CRT colorimetry. Part II: Metrology

The colorimetric characterization of computer-controlled CRT displays require radiometric measurements with high precision and accuracy in order to achieve acceptable colorimetric accuracy in defining stimuli generated with this type of imaging modality. Precision and accuracy requirements for photometers, colorimeters, and spectroradiometers were evaluated. When models are used to relate digital counts defining a stimulus and resulting spectral radiant exitance, displays are assumed to exhibit channel and spatial independence. A variety of tests and the results of evaluating four imaging systems are described. From these analyses, measurement accuracy is mainly limited by wavelength scale in the case of spectro-radiometers and filter fit in the case of colorimeters. Measurement precision is limited by the number of significant figures for fixed-range devices and signal-to-noise limitations for low-luminance stimuli. Display accuracy is limited by a lack of channel and spatial independence. Display precision is mainly limited by the electronic design of the display and the stability and load independence of the gun amplifiers. © 1993 John Wiley & Sons, Inc.     

Minimum reflux conditions,part I: Theory

This paper presents a new formulation of the infinite plate or minimum reflux limit of a multicomponent distillation column. Based on this model, two new calculation methods are developed. The first is a short-cut method which extends Underwood's classic minimum reflux treatment to variable molar overflow situations. The second is a rigorous method which is similar to a multicomponent flash calculation and represents a significant computational advance over other rigorous methods.     

Melt-electrospinning part I: processing parameters and geometric properties

The effects of various melt-electrospinning parameters on the morphology and fiber diameter of polypropylene of different tacticities were studied. The effect of the electric field strength at various melt flow indexes of polypropylene on fiber uniformity, morphology, and diameter was measured. It was shown that the molecular weight was the predominant factor in determining the fiber diameter of the collected fibers. Observations prove that the tacticity also influences the fiber diameter. Atactic polymers having molecular chains incapable of crystallization tend to produce larger diameter fibers than isotactic polymers capable of crystallization even at lower molecular weights. The polymer volume, at a given time, supplied to the electric field affected fiber diameter. Those systems supplying the smallest volume, at a given time, produced the smallest fiber diameter.     

Vertical two-phase flow part I. Flow pattern correlations

Two-phase gas-liquid flow has been investigated in a 1-inch internal diameter vertical tube coil containing two risers and a downcomer all connected by “U” bends. Flow pattern data were obtained in the three vertical tubes, each 17.30 ft. long, for five different air-liquid systems at about 25 psia over flow ranges of 0–700 lb_m air/min-ft² and 140–25300 lb_m liquid/min-ft². Liquid phase viscosities ranged from 1 to 12 cp. A flow pattern classification with six regimes including coring-bubble, bubbly-slug, falling film, falling bubbly-film, froth and annular flow regimes was established for downflow. Flow patterns in the bends were also classified. Data from the present investigation were used to formulate an empirical flow pattern graphical correlation for both upflow and downflow which is based upon the coordinates (R_v)^1/2 and Fr_TP/A, where R_v is the delivered gas-to-liquid volume ratio, Fr_TP is the mixture Froude number, and A = μ_s/(S_L^σ_s³)^1/4 in which μ_s, S_L, σ_s are specific viscosity, specific density and specific surface tension respectively of the liquid with reference to water. The correlation was satisfactorily tested with independent literature data for upflow systems, including air-water, steam-water at various pressures, nitrogen-mercury and air-heptane, and data from flowing gas-oil wells. No independent literature data appear to be available for testing the correlation for downflow systems, but it is anticipated that the correlation will prove to be generally applicable. The coring phenomenon in downward bubble flow was examined by means of high speed motion photography and is explained by the development of a lift force on a bubble.     

Nucleation of microcellular foam: Theory and practice

Microcellular polymer foams exhibit greatly improved mechanical properties as compared to standard foams due to the formers' small bubble size. Microcellular foams have bubbles with diameters on the order of 10 microns, volume reductions of 30 to 40 percent, and six or seven times the impact strength of solid parts. They are produced through the use of thermodynamic instabilities without the use of foaming agents. This method leads to a very uniform cell size throughout a part's cross section. A theoretical model for the nucleation of microcellular foams in thermoplastic polymers has been developed and experimentally confirmed. This model explains the effect of various additives and processing conditions on the number of bubbles nucleated. At levels of secondary constituents below their solubility limits, an increase in the concentration of the additive or the concentration of gas in solution with the polymer increases the number of bubbles nucleated. Nucleation in this region is homogeneous. Above the solubility limit of additives, nucleation is heterogeneous and takes place at the interface between second phase inclusions and the polymer. The number of bubbles nucleated is dependent on the concentration of heterogeneous nucleation sites and their relative effect on the activation energy barrier to nucleation. In the vicinity of the solubility limit, the two mechanisms compete.     

Emulsion liquid membranes part I: Phenomenon and industrial application

Emulsion liquid membrane processes are discussed. The characteristics of the processes, research activities and commercial applications are surveyed and the advantages and disadvantages are outlined. The first large-scale plant for the separation of zinc is described as well as several pilot plants for the separation of various metals from aqueous solutions.     

Glass bead-filled polypropylene part I: Rheological and mechanical properties

Five glass bead-filled polypropylene composites were rheologically characterized at 240°C using two rotational rheometers to obtain low shear-rate data and a capillary rheometer to obtain high shear-rate data. Both steady and dynamic properties were measured at low shear rates. Each composite was also injection molded into tensile and flexural test bars for a mechanical properties profile at 25°C. The tensile modulus was determined from a simple extensional deformation whereas the flexural modulus was determined from a three-point-bend test. The relative shear viscosity and relative loss modulus are different nonlinear functions of the volume fraction of beads at a constant shear rate, while the relative storage modulus appears to be a linear function of bead fraction. The relative viscosity decreases with increasing shear rate and the zero shear-rate data are in very good agreement with the Guth-Gold equation. The relative tensile modulus and relative flexural modulus are each linear functions of bead fraction over the entire range of filler concentration, 0-29 vol percent. From these data it is concluded that a simple correspondence between slow viscous flow and small strain elasticity does not exist for these composites.     

Determination of nonionic surfactant biodegradability: Physical properties vs. colorimetry

Biodegradation studies with three alkyl phenol nonionic products have revealed that loss of cobaltothiocyanate colorimetric sensitivity may not necessarily correlate with loss of surface tension lowering and foaming properties when these type structures are exposed to microbial attack. Where this type of disagreement between analytical methods is present, only the surface tension and foam data are valid measurements of biodegradation. Presented at the AOCS meeting, Houston, Texas, April 1965.     

Ultrasonic welding using tie-layer materials. part I: Analysis of process operation

Ultrasonic welding of oriented polypropylene (OPP) using tie-layer materials has been examined. The thermal cycle at the joint interface was evaluated using a high speed data acquisition system, and concurrent changes in horn displacement (penetration) and the output power were monitored. The model explaining process operation involves four phases, i.e., I–where heating occurs because of the stresses generated in asperities on the contacting surfaces; II–where the whole tie-layer reaches the melting point; III–where the polymer melt is subjected to intense heating from viscous dissipation and is squeezed out; and IV–where the joint cools after welding. In the early stages of ultrasonic welding the heat generated at asperities on the contacting surfaces leads to melting of the tie-layer/oriented polypropylene interface within 50 ms. The tie-layer heats up because of a combination of viscoelastic dissipation and heat conduction from the oriented polypropylene/tie-layer interface, and the rate of temperature rise at the midline of the tie-layer is in the range 200°/s to 400°/s. The reduction in thickness of the test specimens (penetration) is negligible up to the time when the tie-layer melts completely, and then changes rapidly when the melted polymer at the joint interface is squeezed out. The influence of machine parameters (amplitude and contact pressure) and of tie-layer Melt Flow Index is also examined. The total time required for completion of the welding process decreases when the amplitude and applied pressure are increased. The use of low Melt Flow Index tie-layers produces peak temperature as high as 600° at the bondline, and little material is ejected during the ultrasonic welding operation.     

Strengths of ceramic fiber bundles: Theory and practice

The Weibull modulus and reference strength of ceramic fibers can be inferred from measurements of the tensile stress‐strain response of a bundle of such fibers. The goal of the present article is to address issues in the fidelity of results stemming from fiber bundle tests and strategies to optimize outcomes. The issues are addressed through established theorems in uncertainty propagation, Monte Carlo simulations of fiber bundle fracture, and experimental measurements on bundles of SiC fibers of various length and surface condition. The study shows that optimal results are obtained when: (i) tests are performed on fiber bundles with a gauge length that exceeds a critical value (specifically, that needed to prevent mechanical instabilities in the post‐load‐maximum domain); (ii) bundles are lubricated with a low‐viscosity oil, to mitigate both inter‐fiber friction and dynamic coupling associated with release waves following fiber fracture; and (iii) the Weibull parameters are obtained by directly fitting the measured stress‐strain curves with the function predicted by fiber bundle theory, rather than using methods based on either linear regression analysis of Weibull probability plots or fitting of the peak stress and strain alone.     

Toward a more accurate and extensible colorimetry. Part Ii. Discussion

Technical advances in the forty years since the Stiles-Burch color-matching work-among them the bright split-field visual colorimeter coupled by quartz light pipe to a spectroradiometer-allow measurement of an accurate absolute spectral power distribution (SPD) of every viewed light. Furthermore, the ability to measure accurately the power-content of each spectral constituent of a viewed light has clarified both colorimetric procedures and signficance, for example, of color-matching functions (CMFs) and tristimulus values. Three disparate sets of three spectral primaries were used throughout the work. This has not been done before, and its use elucidated much of the difficulty (as described by Judd, Stiles, MacAdam, Wyszecki, and others) inherent in traditional colorimetry. Errors in computed chromaticities of sets of 28 visually-matching lights depend strongly on their spectral content, and are particularly large in the presence of high spectral content in the violet, deep red, and near 500 nm or 580 nm. Peaks of visual efficiency, and minima in chromaticity errors, were found with power in three intermediate spectral regions near 450 nm, 530 nm, and 610 nm. Computed luminance (1964 CIE Standard Observer) and power-content also depend strongly on spectral content of the visually-matching white lights. That this is true of luminance is generally unknown. Perceived brightness of single spectral lights in isolation, and of mixtures, was examined at length: As a rule, removing one spectral component from a mixture increases perceived brightness, thus invalidating both luminance and R + G + B as correlates of brightness. Visual tests of the Grassmann proportionality and additivity assumptions, with highly metameric mixtures, tended to confirm them. Nevertheless, numerous tests-substituting pairs of actual visually-matching lights from one primary-set for pairs from another, which is how “transformation of primaries” is (mathematically) carried out-led to the inescapable conclusion that the normal human visual system does not honor such transformation. At the same time, numerous indications supported a particular set of primaries as an invariant of the visual system, making transformation needless as well as invalid. Chromaticity errors are not the fault of the particular maximum-saturation CMFs utilized; the observer's own CMFs do no better, whatever the primary-set. Soundness of traditional construction of the chromaticity diagram is shown to depend on the primary-set, breakdown occurring for some otherwise legitimate primary-sets.     

Improving the wet slaking of coke: Theory and practice

Theoretical and practical aspects of wet slaking that combines pulsed and dual (two-loop) cooling of the coke are outlined. The introduction of the new technology at ZAO Makeevkoks reduces the overall moisture content of blast-furnace coke and improves its uniformity, while reducing atmospheric emissions and slowing the corrosion of the slaking car.     

The injection molding of thermoplastics part I: Theoretical model

A mathematical model is proposed for the quantitative treatment of the injection molding of thermoplastics as it relates to the behavior of polymer in the cavity. The model is based on setting up the equations of continuity, motion, and energy for the system during each of the stages of the injection molding cycle (filling, packing and cooling) and the coupling of these equations with practical boundary conditions. The treatment takes into consideration the non-Newtonian behavior of the melt, the effect of temperature on density and viscosity, the latent heat of solidification, and the differences in thermal properties between the solid and the melt. In employing the model, it is necessary to know the pressure-time variation at the cavity entrance. Numerical solutions have been obtained for the case of spreading radial flow in a semi-circular cavity. The numerical results yield significant data on the progression of the melt front, the flow rate, and the velocity profiles at different times and positions in the cavity. They also yield temperature and pressure profiles throughout the packing and cooling stages.     

Theory and practice of resin-catalyzed epoxidation

Summary Commercial polystyrene sulfonic acid resins have been shown to be effective in catalyzing epoxidation of unsaturated fatty esters with hydrogen peroxide and acetic acid because they catalyze peracid formation but do not promote by-product formation when used under proper conditions. Special resins with less cross-linkage have been shown to yield mostly by-products. Best catalyst life has been obtained with a special resin prepared with a low metal content. A continuous process based on the cascade principle has been demonstrated in the laboratory. The problem of resin re-use for both continuous and batch processes can best be solved by using the optimum 10–15% based on oil weight and by replacing about 10% of the resin after each use. Presented at the annual meeting of the American Oil Chemists’ Society, Cincinnati, O., September 30–October 2, 1957.     

Machine learning-based predictive control of nonlinear processes. Part I: Theory

This article focuses on the design of model predictive control (MPC) systems for nonlinear processes that utilize an ensemble of recurrent neural network (RNN) models to predict nonlinear dynamics. Specifically, RNN models are initially developed based on a data set generated from extensive open-loop simulations within a desired process operation region to capture process dynamics with a sufficiently small modeling error between the RNN model and the actual nonlinear process model. Subsequently, Lyapunov-based MPC (LMPC) that utilizes RNN models as the prediction model is developed to achieve closed-loop state boundedness and convergence to the origin. Additionally, machine learning ensemble regression modeling tools are employed in the formulation of LMPC to improve prediction accuracy of RNN models and overall closed-loop performance while parallel computing is utilized to reduce computation time. Computational implementation of the method and application to a chemical reactor example is discussed in the second article of this series.     

Fiber orientation in simple injection moldings. Part I: Theory and numerical methods

This paper sets out the theory and numerical methods used to simulate filling and fiber orientation is simple injection moldings (a film-gated strip and a center-gated disk). Our simulation applies to these simple geometry problems for the flow of a generalized Newtonian fluid where the velocities can be solved independently of fiber orientation. This simplification is valid when the orientation is so flat that the fibers do not contribute to the gapwise shear stresses. A finite difference solution calculates the temperature and velocity fields along the flow direction and through the thickness of the part, and fiber orientation is then integrated numerically along pathlines. Fiber orientation is three-dimensional, using a second-rank tensor representation of the orientation distribution function. The assumptions used to develop the simulation are not valid near the flow front, where the recirculating fountain flow complicates the problem. We present a numerrical scheme that includes the effect of the fountain flow on temperature and fiber orientation near the flow front. The simulation predicts that the orientation will vary through the thickness of the part, causing the molding to appear layered. The outer “skin” layer is predicted only if the effects of the fountain flow and heat transfer are included in the simulation.     

Momentum-Balance Aspects of Free-Settling Theory. I. Batch Thickening

Abstract

The theory of batch gravity thickening of an initially free-settling slurry is considered, taking into account the momentum-balance relationships for the system. It is concluded that graded-concentration zones which develop during the process must lie in the compression concentration range; retarding forces necessary to produce increase in concentration are not present in free settling.