An efficient delegation protocol with delegation traceability in the X.509 proxy certificate environment for computational grids

The X.509 proxy certificate is widely used to delegate an entity’s right to another entity in the computational grid environment. However, this proxy certificate has two drawbacks: the potential security threat caused by non-traceability of a delegation chain and the inefficiency caused by an interactive communication between the right grantor and the right grantee on the delegation protocol. To address these problems, a new delegation protocol is presented. The proposed protocol employs an ID-based key generation technique to support delegation traceability and non-interactive delegation. Since access-right delegation occurs frequently in the computational grid environment, the proposed protocol can enhance security by providing delegation traceability and can enhance efficiency by reducing the inter-domain communication cost.     

Solving the constrained coverage problem

Coverage problem which is one of the challenging problems in facility location studies, is NP-hard. In this paper, we focus on a constrained version of coverage problem in which a set of demand points and some constrained regions are given and the goal is to find a minimum number of sensors which covers all demand points. A heuristic approach is presented to solve this problem by using the Voronoi diagram and p-center problem's solution. The proposed algorithm is relatively time-saving and is compared with alternative solutions. The results are discussed, and concluding remarks and future work are given.     

Solving the collision detection problem

Considers how a happy convergence of factors in the mid 195Os led CEIT and the University of Navarre to team up for an ambitious project. First, we accumulated expertise in the fields of computer graphics, mechanism analysis and solid modeling. Second, the appearance of 3D graphics workstations on the market allowed us to put our experience to work to develop CompAMM (Computer Analysis of Machines and Mechanisms), a general-purpose program to simulate and visualize in real time the kinematic analysis of complex articulated bodies. We got a Hewlett Packard 350 SRX in July 1987 and made our first presentation of the real-time analysis and visualization of 3D mechanisms at an international congress in Seville two months later. Target applications included robotics, vehicles, mechanisms, spaceship manoeuvres, teleoperator training, astronaut motion, and ergonomics inside vehicles     

OTTER and the Moufang identity problem

This article provides additional evidence of the value of using an automated reasoning program as a research assistant. Featured is the use of Bill McCune's program OTTER to find proofs of theorems taken from the study of Moufang loops, but not just any proofs. Specifically, the proofs satisfy the property of purity. In particular, when given, say, four equivalent identities (which is the case in this article), one is asked to prove the second identity from the first, the third from the second, the fourth from the third, and the first from the fourth. If the proof that 1 implies 2 does not rely on 3 or 4, then by definition the proof is pure with respect to 3 and 4, or simply the proof is pure. If for the four identities one finds four pure proofs showing that 1 implies 2, 2 implies 3, 3 implies 4, and 4 implies 1, then by definition one has found a circle of pure proofs. By finding the needed twelve pure proofs, this article shows that there does exist a circle of pure proofs for the four equivalent identities for Moufang loops and for all orderings of the identities; however, for much of this article, the emphasis is on the first three identities. In addition — in part to promote the use of automated reasoning programs and to answer questions concerning the choice of options — featured here is the methodology that was employed and a discussion of some of the obstacles, some of which are subtle. The approach relies on paramodulation (which generalizes equality substitution), on demodulation, and — so crucial for attacking deep questions and hard problems — on various strategies, most important of which are the hot list strategy, the set of support strategy, and McCune's ratio strategy. To permit verification of the results presented here, extension of them, and application of the methodology to other unrelated fields, a sample input file and four proofs (relevant to a circle of pure proofs for the four identities) are included. Research topics and challenges are offered at the close of this article.This work was supported by the Mathematical, Information, and Computational Sciences Division subprogram of the Office of Computational and Technology Research, U.S. Department of Energy, under Contract W-31-109-Eng-38.     

Solving the multi-vehicle multi-covering tour problem

The well-known multi-vehicle covering tour problem (m-CTP) involves finding a minimum-length set of vehicle routes passing through a subset of vertices, subject to constraints on the length of each route and the number of vertices that it contains, such that each vertex not included in any route is covered. Here, a vertex is considered as covered if it lies within a given distance of at least a vertex of a route. This article introduces a generalized variant of the m-CTP that we called the multi-vehicle multi-covering Tour Problem (mm-CTP). In the mm-CTP, a vertex must be covered at least not only once but several times. Three variants of the problem are considered. The binary mm-CTP where a vertex is visited at most once, the mm-CTP without overnight where revisiting a vertex is allowed only after passing through another vertex and the mm-CTP with overnight where revisiting a vertex is permitted without any restrictions. We first propose graph transformations to convert the last two variants into the binary one and focus mostly on solving this variant. A special case of the problem is then formulated as an integer linear program and a branch-and-cut algorithm is developed. We also develop a Genetic Algorithm (GA) that provides high-quality solutions for the problem. Extensive computational results on the new problem mm-CTP as well as its other special cases show the performance of our methods. In particular, our GA outperforms the current best metaheuristics proposed for a wide class of CTP problems.     

Solving the Java object storage problem

Today's Internet driven view of information systems is helping to popularize Java as an application development language. Developers are beginning to use Java to create multi tier application architectures that often integrate relational data stores with new data types, in order to package information in easier to use, dynamic ways. Java's object oriented nature is ideally suited to this new world. Using objects, Java developers can encapsulate both data and data manipulation methods to give applications a runtime dynamism and self-contained intelligence that is difficult to achieve using other methods. Java application developers need to be able to store these Java objects-technically, to give them persistence-in order to take advantage of these capabilities. We examine the development issues surrounding Java object storage, including a brief overview of the ODMG Java binding, a standard that adds object persistence to Java. We compare this with the much greater level of effort required to implement the same application using the lower level JDBC interface, which supports Java object storage in relational databases. The ODMG binding for Java and JDBC are not competitive specifications: ODMG interfaces can be built on top of JDBC     

Solving the parity problem in one-dimensional cellular automata

The parity problem is a well-known benchmark task in various areas of computer science. Here we consider its version for one-dimensional, binary cellular automata, with periodic boundary conditions: if the initial configuration contains an odd number of 1s, the lattice should converge to all 1s; otherwise, it should converge to all 0s. Since the problem is ill-defined for even-sized lattices (which, by definition, would never be able to converge to 1), it suffices to account for odd-sized lattices only. We are interested in determining the minimal neighbourhood size that allows the problem to be solvable for any arbitrary initial configuration. On the one hand, we show that radius 2 is not sufficient, proving that there exists no radius 2 rule that can solve the parity problem, even in the simpler case of prime-sized lattices. On the other hand, we design a radius 4 rule that converges correctly for any initial configuration and formally prove its correctness. Whether or not there exists a radius 3 rule that solves the parity problem remains an open problem; however, we review recent data against a solution in radius 3, thus providing strong empirical evidence that there may not exist a radius 3 solution even for prime-sized lattices only, contrary to a recent conjecture in the literature.     

Evaluating leadership,IT quality,and net benefits in an e-government environment

US Government organizations are creating value for their citizens and businesses by improving their public service delivery through good websites. Our study examined leadership and IT quality, and their effect on positive delivery outcomes in an e-government environment. We first developed a theoretically based model using elements of the model developed for the Malcolm Baldrige National Quality Award (MBNQA) and DeLone and McLean's IS Success model. To test this model, we conducted a field survey at a municipal city government. The results supported our hypothesis that the MBNQA leadership triad (leadership, strategic planning, and customer/market focus) had a positive impact on the IT quality triad (information, system, and service quality). We also found that both leadership and IT quality increased the benefits.     

Solving the hazmat transport network design problem

In this paper, we consider the problem of network design for hazardous material transportation where the government designates a network, and the carriers choose the routes on the network. We model the problem as a bilevel network flow formulation and analyze the bilevel design problem by comparing it to three other decision scenarios. The bilevel model is difficult to solve and may be ill-posed. We propose a heuristic solution method that always finds a stable solution. The heuristic exploits the network flow structure at both levels to overcome the difficulty and instability of the bilevel integer programming model. Testing on real data shows that the linearization of the bilevel model fails to find stable solutions and that the heuristic finds lower risk networks in less time. Further testing on random instances shows that the heuristically designed networks achieve significant risk reduction over single-level models. The risk is very close to the least risk possible. However, this reduction in risk comes with a significant increase in cost. We extend the bilevel model to account for the cost/risk trade-off by including cost in the first-level objective. The biobjective–bilevel model is a rich decision-support tool that allows for the generation of many good solutions to the design problem.     

Solving the dynamic traveling salesman game problem

A game problem of the successive capture of a team of evaders by a single pursuer under conditions of “simple motions” of the players is analyzed. The performance criterion is the total time all the evaders are captured. It is assumed that the pursuer is guided by the parallel pursuit law. In such a case, the optimal response of the evaders is the straightforward motion with maximum speed. The original infinite-dimensional problem can therefore be reduced to two finite-dimensional problems.     

Solving the optimal attention allocation problem in manual control

Within the context of the optimal control model of human response, analytic expressions for the gradients of closed-loop performance metrics with respect to human operator attention allocation are derived. These derivatives serve as the basis for a gradient algorithm that determines the optimal attention that a human should allocate among several display indicators in a steady-state manual control task. Application of the human modeling techniques are made to study the hover control task for a CH-46 VTOL flight tested by NASA.     

Solving a furnace loading problem

This paper presents a heuristic solution procedure for the furnace loading problem in metallurgical industry. The problem is decomposed into two stages: ingot order selection and candidate ingot loading. The 2-stage problems are then iteratively solved. It is shown that practical sized problems can be efficiently solved using the proposed approach.     

SOA环境中的跨域认证方案研究

鉴于现在的网络越来越复杂,其中,用户数量大、服务类型多、安全机制不统一的特点决定了SOA环境中异构多域的情况,给出了一种基于模糊理论的信任管理方法,并将该方法与证书转换服务结合起来提出了一种 SOA 环境中的跨域认证方案,在该方案中,用户域使用信任管理方法来保证安全性,服务域结合信任管理与证书认证来保证安全性,并且用户可以透明地访问采用不同底层安全机制的域中服务,实现安全跨域认证。分析表明,该方案具有安全与普适的优势,可以满足SOA环境下身份认证的需求。     

Solving the set cover problem on a supercomputer

Supercomputers, such as CRAY-1, CRAY X-MP, CYBER 205, ETA10, … etc, have been regularly used for solving numerical problems. It is very rare that supercomputers are used to solve combinatorial problems. In this paper, we present an efficient vectorized algorithm to solve the set cover problem, which was proved to be NP-complete, on a supercomputer, ETA10-Q108. This algorithm fully utilizes vector instructions. Experiments are performed both on ETA10-Q108 and VAX/8550 for comparison. It takes VAX/8550 1174.5 seconds to solve a set of problem instances while it takes ETA10-Q108 only 26.6 seconds to solve the same set of problems. For a problem instance involving 7000 elements in a set, it takes 47.74 seconds for the supercomputer to solve it. If VAX/8550 is used, it will need roughly 15 hours. Thus we conclude that it is quite feasible to solve the set cover problem by using supercomputers.     

Solving an advection-diffusion problem on the connection machine

An algorithm is presented that solves a linear advection-diffusion problem using a least-squares formulation and a conjugate gradient method to solve the corresponding minimization problem. An implementation in CM-Fortran on a Thinking Machines CM-2 is compared with a serial implementation on an IBM RS6000. The maximum speed-up obtained is a factor of 70. For fine grids, the CPU time scales almost ideally when the number of processors is increased from 4096 to 8192.     

Solving the bus evacuation problem and its variants

In this paper we address the problem of transporting passengers from their origins to multiple gathering centers. We consider two interesting and related cases of this transportation problem: (a) the case of evacuation in anticipation of major natural threats, and (b) the case of transporting casualties after an emergency or terrorist incident, or from a battlefield. Both problem cases share common characteristics and restrictions, i.e. limited available vehicles and limited capacity of the collection/gathering centers, but differ in terms of objectives and the scale of demand. To address the evacuation problem and its variants we have proposed two-index, mixed integer, linear formulations, and we have developed a Hybrid Solution Framework. Extensive experimental results indicate that for both cases the proposed framework provides efficient solutions in reasonable computational times.