一方圆玺 一朝国事

一方圆玺,不知见证了多少的历史风云!     

A SIMULATION OF A MOTIONLESS MIXER

Continuous laminar mixing in segmented twisted-tape motionless mixers is considered. A solution to the steady isothermal creeping flow of a Newtonian fluid in a twisted-tape mixer has been obtained via two-dimensional numerical procedures. The developed flow within a section of the mixer has been solved in a helical coordinate system by an iterative scheme. The resulting solution is rigorously correct in the absence of entrance and exit flows at the junction between sections. An algorithm is presented for the modelling of these junction flows via two-dimensional procedures. Simulated cross-sectional mixing patterns have been generated for comparison with experimental results

The performance of twisted-tape mixers is simulated for various designs, beginning with the particular geometry of the Kcnics Static Mixer, and for different operating conditions Results suggest that the rate of mixing as a function of the total twist per section is optimized with respect to pressure drop when sections contain 80 degrees of twist. The capability for rational improvement in other design and operating parameters is illustrated. The mechanisms of laminar mixing are discussed and quantified; of primary importance is the tendency for interfacial area to assume an orientation within each section which is favorable to mixing in subsequent sections.     

A MATHEMATICAL ANALYSIS OF A MEMBRANE BIOREACTOR CONTAINING A SLUDGE DISINTEGRATION SYSTEM

The activated sludge process is widely used to treat domestic and industrial wastewater. A significant drawback of this process is the production of “sludge”, the disposal of which can comprise a significant proportion of the total operating costs of a wastewater treatment plant. We analyze the steady-state operation of a membrane bioreactor system (MBR) incorporating a sludge disintegration unit (SDU) to reduce sludge production. We provide a qualitative understanding of the model by finding analytically the steady-state solutions of the model and determining its stability as a function of the residence time. In practice a target value of the mixed liquor suspended solids (MLSS) content within the membrane reactor is specified. Applying the mathematical technique of singularity theory we show that if the sludge disintegration factor is sufficiently high then the MLSS content is guaranteed to be below the target value. This model prediction, of key interest from a practical perspective, was not identified in the original investigation of this model, which relied upon numerical integration of the governing equations.     

千碉之国·丹巴

丹巴县是四川省甘孜州的东大门.被誉为"深藏在横断山脉中的世外桃源",是嘉绒藏族风情文化的中心,属岷山、邛崃山区,是川西高山峡谷的一部分.文化底蕴厚重,民俗风情浓郁,区内遍布的古碉是藏族先民的建筑艺术杰作,具有悠久灿烂的历史.     

一种新型传动结构的斜坡辊道

浮法玻璃厂联合车间受工艺限制,往往将2楼熔制成形车间和1楼包装车间用斜坡辊道连接起来。而2楼与斜坡之间衔接的凸弧辊道、1楼与斜坡之间衔接的凹弧辊道,其结构形式往往成为设计及安装调试的难点。传统的弧段结构采用锥齿轮箱和同步带传动结构,与当前主流的通轴弧齿锥齿轮结构相比较为落后。本文对浮法玻璃车间斜坡辊道结构进行详细阐述,并提出了一种新的凸、凹弧辊道的传动结构。     

一起制氮设备的故障分析

在浮法玻璃生产过程中,氮气流量保持恒定,是保持锡槽工况稳定的重要条件,是生产优质浮法玻璃的重要前提条件之一.只有制氮设备的稳定运行,才能保证氮气供应.本文就制氮空压机运行中出现的故障现象、原因进行了分析,并提出了改进措施.     

四川省某酒业集团废水处理工程

介绍了采用EGSB＋CASS工艺处理酿酒废水的工程实例,废水COD浓度在12000mg／L左右时,经本工艺处理后出水COD浓度小于100mg／L,达到国家排放标准,为类似废水的处理提供借鉴经验。     

Guanosine-Mediated Anxiolytic-Like Effect: Interplay with Adenosine A1 and A2A Receptors

Acute or chronic administration of guanosine (GUO) induces anxiolytic-like effects, for which the adenosine (ADO) system involvement has been postulated yet without a direct experimental evidence. Thus, we aimed to investigate whether adenosine receptors (ARs) are involved in the GUO-mediated anxiolytic-like effect, evaluated by three anxiety-related paradigms in rats. First, we confirmed that acute treatment with GUO exerts an anxiolytic-like effect. Subsequently, we investigated the effects of pretreatment with ADO or A₁R (CPA, CCPA) or A_2AR (CGS21680) agonists 10 min prior to GUO on a GUO-induced anxiolytic-like effect. All the combined treatments blocked the GUO anxiolytic-like effect, whereas when administered alone, each compound was ineffective as compared to the control group. Interestingly, the pretreatment with nonselective antagonist caffeine or selective A₁R (DPCPX) or A_2AR (ZM241385) antagonists did not modify the GUO-induced anxiolytic-like effect. Finally, binding assay performed in hippocampal membranes showed that [³H]GUO binding became saturable at 100–300 nM, suggesting the existence of a putative GUO binding site. In competition experiments, ADO showed a potency order similar to GUO in displacing [³H]GUO binding, whereas AR selective agonists, CPA and CGS21680, partially displaced [³H]GUO binding, but the sum of the two effects was able to displace [³H]GUO binding to the same extent of ADO alone. Overall, our results strengthen previous data supporting GUO-mediated anxiolytic-like effects, add new evidence that these effects are blocked by A₁R and A_2AR agonists and pave, although they do not elucidate the mechanism of GUO and ADO receptor interaction, for a better characterization of GUO binding sites in ARs.     

A MATHEMATICAL MODEL FOR A YANKEE HOOD

Drying of thin paper sheet on a Yankee cylinder equipped with a steam heated high velocity hood is examined. When possible infiltration of air from the surroundings is considered, then the process is fully determined by twelve variables. One of these can be chosen as an independent variable. An equation group of eleven equations is derived. The method of solution is iterative. Finally, a numerical demonstration example is presented.     

A MODEL OF MIXING IN A MOTIONLESS MIXER

This paper deals with the modelling of a Sulzer-Koch motionless mixer. A flow model involving convection and diffusion has been solved to characterize the dispersive mixing in one node of the network and this result was then complemented by a network analysis to obtain the flow distribution. Experimental data are in general agreement with the theory. The approach of this study is shown to provide valuable conclusions about the design of the mixer and to complement the more commonly used integral or statistical treatments. In particular, it has been shown that the ratio of internal resistances controls the distributive mixing in one mixer unit and that significant convective mass transport takes place within the node even when there is no net cross-flow.     

DIFFUSION FROM A CYLINDRICAL DOMAIN THROUGH A MEMBRANE

The method of integral transforms is used to solve the problem of permeation from a polymer-thickened cylinder which is in contact with a permeable membrane at one end. The opposite side of the membrane is kept at zero concentration by a sweeping medium. It is assumed that the diffusion in the cylinder is one-dimensional and that the coupling conditions at the interface are given by the mass and solubility conservations. The mass dux through the membrane is formally approximated. The model can be applied to problems associated with such areas as the testing of protective clothing and controlled release devices.     

A Mathematical Model of SOFC: A Proposal

The mathematical model of the solid oxide fuel cell (SOFC) is presented. The new approach for modeling the voltage of SOFC is proposed. Electrochemical, thermal, electrical, and flow parameters are collected in the 0D mathematical model. The aim was to combine all cell working conditions in as a low number of factors as possible and to have the factors relatively easy to determine. A validation process for various experimental data was made and adequate results are shown. The presented model was validated for various fuel mixtures in relatively wide ranges of parameters as well as for various cell design parameters (e.g. electrolyte thickness, anode porosity, etc.). A distinction is made between the “design‐point” and “off‐design operation”.     

A NUMERICAL SOLUTION OF THE FLOW AROUND A SPHERE IN A CIRCULAR CYLINDER

A numerical solution of the Navier-Stokes equations is presented for Poiseuille flow around an axially placed, fixed sphere in a circular cylinder. Streamlines and isovorticity lines are calculated from the governing equations for the strearnfunction and the vorticity. Isobars are calculated from a Poisson equation, derived from the Navier-Stokes equations. The pressure and vorticity distribution on the surface of the sphere, the additional pressure drop and the drag coefficients are presented. Solutions are obtained for Reynolds numbers up to 150 (based on cylinder diameter and mean velocity). The wall effects are examined by comparison with results of previous investigations for an unbounded flow around a sphere.     

A HYBRID MODELING APPROACH TO IDENTIFY A CONTINUOUS PROCESS IN A CLOSED LOOP

A hybrid modeling approach is proposed for modeling and identification of an uniformly sampled continuous process in a closed loop where noises exist. This approach combines the determination of an ARMAX model with the determination of a continuous model as an integrated modeling procedures. The resulted model is designated as the HM(n,m,s) model. By using this modeling approach, the identifiability of the HM(n,m,s) model will be regardless to the regulator that is being used in the closed loop. Besides, the HM(n,m,s) model provides more accurate dynamic information than those of the conventionally estimated ARMAX model, which may be quite misleading sometimes. A systematic modeling strategy is proposed to obtain an adequate low order model. Numerical examples that use the simulated data and the proposed HM(n,m,s) modeling approach are also given. The results of the examples reveal that the advantage of the HM(n,m,s) modeling approach is remarkable.     

A HYBRID MODELING APPROACH TO IDENTIFY A CONTINUOUS PROCESS IN A CLOSED LOOP

A hybrid modeling approach is proposed for modeling and identification of an uniformly sampled continuous process in a closed loop where noises exist. This approach combines the determination of an ARMAX model with the determination of a continuous model as an integrated modeling procedures. The resulted model is designated as the HM(n,m,s) model. By using this modeling approach, the identifiability of the HM(n,m,s) model will be regardless to the regulator that is being used in the closed loop. Besides, the HM(n,m,s) model provides more accurate dynamic information than those of the conventionally estimated ARMAX model, which may be quite misleading sometimes. A systematic modeling strategy is proposed to obtain an adequate low order model. Numerical examples that use the simulated data and the proposed HM(n,m,s) modeling approach are also given. The results of the examples reveal that the advantage of the HM(n,m,s) modeling approach is remarkable.     

DISPLACEMENT OF A HYDROCARBON OIL FROM A METAL SURFACE USING A SURFACTANT SOLUTION

ABSTRACT

Separation of oils from solid surfaces is important in cleaning and degreasing operations. Water and oils are immiscible requiring the use of an additive which is miscible with water yet has an affinity for oils. Surface active agents, known as surfactants, have this property, being miscible with water while having an affinity for hydrocarbons. In some cases, surfactant solutions displace oils from a solid surface (i.e., remove oil by replacing the oil/solid interfacial area with surfactant solution/solid interfacial area). The presence of alkalinity as well as surfactant concentration is known to affect the ability of a surfactant solution to wet the solid surface and displace the oil. Experiments have been performed to determine quantitatively the effects of surfactant concentration and pH on the displacement of an oil from a metal surface. The displacement is measured in terms of the contact angle formed by the oil on the solid surface in the presence of the surfactant solution, the amount of time needed for the surfactant solution to cause part of the oil to detach from the solid surface, and the volume of the detached oil. Measuring the contact angle of the oil as a function of time shows that surfactant concentration and pH affect the displacement of oil from a metal surface. Increasing the pH of a solution of Triton X-100, a non-ionic surfactant, enhances oil displacement. Increasing the surfactant concentration also enhances oil displacement. The volume of oil which detaches from the solid surface increases with increasing pH and increasing surfactant concentration.