Caffeine hazards and their prevention in germinating seeds of coffee (Coffea arabica L.)

The inhibition of growth of seedlings of coffee (Coffea arabica L.) exposed to 10 m M caffeine was found to occur in the rootlet: mitosis and cell plate formation were also inhibited. Since concentrations of endogenous caffeine in the imbibed seed are 40–60 mM, 4–6 times as high as in the seedlings, we conclude that coffee embryos have specific means of avoiding caffeine autotoxicity. Observations indicate that cell divisions in root tips start only after the latter are pushed away from the caffeine-rich endosperm by elongation of the hypocotyl and maintained through cell elongation. Caffeine is introduced into the embryonic cotyledons mostly after cell division is completed there. Thus, coffee seedlings may avoid autotoxic effects of endogenous caffeine by separation between sites where mitosis is occurring and those where caffeine is stored. This is achieved in root tips by separation is space but in the cotyledons by separation in time. Caffeine is liberated from the tree litter in coffee plantations and eventually will produce autotoxic effects, resulting in some degeneration.     

Dyeing,fastness, and deodorizing properties of cotton,silk, and wool fabrics dyed with coffee sludge (Coffea arabica L.) extract

A natural colorant was extracted from Coffea arabica L., using water as extractant at 90°C for 90 min. Studies have been made on the dyeing, color fastness, and deodorization properties of cotton, silk, and wool fabrics dyed with Coffea arabica L. extract solutions. The best mordants were found to be FeSO_4, CuSO₄, and SnSO₄ for improving the color strength (K/S) of cotton, silk, and wool fabrics. Mordants MnSO₄, ZnSO₄, and NiSO₄ for cotton (Rating 3), and all mordants except MnSO₄ for silk (Rating 3), mordants CuSO₄, FeSO₄, CoSO₄, Al₂(SO₄)₃, and MnSO₄ for wool (Rating 4) were the best mordants to improve the light fastness. It was found that FeSO₄ and CuSO₄ were the best mordants for the improvements of color strength (K/S) and light fastness for silk and wool fabrics. In addition, it was found that cotton, silk, and wool fabrics dyed with the Coffea arabica L. extract showed good deodorization performance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 251–257, 2007     

Finite element simulation of deep bed filtration

In this paper, the numerical model for separation efficiency and transport in periodic porous media is studied. Finite element method was used to simulate the development of a predictive model of behavior of porous media during injection of particles. This paper describes the effects of injected particle size, Reynolds number and particle drag coefficient. The numerical results show that the separation efficiency increased with injected particle size increase. The separation efficiency is found to increase with increasing Reynolds number. For the effect of drag force, C_D, in porous media, numerical results show that for C_D<10 and C_D>100, the separation efficiency is not affected by drag coefficient in the range of drag coefficient from 10 to 100, and the separation efficiency significantly depends on the Reynolds number.     

滚动状态下轮胎漏气过程的有限元模拟

在考虑轮胎与轮辋及地面接触的情况下,借助ABAQUS有限元分析软件,建立了轮胎的平面轴对称模型和三维有限元分析模型。首先,利用平面模型分析了轮胎与轮辋的装配过程和充气过程;然后,利用轴对称到三维的分析方法,分析了轮胎在垂直载荷作用下的接地问题和在低速滚动下轮胎的漏气过程。给出了轮胎与地面接触界面上的压力分布;分析了在不同时刻漏气后轮胎的变形情况,并预测了漏气过程中轮胎下沉量与时间的关系。     

Finite element simulation of straight plunge grinding for advanced ceramics

The objective of this work is to model the grinding forces and the associated stress and deformation fields generated in a ceramic workpiece during plunge surface grinding. A two-dimensional finite element model is constructed with the grinding parameters and the mechanical properties of the workpiece as input variables. The size of the geometric model is several times larger than the size of the cutting zone, using approximately 5200 rectangular solid elements with a finer mesh in the cutting zone and with fixed remote boundaries. The loading in the cutting zone is imposed by displacement vectors proportional to the local undeformed chip thickness, which is a function of grinding parameters. For a given set of inputs, the model predicts the normal and tangential forces generated by the grinding wheel, as well as the deformation and the stress fields within the workpiece. As an example, the simulation is applied to a silicon nitride workpiece. Analysis of the stress fields developed in this material suggests that shear failure within the cutting zone is the dominant mode of subsurface failure, which could lead to the formation of shear micro- cracks at the grain interfaces. The depth of the subsurface shear failure zone increases with an increase in maximum undeformed chip thickness or the wheel depth of cut. The resulting local grinding force vectors, maximum stresses and damage zone sizes are predicted as a function of maximum undeformed chip thickness (or the wheel depth of cut).     

环形D模机头流道有限元数值模拟

通过有限元分析软件POLYFLOW建立了环形口模机头的三维等温流场模型.在改变机头流道结构参数以及工艺条件的情况下,对流道的压力场、黏度场及翦切场进行了研究.模拟的数字结果显示,随着口模间隙的增大,流道内的压力场减弱并随着间隙的增大而迅速降低,容易导致聚丙烯在机头内提前发泡.     

环形口模机头流道有限元数值模拟

通过有限元分析软件POLYFLOW建立了环形口模机头的三维等温流场模型。在改变机头流道结构参数以及工艺条件的情况下,对流道的压力场、黏度场及剪切场进行了研究。模拟的数字结果显示,随着口模间隙的增大,流道内的压力场减弱并随着间隙的增大而迅速降低,容易导致聚丙烯在机头内提前发泡。     

复合材料电缆支架结构强度的有限元仿真计算

介绍了复合材料电缆支架的应用背景,基于使用现场的实际受力工况,利用ABAQUS分析软件,对复合材料电缆支架的经典三托臂结构进行了静态有限元仿真计算,并进行了各种工况下的实验室测试。3种不同受力状态下的应力应变计算结果和实验室测试结果表明,该结构设计能够满足在静态力作用下的材料强度要求。     

Finite element simulation of geogrid manufacture using large deformation elastic formulation

Abstract

An elastic model of large solid polymer deformations has been used as a basis for numerical predictions of the shapes of polyethylene geogrids. These netlike products are made by solid phase deformation at elevated temperatures of extruded sheet containing arrays of suitably shaped holes. The elastic constitutive model is based on a theory of interacting polymer chains and is implemented within the finite element package ABAQUS in both two and three dimensions. Deformations correspond to extension ratios of up to 8. Good predictions of the final shapes of the geogrid products are obtained. It is concluded that the methods used are a valuable product development tool.     

收敛流道内聚合物熔体流动的有限元模拟

利用Polyflow软件包,对收敛流道内聚合物熔体的三维流动进行了模拟,得出了压力、速度、剪切速率和延伸应变速率的分布.在此基础上,对熔体在收敛流道内的流动规律及特点进行了分析.这为流场参数的控制和机头结构的优化设计和改进提供了理论依据.     

超高压厚壁圆筒自增强处理有限元仿真与残余应力分析

为了研究超高压厚壁圆筒不同端部结构形式对其自增强处理残余应力的影响,用大型有限元软件ANSYS仿真了不同端部结构处理方式下厚壁圆筒自增强处理过程,并分析了残余应力的分布状态。     

换热器管子-管板液压胀接的有限元模拟

采用ANSYS/CAE软件 ,对锅炉、换热器管子 管板的液压胀接过程进行了模拟。管子与管板孔之间采用面 面接触元以模拟相互之间的间隙及管子产生塑性变形并贴紧管板孔后对管板的作用。通过本文的模拟分析 ,可获得胀接时接头处的弹 塑性应力状态及卸除胀接压力后管子与管板之间的残余接触压力。值得注意的是此接触压力沿管板厚度方向分布是不均匀的 ;在管孔槽处会出现较高的数值 ;在管板内侧处 ,管子的过渡区会出现较大的残余拉应力     

机械式轮胎定型硫化机有限元分析

采用I-DEAS软件将机械式轮胎定型硫化机分为与上横梁和底座相关的两个部分,分别进行整体接触有限元分析。结果表明,横梁最大应力出现在侧板与主轴配合孔的下部区域,主轴最大应力出现在与曲柄齿轮配合端的下部区域,底座最大应力发生在主轴与曲柄齿轮配合孔上部很小的区域内,均小于材料的屈服强度,因此硫化机的设计是安全的。     

全钢载重子午线轮胎模态的有限元分析

采用ABAQUS软件对12.00R20规格全钢载重子午线轮胎建立三维有限元模型,并对该模型进行模态分析, 得到了在标准充气压力和额定负荷工况下轮胎的固有频率和相应的振型,同时还研究了气压和负荷对轮胎固有频率的影响.结果表明,在允许充气压力范围内,随着充气压力和负荷增大,轮胎的固有频率提高.轮胎模态的有限元分析能够为研究轮胎动态特性以及轮胎与整车匹配提供理论指导.     

Finite element simulation of three-dimensional viscoelastic planar contraction flow with multi-mode FENE-P constitutive model

Viscoelasticity is a characteristic of many complex fluids like polymer melts, petroleum, blood, etc. The investigation of viscoelastic flow mechanism has practical significance in both scientific and engineering field. Owing to strongly nonlinear, numerical method becomes a practical way to solve viscoelastic flow problem. In the study, the mathematical model of three-dimensional flow of viscoelastic fluids is established. The planar contraction flow as a benchmark problem for the numerical investigation of viscoelastic flow is solved by using the penalty finite element method with a decoupled algorithm. The multi-mode finitely extensible nonlinear elastic dumbbell with a Peterlin closure approximation (FENE-P) constitutive model is used to describe the viscoelastic rheological properties. The discrete elastic viscous split stress formulation in cooperating with the inconsistent streamline upwind scheme is employed to improve the computation stability. The numerical methods proposed in the study can be well used to predict complex flow patterns of viscoelastic fluids.     

子午线轮胎接触摩擦问题有限元分析

依据185/70R14C半钢子午线轮胎的实际结构,考虑轮胎与轮辋的接触,借助MARC有限元分析软件,建立了轮胎的平面轴对称模型和三维有限元分析模型。首先,利用平面模型分析了轮胎与轮辋的装配过程和充气过程。然后,为简化计算量,利用了先进的轴对称到三维的分析方法,利用三维模型分析了轮胎在垂直载荷作用下的接地问题和在低速下的稳态滚动过程。给出了轮胎与轮辋接触界面上的法向力分布;研究了轮胎与刚性地面接触时,不同速度下的接触摩擦力分布以及轮胎静态垂直负荷与下沉量的关系。     

Orthodontic bonding: Finite element for standardized evaluations

This study proposes a behavioural model to describe tooth–adhesive–bracket devices, which can assess objectively and optimize the hardening of orthodontic bonds in different clinical situations.A numerical study is carried out and the mechanical strength of the joint is assessed with regard to several parameters: the direction of the loading of the bracket/adhesive/enamel system, the value of the elasticity modulus of the dental enamel, the thickness of the joint and the position of the bracket on the vestibular side of the tooth.The results show that the mechanical strength of the joint depends on the thickness of the adhesive, the specific position of the bracket on the vestibular side and the loading mode.     

基于有限元方法的CeCl3和NdCl3在LiCl-KCl熔盐中的电极动力学模拟

充分理解锕系元素和镧系元素在熔盐中的行为和性质是实现反应堆乏燃料熔盐电解后处理的关键,然而熔盐电解实验所需的高温环境、腐蚀性熔盐甚至放射性物质等条件限制了实验的广泛开展。为寻求一种低成本且可靠的获取元素在熔盐中性质的途径,采用有限元方法在不同温度下模拟了不同浓度的三氯化铈和三氯化钕在LiCl-KCl熔盐中的循环伏安曲线,并与实验数据做了对比。结果表明,有限元方法能够较为准确地反映实际电化学过程,继而为乏燃料熔盐电解后处理提供数据支持。     

Finite element simulation and experimental analysis of B4C-TiB2-SiC ceramic cutting tools

Here, cutting properties and wear mechanism of the home-made B₄C-TiB₂-SiC ceramic cutting tools in turning of AISI 4340 steel workpieces were studied through a combination of finite element simulation using Deform-3D software and turning experiments. Simulation results show that cutting parameters have significant effects on the main cutting force and tool temperature of the B₄C-TiB₂-SiC cutting tool. The optimal cutting parameters for the ceramic cutting tool are cutting speed of 300 m/min, depth of cut of .3 mm, and feed rate of .1 mm/r. Experimental results show the cutting length of the B₄C-TiB₂-SiC cutting tool is about 101 m, which is 21.0% and 32.9% larger than that of the home-made B₄C-TiB₂ ceramic cutting tool and commercially available tungsten carbide tool, indicating that the B₄C-TiB₂-SiC cutting tool has a desired service life. The surface roughness of the workpieces processed by the B₄C-TiB₂-SiC cutting tool is 2.43 µm, which is 29.4% lower than that of the workpieces processed by the B₄C-TiB₂ cutting tool, indicating that the B₄C-TiB₂-SiC cutting tool has a satisfying machining accuracy. Wear forms of the B₄C-TiB₂-SiC ceramic cutting tool involve craters, chipping, and flank wear, and the main wear mechanisms are abrasive, adhesive, oxidative, and diffusion wear.