The effects of orthokinetic collision,acoustic wake,and gravity on acoustic agglomeration of polydisperse aerosols

A new concept of effective agglomeration length, which measures the maximum particle separation distance for effective collisions, is proposed for study of acoustic agglomeration of polydisperse aerosols with respect to the separate and combined effects of orthokinetic collision and acoustic wake in a horizontal acoustic wave when particle gravity is included. Particle gravity is found to be significant for the acoustic wake effect while the particle collision efficiency is important for the orthokinetic collision. Results indicate that orthokinetic collision dominates at low frequencies for intermediate size ratios while the acoustic wake effect is more significant at higher frequencies for all particles. The optimum frequency for orthokinetic collision is confirmed but shifts downward with the increase of sound power. For the acoustic wake effect, the agglomeration increases monotonically with sound frequency. Results also show that the orthokinetic collision is not effective for agglomeration of sub-micron particles because of low particle collision efficiency.     

Shape normalization of catalyst pellet

A shape normalization, which is applicable in the entire range of Thiele modulus φ, is developed. A shape normalization established here for small φ and the shape normalization already established here for large φ are used in developing the normalization for all φ. This normalization brings the η - φ curves for all pellet shapes to a single curve corresponding to infinite slab geometry for all φ. The effectiveness factor for any shape of catalyst is simply the effectiveness factor for an infinite slab when the Thiele modulus for the slab is properly defined in terms of the characteristic pellet length and the reaction kinetics. The shape normalization is shown to give negligible error for any pellet configuration and first order reaction, and is postulated to hold for general kinetics and any pellet configuration, by proper definition of the Thiele modulus.     

Exact conditional maximized sequential probability ratio test adjusted for covariates

Sequential analysis is now commonly used for post-market drug and vaccine safety surveillance, and a Poisson stochastic process is typically used for rare adverse events. The conditional maximized sequential probability ratio test, CMaxSPRT, is a powerful tool when there is uncertainty in the estimated expected counts under the null hypothesis. This paper derives exact critical values for CMaxSPRT, as well as statistical power and expected time to signal. This is done for both continuous and group sequential analysis, and for different rejection boundaries. It is also shown how to adjust for covariates in the sequential design. A table of critical values is provided for selected parameters and rejection boundaries, while new functions in the R Sequential package can be used for other calculations. In addition, the method is illustrated for monitoring adverse events after pediarix vaccination data.     

高纯过氧化氢生产中有机物杂质的净化技术进展

介绍了工业级过氧化氢中有机物杂质的来源,综述了高纯过氧化氢生产中有机物杂质的净化技术研究进展,包括精馏、吸附、离子交换树脂、溶剂萃取、结晶、膜分离技术以及这些技术的组合净化技术。精馏净化产品纯度不高,但技术成熟,可工业放大;膜分离净化技术较安全,但膜的寿命短;吸附树脂工艺简单、净化效率高,但树脂易被氧化。指出以精馏为前净化技术,再与膜分离、树脂吸附相结合是有机碳杂质去除技术的发展趋势。     

大牛地气田水平井泡沫排水技术优化研究

泡沫排液采气工艺是对付自喷能力不足,气流速度低于临界流速气井较有效的排水方法,其设备简单、操作简便,一般适合于有一定自喷能力、产液量低于100m^3／d、井深小于3500m的产水气井。该工艺在大牛地气田已运用多年,其应用的井数在逐年增多,且通过新泡排制度的摸索施行其成功率也在逐年提高。然而过去的泡排工艺大都针对直井,随大牛地气田近年来水平井数量的逐渐增加,有必要同时对水平井的泡沫排液采气工艺也进行评价和优化设计,完善大牛地气田泡排工艺技术。     

Nonuniform initiation of photoreactions II. Diffusion of reactive intermediates

The influence of spatially nonuniform initiation is investigated for a class of photoreactions in which diffusion of intermediates is important. The investigation is centered on a differential equation for reaction and diffusion of reactive intermediates. The circumstances are set forth under which the equation is valid for several kinetically similar reaction types. A solution is obtained for Lambert's law attenuation. The characteristics of this solution and the solution obtained by Noyes for linear attenuation are discussed. The practical consequences of these solutions are shown through illustrative calculations based on the photochlorination of tetrachloroethylene.     

发展甲醇 实施碳铵企业产品结构调整

概述了碳铵企业进行产品结构调整的迫切性。叙述了碳铵企业产品结构调整的方案,介绍了主体系统实施改造的技术以及有关回收气体和甲醇、氨延伸产品的生产技术。     

Analysis of pulsatile flow and its role on particle removal from surfaces

The use of pulsatile flow for energy efficient particle removal from surfaces is evaluated through modeling calculations. The governing equation for pulsatile flow in a channel between parallel plates with an oscillatory pressure input is solved and wall shear stress, identified as a measure for particle removal, calculated for fixed power input. It is observed that as the frequency of oscillation is increased the average wall shear stress with an oscillatory pressure input is higher than the corresponding steady state value only above a critical frequency. Similar results are obtained for pulsatile flow in a pipe. Explanation for this observation is presented based on how velocity profile changes as a function of frequency and consequently its effect on wall shear stress versus power dissipated. Based on these observations we propose that there is a critical frequency above which an oscillatory pressure input will be energy efficient for particle removal.     

Calculating the vapor-liquid phase equilibrium for multicomponent systems using the Soave-Redlich-Kwong equation

An algorithm for calculating the vapor-liquid phase equilibrium for multicomponent gases is presented. A six-component gas mixture is considered. The algorithm for calculating phase equilibrium is based on the solution to the Soave-Redlich-Kwong equation of state for real gases. An iteration algorithm for updating phase equilibrium constants is used. The total vapor fraction is determined using the solution to the Rachford-Rice equation. The difficulties of developing such algorithms are considered in full detail. The derived solution is compared with results obtained in the commercial package HYSYS (version 3.2) when the Soave-Redlich-Kwong equation is also used.     

Permeability model for a woven fabric

The resin transfer molding (RTM) method is used to manufacture composite parts. The reinforcing fibers are placed in a mold cavity and the resin is injected to fill up the empty spaces. After the resin cures, the mold is opened and the part ejected. To predict necessary pressures and filling times and the proper locations for the inlet ports for resin injection and vents for air ejection it is necessary to model the resin infiltration process. A key to this modeling is permeability which characterizes the resistance of fibers to the flow of infiltrating resin. A simplified model for in-plane permeability of fabric reinforcement (preform) is developed here. This model uses lubrication theory for modeling the flow through open pores and Darcy's law for the transverse flow through the reinforcement. Scaling analysis is provided to justify the simplification and to estimate the range of validity for resulting expressions. Extension of the model to cover multi-layered preforms is derived. Boundary conditions and the data necessary to specify the problem geometry are discussed. A numerical experiment is conducted to estimate the influence of the transverse permeability of the preform on the solution. A calculation is provided for the permeability of a plain weave fabric.     

Sintering of Inhomogeneous Binary Powder Mixtures

A geometric model for the sintering of inhomogeneous, binary powder mixtures having a large size ratio is presented. The model is demonstrated for a hypothetical mixture in which the heterogeneity is described by a normal distribution function. The model is demonstrated for the case of the fine fraction sintering only and for the case of both components sintering. Relative to the prediction for the homogeneous mixture, shrinkage is observed to be either "enhanced,""retarded," or the same, depending on the compositional limits of heterogeneity and the level of sintering.     

交联聚乙烯绝缘料用基础树脂的性能研究

利用拉伸试验、红外光谱、凝胶渗透色谱、差示扫描量热法、流变表征等方法测试了交联聚乙烯绝缘料用基础树脂的性能,并研究了制备硅烷交联和过氧化物交联聚乙烯绝缘料的基础树脂组成。结果表明,交联聚乙烯绝缘料用LDPE树脂的基本性能:MFR为2.0g/10 min,密度为0.920g/cm3,熔点为107℃左右,拉伸强度大于12MPa,断裂伸长率大于580%,介电常数小于2.3,相对支化度2.34左右。硅烷交联聚乙烯绝缘料宜用LLDPE和LDPE的共混物做基础树脂,而过氧化物交联聚乙烯绝缘料的基础树脂用LDPE即可。     

A Genetic Algorithm Based Approach to Coalescence Parameters: Estimation in Liquid‐Liquid Extraction Columns

The population balance model is a useful tool for the design and prediction of a range of processes that involve dispersed phases and particulates. The inverse problem method for the droplet population balance model is applied to estimate coalescences parameters for two‐phase liquid‐liquid systems. This is undertaken for two systems, namely toluene/water and n‐butyl acetate/water in a rotating disc contactor (RDC), using a droplet population balance model. In the literature, the estimation procedure applied to this problem is often based on the deterministic optimization approach. These methods generate instabilities near a local minimum, inevitably requiring information about the derivatives at each iteration. To overcome these limitations, a method providing an estimate for the coalescences parameters is proposed. It is based on a simple and adapted structure of the genetic algorithm, for this particular problem. The agreement between the experimental observations and the simulations is encouraging and, in particular, the models used have proven to be suitable for the prediction of hold‐up and Sauter diameter profiles for these systems. Finally, these results demonstrate that the optimization procedure proposed is very convenient for estimating the coalescences parameters for extraction column systems.     

The asymptotic status of the Sherwood-Pigford model in the theory of absorption with chemical reaction

The Sherwood-Pigford model for absorption accompanied by instantaneous irreversible chemical reaction is an essentially discontinuous one, where a moving front across which concentration gradients suffer a discontinuity is assumed to exist. The case where the reaction is both instantaneous and irreversible is a doubly singular one. In this paper, a boundary-layer analysis is developed which shows that, for irreversible reactions, the Sherwood-Pigford model equations are approached asymptotically for arbitrary kinetics when an appropriate time scale of the reaction becomes sufficiently small. It is also shown that the same limit is approached for arbitrary stoichiometry in the case of instantaneous reactions when the ratio of the interface to the bulk concentration of volatile component becomes sufficiently large. Finally, a general estimate is obtained of the thickness of the reaction zone (which is assumed to be zero in the Sherwood-Pigford model) for the general case where the reaction is neither instantaneous nor irreversible.     

聚酯亚胺多元醇酸值分析的新方法

聚酯亚胺多元醇酸值是聚氨酯的一个重要指标一通常测定酸值时，一般使用酚酞作为指示剂。但是对于改性聚酯多元醇，用酚酞作为指示剂其终点难以判断，故采用电位滴定法测聚酯亚胺多元醇的酸值，同时使用各种酸碱指示剂用来指示滴定终点，结合两得出一个最件的指示剂。研究表明溴百里酚蓝为测定聚酯亚胺多元醇测定酸值最合适的指示剂。提供了聚酯亚胺多元醇起始电位值与酸值的标准曲线图．能快速、简便地查出相同条件下不同样品的酸值。     

Polymer flow in the clearance between closely spaced candle filter elements

A mathematical model for polymer flow in the clearance between high-resistance filter elements is developed. An analytical solution is obtained for pressure and velocity profiles for Newtonian fluids. A numerical solution is obtained for elastic fluids displaying power-law behavior in viscosity and entrance pressure loss. Elasticity of the polymer melt or solution is shown to be a significant factor in, determining these profiles. An example of the model's application, using rheological data for a commercial polyethylene, is given, and the impact of clearance flow pressure losses on the mechanical side loading of the filter elements is discussed.     

型煤用添加剂研究的新进展

概述了型煤发展技术、对型煤所用粘结剂进行了综合评述，认为开发多功能复合粘结剂是发展清洁，高效燃烧型煤的技术关键。     

Dispersion models of unsteady tubular reactors

Axial dispersion in time-variable laminar flow in a tubular reactor is analyzed using an exact procedure for the case of a homogenous first-order reaction. For the first time since the Taylor Dispersion model was originally introduced for the modeling of reactors, its validity is examined over a wide range of the reaction rate parameter by comparison against an exact analysis. It is shown that a constant coefficient dispersion model can be obtained from first principles for large values of time only for initial distribution problems; however, this simple approximate model also is reasonably good for describing concentration distributions for the present inlet distribution problem for slow reactions and for axial locations sufficiently far away from the inlet. For rapid reactions, while the dispersion model is inaccurate in describing axial concentration distributions, it is surprisingly good for predicting the reactor length required for complete conversion. In contrast to the conclusion of a recent article, it will be shown that the dispersion coefficient is independent of the reaction rate constant.