基于本体映射的MDA模型转换研究

模型转换是MDA框架中的重要环节之一,以往的模型转换方法可能会因为缺乏语义保证而出现错误。本文通过本体映射来研究MDA模型转换,提出实现MDA模型语义层转换的方法,并提高模型转换的效率和准确率。     

Java Bytecode Transformations for Efficient, Portable CPU Accounting

Resource management is essential to build reliable middleware and to host potentially untrusted software components. Resource accounting allows to study and optimize program performance and to charge users for the resource consumption of their deployed components, while resource control can limit the resource consumption of components in order to prevent denial-of-service attacks. In the approach presented here, program transformations enable resource management in Java-based environments, even though the underlying runtime system may not expose information concerning the resource consumption of applications. We present a fully portable program transformation scheme to enhance standard Java runtime systems with mechanisms for CPU management. We implemented several optimizations in order to reduce the overhead of our CPU accounting scheme. Detailed performance measurements quantify this overhead and show the impact of various optimizations.     

On transformation of authorization policies

In this paper, we propose a logic based approach to specify and to reason about transformation of authorization policies. The authorization policy is specified using a policy base which comprises a finite set of facts and access constraints. We define the structure of the policy transformation and employ a model-based semantics to perform the transformation under the principle of minimal change. Furthermore, we extend model-based semantics by introducing preference ordering to resolve possible conflicts during transformation of policies. We also discuss the implementation of the model-based transformation approach and analyse the complexity of the algorithms introduced. Our system is able to represent both implicit and incomplete authorization requirements and reason about nonmonotonic properties.     

Extended Transformed Stress Space for Geomaterials and Its Application

Because the three-dimensional strength of soil, rock, and concrete is influenced nonlinearly by the hydrostatic pressure and Lode’s angle, the failure surface is irregular in stress space, especially in the large stress range. Based on Lade’s criterion, exponential failure function in coordinate p-q, and the concept of original transformed stress space, an extended transformed stress space and its corresponding transformed stress tensors are proposed in this paper. Compared with original transformed stress space, the extended one would be suitable to the large stress range. Processing test results in extended transformed stress space, the unified stress-strain relationship for a certain geomaterial can be easily obtained from the test results. The validity of extended transformed stress space is confirmed by test results of soil, rock, and concrete. Based on extended transformed stress space and the Modified Cam-Clay Model, a new constitutive model is also proposed in this paper, which can be used to predict three-dimensional stress-strain relationship for soils in the large stress range. The capacity of this model is demonstrated using triaxial test results of Toyoura sand with different stress paths in the large stress range.     

肝-胆排泄模型的数学表达

本文提出肝－胆排泄模型的数学表达，以注入血液的^99mTc标记的亚氨基二乙酸（IDA）衍生物为例，说明该数学表达的应用，得到与ICRP相应值几无差别的结果。     

The constant false alarm rate property in transformed noncoherent detection processes

Recently a transformation approach for noncoherent radar detector design has been introduced, where the classical constant false alarm rate detectors for Exponentially distributed clutter are modified to operate in any clutter intensity model of interest. Recent applications of this approach have introduced new decision rules for target detection in Pareto and Weibull distributed clutter. These transformed detectors tended to lose the constant false alarm rate property with respect to one of the clutter parameters. A closer examination of this transformation process yields conditions under which the constant false alarm rate property can be retained. Based upon this, a new model for X-band maritime radar returns is investigated, and corresponding detectors are developed. The relative merits of this new development are investigated with synthetic and real X-band data.     

Parallelization of divide-and-conquer in the Bird-Meertens formalism

An SPMD parallel implementation schema for divide-and-conquer specifications is proposed and derived by formal refinement (transformation) of the specification schema. The specification is in the form of a mutually recursive functional definition. In a first phase, a parallel functional program schema is constructed which consists of a communication tree and a functional program that is shared by all nodes of the tree. The fact that this phase proceeds by semantics-preserving transformations in the Bird-Meertens formalism of higher-order functions guarantees the correctness of the resulting functional implementation. A second phase yields an imperative distributed message-passing implementation of this schema. The derivation process is illustrated with an example: a two-dimensional numerical integration algorithm.Parts of this paper were presented at the International Parallel Processing Symposium, Mexico, 1994 [GoL94] and at the World Transputer Congress, Italy, 1994 [Gor94]     

Hierarchical Deformation of Locally Rigid Meshes

We propose a method for calculating deformations of models by deforming a low‐resolution mesh and adding details while ensuring that the details we add satisfy a set of constraints. Our method builds a low‐resolution representation of a mesh by using edge collapses and performs an as‐rigid‐as‐possible deformation on the simplified mesh. We then add back details by reversing edge‐collapses so that the shape of the mesh is locally preserved. While adding details, we deform the mesh to match the predicted positions of constraints so that constraints on the full‐resolution mesh are met. Our method operates on meshes with arbitrary triangulations, satisfies constraints over the full‐resolution mesh and converges quickly.