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Search Results: 1 - 10 of 28276 matches for " Zixin Zhu "
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Research of Enterprise Storage Ecosystem Based on Storage Theory and Nonlinear Discrete Optimization  [PDF]
Zixin Lu, Jiaqi Zhu, Yufeng Gui
Applied Mathematics (AM) , 2018, DOI: 10.4236/am.2018.96051
Abstract:
Warehousing and transferring strategies are an important part of business operations. The issue of optimal warehousing and transferring strategy is studied in this paper. Wal-Mart in Wuhan serves as an example to establish a (s, S) random storage strategy model, a Markov chain model, and a nonlinear discrete programming model, aiming at maximizing the profit per cycle of every branch and further maximizing the company’s total profit per cycle. Among them, the random storage strategy model establishes a security zone of inventory for every branch, that is, it can meet consumers’ demand without spending too much storage costs. The Markov chain model is used to get the probability of losing sales opportunities in every branch. The nonlinear discrete programming model takes into account the horizontal transferring among branches, which further maximizes the company’s overall profit expectations. The three models above can be used to formulate inventory strategies, assess risks, and provide advice for every branch in order to form a complete storage ecosystem and provide constructive suggestions for the company’s operations.
An automated and simple method for brain MR image extraction
Haiyan Zhang, Jiafeng Liu, Zixin Zhu, Haiyun Li
BioMedical Engineering OnLine , 2011, DOI: 10.1186/1475-925x-10-81
Abstract: The method uses an improved geometric active contour model which can not only solve the boundary leakage problem but also is less sensitive to intensity inhomogeneity. The method defines the initial function as a binary level set function to improve computational efficiency. The method is applied to both our data and Internet brain MR data provided by the Internet Brain Segmentation Repository.The results obtained from our method are compared with manual segmentation results using multiple indices. In addition, the method is compared to two popular methods, Brain extraction tool and Model-based Level Set.The proposed method can provide automated and accurate brain extraction result with high efficiency.Brain extraction which segments magnetic resonance (MR) head images into brain and non-brain region is often required for analyses of neuroimage data. Accurate and automated brain extraction plays an important role in the analyses because brain region should be isolated before other processing algorithms such as tissue classification, registration or cortical surface reconstruction can be made [1-3]. For example, functional images such as Functional magnetic resonance image (FMRI) and Positron Emission Tomography (PET) image usually contain few non-brain tissues, whereas high resolution MR images often contain some non-brain tissues(i.e., skin, fat, muscle, etc.), and if the non-brain tissues of MR images can be accurately removed beforehand, the registration robustness will be improved greatly [2]. Furthermore, as a pre-processing step, brain extraction is usually performed before a full segmentation of the brain region into grey matter (GM), white matter (WM), and cerebrospinal fluid (CSF), so that the segmentation problem can be simplified [4,5]. On the other hand, brain extraction is also a difficult and time-consuming pre-processing step performed in neuroimage analysis due to the complexity of human brain anatomy and weak boundaries between brain and non-brain t
Design of an Acoustic Communication System Based on FHMA for Multiple Underwater Vehicles  [PDF]
Zixin Zhao, Shuxiang Guo
Wireless Engineering and Technology (WET) , 2010, DOI: 10.4236/wet.2010.11005
Abstract: This paper designs an underwater acoustic communication system based on tamed spread spectrum and Frequency Hopping Multiple Access (FHMA) for multiple underwater vehicles. In this system, multiple underwater vehicles can communicate with the console on the water surface simultaneously successfully. The communication system is com-posed of tamed spread spectrum modulation and demodulation, frequency hopping modulation and demodulation with synchronization function, 4FSK modulation and demodulation and Rake Receiver. In order to make the system more feasible, underwater channel and the effect of user number on Bit Error Ratio (BER) are also taken into account. The simulation results indicate that it is feasible to use this system to accomplish underwater communication reliably for multiple users due to the low BER.
Wallerian Degeneration in Central Nervous System: Dynamic Associations between Diffusion Indices and Their Underlying Pathology
Wen Qin, Min Zhang, Yueshan Piao, Deyu Guo, Zixin Zhu, Xin Tian, Kuncheng Li, Chunshui Yu
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0041441
Abstract: Background Although diffusion tensor imaging has been used to monitor Wallerian degeneration, the exact relationship between the evolution of diffusion indices and its underlying pathology, especially in central nervous system, remains largely unknown. Here we aimed to address this question using a cat Wallerian degeneration model of corticospinal tract. Methodology/Principal Findings Twenty-five domestic mature Felis catus were included in the present study. The evolution of diffusion indices, including mean diffusivity (MD), fractional anisotropy (FA), primary (λ1) and transverse eigenvalues (λ23) of the degenerated corticospinal tract, were observed at baseline (before modeling) and at 2, 4, 6, 8, 10, 15, 20, 25, 30, 45 and 60 days after modeling in 4 cats. Pathological examinations were performed at eight time points mentioned above. Wallerian degeneration can be detected as early as the 2nd day after modeling by both diffusion tensor imaging and pathology. According to the evolution of diffusion indices, Wallerian degeneration can be classified into 2 stages. During the early stage (within 8 days after modeling), progressive disintegration of axons and myelin sheaths underlies the decreases in FA and λ1 and the increase in λ23. However, during the late stage (after 8 days), the gradual increases in FA, MD and λ1 and the unchanged λ23 seem to be a comprehensive reflection of the pathological processes including microglia activation, myelin clearance, and astrocytosis. Conclusions/Significance Our findings help the understanding of the altered diffusion indices in the context of pathology and suggest that diffusion tensor imaging has the potential to monitor the processes of Wallerian degeneration in the central nervous system in vivo after acute damage.
Assignment of EC Numbers to Enzymatic Reactions with Reaction Difference Fingerprints
Qian-Nan Hu, Hui Zhu, Xiaobing Li, Manman Zhang, Zhe Deng, Xiaoyan Yang, Zixin Deng
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0052901
Abstract: The EC numbers represent enzymes and enzyme genes (genomic information), but they are also utilized as identifiers of enzymatic reactions (chemical information). In the present work (ECAssigner), our newly proposed reaction difference fingerprints (RDF) are applied to assign EC numbers to enzymatic reactions. The fingerprints of reactant molecules minus the fingerprints of product molecules will generate reaction difference fingerprints, which are then used to calculate reaction Euclidean distance, a reaction similarity measurement, of two reactions. The EC number of the most similar training reaction will be assigned to an input reaction. For 5120 balanced enzymatic reactions, the RDF with a fingerprint length at 3 obtained at the sub-subclass, subclass, and main class level with cross-validation accuracies of 83.1%, 86.7%, and 92.6% respectively. Compared with three published methods, ECAssigner is the first fully automatic server for EC number assignment. The EC assignment system (ECAssigner) is freely available via: http://cadd.whu.edu.cn/ecassigner/.
Ecological Tunnel for the 21st Century: A New Conception and Methodology  [PDF]
Zixin Zhang, Qinghua Lei, Qiang Xue
Journal of Transportation Technologies (JTTs) , 2011, DOI: 10.4236/jtts.2011.13008
Abstract: This paper presents a new conception—ecological tunnel, which is contrived to meet increasingly tough challenges in the 21st century. Ecological tunnel refers to integrating ecological principles into tunnel design, construction and operation in order to create a balanced and sustainable tunnel-nature system. It consists of four elements: green tunneling, green lighting, green lining, and green recycling of excavated material. The conception, function and implementation of each part are elaborated in the paper. In addition, computer visualization technique is applied to simulate complicated internal conditions of an ecological tunnel.
In Vitro Characterization of Echinomycin Biosynthesis: Formation and Hydroxylation of L-Tryptophanyl-S-Enzyme and Oxidation of (2S,3S) β-Hydroxytryptophan
Chen Zhang, Lingxin Kong, Qian Liu, Xuan Lei, Tao Zhu, Jun Yin, Birun Lin, Zixin Deng, Delin You
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0056772
Abstract: Quinoxaline-2-carboxylic acid (QXC) and 3-hydroxyquinaldic acid (HQA) feature in quinomycin family and confer anticancer activity. In light of the significant potency against cancer, the biosynthetic gene clusters have been reported from many different Streptomyces strains, and the biosynthetic pathway were proposed mainly based on the in vivo feeding experiment with isotope labeled putative intermediates. Herein we report another gene cluster from Streptomyces griseovariabilis subsp. bandungensis subsp. nov responsible for the biosynthesis of echinomycin (a member of quinomycin family, also named quinomycin A) and presented in vitro evidence to corroborate the previous hypothesis on QXC biosynthesis, showing that only with the assistance of a MbtH-like protein Qui5, did the didomain NRPS protein (Qui18) perform the loading of a L-tryptophan onto its own PCP domain. Particularly, it was found that Qui5 and Qui18 subunits form a functional tetramer through size exclusion chromatography. The subsequent hydroxylation on β-carbon of the loaded L-tryptophan proved in vitro to be completed by cytochrome P450-dependent hydroxylase Qui15. Importantly, only the Qui18 loaded L-tryptophan can be hydroxylated by Qui15 and the enzyme was inactive on free L-tryptophan. Additionally, the chemically synthesized (2S,3S) β-hydroxytryptophan was detected to be converted by the tryptophan 2,3-dioxygenase Qui17 through LC-MS, which enriched our previous knowledge that tryptophan 2,3-dioxygenase nearly exclusively acted on L-tryptophan and 6-fluoro-tryptophan.
Automorphisms with order three of affine Lie algebras
Quanqin Jin,Zixin Hou
Chinese Science Bulletin , 1998, DOI: 10.1007/BF02883374
Abstract: Some properties of automorphisms of affine Lie algebras are presented. Automorphisms with order three are classified up to conjugacy, and their fixed point sets are also computed. As a corollary, it is proved that two automorphisms of order three are conjugate if and only if their fixed point sets are isomorphic.
A Novel Voltage Balancing Method of Modular Multilevel Converters  [PDF]
Zunfang Chu, Zixin Li, Ping Wang, Yaohua Li
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.54B222
Abstract: In this paper, a novel voltage balancing method of modular multilevel converters (MMCs) is proposed. This method divides the voltages of sub-module capacitors in each arm into several groups and the voltage balancing is based on these groups. The proposed method can save sorting time greatly compared with the conventional method. Simulation results on a MMC based three-phase inverter show validity of the proposed method.

 

Shrinkage Estimation of Semiparametric Model with Missing Responses for Cluster Data  [PDF]
Mingxing Zhang, Jiannan Qiao, Huawei Yang, Zixin Liu
Open Journal of Statistics (OJS) , 2015, DOI: 10.4236/ojs.2015.57076
Abstract:

This paper simultaneously investigates variable selection and imputation estimation of semiparametric partially linear varying-coefficient model in that case where there exist missing responses for cluster data. As is well known, commonly used approach to deal with missing data is complete-case data. Combined the idea of complete-case data with a discussion of shrinkage estimation is made on different cluster. In order to avoid the biased results as well as improve the estimation efficiency, this article introduces Group Least Absolute Shrinkage and Selection Operator (Group Lasso) to semiparametric model. That is to say, the method combines the approach of local polynomial smoothing and the Least Absolute Shrinkage and Selection Operator. In that case, it can conduct nonparametric estimation and variable selection in a computationally efficient manner. According to the same criterion, the parametric estimators are also obtained. Additionally, for each cluster, the nonparametric and parametric estimators are derived, and then compute the weighted average per cluster as finally estimators. Moreover, the large sample properties of estimators are also derived respectively.

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