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991.
In this paper we prove Gårding's inequality for linear differential operators in generalized divergence form which satisfy a generalized Ehrling inequality, an ellipticity condition and a condition on the coefficients. Using a compact imbedding between certain anisotropic Sobolev spaces we substitute the first condition (Ehrling's inequality) by a simple condition on a set of multi-indices. 相似文献
992.
We report the variation of the thermal diffusivity in the high temperature superconductor YBa2Cu3O7−δ below the transition temperature measured using photo-acoustic technique α is found to increase sharply belowT
c. Qualitative explanations are given. 相似文献
993.
We study the free energy of continuous spin-systems on Z
d
, in the framework of Laplace integrals and transfer operators. Under a weak coupling condition, we show that the free energy in the low-temperature limit is determined, up to an exponentially small error, by the restriction to a neighbourhood of global minima of the energy. We have results for some single- and double-well problems. 相似文献
994.
Reversed phase ion pair chromatography is a highly selective separation technique for the determination of free porphyrin carboxylic acids from human materials. Isocratic and gradient elution methods can be used to analyse porphyrin isomers and to establish porphyrin profiles for the biochemical diagnosis of porphyrias. Ion pair high performance liquid chromatography led to the discovery of the atypical isomers II and IV of uroporphyrin and coproporphyrin in human urine. Advantages and limitations of the ion pair technique are discussed. 相似文献
995.
The glass transition in Ge
x
Se1−x
) (0·1 ⩽x ⩽ 0·25) glasses has been investigated using the photoacoustic (PA) technique. It is found that the PA amplitude and phase
undergo anomalous changes at the glass transition temperatureT
g. The amplitude has critical minimum and phase has maximum values atT
g. The variation of the thermal diffusivity, determined by measuring the frequency dependence of the PA amplitude and phase,
with temperature shows sharp decrease near the glass transition temperature. The temperature dependence of the optical energy
gap also has been measured and it shows a decrease with temperature for all compositions, the rate of decrease being higher
for temperatures greater thanT
g. 相似文献
996.
We present an algorithm that solves a two-dimensional case of the following problem which arises in robotics: Given a body B, and a region bounded by a collection of “walls”, either find a continuous motion connecting two given positions and orientations of B during which B avoids collision with the walls, or else establish that no such motion exists. The algorithm is polynomial in the number of walls (O(n5) if n is the number of walls), but for typical wall configurations can run more efficiently. It is somewhat related to a technique outlined by Reif. 相似文献
997.
Zusammenfassung Die Pfropfung der Cellulose mit Styrol im Wege der Kettenübertragung wird bei Abwandlung der Menge des Initiators, der Konzentration des Monomeren, der Reaktionsdauer und der Reaktionstemperatur untersucht. Die Verwendung von anderen Initiatoren wie auch der Einsatz anderer Monomeren (Acrylnitril, Methylacrylat) werden einer kurzen Prüfung unterzogen.
Mit 2 Abbildungen
Herrn Prof. Dr.Anton v. Wacek zu seinem 70. Geburtstag gewidmet. 相似文献
Grafting of cellulose with styrene by means of chain transfer has been investigated by varying the amount of initiator, concentration of monomer, reaction time and temperature. The use of other initiators and other monomers (acrylonitrile, methylacrylate) has been tested.
Mit 2 Abbildungen
Herrn Prof. Dr.Anton v. Wacek zu seinem 70. Geburtstag gewidmet. 相似文献
998.
After a review of the two techniques based on sedimentation rate and equilibrium in binary medium, more recent methods involving the presence of a second non-macromolecular solute are described. Application of these methods to synthetic polymers is still rare but of increasing interest. The use of computers simplifies the exploitation of the measurements. 相似文献
999.
Jacob Palme 《BIT Numerical Mathematics》1968,8(3):203-209
The general purpose simulation language SIMULA is compared with the ordinary scientific programming language FORTRAN. A typical military simulation model is programmed in both SIMULA and FORTRAN.The SIMULA program is found to be 24% shorter than the FORTRAN version. The SIMULA version is also more straightforward and gives a better picture of the simulated model. On the other hand, execution time for production runs is 64% longer with SIMULA. Weighing pros and cons shows that SIMULA will be more and more profitable, with higher personnel costs and lower computer costs to be expected in the future. 相似文献
1000.
Our objective is to explain the phenomenon of permanent currents within the context of the Ginzburg-Landau model for superconductors. Using variational techniques we make a connection between the formation of permanent currents and the topology of the superconducting sample.Research supported in part by the Fund for the Promotion of Research at the Technion.Research supported in part by a grant from the National Science Foundation. 相似文献