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Search Results: 1 - 10 of 120175 matches for " Lifang Wang "
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Operator Product Formula for a Special Macdonald Function  [PDF]
Lifang Wang, Ke Wu, Jie Yang
Applied Mathematics (AM) , 2018, DOI: 10.4236/am.2018.94033
Abstract:
In this paper, we construct two sets of vertex operators S+ and S? from a direct sum of two sets of Heisenberg algebras. Then by calculating the vacuum expectation value of some products of vertex operators, we get Macdonald function in special variables xi = t i-1 ( i = 0,1, 2,\"\"). Hence we obtain the operator product formula for a special Macdonald function Pλ (1,t,\"\",tn-1;q,t ) when n is finite as well as when n goes to infinity.
A note on products of finite groups
Lifang Wang,Yanming Wang
International Journal of Algebra , 2012,
Abstract:
Marginal Distribution in Copula Estimation of Distribution Algorithm Based Dynamic K-S test
Zhao Hui,Wang Lifang
International Journal of Computer Science Issues , 2012,
Abstract: Estimation of distribution algorithms based on copula, and a number of different distribution functions were selected as the dimension of the marginal distribution function by applying K-S test. Dynamic K-S test, that is, dynamic adjust frequency of K-S test in different stages. In the estimation of the probability model stage, according to the actual distribution of the dominant group respectively subject to inspection of the distribution function of each dimension. In the parameter estimation stage, according to fix the copula function parameters to make the emulation experiment. According to the obedience of the different marginal distribution function to sample separately, thus increasing the diversity of the population, and improving an execution efficiency of the estimation of distribution algorithms based on copula.
Total Flavonoid Content, the Antioxidant Capacity, Fingerprinting and Quantitative Analysis of Fupenzi (Rubus chingii Hu.)  [PDF]
Huajin Zeng, Ran Yang, Lifang Lei, Yaping Wang
Chinese Medicine (CM) , 2015, DOI: 10.4236/cm.2015.64023
Abstract: Objective: In this study, one of the objectives was to investigate the total flavonoid contents of Fupenzi (R. chingii Hu.) obtained from different regions of China and to evaluate their anatioxidant activities. And the second objective of this study was to develop a validated HPLC method for chromatographic fingerprints of the samples extracts of Fupenzi. Method: The total flavonoid contents were determined by a colorimetric method and the antioxidant activity was determined spectrophotometrically by DPPH and ABTS radical scavenging assays. The chromatographic fingerprint was developed by high-performance liquid chromatography coupled with diode array detection for the control of Fupenzi. Results: A significant correlation between antioxidant activity and the total flavonoid content was observed for the DPPH assay (r2 = 0.758, ρ = 0.004) and the ABTS assay (r2 = 0.788, ρ = 0.002). Under the optimized chromatographic conditions, the validated method was successfully applied to assessment of chemical fingerprinting of 12 batches of FPZ collected from different regions of China. Comparisons of the chromatograms showed that 15 characteristic peaks could be selected as markers for identification and evaluation of Fupenzi. In addition, the proposed method was also successfully applied to simultaneous determination of five compounds (including puerarin, rutin, hyperin, quercetin and kaempferol) in these samples. Conclusions: The qualitative and quantitative analysis described in this paper could be used for identification and evaluation of Fupenzi.
Application of Multi-Attribute Crossplots to Tight Gas in X Area, Western China  [PDF]
Lifang Cheng, Yanchun Wang, Zhiguo Li, Fei Li, Fuxiu Gong
Open Journal of Geology (OJG) , 2016, DOI: 10.4236/ojg.2016.64022
Abstract: The gas-bearing reservoir in X area is mainly the tight sandstone reservoir characterized by low porosity and permeability, frequently lateral variation and poor connectivity of single sand. The previous research results reveal that the general seismic attributes analysis cannot meet the requirement of fluid identification. This is because the relationship between seismic attributes and their implication is uncertain and ambiguous, which decreases the precision of both reservoir prediction and fluid identification. To overcome the problem, multi-attribute crossplot technology is proposed from the mathematical statistical point of view rather than the correspondence between the seismic attributes and their geological implication. In this method, the wells which have the same statistical law are classified firstly, and then all the interest wells are retained while the wells beyond the statistical law are eliminated, and the seismic attributes sensitive to the same types of eliminated wells are optimized and used to generate crossplots. The nonzero area of their crossplots results just predicts the potential distribution. The discontinuity of subsurface geological conditions results in the non-continuous shape and the seismic bin lead to the mosaic form. The optimization of sensitive attributes relative to the same types of wells is independent from each other, and thus the order of attributes in crossplots does not affect the final prediction results. This method is based on the statistical theory and suitable for the areas such as the study area abundant of lots of well data. Application to X area proves the effectiveness of this method and predicts plane distribution about different types of gas production. Due to the effect of faults and other geological factors, the partition prediction results using multi-attribute crossplots reach 95% of coincidence which is obviously and far higher than the results of the whole area. The final prediction results show that the potential areas with medium and high gas production are mainly concentrated in the northern part of the study area, where lots of development research will be strengthened.
Prediction of Tight Sand Reservoir with Multi-Wavelet Decomposition and Reconstructing Method  [PDF]
Lifang Cheng, Yanchun Wang, Zhiguo Li, Fuxiu Gong
International Journal of Geosciences (IJG) , 2016, DOI: 10.4236/ijg.2016.74040
Abstract: Special reservoir or fluid has an abnormal response to some certain frequencies, so that seismic decomposition and reconstruction are used to highlight the seismic reflection at certain frequencies useful to identify special geological bodies. Because seismic wavelets are time-varying and spatial-variable in the propagation, synthetic traces based on single wavelet make some weak but useful information lost, and make artifacts form. However, Morlet wavelet aggregation with mathematical analytical expression is able to fully and correctly reflect the variations of wavelet in the propagation of underground medium. The matching pursuit algorithm on the basis of Morlet wavelet improves the calculating efficiency in decomposition and reconstruction greatly. This method is applied to the actual study area to do conjoint analysis of single well and well-tie multi-wavelet decomposition. It is found that frequencies sensitive to interest reservoirs range from 8 to 34 Hz. Reconstructing the wavelets at those special frequencies and analyzing the reconstructed seismic data, it is pointed out that interest reservoirs have abnormal characteristics with respectively strong RMS amplitude in the reconstructed data. Crossplot of gamma value at wells and reconstructed RMS amplitude suggests that anomalies caused by interest reservoirs are well separated from the background anomalies when the reconstructed RMS amplitude is greater than 3650. Quantitative prediction results of interest reservoirs distribution in the study area reveal that interest reservoirs of western and northern study area are distributed annularly and bandedly, while most contiguous sandstone in eastern regions appears sporadically.
The Application of Reverse-Time Migration in the Z Area of PRM Basin  [PDF]
Run He, Yuan Fang, Yanchun Wang, Lifang Cheng, Xi Zheng
International Journal of Geosciences (IJG) , 2016, DOI: 10.4236/ijg.2016.76060
Abstract: Reverse time migration (RTM) is an accurate migration method, which is based on two-way wave equation, eliminates angle limitation, and can be capable for imaging of reverse branch and multiple. In the development of an oilfield in Pearl River Mouth (PRM) Basin, RTM has been applied to solve the problems of fault shadow and structure in distinction and the drilling has proven that the RTM result is reliable. This paper introduces the theory of RTM and emphatically discusses parameter selection. The results of RTM showed that it had advantages in resolving fault shadow and the imaging of steep dip structure, and could be utilized in the oilfield.
Corrigendum. Finite Groups in which (S )Semipermutability is a Transitive Relation, International Journal of Algebra, 2(3), 2008, 143-152
Lifang Wang,Yangming Li,Yanming Wang
International Journal of Algebra , 2012,
Abstract:
Systematic Analysis of Conducted Electromagnetic Interferences for the Electric Drive System in Electric Vehicles
Yanjie Guo;Lifang Wang;Chenglin Liao
PIER , 2013, DOI: 10.2528/PIER12092816
Abstract: There are serious electromagnetic compatibility (EMC) problems in electric vehicles. In order to explain and solve them, a systematic method to analyze conducted interferences of the electric drive system is shown in this paper. This method represents the effects of the power battery which is the most different part between electric drive systems used in electric vehicles and other cases. Also, Equivalent models are established from power electronics devices to the entire system by considering both the working mechanism and stray parameters. Firstly, insulated gate bipolar transistor (IGBT) and inverter are studied as the main interference source. A new expression is put forward to estimate the frequency domain features of the inverter disturbances. Then, power battery and electric motor are discussed as the main propagation paths. Their high frequency circuit models are given with parameters obtained from tests and measurements. Finally, the system model is established. The system interferences are analyzed to get their generation causes, influence factors and frequency domain characteristics. Comparisons between simulations and experiments verify the correctness of the models and the method.
Modeling and Analysis of Conducted Electromagnetic Interference in Electric Vehicle Power Supply System
Yanjie Guo;Lifang Wang;Chenglin Liao
PIER , 2013,
Abstract: Electromagnetic interference (EMI) of the power supply system in electric vehicles will seriously affect the safety of the vehicle and passengers' health. So a model of power supply system is presented to analyze its conducted EMI in the paper. This model shows the effects of paralleled interleaving DC/DC converter, which contains the new circular current EMI characteristics. Also, a novel power battery model is established considering both the energy dynamic processes and the high frequency features. Firstly, the power electronics devices are studied as the most important part of the DC/DC converter. Then, the equivalent model of the paralleled interleaving DC/DC converter is set up to express the interference source features. Also, the power battery, which is the main energy storage equipment in electric vehicles, is modeled as EMI propagation paths. Furthermore, loads of the power supply system, such as lead acid battery and low voltage devices, are investigated to evaluate their immunity. Finally, the system model is established. The system EMI is analyzed to get their generating causes, time domain and frequency domain characteristics based on both simulations and experiments.
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