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Search Results: 1 - 10 of 144770 matches for " Ren-Bo Wang "
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Death Line of Gamma-ray Pulsars with Outer Gaps
Ren-Bo Wang,Kouichi Hirotani
Physics , 2011, DOI: 10.1088/0004-637X/736/2/127
Abstract: We analytically investigate the condition for a particle accelerator to be active in the outer magnetosphere of a rotation-powered pulsar. Within the accelerator (or the gap), magnetic-field-aligned electric field accelerates electrons and positrons, which emit copious gamma-rays via curvature process. If one of the gamma-rays emitted by a single pair materializes as a new pair on average, the gap is self-sustained. However, if the neutron-star spin-down rate decreases below a certain limit, the gap becomes no longer self-sustained and the gamma-ray emission ceases. We explicitly compute the multiplicity of cascading pairs and find that the obtained limit corresponds to a modification of previously derived outer-gap death line. In addition to this traditional death line, we find another death line, which becomes important for millisecond pulsars, by separately considering the threshold of photon-photon pair production. Combining these traditional and new death lines, we give predictions on the detectability of gamma-ray pulsars with Fermi and AGILE. An implication on the X-ray observations of heated polar-cap emission is also discussed.

WANG Kui-hua,QUE Ren-bo,XIA Jian-zhong,

岩石力学与工程学报 , 2005,
Abstract: By modeling soil as a three-dimensional axisymmetric continuum and taking its radial and vertical displacement into account,the interaction between a soil layer and an integral end bearing pile undergoing vertical harmonic load is theoretically investigated. The pile is assumed to be vertical,elastic and of uniform cross-section, and the soil is considered as a linear visco-elastic layer with hysteretic type damping. With the aid of two potentials,the displacement of soil layer is decomposed and then its dynamic equilibrium equation is uncoupled and solved first. Thus the resistance factor and vibration modes of the soil layer are obtained and used to analyze the pile response. By considering the interaction between the soil layer and the pile with boundary condition of displacement continuity and force equilibrium at the interface of them,the dynamic equilibrium equation of pile is solved and an analytical solution for the pile response in frequency domain is yielded,which is used to define complex stiffness of the pile head and the soil local complex stiffness. When governing parameters are varying,a comparison is made with simplified solutions obtained at the condition of plane strain hypothesis or neglecting radial displacement. The comparison involves the soil resistance factor,the soil local complex stiffness and the complex stiffness of the pile head. It proves that in the case of low frequency,stiff soil and slender pile,there can be significant discrepancies between them,but with frequency increasing,the simplified solutions converge to the same.
Characterization and Bioactivity of Polysaccharides Obtained from Pine Cones of Pinus koraiensis by Graded Ethanol Precipitation
Pan Zou,Xin Yang,Wei-Wei Huang,Hai-Tian Zhao,Jing Wang,Ren-Bo Xu,Xing-Long Hu,Si-Yan Shen,Di Qin
Molecules , 2013, DOI: 10.3390/molecules18089933
Abstract: Pinus koraiensis polysaccharides (PKP) were extracted by hot water from P. koraiensis pine cones. Five polysaccharide fractions named PKP-A, PKP-B, PKP-C, PKP-D and PKP-E were successfully separated at final ethanol concentrations of 30%, 50%, 60%, 70% and 80%, respectively. HPLC, FT-IR, GC-MS and automatic amino-acid analysis were applied to investigate their chemical characteristics. Monosaccharide component analysis indicated that the five fractions were all composed of d-ribose, l-rhamnose, l-arabinose, d-xylose, d-mannose, d-glucose and d-galactose, but their molar ratios were quite different. HPLC results revealed that the polysaccharides precipitated by higher concentrations of ethanol solution had lower molecular masses. Moreover, the antioxidant activities of the five fractions were studied on the basis of hydroxyl radical and ABTS radical scavenging tests. The five graded polysaccharide fractions exhibited good inhibitory power, and MTT tests in vitro showed the IC 50 of PKP-A and PKP-E were 1,072.5 and 2,070.0 μg·mL ?1, respectively. These results demonstrated that the PKP could be a potential source of natural antioxidants or dietary supplements.
Chemical Composition and Antioxidant Activities of Three Polysaccharide Fractions from Pine Cones
Ren-Bo Xu,Xin Yang,Jing Wang,Hai-Tian Zhao,Wei-Hong Lu,Jie Cui,Cui-Lin Cheng,Pan Zou,Wei-Wei Huang,Pu Wang,Wen-Jing Li,Xing-Long Hu
International Journal of Molecular Sciences , 2012, DOI: 10.3390/ijms131114262
Abstract: The traditional method of gas chromatography-mass spectrometry for monosaccharide component analysis with pretreatment of acetylation is described with slight modifications and verified in detail in this paper. It was then successfully applied to the quantitative analysis of component monosaccharides in polysaccharides extracted from the pine cones. The results demonstrated that the three pine cone polysaccharides all consisted of ribose, rhamnose, arabinose, xylose, mannose, glucose and galactose in different molar ratios. According to the recovery experiment, the described method was proved accurate and practical for the analysis of pine cone polysaccharides, meeting the need in the field of chemical analysis of Pinus plants. Furthermore; the chemical characteristics, such as neutral sugar, uronic acids, amino acids, molecular weights, and antioxidant activities of the polysaccharides were investigated by chemical and instrumental methods. The results showed that the chemical compositions of the polysaccharides differed from each other, especially in the content of neutral sugar and uronic acid. In the antioxidant assays, the polysaccharide fractions exhibited effective scavenging activities on ABTS radical and hydroxyl radical, with their antioxidant capabilities decreasing in the order of PKP > PAP > PSP. Therefore, although the polysaccharide fractions had little effect on superoxide radical scavenging, they still have potential to be developed as natural antioxidant agents in functional foods or medicine.


物理学报 , 1974,
Abstract: The directivity patterns of angle probes commonly used in ultrasonic material-testing are studied both theoretically and experimentally. Expressions are obtained for longitudinal waves and transverse waves radiating into the body under test and for surface waves propagating over the surface of the body, treated as a semi-infinite isotropic medium. Numerical computations are given in all three cases for a steel object. The theoretical deductions are partially checked by experiments for the case of longitudinal and surface waves. Some problems to be considered in ultrasonic testing are pointed out.


物理学报 , 2001,
Abstract: Using the Sellmeier equations of GdCOB and YCOB, we determined the wavelength range in which non-critical phase matching in GdxY1-xCOB can be realized. Using a 704-5 type optical parametric amplifier, we measured the non-critical phase-matching wavelengths in several GdxY1-xCOB crystals with different compositional parameter x.
Investigation on Performances of the Novel Ammonia-based Hydrogen Storage Material CaCl2

LIN Ren-Bo,LIU Yong-Feng,GAO Ming-Xia,WANG Jian-Hui,GE Hong-Wei,PAN Hong-Ge,

无机材料学报 , 2008,
Abstract: 研究了工作温度、起始氨压和球磨处理对无水CaCl2的吸放氨性能的影响. 结果发现, 球磨2h样品在温度20℃和氨压0.55MPa的条件下, 15min内即可完全氨化, 形成CaCl2(NH3)8, 其吸氨量可达55.1wt%, 相当于储氢量9.72wt%. CaCl2(NH3)8在20~300℃的范围内可通过三步反应实现完全脱氨, 脱氨反应受温度和压力控制, 其中6个NH3分子在常温、常压下即可脱附. 如果与NH3分解催化剂联用, 可能是一种较好的以NH3为介质的高容量储氢材料. 进一步研究表明, 较高的工作温度和起始氨压可以提高CaCl2的吸氨动力学性能, 而球磨时间的增加可以显著降低其放氨工作温度, 提高其放氨动力学性能.
Elastic constants and thermodynamic properties of Mg2SixSn1-x from first-principles calculations

Liu Na-N,Song Ren-Bo,Du Da-Wei,

中国物理 B , 2009,
Abstract: This paper stuides the elastic constants and some thermodynamic properties of Mg2SixSn1-x (x=0, 0.25, 0.5, 0.75, 1) compounds by first-principles total energy calculations using the pseudo-potential plane-waves approach based on density functional theory, within the generalized gradient approximation for the exchange and correlation potential. The elastic constants of Mg2SixSn1-x were calculated. It shows that, at 273 K, the elastic constants of Mg2Si and Mg2Sn are well consistent with previous experimental data. The isotropy decreases with increasing Sn content. The dependences of the elastic constants, the bulk modulus, the shear modulus and the Debye temperatures of Mg2Si and Mg2Si_{0.5}Sn_{0.5} on pressure were discussed. Through the quasi-harmonic Debye model, in which phononic effects were considered, the specific heat capacities of Mg2SixSn1-x at constant volume and constant pressure were calculated. The calculated specific heat capacities are well consistent with the previous experimental data.
Monocular pose determination from coplanartwo points and one line features

LIU Chang,ZHU Feng,XIA Ren-bo,
刘 昶
,朱 枫,夏仁波

计算机应用研究 , 2012,
Abstract: This paper studied monocular pose determination problem from point and line mixed features. It presented a method to calculate the pose parameters between a camera and an object if coplanar two points and one line features on the object and their given correspondences on the image. It described detailed algorithm according to the geometric relationship of the three features in two cases, and translated the problem into solving a quadratic equation. The real experiment shows the method is effective. It provides a new method for pose determination using monocular vision.
The electronic structure and thermodynamic properties of Mg2Sn from first-principles calculations

Liu Na-N,Song Ren-Bo,Sun Han-Ying,Du Da-Wei,

物理学报 , 2008,
Abstract: Electronic structure, elastic constants and thermodynamic properties of Mg2Sn have been calculated by using the first-principles pseudopotential method. As shown by the calculated results, the band gap of Mg2Sn is 0.1198 eV. The linear response method is applied to determine the phonon dispersion relations and phonon density of states. The thermodynamic properties such as the constant-volume specific heat and Debye temperature are calculated. The calculated thermal conductivity is compared with the experimental data.
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