The influence of near-wall density and viscosity gradients on turbulence in channel flows

The influence of near-wall density and viscosity gradients on near-wall turbulence in a channel are studied by means of Direct Numerical Simulation (DNS) of the low-Mach number approximation of the Navier--Stokes equations. Different constitutive relations for density and viscosity as a function of temperature are used in order to mimic a wide range of fluid behaviours and to develop a generalised framework for studying turbulence modulations in variable property flows. Instead of scaling the velocity solely based on local density, as done for the van Driest transformation, we derive an extension of the scaling that is based on gradients of the semi-local Reynolds number $Re_\tau^*$. This extension of the van Driest transformation is able to collapse velocity profiles for flows with near-wall property gradients as a function of the semi-local wall coordinate. However, flow quantities like mixing length, turbulence anisotropy and turbulent vorticity fluctuations do not show a universal scaling very close to the wall. This is attributed to turbulence modulations, which play a crucial role on the evolution of turbulent structures and turbulence energy transfer. We therefore investigate the characteristics of streamwise velocity streaks and quasi-streamwise vortices and found that, similar to turbulent statistics, the turbulent structures are also strongly governed by $Re_\tau^*$ profiles and that their dependence on individual density and viscosity profiles is minor. Flows with near-wall gradients in $Re_\tau^*$ ($d {Re_\tau^*}/dy \neq 0$) showed significant changes in the inclination and tilting angles of quasi-streamwise vortices. These structural changes are responsible for the observed modulation of the Reynolds stress generation mechanism and the inter-component energy transfer in flows with strong near-wall $Re_\tau^*$ gradients.Comment: Submitted manuscript under review in JF

Solar Cell Parameters Extraction from a Current- Voltage Characteristic Using Genetic Algorithm

The determination of solar cell parameters is very important for the evaluation of the cell performance as well as to extract maximum possible output power from the cell. In this paper, we propose a computational based binary-coded genetic algorithm (GA) to extract the parameters (I0, Iph and n) for a single diode model of solar cell from its current-voltage (I-V) characteristic. The algorithm was implemented using LabVIEW as a programming tool and validated by applying it to the I-V curve synthesized from the literature using reported values. The values of parameters obtained by GA are in good agreement with those of the reported values for silicon and plastic solar cells. change to “After the validation of the program, it was used to extract parameters for an experimental I-V characteristic of 4 × 4 cm2 polycrystalline silicon solar cell measured under 900 W/m. The I-V characteristic obtained using GA shows excellent match with the experimental one. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3100

Enhancing the dissolution rate of poorly soluble drug Febuxostat using spray dried amorphous solid dispersion technique

Introducción: El febuxostat pertenece a los fármacos clase II del Sistema de Clasificación Biofarmacéutica, los cuales presentan baja solubilidad y alta permeabilidad. La dispersión sólida amorfa es una de las técnicas que pueden ser útiles para mejorar la solubilidad y las características del polvo. Objetivo: optimizar la concentración de polímeros hidrofílicos e hidrofóbicos para mejorar la velocidad de disolución y la solubilidad de las tabletas de febuxostat. Métodos: La dispersión sólida amorfa de febuxostat se preparó mediante el método de secado por aspersión utilizando Kolliphor P237 (1:2). Esta dispersión sólida amorfa se utilizó además para comprimir el comprimido. Para mejorar la solubilidad y la tasa de disolución, se aplicó un diseño factorial completo para optimizar la concentración crítica de KollidonSR e hidroxi propil metil celulosa (HPMC K4M). Los comprimidos preparados se caracterizaron por parámetros de precompresión y poscompresión. Resultados: La velocidad de liberación del fármaco se mantuvo mediante la formulación de una técnica de dispersión sólida amorfa. Se encontró que el lote optimizado (FSRT-OB) era apto para la liberación promedio del 93,30 % del fármaco en forma de liberación sostenida hasta 12 horas. Los datos de la cinética de liberación sugieren que la liberación del fármaco estuvo controlada por una combinación de mecanismo de relajación de cadena y difusión. Se encontró que la concentración optimizada para Kollidon SR y HPMC K4M era 38,50 % y 7,72 % respectivamente. Conclusión: La técnica de dispersión sólida amorfa es útil para mejorar la solubilidad, la velocidad de disolución y la biodisponibilidad de la tableta de Febuxostat.Introduction: Febuxostat belongs to Biopharmaceutical classification system (BCS) class II drugs, which have low solubility and high permeability. Amorphous solid dispersion is one of the techniques which can be useful to improve solubility and powder characteristics. Objective: To optimize the concentration of hydrophilic and hydrophobic polymers to improve the dissolution rate and solubility of febuxostat tablets. Methods: The amorphous solid dispersion of febuxostat was prepared by spray drying method using Kolliphor P237 (1:2). This amorphous solid dispersion was further used to compress the tablet. To improve solubility and dissolution rate, a full factorial design was applied to optimize the critical concentration of Kollidon SR and hydroxypropyl methyl cellulose (HPMC K4M). The prepared tablets were characterized by pre-compression and post-compression parameters. Result: The rate of drug release was sustained by formulating an amorphous solid dispersion technique. The optimized batch (FSRT-OB) was found to be fit for release average 93.30 % of the drug in sustain release manner up to 12hrs. The release kinetic data suggests that the drug release was controlled by combination of diffusion and chain relaxation mechanism. The optimized concentration for Kollidon SR and HPMC K4Mwas found to be 38.50 % and 7.72 % respectively. Conclusion: Amorphous solid dispersion technique is useful to enhance solubility, dissolution rate, and bioavailability of the Febuxostat tablet

Cloud Computing Security, Privacy Improvements Using Virtualized High Trust Zone

The benefits of cloud computing are clearly well known which include rapid deployment, ease of customization, reduce cost and low risks. However, some high profile security breaches confuse organizations as they attempt to deploy cloud services in their businesses. Although, the cloud service providers pitch the security of their services. Enhancements in existing security measures and advanced solutions are needed to ensure high level security and privacy of data on cloud. This paper provides a holistic overview of cloud security issues by encompassing unique threats in cloud computing and presents findings of a survey of practitioners view on cloud security. A Virtualized High Trust Zone (VHTZ) is then presented as a solution, especially for infrastructure based cloud services to tackle the attacks and network monitoring in a virtualized infrastructure

Importance of Cement Based Unfired Building Blocks in Construction

The need of sustainable and low cost building material is one of the prime concerns for the researchers. This is due to ever increasing demand of conventional building materials that are dependent to natural resources. Conventional clay bricks are one of the important building materials for construction industries. Superior engineering properties of clay bricks makes it most preferable building material for making non-structural elements. Production of conventional bricks is dependent to natural resources like clay, river sand and dirt and exploration of such resources is always harmful for environment. The manufacturing process of conventional bricks is fuel consuming and also emits greenhouse gases in bulk. This research focuses towards promoting cement based unfired building blocks along with the use of conventional clay bricks. Review of researches shows that the use of non-biodegradable abundantly available wastes such as fly ash, brick waste or debris, quarry dust, gypsum etc., in the form of fillers for cement based building blocks, provides the best solution to minimize the load bear by conventional clay bricks

Study and Implementation of Cryptographic Algorithms

Cryptography has a long and fascinating history. Over the centuries, an elaborate set of protocols and mechanisms has been created to deal with information security issues when the information is conveyed by physical documents. Often the objectives of information security cannot solely be achieved through mathematical algorithms and protocols alone, but require procedural techniques and abidance of laws to achieve the desired result. For example, privacy of letters is provided by sealed envelopes delivered by an accepted mail service. The physical security of the envelope is, for practical necessity, limited and so laws are enacted which make it a criminal offense to open mail for which one is not authorized. It is sometimes the case that security is achieved not through the information itself but through the physical document recording it. For example, paper currency requires special inks and material to prevent counterfeiting

Identification of chalcone derivatives as putative non-steroidal aromatase inhibitors potentially useful against breast cancer by molecular docking and ADME prediction

Aromatase is an influential target to overcome estrogen receptor positive breast cancer, as the enzyme is responsible for conversion of androstenedione to estrone, a promising drug target for therapeutic management of breast cancer. Chalcones are prominent biosynthetic compounds and parent candidate for the synthesis of heterocycles with diversified biological activities. The prime objective of the present study is to evaluate the binding interaction of 2-hydroxyphenyl- prop-2-en-1-one (1A-1X), 2-hydroxy-4-methoxyphenyl- prop-2-en-1-one (3A-3X), 2,4-dihydroxyphenyl- prop-2-en-1-one (9A-9X) and 1-hydroxynaphthalen-2-yl-prop-2-en-1-one (5A-5X) derivatives with aromatase enzyme by molecular docking study and also check their ADME properties by maestro suit. The designed chalcones derivatives have been docked against our target protein with PDB id 3S7S retrieved from the protein data bank, whereas exemestane has been taken as the positive control. As docking data revealed that docking score of 1K, 1U, 1B 3K 3N, 5K, 5U, 9S, 9K, 9N and 9F compounds found less than exemestane and all of these compounds with appropriate ADME properties have proven their excellent absorption as well as solubility characteristics. The present findings provided valuable information about binding interactions of chalcones derivatives to the active site of aromatase. These compounds may serve as potential lead compound for developing new aromatase inhibitors in breast cancer treatment

Identification of chalcone derivatives as putative non-steroidal aromatase inhibitors potentially useful against breast cancer by molecular docking and ADME prediction

283-293Aromatase is an influential target to overcome estrogen receptor positive breast cancer, as the enzyme is responsible for conversion of androstenedione to estrone, a promising drug target for therapeutic management of breast cancer. Chalcones are prominent biosynthetic compounds and parent candidate for the synthesis of heterocycles with diversified biological activities. The prime objective of the present study is to evaluate the binding interaction of 2-hydroxyphenyl- prop-2-en-1-one (1A-1X), 2-hydroxy-4-methoxyphenyl- prop-2-en-1-one (3A-3X), 2,4-dihydroxyphenyl- prop-2-en-1-one (9A-9X) and 1-hydroxynaphthalen-2-yl-prop-2-en-1-one (5A-5X) derivatives with aromatase enzyme by molecular docking study and also check their ADME properties by maestro suit. The designed chalcones derivatives have been docked against our target protein with PDB id 3S7S retrieved from the protein data bank, whereas exemestane has been taken as the positive control. As docking data revealed that docking score of 1K, 1U, 1B 3K 3N, 5K, 5U, 9S, 9K, 9N and 9F compounds found less than exemestane and all of these compounds with appropriate ADME properties have proven their excellent absorption as well as solubility characteristics. The present findings provided valuable information about binding interactions of chalcones derivatives to the active site of aromatase. These compounds may serve as potential lead compound for developing new aromatase inhibitors in breast cancer treatment

The analysis of material removal rate of WEDM miniature gears

Gear fabrication in wire electrical discharge machining (WEDM) plays an important role in manufacturing industries. This paper describes the analysis and optimization of process parameters for the fabrication of spur gear on brass spur gear on brass workpiece (10cmx15cmx6mm) material by wire EDM process. The experiments were performed by using the design of experiment (DoE) approach and the material removal rate (MRR) was analyzed by response surface methodology technique. The effect of input parameters i.e. pulse on time, pulse off time and feed rate on MRR has been investigated. The surface geometry of the gears has been analysed by the Scanning Electron Microscopy (SEM). This study found that 0.4 μs for pulse on time, 60 μs for pulse-off time and 6 mm/min for feed rate provides improved material removal rate. The analysis of variance shows that pulse on time and feed rate are the significant parameters for the wire EDM process. The SEM image exhibits the capability of WEDM to machined miniature gear with a uniform distribution of regular-shaped craters and defect-free flank surface