Modern Physics Letters B

In nonequilibrium states, the entropy is reduced from its maximum thermodynamic equilibrium value by virtue of an external energy supply. Such states are characterized by a higher ordering compared to the equilibrium. Human beings represent the highest level of nonequilibrium state, at least in the known part of the Universe. Other physical systems are also well-known, for example, quantum generators, e.g., lasers. Their operation requires a high level of deviation from equilibrium called inverse population. In turn, states out of equilibrium require energy influx for their maintenance, i.e., they should be open systems. In this short review we describe in the form of dialogue between Prof. A. M. Gulian and his younger colleagues Dr. Rajendra Dulal, Dr. Serafim Teknowijoyo and Dr. Sara Chahid the task of achieving inverse population in superconductors. Then, the dialogue moves towards experimental consequences that nonequilibrium superconductors can yield. These include topics related with deeper understanding of mechanisms of superconductivity in novel materials, in particular related to the “glue” which pairs electrons in Cooper pairs. Such understanding will facilitate development of Bose-field quantum generators like lasers, and coherent acoustic as well as paramagnon quantum sources, none of which are yet realized in nonequilibrium superconductors.

Two-dimensional segregation effect in vertically vibrated binary granular mixtures with same size is studied by molecular dynamic simulation. The results show that the lighter and mixed state, in which the lighter particles tend to rise and form a pure layer on top of the system while the heavier particles and some of the lighter ones stay at the bottom and form a mixed layer, also exists in the two-dimensional system. The validity of the scheme of the lighter and mixed state is testified by comparing the distribution profiles implied by the scheme with that of the real simulated state. We further propose to use twice the ratio of the thickness of the top layer to that of the whole system as an order parameter to describe the degree of the segregation quantitatively, and present a method that can accurately calculate the order parameter in the simulation. By use of the order parameter, we show that the order parameter is a convex monotonic function of the density ratio between the heavier and lighter particles.

By symbolic computation and searching for the solutions of the positive quadratic functions of the related bilinear equations, two kinds of lump solutions of the (3+1)-dimensional weakly coupled Hirota bilinear equation are derived, and the practicability of this method is verified. Then we add an exponential function to the original positive quadratic function, and obtain a new solution of the Hirota bilinear equation. The interaction between the lump solutions and lump-kink solutions is included in the new solution. On this basis, we give the possibility of adding multiple exponential functions. Finally, we give the coupled reduced Hirota bilinear equation lump-kink solitons by combining the above two methods. In order to ensure the analyticity and reasonable localization of the block, two sets of necessary and sufficient conditions are given for the parameters involved in the solution. The local characteristics and energy distribution of bulk solution are analyzed and explained.

In this work, the researchers for computing an exact solution of the (2+1) dimensions Kundu–Mukherjee–Naskar (KMN) equation used a newly developed technique, namely, the new extended direct algebraic method. This powerful method gives an exact solution to the KMN equation considered in this paper. The results are new and attest to the efficiency of the proposed method.

A CMOS fully differential current-mode front-end for SAW-less receivers is proposed. The noise-canceling LNTA has a main path of the common-gate (CG) stage and an auxiliary path of the inverter stage. A current mirror is used to combine the signals from the main and auxiliary paths in current mode. The stacked nMOS/pMOS configurations improve their power efficiency. The traditional stacked tri-state inverter as D-latch replaced by the discrete inverter and transmission gate enables a reduced supply voltage of divider core. LO generator based on the improved divider provides quarter LO signals to drive the proposed LNTA-shared receiver front-end. Simulation results in 180 nm CMOS indicate that the integrated receiver front-end provides an NF of 2.4 dB, and a maximum gain of 45 dB from 0.2 to 3.3 GHz. The in-band (IB) and out-of-band (OB) IIP3 of 2.5 dBm and 4 dBm, are obtained, respectively. With CMOS scaling down continuously, CMOS devices are providing increased transit frequency and reduced intrinsic parasitics which are important for radio frequency (RF) and millimeter-wave applications. As a promising solution, CMOS RF delivers comparable performance to silicon bipolar and GaAs devices but at a much lower cost and higher integration level. Supply voltage reduction with CMOS scaling down also poses a stringent linearity requirement. Avoiding the conventional trade-off between the supply voltage and linearity headroom, the proposed receiver front-end based on the current mode principle is with weak linearity dependency on the supply voltage and provides excellent anti-blocker interference capability.

An extended lattice hydrodynamic model with time delay is proposed under non-lane discipline. We try to grasp the impacts of the non-lane discipline of the considered lattice sites. Linear stability analysis of the proposed model is executed and the stability criterion is obtained. Using the reductive perturbation method, we investigate nonlinear analysis of the proposed model and derive the mKdV equation and its solution, which could reveal the propagation of density waves. We analyze the effect of time delay, the ratio of lane deviation and the control coefficient on the stability of traffic flow via numerical experiments. We find that those indices play an important role in the stability of traffic flow. The longer the time delay, the more unstable the system becomes. Also, the ratio of lane deviation and the control coefficient is able to more quickly dissipate the traffic congestions occurring in traffic flow.

TiO₂ films of different thickness are deposited on silicon substrate at low temperature and pressure by a Helicon-PECVD reactor. The evolution of film morphology and topography is observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM), meanwhile the spectroscopic ellipsometry (SE) measurements are performed to investigate the film growth mechanism and optical constants. The SEM and AFM observations show that all the films exhibit a columnar structure, moreover all the columns are vertical grown and well-organized when the thickness below $\sim$80 nm. As the thickness is increased to $\sim$150 nm, 250 nm and 450 nm, the column size is increased in the top layers, the whole film morphology becomes inhomogeneous, which leads to a decreased density and rougher surface. By fitting the SE measurements, a suitable gradient physical model is found to describe the film morphologies, the model consists of a native SiO₂ layer on Si substrate, a mediate layer mixed TiO₂ with void whose concentration gradient changed from bottom to top, and a top roughness layer. For thick films ($\ge \sim$450 nm), the absorption and scattering on the rough surface is considered in order to keep the precision of SE fits. It is found that the optical index is decreased with film thickness, which is related to the evolution of structure in the top layers.

By using first-principles calculations and the non-equilibrium Green’s function, we theoretically study the electronic transport properties of a $Z$-shaped phosphorene nanoribbon (PNR) device, which is called ZSZ-PNR because it is composed of a left zigzag PNR electrode, an intermediate skewed armchair PNR (saPNR), and a right zigzag PNR electrode. First, we investigate the influences of the length and the width of the central saPNR on the ZSZ-PNR transport. The results show that the negative differential conductance (NDC) always appears in the case of the short central saPNR, and is independent of its width, while the NDC is inclined to vanish with the increase of the length. Also, an anomaly on the current–voltage ($I$–$V$) curves is observed for the ZSZ-PNR with a short saPNR. Next, the transport properties are analyzed according to the evolution of the energy bands of the electrodes, the molecular energy levels (MELs) of the central saPNR, as well as the transmission coefficients, the transmission eigenstates, and the eigenstates of the self-consistent Hamiltonian of the saPNR. Finally, we use a top gate and two parallel gates to manipulate the transport of the ZSZ-PNR, and find that all these gates can strengthen or suppress the ZSZ-PNR transport.

In this paper, we consider the (2+1)-dimensional nonlocal complex modified Korteweg-de Vries and Maxwell–Bloch (cmKdV-MB) equations. According to the relevant Lax pair presented, we construct one- and two-fold Darboux transformations (DT). The exact solutions are derived from the trivial seeds by DT and the dynamic behaviors of soliton solutions are analyzed by individual pictures.

E-beam irradiation is one of the favorite methods of recent years and it can deliver the irradiation dose in just a few seconds to form nanoparticles. It is possible to obtain nanoparticles with different properties by changing the experimental conditions, as well as radiolytic reduction process can be adjusted through accelerators, it is possible to obtain oxides and hydroxides of metal nanoparticles. This paper reports the investigation of high-energy electron beams (EBs) on the crystal structure of 40–60 nm nanoscale Al particles. The crystal structure of the samples was calculated using the Rietveld method in the FullProf program. Structure analysis of three different irradiated ($4.16\times 10^{16}{\mathrm{\text{cm}}}^{-2}$, $1.20\times 10^{17}{\mathrm{\text{cm}}}^{-2}$, $1.03\times 10^{18}{\mathrm{\text{cm}}}^{-2}$) Al samples and nonirradiated Al samples was performed by XRD. Occurring energy during the process of linear electron acceleration was around $\sim$2–3 MeV. All samples were irradiated at room temperature. In addition to STP, temperature changes can be observed when the particles are exposed to high energy for a long time. At STP, nanoscale Al particles combine with the oxygen of the air and form Al₂O₃. Also, X-ray diffraction study showed that the instability does not only belong to Al particles but also to Al₂O₃ in view of the fact that precarious Al(OH)₃ crystal structures were observed. Thus, radiation dependence of lattice parameters was obtained, the mechanism of change of lattice parameters was determined due to radiation.

A novel scheme for integrated optical filters with narrow bandwidth is proposed to dramatically improve its compactness on the basis of slow-light waveguide, which provides a large optical path in a short geometry length. By introducing the one-dimensional grating waveguide (ODGW), a kind of slow-light waveguide, into a micro-ring resonator (MRR), the area of MRR is reduced by three orders of magnitude compared to the MRR without ODGW. As a proof of concept, an ultra-compact on-chip filter with narrow bandwidth of 2.1 pm (263 MHz) is conceived by cascading six MRRs with ODGW. Additionally, the designed optical filter shows excellent performances of roll-down speed, out-of-band signal suppression, and in-band ripple. Our proposal offers a promising solution to miniaturize the integrated optical filters with narrow bandwidth, and hence improve the integration density of on-chip photonic networks.

A transient continuum model of the ODEP chip containing single circular particle inside is constructed based on multi-physical field coupling. The dielectrophoresis force and liquid viscous resistance acting on particle are calculated by employing the full Maxwell stress tensor. The coupled flow field, electric field and particle are solved by the arbitrary Lagrange–Euler (ALE) method simultaneously. The throughout dynamic process of particle in the ODEP chip is demonstrated, and the effect of several critical parameters on particle electrodynamics is illuminated. The additional disturbing effect of the photoconductive layer on the electric field as well as the micro-channel wall on the flow field is presented to clarify the particle motion in the vertical direction. The results in this study provide a detailed understanding of the particle dynamics in the ODEP chip.

With an advancement in wireless technologies, Internet of Things (IoT) are becoming popular in modern era because of its wide range of applications. In this paper, an IoT enable smart classroom is considered. However, IoT nodes are battery constrained, therefore, development and implementation of energy efficiency IoT based smart classroom turn out be more challenging issue. Recently, many clustering and inter-cluster data aggregation techniques are implemented to minimize the energy consumption of IoT devices. However, designing an energy aware IoT protocol is defined as a NP-hard problem. Therefore, many researchers have utilized various metaheuristic techniques to implement energy aware protocol. However, generally metaheuristic techniques suffer from various issues such as pre-mature convergence, stuck in local optima, poor convergence speed, etc. Therefore, in this paper, an integrated multi-objective optimization is designed for IoT based smart classroom by considering ant colony optimization and crossover operator. The proposed technique is used to improve the inter-cluster data aggregation of IoT based smart classroom. Extensive experiments are performed by considering various performance metrics. Comparative analyses show that the proposed protocol achieves remarkably significant results as compared to the competitive techniques.

Today in the age of advanced ceramic civilization, there are a variety of applications for modern ceramics materials with specific properties. Our up-to date research recognizes that ceramics have a fractal configuration nature on the basis of different phenomena. The key property of fractals is their scale-independence. The practical value is that the fractal objects’ interaction and energy is possible at any reasonable scale of magnitude, including the nanoscale and may be even below. This is a consequence of fractal scale independence. This brings us to the conclusion that properties of fractals are valid on any scale (macro, micro, or nano). We also analyzed these questions with experimental results obtained from a comet, here 67P, and also from ceramic grain and pore morphologies on the microstructure level. Fractality, as a scale-independent morphology, provides significant variety of opportunities, for example for energy storage. From the viewpoint of scaling, the relation between large and small in fractal analysis is very important. An ideal fractal can be magnified endlessly but natural morphologies cannot, what is the new light in materials sciences and space.