摘要：In order to maintain a uniform distribution of pareto-front solutions, a modified NSGA-II algorithm coupled with a dynamic crowding distance(DCD) method is proposed for the multi-objective optimization of a mixed-flow pump impeller. With the pump meridional section fixed, ten variables along the shroud and hub are selected to control the blade load by using a three-dimensional inverse design method. Hydraulic efficiency, along with impeller head, is applied as an optimization objective; and a radial basis neural network(RBNN) is adopted to approximate the objective function with 82 training samples. Local sensitivity analysis shows that decision variables have different impacts on the optimization objectives. Instead of randomly selecting one solution to implement, a technique for ordering preferences by similarity to ideal solution(TOPSIS) is introduced to select the best compromise solution(BCS) from pareto-front sets. The proposed method is applied to optimize the baseline model, i.e. a mixed- flow waterjet pump whose specific speed is 508 min?1?m3s?1?m. The performance of the waterjet pump was experimentally tested. Compared with the baseline model, the optimized impeller has a better hydraulic efficiency of 92% as well as a higher impeller head at the design operation point. Furthermore, the off-design performance is improved with a wider highefficiency operation range. After optimization, velocity gradients on the suction surface are smoother and flow separations are eliminated at the blade inlet part. Thus, the authors believe the proposed method is helpful for optimizing the mixed-flow pumps.

摘要：The seakeeping performance of a luxury cruise ship was evaluated during the concept design *** comparing numerical predictions based on 3-D linear potential flow theory in the frequency domain with the results of model tests, it was shown that the 3-D method predicted the seakeeping performance of the luxury cruise ship *** on the model, the seakeeping features of the luxury cruise ship were analyzed, and then the influence was seen of changes to the primary design parameters (center of gravity, inertial radius, etc.).Based on the results, suggestions were proposed to improve the choice of parameters for luxury cruise ships during the concept design *** should improve seakeeping performance.

摘要：A nonlinear sliding mode adaptive controller for a thin-film diffractive imaging system is designed to achieve accurate pointing direction over the attitude of subarrays in large-diameter mirror *** kinematics and dynamics equations based on error quaternion and angular velocity are derived,and a diffractive thin-film sub-mirror array controller is designed to point ***,the global stability of the controller is proved by the Lyapunov *** the controller can adaptively identify the inertia matrix of each sub-mirror system,it is robust to bounded disturbances and changes in inertia *** the same time,the continuous arctangent function is introduced,which is effectively *** simulation results show that the designed controller can ensure the accurate tracking of the diffractive film in each sub-mirror in the presence of rotational inertia matrix uncertainty and various disturbances.

摘要：The authors previously introduced a semi-empirical formula that enabled fast estimation of the added resistance of ships in head waves, and in this study the formula is further refined for easy use in engineering applications. It includes an alternative ship draft correction coefficient, which better accounts for the wave pressure decay with ship’s draft. In addition, it only uses the speed and main characteristics of the ship and wave environment as input, and has been simplified to the extent that it can be readily processed using a pocket calculator. Extensive validations are conducted for different ship types at low to moderate speeds in various typical irregular sea conditions, and encouraging results are obtained. This relevant and topical research lies within the framework of the recent IMO MEPC.232（65） （2013） EEDI guidelines for estimating the minimum powering of ships in adverse weather conditions, which specify for the use of simple methods in current Level 2 assessment within engineering ***： added resistance, minimum power, IMO regulation, EEDI regulation, weather coefficient, semi-empirical formulas, ships, head waves

摘要：A tunneled planing hull has unique hybrid hydrodynamic and aerodynamic characteristics due to the presence of a *** this paper,experimental and numerical investigations on hydrody namic analysis of a tunneled planing hull are carried *** resistance tests of models with three dif ferent masses(127.4 kg,159.5 kg,202.9 kg)are conducted for the Froude number in the range of 0.761≤Fn≤*** results of resistance measured by towing tank imply that the tunneled planing hull with a larger displacement has a superior resistance *** numerical simulation of Reynolds Average Navier Stokes(RANS)equations based on the finite volume method is performed to analyze the hull characteristics in calm water(M=159.5 kg)with two degrees of freedom(sinkage and trim).The numerical results are compared with the experimental data,which shows good *** distribution,wave profiles and lift forces obtained by SST k-ωand Realizable k-εturbulence models are compared and ***,the local fluid flow of streamline around the hull can be divided into four regions due to the presence of a tunnel,which is different from the behaviors of the conventional planing monohull with prismatic form.