Assessment of spray quality from an external mix nozzle and its impact on SQL grinding performance

Spray quality is the critical factor which decides the efficacy of Small Quantity Lubrication (SQL) technology in a high specific energy involved machining process like grinding. Yet, the understanding about spray quality, the actual process mechanics and its effect on machining performance is inadequate. The present work is an attempt to establish a correlation between the spray input variables, quality of the spray and machining performance of SQL grinding through modelling and experiments. Using computational fluid dynamic techniques, the variation of droplet size, droplet velocity, number of droplets and heat transfer coefficient have been analysed at different input parameters and the computed trends have been verified and validated. CFD modelling of spray indicates that it is possible to produce aerosol medium with high heat dissipation ability at moderately high air pressure and low flow rate. It also shows that any increase in atomising air pressure favourably leads to notable increase in wetting area and also results in substantial enhancement in heat dissipation ability. Reduction of residual stress is thus remarkably good. On the other hand, grinding fluid flow rate, if increased, offers significantly better lubricity and reduces the grinding force which also reduces tensile residual stress. Short spell grinding test results are found to be in good agreement with CFD results.     

Study of fuel insolubles: Formation conditions and characterization of copper compounds

The solids formed in the systems containing copper in different oxidation states, in the presence and absence of hexanoic acid and dodecanethiol, together and separately, at room temperature, were studied. The experiments were performed in a mineral oil matrix, free of sulfur compounds and metals; a diesel oil matrix; and the reagents alone, without any matrix. The deposits formed were analyzed by elemental analysis (EA), infrared spectroscopy (IR), thermogravimetric analysis (TGA) and total copper by inductively coupled plasma-optical emission spectrometry (ICP-OES), for their identification and determination of the probable structures. In samples containing both hexanoic acid and dodecanethiol, when there is copper(I), anhydrous copper(II) hexanoate is preferentially formed, but in samples of copper(II), copper(II) mercaptate is formed first. In samples of metallic copper in mineral oil matrix, no deposit formations occur. In all cases in which deposits were formed, they were the same as in diesel oil matrix.     

Blockwise projection matrix versus blockwise data on undersampled problems: Analysis,comparison and applications

Linear subspace methods are extensively used in many areas such as pattern recognition and machine learning. Among them, block subspace methods are efficient in terms of the computational complexity. In this paper, we perform a thorough analysis on block subspace methods and give a theoretical framework for understanding block subspace methods. It reveals the relationship between block subspace methods and classical subspace methods. We theoretically show that blockwise PCA has larger reconstruction errors than classical PCA and classical LDA has stronger discriminant power than blockwise LDA in the case of the same number of reduced features. In addition, based on the Fisher criterion, we also give a strategy for selecting an approximate block size for classification problems. The comprehensive experiments on face images and gene expression data are used to evaluate our results and a comparative analysis for various methods is made. Experimental results demonstrate that overly combining subspaces of block subspace methods without considering the subspace distance may yield undesirable performance on undersampled problems.     

Iterated non-linear model predictive control based on tubes and contractive constraints

This paper presents a predictive control algorithm for non-linear systems based on successive linearizations of the non-linear dynamic around a given trajectory. A linear time varying model is obtained and the non-convex constrained optimization problem is transformed into a sequence of locally convex ones. The robustness of the proposed algorithm is addressed adding a convex contractive constraint. To account for linearization errors and to obtain more accurate results an inner iteration loop is added to the algorithm. A simple methodology to obtain an outer bounding-tube for state trajectories is also presented. The convergence of the iterative process and the stability of the closed-loop system are analyzed. The simulation results show the effectiveness of the proposed algorithm in controlling a quadcopter type unmanned aerial vehicle.     

Pulse-modulation eddy current probes for imaging of external corrosion in nonmagnetic pipes

Since the nonmagnetic pipe is normally utilized in corrosive and hostile environment, it is prone to the external corrosion which occurs on the outer surface of the pipe and severely undermines the structural integrity and safety. Although Pulsed Eddy Current technique (PEC) is currently preferred for detection and evaluation of subsurface defects in tubular conductors, it is subject to technical drawbacks. In light of this, Pulse-modulation Eddy Current technique (PMEC) is intensively investigated in the paper for enhancement of the evaluation sensitivity to external corrosion and accuracy of corrosion imaging. Closed-form expressions of the PMEC response and its sensitivity to external corrosion in tubular conductors are formulated via the Extended Truncated Region Eigenfunction Expansion (ETREE) modeling. Following simulations for analysis and comparison of field signals and evaluation sensitivities of PMEC and PEC, experiments of PMEC for evaluation and imaging of external corrosion are carried out. Through theoretical and experimental investigation, it has been found that regarding the evaluation and imaging of external corrosion in nonmagnetic pipes, the PMEC-based probe have higher sensitivity and imaging accuracy than that based on PEC. The superiority of PMEC to PEC in inspection of tubular conductors is further identified.     

Provably secure blockchain privacy-preserving smart contract centric dynamic group key agreement for large WSN

The Journal of Supercomputing - The contemporary Group Key Agreement (GKA) entails lightweight computing, reduced communication, decentralized certification, personal privacy protection,...     

A facile,efficacious and reusable Sm2O3/ZrO2 catalyst for the novel synthesis of functionalized 1,4-dihydropyridine derivatives

An efficient four component/one-pot protocol was developed for synthesis of novel functionalized 1,4-dihydropyridines at room temperature by a reaction of malononitrile, substituted aldehydes, dimethylacetylenedicarboxylate and 4-fluoroaniline in ethanol and using Sm₂O₃/ZrO₂ as catalyst. All reactions were completed in < 20 min. The structures of all the new compounds were confirmed by different spectral analyses. The catalyst, Sm₂O₃/ZrO₂ was synthesized and characterized by various techniques including powder X-ray diffraction, N₂ adsorption/desorption, scanning electron microscopy, and transmission electron microscopy analysis. The key advantages of this process are good to high yields (87 to 96%), short reaction times, easy work-up, reusability and no chromatographic purification.     

DSTATCOM modelling for voltage stability with fuzzy logic PI current controller

In recent years, applications of inverter based power quality conditioners have been growing for reactive power compensation in distribution systems due to their faster response times as compared to the conventional compensators. Distribution Static Synchronous Compensator (D-STATCOM) is an inverter based power quality conditioner device used to improve the power quality issues in distribution systems. Control of D-STATCOM is usually realized by Proportional-Integral (PI) controllers with fixed parameters. However, the overall control performance may be unsatisfactory due to its nonlinear structure. In this paper, Fuzzy-PI controller which has a nonlinear and robust structure is proposed for control of D-STATCOM’s direct and quadrature axes currents. The article presents the fuzzy logic control of the D-STATCOM which tries to improve the damping of a power system. Simulation of Fuzzy-PI current controlled D-STATCOM is performed by MATLAB/Simulink software. In simulation study, the dynamic response of D-STATCOM is observed by changing the reference reactive current. A comparison of the simulation results between the proposed technique and the conventional PI controller has been presented.     

Forced convection in a channel partly occupied by a bidisperse porous medium: Asymmetric case

This paper presents an analytic investigation of forced convection in parallel-plate channel partly occupied by a bidisperse porous medium and partly by a fluid clear of solid material, the distribution being asymmetrical. The walls of the channel are subject to an uniform heat flux; the flow is assumed to be hydrodynamically and thermally fully developed. The layer of a bidisperse porous medium is attached to one of the channel walls; it is modeled utilizing a two-velocity two-temperature formulation using Darcy’s law. The Beavers–Joseph boundary condition is employed at the bidisperse porous medium/clear fluid interface. The dependences of the Nusselt number on a conductivity ratio, a velocity ratio, a volume fraction, internal heat exchange parameter, and the position of the porous-fluid interface are investigated. Both cases of symmetric and asymmetric heating are investigated, which is specified by the asymmetry heating parameter introduced here. For the case of asymmetric heating, a singular behavior of the Nusselt number is found and explained.     

A 3D shock computational strategy for real assembly and shock attenuator

The extension of an approach, suitable for bolting structures impact computation with a large number of unilateral friction contact surfaces, and with local plasticity of the bolts, is presented. It is a modular approach based on a mixed domain decomposition method and the LATIN method. This iterative resolution process operates over the entire time–space domain. A 3D Finite-Element code is presented and dedicated to applications concerning connection refined models for which the structure components are assumed elastic. Several examples are analysed to show the method's capability of describing shocks throw real three-dimensional assembly. Comparisons between classical dynamic code LS-DYNA3D are presented.