• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1398
  • 1011
  • 380
  • 88
  • 62
  • 59
  • 45
  • 38
  • 21
  • 19
  • 14
  • 12
  • 11
  • 8
  • 8
  • Tagged with
  • 3655
  • 1140
  • 591
  • 492
  • 382
  • 356
  • 299
  • 251
  • 249
  • 248
  • 229
  • 224
  • 217
  • 215
  • 209
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
151

Set-Up and Validation of a Dynamic Solid/Gas Bioreactor

Lloyd-Randol, Jennifer D. 05 1900 (has links)
The limited availability of fossil resourses mandates the development of new energy vectors, which is one of the Grand Challenges of the 21st Century [1]. Biocatalytic energy conversion is a promising solution to meet the increased energy demand of industrialized societies. Applications of biocatalysis in the gas-phase are so far limited to production of fine chemicals and pharmaceuticals. However, this technology has the potential for large scale biocatalytic applications [2], e.g. for the formation of novel energy carriers. The so-called solid/gas biocatalysis is defined as the application of a biocatalyst immobilized on solid-phase support acting on gaseous substrates [3]. This process combines the advantages of bio-catalysis (green chemistry, mild reaction conditions, high specicity & selectivity) and heterogeneous dynamic gas-phase processes (low diffusion limitation, high conversion, simple scale-up). This work presents the modifications of a PID Microactivity Reference reactor in order to make it suitable for solid/gas biocatalysis. The reactor design requirements are based on previously published laboratory scale solid/gas systems with a feed of saturated vapors [4]. These vapors are produced in saturation flasks, which were designed and optimized during this project. Other modifications included relocation of the gas mixing chamber, redesigning the location and heating mechanism for the reactor tube, and heating of the outlet gas line. The modified reactor system was verified based on the Candida antarctica lipase B catalyzed transesterication of ethyl acetate with 1-hexanol to hexyl acetate and ethanol and results were compared to liquid-phase model reactions. Products were analyzed on line by a gas chromatograph with a flame ionization detector. C. antarc- tica physisorbed on silica particles produced a 50% conversion of hexanol at 40 C in the gas-phase. A commercial immobilized lipase from Iris Biotech produced 99% and 97% conversions of hexanol in similar experiments. This project achieved its goal to design, establish and successfully verify a solid/- gas biocatalysis reactor. Future work will target optimization of the reactor's operating conditions and the development of whole cell catalysts for energy production reactions. Potential experiments include the study of hydrogenolytic carbon dioxide reduction to methanol by free enzymes or methanogenic organisms [5], and the investigation of hydrogen production by water splitting of algae or cyanobacteria.
152

Simulation Validation with Real Measurements of an Intelligent Home Energy Management System.

Panangat, James Jose January 2021 (has links)
This thesis's main objective is to conduct a comparison study between measured values and simulated results of a demonstrator, of the intelligent home energy management (iHEM) project. The comparison helps to validate the simulation. TRNSYS software is used for the design. In this study, only the thermal energy side of the project is considered. In which system-level (both domestic hot water (DHW), space heating (SH)) and component level (solar collector, gas boiler) are considered as the parameters to compare. An attempt is made to optimize both system-level and component-level simulation outputs with measured values by adopting measured boundary conditions as simulation inputs.During the comparison, the DHW loop simulation design is modified. The measured data were given as input files for simulation, replacing the estimated values used before. This is done to optimize the simulation output with measured data. In the space heating loop (SH), the simulated building model’s parameters were changed to optimize the SH demand. After the system-level validation and optimization, the component level comparison is carried out. For this, the simulation output of solar thermal collectors and gas boiler are compared with measured values. The solar collector loop in the simulation is modified to optimize the simulated results. The seasonal and yearly efficiencies of the collector have been calculated. Solar supply fraction and gas boiler supply fraction is also determined. For the comparison, graphs are plotted for three different weeks, representing the spring, summer, and winter months of 2018.The final optimized simulation output of DHW demand is 7% less than the measured value. Even after optimizing the Space heating loop (SH), the simulated building demand is 17% more heat than the demonstrator building. The simulation's solar collector output is optimized close to the measured values. The simulated gas boiler produces 19% more than the demonstrator system to meet excess SH demand in the simulation (including losses). The overall yearly collector efficiency calculated for measured and simulated values are 58% and 50%, respectively. The estimated solar collector supply fraction and gas boiler supply fraction is 26%, 76% for measured, and 23%, 81% for simulation, respectively.
153

HPLC analýza léčiv / HPLC Analysis of Drugs

Kouřil, Tomáš January 2018 (has links)
Charles University Faculty of Pharmacy in Hradec Králové Department of Biophysics and Physical Chemistry Candidate: Tomas Kouril Consultant: Ing. Vladimir Kubicek, CSc. Title of Thesis: HPLC analysis of Drugs The diploma thesis describes selection of the most suitable conditions for determination of a two enantiomers of drugs betaxolol and bisoprolol with a method HPLC. The aim of the thesis was to find a suitable isocratic method for the substances for extraction from plasma. The chromatographic column Daicel Chiralcel ® OD-R 4,6 mm x 250 m was utilized. The best results were achieved with mobile phase consisting of acetonitrile and aqueous solution of sodium perchlorate (1 molar) in volume ratio 50:50 for betaxolol and 35:65 for bisoprolol. The column was thermostated at 25 řC. UV detection (λ = 190 nm) was applied to get a sufficient sensitivity. Tramadol and O-desmethyltramadol was tested as an internal standard. Biological samples were tested by LLE before the HPLC analyses. Furthermore, the LLE method for biological samples was tested before performing HPLC.
154

Development and Validation of a Liquid Chromatography-Mass Spectrometry Based Analytical Assay for Determination of Cromolyn Sodium in Skin Permeation Studies

Holman, Miranda K, Frempong, Dorcas, Brown, Stacy, Dinh, Steven, Puri, Ashana 18 March 2021 (has links)
Cromolyn sodium (CS) is a mast cell stabilizer which has been used to treat systemic mastocytosis, allergic- and exercise-induced asthma, and allergic reactions induced by atopic dermatitis. Presently, CS is administered orally and intranasally, and with a short half-life and poor absorption, 4 to 8 doses are required daily for treatment. Developing a transdermal product for CS would eliminate such drawbacks that lead to inconsistent patient dosing and provide sustained therapeutic effects when administered via skin. Our long-term goal is to determine the feasibility of delivering CS through skin. However, a prerequisite for evaluating the performance of any transdermal system is to have a sensitive analytical method that can selectively detect and quantify the drug without any interference from compounds that may leach from skin during permeation studies. Therefore, our preliminary goal was to develop and validate such a method that can be employed for transdermal studies. The optimized liquid chromatography-mass spectrometry (LC-MS) method utilized a chromatographic separation which involved an isocratic mobile phase (10mM ammonium bicarbonate, pH 8.0, 90% and acetonitrile, 10%) at a flow rate of 0.2500 mL/min. Detection involved direct MS/MS channels with m/z 467.0255 (precursor) and m/z 379.0517 (fragment) with argon as the collision gas. CS calibrants were prepared in phosphate-buffered saline (PBS), pH 7.4, for validation (0.1, 0.25, 0.5, 0.75, 1, and 2.5 μg/mL). To ensure no skin interference, dermatomed porcine ear skin was minced, placed in PBS, and shaken for 15 hours to extract any possible interfering components. The extract was filtered and analyzed with the optimized LC-MS conditions. Calibrants were also analyzed over 3 days with each day examining 6 injections (20 μL) of each sample. Peak areas determined by LC-MS were used to construct calibration curves for CS and to calculate % error and % RSD to elucidate accuracy and precision of the method. Results showed CS retention time to be around 4.4 minutes with no interfering peak from skin extract, and linearity was observed between 0.1-2.5 μg/mL. Inter- and intra-day accuracy and precision of the method were within the acceptable limit of ±20% at the lower limit of quantitation and ±15% at other concentrations. Future studies will involve using the validated method for quantification of CS in skin permeation studies to investigate our long-term goal.
155

Validation Of The Facet Satisfaction Scale (Fss): An Evaluative Approach To Assessing Facet Job Satisfaction

Yeoh, Terence Eng Siong 12 1900 (has links)
Job satisfaction has, and continues to be an important construct of interest to researchers and practitioners alike. However, conflicting operational definitions and inconsistent measurement systems have reduced the efficacy of the construct in predicting important job-related outcomes for organizations and their employees. The Facet Satisfaction Scale (FSS) was designed to overcome these deficiencies by creating a facet-based measure that assesses job satisfaction in accordance with recent definitions of the construct. Reliability and validity analyses were conducted on both the complete and shortened version of the scale. The FSS exhibited evidence of reliability (ranging from .52 to .93 for the shortened FSS, and .53 to .96 for the complete FSS). Evidence of scale validity was also obtained through the use of construct, content, and criterion-related validity measures. Implications of the study on future research on job satisfaction are discussed.
156

On validation of a wheel-rail wear prediction code

Sánchez Arandojo, Adrián January 2013 (has links)
During the past years, several tools have been developed to try predicting wheel and rail wear of railway vehicles in an e-cient way. In this MSc thesis a new wear prediction tool developed by I.Persson is studied and compared with another wear prediction tool, developed by T.Jendel, which has been already validated and is in use since several years ago. The advantages that the new model gives are simpler structure, the consideration of wear as a continuous variable and that all the code is integrated in the same software. The two models have the same methodology until the part of the wear calculations and the post-processing. Wheel-rail geometry functions and time domain simulations are performed with the software GENSYS. In the simulation model the track and the vehicle are dened as well as other important properties such as vehicle speed and coe-cient of friction. Three simple tracks are used: tangent track, R=500 m curve with a cant of ht=0.15 m on the outer rail and R=1000 m curve with a cant of ht=0.1 m on the outer rail. The model is assumed to be symmetric so just outer (first and fourth axle) and inner (second and third axles) wheels are considered. During the vehicle-track interaction, the normal and tangential problems are solved. The wheel-rail contact is modelled according to Hertz's theory and Kalker's simplied theory with the help of the algorithm FASTSIM. Then wear calculations are performed according to Archard's wear law. It is applied in dierent ways, obtaining wear depth directly in Jendel's and wear volume rate in Persson's model. Jendel's model is rstly analyzed. Its specifc methodology is briefly explained and modications are performed on the code to make it work as similar as possible to Persson's model. Also parameters regarding the distance in which wear calculations are taken, the discretization of the width of the wheel and the discretization of the contact patch are analyzed. The methodology of Persson's model is also studied, most of all the performance of the post-processing which is one of the keys to the code. The parameters analyzed in this code are the ones regarding a statistical analysis performed during the post-processing and the discretization of the contact patch. Finally the comparisons between the wear depth obtained for both models are carried out. The discrepancies between the models are explained with the parameters analyzed and the dynamic behaviour of both models. Also a theoretical case is used as reference for comparison.
157

Simulation Validation with Real Measurements of an Intelligent Home Energy Management System.

Jose Panangat, James January 2021 (has links)
This thesis's main objective is to conduct a comparison study between measured values and simulated results of a demonstrator, of the intelligent home energy management (iHEM) project. The comparison helps to validate the simulation. TRNSYS software is used for the design. In this study, only the thermal energy side of the project is considered. In which system-level (both domestic hot water (DHW), space heating (SH)) and component level (solar collector, gas boiler) are considered as the parameters to compare. An attempt is made to optimize both system-level and component-level simulation outputs with measured values by adopting measured boundary conditions as simulation inputs.During the comparison, the DHW loop simulation design is modified. The measured data were given as input files for simulation, replacing the estimated values used before. This is done to optimize the simulation output with measured data. In the space heating loop (SH), the simulated building model’s parameters were changed to optimize the SH demand. After the system-level validation and optimization, the component level comparison is carried out. For this, the simulation output of solar thermal collectors and gas boiler are compared with measured values. The solar collector loop in the simulation is modified to optimize the simulated results. The seasonal and yearly efficiencies of the collector have been calculated. Solar supply fraction and gas boiler supply fraction is also determined. For the comparison, graphs are plotted for three different weeks, representing the spring, summer, and winter months of 2018.The final optimized simulation output of DHW demand is 7% less than the measured value. Even after optimizing the Space heating loop (SH), the simulated building demand is 17% more heat than the demonstrator building. The simulation's solar collector output is optimized close to the measured values. The simulated gas boiler produces 19% more than the demonstrator system to meet excess SH demand in the simulation (including losses). The overall yearly collector efficiency calculated for measured and simulated values are 58% and 50%, respectively. The estimated solar collector supply fraction and gas bo
158

The development and validation of a virtuous leadership scale

Ou, Yang Annie 08 March 2022 (has links)
There is a need for virtuous leaders that have a sound moral compass that guide their actions and decisions towards good and honourable outcomes. In particular, the current research study responded to a call in literature to address an African context perspective of virtuous leadership. Based on this, the aim was to formulate a theoretical conceptualisation of virtuous leadership that was grounded in an African contextual perspective to develop and validate a Virtuous Leadership Scale (VLS). The current research study was a descriptive research design with a cross-sectional approach. Secondary quantitative data and primary qualitative and quantitative data was utilised by means of convenience sampling strategy and snowball technique. A realised sample for the secondary quantitative data (n = 193) and the primary quantitative data (n = 72) was collected from the general working population. A conceptual/theoretical model of virtuous leadership was proposed, which captured seven virtues that encompassed an African contextual perspective: 1) courage; 2) humanity; 3) humility; 4) integrity; 5) justice; 6) prudence; and 7) temperance. Based on this model, items were generated and analysed prior to the development of the VLS. Exploratory Factor Analysis confirmed the unidimensionality of each virtue subscale. Utilising Confirmatory Factor Analysis, the measurement model was found to be a good fit. Furthermore, empirical evidence of reliability, discriminant and convergent validity was found, however, predictive validity was not supported. The current research study developed a valid and reliable scale that measures the virtuous leadership construct. There are limitations, recommendations and theoretical contributions discussed.
159

A Revalidation of the Level of Service Inventory–Revised (LSI-R)

Towers, Crystal Murani January 2020 (has links)
In the United States, the large number of incarcerated individuals presents heavy social and economic burdens. To lessen these strains, many criminal justice agencies utilize risk assessment to determine which individuals are at a higher risk of recidivating and allocate limited intervention resources accordingly. To ensure these interventions are being delivered to those persons most in need, these risk assessment instruments must be tested for predictive validity. The present research seeks to revalidate one such risk assessment tool, the Level of Service Inventory Revised (LSI-R), on an adult offender population of a Midwest state. Additionally, this research expands on previous LSI-R validation studies by assessing the predictive validity of the LSI-R on an understudied population, Native Americans. The analyses utilized in this research include univariate descriptive statistics, bivariate correlation, and Receiver Operator Characteristic/Area Under the Curve analysis. Results are presented. Policy implications and recommendations for future research are discussed.
160

Preliminary Development and Content Validation of a Rating Scale for Assessing Attention-Deficit Hyperactivity Disorder in Children

Holland, Melissa Lea 01 May 1997 (has links)
Attention-Deficit Hyperactivity Disorder (ADHD) is currently one of the most frequent problems for which children are referred to mental health clinics in this country, affecting approximately 3-5% of the childhood population. Although adequate assessment and identification of this disorder is imperative, most of the currently existing measures to assess for ADHD in children are inadequate . The present research study involved the development and content validation of a new behavior rating scale prototype for assessing ADHD in the school-age (K-12) population. This research was conducted in five distinct steps: (a) item development; (b) development of the prototype; (c) content validation by an expert panel; (d) evaluation of the prototype; and ( e) modification of the prototype. Initial behavioral descriptors were obtained from a comprehensive and systematic review of the literature related to ADHD in school-age children. Potential items were then reviewed by a panel of experts in the area of ADHD in children. A panel of teachers and a panel of parents rated the usability of the prototype and the overall quality of the items. Two different types of rating formats were developed to help determine, through the content validation and the usability ratings of the prototype, which rating format would be most appropriate and useful for the eventual users of the rating scale. A final version of the prototype was constructed, including the revised items, a rating scale format, instructions to the informant, questions regarding the demographic characteristics of the child being assessed, and a mixed order presentation of the items.

Page generated in 0.0435 seconds