Failure characteristics of three-body model composed of rock and coal with different strength and stiffness

Four different types of three-body model composed of rock and coal with different strength and stiffness were established in order to study the failure characteristics of compound model such as roof-coal-floor. Through stress analysis of the element with variable strength and stiffness extracted from the strong-weak interface, the tri-axial compressive strength of the weak body and strong body near the interface as well as the areas away from the contact surface was found. Then, on the basis of three-dimensional fast Lagrangian method of continua and strain softening constitutive model composed of Coulomb-Mohr shear failure with tensile cut-off, stress and strain relationship of the four three-body combined models were analyzed under different confining pressures by numerical simulation. Finally, the different features of local shear zones and plastic failure areas of the four different models and their development trend with increasing confining pressure were discussed. The results show that additional stresses are derived due to the lateral deformation constraints near the strong-weak interface area, which results in the strength increasing in weak body and strength decreasing in strong body. The weakly consolidated soft rock and coal cementation exhibit significant strain softening behavior and bear compound tension-shear failure under uni-axial compression. With the increase of confining pressure, the tensile failure disappears from the model, and the failure type of composed model changes to local shear failure with different number of shearing bands and plastic failure zones. This work shows important guiding significance for the mechanism study of seismic, rock burst, and coal bump.

Short Group Signatures Without Random Oracles

We propose short group signature （GS） schemes which are provably secure without random oracles. Our basic scheme is about 14 times shorter than the Boyen-Waters GS scheme at Eurocrypt 2006, and 42% shorter than the recent GS schemes due to Ateniese et al. The security proofs are provided in the Universally Composable model, which allows the proofs of security valid not only when our scheme is executed in isolation, but also in composition with other secure cryptographic primitives. We also present several new computational assumptions and justify them in the generic group model. These assumptions are useful in the design of high-level protocols and may be of independent interest.

A methodology for quantitative assessment of the features and capabilities of software frameworks for model composition

A software framework is an infrastructure or architecture intended to enable the integration and interoperation of a set of software components.A specialized type of software frameworks are those specifically designed to support the composition of models or other components within a simulation system.Such frameworks are intended to simplify the process of assembling a complex model or simulation system from simpler component models as well as to promote the reuse of the component models.Several different types of software frameworks for model composition have been designed and implemented;the various framework types have different component types,processes for composing models,and intended applications.The different framework types and the implemented examples of them vary widely in terms of features and capabilities.Comparing alternative frameworks so as to assess their likely utility for a specific application has heretofore been largely subjective and qualitative,and consequently of uncertain reliability.To address this issue an assessment methodology specifically designed for comparing model composition frameworks is developed and explained.The methodology employs a quantitative metric based on a set of well-defined criteria relating to the features and capabilities of simulation frameworks and is intended to be objective and quantitative.The methodology is illustrated and demonstrated by applying it to a set of existing model composition frameworks.The assessment results suggest that using the methodology can,at a minimum,improve the objectivity and reliability of framework selection decisions.The assessment criteria may also be useful as guidelines when designing and developing a framework.