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Search Results: 1 - 10 of 29442 matches for " Xiaofeng Sun "
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Considerations on Research of Environmental Risk Prevention and Control in “12th Five-Year Plan” Period  [PDF]
Pengli Xue, Xiaofeng Sun, Yun Song, Yanjun Cheng, Dezhi Sun
Computational Water, Energy, and Environmental Engineering (CWEEE) , 2013, DOI: 10.4236/cweee.2013.22B012
Abstract: Along with the environmental pollution causes complexity and diversity increases ceaselessly, “national environmental protection” Twelfth Five “planning” (hereinafter referred to as “planning”) will be the environmental risk prevention as the “12th Five-Year Plan” one of the important tasks, including advancing environmental risk management in the whole process, key areas the environmental risk prevention measures. The whole process environmental risk management covers a risk source recognition, receptor vulnerability assessment, environmental risk characterization, risk decision and risk assessment of accident loss. This article from the environmental risk source classification, environmental risk classification management, environmental emergency response and environmental risk and insurance environment four aspects put forward the “12th Five-Year Plan” whole process environmental risk management content, to further reduce our country environmental pollution accident risk and policy makers to provide some decision support.
Weil-Petersson geometry on moduli space of polarized Calabi-Yau manifolds
Zhiqin Lu,Xiaofeng Sun
Mathematics , 2005,
Abstract: In this paper, we define and study the Weil-Petersson geometry. Under the framework of the Weil-Petersson geometry, we study the Weil-Petersson metric and the Hodge metric. Among the other results, we represent the Hodge metric in terms of the Weil-Petersson metric and the Ricci curvature of the Weil-Petersson metric for Calabi-Yau fourfold moduli. We also prove that the Hodge volume of the moduli space is finite. Finally, we proved that the curvature of the Hodge metric is bounded if the Hodge metric is complete and the dimension of the moduli space is 1.
On the Weil-Petersson volume and the first Chern Class of the moduli space of Calabi-Yau manifolds
Zhiqin Lu,Xiaofeng Sun
Mathematics , 2005, DOI: 10.1007/s00220-005-1441-3
Abstract: In this paper, we proved that the Weil-Petersson volume of Calabi-Yau moduli is a rational number. We also proved that the integrations of the invariants of the Ricci curvature of the Weil-Petersson metric with respect to the Weil-Petersson volume form are all rational numbers.
Theoretical Insights Elucidate Novel Active Phosphonate Esters—Cephalosporin Antibiotics’ Intermediate  [PDF]
Youmin Sun, Huixue Ren, Xiaofeng Wei, Guiqin Zhang
Open Journal of Inorganic Chemistry (OJIC) , 2016, DOI: 10.4236/ojic.2016.64017
Abstract: Theoretical insights elucidate a series of active phosphonate esters application in preparation of Cephalosporin antibiotics’ intermediate. The B3LYP/6-311+G(d,p) method was employed to obtain the stable equilibrium geometries including comparing to the AE-active ester. It was found that the Ethyl-aminothiazoly Loximate (AT) molecule fragment is almost planar sheet, but it is almost perpendicular to the plane of phosphoryl ester. Moreover, the calculated Mulliken atomic charge distribution and frontier molecular orbital analysis of these esters showed that the amino N atom connected to the Thiazole ring of the AT had the maximum negative charge, which suggested that this area had high molecular activity. The value of ΔEL-H was energy gap between EHOMO and ELUMO and indicated that compound 6a had high reaction activity. The theory calculation results can explain the reaction mechanism well and predict that the novel active phosphonate ester has a hopeful application prospect in preparation of Cephalosporin antibiotics’ intermediate.
A Novel Dual-Band Bandpass Filter Using Generalized Trisection Stepped Impedance Resonator with Improved Out-of-Band Performance
Xiaofeng Sun;Eng Leong Tan
PIER Letters , 2011, DOI: 10.2528/PIERL10120606
Abstract: This paper presents the synthesis of a novel dual-band bandpass filter with improved out-of-band performance. The proposed circuit is constructed by cascading a dual-band filter using trisection stepped impedance resonators (SIRs) and an L-C ladder lowpass filter using open-circuited stubs. The dual-band trisection SIR can provide the desired dual-band response, and the lowpass filter can improve the out-of band performance by suppressing the harmonics and spurious responses. The proposed filter has been fabricated and measured. Simulation and measurement results are found to be in good agreement.
EFFECT OF METAL-OXIDE DIFFUSION BARRIER ON INTERDIFFUSION OF ELEMENTS BETWEEN COATING AND SUBSTRATE
SUN Biwu GUAN Hengrong SUN Xiaofeng LI Tiefan,
SUN
,Biwu,GUAN,Hengrong,SUN,Xiaofeng

金属学报(英文版) , 1991,
Abstract: The effect of LPPS Ni_3Al-Y_2O_3 diffusion barrier layer on interdiffusion of elements between coating and substrate has been investigated.It was found that the retardation of interdiffusion is related to the amount of oxide in the diffusion barrier layer.The retardation is not remark- able when the content of Y_2O_3 is 8 wt-%,whereas the diffusion of Al,Co or Cr has all been notably retarded when the content of Y_2O_3 reaches 30 wt-%.The retardation effect of diffu- sion barrier is different for different elements such as Al,Co or Cr.
Characterization of the interactions between the active site of a protein tyrosine kinase and a divalent metal activator
Xiaofeng Lin, Marina K Ayrapetov, Gongqin Sun
BMC Biochemistry , 2005, DOI: 10.1186/1471-2091-6-25
Abstract: Experiments in this communication characterize the interaction between M2 and Csk. Csk activity is sensitive to pH in the range of 6 to 7. Kinetic characterization indicates that the sensitivity is not due to altered substrate binding, but caused by the sensitivity of M2 binding to pH. Several residues in the active site with potential of binding M2 are mutated and the effect on metal activation studied. An active mutant of Asn319 is generated, and this mutation does not alter the metal binding characteristics. Mutations of Glu236 or Asp332 abolish the kinase activity, precluding a positive or negative conclusion on their role in M2 coordination. Finally, the ability of divalent metal cations to activate Csk correlates to a combination of ionic radius and the coordination number.These studies demonstrate that M2 binding to Csk is sensitive to pH, which is mainly responsible for Csk activity change in the acidic arm of the pH response curve. They also demonstrate critical differences in the metal activator coordination sphere in protein tyrosine kinase Csk and a protein Ser/Thr kinase, the cAMP-dependent protein kinase. They shed light on the physical interactions between a protein tyrosine kinase and a divalent metal activator.Protein tyrosine kinases (PTK)1 are a large family of enzymes that transfer the γ-phosphate of ATP to tyrosine hydroxyl groups in proteins. By phosphorylation, PTKs regulate the conformation and function of their protein substrates [1]. This covalent modification is a fundamental mechanism of signal transduction in mammalian cells. Aberrant activation of many specific protein tyrosine kinases causes mishaps in cell signalling, and results in proliferative diseases, such as cancer [2]. Many protein tyrosine kinases are considered as important targets for drug development against such diseases [3]. For full understanding of phosphorylation-mediated signalling and to provide a knowledge base for anti-PTK drug discovery, it is important to underst
Asymptotic Behavior of Solutions of Higher-Order Dynamic Equations on Time Scales
Taixiang Sun,Hongjian Xi,Xiaofeng Peng
Advances in Difference Equations , 2011, DOI: 10.1155/2011/237219
Abstract:
Asymptotic Behavior of Solutions of Higher-Order Dynamic Equations on Time Scales
Sun Taixiang,Xi Hongjian,Peng Xiaofeng
Advances in Difference Equations , 2011,
Abstract: We investigate the asymptotic behavior of solutions of the following higher-order dynamic equation , on an arbitrary time scale , where the function is defined on . We give sufficient conditions under which every solution of this equation satisfies one of the following conditions: (1) ; (2) there exist constants with , such that , where are as in Main Results.
Commercial Banking Efficiency in Nepal: Application of DEA and Tobit Model
Suvita Jha,Xiaofeng Hui,Baiqing Sun
Information Technology Journal , 2013,
Abstract: The competitive scenery of the global economic activity needs the productivity-driven banking industry to be paying special attention for its relative level of efficacy compared to its competitors. The study presents technical efficiency, pure technical efficiency and scale efficiency of the selected eighteen commercial banks in Nepal using input-oriented data envelopment analysis for the period 2005-2010. The mean technical inefficiency of the commercial banks was 16.0% while the average pure technical and scale inefficiencies were 11.16 and 5.50%, respectively. The tobit model to estimate the impact of risk management factors indicates that the capital risk (CAR), Liquidity risk (CDR), profitable ratios (ROA and ROE) have influenced the efficiencies, however, credit risk (NPL) reduced the levels of the commercial banks efficiency. Commercial bank size had consistently inverse impact on technical, pure technical and scale efficiencies. It can be concluded that the Nepalese commercial banks inefficiency was attributed to pure technical inefficiency rather than scale inefficiency, ensuring the commercial banks were performing at their best levels of operations. Furthermore, the joint venture and domestic private banks were more efficient than public sector banks, which suffered managerial underperformance and choice of inappropriate scale size.
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