Evaluation of the structural thermal shock resistance of a lining

Conclusions The possibility of crack formation in refractory bricks under the conditions of unilateral heating was theoretically demonstrated. The relationship between the tensile stresses responsible for chip (split) formation and the dimensions of the bricks was studied. Certain recommendations were given with regard to the choice of the specimen dimensions for conducting an experimental study on the permissible heating rates of the refractory linings.Translated from Ogneupory, No. 5, pp. 9–13, May, 1988.     

The effects of spinning conditions on the structure formation and the dimension of the hollow-fiber membranes and their relationship with the permeability in dry–wet spinning technology

Hollow-fiber membranes were prepared by dry–wet spinning under different spinning conditions. The used spinneret was tube-in-orfice type and the membrane material was polysulfone (Udel P-3500). N-methyl-2-pyrrolidinone (NMP) and water were used as solvent and coagulant, respectively. The concentration of the dope solution was 22 wt %. The effects of the three spinning factors—spinning height; extrusion rates of dope solution and inner coagulant; dimensions (inner diameter, outer diameter, and thickness) and permeation properties of the hollow-fiber membranes—were studied. The results were as follows: With changes in the spinning factors, spinning velocity and falling time before the membrane entered the water (coagulant) were changed; consequently, the structures and the dimensions of the hollow-fiber membranes varied with a certain tendency. The permeation properties of the hollow fibers were related very closely to the changes in the fibers' structures and dimensions. © 1995 John Wiley & Sons, Inc.     

PET/PTT合金结晶形态的研究

采用XP-201热台偏光显微镜研究了对苯二甲酸乙二醇酯（PET）/对苯二甲酸丙二醇酯（PTT）合金等温结晶时的结晶形态及影响因素。研究结果表明：随着等温结晶温度的升高,PET/PTT(40/60)合金的结晶诱导期变长;在观察的时间范围内各样品的球晶尺寸随着时间的延长而增大;随着PTT含量的增加,样品球晶的线生长速率增大,球晶尺寸增大;对比不同温度下等温结晶的球晶形态,PET/PTT(100/0)样品在190℃结晶时球晶尺寸最大, PET/PTT(40/60)样品和PET/PTT(100/0)样品在180℃结晶时球晶尺寸最大; PET/PTT(0/100)样品等温结晶时呈现出了复杂的条带球晶。     

Study on morphology evolution and fractal character of the miscible blend between isotactic polypropylene and copolymer of ethylene and propylene

The compatibility of isotactic polypropylene (iPP) with a block copolymer of ethylene and propylene (mEP) was evaluated by glass transition temperature measurements and Han curves. The morphology of the dispersed phase in alloys of iPP with mEP was observed by scanning electron microscopy (SEM). The average diameters, dp, of the dispersed phase in iPP/mEP alloys were calculated from SEM images. The results indicated that dp depends on the composition and mixing condition of the alloys. The distribution of dp was studied using graph-estimation methods and found to be log-normal in character. The calculated standard deviation, σ, characterizes the dispersed phase particle distribution width, and depends on the composition and mixing conditions of the blends. The fractal behavior of the phase morphology shown by SEM images of the alloys was studied, and the fractal dimensions were calculated by the changing coarse-graining level and measure relations methods. The self-similarity of the systems is discussed. The fractal dimensions depend on the composition and mixing conditions of the alloys.     

Determination of Kt Curves for Plastic Parts with a Triangular Stress Concentrator

Influence of a triangular stress concentrator on the mechanical properties of polymer-injected parts was studied. Crystal polystyrene (PS) plaques with a different dimensions concentrator were injected. Specifically, the influence of the dimensions of a stress concentrator over the stress concentrator factor (Kt) was studied. It was verified that Kt depends on geometrical parameters, and it was obtained as a trend similar to that reported on metals.     

Application of carbon fibers to the template synthesis of titanium dioxide

The applicability of carbon fibers as a combustible matrix in the template synthesis of nanostructured titanium dioxide was studied. It was found that the carbon matrix was completely combusted upon thermal treatment in a range of 500-800°C with an isothermal exposure at 800°C. As a result, the nanostructured fibers of titanium dioxide whose geometric dimensions repeated those of the initial carbon template were formed.     

由吸附等温线分析膨润土的分形孔隙

膨润土是一种多孔的粘土材料，对气相和液相中的污染物均有很好的净化效果。为了了解其对气体的吸附性能，用氮气吸附等温线分析了2种膨润土和1种活性白土的BET比表面积和孔隙分布，并应用基于FHH模型的方法计算了它们的分形维数。结果表明，普通膨润土的分形维数接近2，而活性白土的达到了2．59。讨论了孔隙度、比表面积以及分形维数等参数与吸附量的关系，表明分形维数更能反映膨润土对气体的吸附性能。     

径向基神经网络在粉煤灰混凝土二维和三维碳化分析中的应用

研究了不同粉煤灰掺量(0%,15%,40%,60%)、不同水灰比(0.3,0.35,0.4)、不同强度等级下(C30～C50)高性能混凝土二维和三维碳化深度;应用多因子输入向量的径向基神经网络(RBF)进行二维和三维碳化深度的预测。试验表明,采用多因子输入向量的径向基神经网络能够在试验样本数量较少的情况下建立高效准确的预测网络,可以较好地预测混凝土的碳化深度,其二维和三维碳化深度预测精度比一维精度高,其一维,二维和三维碳化深度的预测值和试测值相对误差分别为10.9%,5.6%,7.1%。混凝土二维和三维碳化研究对混凝土结构耐久性和寿命预测具有现实意义。     

A perspective of the interlamellar region of organo-clays by adsorption of aromatic hydrocarbons

Adsorption of aromatic hydrocarbons has been investigated on montmorillonite with and without surfactant modification. The enhanced space created in the surfactant modified organo-clay using quaternary ammonium species increased the amount of adsorption of aromatics depending on the size of the alkyl group attached to benzene ring. The diffusivity values calculated, indicate that diffusivity of all the aromatics studied decreased in the organo-clay. The extent of interlayer space available in the modified clay is compared with that in zeolites having different pore dimensions. A bulky molecule like nitron, though enhanced the interlayer distance, simultaneously blocked the access to newly created space in the hexadecyl trimethyl ammonium (HDTMA)-modified clay. Thus the increase in the interlamellar distance may not reveal the effective interlamellar space but depends on the type of quaternary species used. The available interlamellar space in the modified clay is best studied by adsorbing hydrocarbons of different dimensions.     

Fractal Modeling and Simulation of the Developing Process of Stress Cracks in Corn Kernel

Stress-cracks are fine fissures in grain kernel endosperm and caused by rapid drying at high temperatures. Fractal analysis on stress cracks in corn kernel was carried out in this study. The irregular and rough profile of stress cracks of corn kernel can be regarded as having the property of self-similarity statistically, and was studied according to the fractal theory. Four types of fractal propagating models of stress cracks were established. The fractal dimensions were developed. The propagating process of whole and partial sections was simulated.     

酶活性部位柔性的分形分析

引言蛋白质三维结构的研究一直是生物学上一个重要而复杂的问题。通过X晶体衍射和核磁共振技术,人们已经积累了大量的蛋白质结构数据,但进一步解析蛋白质结构与功能间的关系,尚存在一定难度。作为非线性科学分支的分形理论(fractaltheory),以其独特的研究方法揭示了自然界中非线性过程内在的随机性及其所具有的特殊规律性。虽然分形理论在20世纪70年代才首次提出[1],但     

Numerical Simulation of the Separating Performance of Hydrocyclones

The flow behavior in hydrocyclones is quite complex. The Computational Fluid Dynamics (CFD) method was used to simulate the flow fields inside a hydrocyclone in order to improve its separation efficiency. The RSM turbulent model (Reynolds Stress Model), which abandons the isotropic eddy‐viscosity hypothesis, was used to analyze the highly swirling flow fields in hydrocyclones. The ASM Model (Algebraic Slip Mixture Model) was used to simulate the separation performance. The volume fraction distribution and grade efficiency curve are given. The separating efficiency for 60 μm water particles is more than 90 %. The majority of 60 μm water particles are carried to the underflow. An increase in particle size will improve the efficiency by increasing the centrifugal force on the particles. Based on the simulation, the effects of the overflow tube dimensions on the separation performance were studied. The overflow tube dimensions of the hydrocyclone were modified, and the results showed that the Reynolds Stress Model successfully predicted the characteristics of the flow, and the simulated performances were in good agreement with those obtained by tests.     

PO／PS合金的相态结构与力学性能

以氢化ＳＢＳ（ＳＥＢＳ）为增容剂的聚烯烃／聚苯乙烯（ＰＯ／ＰＳ）合金，与聚烯烃相比具有更好的力学性能，尤其是抗冲击强度随机容剂的增加而大幅度提高，应用ＴＥＭ，ＳＥＭ、ＤＳＣ、偏光显微技术对一系列合金相形态，相容程度及分散相颗粒尺的考察研究发现，合金中分散相多数呈卵石状，随ＳＥＢＳ含量增加，分散相粒径显著变小，而合金抗冲击强度增大，分散相形态结构。颗粒尺寸与材料力学性能密切相联。     

水冷壁气化炉熔渣表面形态的几何特性

在小型气流床气化炉中进行了水冷壁结渣实验,研究了不同温度下炉内熔渣的表面形态,并进行了定量分析。本文提出了当量温度T的概念,T等于熔渣温度与灰熔点的比值。利用图像分析软件ImageJ测得熔渣表面粗糙度,当量温度小于1时,粗糙度较高;当量温度大于1时,粗糙度较低。用“小岛法”求得了熔渣表面的分形维数,并得到了当量温度与分维数之间的关系。     

Effect of processing conditions on dimensions of sisal fibers in thermoplastic biodegradable composites

Biodegradable composites based on treated and untreated sisal fiber and mater Bi‐Z were processed using an internal batch mixer. The effect of processing conditions (temperature, speed of rotation, and time of mixing) and alkaline treatment on the dimensions of sisal fiber was studied. The length and diameter of the initial fibers were reduced during mixing and this effect was correlated to the magnitude of the shear stress developed in the mixer. An increase of the speed of rotation and/or a reduction of temperature produced fibers of smaller dimensions but with a higher aspect ratio l/d. Alkaline treatment increased the kinetics associated to the reduction of the fiber's dimensions. A semiempirical model was employed to predict the size of the fibers versus the time of mixing. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1084–1091, 2001     

Physical properties of some organophosphazene copolymers. II. Thermoelasticity andin situ reinforcement of the cross-linked networks

Aryloxy phosphazene copolymers with phenoxy andp-ethyl phenoxy substituents were cross-linked into elastomeric networks and studied with regard to their stress-strain and thermoelastic (force-temperature) behavior. The thermoelastic results showed that the energetic contribution to the elastic force was negative, indicating that the unperturbed dimensions of the polymer chains decrease with increases in temperature.In situ precipitation of silica into the elastomers by hydrolysis of an absorbed alkoxysilane was found to give excellent network reinforcement.     

Finite Element Modeling of a Donut Flextensional Transducer

A new flextensional transducer based on the cymbal device was designed and fabricated. The endcap shape of this device, called the donut, was developed through finite element modeling using the commercially available software code ATILA^®. Endcap dimensions that were studied in this research include cap thickness, flange width, and cavity depth. Other parameters considered included piezoelectric material type, thickness of the piezoelectric disk, epoxy thickness, and endcap metal. Fundamental flextensional resonance frequency and effective coupling coefficient, which are two important characteristics that determine the performance and the application opportunities of the transducer, were predicted. Finite element analysis coupled with experimental results suggest that these devices have higher flextensional resonance frequencies compared with cymbals of similar dimensions. Impedance spectroscopy of the donut devices also suggests that the effective electromechanical coupling coefficient is higher than cymbal devices of similar dimensions.     

Physical properties of some organophosphazene copolymers. II. Thermoelasticity andin situ reinforcement of the cross-linked networks

Aryloxy phosphazene copolymers with phenoxy andp-ethyl phenoxy substituents were cross-linked into elastomeric networks and studied with regard to their stress-strain and thermoelastic (force-temperature) behavior. The thermoelastic results showed that the energetic contribution to the elastic force was negative, indicating that the unperturbed dimensions of the polymer chains decrease with increases in temperature.In situ precipitation of silica into the elastomers by hydrolysis of an absorbed alkoxysilane was found to give excellent network reinforcement.     

Study of the Formation of Nano-Networks in Colloidal Particles

The authors studied the formation of a wafer-scale network of connected colloidal beads by reactive ion etching. The dimensions of the connections have been studied as a function of etching time for colloidal beads of different sizes, and could be well controlled. The authors have found that the nano-network forms and disappears for the same time of etching independent of the diameter of the polystyrene beads. With recent interest of connected colloidal networks in various optical sensing applications, such as photonic crystals, as surface-enhanced Raman scattering substrates, the studies have potential uses in the development of wafer-scale nanophotonic sensors.     

Simulation of the Erosion Burning of a Granular Propellant

For combustion of axisymmetric propellant grains under blowing conditions, a mathematical model is proposed and numerical simulation is performed. The effects of incoming–flow parameters (velocity, pressure, and temperature) and surface dimensions and geometry on grain–burning rate are studied. Physical patterns of flow around burning propellant grains are presented.