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181.
The stability of an encapsulated bubble filled with gas is studied where gas is allowed to diffuse out of the bubble. A mechanistic model that takes into account shell stiffness and surface tension is considered. A critical shell radius for loss of mechanical stability is derived based on a technique adapted for small radius, where surface tension effects become substantial. A new parameter is defined that determines the relative importance of surface tension forces and shell stiffness for shell stability. The developed technique allows to predict, for a given bubble population and gas saturation level of the surrounding liquid, a range of bubble sizes which may collapse in time. Surface tension effects are dominant in determining the critical radius but have a negligible effect on the minimal radius for collapse. The influence of the surface tension on the stability of the shell is illustrated for Optison, a typical ultrasound contrast agent. 相似文献
182.
Møller’s energy-momentum complex is employed in order to determine the energy and momentum distributions for a spacetime described by a “generalized Schwarzschild” geometry in (3+1)-dimensions on a noncommutative curved D3-brane in an effective, open bosonic string theory. The geometry considered is obtained by an effective theory of gravity coupled with a nonlinear electromagnetic field and depends only on the generalized (effective) mass and charge which incorporate corrections of first order in the noncommutativity parameter. 相似文献
183.
Koji Hashimoto 《Applied Surface Science》2011,257(19):8141-8150
Amorphous alloys have many attractive characteristics including extremely high corrosion resistance if the sufficient amounts of corrosion-resistant elements are added. The superiority of amorphous alloys is based on the homogeneous single phase nature without any chemical and physical heterogeneities. Although there are processing limitations to avoid the formation of heterogeneous crystalline structure in addition to no welding technology without crystallization, the application of corrosion-resistant amorphous alloys is expected particularly to the very aggressive environments, where any conventional crystalline metallic materials cannot be used. Some amorphous bulk alloys showed zero corrosion mass loss due to spontaneous passivation even in 12 M HCl. Production of amorphous bulk alloys became possible for selected compositions. The homogeneous single phase nature is also effective to form useful catalysts with unique composition and structure. An example of catalysts is for carbon dioxide methanation useful for supply of renewable energy in the form of methane. 相似文献
184.
Three-dimensional (3-D) ZnO random-wall nanostructures and one-dimensional (1-D) ZnO nanorods were prepared on silicon substrates by a simple solid-vapour phase thermal sublimation technique. Optical pumped random lasing has been observed in the ZnO random-wall arrays with a threshold intensity of 0.38 MW/cm2 in the emission wavelength from 380 to 395 nm. The optical gain was attributed to the closed-loop scattering and light amplification of the ZnO random-wall. The experimental result suggests that the morphology of nanostructure is the key factor to effect random lasing. 相似文献
185.
186.
X. N. Song D. G. Seiler M. R. Loloee 《Applied Physics A: Materials Science & Processing》1989,48(2):137-141
Both nonlinear oscillations and chaotic behavior in n-InSb are experimentally investigated for the case of impact ionization of shallow donors at low temperatures. Complex behavior including a simple periodic oscillation, a period-doubling route to chaos, and quasiperiodic behavior are observed with increasing electric field as the parameter. For the first time, a type of pitchfork bifurcation (period halving) is seen. 相似文献
187.
J. Hebling J. Klebniczki P. Heszler Zs. Bor B. Rácz 《Applied physics. B, Lasers and optics》1989,48(5):401-403
A new experimental realisation of the travelling-wave amplified spontaneous emission (TWASE) is described utilising a prismatic arrangement to get the pulse front delay in the pump beam. Rhodamine dye solutions were pumped by the amplified 25 ps long 555 nm pulses of a distributed feedback dye laser. The pulse shortening in the TWASE resulted in 12 ps output pulses with 18% energy efficiency. The observed spectrum showed numerous lines, and it contained the amplified Raman line of the pump beam. Several spots were found in the far-field zone of the generated TWASE. 相似文献
188.
Martin Schlichenmaier 《Letters in Mathematical Physics》1990,19(2):151-165
Krichever-Novikov algebras of meromorphic vector fields with more than two poles on higher genus Riemann surfaces are introduced. The structure of these algebras and their induced modules of forms of weight is studied. 相似文献
189.
Kazimierz Bragiel 《Letters in Mathematical Physics》1990,20(3):251-257
It is proved that C(S
U(N)) is a type I C
*-algebra. 相似文献
190.
I set forth and discuss I.I. Rabis views on the nature of science and society, focusing specifically on Rabis views on science and government, science and education, and science and religion. I also explore the influence of Rabi and C.P. Snow on each other. In the 1960s, Rabi set forth his mature and boldest positions, advocating science as the center of education and science as the replacement for religion. His positions culminate in science as the universal culture. I highlight Rabi not only as a scientist and public servant, but also as a public intellectual actively engaged with and connected to major issues of his time.Michael A. Day is Professor of Physics at Lebanon Valley College. He holds doctorates in both physics and philosophy. 相似文献