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991.
西藏羊八井位于东经90.53°, 北纬30.11°, 海拔4310m, 垂直地磁截止刚度14.1GV. 2005年1月20日羊八井太阳中子望远镜和中子监测器探测到与X7.1/2b太阳耀斑相关的GLE事件, 其中太阳中子望远镜能量>40MeV的能道在5min(07:00—07:05UT)和20min(07:00—07:20UT)的时间间隔内计数率增长的统计显著性分别是3.7σ和6.0σ, 同时羊八井中子监测器也探测到计数率的增长,初始时间为06:51—06:52UT. 观测表明在这次GLE事件中太阳质子可被加速到能量大于10GeV. 相似文献
992.
993.
背部支撑主反射镜的面形分析与支撑点优化 总被引:1,自引:0,他引:1
应用有限元方法对背部支撑的主反射镜进行静力学分析.分别对三点支撑和九点支撑进行计算,得到主镜反射面的变形值.以齐次坐标变换法和最小二乘法为理论依据求解反射面变形的PV/RMS值.利用有限元分析软件提供的二次开发功能,编写计算程序,在软件内部调用该程序直接获得PV/RMS值,利用该值作为优化分析的目标函数,寻求背部支撑的最佳支撑点位置. 相似文献
994.
995.
Ying Huang Grant A. Risha Vigor Yang Richard A. Yetter 《Proceedings of the Combustion Institute》2007,31(2):2001-2009
The combustion of bimodal nano/micron-sized aluminum particles with air is studied both analytically and experimentally in a well-characterized laminar particle-laden flow. Experimentally, an apparatus capable of producing Bunsen-type premixed flames was constructed to investigate the flame characteristics of bimodal-particle/air mixtures. The flame speed is positively affected by increasing the mass fraction of nano particles in the fuel formulation despite the lower flame luminosity and thicker flame zone. Theoretically, the flames are assumed to consist of several different regimes for fuel-lean mixture, including the preheat, flame, and post flame zones. The flame speed and temperature distribution are derived by solving the energy equation in each regime and matching the temperature and heat flux at the interfacial boundaries. The analysis allows for the investigation of the effects of particle composition and equivalence ratio on the burning characteristics of aluminum-particle/air mixtures. Reasonable agreement between theoretical results and experimental data was obtained in terms of flame speed. The flame structure of a bimodal particle dust cloud may display either an overlapping or a separated configuration, depending on the combustion properties of aluminum particles at different scales. At low percentages of nano particles in the fuel formulation, the flame exhibits a separated spatial structure with a wider flame regime. At higher nano-particle loadings, overlapping flame configurations are observed. 相似文献
996.
The spinel structure LiV2O4 is studied by local density approximation (LDA) as well as including strong correlation correction potential, i.e. the LDA+U scheme, which concerns the strongly correlated interaction. With LDA, the orbitals of V 3d and O 2p are well separated so that it presents purely metallic heavv fermion behaviour. The total energy of ferromagnetic phase is slightly lower than that of paramagnetic phase within the LDA ap- proach. This implies that the ferromagnetic instability as a consequence of spin frustrated magnetism can be observed in experiments. The strong correlation interaction by using LDA+U enhances the exchange splitting. The heavy-fermion feature can be derived from the sharp peak around the Fermi level from the density of states. 相似文献
997.
A modified Woods-Saxon (MWS) potential is proposed for describing nucleus-nucleus interaction based on the Skyrme energy-density functional approach. Fusion barriers for a large number of fusion reactions from light to heavy systems can be described well with this potential. The suitable incident energies for fusion reactions leading to superheavy nuclei are also explored. It seems to us that the MWS potential is useful for selecting the suitable incident energies for fusion reactions for producing super-heavy nuclei. 相似文献
998.
Absorption and refraction of the inner transition F2\leftrightarrow
F3 of the closed four level N-type atom have been investigated under a
weak field. The outer transitions F1\leftrightarrow F3 and
F2\leftrightarrow F4 are resonantly interacted with drive field with
frequency \omegac and Rabi frequency \Omegac, and saturation
field with \Omegas and \Omegas, respectively. For the suitable Rabi
frequencies \Omegac and \Omegas, we obtain
the Mollow absorption
spectrum of probe field. The reason is that the drive field excites the atom
to the upper level Fc and simultaneously the saturation field takes
the atom out of the lower level F2, leading to the stimulated emission.
Meanwhile, due to the dynamic energy splitting induced by the drive and
saturation fields, the two- and four-peaked absorption spectra are observed.
At the zero off-resonance detuning of probe field, we also find the transfer
of dispersion from negative to positive with an increment of \Omegas.
Finally, the refractive index enhancement is predicted for a wide spectral
region. 相似文献
999.
Controlling optical responses through local dielectric resonance in nanometre metallic clusters 下载免费PDF全文
Optical responses in dilute composites are controlled through the
local dielectric resonance of metallic clusters. We consider two
located metallic clusters close to each other with admittances
\varepsilon1 and \varepsilon2. Through varying the
difference admittance ratio \eta [ = (\varepsilon2- \varepsilon
0) / (\varepsilon1- \varepsilon0)], we find that their
optical responses are determined by the local resonance. There is a
blueshift of absorption peaks with the increase of \eta.
Simultaneously, it is known that the absorption peaks will be
redshifted by enlarging the cluster size. By adjusting the
nano-metallic cluster geometry, size and admittances, we can control
the positions and intensities of absorption peaks effectively. We
have also deduced the effective linear optical responses of
three-component composites \varepsilone= \varepsilon0
\bigl(1 + \sumn=1^{ns} [(\gamman2+ \eta \gamman2)/({\varepsilon0(s - sn))]} \bigr), and the sum
rule of cross sections: \sumn=1^{ns} {(\gamman2+
\eta \gamman2 ) = Nh1+ Nh2, where Nh1and
Nh2 are the numbers of \varepsilon1 and \varepsilon2
bonds along the electric field, respectively. These results may be
beneficial to the study of surface plasmon resonances on a nanometre
scale. 相似文献
1000.
Dependences of spin polarization on the control parameters in the spin-polarized injection through the magnetic p-n junction 下载免费PDF全文
Effective spin-polarized injection from magnetic semiconductor (MS)
to nonmagnetic semiconductor (NMS) has been highlighted in recent
years. In this paper we study theoretically the dependence of
nonequilibrium spin polarization (NESP) in NMS during spin-polarized
injection through the magnetic p-n junction. Based on the theory in
semiconductor physics, a model is established and the boundary
conditions are determined in the case of no external spin-polarized
injection and low bias. The control parameters that may influence the
NESP in NMS are indicated by calculating the distribution of spin
polarization. They are the doping concentrations, the equilibrium
spin polarization in MS and the bias. The effective spin-polarized
injection can be realized more easily by optimizing the above
parameters. 相似文献