Numerical simulation of the effect of flange radial length on strain growth of cylindrical containment vessels

In this paper, the effect of radial length of flange on the strain growth in the elastic range of the cylindrical shell is studied by numerical simulation using LS-DYNA. It is found that the influence of the flange length on the first strain peak is small. As the radial length of the flange increases, the bending disturbance of the various frequencies of the cylindrical shell is excited which makes the linear modal coupling response is enhanced, so that the strain growth factor is increased. When more high-frequency parts are introduced into the strain response, the strain growth time will be correspondingly shortened. Therefore, it is recommended to use a flange as small as possible when designing the explosion containment vessel

Sliding Mode Control of Time-Delay Systems with Delayed Nonlinear Uncertainties

This paper considers a class of time delay systems with delayed states and non-linear uncertainties using sliding mode techniques. In order to improve robustness, matched and mismatched disturbances are considered and assumed to be nonlinear functions of system states and delayed states. A sliding function is designed and a set of su?cient conditions is derived to guarantee the stability of the corresponding sliding motion by using Lyapunov-Razumikhin approach which allows large time varying delay with fast changing rate. A delay dependent sliding mode control is synthesized to drive the system to the sliding surface in ?nite time and maintain a sliding motion thereafter. E?ectiveness of the proposed method is tested via a case study on a continuous stirred tank reactor system

Versatile stack management for multitasking sensor networks

The networked application environment has motivated the development of multitasking operating systems for sensor networks and other low-power electronic devices, but their multitasking capability is severely limited because traditional stack management techniques perform poorly on smallmemory systems. In this paper, we show that combining binary translation and a new kernel runtime can lead to efficient OS designs on resource-constrained platforms. We introduce SenSmart, a multitasking OS for sensor networks, and present new OS design techniques for supporting preemptive multi-task scheduling, memory isolation, and versatile stack management. We have implemented SenSmart on MICA2/MICAz motes. Evaluation shows that SenSmart performs efficient binary translation and demonstrates a significantly better capability in managing concurrent tasks than other sensornet operating systems. © 2010 IEEE

Spatial planning for urban ventilation corridors by urban climatology

Ventilation corridors in cities can decrease air pollution and alleviate heat island problems but there remains a need to fully assess their effectiveness. Few urban managers have been able to take city-scale approaches to the construction of urban ventilation corridors. This study aimed to introduced the Ventilation Corridor Planning (VCP) model, which is a multi-criteria evaluation method combined with a geographical information system (GIS) to determine where the ventilated environment is most appropriate. Specifically, the VCP model took Bozhou, China as the research object and contained two scales, including mesoscale and local scale. In mesoscale scale, we got three outputs to build urban ventilation corridors, including 1) background wind environment, 2) ventilation potential, 3) heat island intensity. In local scale, we used traditional computational fluid dynamics (CFD) model to verify the impact of VCP criteria. The results revealed that compared with the traditional CFD model, the proposed VCP model has advantages in establishing a comprehensive evaluation standard. In addition, the application of VCP model in macro and micro also enhances the efficiency of ventilation corridor construction. Overall, this study introduced a effective modeling method to urban ventilation corridors planning, and provide a way to study the urban climate

Creep deformation behavior during densification of ZrB2-SiBCN ceramics with ZrO2 additive

Abstract ZrB2-SiBCN ceramics with ZrO2 additive are hot-pressed under a constant applied pressure. The densification behavior of the composites is studied in a view of creep deformation by means of the Bernard-Granger and Guizard model. With determination of the stress exponent (n) and the apparent activation energy (Q d), the specific deformation mechanisms controlling densification are supposed. Within lower temperature ranges of 1300–1400 °C, the operative mechanism is considered to be grain boundary sliding accommodated by atom diffusion of the polymer-derived SiBCN (n = 1, Q d = 123±5 kJ/mol) and by viscous flow of the amorphous SiBCN (n = 2, Q d = 249±5 kJ/mol). At higher temperatures, the controlling mechanism transforms to lattice or intra-granular diffusion creep (n = 3–5) due to gradual consumption of the amorphous phase. It is suggested that diffusion of oxygen ions inside ZrO2 into the amorphous SiBCN decreases the viscosity, modifies the fluidity, and contributes to the grain boundary mobility