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A visualization experiment of a venturi tube unsteady cavitating flows was conducted, by combining high speed visualization and dynamic pressure measurement technology, on the base of simulating the dynamical boundary conditions of the engine feed system. The detailed interior structure of cavitating flows and the pressure fluctuation data were captured. The variation of cavity shapes and the unsteady characteristics were analyzed. The experiment results indicate that as the cavitation number decreases, the venturi tube cavitating flow is changed from inception cavitation to film cavitation, and to cloud cavitation. At cloud cavitation stage, the venturi tube cavitating flows are revealed as some very complex dynamical processes. The cloud cavitating zone can be divided as attached annular cavity film and detached cavity cloud. The attached cavity film is relatively stable as a whole, and its inner pressure fluctuation is really little. It is found that large part of cavity cloud is breaking and shedding from the total detached cavity cloud, and is going to collapse. These processes induce evident pressure fluctuation pulses, which have wide frequency range but not fixable frequency peak in the frequency region. At the aft end of the cavity cloud, the local high velocity re-entrant flow is discovered, which drives the axial length of attached cavity film shortening and extending, and induces the film length obviously unequal along the circle. The self-oscillation of 290--400 Hz also takes place at the downstream system of venturi tube, at the cloud cavitation stage.

The one-machine scheduling problem with time lags while minimizing the completion time is NP-hard. The problem typically arises in a manufacturing where the next job has to be carried out in a specific time window after the completion of the immediately proceeding job. Scheduling the jobs is to find a shortest path that passes all the nodes and meets all precedence constraints and time lags constraints on AON (Activity-On-Node) net. A nonlinear mathematic optimization model is established based on AON net. A neighborhood search algorithm is proposed to convert the nonlinear model into a linear programming model that could be solved by standard software. Computational results prove that the proposed neighborhood search algorithm is effective.

Plate hot rolling scheduling is a type of single-machine scheduling problem with waiting time constraints and finite buffer capacity. The aim is to determine when the plate is rolled, decrease the mill idle time and increase mill utilization. Three scheduling methods, i.e. uniformity alternate scheduling method, symmetry alternate scheduling method and group alternate scheduling method are proposed. For every scheduling method, start rolling time interval and mill utilization formulas are given respectively. Some parameters of the formulas should be adjusted according to the roll table length. Based on the three scheduling methods, a heuristic scheduling approach is proposed for the plate hot rolling scheduling problem. Computation examples demonstrated the application of the heuristic scheduling approach.