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排序方式: 共有48条查询结果,搜索用时 15 毫秒
1.
P. Spacu C. Gheorghiu M. Constantinescu I. Pascaru O. Contantinescu 《无机化学与普通化学杂志》1971,384(2):184-190
Copper(II) coordination compounds with p-chlorphenylbiguanide of the type: [Cu(Cl-PhBig)2]X2 and [Cu(Cl–PhBig)X2] with X =Cl?, Br? NO3, OH?, NCS?, NCO?, N3, have been studied by EPR spectroscopy using polycrytalline powders and solutions in DMF. The parameters of the EPR spectra have been used to estimate molecular orbital coefficient, in these compounds and to discuss details of the chemical bonding. 相似文献
2.
Cornelia Uncuta Teodor-Silviu Balaban Mircea D. Gheorghiu Ligia Stănescu Aurica Petride Alexandru T. Balaban 《Tetrahedron letters》1985,26(38):4673-4676
Two Isomeric pyridines were designed and prepared : 2-isopropyl-4,5,6-trimethyl-(3) and 2-isopropyl-3,4,6-trimethyl-pyridine (7); the latter, with a buttressed isopropyl, leads to much lower induced shifts by Eu(dpm)3 and Pr(dpm)3 than the former, owing to the conformation in which the Janus-type iPr group how to the LSR a t-butyl-like face. 相似文献
3.
The stereochemistry of the cyclobutanones 1-7, resulted from the reaction of t-butylcyanoketene with bicyclo[2.2.1]heptene, bicyclo[2.2.1]heptadiene, 1,4 - dihydro - 1,4 - methanonaphthalene, 1,4 - dihydro - 9 - (1 - methylethylidene) - 1,4 - methanonaphthalene, 1,4 - dihydro - 1,4 - epoxynaphthalene, l,4,4a,8b - tetrahydro - 1,4 - methanobiphenylene (l,4,4a,8b) and 1,4,4a,8b - tetrahydro - 1,4 - methanobiphenylene(1,4,4aβ,8bβ) was established as having the cyclobutanone ring exo and the t-Bu group in the configuration. These findings represent a stereochemical argument in favour of a π2s + π2a reaction mode of t-butylcyanoketene to the above mentioned bicyclo[2.2.1]heptene derivatives. Observations regarding preservation of the original configurations of alkenes as well as the geometrical distorsion of the cyclobutanones are shortly discussed. 相似文献
4.
A simple model is presented which interprets conductivity variations due to crystallization in amorphous layers and allows the determination of the growth rate of crystallization. The validity of this model is demonstrated in the case of germanium. 相似文献
5.
C. -I. Gheorghiu 《Physics of Particles and Nuclei Letters》2008,5(3):286-289
The paper considers two static problems from capillarity. The first one consists in the determination of the surface of a
liquid in a capillary tube and the second in the computation of the shape of a sessile or pendent drop of liquid of a given
volume, both configurations being considered in the gravitational field. From a mathematical point of view, both problems
are nonlinear two-point boundary value problems which include in their formulations additional geometrical unknowns, i.e.,
the so-called free boundary value problems. Computational, they are laborious problems owing to the fact that they involve
nonnormal Jacobian matrices. The resulting numerical difficulties are considerably reduced by treating these problems by a
collocation method in conjunction with the continuation with respect to the parameters. The method is implemented by the MATLAB
code bvp4c. The numerical evaluations of the free surfaces are in reasonable accordance with asymptotic estimations.
The text was submitted by the author in English. 相似文献
6.
7.
Résumé Les auteurs décrivent le dosage des acides gras extraits du sang, par oxydation en tube fermé à 200°C avec de l'acide iodique dissout dans l'acide sulfurique concentré.Après dilution on distille l'iode séparé, qu'on titre avec du thiosulfate n/25.
Summary An account is given of the determination of fatty acids isolated from blood. The oxidation is effected by means of potassium iodate dissolved in concentrated sulphuric acid, in a scaled tube at 200°.After dilution with water the liberated iodine is distilled off, and titrated with 0,04N-thiosulphate solution.
Zusammenfassung Es wird über die Bestimmung der aus dem Blute isolierten Fettsäuren berichtet. Die Oxydation erfolgt im geschlossenen Rohr bei 200° mit Hilfe von Jodsäure, die in konzentrierter Schwefelsäure gelöst ist.Nach Verdünnen mit Wasser destilliert man das ausgeschiedene Jod ab und titriert es mit1/25 n-Thiosulfatlösung.相似文献
8.
Mariana Cristea Daniela Gheorghiu Ionita Maria Bruma B. C. Simionescu 《Journal of Thermal Analysis and Calorimetry》2008,93(1):63-68
Two aromatic polyimides and the corresponding poly(amic acid)s, with oxadiazole and para/meta phenoxyphenylene rings in the backbone, were synthesized and the structure — thermal properties correlation was followed
by dynamic mechanical analysis. Concerning the poly(amic acid)s, the glass transition domain was emphasized only for the compound
with meta-oriented rings because the process of imidization takes place with increasing temperature. A multiplex experiment was performed
to calculate the activation energy of the transition localized under 200°C. Consecutive heating-cooling-heating cycles were
accomplished. All phenomena are discussed by cross-examination of the storage modulus (E′), loss modulus (E″) and loss factor tanδ variation with temperature. 相似文献
9.
I. Chiorean A. B. Németh C. I. Gheorghiu Mihai Putinar V. Kalashnikov 《Acta Appl Math》1994,35(3):299-302
10.
Călin-Ioan Gheorghiu 《Numerical Algorithms》2018,77(1):77-93
In this paper, we consider the numerical treatment of singular eigenvalue problems supplied with eigenparameter dependent boundary conditions using spectral methods. On the one hand, such boundary conditions hinder the construction of test and trial space functions which could incorporate them and thus providing well-conditioned Galerkin discretization matrices. On the other hand, they can generate surprising behavior of the eigenvectors hardly detected by analytic methods. These singular problems are often indirectly approximated by regular ones. We argue that spectral collocation as well as tau method offer remedies for the first two issues and provide direct and efficient treatment to such problems. On a finite domain, we consider the so-called Petterson-König’s rod eigenvalue problem and on the half line, we take into account the Charney’s baroclinic stability problem and the Fourier eigenvalue problem. One boundary condition in these problems depends on the eigenparameter and additionally, this also could depend on some physical parameters. The Chebyshev collocation based on both, square and rectangular differentiation and a Chebyshev tau method are used to discretize the first problem. All these schemes cast the problems into singular algebraic generalized eigenvalue ones which are solved by the QZ and/or Arnoldi algorithms as well as by some target oriented Jacobi-Davidson methods. Thus, the spurious eigenvalues are completely eliminated. The accuracy of square Chebyshev collocation is roughly estimated and its order of approximation with respect to the eigenvalue of interest is determined. For the problems defined on the half line, we make use of the Laguerre-Gauss-Radau collocation. The method proved to be reliable, accurate, and stable with respect to the order of approximation and the scaling parameter. 相似文献