Numerical simulation of transport phenomena due to array of round jets impinging on hot moving surface

An attempt has been made to numerically evaluate the heat transfer from a moving surface due to impingement of array of round jets. This paper reports the effect of surface velocity on heat transfer. Transition SST model has been used for simulation to predict heat transfer under laminar, transition, and turbulent regimes. This model has been used as it bridges all flow conditions seamlessly. The computational domain considered in this study is a 3D model with symmetric planes on two sides and periodic interface on two sides, so as to represent an array of round jets. The range of Reynolds number adopted here is 100–5,000. Results were first validated with the correlation given by Martin^[1 Martin, H. Heat and Mass transfer between impinging gas jets and solid surfaces. Advances in Heat Transfer 1977, 13, 1–60.[Crossref] , [Google Scholar]^] for array of round nozzles with stationary isothermal surface under turbulent conditions with an average error of 5.88%. It is observed that at higher surface velocities, the heat transfer from the moving surface is more than the case of heat transfer from a stationary surface. The value of surface velocity at which the heat transfers from moving surface is minimum decreases with increase in Reynolds number. An artificial neural network has been trained to accurately predict the Nusselt number for the given Reynolds number and surface velocity.     

Improvement in thermomechanical properties of off‐grade natural magnesite by addition of Y2O3

Small amount of Y₂O₃ (0‐3 wt%) was added into off‐grade natural magnesite and its effects on the phase assemblage, microstructural evolution in correlation with mechanical and thermomechanical properties were investigated. Presence of Y₂O₃ facilitated the formation of calcium yttrium silicate and yttrialite phases, which prohibited the formation of detrimental‐phase monticellite, which was gradually reduced with the increase in Y₂O₃ content. Y₂O₃ promoted periclase grain growth and segregated the secondary phases at triple‐point junction of periclase grains. Also, high‐temperature (at 1200°C) flexural strength of the samples increased from 77.2 MPa (without Y₂O₃) to 137.45 MPa with the addition of 2 wt% Y₂O₃. Greater degree of direct bonding among periclase grains, compact microstructure, and uniform grain size distribution in addition to reduced amount of monticellite were responsible for the improvement in mechanical and thermomechanical properties.     

基于光敏耦合定时器的压频转换器的实现

研制了基于定时器的压频转换器, 电路主要由工作于非稳态多谐振荡器模式下的定时器LM555和两个光敏电阻构成. 由于数字存储振荡器测得的定时器输出波频率与所施加的输入电压基本呈线性比例关系, 所研制的转换器为类数字输出, 因此具有线性输入/输出关系、 体积小、 易携带和高性价比等优点. 此外, 定时器输出波可以直接与PC机、 微处理器或微控制器相连, 不需要模/数转换器就能完成对输入电压信号的进一步处理.     

Polymeric decontaminant 2 (N,N‐dichloropolystyrene sulfonamide): Synthesis,characterization, and efficacy against simulant of sulfur mustard

A polymeric decontaminant N,N‐dichloropolystyrene sulfonamide was synthesized by different steps from starting material polystyrene and followed by sulfonation, chlorosulfonation, and amidification. Halogeno‐sulfonamide was obtained by treatment of sodium hypochlorite with sulfonamide resin. It was characterized by FTIR, solubility, viscosity, DSC, and TGA techniques. Efficiency of this polymer as decontaminant was evaluated by reaction with 2‐chloro ethyl phenyl sulfide, a simulant of sulfur mustard (SM) at room temperature. This decontamination reaction was monitored by gas chromatography (GC) and products were identified by gas chromatography‐mass spectrometry (GC‐MS). The positive chlorine content of this polymer was checked by standard iodometry titration. The synthesized positive chlorine compound is observed to be a promising decontaminant against simulant of sulfur mustard, chiefly in the situation where use of aqueous medium such as acetonitrile : water (2 : 1) is precluded. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Nonisothermal crystallization kinetics of polyamide 6 and ethylene‐co‐butyl acrylate blends

The nonisothermal melt‐crystallization behavior of PA6 and EBA blends at varying EBA content was investigated using differential scanning calorimetry at different scanning rates. Several macrokinetic models such as Avrami, Jeziorny, Ozawa, Liu, Ziabicki, and Tobin were applied to analyze the crystallization behavior thoroughly under nonisothermal conditions. The Avrami and Tobin model predicted that, for pure PA6 and PA6/EBA blends, simultaneous growth of all forms of crystal structures such as fibrillar, disc‐like, and spherulitic proceeds at an increasing nucleation rate. However, when applied to blends for isothermal crystallization, the Avrami model predicted that the crystallization process is diffusion‐controlled for pure PA6 and PA6/EBA blend containing higher content of EBA (50 phr), where the nylon‐6 chains were able to diffuse freely to crystallize under isothermal conditions. Liu model predicted that, at unit crystallization time, a higher cooling rate should be used to obtain a higher degree of crystallinity for both PA6 and PA6/EBA blends. The kinetic crystallizability of PA6 in the blends calculated using Ziabicki's approach varies depending upon the nucleation density and PA6‐rich regions present in the blend compositions. Nucleation activity of the blends estimated by Dobreva and Gutzowa method reveals that the EBA particles are inert at lower concentrations of EBA and do not act as nucleating agent for PA6 molecules in the blends. The activation energy of nonisothermal crystallization, calculated using Augis–Bennett, Kissinger, and Takhor methods indicated that the activation energy is slightly lower for the blends when compared to the neat PA6. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Degradation mechanism and kinetic model for photocatalytic oxidation of PVC-ZnO composite film in presence of a sensitizing dye and UV radiation

White or plastic pollution has become a serious concern to the environmentalists for the last few years. Degradation of waste plastics in conventional incinerators leads to emission of carcinogenic dioxins to the atmosphere. In this work, an attempt has been made for the photocatalytic degradation of polyvinyl chloride (PVC) using ZnO as semi-conductor catalyst in the form of PVC-ZnO composite film. The surface morphology as well as the FTIR spectroscopy of the irradiated film has been critically examined. The degradation was measured by weight loss data and was found to follow a pseudo-first order rate equation. The various parameters studied were loading of the semi-conductor, intensity of UV radiation and presence of Eosin Y as a sensitizing dye. It was observed that dye-sensitization enhanced degradation of PVC to a large extent. A possible mechanism has been suggested and the corresponding rate equation has been modeled for the dye-sensitized rate of degradation. The model has been validated by the experimental data.     

Selective growth of silica nanowires using an Au catalyst for optical recognition of interleukin-10

The vapor-liquid-solid (VLS) growth procedure has been extended for the selective growth of silica nanowires on SiO(2) layer by using Au as a catalyst. The nanowires were grown in an open tube furnace at 1100?°C for 60?min using Ar as a carrier gas. The average diameter of these bottom-up nucleated wires was found to be 200?nm. Transmission electron microscopy analysis indicates the amorphous nature of these nanoscale wires and suggests an Si-silica heterostructure. The localized silica nanowires have been used as an immunoassay template in the detection of interleukin-10 which is a lung cancer biomarker. Such a nanostructured platform offered a tenfold enhancement in the optical response, aiding the recognition of IL-10 in comparison to a bare silica substrate. The role of nanowires in the immunoassay was verified through the quenching behavior in the photoluminescence (PL) spectra. Two orders of reduction in PL intensity have been observed after completion of the immunoassay with significant quenching after executing every step of the protocol. The potential of this site-specific growth of silica nanowires on SiO(2) as a multi-modal biosensing platform has been discussed.     

Impact of carbon nanotubes on the ingestion and digestion of bacteria by ciliated protozoa

Research on the toxicity of carbon nanotubes has focused on human health risks, and little is known about their impact on natural ecosystems. The ciliated protozoan Tetrahymena thermophila has been widely studied by ecotoxicologists because of its role in the regulation of microbial populations through the ingestion and digestion of bacteria, and because it is an important organism in wastewater treatment and an indicator of sewage effluent quality. Here we show that single-walled carbon nanotubes are internalized by T. thermophila, possibly allowing the nanotubes to move up the food chain. The internalization also causes the protozoa to aggregate, which impedes their ability to ingest and digest their prey bacteria species, although it might also be possible to use nanotubes to improve the efficiency of wastewater treatment.     

Quinolinyl‐moiety‐containing 3‐ester‐substituted polythiophenes showing fluorescence efficiency

Polythiophenes with ester substituents at the 3‐position of the thiophene ring were synthesized by ferric chloride oxidative polymerization. The polythiophenes are partially soluble in tetrahydrofuran, and these solutions were used to characterize the polythiophenes using Fourier transform infrared, ¹H NMR, UV‐visible and fluorescence spectroscopy, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry and cyclic voltammetry. The electrochemical band gap of the polymers is in the range 1.6–2.3 eV. The effect of the various substituents on the fluorescence behaviour was studied in detail. The quinolinyl‐moiety‐containing polythiophene ester has the highest fluorescence quantum yield. The incorporation of Al³⁺ and Zn²⁺ ions increases greatly the fluorescence intensity. The electroluminescence properties of the polymers were evaluated with a device configuration of ITO/PEDOT:PSS/polymer/LiF/Al. The polymers show a yellow emission in electroluminescence spectra. The results suggest that the quinoline‐containing ester‐substituted polythiophene is a promising electronic and optoelectronic material. Copyright © 2011 Society of Chemical Industry     

An Approach to Build Process‐Oriented Basis for Causation‐Based Multivariate SPC and Process Capability Analysis

Although various multivariate process monitoring techniques have been developed, they do not diagnose the process for finding the root causes of irregularities during production. There have been recent studies on a new method that involves process‐oriented basis representation, which links the process variation to its causes, and thus helps in monitoring and diagnosing a process. However, all the studies done so far focused on its application. In this paper, a method is proposed to build the process‐oriented basis for a process irrespective of the number of variables characterizing it. Along with various other statistical techniques, factor analysis and cluster analysis, with customized distance function, are used in developing the method. The built in process‐oriented basis is further used for multivariate statistical process control and process capability analysis. Multivariate solder‐paste problem from electronics industry is used for illustration. Copyright © 2012 John Wiley & Sons, Ltd.