International Journal of Modern Physics B

Kenneth Wilson's Nobel Prize winning breakthrough in the renormalization group theory of phase transition and critical phenomena almost overlapped with the violent "cultural revolution" years (1966–1976) in China. An unexpected chance in 1972 brought the author of these lines close to the Wilson–Fisher ϵ-expansion of critical exponents and eventually led to a joint paper with Lu Yu published entirely in Chinese without any English title and abstract. Even the original acknowledgment was deleted because of mentioning foreign names like Kenneth Wilson and Kerson Huang. In this article I will tell the 40-year old story as a much belated tribute to Kenneth Wilson and to reproduce the essence of our work in English. At the end, I give an elementary derivation of the Callan–Symanzik equation without referring to field theory.

In this study, we propose a configuration of partially blocked oxidant channel with baffle plate(s) transversely inserted in the cathode channel and their effect on the oxygen transport and fuel cell performance is investigated. In order to investigate the effects of the selected shape, size and the number of baffles on the oxygen transport in the gas diffusion layer (GDL) and fuel cell performance a numerical modeling is carried out in 27 cases. With the consideration of both maximum oxygen concentration in the GDL and reasonable pressure drop criterions, the results indicate that in all cases, an increase in baffle height is more effective than an increase in number of baffle plates. Also, installing many large rectangular baffles seem quite appropriate, but when there is restriction in securing pressure in fuel cell, installing the semicircle baffle is better than the rectangular one.

The electron doped rare earth copper oxide superconductors R_2-xCe_xCuO₄ exhibit anomalous heavy fermion behavior at low temperature with large Sommerfeld specific heat coefficient which is different from the conventional heavy fermion systems. The system is described by a model Hamiltonian consisting of staggered magnetic field in the two sub-lattices of the copper sites in presence of hybridization between the localized 4f electrons of Nd atom and the conduction electrons as well as the f-electron kinetic energy term. The Hamiltonian is solved by Zubarev's Green's function technique and the sub-lattice magnetization is calculated and solved self-consistently. The entropy and specific heat are calculated from the free energy of the system. The temperature dependent entropy and specific heat are numerically evaluated by successive differentiations of sub-lattice magnetization and temperature dependent entropy. It is observed that when the position of the f-level of Nd atom is of the order of hybridization strength, the sub-lattice magnetization is destroyed drastically at lower temperatures. As a result, the specific heat exhibits a large enhancement at low temperatures suggesting the enhancement of the electron density of states and the effective mass of the itinerant electrons exhibiting the heavy fermion character. Similarly, the specific heat shows anomalously sharp jump near the Néel temperature.

As traffic phenomena can be explained by physical method, this interdisciplinary domain has attracted many physicists to explore. The primary object of this research is to reveal the physical characteristics of heterogeneous nonmotorized vehicle traffic composing of conventional bicycles and electric bicycles. Cellular automaton (CA) model is an effective method to reveal the characteristics of the traffic, so a new CA model is proposed to simulate the flow characteristics, overtaking maneuvers patterns and segregation effect in the heterogeneous traffic. In order to realistically describe the traffic characteristics, the new model incorporates the honk effect, performance variance and erratic riding behavior of the nonmotorized vehicles. The simulations achieve three conclusions. First, increasing the ratio of electric bicycles can obtain higher flow and increase the number of overtaking maneuvers. Second, the honk can influence the density-flow diagram and stir up more overtaking maneuvers in the intermediate density region. Third, the existence of segregation effect which means conventional bicycles and electric bicycles could respectively gather together to form clusters is verified and elucidated in the heterogeneous traffic.

A theoretical model is presented for the frequency response of magnetoelectric (ME) effect in the magnetostrictive-piezoelectric (MS-PE) disk–ring composite structures with the PE ring polarized radially. Based on the governing equations of materials and elastodynamic equations of continuum media, the expressions of the ME voltage coefficients for the axial and vertical mode are derived in terms of materials parameters and geometry dimensions. Estimated ME voltage coefficient versus frequency profiles predict a giant ME effect at the electromechanical resonance (EMR) with strong interfacial mechanical coupling. It is shown that increased effective length due to radial polarization instead of thickness polarization of PE-ring is responsible for the improved ME effect in the radially polarized disk–ring structure. The dependences of low-frequency ME effect, resonance frequency and resonance ME effect on geometry dimensions are predicted by our model. Some of the theoretical results are compared with the experimental results, showing good coincidence. It is suggested that proper resonance frequency and better ME effect in the disk–ring structure can be obtained by selecting appropriate materials, optimizing polarization direction and varying its geometry dimensions, which is of interest for the potential application of ME composites in novel multifunctional devices, such as sensors, transducers and memories.

Indium Oxide quasi one-dimensional (1D) nanostructures known as nanowires and nanorods synthesis using the thermal evaporation method, has been articulated. To nucleate growth sites, substrate seeding promoted 1D nanostructures growth. The catalyst-mediated growth mechanism showed more favorable morphologies and physical properties in under vacuum conditions associated with bottom-up technique. Scanning electron microscopy (SEM) results showed that the Zn-doped 1D nanostructures had spherical caps. The X-ray diffraction (XRD) pattern and energy-dispersive X-ray (EDX) spectrum indicated that these caps intensively associated with ZnO. Therefore, it was reasonable that the vapor–liquid–solid mechanism (VLS) was responsible for the growth of the In₂O₃-ZnO heterostructure nanowires. This technique enhances optical and electrical properties in nanostructures. The photoluminescence (PL) analysis in Zn-doped In₂O₃ nanowires and nanorods shows that the intensity of the visible and UV-region emissions overwhelmingly increases and resistance measurement professes the improvement of linear conductance in VLS growth mechanism.

A synthetic process for the formation of Zr_xY_1-xO_y nanostructures is demonstrated by the reaction of yttrium nitrate hexahydrate with zirconium propoxide. The reactions are carried out at temperature 60°C and pressure 0.1 MPa. The energy dispersive X-ray (EDX) spectroscopy measurements confirm formation of Zr_xY_1-xO_y nanostructures and the presence of carbonate and hydroxide species which are removed after high temperature anneals. It was found that the oxygen pressure during synthesis plays a determinant role on the structural properties of the nanostructure. This effect is further studied by atomic force microscopy (AFM) measurements and scanning electron microscope (SEM), which showed the formation of an isotopically organized structure. X-ray diffraction (XRD) measurement reveals that these changes in the nanostructural efficiency are associated with structural and compositional changes among the substrate. The dielectric constant as measured by the capacitance–voltage (C–V) technique is estimated to be around 39.05. C–V measurements taken at 1 MHz show the maximum capacitance for the Zr_0.05Y_0.95O_y film. The leakage current densities were below 10^-5 A/cm² for the Zr_0.05Y_0.95O_y film.

The effects of time delay on the vibrational resonance (VR) in a discrete neuron system with a low-frequency signal and a high-frequency signal are investigated by numerical simulations. The results show that there exists a delay time that optimizes the phase synchronization between the low-frequency input signal and the output signal. VR is induced by the time delay. Furthermore, the time delay can improve the response to a low-frequency input signal. Therefore, the time delay plays a constructive role in the transmission of a low-frequency signal by inducing and enhancing VR.

We report on the theoretical analysis of locally resonant sonic band gaps (BGs) in a phononic crystal (PC) structure constituted by a square array of inclined cylindrical dots deposited on a thin homogeneous plate. Based on an efficient finite element method (FEM), we show that the PC plate with inclined dots can lower Lamb wave BGs due to a weak localized resonance of the edge of the upper surface of the inclined dots. The BGs can be effectively shifted by changing the value of the incline. The total displacement fields are computed to explain how the inclined dot induces the lowering of the locally resonant BGs. Transmission power spectra (TPS) are calculated to demonstrate the existence of the BGs and it matches well with the band structure. BGs evolution as a function of geometrical parameters of the PC plate with inclined dot is also studied.