A Hierarchical Autonomous System Based Topology Control Algorithm in Space Information Network

( Wei Zhang ),( Gengxin Zhang ),( Liang Gou ),( Bo Kong ),( Dongming Bian ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.9

This article investigates the topology control problem in the space information network (SIN) using a hierarchical autonomous system (AS) approach. We propose an AS network topology control (AS-TC) algorithm to minimize the time delay in the SIN. Compared with most existing approaches for SIN where either the purely centralized or the purely distributed control method is adopted, the proposed algorithm is a hybrid control method. In order to reduce the cost of control, the control message exchange is constrained among neighboring sub-AS networks. We prove that the proposed algorithm achieve logical k-connectivity on the condition that the original physical topology is k-connectivity. Simulation results validate the theoretic analysis and effectiveness of the AS-TC algorithm.

Influence of Screw Rotors Tip Angle on Mixing Performance for One Novel Twin-screw Kneader

Jing Wei,Dabing Chen,Dongming Zhou,Aiqiang Zhang,Yuliang Yang 한국고분자학회 2015 폴리머 Vol.39 No.3

Twin-screw kneader is an efficient polymer processing equipment. In this paper, the mixing performance of one novel intermeshing counter-rotating twin-screw kneader with different tip angles of the male rotor is simulated using the mesh superimposition technique (MST). Statistical analysis is carried out for the flow field using particle tracking technique, and distributive mixing performance is evaluated using the residence time distribution and segregation scale, while the dispersive mixing performance is estimated using the parameters such as shear rate, stretching rate and mixing index. The results show that the best distributive mixing performance is achieved when the tip angle is 0˚, while the optimal dispersive mixing performance is obtained when the tip angle is 20˚. The results in this paper provide a data basis for the selection of parameters and optimization of the performance for the screw rotors.

A comparative analysis of sheeting die geometries using numerical simulations

Igali, Dastan,Wei, Dongming,Zhang, Dichuan,Perveen, Asma Techno-Press 2020 Advances in computational design Vol.5 No.2

The flow behavior of polymer melts within a slit die is an important consideration when designing a die geometry. The quality of the extruded polymer product can be determined through an evaluation of the flow homogeneity, wall shear rate and pressure drop across the central height of the die. However, mathematical formulations cannot fully determine the behavior of the flow due to the complex nature of fluid dynamics and the nonlinear physical properties of the polymer melts. This paper examines two slit die geometries in terms of outlet velocity uniformity, shear rate uniformity at the walls and pressure drop by using the licensed computational fluid dynamics package, Ansys POLYFLOW, based on the finite element method. The Carreau-Yasuda viscosity model was used for the rheological properties of the polypropylene. Comparative analysis of the simulation results will conclude that the modified die design performs better in all three aspects providing uniform exit velocity, uniform wall shear rates, and lower pressure drop.

Data Dissemination in Wireless Sensor Networks with Instantly Decodable Network Coding

Liang Gou,Gengxin Zhang,Dongming Bian,Wei Zhang,Zhidong Xie 한국통신학회 2016 Journal of communications and networks Vol.18 No.5

Wireless sensor networks (WSNs) are widely applied inmonitoring and control of environment parameters. It is sometimesnecessary to disseminate data through wireless links after they aredeployed in order to adjust configuration parameters of sensors ordistribute management commands and queries to sensors. Severalapproaches have been proposed recently for data dissemination inWSNs. However, none of these approaches achieves both high effi-ciency and low complexity simultaneously. To address this problem,cluster-tree based network architecture, which divides aWSN intohierarchies and clusters is proposed. Upon this architecture, datais delivered from base station to all sensors in clusters hierarchyby hierarchy. In each cluster, father broadcasts data to all his chil-dren with instantly decodable network coding (IDNC), and a novelscheme targeting to maximize total transmission gain (MTTG) isproposed. This scheme employs a new packet scheduling algorithmto select IDNC packets, which uses weight status feedback matrix(WSFM) directly. Analysis and simulation results indicate that thetransmission efficiency approximate to the best existing approachmaximum weight clique, but with much lower computational over-head. Hence, the energy efficiency achieves both in data transmis-sion and processing.

Extended Equal Service and Differentiated Service Models for Peer-to-Peer File Sharing

Jianwei Zhang,Yongchao Wang,Wei Xing,Dongming Lu 한국통신학회 2013 Journal of communications and networks Vol.15 No.2

Peer-to-peer (P2P) systems have proved the most effective and popular file sharing applications in recent years. Previous studies mainly focused on equal service and differentiated service strategies when peers have no initial data before their downloads. For an upload-constrained P2P file sharing system, wemodel both the equal service process and the differentiated service process when the initial data distribution of peers satisfies some special conditions. Moreover, we show how to minimize the time required to distribute the file to any number of peers. The proposed fluid-based models can reveal the intrinsic relations among the initial data amount, the peer set size, and the minimum last finish time. The closed-form expressions derived from the extended models can closely approximate chunk-based models and systems, especially for relatively large files. As an application of the extended models, we show how to provide differentiated service efficiently to multiple peer sets. Since no limits are imposed on the upload bandwidth of peers or the size of each peer set, we believe that our analytic process and the results achieved can provide not only fundamental insights into bandwidth allocation and data scheduling but also a helpful reference for both improving systemperformance and building an effective incentive mechanism for P2P file sharing systems.

Data Dissemination in Wireless Sensor Networks with Instantly Decodable Network Coding

Gou, Liang,Zhang, Gengxin,Bian, Dongming,Zhang, Wei,Xie, Zhidong The Korea Institute of Information and Commucation 2016 Journal of communications and networks Vol.18 No.5

Wireless sensor networks (WSNs) are widely applied in monitoring and control of environment parameters. It is sometimes necessary to disseminate data through wireless links after they are deployed in order to adjust configuration parameters of sensors or distribute management commands and queries to sensors. Several approaches have been proposed recently for data dissemination in WSNs. However, none of these approaches achieves both high efficiency and low complexity simultaneously. To address this problem, cluster-tree based network architecture, which divides a WSN into hierarchies and clusters is proposed. Upon this architecture, data is delivered from base station to all sensors in clusters hierarchy by hierarchy. In each cluster, father broadcasts data to all his children with instantly decodable network coding (IDNC), and a novel scheme targeting to maximize total transmission gain (MTTG) is proposed. This scheme employs a new packet scheduling algorithm to select IDNC packets, which uses weight status feedback matrix (WSFM) directly. Analysis and simulation results indicate that the transmission efficiency approximate to the best existing approach maximum weight clique, but with much lower computational overhead. Hence, the energy efficiency achieves both in data transmission and processing.

Extended Equal Service and Differentiated Service Models for Peer-to-Peer File Sharing

Zhang, Jianwei,Wang, Yongchao,Xing, Wei,Lu, Dongming The Korea Institute of Information and Commucation 2013 Journal of communications and networks Vol.15 No.2

Peer-to-peer (P2P) systems have proved the most effective and popular file sharing applications in recent years. Previous studies mainly focused on equal service and differentiated service strategies when peers have no initial data before their downloads. For an upload-constrained P2P file sharing system, we model both the equal service process and the differentiated service process when the initial data distribution of peers satisfies some special conditions. Moreover, we show how to minimize the time required to distribute the file to any number of peers. The proposed fluid-based models can reveal the intrinsic relations among the initial data amount, the peer set size, and the minimum last finish time. The closed-form expressions derived from the extended models can closely approximate chunk-based models and systems, especially for relatively large files. As an application of the extended models, we show how to provide differentiated service efficiently to multiple peer sets. Since no limits are imposed on the upload bandwidth of peers or the size of each peer set, we believe that our analytic process and the results achieved can provide not only fundamental insights into bandwidth allocation and data scheduling but also a helpful reference for both improving system performance and building an effective incentive mechanism for P2P file sharing systems.

Geometry optimization of a double-layered inertial reactive armor configured with rotating discs

Bekzat Ajan,Dichuan Zhang,Christos Spitas,Elias Abou Fakhr,Dongming Wei Techno-Press 2023 Advances in computational design Vol.8 No.4

An innovative inertial reactive armor is being developed through a multi-discipline project. Unlike the well-known explosive or non-explosive reactive armour that uses high-energy explosives or bulging effect, the proposed inertial reactive armour uses active disc elements that is set to rotate rapidly upon impact to effectively deflect and disrupt shaped charges and kinetic energy penetrators. The effectiveness of the proposed armour highly depends on the tangential velocity of the impact point on the rotating disc. However,for a single layer armour with an array of high-speed rotating discs, the tangential velocity is relatively low near the center of the disc and is not available between the gap of the discs. Therefore, it is necessary to configure the armor with double layers to increase the tangential velocity at the point of impact. This paper explores a multi-objective geometry design optimization for the double-layered armor using Nelder-Mead optimization algorithm and integration tools of the python programming language. The optimization objectives include maximizing both average tangential velocity and high tangential velocity areas and minimizing low tangential velocity area. The design parameters include the relative position (translation and rotation) of the disc element between two armor layers. The optimized design results in a significant increase of the average tangential velocity (38%), increase of the high tangential velocity area (71.3%), and decrease of the low tangential velocity area (86.2%) as comparing to the single layer armor.