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991.
Preparation and heat transfer properties of nanoparticle-in-transformer oil dispersions as advanced energy-efficient coolants 总被引:1,自引:0,他引:1
Three kinds of nanofluids are prepared by dispersing Al2O3 and AlN nanoparticles-in-transformer oil. The thermal conductivity of the nanoparticle–oil mixtures increases with particle volume fraction and thermal conductivity of the solid particle itself. The AlN nanoparticles at a volume fraction of 0.5% can increase the thermal conductivity of the transformer oil by 8% and the overall heat transfer coefficient by 20%. From the natural convection test using a prototype transformer, the cooling effect of Al2O3/AlN-oil nanofluids on the heating element and oil itself is confirmed. However, the excess quantity of surfactant has a harmful effect on viscosity, thermal property, chemical stability, and thus it is strongly recommended to control the addition of the surfactant with great care. 相似文献
992.
On the basis of high pressure diamond-anvil compression studies for the precious metals Ru, Ir, and Os we report the surprising discovery that metallic osmium has a lower compressibility than covalently bonded diamond. We also find that Ir and Ru are as incompressible as Re. In addition, we have performed first principles calculations that confirm the trend in the measured transition metal compressibilities. 相似文献
993.
We give a simple unified proof and an extension of some of the characterization theorems of classical orthogonal polynomials of Jacobi, Bessel, Laguerre, and Hermite. In particular, we prove that the only orthogonal polynomials whose derivatives form a weak orthogonal polynomial set are the classical orthogonal polynomials. 相似文献
994.
A high-performance liquid chromatographic method is developed for use in the electrospray mass spectrometric (MS)-MS analysis of alkaloids contained in Cephalotaxus harringtonia leaves. Nine alkaloids having ester groups can be separated and detected with good sensitivity. The MS and MS-MS spectra obtained provides information on their chemical structures. Supercritical fluid extraction is also applied in order to improve the extraction efficiency of Cephalotaxus alkaloids such as cephalotaxine, harringtonine, homoharringtonine, and isoharringtonine. When carbon dioxide-methanol-water (80:18:2, v/v) is used the extraction yield is found to be higher than that using the other supercritical solvents evaluated and conventional organic solvent extraction. 相似文献
995.
An efficient synthesis of a configurationally stable l-serinal derivative 8 was achieved using an N-hydroxymethyl group in about 50% overall yield in four steps from l-serine. Not more than 1% racemization was observed during the preparation of 8. Its enantiomeric integrity was maintained for at least 15 days at room temperature, and it was stable on silica gel. The orthogonal protective groups of 8 would make it a useful chiral synthon. 相似文献
996.
Newkome GR Yoo KS Kim HJ Moorefield CN 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(14):3367-3374
Routes for the syntheses of isomeric, zwitterionic, bisterpyridine-Ru(II)-based macromolecules are described. Access to these novel architectures is facilitated by the construction of terpyridine-modified, 1-->3 C-branched, ester-terminated building blocks. Constitutional isomers result from the interchangable placement of methyl and tert-butyl ester groups on both the branched framework near the Ru(II) centers and the termini of the branched construct. Water solubility is imparted to each isomer through selective transformation of the tert-butyl esters to their corresponding carboxylates. Along with the standard characterization techniques, electrochemical and spectroscopic data also support the structural formation. 相似文献
997.
Synthesis and physical properties of novel multibranched two-photon materials are reported. The compound with three units of 4-(p-diphenylaminostyryl)-2,5-dicyanostyryl moieties attached to the central triphenylamine core exhibits a very large two-photon absorption cross-section. 相似文献
998.
Dong-Wan Tcha Hyung-Bong Ro Chun-Beon Yoo 《The Journal of the Operational Research Society》1988,39(9):873-878
This paper presents a heuristic method for solving the uncapacitated facility-location problem (UFLP), which is similar to Erlenkotter's ‘dual ascent’ procedure. The heuristic is of the ‘add’ type, which progressively selects facilities to open according to a certain criterion derived from the analysis of the linear programming dual. Computational experience with both (static) UFLPs and dynamic UFLPs reveals that the heuristic method yields solutions in most cases superior in quality to those achieved by the dual-ascent procedure, with barely noticeable additional computation time. 相似文献
999.
Wan-Suk Yoo Jeong-Han Lee Su-Jin Park Jeong-Hyun Sohn Oleg Dmitrochenko Dmitri Pogorelov 《Nonlinear dynamics》2003,34(1-2):3-29
Many papers have studied computer-aided simulations of elastic bodies undergoing large deflections and large deformations. But there have not been many attempts to check the validity of the numerical formulations used in these studies. The main aim of this paper is to demonstrate the validity of one such numerical formulation, the absolute nodal coordinate formulation (ANCF), by comparing the results it generates with the results of real experiments. Large oscillations of a thin cantilever beam are studied in this paper to numerically model the beam, which also accounts for the effects of an attached end-point weight and damping forces. The experiments were carried out using a high-speed camera and a data acquisition system. 相似文献
1000.
P. Allenspach B. W. Lee D. A. Gajewski V. B. Barbeta M. B. Maple G. Nieva S. -I. Yoo M. J. Kramer R. W. McCallum L. Ben-Dor 《Zeitschrift für Physik B Condensed Matter》1995,96(4):455-464
Low temperature heat-capacity measurements have been performed to study the magnetic ordering in NdBa2Cu3O
x
and DyBa2Cu3O
x
. In order to investigate the type of ordering, magnetic fields up to 6 T and hydrostatic pressures up to 4.5 kbar were applied. While for NdBa2Cu3O
x
and DyBa2Cu3O
x
both the fully oxidized and the fully oxygen reduced samples display long rang antiferromagnetic ordering, only magnetic short range interaction could be found for samples in an intermediate range of oxygen concentration. For NdBa2Cu3O
x
, where superexchange is believed to be the dominant magnetic interaction,T
N
is three times higher in the sample withx=6.26 compared to the one withx=6.98. In contrast,T
N
of DyBa2Cu3O
x
is almost oxygen independent as expected for this mainly dipolar interacting system. 相似文献