Hot Corrosion Behavior and Microstructural Change of Al-Gradient CoNiCrAlYSi Coatings, Produced by LVPS and Diffusional Processes

Conventional and gradient CoNiCrAlYSi coatings were produced by using low vacuum plasma spray and an additional step of diffusional over aluminizing (pack cementation) techniques on an Inconel-738 substrate. Hot corrosion of these coatings was investigated using Na₂SO₄–20wt%NaVO₃ molten salt at 880?°C for 800?h. Hot corrosion rate was determined by measuring the weight gain of the specimens at regular intervals for a duration of 20?h. X-ray diffraction, field emission scanning electron microscopy and electron probe micro analysis techniques were used to determine the nature of phases, investigation of the thermally grown oxide, examination of the surface attack and determination of the elemental distribution. The gradient coating showed better performance by re-healing alumina scale due to its possession of more β phase as Al reservoir. Results indicated that pack cementation process caused an increase in amount of aluminum-rich β phase and better hot corrosion properties of gradient coatings owing to the Al enrichment in the outer layer and rapid formation of protective oxide on the surface.     

Effect of different size of joint enlargement on seismic behavior of gravity load designed RC beam‐column connections

Effect of different size of planer joint enlargement as a noninvasive and practical strategy for seismic retrofit of gravity load designed external reinforced concrete beam‐column connections was experimentally investigated. The joint region was enlarged using steel angles that are mounted using prestressed cross‐ties. Reverse cyclic load tests on five half‐scale control and retrofitted external RC beam‐column connections were conducted. Three different size of planer joint enlargement being 180, 140, and 90 mm were considered for retrofitted specimens. The performance of the retrofitted specimens is compared with that of the control gravity load designed beam‐column connections, in terms of load–displacement hysteresis curve, energy dissipation and ductility capacities, and global strength and stiffness degradation behavior. The experimental results showed that increasing the size of planer joint enlargement significantly enhances the seismic capacity of the retrofitted connections, in terms of strength, stiffness, energy dissipation, and ductility capacity and also planer joint enlargement can relocate beam plastic hinges to outside the joint panel.     

No-wait two stage hybrid flow shop scheduling with genetic and adaptive imperialist competitive algorithms

This article studies a no-wait two-stage flexible flow shop scheduling problem with setup times aiming to minimize the total completion time. The problem is solved using an adaptive imperialist competitive algorithm (AICA) and genetic algorithm (GA). To test the performance of the proposed AICA and GA, the algorithms are compared with ant colony optimisation, known as an effective algorithm in the literature. The performance of the algorithms are evaluated by solving both small and large-scale problems. Their performance is evaluated in terms of relative percentage deviation. Finally the results of the study are discussed and conclusions and potential areas for further study are highlighted.     

An intelligent hybrid meta-heuristic for solving a case of no-wait two-stage flexible flow shop scheduling problem with unrelated parallel machines

This paper addresses the problem of no-wait two-stage flexible flow shop scheduling problem (NWTSFFSSP) considering unrelated parallel machines, sequence-dependent setup times, probable reworks and different ready times to actualize the problem. The performance measure used in this study is minimizing maximum completion time (makespan). Because of the complexity of addressed problem, we propose a novel intelligent hybrid algorithm [called hybrid algorithm (HA)] based on imperialist competitive algorithm (ICA) which are combined with simulated annealing (SA), variable neighborhood search (VNS) and genetic algorithm (GA) for solving the mentioned problem. The hybridization is carried out to overcome some existing drawbacks of each of these three algorithms and also for increasing the capability of ICA. To achieve reliable results, Taguchi approach is used to define robust parameters' values for our proposed algorithm. A simulation model is developed to study the performance of our proposed algorithm against ICA, SA, VNS, GA and ant colony optimization (ACO). The results of the study reveal the relative superiority of HA studied. In addition, potential areas for further researches are highlighted.     

Group velocity dispersion of dyes in solution measured with white-light interferometry

The group velocity dispersion (GVD) coefficient of four different dyes in solution is measured as a function of wavelength and concentration using a white-light Michelson interferometer. We find that the wavelength dependence of the GVD can be considerably different at wavelengths above and below the absorption resonance in a dye. Above the absorption resonance, the dye molecules can make a strong, wavelength-dependent contribution to the GVD of the solution. Below the absorption resonance, the dye molecules tend to contribute negligibly to the GVD of the solution. We find that the contribution of the dye molecules to the GVD can be modeled quite accurately using a simple Lorentz model with parameters set using the measured linear absorption properties of the dye.     

The open surgical approach to subglottic hemangioma

The monthly distribution of relapses in ulcerative colitis was analysed retrospectively to assess seasonal variation. In 338 patients who were regularly followed up at the colitis clinic, 1013 relapses occurred during the period 1977 to 1988. A peak of relapses occurred in the spring and autumn, with a decrease in the summer; the ratio of the observed to expected number of relapses was 201:255.3 for the summer, 289:252.6 for the autumn, 243:249.8 for the winter, and 280:255.3 for the spring. In contrast, month of diagnosis was evenly distributed without seasonality. The data support the concept that exacerbations in ulcerative colitis are influenced by seasonal factors.     

Optimum design and operation of batch rectification accompanied by chemical reaction

Batch processes are widespread in the chemical industry. If batch synthesis or separation processes are to run economically, the operating conditions must be optimized and an appropriate arrangement of equipment must be chosen. In this paper, we demonstrate that optimization of operaiong conditions and plant-equipment by simulation during the planning-stages can yield large advantages. In contrast to previous studies, our models include the non-ideal behaviour of multicomponent mixtures and the kinetics of chemical reactions in the column. The results of the calculations are control functions that permit optimum operation to be realized.

As an example, the reactionin a distillation column was optimized. Compared with conventional operation, the calculated control functions give an advantage in capacity of 65% and in energy consumption of 40%. The calculation was confirmed by measurements. A control algorithm is evaluated.     

Einsatz von mathematischer Simulation und Miniplant-Technik in der Verfahrensentwicklung

Use of mathematical simulation and miniplant techniques in process development . An integrated study of synthesis and workup or of entire processes is often required in the development of chemical processes. This leads to a large number of possible solutions, of which the most economic one must be selected. This variety can only be mastered at reasonable expense with the aid of present-day techniques. Examples are presented to show how just a few economic possibilities can be selected and optimized from the plethora of alternatives in simulation calculations based on just a few properties of the materials involved. Economics is the basis of all evaluation. Use of miniplants is considered in the second part of the article, and costs and time-expenditure are compared with those for industrial pilot plants. Planning and evaluation of experiments raise the effectiveness of this empirical work. Problems of scale-up are considered, and the advantages of physico-chemically sound scale-up models are demonstrated.