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Search Results: 1 - 10 of 104368 matches for " Guofang Zhang "
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The Sasaki-Ricci flow on Sasakian 3-spheres
Guofang Wang,Yongbing Zhang
Mathematics , 2013,
Abstract: We show that on a Sasakian 3-sphere the Sasaki-Ricci flow initiating from a Sasakian metric of positive transverse scalar curvature converges to a gradient Sasaki- Ricci soliton. We also show the existence and uniqueness of gradient Sasaki-Ricci soliton on each Sasakian 3-sphere.
A conformal integral invariant on Riemannian foliations
Guofang Wang,Yongbing Zhang
Mathematics , 2011,
Abstract: Let $M$ be a closed manifold which admits a foliation structure $\mathcal{F}$ of codimension $q\geq 2$ and a bundle-like metric $g_0$. Let $[g_0]_B$ be the space of bundle-like metrics which differ from $g_0$ only along the horizontal directions by a multiple of a positive basic function. Assume $Y$ is a transverse conformal vector field and the mean curvature of the leaves of $(M,\mathcal{F},g_0)$ vanishes. We show that the integral $\int_MY(R^T_{g^T})d\mu_g$ is independent of the choice of $g\in [g_0]_B$, where $g^T$ is the transverse metric induced by $g$ and $R^T$ is the transverse scalar curvature. Moreover if $q\geq 3$, we have $\int_MY(R^T_{g^T})d\mu_g=0$ for any $g\in [g_0]_B$. However there exist codimension 2 minimal Riemannian foliations $(M,\mathcal{F},g)$ and transverse conformal vector fields $Y$ such that $\int_MY(R^T_{g^T})d\mu_g\neq 0$. Therefore, it is a nontrivial obstruction for the transverse Yamabe problem on minimal Riemannian foliation of codimension 2.
Gaseous and Electrochemical Hydrogen Storage Properties of Nanocrystalline Mg2Ni-Type Alloys Prepared by Melt Spinning  [PDF]
Zhihong Ma, Bo Li, Huiping Ren, Zhonghui Hou, Guofang Zhang, Yanghuan Zhang
Materials Sciences and Applications (MSA) , 2011, DOI: 10.4236/msa.2011.23018
Abstract: A partial substitution of Ni by Cu has been carried out in order to improve the hydrogen storage characteristics of the Mg2Ni-type alloys. The nanocrystalline Mg20Ni10-xCux (x = 0, 1, 2, 3, 4) alloys are synthesized by the melt-spinning technique. The structures of the as-cast and spun alloys have been characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM). The electrochemical performances were evaluated by an automatic galvanostatic system. The hydrogen absorption and desorption kinetics of the alloys were determined by using an automatically controlled Sieverts apparatus. The results indicate that the substitution of Cu for Ni does not alter the major phase Mg2Ni. The Cu substitution significantly ameliorates the electrochemical hydrogen storage performances of alloys, involving both the discharge capacity and the cycle stability. The hydrogen absorption capacity of alloys has been observed to be first increase and then decrease with an increase in the Cu contents. However, the hydrogen desorption capacity of the alloys exhibit a monotonous growth with an increase in the Cu contents.
Oral and maxillofacial surgery in China: Past, present and future  [PDF]
Jiawei Zheng, Bing Fang, Shanyong Zhang, Chi Yang, Guofang Shen, Weiliu Qiu, Zhiyuan Zhang
Open Journal of Stomatology (OJST) , 2013, DOI: 10.4236/ojst.2013.37060
Abstract:

China is the most highly populated developing country. As with other scientific disciplines, dentistry (stomatology) is progressively growing since 1949 when the new China was founded. Due to the closing of the country to international discourse for several decades, international counterparts know very little about dentistry or stomatology, including the sub-discipline oral and maxillofacial surgery. This paper is aimed to introduce the scope, give a brief history, update clinical and basic research, and discuss the future of oral and maxillofacial surgery in China. It will hopefully help international colleagues to have an insight into the developmental history, education system, clinical and basic research achievements, as well as the prospective future of oral and maxillofacial surgery in China

Isolation and Identification of a Strain of Aspergillus Tubingensis With Deoxynivalenol Biotransformation Capability
Chenghua He,Yanhong Fan,Guofang Liu,Haibin Zhang
International Journal of Molecular Sciences , 2008, DOI: 10.3390/ijms9122366
Abstract: Deoxynivalenol (DON) is one of the most common contaminants of various foodstuffs. A biotransformation system was used in order to lessen the toxicity of DON. A strain of Aspergillus (NJA-1) was isolated from soil and cultured in an inorganic salt medium containing DON. Bt2a/Bt2b primers were used to amplify the β-tubulin gene of NJA-1. Sequence analysis the PCR product and morphology observation indicated that NJA-1 belonged to Aspergillus tubingensis (aerobic fungi). The DNA sequence information of the PCR product was deposited in GenBank (accession number DQ9025790). The DNA sequence had 99% similarity to the Aspergillus tubingensis accession number AY820009. An unknown compound in NJA-1 showed the ability to convert DON into another product. The molecular weight of the bioconversion product was 18.1 D (H2O) larger than that of DON. The analysis showed that DON could be hydrolyzed by NJA-1. The mean DON biotransformation rate was 94.4% after two weeks of cultivation. The finding presents a new method for DON biotransformation.
BLOCK ADAPTIVE RECUSIVE ALGORITHM FOR VIDEO CONFERENCE CODING
会议电视编码中的块自适应递归算法

Tu Guofang,Zhang Can,
涂国防
,张灿

电子与信息学报 , 1996,
Abstract: This paper presents a new motion estimation algorithm for video conference signal coding. This type of algorithm is called block adaptive recursive algorithm (BARA). Simulation results show that this new algorithm has better performance than that of conventional ones.
Joint Source and Channel Decoding for Variable Length Encoded Turbo Codes
Jianjun Liu,Guofang Tu,Can Zhang,Yang Yang
EURASIP Journal on Advances in Signal Processing , 2007, DOI: 10.1155/2008/149839
Abstract: Joint source and channel decoding (JSCD) has been proved to be an effective technique which can improve decoding performance by exploiting residual source redundancy. Most previous publications on this subject focus on a traditional coding scheme in which the source variable-length coding (VLC) is serially concatenated with a channel code. In this paper, a parallel concatenated coding scheme for the VLC combined with a turbo code is presented. By merging a symbol-level VLC trellis with a convolutional trellis, we construct a symbol-level joint trellis with compound states. Also, a solution of the symbol-by-symbol a posteriori probability (APP) decoding algorithm based on this joint trellis is derived, which leads to an iterative JSCD approach in the similar way to the classical turbo decoder. The simulation results show that our joint source-channel en/decoding system achieves some gains at the cost of increasing decoding complexity, when compared to the joint iterative decoding based on the bit-level super trellis for the separate coding system.
Manifolds with A Lower Ricci Curvature Bound
Guofang Wei
Mathematics , 2006,
Abstract: This paper is a survey on the structure of manifolds with a lower Ricci curvature bound.
Ricci Curvature and Betti Numbers
Guofang Wei
Mathematics , 1994,
Abstract: We derive a uniform bound for the total betti number of a closed manifold in terms of a Ricci curvature lower bound, a conjugate radius lower bound and a diameter upper bound. The result is based on an angle version of Toponogov comparison estimate for small triangles in a complete manifold with a Ricci curvature lower bound. We also give a uniform estimate on the generators of the fundamental group and prove a fibration theorem in this setting.
Biomimetic fluorapatite films for conservation of historic calcareous stones
FuWei Yang,Yan Liu,GuoFang Zuo,YuanCheng Zhu,BingJian Zhang,PingNing Hua
Chinese Science Bulletin , 2012, DOI: 10.1007/s11434-012-5026-1
Abstract: Fluorapatite protective films were prepared on marble substrates using a biomimetic method. By mimicking the mineralization mechanism of enamel, phosphorus and fluorine were introduced on the surface of the marble substrate. In the presence of a biological template, namely collagen, an integrated fluorapatite film was produced and the marble substrate was entirely covered. The prepared fluorapatite films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray (EDX) spectroscopy. The performances of the fluorapatite films were evaluated by color changes, capillary water absorption, and acid resistance tests. The results revealed that the fluorapatite films had good compatibility with the marble substrate; the physical properties such as color and capillary water adsorption of the marble substrates were unchanged. The fluorapatite films also had good acid resistance and were stable even in heavy acid rain.
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