International Journal of Modern Physics B

Liquid crystal (LC) research in China started during the Cultural Revolution years in the late 1960s. It was motivated partly by the potential application in liquid-crystal display (LCD) digital television (TV) and movies, deemed good for the government’s political propaganda agenda. The large-screen LCD TV/ movie project was initiated and done at the Tsinghua University, Beijing, which became successful in 1976 with prototypes built. Although it never reached the commercial stage, the research achievement was world-leading then. Here, the history of this project and other LC research at the Tsinghua University in the 1970s and 1980s are described for the first time, with appropriate historical backgrounds provided. Tsinghua’s significant contributions in basic LC research and a description of the founding and workings of the Chinese Liquid Crystal Society are also included. Finally, lessons drawn from this piece of science history are presented.

We review various bounds concerning out-of-equilibrium dynamics in few-level and many-body quantum systems. We primarily focus on closed quantum systems but will also mention some related results for open quantum systems and classical stochastic systems. We start from the speed limits, the universal bounds on the speeds of (either quantum or classical) dynamical evolutions. We then turn to review the bounds that address how good and how long would a quantum system equilibrate or thermalize. Afterward, we focus on the stringent constraint set by locality in many-body systems, rigorously formalized as the Lieb–Robinson bound. We also review the bounds related to the dynamics of entanglement, a genuine quantum property. Apart from some other miscellaneous topics, several notable error bounds for approximated quantum dynamics are discussed. While far from comprehensive, this topical review covers a considerable amount of recent progress and thus could hopefully serve as a convenient starting point and up-to-date guidance for interested readers.

In the face of increasing application requirements for instantaneous transmission in ICU. Many medical devices collect large-scale data but do not have the computing power to match. Features such as low latency, fast response and privacy encryption are becoming more and more urgent. So far, traditional IoT cloud computing has been unable to solve this problem, and only edge computing has the potential to solve these problems. Edge computing is an open platform that provides endpoint services close to the side of the object or data source using core capabilities such as network, computing, storage and application as one. There are two types of task offloading, binary offloading and partial offloading. Binary offloading is the classic task offloading method, especially in traditional cloud computing, but this offloading method has its own drawbacks. We propose a group wisdom-aware partial offloading algorithm that addresses a series of challenges posed by binary offloading. The algorithm introduces the concept of group wisdom awareness and compares several other mainstream task offloading strategies through experiments. The experimental results show that the algorithm has certain theoretical value and reference significance.

In this study, the impact of activation energy and transiting parameters on the two-dimensional stagnation point flow of magnetized Sutterby nanofluid of nano-biofilm incorporating with microorganisms over the porous surface has been examined. Prior research suggests that both the fluid viscosity and thermal conductance are temperature-dependent. Also, the effects of solutal concentration on fluid viscosity, heat capacity and nanofluid properties have been elaborated. In recent years, numerous technical strategies comprising hydromagnetic fluxes and thermal intensification in porosity media, like molding, condenser heat exchanger, liquefied metal filtration, fusion control and nuclear reactor coolant, have been addressed. According to numerous empirical studies, the viscosity and thermal conductivity of the nanoparticles are largely dependent on the intensity of nanoparticles rather than the temperature. The classical RK-4 method with shooting technique has been used. The significance of involving parameters in the domains of heat, velocity, density and concentration has been illustrated. The effect of nondimensional parameters on the skin friction factor, Nusselt number and Sherwood number has been discussed. The nanoparticle density increases with the activating energy effects and thermophoresis factor and rapidly decreases for Lewis number and Brownian factor. The velocity, temperature and concentration profiles increase as the concentration-dependent properties do, but all physical quantities deteriorate for all concentration-varying factors.

This study inspects the steady flow of a Jeffrey nanofluid stimulated by the linear stretching of a curved sheet. Working fluid is made up of graphene nanoparticles in a base medium of water. The heat sink/ source and convective boundary condition phenomenon highlights the heat transfer of the flow. The effect of liquid–solid interfacial layer and the nanoparticle diameter is also presented at the molecular level to illustrate the thermal integrity of the considered flow. Leading equations are numerically assessed after being transformed into dimensionless forms by using similarity transformations. To enhance the analysis part, several graphs and tables are shown. The features of a wide range of parameters are explored and discussed. The impact of these parameters on the rate of heat transport is also explored. Results reveal that the nanofluid velocity increases for curvature parameter. In addition, the heat transmission amplifies for heat source parameter and convective parameter. The rate of heat transport amplifies for curvature parameter and Biot number but deteriorates for heat source/ sink parameter.

In this paper, we have considered the properties of surface electronic states in quasi-two-dimensional organic conductors for an out-of-plane orientation of the magnetic field. The energies of these states have be calculated which allow the resonance magnetic fields and resonance angles corresponding to the positions of the peaks in oscillation spectra of surface resistance to be determined. We find that the energies of the magnetic-field induced surface states are decreasing significantly with increasing tilt angle from the surface. This is related to the fact that the surface states are realized due to electron transitions between different in size elliptical closed orbits obtained as cross-section of the Fermi surface with the plane $𝜀(p)={𝜀}_F$, $p_B=$ const. In comparison to the case of in-plane magnetic field, where only the small closed orbits on the sides of the Fermi surface are involved in formation of the surface states, for out-of-plane magnetic field there are additionally present other, larger orbits that are spanning across the Fermi surface. We also find that the coordinate of the center of electron revolution is increasing significantly with increasing tilt angle but the maximum distance from the surface for the electrons involved in the surface states shows a steady increase indicating that the skipping trajectories are well confined within skin layer of the conductor. This indicates that the surface states can be observed for almost each field direction from the surface including those with higher quantum number. These studies allow to determine more accurately certain Fermi surface parameters such as the local radius of curvature in the plane perpendicular to the magnetic field as well as the Fermi velocity at each point on the elliptical cross-sections. We are highly convinced that our results will motivate new experimental investigations of surface phenomena in order to exploit the properties of surface electronic states for various scientific applications.

Elastic metamaterial (EM) beam is a kind of special composite structure with peculiar dynamic properties that are beneficial for relevant vibration isolating applications. The vibration properties and proper analysis methods of these special structures are the main concerns in practical designs and analyses. Existing analytic methods can only be applied to a few cases with simple geometric shapes and boundary conditions, hence more general analysis means are needed to be developed. In this paper, a general analysis method is proposed by combining the effective medium theory (EMT) and Rayleigh–Ritz method. Based on the method, the natural vibration properties of a typical EM beam are revealed clearly and correctly, such as absence of natural frequencies within bandgap, gathering of natural frequencies in the vicinity of band edges and particular modal correspondence before and behind bandgap. The effectiveness of the proposed method is validated by the analysis results, thus providing a feasible way for analyzing many complex cases where EM beams are included.

In this paper, the phase space representation for a semiconfined harmonic oscillator model with a position-dependent effective mass is constructed. We have found the Husimi distribution function for the stationary states of the oscillator model under consideration for both cases without and with the applied external homogeneous field. The obtained function is expressed through the double sum of the parabolic cylinder function. Different special cases and the limit relations are discussed, too.

This paper presents three different structures of SOI-TFET. Using silicon and germanium as source material and placing a high-doped $N^{+}$ layer at the source/ channel interface, these different structures are formed. All of the architectures have a $T$-shaped channel and the thickness of the source and drain regions are less than the channel thickness. At first, the impact of gate-to-source overlap on the DC performance metrics of these tunneling field-effect transistor (TFETs) is investigated by 2D numerical simulations. The results indicate that the gate overlap on the source can improve the performance of the devices with $T$-shaped channels. Then, the proposed structures have been analyzed in terms of AC analysis when the overlap of the gate on the source is 50%. It is confirmed that the Ge-source $T$-channel SOI-TFET with gate-source overlap shows better results overall in comparison to the other structures. This device provides $g_m=82.5\times 10^{-4}$ S, $A_V=197$, $f_T=2.9\times 10^{11}$ Hz and shows strong potential to design fast electronic switches.

A new generalized KdV equation, describing the motions of long waves in shallow water under the gravity field, is considered in this paper. By adopting a series of well-organized methods, the Bäcklund transformation, the bilinear form and diverse wave structures of the governing model are formally extracted. The exact solutions listed in this paper are categorized as lump-type, complexiton, and soliton solutions. To exhibit the physical mechanism of the obtained solutions, several graphical illustrations are given for particular choices of the involved parameters. As a direct consequence, diverse wave structures given in this paper enrich the studies on the KdV-type equations.