Modeling of fouling in cross-flow microfiltration of suspensions

Cross-flow filtration of fine suspensions through microsieves occurs in microprocessing. The interaction of particles with surfaces in microenvironments has been extensively studied, but predominantly in monolayers and not with an eye to microfiltration. Here, we introduce a microfiltration model that pertains to particles that might be seen as fine in a macroscopic environment, but are large enough to intrude significantly into the shear layer of a microchannel. Thus, particle accumulation upon the sieve couples the steady-state filtrate flux and the suspension flow through the microchannel that feeds the sieve. We envision and create a stable, stationary multilayer of particles whose thickness is shear-limited and we identify and verify the structure and parameters that limit steady filtration in this environment. At first, a packed bed of particles forms, growing into and regulated by the micro channel's shear flow. A critical shear stress is shown to determine the thickness of the bed, seen as a stationary and stable multilayer of particles through which filtration may occur. As the bed thickens, at the expense of channel area for suspension flow, surface shear stress increases until no further particle adherence is possible. We built a simple example using hard noninteracting polymer microspheres and conducted cross-flow filtration experiments over Aquamarijn™ microsieves (uniform pore size of 0.8 μm). We observed a steady cake-layer thickness and because of the simple geometry afforded by uniform spheres, we could approximate the force balance, cake resistance, and filtration rate from first principles. The good fit of our data to the proposed mechanism lays a firm basis for the semiquantitative analysis of the behavior of more complex suspensions. © 2018 American Institute of Chemical Engineers AIChE J, 65: 207–213, 2019     

Cottonseed flavonoids as lipid antioxidants

Methanolic extracts of cottonseeds were found to possess antioxidant activity. Separation of antioxidant components was achieved by paper, thin layer (TLC) and gas liquid chromatography (GLC) and spectral analysis. Chromatographic technique indicated that the flavonoids quercetin and rutin were the major flavonoids present. GLC analysis of the cottonseed extract eluted from TLC plates, developed in n-butanol/acetic acid/water (4:1:5, v/v/v) and ethyl acetate/methyl ethyl ketone/formic acid/water (5:3:1:1, v/v/v) solvents, corresponded in retention times to the rutin standard (10⁻⁴ M). TMS derivatives of the aglycone fraction, prepared by acid hydrolysis, correlated to the retention time of quercetin. Spectral analysis of the aglycone fraction also indicated quercetin derivatives to be present in cottonseed. The glycosyl substitution of the flavonoids were identified by the 3 chromatographic procedures to be glucose and rhamnose. Chromogenic spray reagents were used to further characterize the cottonseed flavonoids and flavonoid components on TLC and paper chromatography. The investigation, therefore, demonstrated that quercetin derivatives appear to be the main flavonoid species in cottonseed. Rutin was found to be one of the major quercetin glycosides. Quercetin and rutin are shown to possess potent antioxidant activity.     

Customer Thermal Energy Storage a Marketing Opportunity for Cooling off Electric Peak Demand

Traditionally, electric utilities have forecast the demand for their product and planned a supply system to satisfy the market. Rather than treating the forecast demand as a given, Florida Power & Light Company (FPL), has established a marketing planning function to alter future demand through direct involvement in the marketplace. The crucial element in management's evaluation of opportunities to build, maintain, shift, or reduce customer load is a better understanding of our customers, including their preferences and behavior in purchasing energy. A market analysis utilizing a comprehensive marketing planning model, the Load Management Strategy Testing Model (LMSTM), indicates that the commercial sector, in general, and customer thermal energy storage, in particular, is a demand-side option the Company will actively promote. That identification is made by a detailed market feasibility study FPL is currently managing.     

Evaluation of students' clinical competence.

In this article we describe a clinical proficiency review required of 3rd-year graduate students, and we present data from a study of its psychometric properties and utility. Students' oral and written case presentations were evaluated on seven dimensions by a six-member panel composed of faculty and students. Moderately high interjudge reliabilities were achieved, although the level of agreement between rater pairs was related to the level of similarity of their theoretical orientation. Significant correlations were obtained between panel ratings and those of current field placement supervisors, but not with supervisor's ratings from prior or subsequent placements. Performance on the clinical proficiency review was relatively independent of academic performance measures such as course grades and scores on a six-part comprehensive examination. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The therapist's dilemma: Using nomothetic information to answer idiographic questions.

The therapist is faced with the dilemma of conducting therapy at an idiographic level while psychology research is conducted and organized at a nomothetic level. Increasingly, psychiatric diagnosis serves as the conceptual bridge from the science of psychology to its clinical applications. Yet diagnosis has a number of well-known limitations for determining treatment. An alternative conceptual bridge from nomothetic science to clinical applications draws from 3 overlapping categories: (1) general causal principles derived from all areas of scientific psychology; (2) probabilities and base rate data associated with the covariation of psychological problems; and (3) clinical outcome research. Suggestions as to how therapists can use these nomothetic categories to form treatment strategies are given. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hybrid threshold optimization between global image and local regions in image segmentation for melasma severity assessment

Melasma image segmentation plays a fundamental role for computerized melasma severity assessment. A method of hybrid threshold optimization between a given image and its local regions is proposed and used for melasma image segmentation. An analytic optimal hybrid threshold solution is obtained by minimizing the deviation between the given image and its segmented outcome. This optimal hybrid threshold comprises both local and global information around image pixels and is used to develop an optimal hybrid thresholding segmentation method. The developed method is firstly evaluated based on synthetic images and subsequently used for melasma segmentation and severity assessment. Statistical evaluations of experimental results based on real-world melasma images show that the proposed method outperforms other state-of-the-art thresholding segmentation methods for melasma severity assessment.     

Comparison between the design of experiments and simulation in the three-phase distillation in a sieve tray column for glycerine dehydration

Design of experiments (DOE) is a value scientific approach used to understand the processes in a better way and to determine how the inputs affect the response(s). In this work, this method has been applied to study the behavior of the three-phase distillation in a sieve tray column, through the effects of the process and geometrical variables. The experimental values were compared with predicted values obtained by simulation using the equilibrium and nonequilibrium models. Three-phase distillation has been used for glycerine dehydration using toluene as entrainer, in order to avoid the glycerol degradation by distillation at atmospheric pressure. The best conditions found were: vapor flow rate of toluene = 23.5 kg/h, feed flow rate = 2.2 kg/h and feed concentration = 50 wt% glycerol, using the layout L₄ with fractional hole area = 0.04 and weir height = 70 mm. The nonequilibrium model based on Eckert and Vanek's approach (2001) and Chen–Chuang's correlation (1993) have been used to estimate the binary coefficients of mass transport. The predicted values obtained by the experimental model and by the nonequilibrium model have represented the behavior of the dehydration in the sieve tray column studied. Both models underpinned the experimental results obtained for this column.     

Effect of Al2O3 ALD coating on thermal stability of silica aerogel

Journal of Porous Materials - An optically transparent and thermally insulating (OTTI) silica aerogel demonstrates promising results for various solar thermal applications, particularly...