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Search Results: 1 - 10 of 68127 matches for " SU Hong-Xin "
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Measurement of the argon-gas-induced broadening and shifting of the barium Rydberg levels by two-photon resonant nondegenerate four-wave mixing

Sun Jiang,Sun Juan,Wang Ying,Su Hong-Xin,

物理学报 , 2012,
Abstract: We apply two-photon resonant nondegenerate four-wave mixing with a resonant intermediate state for observing the broadening and the shifting of the barium Rydberg 6snd 1D2 series by collision with argon. The collision broadenings and the collision shifting cross sections are measured for n=16--33. This technique is a purely optical means, and can achieve Doppler-free resolution of narrow spectral structures of Rydberg levels when the incident lasers have narrow bandwidths. Different from other experimental methods of studying the pressure dependence of the longitudinal relaxation rate of Rydberg states, our method is to investigate the pressure dependence of the transverse relaxation rate of the transition.
Seasonal dynamics in leaf area index in three typical temperate montane forests of China:a comparison of multi-observation methods

SU Hong-Xin,BAI Fan,LI Guang-Qi,

植物生态学报 , 2012,
Abstract: Aims Leaf area index (LAI) is one of the most frequently used parameters for analysis of canopy structure and forest productivity. It can be determined by direct or indirect methods. Sources of errors in indirect LAI measurements with optical instruments include non-photosynthetic components, element clumping, and a topography effect. Our objective was to find an appropriate method for evaluating LAI and its seasonal dynamics in typical temperate montane forest. Methods We examined the applicability of three indirect methods (LAI-2000 plant canopy analyzer, CI-110 plant canopy analyzer and digital hemispherical photograph (DHP)) and one direct method (litterfall) to determine the seasonal dynamics of LAI in three typical temperate forests in Dongling Mountain of Beijing. The forests included a secondary deciduous broad-leaved forest dominated by Quercus mongolica and two plantations (Larix gmelinii var. principis-rupprechtii and Pinus tabuliformis). These represent deciduous broad-leaved forest, deciduous needle-leaved forest and evergreen needle-leaved forest, respectively. The optically-based effective leaf area index (LAIe) values were corrected to eliminate wood elements and clumping effects and then compared with the direct measurement of LAI based on litter collection. Important findings For all the three forests, the LAI seasonal dynamic shows a uni-modal pattern with a peak in July. Optically-based LAIe underestimated the amplitude of the seasonal dynamics. Wood element elimination can strengthen the seasonal sensitivity of LAI, especially in the seasonally distinct deciduous forest. The order of LAIe measured by the three optically-based methods in three stands is LAI-2000 plant canopy analyzer > DHP > CI-110 plant canopy analyzer. There was good correspondence with the direct measurement LAI for the corrected LAI of LAI-2000 plant canopy analyzer and DHP. The correction method based on gap-size distribution was appropriate for the LAI-2000 plant canopy analyzer and the method based on both gap fraction and gap-size distribution for DHP. Considering economics and practical convenience, we recommend DHP for LAI evaluation in these temperate montane forests.
Improvement of photorefractive properties in Hf:Fe:LiNbO3 crystals with various [Li]/[Nb] ratios

Sun Xiu-Dong,Shi Hong-Xin,Luo Su-Hu,Meng Qing-Xin,Jiang Yong-Yuan,

中国物理 B , 2010,
Abstract: Photorefractive properties of Hf:Fe:LiNbO3 crystals with various Li]/Nb] ratios have been investigated at 488 nm wavelength based on the two-wave coupling experiment. High diffraction efficiency and large recording sensitivity are observed and explained. The decrease in Li vacancies is suggested to be the main contributor to the increase in the photoconductivity and subsequently to the induction of the improvement of recording sensitivity. The saturation diffraction efficiency is measured up to 80.2%, and simultaneously the recording sensitivity of 0.91 cm/J is achieved to in the Hf:Fe:LiNbO3 crystal grown from the melt with the Li]/Nb] ratio of 1.20, which is significantly enhanced as compared with those of the Hf:Fe:LiNbO3 crystal with the Li]/Nb] ratio of 0.94 in melt under the same experimental conditions. Experimental results definitely show that increasing the Li]/Nb] ratio in crystal is an effective method for Hf:Fe:LiNbO3 crystal to improve its photorefractive properties.
Chemical constituents from Chirita longgangensis var. hongyao with inhibitory activity against porcine respiratory and reproductive syndrome virus
Su, Yao;Bi, Jun-Long;Wang, Yue-Hu;Tan, Ying;Yang, Jun;Liu, Hong-Xin;Gu, Wei;Yin, Ge-Fen;Long, Chun-Lin;
Journal of the Brazilian Chemical Society , 2012, DOI: 10.1590/S0103-50532012005000068
Abstract: two new quinonoids chiritalone a and b, and a new neolignan 7'e-4,9-dihydroxy-3,3',5'-trimethoxy-8,4'-oxyneolign-7'-en-9'-al, along with known (-)-8-hydroxy-α-dunnione, digiferruginol, 2,5-dimethoxy-1,4-benzoquinone and hederagenin, were isolated from the stems of chirita longgangensis var. hongyao. the structures of the new compounds were elucidated by detailed analysis from nmr (nuclear magnetic resonance) and ms (mass spectrometry) data, and the absolute configuration of chiritalone a was determined by single crystal x-ray diffraction analysis using the flack parameter. the inhibitory activity of compounds against porcine respiratory and reproductive syndrome virus (prrsv) was measured by the cytopathic effect (cpe) method. digiferruginol and hederagenin showed weak effect on prrsv with an ic50 value of 80.5 ± 16.9 μmol l-1 (si = 19.9) and 43.2 ± 7.4 μmol l-1 (si = 13.1), respectively.
The three-photon resonant nondegenerate six-wave mixing via quantum interference in the middle level

Sun Jiang,Sun Juan,Wang Ying,Su Hong-Xin,Cao Jin-Feng,

物理学报 , 2012,
Abstract: We study the quantum interference in three-photon resonant nondegenerate six-wave mixing (NSWM) of a five-level system in which the middle level of six-wave mixing and other levels are coupled by a strong laser field. The coupling field-dependence of the NSWM signal intensity, and the spectrum of the NSWM with a coupling field, are discussed. We find that in the presence of a strong coupling field, the three-photon resonant NSWM spectrum exhibits Autler-Townes splitting, which reflects the levels of the dressed states. It also leads to either suppression or enhancement of the NSWM signal. Due to the enhancement of NSWM signal caused by quantum interference, the dressed state created by a coupling field can replace the atom intrinsic level and serve as the middle level of three-photon resonance. Thus the middle level of three-photon resonance can be controlled by a coupling field.
Study of the satellite line in measurement of the argon -gas-induced broadening of the barium Rydberg levels by two-photon resonant nondegenerate four-wave mixing

Sun Jiang,Liu Peng,Sun Juan,Su Hong-Xin,Wang Ying,

物理学报 , 2012,
Abstract: We study the satellite lines in measurement of the foreign-gas-induced broadening of the barium Rydberg levels by two-photon resonant nondegenerate four-wave mixing (NFWM). The NFWM spectra of the 6s2 1S0-6snd 1D2 (n=16, 22, 36) transitions at different argon pressures are measured. The plots of the center of satellite line principal quantum number and versus pressure are discussed. The contribution of satellite line to the NFWM spectral profile is analyzed. We find that the pressure-broadening rate coefficient can be corrected when the contribution of satellite line is considered.
Three-Photon Resonant Nondegenerate Six-Wave Mixing in a Dressed Atomic System

SUN Jiang,FU Guang-Sheng,SU Hong-Xin,ZUO Zhan-Chun,WU Ling-An,FU Pan-Ming,

中国物理快报 , 2008,
Abstract: We report a three-photon resonant nondegenerate six-wave mixing (NSWM) in a dressed cascade five-level system. It has advantages that phase match condition is not stringent and NSWM signal is enhanced tremendously due to the multiple resonance with the atomic transition frequencies. In the presence of a strong coupling field, the three-photon resonant NSWM spectrum exhibits Autler--Townes splitting. This technique provides a spectroscopic tool for measuring not only the resonant frequency and dephasing rate but also the transition dipole moment between two highly excited atomic states.

ZHANG Jin-Jiang,WU Hong-Xin,LI Ji-Su,ZOU Guang-Rui,

自动化学报 , 2002,
Abstract: The criteria of overcoming low-speed slip-stick phenomenon of third-order system is given by using phase plane method, algebra analyzing method and Lyapunov stability theorem. The relationship between system parameter and low-speed slip-stick phenomenon is found, and the condition of choosing the parameter of PID is given, which should satisfy the purpose of overcoming low-speed stick-slip and guaranteeing the stability. This method is simple and easy to implement. It has directive significance to high precision servo system.

LIU Rui-Gang,LI Na,SU Hong-Xin,SANG Wei-Guo,

植物生态学报 , 2009,
Abstract: 使用LPJ-GUESS植被动态模型,在北京山区研究了未来100 a以辽东栎(Quercus liaotungensis)为优势种的落叶阔叶林、以白桦(Betula platyphylla)为主的阔叶林和油松(Pinus tabulaeformis)为优势种的针阔混交林的碳变化,定量分析了生态系统净初级生产力(NPP)、土壤异养呼吸(Rh)、净生态系统碳交换(NEE)和碳生物量(Carbon biomass)对两种未来气候情景(SRES A2和B2)以及相应大气CO2浓度变化情景的响应特征.结果表明:1)未来100 a两种气候情景下3种森林生态系统的NPP和Rh均增加,并且A2情景下增加的程度更大;2)由于3种生态系统树种组成的不同,未来气候情景下各自NPP和Rh增加的比例不同,导致三者NEE的变化也相异:100 a后辽东栎林由碳汇转变为弱碳源,白桦林仍保持为碳汇但功能减弱,油松林成为一个更大的碳汇;3)3种森林生态系统的碳生物量在未来气候情景下均增大,21世纪末与20世纪末相比:辽东栎林在A2情景下碳生物量增加的比例为27.6%,大于B2情景下的19.3%;白桦林和油松林在B2情景下碳生物量增加的比例分别为34.2%和52.2%,大于A2情景下的30.8%和28.4%.
Precise Prediction on the Operating Peak Junction Temperature for Power Microwave Si BJT

ZHANG Hong-xin,

半导体学报 , 2001,
Abstract: 三维全热程热电一体地模拟了 Si BJT微波功率器件 .热场计算包括从芯片的有源区经芯片 -粘接层 -基片 -粘接层 -底座直到固定于 70℃的安装台面的整个散热过程 .在处理热电正反馈时把有源区的 6 0个基本单元 (子胞 )当成 6 0个并联子胞晶体管进行建模 ,子胞模型包括子胞晶体管本身、基区横向扩展电阻、发射区横向扩展电阻 .热电一体分析除了涉及 Vbe随温度变化外 ,还有子胞发射极有效面积随子胞发射极电流上升而下降的效应 (以下称面积效应 ) .与对有源区各点直接进行分析相比 ,子胞建模不仅大大简化了计算 ,而且摸拟结果与器件结构、版图结构、工艺参
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