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991.
Renfu Li George A. Kardomateas George J. Simitses 《International Journal of Solids and Structures》2009,46(10):2216-2223
This work analyzes the nonlinear impulse response of a composite sandwich plate exposed to a sudden point-wise transverse loading on the top face sheet. The nonlinearity arising from the core compressibility in the thickness direction is modeled and incorporated into the constitutive relations explicitly. As such, one can have a deep insight regarding the stress, strain and displacement profiles into the sandwich plate. The sandwich plate is assumed to be perfectly bonded at the face sheet/core interfaces. The equations of motion are formulated using Hamilton’s principle. The simply supported case is used to illustrate the procedure for solving the nonlinear equations. Numerical results are presented to demonstrate the response in terms of the transverse deformation and stresses in the composite sandwich plate. The effects of the variation of the geometrical parameters of the structure on the blast impulse response are also studied. Some conclusions are suggested regarding the associated optimal design of sandwich plates. 相似文献
992.
Dale Magnar Ekrann Steinar Mykkeltveit Johannes Virnovsky George 《Transport in Porous Media》1997,26(3):229-260
The paper presents an analytical construction of effective two-phase parameters for one-dimensional heterogeneous porous media, and studies their properties. We base the computation of effective parameters on analytical solutions for steady-state saturation distributions. Special care has to be taken with respect to saturation and pressure discontinuities at the interface between different rocks. The ensuing effective relative permeabilities and effective capillary pressure will be functions of rate, flow direction, fluid viscosities, and spatial scale of the heterogeneities.The applicability of the effective parameters in dynamic displacement situations is studied by comparing fine-gridded simulations in heterogeneous media with simulations in their homogeneous (effective) counterparts. Performance is quite satisfactory, even with strong fronts present. Also, we report computations studying the applicability of capillary limit parameters outside the strict limit. 相似文献
993.
A facile synthesis of aryl and heteroaryl iodides from water-soluble complexes of aryl- and heteroarylboronic acids has been developed. 相似文献
994.
995.
996.
In previous papers1,2, we reported our recent findings that chalcone (l,3-dipheny1-2-propen-1-one) derivatives are novel potential antimalarials that are active against chloroquine-resistant strains of Plasmodium falciparum. According to our structure-activity relationships (SAR) and computer modeling data1,2, we expect the chalcone derivatives with hydroxyl functionality on one of the aromatic rings and with some other appropriate substitutions on the other ring will be even more potent as a… 相似文献
997.
998.
Soo-Jin Park George G. Chase Kwang-Un Jeong Hak Yong Kim 《Journal of Sol-Gel Science and Technology》2010,54(2):188-194
Flexible mats of titania fibers are prepared by calcination of electrospun polyvinylpyrrolidone fibers containing titanium
isopropoxide precursor. Structural investigation of the calcinated nanofibers by X-ray diffraction (XRD) and electron diffraction
(ED) combined with the morphologies by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show
the titania fibers, with an average diameter of 180 nm, were comprised of anatase and rutile crystals. The mechanical, chemical
and thermal properties of the titania fiber mats are further investigated by the techniques of Instron mechanical tester,
thermogravimetric analyzer (TGA), and Fourier transform infrared spectroscopy (FT-IR). The titania fiber mat prepared in this
method exhibited a significant flexibility with 461 MPa Young’s modulus. 相似文献
999.
1000.
George C. Rhoderick 《Analytical and bioanalytical chemistry》2010,398(3):1417-1425
Studies of climate change increasingly recognize the diverse influences exerted by terpenes in the atmosphere, including roles
in particulates, ozone formation, and their oxidizing potential. Measurements of key terpenes suggest atmospheric concentrations
ranging from low pmol/mol (parts per trillion) to nmol/mol (parts per billion), depending on location and compound. To accurately
establish concentration trends, assess the role of terpenes in atmospheric chemistry, and relate measurement records from
many laboratories and researchers, it is essential to have good calibration standards. The feasibility of preparing well-characterized,
stable gas cylinder standards for terpenes at the nmol/mol level is not yet well established. Several of the world’s National
Metrology Institutes (NMIs) are researching the feasibility of developing primary and secondary reference gas standards at
the nmol/mol level for terpenes. The US NMI, the National Institute of Standards and Technology, has prepared several nmol/mol
mixtures, in treated aluminum gas cylinders, containing terpenes in dry nitrogen at nominal 5 nmol/mol for stability studies.
Overall, 11 terpenes were studied for stability. An initial gas mixture containing nine terpenes, one oxygenate, and six aromatic
compounds, including benzene as an internal standard, was prepared. Results for four of the nine terpenes in this initial
mixture indicate stability in these treated aluminum gas cylinders for over 6 months and project long term (years) stability.
Interesting results were seen for β-pinene, which when using a linear equation rate decline predicts that it will reach a
zero concentration level at day 416. At the same time, increases in α-pinene, d-limonene (R-(+)-limonene), and p-cymene were observed, including camphene, a terpene not prepared in the gas mixture, indicating a chemical transformation
of β-pinene to these species. Additional mixtures containing combination of either α-pinene, camphor, α-terpinene, and benzene
indicate a second-order quadratic rate decline for the α-pinene and α-terpinene, a linear rate decline for camphor, and a
second-order quadratic rate increase of camphene. 相似文献