OALib Journal期刊

ISSN: 2333-9721




2018 ( 7 )

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2016 ( 347 )

2015 ( 3576 )


匹配条件: “Xiaojing Li” ,找到相关结果约119722条。
Matrix Padé-Type Method for Computing the Matrix Exponential  [PDF]
Chunjing Li, Xiaojing Zhu, Chuanqing Gu
Applied Mathematics (AM) , 2011, DOI: 10.4236/am.2011.22028
Abstract: Matrix Padé approximation is a widely used method for computing matrix functions. In this paper, we apply matrix Padé-type approximation instead of typical Padé approximation to computing the matrix exponential. In our approach the scaling and squaring method is also used to make the approximant more accurate. We present two algorithms for computing and for computing with many espectively. Numerical experiments comparing the proposed method with other existing methods which are MATLAB’s functions expm and funm show that our approach is also very effective and reliable for computing the matrix exponential . Moreover, there are two main advantages of our approach. One is that there is no inverse of a matrix required in this method. The other is that this method is more convenient when computing for a fixed matrix A with many t ≥ 0.
Analysis of a Residual Model for the Decomposition of Polarimetric SAR Data  [PDF]
Xiaojing Bai, Binbin He, Xiaowen Li
Advances in Remote Sensing (ARS) , 2013, DOI: 10.4236/ars.2013.22016

Accurate estimation of the double-bounce scattering fd and surface scattering fs coefficients with Freeman-Durden decomposition is still difficult. This difficulty arises because overestimation of the volume scattering energy contribution Pv leads to negative values for fd and fs. A generalized residual model is introduced to estimate fd and fs. The relationship between Pv and the residual model is analyzed. Eigenvalues computed from the residual model must be positive to explain physical scattering mechanisms. The authors employ a new volumetric scattering model to minimize Pv as calculated by several decomposition methods. It is concluded that decreasing Pv can help reduce negative energy. This conclusion is validated using actual polarimetric SAR data.

Electric-field switching of exciton spin splitting in coupled quantum dots
Xiaojing Li,Kai Chang
Physics , 2008, DOI: 10.1063/1.2952509
Abstract: We investigate theoretically the spin splitting of the exciton states in semiconductor coupled quantum dots (CQDs) containing a single magnetic ion. We find that the spin splitting can be switched on/off in the CQDs \textit{via} the \textit{sp-d}exchange interaction using the electric field. An interesting bright-to-dark exciton transition can be found and significantly affects the photoluminescence spectrum. This phenonmenon is induced by the transition of the ground exciton state, arising from the hole mixing effect, between the bonding and antibonding states.
Microfinance in Fisheries in China  [PDF]
Xiaojing Wang
Open Journal of Social Sciences (JSS) , 2015, DOI: 10.4236/jss.2015.35001

Because of lack of collateral and formal financial information, family aquacultures and small boat owners find it difficult to get loans from formal financial institutions. Fishery microfinance can partly solve the information asymmetry and incomplete contract problems in rural financial market, and it is an effective complement to formal fishery finance. The service object of fishery microfinance is mainly micro-enterprises in fisheries, including family aquacultures and small fishing boats. Fishery microfinance providers include formal financial institutions and many kinds of micro-financial institutions, among which China Fishery Mutual Insurance Association (FMIA) is the most famous one. Although micro-finance has a 20-year-history in China, there are still some problems that block its advance. The market is huge, but the existing providers are not providing good services and most are not sustainable. There is still a long way towards commercial operation and financial sustainability.

Classification of protein quaternary structure by functional domain composition
Xiaojing Yu, Chuan Wang, Yixue Li
BMC Bioinformatics , 2006, DOI: 10.1186/1471-2105-7-187
Abstract: To explore this problem, we adopted an approach based on the functional domain composition of proteins. Every protein was represented by a vector calculated from the domains in the PFAM database. The nearest neighbor algorithm (NNA) was used for classifying the quaternary structure of proteins from this information. The jackknife cross-validation test was performed on the non-redundant protein dataset in which the sequence identity was less than 25%. The overall success rate obtained is 75.17%. Additionally, to demonstrate the effectiveness of this method, we predicted the proteins in an independent dataset and achieved an overall success rate of 84.11%Compared with the amino acid composition method and Blast, the results indicate that the domain composition approach may be a more effective and promising high-throughput method in dealing with this complicated problem in bioinformatics.The structure hierarchy of proteins is defined in terms of four levels: primary, secondary, tertiary, and quaternary. The term quaternary structure was first introduced by Bernal in 1958 [1-3]. It refers to the non-covalent interactions of protein subunits to form oligomers and the spatial arrangement of the subunits.Oligomeric proteins are very common in nature. They can be divided further into two classes: homo-oligomers and hetero-oligomers; the former are composed of identical subunits while the latter are composed of non-identical subunits. For example, the potassium channel is formed by a homo-tetramer [4] , and the gamma-aminobytyric acid type A (GABAA) receptor is formed by a hetero-pentamer [5]. The subunit construction of proteins provides the structural basis for their activities and functions in various biological processes, which include metabolism, signal transduction and chromosome replication [3,6]. From an evolutional point of view, the oligomeric proteins have more advantages than the monomers [7,8]. It is easier for multi-subunit proteins to repair their defects by s
Progress in study on irrigation practice with saline groundwater on sandlands of Taklimakan Desert Hinterland
Xinwen Xu,Bingwen Li,Xiaojing Wang
Chinese Science Bulletin , 2006, DOI: 10.1007/s11434-006-8221-0
Abstract: The study on the distribution and dynamic changes of soil moistures and salts under different irrigating methods and managements of using saline groundwater on the sand lands of the hinterland of the Taklimakan Desert, started in 1997. The results show that drip irrigation can be applied to seedlings (furrow irrigation can be applied to level lands) using saline groundwater in the process of constructing the biological shifting sand control system along the desert highway in the hinterland of the Taklimakan Desert; an irrigation frequency of 20 days and an irrigation amount of 30 kg/m2·time are suitable to the shifting sand control forest belts at the same year as they were afforested. Along with the increase of forest age, the irrigation norm can be properly increased, the irrigation interval can be prolonged.
Using P systems to Solve the Discrete Logarithm Problem used in Diffie-Hellman Key Exchange Protocol
Xiaojing Ma,Zhitang Li,Hao Tu
International Journal of Computer Network and Information Security , 2009,
Abstract: The discrete logarithm problem has been used as the basis of several cryptosystems, especially the Diffie- Hellman key exchange protocol. P systems are a cluster of distributed parallel computing devices in a biochemical type. This paper presents a P system with active membranes and strong priority to solve the discrete logarithm problem used in Diffie-Hellman key exchange protocol. To the best of our knowledge, it’s the first time to solve the problem using P systems.
Reversible Data Hiding Scheme Based On H.264/AVC without Distortion Drift
YunXia Liu,Zhitang Li,Xiaojing Ma
Journal of Software , 2012, DOI: 10.4304/jsw.7.5.1059-1065
Abstract: There is greater possibility that reversible video data hiding scheme causes more distortions than reversible image data hiding. In H.264/AVC video streams, intra-frame distortion drift is a big problem in data hiding. This paper proposes a novel readable reversible data hiding scheme in H.264/AVC which can avert the distortion drift. We embed data into the quantized discrete cosine transform (DCT) coefficients of I frames which meet the directions of intra-frame prediction, and the directions of intra-frame prediction are utilized to avert the distortion drift. It is proved analytically and shown experimentally that the proposed algorithm can achieve high embedding capacity and low visual distortion, and the original compressed video can be recovered exactly after the hidden data, in addition, the proposed system is fast and simple. Performance comparisons with other existing schemes are provided to demonstrate the superiority of the proposed scheme.
System Dynamics Model for VMI&TPL Integrated Supply Chains
Guo Li,Xiaojing Wang,Zhaohua Wang
Discrete Dynamics in Nature and Society , 2013, DOI: 10.1155/2013/178713
Abstract: This paper establishes VMI-APIOBPCS II model by extending VMI-APIOBPCS model from serial supply chain to distribution supply chain. Then TPL is introduced to this VMI distribution supply chain, and operational framework and process of VMI&TPL integrated supply chain are analyzed deeply. On this basis VMI-APIOBPCS II model is then changed to VMI&TPL-APIOBPCS model and VMI&TPL integrated operation mode is simulated. Finally, compared with VMI-APIOBPCS model, the TPL’s important role of goods consolidation and risk sharing in VMI&TPL integrated supply chain is analyzed in detail from the aspects of bullwhip effect, inventory level, service level, and so on. 1. Introduction Under vendor-managed inventory (VMI) operation mode, many suppliers outsource their logistics to third-party logistics (TPL) due to their poor logistics capabilities. So far, that TPL participates in VMI has been widely used in many industries. For example, Dell and Lenovo both chose Burlington Company to help them operate VMI service, and Wuhan Shenlong Automobile Company in China allows GEFCO to provide VMI service with components supply. On the one hand, this integrated operational model combining VMI with TPL ensures that the supply chain information is shared fully on one central platform. On the other hand, it can take full advantage of TPL and reduce the total operational cost of the supply chain. As to the research of VMI&TPL integrated replenishment and delivery, ?etinkaya et al. [1] take Dell as an example, which outsources VMI business to Burlington Logistics, and analyze TPL replenishment and delivery strategies. They do not only consider the optimal delivery strategies about logistics outsourcing but also find out differences of the optimal delivery strategies before and after outsourcing. Based on the above study, ?etinkaya and Lee [2] consider the time-based delivery policy and obtain the optimal delivery time structure with transportation lot constraints and capability limitations while the demand of retailers obeys the Poisson distribution. Lee et al. [3] assume that the replenishment and delivery can be started at the beginning of each period with determined demand and finite horizon and that the lead time for delivery of the replenishment is zero. They consider the problem of inventory and transportation integration, which is similar to ?etinkaya and Lee [2]. In order to achieve economies of transport scale, TPL implements goods consolidation strategy. As a result, products may be delivered to retailers in an earlier or later time, which would lead to the inventory
Pasture Monitoring Using SAR with COSMO-SkyMed, ENVISAT ASAR, and ALOS PALSAR in Otway, Australia
Xin Wang,Linlin Ge,Xiaojing Li
Remote Sensing , 2013, DOI: 10.3390/rs5073611
Abstract: Because of all-weather working ability, sensitivity to biomass and moisture, and high spatial resolution, Synthetic aperture radar (SAR) satellite images can perfectly complement optical images for pasture monitoring. This paper aims to examine the potential of the integration of COnstellation of small Satellites for the Mediterranean basin Observasion (COSMO-SkyMed), Environmental Satellite Advanced Synthetic Aperture Radar (ENVISAT ASAR), and Advanced Land Observing Satellite Phased Array type L-band Synthetic Aperture Radar (ALOS PALSAR) radar signals at horizontally emitted and received polarization (HH) for pasture monitoring at the paddock scale in order to guide farmers for better management. The pasture site is selected, in Otway, Victoria, Australia. The biomass, water content of grass, and soil moisture over this site were analyzed with these three bands of SAR images, through linear relationship between SAR backscattering coefficient, and vegetation indices Normalized Differential Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), Enhanced Vegetation Index (EVI)), together with soil moisture index (MI). NDVI, NDWI, and MI are considered as proxy of pasture biomass, plant water content, and soil moisture, respectively, and computed from optical images and climate data. SAR backscattering coefficient and vegetation indices are computed within a grass zone, defined by classification with MODIS data. The grass condition and grazing activities for specific paddocks are detectable, based on SAR backscatter, with all three wavelengths datasets. Both temporal and spatial analysis results show that the X-band SAR has the highest correlation to the vegetation indices. However, its accuracy can be affected by wet weather due to its sensitivity to the water on leaves. The C-band HH backscattering coefficient showed moderate reliability to evaluate biomass and water content of grass, with limited influence from rainfall in the dry season. The L-band SAR is the less accurate one for grass biomass measurement due to stronger penetration.

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