铸造桩核冠修复上颌中切牙模拟力学模型的建立和初步应用

目的:采用密胺材质人工牙建立具有完整牙本质肩领的铸造桩核冠修复上颌中切牙的模拟力学模型,并初步用于研究加载位置与角度对修复后患牙抗折性能的影响。方法:采用密胺材料人工牙经机械加工制备48个拟铸造桩核冠修复的上颌中切牙预备体试件,用随机数法随机将其分为A、B两组,A组:加载力方向与牙长轴的夹角为45°,B组:加载力方向与牙长轴的夹角为60°,每组再随机分为1、2、3三个亚组,每亚组8个试件,加载位置分别位于舌面切缘下3mm、5mm、7mm。所有试件行铸造桩核冠修复后,用特制夹具固定于万能材料试验机加载平台上,以1mm/min的速率静态加载至试件发生破坏,并记录试件破坏时的载荷和折裂方式。结果:6组样本的折裂载荷如下:A1组754.82±94.75N,B1组556.12±35.90N,A2组1228.56±162.11N,B2组817.11±135.81N,A3组1682.34±251.96N,B3组1097.00±156.89N,加载位置和加载角度均会显著影响试件的折裂载荷,且两者之间存在明显的交互效应(P<0.05)。所有试件均表现为低于树脂包埋平面的不可修复性折裂,各组试件之间的折裂方式没有统计学差异(P>0.05)。结论:在牙本质肩领充足的条件下,加载位置和加载角度会对铸造桩核冠修复上中切牙的抗折性能产生显著影响,且两者之间存在交互作用。

一个恒星能量系统动力学模拟模型

本文运用类比法，建立一个恒星系统动力学模拟模型．运用Ｌｉａｐｕｎｏｖ

水动力学模拟模型在盐碱地改良中的应用

松嫩平原土地盐碱化现象较为严重,水利工程措施法仍为主要的盐碱地改良方法。为更好的发挥水利工程的作用,提出通过水动力学模拟模型与水利工程措施相结合,在设计阶段通过水动力学模拟模型对水利工程措施效果进行论证分析,在运行管理阶段通过模拟分析获取最佳调度方案的思路,以发挥水利工程最大效果,促进盐碱地改良。

纳米金颗粒熔化与烧结过程的分子动力学模拟

利用分子动力学模拟的方法,采用嵌入原子势能模型,研究不同尺寸的纳米Au颗粒的熔化及烧结过程。结果表明,纳米金颗粒的熔点低于其块体材料的熔点,熔化过程从表面向内部进行。根据烧结颈的长大曲线确定不同尺寸的纳米Au颗粒的起始烧结温度,颗粒的最佳烧结温度范围为起始烧结温度至纳米颗粒完全熔化的温度,且升温过程中颗粒的表面熔化温度和熔点等特征温度与N-1/3成线性关系(N为Au纳米颗粒的原子数)。纳米颗粒烧结过程中原子的迁移和烧结颈长大主要有表面扩散、晶界扩散或粘性流动等机制。

地磁逆转随机性的模拟

本文在地磁场逆转的力学模拟模型的基础上提出了一个带分路的多盘发电机模型,并用它的解来模拟地磁逆转的变化规律,获得了较为满意的结果.

城市雨水管网水力学计算方法研究

根据城市雨水管网的特点，推导雨水管道非恒定非均匀流的偏微分方程组，并给出管道的初始条件和边界条件．介绍雨水管网求解方程组的方法和一些实用简化模型．

城市雨水管网水力学计算方法研究

根据城市雨水管网的特点，推导了雨水管道非恒定非均匀流的偏微分方程组，并给出了管道初始条件和边界条件．介绍了对于雨水管网求解方程组的方法和一些实用简化模型．

Case study on the mechanics of NPR anchor cable compensation for large deformation tunnel in soft rock in the Transverse Mountain area,China

A study was conducted to analyze the deformation mechanism of strongly weathered quartz schist in the Daliangshan Tunnel,located in the western Transverse Mountain area.A large deformation problem was experienced during the tunnel construction.To mitigate this problem,a support system was designed incorporating negative Poisson ratio(NPR)anchor cables with negative Poisson ratio effect.Physical model experiments,field experiments,and numerical simulation experiments were conducted to investigate the compensation mechanical behavior of NPR anchor cables.The large deformations of soft rocks in the Daliangshan Tunnel are caused by a high ground stress,a high degree of joint fracture development,and a high degree of surrounding rock fragmentation.A compensation mechanics support system combining long and short NPR anchor cables was suggested to provide sufficient counter-support force(approximately 350 kN)for the surrounding rock inside the tunnel.Comparing the NPR anchor cable support system with the original support system used in the Daliangshan tunnel showed that an NPR anchor cable support system,combining cables of 6.3 m and 10.3 m in length,effectively prevented convergence of surrounding rock deformation,and the integrated settlement convergence value remained below 300 mm.This study provides an effective scientific basis for resolving large deformation problems in deeply buried soft rocks in western transverse mountain areas.

Local structure of calcium silicate melts from classical molecular dynamics simulation and a newly constructed thermodynamic model

The distributions of local structural units of calcium silicate melts were quantified by means of classical molecular dynamics simulation and a newly constructed structural thermodynamic model. The distribution of five kinds of Si-O tetrahedra Qi from these two methods was compared with each other and also with the experimental Raman spectra, an excellent agreement was achieved. These not only displayed the panorama distribution of microstructural units in the whole composition range, but also proved that the thermodynamic model is suitable for the utilization as the subsequent application model of spectral experiments for the thermodynamic calculation. Meanwhile, the five refined regions mastered by different disproportionating reactions were obtained. Finally, the distributions of two kinds of connections between Qi were obtained, denoted as Qi-Ca-Qj and Qi-[Ob]-Qj, from the thermodynamic model, and a theoretical verification was given that the dominant connections for any composition are equivalent connections.

人体组织液定向流动与经络

关于人体经络本质的研究发现了许多新的现象,如在穴位注射放射性核素标记的小分子可观察到物质沿和古人描述的经络差不多的经线迁移,人们不仅得到了这样迁移的图像,而且还测量到了迁移的速度。但对这种循经的物质迁移一直没能从理论上给予解释。通过对人体小腿段胆经和胃经“地”的位置巨微解剖观察发现,经络线位置的骨间膜腓侧和胫侧的血管自上而下呈不均匀分布,在穴位区毛细血管密集,且在穴位和经线上的毛细血管排列呈与经线平行状,根据这一解剖事实,建立了一种毛细血管血浆与组织液交换的血液动力学模型,通过对模型的数值模拟发现,在这样的解剖结构下,组织液能产生一种定向的流动并在毛细血管密集的穴位区获得加速,并不断接力构成一条与经络线相吻合的流线。在这种流线上物质可以定向输运,计算表明在生理状态下这种输运的速度为数厘米至数十厘米每分,这和实验观察到的循经感传速度及放射性核素循经迁移速度相一致。进一步的研究还发现组织压力增高、动脉压改变以及血管壁通透性的变化都会影响流速,这和人体经络的特征是相符合的,为解释经络的科学机理提供了一种新的理论和方法。

Coarse-graining Calcium Dynamics on Stochastic Reaction-diffusion Lattice Model

We develop a coarse grained （CG） approach for efficiently simulating calcium dynamics in the endoplasmic reticulum membrane based on a fine stochastic lattice gas model. By grouping neighboring microscopic sites together into CG cells and deriving CG reaction rates using local mean field approximation, we perform CG kinetic Monte Carlo （kMC） simulations and find the results of CG-kMC simulations are in excellent agreement with that of the microscopic ones. Strikingly, there is an appropriate range of coarse proportion rn, corresponding to the minimal deviation of the phase transition point compared to the microscopic one. For fixed m, the critical point increases monotonously as the system size increases, especially, there exists scaling law between the deviations of the phase transition point and the system size. Moreover, the CG approach provides significantly faster Monte Carlo simulations which are easy to implement and are directly related to the microscopics, so that one can study the system size effects at the cost of reasonable computational time.

Pre-processing and post-processing method for geostress simulation using seismic interpretation results

In order to carry out numerical simulation using geologic structural data obtained from Landmark(seismic interpretation system), underground geological structures are abstracted into mechanical models which can reflect actual situations and facilitate their computation and analyses.Given the importance of model building, further processing methods about traditional seismic interpretation results from Landmark should be studied and the processed result can then be directly used in numerical simulation computations.Through this data conversion procedure, Landmark and FLAC(the international general stress software) are seamlessly connected.Thus, the format conversion between the two systems and the pre-and post-processing in simulation computation is realized.A practical application indicates that this method has many advantages such as simple operation, high accuracy of the element subdivision and high speed, which may definitely satisfy the actual needs of floor grid cutting.

CFD aided investigation of single droplet coalescence

This article describes the development of a coalescence model using various CFD work packages,and is validated using as toluene water model system.Numerical studies were performed to describe droplet interactions in liquid–liquid test systems.Current models use adjustable parameters to describe these phenomena.The research in the past decades led to different correlations to model coalescence and breakage depending on the chemical system and the apparatus geometry.Especially the complexity of droplet coalescence requires a detailed investigation of local phenomena during the droplet interaction.Computational fluid dynamics(CFD) studies of single droplet interactions were performed and validated with experimental results to improve the understanding of the local hydrodynamics and film drainage during coalescence.The CFD simulations were performed for the interaction of two differently sized droplets at industrial relevant impact velocities.The experimental verification and validation of the numerical results were done with standardized high-speed imaging studies by using a special test cell with a pendant and a free rising droplet.An experimental based algorithm was implemented in the open source code OpenF OAM to account for the contact time and the dimple formation.The standard European Federation of Chemical Engineering(EFCE) test system toluene/water was used for the numerical studies and the experimental investigations as well.The results of the CFD simulations are in good accordance with the observed coalescence behavior in the experimental studies.In addition,a detailed description of local phenomena,like film rupture,velocity gradients,pressures and micro-droplet entrainment could be obtained.

Hydrodynamic Comparison of a Semi-submersible,TLP,and Spar:Numerical Study in the South China Sea Environment

The South China Sea contains tremendous oil and gas resources in deepwater areas. However, one of the keys for deepwater exploration, the investigation of deepwater floating platforms, is very inadequate. In this paper, the authors studied and compared the hydrodynamics and global motion behaviors of typical deepwater platforms in the South China Sea environment. The hydrodynamic models of three main types of floating platforms, e.g. the Semi-submersible, tension leg platform （TLP）, and Truss Spar, which could potentially be utilized in the South China Sea, were established by using the 3-D potential theory. Additionally, some important considerations which significantly influence the hydrodynamics were given. The RAOs in frequency domains as well as global motions in time domains under time-varying wind, random waves, and current in 100-y, 10-y, and 1-y return period environment conditions were predicted, compared, and analyzed. The results indicate that the heave and especially the pitch motion of the TLP are favorable. The heave response of the Truss Spar is perfect and comparable with that of the TLP when the peak period of random waves is low. However, the pitch motion of Truss Spar is extraordinarily lar^er than that of Semi-submersible and TLP.

Vector modeling and track simulation in axial turn-milling motion

Through vector analysis the kinetic vector model is built in a machining cylinder surface through axial turn-milling. When building a kinetic vector model in the machining field, machining through axial turn-milling and using equilateral triangles and square prism surfaces, the kinetic vector model is given any equilateral polygon prismic surface. Kinetic tracks are simulated through these kinetic models respectively, thus it can be seen that the axial turn-milling is a very effective method in manufacturing any equilateral, polygon, prismic surface.

Spacecraft formation control strategy on Sun-Earth Lissajous orbit

To carry out the deep space exploration tasks near Sun-Earth Libration point L2, the CRTBP dynamic model was built up and the numerical conditional quasi-periodic orbit （Lissajons orbit） was computed near L2. Then, a formation controller was designed with linear matrix inequality to overcome the difficuhy of parameter tuning. To meet the demands of formation accuracy and present thruster＇s capability, a threshold scheme was adopted for formation control. Finally, some numerical simulations and analysis were completed to demonstrate the feasibility of the proposed control strategy.

基于流路设计的斜隔板引流喷射换热器研究

为提高原油加热等壳程蒸汽冷凝换热工况的换热效果,本文基于流路设计提出了一种斜隔板层间引流喷射型换热器,并采用数值模拟方法进行分析.分别探究了斜隔板倾角、进口流速、层间引流喷射、换热单元层数对换热性能的影响,获得了换热器综合性能(JF因子)与倾斜角、进口流速的经验关联式.结果表明:壳程斜隔板结构能够提高换热器的JF因子,且倾斜角和进口流速的适当增大有利于换热器性能的提高;多段引流喷射能利用进料气引流上一层的乏汽,提高上层乏汽热品位;斜隔板引流喷射结构放大效应小,有利于工业生产.

Combustion simulation and key parameter optimization for opposite axial piston engine in small-scale

As potential alternative power sources used in portable electric generators, opposite axial piston engines in small-scale were investigated to show their advantages in power density. A novel cylinder charge system was introduced, based on which a quasi-dimension model and a CFD(computational fluid dynamics) model were established. Comparison of those two models was carried out to validate the quasi-dimension model. Furthermore, optimal diameter of charge cylinder and speed were determined after evaluating the quasi-dimension model based on different parameters. High agreement between the quasi-dimension model and the CFD model validates the quasi-dimension model. Further studies show that the power of engine increases with the diameter of charge cylinder. However, a too big charge cylinder lowers the fuel efficiency instead. Taking economic influence into consideration the charge cylinder should be 1.4 times power cylinder, which could ensure the power density, volumetric efficiency and fuel economic at the same time. Axial piston engine running at 1.0×104 r/min could achieve a better overall performance. The maximal power of engine with optimal parameters is 0.82 k W, which fits the power need of the portable electric generators completely.

Kinetic Model and Simulation Analysis for Toluene Disproportionation and C9-Aromatics Transalkylation

A new kinetic model for commercial unit of toluene disproportionation and C9-armatiocs transalkylation is developed based on the reported reaction scheme.A time based catalyst deactivation function taking weight hourly space velocity(WHSV)into account is incorporated into the model,which reasonably accounts for the loss in activity because of coke deposition on the surface of catalyst during long-term operation.The kinetic parameters are benchmarked with several sets of balanced plant data and estimated by the differential variable metric optimiza- tion method.Sets of plant data at different operating conditions are applied to make sure validation of the model and the results show a good agreement between the model predictions and plant observations.The simulation analysis of key variables such as temperature and WHSV affecting process performance is discussed in detail,giv- ing the guidance to select suitable operating conditions.

CFD modeling of methane distribution at a continuous miner face with various curtain setback distances

Knowledge of the airflow patterns and methane distributions at a continuous miner face under different ventilation conditions can minimize the risks of explosion and injury to miners by accurately forecasting potentially hazardous face methane levels. This study focused on validating a series of computational fluid dynamics(CFD) models using full-scale ventilation gallery data that assessed how curtain setback distance impacted airflow patterns and methane distributions at an empty mining face(no continuous miner present). Three CFD models of face ventilation with 4.6, 7.6 and 10.7 m(15, 25, and 35 ft) blowing curtain setback distances were constructed and validated with experimental data collected in a full-scale ventilation test facility. Good agreement was obtained between the CFD simulation results and this data.Detailed airflow and methane distribution information are provided. Elevated methane zones at the working faces were identified with the three curtain setback distances. Visualization of the setback distance impact on the face methane distribution was performed by utilizing the post-processing capability of the CFD software.