The topological properties of peer-to-peer overlay networks are critical factors that dominate the performance of these systems. Several non-constant and constant degree interconnection networks have been used as topo...
详细信息
The topological properties of peer-to-peer overlay networks are critical factors that dominate the performance of these systems. Several non-constant and constant degree interconnection networks have been used as topologies of many peer-to-peer networks. One of these has many desirable properties: the Kautz digraph. Unlike interconnection networks, peer-to-peer networks need a topology with an arbitrary size and degree, but the complete Kautz digraph does not possess these properties. In this paper, we propose Moore: the first effective and practical peer-to-peer network based on the incomplete Kautz digraph with O (log d N ) diameter and constant degree under a dynamic environment. The diameter and average routing path length are [log d ( N ) - log d (1 + 1/ d )] and log d N , respectively, and are shorter than that of CAN, butterfly, and cube-connected-cycle. They are close to that of complete de Bruijn and Kautz digraphs. The message cost of node joining and departing operations are at most 2.5 d log d N and (2.5 d + 1) log d N , and only d and 2 d nodes need to update their routing tables. Moore can achieve optimal diameter, high performance, good connectivity and low congestion evaluated by formal proofs and simulations.
Quadratic trigonometric spline curves with multiple shape parameters are presented in this *** to the cubic B-spline curves, each trigonometric spline curve segment is generated by four consecutive control points. The...
详细信息
Quadratic trigonometric spline curves with multiple shape parameters are presented in this *** to the cubic B-spline curves, each trigonometric spline curve segment is generated by four consecutive control points. The trigonometric spline curves with a non -uniform knot vector are C1 continuous. With a uniform knot vector, the trigonometric spline curves are C3 continuous when all shape parameter λ1 =I. Taking different values of the shape parameters,one can globally or locally adjust the shapes of the curves,so that the trigonometric spline curves can be close to the cubic B-spline curves or closer to the given control polygon than the cubic B-spline curves. The trigonometric spline curves also can represent ellipse and generate a family of ellipse with the same control points. A quadratic trigonometric B閦ier curves are also introduced as a special case of the given trigonometric spline curves.
Based on the low voltage transfer ratio of conventional matrix converter, a new matrix converter referred to as a Boost matrix converter was proposed. The basic configuration of this new topology and its fundamental w...
详细信息
Based on the low voltage transfer ratio of conventional matrix converter, a new matrix converter referred to as a Boost matrix converter was proposed. The basic configuration of this new topology and its fundamental were introduced, the analytic expression concerning functions relation of voltage transfer ratio to duty cycle was deduced, the two effective control strategies, i.e., sliding mode control and double-loop control, were expounded particularly and their different attributes were compared. The validity and feasibility of the new topology were tested by simulation. The results show that the modulation of voltage transfer ratio and output frequency can be achieved optionally through this new converter by means of the two control strategies and an ideal sine output wave with less distortion can be gotten, so the inherent problem of conventional matrix converter with low voltage transfer ratio is solved effectively.
Stem algorithm is a robust static software watermarking scheme. It can resist many common attacks except collusive attacks. In this paper we propose an improved Stern algorithm, make it has the ability of resisting co...
详细信息
Stem algorithm is a robust static software watermarking scheme. It can resist many common attacks except collusive attacks. In this paper we propose an improved Stern algorithm, make it has the ability of resisting collusive attacks and simplify its implementation at the same time. Furthermore, we describe the implementation of our algorithm and the issues that arise when targeting MSIL. We then validated it by experiments against a variety of attacks.
Titanium alloy parts were prepared by metal injection molding, binder was removed from the parts by solvent debinding process, and the brown parts were densified in vacuum atmosphere. The as-sintered specimens were tr...
详细信息
Titanium alloy parts were prepared by metal injection molding, binder was removed from the parts by solvent debinding process, and the brown parts were densified in vacuum atmosphere. The as-sintered specimens were treated through hot-isostatic pressure at 960°C and 140 MPa, and titanium alloy compacts were annealed at 720-760°C for 1-1.5 h. SEM observations showed that the titanium alloy had a uniform dial microstructure with many equiaxed α grains and a little β grains. XRD results indicated that Ti3Al phase was found in the alloy when the annealing temperature was higher than 800°C.
On line system is hard to evolve dynamically because its runtime SA (Software Architecture) exists implicitly.A model of runtime SA based on design space is put forward, in the model runtime SA is expressed explicitly...
详细信息
On line system is hard to evolve dynamically because its runtime SA (Software Architecture) exists implicitly.A model of runtime SA based on design space is put forward, in the model runtime SA is expressed explicitly as first-class *** concept separation between abstract SA (ASA)on meta-layer and physical SA (PSA)on base-layer provides methods to take on SA views at diverse levels of abstraction and manage SA for users, thereby supports the reuse of software framework and component when system is running, and enhances system flexibility and *** we have given an ADL (dynamic architecture description) of runtime software architecture model based on design ***, we discuss dynamic structure reconfiguration issues.
Authorization is an essential part in Workflow management systems (WfMS) and the role-based authorization model is commonly adopted in most commercial and research workflow systems. However, role-based model alone is ...
详细信息
Authorization is an essential part in Workflow management systems (WfMS) and the role-based authorization model is commonly adopted in most commercial and research workflow systems. However, role-based model alone is not sufficient to meet the authorization requirements when not considering the organization hierarchy. In this paper, we present a role-based semantic authorization framework for WfMS, which combines organizational levels and roles together to construct a 2-tuple atomic authorization term. To implement this framework, an authorization model is introduced. A set of atomic authorization predicates are presented. Based on these predicates, formal authorization expression can be composed to express the assignment of authorization terms to workflow activities.
Sn-20Bi lead-free solders were studied in alloying method. Adding alloy element Ag, In, Ga or Sb into Sn-20Bi, the influences of the change of Ag, In, Ga or Sb contents on their microstructure and physical properties ...
详细信息
Sn-20Bi lead-free solders were studied in alloying method. Adding alloy element Ag, In, Ga or Sb into Sn-20Bi, the influences of the change of Ag, In, Ga or Sb contents on their microstructure and physical properties were investigated. The results showed that, when the content of Ag was 0.7%, Ga was 0.5%, or In was 0.1%, the melting points of the solder reduced correspondingly and the segregation of Bi decreased, and the microstructure and physical properties were better. Sb was not suitably added solely, and the microstructure of Sn-Bi-Sb solder was a little worse than that of Sb-free alloys, but the hardness increased.
This paper focused on the effects of the fixed-rerouting path scheme and the variable-rerouting path scheme upon the anonymity degree in anonymity system based on rerouting. The probability method was adopted to prove...
详细信息
This paper focused on the effects of the fixed-rerouting path scheme and the variable-rerouting path scheme upon the anonymity degree in anonymity system based on rerouting. The probability method was adopted to prove that senders sending packets by either fixed-rerouting path or variable-rerouting path were vulnerable to certain attacks, thus degrading the anonymity degree of the sender. The dynamic fixed-rerouting path scheme was presented to resist the attacks efficiently, which were aimed at both the fixed-rerouting path scheme and the variable-rerouting path scheme, thus improving the anonymity degree of the sender. Theoretical analyses have shown that anonymity system adopting the dynamic fixed-rerouting path scheme provides a higher anonymity degree than anonymity system adopting either the fixed-rerouting path scheme or the variable-rerouting path scheme.
A measurement-based call admission control (CAC) algorithm was presented. The scheme measures the state parameters of cellular system, i.e., the number of handoff-dropping calls and the handoff-dropping probability at...
详细信息
A measurement-based call admission control (CAC) algorithm was presented. The scheme measures the state parameters of cellular system, i.e., the number of handoff-dropping calls and the handoff-dropping probability at each interval, and forecasts the possible number of handoff dropping calls at next interval. Based on the forecasting value and the current handoff-dropping probability, the reservation threshold is updated. Also, a Hopfield neural network (HNN) is used to allocate bandwidth resources adaptively and fairly among the calls. The simulation results show that our CAC algorithm can guarantee the predefined handoff-dropping probability while increasing the statistical multiplexing gain in providing acceptable service grades for every connection.
暂无评论