The effects of contact between hydrazine solutions and some polymer materials

Extensive tests have been carried out on the effects of different polymer materials in extended contact with aqueous solutions containing hydrazine at temperatures up to 70°C. Estimates of the change in hydrazine content of solutions confirm that polyethylene is entirely suitable as a material of construction in contact with hydrazine solution. The results have been supported by additional tests relating to the structure. PVC was found not to be compatible with hydrazine solutions.     

MHD flow of a micropolar fluid towards a vertical permeable plate with prescribed surface heat flux

The problem of a steady mixed convection stagnation point flow towards a permeable vertical plate with prescribed surface heat flux immersed in an incompressible micropolar fluid is studied numerically. The governing partial differential equations are first transformed into a system of ordinary differential equations using a similarity transformation, before being solved numerically by a finite-difference scheme known as the Keller-box method and the Runge–Kutta–Fehlberg method with shooting technique. The effects of the material parameter, buoyancy parameter, suction/injection parameter and the Prandtl number on the fluid flow and heat transfer characteristics are discussed. It is found that dual solutions exist for both assisting and opposing flows. The skin friction coefficient and the local Nusselt number increase in the presence of suction and magnetic field. Moreover, suction as well as fluids with larger Prandtl number widens the range of the buoyancy parameter for which the solution exists.     

Periodic mesoporous silica and organosilica with controlled morphologies as carriers for drug release

In this paper, we report the effects of morphology, wall composition of mesoporous materials and different buffer solutions on drug delivery profiles. Hollow spheres of periodic mesoporous organosilica (PMO) were prepared and used as drug carriers which exhibited higher loading capacity and slower release rate compared to the conventional periodic mesoporous silica (PMS) spheres and solid spheres of PMO. This hollow PMO showed promising properties as a reservoir to encapsulate and store larger quantities of guest molecules within its “empty” core. Moreover, its organic reactive sites allowed stronger interactions to the hydrophobic guest molecules, in contrast to inorganic wall possessed by PMS materials. Antibiotic tetracycline was used as a model drug to study the effect of framework difference between PMO and PMS materials on the loading and release processes. Two kinds of release medium, simulated body fluid (SBF) solution (pH 7.4) and phosphate buffer (PB) solution (pH 1.5) were used in this study, which revealed very different release profiles. A slower delivery rate was observed in SBF solution, attributed to the different ionic interactions between the guest molecule and the host material in the two different pH solutions. Overall, hollow PMO shows the lowest release rate and the highest loading amount compared to the other two materials studied herein. The kinetic study reveals that drug release from host material follows the second order kinetic model better than the first order mass transfer model.     

Nonlinear stress analysis in adhesively bonded single-lap joint

In this investigation, an analytical elastic–plastic solution was proposed for a single-lap joint. A ductile adhesive joint material was used as the bond material. FM-73 was utilized in the study. The influence of the bending moment was neglected in the solution. The solution was modified for shear stresses. The analytical solution was compared with the FEM solution. An ANSYS 10.0 solution was employed in the numerical solution. Both solutions were compared with each other. These two solutions produced close agreements.     

Statistical methods in model discrimination

Particularly in the chemical kinetic field but also in others in chemistry and engineering there has been much recent attention on the use of statistics in discriminating between rival models. There are two related basic problems. The first is to design experiments which will be most informative in determining which of several possible mathematical models is the “correct” one. Simple illustrations are given of the solution of this problem by different methods, such as the criteria of Roth, Box and Hill and of others, including some work done by R. S. Hawkins and the author on expected entropy change. The second problem is to analyze the data when received. A sampling of likelihood and Bayesian approaches to this problem is described with examples.     

纸塑复合包装材料中化学物迁移的改进预测模型及其通用性

以真实纸塑包装-化学物-食品体系为依据,基于一维Fick扩散理论,考虑化学物在纸和塑料涂层内具有不同的扩散系数及纸的厚度为有限厚,引入纸和塑料涂层界面处的分配系数,给出初始条件和边界条件,建立迁移预测模型,得到解析解。同时,对模型进行简化处理,分析其用于双层同种塑料-化学物-食品体系的使用通用性,并与Laoubi-Vergnaud模型进行对比分析,结果发现所建模型不仅可用于纸塑复合包装材料中化学物的迁移预测,同时还可用于双层同种塑料包装材料中化学物的迁移预测。     

铁碳微电解技术在难治理废水中的研究进展

铁碳微电解技术具有处理效率高、操作方便、占地面积小、原材料廉价和适用范围广等优点。但在机理研究以及具体的实际应用过程中,仍存在一些问题有待解决。因此,本文综合分析了铁碳微电解技术去除难治理废水中污染物的过程和机理,指出微电解作用机理的定量化及耦合关系是一个重要研究方向。在应用研究方面,目前主要存在两个问题：①微电解材料的板结和钝化问题;②如何提高微电解工艺适用的pH范围。本文从材料合成和反应器的改进方面进行分析,针对前者问题,提出可采用纳米技术以及高温烧结技术合成新型微电解材料,以及采用流化床和内循环微电解反应器也可解决该问题;针对后者问题,提出可改性微电解材料,以及在微电解反应器上外加电场和采用臭氧曝气微电解。最后,系统总结了该技术在印染废水、垃圾渗沥液、制药废水和重金属废水的应用概况。     

考虑材料拉压模量不同及应变软化的厚壁圆筒解析解

基于三剪应力统一强度理论和弹脆塑性模型,同时考虑材料拉压模量不同及应变软化、中间主应力效应,推导了单层厚壁圆筒均匀内压与塑性软化区半径的关系、双层厚壁圆筒均匀内压作用下的弹脆塑性极限承载力,分析了参数b、c、半径比r_b/r_a、材料的拉压模量系数λ对双层组合厚壁圆筒的影响特性。通过算例分析表明:双层组合厚壁圆筒弹性极限承载力P_emax随b的增大而增大,随c的增大而减小,随材料的拉压模量系数λ增大而减小;对理想弹塑性材料,脆塑性极限承载力P_u1随b的增大而增大,随c的增大而减小,随半径比r_b/r_a的增大而增大,与材料的拉压模量系数λ无关;对其它材料,脆塑性极限承载力P_u3随b的增大而增大,随c的增大而减小,随材料的拉压模量系数λ增大而减小。三剪应力统一强度理论解包含了Mohr-Coulomb解及双剪统一强度理论解,还能得到一系列化的新解,对单层和双层组合厚壁圆筒的设计及应用具有参考价值。     

ANALYTICAL STUDY OF HEAT TRANSFER TO LAMINAR FLOW OF NON-NEWTONIAN FLUIDS IN ANNULUS

An analytical study is made of the problem of laminar flow heat transfer to pseudoplastic fluids in a concentric circular tube annulus. The solution is obtained for simultaneously developing velocity and temperature profiles and constant wall heat flux. Constant property results are presented for different values of flow behavior index, n, and several inner to outer tube radius ratios and Prandtl numbers. Variable property solutions, with strongly temperature-dependent consistency index are obtained. The effect of viscous dissipation on the results of heat transfer is also presented.     

Adsorption of MS2 bacteriophage on ultrafiltration membrane laboratory equipments

Virus adsorption has been quantified (i) on different materials including various containers made of glass, plastic or stainless steel and hollow fiber membranes made of polyethersulfone, polysulfone, PVDF or cellulose acetate (with two configurations: in/out and out/in and various molecular weight cut-offs); and (ii) on the filtration equipment. The selected virus is MS2 bacteriophage used as a model to estimate viral survival in water or to quantify virus elimination by membrane filtration. A series of experiments have been conducted with suspensions of MS2 at different concentrations prepared in a sterilized saline solution (8 g/L of KCl) or in sterilized distilled water. This study has shown that the most appropriate material to be used as a filtration test tank is Pyrex glass. We show that an addition of a virus solution 15 min after the beginning of the experiment allows keeping the virus concentration at a high level in the system (including tank, tubing, and pump). No adsorption was observed on membrane materials tested during soaking.     

SPE International Award Address–1978 Barrier properties and migration problems of plastics

The present state of knowledge of the manner in which small molecules dissolve and diffuse in plastic materials is briefly described. The advantages and disadvantages of these phenomena are outlined. Two aspects, one positive and one negative, are reviewed in more detail. The use of plastic materials as barriers to gas and vapor transport particularly in packaging applications is described and illustrated by examples. Typical permeability values for water vapor, oxygen and carbon dioxide in various polymer films are given. Values for hydrogen and helium are included to illustrate the possible use of plastic films for gas separations. On the negative side, the migration of residual monomers and other, possibly toxic, substances out of plastic materials can be a serious problem. Some of the basic considerations and practical solutions to the migration problem are discussed in more detail.     

NUMERICAL EXPERIMENTS ON THE SIMULATION OF BENARD CONVECTION USING MARKER AND CELL METHOD

The two-dimensional Benard convection process is numerically simulated using a modified Marker and Cell finite difference method where the temperature equation is solved implicitly at every time step. Effects of the initial conditions, end-wall boundary conditions, Rayleigh number, Prandtl number, and aspect ratio on the development of the convection process and steady-state solution have been investigated. It is found that the Benard convection process is an initial value problem in the sense that the steady-state solution depends on the initial perturbation. If small scale perturbations are added in the initial temperatures, flow development and steady-state convergence is quicker. It is also found that when an appropriate aspect ratio is chosen, an infinite horizontal extent Benard system can be successfully and economically simulated using a small computational domain with periodic end-wall boundary conditions. The critical Rayleigh numbers are also predicted which agree closely with other published values. The critical Rayleigh number for infinite horizontal extent system is found to be independent of the fluid Prandtl number. The Row behavior and patterns at higher Rayleigh numbers are also investigated.     

An Experimental Study of the Static Torque Capacity of the Adhesively-Bonded Tubular Single Lap Joint

With the wide application of fiber-reinforced composite materials in aircraft, space structures and robot arms, the design and manufacture of composite joints have become a very important research area because they are often the weakest areas in composite structures. In this study, the effects of the adhesive thickness and tensile thermal residual stress on the torque capacity of tubular single lap joints were studied. The torque capacities of the adhesive joints were experimentally determined and found to be inversely proportional to the adhesive thickness. In order to match the experimental results to the theoretical analyses, the elastic-perfectly plastic material properties of the adhesive were used in the closed form solution. Also, the tensile thermal residual stresses of the joints were calculated by the finite element method and it was found that the thermal residual stresses could play an important role in the torque capacity when the adhesive thickness was large.     

Numerical investigation of indentation tests on a transversely isotropic elastic material by power-law shaped axisymmetric indenters

Nowadays, there exist many well-known classical models of frictionless adhesive contact including the Johnson–Kendall–Roberts (JKR) model, the Derjaguin–Muller–Toporov (DMT) model, and the Maugis solution for the JKR-type-to-DMT-type transition regimes. These models are very helpful for studying molecular adhesion between two contacting linearly elastic isotropic spherical bodies. However, in experimental studies, such as nanoindentation tests, the shapes of the indenters are often more general than the spherical or flat ones. Moreover, very often, the materials to be tested are anisotropic. A special case of anisotropy is transverse isotropy, which contains a plane of isotropy, implying that the material can be rotated with respect to the loading direction about one axis without measurable effect on the material’s response. In this paper, numerical studies on JKR-type frictionless adhesive contact between power-law shaped indenters and transversely isotropic materials are presented. It shows that the formulae for numerical simulations of JKR-type frictionless adhesive contact for transversely isotropic materials have the same mathematical form as the corresponding formulae for isotropic materials, except that the effective elastic contact modulus has different expression for different materials. The DMT-type and JKR-type-to-DMT-type transition regimes have been explored by conducting the simulations using smaller values of Tabor parameters. The good agreement between numerical simulation results and existing analytical solutions shows that this numerical simulation method can be extended to simulate indentation tests using indenters of arbitrary shapes.     

蠕动泵泵管对标准物质化学相容性的研究

对蠕动泵泵管与标准物质的化学相容性作了相关的实验研究,挑选Tygon、Chem-Durance、Viton 3种常用于输送化学溶液的泵管对4种性质不同的滴定溶液标准物质进行浸泡实验,通过标准物质特性值变化及泵管性状变化评价了这3类泵管对溶液的影响。实验结果证明不同性质的标准物质对各类泵管的化学相容性不同。通过实验结果推测,Tygon泵管对碱性、酸性、氧化性类标准物质的耐受性较好;Chem-Durance泵管适用于酸性类标准物质;Viton泵管抗吸附性较好,对还原性标准物质表现出优异的相容性,为挑选特性合适、经济合理的灌装用泵管提供了参考依据。     

Dr. Carl W. Hall,Founding Editor

Current methods in alleviating the wall deposition problem in spray drying emphasize mainly controlling the stickiness of the drying particles and less attention is placed on the properties of the dryer wall. In this experimental study, the effect of wall surface properties on the deposition mechanism has been investigated. Properties considered in classifying different wall materials were surface energy, roughness, and dielectric properties. The model solution contained sucrose, representing low-molecular-weight sugars commonly encountered in spray drying of fruit and vegetable juices. The effect of wall properties on deposition was explored at different drying rates producing particles of different surface rigidity. Larger surface roughness produced higher deposition fluxes for particles with high impact velocity and moisture. Surface energy and surface roughness were found to have no significant effect for dry rigid particles at the middle and bottom elevation of the drying chamber. However, material with lower surface energy (Teflon) exhibited less deposition for rubbery particles at such elevations. Analysis shows that dielectric wall material (Teflon) tends to enhance deposition of dry particles because of attrition at the surface. Higher wall temperature was found to produce slightly more deposition. The results of this work give a general indication of the effect of wall material on the deposition problem and provide the fundamental understanding for further studies along this line. Proper selection of dryer wall material will provide potential alternatives for reducing the deposition problem.     

Molecular dynamic simulation for nanometric cutting of single-crystal face-centered cubic metals

In this work, molecular dynamics simulations are performed to investigate the influence of material properties on the nanometric cutting of single crystal copper and aluminum with a diamond cutting tool. The atomic interactions in the two metallic materials are modeled by two sets of embedded atom method (EAM) potential parameters. Simulation results show that although the plastic deformation of the two materials is achieved by dislocation activities, the deformation behavior and related physical phenomena, such as the machining forces, machined surface quality, and chip morphology, are significantly different for different materials. Furthermore, the influence of material properties on the nanometric cutting has a strong dependence on the operating temperature.     

Effect of Wall Surface Properties at Different Drying Kinetics on the Deposition Problem in Spray Drying

Current methods in alleviating the wall deposition problem in spray drying emphasize mainly controlling the stickiness of the drying particles and less attention is placed on the properties of the dryer wall. In this experimental study, the effect of wall surface properties on the deposition mechanism has been investigated. Properties considered in classifying different wall materials were surface energy, roughness, and dielectric properties. The model solution contained sucrose, representing low-molecular-weight sugars commonly encountered in spray drying of fruit and vegetable juices. The effect of wall properties on deposition was explored at different drying rates producing particles of different surface rigidity. Larger surface roughness produced higher deposition fluxes for particles with high impact velocity and moisture. Surface energy and surface roughness were found to have no significant effect for dry rigid particles at the middle and bottom elevation of the drying chamber. However, material with lower surface energy (Teflon) exhibited less deposition for rubbery particles at such elevations. Analysis shows that dielectric wall material (Teflon) tends to enhance deposition of dry particles because of attrition at the surface. Higher wall temperature was found to produce slightly more deposition. The results of this work give a general indication of the effect of wall material on the deposition problem and provide the fundamental understanding for further studies along this line. Proper selection of dryer wall material will provide potential alternatives for reducing the deposition problem.     

OPTIMAL DESIGN OF MULTISITE BATCH-STORAGE NETWORK UNDER SCENARIO-BASED DEMAND UNCERTAINTY

An effective methodology is reported for the optimal design of multisite batch production/transportation and storage networks under uncertain demand forecasting. We assume that any given storage unit can store one material type that can be purchased from suppliers, internally produced, internally consumed, transported to or from other plant sites, and/or sold to customers. We further assume that a storage unit is connected to all processing and transportation stages that consume/produce or move the material to which that storage unit is dedicated. Each processing stage transforms a set of feedstock materials or intermediates into a set of products with constant conversion factors. A batch transportation process can transfer one material or multiple materials at once between plant sites. The objective for optimization is to minimize the probability averaged total cost, which consists of the raw material procurement cost, the cost of setting up processes, inventory holding costs of the storage units, and the capital costs of processes and storage units. A novel production and inventory analysis formulation, the PSW (periodic square wave) model, provides useful expressions for the upper/lower bounds and average level of the storage inventory. The expressions for the Kuhn-Tucker conditions of the optimization problem can be reduced to two sub-problems. The first yields analytical solutions for determining lot sizes, and the second is a separable concave minimization network flow sub-problem whose solution yields the average material flow rates through the networks for the given demand forecast scenario. The result of this study will contribute to the optimal design and operation of large-scale supply chain systems.     

THE RESONANT SUPERCOMPRESSION AND SONOLUMINESCENCE OF A GAS BUBBLE IN A LIQUID-FILLED FLASK

The spherically-symmetric problem of the oscillations of a small gas bubble in the center of a spherical flask filled with a compressible liquid that is excited by small radial displacement of the flask's wall is considered. Two asymptotic solutions have been found for the low Mach number stage. The first one is an asymptotic solution for the field far from the bubble, and it corresponds to linear wave theory. The second one is an asymptotic solution for the boundary layer near the bubble and it corresponds to an incompressible fluid. In the analytical solution of the low Mach number step matching of these asymptotic solutions is done. A generalization of the Rayleigh = Plesset equation for a compressible liquid is given in the form of two ordinary difference-differential equations that take into account the pressure waves which are reflecting from the bubble and those that are incident on the bubble from the flask wall. The initial value problem for the initiation of the bubble oscillations due to flask wall excitation and for the evolution of these oscillations was considered. Linear and non-linear periodic bubble oscillations were analyzed analytically, and resonant frequencies were identified. Non-linear resonant and near-resonant solutions for the bubble's non-harmonic oscillations, which are excited by harmonic pressure or velocity oscillations on the flask wall, are obtained.