Vorspannkochungen ausgemauerter Behälter unter Berücksichtigung des thermischen Fließens von Kondensationsharzkitten

Prestressing of Brick Lined Vessels with Regard to the Thermal Creeping of Mortars Based on Condensating Resins Ceramic linings, applied in steel vessels to protect these from chemical attacks, have a lower thermal expansion coefficient than the steel shell. Moreover ceramic is very sensitive to tensile stress. If temperature in the subsequent operation exceeds very much those during application of the brick lining, the greater expansion of the steel shell put the lining under tensile stress and may cause cracks which nullify its protection effect. Remedy by thicken the brick lining or by external heating of the shell during the application of the masonry is limited only. More effective is a pre-stressing of the brick lining before or whilst the start up. This procedure bases on the property of irreversible thermal creeping, owned by the phenolic and furan resin based mortars, which are used for bedding and pointing of the brick linings. This property of the above mortars formerly has been taken for mere swelling. It was not yet exactly determinable and so making use of it was rather unsave. This treatise contains data about the possible dimensions of the thermal creeping, depending on kind and age of the mortar as well as on the thermal increase and the reached amount of temperature. Reference is given to the practical use of this knowledge for the execution of prestress cooking.     

非均匀载荷作用下偏心磨损套管稳定性准则

采用小参数摄动法建立了非均匀载荷作用下具有初始椭圆度的磨损套管稳定性准则,根据计算得到的磨损套管相对应变及其临界值之间的关系确定磨损套管是否发生挤毁失效。分析了磨损套管相对应变及其临界值与套管外径、壁厚、磨损深度、载荷非均匀度、初始椭圆度之间的关系。套管外径增加导致失稳临界应变减少,磨损套管保持其稳定的壁厚也随之增加。非均匀载荷作用下磨损套管相对应变与初始椭圆度之间是线性关系,套管初始椭圆度越大,相对应变越大。相对应变与载荷非均匀性之间是抛物线关系。磨损套管载荷非均匀性越大,相对应变越大。非均匀载荷作用下磨损套管的相对应变随磨损深度线性增加。该准则能够用于评价非均匀载荷作用下含磨损缺陷套管的井筒的完整性。     

65 m高砖烟囱定向拆除爆破

一座65 m高的砖烟囱与砖窑连体,文章介绍了烟囱定向爆破拆除的爆破方案、爆破参数和施工方法,爆破效果良好.     

40m高钢筋混凝土水塔烟囱定向爆破

介绍了采用定向爆破法成功地拆除了复杂环境下40m高钢筋混凝土水塔烟囱的具体工程实例。通过对钢筋混凝土水塔烟囱的结构分析和各部分的重量计算,以及对铆固螺栓、内衬砖的受力分析和强度计算,初步探索出下部内衬拆除时防止上部内衬下落的方法,可供同类工程参考和借鉴。     

Translational and rotational dynamics of methane in ZSM-5 zeolite: A quasi-elastic neutron scattering study

The translational and rotational motions of methane adsorbed at different loadings in NaZSM-5 have been studied by quasi-elastic neutron scattering at two temperatures: 200 and 250 K. The translational motion does not simply follow Fick's law, but a jump diffusion model with a Gaussian distribution of jump lengths satisfactorily simulates the experimental results. The diffusion coefficient that is obtained for long-range translational motion does not vary much on the loading in the range that was studied: it is of ⋍ 2.7 × 10⁻⁵ cm² s⁻¹ at 200 K and ⋍ 5.5 × 10⁻⁵ cm² s⁻¹ at 250 K. Good agreement is found between the neutron and n.m.r. results for this motion, but large discrepancies are observed with the macroscopic measurements. The rotational motion is well described by an isotropic rotational diffusion model, and this motion is found to be much slower in the zeolite than in physisorbed layers or in bulk solid methane.     

苏州御窑金砖文创产品设计研究

目的 苏州御窑金砖制作技艺虽然被首批列入国家级非物质文化遗产名录,但知名度却不及同期其他国家级非物质文化遗产高。为了使御窑金砖制作技艺活化传承和保护工作获得社会公众更多的关注和支持,对其文创产品设计路径进行研究。方法 分析苏州御窑金砖的造物思想、造型审美、工艺特点以及现有的文创产品情况,归纳和总结其设计的瓶颈和问题,针对问题结合文创产品特点探讨其设计路径,并通过设计实践进行论证。结果 得出御窑金砖文创产品的造物思想,以及重塑审美情感、刻画工匠精神的设计路径。结论 将古人凝结于非物质文化遗产中的无形财富提炼并物质化、产品化,是御窑金砖文创设计的重要思路,可以使更多人通过产品了解和认识其文化的精髓,唤醒大众的文化自觉。     

Experimental investigation of the axial discharging velocity of particles from rotary kilns

The axial discharging velocity of the particles was experimentally investigated at the discharge end of two rotary kilns with 400 and 250 mm internal diameter, respectively. Sand, glass beads and clinker were used as experimental materials. A physical method without using imaging technology was developed to measure the axial discharging velocity based on the discharge behavior. The mass flow and the rotational speed of kiln were changed in a wide range. The axial discharging velocity can be directly determined by the volume flow rate of solid bed divided by the whole cross section area of the bed at the kiln discharge end. The axial discharge velocity can be nominally expressed as the function of the axial transport velocity, if the kiln is fully loaded by the materials and the radial rotational velocity of the cylinder. Clinker among other two materials presents a higher difference of the extreme discharge velocities because of the wider particle size difference.     

Mechanical behaviour analysis of a buried steel pipeline under ground overload

Ground overload is one of the most important factors that threaten the safe operations of oil and gas pipelines. The mechanical behaviour of a buried pipeline under ground overload was investigated using the finite element method in this paper. The effects of the overload parameters, pipeline parameters and surrounding soil parameters on the stress–strain response of the buried pipeline were discussed. The results show that the maximum von Mises stress appears on the top of the buried pipeline under the loading area when the ground load is small, and the stress distribution is oval. As the ground load increases, the maximum stress increases, and the high stress area extends. The von Mises stress, plastic strain, plastic area size, settlement and ovality of the buried pipeline increase as the ground load and loading area increase. The buckling phenomenon of the no-pressure buried pipeline is more serious than the pressure pipeline. As the internal pressure increases, the high stress area and the maximum plastic strain of the buried pipeline first decrease and then increase, the settlement of the buried pipeline increases, and the ovality decreases. The von Mises stress, maximum plastic strain, settlement and ovality of the buried pipeline decrease with increasing buried depth, the surrounding soil's elasticity modulus, Poisson's ratio and cohesion. The maximum von Mises stress, high stress area, the maximum plastic strain, plastic area and ovality increase as the diameter–thickness ratio increases. The critical diameter–thickness ratio is 60, and the settlement of the buried pipeline first increases and then decreases as the diameter–thickness ratio increases. Finally, a protective device of the buried pipeline is designed for preventing ground overload. It can be repaired in a timely manner without stopping the transmission of oil and gas and widely used in different locations because of its simple structure and convenient installation.     

SOLID ELEMENTS WITH ROTATIONAL DOFs BY EXPLICIT HYBRID STABILIZATION

Two brick elements equipped with Allman's rotation are presented. Strain energy of both elements is sub-integrated by the second order quadrature which gives rise to the hourglass mechanisms. Inasmuch as Allman's rotation is employed, the elements are also plagued by the equal-rotation mechanisms. Variational functional containing independently assumed stress, displacement and rotation is employed to formulate the stabilization devices for the elements. Computational cost of the elements is reduced by incorporating the explicit hybrid stabilization technique. Popular numerical benchmarks are studied and the present elements are found to be competitive to other state-of-the-art elements.     

Corrosion Failure of 304 Stainless Steel Hooks in a Brick Kiln

Failure analysis was carried out on the stainless steel hooks in a brick kiln to confirm its failure mechanism. The collected evidence indicated that chemical composition of the stainless steel hook was consistent with the standard requirements for 304 stainless steel. The metallographic test showed that the microstructure of the stainless steel hook in the non-damaged areas was normal. However, serious chromium segregation which might be caused by secondary phase formation at the high temperature was found in the damaged material. This dramatically reduced the corrosion resistance of the material. The corrosion elements such as oxygen and sulfur were found playing a major role in the corrosion process. Thus, the failure of the stainless steel hook was induced by corrosion due to the chromium segregation and the existence of corrosive elements including oxygen and sulfur.     

Salt diffusion in brick structures Part II The effect of temperature, concentration and salt

This is our second article concerning salt diffusion measurements in porous brick materials. In the first article a method for measuring the rate of diffusion of salt in ceramic material was presented and applied to the measurement of diffusivity of NaCl in different brick materials. In this work the same method was applied to other water-soluble salts commonly found in building materials. The binary diffusion coefficients were measured for KCl, NaNO₃, CaCl₂, Na₂SO₄, MgCl₂ and Na₂CO₃. The result for the diffusivity of 0.05 molar salts in water in new Finnish red brick varied between (0.271–0.544)*10^–5 cm²/s at a temperature of 25 ± 0.05°C. The effect of temperature and concentration on the diffusivity of NaCl in new red brick was also measured. The rate of change of diffusivity as a function of temperature, concentration and the type of salt was very similar to that in free solutions. However, the values of the diffusion coefficients were lower in the porous medium than in solution. A mutual relation between the binary diffusion coefficient and the viscosity of the salt-water solution was observed in the porous brick.     

Nonlinear finite element analysis of masonry wall strengthened with CFRP strips

In many experimental studies, it has been proved that unreinforced masonry (URM) brick walls have high strength against lateral forces acting in plane. However, out-of-plane strength of URM brick walls against lateral forces has found to be quite low. According to the experiences that were obtained from the major earthquakes, the low out-of-plane performance of URM brick walls resulted in excessive loss of human lives during an earthquake, hence the strengthening of URM brick walls with CFRP strips has been appeared to be a very important subject. However, very limited literature has been found. Especially, the data obtained from experimental studies must be increased for the true understanding of the behavior of strengthened brick walls under out-of-plane lateral forces. However, in most cases, this procedure required large number of expensive experiments. At this stage, numerical analysis can be an appropriate choice, thus in this paper a finite element model is presented for modeling URM brick walls that are strengthened with CFRP strips. The numerical results are compared with the experimental ones and consistent results are obtained from the finite element model. General purpose finite element analysis software ANSYS is used throughout this study. Contact elements are used along the masonry wall–CFRP strip interfaces for the investigation of the stress distribution and load – strain behavior.     

物料与窑壁间歇接触对回转窑传热过程的强化效应

根据回转窑内物料颗粒的运动特点，推导了颗粒团在贴壁运动过程中的非稳态导热系数及界面处的接触传热系数，进而得出了物料与封盖窑壁间的换热系数；结合已有研究成果，建立了回转窑的传热数学模型。计算表明，未考虑物料与窑壁间歇接触对回转窑传热过程的强化效应时，物料温度偏低；温度越高，强化效应对物料温度的影响越大；考虑物料与窑壁间歇接触对回转窑传热过程的强化效应，有利于提高回转窑煅烧熟料的质量和热效率。     

A HYBRID STRESS QUADRILATERAL SHELL ELEMENT WITH FULL ROTATIONAL D.O.F.S

A 4-node hybrid stress quadrilateral shell element with 3 rotational d.o.f.s per node is presented. The mid-surface displacement of the element is founded on Allman's rotation. The equal-rotation mode intrinsic to the rotation is suppressed by a stabilization vector. The assumed stress field and the stabilization scalar is chosen such that membrane locking can be avoided. Computational efficiency of the element is improved by employing orthogonal stress modes and admissible matrix formulation. Popular benchmark tests are attempted and the results are found to be satisfactory. © 1997 by John Wiley & Sons, Ltd.     

On improved hybrid finite elements with rotational degrees of freedom

A set of three new hybrid elements with rotational degrees-of-freedom (d.o.f.'s) is introduced. The solid, 8-node, hexahedron element is developed for solving three-dimensional elasticity problems. This element has three translational and three rotational d.o.f.'s at each node and is based on a 42-parameter. three-dimensional stress field in the natural convected co-ordinate system. For two-dimensional, plane elasticity problems, an improved triangular hybrid element and a quadrilateral hybrid element are presented. These elements use two translational and one rotational d.o.f. at each node. Three different sets of five-parameter stress fields defined in a natural convected co-ordinate system for the entire element are used for the mixed triangular element. The mixed quadrilateral element is based on a nine-parameter complete linear stress field in natural space. The midside translational d.o.f.'s are expressed in terms of the corner nodal translations and rotations using appropriate transformations. The stiffness matrix is derived based on the Hellinger–Reissner variational principle. The elements pass the patch test and demonstrate an improved performance over the existing elements for prescribed test examples.     

Electron–photon equation of motion with application to the Lamb shift

An equation of motion (EOM) is proposed for the electron which includes the effect of the radiation field on the electron's motion. The new EOM – the electron–photon EOM (EPEOM) – is the same as Dirac's equation with the ‘bare’ or mechanical mass replaced by a complex electromagnetic mass whose real part is interpreted as the observed mass of the electron. The Lamb shift is calculated from the difference of the EPEOM energy and the Dirac-equation energy.     

A comparative study on the approximate analysis of masonry structures

In this paper, numerical analysis of structural masonry subject to a uniform in-plane tensile stress/strain field is investigated employing various homogenisation techniques. Here, structural masonry is regarded as a composite material with brick, bed joints and head joints as its constituents. Assuming a perfect bonding between constituents. Assuming a perfect bonding between constituent materials, two homogenisation techniques based on the strain energy approach are applied to derive equivalent elastic moduli of masonry. Structural relationships for the constituent materials are next derived to relate strains and stresses in constituents to the average strains and stresses in the masonry. In addition, a slightly different concept of the homogenisation technique based on Eshelby's solution of the ellipsoidal inclusion problem is also applied to compare the results with the energy based methods. The tensile strength of the masonry is found on the basis of the failure of any of the constituent materials. It is shown that tensile strength is a function of the elastic parameters of brick/mortar as well as the tensile strength of mortar. These studies also show that, although initial cracking occurs under horizontal tensile forces, the ultimate strength of the panel is higher in this direction than in the vertical direction.     

Durability of proprietary cementitious materials for use in wastewater transport systems

Several methods and materials, such as high performance coatings, fiber glass reinforced linings, special mortars, brick or ceramic linings, etc., are used to protect concrete from sulfuric acid attack in a sewage environment. Two proprietary high alumina cementitious lining materials, CC and SC, are recent additions to the list of protective materials used in the Arabian Gulf. This paper documents the findings of a laboratory study under accelerated conditions as well as a two-year field study of CC and SC in a wastewater lift station in Jubail, Saudi Arabia. In the laboratory investigations, 50 mm cube mortar specimens prepared using: (1) SC, (2) CC, (3) Type I+8% silica fume cement, (4) Type I+20% fly ash cement and (5) Type I cement were exposed to 2% sulfuric acid for 150 days. The laboratory specimens were tested for weight reduction, compressive strength, sulfate content, and alkalinity. In the field, the walls and ceiling of a wastewater manhole were coated using the proprietary lining materials, SC and CC, and were exposed to a normal sewage service environment. Performance of the liner materials was monitored for sulfate content and alkalinity after 6, 12 and 24 months of exposure. The analysis and evaluation test data generated from the accelerated laboratory study and the field study, which lasted for 24 months, showed that SC performed better than other materials tested in this investigation.     

Defluoridation of groundwater using brick powder as an adsorbent

Defluoridation of groundwater using brick powder as an adsorbent was studied in batch process. Different parameters of adsorption, viz. effect of pH, effect of dose and contact time were selected and optimized for the study. Feasible optimum conditions were applied to two groundwater samples of high fluoride concentration to study the suitability of adsorbent in field conditions. Comparison of adsorption by brick powder was made with adsorption by commercially available activated charcoal. In the optimum condition of pH and dose of adsorbents, the percentage defluoridation from synthetic sample, increased from 29.8 to 54.4% for brick powder and from 47.6 to 80.4% for commercially available activated charcoal with increasing the contact time starting from 15 to 120 min. Fluoride removal was found to be 48.73 and 56.4% from groundwater samples having 3.14 and 1.21 mg l(-1) fluoride, respectively, under the optimized conditions. Presence of other ions in samples did not significantly affect the deflouridation efficiency of brick powder. The optimum pH range for brick powder was found to be 6.0-8.0 and adsorption equilibrium was found to be 60 min. These conditions make it very suitable for use in drinking water treatment. Deflouridation capacity of brick powder can be explained on the basis of the chemical interaction of fluoride with the metal oxides under suitable pH conditions. The adsorption process was found to follow first order rate mechanism as well as Freundlich isotherm.