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This paper aims to clarify some aspects of the application of the Godunov method for the Baer–Nunziato equations solution on the example of the problem of shock wave – dense particles cloud interaction.

The statement of the problem corresponds to the natural experiment. Mathematical model is based on the Baer–Nunziato system of equations with algebraic right-hand side source terms that takes into account the interphase friction force. Two numerical approaches are used: Harten-Lax-van Leer method and Godunov method.

For the robust simulation using Godunov method, the application of the pressure relaxation procedure is proposed. The comparative analysis of the simulation results using two methods is carried out. The Godunov method provides significantly smaller numerical diffusion of the solid phase volume fraction in the cloud that leads to the much better agreement of the pressure curves on transducers and the dynamics of the cloud motion with the experimental data.

Godunov method for the Baer–Nunziato equations is applied for the simulation of the natural experiment on the shock wave particles cloud interaction. Up to now, the examples of the application of the Godunov method for the Baer–Nunziato equations to the investigation of the practical problems have been limited by the works of the authors of the method and the field of detonation in the heterogeneous explosives. For the robust simulations in the presence of interphase boundaries, it is proposed to use the Godunov method together with the pressure relaxation procedure.

The purpose of this paper is to quantify the relative importance of the multiphase model for the simulation of a gas bubble impacted by a normal shock wave in water. Both the free-field case and the collapse near a wall are investigated. Simulations are performed on both two- and three-dimensional configurations. The main phenomena involved in the bubble collapse are illustrated. A focus on the maximum pressure reached during the collapse is proposed.

Simulations are performed using an inviscid compressible homogeneous solver based on different systems of equations. It consists in solving different mixture or phasic conservation laws and a transport-equation for the gas volume fraction. Three-dimensional configurations are considered for which an efficient massively parallel strategy was developed. The code is based on a finite volume discretization for which numerical fluxes are computed with a Harten, Lax, Van Leer, Contact (HLLC) scheme.

The comparison of three multiphase models is proposed. It is shown that a simple four-equation model is well-suited to simulate such strong shock-bubble interaction. The three-dimensional collapse near a wall is investigated. It is shown that the intensity of pressure peaks on the wall is drastically increased (more than 200 per cent) in comparison with the cylindrical case.

The study of bubble collapse is a key point to understand the physical mechanism involved in cavitation erosion. The bubble collapse close to the wall has been addressed as the fundamental mechanism producing damage. Its general behavior is characterized by the formation of a water jet that penetrates through the bubble and the generation of a blast wave during the induced collapse. Both the jet and the blast wave are possible damaging mechanisms. However, the high-speed dynamics, the small spatio-temporal scales and the complicated physics involved in these processes make any theoretical and experimental approach a challenge.

Cavitation erosion is a major problem for hydraulic and marine applications. It is a limiting point for the conception and design of such components.

Such a comparison of multiphase models in the case of a strong shock-induced bubble collapse is clearly original. Usually models are tested separately leading to a large dispersion of results. Moreover, simulations of a three-dimensional bubble collapse are scarce in the literature using such fine grids.

Development and application of a new systematic approach for design of a control system in order to control the mixture ratio of liquid propellant engines.

The design approach is based on a full nonlinear dynamic model of the engine, and the controller design method is based on describing function models of the engine coupled with the factorization theory. The presented systematic design procedure is comprised of five primary steps. The developed software for the design approach is in the MATLAB environment.

It is found that the presented design approach may successfully be used to control the mixture ratio of a class of liquid propellant engines whose control loops are decoupled. The performance and robustness of the designed controller is found to be satisfactory.

At present, the research is limited to liquid propellant engines whose control loops are decoupled.

The major outcome of this research is that complicated hydromechanical control valves that are used to control the mixture ratio may be replaced by simple microprocessor based servomechanisms that drive simple valves. This will allow for the engine to accept various set point values for mixture ratio as is required in multi‐regime engines.

This is the first paper in the area of mixture ratio control of a liquid propellant engine that is based on the application of describing function approach coupled with the factorization theory.

This paper aims to investigate the collision avoidance problem for a mobile robot by constructing an artificial potential field (APF) based on geometrically modelling the obstacles with a new method named the obstacle envelope modelling (OEM).

The obstacles of arbitrary shapes are enveloped in OEM using the primitive, which is an ellipse in a two-dimensional plane or an ellipsoid in a three-dimensional space. As the surface details of obstacles are neglected elegantly in OEM, the workspace of a mobile robot is made simpler so as to increase the capability of APF in a clustered environment.

Further, a dipole is applied to the construction of APF produced by each obstacle, among which the positive pole pushes the robot away and the negative pole pulls the robot close.

As a whole, the dipole leads the robot to make a derivation around the obstacle smoothly, which greatly reduces the local minima and trajectory oscillations. Computer simulations are conducted to demonstrate the effectiveness of the proposed approach.

Gas explosion is one of the most major types of accident in mining projects, and the flame front with high temperature is major hazardous factor induced by this kind of accident. Support engineering provides an available way to solve problems related to ground movements, but very likely has a great influence on the gas explosion accident process, especially the flame propagation, and then aggravates mining risk. However, until now it has not been received much attention from scientific works. The paper aims to discuss these issues.

A commercial CFD software package AutoReaGas suitable for gas explosion is used to carry out the numerical investigation of gas explosion process in a straight coal tunnel with typical support engineering, especially the unsteady explosion field and the flame propagation process in it.

Support engineering composed by multiple bars take positive influence on flame acceleration: the flame speed is much faster than that under no support bars, and the smaller support spacing induces greater flame speed near the ignition. The support bars also exert negative influence on flame acceleration: the larger support spacing induces greater flame speed in most region of the tunnel. Furthermore, a traditional viewpoint that denser obstacles induce greater explosion effects is one-sided according to this study.

At present, no one concerns the aggravating influence of support engineering on accident risk in practical mining projects because of small geometric dimension. This work examines the effect of steel support system on evolution processes of gas explosion accidents, especially the flame propagation. The conclusions provide quantitative scientific basis for this kind of the accidents in risk evolution and accident investigation of mining engineering.

This paper intent to design, develop, and fabricate a robust cascaded controller based on the dual loop concept i.e. Fuzzy Sliding Mode concept in the inner loop and traditional Proportional Integral controller in the outer loop to reduce the unknown dynamics and disturbances that occur in the DC-DC Converter.

The proposed Fuzzy sliding mode approach combines the merits of both SMC and Fuzzy logic control. FSMC approach reduces the chattering phenomena that commonly occurs in the sliding mode control and speed up the response of the controller.

In most of the research work, the inner current loop of cascaded controller was designed by sliding mode control. In this paper FSMC is proposed and its efficacy is confirmed with SMC -PI. In most uncertainties, FSMC-PI produces null maximum peak overshoot and a very less settling time of 0.0005 sec.

The presence of Fuzzy SMC in the inner loop ensure satisfactory response against all uncertainties such as steady state, circuit parameter variations and sudden line and load disturbances.

Most methods of reliability analysis of cold standby systems assume that the precise probability distributions of the component times to failure are available. However, this assumption may be unreasonable in a wide scope of cases (software, human‐machine systems). Therefore, the imprecise reliability models of cold standby systems are proposed in the paper. These models suppose that arbitrary probability distributions of the component time to failure are possible and they are restricted only by available information in the form of lower and upper probabilities of some events. It is shown how the reliability assessments may vary with a type of available information. The impact of the independence condition on reliability of systems is studied. Numerical examples illustrate the proposed models.

Refers to various types of data envelopment analysis (DEA) literature and puts forward a technique aimed at helping managers to visualize the results of DEA modelling without loss of mathematical rigour. Explains how DEA optimization models can determine different points on the frontier and applies the method to analyse the efficiency of 150 Russian banks in Sptember 1998. Illustrates the results and describes their multiple dimensions in words.

The aims of the paper are to improve the dynamic response of an induction motor based position servo system and to remove the chattering problem in the sliding mode control theory by using fuzzy logic principles. The obtained results are also compared with conventional sliding mode controller to show its performance.

The main method used for the research is to form a thin boundary layer neighboring the switching surface by using fuzzy logic. The sliding mode control law is inherently discontinuous naturally. Therefore, there are some difficulties such as so many switches occurring between the control bounds, which cannot be carried out by real controllers. Therefore, fuzzy logic is used in the thin boundary layer to determine the control signal current. Thus, the chattering is eliminated.

The results show that the designed controller has superior performance. But, there are also some difficulties. It is difficult to obtain fuzzy rules. The rules can be obtained by using genetic algorithms without expert's knowledge. However, sliding surface slope C can be optimized to increase system's dynamic performance.

A new boundary layer consisting of the fuzzy rules in the sliding mode control is formed.

The purpose of this paper is position control scheme for a servo induction motor (SIM) with uncertainty has been designed using a new observer issue and a dynamic sliding mode control (DSMC).

In DSMC, the chattering is removed due to the integrator (or a low-pass filter) which is placed before the input control of the plant. However, in DSMC, the augmented system has one dimension bigger than the actual system (if integrator is used) and then, the plant model should be completely known. To solve this problem in SIM, the use of a new adaptive state observer (ASO) is proposed.

The advantage of the proposed approach is to maintain the system controlled under the external load torque variations. Then, the load variations do not affect the motor positioning. Moreover, it is demonstrated that the observer error converges to zero based on the Lyapunov stability theory.

The knowledge of the upper bound for the system uncertainty is not necessary in an adaptive state observer, which is important in practical implementation. Simulation results are presented to demonstrate the performance of the proposed approach.