Small Transmission Coefficient Research Articles

Wave blocking performance of the symmetrical double-wing floating breakwater

In this paper, a double-wing floating breakwater (DWFB) is proposed, that is, the wing with a curved upper surface and flat lower surface is installed on both sides of the box-type floating breakwater (FB). The analytical model of the DWFB under wave action is established to solve the wave diffraction problem. The modified mild slope equation (MMSE) is used to deal with the unsteady water depth problem above the wing, and the reflection coefficient, transmission coefficient, and the wave excitation force in the surge, heave, and pitch are obtained. After the analytical model is verified, the effect of the wing shape and wing size (height and length) on the wave blocking performance of the DWFB is analyzed, and then the single-wing FB and DWFB are compared. The results show that the increase in wing length is obvious to reduce the transmission coefficient. The single-wing floating breakwater (SWFB) with a longer wing length but similar cross-sectional area to the DWFB has a smaller transmission coefficient when the wave number is between 0.45 and 0.85. However, as the wave number continues to increase, the wave blocking performance of the DWFB is relatively better.

Analysis of submerged breakwater models using ripple tank

A breakwater is an infrastructure that functions to dampen wave energy. To secure the area directly adjacent to the coast, an effective breakwater model is needed based on the analysis of the dissipation coefficient value ( ). This study aims to determine a good breaker model based on the value using a ripple tank. The data analyzed were wave heights before and after passing through the breakwaters of the three concrete models whose arrangement was varied. The results showed that the breaker model that is effective in reducing wave energy is the Grooved cube model with holes arranged horizontally based on the resulting small reflection coefficient ( ) and transmission coefficient ( ) values and large values

A semi-analytical solution for water wave scattering by partially immersed perforated and solid barriers with a quadratic pressure discharge condition

Partially immersed perforated and/or solid barriers in the ocean are often considered as important components of many marine applications, and they have received significant attentions by ocean engineering research community with potential flow methods. In this study, water wave interaction with a system that consists of a vertical perforated front barrier and a vertical impermeable rear barrier, as a representative unit, is investigated based on the linear potential flow theory. A semi-analytical solution for this problem is derived using an eigenfunction expansion method and an iterative resolution method. To model the flow passing through the perforated barrier, a quadratic pressure discharge condition of practical validity is applied. The reflection coefficient predicted by the present analytical model agrees well with the published theoretical result. The validated model is used to perform a parametric study to examine the effects of the width, submergence depth, porosity, incident wave steepness and wave frequency on the hydrodynamic characteristics of the perforated system. It is found that larger incident wave steepness can result in smaller transmission coefficient and dimensionless horizontal wave force acting on the impermeable rear barrier and larger dimensionless horizontal wave force acting on the perforated front barrier due to the nonlinear nature of the quadratic pressure discharge condition. By examination over a broad range of circumstances, we find that the partially immersed perforated system is more effective when the ratio of the width to the incident wavelength B/L is located between 0.2+0.5n and 0.35+0.5n (n=1,2,…). The present study can be utilized for a range of marine applications in wave preventing and wave energy absorption or conversion.

Study of the transport properties of cobalt atomic contact under mechanical strain in a nitrogen atmosphere

Achieving an efficient spin-filter effect and large magneto-resistance in molecular junctions is very important in spintronics. By employing the non-equilibrium Green's function formalism combined with the density functional theory, this study investigated the atomic structures and spin-resolved transport properties of molecular junctions consisting of nitrogen (N2) sandwiched between two cobalt (Co) electrodes with different crystal lattices as a function of stretching distance. In the case of face-centred cubic Co electrodes, our calculations showed that the transport properties depend strongly on the stretching process, which changes the contact between the N2 and Co electrodes. Specifically, the maximum spin polarization is due to the configuration of N2 molecules sitting in parallel with the protruding Co atoms. Furthermore, the Co dxz,yz orbitals interact with the N px,y orbitals, which contribute to the high transmission coefficient at the Fermi level for spin-down electrons. Meanwhile, the Co s-dz2 hybridization orbitals, which interact weakly with the N p orbitals, contribute to the small transmission coefficient at the Fermi level. This can also be verified by the molecular junction model adopting simple monatomic Co chain electrodes, which also show a perfect spin-filter effect and achieve an ideal magnetoresistance. In contrast, in the case of hexagonal Co electrodes, the spin-filter effect disappears. However, the effect appears again by adding one more Co atom to the central point contact. Our findings show that the spin-resolved electronic transport of molecular junctions depends on the stretching process and the nature of the electrodes, which can help in the future design of molecular devices based on the spin degree of freedom.

Experimental study on stress wave propagation in jointed rock coupling the effect of JMC & JRC

The objective of this study is to experimentally investigate how the rough joints effect the stress wave propagation through jointed rocks coupling the effect of the joint matching coefficient (JMC) and joint roughness coefficient (JRC). The Split Hopkinson Pressure Bar (SHPB) apparatus was adopted to conduct uniaxial compression experiments on jointed specimens. The joint matching coefficient (JMC) and joint roughness coefficient (JRC) are introduced as morphology parameters to estimate joint roughness. Based on SHPB experiments, we found out that the joint matching coefficient (JMC) has a greater influence on the transmission and reflection coefficient than the joint roughness coefficient (JRC). Jointed specimens with lower JMC and JRC make less energy transmitted through it and have a smaller transmission coefficient and bigger reflection coefficients. Also, the joint with lower JMC and JRC has less initial stiffness and greater maximum closure.

EVALUATION OF HYDRAULIC PERFORMANCE OF WAVE DISSIPATING BLOCK USING POROSITY

The reflection and transmission of wave dissipating work mainly depend on the shape and porosity of wave dissipating block. However, the influence of the shape and porosity of wave dissipating block on the reflection and transmission has not been investigated sufficiently. The purpose of this study is to investigate the influence of the porosity of wave dissipating block on the reflection and transmission coefficients through a series of hydraulic experiments where four kinds of wave dissipating blocks were used. Wave dissipating blocks with smaller porosity provided a larger reflection coefficient and a smaller transmission coefficient as a whole. However, a wave dissipating block provided a smaller reflection coefficient and a smaller transmission coefficient in spite of relatively larger porosity. The measured reflection and transmission coefficients were compared with those estimated by existing equations.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/lqyzabMw66U

Reaction rate of H2CO (1A) and (3A) via TST.

In this work, we present the reaction rate and dissociation of formaldehyde H2CO, where we found three possible pathways for the singlet state (1A), and two for triplet state (3A). The optimized geometries and frequencies were determined at B3LYP/6-311g(2d,d,p) internal to CBS-QB3 methods. The reaction rates are calculated using the APUAMA code, applying the tunneling correction of Wigner, Eckart, and small curvature transmission coefficient (SCT), and the total reaction rate is presented in the Arrhenius form as [Formula: see text] and [Formula: see text], for singlet and triplet state, respectively. Graphical Abstract PES for singlet and triplet formaldehyde.

Marginal States of Light

We introduce marginal states of light which are barely classical and hence lie on the boundary between classical and nonclassical states. A marginal state may be obtained as an output of a beam splitter with vanishingly small transmission coefficient and a very intense nonclassical light as an input. We also point out that any marginal state can be made to be maximally nonclassical by adding a single photon. The close relation between nonclassicality and the particle nature of light is addressed.

Solvent exchange in liquid methanol and rate theory

To enhance our understanding of the solvent exchange mechanism in liquid methanol, we report a systematic study using molecular dynamics simulations. We use transition state theory, the Impey–Madden–McDonald method, the reactive flux method, and Grote–Hynes theory to compute the rate constants for this process. Solvent coupling was found to dominate, resulting in a significantly small transmission coefficient. We predict a positive activation volume for methanol exchange. The essential features of the dynamics as well as the pressure dependence are recovered from a Generalized Langevin Equation description of the dynamics. We find that the response to anharmonicity can be decomposed into two time regimes, one corresponding to short time response (<0.1ps) and long time response (>5ps). An effective characterization of the process is obtained from launching dynamics from the planar hypersurface corresponding to Grote–Hynes theory, resulting in improved numerical convergence of correlation functions.

High-performance AlGaInP tunneling heterostructure-emitter bipolar transistor

In this paper, a high-performance heterostructure-emitter bipolar transistor employing an AlGaInP quaternary compound tunneling layer is fabricated and demonstrated. In the studied device, a 50Å n-AlGaInP tunneling emitter layer together with a 200Å n-GaAs layer forms the heterostructure emitter to decrease the collector–emitter offset voltage. On the other hand, due to the relatively large valence band discontinuity (∼0.4eV) at AlGaInP/GaAs heterojunction and the small hole transmission coefficient across the AlGaInP tunneling layer, most of holes injecting from base to emitter will be blocked at AlGaInP/GaAs heterojunction and then high collector current and current gain are achieved. The experimental results exhibit a large collector current of 92mA, a large current gain of 446, and a relatively low offset voltage of only 45mV, respectively. Furthermore, a large current-gain cutoff frequency ft up to 63.7GHz is obtained for the device with a thin tunneling layer.

Comparative investigation of InP/InGaAs heterostructure-emitter tunneling and superlattice bipolar transistors

In this article, the characteristics of InP/InGaAs heterostructure-emitter bipolar transistors with 30 n-InP layer tunneling layers and a five-period InP/InGaAs superlattice are demonstrated and comparatively investigated by experimentally results and analysis. In the three devices, a 200 A n-In0.53Ga0.47As layer together with an n-InP tunneling emitter layer (or n-InP/n-InGaAs superlattice) forms heterostructure emitter to decrease collector-emitter offset voltage. The results exhibits that the largest collector current and current gain are obtained for the tunneling transistor with a 30 A n-InP tunneling emitter layer. On the other hand, some of holes injecting from base to emitter will be blocked at n-InP/n-InGaAs heterojunction due to the relatively small hole transmission coefficient in superlattice device, which will result in a considerable base recombination current in the n-InGaAs layer. Therefore, the collector current and current gain of the superlattice device are the smallest values among of the devices.

Research on Complex Channel Characteristic for Hypersonic Vehicles

Hypersonic vehicles experience complex and bad communication environment including high dynamic Doppler and unique plasma sheath. Characteristics of the complex channel environment, which is divided into two distinguished channel part, will be discussed. The atmospheric propagation part of the complex channel is modeled as frequency-selective fast fading channel based on analysis of its coherence time and coherence bandwidth. The plasma sheath channel transmission (attenuation) and phase shift characteristics when radio wave pass through it is obtained by the scatter matrix method and FDTD algorithm. Finally a typical blunt conical hypersonic vehicle model is simulated to evaluate plasma sheath channel transmission and phase shift features, results show that communications might completely interrupted under high speed above 16 Mach because of small transmission coefficient and large phase shift.

Reflectivity and transmissivity of a cavity coupled to two-level systems: Coherence properties and the influence of phase decay

We consider $N$ identical two-level systems coupled to a cavity, which is coherently driven by an external field. In the limit of small excitation, the reflection and transmission coefficients for both fields and intensities are calculated analytically. In addition, the frequency content of the cavity field and hence also the emission spectrum of the cavity are determined. A discussion is presented regarding how, in particular, individual collisional dephasing and common energy-level fluctuations prevent the cavity field from being in a coherent state, which in turn affects the outgoing fields.

Protein Collective Motions Coupled to Ligand Migration in Myoglobin

Ligand migration processes inside myoglobin and protein dynamics coupled to the migration were theoretically investigated with molecular dynamics simulations. Based on a linear response theory, we identified protein motions coupled to the transient migration of ligand, carbon monoxide (CO), through channels. The result indicates that the coupled protein motions involve collective motions extended over the entire protein correlated with local gating motions at the channels. Protein motions, coupled to opening of a channel from the distal pocket to a neighboring xenon site, were found to share the collective motion with experimentally observed protein motions coupled to a doming motion of the heme Fe atom upon photodissociation of the ligand. Analysis based on generalized Langevin dynamics elucidated slow and diffusive features of the protein response motions. Remarkably small transmission coefficients for rates of the CO migrations through myoglobin were found, suggesting that the CO migration dynamics are characterized as motions governed by the protein dynamics involving the collective motions, rather than as thermally activated transitions across energy barriers of well-structured channels.

Path Sampling Calculation of Methane Diffusivity in Natural Gas Hydrates from a Water-Vacancy Assisted Mechanism

Increased interest in natural gas hydrate formation and decomposition, coupled with experimental difficulties in diffusion measurements, makes estimating transport properties in hydrates an important technological challenge. This research uses an equilibrium path sampling method for free energy calculations [Radhakrishnan, R.; Schlick, T. J. Chem. Phys. 2004, 121, 2436] with reactive flux and kinetic Monte Carlo simulations to estimate the methane diffusivity within a structure I gas hydrate crystal. The calculations support a water-vacancy assisted diffusion mechanism where methane hops from an occupied "donor" cage to an adjacent "acceptor" cage. For pathways between cages that are separated by five-membered water rings, the free energy landscape has a high barrier with a shallow well at the top. For pathways between cages that are separated by six-membered water rings, the free energy calculations show a lower barrier with no stable intermediate. Reactive flux simulations confirm that many reactive trajectories become trapped in the shallow intermediate at the top of the barrier leading to a small transmission coefficient for these paths. Stable intermediate configurations are identified as doubly occupied off-pathway cages and methane occupying the position of a water vacancy. Rate constants are computed and used to simulate self-diffusion with a kinetic Monte Carlo algorithm. Self-diffusion rates were much slower than the Einstein estimate because of lattice connectivity and methane's preference for large cages over small cages. Specifically, the fastest pathways for methane hopping are arranged in parallel (nonintersecting) channels, so methane must hop via a slow pathway to escape the channel. From a computational perspective, this paper demonstrates that equilibrium path sampling can compute free energies for a broader class of coordinates than umbrella sampling with molecular dynamics. From a technological perspective, this paper provides one estimate for an important transport property that has been difficult to measure. In a hydrate I crystal at 250 K with nearly all cages occupied by methane, we estimate D approximately 7 x 10(-15) X m(2)/s where X is the fraction of unoccupied cages.

Precipitation fronts and the reflection and transmission of tropical disturbances

AbstractThis paper investigates the interactions between precipitation and the circulation in an idealized model for the tropical atmosphere where convection is represented by a quasi‐equilibrium closure. When studying large‐scale circulation in the Tropics, the governing equations can be further simplified by making the strict quasi‐equilibrium assumption which considers that convection acts to instantaneously adjust the atmospheric temperature profile to a moist adiabatic lapse rate. It is shown here that, under this assumption, the interface between the precipitating and non‐precipitating regions exhibits a discontinuity in the precipitation rate and vertical velocity. Furthermore, this interface, referred to as a precipitation front, moves at a velocity distinct from the propagation speed of dry and moist disturbances. The theory predicts the existence of three types of precipitation fronts: drying fronts, slow moistening fronts and fast moistening fronts. In previous studies, numerical simulations have demonstrated the existence of the three types of front, and have also confirmed that the precipitation front theory offers a good approximation for the behaviour of the interface between dry and moist regions for finite value of the convective adjustment time.A new framework is proposed here in which the encounter of an atmospheric disturbance and the edge of a precipitation region is recast as a Riemann problem. It is shown that, for any precipitation fronts, there are three incident characteristics but only two outgoing characteristics. This makes it possible to solve simultaneously for the intensity of the outgoing invariants and the propagation speed of the front. This also implies that atmospheric disturbances will be partially transmitted and partially reflected when encountering a precipitation front. For small perturbations, linear reflection and transmission coefficients can be computed analytically. These results also indicate that that disturbances can be amplified through over‐transmission or over‐reflection. These theoretical results are confirmed in numerical simulations of an idealized Walker circulation. A solution that includes a stationary precipitation front is perturbed by adding a small‐amplitude gravity wave, convectively coupled gravity wave, or moisture disturbance. All numerical simulations exhibit reflection and transmission of the incoming signal, and one simulation shows a case of over‐transmission of the incoming disturbance. Copyright © 2008 Royal Meteorological Society

MATHEMATICAL STUDY OF THE IMPACT OF QUARANTINE, ISOLATION AND VACCINATION IN CURTAILING AN EPIDEMIC

The quarantine of suspected cases and isolation of individuals with symptoms are two of the primary public health control measures for combating the spread of a communicable emerging or re-emerging disease. Implementing these measures, however, can inflict significant socio-economic and psychological costs. This paper presents a deterministic compartmental model for assessing the single and combined impact of quarantine and isolation to contain an epidemic. Comparisons are made with a mass vaccination program. The model is simulated using parameters for influenza-type diseases such as SARS. The study shows that even for an epidemic in which asymptomatic transmission does not occur, the quarantine of asymptomatically-infected individuals can be more effective than only isolating individuals with symptoms, if the associated reproductive number is high enough. For the case where asymptomatic transmission occurs, it is shown that isolation is more effective for a disease with a small basic reproduction number and transmission coefficient of asymptomatically-infected individuals. If asymptomatic individuals transmit at a rate that is at least 20% that of symptomatic individuals, quarantine is always more effective. The study further shows that the reduction in disease burden obtained from a combined quarantine and isolation program can be comparable to that obtained by a vaccination program, if the former is implemented quickly enough after the onset of the outbreak. If the implementation of such a quarantine/isolation program is delayed, however, even for a short while, its effectiveness decreases rapidly.

Optical transmission of ceramic shielding blocks made from Al2O3

We have studied the transmission of bulk Al2O3 ceramic used as heat shields for the working chamber of a turbine. We have established that radiation scattered from such an object has a pronounced speckle structure, while the scattering indicatrix is the same as the indicatrix for an ideal scatterer. We show that existing highpower semiconductor laser sources make it possible to penetrate sufficiently deeply into such materials, and the small transmission coefficient is not the limiting factor for development of optical methods for inspecting the quality of ceramic shielding blocks.

Effect of tunneling current on the decay rate of a quantum dot

We use many-body quantum theory to calculate the decay rate of a quantum state in a junction barrier undergoing Coulombic interaction with a tunneling current flowing through the junction. The tunneling current effectively measures the junction state occupation, and we find the measurement generaly acts to increase the decay rate in the limit of small junction transmission coefficient.

Wave damping characteristics of vertically stratified porous structures under oblique wave action

The characteristics of wave damping for the vertically stratified porous breakwaters are investigated under oblique wave action. It is found that for common angles of incidence, the wave damping efficiency of a vertically stratified porous structure behaves very similar to a simple structure. The reflection coefficient decreases with increasing angle of incidence while the transmission coefficient only slightly increases as the angle of incidence increases. It is shown that the wave energy loss is in direct proportional to the structure thickness and its porosity regardless of the angle of incidence. Considering small transmission coefficient as a basic requirement and if a moderate reflection coefficient is accepted, a structure thickness of b/ h=1 is proposed. In this situation, since the structure does not have a very large thickness, adopting a vertically stratified structure is not an effective way to improve its wave damping efficiency.