A comparison of various nonlinear models of cochlear compression

The vibration response of the basilar membrane in the cochlea to sinusoidal excitation displays a compressive nonlinearity, conventionally described using an input-output level curve. This displays a slope of 1 dB/dB at low levels and a slope m < 1 dB/dB at higher levels. Two classes of nonlinear systems have been considered as models of this response, one class with static power-law nonlinearity and one class with level-dependent properties (using either an automatic gain control or a Van der Pol oscillator). By carefully choosing their parameters, it is shown that all models can produce level curves that are similar to those measured on the basilar membrane. The models differ, however, in their distortion properties, transient responses, and instantaneous input-output characteristics. The static nonlinearities have a single-valued instantaneous characteristic that is the same at all input levels. The level-dependent systems are multi-valued with an almost linear characteristic, for a given amplitude of excitation, whose slope varies with the excitation level. This observation suggests that historical attempts to use functional modeling (i.e., Wiener of Volterra series) may be ill founded, as these methods are unable to represent level-dependent nonlinear systems with multi-valued characteristics of this kind.     

Time-reversal characteristics of quantum normal diffusion: time-continuous models

In quantum map systems exhibiting normal diffusion, time-reversal characteristics converge to a universal scaling behavior which implies a prototype of irreversible quantum process [H.S. Yamada, K.S. Ikeda, Eur. Phys. J. B 85, 41 (2012)]. In the present paper, we extend the investigation of time-reversal characteristic to time-continuous quantum systems which show normal diffusion. Typical four representative models are examined, which is either deterministic or stochastic, and either has or not has the classical counterpart. Extensive numerical examinations demonstrate that three of the four models have the time-reversal characteristics obeying the same universal limit as the quantum map systems. The only nontrivial counterexample is the critical Harper model, whose time-reversal characteristics significantly deviates from the universal curve. In the critical Harper model modulated by a weak noise that does not change the original diffusion constant, time-reversal characteristic recovers the universal behavior.     

On improving weakly coupled cavity models for vibro-acoustic predictions and design

The vibro-acoustic characteristics of a cavity based on its vibro-acoustic FE model at times do not correlate well with the corresponding measured vibro-acoustic characteristics. Structural dynamic modeling errors that are often associated with the structural domain of the cavity are the main reasons for this discrepancy. This paper addresses this issue and deals with the improvement of the vibro-acoustic FE models of weakly coupled cavities. This particular application, hitherto, has not been much addressed, though the improvement of purely structural dynamic systems has been researched a lot. An experimental example of a 3D rectangular-box cavity with a flexible plate is considered. The study demonstrates that the improvement of the vibro-acoustic FE models through FE model updating can be an effective approach to obtain more accurate vibro-acoustic predictions. The study further addresses the question whether these improved vibro-acoustic models are suitable for vibro-acoustic design. This is answered by analyzing the accuracy with which the improved vibro-acoustic FE model predicts the effects of the structural modifications. It is finally concluded that the predictions based on the unimproved vibro-acoustic models may not be reliable and can have significant error, while the improved vibro-acoustic models give an improvement in the predictive capability of the model and are also found suitable for vibro-acoustic design.     

Spherically symmetric anisotropic and inhomogeneous cosmological models

Spherically symmetric cosmological models filled with dust (pressure-free fluid) content are analyzed. It has been pointed out that these models are anisotropic (of non-vanishing shear) and inhomogeneous (∂p/ρr ≠ 0), the characteristics related directly to the presence of the free gravitational field. It is demonstrated that when the free gravitational field vanishes these models degenerate to the corresponding Friedmann-Robertson-Walker (FRW) models. It is further shown that the energy density of the free gravitational field can be introduced into observational cosmology as a new parameter since it enters into the expansion and deceleration equations, as well as conservation law for total energy, implying that the present Hubble velocity can be reached in a shorter time from the big bang. Finally, the effect of shear on the redshift is also discussed. This paper is dedicated to my teacher Professor V V Narlikar on the occasion of his 81st birthday.     

Review of viscosity prediction models of liquid pure metals and alloys

Viscosity is an important property which could determine the flow liquid metal characteristics and reflect the liquidus structure. Therefore, the existence of an accurate model is necessary to calibrate the experimental measurement value of viscosity. At present, many models have been proposed to estimate the viscosity of pure liquid metal, the temperature dependence of viscosity and the viscosity of multicomponent alloy systems. In this paper, a number of the familiar models are given, and their fundamental modelling theory, model characteristics and applicability are adequately discussed. The general semi-empirical models which have been very successful in predicting the viscosity of pure liquid metal are divided into Andrade and Eyring two branches. The common multivariate melt viscosity prediction models are mostly based on the fundamental molecular theory method, which combines the thermodynamic parameters and achieves good validity. It is expected in the final that the corresponding viscosity prediction model of phase diagram might be more likely to replace the independent general prediction equation in the future.     

Fusion of deep shallow features and models for speaker recognition

In order to further improve the performance of speaker recognition, features fusion and models fusion are proposed. The features fusion method is to fuse deep and shallow features. The fused feature describes speaker characteristics more comprehensively than a single feature because of the complementarity between different levels of features. The models fusion method is to fuse i-vectors extracted from different speaker recognition systems. The fused model can combine advantages of different speaker recognition systems. Experimental results show the effectiveness of the proposed methods. Compared with the state-of-the-art system on CASIA North and South dialect corpus,the proposed features fusion system and models fusion system achieved about 54.8% and 69.5% relative improvement on the equal error rate(EER),respectively.     

Product directivity models for parametric loudspeakers

In a recent work, the beamsteering characteristics of parametric loudspeakers were validated in an experiment. It was shown that based on the product directivity model, the locations and amplitudes of the mainlobe and grating lobes could be predicted within acceptable errors. However, the measured amplitudes of sidelobes have not been able to match the theoretical results accurately. In this paper, the original theories behind the product directivity model are revisited, and three modified product directivity models are proposed: (i) the advanced product directivity model, (ii) the exponential product directivity model, and (iii) the combined product directivity model. The proposed product directivity models take the radii of equivalent Gaussian sources into account and obtain better predictions of sidelobes for the difference frequency waves. From the comparison between measurement results and numerical solutions, all the proposed models outperform the original product directivity model in terms of selected sidelobe predictions by about 10 dB.     

Gallagher index for sociophysical models

The use of physical formalism and methods as a tool for the analysis of sociological problems became popular since the papers of Galam or Stauffer, followed by the authors of some interesting models, based often on the study of cellular automata evolution. In this paper we are going to deduce some characteristics concerning the results of elections on the basis of the multi-opinion Sznajd model. The values of interest are: Gallagher index, measuring the disproportionality of elections; the efficiency of election process measured with the possibility of government creation and government stability. The results show that it is possible to obtain some well known effects even using quite a simple model of social behaviour and that different methods of votes counting respond to different needs formulated as the aim of elections.     

On the compatibility of polarisable and non-polarisable models for liquid water

The properties of water at physiological conditions can be modelled at different levels of resolution: (1) sub-atomic models that take into account electronic degrees of freedom, (2) atomic models that only account for atomic degrees of freedom and (3) supra-molecular models that only involve some supra-molecular degrees of freedom. To enhance the computational efficiency of molecular simulation, models at different levels of resolution should be simultaneously usable for different parts of a system for which the level of detail of interest is different. This requires these different types of models to be compatible with each other. In the present study, the compatibility of two polarisable models for liquid water, COS/G2 and COS/D, with a non-polarisable model for liquid water, SPC, is investigated. It is shown that these models are compatible. The polarisable models can thus be used to solvate biomolecules described by a biomolecular force field that is compatible with the SPC water model.     

Multilevel crystal plasticity models of single- and polycrystals. Direct models

The paper continues the review of works on the development and application of multiscale physical models to analyzing the behavior of single- and polycrystals under severe plastic deformation. Unlike mathematical models of plasticity, this class of models operates with meso- and microstructures of deformed material and allows analysis of their evolution. The recently much used so-called direct models that are based on crystal plasticity theories and numerical methods are discussed.     

描述激光二极管远场光强分布的理论模型

 介绍了描述激光二极管远场光强分布的几种典型理论模型,并与实验结果作了详细比较。结果表明：激光二极管的传输和远场特性应当用非傍轴理论描述,并且远场光强分布一般与输出功率大小有关。在不同功率水平下,异质结激光二极管快轴与慢轴方向的远场行为应选用不同的模型模拟。此外,还对厄米-高斯模型做了修正,考虑了奇数阶厄米-高斯模的贡献,并用厄米-高斯模的非相干叠加代替厄米-高斯模的相干叠加。改进的厄米-高斯模型能更好描述100 mW双异质结GaAlAs LD慢轴方向的远场光强分布。     

On the modeling of synchronized flow in cellular automaton models

In this paper,we further analyze our cellular automaton(CA)traffic flow model.By changing some parameters,the characteristics of our model can be significantly varied,ranging from the features of phase transitions to the number of traffic phases.We also review the other CA models based on Kerner’s three-phase traffic theory.By comparisons,we find that the core concepts for modeling the synchronized flow in these models are similar.Our model can be a good candidate for modeling the synchronized flow,since there is enough flexibility in our framework.     

Topological massive sigma models

In this paper we construct topological sigma models which include a potential and are related to twisted massive supersymmetric sigma models. Contrary to a previous construction these models have no central charge and do not require the manifold to admit a Killing vector. We use the topological massive sigma model constructed here to simplify the calculation of the observables. Lastly it is noted that this model can be viewed as interpolating between topological massless sigma models and topological Landau-Ginzburg models.     

Testing the Amado-Woloshyn-Frankel and Blankenbeckler-Schmidt models by antineutrinos

We used two nuclear wave function models to describe deep-inelastic neutrino-nucleus scattering with emergence of a fast proton in the backward hemisphere. The results of the calculation are compared with experiment to show that these models in their present form meet with serious difficulties in describing the total yield and the deep-inelastic characteristics of the events in question.     

Theoretical models for designing a 220-GHz folded waveguide backward wave oscillator

In this paper,the basic equations of beam-wave interaction for designing the 220 GHz folded waveguide(FW)backward wave oscillator(BWO) are described.On the whole,these equations are mainly classified into small signal model(SSM),large signal model(LSM),and simplified small signal model(SSSM).Using these linear and nonlinear one-dimensional(1D) models,the oscillation characteristics of the FW BWO of a given configuration of slow wave structure(SWS) can be calculated by numerical iteration algorithm,which is more time efficient than three-dimensional(3D)particle-in-cell(PIC) simulation.The SSSM expressed by analytical formulas is innovatively derived for determining the initial values of the FW SWS conveniently.The dispersion characteristics of the FW are obtained by equivalent circuit analysis.The space charge effect,the end reflection effect,the lossy wall effect,and the relativistic effect are all considered in our models to offer more accurate results.The design process of the FW BWO tube with output power of watt scale in a frequency range between 215 GHz and 225 GHz based on these 1D models is demonstrated.The 3D PIC method is adopted to verify the theoretical design results,which shows that they are in good agreement with each other.     

Mathematical models to characterize early epidemic growth: A review

There is a long tradition of using mathematical models to generate insights into the transmission dynamics of infectious diseases and assess the potential impact of different intervention strategies. The increasing use of mathematical models for epidemic forecasting has highlighted the importance of designing reliable models that capture the baseline transmission characteristics of specific pathogens and social contexts. More refined models are needed however, in particular to account for variation in the early growth dynamics of real epidemics and to gain a better understanding of the mechanisms at play. Here, we review recent progress on modeling and characterizing early epidemic growth patterns from infectious disease outbreak data, and survey the types of mathematical formulations that are most useful for capturing a diversity of early epidemic growth profiles, ranging from sub-exponential to exponential growth dynamics. Specifically, we review mathematical models that incorporate spatial details or realistic population mixing structures, including meta-population models, individual-based network models, and simple SIR-type models that incorporate the effects of reactive behavior changes or inhomogeneous mixing. In this process, we also analyze simulation data stemming from detailed large-scale agent-based models previously designed and calibrated to study how realistic social networks and disease transmission characteristics shape early epidemic growth patterns, general transmission dynamics, and control of international disease emergencies such as the 2009 A/H1N1 influenza pandemic and the 2014–2015 Ebola epidemic in West Africa.     

A comparison of models used as alternative magnetic resonance image reconstruction methods

In magnetic resonance (MR) imaging, excellent reconstructions are obtained on large data sets using the inverse discrete Fourier transform (IDFT). Modeling procedures have been proposed to overcome the image artifacts from the truncation of small data sets. In this paper, a relationship between image reconstruction using modeling and the standard IDFT is presented. A comparison of the assumptions behind the Smith and Haacke models is given and an experimental evaluation of the validity of the models provided. Various methods of evaluating model coefficients are discussed. Images are reconstructed from both models using the Transient Error reconstruction approach (TERA) algorithm. TERA is an algorithm that reintroduces data information components that cannot be modeled: useful when the assumed model characteristics do not completely match all portions of the image. Although very different in their basic assumptions, both the Smith and Haacke models were found to reduce truncation artifacts and improve resolution when used with the TERA algorithm.     

Honking noise corrections for traffic noise prediction models in heterogeneous traffic conditions like India

In developing countries like India, the nature of the composition of traffic is heterogeneous. A heterogeneous traffic flow consists of vehicles that have different sizes, speeds, vehicle spacing and operating characteristics. As a result of the widely varying speeds, vehicular dimensions, lack of lane disciplines, honking becomes inevitable. In addition, it changes the urban soundscape of developing countries. In heterogeneous traffic conditions, horn events increase noise level (L_den) by 0.5–13 dB(A) as compared to homogenous traffic conditions. Therefore, the traffic prediction models that are used for homogenous traffic conditions are not applicable in heterogeneous traffic conditions. To increase the accuracy of noise prediction models, in depth understanding of heterogeneous traffic noise is required. Understanding the real traffic noise characteristics requires quantification of some of the basic traffic flow characteristics such as speed, flow, Level Of Service (LOS) and density. In a given roadway, the noise level changes with density and LOS on the road. In this paper, a new factor for horn correction is introduced with respect of Level Of Service (LOS). The horn correction values can be incorporated in traffic noise models such as CRTN, FHWA, and RLS 90, while evaluating heterogeneous traffic conditions.     

Critical exponents for integrable models

Phase transition in quantum systems in two space-time dimensions takes place at zero temperature. A general formula is obtained for the critical exponent describing the power decrease of zero-temperature correlation functions as long distances. This formula is valid for a large class of Bethe ansatz solvable models including the Heisenberg magnet and the one-dimensional Bose gas. The critical exponent is connected with the fractional charge; it is also expressed in terms of macroscopic characteristics of the models.