共查询到20条相似文献,搜索用时 15 毫秒
1.
John McLaughlin 《Journal of statistical physics》1976,15(4):307-326
A model of interacting normal modes in a nonlinear, dissipative system is constructed in order to analyze speculations by Ruelle and Takens. The first bifurcation leads to a periodic state. The second bifurcation leads to phaselocking, if the first mode is sufficiently energetic. A third bifurcation leads to stochastic behavior. Possible relevance of these phenomena for physical systems is discussed. 相似文献
2.
The non-singlet structure functions have been obtained by solving Dokshitzer, Gribove, Lipatov, Alterelli, Parisi (DGLAP) evolution equations in leading order (LO) and next to leading order (NLO) at the small x limit. Here a Taylor Series expansion has been used and then the method of characteristics has been used to solve the evolution equations. We have also calculated t and x-evolutions of deuteron structure function and the results are compared with the New Muon Collaboration (NMC) and E665 data. 相似文献
3.
4.
Highly collimated, plasma-filled magnetic-flux tubes are frequently observed on galactic, stellar, and laboratory scales. We propose that a single, universal magnetohydrodynamic pumping process explains why such collimated, plasma-filled magnetic-flux tubes are ubiquitous. Experimental evidence from carefully diagnosed laboratory simulations of astrophysical jets confirms this assertion and is reported here. The magnetohydrodynamic process pumps plasma into a magnetic-flux tube and the stagnation of the resulting flow causes this flux tube to become collimated. 相似文献
5.
Parvathi Krishnakumar 《Molecular physics》2017,115(24):3224-3233
The effect of microhydration on the simplest dicarboxylic acid, namely oxalic acid, leading to the dissociation of its proton, is studied using first principle-based electronic structure calculations. The geometry of the hydrated clusters of oxalic acid considering up to seven water molecules is determined at ωB97X-D/aug-cc-pVDZ level of theory. Solvent stabilisation and interaction energy parameters are calculated applying CCSD(T) level of theory. The calculated free energy of formation shows that the hydrated oxalic acid clusters are stable only at low temperature and pressure. Though the solvent stabilisation energy increases linearly with an increase in the size of the hydrated cluster, the calculated interaction energy, acidic O–H bond dipole moment and hydrogen bond energy show characteristic features of ion pair formation. The spectral manifestation of the weakening hydroxyl bond is observed as red shift in its stretching frequency. A rigid potential energy scan, altering the dissociating O–H bond length of the oxalic acid molecule, shows an energy barrier for acid to water proton transfer in all cases except hepta-hydrate of oxalic acid, where a barrier-less proton transfer occurs. The number of water molecules (n) needed for dissociation of oxalic acid molecule is consistent with the value obtained from recently reported emperical correlation between n and pKa. 相似文献
6.
From fractional Fourier transformation to quantum mechanical fractional squeezing transformation
下载免费PDF全文

By converting the triangular functions in the integration kernel of the fractional Fourier transformation to the hyperbolic function,i.e.,tan α→ tanh α,sin α→ sinh α,we find the quantum mechanical fractional squeezing transformation(FrST) which satisfies additivity.By virtue of the integration technique within the ordered product of operators(IWOP) we derive the unitary operator responsible for the FrST,which is composite and is made of e~(iπa~+a/2) and exp[iα/2(a~2 +a~(+2)).The FrST may be implemented in combinations of quadratic nonlinear crystals with different phase mismatches. 相似文献
7.
J O Newton 《Pramana》1989,33(1):175-208
An introduction is given to the physics of the equilibrium transition-state model and of dissipative nuclear dynamics. Experimental
data on pre-scission particle and gamma-ray emission and their interpretation are reviewed. They appear to indicate overdamped
motion of the nuclear fluid. A time scale for compound-nucleus fission of about 30 × 10−21 s or greater is indicated, whilst that for quasi- or fast-fission is somewhat shorter. 相似文献
8.
This paper considers the newly discovered laws on reflection and refraction reported in 2005 by the author. A brief review of the said discovery has been made. To give the discovery a concrete foundation and to show the efficiency of the photon theory, theoretical proof of each of those discovered laws on reflection and refraction has been offered making use of the photon theory and on further application of the principle of conservation of momentum. 相似文献
9.
G.D. Roston Z.F. Ghatass 《Journal of Quantitative Spectroscopy & Radiative Transfer》2009,110(3):175-183
The classical theory of collisional broadening and shift parameters (β, δ) of an isolated spectral line was used to obtain simple analytical formulas for calculating both β and δ. These formulas were obtained on the assumption that the short range interaction is effective only in the broadening while the long range is effective in the shift of the spectral line. These parameters β and δ depend on the limiting phase shifts responsible for broadening ηb and shift ηδ. It was found that the values of ηb and ηδ are not equal to each other as was proposed by Weisskopf ηb=ηδ=1. The maximum and average values of ηb (ηb max, ηb av) and ηδ (ηδ max, ηδ av) were obtained by numerical evaluation, using different inverse power potentials. By introducing these parameters into the approximated formulas for β and δ using Van der Waals and Lennard-Jones potential, it was found that the results of calculations for (β and δ) with different atomic transitions perturbed by different inert gases are in close agreement with earlier results. Those results, obtained earlier, were based on the Lindholm-Foley theory especially with the average values of ηb [ηb av=0.6057] and the maximum values of ηδ [ηδ max=1.57625]. The impact parameters ρb and ρδ leading to the broadening and shift of the spectral line were also obtained for different interactions. It was found that the end parameter for the broadening ρb is not equal to the starting parameter for the shift ρδ. 相似文献
10.
The phase transition of metavariscite into berlinite has been studied by means of different techniques, namely electron probe micro analysis, environmental scanning electron microscopy, high-temperature X-ray diffraction, differential thermal analysis, thermogravimetry, thermoluminescence, and thermo Raman. The application of these techniques indicates that: (i) from room temperature to 150°C metavariscite (monoclinic dimorph AlPO4 ? 2H2O) appears as the main phase, (ii) in the range of 100–300°C metavariscite starts to lose the water molecules giving rise to form α-berlinite (trigonal AlPO4) that is the stable phase up to ca 540°C, and (iii) from 550°C onwards the structure adopts the more stable configuration, tetragonal β-berlinite. 相似文献
11.
A. Desaix O. Roubeau J. Jeftic J.G. Haasnoot K. Boukheddaden E. Codjovi J. Linarès M. Noguès F. Varret 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(2):183-193
We investigate the behaviour of photo-excitable, bistable systems, under permanent light irradiation, in presence of relaxation
towards the non-excited state. Cooperativity causes bistability of the steady state, leading to light-induced thermal and
optical hysteresis (LITH and LIOH). The light-induced instability is expected to induce demixtion, i.e. the coexistence of domains of the two stable steady states. Such effects are evidenced by magnetic and reflectivity measurements
on the spin-crossover solid solution: , with x= 0.3, 0.5, 0.85. Experimental data are in quantitative agreement with a simple macroscopic model which includes a non-linear
relaxation term in the master equation.
Received: 5 June 1997 / Accepted: 17 July 1998 相似文献
12.
由于金属离子包括铜离子对人体的重要性,报道了一种含单个色氨酸的新型多肽分子(WDAHSS),证明利用这种分子可以通过荧光光谱测量的方法实现铜离子灵敏检测。WDAHSS的荧光由其包含的色氨酸残基的本征荧光贡献,易被铜离子猝灭。通过分析铜离子在不同pH值条件下与WDAHSS作用的荧光光谱并与单个色氨酸分子的光谱相比较,详细研究了铜离子猝灭WDAHSS荧光的机理。研究表明,WDAHSS结构中的组氨酸通过金属配位与铜离子作用,并联合肽键形成稳固的四方形平面结构,螯合铜离子,致使色氨酸残基发生荧光猝灭。同时详细讨论了不同pH值环境对WDAHSS荧光光谱的影响。通过荧光光谱测量和数值拟合,推测了WDAHSS和铜离子的结合常数。为了增强WDAHSS抗pH干扰的能力,特意对其氨基端乙酰化,在生理pH值范围内稳定了其荧光发射。此外,WDAHSS也采用了一些特殊设计的结构,很好地增强了它对铜离子灵敏探测的特异选择性和生物相容性。对WDAHSS的进一步研究有望用于生物体内或细胞内荧光成像检测。 相似文献
13.
M. Veselsky 《Physics of Atomic Nuclei》2003,66(6):1086-1094
The mechanism of fusion hindrance, an effect observed in the reactions of cold, warm, and hot fusion leading to production of superheavy elements, is investigated. A systematics of transfermium production cross sections is used to determine fusion probabilities. The mechanism of fusion hindrance is described as a competition of fusion and quasifission. Available evaporation residue cross sections in the superheavy region are reproduced satisfactorily. Analysis of the measured capture cross sections is performed and a sudden disappearance of the capture cross sections is observed at low fusion probabilities. A dependence of the fusion hindrance on the asymmetry of the projectile-target system is investigated using the available data. The most promising pathways for further experiments are suggested. 相似文献
14.
U. A. Wiedemann 《The European Physical Journal C - Particles and Fields》2005,43(1-4):215-222
In nucleus-nucleus collisions at the Relativistic Heavy Ion Collider (RHIC), one generically observes a strong medium-induced suppression of high- pT hadron production. This suppression is accounted for in models which assume a significant medium-induced radiative energy loss of high- pT parent partons produced in the collision. How can we further test the microscopic dynamics conjectured to underlie this abundant high- pT phenomenon? What can we learn about the dynamics of parton fragmentation, and what can we learn about the properties of the medium which modifies it? Given that inelastic parton scattering is expected to be the dominant source of partonic equilibration processes, can we use hard processes as an experimentally well-controlled window into QCD non-equilibrium dynamics? Here I review what has been achieved so far, and which novel opportunities open up with higher luminosity at RHIC, and with the wider kinematical range accessible soon at the LHC.Received: 15 February 2005, Published online: 3 June 2005PACS:
12.38.Mh, 24.85. + p 相似文献
15.
We report an experimental study of the secondary modulational instability of a one-dimensional nonlinear traveling wave in a long bounded channel. Two qualitatively different instability regimes involving fronts of spatiotemporal defects are linked to the convective and absolute nature of the instability. Both transitions appear to be subcritical. The spatiotemporal defects control the global mode structure. 相似文献
16.
The behavior of rank-ordered distributions of phenomena present in a variety of fields such as biology, sociology, linguistics, finance and geophysics has been a matter of intense research. Often power laws have been encountered; however, their validity tends to hold mainly for an intermediate range of rank values. In a recent publication (Martínez-Mekler et al., 2009 [7]), a generalization of the functional form of the beta distribution has been shown to give excellent fits for many systems of very diverse nature, valid for the whole range of rank values, regardless of whether or not a power law behavior has been previously suggested. Here we give some insight on the significance of the two free parameters which appear as exponents in the functional form, by looking into discrete probabilistic branching processes with conflicting dynamics. We analyze a variety of realizations of these so-called expansion-modification models first introduced by Wentian Li (1989) [10]. We focus our attention on an order-disorder transition we encounter as we vary the modification probability p. We characterize this transition by means of the fitting parameters. Our numerical studies show that one of the fitting exponents is related to the presence of long-range correlations exhibited by power spectrum scale invariance, while the other registers the effect of disordering elements leading to a breakdown of these properties. In the absence of long-range correlations, this parameter is sensitive to the occurrence of unlikely events. We also introduce an approximate calculation scheme that relates this dynamics to multinomial multiplicative processes. A better understanding through these models of the meaning of the generalized beta-fitting exponents may contribute to their potential for identifying and characterizing universality classes. 相似文献
17.
This paper deals with the application of Huygens’ wave theory of light for the derivation of the generalized vectorial laws of reflection and refraction discovered by the author in 2005. The long-running literature falls short of such a theoretical proof of the generalized vectorial laws of reflection and refraction on the basis of wave theory. As such the present work is novel and original. At the same time it also enhances the theoretical foundation of the discovery of the generalized vectorial laws of reflection and refraction there by proving the efficiency and increasing the range of applicability of the wave theory of light as well. 相似文献
18.
Inomoto M Gerhardt SP Yamada M Ji H Belova E Kuritsyn A Ren Y 《Physical review letters》2006,97(13):135002
The coupling between the global reconnection geometry and the local microphysics, caused by the Hall effect, is studied during counterhelicity plasma merging in the magnetic reconnection experiment. The structure of the reconnection layer is significantly modified by reversing the sign of the toroidal fields, which affects the manifestation of the Hall effect in the collisionless regime. The local two-fluids physics changes the global boundary conditions, and this combination effect consequently provides different reconnection rates, magnetic field structure, and plasma flow patterns for two different counterhelicity merging cases in the collisionless regime. 相似文献
19.
On the mechanism of heavy ion collision leading to a compound system and to deep inelastic reactions
A model is presented that describes the dynamics of heavy ion collisions leading into the compound system. By indluding an anisotropic friction and using folding potentials it is able to reproduce most of the data on the compound formation cross-section. In addition. In addition the qualitative features of deep inealastic direct reaction appears in a natural way. 相似文献
20.
In medical ultrasound imaging, the desired lateral field distribution at each focal distance can be obtained by optimal apodization. On the other hand, the lateral field is a function of focal distance. Hence, finding the optimal apodization is a very arduous process. To overcome this, we have introduced a suboptimal method by which optimal apodization can be calculated in any distance through a nonlinear transformation by the knowledge of the optimal one at a distance. This transformation is established on a fact that the lateral field distribution at focal distance can be expressed as the Fourier transform of a nonlinear function of the aperture weighting, instead of direct expression as the Fourier transform of the above. We have applied this method to map the apodization which obtains the desired beam pattern into the apodization which maintains the same properties on the lateral field distribution. For example, applying this method on a 50-elements λ/2 spaced linear array with length D has resulted in apodization that is optimal at distances D or D/2 by precision better than 9%. This method is useful especially in optimization problems, having no explicit constraint on the main lobe width, such as minimizing the sidelobe levels or minimizing main lobe width constrained to a predetermined value of sidelobe level. However, as the results show, this technique provides acceptable results in other cases. 相似文献