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Rotational Mode (rotational + mode)
Selected AbstractsStudy on the action of the active earth pressure by variational limit equilibrium methodINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 10 2010Li Xinggao Abstract Within the framework of limiting equilibrium approach, the problem of active earth pressure on rigid retaining wall is formulated in terms of the calculus of variations by means of Lagrange multipliers. It is transcribed as the functional of extreme-value problem by two undetermined function arguments, and is further transformed into determining the minimax solution of restrained functions incorporating the geometrical relations of the problem. The function of (fmincon) in the optimization toolbox of MATLAB 6.1 can be used to find the minimax solution. Computation results show there exist two kinds of modes of failure sliding along plane surface and rotating around log-spiral cylinder surface when the soil behind the walls reaches the critical active state. The magnitude of active earth pressure in the case of translational mode is less than that in the case of rotational mode. The location of action point of earth pressure in the case of translational mode is at or below height of the wall, and in the case of rotational mode, is above height of the wall. Preliminary study indicates a pair of numbers by two theoretical modes can be regarded as an interval estimation of active pressure. Copyright © 2009 John Wiley & Sons, Ltd. [source] The Aqualon SLT: A novel device for measuring hair stiffness and lubricityINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 2 2010K. A. Vaynberg J. Cosmet. Sci., 60, 135,141 (March/April 2009) Synopsis The ability to quantify hair property changes in response to treatment is essential to the successful development of new formulations and benefiting agents. In the attempt to expand the toolbox of hair tress testing tools, we developed a device that allows hair scientists to measure hair tress changes in stiffness and lubricity. The tool is based on a system of pins mounted on free rotating bearings and is operated in two modes: rotating and stationary. The hair attributes are measured by threading a hair tress through the pin assembly and measuring the total work of pulling through in rotational and stationary modes (the latter mode is obtained by immobilizing pins by a retaining plate). The data thus obtained is de-convoluted into the work of apparent stiffness (rotational mode) and the work of the friction-on-pins or lubricity (stationary mode minus the apparent stiffness). The data can be further reduced to produce an apparent friction coefficient defined as a ratio of the apparent lubricity to the apparent stiffness. This work demonstrates the utility of the parameters measured by the Aqualon SLT and illustrates how the device can be used to predict and understand the impacts of various hair treatments. [source] Effects of entropy on the gas-phase pyrolysis of ethyl N,N -dimethylcarbamateJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 3 2007Chang K. Kim Abstract In this study, we examined the gas-phase pyrolysis of ethyl N,N -dimethylcarbamate theoretically at various theoretical levels. The reaction consists of a two-step mechanism, with N,N -dimethylcarbamic acid and ethylene as reaction intermediates. In the first step, the reaction proceeds via a six-membered cyclic transition state (TS), which is more favorable than that via a four-membered cyclic TS. Here, the contribution of entropy to the overall potential energy surface was found to play an important role in determining the rate-limiting step, which was found to be the second step when viewed in terms of the enthalpy of activation (,H,), but the first step when entropy changes (,T,S,) were considered. These results are consistent with experimental findings. Moreover, the experimental activation entropy can be reproduced by using the hindered rotor approximation, which converts some low vibration frequencies that correspond to internal rotational modes into hindered rotors. © 2006 Wiley Periodicals, Inc. J Comput Chem 28: 625,631, 2007 [source] Multirotations of (Anilinium)([18]Crown-6) Supramolecular Cation Structure in Magnetic Salt of [Ni(dmit)2],CHEMISTRY - AN ASIAN JOURNAL, Issue 9 2007Sadafumi Nishihara Dr. Abstract A solid-state dynamic supramolecular structure consisting of (anilinium)([18]crown-6) was arranged as the cation in a salt of [Ni(dmit)2], (dmit=2-thioxo-1,3-dithiole-4,5-dithiolate). With the ammonium moiety of anilinium located within the cavity of [18]crown-6, a hydrogen-bonded supramolecular structure is formed, with an orthogonal arrangement between the ,,plane of anilinium and the mean O6 plane of [18]crown-6. In this supramolecular cation, both anilinium and [18]crown-6 act as dynamic units with different rotational modes in the solid state. The uniform stacks of cations form an antiparallel arrangement, thus producing a layer structure. Sufficient space for the 180° flip-flop motion of the phenyl ring and the rotation of [18]crown-6 was observed in the cation layer. Thermally activated 180° flip-flop motions, with a frequency of 6,MHz at room temperature and an activation energy of 31,kJ,mol,1, were confirmed by temperature-dependent 2H,NMR spectra of ([D5]anilinium)-([18]crown-6)[Ni(dmit)2]. A double-minimum potential for the molecular rotation of anilinium, with a barrier of approximately 40,kJ,mol,1, was indicated by ab,initio calculations. The wide-line 1H,NMR spectra indicated a thermally activated rotation of [18]crown-6 at temperatures above 250,K. Therefore, multiple molecular motions of the 180° flip-flop motion of the phenyl ring and the rotation of [18]crown-6 occur simultaneously in the solid state. The temperature-dependent dielectric constants revealed that the molecular motion of [18]crown-6, other than the flip-flop motion, dominates the dielectric response in the measured temperature and frequency range. [source] | ||||||||||