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11.
Z-configured 1,4-diene or β,γ-unsaturated carbonyl systems are readily available by the Wittig reaction. Isomerization required for access into the E-series can easily be accomplished by irradiation using an ordinary tungsten lamp and diphenyl disulphide sensitizer. There is very little formation of conjugated isomers (less than 1%). 相似文献
12.
13.
In the literature one basic work can be found that describes an attempt to verify the applicability of the orthotropic plate wave theory to paper. In the present study we have repeated the key experiment and also modified the original experimental set-up to be able to make new complementary measurements. The performed verification attempt is based on a key experiment in which an ultrasonic resonance method is used. When it is applied to paper, a second resonance can be observed in addition to the one that originates from the asymmetric A0 mode. The result of the verification experiment is conclusive only if the source of this second resonance is the symmetric S0 mode. Our results show that the second resonance is not generated by the S0 mode. Instead, they indicate that the source is a longitudinal wave propagating in the thickness direction of the paper. We therefore conclude that the applicability of the orthotropic plate wave theory to paper cannot be verified by performing the key experiment that is described in the literature. 相似文献
14.
Jorma Heikkinen 《Heat and Mass Transfer》2007,43(4):341-350
The fin efficiency in a heat exchanger element that is a simplification of one row in a tube-and-fin heat exchanger was theoretically
examined within wide ranges of the affecting variables: the conventional fin efficiency and the isothermal effectiveness of
the heat exchanger. These variables are suggested for use also in the further studies. An analytical solution can be found
for the case of a constant heat transfer coefficient. The ambient temperature variation alone decreases the fin efficiency
less than 4%. The local heat transfer coefficient obtained from the numerical fluid flow simulations is strongly affected
by the fin properties because the thermal boundary conditions for the fluid flow changes. On a poorly conducting fin surface
the heat transfer coefficient in front of the fin base is much larger than on an isothermal fin because the heat flux is increasing
in the flow direction. At low fin efficiencies this compensates for the decrease in fin efficiency due to ambient temperature
variation. 相似文献
15.
The C(21)-C(40) fragment of fibrinogen receptor inhibitor tetrafibricin was prepared in 12 steps from propane diol (longest linear sequence). In this approach, 6 C-C bonds are formed via asymmetric iridium catalyzed transfer hydrogenative carbonyl allylation and 2 C═C bonds are formed via Grubbs olefin cross-metathesis. 相似文献
16.
In this paper we derive the existence and comparison results for second order initial value problems in ordered Banach spaces. The considered problems can be implicit, singular, functional, discontinuous and nonlocal. The main tools are fixed point results in ordered spaces and the theory of locally HL integrable vector-valued functions. 相似文献
17.
The random waypoint model (RWP) is one of the most widely used mobility models in performance analysis of mobile wireless networks. In this paper we extend the previous work by deriving an analytical formula for the stationary distribution of a node moving according to a RWP model in n-dimensional space. 相似文献
18.
The kinetics of the reaction between CH3 and HCl was studied in a tubular reactor coupled to a photoionization mass spectrometer. Rate constants were measured as a function of temperature (296–495 K) and were fitted to an Arrhenius expression: k1 = 5.0(±0.7) × 10?13 exp{?1.4(±0.3) kcal mol?1/RT} cm3 molecule?1 s?1. This information was combined with known kinetic parameters of the reverse reaction to obtain Second Law determinations of the methyl radical heat of formation {34.7(±0.6) kcal mol?1} and entropy {46(±2) cal mol?1 K?1} at 298 K. Using the known entropy of CH3, a more accurate Third Law determination of the CH3 heat of formation at this temperature was also obtained {34.8(±0.3) kcal mol?1}. The values of k1 obtained in this study are between those reported in prior investigations. The results were also used to test the accuracy of the thermochemical information which can be obtained from kinetic studies of R + HX (X = Cl, Br, I) reactions of the type described here. 相似文献
19.
Solution of linear equations with Hankel and Toeplitz matrices 总被引:1,自引:0,他引:1
Jorma Rissanen 《Numerische Mathematik》1974,22(5):361-366
Summary An algorithm is described for solving a linear equationA x=c, whereA is ann×n Hankel or Toeplitz matrix, inO (n
2) arithmetic operations. As contrasted with earlier such algorithms the present one does not require the principal minors ofA to be non-zero except detA. 相似文献
20.
A. Passoja R. Julin J. Kantele J. Kumpulainen M. Luontama W. Trzaska 《Nuclear Physics A》1985,438(2):413-428
The E0 and E2 transitions depopulating the excited 0+ states in 64,66,68Zn are investigated. Several methods of γ-ray, conversion-electron and internal-pair spectrometry are employed, including a new time measurement technique. A total of 5 E0 transitions are observed and the monopole strengths ρ2(0i+ → 0i+) for most of them are extracted. The results and the nature of the excited 0+ states are discussed in terms of several nuclear models. 相似文献