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Search Results: 1 - 10 of 45341 matches for " Si-wen Tang "
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Preparation of Spraying Powders and Microstructureof MolybdenumDisilicide Coating
YAN Jian-Hui, TANG Si-Wen, ZHANGHou-An
无机材料学报 , 2010, DOI: 10.3724/sp.j.1077.2011.00203
Abstract: With the size of 1―2μm MoSi2powder as raw material, MoSi2 powderideal for air plasma spraying was prepared by spray drying and vacuumsintering. By using MoSi2 powders (9.68μm ) and agglomeration powders (38―72μm) as the spray feedstock, MoSi2 coatings weresuccessfully prepared using air plasma spraying. The phase composition and microstructure of the coatingwere studied.The results show that the mobility and loosedensity of theagglomeration powders sintered at 1300 for 1h are 17.1s/50g and 2.1g/cm3, respectively. Compared with the unsintered powders, the mobility and loose density of the sintered agglomeration powders increaseby 57.0% and 46%, respectively. XRD patterns shows the main phasesare Mo and Mo5Si3 phases in the coating prepared by thepowders with the size of 9.68 μm.In case of spraying withagglomeration powders, the main phase of the dense coating is MoSi2. The meshmicrostructure of molybdenum―rich phase is produced in the coatingprepared by the agglomeration powders.
Fault Diagnosis of Rotating Machinery Based on Multisensor Information Fusion Using SVM and Time-Domain Features
Ling-li Jiang,Hua-kui Yin,Xue-jun Li,Si-wen Tang
Shock and Vibration , 2014, DOI: 10.1155/2014/418178
Abstract: Multisensor information fusion, when applied to fault diagnosis, the time-space scope, and the quantity of information are expanded compared to what could be acquired by a single sensor, so the diagnostic object can be described more comprehensively. This paper presents a methodology of fault diagnosis in rotating machinery using multisensor information fusion that all the features are calculated using vibration data in time domain to constitute fusional vector and the support vector machine (SVM) is used for classification. The effectiveness of the presented methodology is tested by three case studies: diagnostic of faulty gear, rolling bearing, and identification of rotor crack. For each case study, the sensibilities of the features are analyzed. The results indicate that the peak factor is the most sensitive feature in the twelve time-domain features for identifying gear defect, and the mean, amplitude square, root mean square, root amplitude, and standard deviation are all sensitive for identifying gear, rolling bearing, and rotor crack defect comparatively. 1. Introduction Typical rotating machinery systems such as water turbine, steam turbine, wind turbine, and rotary kiln are critical core equipment support of the important industries of the national economy [1, 2]. The safety, reliability, efficiency, and performance of rotating machinery are major concerns in industry, so, the task of condition monitoring and fault diagnosis of rotating machinery is significant [3]. The common mechanical defects of rotating machinery are divided into three categories: rotor body defects, such as unbalance, misalignment, rubbing, and rotor crack; rotor support-bearing defects, such as inner race, outer race or ball defect of rolling bearing, and oil whirl or oil whip of sliding bearing; transmission gear defects, such as chipped tooth defect or missing tooth defect. In-process monitoring and diagnostics of rotating machinery require reasoning about defect and process states from sensor readings. Often the relationship between the sensor readings and the process states is complex and nondeterministic. For a complex system, a single sensor is incapable of collecting enough data for accurate condition monitoring and fault diagnosis. Multiple sensors are needed in order to do a better job. When multiple sensors are used, data collected from different sensors may contain different partial information about the same machine condition. The diagnostic object can be described more comprehensively [4–6]. Compared with single sensor, the time-space scope and the quantity
Baryon Transition in Holographic QCD
Si-wen Li
Physics , 2015,
Abstract: We propose a mechanism of holographic baryon transition in the Sakai-Sugimoto (SS) model: baryons in this model can jump to different states under the mediated effect of gravitons (or glueballs by holography). We consider a time-dependent gravitational perturbation from M5-brane solution of D=11 supergravity and by employing the relations between 11D M-theory and IIA string theory, we get its 10 dimensional counterpart in the SS model. Such a perturbation is received by the D4-branes wrapped on the $S^{4}$ part of the 10D background, namely the baryon vertex. Technically, baryons in the SS model are described by BPST instanton ansatz and their dynamics can be analyzed using the quantum mechanical system in the instanton's moduli space. In this way, different baryonic states are marked by quantum numbers of moduli space quantum mechanics. By holographic spirit, the gravitational perturbation enters the Hamiltonian as a time-dependent perturbation and it is this time-dependent perturbative Hamiltonian produces the transition between different baryonic states. We calculate the transition probability and get the selection rule and also compute the condition for baryon transition and give the possible transition processes in the limit $\omega\gg\left|\vec{k}\right|^{2}$. Since in 10D language, the fluctuation from 11D metric are the perturbation of 10D metric and dilaton which are the modes carried by close strings, thus from the string theory point of view, our proposition can be accounted as the baryonic D4 brane jumps to different states by emitting or absorbing close strings coming from the bulk. In the viewpoints of QCD, it could be interpreted as that baryons transform to different states by interacting with glueballs as a low energy effective theory.
Control and measure of satellite magnetic cleanliness

CHEN Si-wen,

地球物理学进展 , 2009,
Abstract: 本文叙述卫星磁洁净的重要性、空间磁场的分布、卫星磁性的要求、卫星磁矩的来源、卫星的磁设计和控制、卫星和它的部件的磁矩的测量方法、内容、过程、装置和一些部件的测量结果.卫星磁矩来自三个方面,它们是永磁铁,软磁材料和杂散磁场(电流产生的磁场).磁性设计包括材料选择、器件的测试、电子线路的布置和元件的安排等.
Matrix model and Holographic Baryons in the D0-D4 background
Si-wen Li,Tuo Jia
Physics , 2015, DOI: 10.1103/PhysRevD.92.046007
Abstract: We study on the spectrum and short-distance two-body force of holographic baryons by the matrix model, which is derived from Sakai-Sugimoto model in D0-D4 background (D0-D4/D8 system). The matrix model is derived by using the standard technique in string theory and it can describe multi-baryon system. We re-derive the action of the matrix model from open string theory on the wrapped baryon vertex, which is embedded in the D0- D4/D8 system. The matrix model offers a more systematic approach to the dynamics of the baryons at short distances. In our system, we find that the matrix model describe stable baryonic states only if $\zeta=U_{Q_{0}}^{3}/U_{KK}^{3}<2$, where $U_{Q_{0}}^{3}$ is related to the number density of smeared D0-branes. This result in our paper is exactly the same as some previous presented results studied on this system as \cite{key-24 Baryons in D0-D4}. We also compute the baryon spectrum ($k=1$ case) and short-distance two-body force of baryons ($k=2$ case). The baryon spectrum is modified and could be able to fit the experimental data if we choose suitable value for $\zeta$. And the short-distance two-body force of baryons is also modified by the appearance of smeared D0-branes from the original Sakai-Sugimoto model. If $\zeta>2$, we find that the baryon spectrum would be totally complex and an attractive force will appear in the short-distance interaction of baryons, which may consistently correspond to the existence of unstable baryonic states.
Friction and Wear Behavior of La2O3- and WSi2-Reinforced MoSi2 Composite

ZHANG Hou-an,CHEN Ping,YAN Jian-hui,HU Xiao-ping,TANG Si-wen,

摩擦学学报 , 2005,
Abstract: 选用MRH-5A型环-块摩擦磨损试验机测定了3种载荷和2种转速条件下La2O3和WSi2增强MoSi2基复合材料在滑动干摩擦时的摩擦磨损性能,采用扫描电子显微镜分析了复合材料磨损表面形貌.结果表明:La2O3和WSi2增强MoSi2基复合材料的抗磨性能优于MoSi2及WSi2/MoSi2材料;当载荷与速度乘积(pv)值小于183.04N·m/s时,La2O3和WSi2增强MoSi2基复合材料的磨损质量损失仅为相同条件下MoSi2的1/4~1/6和WSi2/MoSi2的1/2;这是由于La2O3和WSi2复合增强相存在硬化和韧化协同作用所致;随着pv值增加,La2O3和WSi2增强MoSi2基复合材料依次呈现犁削、粘着磨损和疲劳磨损特征.
Friction and Wear Behavior of La_2O_3- and WSi_2-Reinforced MoSi_2 Composite

ZHANG Hou-an,CHEN Ping,YAN Jian-hui,HU Xiao-ping,TANG Si-wen hanical Equipment,Hunan University of Science,Technology,Xiangtan,China,

摩擦学学报 , 2005,
Abstract: 选用MRH-5A型环-块摩擦磨损试验机测定了3种载荷和2种转速条件下La2O3和WSi2增强MoSi2基复合材料在滑动干摩擦时的摩擦磨损性能,采用扫描电子显微镜分析了复合材料磨损表面形貌.结果表明:La2O3和WSi2增强MoSi2基复合材料的抗磨性能优于MoSi2及WSi2/MoSi2材料;当载荷与速度乘积(pv)值小于183.04N·m/s时,La2O3和WSi2增强MoSi2基复合材料的磨损质量损失仅为相同条件下MoSi2的1/4~1/6和WSi2/MoSi2的1/2;这是由于La2O3和WSi2复合增强相存在硬化和韧化协同作用所致;随着pv值增加,La2O3和WSi2增强MoSi2基复合材料依次呈现犁削、粘着磨损和疲劳磨损特征.
Experimental Study of Beam Quality Measurement for High-energy Laser

WANG Si-Wen,

红外 , 2012,
Abstract: High-energy lasers are widely used in the fields of science, industry and military. Because of the influence of atmosphere on the transmission of a laser, the investigation of far-field beam quality of a high-power laser is always a problem. To obtain the optical intensity distribution of a 1.4 kW pulsed TEA CO2 laser at the distance of 500 m, a relative measurement method combined with absolute measurement is proposed. The measurement data are discussed and analyzed. The experimental result shows that the maximum power density on the target is 1.65 W/cm2 and the divergence angle in the cross direction is up to 0.96 mrad. The result is valuable to the optimization design of laser systems.
From holography towards real-world nuclear matter
Si-wen Li,Andreas Schmitt,Qun Wang
Physics , 2015, DOI: 10.1103/PhysRevD.92.026006
Abstract: Quantum chromodynamics is notoriously difficult to solve at nonzero baryon density, and most models or effective theories of dense quark or nuclear matter are restricted to a particular density regime and/or a particular form of matter. Here we study dense (and mostly cold) matter within the holographic Sakai-Sugimoto model, aiming at a strong-coupling framework in the wide density range between nuclear saturation density and ultra-high quark matter densities. The model contains only three parameters, and we ask whether it fulfills two basic requirements of real-world cold and dense matter, a first-order onset of nuclear matter and a chiral phase transition at high density to quark matter. Such a model would be extremely useful for astrophysical applications because it would provide a single equation of state for all densities relevant in a compact star. Our calculations are based on two approximations for baryonic matter, firstly an instanton gas and secondly a homogeneous ansatz for the non-abelian gauge fields on the flavor branes of the model. While the instanton gas shows chiral restoration at high densities but an unrealistic second-order baryon onset, the homogeneous ansatz behaves exactly the other way around. Our study thus provides all ingredients that are necessary for a more realistic model and allows for systematic improvements of the applied approximations.
Advance in Bone Morphogenetic Protein-15 Gene
骨形成蛋白15基因的研究进展 Advance in Bone Morphogenetic Protein-15 Gene

Zhen-Ping Hou,Si-Wen Jiang,
,蒋思文HOU Zheng-Ping,JIANG Si-Wen

遗传 , 2003,
Abstract: Bone morphogenetic proteins (BMPs) are secreted signalling molecules belonging to the transforming growth factor-beta (TGF-beta) surperfamily. Up to date,more than 30 members of BMPs are identified. Bone morphogenetic protein-15 is only expressed in oocytes. Oocyte-specific BMP-15 might promote follicle growth in vivo, while preventing premature luteinization. This paper briefly discusses the progress in the research area of BMP-15 gene being as a candidate gene for litter size.
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