A comparative study on the metaheuristic-based optimization of skew composite laminates

Engineering with Computers - Plate structures are the integral parts of any maritime engineering platform. With the recent focus on composite structures, the need for optimizing their design and...     

Optimizing process parameters for laser beam micro-marking using genetic algorithm and particle swarm optimization

Laser micro-marking is an efficient technique for permanent marking and logo printing on materials. This study details the selection of an optimal parametric combination for laser micro-marking. In this work, markings were performed on Gallium Nitride (GaN) with varying the levels of marking parameters. The parameters considered in the present work are current (A), pulse frequency (Hz), and scanning speed (mm/sec). This experiment was designed using a “central composite design,” grounded in the response surface methodology. Mark intensity, which is a prominent response in laser marking, was considered the output response. The data interpretation involved analysis of variance (ANOVA) and mathematical modelling between the input parameters. It is essential to determine the relationship and significance of input-output variation. The interaction effect of various input parameters on mark intensity was also studied. Finally, two techniques, namely genetic algorithm (GA) and particle swarm optimization (PSO), were applied, and the optimal settings of input constraints were predicted.     

Effect of Alumina on the Structure and Mechanical Properties of Spark Plasma Sintered Boron Carbide

Uniform densification of relatively thick (~7 mm) consolidated boron carbide plates at relatively low temperatures (e.g. 1800°C) and low facture toughness are two of the primary challenges for further development of boron carbide applications. This work reports that these two challenges can be overcome simultaneously by adding 5 wt% alumina as a sintering aid. Nearly fully dense (97%), fine grained boron carbide (B₄C) samples were produced using spark plasma sintering at 1700°C and above in the B₄C‐5 wt% Al₂O₃ system. The alumina and boron carbide matrix reacted to form an Al₅O₆BO₃ (a mullite‐like phase) during sintering. The Al₅O₆BO₃ phase facilitated uniform densification via liquid phase sintering. This secondary phase is dispersed throughout the intergranular pores, providing obstacles for crack propagation and resulting in tougher boron carbide ceramics.     

Variability in nanometer CMOS: Impact, analysis, and minimization

Variation is a significant concern in nanometer-scale CMOS due to manufacturing equipment being pushed to fundamental limits, particularly in lithography. In this paper, we review recent work in coping with variation, through both improved analysis and optimization. We describe techniques based on integrated circuit manufacturing, circuit design strategies, and mathematics and statistics. We then go on to discuss trends in this area, and a future technology outlook with an eye towards circuit and CAD-solutions to growing levels of variation in underlying device technologies.     

Development of amine–acid cured Annona squamosa oil epoxy anticorrosive polymeric coatings

Forecasts for exhaustion of depleting petroleum resources in the years to come and escalating prices of petro-based chemicals, advocate the utilization of monomers/polymers derived from sustainable resources as an alternative. Oils of certain seeds may hold considerable promise as a source of unsaturated hydrocarbon, an excellent starting material for epoxidation and subsequent polymer production. Seeds of Annona squamosa (oil content 42–45%), go as a natural waste. Oil obtained from these seeds contains good amount of unsaturation; however, it has not been reported to be epoxidised, yet. Thus, epoxidation of A. squamosa oil (AOE) has been carried out in our effort to utilize a sustainable resource through the development of an anticorrosive coating material. AOE was further cured with different curing agent systems (ethylenediamine/phthalic acid (EDA–PA), 1,3-propanediamine/phthalic acid (PDA–PA), ethylenediamine/adipic acid (EDA–AA), 1,3-propanediamine/adipic acid (PDA–AA), p-phenylenediamine/adipic acid (PhDA–AA). AOE and AOE curing agent systems were subjected to structural elucidation by spectroscopic techniques (IR and ¹H NMR) and physico-chemical characterization (refractive index, specific gravity, iodine value, saponification value, hydroxyl value) involving standard methods. Thermal stability of these resins was investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Coatings of oil epoxy curing agent combinations prepared on Fe- and Al-alloys (mild steel and aluminium-24345) were subjected to physico-mechanical and anticorrosive tests in various corrosive media (water, saline water, acid and alkali) along with abrasion and steam resistance, light fastness, water vapour transmission, gloss, salt fog and humidity tests. These systems apprise satisfactory performance under different corrosive environments. The approach offers an alternate way for resource utilization and overcomes the drawbacks (poor load-bearing capacity and hardness) of oil epoxy-based coatings.     

Hybrid Metamodel—NSGA-III—EDAS Based Optimal Design of Thin Film Coatings

In this work, diamond-like carbon (DLC) thin film coatings are deposited on silicon substrates by using plasma-enhanced chemical vapour deposition (PECVD) technique. By varying the hydrogen (H₂) flow rate, CH₄−Argon (Ar) flow rate and deposition temperature (T_d) as per a Box-Behnken experimental design (BBD), 15 DLC deposition experiments are carried out. The Young’s modulus (E) and the coefficient of friction (COF) for the DLCs are measured. By using a second-order polynomial regression approach, two metamodels are built for E and COF, that establish them as functions of H₂ flow rate, CH₄-Ar flow rate and T_d. A non-dominated sorting genetic algorithm (NSGA-III) is used to obtain a set of Pareto solutions for the multi-objective optimization of E maximization and COF minimization. According to various practical scenarios, evaluation based on distance from average solution (EDAS) approach is used to identify the most feasible solutions out of the Pareto solution set. Confirmation experiments are conducted which shows the efficacy of the polynomial regression—NSGA-III—EDAS hybrid approach. The surface morphology of the DLCs deposited as per the optimal predictions is also studied by using atomic force microscopy.     

Influence of Interface Roughness, Film Texture, and Magnetic Anisotropy on Exchange Bias in [Pt/Co]3/IrMn and IrMn/[Co/Pt]3 Multilayers

Co/Pt multilayers can exhibit considerable exchange bias along the film normal when grown onto or covered by an antiferromagnetic IrMn layer. The magnitude of the bias effect depends strongly on the selection of the buffer layers and is largest for Co/Pt multilayers with small perpendicular anisotropy. This counterintuitive result is explained by opposite dependencies of exchange bias and magnetic anisotropy on the degree of film texture and grain size. Interface roughness also influences the perpendicular exchange bias field. The largest biases are measured on smooth films. Interlayer mixing during post-deposition annealing procedures decreases the exchange bias field of IrMn-capped Co/Pt multilayers.     

A KINETIC APPROACH TO EVALUATE THE ENERGY AND ENTROPY OF ACTIVATION FOR THE EXCHANGE OF ALKALINE EARTH METAL IONS ON TIN(IV) TUNGSTATE CATION EXCHANGER

Abstract

A new approach based on the Nernst-Planck equations has been applied to study the reaction kinetics on the surface of tin(IV) tungstate for the Mg(II)-H(I), Ca(II)-H(I), Sr(II)-H(I) and Ba(IT)-H(I) exchanges under the conditions favouring a particle diffusion phenomenon. On the basis of these studies the various physical parameters such as the effective diffusion coefficients, activation energies and entropies of activation have been evaluated which give some informations regarding the mechanism of ion-exchange on the surface of inorganic materials.     

Verbal discrimination learning: A review of the acquisition, transfer, and retention literature through 1972.

This review of the literature pertaining to verbal discrimination acquisition, transfer, and retention includes discussions of frequency theory, extensions to the frequency theory, and hypotheses independent of the frequency theory. It is generally concluded that the frequency theory is suitable for the explanation and prediction of data in experiments which require only recognition memory, and that other theoretical accounts or extensions are needed to predict and explain verbal discrimination problems which require processes other than simple recognition memory. (118 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tribological Investigation of Effect of Grain Size in 304 Austenitic Stainless Steel

Stainless steels are widely used in a variety of engineering applications such as food appliances, surgical instruments, nuclear reactors and cryogenic applications. The properties of stainless steel are greatly affected by the grain size. The present study investigates the effect of grain size on sliding wear behavior of AISI 304 stainless steel. The sliding wear properties are measured using a Pin-on-Disc machine. Annealing heat treatment process varies the grain size of steel at 1100 °C. The wear test is performed on different grain sizes of AISI 304 steel at various sliding speeds under dry condition. The wear rate of the steels at different sliding distances is plotted as a function of grain size. The maximum wear rate is obtained at an intermediate grain size. It is noted that frictional force and temperature initially increases and then reaches the saturation plateau. The results are used to establish a correlation between the grain size and sliding wear properties of stainless steel. The present study is useful in enhancing the life of various components made of the stainless steel.