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71.
A. V. Tarasov P. O. Yablonsky Yu. A. Moskvichev 《Chemistry of Heterocyclic Compounds》2003,39(1):119-122
Various methods were studied for the oxidation of 2-methyl-5-(phenylsulfonyl)benzenesulfamide and its derivatives. The oxidation by sodium dichromate in sulfuric acid was found most efficient. The effects of temperature, concentration, reagent ratio, and time of the oxidation reaction on the yield of the desired product were investigated. Conditions were proposed for obtaining the desired product in yields up to 95%. A synthesis was developed for a series of new saccharin derivatives. 相似文献
72.
We prove that, under the assumption of the Generalized Riemann Hypothesis, the exponent of the ideal class group of a CM-field
goes to infinity with its absolute discriminant. This gives a positive answer to a question raised by Louboutin and Okazaki
[4].
Received September 10, 2001; in revised form April 5, 2002 相似文献
73.
A computer search in the finite projective spaces PG(n, q) for the spectrum of possible sizes
k
of complete k-caps is done. Randomized greedy algorithms are applied. New upper bounds on the smallest size of a complete cap are given for many values of n
and q. Many new sizes of complete caps are obtained. 相似文献
74.
Three fixtures for conducting laboratory fretting fatigue tests are described and their respective testing methods and the
results of the analysis are compared. Each of these fixtures has been used to investigate the effects of various parameters
of interest in fretting fatigue. These fixtures include a unique apparatus in which all load applied to the specimen is transferred
to the fretting pads, an apparatus similar to many found in the literature where partial load transfer occurs across the pads,
and a simplified dovetail fixture in which the clamping load, P, and the shear load, Q, are varied in phase. Select test conditions from prior experiments performed on identical material and resulting in similar
lives ranging from one to ten million cycles from these fixtures are identified. The various testing conditions were used
to compute the unique stress field for each case. The resulting contact stresses were used to calculate crack initiation based
criteria, and to calculate stress intensity factors. The three fixtures were shown to be able to accommodate a range of loads,
fretting pad contours, and specimen geometries that produced a variety of stress fields. A crack-initiation-based criterion
was shown to predict the failure lives of thinner specimens accurately. The stress intensity factor calculations showed the
possibility of a crack arresting for a stress field that decays rapidly and the possibility of a local minimum for K as a function of depth. The fixtures are shown to be complementary in generating data for development of robust fretting
fatigue models that use these criteria. 相似文献
75.
Y. A. Abdu T. Ericsson H. Annersten 《Journal of magnetism and magnetic materials》2004,280(2-3):395-403
Fe–Ni alloys below the Invar region with compositions Fe100−xNix (x=21, 24, and 27 at%) were prepared by high-energy ball milling technique (mechanical alloying). The as-milled samples, characterized by X-ray diffraction and Mössbauer spectroscopy, contain a mixture of (BCC) and γ (FCC) phases, whereas the samples annealed at 650°C for 0.5 h show a single γ (FCC) phase displaying a single line Mössbauer spectrum at room temperature (RT). At low temperature, the Mössbauer spectra of annealed Fe76Ni24 and Fe73Ni27 alloys show the existence of a magnetically split pattern together with a broad singlet, which are ascribed to a high-moment ferromagnetic Ni-rich phase and a low-moment Fe-rich phase, respectively. The Fe-rich phase in annealed Fe76Ni24 alloy, which is paramagnetic at RT, undergoes antiferromagnetic ordering at 40 K, estimated from the dramatic line broadening of its spectrum, giving rise to a small hyperfine field (e.g. 2 T at 6 K). The coexistence of these phases is attributed to phase segregation occurring in these alloys as a result of enhanced atomic diffusion. The stability of these alloys towards martensitic (FCC→BCC) transformation at low temperatures is discussed in connection with the Fe–Ni phase diagram below 400°C. 相似文献
76.
77.
78.
We present two methods for the creation of two-particle entangled states of excitons in a coupled quantum dot system. The system contains two identical quantum dots that are coupled by an inter-dot hopping process. The manipulation of the system is succeeded by proper application of an external laser field. 相似文献
79.
In this paper, we prove some existence results for the Webster scalar curvature problem on the three dimensional CR compact manifolds locally conformally CR equivalent to the unit sphere S3 of C2. Our methods are based on the techniques related to the theory of critical points at infinity. 相似文献
80.