- Rong Jiang;Rongxing Lu;Ye Wang;Jun Luo;Changxiang Shen;Xuemin(Sherman) Shen;
With the proliferation of smart grid research,the Advanced Metering Infrastructure(AMI) has become the first ubiquitous and fixed computing platform. However,due to the unique characteristics of AMI,such as complex network structure,resource-constrained smart meter,and privacy-sensitive data,it is an especially challenging issue to make AMI secure. Energy theft is one of the most important concerns related to the smart grid implementation. It is estimated that utility companies lose more than $25 billion every year due to energy theft around the world. To address this challenge,in this paper,we discuss the background of AMI and identify major security requirements that AMI should meet. Specifically,an attack tree based threat model is first presented to illustrate the energy-theft behaviors in AMI. Then,we summarize the current AMI energy-theft detection schemes into three categories,i.e.,classification-based,state estimation-based,and game theory-based ones,and make extensive comparisons and discussions on them. In order to provide a deep understanding of security vulnerabilities and solutions in AMI and shed light on future research directions,we also explore some open challenges and potential solutions for energy-theft detection.
2014年02期 v.19 105-120页 [查看摘要][在线阅读][下载 931K] [下载次数：154 ] |[网刊下载次数：0 ] |[引用频次：57 ] |[阅读次数：0 ] - Jiye Wang;Kun Meng;Junwei Cao;Zhen Chen;Lingchao Gao;Chuang Lin;
The technology of Ultra-High Voltage(UHV) transmission requires higher dependability for electric power grid. Power Grid Communication Networking(PGCN),the fundamental information infrastructure,severs data transmission including control signal,protection signal,and common data services. Dependability is the necessary requirement to ensure services timely and accurately. Dependability analysis aims to predicate operation status and provide suitable strategies getting rid of the potential dangers. Due to the dependability of PGCN may be affected by external environment,devices quality,implementation strategies,and so on,the scale explosion and the structure complexity make the PGCN's dependability much challenging. In this paper,with the observation of interdependency between power grid and PGCN,we propose an electricity services based dependability analysis model of PGCN. The model includes methods of analyzing its dependability and procedures of designing the dependable strategies. We respectively discuss the deterministic analysis method based on matrix analysis and stochastic analysis model based on stochastic Petri nets.
2014年02期 v.19 121-132页 [查看摘要][在线阅读][下载 858K] [下载次数：59 ] |[网刊下载次数：0 ] |[引用频次：10 ] |[阅读次数：0 ] - Yuxin Wan;Junwei Cao;Shuqing Zhang;Guoyu Tu;Chao Lu;Xingtao Xu;Keqin Li;
The concept of Cyber-Physical Systems(CPSs),which combine computation,networking,and physical processes,is considered to be beneficial to smart grid applications. This study presents an integrated simulation environment to provide a unified platform for the investigation of smart grid applications involving power grid monitoring,communication,and control. In contrast to the existing approaches,this environment allows the network simulator to operate independently,importing its results to the power system simulation. This resolves conflicts between discrete event simulation and continuous simulation. In addition,several data compensation methods are proposed and investigated under different network delay conditions. A case study of wide-area monitoring and control is provided,and the efficiency of the proposed simulation framework has been evaluated based on the experimental results.
2014年02期 v.19 133-143页 [查看摘要][在线阅读][下载 1245K] [下载次数：110 ] |[网刊下载次数：0 ] |[引用频次：37 ] |[阅读次数：0 ]
- Siyi Xie;Jian Cai;Qian Wang;Lu Wang;Ziyu Liu;
In this study,TiN films were deposited on SiO2 substrates by Atomic Layer Deposition(ALD) using TiCl4and NH3 as precursors. Properties and morphology of the TiN films were characterized by different methods.Using Grazing Incidence X-Ray Diffraction(GIXRD),TiN films demonstrated polycrystalline structure with(111)preferred orientation. Film thickness was measured by Spectroscopic Ellipsometry(SE) and a stable growth rate of 0.0178 nm/cycle was reached after 500 deposition cycles,which was consistent with the essence of ALD as a surface-saturated self-limiting reaction. Film resistivity measured by a four-point probe continuously decreased with increasing deposition cycles until it reached the minimum value of 300μΩ cm at 5000 deposition cycles with a thickness of 87.04 nm. The surface roughness and morphology of the TiN films at different deposition cycles ranging from 50 to 400 were analyzed by Atomic Force Microscopy(AFM). The AFM results indicated that the initial film growth follows the Stranski-Krastanov mode.
2014年02期 v.19 144-149页 [查看摘要][在线阅读][下载 373K] [下载次数：74 ] |[网刊下载次数：0 ] |[引用频次：9 ] |[阅读次数：0 ] - Tiwei Wei;Jian Cai;Qian Wang;Yang Hu;Lu Wang;Ziyu Liu;Zijian Wu;
The barrier/seed layer is a key issue in Through Silicon Via(TSV) technology for 3-D integration.Sputtering is an important deposition method for via metallization in semiconductor process. However,due to the limitation of sputtering and a "scallop" profile inside vias,poor step coverage of the barrier/seed layer always occurs in the via metallization process. In this paper,the effects of several sputter parameters(DC power,Ar pressure,deposition time,and substrate temperature) on thin film coverage for TSV applications are investigated.Robust TSVs with aspect ratio 5 1 were obtained with optimized magnetron sputter parameters. In addition,the influences of different sputter parameters are compared and the conclusion could be used as a guideline to select appropriate parameter sets.
2014年02期 v.19 150-160页 [查看摘要][在线阅读][下载 872K] [下载次数：63 ] |[网刊下载次数：0 ] |[引用频次：4 ] |[阅读次数：0 ] - Yanhang Zhang;Zhaohua Zhang;Bo Pang;Li Yuan;Tianling Ren;
This study presents a tiny pressure sensor which is used to measure the Intracranial Pressure(ICP). The sensor is based on the piezoresistive effect. The piezoresistive pressure sensor is simulated and designed by using nonlinear programming optimizing and Finite Element Analysis(FEA) tools. Two kinds of sensor sizes are designed in the case of childhood and adult. The sensors are fabricated by Microelectro Mechanical Systems(MEMS)process. The test results yield sensitivities of 1.033 10 2mV/kPa for the childhood type detection and 1.257 10 2mV/kPa for the adult detection with sensor chip sizes of 0.40 0.40 mm2and 0.50 0.50 mm2,respectively. A novel method for measuring ICP is proposed because of the tiny sizes. Furthermore,relative errors for sensitivity of pressure sensors are limited within 4.76%. Minimum Detectable Pressure(MDP) reaches 128.4 Pa in average.
2014年02期 v.19 161-167页 [查看摘要][在线阅读][下载 518K] [下载次数：98 ] |[网刊下载次数：0 ] |[引用频次：11 ] |[阅读次数：0 ] - Bing Yang;Zongguang Yu;Jinghe Wei;
With the rapid development in spaceflights and aeroplanes,the demand for low-power and miniaturization techniques has become insistent in modern radar systems. A new framework for low-power modern radar System on a Chip(SoC) based on ASIX core is presented. Pivotal modules and low-power design flows are described in detail. The dynamic clock-distribution mechanism of the power management module and the influence of the chip power are both stressed. This design adopts the SMIC 0.18-?m 1P6M Salicide CMOS process,the area is 7.825mm 7.820 mm,there are approximately 2 million gates and the frequency is 100 MHz. The results show that the modern radar SoC passes the test on modern radar application system and meets the design requirements. The chip incurs power savings of 42.79% during the fore-end phase and 12.77% during the back-end phase. The total power is less than 350 mW for a 100-MHz operating environment.
2014年02期 v.19 168-173页 [查看摘要][在线阅读][下载 543K] [下载次数：33 ] |[网刊下载次数：0 ] |[引用频次：3 ] |[阅读次数：0 ]
- Xiao Yu;Yueting Chai;Yi Liu;Hongbo Sun;
E-commerce has grown extraordinarily since the emergence of the internet,and many types of services are employed to accelerate this process. Service quality and productivity are two critical indicators to evaluate the competitiveness of e-commerce companies. Deciding which provision mode of e-commerce services(buy,sell,or self-provide) to adopt is a key operational strategy issue. This paper investigates the conditions and limitations of e-commerce services' optimal supply modes,and proposes a cost oriented infra-marginal model where service demand is considered an exogenous variable due to its non-elastic and unprofitable characteristics. By analyzing the main impact factors of this model,this paper infers provision mode selection strategies,which are determined by four factors: transaction cost,service price,service demand,and competitive advantages. Decision trees are derived from these strategies to help e-commerce companies make appropriate decisions. Finally,the proposed model's feasibility is verified by two case studies.
2014年02期 v.19 174-183页 [查看摘要][在线阅读][下载 232K] [下载次数：317 ] |[网刊下载次数：0 ] |[引用频次：7 ] |[阅读次数：0 ] - Yuanyuan Liu;Jianping Cheng;Li Zhang;Yuxiang Xing;Zhiqiang Chen;Peng Zheng;
Dual Energy CT(DECT) has recently gained significant research interest owing to its ability to discriminate materials,and hence is widely applied in the field of nuclear safety and security inspection. With the current technological developments,DECT can be typically realized by using two sets of detectors,one for detecting lower energy X-rays and another for detecting higher energy X-rays. This makes the imaging system expensive,limiting its practical implementation. In 2009,our group performed a preliminary study on a new low-cost system design,using only a complete data set for lower energy level and a sparse data set for the higher energy level. This could significantly reduce the cost of the system,as it contained much smaller number of detector elements.Reconstruction method is the key point of this system. In the present study,we further validated this system and proposed a robust method,involving three main steps:(1) estimation of the missing data iteratively with TV constraints;(2) use the reconstruction from the complete lower energy CT data set to form an initial estimation of the projection data for higher energy level;(3) use ordered views to accelerate the computation. Numerical simulations with different number of detector elements have also been examined. The results obtained in this study demonstrate that 1 + 14% CT data is sufficient enough to provide a rather good reconstruction of both the effective atomic number and electron density distributions of the scanned object,instead of 2 sets CT data.
2014年02期 v.19 184-194页 [查看摘要][在线阅读][下载 1035K] [下载次数：38 ] |[网刊下载次数：0 ] |[引用频次：8 ] |[阅读次数：0 ] - Huabin Ruan;Xiaomeng Huang;Haohuan Fu;Guangwen Yang;
The Gaussian Copula Probability Density Function(PDF) plays an important role in the fields of finance,hydrological modeling,biomedical study,and texture retrieval. However,the existing schemes for evaluating the Gaussian Copula PDF are all computationally-demanding and generally the most time-consuming part in the corresponding applications. In this paper,we propose an FPGA-based design to accelerate the computation of the Gaussian Copula PDF. Specifically,the evaluation of the Gaussian Copula PDF is mapped into a fully-pipelined FPGA dataflow engine by using three optimization steps: transforming the calculation pattern,eliminating constant computations from hardware logic,and extending calculations to multiple pipelines. In the experiments on 10 typical large-scale data sets,our FPGA-based solution shows a maximum of 1870 times speedup over a well-tuned singlecore CPU-based solution,and 610 times speedup over a well-optimized parallel quad-core CPU-based solution when processing two-dimensional data.
2014年02期 v.19 195-202页 [查看摘要][在线阅读][下载 385K] [下载次数：47 ] |[网刊下载次数：0 ] |[引用频次：1 ] |[阅读次数：0 ] - Qi Li;Xinru Qu;Liuguo Yin;Jianhua Lu;
In this study,a class of Generalized Low-Density Parity-Check(GLDPC) codes is designed for data transmission over a Partial-Band Jamming(PBJ) environment. The GLDPC codes are constructed by replacing parity-check code constraints with those of nonsystematic Bose-Chaudhuri-Hocquenghem(BCH),referred to as Low-Density Parity-Check(LDPC)-BCH codes. The rate of an LDPC-BCH code is adjusted by selecting the transmission length of the nonsystematic BCH code,and a low-complexity decoding algorithm based on messagepassing is presented that employs A Posteriori Probability(APP) fast BCH transform for decoding the BCH check nodes at each decoding iteration. Simulation results show that the LDPC-BCH codes with a code rate of 1/8.5have a bit error rate performance of 1 10 6at signal-noise-ratios of 6.97 dB,4.63 dB,and 2.48 dB when the fractions of the band jammed are 30%,50%,and 70%,respectively.
2014年02期 v.19 203-210页 [查看摘要][在线阅读][下载 652K] [下载次数：29 ] |[网刊下载次数：0 ] |[引用频次：12 ] |[阅读次数：0 ] - Hui Kong;Fei He;Xiaoyu Song;Ming Gu;Hongyan Tan;Jiaguang Sun;
To verify the safety of nonlinear dynamical systems based on inductive invariants,key issues include defining the most complete inductive condition and discovering an inductive invariant that satisfies the specified inductive condition. In this paper,to lay a solid foundation for future research into the safety verification of semialgebraic dynamical systems,we first establish a formal framework for evaluating the quality of continuous inductive conditions. In addition,we propose a new complete and computable inductive condition for verifying the safety of semi-algebraic dynamical systems. Compared with the existing complete and computable inductive condition,this new inductive condition can be easily adapted to achieve a set of sufficient inductive conditions with different level of conservativeness and computational complexity,which provides us with a means to trade off between the verification power and complexity. These inductive conditions can be solved by quantifier elimination and SMT solvers.
2014年02期 v.19 211-222页 [查看摘要][在线阅读][下载 376K] [下载次数：22 ] |[网刊下载次数：0 ] |[引用频次：0 ] |[阅读次数：0 ] -
<正>Since 1996,Tsinghua Science and Technology has been published bimonthly as an international academic journal,sponsored by Tsinghua University.The journal focuses on presenting the state-of-art scientific achievements in computer science and IT technologies.As an indication of its influence,a paper on cloud computing(volume18,issue 1,February 2013)has been ranked among the top 20 of IEEE download list continuously for a year
2014年02期 v.19 223页 [查看摘要][在线阅读][下载 52K] [下载次数：13 ] |[网刊下载次数：0 ] |[引用频次：0 ] |[阅读次数：0 ] <正>The publication of Tsinghua Science and Technology was started in 1996.Since then,it has been an international academic journal sponsored by Tsinghua University and published bimonthly.This journal aims at presenting the state-of-art scientific achievements in computer science and other IT fields.This special section is devoted to gather and present high level research and review papers that address the challenges in the broad areas of Microelectronics.Microelectronics has become a highly active research area because of the potential of providing diverse services to broad range of applications,not only on science and engineering,but
2014年02期 v.19 224页 [查看摘要][在线阅读][下载 50K] [下载次数：25 ] |[网刊下载次数：0 ] |[引用频次：0 ] |[阅读次数：0 ]