以优化的链路状态路由(optimized link state routing,OLSR)协议为原型,为无线Mesh网设计了一种基于节点区分和跨层设计的优化链路状态路由协议NDCL-OLSR(node-differentia-tion and cross-layer based optimized link state routing)....以优化的链路状态路由(optimized link state routing,OLSR)协议为原型,为无线Mesh网设计了一种基于节点区分和跨层设计的优化链路状态路由协议NDCL-OLSR(node-differentia-tion and cross-layer based optimized link state routing).该协议采用了一种新的路由判据NDCLM(node-differentiation and cross-layer metric),在路由计算过程中通过跨层操作机制综合考虑了节点当前负载和链路投递率2个因素对链路质量的影响,并且对节点的类型进行了区分,使得网络流量尽量绕开业务繁忙的超网关节点(SGW),从而大大优化了路由选择的效果.仿真结果表明,NDCL-OLSR能够从很大程度上提高网络的吞吐量,降低端到端的延时,并且能够达到负载均衡的路由效果.展开更多
In fracture simulation,how to model the pre-existing cracks and simulate their propagation without remeshing is an important topic.The newly developed triangular element partition method(TEPM)provides an efficient app...In fracture simulation,how to model the pre-existing cracks and simulate their propagation without remeshing is an important topic.The newly developed triangular element partition method(TEPM)provides an efficient approach to this problem.It firstly meshes the cracked body regardless of the geometry integrity of the interesting object with triangular elements.After the meshing procedure is completed,some elements are intersected by cracks.For the element intersected by a crack,the TEPM takes the element partition technique to incorporate the discontinuity into the numerical model without any interpolation enrichment.By this approach,the TEPM can simulate fracture without mesh modification.In the TEPM,all the cracked elements are treated as the usual partitioned elements in which the crack runs through.The virtual node pairs(the intersection points of crack faces and elements)at the opposite faces of the crack move independently.Their displacements are respectively determined by their neighbor real nodes(nodes formatted in the original mesh scheme)at the same side of the crack.However,among these cracked elements,the element containing a crack tip,referred to as the crack tip element thereafter,behaves differently from those cut through by the crack.Its influence on the singular field at the vicinity of the fracture tip becomes increasingly significant with the element size increasing.In the crack tip element,the virtual node pair at the crack tip move consistently before fracture occurs while the virtual node pair separate and each virtual node moves independently after the fracture propagates.Accordingly,the crack tip element is automatically transformed into the usual partitioned element.In the present paper,the crack tip element is introduced into the TEPM to account for the effect of the crack tip.Validation examples indicate that the present method is almost free from the element size effect.It can reach the same precision as the conventional finite element method under the same meshing scheme.But the TEPM is much more efficient and convenient than the conventional finite element method because the TEPM avoids the troubles that the conventional finite element method suffers,e.g.,the meshing problem of cracked body,modification of mesh scheme,etc.Though the extended finite element method can also avoid these troubles,it introduces extra degrees of freedom due to node interpolation enrichment.Due to the simplicity of the present TEPM,it is believed that its perspective should be highly inspiring.展开更多
文摘以优化的链路状态路由(optimized link state routing,OLSR)协议为原型,为无线Mesh网设计了一种基于节点区分和跨层设计的优化链路状态路由协议NDCL-OLSR(node-differentia-tion and cross-layer based optimized link state routing).该协议采用了一种新的路由判据NDCLM(node-differentiation and cross-layer metric),在路由计算过程中通过跨层操作机制综合考虑了节点当前负载和链路投递率2个因素对链路质量的影响,并且对节点的类型进行了区分,使得网络流量尽量绕开业务繁忙的超网关节点(SGW),从而大大优化了路由选择的效果.仿真结果表明,NDCL-OLSR能够从很大程度上提高网络的吞吐量,降低端到端的延时,并且能够达到负载均衡的路由效果.
基金supported by the National Natural Science Foundation of China (Grant No. 11172172)the National Basic Research Program of China ("973" Project) (Grant No. 2011CB013505)
文摘In fracture simulation,how to model the pre-existing cracks and simulate their propagation without remeshing is an important topic.The newly developed triangular element partition method(TEPM)provides an efficient approach to this problem.It firstly meshes the cracked body regardless of the geometry integrity of the interesting object with triangular elements.After the meshing procedure is completed,some elements are intersected by cracks.For the element intersected by a crack,the TEPM takes the element partition technique to incorporate the discontinuity into the numerical model without any interpolation enrichment.By this approach,the TEPM can simulate fracture without mesh modification.In the TEPM,all the cracked elements are treated as the usual partitioned elements in which the crack runs through.The virtual node pairs(the intersection points of crack faces and elements)at the opposite faces of the crack move independently.Their displacements are respectively determined by their neighbor real nodes(nodes formatted in the original mesh scheme)at the same side of the crack.However,among these cracked elements,the element containing a crack tip,referred to as the crack tip element thereafter,behaves differently from those cut through by the crack.Its influence on the singular field at the vicinity of the fracture tip becomes increasingly significant with the element size increasing.In the crack tip element,the virtual node pair at the crack tip move consistently before fracture occurs while the virtual node pair separate and each virtual node moves independently after the fracture propagates.Accordingly,the crack tip element is automatically transformed into the usual partitioned element.In the present paper,the crack tip element is introduced into the TEPM to account for the effect of the crack tip.Validation examples indicate that the present method is almost free from the element size effect.It can reach the same precision as the conventional finite element method under the same meshing scheme.But the TEPM is much more efficient and convenient than the conventional finite element method because the TEPM avoids the troubles that the conventional finite element method suffers,e.g.,the meshing problem of cracked body,modification of mesh scheme,etc.Though the extended finite element method can also avoid these troubles,it introduces extra degrees of freedom due to node interpolation enrichment.Due to the simplicity of the present TEPM,it is believed that its perspective should be highly inspiring.