Characterization of Oxide Dispersed AlCoCrFe High Entropy Alloy Synthesized by Mechanical Alloying and Spark Plasma Sintering

The present study deals with phase evolution of oxide dispersed AlCoCrFe high entropy alloy during mechanical alloying and spark plasma sintering. Mechanical alloying of AlCoCrFe resulted in a single BCC phase. However, ordering of BCC phase with evolution of chromium carbide and sigma phase were observed after spark plasma sintering. High hardness of 1,050 ± 20 HV₁ and 1,070 ± 20 HV₁ was observed for AlCoCrFe high entropy alloy without and with oxide dispersion, respectively. Significant contribution from solid solution strengthening effect in high entropy alloys appears to have overwhelmed the effect of oxide dispersion on hardness.     

Querying in Packs: Trustworthy Data Management in Ad Hoc Networks

We describe a trust-based data management framework enabling mobile devices to access the distributed computation, storage, and sensory resources available in pervasive computing environments. Available resources include those in the fixed surrounding infrastructure as well as services offered by other nearby mobile devices. We take a holistic approach that considers data trust, security, and privacy and focus on the collaborative mechanisms providing a trustworthy data management platform in an ad hoc network. The framework is based on a pack formation mechanism that enables collaborative peer interactions using context information and landmarks. A pack provides a routing substrate allowing devices to find reliable information sources and coordinated pro-active and reactive mechanisms to detect and respond to malicious activity. Consequently, a pack forms a foundation for distributed trust management and data intensive interactions. We describe our data management framework with an emphasis on pack formation in mobile ad hoc networks and present preliminary results from simulation experiments.     

Discrete bacteria foraging optimization algorithm for graph based problems – a transition from continuous to discrete

Bacteria Foraging Optimisation Algorithm is a collective behaviour-based meta-heuristics searching depending on the social influence of the bacteria co-agents in the search space of the problem. The algorithm faces tremendous hindrance in terms of its application for discrete problems and graph-based problems due to biased mathematical modelling and dynamic structure of the algorithm. This had been the key factor to revive and introduce the discrete form called Discrete Bacteria Foraging Optimisation (DBFO) Algorithm for discrete problems which exceeds the number of continuous domain problems represented by mathematical and numerical equations in real life. In this work, we have mainly simulated a graph-based road multi-objective optimisation problem and have discussed the prospect of its utilisation in other similar optimisation problems and graph-based problems. The various solution representations that can be handled by this DBFO has also been discussed. The implications and dynamics of the various parameters used in the DBFO are illustrated from the point view of the problems and has been a combination of both exploration and exploitation. The result of DBFO has been compared with Ant Colony Optimisation and Intelligent Water Drops Algorithms. Important features of DBFO are that the bacteria agents do not depend on the local heuristic information but estimates new exploration schemes depending upon the previous experience and covered path analysis. This makes the algorithm better in combination generation for graph-based problems and combination generation for NP hard problems.     

Alkyl amine functional dextran macromonomer‐based thin film composite loose nanofiltration membranes for separation of charged and neutral solutes

Thin film composite (TFC) nanofiltration membranes with defined porous structure of the separation layer are desirable for the concentration of neutral solute and separation of salts from a mixture. Herein, we report the formation of TFC membranes composed of polyamide (PA) separation layer by the interfacial polymerization between new dextran‐butyl amine (Dex‐NH₂) macromonomer and trimesoyl chloride on polysulfone support membrane. The membranes prepared with 1%–1.5% (wt/vol) of Dex‐NH₂ exhibited water permeance of 110–116 L m^?2 h^?1 MPa^?1 with 62%–71% rejection of Na₂SO₄ and 12%–14% rejection of MgCl₂. The membranes also showed about 91% rejection of poly(ethylene glycol) of molecular weight 2000 g/mol and about 11% rejection of NaCl. A decrease in permeance and ions selectivity was observed with increasing concentration of Dex‐NH₂. The dextran chains attached to the PA network restrict the diffusion of Dex‐NH₂ toward the interfacial zone and thereby assist the formation of porous and thin PA layer compared to that when free amine (alkyl diamine) was used. These membranes are applicable for the separation of small molecular weight neutral solutes from mixture containing monovalent salts. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45301.     

Impact behaviour of GFRP and Kevlar/epoxy sandwich composite plate: Experimental and FE analyses

In this paper, dynamic response of GFRP composite plate under ballistic impact has been studied by experimental tests and also by an efficient FE model. Material characterization of GFRP composite is performed as required for progressive damage analysis of laminate due to impact. Shock effect of impact is considered in the material modeling of composite plate. The influence of the target thickness on the ballistic performance of the composite plate is also studied by considering 3.12, 6.24 and 9.36 mm thick targets. Moreover, sandwich composite plate consisting of GFRP and Kevlar/epoxy in three different combinations of laminate layers is considered to obtain suitable combination for structural application that offer better penetration resistance. Damage pattern, contact force histories and stresses in composite plate are studied in addition to residual velocity and acceleration of projectile. Numerical results from present FE model in terms of residual velocities and damage patterns in composite plate show good agreement with the experimental results.

     

Development of intuitionistic fuzzy special embedded convolutional neural network for mammography enhancement

This article proposes a novel mammogram enhancement approach using adaptive intuitionistic fuzzy special set (IFSS) with deep convolutional neural network (called MECNNIFS) for visual interpretation of mammography lesions, lumps, and abnormal cells in low‐dose X‐ray images. The proposed MECNNIFS scheme utilizes the membership grade modification by IFSS on low‐dose X‐ray images (mammography). The suggested model attempts to increase the underexposed and abnormal structural regions such as breast lesions, lumps, and nodules on the mammogram. The proposed algorithm initially separates mammograms using convolutional neural networks (CNNs) into foreground and background areas and then fuzzifies the image by intuitionistic fuzzy set theory. Low‐level features of a mammogram of the adjacent part are integrated with CNN in pixel classification during the separation task stage to improve the performance. Hyperbolic regularization and hesitant score have been applied on fuzzy plane to quantify the uncertainty and fuzziness in spatial domain for the proposed contrast enhancement. Finally, an enhanced mammogram is acquired through the process of defuzzification. The results show better quality and performance for improvement of contrast and visual quality in mammograms compared with other state‐of‐the‐art methods.     

Effect of aging on speech features and phoneme recognition: a study on Bengali voicing vowels

The article studies age related variations of speech characteristics of two age groups, in the Bengali language. The study considers 60 speakers in the each age groups, 60–80 years and 20–40 years, respectively. We have considered different voice source features like fundamental frequency, formant frequencies, jitter, shimmer and harmonic to noise ratio. Cepstral domain feature, Mel Frequency Cepstral coefficients (MFCC) of different voiced Bengali vowels are also analyzed for younger and older adult groups. MFCC feature and Hidden Markov model parameter of different voiced vowels are used to study phoneme dissimilarities measure between two age groups. Age related changes in elderly speech affect the automatic speech recognition performance as was observed in our study, raising the need for specific acoustic models for elderly persons.     

Cost-Sharing Mechanisms for Network Design

We consider a single-source network design problem from a game-theoretic perspective. Gupta, Kumar and Roughgarden (Proc. 35th Annual ACM STOC, pp. 365–372, 2003) developed a simple method for a single-source rent-or-buy problem that also yields the best-known approximation ratio for the problem. We show how to use a variant of this method to develop an approximately budget-balanced and group strategyproof cost-sharing method for the problem. The novelty of our approach stems from our obtaining the cost-sharing methods for the rent-or-buy problem by carefully combining cost-shares for the simpler Steiner tree problem. Our algorithm is conceptually simpler than the previous such cost-sharing method due to Pál and Tardos (Proc. 44th Annual FOCS, pp. 584–593, 2003), and improves the previously-known approximation factor of 15 to 4.6. A preliminary version of this work appears in the Proc. International Workshop on Approximation Algorithms for Combinatorial Optimization Problems, 2004. This research was done in part during the IMA Workshop on Network Management and Design at the University of Minnesota, April 2003. A. Gupta supported in part by an NSF CAREER award CCF-0448095, and by an Alfred P. Sloan Fellowship. A. Srinivasan supported in part by the National Science Foundation under Grant No. 0208005 and ITR Award CNS-0426683. Research of é. Tardos supported in part by ONR grant N00014-98-1-0589, and NSF grants CCR-0311333 and CCR-0325453.     

A MULTIGRID-ACCELERATED THREE-DIMENSIONAL TRANSIENT-FLOW CODE AND ITS APPLICATION TO A NEW TEST PROBLEM

A multigrid-assisted solver for the three-dimensional time-dependent incompressible Navier-Stokes equations on graded Cartesian meshes is developed. The spatial accuracy is third-order for the convective terms and fourth-order for the viscous terms, and a fractional-step strategy ensures second-order time accuracy. To achieve good time-wise efficiency a multigrid technique is used to solve the highly time-consuming pressure-Poisson equation that requires to be solved at every time step. The speed-up achieved by multigrid is shown in tabular form. The performance and accuracy of the code are first ascertained by computing the flow in a single-sided lid-driven cubic cavity with good grid-economy and comparing the results available in the literature. The code, thus validated, is then applied to a new test problem we propose and various transient and asymptotically obtained steady-state results are presented. Given the care taken to establish the credibility of the code and the good spatio-temporal accuracy of the discretization, these results are accurate and may be used for ascertaining the performance of any computational algorithm applied to this test problem.