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Search Results: 1 - 10 of 43767 matches for " Yan Ning "
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Representations of Finite Unipotent Linear Groups by the Method of Clusters
Ning Yan
Mathematics , 2010,
Abstract: The general linear group GL(n, K) over a field K contains a particularly prominent subgroup U(n, K), consisting of all the upper triangular unipotent elements. In this paper we are interested in the case when K is the finite field F_q, and our goal is to better understand the representation theory of U(n, F_q). The complete classification of the complex irreducible representations of this group has long been known to be a difficult task. The orbit method of Kirillov, famous for its success when K has characteristic 0, is a natural source of intuition and conjectures, but in our case the relation between coadjoint orbits and complex representations is still a mystery. Here we introduce a natural variant of the orbit method, in which the central role is played by certain clusters of coadjoint orbits. This "method of clusters" leads to the construction of a subring in the representation ring of U(n, F_q) that is rich in structure but pleasantly comprehensible. The cluster method also has many of the major features one would expect from the philosophy of orbit method.
Research on Modeling of the Agile Satellite Using a Single Gimbal Magnetically Suspended CMG and the Disturbance Feedforward Compensation for Rotors
Peiling Cui,Ning Yan
Sensors , 2012, DOI: 10.3390/s121216964
Abstract: The magnetically suspended Control Moment Gyroscope (CMG) has the advantages of long-life, micro-vibration and being non-lubricating, and is the ideal actuator for agile maneuver satellite attitude control. However, the stability of the rotor in magnetic bearing and the precision of the output torque of a magnetically suspended CMG are affected by the rapid maneuvers of satellites. In this paper, a dynamic model of the agile satellite including a magnetically suspended single gimbal control moment gyroscope is built and the equivalent disturbance torque effected on the rotor is obtained. The feedforward compensation control method is used to depress the disturbance on the rotor. Simulation results are given to show that the rotor displacement is obviously reduced.
Technological paradigm and innovation of EST of SMEs in China
Lu Yan,Cai Ning
环境科学学报(英文版) , 1997,
Abstract: This article described the change of technological paradigm from environmentally unfriendly technology to environmentally sound technology(EST),and reported results from the investigation made in 1993-1995 of how China's small-medium enterprises(SMEs)have been innovating technology in response to environmental pressures and tried to identify factors affecting China' SMEs to innovate more environmentally sound products and processes.
Complexity Analysis of Reed-Solomon Decoding over GF without Using Syndromes
Chen Ning,Yan Zhiyuan
EURASIP Journal on Wireless Communications and Networking , 2008,
Abstract: There has been renewed interest in decoding Reed-Solomon (RS) codes without using syndromes recently. In this paper, we investigate the complexity of syndromeless decoding, and compare it to that of syndrome-based decoding. Aiming to provide guidelines to practical applications, our complexity analysis focuses on RS codes over characteristic-2 fields, for which some multiplicative FFT techniques are not applicable. Due to moderate block lengths of RS codes in practice, our analysis is complete, without big notation. In addition to fast implementation using additive FFT techniques, we also consider direct implementation, which is still relevant for RS codes with moderate lengths. For high-rate RS codes, when compared to syndrome-based decoding algorithms, not only syndromeless decoding algorithms require more field operations regardless of implementation, but also decoder architectures based on their direct implementations have higher hardware costs and lower throughput. We also derive tighter bounds on the complexities of fast polynomial multiplications based on Cantor's approach and the fast extended Euclidean algorithm.
Complexity Analysis of Reed-Solomon Decoding over GF(2m) without Using Syndromes
Ning Chen,Zhiyuan Yan
EURASIP Journal on Wireless Communications and Networking , 2008, DOI: 10.1155/2008/843634
Abstract: There has been renewed interest in decoding Reed-Solomon (RS) codes without using syndromes recently. In this paper, we investigate the complexity of syndromeless decoding, and compare it to that of syndrome-based decoding. Aiming to provide guidelines to practical applications, our complexity analysis focuses on RS codes over characteristic-2 fields, for which some multiplicative FFT techniques are not applicable. Due to moderate block lengths of RS codes in practice, our analysis is complete, without big O notation. In addition to fast implementation using additive FFT techniques, we also consider direct implementation, which is still relevant for RS codes with moderate lengths. For high-rate RS codes, when compared to syndrome-based decoding algorithms, not only syndromeless decoding algorithms require more field operations regardless of implementation, but also decoder architectures based on their direct implementations have higher hardware costs and lower throughput. We also derive tighter bounds on the complexities of fast polynomial multiplications based on Cantor's approach and the fast extended Euclidean algorithm.
Towards Rational Design of Nanoparticle Catalysis in Ionic Liquids
Bin Zhang,Ning Yan
Catalysts , 2013, DOI: 10.3390/catal3020543
Abstract: This feature article introduces the strategies on the design of highly efficient nanoparticle (NP) catalytic systems in ionic liquids (ILs). The employment of functional ILs as the media for NP preparation and catalysis could prove advantageous in terms of enhancing both NP stability and catalytic activity. Hydroxyl group functionalized ILs, in particular, exhibited a remarkable promotion effect on a variety of reactions catalyzed by NPs, such as hydrogenation over Rh NPs, hydrodehalogenation over Pt NPs and Suzuki reaction over Pd NPs. In some cases, tailor-made stabilizer is used in addition to keep the NPs sufficiently stable. For example, a carboxylic group modified polyvinylpyrrolidone endows NPs three-fold stabilization, including steric, electrostatic and ligand stabilizations, which leads to excellent stability of the NPs. The catalytic activities of these NPs, on the other hand, are not compromised, as each of these stabilizations is not too strong. Following that, the article describes our recent work on the rational design of bimetallic NPs in ILs and the development of multifunctional systems involving NPs for a tandem reaction sequence that convert lignin-derived phenolic compounds into fuels.
Cyclotomic FFTs with Reduced Additive Complexities Based on a Novel Common Subexpression Elimination Algorithm
Ning Chen,Zhiyuan Yan
Mathematics , 2007,
Abstract: In this paper, we first propose a novel common subexpression elimination (CSE) algorithm for matrix-vector multiplications over characteristic-2 fields. As opposed to previously proposed CSE algorithms, which usually focus on complexity savings due to recurrences of subexpressions, our CSE algorithm achieves two types of complexity reductions, differential savings and recurrence savings, by taking advantage of the cancelation property of characteristic-2 fields. Using our CSE algorithm, we reduce the additive complexities of cyclotomic fast Fourier transforms (CFFTs). Using a weighted sum of the numbers of multiplications and additions as a metric, our CFFTs achieve smaller total complexities than previously proposed CFFTs and other FFTs, requiring both fewer multiplications and fewer additions in many cases.
Reduced-Complexity Reed--Solomon Decoders Based on Cyclotomic FFTs
Ning Chen,Zhiyuan Yan
Mathematics , 2008, DOI: 10.1109/LSP.2009.2014292
Abstract: In this paper, we reduce the computational complexities of partial and dual partial cyclotomic FFTs (CFFTs), which are discrete Fourier transforms where spectral and temporal components are constrained, based on their properties as well as a common subexpression elimination algorithm. Our partial CFFTs achieve smaller computational complexities than previously proposed partial CFFTs. Utilizing our CFFTs in both transform- and time-domain Reed--Solomon decoders, we achieve significant complexity reductions.
Complexity Analysis of Reed-Solomon Decoding over GF(2^m) Without Using Syndromes
Ning Chen,Zhiyuan Yan
Mathematics , 2008,
Abstract: For the majority of the applications of Reed-Solomon (RS) codes, hard decision decoding is based on syndromes. Recently, there has been renewed interest in decoding RS codes without using syndromes. In this paper, we investigate the complexity of syndromeless decoding for RS codes, and compare it to that of syndrome-based decoding. Aiming to provide guidelines to practical applications, our complexity analysis differs in several aspects from existing asymptotic complexity analysis, which is typically based on multiplicative fast Fourier transform (FFT) techniques and is usually in big O notation. First, we focus on RS codes over characteristic-2 fields, over which some multiplicative FFT techniques are not applicable. Secondly, due to moderate block lengths of RS codes in practice, our analysis is complete since all terms in the complexities are accounted for. Finally, in addition to fast implementation using additive FFT techniques, we also consider direct implementation, which is still relevant for RS codes with moderate lengths. Comparing the complexities of both syndromeless and syndrome-based decoding algorithms based on direct and fast implementations, we show that syndromeless decoding algorithms have higher complexities than syndrome-based ones for high rate RS codes regardless of the implementation. Both errors-only and errors-and-erasures decoding are considered in this paper. We also derive tighter bounds on the complexities of fast polynomial multiplications based on Cantor's approach and the fast extended Euclidean algorithm.
A controlled Intervention Study: Comparison of Intervention on the Antibiotic Prophylaxis of Three Clean Surgeries in Chinese Tertiary Hospitals  [PDF]
Yingdong Zheng, Ying Zhou, Ning Chen, Liang Zhou, Qing Yan
Pharmacology & Pharmacy (PP) , 2013, DOI: 10.4236/pp.2013.45066
Abstract: A controlled intervention study was to promote rational antibiotic prophylaxis in clean surgeries in Chinese tertiary hospitals from 2008 to 2009. The effect of the intervention was measured and compared before and after intervention (intervention group, IG, including twelve hospitals), and compared with the control group (CG, including 164 tertiary hospitals distributed in 31 provinces). There were a total of 3961 and 657 cases identified in IG & CG for the study. Comparing the changes of IG with CG following the 3rd intervention, the proportion of antibiotics use without indication decreased from 61.9% (IG) & 84.4% (CG) (χ2 test, P < 0.01) to 60.9% (IG) & 59.1% (CG) (χ2 test, P > 0.05); the rationality scores increased from 55.4 (IG) & 57.6 (CG) (t test, P > 0.05) to 77.0 (IG) & 64.3 (CG) (t test, P < 0.01) respectively. The results showed that the main problems of irrational antibiotic prophylaxis included antibiotic selection, medication given at wrong time, and the long duration of medication, accounting for 28.1%, 34% and 69.6% of the total indicated cases respectively. Significant improvements in using antibiotics with indication would help enhance rational use of the antibiotics. There were complicated factors affecting the antibiotics use decision making beyond the capacity of technical interventions.
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