Mamtimin Geni

Stress Analysis of Gear Meshing Impact Based on SPH Method

Based on the kinetic equations of the gear mesh impact, SPH discrete equations were established. Numerical simulation was carried out on the meshing impact process of the gear, and stress and strain of each discrete point were obtained. After data processing, stress propagation was calculated, which shows stress distribution on tooth-profile surface. It is concluded that the stress concentrate mainly occurs in the pitch circle. The paper provides an effective new numerical simulation algorithm to gear mechanical properties analysis.

The effect of isotropic and anisotropic scattering in drain region of ballistic channel diode

The effect of isotropic and anisotropic scattering within the drain region of diode with ballistic channel is investigated using the semiclassical Monte Carlo simulation, and the results are discussed. The results show that the isotropic scattering can severely degrade the steady-state current, the electrons mean velocity, and increase the electrons concentration in channel because some hot electrons can back into the channel from drain, and even return to the source. On the contrary, anisotropic scattering can suppresses the backward flow of hot electrons. We conclude that the isotropic scattering in the drain region seriously influences the carrier transport relative to anisotropic scattering.

Effects of Scattering Direction of Hot Electrons in the Drain of Ballistic n+--i--n+ Diode

Ionized impurity scattering has a weak influence on hot electron transport at low doping concentrations owing to the fact that ionized impurity scattering is an anisotropic scattering with a high preference for forward scattering and most hot electrons are absorbed in the drain after undergoing ionized impurity scattering. On the other hand, ionized impurity scattering approaches isotropic characteristics at sufficiently high doping concentrations and enhances the scattering of hot electrons in the backward direction and severely degrades the peak of the mean velocity of electrons in the channel and the steady-state current. We conclude that the scattering direction is an important factor for hot electron transport in the drain region of semiconductor devices.

Simulation of Droplet Impacting on Elastic Solid with the SPH Method

The phenomenon of droplet impacting on solid surfaces widely exists in both nature and engineering systems. However, one concern is that the microdeformation of solid surface is difficult to be observed and measured during the process of impacting. Since the microdeformation can directly affect the stability of the whole system, especially for the high-rate rotating components, it is necessary to study this phenomenon. Aiming at this problem, a new numerical simulation algorithm based on the Smoothed Particle Hydrodynamics (SPH) method is brought forward to solve fluid-solid coupling and complex free surface problems in the paper. In order to test and analyze the feasibility and effectiveness of the improved SPH method, the process of a droplet impacting on an elastic plate was simulated. The numerical results show that the improved SPH method is able to present more detailed information about the microdeformation of solid surface. The influence of the elastic modulus of solid on the impacting process was also discussed.

The Effects of Multiple Scattering on Performance of Ballistic Channel Strained-Si Diodes

We have investigated the effects of multiple scattering on electron velocity, current and energy in the drain regions of the Strained-Si diodes. The covered cases in this study are ballistic channel Si-diodes with strained channel or drain, and with strained channel and drain, respectively. For a selected Ge content, the simulation results show that the velocity of electrons in the drain regions of strained channel and drain is lower than that of strained drain at the lower bias voltages (Vd 0.5V), the velocity in the drain regions of strained channel and drain regions is lower than that of strained drain regions. Meanwhile, the velocity of electrons in the drain regions of ballistic channel diodes with strained channel and drain reduces due to optical phonon scattering, when bias voltage increases.

Numerical Modeling for Discrete Multibody Interaction and Multifeild Coupling Dynamics Using the SPH Method

Discrete multibody interaction and contact problems and the multiphase interactions such as the sand particles airflow interactions by Aeolian sand transport in the desert are modeled by using the different kernel smoothing lengths in SPH method. Each particle defines a particular kernel smoothing length such as larger smoothing length which is used to calculate continuous homogenous body. Some special smoothing lengths are used to approximate interaction between the discrete particles or objects in contact problems and in different field coupling problem. By introducing the Single Particle Model (SPM) and the Multiparticle Model (MPM), the velocity exchanging phenomena are discussed by using different elastic modules. Some characteristics of the SPM and MPM are evaluated. The results show that the new SPH method can effectively solve different discrete multibody correct contact and multiphase mutual interference problems. Finally, the new SPH numerical computation and simulation process are verified.

The effects of drain scatterings on the electron transport properties of strained-Si diodes with ballistic and non-ballistic channels*

The effects of multiple scattering on the electron transport properties in drain regions are numerically investigated for the cases of strained-Si diodes with or without scattering in the channel. The performance of non-ballistic (with scattering) channel Si-diodes is compared with that of ballistic (without scattering) channel Si-diodes, using the strain and scattering model. Our results show that the values of the electron velocity and the current in the strain model are higher than the respective values in the unstrained model, and the values of the velocity and the current in the ballistic channel model are higher than the respective values in the non-ballistic channel model. In the strain and scattering models, the effect of each carrier scattering mechanism on the performance of the Si-diodes is analyzed in the drain region. For the ballistic channel model, our results show that inter-valley optical phonon scattering improves device performance, whereas intra-valley acoustic phonon scattering degrades device performance. For the strain model, our results imply that the larger energy splitting of the strained Si could suppress the inter-valley phonon scattering rate. In conclusion, for the drain region, investigation of the strained-Si and scattering mechanisms are necessary, in order to improve the performance of nanoscale ballistic regime devices.

Experimental Observation of the Skeletal Adaptive Repair Mechanism and Bionic Topology Optimization Method

Bone adaptive repair theory considers that the external load is the direct source of bone remodeling; bone achieves its maintenance by remodeling some microscopic damages due to external load during the process. This paper firstly observes CT data from the whole self-repairing process in bone defects in rabbit femur. Experimental result shows that during self-repairing process there exists an interaction relationship between spongy bone and enamel bone volume changes of bone defect, that is when volume of spongy bone increases, enamel bone decreases, and when volume of spongy bone decreases, enamel bone increases. Secondly according to this feature a bone remodeling model based on cross-type reaction-diffusion system influenced by mechanical stress is proposed. Finally, this model coupled with finite element method by using the element adding and removing process is used to simulate the self-repairing process and engineering optimization problems by considering the idea of bionic topology optimization.

Structural Topology Optimization Method Based on Bone Remodeling

Bone is a dynamic living tissue that undergoes continuous adaptation of its mass and structure in response to mechanical and biological environment demands. In this paper, we firstly propose a mathematical model based on cross-type reaction diffusion equations of bone adaptation during a remodeling cycle due to mechanical stimulus. The model captures qualitatively very well the bone adaptation and cell interactions during the bone remodeling. Secondly assuming the bone structure to be a self-optimizing biological material which maximizes its own structural stiffness, bone remodeling model coupled with finite element method by using the add and remove element a new topology optimization of continuum structure is presented. Two Numerical examples demonstrate that the proposed approach greatly improves numerical efficiency, compared with the others well known methods for structural topology optimization in open literatures.

A New Bionic Topology Optimization Method Based Model of Bone Adaptation

A new bionic topology optimization method by combining reaction-diffusion equations describing bone adaptation process with finite element analysis is presented in this study. The major idea of the present approach is to consider the structure to be optimized as a piece of bone that obeys bone adaptation and the process of finding the optimum topology of a structure is equivalent to the bone remodeling process. Two widely used numerical examples demonstrate that the proposed approach greatly improves numerical efficiency compared with the othert well known methods for structural topology optimization in open literature. The results show that the optimal designs from the present bionic topology optimization method without use mathematical programming and numerical instability control techniques. The proposed method results in a better and faster convergence.