顶驱钻井装置的计算机仿真

初步研究了机械系统计算机建模、仿真和分析的常用软件Pro／E，ADAMS和ANSYS及它们之间的接口标准，总结出一套实用的借助这些软件和接口做机械系统建模、仿真和分析的路线图和总体框架；对顶驱钻井装置建模、仿真和分析中应注意的问题做了阐明；对顶驱钻井装置中挟杆机构做了设计研究，集成了连杆连续柔性模块和连杆离散柔性模块，对其做了初步的仿真和分析；对顶驱钻井装置中起升系统做了等效弹簧模型和集成了钻柱离散柔性模块，并进行了初步的仿真和分析；建立了顶驱装置开钻时的模型，并集成了导轨连续柔性模块，做了初步的仿真和分析。     

Imaging of Bernal stacked and misoriented graphene and boron nitride: experiment and simulation

Experimental atomic resolution bright and high angle dark field transmission electron microscopy images of mono- and few-layer graphene and boron nitride, as well as of turbostratic arrangements in both materials, are compared to their simulated counterparts. Changes in the images according to defocus, layer number and accelerating voltage are discussed. It emerges that simulations with realistic microscope parameters accurately depict experimental graphene and boron nitride images and present a reliable tool for their interpretation.     

Tribological properties of few-layer graphene oxide sheets as oil-based lubricant additives

The performance of a lubricant largely depends on the additives it involves. However, currently used additives cause severe pollution if they are burned and exhausted. Therefore, it is necessary to develop a new generation of green additives. Graphene oxide (GO) consists of only C, H and O and thus is considered to be environmentally friendly. So the tribological properties of the few-layer GO sheet as an additive in hydrocarbon base oil are investigated systematically. It is found that, with the addition of GO sheets, both the coefficient of friction (COF) and wear are decreased and the working temperature range of the lubricant is expanded in the positive direction. Moreover, GO sheets has better performance under higher sliding speed and the optimized concentration of GO sheets is determined to be 0.5wt%. After rubbing, GO is detected on the wear scars through Raman spectroscopy. And it is believed that, during the rubbing, GO sheets adhere to the sliding surfaces, behaving like protective films and preventing the sliding surfaces from contacting with each other directly. This paper proves that the GO sheet is an effective lubricant additive, illuminates the lubrication mechanism, and provides some critical parameters for the practical application of GO sheets in lubrication.     

Vibration analysis of nano-structure multilayered graphene sheets using modified strain gradient theory

In this paper, for the first time, the modified strain gradient theory is used as a new size-dependent Kirchhoff micro-plate model to study the effect of interlayer van der Waals (vdW) force for the vibration analysis of multilayered graphene sheets (MLGSs). The model contains three material length scale parameters, which may effectively capture the size effect. The model can also degenerate into the modified couple stress plate model or the classical plate model, if two or all of the material length scale parameters are taken to be zero. After obtaining the governing equations based on modified strain gradient theory via principle of minimum potential energy, as only infinitesimal vibration is considered, the net pressure due to the vdW interaction is assumed to be linearly proportional to the deflection between two layers. To solve the governing equation subjected to the boundary conditions, the Fourier series is assumed for w=w(x, y). To show the accuracy of the formulations, present results in specific cases are compared with available results in literature and a good agreement can be seen. The results indicate that the present model can predict prominent natural frequency with the reduction of structural size, especially when the plate thickness is on the same order of the material length scale parameter.     

面向主体行为的供应链运作过程仿真模型

为了在供应链协调仿真中体现成员行为特性,提出一种面向主体行为的供应链运作过程集成仿真模型。重点对成员主体结构模型进行了研究,基于该主体结构模型进一步对成员行为进行了详细描述,并对成员行为过程的相关行为协议展开了系统化研究。基于提出的集成仿真模型开发了一个五级供应链运作过程仿真平台,实现了面向供应链成员行为的可视化建模与仿真功能,并通过仿真实验初步验证了所提集成仿真模型的有效性。实验结果表明:面向供应链成员行为的仿真能够通过调整行为协议对供应链运作过程行为策略进行优化,为供应链运作过程的协调建模、协调仿真和协调管理提供一种量化和动态的研究方法。     

Nanostructured active chitosan-based films for food packaging applications: Effect of graphene stacks on mechanical properties

Bioactive food-preserving materials are based on the use of a natural antimicrobial compound loaded in a carrier material, which is able to trigger its release when requested and to modulate the rate of release, thus using either toxic or inhibitory properties against pathogens or bacteria due to food decomposition. In this study, the Schiff base formation for chitosan functionalization was achieved by the reaction of chitosan with cinnamaldehyde at different concentrations. Cinnamaldehyde is an aromatic α,β-unsaturated aldehyde, and the major component in essential oils from some cinnamon species. It has been shown to exert antimicrobial action against a large number of microorganisms including bacteria, yeasts, and mould. The formation of the Schiff base is reversible under suitable conditions, and this might allow the release of the active cinnamaldehyde from chitosan, used as the carrier. The reaction kinetics was investigated by means of rheological measurements, while infrared spectroscopy was used to assess the efficacy of the functionalization. The addition of nanometric graphene stacks to the cinnamaldehyde-functionalized chitosan films was evaluated with the aim to increase the mechanical properties of the film. Finally, the films were tested for antifungal properties with bread slices against a selected mould line.     

VBA及MATLAB环境下焊接机器人计算机图形仿真系统的开发

论述AutoCAD2004环境下，以VBA为二次开发工具，实行VBA和数学软件MATLAB的混合编程，把MATLAB作为后拿矩阵计算引擎，成功地实现了焊接机器人计算机三维动态图形仿真。该系统对机器人的研制、设计和试验有实际应用价值。     

Electrochemical determination of sulfite and phenol using a carbon paste electrode modified with ionic liquids and graphene nanosheets: Application to determination of sulfite and phenol in real samples

Benzoylferrocene was used to construct a modified-graphene paste electrode. Also, hydrophilic ionic liquid (n-hexyl-3-methylimidazolium hexafluoro phosphate) was used as a binder to prepare the modified electrode. The electro-oxidation of sulfite at the surface of the modified electrode was studied using electrochemical approaches. This modified electrode offers a considerable improvement in voltammetric sensitivity toward sulfite, compared to the bare electrode. Square wave voltammetry (SWV) exhibits a linear dynamic range from 5.0 × 10⁻⁸ to 2.5 × 10⁻⁴ M and a detection limit of 20.0 nM for sulfite. The diffusion coefficient and kinetic parameters (such as electron transfer coefficient and the heterogeneous rate constant) for sulfite oxidation were also determined. The prepared modified electrode exhibits a very good resolution between the voltammetric peaks of sulfite and phenol that makes it suitable for the detection of sulfite in the presence of phenol in real samples.     

Numerical simulation of metal removal in laser drilling using symmetric smoothed particle hydrodynamics

A simple numerical model is proposed for predicting the penetration depth of metal laser drilling. A simplified 2D axisymmetric model for transient metal laser drilling is introduced. Strong-form of Symmetric Smoothed Particle Hydrodynamics (SSPH) method is used to harness its significant reduction in computational time. The 2D axisymmetric domain is discretized, then SSPH formulation is used to obtain shape functions. Collocation method is used to discretize governing and boundary conditions equations to construct the global stiffness matrix. Laser beam is assumed to be continuous wave with Gaussian distribution. MATLAB code is constructed for numerical simulation, and the results are compared with published work. A good agreement is shown, and thus the proposed numerical model is found to be computationally efficient and accurate standalone platform for predicting the penetration depth of metal laser drilling process.     

利用微机串口进行TMS320C25的在线编程

TMS320C25是一种高速数字信号处理器,由于它的高速性,要求开发系统的仿真头电缆线尽量短,这就给实际联调或外场实验中调试程序带来许多不便,此外,TMS320C25的程序一般固化在E-PROM中,联调时要反复修改程序就需反复擦写EPROM,本文介绍了一种TMS320C25的在线编程方法,该方法脱离开TMS320C25的开发系统,利用微机串口直接将微机中的程序写入TMS320C25的外部存储器RAM中,避免了反复擦写EPROM,给实际联调工作带来了极大方便.     

Modelling and simulation of structure surface generation using computer controlled ultra-precision polishing

The applications of structured surfaces have been more widespread. However, research on the fabrication of these surfaces is still far from complete. The paper presents a theoretical and experimental investigation of the generation of structured surfaces by using Computer Controlled Ultra-precision Polishing (CCUP). A surface topography simulation model and hence a model-based simulation system for the modelling and simulation of the generation of structure surfaces by using CCUP have been established and verified through a series of simulation and practical polishing experiments. The results of experiments demonstrate the capability of the model-based simulation system in predicting the form error and the pattern of the 3D-texture generated by using CCUP.     

异型石材样件的数控加工与仿真

对一种新型异型石材加工中心的程序编制、后置处理及加工工艺进行了研究,并成功应用于典型浮雕样件——万里长城的制作之中.首先通过UG/CAD模块,建立万里长城浮雕实体模型.分析毛坯石材的铣削特性,结合实体造型与材质特性,选择合适的刀具,通过计算得出切削深度,切削速度,进给速度,主轴转速等工艺参数.利用UG/CAM模块对模型...     

Design of gauges and multipoint measuring systems using coordinate-measuring-machine data and computer simulation

The existing coordinate-measuring-machine programs using least square methods for the calculation of geometric elements are not suitable for the evaluation of component fitting. However, evaluation programs that supply statements that are comparable with those of gauge inspection can be used to support the design of gauges and multipoint measuring systems. How to optimize an inspection device by simulation in practice is shown by the example of a forged bevel gear.     

Evaluation of the pacing rate response to treadmill exercise using computer simulation of a temperature-based, rate-adaptive algorithm

A temperature-based, rate-adaptive, pacing algorithm was developed to benefit the patient. Rate-adaptive pacemakers use a physiologic parameter to identify the need for increased pacing rate. Parameters that have been clinically investigated include venous pH, Q-T interval, respiration, body motion, and blood temperature. The objective of this study was to provide pacing rates resembling normal heart rates in response to various levels and types of activity. A rapid response time (within 30 s of exercise onset) was also sought. Blood temperature, which reflects metabolic activity of all regions, was selected as the physiologic parameter. Right ventricular blood temperature was recorded in 25 patients with implanted Kelvin 500 pacemakers (Cook Pacemaker) during rest and treadmill exercise. The patient population included 16 men and 9 women, age 44-81 years (mean = 72). Indications for pacing were sinus node disease, atrioventricular block, and atrial fibrillation with slow ventricular response. The temperature changed with physical activity and emotional stress. Temperature typically dropped briefly at exercise onset, increased with continued exercise, and returned to the resting level after exercise. These components were employed in developing the temperature-based rate-adaptive algorithm, which was designed to use the rate of temperature change (dT/dt), temperature change (delta T), and baseline temperature (T). The temperature profiles were used to produce simulated pacing rates as determined by the algorithm. The drop in temperature at onset of activity was utilized to provide a rapid increase in pacing rate. As dT/dt became positive and delta T increased, pacing rate was further increased.(ABSTRACT TRUNCATED AT 250 WORDS)     

Use of a computer molecular simulation to describe lubricating layer structure

The potential of methods of computer molecule dynamics for determining the characteristics of lubricating layers are considered for hydrodynamic and boundary lubrication regimes. Examples of finding parameters of adsorption, supermolecular self-organization, and rheology in lubricating layers are given for model lubricants.     

面向制造的产品三维建模特征规划研究

产品三维建模模型的创建过程是否合理,直接影响到模型的后续应用。建模前的特征规划是使所建模型具有合理性、智能性、灵活性和可扩展性的关键。从产品三维建模角度,给出面向产品建模的形状特征分类方法,探讨了形状特征规划的有关问题。     

Measurement and simulation of pollutant emissions from marine diesel combustion engine and their reduction by exhaust gas recirculation

Taking into account the complexity and cost of a direct experimental approach, the recourse to simulation, which can also predict inaccessible information by measurement, offers an effective and fast alternative to apprehend the problem of pollutant emissions from internal combustion engines. An analytical model based on detailed chemical kinetics employed to calculate the pollutant emissions of a marine Diesel engine in general gave satisfactory results compared to experimentally measured results. Especially, the nitric oxide (NO) emission values were found to be higher than the limiting values tolerated by the International Maritime Organization (IMO). Thus, this study was undertaken to reduce to the maximum these emissions. The reduction of pollutant emissions is apprehended with exhaust gas recirculation (EGR). This paper was recommended for publication in revised form by Associate Editor Kyoung Doug Min Nader Larbi, born on 28 of August 1973 in Tunis, received a Diploma of 2nd class from Merchant Navy of Sousse as an Engineer Officer, and went on to receive his Master and Ph.D. degrees from the Nation School of Engineers of Tunis.     

Modelling the evolution of residual stresses during tensile testing of elastoplastic wires subjected to a previous bending operation

During coiling operations high residual stresses are frequently developed in steel wire. In this paper the stress distribution in wires during coiling, unwinding and subsequent tensile testing is modelled for numerous bending degrees, assuming perfect Voce plastic deformation and linear elastic behaviour. The influence of such residual stresses on the observed tensile test data can be deduced. It is shown that coiling with spool radii as used today industrially can lead to measurement of wire properties deviating significantly from the “true” properties of a properly coiled wire. Also, a method is proposed to deduce the original flow behaviour of coiled samples from tensile test curves, hence filtering the effect of the residual stresses.     

Repair of a cracked Timoshenko beam subjected to a moving mass using piezoelectric patches

This paper presents an analytical method for the application of piezoelectric patches for the repair of cracked beams subjected to a moving mass. The beam equations of motion are obtained based on the Timoshenko beam theory by including the dynamic effect of a moving mass traveling along a vibrating path. The criterion used for the repair is altering the first natural frequency of the cracked beam towards that of the healthy beam using a piezoelectric patch. Conceptually, an external voltage is applied to actuate a piezoelectric patch bonded on the beam. This affects the closure of the crack so that the singularity induced by the crack tip will be decreased. The equations of motion are discretized by using the assumed modes method. The cracked beam is modeled as number of segments connected by two massless springs at the crack locations (one, extensional and the other, rotational). The relationships between any two spans can be obtained by considering the compatibility requirements on the crack section and on the ends of the piezoelectric patch. Using the analytical transfer matrix method, eigensolutions of the system can be calculated explicitly. Finally, numerical simulations are performed with respect to different conditions such as the moving load velocity. It is seen that when the piezoelectric patch is used, the maximum deflection of the cracked beam approaches maximum deflection of the healthy beam.