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We report efficacious vibration damping of carbon black reinforced nitrile butadiene rubber-polyvinyl chloride blend (NVC) vulcanizates in a constrained layer damping (CLD) configuration. The objective is to compare numerical simulations using finite element method (FEM) and the widely used Ross-Kerwin-Ungar (RKU) model with the experimental results. NVC blend (50:50 by weight), was compounded with carbon black as reinforcing filler and vulcanized using a sulfur-based curative system. Significant reinforcement and toughening were observed for the carbon black reinforced vulcanizates compared to the pristine blend. The viscoelastic properties of the vulcanizates were assessed using dynamic mechanical analysis (DMA), exploring their behavior concerning temperature variations and different frequencies to generate the Prony series coefficients for input in FEM analysis. Vibration damping experiments were conducted using the Oberst beam method in a single cantilever mode, with steel as the vibrating substrate, aluminum as the constraining layer, and the NVC vulcanizates as viscoelastic materials (VEM). Numerical simulations were performed using FEM to analyze mode shapes and frequency response function (FRF), and the RKU model was employed to quantify CLD system loss factors (SLF). The salient finding of this study was the observed SLF values in the range of 0.08-0.20 in the frequency regime of 200-2000 Hz. These values qualify the studied material as effective VEMs for CLD treatment of structural vibrations. This study supports design optimization efforts in a wide range of engineering applications where effective vibration damping is critical. Highlights * Enhancement of NVC blend properties through carbon black reinforcement. * Detailed analysis of viscoelastic behavior using DMA. * Validation of findings through experimental modal analysis. * Promising results in terms of system loss factors for CLD applications. KEYWORDS carbon black, constrained layer damping, dynamic mechanical analysis, finite element method, PVC-NBR blend, Ross-Kerwin-Ungar model, 1 | INTRODUCTION The issue of uncontrolled mechanical vibration is prevalent in various domains, leading to the reduced operational efficiency of instruments and creating disturbances in the work environment. While [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2009.09.017 Byline: Christopher Lee (a), Stephen R. Lewis (b), Peter L. Read (c) Keywords: Venus Abstract: A condensing cloud parameterization is included in a super-rotating Venus General Circulation Model. A parameterization including condensation, evaporation and sedimentation of mono-modal sulfuric acid cloud particles is described. Saturation vapor pressure of sulfuric acid vapor is used to determine cloud formation through instantaneous condensation and destruction through evaporation, while pressure dependent viscosity of a carbon dioxide atmosphere is used to determine sedimentation rates assuming particles fall at their terminal Stokes velocity. Modifications are described to account for the large range of the Reynolds number seen in the Venus atmosphere. Two GCM experiments initialized with 10 ppm-equivalent of sulfuric acid are integrated for 30 Earth years and the results are discussed with reference to 'Y' shaped cloud structures observed on Venus. The GCM is able to produce an analog of the 'Y' shaped cloud structure through dynamical processes alone, with contributions from the mean westward wind, the equatorial Kelvin wave, and the mid-latitude/polar Mixed Rossby/Gravity waves. The cloud top height in the GCM decreases from equator to pole and latitudinal gradients of cloud top height are comparable to those observed by Pioneer Venus and Venus Express, and those produced in more complex microphysical models of the sulfur cycle on Venus. Differences between the modeled cloud structures and observations are described and dynamical explanations are suggested for the most prominent differences. Author Affiliation: (a) Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd., M/C 150-21, Pasadena, CA 91125, USA (b) Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes, UK (c) Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, UK Article History: Received 9 July 2009; Revised 9 September 2009; Accepted 28 September 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2008.02.010 Byline: N. Steiner (a), K. Denman (a)(b) Abstract: We have developed a marine DMS (dimethylsulfide) module and implemented it in a 1-D coupled atmosphere-ocean-biogeochemical model. In developing the marine sulphur model we have found that several parameters used in the model are not known to even an order of magnitude. Our approach is used to test the model's sensitivity to these parameters. A parameter change of [+ or -]25% is applied to test the respective range of changes in the DMS fluxes. The model is run for a 3-year time period as well as for the time period of the Subarctic Ecosystem Response to Iron Enrichment Study (SERIES) in July 2002. The simulated seasonal cycle is in agreement with available observations: Near surface DMS concentrations vary from 1.5nmolL.sup.-1 in winter to 13.5nmolL.sup.-1 in summer. Simulated DMS production is found to be most sensitive to variations of the S:N ratio and the bacterial consumption rate of DMS. Implementing light or UV limited bacterial activity shows a negligible effect in winter and increases DMS concentrations by 0.2-0.6nmolL.sup.-1 in summer. Similarly a yield increase under UV stress increases summer values by 1-2nmolL.sup.-1. The simulated diel cycle in surface DMS concentration is no more than 2.5nmolL.sup.-1, even when light-dependent changes in bacterial activity are considered. Simulating the DMS response to iron fertilization with the standard run leads to overestimation during an initial bloom of small phytoplankton. While implementing light-dependent bacterial activity has a minor effect, the implementation of yields that depend on nutrient availability significantly improves the results. The model confirms earlier results showing the importance of including atmospheric DMS concentrations in gas flux calculations when there are high surface concentrations and small atmospheric boundary layer heights. Simulated summer concentrations in the upper layer can be underestimated by 2nmolL.sup.-1 or more if the atmospheric concentration is set to zero. Our study shows that inclusion of mechanistic DMS modules in comprehensive climate models requires better knowledge of the variation of key parameters in the marine sulphur cycle. Even though there are still open questions, the model reasonably reproduces the mean annual cycle; and including variable DMS yield improves the simulation of the DMS response to iron fertilization during SERIES. Author Affiliation: (a) Environment Canada, Canadian Centre for Climate Modelling and Analysis, University of Victoria, P.O. Box 1700, Victoria, BC, Canada V8W 2Y2 (b) Fisheries and Oceans Canada, Institute of Ocean Sciences, Sidney, BC, Canada Article History: Received 1 August 2007; Revised 18 January 2008; Accepted 30 March 2008

Research describing the use of molecular modeling to devise a new catalytic process to isomerize pure trans isomer from cis isomer is presented. The use of hypervalent sulfur fluorides as the structural building blocks for organic materials which are functional is also discussed.