Benchmarking large-scale data management for Internet of Things

The Journal of Supercomputing - In the current era of the Internet of Things (IoT), massive number of sensors are used in our daily lives. Sensors are everywhere around us. They exist in our homes,...     

Improved algorithms for resource allocation under varying capacity

We consider the problem of scheduling a set of jobs on a system that offers certain resource, wherein the amount of resource offered varies over time. For each job, the input specifies a set of possible scheduling instances, where each instance is given by starting time, ending time, profit and resource requirement. A feasible solution selects a subset of job instances such that at any timeslot, the total requirement by the chosen instances does not exceed the resource available at that timeslot, and at most one instance is chosen for each job. The above problem falls under the well-studied framework of unsplittable flow problem on line. The generalized notion of scheduling possibilities captures the standard setting concerned with release times and deadlines. We present improved algorithms based on the primal–dual paradigm, where the improvements are in terms of approximation ratio, running time and simplicity.     

An efficient video watermarking based security model

Microsystem Technologies - Watermarking is defined as about hiding any valuable information set in the particular digital media by itself through modifying the particular graphic contents. In our...     

A facile template-free electrodeposition method for vertically standing nanorods on conductive substrates and their applications for photoelectrochemical catalysis

A facile template-free electrodeposition technique is developed for large-scale fabrication of vertically standing silver nanorods (NRs) on transparent and conductive substrates. The diameter, length, and surface coverage of Ag NRs are dependent on the electrodeposition time and choice of substrates. The growth mechanism of vertically standing Ag NRs is investigated by tracking their morphology evolution as a function of deposition time. Because of their large specific surface area, oriented alignment, broad range light scattering, and light absorption tunability, these vertically standing NRs can be used as ideal substrates for thin layer photocatalysts for enhancing light absorption and charge collection. Preliminary tests on photoelectrochemical performance of bare Ag NRs, CdS modified Ag NRs, and Ag NRs converted to Ag₂S NRs are presented. This simple NR fabrication method has been successfully applied to prepare Fe NRs as well. This technique can be extended to other conductive substrates and other materials for obtaining vertically standing NR structures.     

System for computer-aided cavity layout design for die-casting dies

Die-casting is one of the methods used to produce a large number of components with a good surface finish by injecting cast alloys into a metal mould under high pressure. The design of a die-casting die requires human expertise and is normally performed by trial and error, which leads to monetary and time losses. Automation at the initial die design stage would result in higher productivity and would reduce the production lead time. Decisions regarding the number of cavities, the layout pattern and the placement of cavities in die-casting are critical for die design and manufacturing. This paper presents research work on a system for computer-aided cavity layout design for die-casting dies. The proposed system consists of three modules: (1) determination of number of cavities; (2) selection of layout pattern; and (3) placement of cavities in the die base. It enables die designers to generate a cavity layout design automatically from a computer-aided design (CAD) file of the part with little information provided manually. The optimal number of cavities is determined by considering economic, technical, geometrical and time limitations, followed by the selection of a layout pattern. Thereafter, cavities are placed in the die base. The developed system depends on a database of die-casting machines and materials along with a knowledge base of die design. This system has been tested on a number of die-casting parts and results have been found to be along the lines of those obtained by the industry. The proposed system is more comprehensive than those presently available and is a step in the right direction for design-manufacturing integration for die-casting.     

Guest–host interaction in ferroelectric liquid crystal–nanoparticle composite system

The present paper deals with the characterization of a ferroelectric liquid crystal–nanoparticle (FLC–NP) composite system. The dielectric, electrical and polarization property of the FLC–NP composite system have been studied as a function of temperature and frequency. Ferroelectric Cu-doped ZnO (Cu–ZnO) nanoparticles have been added to the pure ferroelectric liquid crystal (FLC) Felix 17/100. The nanoparticles are bigger in size as compared to FLC molecules; therefore, they distort the existing geometry of FLC matrix and set up an antiparallel correlation with the dipole moments of the host FLC molecules. This antiparallel correlation of guest–host geometry reduces the net ferroelectricity of the composite system and modifies all the physical properties of the pure FLC. The change in properties has been analysed and explained in the light of guest–host interaction.     

Optimization of processing parameters of medium density fiberboard using response surface methodology for multiwalled carbon nanotubes as a nanofiller

In the present work, medium density fiberboard (MDF) panels were produced using multiwalled carbon nanotubes (MWCNT) reinforced urea formaldehyde resin. Response surface methodology was employed to optimize the relationship between the three variables, viz. pressing time, percentage of UF resin and percentage of MWCNT, used in the fabrication of MDF, and the influence of variables on the internal bonding (IB) and modulus of rupture (MOR) was studied. The optimum conditions based on the IB strength were determined as 8.18 % of UF resin, pressing time of 232 s, and MWCNT of 3.5 %. Similarly, the optimized conditions for MOR are also reported in this paper.     

Pool Boiling Enhancement through Graphene and Graphene Oxide Coatings

ABSTRACT

Boiling has served as an effective means to dissipate large quantities of heat over small areas. Graphene, a two-dimensional material, has garnered significant attention of researchers due to its excellent thermal properties. In this study, copper test chips are dip coated with a solution consisting of graphene oxide and graphene and its pool boiling performance with distilled water at atmospheric pressure was investigated. The surfaces were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy which confirmed the presence of graphene and graphene oxide. The contact angles measured on the coated surfaces indicated hydrophobic wetting behavior. Four heat transfer surfaces were prepared with dip coating durations of 120 s, 300 s, 600 s, and 1200 s, respectively. A Critical Heat Flux (CHF) of 182 W/cm² and a heat transfer coefficient (HTC) of 96 kW/m²°C was obtained with the shortest coating duration which translated to an enhancement of 42% in CHF and 47% in HTC when compared to a plain uncoated surface under similar conditions. Contact angle changes were not seen to be responsible, although roughness was seen as an influencing factor contributing to the enhancement. Further studies are needed to explain the enhancement mechanism.     

Pressure Drop Studies on Flow of Viscoelastic Fluid Through a Packed Bed

In the present study, pressure drop-flow rate behavior for the flow of viscoelastic fluid through porous media has been investigated. Aqueous solutions of polyacrylamide (PAM) and water in the concentration range of 0.02 to 0.1% wt/vol were used to elucidate the effect of fluid elasticity on bed pressure drop. Based on the observed data, the existing pore model was extended to predict the bed pressure drop for viscoelastic fluid flowing through a porous media. A statistical comparison between the existing models and the present model was made. The proposed correlation based on modified pore model predicts the data well to within a reasonable accuracy of ±10% with arithmetic relative error (%ARE) and mean relative quadratic error (MRQE) of 8.3% and 0.122, respectively.     

Effect of Post Heat Treatment on Corrosion Resistance of Phytic Acid Conversion Coated Magnesium

An environment friendly chemical conversion coating for magnesium was obtained by using a phytic acid solution. The effect of post-coating 1heat treatment on the microstructures and corrosion properties of phytic acid conversion coated magnesium was investigated. It was observed that the microstructure and corrosion resistive properties were improved for the heat treated samples. The corrosion current density for bare magnesium, phytic acid conversion coated magnesium, and post-coating heat treated magnesium was calculated to be 2.48×105 , 1.18×106 , and 9.27×107 A/cm2 , respectively. The lowest corrosion current density for the heat treated sample indicated its highest corrosion resistive effect for the magnesium. The maximum corrosion protective nature of the heat treated sample was further confirmed by the largest value of impedance in electrochemical impedance spectroscopy studies.