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141.
142.
Eiji Tokunaga Naoto Sato Jiro Korenaga Takayuki Imai Shin Sato Hiro-o Hamaguchi 《Optical Review》2010,17(3):341-345
Visible nonlinear band-edge luminescence in ZnSe and CdS bulk crystals was observed upon excitation by a mid-infrared free-electron
laser (mid-IR FEL) at approximately 9 mm. The emission intensity is proportional to the 74th and 45th powers of the excitation
intensity for ZnSe and CdS, respectively. For ZnSe, the temporal profile of the emission intensity does not follow the profile
of the excitation macropulse of the FEL, but sharply rises and decays only at the maximum of the macropulse profile. These
features are in marked contrast to those of a previous report, where the emission profile follows that of the macropulse,
and the emission intensity scales with the 4th power of the excitation intensity. The experimental observations were reproduced
by a numerical simulation based on impact ionization and avalanche ionization by electrons accelerated by the optical electric
field of the FEL. The large nonlinearity in the bandedge emission comes from the macropulse temporal structure, which consists
of micropulses densely spaced to allow excited carriers to survive when the next micropulse arrives. They work as seed carriers
in the next carrier multiplication step. 相似文献
143.
Shirakawa E Hironaka K Otsuka H Hayashi T 《Chemical communications (Cambridge, England)》2006,(37):3927-3929
The combination of hexamethyldisilane and a catalytic amount of [PdCl(eta3-C3H5)]2-PPh3 was found to be effective for the trimethylsilylation of alcohols, where both of the two trimethylsilyl groups of hexamethyldisilane were transferred to alcohols without coproduction of any stoichiometric amount of byproduct but H2. 相似文献
144.
145.
We report that hybridizing semiconductor quantum dots with plasmonic metamaterial leads to a multifold intensity increase and narrowing of their photoluminescence spectrum. The luminescence enhancement is a clear manifestation of the cavity quantum electrodynamics Purcell effect and can be controlled by the metamaterial's design. This observation is an essential step towards understanding loss compensation in plasmonic metamaterials with gain media and for developing metamaterial-enhanced gain media. 相似文献
146.
We show that quasi-Nambu-Goldstone (NG) modes, which play prominent roles in high energy physics but have been elusive experimentally, can be realized with atomic Bose-Einstein condensates. The quasi-NG modes emerge when the symmetry of a ground state is larger than that of the Hamiltonian. When they appear, the conventional vacuum manifold should be enlarged. Consequently, topological defects that are stable within the conventional vacuum manifold become unstable and decay by emitting the quasi-NG modes. Contrary to conventional wisdom, however, we show that the topological defects are stabilized by quantum fluctuations that make the quasi-NG modes massive, thereby suppressing their emission. 相似文献
147.
Kentaro?NagaharaEmail author Eiji?Yanagida 《Calculus of Variations and Partial Differential Equations》2018,57(3):80
This paper is concerned with a nonlinear optimization problem that naturally arises in population biology. We consider the effect of spatial heterogeneity on the total population of a biological species at a steady state, using a reaction–diffusion logistic model. Our objective is to maximize the total population when resources are distributed in the habitat to control the intrinsic growth rate, but the total amount of resources is limited. It is shown that under some conditions, any local maximizer must be of “bang–bang” type, which gives a partial answer to the conjecture addressed by Ding et al. (Nonlinear Anal Real World Appl 11(2):688–704, 2010). To this purpose, we compute the first and second variations of the total population. When the growth rate is not of bang–bang type, it is shown in some cases that the first variation becomes nonzero and hence the resource distribution is not a local maximizer. When the first variation becomes zero, we prove that the second variation is positive. These results implies that the bang–bang property is essential for the maximization of total population. 相似文献
148.
Eiji Onodera 《偏微分方程通讯》2013,38(6):1130-1144
We prove time-global existence of solutions to the initial value problem for a third order dispersive flow into compact locally Hermitian symmetric spaces. The equation under consideration generalizes two-sphere-valued completely integrable systems modeling the motion of vortex filament. Unlike one-dimensional Schrödinger maps, our third order equation is not completely integrable under the curvature condition on the target manifold in general. The idea of our proof is to exploit two conservation laws and an “almost conserved quantity” which prevents the formation of a singularity in finite time. 相似文献
149.
We report room-temperature broadband laser emission in the near-ultraviolet to the blue-green spectral range using color centers in MgO microcrystals. The lasing MgO microcrystals are obtained through a solid phase reaction between SiO and Mg at 450 degrees C in an argon atmosphere and are mostly composed of an accumulation of microcubes enclosed by [100] facets. The laser action was observed in the wavelength region from 350 to 600 nm without using cavity mirrors. In the present MgO microcrystals, some of the color centers will be stabilized at the interfaces and/or boundaries of the microcrystalline domains, probably explaining the stable laser action even at room temperature. 相似文献
150.
AbstractIn the enthalpy relaxation of poly(vinyl chloride), a decrease in enthalpy upon the isothermal ageing was measured using the differential scanning calorimetry method as a function of ageing time (tA) and ageing temperature. The range of the ageing temperature was from 56?°C (Tg ? 25?°C) to 72?°C (Tg ? 9?°C) where Tg denotes the glass transition temperature. The limiting value of the decrease in enthalpy was determined by applying a stretched exponential function to the measured enthalpy data. The relaxation function (?) was derived from the measured enthalpy and the construction of a master curve was tried by shifting the ? ? tA curves of the respective ageing temperatures horizontally. Although there was no agreement between the shift factors (aT) and the relaxation times of the ? ? tA curves, the superposition was successfully constructed and the aT values obtained for the poly(vinyl chloride) sample were found to be comparable to those reported for viscoelastic experiments over a broad temperature range above and below Tg carried out for different polymers. The origin of the decrease in enthalpy was briefly discussed in terms of the chain dynamics in the isothermal condition. 相似文献