针对OLAP查询的特点,提出基于缓冲池描述的DBMS分层排队网络模型,以构建这一模型为例示范构建DBMS分层排队网络模型的方法和步骤。对比分析分层排队网络模型的两种求解算法——MOL(the Method of Layer)和SRVN(the Stochastic Rendezvou...针对OLAP查询的特点,提出基于缓冲池描述的DBMS分层排队网络模型,以构建这一模型为例示范构建DBMS分层排队网络模型的方法和步骤。对比分析分层排队网络模型的两种求解算法——MOL(the Method of Layer)和SRVN(the Stochastic Rendezvous of Network)在算法结构、模型限制、描述能力、求解精度上的差别,总结出模型参数获取的三种途径。展开更多
Manipulating the directional movement of liquid droplets is of significance for design and fabrication of some microfluidic devices, An energy-based method is adopted to analyse the directional movement of a droplet d...Manipulating the directional movement of liquid droplets is of significance for design and fabrication of some microfluidic devices, An energy-based method is adopted to analyse the directional movement of a droplet deposited in a conical tube or on a conical fibre. We perform an experiment to investigate the directional motion of a droplet in an open conical tube. Our theoretical analysis and experimental observations both demonstrate that surface tension can drive the droplet to move in the conical tube. The critical condition of the liquid moving in the conical tube is presented. We also analyse a droplet on a conical hydrophilic fibre, which can move from the thinner to the thicker end.展开更多
A 2 1/2-dimensional electromagnetic particle-in-cell （PIC） simulation code is used to investigate electron behaviour in collisionless magnetic reconnectfon. The results show that the ion/electron mass ratio （mi/me...A 2 1/2-dimensional electromagnetic particle-in-cell （PIC） simulation code is used to investigate electron behaviour in collisionless magnetic reconnectfon. The results show that the ion/electron mass ratio （mi/me） almost has no impact on the reconnection rate, however it can significantly affect electron behaviour in the diffusion region. For the case with larger mass ratio, the width of electron current sheet becomes smaller and the outflow region along the separatrix is smaller, hence the peak of the electron outflow speed is essentially larger. Density cavities and the parallel electric field E// along the separatrix can be found in the case with larger mass ratio, which may have significant influences on the acceleration and heating of the electrons near the X point.展开更多
We design and prepare three-layer graded ZnO nanowhisker/polyester composites. The dispersion configuration of ZnO nanowhiskers in the polyester is investigated, and their microwave reflectivity curves are also measur...We design and prepare three-layer graded ZnO nanowhisker/polyester composites. The dispersion configuration of ZnO nanowhiskers in the polyester is investigated, and their microwave reflectivity curves are also measured. Experimental results have shown that the graded dispersion with ZnO nanowhiskers contributes to broadband microwave absorption. In other words, the absorption band depends on the graded dispersion configuration of ZnO nanowhiskers in polyester matrix.展开更多
We report a femtosecond optical parametric oscillator based on MgO-doped PPLN synchronously pumped by a mode-locked Ti：sapphire laser. The wavelengths of the signal and idler are continuously tuned from 1100 to 1300h...We report a femtosecond optical parametric oscillator based on MgO-doped PPLN synchronously pumped by a mode-locked Ti：sapphire laser. The wavelengths of the signal and idler are continuously tuned from 1100 to 1300hm and from 2080 to 2930nm, respectively, by changing the pump wavelength and the OPO cavity length. The maximum signal output power of 130mW at the wavelength of 1225nm is obtained, pumped by 900roW of 800hm laser radiation. This corresponds to a total conversion efficiency of 22.1%. The signal pulse duration is measured to be 167fs by intensity autocorrelation with chirped mirrors for intracavity dispersion compensation.展开更多
We theoretically analyse the temperature effects on a surface plasmon resonance （SPR） sensor in Kretschmann configuration. The temperature effects include the thermo-optic effect and the dispersion of thermal-optic ...We theoretically analyse the temperature effects on a surface plasmon resonance （SPR） sensor in Kretschmann configuration. The temperature effects include the thermo-optic effect and the dispersion of thermal-optic coefficient in the dielectric along with the thermal expansion effect, phonon-electron scattering and electron-electron scattering in the metal layer. We simulate the temperature dependence of the resonance position and the sensitivity of the SPR sensor under wavelength-interrogation and angular-interrogation mode of operation and the differences are pointed out in the two modes.展开更多
This study explored the performances of CZTS-based thin-film solar cell with three novel buffer layer materials ZnS, CdS, and CdZnS, as well as with variation in thickness of buffer and absorber-layer, doping concentr...This study explored the performances of CZTS-based thin-film solar cell with three novel buffer layer materials ZnS, CdS, and CdZnS, as well as with variation in thickness of buffer and absorber-layer, doping concentrations of absorber-layer material and operating temperature. Our aims focused to identify the most optimal thin-film solar cell structure that offers high efficiency and lower toxicity which are desirable for sustainable and eco-friendly energy sources globally. SCAPS-1D, widely used software for modeling and simulating solar cells, has been used and solar cell fundamental performance parameters such as open-circuited voltage (), short-circuited current density (), fill-factor() and efficiency() have been optimized in this study. Based on our simulation results, it was found that CZTS solar cell with Cd<sub>0.4</sub>Zn<sub>0.6</sub>S as buffer-layer offers the most optimal combination of high efficiency and lower toxicity in comparison to other structure investigated in our study. Although the efficiency of Cd<sub>0.4</sub>Zn<sub>0.6</sub>S, ZnS and CdS are comparable, Cd<sub>0.4</sub>Zn<sub>0.6</sub>S is preferable to use as buffer-layer for its non-toxic property. In addition, evaluation of performance as a function of buffer-layer thickness for Cd<sub>0.4</sub>Zn<sub>0.6</sub>S, ZnS and CdS showed that optimum buffer-layer thickness for Cd<sub>0.4</sub>Zn<sub>0.6</sub>S was in the range from 50 to 150nm while ZnS offered only 50 – 75 nm. Furthermore, the temperature dependence performance parameters evaluation revealed that it is better to operate solar cell at temperature 290K for stable operation with optimum performances. This study would provide valuable insights into design and optimization of nanotechnology-based solar energy technology for minimizing global energy crisis and developing eco-friendly energy sources sustainable and simultaneously.展开更多
The ground-state energy and effective mass of an acoustic polaron in one dimension are calculated by using an electron-longitudinal-acoustic-phonon interaction Hamiltonian derived here. The self-trapping of the acoust...The ground-state energy and effective mass of an acoustic polaron in one dimension are calculated by using an electron-longitudinal-acoustic-phonon interaction Hamiltonian derived here. The self-trapping of the acoustic polaron is discussed. It is found that the critical coupling constant shifts toward weaker electron-phonon interaction with the increasing cutoff wave vector and the products of the critical coupling constant by the cutoff wave vector tend to a certain value. The self-trapping of acoustic polarons in one dimension is easier to be realized than that in three- and two-dimensional systems. The self-trapping transition of acoustic polarons is expected to be observed in the one dimensional systems of alkali halides and wide-band-gap semiconductors.展开更多
Tunable diode laser absorption spectroscopy detection of N2 0 around 2.1 μm is demonstrated by using a homemade InGaAsSb/AlGaAsSb MQW laser diode and an InGaAs wavelength extended photodiode. Details of the devices a...Tunable diode laser absorption spectroscopy detection of N2 0 around 2.1 μm is demonstrated by using a homemade InGaAsSb/AlGaAsSb MQW laser diode and an InGaAs wavelength extended photodiode. Details of the devices and the detection system are described. In the system, the laser is driven by low frequency pulses with long duration to form a wavelength scan around 4741 cm^-1; the absorption information is obtained from the detected signal of the photodiode. By using a gas cell with 15cm path length, a detection limit is estimated to be smaller than 0.2 Torr.展开更多
We investigate the influence of vacuum organic contaminations on laser-induced damage threshold （LIDT） of optical coatings. Anti-reflective （AIR） coatings at 1064 nm made by Ta2 O5/SiO2 are deposited by the ion be...We investigate the influence of vacuum organic contaminations on laser-induced damage threshold （LIDT） of optical coatings. Anti-reflective （AIR） coatings at 1064 nm made by Ta2 O5/SiO2 are deposited by the ion beam sputtering method. The LIDTs of AR coatings are measured in vacuum and in atmosphere, respectively. It is exhibited that contaminations in vacuum are easily to be absorbed onto optical surface because of lower pressure, and they become origins of damage, resulting in the decrease of LIDT from 24.5J/cm^2 in air to 15.TJ/cm^2 in vacuum. The LIDT of coatings in vacuum has is slightly changed compared with the value in atmosphere after the organic contaminations are wiped off. These results indicate that organic contaminations are the main reason of the LIDT decrease in vacuum. Additionally, damage morphologies have distinct changes from vacuum to atmosphere because of the differences between the residual stress and thermal decomposability of filmy materials.展开更多
文摘针对OLAP查询的特点,提出基于缓冲池描述的DBMS分层排队网络模型,以构建这一模型为例示范构建DBMS分层排队网络模型的方法和步骤。对比分析分层排队网络模型的两种求解算法——MOL(the Method of Layer)和SRVN(the Stochastic Rendezvous of Network)在算法结构、模型限制、描述能力、求解精度上的差别,总结出模型参数获取的三种途径。
基金Supported by the National Natural Science Foundation of China under Grant Nos 10732050, 10525210 and 10121202
文摘Manipulating the directional movement of liquid droplets is of significance for design and fabrication of some microfluidic devices, An energy-based method is adopted to analyse the directional movement of a droplet deposited in a conical tube or on a conical fibre. We perform an experiment to investigate the directional motion of a droplet in an open conical tube. Our theoretical analysis and experimental observations both demonstrate that surface tension can drive the droplet to move in the conical tube. The critical condition of the liquid moving in the conical tube is presented. We also analyse a droplet on a conical hydrophilic fibre, which can move from the thinner to the thicker end.
基金Supported by the Knowledge Innovation Project of Chinese Academy of Sciences under Grant No KZCX3-SW-144, the National Science Foundation of China under Grant Nos 60608015, and the Doctoral Fund of Qingdao University of Science and Technology.
文摘A 2 1/2-dimensional electromagnetic particle-in-cell （PIC） simulation code is used to investigate electron behaviour in collisionless magnetic reconnectfon. The results show that the ion/electron mass ratio （mi/me） almost has no impact on the reconnection rate, however it can significantly affect electron behaviour in the diffusion region. For the case with larger mass ratio, the width of electron current sheet becomes smaller and the outflow region along the separatrix is smaller, hence the peak of the electron outflow speed is essentially larger. Density cavities and the parallel electric field E// along the separatrix can be found in the case with larger mass ratio, which may have significant influences on the acceleration and heating of the electrons near the X point.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50572010, 50742007 and 10672020, the National Defense Founds of China under Grant Nos A2220061080, and the National Key Basic Research Programme of China under Grant No 5131803.
文摘We design and prepare three-layer graded ZnO nanowhisker/polyester composites. The dispersion configuration of ZnO nanowhiskers in the polyester is investigated, and their microwave reflectivity curves are also measured. Experimental results have shown that the graded dispersion with ZnO nanowhiskers contributes to broadband microwave absorption. In other words, the absorption band depends on the graded dispersion configuration of ZnO nanowhiskers in polyester matrix.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60490280, 60621063 and 60308001. We gratefully acknowledge HC Photonics Co. for providing excellent PPLN crystal. We thank NIE Yu- Xin and HAN Hai-Nian for helpful discussions.
文摘We report a femtosecond optical parametric oscillator based on MgO-doped PPLN synchronously pumped by a mode-locked Ti：sapphire laser. The wavelengths of the signal and idler are continuously tuned from 1100 to 1300hm and from 2080 to 2930nm, respectively, by changing the pump wavelength and the OPO cavity length. The maximum signal output power of 130mW at the wavelength of 1225nm is obtained, pumped by 900roW of 800hm laser radiation. This corresponds to a total conversion efficiency of 22.1%. The signal pulse duration is measured to be 167fs by intensity autocorrelation with chirped mirrors for intracavity dispersion compensation.
基金Supported by the National Basic Research Programme of China under Grant No 2006cb302905, the National Science Foundation of China under Grant No 10474093, the Knowledge Innovation Project of Chinese Academy of Sciences under Grant No KJCX3.Syw.H02, and the National High-Technology Research and Development Programme of China under Grant No 2007AA06Z420.
文摘We theoretically analyse the temperature effects on a surface plasmon resonance （SPR） sensor in Kretschmann configuration. The temperature effects include the thermo-optic effect and the dispersion of thermal-optic coefficient in the dielectric along with the thermal expansion effect, phonon-electron scattering and electron-electron scattering in the metal layer. We simulate the temperature dependence of the resonance position and the sensitivity of the SPR sensor under wavelength-interrogation and angular-interrogation mode of operation and the differences are pointed out in the two modes.
文摘This study explored the performances of CZTS-based thin-film solar cell with three novel buffer layer materials ZnS, CdS, and CdZnS, as well as with variation in thickness of buffer and absorber-layer, doping concentrations of absorber-layer material and operating temperature. Our aims focused to identify the most optimal thin-film solar cell structure that offers high efficiency and lower toxicity which are desirable for sustainable and eco-friendly energy sources globally. SCAPS-1D, widely used software for modeling and simulating solar cells, has been used and solar cell fundamental performance parameters such as open-circuited voltage (), short-circuited current density (), fill-factor() and efficiency() have been optimized in this study. Based on our simulation results, it was found that CZTS solar cell with Cd<sub>0.4</sub>Zn<sub>0.6</sub>S as buffer-layer offers the most optimal combination of high efficiency and lower toxicity in comparison to other structure investigated in our study. Although the efficiency of Cd<sub>0.4</sub>Zn<sub>0.6</sub>S, ZnS and CdS are comparable, Cd<sub>0.4</sub>Zn<sub>0.6</sub>S is preferable to use as buffer-layer for its non-toxic property. In addition, evaluation of performance as a function of buffer-layer thickness for Cd<sub>0.4</sub>Zn<sub>0.6</sub>S, ZnS and CdS showed that optimum buffer-layer thickness for Cd<sub>0.4</sub>Zn<sub>0.6</sub>S was in the range from 50 to 150nm while ZnS offered only 50 – 75 nm. Furthermore, the temperature dependence performance parameters evaluation revealed that it is better to operate solar cell at temperature 290K for stable operation with optimum performances. This study would provide valuable insights into design and optimization of nanotechnology-based solar energy technology for minimizing global energy crisis and developing eco-friendly energy sources sustainable and simultaneously.
基金Supported by the PhD Progress Foundation of Higher Education of China under Grant No 20040126003, and the Natural Science Foundation of Inner Mongol of China under Grant No 200408020101.
文摘The ground-state energy and effective mass of an acoustic polaron in one dimension are calculated by using an electron-longitudinal-acoustic-phonon interaction Hamiltonian derived here. The self-trapping of the acoustic polaron is discussed. It is found that the critical coupling constant shifts toward weaker electron-phonon interaction with the increasing cutoff wave vector and the products of the critical coupling constant by the cutoff wave vector tend to a certain value. The self-trapping of acoustic polarons in one dimension is easier to be realized than that in three- and two-dimensional systems. The self-trapping transition of acoustic polarons is expected to be observed in the one dimensional systems of alkali halides and wide-band-gap semiconductors.
文摘Tunable diode laser absorption spectroscopy detection of N2 0 around 2.1 μm is demonstrated by using a homemade InGaAsSb/AlGaAsSb MQW laser diode and an InGaAs wavelength extended photodiode. Details of the devices and the detection system are described. In the system, the laser is driven by low frequency pulses with long duration to form a wavelength scan around 4741 cm^-1; the absorption information is obtained from the detected signal of the photodiode. By using a gas cell with 15cm path length, a detection limit is estimated to be smaller than 0.2 Torr.
文摘We investigate the influence of vacuum organic contaminations on laser-induced damage threshold （LIDT） of optical coatings. Anti-reflective （AIR） coatings at 1064 nm made by Ta2 O5/SiO2 are deposited by the ion beam sputtering method. The LIDTs of AR coatings are measured in vacuum and in atmosphere, respectively. It is exhibited that contaminations in vacuum are easily to be absorbed onto optical surface because of lower pressure, and they become origins of damage, resulting in the decrease of LIDT from 24.5J/cm^2 in air to 15.TJ/cm^2 in vacuum. The LIDT of coatings in vacuum has is slightly changed compared with the value in atmosphere after the organic contaminations are wiped off. These results indicate that organic contaminations are the main reason of the LIDT decrease in vacuum. Additionally, damage morphologies have distinct changes from vacuum to atmosphere because of the differences between the residual stress and thermal decomposability of filmy materials.
