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This paper presents a simulation model for a preemptive transportation system where vehicles can have tasks dynamically reassigned to optimize overall efficiency. The model, built using Flexsim software, includes 9 storage areas and 8 vehicles. Exponential distributions, validated with real logistics warehouse data, generate stochastic task arrivals. Recursive logic implements the preemption algorithm. Comparative analysis over a 10-hour duration shows that the preemptive mode increases average transport volume by 13 % and reduces vehicle travel distance by 13 % compared to a non-preemptive baseline. The results demonstrate the value of preemptive transportation in enhancing system responsiveness and operational efficiency. [ABSTRACT FROM AUTHOR]

Parallel mechanism is widely used due to its high stiffness, strong bearing capacity, small accumulated error, and good dynamic performance. In this paper, a planar three-degree-of-freedom (3-DOF) redundantly actuated parallel mechanism is proposed. Firstly, the position constraint equation is investigated and the inverse position solution is derived. The center velocity mapping model of the moving platform is established and the Jacobian matrix of the mechanism is obtained. The theoretical model based on Mathematica and the simulation model based on ADAMS are compared to validate the correctness of the theoretical results, and the peak deviation of the results is within 5 %. Then, the constraint conditions are conducted, and the workspace of the mechanism is solved by numerical method. Finally, the influence relationship curves of rod parameters on the proportion of workspace are obtained respectively. And the size parameters are optimized to carry out a comparative analysis of the workspace. [ABSTRACT FROM AUTHOR]

This paper focuses on a challenging problem in the internal model control (IMC) strategy: the model inversion to design the IMC controller for non-square systems. Several existing approaches for the synthesis of a specific inversion of the identified model will be presented in this paper to deal with the differences between the system's inputs and outputs numbers. The non-square effective relative gain is firstly presented. It consists of the measurement of interactions between the loops of the system in order to square the system and make it invertible. The equivalent transfer function method is presented as well. It is based on tuning the pseudo-inverse of the process to design the internal model controller. These methods are then compared with a novel proposed model inversion approach based on virtual outputs method. Virtual adding is considered in order to obtain an invertible square transfer matrix to design the internal model controller. This simple yet effective method ensures robust control performance. Its efficiency and availability, as compared with other presented methods, is illustrated through simulations on an overactuated system with three inputs/two outputs. [ABSTRACT FROM AUTHOR]

Background: The overcrowded patients, which cause the long waiting time in public hospitals, become significant problems that affect patient satisfaction toward the hospital. Particularly, the bottleneck usually happens at front-end departments (e.g., the triage and medical record department) as every patient is firstly required to visit these departments. The problem is mainly caused by ineffective resource management. In order to support decision making in the resource management at front-end departments, this paper proposes a framework using simulation and multi-objective optimization techniques considering both operating cost and patient satisfaction.Methods: To develop the framework, first, the timestamp of patient arrival time at each station was collected at the triage and medical record department of Thammasat University Hospital in Thailand. A patient satisfaction assessment method was used to convert the time spend into a satisfaction score. Then, the simulation model was built from the current situation of the hospital and was applied scenario analyses for the model improvement. The models were verified and validated. The weighted max-min for fuzzy multi-objective optimization was done by minimizing the operating cost and maximizing the patient satisfaction score. The operating costs and patient satisfaction scores from various scenarios were statistically compared. Finally, a decision-making guideline was proposed to support suitable resource management at the front-end departments of the hospital.Result: The three scenarios of the simulation model were built (i.e., a real situation, a one-stop service, and partially shared resources) and ensured to be verified and valid. The optimized results were compared and grouped into three situations which are (1) remain the same satisfaction score but decrease the cost (cost decreased by 2.8%) (2) remain the same satisfaction score but increase the cost (cost increased up to 80%) and (3) decrease the satisfaction score and decrease the cost (satisfaction decreased up to 82% and cost decreased up to 59%). According to the guideline, the situations 1 and 3 were recommended to use in the improvement and the situation 2 was rejected.Conclusion: This research demonstrates the resource management framework for the front-end department of the hospital. The experimental results imply that the framework can be used to support the decision making in resource management and used to reduce the risk of applying a non-improvement model in a real situation. [ABSTRACT FROM AUTHOR]

Modelling and simulation is a major area of interest for states and international organizations in the context of the operational environment characterized by complexity, dynamism and unpredictability. At the moment, in NATO, the standard architecture for the field of modelling and simulation is High Level Architecture (HLA), but lately the concept of Service Oriented Architecture (SOA) has aroused the interest of specialists within the Alliance. In this paper, a comparative analysis is performed between the two types of architectures in order to determine the optimal variant for the field of military modelling and simulation. Following the analysis, it was concluded that a combined approach of the two types of architectures is needed to maximize the efficiency of modelling and simulation applications. [ABSTRACT FROM AUTHOR]

Highlights • A parameterized SILs verification approach is proposed on baseline of IEC61508. • Fully correctness proving is done by implementing and comparing with IEC61508-6. • Parametric features facilitate model reuse in large-scale, complex systems. • PFH relies on the balance between CCF and the number of the redundancy channels. • Systems with static components can be simulated by this approach. Abstract The paper proposed an approach of verifying the Safety Integrity Level (SIL) for the high demand safety system. This approach is based on the Stochastic Petri Nets models and Monte Carlo simulation (SPN-MC) and follows the requirements of IEC61508, which is a commonly accepted standard in the domain of functional safety of programmable electronic and control engineering systems. The paper provides a comparative analysis of the SIL with the application of SPN-MC and the Reliability Block Diagram (RBD) method given by EN61508 to prove the correctness and feasibility of the SPN-MC approach. Additionally, a typical large scaled complex system was adopted to apply the novel approach, which is hard for classical analytical methods. [ABSTRACT FROM AUTHOR]

Make-To-Stock (MTS) and Make-To-Order (MTO) are the two traditional strategies in production management. In the case of the MTS there is a growing demand for a new approach, which is called Make-To-Availability (MTA) strategy. The paper characterizes and compares the MTS and MTA strategies. The comparative analysis based, among others, on computational experiments carried out in a computer program developed in Microsoft Visual Studio 2017 Environment was presented. The models have been prepared for both strategies with the same assumptions: external conditions (market demand) and internal conditions (structure of the production process). The investigation of how the strategies respond to various scenarios of demand intensity was done. The simulation models were prepared and validated for the case of the production line in one of the industrial automation company. The research shows that the use of the MTA strategy in the majority of cases gives much better results than the use of the MTS strategy due to the minimization of storage costs and the costs of non-fulfillment of the customers' demand. The directions for further research were also presented. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a parallel continuous simulated tempering (PCST) method for enhanced sampling in studying large complex systems. It mainly inherits the continuous simulated tempering (CST) method in our previous studies [C. Zhang and J. Ma, J. Chem. Phys. 130, 194112 (2009); 132, 244101 (2010)], while adopts the spirit of parallel tempering (PT), or replica exchange method, by employing multiple copies with different temperature distributions. Differing from conventional PT methods, despite the large stride of total temperature range, the PCST method requires very few copies of simulations, typically 2-3 copies, yet it is still capable of maintaining a high rate of exchange between neighboring copies. Furthermore, in PCST method, the size of the system does not dramatically affect the number of copy needed because the exchange rate is independent of total potential energy, thus providing an enormous advantage over conventional PT methods in studying very large systems. The sampling efficiency of PCST was tested in two-dimensional Ising model, Lennard- Jones liquid and all-atom folding simulation of a small globular protein trp-cage in explicit solvent. The results demonstrate that the PCST method significantly improves sampling efficiency compared with other methods and it is particularly effective in simulating systems with long relaxation time or correlation time. We expect the PCST method to be a good alternative to parallel tempering methods in simulating large systems such as phase transition and dynamics of macromolecules in explicit solvent. [ABSTRACT FROM AUTHOR]

Availability of a common, shared benchmark to provide repeatable, quantifiable, and comparable results is an added value for any scientific community. International consortia provide benchmarks in a wide range of domains, being normally used by industry, vendors, and researchers for evaluating their software products. In this regard, a benchmark of untimed Petri net models was developed to be used in a yearly software competition driven by the Petri net community. However, to the best of our knowledge there is not a similar benchmark to evaluate solution techniques for Petri nets with timing extensions. In this paper, we propose an evaluation framework for the comparative analysis of generalized stochastic Petri nets (GSPNs) simulation techniques. Although we focus on simulation techniques, our framework provides a baseline for a comparative analysis of different GSPN solvers (e.g., simulators, numerical solvers, or other techniques). The evaluation framework encompasses a set of 50 GSPN models including test cases and case studies from the literature, and a set of evaluation guidelines for the comparative analysis. In order to show the applicability of the proposed framework, we carry out a comparative analysis of steady-state simulators implemented in three academic software tools, namely, GreatSPN, PeabraiN, and TimeNET. The results allow us to validate the trustfulness of these academic software tools, as well as to point out potential problems and algorithmic optimization opportunities. [ABSTRACT FROM AUTHOR]

The microscopic structure of fluids of simple spheres is well known. However, the constituents of most real-life fluids are non-spherical, leading to a coupling between the rotational and translational degrees of freedom. The structure of simple dense fluids of spheroids - ellipsoids of revolution - was only recently determined by direct experimental techniques [A. P. Cohen, E. Janai, E. Mogilko, A. B. Schofield, and E. Sloutskin, Phys. Rev. Lett. 107, 238301 (2011)]. Using confocal microscopy, it was demonstrated that the structure of these simple fluids cannot be described by hard particle models based on the widely used Percus-Yevick approximation. In this paper, we describe a new protocol for determining the shape of the experimental spheroids, which allows us to expand our previous microscopy measurements of these fluids. To avoid the approximations in the theoretical approach, we have also used molecular dynamics simulations to reproduce the experimental radial distribution functions g(r) and estimate the contribution of charge effects to the interactions. Accounting for these charge effects within the Percus-Yevick framework leads to similar agreement with the experiment. [ABSTRACT FROM AUTHOR]

A practical model predictive control (MPC) for path following of underactuated marine vessels, which is a representative marine application, is presented in this paper. Taking advantage of the capability of dealing with multivariable system and input saturation, the MPC method is used to transform the underactuated control problem into the optimization problem with incorporation of input (rudder) constraints. Considering the implementation obstacle of solving optimization problem formulated by the MPC method efficiently, the projection neural network, which is known as parallel computational capability, is employed here to improve the computational efficiency. The full information of ship motion is normally difficult to obtain directly due to the lack of enough measurements; therefore, the state observer is also included. A simple linear model represented the main dynamics of path following of underactuated marine vessels is conceived as predictive (control design) model; meanwhile, in order to demonstrate the effectiveness of proposed control design, all the comparative studies are conducted on a nonlinear high-fidelity simulation model. The simulation results validate that the proposed control design is effective and efficient. [ABSTRACT FROM AUTHOR]

Aiming at the problem of large residual current in single-phase grounding fault of resonant grounding system of distribution network, an active arc extinction scheme based on proportional resonant controller is proposed. From the perspective of tracking accuracy of the control strategy, this paper makes a comparative analysis of PR control and the generally adopted traditional PI control and feedforward PI control strategy, it is found that the traditional PI and feedforward PI control strategies have large steady-state errors in tracking sinusoidal signals, while the steady-state error under PR control is almost zero. Matlab is used for modeling and simulation, the results show that the PR control strategy can improve the compensation accuracy of residual current and realize reliable arc quenching. [ABSTRACT FROM AUTHOR]

In spite of the wide improvements in computer simulation packages, many complex simulation models, particularly under uncertainty, may be inefficient to run in terms of time, computation, and resources. To address such a challenge, integrating metamodels and robust design optimization has been applied. In the current paper, a systematic comparative study is implemented to evaluate the performance of three common metamodels, namely polynomial regression, kriging, and radial basis function. The required experiments are designed by different space-filling methods including the orthogonal array design and three forms of Latin hypercube sampling such as randomized, maximin, and correlation approaches. Although, the impact of sample size on the performance of metamodels in robust optimization results are investigated. All methods are analyzed using five two-dimensional test problems and one engineering problem while all of them are considered in two forms that are expensive (with a small sample size) and semi-expensive (with a large sample size). Uncertainty is assumed in all problems as a source of variability, so all test problems are conducted in the format of robust optimization in the class of dual response surface in order to estimate robust Pareto frontier. The performances of methods are studied in two terms of accuracy and robustness. Finally, the results of comparison, an applicable guideline is provided to aid the practitioners in selecting the appropriate combination of metamodels and sampling design methods for investigating set of robust optimal points (estimated Pareto frontier) in simulation–optimization problems under uncertainty. [ABSTRACT FROM AUTHOR]

After the diagnosis of a disease, one major objective is to predict cumulative probabilities of events such as clinical relapse or death from the individual information collected up to a prediction time, usually including biomarker repeated measurements. Several competing estimators have been proposed, mainly from two approaches: joint modelling and landmarking. These approaches differ by the information used, the model assumptions and the complexity of the computational procedures. This paper aims to review the two approaches, precisely define the derived estimators of dynamic predictions and compare their performances notably in case of misspecification. The ultimate goal is to provide key elements for the use of individual dynamic predictions in clinical practice. Prediction of two competing causes of prostate cancer progression from the history of prostate-specific antigen is used as a motivated example. We formally define the quantity to estimate and its estimators, propose techniques to assess the uncertainty around predictions and validate them. We then conduct an in-depth simulation study compare the estimators in terms of prediction error, discriminatory power, efficiency and robustness to model assumptions. We show that prediction tools should be handled with care, in particular by properly specifying models and estimators. [ABSTRACT FROM AUTHOR]

Extreme learning machines have gained a lot of attention by the machine learning community because of its interesting properties and computational advantages. With the increase in collection of information nowadays, many sources of data have missing information making statistical analysis harder or unfeasible. In this paper, we present a new model, coined spatial extreme learning machine, that combine spatial modeling with extreme learning machines keeping the nice properties of both methodologies and making it very flexible and robust. As explained throughout the text, the spatial extreme learning machines have many advantages in comparison with the traditional extreme learning machines. By a simulation study and a real data analysis we present how the spatial extreme learning machine can be used to improve imputation of missing data and uncertainty prediction estimation. [ABSTRACT FROM AUTHOR]

In order to interpret measured intensity autocorrelation functions obtained in evanescent wave scattering, their initial decay rates have been analyzed recently [P. Holmqvist, J. K. G. Dhont, and P. R. Lang, Phys. Rev. E 74, 021402 (2006); B. Cichocki, E. Wajnryb, J. Blawzdziewicz, J. K. G. Dhont, and P. R. Lang, J. Chem. Phys. 132, 074704 (2010); J. W. Swan and J. F. Brady, ibid. 135, 014701 (2011)]. A theoretical analysis of the longer time dependence of evanescent wave autocorrelation functions, beyond the initial decay, is still lacking. In this paper we present such an analysis for very dilute suspensions of spherical colloids. We present simulation results, a comparison to cumulant expansions, and experiments. An efficient simulation method is developed which takes advantage of the particular mathematical structure of the time-evolution equation of the probability density function of the position coordinate of the colloidal sphere. The computer simulation results are compared with analytic, first and second order cumulant expansions. The only available analytical result for the full time dependence of evanescent wave autocorrelation functions [K. H. Lan, N. Ostrowsky, and D. Sornette, Phys. Rev. Lett. 57, 17 (1986)], that neglects hydrodynamic interactions between the colloidal spheres and the wall, is shown to be quite inaccurate. Experimental results are presented and compared to the simulations and cumulant expansions. [ABSTRACT FROM AUTHOR]

In biochemical reaction systems dominated by delays, the simulation speed of the stochastic simulation algorithm depends on the size of the wait queue. As a result, it is important to control the size of the wait queue to improve the efficiency of the simulation. An improved accelerated delay stochastic simulation algorithm for biochemical reaction systems with delays, termed the improved delay-leaping algorithm, is proposed in this paper. The update method for the wait queue is effective in reducing the size of the queue as well as shortening the storage and access time, thereby accelerating the simulation speed. Numerical simulation on two examples indicates that this method not only obtains a more significant efficiency compared with the existing methods, but also can be widely applied in biochemical reaction systems with delays. [ABSTRACT FROM AUTHOR]

The hydrodynamic interaction is an essential effect to consider in Brownian dynamics simulations of polymer and nanoparticle dilute solutions. Several mathematical approaches can be used to build Brownian dynamics algorithms with hydrodynamic interaction, the most common of them being the exact but time demanding Cholesky decomposition and the Chebyshev polynomial expansion. Recently, Geyer and Winter [J. Chem. Phys. 130, 1149051 (2009)] have proposed a new approximation to treat the hydrodynamic interaction that seems quite efficient and is increasingly used. So far, a systematic comparison among those approaches has not been clearly made. In this paper, several features and the efficiency of typical implementations of those approaches are evaluated by using bead-and-spring chain models. The different sensitivity to the bead overlap detected for the different implementations may be of interest to select the suitable algorithm for a given simulation. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations were conducted to investigate the structural properties of melts of nonconcatenated ring polymers and compared to melts of linear polymers. The longest rings were composed of N = 1600 monomers per chain which corresponds to roughly 57 entanglement lengths for comparable linear polymers. For the rings, the radius of gyration squared, , was found to scale as N4/5 for an intermediate regime and N2/3 for the larger rings indicating an overall conformation of a crumpled globule. However, almost all beads of the rings are 'surface beads' interacting with beads of other rings, a result also in agreement with a primitive path analysis performed in the next paper [J. D. Halverson, W. Lee, G. S. Grest, A. Y. Grosberg, and K. Kremer, J. Chem. Phys. 134, 204905 (2011)]. Details of the internal conformational properties of the ring and linear polymers as well as their packing are analyzed and compared to current theoretical models. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations were conducted to investigate the dynamic properties of melts of nonconcatenated ring polymers and compared to melts of linear polymers. The longest rings were composed of N = 1600 monomers per chain which corresponds to roughly 57 entanglement lengths for comparable linear polymers. The ring melts were found to diffuse faster than their linear counterparts, with both architectures approximately obeying a D ∼ N-2.4 scaling law for large N. The mean-square displacement of the center-of-mass of the rings follows a sub-diffusive behavior for times and distances beyond the ring extension , neither compatible with the Rouse nor the reptation model. The rings relax stress much faster than linear polymers, and the zero-shear viscosity was found to vary as η0 ∼ N1.4 ± 0.2 which is much weaker than the N3.4 behavior of linear chains, not matching any commonly known model for polymer dynamics when compared to the observed mean-square displacements. These findings are discussed in view of the conformational properties of the rings presented in the preceding paper [J. D. Halverson, W. Lee, G. S. Grest, A. Y. Grosberg, and K. Kremer, J. Chem. Phys. 134, 204904 (2011)]. [ABSTRACT FROM AUTHOR]

Tau leaping methods enable efficient simulation of discrete stochastic chemical systems. Stiff stochastic systems are particularly challenging since implicit methods, which are good for stiffness, result in noninteger states. The occurrence of negative states is also a common problem in tau leaping. In this paper, we introduce the implicit Minkowski-Weyl tau (IMW-τ) methods. Two updating schemes of the IMW-τ methods are presented: implicit Minkowski-Weyl sequential (IMW-S) and implicit Minkowski-Weyl parallel (IMW-P). The main desirable feature of these methods is that they are designed for stiff stochastic systems with molecular copy numbers ranging from small to large and that they produce integer states without rounding. This is accomplished by the use of a split step where the first part is implicit and computes the mean update while the second part is explicit and generates a random update with the mean computed in the first part. We illustrate the IMW-S and IMW-P methods by some numerical examples, and compare them with existing tau methods. For most cases, the IMW-S and IMW-P methods perform favorably. [ABSTRACT FROM AUTHOR]

Data on rates, percentages, or proportions arise frequently in many different applied disciplines like medical biology, health care, psychology, and several others. In this paper, we develop a robust inference procedure for the beta regression model, which is used to describe such response variables taking values in (0, 1) through some related explanatory variables. In relation to the beta regression model, the issue of robustness has been largely ignored in the literature so far. The existing maximum likelihood-based inference has serious lack of robustness against outliers in data and generate drastically different (erroneous) inference in the presence of data contamination. Here, we develop the robust minimum density power divergence estimator and a class of robust Wald-type tests for the beta regression model along with several applications. We derive their asymptotic properties and describe their robustness theoretically through the influence function analyses. Finite sample performances of the proposed estimators and tests are examined through suitable simulation studies and real data applications in the context of health care and psychology. Although we primarily focus on the beta regression models with a fixed dispersion parameter, some indications are also provided for extension to the variable dispersion beta regression models with an application. [ABSTRACT FROM AUTHOR]

Publication bias can significantly limit the validity of meta-analysis when trying to draw conclusion about a research question from independent studies. Most research on detection and correction for publication bias in meta-analysis focus mainly on funnel plot-based methodologies or selection models. In this paper, we formulate publication bias as a truncated distribution problem, and propose new parametric solutions. We develop methodologies of estimating the underlying overall effect size and the severity of publication bias. We distinguish the two major situations, in which publication bias may be induced by: (1) small effect size or (2) large p-value. We consider both fixed and random effects models, and derive estimators for the overall mean and the truncation proportion. These estimators will be obtained using maximum likelihood estimation and method of moments under fixed- and random-effects models, respectively. We carried out extensive simulation studies to evaluate the performance of our methodology, and to compare with the non-parametric Trim and Fill method based on funnel plot. We find that our methods based on truncated normal distribution perform consistently well, both in detecting and correcting publication bias under various situations. [ABSTRACT FROM AUTHOR]

This paper presents a survey in the field of two-link flexible manipulators (TLFMs). Two-link flexible manipulators are more used in comparison with other types of flexible manipulators. Therefore, this paper discusses various aspects of the reported works of TLFMs available in the literature. The papers based on TLFMs are classified into modeling methods, dynamical analyses, complexities involved and control schemes used. The modeling methods discuss the various types of modeling used for a TLFM. A brief note on the complexities involved in the flexible manipulators are presented. The main categories of the control problems addressed by the available papers are also discussed. The classification of the control techniques is made according to the nature of controllers. It is also mentioned in the paper as to whether the reported work deals with only simulation based results or are validated with the experimental work. [ABSTRACT FROM AUTHOR]

This paper highlights a preference evaluation methodology for text entry methods in a touch keyboard smartphone using analytic network process (ANP). Evaluation of text entry methods in literature mainly considers speed and accuracy. This study presents an alternative means for selecting text entry method that considers user preference. A case study was carried out with a group of experts who were asked to develop a selection decision model of five text entry methods. The decision problem is flexible enough to reflect interdependencies of decision elements that are necessary in describing real-life conditions. Results showed that QWERTY method is more preferred than other text entry methods while arrangement of keys is the most preferred criterion in characterizing a sound method. Sensitivity analysis using simulation of normally distributed random numbers under fairly large perturbation reported the foregoing results reliable enough to reflect robust judgment. The main contribution of this paper is the introduction of a multi-criteria decision approach in the preference evaluation of text entry methods. [ABSTRACT FROM AUTHOR]

The past one and a half decade a rapid evolution in the sophistication of micro-simulation models have been seen, as well as a major expansion of their use in transportation engineering and planning practices. Models of the mid-nineties required inputs which were expensive to collect and not accurate enough to reflect the full range of traffic behaviour. Trough introduction of new technologys for advanced traffic control and information systems next generation models abound a source of data which can be used to reduce the cost of collecting the required data and improving its fidelity. The new datasets will help both the validation and calibration exercises. Continuing improvements in computer hardware will allow more detailed models to be developed, more simulation runs to be carried out, bigger networks to be modelled and for better visualisation of results. This lead to new challenges for software developers to fulfil customer needs. In this context this paper aims to perform as an overview that combines both, current traffic simulation systems - TSS capabilities and customer expectations. Therefore, a comparison of simulation tools as well as SWOT analysis has been conducted by analysing scientific papers and technical specifications. [ABSTRACT FROM AUTHOR]

This paper proposes an extended approach to develop a new sustainable process to produce tert-amyl-methyl ether (TAME) using as feedstock enriched C 5 fraction (LCN – light cracking naphtha) from fluid catalytic cracking (FCC). To the best of our knowledge, up to now, different authors developed the separation section without considering all possible options. The main contribution is to bring together for comparison different separation techniques of the given mixture and to develop new configurations for the separation section of the plant. In this respect, pressure swing is combined with liquid–liquid separation. Existing technologies consider methanol (MeOH) separation from reactor effluent only by water extraction, combined with distillation. Conceptual design based on residual curve maps (RCM) analysis, considered in this paper, reveals new possibilities to use pressure swing, eventually combined with liquid–liquid separation. Thus, compared to other results reported in literature, new separation sequences are proposed for TAME synthesis reactor effluent separation, in the frame of an extended and detailed analysis for the whole process. To underline process characteristics, three case studies, with those different configurations are presented and analysed using Aspen HYSYS ® v8.4. Main details are obtained using process simulation, process integration and environmental impact computer tools. In the first case study, classical MeOH separation using water extraction is considered. The second case study is based only on pressure swing distillation to separate the azeotropes between hydrocarbons and methanol. In the third case study, pressure swing distillation is combined with separation based on hydrocarbon–methanol liquid–liquid phase equilibrium. Using process simulation results, setup with Aspen HYSYS ® v8.4, heat integration analysis, performed with SPRINT ® v2.8, is accomplished to exploit energy savings. Environmental impact calculations are performed using WAR algorithm, considering different fuel types for utilities generation. Results show that the elimination of water in separation section and the use of liquid–liquid phase separation ensure lower energy consumption (overall heat recovery in case study 3 is 9.87 MW, compared to 7.47 MW for case study 2) and better environmental performance. Economic indicators calculated with Aspen Process Economic Analyzer ® allow identification of attractive process changes, for the new proposed process configuration. [ABSTRACT FROM AUTHOR]

In this paper, local load-redistribution is employed to study the vulnerability of the US power grid subjected to attacks, and the initial load of power node is assumed as the linear summation of its degree and the sum of its neighbors’ degrees. Based on the simulation results, we find that with the decrease of the initial load of power node, the critical threshold of tolerance parameter increases subjected to the highest load node-based attack, but the critical threshold decreases subjected to the lowest load node-based attacks. Meanwhile, we discover that the critical threshold subjected to the lowest load node-based attack is larger than that subjected to the highest load node-based attack when the tunable parameter α ∈ [0.1, 0.9]. Moreover, this paper compares the new model with the other two existing models, and the results illustrate that there are many similarities between these two existing models, but they are different from the new model presented in this paper. Furthermore, the infimum of tolerance parameter is proposed to portray the minimum cost of power grid, which can give a method to construct more robust power grids in the future. [ABSTRACT FROM AUTHOR]

This paper considers theH∞control problem for a class of linear singularly perturbed systems in the finite frequency range. A mixed output feedback controller comprising of a static output feedback controller and a dynamic output feedback controller is developed for the system stabilisation. Based on the generalised Kalman–Yakubovich–Popov (GKYP) lemma, the frequency-domain inequalities can be converted into linear matrix inequalities which are numerically tractable. Compared with the existing full frequency approaches, better results are obtained. Moreover, the selection methods of the cut-off frequencies in both low and high frequency ranges are extensively studied with a view to reduce the conservativeness in output feedback control design. Simulation results suggest the asymptotic validity of the main results in this paper. [ABSTRACT FROM PUBLISHER]

Simulation, as a powerful tool for evaluating transportation systems, has been widely used in transportation planning, management, and operations. Most of the simulation models are focused on motorized vehicles, and the modeling of nonmotorized vehicles is ignored. The cellular automata (CA) model is a very important simulation approach and is widely used for motorized vehicle traffic. The Nagel-Schreckenberg (NS) CA model and the multivalue CA (M-CA) model are two categories of CA model that have been used in previous studies on bicycle traffic flow. This paper improves on these two CA models and also compares their characteristics. It introduces a two-lane NS CA model and M-CA model for both regular bicycles (RBs) and electric bicycles (EBs). In the research for this paper, many cases, featuring different values for the slowing down probability, lane-changing probability, and proportion of EBs, were simulated, while the fundamental diagrams and capacities of the proposed models were analyzed and compared between the two models. Field data were collected for the evaluation of the two models. The results show that the M-CA model exhibits more stable performance than the two-lane NS model and provides results that are closer to real bicycle traffic. [ABSTRACT FROM AUTHOR]

Taxiway path planning is one of the effective measures to make full use of the airport resources, and the optimized paths can ensure the safety of the aircraft during the sliding process. In this paper, the taxiway path planning based on conflict detection is considered. Specific steps are shown as follows: firstly, make an improvement on A * algorithm, the conflict detection strategy is added to search for the shortest and safe path in the static taxiway network. Then, according to the sliding speed of aircraft, a time table for each node is determined and the safety interval is treated as the constraint to judge whether there is a conflict or not. The intelligent initial path planning model is established based on the results. Finally, make an example in an airport simulation environment, detect and relieve the conflict to ensure the safety. The results indicate that the model established in this paper is effective and feasible. Meanwhile, make comparison with the improved A*algorithm and other intelligent algorithms, conclude that the improved A*algorithm has great advantages. It could not only optimize taxiway path, but also ensure the safety of the sliding process and improve the operational efficiency. [ABSTRACT FROM AUTHOR]

This paper presents a quantitative method for analysing process models of designing independently of the specific design domain. The method uses the situated function-behaviour-structure framework as the basis for a simulation model of a designer acting according to these models. The results of these simulations are sequences of design issues that are analysed using cumulative occurrence graphs with associated quantitative measures. The paper illustrates the approach by analysing and comparing three models of designing from different domains: Pahl and Beitz' model of engineering design, the rational unified process of software design and a model of design for six sigma in service design. The quantitative results indicate some commonalities across the different models. These commonalities are related to the start of cognitive effort spent on design issues, the continuity of the cognitive effort throughout the design process and the constancy of the speed with which design issues are generated. [ABSTRACT FROM AUTHOR]

In this paper, three multiscale methods for coupling of mesoscopic (compartment-based) and microscopic (molecular-based) stochastic reaction–diffusion simulations are investigated. Two of the three methods that will be discussed in detail have been previously reported in the literature; the two-regime method (TRM) and the compartment–placement method (CPM). The third method that is introduced and analysed in this paper is called the ghost cell method (GCM), since it works by constructing a “ghost cell” in which molecules can disappear and jump into the compartment-based simulation. Presented is a comparison of sources of error. The convergent properties of this error are studied as the time step Δ t (for updating the molecular-based part of the model) approaches zero. It is found that the error behaviour depends on another fundamental computational parameter h , the compartment size in the mesoscopic part of the model. Two important limiting cases, which appear in applications, are considered: (i) Δ t → 0 and h is fixed; (ii) Δ t → 0 and h → 0 such that Δ t / h is fixed. The error for previously developed approaches (the TRM and CPM) converges to zero only in the limiting case (ii), but not in case (i). It is shown that the error of the GCM converges in the limiting case (i). Thus the GCM is superior to previous coupling techniques if the mesoscopic description is much coarser than the microscopic part of the model. [ABSTRACT FROM AUTHOR]

This paper introduces a temperature-based approach – called the Days Exceeding Threshold-Toa (DET-Toa) method to detect persisting small increase or decrease in the normal building energy consumption. This method identifies an abnormal energy consumption fault when the deviation between the measured and simulated consumption is greater than one standard deviation of the residuals in the baseline period and persists for at least 20 days which are consecutive when ordered according to increasing or decreasing outside air temperature. The fault detection capability of the method is evaluated with simulation tests with two on-campus buildings. Ten synthetic control changes were assumed to happen and lasted for one year for each building. In the test, the DET-Toa method showed superior capacity for detecting abnormal building energy consumption compared with the DET-Date method. It successfully detected 19 synthetic control changes in the 20 simulation test cases. The reason for the better performance of the DET-Toa method is discussed and demonstrated in an example case. The smallest faults that could be identified by the DET-Toa method in the two analyzed buildings and their related energy consumption impact statistics are also provided in the paper. [ABSTRACT FROM AUTHOR]

This paper presents a dynamic DG planning problem considering uncertainties related to the intermittent nature of the DG technologies such as wind turbines and solar units in addition to the stochastic economic conditions. The stochastic economic situation includes the uncertainties related to the fuel and electricity price of each year. The Monte Carlo simulation is used to generate the possible scenarios of uncertain situations and the produced scenarios are reduced through backward reduction program. The aim of this paper is to maximize the revenue of the distribution system through the benefit cost analysis alongside the encouraging and punishment functions. In order to close to reality, the different growth rates for the planning period are selected. In this paper the Covariance Matrix Adaptation Evolutionary Strategy is introduced and is used to find the best planning scheme of the DG units. The different DG types are considered in the planning problem. The main assumption of this paper is that the DISCO is the owner of the distribution system and the DG units. The proposed method is tested on a 9 bus test distribution system and the results are compared with the known genetic algorithm and PSO methods to show the applicability of the CMAES method in this problem. [ABSTRACT FROM AUTHOR]

Offline cursive script recognition and their associated issues are still fresh despite of last few decades' research. This paper presents an annotated comparison of proposed and recently published preprocessing techniques with reported work in the offline cursive script recognition. Normally, in the offline script analysis, the input is a paper image or a word or a digit and the desired output is ASCII text. This task involves several preprocessing steps, and some of them are quite hard such as line removal from text, skew removal, reference line detection (lower/upper baselines), slant removal, scaling, noise elimination, contour smoothing and skeleton. Moreover, subsequent stage of segmentation (if any) and recognition is also highly dependent on these preprocessing techniques. This paper presents an analysis and annotated comparison of latest preprocessing techniques proposed by authors with those reported in the literature on IAM/CEDAR benchmark databases. Finally, future work and persist problems are highlighted. [ABSTRACT FROM AUTHOR]

Computational fluid-dynamics (CFD) simulations have become an important tool for the assessment of airflow in urban areas. However, large discrepancies may appear when simulated predictions are compared with field measurements because of the complexity of airflow behaviour around buildings and difficulties in defining correct sets of parameter values, including those for inlet conditions. Inlet conditions of the CFD model are difficult to estimate and often the values employed do not represent real conditions. In this paper, a model-based data-interpretation framework is proposed in order to integrate knowledge obtained through CFD simulations with those obtained from field measurements carried out in the urban canopy layer (UCL). In this framework, probability-based inlet conditions of the CFD simulation are identified with measurements taken in the UCL. The framework is built on the error-domain model falsification approach that has been developed for the identification of other complex systems. System identification of physics-based models is a challenging task because of the presence of errors in models as well as measurements. This paper presents a methodology to estimate modelling errors. Furthermore, error-domain model falsification has been adapted for the application of airflow modelling around buildings in order to accommodate the time variability of atmospheric conditions. As a case study, the framework is tested and validated for the predictions of airflow around an experimental facility of the Future Cities Laboratory, called “BubbleZERO”. Results show that the framework is capable of narrowing down parameter-value sets from over five hundred to a few having possible inlet conditions for the selected case-study. Thus the case-study illustrates an approach to identifying time-varying inlet conditions and predicting wind characteristics at locations where there are no sensors. [ABSTRACT FROM AUTHOR]

This paper studies online travelling wave methods for fault location on a crossbonded cable system using sheath currents. During the construction of the electrical connection to the 400 MW off shore wind farm Anholt, it was possible to perform measurements on a 38.4 km crossbonded cable system. At 31.4 km, all cables were accessible which made it possible to apply a fault using an arc free breaker and measure the travelling waves at each end of the cable. On a crossbonded cable system, the sheaths are short circuited and grounded at both ends. This makes possible the use of low voltage Rogowski coils if the sheath currents contain the necessary information for accurate fault location. In this paper, this is examined by analysis of field measurements and through a study of simulations. The wavelet transform and a visual inspection method are used and the accuracy is compared. Field measurements and simulations are compared for testing the reliability of using simulations for studying fault location methods. [ABSTRACT FROM AUTHOR]

The main focus of our paper is to compare the performance of different model selection criteria used for multivariate reduced rank time series. We consider one of the most commonly used reduced rank model, that is, the reduced rank vector autoregression (RRVAR (p, r)) introduced by Velu et al. [Reduced rank models for multiple time series. Biometrika. 1986;7(31):105–118]. In our study, the most popular model selection criteria are included. The criteria are divided into two groups, that is, simultaneous selection and two-step selection criteria, accordingly. Methods from the former group select both an autoregressive orderpand a rankrsimultaneously, while in the case of two-step criteria, first an optimal orderpis chosen (using model selection criteria intended for the unrestricted VAR model) and then an optimal rankrof coefficient matrices is selected (e.g. by means of sequential testing). Considered model selection criteria include well-known information criteria (such as Akaike information criterion, Schwarz criterion, Hannan–Quinn criterion, etc.) as well as widely used sequential tests (e.g. the Bartlett test) and the bootstrap method. An extensive simulation study is carried out in order to investigate the efficiency of all model selection criteria included in our study. The analysis takes into account 34 methods, including 6 simultaneous methods and 28 two-step approaches, accordingly. In order to carefully analyse how different factors affect performance of model selection criteria, we consider over 150 simulation settings. In particular, we investigate the influence of the following factors: time series dimension, different covariance structure, different level of correlation among components and different level of noise (variance). Moreover, we analyse the prediction accuracy concerned with the application of the RRVAR model and compare it with results obtained for the unrestricted vector autoregression. In this paper, we also present a real data application of model selection criteria for the RRVAR model using the Polish macroeconomic time series data observed in the period 1997–2007. [ABSTRACT FROM AUTHOR]

Two discrete element models, super-ellipsoid model and multi-sphere model, are employed in this paper to describe the ellipsoidal particles. And the packing and flow behavior of ellipsoidal particles are investigated by the discrete element method (DEM) simulation and experiment. To compare the two models for ellipsoid, three tests are conducted: (i) the packing of ellipsoidal particles in a rectangular container, (ii) the flow of ellipsoidal particles in a horizontal rotating drum, and (iii) the discharge of ellipsoidal particles from a flat bottom hopper. Simulation results show that the super-ellipsoid model can accurately reproduce the packing and flow behavior of ellipsoidal particles. In the simulations using multi-spheres, when the spheres are more in a multi-sphere particle, the accuracy of simulation is acceptable while the computational time is much longer than the super-ellipsoid model. When fewer spheres are used to approximate the ellipsoidal particle, the computational time can be saved while the accuracy of the simulation decreases. [ABSTRACT FROM AUTHOR]

Eccentricity problem is always ineluctable in rotating electric machine, especially in large electric machine. Hence, the influence of eccentricity in operating machine is necessary to be investigated. According to the investigation, current of different parallel branches are varied under the same eccentricity. This paper focuses on comparative current analysis on two types of parallel branches in consideration of static and dynamic eccentricities. Parallel branch model in circumferential position is established for analysis and explanation of branch current due to eccentricity. Stator winding current and rotor wingding current are worked out under static and dynamic eccentricity at two types of parallel branches. Their winding losses are calculated for comparison, respectively. Finite element model simulations are used for validation. [ABSTRACT FROM AUTHOR]

This paper presents the details of JFETIDG, a compact model for independent dual-gate junction field-effect transistors with any combination of p-n junction or MOS gates. JFETIDG accounts for nonlinearity from depletion pinching, velocity saturation, and self-heating, and includes extensive modeling of geometry and temperature dependences, parasitics, noise, and statistical variations. We also demonstrate that it accurately models long channel junctionlessMOS transistors. Themodel is verified by comparison with TCAD simulations and experimental data. Verilog-A code for JFETIDG is available in the public domain. [ABSTRACT FROM AUTHOR]

Unmanned traffic management (UTM) systems rely on collaborative position reporting to track unmanned aerial system (UAS) operations over wide unsurveilled (with counter-UAS systems) areas. Many different technologies, such as Remote-ID, ADS-B, FLARM, or MLAT might be used for this purpose, in addition to the direct exploitation of C2 telemetry, relayed though cellular networks. This paper provides an overview of the most used collaborative sensors and surveillance systems in this context, analyzing their main technical parameters and performance effects. In addition, this paper proposes an abstracted general statistical simulation model covering message encoding, network capacity and access, sensors coverage and distribution, message transmission and decoding. Making use of this abstracted model, this paper proposes a particularized set of simulation models for ADS-B, FLARM and Remote-Id; it is thus useful to test their potential integration in UTM systems. Finally, a comparative analysis, based on simulation, of these systems, is performed. It is shown that the most relevant effects are those related with quantification and the potential saturation of the communication channels leading to collisions and delays. [ABSTRACT FROM AUTHOR]

This paper presents the compact analytical model of underlap gate stack (GS) graded channel (GC) junction accumulation mode (JAM) junctionless (JL) FET. At first, a comparative analysis between the two different graded channel schemes and non-graded channel is performed based on I ON , I OFF and I ON / I OFF ratio. The scheme that yields the higher I ON / I OFF ratio along with smaller I OFF , is adopted in the proposed JL FET for further analysis. The 2D analytical modeling of the GS-GC-JAM-JL FET deals with the determination of surface potential, threshold voltage, subthreshold drain current, DIBL and subthreshold swing. Results obtained from analytical model and simulations are compared and an excellent match is found. Thus the present paper establishes the outstanding ability of proposed underlap GS-GC-JAM-JL FET architecture to shield the short channel effects without sacrificing its performance, and therefore, proves it as a potential candidate for ultra-low power applications. • Analytical modeling of GS-GC-JAM-JL FET is presented here. • Comparative analysis between the various graded channel schemes with non-graded channels is done based on I ON , I OFF and I ON /I OFF ratio. • Graded channel scheme that yields the higher I ON /I OFF ratio with smaller I OFF , is incorporated in the proposed JL FET for further analysis. • Proposed underlap GS-GC-JAM-JL FET architecture shields the short channel effects without sacrificing its performance. [ABSTRACT FROM AUTHOR]

Abstract: Channel scheduling is an important aspect in optical burst switching (OBS) networks. OBS is a promising solution for the future Internet backbone. In OBS network a key issue is data channel scheduling. In this paper we propose a channel scheduling scheme to optimize channel utilization for OBS networks with segmentation. In this paper, we propose an efficient way to organize the void intervals. The channel scheduling method is compared with existing scheduling schemes. Simulation results show that both channel utilization and burst loss ratio performance improved as compared to existing scheduling schemes. [Copyright &y& Elsevier]

Abstract: Objectives: The objective of this study is to design a method for modeling hepatitis C virus (HCV) infection using multi-agent simulation and to verify it in practice. Methods and materials: In this paper, first, the modeling of HCV infection using a multi-agent system is compared with the most commonly used model type, which is based on differential equations. Then, the implementation and results of the model using a multi-agent simulation is presented. To find the values of the parameters used in the model, a method using inverted simulation flow and genetic algorithm is proposed. All of the data regarding HCV infection are taken from the paper describing the model based on the differential equation to which the proposed method is compared. Results: Important advantages of the proposed method are noted and demonstrated: these include flexibility, clarity, re-usability and the possibility to model more complex dependencies. Then, the simulation framework that uses the proposed approach is successfully implemented in C++ and is verified by comparing it to the approach based on differential equations. The verification proves that an objective function that performs the best is the function that minimizes the maximal differences in the data. Finally, an analysis of one of the already known models is performed, and it is proved that it incorrectly models a decay in the hepatocytes number by 40%. Conclusions: The proposed method has many advantages in comparison to the currently used model types and can be used successfully for analyzing HCV infection. With almost no modifications, it can also be used for other types of viral infections. [Copyright &y& Elsevier]

This paper deals with the problem of optimal portfolio strategy under the constraints of rolling economic maximum drawdown. A more practical strategy is developed by using rolling Sharpe ratio in computing the allocation proportion in contrast to existing models. Besides, another novel strategy named "REDP strategy" is further proposed, which replaces the rolling economic drawdown of the portfolio with the rolling economic drawdown of the risky asset. The simulation tests prove that REDP strategy can ensure the portfolio to satisfy the drawdown constraint and outperforms other strategies significantly. An empirical comparison research on the performances of different strategies is carried out by using the 23-year monthly data of SPTR, DJUBS, and 3-month T-bill. The investment cases of single risky asset and two risky assets are both studied in this paper. Empirical results indicate that the REDP strategy successfully controls the maximum drawdown within the given limit and performs best in both return and risk. [ABSTRACT FROM AUTHOR]