An effective ant-colony based routing algorithm for mobile ad-hoc network

An effective Ant-Colony based routing algorithm for mobile ad-hoc network is proposed in this paper. In this routing scheme, each path is marked by path grade, which is calculated from the combination of multiple constrained QoS parameters such as the time delay, packet loss rate and bandwidth, etc. packet routing is decided by the path grade and the queue buffer length of the node. The advantage of this scheme is that it can effectively improve the packet delivery ratio and reduce the end-to-end delay. The simulation results show that our proposed algorithm can improve the packet delivery ratio by 9%-22% and the end-to-end delay can be reduced by 14%-16% as compared with the conventional QAODV and ARA routing schemes

Including UPFC dynamic phasor model into transient stability program

In this paper a novel time simulation approach is introduced to implement transient stability analysis with FACTS devices, in which FACTS devices will use dynamic phasor models and interface properly with conventional electromechanical transient-model-based stability program. The unified power flow controller (UPFC) is used as an example to demo the realization of the approach. In the paper, the UPFC dynamic phasor model and control scheme are presented first and followed by the interface formulation. Sequential solution method is proposed to implement step by step simulation. Computer test results from a SMIB power system show clearly the accuracy of dynamic phasor model as compared with EMT model for UPFC; while computer test results from a two-area power system illustrate solidly the effectiveness of the suggested interface and simulation approach to include dynamic-phasor-based FACTS device models into conventional transient stability program. ©2005 IEEE.published_or_final_versio

Observation of a pressure-induced transition from interlayer ferromagnetism to intralayer antiferromagnetism in Sr4Ru3O10

Sr4Ru3O10 is a Ruddlesden-Popper compound with triple Ru-O perovskite layers separated by Sr-O alkali layers. This compound presents a rare coexistence of interlayer (c-axis) ferromagnetism and intralayer (basal-plane) metamagnetism at ambient pressure. Here we report the observation of pressure-induced, intralayer itinerant antiferromagnetism arising from the interlayer ferromagnetism. The application of modest hydrostatic pressure generates an anisotropy that causes a flattening and a tilting of RuO6 octahedra. All magnetic and transport results from this study indicate these lattice distortions diminish the c-axis ferromagnetism and basal-plane metamagnetism, and induce a basal-plane antiferromagnetic state. The unusually large magnetoelastic coupling and pressure tunability of Sr4Ru3O10 makes it a unique model system for studies of itinerant magnetism.Comment: 6 figure

Deregulation of power systems in Asia: Special consideration in developing countries

Power industry is undergoing restructuring throughout the world. The traditional vertically monopolistic structure has been deregulated and replaced by gencos, transcos and discos with competition introduced to gencos and discos in order to reach higher efficiency in electricity production and utilization. A lot of power markets have been established for the purpose. However for different countries, the principal objectives and considerations of power system deregulation are different. In this paper special considerations on power system deregulation of developing countries in Asia are discussed. Two regional power markets in China are used as examples. It is shown that for developing countries, the main objectives of power system deregulation are to attract various investments to power industry in order to meet the fast growth of electric demand caused by blooming economy and in the meantime to reduce government commitment and functions in power industry. Only this way, the power industry, as a significant infrastructure, can realize sustainable development at high efficiency. It is also shown that in the market environment, how to realize optimal system planning and reliable operation at acceptable electricity prices with qualifies service and how to transit to the market environment smoothly at lowest costs and lowest risks should be considered thoroughly. © 2005 IEEE.published_or_final_versio

Kalman filter based estimation of neutral-axis position of bridge deck sections using strain monitoring data

The neutral-axis position has been recognized as a damage indicator for bridge deck assessment because of its high sensitivity to local damage on deck sections. It can be estimated when strain responses at the top and bottom of a deck cross-section under traffic loading are measured. However, the accuracy of neutral-axis position estimation directly using the measured strain responses might be significantly distorted in the presence of measurement noise and varying traffic load patterns. In this study, a Kalman filter (KF) estimator is formulated to locate the neutral-axis position from measured strain responses under traffic loading. Its capability for consistently locating the neutral-axis position under varying traffic load patterns is verified using the field monitoring data of traffic-induced strain responses acquired from the suspension Tsing Ma Bridge under diverse load scenarios (highway traffic, railway traffic, and their combination). The results indicate that the proposed KF estimator gives rise to consistent neutral-axis position estimation results which are independent of load conditions and patterns

Multi-infeed HVDC/AC power system modeling and analysis with dynamic phasor application

In this paper, dynamic phasor method has been applied to HVDC transmission system and FACTS device modeling. A hybrid-model simulation algorithm is suggested for transient stability analysis with HVDC transmission system and FACTS devices in dynamic phasor models and other ac system elements in electromechanical models. Computer test results show clearly that the proposed hybrid-model simulation algorithm can be applied for transient stability analysis effectively and accurately. A multi-infeed HVDC/AC (MIDC/AC) system is studied using the suggested hybrid-model transient stability program. The dynamic behaviors of MIDC/AC system under different circumstances are discussed. The characteristics of HVDC system recovery and recovery strategy for MIDC system are considered in the stability analysis. Furthermore, the impacts of advanced FACTS controllers such as STATCOM on system dynamic are studied for enhance system operation security. © 2000 IEEE.published_or_final_versio