DATA ADJUSTMENT FOR NON-REACTIVE BATCH OR STEADY-STATE PROCESSES

An analytical method was developed to adjust inconsistent process data by a least-sum-of-squares technique to “best” meet all material balance constraints. One complete data set composed of “M” stream flow rates with “N” components in each stream was used from either batch or steady-state non-reactive processes to define an unconstrained sum-of-squares adjustment function

Derivatives of the unconstrained sum-of-squares adjustment function with respect to each variable were set to zero yielding a set of non-linear algebraic equations. The entire non-linear set was solved by converging on only M— 2 search variables as compared to conventional methods requiring N(M — 1) — 1 search variables.     

Development of a dynamic circulation-interaction model for mechanically agitated,liquid-liquid reactors

A mathematical model based on the circulation-interaction concept was developed for the dynamic behaviour of continuous, mechanically-agitated, liquid-liquid reactors. The model is described by a set of ordinary, non-linear differential equations and a set of algebraic equations. These equations provide the relationships between the state variables of the system and the inputs to the system. The model permits the study of the dynamic response of the state variables of a liquid-liquid reactor to disturbances and manipulation of the operating conditions. The model can assist in understanding the dynamics of such a system and should be useful for reactor design and design of control systems. Two numerical examples with reasonable and realistic parameters and data values were studied. “Hot” spots can develop during steady-state operations and sensitive and dangerous cases can develop during the dynamic response.     

Iterative Stochastic Elimination for Solving Complex Combinatorial Problems in Drug Discovery

Iterative Stochastic Elimination (ISE) is a novel algorithm that was originally developed to solve extremely complex problems in protein structure and interactions, and has since been applied to diverse topics that share a few general “ingredients”: they are extremely complex, of combinatorial nature, may be presented as large sets of variables that can each have many alternative values, there is some interdependence of the variables on each other, and there is a scoring function that can evaluate each choice of the problems “configuration”; this is the set of single values of each of the variables that constitute its full presentation. Those are picked randomly in a large sample, the analysis of which allows decisions to be made for rejecting some values for each of the variables; thus resulting in a smaller set of potential combinations. This continues in iterations until the number of combinations allows all the remaining options to be computed exhaustively and to order them by their scores. ISE has been mainly applied to problems that are relevant to drug design and discovery. We demonstrate, among others, the use of ISE to determine the properties of molecular ensembles and to pick the best molecules (“focused libraries”) for hitting a specific target. Future ideas for using ISE are discussed, as well as mentioning its contributions to the construction of two start-up companies.     

Three are Not Enough: An INDSCAL Analysis Suggesting that Color Space Has Seven (£1) Dimensions

Forty-five subjects, including color normals, protanomalous, deuteranomalous, protanopes, and deuteranopes, judged dissimilarities of 26 Munsell color chips chosen to span the full color space (i.e., all three parameters—hue, saturation, and lightness—were varied). Each of the 325 pairs of colors was mounted on a standard grey background board. They were presented to subjects in different random orders and were viewed under a Macbeth daylight lamp. For each pair the subject circled a number varying from 0 (for “identical”) to 9 (for “maximally dissimilar”). Fifty data matrices obtained from 45 subjects (5 were from the same subject on different dates and 2 were from another subject) were analyzed by the INDSCAL method. The three-dimensional solution yielded the “standard” three dimensions (lightness, red-green, and yellow-blue) with the classical “color circle” emerging, in a slightly distorted form, in the plane of the second and third dimensions. Seven dimensions seemed necessary to account fully for these data, however. In seven dimensions each of the “standard” dimensions is paired with a “folded” version. Accompanying lightness is a “folded” lightness dimensions, which we have called “lightness contrast.” The light and dark colors are at one end, contrasted with medium colors at the other. Similarly, “folded” red-green roughly contrasts red and green with blue, yellow, and the greys, while “folded” yellow-blue contrasts blue and yellow with red, green, and the greys. The seventh dimension, which may be artifactual, was called “split yellow.” It contrasts very brilliant (high Munsell value and chroma) yellow and orange colors with all the other colors. It is speculated that some of these extra dimensions may relate to anomalous receptor processes characteristic of deviant subjects. The INDSCAL subject space enables discrimination among all five subject types. Specifically, one of the “natural planes” (the red-green versus “folded” yellow-blue plane) of the seven-dimensional solution can be divided into contiguous and fairly compact regions, with each subject type occupying a unique region.     

Identification of parameters in systems of ordinary differential equations using quasilinearization and data perturbation

Given a set of observed data for a particular physical phenomenon, the problem of computing the “best fit” parameters for the mathematical model describing the phenomenon is a common problem in process or reaction mechanism identification. If the mathematical model comprises a set of non-linear ordinary differential equations, this leads to a non-linear boundary value problem. A very powerful way of attacking this class of problem uses an adaptation of the Newton-Raphson-Kantorovich procedure, called quasilinearization, which regards the non-linear problem as the limit of a sequence of linear problems. Starting from an initial trial solution, convergence if it does occur, occurs rapidly; further, convergence is assured if the initial guess is “close enough” to the true solution. The difficulty of making a good initial guess, a serious limitation of the method in the past, can in principle be overcome by the algorithm proposed. When a given vector may not be within the domain of convergence of the original problem, it must be within the domain of convergence of some other derived problem. The latter may then be perturbed towards the original problem in a finite number of steps. In the case of process identification, new data points are derived; these are subsequently adjusted until they coincide with the original data. The algorithm has been successfully applied to several examples from recent chemical engineering literature.     

天然气水合物生成条件的测定和计算

利用全透明蓝宝石水合物静力学实验装置,测定了4种塔里木油田天然气在纯水中的水合物生成条件.将Chen-Guo 水合物模型应用于天然气水合物生成条件的计算,实验测定的4种天然气水合物生成条件的计算结果和实验结果符合得很好.     

Performance of combined cobalt—nickel—zirconia and HZSM-5 catalyst systems for carbon monoxide hydrogenation

The synthesis of hydrocarbons via hydrogenation of carbon monoxide was investigated over cobalt—nickel—zirconia catalysts of various compositions in combination with zeolite HZSM-5 in “mixed bed” and “follow bed” arrangements. These combinations resulted in the formation of aromatics in amounts as high as 30-35 wt% under relatively mild operating conditions (1 atm, 250–280°C). Although the olefinicity of C₂ and C₃ fractions in the product stream was higher in the mixed bed compared to the follow bed arrangement, the selectivities to aromatics were comparable in the two bed arrangements. The aromatic selectivity was found to be sensitive to operating conditions. The formation of aromatics was favored at high HZSM-5/metal catalyst ratios, low space velocities and high reaction temperatures. The product distributions obtained using various metal/zeolite bifunctional catalysts have been discussed.     

Understanding of resonance phenomena on a catalyst under forced concentration and temperature oscillations

Resonance is an interesting phenomenon that may be observed for reactions on catalytic surfaces during periodic forcing of operating variables. Forcing of the variables for non-linear systems may result in substantially changed time averaged behaviour. These resonance phenomena have been observed experimentally by coincidence rather than by systematic analysis. It is not clear for what type of reaction kinetics such behaviour may be expected and predictions are therefore impossible. Clearly, this forms a serious obstacle for any practical application. In this work we set out to analyse the nature of resonance behaviour in heterogeneously catalysed reactions. A Langmuir Hinshelwood microkinetic model is analysed. It is demonstrated that for weakly non-linear forcing variables — as inlet concentrations — forcing leads to resonance phenomena in terms of the reaction rate only in case high total surface occupancies exist in the steady state. In contrast, forcing of strongly non-linear variables — like temperature — may give rise to resonance phenomena for both low and high surface occupancies. Necessary conditions for resonance to occur are derived. The analysis of resonance phenomena is greatly simplified by the availability of explicit analytical expressions as can be derived from Carleman linearization. We will demonstrate the merits of Carleman linearization as compared to numerical integration.     

Capture rate consequences of multispherule aggregate formation in gases—combined roles of direct interception and interspherule momentum “shielding”

Our recent work on the consequences of multispherule cluster aggregate (CA) formation and deposition-rates on much larger solid targets has emphasized the decisive role of “momentum-shielding” in determining aggregate “mobility” compared to N isolated spherules in the same gaseous environment—an effect analogous to the drag-reduction advantages experienced by birds electing to move “in formation.” The extent of “momentum shielding” is conveniently quantified via a dimensionless function: S_mom(N;Kn₁, aggregate structure), which facilitates predicting the deposition-rate consequences of aggregation in aerosol flow systems when the cluster deposition mechanism is dominated by either: (i) isothermal convective-diffusion (C-D), (ii) thermophoresis (T-P) or: (iii) inertial impaction (I-I). Significantly, isothermal C-D was found to be the only transport-mechanism leading to aggregation-induced reductions in spherule deposition rates on large targets (cf. isolated spherules present at the same mainstream spherule volume fraction). However, we demonstrate here that, for aggregate deposition on sufficiently small solid targets—e.g., fibrous filter elements with diameters of O(10 μm)—even these reductions, which exceed one decade for N = O(10³), can be overcome by the mechanism of “direct-interception” (D-I) associated with nonzero effective aggregate size, without the need to invoke either inertial impaction or thermophoresis. This is especially true for Diffusion-Limited (i.e., “open”) CAs (with D_f = 1.8) at gas pressures such that the constituent spherules are near the continuum (Kn₁ << 1) limit. Our present analysis and numerical illustrations exploit the fact that direct-interception is expected to play a negligible role for the capture of individual (dense) nanospherules (perhaps comparable in size to the prevailing gas molecule mean-free-path) but the underlying theory, exploited, extended, and illustrated here, was developed with the help of initial capture rate experimental data for much larger diameter (but unaggregated) aerosols on single filter fibers in low Re crossflow. With such small diameter targets, we demonstrate that this “interception” augmentation for large CAs can occur even for the limiting case of rcp D_f = 3 aggregates, before the expected onset of CA-inertial effects–i.e., Stk_N << Stk_crit, where, for Re = O(1), Stk_crit is also O(1). A simple method is also presented for predicting interception-modified spherule deposition rates in the presence of log-normal type aggregate size distributions.

Copyright © 2018 American Association for Aerosol Research     

Use of basic color terms by red–green dichromats: 1. General description

Abstract: In this article we present data comparing red–green dichromats' use of “Basic Color Terms” (BCTs) with that of standard trichromats. In a complementary article (Color Res Appl 2013) we use these data to evaluate two models of the mechanisms underlying dichromats' use of BCTs. There were three groups of observers—trichromats, protanopes, and deuteranopes—that each performed two tasks: “mapping” (which of these are exemplars of X?) and “best exemplar” (which is the best instance of X?), where X took the value of each Spanish BCT. The mapping task results were subjected to multidimensional scaling that revealed that dichromats differ from trichromats in the number and nature of the dimensions needed for describing BCTs' use. Trichromats required three dimensions closely related to the opponent color mechanisms (red–green, yellow–blue) and the light‐dark channel. In contrast, tridimensional solution for dichromats was difficult to interpret, whereas the fit for the bidimensional solution was very good and revealed a chromatic dimension, which did not match any of the trichromatic dimensions, and an achromatic one. There were also some error‐asymmetries (sometimes “A” was the predominant error when choosing exemplars of “B”, but not vice versa) and the groups differed in the frequency of use of some BCTs (e.g., protanopes chose more stimuli as orange than trichromats and deuteranopes). As expected, the best exemplar task produced more correct responses than the mapping task, and for both tasks, “primary” BCTs (black, white, red, green, yellow, and blue) produced better results than “derived” ones (brown, purple, orange, pink, and grey). © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 360–371, 2014     

撞击流反应器内幂律流体流动特性的数值模拟

采用数值模拟方法对撞击流反应器内幂律流体的流动特性进行研究,分析了不同喷嘴间距和入口流速下清水和不同质量分数幂律流体的径向射流扩展率、径向速度衰减率、剪切应力、表观黏度等分布规律,研究表明：幂律流体中径向射流的径向速度分布规律与清水径向射流相似。随喷嘴间距的增大,扩展率增大,径向速度衰减率减小,平均剪切应力呈先增大后减小的变化规律,其中L=3D时平均剪切应力值最大,更利于流体混合。入口流速越大,扩展率越小,径向速度衰减率越大,平均剪切应力也随之增大。幂律流体的平均剪切应力大于清水,且随质量分数的增大,其扩展率增大,为清水扩展率的1.3~3.3倍,而幂律流体的径向速度衰减率从-1.268~-1.125降低到-1.144~-1.082,逐渐小于清水。幂律流体径向射流区域的剪切应力呈“M”形分布,表观黏度则呈“W”形分布,流体的流变性质对撞击流反应器内流体的流动规律影响显著。     

Real and Ideal Relationships between Selectivity,Reactivity and Equilibrium

Reactivity and selectivity are discussed in terms of quadratic rate—equilibrium relationships for reaction series sharing a common intrinsic barrier, notably Marcus' equation. R.D. Levine's emphasis on such reactions as forming a “Brønsted Series” is suggested as a basis for defining “ideal” reactivity behavior. Ideal relationships between selectivity and reactivity and selectivity and equilibrium are derived based on reaction schemes drawing a formal distinction between reagent and substrate. In a simple Brønsted relationship, the reagent varies and the substrate is held constant. In an extended relationship, in which both substrate and reagent vary, the Brønsted series becomes a selectivity “network” or matrix characterized by direct and cross quadratic coefficients reflecting curvature of a free energy relationship and the dependence of selectivity upon rate or equilibrium respectively. In the ideal case, the quadratic coefficients are equal but, in practice, they generally differ. Inspection of the relevant reaction schemes shows that in evaluating the coefficients, there is greater cancellation of experimental and chemical scatter arising from non-systematic variations in reagent structure for the cross than the direct coefficient; this phenomenon accounts in part for the wider observation of reactivity—selectivity than non-linear free energy relationships. New measurements are reported for reactions of carboxylic acids with enolate and imine substrates. The results are combined with literature data and plotted as reactivity—selectivity and extended Brønsted relationships. The correlations are satisfactorily considered in the context of departures of real from ideal behaviour.     

A graphical approach to cause and effect analysis of chemical processing systems

A method for cause and effect analysis of chemical processing systems has been developed on the concept of a signed directed graph. The signed directed graph, called a “model graph,” is used for representing cause and effect relationships among process variables in a system, and a “Pattern” on the graph is introduced to represent a state of the system, which is specified by “0” for normal state, “ + ” and “ ? ” for larger and smaller deviation from the normal state, respectively. For a given model graph and pattern on it, the cause of state changes and the manner of their propagation are easily found out by the present approach, which is mainly based on the depth-first search algorithm developed by Tarjan. As an illustrative example, a propane vaporizer has been taken to show the usefulness of the present approach.     

Cycles Across an Equilibrium: A Kinetic Investigation of the Reverse and Forward WGS Reaction over a 2% Pt/CeO2 Catalyst (Experimental Data and Qualitative Interpretation)

The forward and reverse water–gas-shift (WGS)-reactions over 2%Pt/CeO₂ catalyst are studied under steady-state conditions using a procedure which entails adjusting feed gas concentrations to cycle back and forth across the equilibrium line. The kinetic data were collected on “both sides” of the equilibrium under varying feed gas compositions (CO and CO₂ concentrations) and temperatures. The obtained data are interpreted using the concept of the apparent “kinetic resistance” developed recently based on the original non-linear theory [see Lazman, M.Z., Yablonsky, G.S., 2008. Overall reaction rate equation of single-route complex catalytic reaction in terms of hypergeometric series. Advances in Chemical Engineering 34, 47–102].     

Absorption of acetone in a two-impinging-streams absorber

The effectiveness of various spray absorption configurations (as shown in Fig. 1 of the paper), which are based on the new technique of “absorption in two-impinging-streams” as well as on conventional absorption techniques in a single spray, were tested by absorbing acetone from air into a water spray. The major conclusions are: (1) absorption rates of acetone into two-impinging-streams (configurations “a” and “c” in Fig. 1) are significantly higher (up to a factor of four) than absorption rates into two streams separately operated (configurations “b” and “d”) under identical conditions and (2) absorption rates of acetone in two-impinging-streams are higher than in a single stream (configurations “e”-“h” in Fig. 1), but the enhancement is less pronounced than above.     

Resolution of molecular weight distributions in slightly pyrolyzed cellulose using the weibull function

Even before weight loss in the low-temperature pyrolysis of cellulose becomes significant, the average degree of polymerization of the partially pyrolyzed samples drops sharply. The gel permeation chromatograms of nitrated derivatives of the samples can be described in terms of a small number of mixed size populations—each component fitted within reasonable limits by a Weibull distribution function. The modal value of each component is taken as an integral multiple of a “macromonomer” of nominal degree of polymerization 228.4. Thus, the data are consistent with a model in which the degradation process is assumed to involve bond rupture at specific “weak links” into particularly favored molecular sizes. Such a mechanism provides a plausible alternative to the commonly assumed random breakdown along the length of the molecule.     

TS法的改进及其在求解化工优化问题中的应用

TS算法属于现代优化算法,是局部领域搜索法的推广,常用于求解组合优化问题.利用TS法搜索过程的有向性和能够跳离局部最优解的特点,对其进行了改造,以适应求解连续变量化工优化问题.首先,根据化工优化问题变量的特性,提出了一种简便的邻域映射方案,并改进了迭代过程中自适应因子的下降函数;进一步分析对比了禁忌步数、自适应因子和初始解等参数对于优化结果的影响.然后通过算例和换热网络优化问题的求解,表明改造后的TS法在求解连续变量化工优化问题中的有效性,及其在化工优化领域的发展价值.     

纤维膜萃取分离器内两相传质特性

纤维膜萃取分离器是一种新型的高效传质设备。本文分别采用两种不同形式的液体分布器,以苯甲酸水溶液-煤油为传质体系,在一直径70 mm、高2630 mm的有机玻璃纤维液膜萃取分离器冷态实验装置上,考察了纤维丝填充密度1.89%～5.08%,水-油或油-水体积流量比3～6的操作区间内,纤维膜分离器内的两相传质性能。结果表明,对于不同的分布器形式、不同的进料顺序、不同的两相流量比,纤维丝最佳填充密度均在3%～3.5%之间。“先油后水”所对应的最佳纤维丝填充密度略低于“先水后油”的情况。根据冷态实验的结果以及最大Reynolds数设计准则,建立了一套0.01 Mt·a^-1的催化汽油脱硫醇工业侧线装置,并进行了工业侧线实验。结果表明,与传统设备比较,采用纤维膜萃取分离器的脱硫醇效果更为理想,脱硫效率至少增加了1个百分点。