A novel method is presented for fast identification of a machine tool selected point temperature rise, based on an adaptive unscented Kalman filter. The major advantage of the method is its ability to predict the selected point temperature rise in a short period of measuring time, like 30 min, instead of 3 to 6 h in conventional temperature rise tests. A fast identification algorithm is proposed to predict the selected point temperature rise and the steady-state temperature. An adaptive law is applied to adjust parameters dynamically by the actual measured temperature, which can effectively avoid the failure of prediction. A vertical machining center was used to validate the effectiveness of the presented method. Taking any selected point, we could identify the temperature rise at that point in 28 min. However, if the method was not used, it took 394 min to obtain the temperature rise curve from the start-up of the machine tool to the time when it reached a steady-state temperature. The root mean square error (RMSE) between the estimated and measured temperatures in the period of 394 min was 0.1291 °C, and the error between the estimated and measured steady-state temperatures was 0.097 °C. Therefore, this method can effectively and quickly identify a machine tool selected point temperature rise.

To improve the multiple performance indices of practical engineering structures under uncertainties, an interval constrained multiobjective optimization model was constructed with structural performance indices included in objectives and constraints being functions of the interval uncertain parameters. An algorithm integrating radial basis function (RBF), interval analysis, and non-dominated sorting genetic algorithm (NSGA-II) was put forward to locate the Pareto-optimal solutions to the interval multiobjective optimization model. A series of RBFs were constructed based on the Latin hypercube experimental design (LHED) and finite element analysis (FEA), which were then integrated with interval analysis to compute the interval bounds of the objective and constraint functions under the fluctuation of uncertain parameters. Then the fitness of every individual during the NSGA-II-based optimization could be obtained. The case study on the optimization of the mechanical performance of a press slider with uncertain material properties demonstrated the feasibility and validity of the proposed methodology.

The transient performance of a phase change material (PCM)-based heat sink may be affected by its inclination angle because natural convection usually occurs and dominates melting during the operation of the heat sink. An experimental setup was designed and used in this study that allows for the alternation of the inclination angle of the heat sink. The inclination angle was varied from 0掳 to 90掳 at increments of 15掳, while two pulsed heat loads (20 and 40 W) were adopted. 1-hexadecanol of a nominal melting temperature of 49 掳C was selected as the PCM. The transient performance of the heat sink was characterized by the temperature variations at the center of the heat spreader under various conditions. The results showed that the transient performance of the heat sink is able to be improved by simply increasing its inclination angle which then facilitates the natural convection during melting. However, the variation in the performance is not a monotonous function of the inclination angle. Although the time-averaged thermal resistances of the heat sink were shown to be only marginally lowered, the maximum operation times may be greatly extended under the given thermal conditions. For a heat load of 40 W and the maximum allowable temperature of 75 掳C, the operation time of the heat sink is extended by up to nearly 67% at an inclination angle of 75掳 when compared to that of the horizontal case. Based on the cases tested, the optimal inclination angle was found to lie between 60掳 and 75掳.

The buffeting of long-span cable-supported bridges under strong winds is one of the key issues in bridge wind engineering. In order to study the effectiveness of the multiple tuned mass dampers (MTMDs) in buffeting control of long-span bridges, the Sutong Cable-stayed Bridge (SCB) with a main span of 1088 m in China is taken as an example in this paper. The spatial finite element model of the SCB is established and the modal analysis is conducted based on ANSYS. After the 3D turbulence wind field of the SCB is simulated using the measured wind parameters, the time-domain buffeting analysis on the SCB is conducted with the aerodynamic self-excited forces included. According to the dynamic characteristics and the time-domain buffeting analysis results of the SCB, the parameter sensitivity analysis on buffeting vibration control with MTMD is conducted in ANSYS. The optimum parameters are then obtained with the construction difficulty and economic factors considered. Results show that the control efficiency is sensitive to the number of the TMD, mass ratio, frequency band-width ratio, and damping ratio. Both the vertical and the lateral vibrations can be effectively controlled when proper design parameters of a MTMD system are used. In addition, the control effect on lateral vibration is better than that on vertical vibration. Results obtained in this study can provide references for anti-wind design and buffeting control of long-span cable-stayed bridges.

This paper proposes an extended design concept and mechanical description for cable-net structures, including 10 states and 15 procedures which are defined according to their physical nature and analytical capabilities. In the pre-stress release analysis, an iterative computational method is developed for the inverse evaluation from the equilibrium state to the zero-stress state, which adopts the least norm least square approach (LNLS) to the compatibility equation because of the indeterminate property of a cable-net structure. In the pre-tensioning development analysis, another iterative computational method is developed for the positive problem from the zero-stress state to the actual pre-stress state by moving the boundary joints, in which the explicit governing equations are formulated based on the particular energy function and a feasible self-stress mode is adopted to avoid the singularity of the initial stiffness matrix. To implement these methods, Matlab algorithms are developed and two examples are investigated. By comparing the results of the iterative method with those of the dynamic relaxation method, this study determines that they are comparable with each other, which validates the efficiency and accuracy of these iterative methods.

For predicting the voltage and temperature dynamics synchronously and designing a controller, a control-oriented dynamic modeling study of the solid oxide fuel cell (SOFC) derived from physical conservation laws is reported, which considers both the electrochemical and thermal aspects of the SOFC. Here, the least squares support vector regression (LSSVR) is employed to model the nonlinear dynamic characteristics of the SOFC. In addition, a genetic algorithm (GA), through comparing a simulated annealing algorithm (SAA) with a 5-fold cross-validation (5FCV) method, is preferably chosen to optimize the LSSVR’s parameters. The validity of the proposed LSSVR with GA (GA-LSSVR) model is verified by comparing the results with those obtained from the physical model. Simulation studies further indicate that the GA-LSSVR model has a higher modeling accuracy than the LSSVR with SAA (SAA-LSSVR) and the LSSVR with 5FCV (5FCV-LSSVR) models in predicting the voltage and temperature transient behaviors of the SOFC. Furthermore, the convergence speed of the GA-LSSVR model is relatively fast. The availability of this GA-LSSVR identification model can aid in evaluating the dynamic performance of the SOFC under different conditions and can be used for designing valid multivariable control schemes.

The original version of this article unfortunately contained two mistakes. In p. 544, the square root on the right side of Eq. (14) and the square root on the right side of Eq. (15) were incorrect. The correct version is given.