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961.
N. X. Vinh 《Journal of Optimization Theory and Applications》1972,9(1):51-58
This paper examines the primer vector which governs optimal solutions for orbital transfer when the central force field has a more general form than the usual inverse-square-force law. Along a null-thrust are that connects two successive impulses, the two sets of state and adjoint equations are decoupled. This allows the reduction of the problem to the integration of a linear first-order differential equation, and hence the solution of the optimal coasting are in the most general central force field can be obtained by simple quadratures. Immediate applications of the results can be seen in solving problems of escape in the equatorial plane of an oblate planet, satellite swing by, or station keeping around Lagrangian points in the three-body problem.This work has been sponsored by the Air Force Office of Scientific Research, under Grant No. AF-AFOSR-71-2129. 相似文献
962.
963.
964.
The structure 2a proposed by Viscontini and Okada for the autoxidation product of 5-methyl-6,7-diphenyl-5,6,7,8-tetrahydropterin 1 was found to be incorrect. Alternative structures 3a, 3b were deduced from spectroscopic data. X-ray analysis of the acetyl derivative 8 proved the oxidation product to be 2-amino-8-methyl-4,9-dioxo-cis-6,7-diphenyl-6,7,8,9-tetrahydro-4H-pyrazino(1,2-a)-s-triazine 3a. The mechanism of the rearrangement may involve an intermediate 4a-peroxy-pterin. A similar rearrangement on peroxide-level was observed for the corresponding lumazine 14. 相似文献
965.
966.
J. P. Mariot P. Michaud S. Lauer D. Astruc A. X. Trautwein F. Varret 《Hyperfine Interactions》1983,14(4):333-346
A Mössbauer study of the title paramagnetic Fe(O) complex was carried out from 4.2 K to 250 K. The electric field gradient (EFG) tensor was found to be temperature independent in accordance with the well isolated nature of state3A2g. Measurements in an applied magnetic field of 6 T confirmed the paramagnetic nature (S=1) of the complex and showed the EFG tensor to be negative. From the thermal variation of the hyperfine field we determined the spin hamiltonian constant D=14 K and find the g-value to be close to the free electron value. Semi-empirical molecular orbital (MO) calculations were carried out with a modelized molecule of D6h symmetry; results are in good agreement with the experimental values (for both the electronic and magnetic properties). 相似文献
967.
A possible cooling of electrons at low temperatures is predicted from a newly-developed approach to steady-state nonlinear transport in the presence of an electric field. The lowering of the electron temperature below the lattice temperature occurs in low-impurity samples and at such a current density for which the average drift velocity of the carriers is near the sound speed. 相似文献
968.
W. Beusch E. Polgar D. Websdale K. Freudenreich F.X. Gentit P. Muhlemann J. Pernegr W. Wetzel P. Astbury J.G. Lee M. Letheren G. Bellini M. Di Corato F. Palombo P.G. Rancoita G. Vegni 《Physics letters. [Part B]》1975,55(1):97-100
In the reaction π? + A → π+π?π? + A at 15.1 GeV/c the coherently produced 3π mass spectrum has a broad peak around 1.1 GeV which consists mainly of a JP = 1+ state and of a smaller fraction of 0-. Comparing the observed dependence of the production of these diffractive states on the atomic weight A of the target nuclei with the optical model, we have studied the absorption of the produced states in nuclear matter. We have found the following values of the absorption cross-sections: σ2(0-) = 49?7+9 mb and σ2(1+) = 15.8?1.3+1.5 mb. 相似文献
969.
B. Pietrzyk R. Barate P. Bareyre P. Bonamy P. Borgeaud M. David F.X. Gentit G. Laurens Y. Lemoigne G. Villet S. Zaninotti P. Astbury A. Duane G.J. King B.C. Nandi R. Namjoshi D.M. Websdale J. Wiejak T. Marshall 《Physics letters. [Part B]》1982,113(1):105-112
A lepton-pair trigger was used to select a hadronic system in different flavour and colour states: properties of the transformation of this system into hadrons were measured in terms of charge flow, multiplicity distribution, and fragmentation function. It is observed that, while the effects of flavour are clearly seen, the colour degrees of freedom are not observed in the region of low pT. 相似文献
970.