VADERMONDE-TYPE ODD-SOLITON SOLUTIONS FOR THE WHITHAM–BROER–KAUP MODEL IN THE SHALLOW WATER SMALL-AMPLITUDE REGIME

Under investigation in this paper, with symbolic computation, is the Whitham–Broer–Kaup (WBK) system for the dispersive long waves in the shallow water small-amplitude regime. N-fold Darboux transformation (DT) for a spectral problem associated with the WBK system is constructed. Odd-soliton solutions in terms of the Vandermonde-like determinant for the WBK system are presented via the N-fold DT and evolution of the three-soliton solutions is graphically studied. Our results could be used to illustrate the bidirectional propagation of the waves in the shallow water small-amplitude regime.     

QUANTITATIVE MEASUREMENT OF THE ULTRASONIC STRESSES IN A TRANSPARENT SOLID BY THE PHOTOELASTIC METHOD

A photoelastic method for the measurement of the difference between principal stresses is extendedto the measurement of a two dimensional ultrasonic stress.The stress of an ultrasonic plane pro-gressive wave or cylindrical progressive wave at any point in a transparent solid can be determined. The method of the measurement and its principle is presented,including the derivation of therelation between the principal stresses difference and the principal stresses for plane or cvlindricalprogressive wave.A practical example of measurement is described,its results being compared withthose of an electrical method.     

EXACT SOLUTIONS OF THE MODIFIED GROSS–PITAEVSKII EQUATION IN "SMART" PERIODIC POTENTIALS IN THE PRESENCE OF EXTERNAL SOURCE

We report wide class of exact solutions of the modified Gross–Pitaevskii equation (GPE) in "smart" Jacobian elliptic potentials, in the presence of external source. Solitonlike solutions, singular solutions, and periodic solutions are found using a recently developed fractional transform in which all the amplitude parameters are nonzero. These results generalize those contained in (T. Paul, K. Richter and P. Schlagheck, Phys. Rev. Lett. 94 (2005) 020404.) for nonzero trapping potential.     

ACOUSTICAL NEWS ADDITIONAL ACOUSTICAL EVENTS IN THE YEAR1989:

M菹rz 13—1 6,1989,Duisburg FGR DAGA’89一alle Gebiete der Akustik—— Am Nachmittag des 13.M百rZ wird ein K0110—— quium mit der Thema“Sonographie”veranstaltet. Anmeldungen an:Prof.Dr.J.Herbetz Ultraschalltechnik Universit~it.GH Duisburg Postfach 10 16 29 4loo Duisburg 1 April 3——5,University of Liverpool U.K. Modem Practice in Stress and Vibration Analysis Contact for further information: The Meetings Officer The Institute of Physics 47 Belgrave Square London SWIX 80…     

A STATUS REPORT OF ISOLAN ——THE ON-LINE ISOTOPE SEPARATOR IN LANZHOU

A new ISOLAN facility has been constructed for on-line use with the heavy ion accelerator HIRFL in Lanzhou.The beam optical principle of an earlier ISOLDE type separator is modified by including a quadrupole doublet lens in front of the magnet.The mass spectra of Ar and Xe isotopes were measured with a scanner inside the collection chamber for an offline test.The resolution power is equal to 700—1200 by only using a single einzel lens.     

THE REFLECTION AND REFRACTION OF A LARGE AMPLITUDE PLANE SOUND WAVE IN TWO DIMENSIONS

By using the successive approximation method,a wave equation,in which the second order ofapproximation is taken into account,has been derived from the basic equations of hydrodynamicsin Lagrangian coordinates.The reflection and refraction of a large amplitude plane sound waveon the plane interface of two non-mixing liquids are studied.It is interesting to point out that thereflection and refraction coefficients of second approximation not only depend on parameters ofmedia,but also relate to the position of sound source.It is found that the amplitudes of the secondorder reflected wave and refracted wave do not keep constant at the wavefront anymore as inlinear acoustics.Hence there are reflected wave and refracted wave which propagate in the directionother than that of waves,travelling along the directions defined by laws of reflection and refractionin linear acoustics.The nonlinear effects have to be taken into account in order to understand thephysical meaning of the results reported by Muir et al..     

THE EFFFECTS OF THE QUANTITY OF SUSPENDNDED DIFFUSERS AND SPECIMEN AREA ON THE TEST RESULTS FOR SOUND ABSORPTION COEFFICIENT IN A SMALL REVERBERATION CHAMBER

The diffusivity of the sound field in a reverberation chamber,which can be improved by dif-fusing elements hanging from the ceiling of the room,usually has a significant effect on the test resultsof sound absorption measurement.We have found that the diffusivity is sufficent when the totalarea of suspended diffusers reaches 60—70% of the floor area in a small chamber,say about 100 m~3.But for some acoustical materials such as perforated fiber tile,we have found the sound absorptioncoefficients are considerably independent on diffusivity.It can be concluded that the acoustical propertyof such material varies little for different angles of incident wave,hence they are not be suitable in usefor the determination of the diffusion improvement of sound field. Test results of many commonly used acoustical materials show that when test specimenarea changesfrom 10m~2 to 6m~2,provided that the ratio of length to width is controlled between 0.7 and 1.0,thedeviation of the sound absorption coefficient obtained is r     

COHERENT POPULATION TRAPPING IN THE SYSTEM OF A Λ-CONFIGURATION MULTILEVEL ATOM DRIVEN BY A TWO-MODE QUANTIZED FIELD

We have studied the atomic coherent population trapping in the system of a two-mode quantized field interacting with a Λ-configuration multilevel atom with one lower discrete state mad two sets of quasicontinuum states, or a set of quasicontinuum states and a set of true continuum states. The influence of the atom's initial preparation and the properties of the atomic upper levels on whether or not atomic coherent population trapping occurs, and the states of the field which trap the atom are analyzed.     

ORBITAL LINEARIZATION IN THE QUADRATIC LOTKA–VOLTERRA SYSTEMS AROUND SINGULAR POINTS VIA LIE SYMMETRIES

In this paper, we consider linearizability and orbital linearizability properties of the Lotka–Volterra system in the neighborhood of a singular point with eigenvalues 1 and -q. In this paper we give the explicit smooth near-identity change of variables that linearizes or orbital linearizes such Lotka–Volterra system with q ∈ ?{0, 1} being seen that these changes are also valid for q ∈ ?{0, 1}.     

PRELIMINARY RESULTS ON THE PREDICTION OF SHIP PROPELLER CAVITATION NOISE POWER SPECTRA FROM THE MEASUREMENT OF ITS MODEL IN A CAVITATION TUNNEL

Propeller cavitation noise spectra were measured in the cavitation tunnel of Shanghai JiaotongUniversity as well as in actual ship.Formulae of prediction for prototype propeller cavitation noisespectra in a ship are derived on the basis of energy relations.The formula with correction of aircontent of bubble gives more accurate results.     

TODA–HEISENBERG CHAIN: INTERACTING σ-FIELDS IN TWO DIMENSIONS

We study a (2 + 1)-dimensional system that can be viewed as an infinite number of O(3) σ-fields coupled by a nearest-neighbour Heisenberg-like interaction. We reduce the field equations of this model to an integrable system that is closely related to the two-dimensional relativistic Toda chain and the Ablowitz–Ladik equations. Using this reduction we obtain the dark-soliton solutions of our model.     

A STUDY ON THE ULTRASONIC VELOCITY AND ATTENU-ATION IN NdFeB MAGNET WITHIN THE TEMPERATURE RANGE OF 80 - 300K (Ⅱ)

Based on the ultrasonic measurements of an isotropic NdFeB magnet in the temperature range of 77 -300 K, it was found that the elastic parameters, such as Young's modulus E, and Poisson ratio v, change abruptly near the spin reorientation temperature T_sr. This indicates that soft mode emerges in the process of spin reorientation. Thermal hysteresis was observed during heating-up and cooling-down processes. Both Debye temperature and heat capacity were calculated, which suggests that the magnetic entropy of the Nd-sublattice is larger in easy-cone state than in easy-axis state.     

A STUDY ON THE ULTRASONIC VELOCITY AND ATTENU-ATION IN NdFeB MAGNET WITHIN THE TEMPERATURE RANGE OF 80 - 300K (Ⅱ)

Based on the ultrasonic measurements of an isotropic NdFeB magnet in the temperature range of 77 - 300 K, it was found that the elastic parameters, such as Young's modulus E, and Poisson ratio v, change abruptly near the spin reorientation temperature Tsr. This indicates that soft mode emerges in the process of spin reorientation. Thermal hysteresis was observed during heating-up and cooling-down processes. Both Debye temperature and heat capacity were calculated, which suggests that the magnetic entropy of the Nd-sublattice is larger in easy-cone state than in easy-axis state.     

HOW TO DETERMINE THE NUCLEAR MATRIX ELEMENT IN 2β-Decay?-A DISCUSSION OF PCAC, 2β-DECAY AND DOUBLE-CHARGE EXCHANGE REACTION OF PIONS ON NUCLEI

It is shown that by applying PCAC, the 2β-decay process can be directly related to double-charge-exchange reaction. Therefore, by studying double-charge-exchange reactions one is able to determine the nuclear matrix element of the relevant 2β-decay experimentally. A preliminary analysis has indicated that if the experimental data of forward-angle cross section on Ca⁴⁰ with pion beam at 164 Mev^[9] are used and extrapolated to Ca⁴⁸, then the squared nuclear matrix element thus determined is smaller than that calculated for Ca⁴⁰→Ti⁴⁸+2e^-+2v^[11] by 10⁵～10⁶.     

The Boltzmann–Langevin approach: A simple quantum-mechanical derivation

We present a simple quantum-mechanical derivation of correlation function of Langevin sources in the semiclassical Boltzmann–Langevin equation. The specific case of electron–phonon scattering is considered. It is shown that the assumption of weak scattering leads to the Poisson nature of the scattering fluxes.     

Covariance-driven subspace identification: A complete input–output approach

In most of the available input–output covariance-driven subspace identification approaches the knowledge of the input is exploited for eigenstructure identification only. In the authors' opinion a complete input–output identification method should also cater for the estimation of the input matrix B and the direct feedthrough matrix D of the state-space model.     

Coupled disease–behavior dynamics on complex networks: A review

It is increasingly recognized that a key component of successful infection control efforts is understanding the complex, two-way interaction between disease dynamics and human behavioral and social dynamics. Human behavior such as contact precautions and social distancing clearly influence disease prevalence, but disease prevalence can in turn alter human behavior, forming a coupled, nonlinear system. Moreover, in many cases, the spatial structure of the population cannot be ignored, such that social and behavioral processes and/or transmission of infection must be represented with complex networks. Research on studying coupled disease–behavior dynamics in complex networks in particular is growing rapidly, and frequently makes use of analysis methods and concepts from statistical physics. Here, we review some of the growing literature in this area. We contrast network-based approaches to homogeneous-mixing approaches, point out how their predictions differ, and describe the rich and often surprising behavior of disease–behavior dynamics on complex networks, and compare them to processes in statistical physics. We discuss how these models can capture the dynamics that characterize many real-world scenarios, thereby suggesting ways that policy makers can better design effective prevention strategies. We also describe the growing sources of digital data that are facilitating research in this area. Finally, we suggest pitfalls which might be faced by researchers in the field, and we suggest several ways in which the field could move forward in the coming years.     

Photon condensation: A new paradigm for Bose–Einstein condensation

Bose–Einstein condensation is a state of matter known to be responsible for peculiar properties exhibited by superfluid Helium-4 and superconductors. Bose–Einstein condensate (BEC) in its pure form is realizable with alkali atoms under ultra-cold temperatures. In this paper, we review the experimental scheme that demonstrates the atomic Bose–Einstein condensate. We also elaborate on the theoretical framework for atomic Bose–Einstein condensation, which includes statistical mechanics and the Gross–Pitaevskii equation. As an extension, we discuss Bose–Einstein condensation of photons realized in a fluorescent dye filled optical microcavity. We analyze this phenomenon based on the generalized Planck’s law in statistical mechanics. Further, a comparison is made between photon condensate and laser. We describe how photon condensate may be a possible alternative for lasers since it does not require an energy consuming population inversion process.