A unified model for electrostatic sensors in fluid media

Nonlinear Dynamics - We present a unified model of electrostatic sensors comprising cantilever microbeam resonators in fluid media. The model couples Euler–Bernoulli beam equation to the...     

Infrared and Raman study of some isonicotinic acid metal(II) halide and tetracyanonickelate complexes

In this study the M(IN)(2)Ni(CN)(4) [where M: Co, Ni, and Cd, and IN: isonicotinic acid, abbreviated to M-Ni-IN] tetracyanonickelate and some metal halide complexes with the following stoichiometries: M(IN)(6)X(2) (M: Co; X: Cl and Br, and M: Ni; X: Cl, Br and I) and Hg(IN)X(2) (X: Cl, Br, and I) were synthesized for the first time. Certain chemical formulas were determined using elemental analysis results. The FT-IR and Raman spectra of the metal halide complexes were reported in the 4000-0 cm(-1) region. The FT-IR spectra of tetracyanonickelate complexes were also reported in the 4000-400 cm(-1) region. Vibrational assignments were given for all the observed bands. For a given series of isomorphous complexes, the sum of the difference between the values of the vibrational modes of the free isonicotinic acid and coordinated ligand was found to increase in the order of the second ionization potentials of metals. The frequency shifts were also found to be depending on the halogen. The proposed structure of tetracyanonickelate complexes consists of polymeric layers of /M-Ni(CN)(4)/(infinity) with the isonicotinic acid molecules bound directly to the metal atom.     

Synthesis of pterocellin A

The first total synthesis of pterocellin A (1) was achieved in 10 linear steps from commercially available kojic acid (6) and 2-bromo-3-pyridinol (11) in a convergent sequence. The key constructive steps are a directed lithiation to couple two pyridines and an intramolecular nucleophilic aromatic substitution to form 1. [structure: see text]     

Synthesis,characterization and computational investigation of poly(styrene-co-1-methylpyrenyl methacrylate): its efficiency as a macrophotoinitiator

Abstract

In this study, it has been demonstrated that poly(styrene-co-1-methylpyrenyl methacrylate) macro-photoinitiator (PSMM) containing side chain pyrene moieties were successfully prepared using “radical polymerization method.” Firstly, 1-pyrene methanol and methacryloyl chloride were reacted in dichloromethane for 24?h at 0?°C in order to give 1-methoxy pyrene methacrylate macromonomer. Then styrene was polymerized with this macromonomer to obtained macro-photoinitiator. The synthesized copolymer is also both computationally and experimentally demonstrated that the macro-photoinitiator obtained has similar absorption characteristics with the parent pyrene molecule. According to obtained results, the synthesized copolymer was more effective in the presence of triethyl amine as a macro-photoinitiator.     

Using Bezier curves for the calculation of retention indices of polycyclic aromatic hydrocarbons in the so-called Lee's scale in temperature-programmed gas chromatography with mass spectrometry detection

The retention indices of some polycyclic aromatic hydrocarbons (PAHs) separated by temperature-programmed gas chromatography are computed by smoothing reference data with Bezier curves of orders 6 are more consistent with the scheme of this retention parameter, and they present standard deviations systematically smaller than those associated with classical retention indices. The Bezier curve possesses the property of local control, (i.e., their graphs are modified only in the neighbourhood of the displaced point). The values thus obtained were compared with the corresponding ones calculated in a classical way. Detailed statistical analysis is presented to describe the retention indices of PAHs expressed in the so-called Lee's scale as a function of retention temperatures (in degrees C). As a training set, experimental retention data of PAHs obtained on a PE-5 phase is used for correlation. As prediction sets, literature experimental retention indices expressed in the so-called Lee's scale obtained on a DB-5 slightly polar stationary phase are applied for comparison. The method developed is successfully used for estimating and predicting the capillary gas chromatography retention index of PAHs.     

A double microbeam MEMS ohmic switch for RF-applications with low actuation voltage

In this paper, we propose the design of an ohmic contact RF microswitch with low voltage actuation, where the upper and lower microplates are displaceable. We develop a mathematical model for the RF microswitch made up of two electrostatically actuated microplates; each microplate is attached to the end of a microcantilever. We assume that the microbeams are flexible and that the microplates are rigid. The electrostatic force applied between the two microplates is a nonlinear function of the displacements and applied voltage. We formulate and solve the static and eigenvalue problems associated with the proposed microsystem. We also examine the dynamic behavior of the microswitch by calculating the limit-cycle solutions. We discretize the equations of motion by considering the first few dominant modes in the microsystem dynamics. We show that only two modes are sufficient to accurately simulate the response of the microsystem under DC and harmonic AC voltages. We demonstrate that the resulting static pull-in voltage and switching time are reduced by 30 and 45%, respectively, as compared to those of a single microbeam-microplate RF-microswitch. Finally, we investigate the global stability of the microswitch using different excitation conditions.     

Stereoselective synthesis of alpha- and beta-glycosylamide derivatives from glycopyranosyl azides via isoxazoline intermediates

Treatment of 2-acetoxy glycopyranosyl azides with Ph3P gave isoxazolines by ring closure of the phosphorimine. Coupling of in situ generated isoxazolines with acylating reagents gave mixtures of alpha- or beta-glycopyranosyl amides. The alpha/beta ratio depended upon the acylating reagent and metal salts employed. For example, coupling of isoxazoline 3 with Z-Asp-(SPy)-OBn in the presence of CuCl2 gave exclusively alpha-N-glucopyranosylasparagine derivative 8. This general procedure has been applied to mono-, di-, and trisaccharide systems.     

Managing capacity flexibility in make-to-order production environments

This paper addresses the problem of managing flexible production capacity in a make-to-order (MTO) manufacturing environment. We present a multi-period capacity management model where we distinguish between process flexibility (the ability to produce multiple products on multiple production lines) and operational flexibility (the ability to dynamically change capacity allocations among different product families over time). For operational flexibility, we consider two polices: a fixed allocation policy where the capacity allocations are fixed throughout the planning horizon and a dynamic allocation policy where the capacity allocations change from period to period. The former approach is modeled as a single-stage stochastic program and solved using a cutting-plane method. The latter approach is modeled as a multi-stage stochastic program and a sampling-based decomposition method is presented to identify a feasible policy and assess the quality of that policy. A computational experiment quantifies the benefits of operational flexibility and demonstrates that it is most beneficial when the demand and capacity are well-balanced and the demand variability is high. Additionally, our results reveal that myopic operating policies may lead a firm to adopt more process flexibility and form denser flexibility configuration chains. That is, process flexibility may be over-valued in the literature since it is assumed that a firm will operate optimally after the process flexibility decision. We also show that the value of process flexibility increases with the number of periods in the planning horizon if an optimal operating policy is employed. This result is reversed if a myopic allocation policy is adopted instead.     

Nonlinear analysis and effectiveness of weakly coupled microbeams for mass sensing applications

Nonlinear Dynamics - Kaplan turbines, also known as movable propeller turbines, are attractive for power generation from water currents. They are controlled by guide vanes and runner blades, whose...