A transformation technique to estimate the process capability index for non-normal processes

Estimating the process capability index (PCI) for non-normal processes has been discussed by many researches. There are two basic approaches to estimating the PCI for non-normal processes. The first commonly used approach is to transform the non-normal data into normal data using transformation techniques and then use a conventional normal method to estimate the PCI for transformed data. This is a straightforward approach and is easy to deploy. The alternate approach is to use non-normal percentiles to calculate the PCI. The latter approach is not easy to implement and a deviation in estimating the distribution of the process may affect the efficacy of the estimated PCI. The aim of this paper is to estimate the PCI for non-normal processes using a transformation technique called root transformation. The efficacy of the proposed technique is assessed by conducting a simulation study using gamma, Weibull, and beta distributions. The root transformation technique is used to estimate the PCI for each set of simulated data. These results are then compared with the PCI obtained using exact percentiles and the Box-Cox method. Finally, a case study based on real-world data is presented.     

A two-phase linear programming methodology for fuzzy multi-objective mixed-model assembly line problem

We develop a fuzzy multi-objective linear programming (FMOLP) model for solving multi-objective mixed-model assembly line problem. In practice, vagueness and imprecision of the goals in this problem make the fuzzy decision-making complicated. The proposed model considers minimizing total utility work, total production rate variation, and total setup cost, using a two-phase linear programming approach. In the first phase, the problem is solved using a max–min approach. The max–min solution not being efficient, in general, we propose a new model in the second phase to maximize a composite satisfaction degree at least as good as the degrees obtained by phase one. To show the effectiveness of the proposed approach, a numerical example is solved and the results are compared with the ones obtained by the fuzzy mixed integer goal programming and weighted additive methods. The computational results show that the proposed FMOLP model achieves lower objective functions as well as higher satisfaction degrees.     

Modal Identification Study of Vincent Thomas Bridge Using Simulated Wind-Induced Ambient Vibration Data

Abstract:   In this article, wind-induced vibration response of Vincent Thomas Bridge, a suspension bridge located in San Pedro near Los Angeles, California, is simulated using a detailed three-dimensional finite element model of the bridge and a state-of-the-art stochastic wind excitation model. Based on the simulated wind-induced vibration data, the modal parameters (natural frequencies, damping ratios, and mode shapes) of the bridge are identified using the data-driven stochastic subspace identification method. The identified modal parameters are verified by the computed eigenproperties of the bridge model. Finally, effects of measurement noise on the system identification results are studied by adding zero-mean Gaussian white noise processes to the simulated response data. Statistical properties of the identified modal parameters are investigated under an increasing level of measurement noise. The framework presented in this article will allow us to investigate the effects of various realistic damage scenarios in long-span cable-supported (suspension and cable-stayed) bridges on changes in modal identification results. Such studies are required to develop robust and reliable vibration-based structural health monitoring methods for this type of bridge, which is a long-term research objective of the authors.     

Inventory lot-sizing with supplier selection using hybrid intelligent algorithm

In supply chain management (SCM), multi-product and multi-period models are usually used to select the suppliers. In the real world of SCM, however, there are normally several echelons which need to be integrated into inventory management. This paper presents a hybrid intelligent algorithm, based on the push SCM, which uses a fuzzy neural network and a genetic algorithm to forecast the rate of demand, determine the material planning and select the optimal supplier. We test the proposed algorithm in a case study conducted in Iran.     

Plasma Spray Deposition Enhancement of Titanium Nitride Layer Using Nitrogen-Contained Plasma Irradiation of Titanium Substrate as a Pre-spraying Method

Reactive plasma spray of TiN ceramic coating attracts much attention over the years because of its ability to deposit thick layers on various metal surfaces. However, some mechanical properties of the coating such as its hardness should be improved. In this study, initially a thin layer of titanium nitride was prepared on a titanium substrate during irradiation of titanium substrate by a thermal DC nitrogen-contained plasma jet. Then, during reactive plasma spraying, Ti particles were injected into plasma jet, converted to titanium nitride and huddled on to the substrate. This new hybrid method (primary plasma irradiation and post-reactive plasma spraying) for deposition of TiN coatings would combine the advantages of both plasma-enhanced chemical vapor deposition and reactive plasma spraying methods in part. It resulted in a thick and hard layer of titanium nitride film. Sample produced by this method was analyzed with x-ray diffraction confirming titanium nitride production. Vickers hardness was measured using optical microscopy which was around 1319 H_v300g. To study the cross section of the layer, optical microscopy and scanning electron microscopy (SEM) were used.     

Preparation,characterization and anticorrosive properties of a novel polyaniline/clinoptilolite nanocomposite

Nanocomposite of polyaniline (PANI) with natural clinoptilolite (Clino) was prepared. Formation of nanocomposite and incorporation of polyaniline in the clinoptilolite channels was confirmed and characterized using FTIR spectroscopy studies, X-ray diffraction (XRD) pattern, scanning electron microscopy (SEM) and cyclic voltammetry techniques. The anticorrosive properties of a 20 μm thickness coating of PANI/Clino nanocomposite with various weight ratios (1, 3 and 5%, w/w) of clinoptilolite content on iron coupons was evaluated and compared with pure polyaniline coating. According to the results in acidic environments PANI/Clino nanocomposite has enhanced corrosion protection effect in comparison to pure polyaniline coating. Comparative experiments revealed that PANI/Clino nanocomposite with 3% (w/w) clinoptilolite content has the best protective properties. Further experiments showed that the PANI/Clino nanocomposite has considerably different corrosion protection efficiencies in various corrosive environments.     

Effectiveness of polypyrrole and polyaniline composites for the removal of lead salts from aqueous solution

The effect of polyaniline and polypyrrole composites and the influence of type and concentration of stabilizer, pH of solution, and type of adsorbent on lead salt removal from aqueous solution were studied. The results indicated that the extents of removal of lead in alkaline solution (pH = 10) were 99.95 and 99.23%, respectively, when polyaniline and Polyaniline/(sodium dodecylbenzenesulfonate) composite were used as adsorbents. The results were compared with those obtained by using cation exchangers such as Purolite and Amberjet, and the observations indicated that Purolite and Amberjet were the better lead removal agents. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

Rheology of whey protein isolate-xanthan mixed solutions and gels. Effect of pH and xanthan concentration

Flow properties at pH 5.5-7.5 of whey protein isolate (WPI)-xanthan solutions containing 0-0.5 w/w% xanthan were studied by viscosimetry, although rigidity and fracture properties of the corresponding heat-set gels (90°C, 30 min) were determined by uniaxial compression. All the studied solutions displayed generalized shearthinning flow behaviour. Synergistic WPI-xanthan interactions has been revealed by observing that rheological parameters [σ_msf, K, n, η (γ)] characterizing blends were larger than those calculated from the two separated solutions. Such a behaviour was attributed to segregative phase separation of whey proteins and xanthan. Effects of xanthan on WPI-xanthan gel properties both depended on pH and xanthan concentration. Simultaneous increased xanthan concentration and decreased pH inhibited gelation of WPI-xanthan blends. Regarding gel strength, synergistic WPI-xanthan interactions were observed at pH >7.0 and low xanthan concentration (0.05 or 0.1 w/w%). Antagonism between the two macromolecules occurred at low xanthan concentration and pH ≤6.5, and high xanthan concentration (0.2 or 0.5 w/w%) at all pH tested. Low xanthan concentration rendered mixed gels more brittle than protein gels, and high xanthan concentration decreased pH effects on gel stress-strain relationships. The balance between strong thermal aggregation of concentrated whey proteins - in presence of incompatible xanthan -, high viscosity of blends and repulsive surface forces of protein molecules was thought to be at the origin of WPI-xanthan gel mechanical properties.     

Absorption of gases by aqueous solutions of acids and alkalis

Unsteady-state absorption of inorganic gases by aqueous solutions of acids and alkalis is considered using the example of two stagnant media (a liquid and a gas). It is shown that, in the general case, only two absorption modes are possible. In one of the modes, the resistance to mass transfer is concentrated in the gas phase, and, in the other, there is an instantaneous chemical reaction, in which the acceleration of two-phase physical absorption is constant. Conditions for each of these modes are found.Translated from Teoreticheskie Osnovy Khimicheskoi Tekhnologii, Vol. 39, No. 2, 2005, pp. 152–162.Original Russian Text Copyright © 2005 by Babak.