Procedia IUTAM最新文献

In this paper we employ an improved thalamo-cortical model to uncover the potential generation mechanisms of pS-WD patterns by means of bursting oscillation's analysis approaches in the process of seizures generation at both fast and slow timescales. Interestingly, it is found that the onset of epileptic discharges can be delayed as an increase of excitatory regulating function of the thalamic relay neuronal population on cortical PY. The obtained numerical results show that the initiation of absence seizures arises from the thalamus and the termination of them in the cortex.

A coupled-process based tide-wave-surge model has been used to simulate Typhoon Cobra in December 14-19, 1944, also best known as the Typhoons of 1944 or Halsey’s Typhoon. The typhoon information of location and direction that were provided to admiral Halsey was not accurate and the third fleet operating 480 km east of Luzon in the Philippine Sea sailed into the center of the typhoon. As a result, the ship was wrecked by strong winds of 87 kt, lowest air pressure of 907 hPa and very high seas. This typhoon resulted in the establishment of Joint Typhoon Warning Center (JTWC) in Hawaii. The model was constructed with fine-mesh finite element model covering the whole South China Sea with inclusion of the Java Sea and adjacent marginal seas and the Philippine Sea. Approximate mesh sizes in the region of interest were formulated as a few tens of meters and the bathymetry of the tidal flat area was described, thus enabling a detailed representation of component in tidal characteristics in the modelled tidal regime. Typhoon and meteorological forcing inputs for the period 13-20, December 1944 are prepared via blending of ECMWF-20C as background meteorological conditions and Holland type vortex typhoon fields. The water elevation determined from the estimation of the Japanese National Astronomical Observatory (NAOTIDE) database was imposed at the tidal open boundary. Time-series outputs of storm waves are produced showing maximum significant wave heights of 12-15 m along the typhoon track.

In order to measure sheet flow near the bottom in the north passage of Yangtze Estuary during the typhoon, a submerged synchronous field survey system composited of Nortek AquaPro, Nortem AquaPro HR, AWAC and OBS 3+ was equipped on a pedestal based structure. The system was used to survey sheet flow field during the flooding season in 2015. The pedestal base synchronous field survey system can give reasonable estimation about stability of itself, and also capture simultaneously the wave climate as well as the current feature and the sediment concentration near the bottom. Analyzing the data collected by the system, it is found that the tidal current dominates the sedimentation concentration near the bottom in the Yangtze Estuary without waves, and the only peak value of suspended sediment concentration occurs at the fall slack time. The suspended sediment concentration above 50cm to the bottom is usually not larger than 15kg/m³, and it is not significantly correlated with the wave. When typhoon happens, the suspended sediment concentration increases significantly below 30cm to the bottom. There are two peaks of the suspended sediment concentration at the spring slack and the fall slack time respectively.

Bifurcation analysis of the orthogonal cutting model with cutting force nonlinearity is presented with special attention to double Hopf bifurcations. The normal form of the system in the vicinity of the double Hopf point is derived analytically by means of center manifold reduction. The dynamics is restricted to a four-dimensional center manifold, and the long-term behavior is illustrated on simplified phase portraits in two dimensions. The topology of the phase portraits reveal the coexistence of periodic and quasi-periodic solutions, which are computed by approximate analytical formulas.

The coherence resonance (CR) and stochastic resonance (SR) in a periodic potential driven by correlated additive and multiplicative noises are studied in this paper. The effects of the system parameters on the probability density function (PDF) of the response are discussed by using the Monte-Carlo simulation. The shapes of the average joint PDF are changed from two independent peaks to a crater shape as the amplitude of the periodic force increases. The output spectrum and qualify factor are introduced to measure the CR. The qualify factor shows a pronounced peak and the intrawell CR appears. The amplitude and the phase lag of the average response first increase with increasing multiplicative noise intensity, attain a maximum, and then decrease. That is, the SR happens.

The inner ear has two main parts, the cochlea, dedicated to hearing, and the vestibular system, dedicated to balance. Dizziness and vertigo are the main symptoms related to vestibular disorders, which commonly affects older people. In order to eliminate these symptoms a vestibular rehabilitation is performed; this consists in a range of movements of the head, known as maneuvers, performed by a clinical professional. This procedure does not always work as expected. The aim of this work is to contribute to a better understanding on how the vestibular system works. This knowledge will help in the development of new techniques that will facilitate a more efficient rehabilitation. In order to achieve that goal, a three-dimensional numerical model of the vestibular system, containing the fluids which promote the body balance, was constructed. The vestibular components will be discretized using the finite element method and the fluid flow will be analyzed using the Smoothed Particle Hydrodynamics.

The results obtained with the numerical model of the semicircular canal built to study the rehabilitation process are presented and compared with other authors. The solution achieved is similar with literature.

This paper considerers the principal feasibility of using cold gas dynamic spraying with laser post treatment technique to create Al-Ni composite coatings. The prepared mixture of two powders was coated on an aluminum substrate and laser annealed. As a result the AlxNy intermetallic phases were observed in the coating. Obtained laser-annealed coatings were studied by means of optical and electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffractometry and compared with as-sprayed coatings. Effects of laser processing parameters, such as scanning speed, power and beam shape on microstructural evolution of the composite coatings were discussed and optimal regimes for laser assisted CS were determined.

This paper studies the adaptive group consensus problem of networked mechanical systems formulated by Lagrangian dynamics under directed acyclic network topology by the use of adaptive control scheme based on neural networks. A distributed group consensus algorithm is proposed for such networked mechanical systems with communication delays, and then a simple yet generic criterion on the convergence for such algorithm over directed acyclic topology is established. Furthermore, the effect of time delays on the performance of adaptive group consensus are numerically investigated. It is shown that the networked mechanical systems with communication delays can always reach the group consensus if each subgroup has a directed spanning tree. Subsequently, numerical examples illustrate and visualize the effectiveness and feasibility of the theoretical results.

Stability of the 1D wave equation with delayed boundary conditions is considered. By means of the traveling wave solution, the original system is transformed into a delay differential equation of neutral type which involves two delays. The complete and exact stability chart is presented for the delayed boundary problem in the parameter plane of the feedback gain between the boundaries and the ratio of the time delays.

We deal with some aspects of the general (mathematical) modeling of sharp interfaces (i.e. two-dimensional surfaces within a three-dimensional body) without and with own thermodynamical activity (i.e. with interfacial densities, fluxes and supplies). Questions of regularity of the quantities involved are especially addressed. We present a classification of sharp interfaces taking their relation to the remaining body as well as their thermodynamic behavior into account. After a short look into local balances at the interface we discuss a model of a shrinking body (due to mechanical treatment, e.g.) in the framework of sharp singular interfaces.