Optimization of electroflocculation of yarns

The empirical equation obtained can be used for designing a flocculated yarn with a given nap cover density. The optimum values of the process parameters for applying nap established as a result of the studies can be the basis for RFPs for designing and manufacturing the unit and process for electroflocculation of yarns.     

Use of graphs for formalizing the laws of functioning of loading-unloading devices

The example of defining a law for operation of a stacking conveyor demonstrates the possibility of a language for algorithm graphs. This language is sufficiently universal and can be used for describing a law for operation of a wide class of manipulators and other similar devices, and it is sufficiently graphic. The algorithm graphs allow accurately, with all necessary details but at the same time concisely, describing any microprogram for operating manipulators and revealing its logical imperfection with both heuristic and formal methods of the theory of graphs. The algorithm graphs obtained can be used as the basis for developing a computer program in any both high- and low-level algorithm language.     

Analysis of Gas Centrifuge Cascade for Separation of Multicomponent Isotopes and Optimal Feed Position

Abstract

Analysis of the concentration distribution in a gas centrifuge cascade for separation of multicomponent isotope mixtures is different from that in a cascade for separation of two-component mixtures. This paper presents the governing equations for a multicomponent isotope separation cascade. Numerically predicted separation factors for the gas centrifuge cascade agree well with the experimental data. A theoretical optimal feed position is derived for a short square cascade for a two-component mixture in a close-separation case. The optimal feed position for a gas centrifuge cascade for separation of multicomponent mixture is discussed.     

Comparative Analysis of the Kinetics of Drying of Disperse Polymers Using Mathematical Models

A comparative analysis of the kinetics showed that the duration of drying anid from beginning to acceptable moisture content is less than for polycaproamide; for example, in conditions of drying in a nitrogen current with a temperature of 140°C and rate of movement of 0.3 m/sec, the drying time for anid is approximately 28% less. As a consequence, for the same efficiency, the dryer for anid can have smaller geometric dimensions than the dryer for polycaproamide with all other conditions being equal.     

Mathematical properties of equations of state

Equations of state (EOS) are considered as solutions of “conservation equations” or of their corresponding first-order partial differential equations. The method of characteristics is used to develop the general form of a continuous EOS. The mathematical conditions for a physically meaningful discontinuity, which is identified as a phase change, are formulated and demonstrated. These conditions can be used either for solving for an EOS from first principles or for a systematic development of empirical EOS.     

Analysis of long-time interaction of perturbations in problems of macrokinetics

We developed an approach for the reduction of systems of nonlinear partial differential equations to the general nonlinear parabolic equation for a complex amplitude of an envelope wave. The equation is complexly derived: by using wave packages, method of many scales, modification of Mandelshtam method and taking into account group velocity of an envelope wave, that is typical for an actual nonlinear dispersive medium. We consider the features of such modeling for a system with nonlinearities occurring in the simplest model of a nonisothermal chemical reaction, in particular, of thermal autoignition and flame propagation.     

Effective Viscosity of Suspensions of Spheres

Modeling the effective viscosity of suspensions of spheres beyond the dilute limit is a difficult problem that has challenged researchers for nearly a century since Einstein derived an equation for dilute suspensions. Hydrodynamics modeling requires complex mathematical treatments of integral equations describing interactions between spheres, and its solutions have been limited to semidilute dispersion of monosized hard spheres. Mechanics modeling treats suspensions in a statistical sense and generally provides upper and lower bounds solutions for polydispersed suspensions. A closed-form solution for the effective viscosity of concentrated suspensions of monosized spheres using both the elastic-viscous analogy and the analogy between the effective dielectric constant of a polarizable medium and the effective viscosity of two-phase flow is derived in the present study. Existing measurements and numerical simulations support present analytical results. A closed-form solution for polydispersed suspensions using a differential model is also derived, and the results are within existing bounds solutions.     

大豆脂肪氧合酶(LOX)的固定化及增强稳定性

以活性白土、滑石粉为载体采用吸附法固定化大豆脂肪氧合酶(LOX)的优化条件为:(1)酶液对活性白土的用量比为897U/mg,在浓度为0 05mol/L、pH=7 0的磷酸盐缓冲液中20℃搅拌吸附30min;(2)酶液对滑石粉的用量比为238U/mg,在浓度为0 05mol/L、pH=8 0的磷酸盐缓冲液中10℃搅拌吸附15min。经放大后实验重复性良好。上述固定化酶置于0～4℃保存20d,酶活损失分别为19 2%和17 7%;与游离酶相比,能加快酶促反应的速度并使产率分别提高9 6%和42 5%。以海藻酸钠为载体采用包埋法得到的固定化酶珠的耐热、耐酸碱、耐有机溶剂能力较游离酶有很大提高,在φ(甘油)=75%的水溶液中保存33d,酶活基本保持不变;在50℃热处理60min后酶活仍能保持90%。     

Analysis of transient thickness of pneumatic foams

This paper presents a simple, experimentally validated approach to analyze the transient formation of a foam layer produced by injecting gas bubbles into a foaming solution. Based on experimental observations, three different regimes in the transient growth of the foam have been identified as a function of the superficial gas velocity. A model based on the mass conservation equation for the gas phase in the foam combined with three different models for the average porosity is proposed. It is shown that for practical calculations a constant average porosity equal to 0.82 can be used. The model predictions show very good agreement with experimental data for low superficial gas velocity and provide an upper limit of the foam thickness for intermediate and large superficial gas velocities. The paper discusses the physical mechanisms that may occur during the foam formation and the effects of the superficial gas velocity on the foam dynamics. The present analysis speculates several mechanisms for the bursting of the bubbles at the top of the foams and proposes the framework for more fundamental and detailed studies.     

Theoretical analysis of the motion and evaporation of exhaled respiratory droplets of mixed composition

The dynamics of droplets exhaled from the respiratory system during coughing or talking is addressed. A mathematical model is presented accounting for the motion of a droplet in conjunction with its evaporation. Droplet evaporation and motion are accounted for under two scenarios: (1) a well mixed droplet and (2) a droplet with inner composition variation. A multiple shells model was implemented to account for internal mass and heat transfer and for concentration and temperature gradients inside the droplet. The trajectories of the droplets are computed for a range of conditions and the spatial distribution and residence times of such droplets are evaluated.     

Kinetics of hydration of tricalcium aluminate in the presence of gypsum

Based on a conceptual model for the stages of hydration of tricalcium aluminate in the presence of gypsum, a mathematical model was developed for the kinetics of hydration. The model was solved, illustrated and compared to experimental heat release data. Analytical equations were presented for the first two stages, while the last stages of hydration reduced to a previously developed model for the hydration of tricalcium aluminate in the absence of gypsum. Results suggested that pore diffusion through a thickening ettringite barrier layer controlled the first stage of hydration, while pore diffusion through a thinning ettringite barrier layer controlled the second stage. After the ettringite layer disappeared, the reaction of the remaining tricalcium aluminate proceeded more rapidly, but by a similar mechanism, than in the absence of sulfate containing species.     

鼠细小病毒感染性滴度测定方法的建立及病毒制备

目的建立鼠细小病毒(MMV)感染性滴度测定方法,并制备高滴度的MMV,为生物制品病毒清除/灭活工艺的验证奠定基础。方法通过分析NB324K细胞接种量、培养时间及病毒吸附时间等参数,建立MMV病毒滴度测定的半数细胞感染剂量法(CCID5)0,并分析其精密性;以A9细胞制备MMV,分析感染复数(MOI)、收获时间及收获样本对病毒滴度的影响,并检测病毒的稳定性。结果NB324K细胞的最佳接种浓度、培养时间及病毒吸附时间分别为5×103个/孔、48h及2h,所建立的检测方法精密性较好;A9细胞沉淀中病毒滴度高于上清,且随病毒MOI值的升高而逐渐增加,在MOI为10时,感染后48h收获,病毒滴度最高。制备的病毒液的平均滴度为8.69CCID50/ml,4℃和37℃保存7d及反复冻融5次,稳定性良好。结论已建立了MMV感染性滴度测定方法,并制备了高滴度的病毒,为以MMV为指示病毒进行病毒清除/灭活工艺验证奠定了基础。     

Stability of chemical reactors in the presence of sustained disturbances

A general method is developed for constructing regions of practical stability for nonlinear lumped-parameter systems. The region of practical stability serves as a bound on the system response for a general class of magnitude-constrained disturbances. The construction method is based on a modified Liapunov approach but is not restricted to a particular type of Liapunov function. The method is applicable to higher order systems in which several disturbance variables are present. Numerical results are presented for a CSTR with magnitude-constrained disturbances in feed composition and feed temperature.     

Analytical solution of a sink model of a two-dimensional counterwasher

Shwartz and Probstein 1 formulated a sink model of a two-dimensional flooded counterwasher operating in the Darcy flow regime. They gave a numerical solution of a special case of this model, but did not provide an analytical solution for its performance characteristics. This solution omitted a parameter which caused it to represent only a restricted case of a counterwasher having certain pressure constraints. In this paper, we repair this omission and present a completely analytical solution for the general sink model. The results are simple formulas for the performance of the counterwasher in terms of the geometric, flow and pressure parameters. Formulas for the brine crown height and shape are also given. These formulas are in good agreement with the numerical solution given by Shwartz and Probstein for their special case.     

A Self-Delamination Method of Measuring the Surface Energy of Adhesion of Coatings

A self-delamination technique is presented to assess the surface energy of adhesion of coatings. By measuring the debond area resulting from a circular hole cut in a film adhered onto a substrate, the surface energy may be determined if the tensile modulus, Poisson's ratio and residual stress level of the film are known. This method is useful for coating thicknesses greater than a critical thickness for self-peeling. Using this technique, the surface energy for a polyimide film (cured up to 220°C) on a glass plate was determined to 3.2 Nm^-1.     

Exergetic analysis of reactions with participation of solid phases

The chemical and thermal components of exergy of solid-phase reaction systems have been analyzed. Chemical exergy is the measure of energy maintenance of chemical reaction; therefore, chemical exergy is intrinsic, not for a particular substance, but rather for a reaction mixture with a particular composition. The temperature dependence of the chemical exergy of the exothermic reaction mixture has a maximum and the temperature dependence of the chemical exergy of endothermic reaction mixture has a minimum. Equations for calculating the exergy components have been suggested, which assume the possibility of the presence of structural polymorphism for the crystal components of reaction mixture.     

Model for filtration combustion of carbon: Approximation of a thermodynamically equilibrium composition of combustion products

A model for stationary filtration combustion of mixtures of carbon with a solid incombustible material in a counterflow a gas containing oxygen and a chemically inert gas is proposed. If the rates of chemical reactions in the combustion zone are sufficiently high, the ratio of carbon monoxide and dioxide in combustion products is assumed to be thermodynamically equilibrium at the combustion temperature. This assumption provides a closure for the balance equations for carbon, oxygen, and energy in the combustion front and gives explicit analytical expressions for the combustion temperature and composition of the products as functions of the composition of the carbon/inert mixture and of the gaseous oxidizer in stoichiometric regimes. Combustion modes are numerically calculated for a wide variation of the compositions. The upper limit of the reagent supply rate until which equilibrium relations can be used is found. A comparison of model predictions with experimental results shows their reasonable qualitative agreement.     

An appraisal of standard methods for determination of flame spread behaviour of materials

Salient features of the standard apparatuses and the methodology adopted by various countries for determination of flame spread behaviour of materials are analysed and discussed with a view to obtain a perspective of the performance of these apparatuses. This study was undertaken to investigate the possible reasons for anamolies in the results obtained using these apparatuses. A need is established for development of a new technique for direct determination of flame spread rate of materials under steady-state conditions which has the potential of overcoming the inherent limitations of the existing apparatuses.     

Modeling of the operation of a batch former

The mathematical tool examined can be used for constructing a system for controlling the movement of a fabric roll from the quality-inspector’s table to the batch formation points for shipment to the customer.     

治理造气污水实现零排放

张家港市化肥厂投资３００万元建立１套造污水处理装置,对造气水进行沉淀处理后经潜水泵送到冷却塔中进行对流曝气,冷却,然后循环复用。沉淀池中的煤渣用自动泵吸式吸泥行车吸至浓缩池进一步分离,浓缩成膏状物再用软管泵加压送至自动箱式板框压滤机压滤,滤饼作为沸腾炉燃料。该装置使用后效果较好,造气污染民实现了闭路循环,达到了零排放,亦取得较好的经济效益。