- 秦兵;赵妍妍;丁效;刘挺;翟国富;
Event extraction is an important research point in information extraction, which includes two important sub-tasks of event type recognition and event argument recognition. This paper describes a method based on automatic expansion of the event triggers for event type recognition. The event triggers are first extended through a thesaurus to enable the extraction of the candidate events and their candidate types. Then, a binary classification method is used to recognize the candidate event types. This method effectively improves the unbalanced data problem in training models and the data sparseness problem with a small corpus. Evaluations on the ACE2005 dataset give a final F-score of 61.24%, which outperforms traditional methods based on pure machine learning.
2010年03期 v.15 251-258页 [查看摘要][在线阅读][下载 366K] [下载次数：106 ] |[网刊下载次数：0 ] |[引用频次：18 ] |[阅读次数：0 ] - Albert WANG;
Electrostatic discharge (ESD) induced parasitic effects have serious impacts on performance of radio frequency (RF) integrated circuits (IC). This paper discusses a comprehensive noise analysis procedure for ESD protection structures and their negative influences on RF ICs. Noise figures (NFs) of commonly used ESD protection structures and their impacts on a single-chip 5.5 GHz low-noise amplifier (LNA) circuit were depicted. A design example in 0.18 μm SiGe BiCMOS was presented. Measurement results confirm that significant noise degradation occurs in the LNA circuit due to ESD-induced noise effects. A practical design procedure for ESD-protected RF ICs is provided for real-world RF IC optimization.
2010年03期 v.15 259-264页 [查看摘要][在线阅读][下载 692K] [下载次数：89 ] |[网刊下载次数：0 ] |[引用频次：1 ] |[阅读次数：0 ] - Albert WANG;
As integrated circuits (IC) technologies advance into very-deep-sub-micron (VDSM), electrostatic discharge (ESD) failure becomes one of the most devastating IC reliability problems and on-chip ESD protection design emerges as a major challenge to radio frequency (RF), analog, and mixed-signal (AMS) IC designs. This paper reviews key design aspects and recent advances in whole-chip ESD protection designs for RF/AMS IC applications in CMOS technologies.
2010年03期 v.15 265-274页 [查看摘要][在线阅读][下载 1115K] [下载次数：73 ] |[网刊下载次数：0 ] |[引用频次：7 ] |[阅读次数：0 ] - Vojislav Kecman;
The adaptive local hyperplane (ALH) algorithm is a very recently proposed classifier, which has been shown to perform better than many other benchmarking classifiers including support vector machine (SVM), K-nearest neighbor (KNN), linear discriminant analysis (LDA), and K-local hyperplane distance nearest neighbor (HKNN) algorithms. Although the ALH algorithm is well formulated and despite the fact that it performs well in practice, its scalability over a very large data set is limited due to the online distance computations associated with all training instances. In this paper, a novel algorithm, called ALH-Fast and obtained by combining the classification tree algorithm and the ALH, is proposed to reduce the computational load of the ALH algorithm. The experiment results on two large data sets show that the ALH-Fast algorithm is both much faster and more accurate than the ALH algorithm.
2010年03期 v.15 275-280页 [查看摘要][在线阅读][下载 312K] [下载次数：33 ] |[网刊下载次数：0 ] |[引用频次：0 ] |[阅读次数：0 ] - William W Guo;Michael Li;Greg Whymark;
Correlations between magnetic susceptibility and contents of magnetic minerals in rocks are important in interpreting magnetic anomalies in geophysical exploration and understanding magnetic behaviors of rocks in rock magnetism studies. Previous studies were focused on describing such correlations using a sole expression or a set of expressions through statistical analysis. In this paper, we use neural network techniques to approximate the nonlinear relations between susceptibility and magnetite and/or hematite contents in rocks. This is the first time that neural networks are used for such study in rock magnetism and magnetic petrophysics. Three multilayer perceptrons are trained for producing the best possible estimation on susceptibility based on magnetic contents. These trained models are capable of producing accurate mappings between susceptibility and magnetite and/or hematite contents in rocks. This approach opens a new way of quantitative simulation using neural networks in rock magnetism and petrophysical research and applications.
2010年03期 v.15 281-287页 [查看摘要][在线阅读][下载 506K] [下载次数：34 ] |[网刊下载次数：0 ] |[引用频次：4 ] |[阅读次数：0 ] - 金德鹏;林世俊;苏厉;周郭飞;曾烈光;
The network-on-chip (NoC) design methodology is an important trend for large system-on-chip designs to reduce the bandwidth and power constraints in traditional synchronous bus architectures. In the design of packet-based NoC, the packet-length plays an important role in the NoC throughput, latency, and energy consumption. The appropriate NoC packet-length was selected based on simulation and analysis of the packet-length effect on NoC for variable average data block length (ADBL) configuration parameters. A trade-off curve among throughput, latency, and energy consumption was developed and shows that the optimum packet length increases as the ADBL increases.
2010年03期 v.15 288-293页 [查看摘要][在线阅读][下载 577K] [下载次数：75 ] |[网刊下载次数：0 ] |[引用频次：2 ] |[阅读次数：0 ] - 李正夷;王煊;杜正伟;龚克;
Reconfigurable antenna arrays increase the flexibility of adaptive MIMO systems. At present, most designs have adopted antenna arrays with reconfigurable elements. However, antenna selection is also an effective method, which has not been fully investigated. In this paper, the potential benefits of a four-element antenna array with selection circuits in the UMTS band (1920-2170 MHz) are explored. The array has eight pin-diodes embedded in the feeding network to select any sub-set of elements. For evaluation, an adaptive MIMO system was set up and a measurement campaign was taken in an indoor multi-path environment. The measurements were performed over a 300 MHz bandwidth centered at 2.05 GHz, covering the UMTS band. The results show that different channel conditions prefer different antenna array configurations. Therefore, in varying channel conditions the antenna array can support antenna selection algorithms to select the best sub-set of elements to increase channel capacity.
2010年03期 v.15 294-298页 [查看摘要][在线阅读][下载 627K] [下载次数：70 ] |[网刊下载次数：0 ] |[引用频次：1 ] |[阅读次数：0 ] - 杨旭;何虎;孙义和;
This paper presents an instruction scheduling and cluster assignment approach for clustered very long instruction words (VLIW) processors. The technique produces high performance code by simultaneously balancing instructions among clusters and minimizing the amount of inter-cluster data communications. The scheme is evaluated based on benchmarks extracted from UTDSP. Results show a significant speedup compared with previously used techniques with speed-ups of up to 44%, with average speed-ups ranging from 14% (2-cluster) to 18% (4-cluster).
2010年03期 v.15 299-306页 [查看摘要][在线阅读][下载 530K] [下载次数：39 ] |[网刊下载次数：0 ] |[引用频次：0 ] |[阅读次数：0 ] - 吴霞;周乐柱;
Accurate simulations of ultra-wideband (UWB) electromagnetic radiation from an antenna were developed based on a time-domain finite element method (TDFEM) based on p-step Lagrange interpolation for the temporal expansion. The motivation was to utilize the good interpolation features and straightforward computations for UWB antenna simulations. Numerical results were obtained from the cases of the cavity resonance problem, a bowtie and a Sierpinski bowtie antenna. Comparisons with an existing TDFEM approach employed linear temporal basis functions show good agreement to demonstrate the validity of the present schemes. The TDFEM with 2-step Lagrange interpolation as the temporal basis functions achieves better numerical results with only a small increase to run time and memory use in terms of the relative errors of the resonant frequency in the cavity for the transverse electric mode and the radiation patterns of the bowtie antenna.
2010年03期 v.15 307-311页 [查看摘要][在线阅读][下载 791K] [下载次数：47 ] |[网刊下载次数：0 ] |[引用频次：0 ] |[阅读次数：0 ] - 戴凌龙;符剑;王军;
Powerline communications (PLC) have drawn great interest in recent years. However, most PLC standards such as HomePlug AV use the cyclic-prefix OFDM (CP-OFDM) technology. This paper presents a broadband PLC system using low density parity check (LDPC) coded time domain synchronous OFDM (TDS-OFDM), whose spectrum efficiency is about 10% higher than that of CP-OFDM. With the same bandwidth and the ability to combat the time delay spread as HomePlug AV, this system can provide a maximum throughput of 199.7 Mbps physical layer data rate. Simulations over the measured practical powerline channel in Beijing, China, show that LDPC in the TDS-OFDM system dramatically improves the bit error rate performance, and verify the feasibility and performance of the TDS-OFDM technology for PLC systems.
2010年03期 v.15 312-318页 [查看摘要][在线阅读][下载 613K] [下载次数：168 ] |[网刊下载次数：0 ] |[引用频次：3 ] |[阅读次数：0 ] - 耿立辉;萧德云;王乾;张涛;宋靖雁;
A two-stage identification method was developed for attitude-control models of on-orbit satellites for accurate attitude control. The attitude-control models are based on a generalized attitude model (GAM) and its corresponding noise model (NM). These are both low order models which are able to characterize the main satellite dynamics and the corresponding noise. These low-order attitude-control models facilitate improved controller design and state estimation. This identification approach uses two open-loop identification processes, with higher order auxiliary models used in the estimation for filtering and with the filtered signals used to identify the low order GAM and NM. An identification experiment with a micro-satellite simulator was used to verify the effectiveness of the two-stage identification method.
2010年03期 v.15 319-324页 [查看摘要][在线阅读][下载 589K] [下载次数：60 ] |[网刊下载次数：0 ] |[引用频次：1 ] |[阅读次数：0 ] - 杨鹏程;陈水明;何金良;
The amplitude of switching overvoltages is a key factor for designing the insulation of UHV equipment. The effect of different arresters needs to be studied, since installing arresters is an important way to suppress switching overvoltages in UHV transmission lines. Switching overvoltages on the 1000 kV Huainan-Huxi double-circuit transmission line were simulated for different operating modes and different arrester designs using the electromagnetic transient program PSCAD/EMTDC. With parallel resistors, the switching overvoltages are less than 1.70 p.u. (1.0 p.u.=1100× 2 /3 kV). If the arrestors are better, the switching overvoltages can be reduced even lower to 1.55 p.u. Without parallel resistors, the arresters can reduce three-phase energizing overvoltages to 1.70 p.u, while the single-phase reclosing overvoltages still exceed the limit. The results show that the parallel resistors cannot be eliminated if the arresters are only installed at each end of the transmission line. Also, better quality arresters significantly lower the switching overvoltages.
2010年03期 v.15 325-328页 [查看摘要][在线阅读][下载 387K] [下载次数：89 ] |[网刊下载次数：0 ] |[引用频次：1 ] |[阅读次数：0 ] - 孙懿;郝久玉;
One of the major issues with multi-carrier systems is their vulnerability to timing synchronization errors resulting in the loss of time synchronization which causes loss of orientation of incoming data at the receiver. This paper presents an acquisition algorithm to timing recovery using the decision-aided extended Kalman filtering (EKF) technique for nonlinear disturbance channels in a wavelet packet transform-based multicarrier modulation communication system. This timing recovery algorithm gives faster convergence, smaller root mean square (RMS) errors, and better bit error rate (BER) performance than traditional timing recovery methods, such as the phase-locked loop (PLL), maximum likelihood (ML), and Kalman filter (KF) methods. Thus, the algorithm is able to handle larger timing errors more reliably and to provide better timing recovery, since the scheme takes into account the nonlinear relationship between the signal samples and timing errors. Simulations for various time-varying channels show that the timing recovery algorithm works well for wavelet packet transform-based multicarrier modulation communication systems.
2010年03期 v.15 329-334页 [查看摘要][在线阅读][下载 421K] [下载次数：43 ] |[网刊下载次数：0 ] |[引用频次：0 ] |[阅读次数：0 ] - 张文;曹军威;钟宜生;刘连臣;吴澄;
Data streaming applications, usually composed of sequential/parallel data processing tasks organized as a workflow, bring new challenges to workflow scheduling and resource allocation in grid environments. Due to the high volumes of data and relatively limited storage capability, resource allocation and data streaming have to be storage aware. Also to improve system performance, the data streaming and processing have to be concurrent. This study used a genetic algorithm (GA) for workflow scheduling, using on-line measurements and predictions with gray model (GM). On-demand data streaming is used to avoid data overflow through repertory strategies. Tests show that tasks with on-demand data streaming must be balanced to improve overall performance, to avoid system bottlenecks and backlogs of intermediate data, and to increase data throughput for the data processing workflows as a whole.
2010年03期 v.15 335-346页 [查看摘要][在线阅读][下载 610K] [下载次数：71 ] |[网刊下载次数：0 ] |[引用频次：0 ] |[阅读次数：0 ] - 胡雄;潘伟伟;史峥;严晓浪;马铁中;
A testing structure was developed to more effectively detect the poly stringer defects in contemporary CMOS ICs. This structure is much more sensitive to poly stringer defects and is closer to the real product layout than the currently widely used structure using an active dummy underneath a poly comb. Many testing structure pieces manufactured in a 0.11 μm copper process line were used to compare the current design with the conventional testing structure. The data shows that the new structure more efficiently detects poly stringers. The results also show that the poly stringers are related to the shallow trench isolation (STI) width. This structure can be used to identify new designs for manufacturing rules for the active space. Thus, this method is very useful for IC foundries to detect poly stringers and to characterize the processing line capability and tune the process recipe to improve product yields.
2010年03期 v.15 347-351页 [查看摘要][在线阅读][下载 2190K] [下载次数：54 ] |[网刊下载次数：0 ] |[引用频次：1 ] |[阅读次数：0 ] - 郭大勇;宣华;付小龙;
A modern teaching support platform was designed based on application integration and the Nolan model. The system design used top-level design, information-sharing, management modeling, and user experience. The system emphasized openness, compatibility, security, extensibility, and practicability. Multi-department management is realized by dividing function domains. Intercommunications and intercon-nections use a level-division modular design, so the system can be easily extended. The teaching support platform is people oriented with people foremost environment for the users, the associated application environment, the integrated data environment, and the operating environment for high availability. The system plays an important role in university information construction.
2010年03期 v.15 352-356页 [查看摘要][在线阅读][下载 560K] [下载次数：83 ] |[网刊下载次数：0 ] |[引用频次：7 ] |[阅读次数：0 ] - 谭春林;汪洪桥;裴得利;
The scale invariant feature transform (SIFT) feature descriptor is invariant to image scale and location, and is robust to affine transformations and changes in illumination, so it is a powerful descriptor used in many applications, such as object recognition, video tracking, and gesture recognition. However, in noisy and non-rigid object recognition applications, especially for infrared human face recognition, SIFT-based algorithms may mismatch many feature points. This paper presents a star-styled window filter-SIFT (SWF-SIFT) scheme to improve the infrared human face recognition performance by filtering out incorrect matches. Performance comparisons between the SIFT and SWF-SIFT algorithms show the advantages of the SWF-SIFT algorithm through tests using a typical infrared human face database.
2010年03期 v.15 357-362页 [查看摘要][在线阅读][下载 585K] [下载次数：258 ] |[网刊下载次数：0 ] |[引用频次：12 ] |[阅读次数：0 ] <正>Tsinghua Science and Technology (Tsinghua Sci TechnoL), a comprehensive academic journal sponsored by Tsinghua University, is published bimonthly. This journal aims at presenting the up-to-date scientific achievements
2010年03期 v.15 363页 [查看摘要][在线阅读][下载 850K] [下载次数：14 ] |[网刊下载次数：0 ] |[引用频次：0 ] |[阅读次数：0 ]