6 research outputs found
Development and Characterization of Novel Floating-Mucoadhesive Tablets Bearing Venlafaxine Hydrochloride
Get PDFThe present investigation is concerned about the development of floating bioadhesive drug delivery system of venlafaxine hydrochloride which after oral administration exhibits a unique combination of floating and bioadhesion to prolong gastric residence time and increase drug bioavailability within the stomach. The floating bioadhesive tablets were prepared by the wet granulation method using different ratios of hydroxypropyl methyl cellulose (HPMC K4MCR) and Carbopol 934PNF as polymers. Sodium bicarbonate (NaHCO3) and citric acid were used as gas (CO2) generating agents. Tablets were characterized for floating properties, in vitro drug release, detachment force, and swelling index. The concentration of hydroxypropyl methyl cellulose and Carbopol 934PNF significantly affects the in vitro drug release, floating properties, detachment force, and swelling properties of the tablets. The optimized formulation showed the floating lag time 72±2.49 seconds and duration of floating 24.50±0.74 hr. The in vitro release studies and floating behavior were studied in simulated gastric fluid (SGF) at pH 1.2. Different drug release kinetics models were also applied. The in vitro drug release from tablets was sufficiently sustained (more than 18 hr) and the Fickian transports of the drug from the tablets were confirmed. The radiological evidence suggests that the tablets remained buoyant and altered position in the stomach of albino rabbit and mean gastric residence time was prolonged (more than > 6 hr)
Benchmarking study of Voltage and Current Source Inverter for Integrated Modular Motor Drives
No full textWith the adoption of Wide Band-gap (WBG) switches in Integrated Modular Motor Drives (IMMDs), the size of the drive is rapidly reduced with increase in efficiency and thermal performance. But with the advantages, use of WBG switches as a direct replacement for Si IGBT/MOSFET in Voltage Source Inverter (VSI) posses challenges in the field of steep dv /dt which leads to problems like over-voltage at motor terminal, degradation of cable and motor insulation leading to bearing current and EMI problems.Current Source Inverter (CSI) mitigates the problems associated with WBG usage in VSI but involves additional components like series SiC diodes leading to additional losses and temperature. This thesis explores design of VSI and CSI topology for High Speed Permanent Motor (HiSPEM) IMMD applications conducts bench-marking study of VSI an CSI based on efficiency and thermal performance of converters. .To begin with, VSI topology for IMMD modelled in PLECS with designing of control strategy. The loss model of SiC MOSFET used in VSI is simulated along with a lookup-table loss model for fast thermal performance evaluation. The current response is verified with the experimental setup with the comparison of loss model and thermal model results.Subsequently, the CSI topology is modelled with designing of multi-loop control strategy. The decoupling of the D and Q axis is performed using feed-forward decoupling method. The calculation of output capacitor filter is performed based on the cutoff frequency. The stability and bandwidth of different controller in the multi-loop are evaluated using bode plot analysis. Later, the diode loss is modelled and a thermal model is constructed using loss lookup-table for both SiC MOSFETs and series SiC didoes.The VSI and CSI typologies are bench-marked against each other on parameters such as converter loss, efficiency and thermal performance revealing the optimum topology to use at different current ratings and switching frequencies.Electrical Engineerin
Modeling the depletion of dissolved oxygen in a lake due to algal bloom: Effect of time delay
No full textDevelopment of spintronics devices and Type 1 heterojunctions from graphene nanoribbon superlattices
Get PDFGraphene physics and edge effects have a substantial influence on the electronic structure of graphene based nanomaterials. In this work, a detailed investigation of the edge effects of graphene nanoribbon superlattices is implemented in order to guide the discovery, design, and development of novel electronic devices. Graphene nanoribbon superlattices are low-dimensional carbon materials that are formed on making junctions with different graphene nanoribbons as components. This leads to a variety of interesting properties as the component ribbons have differing band structures, and edge effects lead to interesting physical applications.
Using Density Functional Theory (DFT), we calculate quasiparticle bandgaps, projected density of states and other electronic structure properties to find that based on the superlattice topology, we can form Type 1 heterojunctions and materials with applications in spintronics. These results were used in conjunction with a nearest-neighbor tight-binding approach to differentiate between three structures formed from graphene nanoribbon superlattices with different interface regions. It was found that slight variations in the interface configuration and structure can result in Type 1 heterojunctions whose behavior could be predicted from a simple 1D effective mass model, or devices with localized magnetism at the interface sites with potential applications in spintronics.
For devices with magnetic interfaces, we show the possibility of forming ferrimagnetic and anti-ferromagnetic materials systems and their possible application areas. We also explain the trends in total and absolute magnetism for these superlattice as parameters of the system considered.Item withdrawn by Mark Zulauf ([email protected]) on 2013-07-12T18:53:26Z
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University of Illinois Theses & Dissertations (ID: 1)
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Release Date: 2015-08-22 11:57:26 UTC
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemItem marked as restricted to the 'Administrator' Group (id=1) by Seth Robbins ([email protected]) on 2013-08-22T16:57:30Z
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Modeling the Control of Algal Bloom in a Lake by Applying Some External Efforts with Time Delay
No full textAn Improved Double Sampling Regression Type Estimator of Population Mean Using Auxiliary Information
Get PDFThis paper provides a new improved double sampling regression type estimator of population mean using auxiliary information. Its bias and mean square error are found and its comparative study with some of the well known estimators is done. From numerical examples it is also observed that the proposed improved regression type estimator performs better than the existing estimators
