Heat transfer characteristics of water flowing through micro-tube heat exchanger with variable fluid properties

The heat transfer characteristics of laminar single-phase forced convective water flow through a micro-tube heat exchanger are numerically investigated in this paper. Two-dimensional simulations are performed to find the effects of variable fluid properties on heat transfer for hydrodynamically and thermally developed flow. The effects of variable fluid properties on convective heat transfer coefficient (h) and Nusselt number (Nu) are significant for micro-convective flow. It is noted that the variation in temperature-dependent thermal conductivity [k(T)] greatly enhances the h as compared to the variation in temperature-dependent viscosity [mu(T)], although water viscosity-temperature sensitivity (S mu T) is greater than that of thermal conductivity-temperature sensitivity (SkT). The effects of variation in wall heat flux (q '' w) and inlet temperature on heat transfer are investigated for variable fluid properties. It is noted that the Nu declines with an augment in q '' w for temperature-dependent density variation [.(T)]. The Nu increases with an increase in q '' w for mu(T) and k(T) variations. The results show that the Nu decreases with an increase in inlet temperature for variable fluid properties. The undevelopment and redevelopment of the flow are observed due to mu(T) variation. Additionally, the effects of wall heat flux, inlet temperature and inlet velocity on the variation of Nu/Pr1/3 with Re are examined for mu(T) variation

Residual stress compensated silicon nitride microcantilever array with integrated poly-Si piezoresistor for gas sensing applications

This work reports a novel method of microfabrication for silicon nitride based piezoresistive microcantilever device, to minimize the residual stress induced bending. The microcantilever of dimension L x W similar to 250 x 100 mu m(2) with stack (Si3N4/Poly-Si/Si3N4/SiO2) thickness similar to 1 mu m was realized, by using standard six masks and bulk silicon micromachining fabrication process. In order to compensate the residual inbuilt stress, asymmetric structure layers for microcantilever was proposed and the presence of thin oxide layer underneath the released microcantilever stack was used to control the bending. The surface profiler measurement results showed the curvature bending in the range of similar to 4 +/- 3 mu m. The microcantilever was characterized further to evaluate its physical parameters such as mechanical deflection sensitivity and spring constant. The deflection sensitivity and spring constant values were similar to 0.161 ppm/nm and similar to 0.2 N/m, respectively. Finally, the practical application of fabricated piezoresistive microcantilevers was demonstrated by using it for explosive vapors sensing

Surface displacements of the 12 November 2017 Iran-Iraq earthquake derived using SAR interferometry

The 2017 M-w 7.3 Iran-Iraq earthquake occurred in the seismically less active northern Zagros Mountains. In this study, DInSAR technique is used to derive the surface displacements of the earthquake using Sentinel-1 and ALOS-2 images. One preseismic, three coseismic and a postseismic interferogram are generated. The coseismic interferograms did not show any signs of a surface rupture and indicate a maximum of 80 cm uplift and 50 cm subsidence. The zenith total delay maps derived from the Generic Atmospheric Correction Online Service for InSAR are used to correct tropospheric delays in the interferograms. After correction, an error of 0-2 cm is observed in the line of sight measurements. The preseismic displacement reveals an indication of ground motion before the earthquake occurrence. The postseismic phase indicates afterslip after the earthquake. Localized displacements corresponding to landslides are observed on the mountainous slopes. The 3D displacements reveal similar to 40 cm of surface motion suggesting westward movement and reverse faulting

Analytical tools for monitoring changes in physical and chemical properties of chromatography resin upon reuse

Protein A resins are often reused for multiple cycles to improve process economy during mAb purification. Significant reduction in binding capacity and product recovery are typically observed due to the presence of unwanted materials (foulants) deposited on the resin upon reuse. In this paper, we have used a wide spectrum of qualitative and quantitative analytical tools (particle size analysis, HPLC, fluorescence, SEM, MS, and FTIR) to compare the strengths and shortcomings of different analytical tools in terms of their capability to detect the fouling of the resin and relate it to chromatographic cycle performance. While each tool offers an insight into this complex phenomena, fluorescence is the only one that can be used for real-time monitoring of resin fouling. A correlation could be established between fluorescence intensity and the process performance attributes (like yield or binding capacity) impacted upon resin reuse. This demonstration of the application of fluorescence for real-time monitoring correlated empirically with process performance attributes and the results support its use as a PAT tool as part of a process control strategy. While the focus of this paper is on fouling of protein A chromatography resin, the approach and strategy are pertinent to other modes of chromatography as well

Redox Non-Innocence and Isomer-Specific Oxidative Functionalization of Ruthenium-Coordinated beta-Ketoiminate

This article deals with isomeric ruthenium complexes [Ru-III(L (R))(2)(acac)] (S=1/2) involving unsymmetric beta ketoiminates (AcNac) (L (R)=RAcNac, R=H (1), Cl (2), OMe (3); acac=acetylacetonate) [R=parasubstituents (H, Cl, OMe) of Nbearing aryl group]. The isomeric identities of the complexes, cct (ciscistrans, blue, a), ctc (cistranscis, green, b) and ccc (cisciscis(,) pink, c) with respect to oxygen (acac), oxygen (L) and nitrogen (L) donors, respectively, were authenticated by their singlecrystal Xray structures and spectroscopic/electrochemical features. Oneelectron reversible oxidation and reduction processes of 13 led to the electronic formulations of [Ru-III(L)(L)(acac)](+) and [Ru-II(L)(2)(acac)] for 1(+)3(+) (S=1) and 13 (S=0), respectively. The triplet state of 1(+)3(+) was corroborated by its forbidden weak halffield signal near g4.0 at 4 K, revealing the noninnocent feature of L. Interestingly, among the three isomeric forms (ac in 13), the ctc (b in 2 b or 3 b) isomer selectively underwent oxidative functionalization at the central beta carbon (CH (R)(R) C=O) of one of the L ligands in air, leading to the formation of diamagnetic [Ru-II(L)(L')(acac)] (L'=diketoimine) in 4/4'. Mechanistic aspects of the oxygenation process of AcNac in 2 b were also explored via kinetic and theoretical studies

Whole field measurements to identify the critical Rayleigh number for the onset of natural convection in top open cavity

We report the results of interferometry-based experiments to identify the onset of natural convection in an air-filled top open cavity. Transition from no flow to the onset of fluid motion was identified as the sharp change in local heat transfer characteristics that occur for a small variation in Rayleigh number. Experiments revealed the presence of a thermally stratified layer at the bottom of the cavity when the Rayleigh number is below its threshold value. However, beyond the critical Rayleigh number, a clear distortion of these layers was observed. Interferometric data provided a direct evidence of the possible breakdown of flow symmetry due to the onset of natural convection. Experiments as well as selected numerical simulations indicated toward the existence of a mirror image solution wherein the flow patterns showed transition from one steady state to another (mirror image of first one) due to the inherent perturbations present in the system

Sliding mode control of uncertain fractional-order systems: A reaching phase free approach

This paper proposes a sliding surface which renders the system dynamics to start directly from itself without a reaching phase. More specifically, the system dynamics is insensitive to matched disturbances/uncertainties throughout the entire system response. The controller design based on reduced-order subsystem is still preserved. It is different from integral sliding mode in which the design is based on the full order of the system to reach the same objective. The simulation results of its application to a fractional inverted pendulum system is demonstrated

Anti-cross validation technique for constructing and boosting random subspace neural network ensembles for hyperspectral image classification

Achieving high classification accuracy is vital in reliable information extraction from images. Single classifiers and existing ensemble methods suffer from data dimensionality, insufficient ground truth information and lack in defining optimal feature selection. This article presents a novel idea for constructing component classifiers that boost random subspace ensemble method in improving its classification performance. It is achieved through sub-optimal training of component classifiers through interference in training process during validation error evaluation. The new approach allows to enforce different class errors among component classifiers, besides improving individual class accuracy. This article demonstrates effectiveness of the anti-cross validation approach using three classical hyperspectral Image (HSI) datasets with significant improvement in classification accuracies from 3 to 10% with the proposed approach

Electric Modulus and Conductivity Scaling Approach to the Analysis of Ion Transport in Solid Polymer Electrolytes

Solid polymer electrolyte films (SPEs) based on poly(methyl methacrylate) are prepared using a solution cast technique. The temperature-dependent behavior of dielectric, modulus spectra and ac conductivity has been investigated. The long tail of the real part of modulus (M ') in the low frequency indicates the capacitive nature of the samples. The frequency dependence of imaginary part of modulus (M '') shows a non-Debye relaxation that has been explained using the Kohlrausch-Williams-Watts stretched exponential function. The activation energy for the relaxation is almost same as the activation energy for the conduction. The relaxation time obtained from the tangent loss graph (tau(delta)) is about two orders of magnitude larger than that obtained from the imaginary part of modulus graph (tau(m)). The ac conductivity has been found to obey Jonscher's universal power law. Transport parameters show that addition of filler creates additional hopping sites for the charge carriers and also increases the charge carrier density. It is also observed that the higher ionic conductivity at higher temperature is due to increased thermally activated hopping rates accompanied by a significant increase in carrier concentration. The contribution of carrier concentration to the total conductivity is also confirmed from Summerfield scaling. POLYM. ENG. SCI., 2019. (c) 2019 Society of Plastics Engineer

High-order discrete-time orthogonal spline collocation methods for singularly perturbed 1D parabolic reaction-diffusion problems

Quasi-optimal error estimates are derived for the continuous-time orthogonal spline collocation (OSC) method and also two discrete-time OSC methods for approximating the solution of 1D parabolic singularly perturbed reaction-diffusion problems. OSC with C-1 splines of degree r >= 3 on a Shishkin mesh is employed for the spatial discretization while the Crank-Nicolson method and the BDF2 scheme are considered for the time-stepping. The results of numerical experiments validate the theoretical analysis and also exhibit additional quasi-optimal results, in particular, superconvergence phenomena