Weakly distributive modules. Applications to supplement submodules

In this paper, we define and study weakly distributive modules as a proper generalization of distributive modules.We prove that, weakly distributive supplemented modules are amply supplemented. In a weakly distributive supplemented module every submodule has a unique coclosure. This generalizes a result of Ganesan and Vanaja. We prove that π-projective duo modules, in particular commutative rings, are weakly distributive. Using this result we obtain that in a commutative ring supplements are unique. This generalizes a result of Camillo and Lima. We also prove that any weakly distributive ⊕-supplemented module is quasi-discrete.     

Using economic X control chart design methodology to estimate and optimize machine efficiency in the case of multimachine assignments

Estimation and optimization of machine efficiency in the case of multi machine assignments is a difficult issue for some industries such as textile industry, due to the machine interference. Although the problem is not new, the solutions proposed are not full satisfactory. For example, the analytical formulas are not suitable for high number of machines; queuing theory approaches are complex and impractical for mill managers. On the other hand, simulation methodology seems to be a perfect tool to estimate and analyze; however, the simulation package programs are expensive and are not suitable for systematic optimization. In this paper, Duncan's economic control chart design methodology is proposed as an alternative way for one of the oldest industrial problems. This study shows that this new approach is a more efficient solution to this stochastic problem. Copyright © 2009 John Wiley & Sons, Ltd.     

Simultaneous Determination of Fluoxetine,Estrone, Pesticides,and Endocrine Disruptors in Wastewater by Gas Chromatography–Mass Spectrometry (GC–MS) Following Switchable Solvent–Liquid Phase Microextraction (SS–LPME)

A simple and sensitive analytical method for the determination of fluoxetine, estrone and selected pesticides and endocrine disruptors has been proposed for wastewater analysis by gas chromatography–mass spectrometry (GC–MS). A switchable solvent was produced with N,N-dimethylbenzylamine by changing its hydrophobic properties by the addition of CO₂ for protonation. Sodium hydroxide was added to switch the solubility of the extraction solvent and to allow phase separation in the sample/standard medium. Analytical parameters affecting the extraction outputs such as volume of switchable solvent, concentration and volume of sodium hydroxide, mixing type and period were investigated to improve the extraction recovery of the selected analytes. Under the optimum conditions, limits of detection and limits of quantification for the analytes were calculated in the ranges of 0.16–8.6?ng mL^?1 and 0.54–29?ng mL^?1, respectively. The developed method was successfully applied to synthetic wastewater and two municipal wastewater samples. None of the selected analytes were detected in the samples. High recovery values demonstrated that the proposed method was reliable and applicable to complex matrices.     

The influence of nitridation time on the structural properties of GaN grown on Si (111) substrate

In the present paper, the effect of in-situ substrate nitridation time on crystalline quality of GaN films grown on Si (111) substrates by metal organic chemical vapor deposition (MOCVD) were investigated. A thin buffer layer of silicon nitride (SiN _x ) with various thicknesses was achieved through the nitridation of substrate at different nitiridation times ranging from 0 to 660 s. The structural characteristics, such as dislocation densities, correlation lengths of columnar crystallites, the tilt and twist of the mosaic structure, and the angles of rotational disorder, were all studied in detail by using a planar and cross-sectional view of high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (HRXRD) performed at different scattering geometries. It was found that the dislocation densities, lateral coherence lengths, vertical coherence lengths, and the tilt and twist of mosaic blocks in GaN films monotonically varies with the nitridation time. The experimental findings showed that the nitridation times had more influence on edge dislocation densities than the screw type.     

Ab Initio Study on Hypothetical Silver Nitride

We perform the ab initio calculations based on norm-conserving pseudopotentials and density functional theory to investigate the structural, elastic, and thermodynamical properties for silver nitride （AgN） compound that is a member of the 4d transition metal group and has not been synthesized yet. The obtained results are compared with the other available theoretical data, and the agreement is, generally, quite good. We also present the pressure-dependent behaviour of some mechanical and thermodynamical properties for the same compounds.     

Differential and substrate-selective reactivity of calix[4]arene derivatives with cyclenyl-Zn(II) modifications at the upper rim

[structure: see text] Novel "cone conformation" calix[4]arene derivatives, carrying either one or two cyclen (1,4,7,10-tetra-azacyclododecane) moieties at the upper rim, have been synthesized. The hydrolytic activities of the Zn(II) complexes of these calixarenes were studied. A surprising behavior was observed with p-nitrophenylstearate; whereas the bis-cyclenyl-2Zn(II) complex showed negligible hydrolytic activity over the background, the mononuclear complex showed a significant 400-fold rate increase at pH 8.5.     

An assessment of the poincare scheme for non-linear oscillators and an improvement of its range of validity

The range of validity of the Poincare method is studied by comparison with the exact solution for the anharmonic and Morse oscillators. The exact solutions for these cases are expressible respectively in terms of elliptic and inverse trigonometric functions. The oscillation frequency is taken as the basis for the comparison. It is seen that the Poincare perturbation gives fairly accurate results up to amplitudes that are 20–30 per cent of the maximum value allowed for periodic solutions depending on the form of the potential energy. A new method is presented as a slight variation over the standard Poincare method. This method differs from the former only by a rearrangement of the differential equation through a collocation approximation for the potential. In spite of its simplicity, the method proves to be a better approximation than the standard Poincare method and gives remarkably accurate results for amplitudes up to 60–70 per cent of the maximum value allowed for periodic solutions.     

Determining the interaction and characterization of asphaltene in alkylbenzene solvents using nuclear-electron double resonance

This study uses ¹H dynamic nuclear polarization (DNP) methods to determine asphaltene aggregates and the interaction between asphaltene extracted from MC800 asphalt and alkylbenzene solvents, as well as elemental analysis for the characterization of asphaltene. The asphaltene sample was characterized using the elemental analysis of carbon (C), hydrogen (H), nitrogen (N), and sulfur (S). The results show that asphaltenes have the highest carbon content. The sulfur and hydrogen contents are nearly the same and nitrogen content is the smallest. The DNP data provided good results for characterizing asphaltene behavior in alkylbenzene solvents.     

In situ preparation of rhodium/n‐heterocyclic carbene complexes and use for addition of arylboronic acids to aldehydes

The in situ prepared three component system [RhCl(COD)]₂/imidazolidinium salts ( 2, 4 ) and KOBu^t catalyses the addition of phenylboronic acid to sterically hindered aldehydes affording the corresponding arylated secondary alcohols in good yields. Four novel 1,3‐dialkylimidazolidinium ( 2‐4 ) salts as NHC precursors were synthesized from N,N′‐dialkylethylenediamine.     

Rate effect on sharing of passive lumbar motion segment under load-controlled sagittal flexion: viscoelastic finite element analysis

Industrial epidemiological studies have shown that jobs requiring a higher speed of trunk motion contribute to a higher risk of industrial low back disorders. Consideration of the loading dynamic characteristics, such as lifting at different speeds, requires modeling of the viscoelastic behavior of passive tissues. Detailed systematic analysis of the effects of loading rate has been lacking in the literature. A validated viscoelastic finite element model of a L2–L3 motion segment was used to identify the load sharing among the passive elements at different loading rates. Force controlled complex flexion movement was simulated by applying load at the top of the upper vertebra without constraining any coupled sagittal rotation, whereas the lower vertebra was fixed at the bottom. The load reached its maximum values of 2000 N compression, 400 N anterior shear, and 20 Nm flexion in three different durations of 0.3, 3 and 30 s to represent fast, medium and slow movement. The global force–displacement response of the motion segment, forces in facet joints and ligaments, stresses and strains in anulus fibrosus, and intradiscal pressure were compared across different rates. The higher rate of loading while reaching a prescribed complex forward flexion loading increased the intradiscal pressure and the stress in the anulus fibers at the posterolateral innermost layers, but reduced the global displacements, ligament forces and facet joint forces. The distribution of stress and strain was markedly affected by the loading rate. Consideration of the time-dependent material properties of passive elements is essential to improve our understanding of the responses of the motion segment to dynamic loading conditions. Speed of the manual materials handling (MMH) tasks should be included as a risk factor in the biomechanical and epidemiological studies and guidelines for safe lifting.