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With the progressive promotion of BIM technology in collaborative design and engineering data management, there are large amounts of project information available for intelligent construction, engineering computation and design optimization. In the construction of subway station, BIM technology is still not mature and the engineering design is generally separate from the engineering safety evaluation. Thus, this paper proposed a technology that integrates BIM and numerical simulation (BIM-FEM/FDM integrated technology) to solve the problem of separation between engineering design and computation. A three-dimensional parametric modeling of subway station excavation was first carried out using the Revit® modeling software. Afterward, a FEM/FDM-process oriented data conversion interface was developed to extract and process the critical information from the parametric BIM model for numerical simulation. Then, under the impetus of an auto-simulation interface, the safety evaluation of subway station excavation was realized automatically and visualized graphically. The research of the BIM-FEM/FDM integrated technology presented in this paper has established a supporting platform to achieve the integration of BIM-based design and safety evaluation for subway station excavation. [ABSTRACT FROM AUTHOR]

The main aim of this paper is to propose new mathematical models for simulation of biosensors and to construct and investigate discrete methods for the efficient solution of the obtained systems of nonlinear PDEs. The classical linear diffusion operators are substituted with nonlocal fractional powers of elliptic operators. The splitting type finite volume scheme is used as a basic template for the introduction of new mathematical models. Therefore the accuracy of the splitting scheme is investigated and compared with the symmetric Crank-Nicolson scheme. The dependence of the approximation error on the regularity of the solution is investigated. Results of computational experiments for different values of fractional parameters are presented and analysed. [ABSTRACT FROM AUTHOR]

This paper presents a systematic study of a mathematical model of glucose and insulin interaction with two time delays, with a focus on analytical studies, bifurcation analysis, and very well numerical simulations. This model based on the Intra-Venous Glucose Tolerance Test (IVGTT) and is presented with two time delays. One delay is the insulin response time to an increase in glucose concentration, and the hepatic glucose production time delay is the other. Then, we establish results on positivity, boundedness, and persistence. We also provide sufficient stability analysis conditions for both local and global asymptotic stability of the proposed models. For the latter, two different strategies are used: stability bifurcation analysis and Lyapunov-Krasovskii functionals. We investigate different regions of parameter space using two approaches, that yield different sets of sufficient conditions for global stability. The bifurcation graphs generated from our extensive and carefully designed simulations complement and confirrm these analytical results. The insulin concentration level peaks after the glucose concentration level, according to the numerical simulations. [ABSTRACT FROM AUTHOR]

The paper begins with a brief introduction and review of international research in the area of water jet streams and their effectiveness in firefighting. Then a general concept of a new numerical model for firefighting process using solid jet produced by water nozzle is presented. The provided description of the model includes main assumptions for extinguishing process and a set of relationships representing a mathematical model. The paper also includes block diagrams of the main program algorithms and procedures designed to determine the value of the surface and sprinkling intensity depending on the input data like nozzle dimensions, position etc. Input parameters which are necessary for the calculation are discussed, together with a general concept of the users input and output interfaces and simulation tests that can be performed using the developed model. Some selected simulation tests in tabular and graphical forms are included. Summary and general conclusions can be found at the end. [ABSTRACT FROM AUTHOR]

Missile homing precision depends mainly on the correct determination of the current angle between the Gyroscope System Axis (GSA) and the target line-of-sight (LOS). A gyroscope automatic control system shall ensure spontaneous levelling of this angle, hence, constant homing of the gyroscope system axis in on the LOS, i.e. tracking the target by the head. The available literature on the subject lacks a description of how to use the controlled gyro system in the process of guiding the missile onto the target. In this paper, the authors present the original development of an optimal control algorithm for a gyro system with a square quality indicator in conditions of interference and kinematic influence of the missile deck. A comparative analysis of the LQR with the PD regulator was made. PD regulator parameters are also selected optimally, using the Golubencev method, so that the transition process of the homing system fades over a minimal time, while simultaneously ensuring the overlapping of the gyroscope axis with the target line-of-sight. The computer simulation results have been obtained in a Matlab-Simulink environment and are presented in a graphic form. [ABSTRACT FROM AUTHOR]

This paper presents the blast responses of ultrahigh-performance concrete (UHPC) structural members obtained using finite element (FE) modelling. The FE model was developed using LS-DYNA with an explicit solver. In the FE simulation, the concrete damage model, which is a plasticity-based constitutive material model, was employed for the concrete material. The simulation results were verified against previous experimental results available in the literature and were shown to be in good agreement with the experimental results. In addition, the developed FE model was implemented in a parametric study by varying the blast weight charges. The numerical results for UHPC members were compared with those for conventional reinforced concrete (RC) members. The numerical responses, such as the maximum deflections, deflected shapes, and damage patterns, of the UHPC members subjected to blast loading were significantly better performance than those of the RC members as a result of the high strength and ductile capacity of UHPC. [ABSTRACT FROM AUTHOR]

The reefing ratio for the first stage of a parachute limits the reefing ratio for the subsequent stages, so its minimal effective value is very important. In this paper, an empirical formula is derived to calculate the minimal effective reefing ratio. The empirical parameters are obtained by the arbitrary Lagrangian-Eulerian/fluid-structure interaction (ALE/FSI) method. By using the FSI method, the typical flow and structure fields of effective and ineffective reefed parachutes are revealed. The numerical results including drag characteristics and final shape are very consistent with wind tunnel tests. The curves of the empirical parameters with reefing ratios are obtained. The minimal effective reefing ratio obtained by the empirical formula is consistent with that of the numerical results, which shows that the empirical formula has high accuracy. [ABSTRACT FROM AUTHOR]

The application of concrete waste for recycled aggregate concrete (RAC) used in structural members is associated with an increased risk for the structure due to, e.g. pollutions in the old crushed concrete and random variable strength. A new concept of RC flexural members like beams and slabs made of RAC with strengthening inclusion was elaborated and presented in the paper based on application of precast concrete inserts made of HSC, located in the compression zone of the members. The paper presents the results of experimental and numerical (FEM) analysis carried out on such composite beams. The results of experimental research on the behavior of such beams and numerical simulations using Diana computer program reveal some positive effects, such as higher stiffness and flexural capacity of the innovative beams compared to the reference beams made fully of RAC. [ABSTRACT FROM PUBLISHER]

In case of the Intelligent Driver Model (IDM) the actual Velocity-Density law V(D) applied by this dynamic system is not defined, only the dynamic behaviour of the vehicles/drivers is determined. Therefore, the logical question is whether the related investigations enhance an existing and known law or reveal a new connection. Specifically, which function class/type is enhanced by the IDM? The publication presents a model analysis, the goal of which was the exploration of a feature of the IDM, which, as yet, 'remained hidden'. The theoretical model results are useful, this analysis important in the practice in the field of hybrid control as well. The transfer of the IDM groups through large-scale networks has special practical significance. For example, in convoys, groups of special vehicle, safety measures with delegations. In this case, the large-scale network traffic characteristics and the IDM traffic characteristics should be taken into account simultaneously. Important characteristics are the speed-density laws. In case of effective modelling of large networks macroscopic models are used, however the IDMs are microscopic. With careful modelling, we cannot be in contradiction with the application of speed-density law, where there IDM convoy passes. Therefore, in terms of practical applications, it is important to recognize what kind of speed-density law is applied by the IDM convoys in traffic. Therefore, in our case the goal was not the validation of the model, but the exploration of a further feature of the validated model. The separate validation of the model was not necessary, since many validated applications for this model have been demonstrated in practice. In our calculations, also the applied model parameter values remained in the range of the model parameters used in the literature. This paper presents a new approach for Velocity-Density Model (VDM) synthesis. It consists in modelling separately each of the density and the velocity (macroscopic parameter). From this study, safety time headway (microscopic parameter) can be identified from macroscopic data by mean of interpolation method in the developed map of velocity-density. By combining the density and the velocity models, a generalized new VDM is developed. It is shown that from this one, some literature VDMs, as well as their properties, can be derived by fixing some of its parameters. [ABSTRACT FROM AUTHOR]

The construction of Personal Rapid Transit (PRT) vehicle made within the framework of Eco-Mobility project has been described in the present paper. Key features of the vehicles were identified - e.g. drive with three-phase linear motor with winding on the vehicle and fixed rotor in the road surface, contactless dynamic vehicle powering. Attention was paid to the difference in dynamic properties compared to rail vehicles, related to the lack of the so-called 'centering mechanism'. A development of a nominal model for the analysis of vehicle drive properties was presented. Results of simulation studies were presented for a vehicle with running-drive system construction, planned for implementation in the city of Rzeszów (Poland). While discussing the problems of building a PRT system, there was a focus on the issue of determining power and traction of the vehicle. A methodology for determining the power and traction energy consumption of the vehicle was presented for assumed conditions of travel on road segments. Input values for the calculation of power are variables describing the curvature (or bends radii) of paths of movement between stops and the course of the current speed. Output values are total traction power or traction energy (where 'traction' refers to the power or mechanical work of drive forces). Three basic elements of traction power were isolated: the power of kinetic energy (for acceleration/delay of vehicle movement) basic (to offset the aerodynamic force of motion resistance at constant speed) and additional losses (to offset additional motion resistance forces operating in turns at constant speed). Due to the lack of vehicle prototypes with assumed structure, it was proposed that these components are determined via simulation. The presented results relate to the calculation of demand for power and energy for the planned test section. The scope of further work was indicated: determining the required traction characteristics of electric drive, selecting the best values for supercapacitor's capacity in the drive system, determining the technical parameters of substation. [ABSTRACT FROM AUTHOR]

Many congestion charging projects charge traffic only within part of a day with predetermined congestion tolls. Demand peaks have been witnessed just around the time when the charge jumps up or down. Such peaks may not be desirable, in particular (a) when the resulting peaks are much higher than available capacities; (b) traffic speeding up to get into the charging zone causes more incidents just before the toll rises up to a higher level; or (c) traffic slowing down or parking on the roadside decreases road traffic throughput just before the toll falls sharply. We term these types of demand peaks 'boundary effects' of congestion charging. This paper investigates these effects in a bottleneck scenario and aims to design charging schemes that reduce undesired demand peaks. For this purpose, we observe and analyse the boundary effects utilising a bottleneck model under three types of toll profiles that are indicative of real charging schemes. The first type maintains a constant toll across the charging period, the second type allows the toll to increase from zero to a given maximum level and then decrease back to zero and the third type allows the toll to rise from zero to a given maximum level, remain at this level for a fixed period and then fall down to zero. This investigation shows that all three types of toll profiles can produce greater boundary peak demands than the bottleneck capacity. A significant contribution of this work is that instead of designing an optimal traffic congestion pricing scheme we analyse how existing sub-optimal congestion pricing schemes could be improved and suggest how observed problems may be overcome. Hence, we propose a set of extra requirements to supplement existing principles or requirements for design and implementation of congestion charging, which aim to reduce the adverse consequences of boundary effects. Concluding remarks are made on implications of this investigation for the improvement of existing congestion charging projects and for future research. [ABSTRACT FROM AUTHOR]

A new structural damage estimation procedure using grey relation coefficient and curvature of displacement influence line in beams using sparse measurement is proposed in this paper. The method is based on static structural response which can be obtained using single sensor. determination of damage location as well as determination of corresponding damage severity can be easily calculated with simple arithmetic operations, which is the main advantage of the proposed method. Conducted numerical simulation for different damage scenarios and various measurement sparseness and experimental validation confirm the effectiveness of proposed damage severity estimation procedure. [ABSTRACT FROM PUBLISHER]

This paper introduces an evolving network model of credit risk contagion containing the average fitness of credit risk contagion, the risk aversion sentiments, and the ability of resist risk of credit risk holders. We discuss the effects of the aforementioned factors on credit risk contagion in the financial market through a series of theoretical analysis and numerical simulations. We find that, on one hand, the infected path distribution of the network gradually increases with the increase in the average fitness of credit risk contagion and the risk aversion sentiments of nodes, but gradually decreases with the increase in the ability to resist risk of nodes. On the other hand, the average fitness of credit risk contagion and the risk aversion sentiments of nodes increase the average clustering coefficient of nodes, whereas the ability to resist risk of nodes decreases this coefficient. Moreover, network size also decreases the average clustering coefficient. [ABSTRACT FROM AUTHOR]

Trust is essential to economic efficiency. Trading partners choose each other and make decisions based on how much they trust one another. The way to assess trust in e-commerce is different from those in brick and mortar businesses, as there are limited indicators available in online environments. One way is to deploy trust and reputation management systems that are based on collecting feedbacks about partners’ transactions. One of the problems within such systems is the presence of unfair ratings. In this paper, an innovative QADE trust model is presented, which assumes the existence of unfairly reported trust assessments. Subjective nature of trust is considered, where differently reported trust values do not necessarily mean false trust values but can also imply differences in dispositions to trust. The method to identify and filter out the presumably false values is defined. In our method, a trust evaluator finds other agents in society that are similar to him, taking into account pairwise similarity of trust values and similarity of agents’ general mindsets. In order to reduce the effect of unfair ratings, the values reported by the non-similar agents are excluded from the trust computation. Simulations have been used to compare the effectiveness of algorithms to decrease the effect of unfair ratings. The simulations have been carried out in environments with varying number of attackers and targeted agents, as well as with different kinds of attackers. The results showed significant improvements of our proposed method. On average 6% to 13% more unfair trust ratings have been detected by our method. Unfair rating effects on trust assessment were reduced with average improvements from 26% to 57% compared to the other most effective filtering methods by Whitby and Teacy. [ABSTRACT FROM AUTHOR]

As part of a research project aimed at designing the structure of a new special-purpose multi-axle semitrailer for transporting large machines and equipment, a simulation study on the manoeuvrability of the semitrailer during its passage through a tight corner was performed. The aim of this study was to determine whether the semitrailer would meet the legal requirements regarding manoeuvrability after it has been implemented for production. The simulations were carried out using a specially designed spreadsheet. The spreadsheet enabled analysis of the movements of the wheels of the tractor-trailer combination, with the assumption that they roll without skidding; it also described changes in the steering angles of trailer wheels, as well as off-tracking and corner-cutting during turning. When the geometrical parameters of the tractor and trailer were changed, the spreadsheet allowed tracing their impact on the manoeuvrability of the whole combination. This paper presents the results of the simulations and points to the desired features of a semitrailer steering system that facilitate negotiating tight corners. [ABSTRACT FROM PUBLISHER]

This paper provides a systematic approach for the analysis and design of construction supply chain operation models. Based on the Supply Chain Operations Reference Model of the Supply Chain Council, this research studies sup- ply and demand behavior, using a bridge superstructure construction process as a case study. This paper uses the SCOR Model and applies Dynamic Simulation software, namely, “SIMPROCESS”, to assist in establishing a hierarchical model to explore the behavior of the construction supply chain process and develop a performance evaluation method that can help improve the supply chain management (SCM) of the construction project. [ABSTRACT FROM PUBLISHER]

Numerical simulations play an essential role in the development and testing of navigation and guidance algorithms, especially when developer must keep the development costs as low as possible. Low budget development focuses mainly on utilization of numerical flight mechanics simulators including optimization and hardware in loop tests. Reliable, high fidelity results can be easily obtained by numerical simulations of flight dynamics utilizing computing power provided by a normal off-the-shelf home PC. However, it still requires a simple, but good and valid model of the aircraft and environment. This paper describes an approach to a numerical simulation of aircraft motion that respects the requirement for a full environment high fidelity model and keeps a good interface for further development of attitude control. The goal is achieved by directly specifying the aerodynamic angles of the vehicle in the simulation environment by the guidance system, which can later be used as input for attitude control algorithms. It is proved how an appropriate selection of reference frames and formulation of laws of motion gives very quick and reliable results by employing large integration time steps that would be difficult to achieve in 6-degree-of-freedom simulations. This paper also investigates the range of applicability, advantages, and drawbacks of this method. An example of an aerodynamic angle-based guidance law for a UAV is explained and demonstrated by figures. [ABSTRACT FROM AUTHOR]

Construction of bridges is associated with uncertainties that rise due to unavailability of resources, equipment breakdown and/or working environment. Bridge construction techniques can be grouped into six main categories: 1) cast-in-situ on false work, 2) cantilever carriage, 3) stepping formwork, 4) launching girder, 5) pre-cast balanced cantilever, and 6) incremental launching. The latter technique is characterised by minimising the use of falsework. Further, the fabrication and casting of bridge segments are executed at a stationary location, named casting yard (which includes several facilities), deck form, concrete mixing unit, and pumping system. This paper presents a special purpose simulation model to capture the uncertainty associated with bridge construction. The model accounts for the interaction between the different involved resources in construction of bridges using incremental launching technique. The paper describes two methods (single form and multiple forms) of execution used for the segments fabrication. The proposed simulation model utilises STROBOSCOPE as a simulation engine and is coded by Visual Basic 6.0. An actual case study is presented to illustrate the capabilities of the developed model and validate its performance. [ABSTRACT FROM AUTHOR]

The paper contains a case study covering forecasting mechanical effects of an explosion which can be generated during a road accident. It illustrates a practical application of the simulation-based procedure developed for such forecasting in the first part of the paper. The case study reveals the amount and character of the knowledge necessary to carry out this forecasting. Its final result is a probabilistic model describing likelihood of occurrence of accidental explosion as well as characteristics of the incident blast wave generated by this explosion. The accident simulation is based on the classical Bayesian approach to risk assessment. The case study described in the paper shows how to formulate the initial knowledge in line with this approach. Particular attention has been given to handling subjective information (expert opinions) within the problem under analysis. It is shown that this information is indispensable for dealing with the sparseness of hard experience data on most of the phenomena leading to an accidental explosion. The stochastic simulation demonstrated in the paper serves the purpose of propagating uncertainties related to these phenomena. The probabilistic action model describing the potential explosion takes account of these uncertainties. [ABSTRACT FROM AUTHOR]

This paper reports a new simulation technique for an aeroelastic system which responds to random external forces. Since the aeroelastic system including the effects of unsteady aerodynamics is ordinarily described in the frequency domain, the Inverse Discrete Fourier Transform (IDFT) can be utilized to simulate its random response. The response caused by the external random noise is calculated through a transfer function first in the frequency domain and then converted to the time domain. The objective of the present study is to provide mathematical time history data for evaluating the various estimation methods of the flutter boundary from subcritical responses in flight and/or wind tunnel testing. An example application to the method of flutter prediction is shown. The technique can also be used to evaluate the effects of the active control device coping with atmospheric turbulence. [ABSTRACT FROM PUBLISHER]

Maintaining dynamicity of business processes is one of the core issues of today's business as it enables businesses to adapt to constantly changing environment. Upon changing the processes, it is vital to assess possible impact, which is achieved by using simulation of dynamic processes. In order to implement dynamicity in business processes, it is necessary to have an ability to change components of the process (a set of activities, a content of activity, a set of activity sequences, a set of rules, performers and resources) or dynamically select them during execution. This problem attracted attention of researches over the past few years; however, there is no proposed solution, which ensures the business process (BP) dynamicity. This paper proposes and specifies dynamic business process (DBP) simulation model, which satisfies all of the formulated DBP requirements. [ABSTRACT FROM AUTHOR]

This article provides information about stress analysis of thin beam webs with and without lighting openings. The study described in this paper was carried out in order to investigate the influence of circular lighting openings in planar webs on critical web shear force, distribution of transverse web deformations, and also strain and stress distribution in the web plate. The main goal was to compare pre- and post-buckling behaviour of a thin web with and without lighting openings under shear load. The procedure was as follows: first of all, seven specimens – beams with a different combination of parameters (web thickness, opening size and web dimension) were calculated using available analytical methods; secondly, the same specimens were produced and tested up to load near failure; thirdly, these specimens were analysed using the Finite element method; finally, the tests results were compared with results of numerical simulations. [ABSTRACT FROM AUTHOR]

As construction projects have become larger and more complex, they develop different features than smaller or traditional projects, which characterize them as complex systems. Still, Construction Engineering and Management (CEM) researchers have mostly relied on traditional approaches to investigate complex management problems, which might produce misleading results. This paper introduces Agent-Based Modeling and Simulation (ABMS) as a research method, and addresses how it could be applied to CEM research. With an illustrative example of the application of ABMS to CEM research, the theoretical background as well as the design, development, and test processes of ABMS are presented. We then made a recommendation on the promising research subjects in CEM area to which ABMS could be suitably applied. [ABSTRACT FROM AUTHOR]

This paper introduces the development of an autonomous driving system in autonomous electric vehicles, which consists of a simplified motion-planning program and a Model-Predictive-Control-Based (MPC-based) control system. The motion-planning system is based on polynomial parameterization, which computes a path toward the expected longitudinal and lateral positions within required time interval in real scenarios. Then the MPC-based control system cooperates the front steering and individual wheel torques to track the planned trajectories, while fulfilling the physical constraints of actuators. The proposed system is evaluated through simulation, using a seven-degrees-of-freedom vehicle model with a ‘magic formula’ tire model. The simulations and validation throughCarSimshow that the proposed planner algorithm and controller are feasible and can achieve requirements of autonomous driving in normal scenarios. [ABSTRACT FROM PUBLISHER]

We consider methods for the numerical simulations of variable density incompressible fluids, modelled by the Navier–Stokes equations. Variable density problems arise, for instance, in interfaces between fluids of different densities in multiphase flows such as appearing in porous media problems. We show that by solving the Navier–Stokes equation for the momentum variable instead of the velocity the corresponding saddle point problem, arising at each time step, no special treatment of the pressure variable is required and leads to an efficient preconditioning of the arising block matrix. This study consists of two parts, of which this paper constitutes Part I. Here we present the algorithm, compare it with a broadly used projectiontype method and illustrate some advantages and disadvantages of both techniques via analysis and numerical experiments. In addition we also include test results for a method, based on coupling of the Navier–Stokes equations with a phase-field model, where the variable density function is handled in a different way. The theory including stability bounds and a second order splitting method is dealt with in Part II of the study. [ABSTRACT FROM AUTHOR]

In order to reduce the energy load, understanding the overall architectural design features and optimizing building orientation are important. They are guided by natural elements like sunlight and its intensity, direction of the wind, seasons of the year and temperature variations. The main aim of presented analysis is to give solutions for architects to design standard and low energy buildings in a proper way. The orientation effect of a non-air-conditioned building on its thermal performance has been analyzed in terms of direct solar gain and temperature index for hot-dry climates. This paper aims at introducing an improved methodology for the dynamic modeling of buildings by the thermal nodal method. The study is carried out using computer simulation. This study examines also the effect of geometric shapes on the total solar insolation received by a real building. As a result, the influence of orientation changing depends on the floors and exterior walls construction materials, the insulation levels and application of the inseparable rules of the bioclimatic design. Solar radiation is the most major contributor to heat gain in buildings. [ABSTRACT FROM PUBLISHER]

Many studies have been done previously on temperature distribution in inhomogeneous composite systems with perfect interface, having no discontinuities along it. In this paper we have determined steady state temperature distribution in two inhomogeneous composite systems with imperfect interface, having discontinuities in temperature and heat flux using decomposed immersed interface method and performed the numerical simulation on MATLAB. [ABSTRACT FROM AUTHOR]

This paper focuses on the development, verification and application of a three-dimensional finite element code for coupled thermal and structural analysis of roller compacted concrete arch dams. The Karun III Arch dam located on Karun River, Iran, which was originally designed as a conventional concrete arch dam, has been taken for the purpose of verification of the finite element code. In this study, RCC technology has been ascertained as an alternative method to reduce the cost of the project and make it competitive. A numerical procedure to simulate the construction process of RCC arch dams is presented. It takes into account the more relevant features of the behavior of concrete such as hydration, ageing and creep. A viscoelastic model, including ageing effects and thermal dependent properties is adopted for the concrete. The different isothermal temperature influence on creep and elastic modulus is taken into account by the maturity concept. Crack index is used to assess the occurrence of crack and evaluate the level of safety of the dam. This study demonstrates that, high tensile stress concentration has been observed at the lower part and the abutment boundaries of the dam. [ABSTRACT FROM AUTHOR]

When renovating a pedestrian area, it is crucial to maintain as normal as possible an operation while the renovation activities are underway. Usually the area is divided into several zones to accommodate the renovation in sections. A zone closure forces the users to take an alternative route that could be longer or more congested. The impact of such rerouting must be minimized by properly planning the work crews. In this paper, the author proposed a model using simulation to estimate the impact of the extra walking distance on pedestrians, and ant colony optimization to search for the nearoptimal work crew schedule. The author applied the model to the renovation of a public pedestrian area in a villa resort. It provides a near-optimal work schedule for a variety of work crews with minimal walking time delay for the pedestrians. This model takes into account total walking time delay, average delay per person, and total duration in order to evaluate all alternatives to allow both owner and contractor to decide the appropriate work schedule. [ABSTRACT FROM AUTHOR]

This paper presents studies on thermal energy efficiency of heating surface at an open space according to structural solutions and climatic conditions. Numerical simulation research was conducted to assess three different types of heating surfaces at an open space over chosen period of time in real weather conditions. Performance parameters such as surface temperature, supply temperature and efficiency of heating surface relative to constructional designs and model of control strategy used were analysed. The number, thickness and type of material layers beneath ground level were modified. The distance between heating pipes and their diameters were kept constant. The carried out analyses show that the used solutions can lead to significant differences in the performance and consequently in the energy efficiency of the heating system for open spaces. [ABSTRACT FROM PUBLISHER]

This paper is part of a wide-ranging investigation on the use of flue gas desulphurisation (FGD) waste in cement-based materials. It reports the results on the porosity and pore size distribution of cement paste containing varying amounts of simulated FGD waste. The water to binder ratio was 0.5. The binder consists of cement and simulated FGD. The FGD is a combination of fly ash and gypsum ranging from 0% to 100%. Cement in the pastes was partially replaced with 25% FGD (by weight). The porosity and pore size distribution of cement pastes was determined during the early stage of hydration. Increasing the amount of gypsum does not increase the pore volume. However, increasing the amount of gypsum in the paste leads to an increase in the threshold diameter and a decrease in the percentage of small pores in the paste, both indicating a coarser pore structure. The results of this investigation were compared with data at longer curing periods. [ABSTRACT FROM PUBLISHER]

Tunnel construction is one of the important infrastructure projects, which is vital for enhancing the transportation networks, especially in congested cities. Tunnel projects are characterized by long durations, large budgets, complexities, repetitive construction tasks, risks, and uncertainties. Several construction techniques have been developed in the tunnel construction industry to improve the constructability of tunnels and decrease the impact on surrounding structures. This paper presents a framework for planning tunnel construction using computer simulation. The proposed tool aids contractors in estimating the required time and cost for construction. Five tunnel construction techniques have been considered in the development of this tool with different ground supporting techniques. The proposed framework consists of three modules: (1) tunnel analyzer module, (2) simulation module, and (3) decision support module, and is capable of selecting the best construction technique using fuzzy group decision-making method based on time, cost and other selection criteria that could be defined during the decision-making phase. This decision method ranks alternatives based on a group of experts and a predefined set of criteria. Numerical examples are introduced to illustrate the capabilities of the proposed framework. [ABSTRACT FROM AUTHOR]

Large scale applications of behaviorally realistic transport models pose several challenges to transport modelers on both the demand and the supply sides. On the supply side, path-based solutions to the user assignment equilibrium problem help modelers in enhancing the route choice behavior modeling, but require them to generate choice sets by selecting a path generation technique and its parameters according to personal judgments. This paper proposes a methodology and an experimental setting to provide general indications about objective judgments for an effective route choice set generation. Initially, path generation techniques are implemented within a synthetic network to generate possible subjective choice sets considered by travelers. Next, ‘true model estimates’ and ‘postulated predicted routes’ are assumed from the simulation of a route choice model. Then, objective choice sets are applied for model estimation and results are compared to the ‘true model estimates’. Last, predictions from the simulation of models estimated with objective choice sets are compared to the ‘postulated predicted routes’. A meta-analytical approach allows synthesizing the effect of judgments for the implementation of path generation techniques, since a large number of models generate a large amount of results that are otherwise difficult to summarize and to process. Meta-analysis estimates suggest that transport modelers should implement stochastic path generation techniques with average variance of its distribution parameters and correction for unequal sampling probabilities of the alternative routes in order to obtain satisfactory results in terms of coverage of ‘postulated chosen routes’, reproduction of ‘true model estimates’ and prediction of ‘postulated predicted routes’. [ABSTRACT FROM PUBLISHER]

Intelligent transportation systems have received increasing attention in academy and industry. Being able to handle uncertainties and complexity, expert systems are applied in vast areas of real life including intelligent transportation systems. This paper presents a traffic signal control method based on expert knowledge for an isolated signalized intersection. The proposed method has the adaptive signal timing ability to adjust its signal timing in response to changing traffic conditions. Based on the traffic conditions, the system determines to extend or terminate the current green signal group. Using the information from its traffic detectors of isolated intersection, the proposed controller gives optimal signals to adapt the phase lengths to the traffic conditions. A comparative analysis between proposed control algorithm, fuzzy logic (FLC) and fixed-timed (pre-timed) controllers has been made in traffic flows control, with varying traffic volume levels, by using simulation software ‘Arena’. Simulation results show that the proposed traffic signal control method (EKC) has better performance over fuzzy logic and conventional pre-time controllers under light and heavy traffic conditions. [ABSTRACT FROM PUBLISHER]

The paper discusses the optimisation of complex management processes, which allows the reduction of investment costs by setting the optimal balance between product demand and supply. The systematisation of existing methods and algorithms that are used to optimise complex processes by linking stochastic discrete-event simulation and multi-objective optimisation is given. The two-phase optimisation method is developed based on hybrid combination of compromise programming, evolutionary computation and response surface-based methods. Approbation of the proposed method is performed on the multi-echelon supply chain planning problem that is widely distributed in industry and its solution plays a vital role in increasing the competitiveness of a company. Three scenarios are implemented to optimise supply chain tactical planning processes at the chemical manufacturing company based on using different optimisation methods and software. The numerical results prove the competitive advantages of the developed two-phase optimisation method. [ABSTRACT FROM AUTHOR]

Double-skin façade (DSF) is an environmental friendly architectural feature. However, fire hazard is a concern. A scenario of having a flashover room fire adjacent to the façade was identified. Heat and mass would be trapped in the façade cavity. This paper examines air flow driven out of a flashover room fire to the cavity of a DSF by Computational Fluid Dynamics. The software Fire Dynamics Simulator developed at the Building and Fire Research laboratory, National Institute of Standards and Technology, USA was selected as the simulation tool. Three DSF features labeled as DSF1, DSF2 and DSF3 were considered. Detailed simulations were carried out to understand the fire-induced aerodynamics in a 5-level model DSF1 with a fire room at the third level. Hot gas spreading out to the façade cavity was simulated under two heat release rates of 1 MW and 5 MW. Air cavity depths of 0.5 m, 1 m, 1.5 m and 2 m were considered. Three stages of flame spreading out to a DSF with a wide air cavity depth were identified. Results suggested that wider air cavity depths would be more dangerous, with higher risk of the upper interior glass pane's breaking. To study spreading of heat and mass up the façade cavity as vertical channel flow, two taller DSF façade features DSF2 and DSF3 with differing air cavity depths were simulated. Both features were of height 24 m but of differing fire room height. Vertical temperature profiles with and without the DSF feature were compared. [ABSTRACT FROM PUBLISHER]

In this paper, a three species reaction-diffusion food-chain system with nonlocal delays is investigated. Sufficient conditions are derived for the global stability of a positive steady state and boundary steady states of the system by using the energy function method. Numerical simulations are carried out to illustrate the theoretical results. [ABSTRACT FROM AUTHOR]

Nowadays, it is widely recognized that computer simulation plays a crucial role in designing oil filters used in the automotive industry. However, even a single direct simulation of the flow usually requires significant computational resources. Thus, it is obvious that solution of optimization problems is only feasible using parallel computers and algorithms. In this paper, we present a general master-slave parallel template, which was specially designed for the easy integration of direct parallel solvers into a parallel optimization tool. We show how an already existing direct solver for the 3D simulation of flow through the oil filter is integrated into our template to obtain a parallel optimization solver. Some capabilities and performance of this solver are demonstrated by solving geometry optimization problem of a filter element. [ABSTRACT FROM AUTHOR]

The paper presents the optimization possibilities of port terminal operations in order to generate maximum gain. Planning these processes is a demanding daily task taken on before dealing with port management, since transhipment operations, cargo loading and dispatching, maintenance and control of transhipment and transportation means are subject to hardy predictable and unexpectable stochastic conditions under which planning optimal terminal operations will include the examination of stochastic processes on the terminal. A model of states and transitions with gain and a model of optimal strategies in terminal management are set up. Furthermore, a model for determining the structure of transhipment equipment is developed. The devised models were adapted to the specificities of a port terminal and tested using the sample of a general cargo terminal. [ABSTRACT FROM AUTHOR]

In this paper, we have considered a nonautonomous stage-structured HIV/AIDS epidemic model through vertical and horizontal transmissions of infections, having two stages of the period of infection according to the developing progress of infection before AIDS defined would be detected, with varying total population size and distributed time delay to become infectious (through horizontal transmission) due to intracellular delay between initial infection of a cell by HIV and the release of new virions. The infected people in the different stages have different ability of transmitting disease. We have established some sufficient conditions on the permanence and extinction of the disease by using inequality analytical technique. We have obtained the explicit formula of the eventual lower bounds of infected people. We have introduced some new threshold values R0 and R* and further obtained that the disease will be permanent when R0 > 1 and the disease will be going to extinct when R* < 1. By Lyapunov functional method, we have also obtained some sufficient conditions for global asymptotic stability of this model. Computer simulations are carried out to explain the analytical findings. [ABSTRACT FROM AUTHOR]

Several criteria must be considered while preparing the schedule of a construction project. The completion time and project cost are analyzed in most cases. Additionally, the risk related to the criteria has to be taken into account as well. Thus, project planning problem can be defined as a multicriteria decision problem under risk. In this paper, a project scheduling problem including time-cost trade-offs is analyzed. We assume that various resource allocations can be considered. A new technique based on computer simulation and interactive approach is proposed. In the first step, simulation experiments are performed to evaluate decision alternatives with respect to the criteria. An interactive technique INSDECM is employed for generating the final solution of the problem. The procedure uses stochastic dominance rules for comparing decision alternatives with respect to the criteria. A numerical example is presented to illustrate the applicability of the technique. [ABSTRACT FROM AUTHOR]

Architectural photogrammetry is a technique for acquiring three-dimensional (volumetric) or two dimensional geometric data of buildings for a CAD model from their images. Usually photogrammetric methods (together with the laser scanning) are implemented for the complex surfaces, the measurement of which by any other means is extremely complicated. However, regular geometric forms can be also measured by this method. This is especially an issue in case of possible comparison of the results obtained by different means. In this paper the photogrammetric measurements of geometric elements of the building, with the comparison and evaluation of quality of the results is presented. [ABSTRACT FROM AUTHOR]

In this paper problems associated with the modeling of HIV/AIDS in Southern Africa are presented. A mathematical model is presented to highlight the three major challenges of modeling HIV/AIDS, i.e condom use, vertical transmission and treatment. The model analysis for the case, where the treatment parameter ρ = 0, is presented in terms of the model reproduction number R and threshold parameters RT and RA that show the contribution of vertical transmission. It is shown that if R, RT , RA < 1, then the disease free equilibrium point is both locally asymptotically and globally stable. Numerical simulations for the model are presented to determine the role of some key epidemiological parameters of the model. [ABSTRACT FROM AUTHOR]

The objective of this paper is to study the quantitative forecasting method for agile forecasting of logistics demand in dynamic supply chain environment. Characteristics of dynamic logistics demand and relative forecasting methods are analyzed. In order to enhance the forecasting efficiency and precision, extended Kalman Filter is applied to training artificial neural network, which serves as the agile forecasting algorithm. Some dynamic influencing factors are taken into consideration and further quantified in agile forecasting. Swarm simulation is used to demonstrate the forecasting results. Comparison analysis shows that the forecasting method has better reliability for agile forecasting of dynamic logistics demand. [ABSTRACT FROM AUTHOR]