistic, yet simple enough, collision simulation. The paper concludes with some remarks and ideas for future work. [ABSTRACT FROM AUTHOR]

One of primary impediments in the use of discrete-event simulation to plan and design construction operations is that decision-makers often do not have the means, the knowledge, and/or the time to check the veracity and the validity of simulation models and thus have little confidence in the results. Visualizing simulated operations in 3D can be of substantial help in the verification, validation, and accreditation of simulation models. In addition, visualization can provide valuable insight into subtleties of modeled operations that are otherwise non-quantifiable and presentable. This paper investigates the efficacy of 3D visualization in verifying and validating discrete-event construction simulation models. The paper presents a case study of a simulation model of an earthmoving operation with fairly complex control logic that was verified and validated by visualizing the operation in 3D. The simulation model for the example was developed using Stroboscope and was visualized using the Dynamic Construction Visualizer. [ABSTRACT FROM AUTHOR]

In this paper new analytical travel time models for the computation of cycle times for unit-load double-deep automated storage and retrieval systems (in continuation double-deep AS/RS) are presented. The proposed models consider the real operating characteristics of the storage and retrieval machine and the condition of rearranging blocking loads to the nearest free storage location during the retrieval process. With the assumption of the uniform distributed storage rack positions and the probability theory, the expressions of the single and modified dual command cycle have been determined. The proposed models enable the calculation of the mean cycle time for single and dual command cycles, from which the performance of the double-deep AS/RS can be evaluated. A simulation model of the selected double-deep AS/RS has been developed to compare the performances of the proposed analytical travel time models. The numerical analyses show that with regard to the examined type of double-deep AS/RS with a different fill-grade factor, the results of the proposed analytical travel time models correlate with the results of simulation models of double-deep AS/RS. [ABSTRACT FROM AUTHOR]

In this paper we describe the main features of the Behavioral Toolbox for modeling of dynamical systems. The Toolbox, recently developed at the University of Groningen, implements the ideas on modeling which are at the heart of behavioral systems theory. In particular, it does not rely on predefined input/output descriptions and thus allows great flexibility in defining interconnections between systems. By means of an example we show how the different phases of a modeling and simulation session can be tackled within the framework provided by the Behavioral Toolbox. [ABSTRACT FROM AUTHOR]

The bucket brigades are self-balancing production lines where each human operator can move from one station to the next to continue working on a given part. When workers finish their job, they walk back to take over the ongoing work of their predecessor. For the bucket brigades, the line balancing emerges spontaneously. Several mathematical models have been proposed in literature for the analysis of bucket brigades, often where the basic assumptions seem to be too constraining. This paper analyses the behaviour of these lines when relaxing some of the usual restrictive assumptions. Two approaches are developed: analysis and simulation. An original analytical model is suggested and using this model, the sufficient condition of self-balancing for a finite backward velocity is studied. Then, a novel technique for the simulation of bucket brigades is proposed. This model uses the software Matlab/Simulink™. The results of simulation study are reported and analysed. The simulation model is flexible and easily extensible, in order to allow further embedding of complex dynamics which have not yet been considered. [ABSTRACT FROM AUTHOR]

A new concept of the dynamic connecting transport automated material handling system (AMHS) is proposed. This paper analyses the performance of the number of vehicles in a dynamic connecting transport AMHS in a simplified 300?mm wafer fab. Discrete-event simulation models are developed in e -M Plant™ to study the system performance. To avoid congestion or idle time in the intrabay system, the control of the upper limit or the lower limit on the number of vehicles can be the feasible solution. Thus, four strategies are identified and their performances are also investigated. In addition, several different operation environments such as the flow rate and the product-mix are used to investigate the performance of the dynamic connecting transport AMHS. [ABSTRACT FROM AUTHOR]

A model for estimating the transient performance of assembly networks is presented in this paper. Based on the fundamental assumption that operation start and finish times are related by the multivariate normal distribution, the approach relies upon computational procedures for estimating the correlations between certain operation finishing times. Fundamental properties of these correlations are identified and used to develop a procedure for estimating transient performance. Evaluated in a set of hypothetical test cases, the approach gave estimates which compare favorably with those derived from a simulation model both in accuracy and runtime. The approach is demonstrated as a decision aid in a case study involving material flow planning. Test results indicate that the approach offers unique capability to model transient operations in assembly networks. [ABSTRACT FROM AUTHOR]

The use of Monte Carlo simulation in construction cost analysis is of interest to construction professionals as part of the risk analysis of construction projects. In recent high profile publications the presentation of Monte Carlo simulation based cost analysis overplays the importance of the choice of which distribution to use to represent input variables and underplays the importance of assessing and including correlations between the variables. The British literature also overplays the suitability of the beta distribution to represent input variables. This paper addresses these issues using a data set comprising elemental rates from 216 office buildings drawn from the BCIS of the RICS. Using a chi-squared test for goodness of fit it is shown that lognormal distributions are superior to beta distributions in representing the data set. Simulation runs of the cost model including and excluding correlations show that correlations must be included in Monte Carlo simulation otherwise the analysis leads to serious misassessment of risk. Simulation results show also that the effect of excluding correlations is more profound than the effect of the choice between lognormal and beta distributions. [ABSTRACT FROM AUTHOR]

This note supplements papers by Chau in an attempt to further the consideration of risk measures in forecasts of construction project costs. The note reviews the application of PERT-based aspects of analysis and simple portfolio theory. Consideration is given to subjective factors in cost forecasting which arise from the natures and experiences of the forecasters as well as pressures to which they (may) feel subjected. Alternative measures of risk exposure are examined and supplementary analyses of the data contained in Chau's paper are reported. Although the log-triangular distribution is confirmed as a superior means of measuring risk, the observed risk measures still exceed those calculated [ABSTRACT FROM AUTHOR]

A pulse tube cryocooler (PTC) for future metrological satellites has been developed at one of the lead centers of the Indian Space Research Organisation in Bangalore, India for cooling on-board Infrared (IR) detectors to 80 K.A study has been conducted on the coldfinger of PTC to understand the off-state heat loads on the cooler by varying the value of gravity numerically in ANSYS FLUENT and experimentally by orienting the setup with respect to gravity. The off-state parasitic losses represent a major heat load in on-board applications that include redundant, viz. nonoperating coolers. To find out the amount of off-state parasitic heat losses in a nonoperating coldfinger of the PTC experimentally, transient warm-up technique was used. Various heat loads were applied experimentally on the cryo-tip at temperatures ranging from 80 to 100 K for determining the parasitic losses. The effect of orientation of PTC on the off-state parasitic heat load with respect to gravity is studied and presented in this paper. Enhancement due to free convection heat flow normalized by gas molecular conduction in pulse tube is analyzed using computational fluid dynamics to verify and compare with experimental results. The best orientation angle where the parasitic is low is when the cold end of the coldfinger of pulse tube cryocooler faces down (0°) and high when the cold end of the coldfinger is oriented to 135°. [ABSTRACT FROM AUTHOR]

This paper proposes a transformative framework where process improvement (standardisation) and staffing optimisation (integer programming) are integrated to enhance the performance of managed care organisations (MCOs) considering future surging demand. Four models (baseline and optimised for current and future states) are developed and compared using simulation. We find significant differences for all performance metrics between three alternatives and baseline model for current state: (1) optimised model for current state achieves cost reduction (31.71%) and higher staff utilisation (63.14%), without significant capacity increase; and (2) baseline model for future state results in significant capacity gain (2.05%), with less significant cost reduction and utilisation. Furthermore, optimised model for future state obtains largest capacity gain (2.31%), greatest cost reduction (44.43%), and highest utilisation (93.43%). All models result in acceptable average queue length. Additionally, process improvement affects all performance metrics, especially capacity, whereas staffing optimisation influences all other performance metrics than capacity. [ABSTRACT FROM AUTHOR]