2009 Vol. 7, No. 3

Communication Technology
Novel Sampling and Reconstruction Method for Non-Bandlimited Impulse Signals
Feng Yang, Jian-Hao Hu, Shao-Qian Li
2009, 7(3): 193-197.
Abstract:
To sample non-bandlimited impulse signals, an extremely high-sampling rate analog-todigital converters (ADC) is required. Such an ADC is very difficult to be implemented with present semiconductor technology. In this paper, a novel sampling and reconstruction method for impulse signals is proposed. The required sampling rate of the proposed method is close to the signal innovation rate, which is much lower than the Nyquist rate in conventional Shannon sampling theory. Analysis and simulation results show that the proposed method can achieve very good reconstruction performance in the presence of noise.
Microwave Magneto-Optic Bragg Modulators with Rectangular MSFVW Pulses
Cheng-You Luo, Bao-Jian Wu, Kun Qiu
2009, 7(3): 198-201.
Abstract:
Microwave magneto-optic (MO) modulators can directly transform radio frequency (RF) signals into optical data through the Bragg diffraction of guided optical waves (GOWs) induced by microwave magneto-static waves (MSWs). According to the MO coupled-mode theory, the modulation of continuous GOWs by a rectangular magneto-static-forwardvolume-wave (MSFVW) pulse in MO film waveguide is studied in the small signal case and the modulated optical pulse at the output is analyzed by means of an analytical form, which is dependent on the instantaneous diffraction intensity determined by the overlap of rectangular MSFVW pulse and light beam aperture. On the basis of it, the characteristics of MSFVW-based MO modulators can be explained well for the case of rectangular pulse modulation. It is also shown that the line codes of optical data generated by MO Bragg modulators can be controlled by adjusting the duty factor of modulating pulse signals.
TaraxOS: An Operation System for Wireless Sensor Networks
Wen-Yong Wang, Wen-Gang Han, Yu Xiang
2009, 7(3): 202-206.
Abstract:
An operation system (OS), named TaraxOS for wireless sensor networks is proposed. The functions of the TaraxOS such as interrupt, memory management and scheduling mechanism are researched and implemented. After introducing the node's working flow, the performances of the TaraxOS are analyzed and some limitations of the scheduling mechanism are discussed. The obtained results show that the proposed TaraxOS has some desirable characteristics including small code capacity, low power consumption, quick response and robustness.
Computer Science and Information Technology
Implementation Method of Non-Intrusive Monitoring Mechanism for Web Services Testing
Lun Cai, Jing-Ling Liu, Xi Wang
2009, 7(3): 207-213.
Abstract:
In web services testing, accessing the interactive contents of measured services and the information of service condition accurately are the key issues of system design and realization. A non-intrusive solution based on axis2 is presented to overcome the difficulty of the information retrieval in web service testing. It can be plugged in server side or client side freely to test pre-deployed or deployed web services. Moreover, it provides a monitoring interface and the corresponding subscription publication mechanism for users based on web services to support the quality assurance grounded on service-oriented architecture (SOA) application service.
Approximation Algorithms for the Connected Dominating Set Problem in Unit Disk Graphs
Gang Lu, Ming-Tian Zhou, Yong Tang, Ming-Yuan Zhao, Xin-Zheng Niu, Kun She
2009, 7(3): 214-222.
Abstract:
The connected dominating set (CDS) problem, which consists of finding a smallest connected dominating set for graphs is an NP-hard problem in the unit disk graphs (UDGs). This paper focuses on the CDS problem in wireless networks. Investigation of some properties of independent set (IS) in UDGs shows that geometric features of nodes distribution like angle and area can be used to design efficient heuristics for the approximation algorithms. Several constant factor approximation algorithms are presented for the CDS problem in UDGs. Simulation results show that the proposed algorithms perform better than some known ones.
Garbage Collection Scheduling of Aperiodic Tasks
Ning Zhang, Guang-Ze Xiong
2009, 7(3): 223-226.
Abstract:
In the previous work of garbage collection (GC) models, scheduling analysis was given based on an assumption that there were no aperiodic mutator tasks. However, it is not true in practical real-time systems. The GC algorithm which can schedule aperiodic tasks is proposed, and the variance of live memory is analyzed. In this algorithm, active tasks are deferred to be processed by GC until the states of tasks become inactive, and the saved sporadic server time can be used to schedule aperiodic tasks. Scheduling the sample task sets demonstrates that this algorithm in this paper can schedule aperiodic tasks and decrease GC work. Thus, the GC algorithm proposed is more flexible and portable.
Bioelectrics and Biomedicine
Enhanced Identifying Gene Names from Biomedical Literature with Conditional Random Fields
Wei-Zhong Qian, Chong Fu, Hong-Rong Cheng, Qiao Liu, Zhi-Guang Qin
2009, 7(3): 227-231.
Abstract:
Identifying gene names is an attractive research area of biology computing. However, accurate extraction of gene names is a challenging task with the lack of conventions for describing gene names. We devise a systematical architecture and apply the model using conditional random fields (CRFs) for extracting gene names from Medline. In order to improve the performance, biomedical ontology features are inserted into the model and post processing including boundary adjusting and word filter is presented to solve name overlapping problem and remove false positive single words. Pure string match method, baseline CRFs, and CRFs with our methods are applied to human gene names and HIV gene names extraction respectively in 1100 abstracts of Medline and their performances are contrasted. Results show that CRFs are robust for unseen gene names. Furthermore, CRFs with our methods outperforms other methods with precision 0.818 and recall 0.812.
Neurofeedback Treatment of College Students' Test on Anxiety, Depression, Personality, and Mood
Dan Zhu, Yuan Li, Jin Yang
2009, 7(3): 232-235.
Abstract:
Biofeedback is used to treat the mental diseases of college students, such as test anxiety, depression, personality, and mood. Anxiety of the colleague students was first tested by test anxiety scale (TAS) and then treated by biofeedback. After getting the biofeedback treatment, the students' TAS scores, blood volume pulse, and skin conductance were decreased, especially, their TAS scores dropped markedly. Meanwhile, the level of EEG (1 rhythm/ rhythm) and peripheral temperature increased observably. Then, neurofeedback (1 rhythm/ rhythm) was applied to treat students' depression, personality, and mood. As a result, these three kinds of symptoms got alleviated. And their therapeutic effects based on neurofeedback were more stable, durative and less recrudescent.
fMRI Study Revealing Neural Mechanisms of the Functions of SOA in Spatial Orienting
Yin Tian, Qian Zhang, De-Zhong Yao
2009, 7(3): 236-239.
Abstract:
It is well documented that orienting attention plays an important role in visual search. However, it remains unclear how the executive brain regions will act when two different stimulus onset asynchrony (SOA) are used in visual search. In this work, event-related fMRI was used to investigate neural mechanisms on the functions of SOA in endogenous and exogenous orienting. The results showed that in the endogenous orienting, long SOA versus short SOA resulted in widespread cortical activation mainly including right medial frontal gyrus and bilateral middle frontal gyri. Conversely, in exogenous orienting, long SOA compared to short SOA resulted in only activations in bilateral middle frontal gyri. These findings indicated that these two spatial orienting involved different brain areas and neural mechanisms.
Electronic Systems and Array Processing
Beam Pattern Design and Performance Analyses for Circular Array with Spherical Baffles
Cheng Zhang, Ke-An Chen, Guo-Yue Chen
2009, 7(3): 240-245.
Abstract:
The influence of a rigid spherical baffle on the response of a uniform circular microphone array (UCA) is analyzed and two eigen-beam beamforming arrays are designed in the eigen-beam subspace derived from the soundfield decomposition. Expressions of white noise gain (WNG) and directivity index (DI) are derived for the designed arrays. Performance analyses are carried out for the designed arrays and compared between those of the delay-and-sum beamforming array using UCA with and without a rigid sphere. Computer simulations demonstrate that the designed arrays have frequency-independent directivity with the cost of reduced robustness at low frequency band. The delay-and-sum beamforming array has constant WNG at all frequencies, while its directivity of which is reduced at low frequency band. The rigid sphere can improve the robustness for all the arrays.
New Model for Synthesis of Symmetrical Thinned Linear Arrays
Ke-Song Chen, Bing-Wei Cui, Zi-Shu He
2009, 7(3): 246-248.
Abstract:
In symmetrical thinned linear arrays design, the positions of thinned array elements are very important for optimal performance in terms of its minimum peak side lobe level (Msll). For the synthesis of thinned arrays with a given thinning rate, it would have almost the same Msll solution between taking only segmental aperture nearby both ends of the aperture into account and taking all the aperture into account. In this paper, the element distribution characteristic over the aperture of many optimum thinned arrays is studied, then the aperture release model is founded by the least square method to synthesize the thinned arrays. This model is vital for the computing burden alleviation and the efficiency optimization, and would hardly bring any degradation of the obtained array performance.
Multi-Parameter Signal Sorting Algorithm Based on Dynamic Distance Clustering
Ai-Ling He, De-Guo Zeng, Jun Wang, Bin Tang
2009, 7(3): 249-253.
Abstract:
A multi-parameter signal sorting algorithm for interleaved radar pulses in dense emitter environment is presented. The algorithm includes two parts, pulse classification and pulse repetition interval (PRI) analysis. Firstly, we propose the dynamic distance clustering (DDC) for classification. In the clustering algorithm, the multi-dimension features of radar pulse are used for reliable classification. The similarity threshold estimation method in DDC is derived, which contributes to the efficiency of the algorithm. However, DDC has large computation with many signal pulses. Then, in order to sort radar signals in real time, the improved DDC (IDDC) algorithm is proposed. Finally, PRI analysis is adopted to complete the process of sorting. The simulation experiments and hardware implementations show both algorithms are effective.
Stability Analysis of Uncertain Discrete-Time Piecewise Linear Systems with Time Delays
Ou Ou, Hong-Bin Zhang, Jue-Bang Yu
2009, 7(3): 254-257.
Abstract:
This paper considers the stability analysis of uncertain discrete-time piecewise linear systems with time delays based on piecewise Lyapunov-Krasovskii functionals. It is shown that the stability can be established for the control systems if there is a piecewise Lyapunov-Krasovskii functional, and moreover, the functional can be obtained by solving a set of linear matrix inequalities (LMIs) that are numerically feasible. A numerical example is given to demonstrate the efficiency and advantage of the proposed method.
Decoupling Control Strategy for Single Phase SPWM Parallel Inverters
Shun-Gang Xu, Jian-Ping Xu, Tai-Qiang Cao
2009, 7(3): 258-262.
Abstract:
A decoupling control strategy of inverter parallel system is proposed based on the equivalent output impedance of single phase voltage source SPWM (sinusoidal pulse width modulation) inverter. The active power and reactive power are calculated in terms of output voltage and current of the inverter, and sent to the other inverters in the parallel system via controller area network (CAN) bus. By calculating and decoupling the circumfluence of the active power and reactive power, the inverters can share load current via the regulation of the reference-signal phase and amplitude. Experimental results of an 110V/2kVA inverter parallel system show the feasibility of the decoupling control strategy.
Complicated Attractor and Novel Route to Chaos via Cubic Nonlinearity Controller
Xiao-Hua Qiao
2009, 7(3): 263-267.
Abstract:
By introducing a nonlinear state feedback controller, a complicated chaotic attractor of fourdimensional continuous autonomous chaotic system evolved from Lorenz system is proposed. The controller consists of a cubic cross-product term of three variables and a self variable term with control parameter. This paper verifies that the proposed system has complex dynamical behavior, which can evolve into periodic and chaotic behavior cyclically. These circular routes to chaos have self-similar bifurcation structure in a wide parameter variation range. An electronic circuit is designed to demonstrate the complicated attractor.
Optoelectronic and Photonic Technologies
Differences of Band Gap Characteristics of Square and Triangular Lattice Photonic Crystals in Terahertz Range
Jie Zha, Zhi-Yong Zhong, Huai-Wu Zhang, Qi-Ye Wen, Yuan-Xun Li
2009, 7(3): 268-271.
Abstract:
Band gap characteristics of the photonic crystals in terahertz range with square lattice and triangular lattice of GaAs cylinders are comparatively studied by means of plane wave method (PWM). The influence of the radius on the band gap width is analyzed and the critical values where the band gap appears are put forward. The results show that the maximum band gap width of photonic crystal with triangular lattice of GaAs cylinders is much wider than that of photonic crystal with square lattice. The research provides a theoretic basis for the development of t rahertz (THz) devices.
Design and Performance of an AlGaN-Based p-i-n Ultraviolet Photodetector
Xing-Li Zhou, Mo-Hua Yang, Jiang-Feng Du
2009, 7(3): 272-276.
Abstract:
An AlGaN-based back-illuminated ultraviolet p-i-n detector is designed and its performance is analysed both simulately and experimentally. The width of p- and i-regions has been optimized to the best theoretic values. It is indicated that the changing of responsivity with increase of bias can not be attributed to the expansion of depletion layer as it is believed, but to two reasons: 1) the effect of GaN/AlGaN heterojunction barrier to block the electrons decreases with higher bias and 2) the recombination rate of excess carriers decreases due to the building up of an electric field in depletion region. At zero bias, the simulated responsivity reaches its maximum of 0.12 A/W with quantum efficiency of 55.1%. The measured peak responsivity is more than 0.09 A/W with quantum efficiency greater than 41.6%. The experimental data are almost consistent with the results of the simulation.
Performance of an Adaptive Optics System with Dual Deformable Mirrors
Shi-Jie Hu
2009, 7(3): 277-280.
Abstract:
One deformable mirror (DM) in conventional adaptive optics system can not meet the needs of large scale and high order aberration compensation. In this paper, a dual DMs way is presented, which needs the decoupling of dual DMs. In dual DMs adaptive optics (AO) system, the decoupling algorithm of dual DMs is deduced. Stroke of one of DMs is large, spatial frequency of the other is high. According to the algorithm, the large stroke DM (LSDM) corrects low order aberration only, and the high spatial frequency DM (HSFDM) corrects other aberration. The experimental result for two 61-DM AO system is presented. The result indicates that the experimental performance of dual DMs AO system is almost the same with that of the conventional AO system using single DM with ideal stroke and equivalent spatial frequency.
Electronic Materials and Devices
Influence of La-Mn-Al Co-Doping on Dielectric Properties and Structure of BST Thick Film
Mao-Yan Fan, Sheng-Lin Jiang
2009, 7(3): 281-285.
Abstract:
A new sol-gel process is applied to fabricate the BST (BaxSr1?xTiO3) sol and nano-powder of La-Mn-Al co-doping with Ba/Sr ratio 65/35, and the BST thick film is prepared in the Pt/Ti/SiO2/Si substrate. The powder and thick film are characterized by X-ray diffraction and transmission electron microscope. The influence of La-Mn-Al co-doping on the dielectric properties and micro-structure of BST thick film is analyzed. The results show that the La, Mn, and Al ions can take an obvious restraint on the growth of BaSrTiO3 grains. The polycrystalline particles come into being during the crystallization of thick film, which may improve the uniformity and compactness of thick film. The influence of unequal-valence and doping amount on the leakage current, dielectric loss, and dielectric property are mainly discussed. The dielectric constant and dielectric loss of thick film are 1200 and 0.03, respectively, in the case of 1mol% La doping, 2mol% Mn doping, and 1mol% Al doping.