The synthesis and characterization of novel 2-nitrobenzyl sulfonate photo-generators of acid

Methodology was developed for the synthesis of novel 2-substituted o-nitrobenzyl chromophores, which were derivatized as the tosylate esters. The thermal stabilities of these new tosylates fell within the range predicted from an empirical model. Lithographic sensitivities of deep UV resists made from these new esters and poly(4-(tert-butoxycarbonyloxy)styrene-sulfone) ranged from 45 to 90 mJ/cm².     

3-D electro-magnetic analyses of a cage induction motor with rotorskew

The paper studied the performance characteristics of a three-phase cage induction motor using a 3D finite element technique. Especially, the effects of rotor skew and the rotor end-rings and the distribution of the electromagnetic field toward the axial direction, which have not been able to be analyzed accurately by 2D analysis, were investigated. Since the 3D analysis enabled the analysis of the continuity of the air gap flux density at the core ends and to take into consideration the rotor end-ring impedance, the motor parameters were calculated with high accuracy, compared with 2D analysis. Firstly, the authors made the relation of the rotor end-ring current with the rotor bar current clear, by analyzing the harmonics of the rotor bar current and the rotor end-ring current in the cases of motors without rotor skew and with rotor skew. Secondly, the torque and the rotor axial force were calculated from the distribution of the electromagnetic field obtained by the 3D analysis in the case of rotor skew. They also calculated the axial forces on the both end-rings in the case of rotor skew. The results obtained in the paper show the importance of 3D analysis for the design of induction motors     

Bromine addition and successive amine substitution of mesoporous ethylenesilica: Reaction, characterizations and arsenate adsorption

Bromination and subsequent ethylenediamine substitution of the CC double bond in mesoporous ethylenesilica were carried out to explore the characteristics of this periodic mesoporous organosilica. The structures of the products (BrPMO and EDA–BrPMO, respectively) were analysed by IR, Br K-edge EXAFS and NMR spectroscopies, as well as X-ray diffraction and nitrogen adsorption. We showed (1) that the formulae of the two products that formed were [CHBrSiO_1.5]_0.45[CHSiO_1.5]_0.55 and [NH₂CH₂CH₂NHCHSiO_1.5]_0.05 [CHBrSiO_1.5]_0.40[CHSiO_1.5]_0.55, respectively, (2) that the addition of Br₂ at room temperature occurred on the CC double bonds with disturbing the framework structure, (3) that IR absorption band of CC bonds that reacted with Br₂ is significantly different from that of inactive CC bond, (4) that the length of the C–Br bond was considerably longer than in conventional alkyl bromides, and (5) that a large proportion of the ν(C–Br) band remained at the same position in the IR absorption spectrum after the ethylenediamine (EDA) substitution, while a new ν(C–Br) absorption also appeared. The mechanisms of these reactions are discussed at both the micro and mesoscopic levels.

Arsenate adsorption on EDA–BrPMO, in which the EDA is directly bound to the “surface” of the mesopores, was compared with adsorption on EDA–Pr–PMO, which was prepared by the direct synthesis of 3-chloropropyl-functionalized mesoporous ethanesilica followed by the substitution of Cl with EDA. The strength of the adsorption, as measured with the distribution coefficient, was greater for the former adsorbent than the latter. The origin of this difference was attributed to the distance between amino group and the surface.     

Probabilistic calibration of discrete element simulations using the sequential quasi-Monte Carlo filter

The calibration of discrete element method (DEM) simulations is typically accomplished in a trial-and-error manner. It generally lacks objectivity and is filled with uncertainties. To deal with these issues, the sequential quasi-Monte Carlo (SQMC) filter is employed as a novel approach to calibrating the DEM models of granular materials. Within the sequential Bayesian framework, the posterior probability density functions (PDFs) of micromechanical parameters, conditioned to the experimentally obtained stress–strain behavior of granular soils, are approximated by independent model trajectories. In this work, two different contact laws are employed in DEM simulations and a granular soil specimen is modeled as polydisperse packing using various numbers of spherical grains. Knowing the evolution of physical states of the material, the proposed probabilistic calibration method can recursively update the posterior PDFs in a five-dimensional parameter space based on the Bayes’ rule. Both the identified parameters and posterior PDFs are analyzed to understand the effect of grain configuration and loading conditions. Numerical predictions using parameter sets with the highest posterior probabilities agree well with the experimental results. The advantage of the SQMC filter lies in the estimation of posterior PDFs, from which the robustness of the selected contact laws, the uncertainties of the micromechanical parameters and their interactions are all analyzed. The micro–macro correlations, which are byproducts of the probabilistic calibration, are extracted to provide insights into the multiscale mechanics of dense granular materials.     

An analytical solution for geotextile-wrapped soil based on insights from DEM analysis

This paper presents a novel analytical solution for geotextile-wrapped soil based on a comprehensive numerical analysis conducted using the discrete element method (DEM). By examining the soil–geotextile interface friction, principal stress distribution, and stress–strain relations of the constituent soil and geotextile in the DEM analysis, a complete picture of the mechanical characterization of geotextile-wrapped soil under uniaxial compression is first provided. With these new insights, key assumptions are verified and developed for the proposed analytical solution. In the DEM analysis, a near-failure state line that predicts stress ratios relative to the maximums at failure with respect to deviatoric strain is uniquely identified; dilation rates are found to be related to stress ratios via a single linear correlation regardless of the tensile stiffness of the geotextile. From these new findings, the assumptions on the stress-state evolution and the stress–dilatancy relation are developed accordingly, and the wrapped granular soil can therefore be modeled as a Mohr–Coulomb elastoplastic solid with evolving stress ratio and dilation rate. The development of the proposed analytical model also demonstrates an innovative approach to take advantage of multiscale insights for the analytical modeling of complex geomaterials. The analytical model is validated with the DEM simulation results of geotextile-wrapped soil under uniaxial compression, considering a wide range of geotextile tensile stiffnesses. To further examine the predictive capacity of the analytical model, the stress–strain response under triaxial compression conditions is solved analytically, taking both different confining pressures and geotextile tensile stiffnesses into account. Good agreement is obtained between the analytical and DEM solutions, which suggests that the key assumptions developed in the uniaxial compression conditions also remain valid for triaxial compression conditions.     

Advanced synthesis for monodisperse polymer nanoparticles in aqueous media with sub-millimolar surfactants

Highly monodisperse polystyrene nanoparticles with mean diameters of less than 100 nm are synthesized via aqueous emulsion polymerization using an amphoteric initiator (VA-057) in the presence of sub-millimolar concentrations of anionic surfactant. Since the net charge on the initiator is almost zero at neutral pH, the resultant latex particle size is mainly determined by surfactant adsorption. Polymerizations were performed in the presence of a range of anionic surfactants with differing critical micelle concentrations (CMC) by varying the concentrations of surfactant, initiator and monomer, and also the ionic strength. Sodium dodecyl benzene sulfonate (SDBS), sodium hexadecyl sulfate (SHS), and sodium octadecyl sulfate (SOS) have relatively low CMCs and so enable formation of highly monodisperse nanoparticles at relatively low (sub-millimolar) surfactant concentrations, C_S (i.e. below the CMC in each case). Empirically, it was found that the particle number, N_p, and coefficient of variation of the particle size, C_V, were strongly dependent on the C_S/CMC ratio: N_p increased almost in proportion with the square of this ratio, while the C_V exhibited a minimum at approximately C_S/CMC = 0.20. Higher ionic strength reduced the particle size, which is consistent with the above relationship because the addition of salt lowers the CMCs of ionic surfactants. Polymer latex particles produced using such formulations form highly regular, close-packed colloidal arrays.     

Oxidation kinetics for <Emphasis Type="Italic">cis</Emphasis>-9,<Emphasis Type="Italic">trans</Emphasis>-11 and <Emphasis Type="Italic">trans</Emphasis>-10,<Emphasis Type="Italic">cis</Emphasis>-12 isomers of CLA

The autoxidation processes of the cis-9,trans-11 (c9,t11) and trans-10,cis-12 (t10,c12) isomers of CLA were separately observed at ca. 0% RH and different temperatures. The t10,c12 CLA oxidized faster than the c9,t11 isomer at all tested temperatures. The first half of the oxidation process of t10,c12 CLA obeyed an autocatalytic-type rate expression, but the latter half followed first-order kinetics. On the other hand, the entire oxidation process of c9,t11 CLA could be expressed by the autocatalytic-type rate expression. The apparent activation energies and frequency factors for the autoxidation of the isomers were estimated from the rate constants obtained at various temperatures based on the Arrhenius equation. The apparent activation energies for the CLA isomers were greater than those for the nonconjugated n−6 and n−3 PUFA or their esters. However, the enthalpyentropy compensation held during the autoxidation of both the CLA and PUFA. This suggested that the autoxidation mechanisms for the CLA and PUFA were essentially the same.     

Numerical simulation of critical current performance in Nb3Sn strand subjected to periodic bending deformation

In the ITER Engineering Design Activity (EDA), four NB₃Sn model coils were developed and successfully tested. However, it was revealed that the critical current of the conductor degraded with the increase of electromagnetic force. One of the explanations of this phenomenon is a strand bending caused by enormous electromagnetic force. The authors therefore developed a simulation code using the distributed circuit model to investigate dependency of the critical current performance on the periodic bending deformation. The simulation results were in good agreement with the experiments. The dependence of the critical current on the periodic transverse load, temperature, periodic load pitch, thickness of Ta barrier which prevents Cu stabilizer from being contaminated by Sn, twist pitch of the strand, and RRR of the bronze matrix was investigated using the developed code. The results showed that the critical current degraded less with decreasing the pitch of the transverse load and increasing the Ta barrier thickness. It suggests that the shorter cabling pitch and the larger bending stiffness prevent the critical current degradation. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(3): 7–15, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20923     

Synthesis of N-doped titanium oxide by hydrothermal treatment

N-doped TiO₂ nanoparticles have been prepared by continuous or batch treatment of the colloidal TiO₂ nanoparticles under hydrothermal conditions with formamide, nitric acid, ammonia or triethylamine. The optical absorption tail of the obtained photocatalysts near the band gap extended to the visible region around λ = 500 nm. The efficiency of nitrogen doping was strongly dependent on the kind of nitrogen compounds, treatment method as well as treatment temperature. The most effective N-doping could be accomplished by the batch treatment with a small amount of triethylamine, which showed the efficient photocatalytic activity for both the reduction of Ag⁺ ions and the degradation of methylene blue under visible light irradiation.     

FI Catalysts: A Molecular Zeolite for Olefin Polymerization

A bis(phenoxyimine) group 4 transition metal catalyst (now known as FI catalysts) can discern ethylene from a mixture of ethylene and propylene at more than 99% selectivity. Denisty function theory (DFT) calculations revealed a spatially confined reaction site in the transition states of the migratory insertion which is just the right size for an ethylene molecule but too small for a propylene one. The substituents adjacent to the phenoxy‐oxygens are of crucial importance in developing the size/shape‐selectivity.