Procedia IUTAM最新文献

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.

Modeling interactive features of storm waves and surges may be one of important but challenging tasks toward more accurate estimations of coastal hazards under severe storms. This paper discusses how storm waves and interactions of waves and surges affect amplification of local inundation characteristics through overviews of several case studies of recent coastal disasters. The paper first describes witnessed inundation characteristics caused by Super Typhoon Haiyan along the coast of San Pedro Bay and also the east coast of Eastern Samar in the Philippines. Along the west coast of San Pedro Bay, neither predicted storm surge nor storm wave can reasonably represent the following observed features: inundation around the mouth of San Pedro Bay started about an hour prior to the time when the inundation was witnessed at the inner part of the bay and the water level quickly descended after the peak around the bay mouth while it was kept high for an hour in the inner part of the bay. Along the east coast of Eastern Samar, deformation of wind wave components strongly depends on bathymetry of fringing coral reefs and refraction, diffraction and wave-wave interactions appear to have significant influence on observed locally varying damage levels and inundation characteristics. Similar locally concentrated inundation was also observed along the west coast of Batan island, the Philippines when the super typhoon Meranti passed north of the island. Significant influence of infra-gravity waves on the locally concentrated inundation characteristics was also observed in the disaster along Seisho coast on the Pacific coast of Japan when the typhoon, Fitow, hit the coast in 2007. Based on these findings, finally, this paper discusses how the numerical model should be extended for better estimations of coastal hazard with brief example of model application to South Pacific islands.

Endolymphatic hydrops (EH) causes fluctuating hearing loss especially at low frequencies. In this paper, we analyze EH with the human cochlear finite element model which includes activity of the outer hair cells (OHC). EH was simulated by loading static pressure on the surface of the basilar membrane (BM) of the cochlear model. The vibrations of the BM in the EH model were calculated by applying sound pressure to the stapes, and the results were compared with those in the normal cochlea model. As a result, the distribution of characteristic frequency (CF) was changed and the displacement of the BM was decreased by loading static pressure to the BM. This suggests that the mechanism of hearing loss was caused by EH.

In order to manifest the extreme hydrodynamic environments for Puti Island wind farm in Bohai Sea, flow and wave climates in the area induced by cold waves are investigated. According to the historical meteorology statistics and taking the global climate change into account, three typical paths (NNE, ENE and NNW) with four high wind speeds for cold waves in Bohai Sea are presumed. After calibrated with field data, the Princeton Ocean Model (POM) and the third-generation wave model, SWAN, are employed to delineate possible extreme hydrodynamic conditions in the area of Puti Island wind farm. The dependence of the extreme current and water wave parameters to the wind speed and wind direction is investigated. The distribution of the extreme current and water wave parameters in the wind farm is discussed.

Flood and tide features atMin River tidal reach are analyzed anda high-resolution flood-tide coupled model which useshigh-resolution GIS data for Minjiang Estuary with the highest grid resolution of 50-100m at key areas isestablished in this paper. Unstructured triangular mesh that can realize the grid resolution of 50-100m at key areas is employed in the model. Zhuqi section is chosen for flood boundary, and three numerical experimentsare conducted for June 6 2006 flood process. The experimental results indicate that, when coupled with tide and flood, the simulation of each tide gauge agrees very well with measured data compared withmodelresults only with flood or tide, and the original tidal features are changedat the different sections in Min River tidal reachedby the flood signals. Obvious flood characteristics are shown in Wenshanli and Jiefang Bridge station and flood-tidal mixed characteristics are shown in Xianan, Baiyantan and Guantou station.The strong interaction between tide and floodoccursin the watercourse (from Xiannan in South Channel to Guantou) because the current velocity is reduced during high water time but increasedduringlow water time.

The paper surveys the recent studies of authors on the dynamic modeling and simulation of soft machines in the frame of multibody system dynamics. The studies focus on the geometric nonlinearity of coupled overall motion and large deformation of a soft body, the physical nonlinearity of a soft body made of hyper-elastic or elastoplastic materials, the frictional impacts and contacts of soft bodies, and the efficient dynamic computation algorithm of soft multibody systems governed by a set of differential-algebraic equations of very high dimensions. The paper presents the validation of proposed approach through three case studies, including the locomotion of a soft quadrupedal robot, the spinning deployment of a solar sail of spacecraft, and the deployment of a mesh reflector of satellite antenna, as well as the corresponding experimental studies. Finally, the paper gives some remarks on future researches.

This proceedings paper contains a review of the work presented in the Sectional Lecture in Solids on August 25 at ICTAM 2016. -- Proteins are long polypeptide chains of amino acids and their structure and biological function are directly related to their amino acid sequence. I will discuss three different biological functions that are dominated by protein mechanics, each at their own specific time and length scale. To relate structure to function, multiscale computational models have been developed for (i) cilia and flagella, (ii) actin filament networks and (iii) the nuclear pore complex.

Bioinspired superhydrophobic surfaces have attracted great interests from fundamental researches to engineering applications. The functionality of superhydrophobicity, especially for an underwater situation, depends on a large area fraction of entrapped liquid-gas interfaces, which, however, are subject to instabilities induced by various physical phenomena, such as pressurization, air diffusion, fluid flow, and condensation. The wetting states strongly affssect the functionality of superhydrophobic surface, like liquid slippage and cavitation. The current work is dedicated to elucidating the underlying mechanisms of stability and wetting transition of underwater superhydrophobicity, providing novel strategies for durable and robust design, and introducing the applications in drag reduction and cavitation control.

InP nanowires, synthesized through a self-seeded growth approach, are used in the fabrication of field-effect transistors which consist of source, drain, and back-gate electrodes. The weak gating voltage dependence implies low carrier concentrations whereas its behavior reveals native n-type doping in InP nanowires. These InP nanowire devices exhibit a vast variation of room-temperature resistance that raises a question about contact resistance. For devices of low room-temperature resistance, electron transport in InP nanowires is investigated using temperature dependent resistance in the temperature range between 80 and 300 K, and it can be analyzed using the model of thermal activation. For other devices of high room-temperature resistance, we take into account nanocontact resistance. Models of both Schottky contact and Mott's variable range hopping (VRH) are considered. The two resistances are connected in parallel to give total contact resistance of InP nanowire devices. After fitting experimental data by the proposed model, we estimate effective Schottky barriers and disorder contributions to nanocontact resistance. The effective Schottky barrier, and the nanocontact Schottky and Mott's VRH resistances are plotted as a function of the device room-temperature resistance which indicates the scale of disorder. Using room-temperature resistance of InP nanowire devices, the devices are classified into nanowire- or contact-dominated devices. The two different class of devices are used to check their photo- and gas-sensitivities. The contact-dominated InP nanowire devices show low dark current and low photocurrent as usual, but these contact-dominated devices give high ratio of photo- to dark-current. That result reveals a high photo-sensitivity for those devices of high nanocontact resistance. On the other hand, for gas sensing experiments, the contact-dominated devices show as well a high ratio of resistance under O₂ to that under N₂ gas exposure.