A multi-objective approach to simultaneous determination of spare part numbers and preventive replacement times

Different models have been proposed in the field of preventive maintenance planning for finding optimal age replacement policies. While previous studies have focused mainly on classical cost objectives, this paper presents a novel multi-objective model for preventive replacement of a part over a planning horizon. The proposed model considers different objectives and practical issues, such as corrective replacement and its consequences, residual lifetime objective, and kind of productivity index. Also, the model determines number of spare parts, required for replacement with the defected part, to be provided at the beginning of the planning horizon. The multi-objective model is applicable for machines or equipments which are repaired through replacing their defected part with new spare part.For solving the multi-objective model, regarding to ability of ε-constraint method to generate different pareto-optimal solutions, a procedure is developed based on this method. The procedure shows how the ε-constraint method can be used for finding preferred solution in situations where there is no access to decision maker. The model and solution procedure are illustrated by a numerical example.     

A general super element for a curved beam

Corrugated panels have gained considerable popularity in a range of engineering applications, particularly in morphing skin applications. The optimum design of these structures needs simple models of the corrugated panels that may be incorporated into multi-disciplinary system models. Considering the geometric and mechanical properties of the corrugated panel, a generic super element of a corrugated core unit cell with elastomeric coating for morphing structures is investigated in this paper. The super element captures the small deformation of a 2D thin curved beam with variable curvature and is based on an exact analytical equivalent model which avoids any homogenization assumption. The stiffness matrix of a general curved beam element for a corrugated unit cell with elastomeric coating is derived. Different geometries are investigated to verify the accuracy and efficiency of the presented super element. The super element uses the geometric and mechanical properties of the panel as variables that may be applied for further topology optimization studies. The parametric studies of different corrugation shapes demonstrate the suitability of the proposed super element for application in further detailed design investigations.     

A Generalization of Schur–Weyl Duality with Applications in Quantum Estimation

Schur–Weyl duality is a powerful tool in representation theory which has many applications to quantum information theory. We provide a generalization of this duality and demonstrate some of its applications. In particular, we use it to develop a general framework for the study of a family of quantum estimation problems wherein one is given n copies of an unknown quantum state according to some prior and the goal is to estimate certain parameters of the given state. In particular, we are interested to know whether collective measurements are useful and if so to find an upper bound on the amount of entanglement which is required to achieve the optimal estimation. In the case of pure states, we show that commutativity of the set of observables that define the estimation problem implies the sufficiency of unentangled measurements.     

The impact of using multiple modalities on students’ acquisition of fractional knowledge: An international study in embodied mathematics across semiotic cultures

Principled by the Embodied, Situated, and Distributed Cognition paradigm, the study investigated the impact of using a research-based curriculum that employs multiple modalities on the performance of grade 5 students on 3 subscales: concept of unit, fraction equivalence, and fraction comparison. The sample included five schools randomly selected from a population of 14 schools in Lebanon. Eighteen 5th grade classrooms were randomly assigned to experimental (using multimodal curriculum) and control (using a monomodal curriculum) groups. Three data sources were used to collect quantitative and qualitative data: tests, interviews, and classroom observations. Quantitative data were analyzed using two methods: reliability and MANOVA. Results of the quantitative data show that students taught using the multimodal curriculum outperformed their counterparts who were instructed using a monomodal curriculum on the three aforementioned subscales (at an alpha level = .001). Additionally, fine-grained analysis using the semiotic bundle model revealed different semiotic systems across experimental and control groups. The study findings support the multimodal approach to teaching fractions as it facilitates students’ conceptual understanding.     

H2O soluble ternary complexes of divalent transition metal ions with AN-(2-acetamido)iminodiacetic acid and heterocyclic diimines

Summary H₂O soluble mixed ligand complexes of the type [M-(ADA)B·H₂O] where M = Ni^II or Cu^II; [ADA]^2- = divalent anion of N-(2-acetamido)iminodiacetic acid, B = heterocyclic diimine (2,2'-bipyridyl or 1,10-phenanthroline), were prepared and characterized by elemental and thermal analyses, i.r. and electronic spectra, as well as conductivity measurements. Formation constants for the 111 ternary cobalt(II), nickel(II) and copper(II) complexes formed in solution were determined potentiometrically at 24 °C and = 0.1mol dm^-3(KNO₃).     

Current density of anodes,recombination rate and luminance in MEH-PPV,MDMO-PPV,and P3HT polymers in polymer light-emitting diodes

The present study examined polymer-based organic light-emitting diodes (PLEDs) with the different active layers using Silvaco Atlas software. The electrical and optical responses of the devices were evaluated through the characteristics of current-voltage, luminance, and recombination rate. The performance of the device strongly depends on the physical properties of the active layer. A better understanding of the effect of varying the parameters of the active layer, such as mobility, lifetime, and band gap, on the functioning of the device is necessary to achieve further improvement in these applications. This work presents a theoretical study of PLEDs having different active layers. Poly[2-methoxy-5-(3’,7’-dimethyloctyloxy)-1,4-phenylenevinylene], poly(3-hexylthiophene), and poly[2-methoxy-5-(2’-ethylhexyloxy)-p-phenylene vinylene] organic layers were deposited on an ITO substrate and the structure of the device was completed by a calcium cathode with a work function of 2.9 eV. The Langevin and Poole-Frenkel models were used to analyze the devices. The Langevin model was used to analyze the recombination rate and investigate the relationship between luminance, recombination rate, and the parameters of the active layer that have been less studied in previous works. Analysis of anode current density, luminance, and recombination rate indicate that poly(3-hexylthiophene) PLED shows better performance than others.     

Removal of Reactive Red 141 Dye from Aqueous Solution by Titanium Hydroxyapatite Pellets

The adsorption of Reactive Red 141 over the pressed and calcined pellets of TiHAp and HAp was investigated by using continuous reflux system. Langmuir isotherm model was found to be the best model to describe the equilibrium data, with maximum adsorption capacity of 20.62 and 28.41 (mg g^?1) for HAp and TiHAp, respectively. Kinetics data was best described by the pseudo-second-order model and intraparticle diffusion determined as sole controlling step of adsorption process. Possible mechanisms of the adsorption dye on the HAp and TiHAp were discussed.     

Hofmeister Effects of Group II Cations as Seen in the Unfolding of Ribonuclease A

This work studies the effects of alkaline-earth cation addition on the unfolding free energy of a model protein, pancreatic Ribonuclease A (RNase A) by differential scanning calorimetry analysis. RNase A was chosen because: a) it does not specifically bind Mg²⁺, Ca²⁺ and Sr²⁺ cations and b) maintains its structural integrity throughout a large pH range. We have measured and compared the effects of NaCl, MgCl₂, CaCl₂ and SrCl₂ addition on the melting point of RNase A. Our results show that even though the addition of group II cations to aqueous solvent reduces the solubility of nonpolar residues (and enhances the hydrophobic effect), their interactions with the amide moieties are strong enough to “salt-them-in” the solvent, thereby causing an overall protein stability reduction. We demonstrate that the amide-cation interactions are a major contributor to the observed “Hofmeister Effects” of group II cations in protein folding. Our analysis suggests that protein folding “Hofmeister Effects” of group II cations, are mostly the aggregate sum of how cation addition simultaneously salts-out hydrophobic moieties by increasing the cavitation free energy, while promoting the salting-in of amide moieties through contact pair formation.     

Design and development of novel single multiplex system incorporating 26 rapidly mutating Y-STRs; 26 RM Yplex

This article details the development of a single multiplex system amplifying 26 rapidly mutating Y-STR markers. A sequenced allelic ladder, constructed for calling alleles of all loci, is introduced. The multiplex system shows the ability to address the limitations of Y-STRs commercial kits in differentiating closely related males. The multiplex performed well in the prevalidation tests and showed great potential to be used in forensic casework.     

Enantioselective Total Synthesis of (+)-Eucophylline

The total enantioselective synthesis of (+)-eucophylline 1 was achieved using as a key-structural motif a chiral piperidinone bearing the natural product all-carbon quaternary stereocenter. The elaboration of the latter is based on two strategies relying on the free-radical carbo-cyanation and sulfonyl-cyanation respectively of enantiopure substituted cyclopropenes and cyclobutenes. Co- or Ni-boride reduction of the nitrile functional group along with the cyclopropane and cyclobutane ring-opening then led to the formation of the chiral piperidinone ring. Further elaboration of the latter into the key 1-azabicyclo[3.3.1]nonane motif followed by its coupling with a 2-cyanoaniline allowed the formation of the tetrahydrobenzo[b][1,8]-naphthyridine skeleton of 1 , which was finally accessible in 17 steps and 5.9 % overall yield from 1,1-dibromobutene.