numerical

摘要： This paper presents the fabrication,characterization and numerical simulation of poly-3-hexylthiophene(P3HT)-based bottom-gate bottom-contact(BGBC)organic thin film transistors(OTFTs).The simulation is based on a drift diffusion charge transport model and density of defect states(DOS)for the traps in the band gap of the P3HT based channel.It combines two mobility models,a hopping mobility model and the Poole-Frenkel mobility model.It also describes the defect density of states(DOS)for both tail and deep states.The model takes into account all the operating regions of the OTFT and includes sub-threshold and above threshold characteristics of OTFTs.The model has been verified by comparing the numerically simulated results with the experimental results.This model is also used to simulate different structure in four configurations of OTFT e.g.bottom-gate bottom-contact(BGBC),bottom-gate top-contact(BGTC),top-gate bottom-contact(TGBC)and top-gate top-contact(TGTC)configurations of the OTFTs.We also present the compact modeling and model parameter extraction of the P3HT-based OTFTs.The extracted compact model has been further applied in a p-channel OTFT-based inverter and three stage ring oscillator circuit simulation.

摘要： A practical method is proposed to search for periodic orbits of elongated asteroids.The method obtains required initial variables of periodic orbits by using the rotating mass dipole with appropriate parameters,and then implement local iterations to obtain the real orbits over an asteroid in the polyhedral model.In this paper the dipole and polyhedral models,and list detailed procedures of the searching method are introduced.A planar single lobe orbit is presented to evaluate the effectiveness of the method,with the asteroid 216 Kleopatra of the triple asteroid system as a representative elongated body.By applying the above method,ten families of periodic orbits around Kleopatra are identified and discussed with respect to their orbital stabilities and periods.One sample of the sombrero orbit is checked by calculating 1000 hours to examine its orbital behavior.Besides the above orbits,the intriguing head-surrounding orbit is also analyzed.

摘要： We perform a set of non-radiative hydro-dynamical(NHD)simulations of a rich cluster sized dark matter halo from the Phoenix Project with three different numerical resolutions,to investigate the effect of hydrodynamics alone on the subhalo population in the halo.Compared to dark matter only(DMO)simulations of the same halo,subhaloes are less abundant for relatively massive subhaloes(Msub>2.5×109h 1M⊙,or Vmax>70 km s 1)but more abundant for less massive subhaloes in the NHD simulations.This results in different shapes in the subhalo mass/Vmax function in two different sets of simulations.At given subhalo mass,the subhaloes less massive than 1010h 1M⊙have larger Vmax in the NHD than DMO simulations,while Vmax is similar for the subhaloes more massive than the mass value.This is mainly because the progenitors of present day low mass subhaloes have larger concentration parameters in the NHD than DMO simulations.The survival number fraction of the accreted low mass progenitors of the main halo at redshift 2 is about 50 percent higher in the NHD than DMO simulations.

摘要： Structural health monitoring(SHM)is a process of implementing a damage detection strategy in existing structures to evaluate their condition to ensure safety.The changes in the material,geometric and/or structural properties affect structural responses,which can be captured and analyzed for condition assessment.Various vibration-based damage detection algorithms have been developed in the past few decades.Among them,wavelet transform(WT)gained popularity as an efficient method of signal processing to build a framework to identify modal properties and detect damage in structures.This article presents the state-of-the-art implementation of various WT tools in SHM with a focus on civil structures.The unique features and limitations of WT,and a comparison of WT and other signal processing methods,are further discussed.The comprehensive literature review in this study will help interested researchers to investigate the use of WT in SHM to meet their specific needs.

摘要： In this paper, we construct a class of semi-implicit difference method for time fractional diffusion equations—the group explicit (GE) difference scheme, which is a difference scheme with good parallelism constructed using Saul’yev asymmetric scheme. The stability and convergence of the GE scheme of time fractional diffusion equation are analyzed by mathematical induction. Then, the theoretical analysis is verified by numerical experiments, which shows that the GE scheme is effective for solving the time fractional diffusion equation.

摘要： The three-level shaft of the mixed pit shaft of Yixin Mine,built in 1983,failed continuously due to the influence of geological structure and the effect of water,which formed a collapsed space with a length of 18m,a depth of 12m,and a height of 12m at the level of-255m and to the southwest end.The 54m pit shaft below the-258m elevation of the pit shaft was filled with collapsed rocks forming a large loose body.The comprehensive processing plan for falling grouting and anchoring was proposed according to the geological conditions of the vertical shaft of the mixed pit shaft,adopting three-dimensional numerical simulation software as well as calculating the mechanical state of the vertical pit shaft surrounding rocks and using 3 to 5 parameters of Williams-Warnke failure criterion.

摘要： Alkali metal DC arc discharge has the characteristics of easy ionization,low power consumption,high plasma temperature and ionization degree,etc,which can be applied in aerospace vehicles in various ways.In this paper,we calculate the physical property parameters of lithium vapor,one of the major alkali metals,and analyze the discharge characteristics of lithium plasma with the magnetohydrodynamic(MHD)model.The discharge effects between constant current and voltage sources are also compared.It is shown that the lithium plasma of DC arc discharge has relatively high temperature and current density.The peak temperature can reach tens of thousands of K,and the current density reaches 6 x 107 A m 2.Under the same rated power,the plasma parameters of the constant voltage source discharge are much higher than those of the constant current source discharge,which can be used as the preferred discharge mode for aerospace applications.

摘要： Modeling two-dimensional overland flow across complex real-world topography is a challenging problem. Predicting the overland flow variables for various whatif rainfall scenarios can facilitate designing water infrastructure components aimed at preventing inundation and urban flooding. Numerical models that are being used range from those that solve the simplified St. Venant equations to CFD models that solve the complete three dimensional Navier-Stokes equations. In this work, the performance of the USGS Diffusion Hydrodynamic Model (DHM) for a series of overland flow test problems was tested by comparing numerical solutions obtained for an event-driven simulation across various sensitive parameter combinations. The reliability of the model and its ability to incorporate various topographical characteristics in the domain are illustrated.

摘要： In the case of lid-driven deep cavity flow, the effects of different resolutions of local grid refinement have been studied in the frame of multiple relaxation times (MRT) lattice Boltzmann method (LBM). In all the cases, the aspect ratio and Reynolds number are set as 1.5 and 3.200, respectively. First, the applied method is validated by comparing it with two reported works, with which agreements are reached. Then, six separate degrees of local grid refinement at the upper left corner, i.e. purely coarse grid, including 1/64, 1/32, 1/16, 1/8, 1/4 refinements of the lattice number in the width direction have been studied in detail. The results give the following indications:① The refinement degrees lower than 1/8 produce similar results;② For single corner refinement, 1/4 refinement is adequate for clearing the noises in the singularity zone to a large extent;③ New noise around the interface between coarse and fine zones are introduced by local grid refinement. Finally, refinement of entire subzone neighboring the lid is examined to avoid introducing new noises and it has been found effective.