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The Guilin University of Electronic Technology is a state university, located in Guilin, Guangxi, China. Wikipedia.

Chen H.,Guilin University of Electronic Technology | Chen H.-H.,National Cheng Kung University
International Journal of Communication Systems

This paper addresses the issues on spectrum sharing in a cognitive radio network consisting of a primary user and a group of cognitive users. Each cognitive user may occupy a non-overlapped sub-band of the primary spectrum, but it needs to perform spectrum sensing independently before accessing the sub-band. To reduce the complexity of spectrum sensing and thus energy consumption, this paper proposes a scheduled spectrum sensing scheme. First, we consider a single spectrum sensing scenario where only one cognitive user is elected to perform spectrum sensing, and then it broadcasts its sensing results to the other cognitive users. The scheduled spectrum sensing scheme works in both network-centric and user-centric ways. Next, the scheduled spectrum sensing scheme is further generalized to work in a multiple spectrum sensing scenario. The results show the effectiveness of the proposed schemes compared with the traditional schemes where all cognitive users may perform spectrum sensing at the same time. Copyright © 2010 John Wiley & Sons, Ltd. Source

Zou Y.,Guilin University of Electronic Technology
Advances in Space Research

The occurrence of ionospheric scintillations with S4 ≥ 0.2 was studied using GPS measurements at Guilin, China (25.29°N, 110.33°E; geomagnetic: 15.04°N, 181.98°E), a station located near the northern crest of the equatorial anomaly. The results are presented for data collected from January 2009 to March 2010. The results show that nighttime amplitude scintillations only took place in February and March of the considered years, while daytime amplitude scintillations occurred in August and December of 2009. Nighttime amplitude scintillations, observed in the south of Guilin, always occurred with phase scintillations, TEC (Total Electron Content) depletions, and ROT (Rate Of change of TEC) fluctuations. However, TEC depletions and ROT fluctuations were weak during daytime amplitude scintillations, and daytime amplitude scintillations always took place simultaneously for most of the GPS satellites which appeared over Guilin in different azimuth directions. Ground-based GPS scintillation/TEC observations recorded at Guilin and signal-to-noise-ratio (SNR) measurements obtained from GPS-COSMIC radio occultation indicate that nighttime and daytime scintillations are very likely caused by ionospheric F region irregularities and sporadic E, respectively. Moreover, strong daytime amplitude scintillations may be associated with the plasma density enhancements in ionospheric E region caused by the Perseid and Geminid meteor shower activities. © 2010 COSPAR. Published by Elsevier Ltd. All rights reserved. Source

Du C.,Shaoyang University | Huang W.,Guilin University of Electronic Technology
Nonlinear Dynamics

The problem of limit cycles for the Kolmogorov model is interesting and significant both in theory and applications. In this paper, we investigate the center-focus problems and limit cycles bifurcations for a class of cubic Kolmogorov model with three positive equilibrium points. The sufficient and necessary condition that each positive equilibrium point becomes a center is given. At the same time, we show that each one of point (1,2) and point (2,1) can bifurcate 1 small limit cycles under a certain condition, and 3 limit cycle can occur near (1,1) at the same step. Among the above limit cycles, 4 limit cycles can be stable. The limit cycles bifurcations problem for Kolmogorov model with several positive equilibrium points are hardly seen in published references. Our result is new and interesting. © 2012 Springer Science+Business Media Dordrecht. Source

Peng Z.-Y.,Guilin University of Electronic Technology
International Journal of Computer Mathematics

This paper is a matrix iterative method presented to compute the solutions of the matrix equation, AXB=C, with unknown matrix X ∈ S, where S is the constrained matrices set like symmetric, symmetric-R-symmetric and (R, S)-symmetric. By this iterative method, for any initial matrix X0 ∈ S, a solution X* can be obtained within finite iteration steps if exact arithmetics were used, and the solution X* with the minimum Frobenius norm can be obtained by choosing a special kind of initial matrix. The solution X̂, which is nearest to a given matrix X̃ in Frobenius norm, can be obtained by first finding the minimum Frobenius norm solution of a new compatible matrix equation. The numerical examples given here show that the iterative method proposed in this paper has faster convergence and higher accuracy than the iterative methods proposed in [G.-X. Huang, F. Yin, and K. Guo, An iterative method for the skew-symmetric solution and the optimal approximate solution of the matrix equation AXB=C, J. Comput. Appl. Math. 212 (2008), pp. 231-244; Y. Lei and A.-P. Liao, A minimal residual algorithm for the inconsistent matrix equation AXB=C over symmetric matrices, Appl. Math. Comput. 188 (2007), pp. 499-513; Z.-Y. Peng, An iterative method for the least squares symmetric solution of the linear matrix equation AXB=C, Appl. Math. Comput. 170 (2005), pp. 711-723; Y.-X. Peng, X.-Y. Hu, and L. Zhang, An iteration method for the symmetric solutions and the optimal approximation solution of the matrix equation AXB=C, Appl. Math. Comput. 160 (2005), pp. 763-777]. © 2010 Taylor & Francis. Source

Wang Z.,Guilin University of Electronic Technology
Journal of Alloys and Compounds

Different electrochemical measurements such as activation and maximum capacity, cyclic stability, selfdischarge property, high-rate dischargeability and electrochemical impedance spectroscopy have been carried out to investigate the electrochemical performances of LaNi4.4-xCo0.3Mn 0.3Alx hydrogen storage alloys at low and high temperatures. We have selected 273 K and 323 K as low and high temperatures respectively. Samples W, X, Y and Z were used to represent alloys LaNi 4.4Co0.3Mn0.3, LaNi4.3Co 0.3Mn0.3Al0.1, LaNi4.2Co 0.3Mn0.3Al0.2 and LaNi4.1Co 0.3Mn0.3Al0.3. XRD patterns show the alloys are all single-phase alloys with hexagonal CaCu5 type structure. The highest maximum discharge capacity is 340.3 mA h/g for alloy X, which is higher than other alloys at same temperature and high temperature. After 50 charge/discharge cycles, capacity retention of 93.6% has been observed at low temperature for alloy Z. The least capacity loss was 13.3% at 273 K during the self-discharge test. At both studied temperatures, alloy Z has the highest high-rate dischargeability (HRD) of 56.6% and 44.9% respectively at a discharge current density of 1800 mA/g. The electrochemical impedance spectroscopy (EIS) analysis was carried out to determine the charge-transfer resistance (R ct) which was further used in the analysis of the HRD. Alloy Z with the highest HRD at 273 K has a lower Rct of 0.9272 mΩ due to the dissolution or presence of Al into the electrolyte which can effectively reduce the total resistance of alloys. Apparently, at the two different testing temperatures, all the alloys possess better electrochemical properties at 273 K than 323 K. © 2013 Elsevier B.V. All rights reserved. Source

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