New method of reliability analysis and calculation on grey maintainable system
A new model for reliability analysis and calculation of the grey maintainable system is put forward based on the grey theory to tackle the problem of lacking information for practical application. The feasibility of the proposed method is confirmed by a numerical example. The feature of this new method is that it can analyze system reliability dynamically and master its development law because it does not depend on the distribution parameters of system. Hence, it can be used to preview the reliability of system.
On air defense communications network connectivity
The authors address the issue of communication network survivability and provide a quantitative measure of the time-varying connectivity of space and ground multimedia networks operating in stressed environments. This measure allows comparison of very different network architectures in terms of connectivity. A generic SBR (Space-Based Radar) constellation was selected for study of the communications connectivity. The SBR, consisting of constellations of low Earth orbit satellites, will require dynamic, robust communication protocols and networks to support the various missions for the Air Force, Navy, and other military organizations. The authors present a methodology that can be used to define connectivity requirements once the threat and system parameters are better defined.<<ETX>>
Effect of stress conditions on collapse deformation behavior of a rockfill material
A set of saturated and dry-saturated large-scale triaxial tests were conducted in order to explore the effects of stress conditions on the saturation-induced collapse deformation behavior of a rockfill material. Specimens were tested in different confining pressures and for dry-saturated tests the specimens were submerged in various shear stress levels. The results indicate that in all of the dry-saturated tests a sudden reduction in the volume of the specimens was observed during the submerging process. The ratio of the minimum axial strength of a submerged specimen (at the end of the saturation process) to the shear strength of the specimen before saturation is defined as the coefficient of stress recovery, Csr. Results of the dry-saturated tests showed that this ratio increases as the confining pressure increases and decreases by increasing the shear stress level. According to the results of dry-saturated tests the values of internal friction angle reduction caused by saturation (Δϕc), the ratio of the elasticity modulus of the material after saturation to its elasticity modulus in dry condition, i.e., Ewet/Edry, and also the saturation induced sudden volumetric strain (εvc) decrease as the confining pressure increases. However the shear stress level does not have any meaningful effect on the variation of Dfc, Ewet/Edry and (εvc).