Showing papers in "Chinese Physics B in 2014"
TL;DR: In this paper, the authors review the investigation of the EB in Co/CoO core-shell nanoparticles, including the effects of the constituent layer thickness, the microstructure and magnetization of the FM layers, and also discuss asymmetric magnetization reversal process in wedged-FM/AFM bilayers.
Abstract: Since the exchange bias (EB) effect was discovered in the Co/CoO core-shell nanoparticles, it has been extensively studied in various ferromagnet (FM)/antiferromagnet (AFM) bilayers due to its crucial role in spintronics devices. In this article, we review the investigation of the EB in our research group. First, we outline basic features of the EB, including the effects of the constituent layer thickness, the microstructure and magnetization of the FM layers, and we also discuss asymmetric magnetization reversal process in wedged-FM/AFM bilayers. Secondly, we discuss the mechanisms of the positive EB and the perpendicular EB. Thirdly, we demonstrate the hysteretic behavior of the angular dependence of the EB and analyze the EB training effect. Finally, we discuss the roles of the rotatable anisotropy in the two phenomena.
201 citations
TL;DR: In this paper, the authors reviewed different aspects of flat bands in a nutshell, starting from the standard band theory, they aim to bridge the frontier of FBs with the textbook solid-state physics and discuss various many-body phases associated with such a singular band structure.
Abstract: It has long been noticed that special lattices contain single-electron flat bands (FB) without any dispersion. Since the kinetic energy of electrons is quenched in the FB, this highly degenerate energy level becomes an ideal platform to achieve strongly correlated electronic states, such as magnetism, superconductivity, and Wigner crystal. Recently, the FB has attracted increasing interest because of the possibility to go beyond the conventional symmetry-breaking phases towards topologically ordered phases, such as lattice versions of fractional quantum Hall states. This article reviews different aspects of FBs in a nutshell. Starting from the standard band theory, we aim to bridge the frontier of FBs with the textbook solid-state physics. Then, based on concrete examples, we show the common origin of FBs in terms of destructive interference, and discuss various many-body phases associated with such a singular band structure. In the end, we demonstrate real FBs in quantum frustrated materials and organometallic frameworks.
159 citations
TL;DR: In this article, the design and fabrication of multifunctional magnetic nanoparticles (MNPs) for magnetic resonance (MR) image-guided photothermal therapy of cancer are reviewed. But the authors do not discuss the application of such nanoparticles in medical applications.
Abstract: Key advances in multifunctional magnetic nanoparticles (MNPs) for magnetic resonance (MR) image-guided photothermal therapy of cancer are reviewed. We briefly outline the design and fabrication of such multifunctional MNPs. Bimodal image-guided photothermal therapies (MR/fluorescence and MR/ultrasound) are also discussed.
155 citations
TL;DR: In this article, the authors provide a brief introduction on magnetic iron oxide nanoparticles in terms of their fundamentals of magnetism, magnetic resonance imaging (MRI), and drug delivery, as well as the synthesis approaches, surface coating, and application examples from recent key literatures.
Abstract: Iron oxide nanoparticles are the most popular magnetic nanoparticles used in biomedical applications due to their low cost, low toxicity, and unique magnetic property. Magnetic iron oxide nanoparticles, including magnetite (Fe3O4) and maghemite (?-Fe2O3), usually exhibit a superparamagnetic property as their size goes smaller than 20 nm, which are often denoted as superparamagnetic iron oxide nanoparticles (SPIONs) and utilized for drug delivery, diagnosis, therapy, and etc. This review article gives a brief introduction on magnetic iron oxide nanoparticles in terms of their fundamentals of magnetism, magnetic resonance imaging (MRI), and drug delivery, as well as the synthesis approaches, surface coating, and application examples from recent key literatures. Because the quality and surface chemistry play important roles in biomedical applications, our review focuses on the synthesis approaches and surface modifications of iron oxide nanoparticles. We aim to provide a detailed introduction to readers who are new to this field, helping them to choose suitable synthesis methods and to optimize the surface chemistry of iron oxide nanoparticles for their interests.
148 citations
TL;DR: In this paper, a novel (G'/G)-expansion method is proposed to search for the traveling wave solutions of nonlinear evolution equations, which provides more general exact solutions than the existing methods.
Abstract: In this article, a novel (G'/G)-expansion method is proposed to search for the traveling wave solutions of nonlinear evolution equations. We construct abundant traveling wave solutions involving parameters to the Boussinesq equation by means of the suggested method. The performance of the method is reliable and useful, and gives more general exact solutions than the existing methods. The new (G'/G)-expansion method provides not only more general forms of solutions but also cuspon, peakon, soliton, and periodic waves.
113 citations
TL;DR: In this paper, the first demonstration of the reversible change of the redox couple of Cu2+/Cu3+ with high storage potential in secondary batteries was presented. But the first two materials can deliver a capacity of around 70 mAh/g.
Abstract: Layered oxides of P2-type Na0.68Cu0.34Mn0.66O2, P2-type Na0.68Cu0.34Mn0.50Ti0.16O2, and O'3-type NaCu0.67Sb0.33O2 were synthesized and evaluated as cathode materials for room-temperature sodium-ion batteries. The first two materials can deliver a capacity of around 70 mAh/g. The Cu2+ is oxidized to Cu3+ during charging, and the Cu3+ goes back to Cu2+ upon discharging. This is the first demonstration of the highly reversible change of the redox couple of Cu2+/Cu3+ with high storage potential in secondary batteries.
101 citations
TL;DR: The anomalous scattering features enabled by plasmonic nanoparticles and nanoclusters are discussed, and it is shown how they may represent the fundamental building blocks of complex nanophotonic architectures.
Abstract: The rise of plasmonic metamaterials in recent years has unveiled the possibility of revolutionizing the entire field of optics and photonics, challenging well-established technological limitations and paving the way to innovations at an unprecedented level. To capitalize the disruptive potential of this rising field of science and technology, it is important to be able to combine the richness of optical phenomena enabled by nanoplasmonics in order to realize metamaterial components, devices, and systems of increasing complexity. Here, we review a few recent research directions in the field of plasmonic metamaterials, which may foster further advancements in this research area. We will discuss the anomalous scattering features enabled by plasmonic nanoparticles and nanoclusters, and show how they may represent the fundamental building blocks of complex nanophotonic architectures. Building on these concepts, advanced components can be designed and operated, such as optical nanoantennas and nanoantenna arrays, which, in turn, may be at the basis of metasurface devices and complex systems. Following this path, from basic phenomena to advanced functionalities, the field of plasmonic metamaterials offers the promise of an important scientific and technological impact, with applications spanning from medical diagnostics to clean energy and information processing.
86 citations
TL;DR: In this article, the steady magnetohydrodynamic (MHD) flow of viscous nanofluid is modeled by a permeable exponentially stretching surface, and the nonlinear partial differential equations governing the flow are reduced to an ordinary differential equation by similarity transformations.
Abstract: This article concentrates on the steady magnetohydrodynamic (MHD) flow of viscous nanofluid. The flow is caused by a permeable exponentially stretching surface. An incompressible fluid fills the porous space. A comparative study is made for the nanoparticles namely Copper (Cu), Silver (Ag), Alumina (Al2O3) and Titanium Oxide (TiO2). Water is treated as a base fluid. Convective type boundary conditions are employed in modeling the heat transfer process. The non-linear partial differential equations governing the flow are reduced to an ordinary differential equation by similarity transformations. The obtained equations are then solved for the development of series solutions. Convergence of the obtained series solutions is explicitly discussed. The effects of different parameters on the velocity and temperature profiles are shown and analyzed through graphs.
72 citations
TL;DR: In this article, the authors present some of the recent progress in preparation methodologies and surface functionalization approaches of silicon nanoparticles, and their promising applications in the fields of energy and electronic engineering are introduced.
Abstract: Silicon nanoparticles have attracted great attention in the past decades because of their intriguing physical properties, active surface state, distinctive photoluminescence and biocompatibility. In this review, we present some of the recent progress in preparation methodologies and surface functionalization approaches of silicon nanoparticles. Further, their promising applications in the fields of energy and electronic engineering are introduced.
65 citations
TL;DR: In this paper, the mechanism for fluid flow at low velocity in a porous medium is analyzed based on plastic flow of oil in a reservoir and the fractal approach, and analytical expressions for flow rate and velocity of non-Newtonian fluid flow in the low permeability porous medium are derived, and the threshold pressure gradient (TPG) is also obtained.
Abstract: In this paper, the mechanism for fluid flow at low velocity in a porous medium is analyzed based on plastic flow of oil in a reservoir and the fractal approach. The analytical expressions for flow rate and velocity of non-Newtonian fluid flow in the low permeability porous medium are derived, and the threshold pressure gradient (TPG) is also obtained. It is notable that the TPG (J) and permeability (K) of the porous medium analytically exhibit the scaling behavior J ~ K−DT/(1=DT), where DT is the fractal dimension for tortuous capillaries. The fractal characteristics of tortuosity for capillaries should be considered in analysis of non-Darcy flow in a low permeability porous medium. The model predictions of TPG show good agreement with those obtained by the available expression and experimental data. The proposed model may be conducible to a better understanding of the mechanism for nonlinear flow in the low permeability porous medium.
60 citations
TL;DR: In this article, the challenges and recent developments associated with writability issues in high-anisotropy magnetic recording media are reviewed, and new alternatives are proposed to solve the writability issue.
Abstract: Challenges and recent developments associated with writability issues in high-anisotropy perpendicular recording media are reviewed. The writing field is limited by the high coercivity caused by the high anisotropy. Some new alternatives are proposed to solve the writability issues, including texture-tilting-assisted, domain-wall-assisted, energy-assisted magnetic recording technologies, and so on. In addition, we propose new alternatives for the next-generation of magnetic recording media.
TL;DR: In this paper, the authors review the recent progress in this research direction of nanoparticle scattering shaping and control through the interference of both electric and optically-induced magnetic responses, and discuss the magnetic resonances supported by various structures in different spectral regimes.
Abstract: Conventional approaches to control and shape the scattering patterns of light generated by different nanostructures are mostly based on engineering of their electric response due to the fact that most metallic nanostructures support only electric resonances in the optical frequency range. Recently, fuelled by the fast development in the fields of metamaterials and plasmonics, artificial optically-induced magnetic responses have been demonstrated for various nanostructures. This kind of response can be employed to provide an extra degree of freedom for the efficient control and shaping of the scattering patterns of nanoparticles and nanoantennas. Here we review the recent progress in this research direction of nanoparticle scattering shaping and control through the interference of both electric and optically-induced magnetic responses. We discuss the magnetic resonances supported by various structures in different spectral regimes, and then summarize the original results on the scattering shaping involving both electric and magnetic responses, based on the interference of both spectrally separated (with different resonant wavelengths) and overlapped dipoles (with the same resonant wavelength), and also other higher-order modes. Finally, we discuss the scattering control utilizing Fano resonances associated with the magnetic responses.
TL;DR: In this article, the surface wave holography method is used for wave-front shaping of near-infrared light through a subwavelength hole, and it can also be used for designing holographic plasmonic lenses for SPs with complex wavefronts in the visible band.
Abstract: The control and application of surface plasmons (SPs), is introduced with particular emphasis on the manipulation of the plasmonic wavefront and light–matter interaction in metallic nanostructures. We introduce a direct design methodology called the surface wave holography method and show that it can be readily employed for wave-front shaping of near-infrared light through a subwavelength hole, it can also be used for designing holographic plasmonic lenses for SPs with complex wavefronts in the visible band. We also discuss several issues of light–matter interaction in plasmonic nanostructures. We show theoretically that amplification of SPs can be achieved in metal nanoparticles incorporated with gain media, leading to a giant reduction of surface plasmon resonance linewidth and enhancement of local electric field intensity. We present an all-analytical semiclassical theory to evaluate spaser performance in a plasmonic nanocavity incorporated with gain media described by the four-level atomic model. We experimentally demonstrate amplified spontaneous emission of SP polaritons and their amplification at the interface between a silver film and a polymer film doped with dye molecules. We discuss various aspects of microscopic and macroscopic manipulation of fluorescent radiation from gold nanorod hybrid structures in a system of either a single nanoparticle or an aligned group of nanoparticles. The findings reported and reviewed here could help others explore various approaches and schemes to manipulate plasmonic wavefront and light–matter interaction in metallic nanostructures for potential applications, such as optical displays, information integration, and energy harvesting technologies.
TL;DR: In this article, the authors investigated the influence of various pertinent parameters, such as the local Nusselt number, the skin friction coefficient, velocity profile, and temperature profile, for different values of the governing parameters for three types of nanoparticles, namely copper, alumina, and titania in the water-based fluid.
Abstract: In this article, the unsteady magnetohydrodynamic (MHD) stagnation point flow and heat transfer of a nanofluid over a stretching/shrinking sheet is investigated numerically. The similarity solution is used to reduce the governing system of partial differential equations to a set of nonlinear ordinary differential equations which are then solved numerically using the fourth-order Runge–Kutta method with shooting technique. The ambient fluid velocity, stretching/shrinking velocity of sheet, and the wall temperature are assumed to vary linearly with the distance from the stagnation point. To investigate the influence of various pertinent parameters, graphical results for the local Nusselt number, the skin friction coefficient, velocity profile, and temperature profile are presented for different values of the governing parameters for three types of nanoparticles, namely copper, alumina, and titania in the water-based fluid. It is found that the dual solution exists for the decelerating flow. Numerical results show that the extent of the dual solution domain increases with the increases of velocity ratio, magnetic parameter, and permeability parameter whereas it remains constant as the value of solid volume fraction of nanoparticles changes. Also, it is found that permeability parameter has a greater effect on the flow and heat transfer of a nanofluid than the magnetic parameter.
TL;DR: In this paper, a radar-infrared stealth-compatible structure with reflectivity below −10 dB in the whole radar X wave band and infrared emissivity less than 0.3 in the infrared region of 8 μm-14 μm is reported.
Abstract: A thin radar-infrared stealth-compatible structure with reflectivity below −10 dB in the whole radar X wave band and infrared emissivity less than 0.3 in the infrared region of 8 μm–14 μm is reported. The designed stealth-compatible structure consists of metallic frequency selective surface (MFSS), resistive frequency selective surface (RFSS), and metal backing from the top down, and it is only 2.1-mm thick. The MFSS is made up of some divided low infrared emissivity metal copper films, and the RFSS consists of a capacitive array of square resistive patches. They are placed close together, working as an admittance sheet because of a mutual influence between them, and the equivalent admittance sheet greatly reduces the thickness of the whole structure. The proposed stealth-compatible structure is verified both by simulations and by experimental results. These results indicate that our proposed stealth-compatible structure has potential applications in stealth fields.
TL;DR: In this paper, spontaneous emission properties and control of the zero phonon line (ZPL) from a diamond nitrogen-vacancy (NV) center coherently driven by a single elliptically polarized control field were investigated.
Abstract: We investigate spontaneous emission properties and control of the zero phonon line (ZPL) from a diamond nitrogen–vacancy (NV) center coherently driven by a single elliptically polarized control field. We use the Schrodinger equation to calculate the probability amplitudes of the wave function of the coupled system and derive analytical expressions of the spontaneous emission spectra. The numerical results show that a few interesting phenomena such as enhancement, narrowing, suppression, and quenching of the ZPL spontaneous emission can be realized by modulating the polarization-dependent phase, the Zeeman shift, and the intensity of the control field in our system. In the dressed-state picture of the control field, we find that multiple spontaneously generated coherence arises due to three close-lying states decaying to the same state. These results are useful in real experiments.
TL;DR: This newly proposed interface circuit, constructed by only two current conveyors, is equipped with three available ports, which can provide six connecting combinations in terms of one resistor, one capacitor, and one memristor.
Abstract: In this paper, a concise but effective interface circuit for transforming a memristor into meminductive and memcapacitive systems is designed This newly proposed interface circuit, constructed by only two current conveyors, is equipped with three available ports, which can provide six connecting combinations in terms of one resistor, one capacitor, and one memristor For the sake of confirming the design effectiveness, theoretical and simulation discussions are hence introduced and all the experimental waveforms provide conclusive evidence to validate the correctness of these new mutators The most attractive features of this new interface circuit are the floating terminals and convenient practical implementation
TL;DR: In this paper, the influence of the gap on the absorption performance of the conventional split ring resonator (SRR) absorber at microwave frequencies was investigated, and the authors revealed that the geometry of the square SRR can be equivalent to a Jerusalem cross (JC) resonator and its corresponding metamaterial absorber (MA) is changed to a JC absorber.
Abstract: The influence of the gap on the absorption performance of the conventional split ring resonator (SRR) absorber is investigated at microwave frequencies Our simulated results reveal that the geometry of the square SRR can be equivalent to a Jerusalem cross (JC) resonator and its corresponding metamaterial absorber (MA) is changed to a JC absorber The JC MA exhibits an experimental absorption peak of 991% at 872 GHz, which shows an excellent agreement with our simulated results By simply assembling several JCs with slightly different geometric parameters next to each other into a unit cell, a perfect multi-band absorption can be effectively obtained The experimental results show that the MA has four distinct and strong absorption peaks at 832 GHz, 98 GHz, 1152 GHz and 1324 GHz Finally, the multi-reflection interference theory is introduced to interpret the absorption mechanism
TL;DR: A novel mapping equivalent approach is proposed in this paper, which can be used for analyzing and realizing a memristor-based dynamical circuit equivalently by a nonlinear dynamical Circuit with the same topologies and circuit parameters.
Abstract: A novel mapping equivalent approach is proposed in this paper, which can be used for analyzing and realizing a memristor-based dynamical circuit equivalently by a nonlinear dynamical circuit with the same topologies and circuit parameters. A memristor-based chaotic circuit and the corresponding Chua's chaotic circuit with two output differentiators are taken as examples to illustrate this approach. Equivalent dynamical analysis and realization of the memristor-based chaotic circuit are performed by using Chua's chaotic circuit. The results indicate that the outputs of memristor-based chaotic circuit and the corresponding outputs of Chua's chaotic circuit have identical dynamics. The proposed approach verified by numerical simulations and experimental observations is useful in designing and analyzing memristor-based dynamical circuits.
TL;DR: This work shows that multi-hop teleportation on distributed wireless quantum networks with partially entangled pairs is feasible and not necessary for the quantum path to be consistent with the classical path.
Abstract: Wireless quantum communication networks transfer quantum state by teleportation. Existing research focuses on maximal entangled pairs. In this paper, we analyse the distributed wireless quantum communication networks with partially entangled pairs. A quantum routing scheme with multi-hop teleportation is proposed. With the proposed scheme, is not necessary for the quantum path to be consistent with the classical path. The quantum path and its associated classical path are established in a distributed way. Direct multi-hop teleportation is conducted on the selected path to transfer a quantum state from the source to the destination. Based on the feature of multi-hop teleportation using partially entangled pairs, if the node number of the quantum path is even, the destination node will add another teleportation at itself. We simulated the performance of distributed wireless quantum communication networks with a partially entangled state. The probability of transferring the quantum state successfully is statistically analyzed. Our work shows that multi-hop teleportation on distributed wireless quantum networks with partially entangled pairs is feasible.
TL;DR: In this article, the boundary layer forced convection flow of a Casson fluid past a symmetric porous wedge is investigated numerically and the results obtained in this study are illustrated graphically and discussed in detail.
Abstract: The aim of this paper is to investigate numerically the boundary layer forced convection flow of a Casson fluid past a symmetric porous wedge. Similarity transformations are used to convert the governing partial differential equations into ordinary ones. With the help of the shooting method, the reduced equations are then solved numerically. Comparisons are made with the previously published results in some special cases and they are found to be in excellent agreement with each other. The results obtained in this study are illustrated graphically and discussed in detail. The velocity is found to increase with an increasing Falkner–Skan exponent whereas the temperature decreases. With the rise of the Casson fluid parameter, the fluid velocity increases but the temperature is found to decrease in this case. Fluid velocity is suppressed with the increase of suction. The skin friction decreases with the increasing value of Casson fluid parameter. It is found that the temperature decreases as the Prandtl number increases and thermal boundary layer thickness decreases with the increasing value of Prandtl number. A significant finding of this investigation is that flow separation can be controlled by increasing the value of the Casson fluid parameter as well as by increasing the amount of suction.
TL;DR: In this article, the thermodynamic and magnetic properties of the spin-1/2 hexagonal Ising nanowire (HIN) system with core/shell structure have been presented.
Abstract: By means of the effective-field theory (EFT) with correlations, the thermodynamic and magnetic quantities (such as magnetization, susceptibility, internal energy, specific heat, free energy, hysteresis curves, and compensation behaviors) of the spin-1/2 hexagonal Ising nanowire (HIN) system with core/shell structure have been presented. The hysteresis curves are obtained for different values of the system parameters, in both ferromagnetic and antiferromagnetic cases. It has been shown that the system only undergoes a second-order phase transition. Moreover, from the thermal variations of the total magnetization, the five compensation types can be found under certain conditions, namely the Q-, R-, S-, P-, and N-types.
TL;DR: In this article, the Boltzmann transport theory and first-principles calculations were used to study the thermoelectric properties of MoS2 with doping based on the Boltzman transport theory.
Abstract: We systematically studied the thermoelectric properties of MoS2 with doping based on the Boltzmann transport theory and first-principles calculations. We obtained an optimal doping region (around 1019 cm−3) for thermoelectric properties along in-plane and cross-plane directions. MoS2 in the optimal doping region has a vanishingly small anisotropy of thermopower possibly due to the decoupling of in-plane and cross-plane conduction channels, but big anisotropies of electrical conductivity σ and electronic thermal conductivity κe arising from the anisotropic electronic scattering time. The κe is comparable to the lattice counterpart κ1 in the plane, while κ1 dominates over κe across the plane. The figure of merit ZT can reach 0.1 at around 700 K with in-plane direction preferred by doping.
TL;DR: In this article, the effect of the initial state of the radiation field on the dynamical evolution of some physical properties such as atomic inversion and entropy squeezing are investigated by considering different initial field states (coherent, squeezed and thermal states).
Abstract: The interaction between a two-level atom and a single-mode field in the k-photon Jaynes—Cummings model (JCM) in the presence of the Stark shift and a Kerr medium is studied. All terms in the Hamiltonian, such as the single-mode field, its interaction with the atom, the contribution of the Stark shift and the Kerr medium effects are considered to be f-deformed. In particular, the effect of the initial state of the radiation field on the dynamical evolution of some physical properties such as atomic inversion and entropy squeezing are investigated by considering different initial field states (coherent, squeezed and thermal states).
TL;DR: In this article, first principles of structural, electronic, optical, elastic, mechanical properties, and Born effective charges of monoclinic HfO2 are performed with the plane-wave pseudopotential technique based on the density-functional theory.
Abstract: First-principles calculations of structural, electronic, optical, elastic, mechanical properties, and Born effective charges of monoclinic HfO2 are performed with the plane-wave pseudopotential technique based on the density-functional theory. The calculated structural properties are consistent with the previous theoretical and experimental results. The electronic structure reveals that monoclinic HfO2 has an indirect band gap. The analyses of density of states and Mulliken charges show mainly covalent nature in Hf-O bonds. Optical properties, including the dielectric function, refractive index, extinction coefficient, reflectivity, absorption coefficient, loss function, and optical conductivity each as a function of photon energy are calculated and show an optical anisotropy. Moreover, the independent elastic constants, bulk modulus, shear modulus, Young's modulus, Poisson's ratio, compressibility, Lame constant, sound velocity, Debye temperature, and Born effective charges of monoclinic HfO2 are obtained, which may help to understand monoclinic HfO2 for future work.
TL;DR: In this article, the most important interface-related quantities determined by band alignment are the barrier heights for charge transport, given by the Fermi level position at the interface, which is determined by X-ray photoelectron spectroscopy (XPS).
Abstract: The most important interface-related quantities determined by band alignment are the barrier heights for charge transport, given by the Fermi level position at the interface. Taking Pb(Zr,Ti)O3 (PZT) as a typical ferroelectric material and applying X-ray photoelectron spectroscopy (XPS), we briefly review the interface formation and barrier heights at the interfaces between PZT and electrodes made of various metals or conductive oxides. Polarization dependence of the Schottky barrier height at a ferroelectric/electrode interface is also directly observed using XPS.
TL;DR: In this article, the boundary layer flow due to an exponentially stretching surface in the presence of an applied magnetic field is numerically examined and the effect of increasing values of the Casson parameter is to suppress the velocity field.
Abstract: This article numerically examines the boundary layer flow due to an exponentially stretching surface in the presence of an applied magnetic field. Casson fluid model is used to characterize the non-Newtonian fluid behavior. The flow is subjected to suction/blowing at the surface. Analysis is carried out in presence of thermal radiation and prescribed surface heat flux. In this study, an exponential order stretching velocity and prescribed exponential order surface heat flux are accorded with each other. The governing partial differential equations are first converted into nonlinear ordinary differential equations by using appropriate transformations and then solved numerically. The effect of increasing values of the Casson parameter is to suppress the velocity field. However the temperature is enhanced when Casson parameter increases. It is found that the skin-friction coefficient increases with increasing values of suction parameter. Temperature also increases for large values of power index n in both suction and blowing cases at the boundary. It is observed that the thermal radiation enhances the effective thermal diffusivity and hence the temperature rises.
TL;DR: It is found that there is a critical density to distinguish whether a pedestrian jam occurs in the evacuation and whether an exit selection strategy is in effect, and that evacuation time and exit selection are dependent on the cognitive coefficient and pedestrian initial density in the in-effect phase with a high density.
Abstract: A mixed strategy of the exit selection in a pedestrian evacuation simulation with multi-exits is constructed by fusing the distance-based and time-based strategies through a cognitive coefficient, in order to reduce the evacuation imbalance caused by the asymmetry of exits or pedestrian layout, to find a critical density to distinguish whether the strategy of exit selection takes effect or not, and to analyze the exit selection results with different cognitive coefficients. The strategy of exit selection is embedded in the computation of the shortest estimated distance in a dynamic parameter model, in which the concept of a jam area layer and the procedure of step-by-step expending are introduced. Simulation results indicate the characteristics of evacuation time gradually varying against cognitive coefficient and the effectiveness of reducing evacuation imbalance caused by the asymmetry of pedestrian or exit layout. It is found that there is a critical density to distinguish whether a pedestrian jam occurs in the evacuation and whether an exit selection strategy is in effect. It is also shown that the strategy of exit selection has no effect on the evacuation process in the no-effect phase with a low density, and that evacuation time and exit selection are dependent on the cognitive coefficient and pedestrian initial density in the in-effect phase with a high density.
TL;DR: In this article, the authors investigated the electrical and dielectric properties of cobalt-doped interfacial polyvinyl alcohol (PVA) layer and interface trap (Dit) effects, and the forward and reverse admittance measurements were carried out in the frequency and voltage ranges of 30 kHz-300 kHz and −5 V-6 V, respectively.
Abstract: In order to investigate of cobalt-doped interfacial polyvinyl alcohol (PVA) layer and interface trap (Dit) effects, Al/p-Si Schottky barrier diodes (SBDs) are fabricated, and their electrical and dielectric properties are investigated at room temperature. The forward and reverse admittance measurements are carried out in the frequency and voltage ranges of 30 kHz–300 kHz and −5 V–6 V, respectively. C–V or e'–V plots exhibit two distinct peaks corresponding to inversion and accumulation regions. The first peak is attributed to the existence of Dit, the other to the series resistance (Rs), and interfacial layer. Both the real and imaginary parts of dielectric constant (e' and e'') and electric modulus (M' and M''), loss tangent (tan δ), and AC electrical conductivity (σac) are investigated, each as a function of frequency and applied bias voltage. Each of the M' versus V and M'' versus V plots shows a peak and the magnitude of peak increases with the increasing of frequency. Especially due to the Dit and interfacial PVA layer, both capacitance (C) and conductance (G/w) values are strongly affected, which consequently contributes to deviation from both the electrical and dielectric properties of Al/Co-doped PVA/p-Si (MPS) type SBD. In addition, the voltage-dependent profile of Dit is obtained from the low–high frequency capacitance (CLF−CHF) method.
TL;DR: In this paper, the relative stability, optimal sliding path between different stacking orders of bilayer MoS2, and (especially) the effect of inter-layer stress, was explored by combining first-principles density functional total energy calculations and the climbing-image nudge-elastic-band (CI-NEB) method.
Abstract: The study of the stacking stability of bilayer MoS2 is essential since a bilayer has exhibited advantages over single layer MoS2 in many aspects for nanoelectronic applications. We explored the relative stability, optimal sliding path between different stacking orders of bilayer MoS2, and (especially) the effect of inter-layer stress, by combining first-principles density functional total energy calculations and the climbing-image nudge-elastic-band (CI-NEB) method. Among five typical stacking orders, which can be categorized into two kinds (I: AA, AB and II: AA', AB', A'B), we found that stacking orders with Mo and S superposing from both layers, such as AA' and AB, is more stable than the others. With smaller computational efforts than potential energy profile searching, we can study the effect of inter-layer stress on the stacking stability. Under isobaric condition, the sliding barrier increases by a few eV/(ucGPa) from AA' to AB', compared to 0.1 eV/(ucGPa) from AB to [AB]. Moreover, we found that interlayer compressive stress can help enhance the transport properties of AA'. This study can help understand why inter-layer stress by dielectric gating materials can be an effective means to improving MoS2 on nanoelectronic applications.