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Low complexity power allocation for hybrid amplify-and-forward opportunistic relay ordering cooperation

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The Journal of China Universities of Posts and Telecommunications 2013年第3期20卷 26-31页

作者： CHENG Yu-lun YANG Long-xiang jiangsu Key Laboratory of Wireless Communications Key Laboratory on Wideband Wireless Communications and Sensor Network Technology of Ministry of Education Nanjing University of Posts and Telecommunications

In this paper, to enhance the robustness against link imbalance, a hybrid cooperative protocol is proposed for amplify-and-forward （AF） opportunistic cooperation, where opportunistic relaying and multi-hop cooperation with relay ordering （RO） are dynamically selected to maximize the end to end signal-noise ratio （SNR）, and the power allocation coefficient is optimized under total power constraint accordingly. Furthermore, a suboptimum allocation scheme with low complexity is proposed by employing the upper bound of harmonic mean. Simulation results show that the proposed scheme outperforms conventional AF opportunistic cooperation in variety of line type topology. Moreover, the efficiency of the proposed suboptimum allocation is also validated in large SNR region.

关键词： opportunistic cooperation multi-hop RO AF power allocation

A COMPARATIVE STUDY ON SHILLING DETECTION METHODS FOR TRUSTWORTHY RECOMMENDATIONS

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Journal of Systems Science and Systems Engineering 2018年第4期27卷 458-478页

作者： Youquan Wang Liqiang Qian Fanzhang Li Lu Zhang College of Computer Science and Engineering Nanjing University of Science and Technology Nanjing 210094 China School of lnformation Engineering Nanjing University of Finance and Economics Nanjing 210003 China College of Computer Science and Technology Soochow University Suzhou 215006 China

Uncovering shilling attackers hidden in recommender systems is very crucial to enhance the robustness and trustworthiness of product recommendation. Many shilling attack detection algorithms have been proposed so far, and they exhibit complementary advantage and disadvantage towards various types of attackers. In this paper, we provide a thorough experimental comparison of several well-known detectors, including supervised C4.5 and NB, unsupervised PCA and MDS, semi-supervised HySAD methods, as well as statistical analysis methods. MovieLens 100K is the most widely-used dataset in the realm of shilling attack detection, and thus it is selected as the benchmark dataset. Meanwhile, seven types of shilling attacks generated by average-filling and random-filling model are compared in our experiments. As a result of our analysis, we show clearly causes and essential characteristics insider attackers that might determine the success or failure of different kinds of detectors.

关键词： Recommender system shilling attack detection supervised classification unsupervisedclustering statistical analysis methods

Effect of hydrological variability on diatom distribution in Poyang Lake, China

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Chinese Journal of Oceanology and Limnology 2017年第1期35卷 174-184页

作者： QIAN Kuimei LIU Xia CHEN Yuwei Poyang Lake LaboratoryJbr Wetland Ecosystem Research State Key Laboratory of Lake Science and Environment Nanjing Institute of Geography and Limnology Chinese Academy of Sciences Nanjing 210008 China College of Environmental Engineering Xuzhou institute of Technology Xuzhou 221111 China

Poyang Lake is the largest freshwater lake in China, and it has a seasonal flooding cycle that significantly changes the water level every year. The aim of this paper was to explain how these hydrological changes influence diatom populations in Poyang Lake. The yearly hydrological cycle can be divided into 4 phases: low water-level phase, increasing water-level phase, high water-level phase and decreasing waterlevel phase. Variations in the abundance of planktonic diatoms were studied using quarterly monitoring data collected from January 2009 to October 2013. Generally, diatoms were dominant in Poyang Lake and accounted for more than 50% of the total phytoplankton biomass except in July 2009(26%) and January 2012(35%). Aulacoseira granulata and Surirella robusta were the predominant species in all four phases, and they accounted for 25.02% to 56.89% and 5.07% to 14.78% of the total phytoplankton biomass, respectively. A redundancy analysis(RDA) showed that changes in physico-chemical parameter were related to the water level, and changes in diatom biomass were related to nitrite levels and p H. These results indicate that changes in environmental parameters related to both seasonal variations and water-level fluctuations caused variations in diatom biomass and community composition in Poyang Lake. Furthermore, extreme hydrological events can have different influences on the diatom community composition in the main channel and lentic regions. This research provides data on the diatom variations in Poyang Lake and will be useful for establishing biological indicators of environmental change and protecting Poyang Lake in the future.

关键词： diatom phytoplankton succession water-level changes Poyang Lake

JOINT LLR-CRC ERROR MITIGATION FOR TWO-WAY ADAPTIVE DENOISE-AND-FORWARD NETWORK CODING

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Journal of Electronics(China) 2013年第4期30卷 352-361页

作者： Cheng Yulun Yang Longxiang jiangsu Key Lab of Wireless Communications Nanjing University of Posts and Telecommunications Key Lab of Broadband Wireless Communication and Sensor Network Technology Ministry of Education Nanjing University of Posts and Telecommunications

Network Coding (NC) brings correlation between the coded signals from different sources, which makes the system more vulnerable to the decode error at relay. Conventional Cyclic Redundancy Code (CRC) has been implemented for error bit detection. However, its error correction is simply ignored. To fully exploit this feature, this paper proposes a novel joint Log-Likelihood Ratio (LLR) CRC error mitigation for NC two way relay channel. Specific thresholds are designed to estimate the error number of data block and identify those which can be recovered if the number is within the error correction scope of CRC. We examine two modes of the thresholds, one based on the average Bit Error Rate (BER) of source-relay link, while the other based on that of instantaneous one. We provide the full analysis for the Pair-wise Error Probability (PEP) performance of the scheme. A variety of numerical results are presented to reveal the superiority of the proposed scheme to conventional CRC NC under independent Rayleigh fading channels. Moreover, the efficiencies of the proposed thresholds are also validated.

关键词： Network Coding (NC) Log-Likelihood Ratio (LLR) Cyclic Redundancy Code (CRC) Denoise-and-forward Pair-wise Error Probability (PEP)

Cable-truss supporting system for gob-side entry driving in deep mine and its application

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International Journal of Mining Science and Technology 2016年第5期26卷 885-893页

作者： Yin Qian Jing Hongwen Dai Dapeng Zhu Tantan Zhao Honghui Meng Bo State Key Laboratory for Geomechanics ＆ Deep Underground Engineering China University of Mining ＆ Technology Xuzhou 221116 China Shanghai Underground Space Architectural Design ＆ Research Institute Shanghai 200020 China East China Environmental ＆ Geotechnical Engineering Branch China Petroleum Qingdao 266000 China

In order to solve the large deformation controlling problem for surrounding rock of gob-side entry driving under common cable anchor support in deep mine, site survey, physical modeling experiment, numerical simulation and field measurement were synthetically used to analyze the deformation and failure characteristics of surrounding rock. Besides, applicability analysis, prestress field distribution characteristics of surrounding rock and the control effect on large deformation of surrounding rock were also further studied for the gob-side entry driving in deep mine using the cable-truss supporting system. The results show that, first, compared with no support and traditional bolt anchor support, roof cable-truss system can effectively restrain the initiation and propagation of tensile cracks in the roof surrounding rock and arc shear cracks in the two sides, moreover, the broken development of surrounding rock, roof separation and extrusion deformation between the two sides of the roadway are all controlled; second, a prestressed belt of trapezoidal shape is generated in the surrounding rock by the cable-truss supporting system, and the prestress field range is wide. Especially, the prestress concentration belt in the shallow surrounding rock can greatly improve the anchoring strength and deformation resisting capability of the rock stratum;third, an optimized support system of ‘‘roof and side anchor net beam, roof cable-truss supporting system and anchor cable of the narrow coal pillar" was put forward, and the support optimization design and field industrial test were conducted for the gob-side entry driving of the working face 5302 in Tangkou Mine, from which a good supporting effect was obtained.

关键词： Deep mine Gob-side entry driving Cable-truss supporting system Deformation and failure Stability

An overview of multi-task learning

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National Science Review 2018年第1期5卷 30-43页

作者： Yu Zhang Qiang Yang Department of Computer Science and Engineering Hong Kong University of Science and Technology

As a promising area in machine learning, multi-task learning(MTL) aims to improve the performance of multiple related learning tasks by leveraging useful information among them. In this paper, we give an overview of MTL by first giving a definition of MTL. Then several different settings of MTL are introduced,including multi-task supervised learning, multi-task unsupervised learning, multi-task semi-supervised learning, multi-task active learning, multi-task reinforcement learning, multi-task online learning and multi-task multi-view learning. For each setting, representative MTL models are presented. In order to speed up the learning process, parallel and distributed MTL models are introduced. Many areas, including computer vision, bio info rmatics, health informatics, speech, natural language processing, web applications and ubiquitous computing, use MTL to improve the performance of the applications involved and some representative works are reviewed. Finally, recent theoretical analyses for MTL are presented.

关键词： multi-task learning

Numerical Analysis of Finite Deformation of Overbroken Rock Mass in Gob Area Based on Euler Model of Control Volume

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Journal of China University of Mining and Technology 2006年第3期16卷 245-248页

作者： LIU Wei-qun MIAO Xie-xing School of Sciences China University of Mining ＆ Technology Xuzhou Jiangsu 221008 China

The overbroken rock mass of gob areas is made up of broken and accumulated rock blocks compressed to some extent by the overlying strata. The beating pressure of the gob can directly affect the safety of mining fields, formarion of road retained along the next goaf and seepage of water and methane through the gob. In this paper, the software RFPA＇2000 is used to construct numerical models. Especially the Euler method of control volume is proposed to solve the simulation difficulty arising from plastically finite deformations. The results show that three characteristic regions occurred in the gob area：（1） a naturally accumulated region, 0-10 m away from unbroken surrounding rock walls, where the beating pressure is nearly zero; （2） an overcompacted region, 10-20 m away from unbroken walls, where the beating pressure results in the maximum value of the gob area; （3） a stable compaction region, more than 20 m away from unbroken walls and occupying absolutely most of the gob area, where the beating pressures show basically no differences. Such a characteristic can exolain the easy-seeoaged “O”-ring phenomena around mining fields very well.

关键词： overbroken rock mass plastically finite deformation method of control volume bearing pressure

Efficient Virtual Network Embedding Algorithm Based on Restrictive Selection and Optimization Theory Approach

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China Communications 2017年第10期14卷 39-60页

作者： Haotong Cao Zhicheng Qu Yishi Xue Longxiang Yang College of Communication and Information Engineering Nanjing University of Posts and Telecommunications Nanjing China Wolfson School of Mechanical Electrical and Manufacturing Engineering Loughborough University Leicestershire UK Key Laboratory of Broadband Wireless Communication and Sensor Network Technique Ministry of Education Nanjing University of Postsand Telecommunications Nanjing China Wireless Communication Key Laboratory of jiangsu Province Nanjing University of Posts and Telecommunications Nanjing China

Network virtualization(NV) is widely considered as a key component of the future network and promises to allow multiple virtual networks(VNs) with different protocols to coexist on a shared substrate network(SN). One main challenge in NV is virtual network embedding(VNE). VNE is a NPhard problem. Previous VNE algorithms in the literature are mostly heuristic, while the remaining algorithms are exact. Heuristic algorithms aim to find a feasible embedding of each VN, not optimal or sub-optimal, in polynomial time. Though presenting the optimal or sub-optimal embedding per VN, exact algorithms are too time-consuming in smallscaled networks, not to mention moderately sized networks. To make a trade-off between the heuristic and the exact, this paper presents an effective algorithm, labeled as VNE-RSOT(Restrictive Selection and Optimization Theory), to solve the VNE problem. The VNERSOT can embed virtual nodes and links per VN simultaneously. The restrictive selection contributes to selecting candidate substrate nodes and paths and largely cuts down on the number of integer variables, used in the following optimization theory approach. The VNE-RSOT fights to minimize substrate resource consumption and accommodates more VNs. To highlight the efficiency of VNERSOT, a simulation against typical and stateof-art heuristic algorithms and a pure exact algorithm is made. Numerical results reveal that virtual network request(VNR) acceptance ratio of VNE-RSOT is, at least, 10% higher than the best-behaved heuristic. Other metrics, such as the execution time, are also plotted to emphasize and highlight the efficiency of VNE-RSOT.

关键词： network virtualization virtual network embedding NP-hard heuristic exact restrictive selection optimization theory

Exact Solutions of VNE: A Survey

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China Communications 2016年第6期13卷 48-62页

作者： Haotong Cao Longxiang Yang Zeyuan Liu Mengting Wu College of Telecommunications and Information Engineering Nanjing University of Posts and Telecommunications Key Laboratory of Broadband Wireless Communication and Sensor Network Technique of Ministry of Education Nanjing University of Posts and Telecommunications College of Electronic Electrical and Systems Engineering University of Birmingham College of Overseas Education Nanjing University of Posts and Telecommunications

Network virtualization is an enabling technology of running multiple virtual networks on a shared substrate network. It aims to deal with the ossification of current network architecture. As a crucial component of network virtualization, virtual network embedding(VNE) can efficiently and effectively allocates the substrate resource to proposed virtual network requests. According to the optimization strategy, VNE approaches can be classified into three categories: exact, heuristic and meta-heuristic solution. The VNE exact solution is the foundation of its corresponding heuristic and meta-heuristic solutions. This paper presents a survey of existing typical VNE exact solutions, and open problems for the future research of VNE exact solutions are proposed.

关键词： network virtualization virtual network requests resource allocation virtual network embedding optimization strategy exact solution