Mixing is a crucial process for many large scale and small scale applications from food industry to cosmetics, from drug industry to petrochemical processes, etc. Changes in parameters (temperature, viscosity, velocity distribution, etc.) during the mixing affect the production process and the end product quality and the cost. Thus, these parameters, mostly the hydrodynamic parameters, should be monitored closely during the process. In order to ensure good and efficient mixing in the solution, high degree of turbulence is maintained while dead zones in the tank should be avoided. In chemical industry, the mixing processes generally involve complex solutions that exhibit non-Newtonian flow behavior that merits a study on the agitation hydrodynamics and mixing time. Thus, in this study agitation of carboxymethyl cellulose (CMC) solution in a laboratory scale mixing tank is investigated. The effects of CMC concentration and agitation speed on the hydrodynamics of the solution and mixing time are studied in detail. CMC concentrations studied are 0.5 wt%, 1 wt% and 2 wt%. Impeller speeds, on the other hand, are set as 150 rpm, 300 rpm and 600 rpm. The hydrodynamics of mixing can be studied easily by Ultrasound Doppler Velocimetry (UDV) which is a fast, non-invasive measuring technique in fluid dynamics. Also, the mixing time measurements were carried out through electrical conductivity of the agitated solution. UDV results show that the flow field has a typical pattern produced by the Rushton turbine. The main characteristics of the flow are that, in the impeller region radial components of the flow dominate. Near the wall flow occurs mainly in the axial direction towards the top and bottom of the tank. Mixing time measurements reveal that mixing time increases with decreasing impeller speed and with increasing solution concentration (i.e. viscosity). Typical mixing time values are in the range of 250-2600 seconds for different impeller speeds and CMC concentrations.

Afin de caractériser l'agitation et le mélange en mélangeur Triaxe® nous avons mis au point un logiciel capable de piloter le mélangeur, de suivre les conditions opératoires — vitesses d'agitation et couples développés par les moteurs — et d'analyser la qualité du mélange obtenu en temps réel.<br /><br />Le suivi des couples développés par les moteurs lors du mélange a permis d'identifier les régimes d'écoulements présents dans ce type de mélangeur.<br /><br />La mise en œuvre et la validation de la méthode d'analyse d'image pour mesurer la qualité du mélange ont permis de suivre l'évolution cinétique de mélanges binaires de deux poudres à écoulement libre — couscous/semoule — et d'une poudre à écoulement libre et d'une poudre cohésive — couscous/lactose.<br /><br />Cette étude a permis de caractériser ce nouvel équipement de mélange, de définir les protocoles opératoires à utiliser en fonction des propriétés des poudres afin d'obtenir un mélange efficace à la fois en terme de temps de mélange court et de puissance consommée faible. Des corrélations basées sur des nombres adimensionnels ainsi qu'une corrélation liant le temps de mélange et les vitesses d'agitation ont été déterminées.

Ce travail de recherche concerne un nouveau procédé de vitrification à l'étude au CEA de Marcoule depuis ces vingt dernières années. Ce procédé, basé sur l'induction directe en creuset froid, est utilisé pour le traitement des déchets nucléaires de haute activité. Il se caractérise par le refroidissement des structures métalliques par circulation d'eau et l'induction directe de courants électriques dans la charge de verre en fusion. Un dispositif d'agitation mécanique permet une homogénéisation du bain de verre fondu. Lors de cette étude, les phénomènes thermiques, hydrodynamiques et électromagnétiques ont été considérés. Une attention particulière est portée sur la modélisation de l'agitation mécanique et la mise en place d'une stratégie de couplage entre les trois phénomènes. La validation de la modélisation a pu être réalisée à partir des résultats expérimentaux acquis sur les pilotes de vitrification.

This study involved 58 persons with dementia living in three rural Canadian long-term care (LTC) facilities. In an attempt to find the relationship between these person's possible pain and levels of agitation, data on five proxy indicators of pain were collected and correlated with scores from the Pittsburgh Agitation Scale (PAS). Results indicated that three of the resident pain measures were significantly correlated with PAS scores. In particular, the palliative consultant pain ratings and the DS-DAT were strongly correlated with total PAS scores, and the five PAS sub-factors. Importantly, the PAS sub-factor of resistance to care was strongly correlated with three of the pain variables. Major study implications include the need for increased use of palliative pain consultants in LTC, and the need for nursing staff to realize that when demented residents resist care, it may be a potential clue that the resident is experiencing untreated pain. / xv, 116 leaves ; 29 cm.

No description available.

Steroidal estrogens and antibiotics used in veterinary and human medicine are detected in livestock manure or sewage sludge and biosolids. Biodegradation is an important process by which estrogenic compounds are removed from organic amendments, but antibiotics have been shown to impede microbial communities. Although both compounds are often present in these media, the fate of estrogens in association with antibiotics has not been previously studied. In this study, both rates of tetracycline (40 and 200 mg kg-1) in liquid swine manure induced a lag phase of 40 to 50 days prior to the onset of a log phase of estrone and 17 β-estradiol mineralization, and tetracycline at 200 mg kg-1 significantly reduced maximum mineralization of estrone and 17 β-estradiol in manure. In soils amended with a high rate of manure, penicillin at 200 mg kg1 also significantly decreased maximum mineralization of estrone and 17 β-estradiol relative to soils free of antibiotics. Estrogen mineralization almost always significantly decreased in the order of: manure > soil amended with a low rate of manure = soil > soil amended with a high rate of manure. In order to examine the relationship between physical and chemical parameters of media and estrogen mineralization, sewage sludge and biosolid samples with vastly different characteristics were selected for a study of 17 β-estradiol and 17 α-ethinylestradiol mineralization in the presence of ciprofloxacin, an antibiotic commonly used to treat urinary and intestinal infections in humans. Ciprofloxacin was persistent in all media, as less than 0.05% mineralization was observed over 133 d. Despite this persistence, no significant effect of ciprofloxacin addition on 17 β-estradiol or 17 α-ethinylestradiol mineralization was observed at 133 days. Consistent with its chemical structure, maximum mineralization of 17 α-ethinylestradiol was always less than that of 17 β-estradiol, indicating resistance to microbial degradation. PCA analysis indicated that total nitrogen, ammonium-nitrogen and total carbon demonstrated a positive association with respiration and maximum mineralization of 17 β-estradiol, but a negative association with 17 α-ethinylestradiol maximum mineralization. Sorption of 17 α-ethinylestradiol was greater than 17 β-estradiol in all media, limiting maximum mineralization of 17 α-ethinylestradiol.

The presence of hydrodynamically generated air bubbles has been observed to enhance fine particle flotation in a high intensity agitation (HIA) flotation cell. In this study, the cavitation in an HIA cell, used in our laboratory, is studied by hydrodynamic computational fluid dynamics. Different types of impellers are studied to obtain flow characteristics such as velocity and pressure distributions and turbulent dissipation rate in a two-baffled HIA cell. A cavitation model in conjunction with a multiphase mixture model is used to predict the vapor generation in the HIA cell. Cavitating flow is simulated as a function of revolution speed (RPM) and dissolved gas concentration to understand the dependency of hydrodynamic cavitation on these operating parameters. For comparison, cavitation in a pressure driven flow through a constriction is also modeled. A population balance model is used to obtain bubble size distributions of the generated cavities in a flow through constriction. / Chemical Engineering

Thesis (M.S.)--University of Michigan, 1999. / Running title: Psychotropics and agitation. Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 1989.

Thesis (M.S.)--University of Michigan, 1999. / Running title: Psychotropics and agitation. Includes bibliographical references.