Application of particle swarm optimization and robust net present value for BOT-type contracts

Major infrastructure construction projects contracted to private companies by governments are important for maximizing profitability. This paper extends an existing build–operate–transfer (BOT) concession model (BOTCcM) for identifying the reasonable concession period which would be profitable both to the government and to the private sector. There are some major limitations with BOTCcM – for example, the total investment cost is pre-given and the impact of uncertainty of parameters affecting the concession period were not considered. In this research, the total investment cost is assumed as variable which should be optimally determined and the uncertainty of net cash flows is considered. Further, the proposed model is implemented to calculate the robust concession period and required capital for the construction period, using the obtained values and particle swarm optimization method.     

Sensitivity analysis and optimisation of suspension bushing using Taguchi method and grey relational analysis

In this paper, a novel method is presented for investigating suspension bushing based on mechanical properties of the bushing, their effective directions, spring stiffness and damping coefficient of bushing. The vehicle vibration model and suspension geometry parameters are used to optimise the vehicle suspension based on multi-body dynamics simulation (ADAMS/CAR) initially. Several experiment tests based on ISO 4128 and ISO 7401 have been performed in one of main Iranian automaker (SAIPA) in order to verify the ADAMS/CAR model. The grey relational analysis based on using Taguchi L27 orthogonal array is used to obtain the optimum suspension. Then the bushing characteristics are optimised considering the indicated method. This method considers a combination of ride comfort and handling qualities of vehicle as objective functions simultaneously. The results of optimum suspension are compared with typical Renault Logan which declares the accuracy and efficiency of this method in optimising suspension bushing.     

Dynamic adaptive finite element analysis of acoustic wave propagation due to underwater explosion for fluid-structure interaction problems

In this paper, an investigation into the propagation of far field explosion waves in water and their effects on nearby structures are carried out. For the far field structure, the motion of the fluid surrounding the structure may be assumed small, allowing linearization of the governing fluid equations. A complete analysis of the problem must involve simultaneous solution of the dynamic response of the structure and the propagation of explosion wave in the surrounding fluid. In this study, a dynamic adaptive finite element procedure is proposed. Its application to the solution of a 2D fluid-structure interaction is investigated in the time domain. The research includes: a) calculation of the far-field scatter wave due to underwater explosion including solution of the time-depended acoustic wave equation, b) fluid-structure interaction analysis using coupled Euler-Lagrangian approach, and c) adaptive finite element procedures employing error estimates, and re-meshing. The temporal mesh adaptation is achieved by local regeneration of the grid using a time-dependent error indicator based on curvature of pressure function. As a result, the overall response is better predicted by a moving mesh than an equivalent uniform mesh. In addition, the cost of computation for large problems is reduced while the accuracy is improved.     

Parametric study of two-body floating-point wave absorber

In this paper, we present a comprehensive numerical simulation of a point wave absorber in deep water. Analyses are performed in both the frequency and time domains. The converter is a two-body floating-point absorber (FPA) with one degree of freedom in the heave direction. Its two parts are connected by a linear mass-spring-damper system. The commercial ANSYS-AQWA software used in this study performs well in considering validations. The velocity potential is obtained by assuming incompressible and irrotational flow. As such, we investigated the effects of wave characteristics on energy conversion and device efficiency, including wave height and wave period, as well as the device diameter, draft, geometry, and damping coefficient. To validate the model, we compared our numerical results with those from similar experiments. Our study results can clearly help to maximize the converter’s efficiency when considering specific conditions.