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81.
82.
83.
Krishna Kumar V Nagalakshmi R 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,66(4-5):924-934
8-hydroxyquinolinium picrate (8-HQP) was synthesized by the addition of equimolar quantities of 8-hydroxyquinoline (8-HQ) and picric acid (PA). Single crystals were grown from N,N dimethyl formamide (DMF) by restricted evaporation method at room temperature. The solubility of 8-HQP was determined in different solvents at various temperatures. The structural characterization of the grown crystals was carried out by X-ray diffraction. Vibrational modes were classified on the basis of group theoretical analysis and the spectral bands were compared with those of parent compounds in order to propose a tentative assignment by recording FT-IR, FT-Raman and polarized Raman spectra in different crystal orientations. The crystal possess lower cut-off at 230 nm and good transparency as confirmed by optical transmittance studies. 相似文献
84.
A shape selection method corresponding to an energy discrimination was used to eliminate unwanted events disturbing evaluation of CR-39 detectors in detecting tracks induced by particles both of perpendicular and oblique incidence. The angular dependence of the response was examined, detecting fast neutrons from 252Cf with shape selection technique at various angles and distances. Also, the CR-39 track detectors with the 252Cf source were exposed to high γ-intensity of a 60Co irradiation facility in the range 0.1 to 4.5 kGy, similar to the exposures inside spent fuel assemblies. Using the two functions the lower limit of burnup could be determined by the method. 相似文献
85.
Monitoring neutrons from spent reactor fuel by bubble detectors 总被引:1,自引:0,他引:1
In order to eliminate the strong temperature-dependence of bubble detectors used for spent fuel assay, a simple way could be to keep them in the water pond but far from fuel assemblies before exposure for about 20 min, until the detectors warm up. Fast neutrons from fuel assemblies in the Paks Nuclear Power Plant, Hungary, were detected by BD-100R type detectors at 28°C (in winter) and at 35°C in summer). Calibration was performed by a standard 252Cf source in borated water. Burnup monitoring inside fuel assemblies can be provided by smaller diameter detectors prepared from BD-100R type ones. 相似文献
86.
The product of an axialvector and a scalar current and its relation to the chiral-odd distribution function h
1 is discussed in the framework of the renormalon approach. Using a bag-model calculation for h
1, we calculate its intrinsic uncertainty due to renormalon poles. The result is given as a function of Bjorken-x as well as for the first moments separately.
Received: 9 November 1998 / Revised version: 22 January 1999 相似文献
87.
On the basis of the experimental data on diffractive processes in πp, pp and pˉp collisions at intermediate, moderately high and high energies, we restore the scattering amplitude related to the t-channel exchange by vacuum quantum numbers by taking account of the diffractive s-channel rescatterings. At intermediate and moderately high energies, the t-channel exchange amplitude turns, with a good accuracy, into an effective pomeron which renders the results of the additive
quark model. At superhigh energies the scattering amplitude provides a Froissart-type behaviour, with an asymptotic universality
of cross sections such as σtot
πp/σtot
pp→ 1 at s→∞. The quark structure of hadrons being taken into account at the level of constituent quarks, the cross sections of pion
and proton (antiproton) in the impact parameter space of quarks, σπ(r
1⊥, r
2⊥; s) and σp(r
1⊥, r
2⊥, r
3⊥; s), are found as functions of s. These cross sections implicate the phenomenon of colour screening: they tend to zero at |r
i⊥−r
k⊥|→ 0. The effective colour screening radius for pion (proton) is found for different s. The predictions for the diffractive cross sections at superhigh energies are presented.
Received: 15 December 1998 相似文献
88.
K. Matan J.S. Helton D. Grohol D.G. Nocera S. Wakimoto K. Kakurai Y.S. Lee 《Physica B: Condensed Matter》2009,404(17):2529
We report polarized neutron scattering studies of spin-wave excitations and spin fluctuations in the lattice antiferromagnet KFe3(OH)6(SO4)2 (jarosite). Inelastic polarized neutron scattering measurements at 10 K on a single crystal sample reveal two spin gaps, associated with in-plane and out-of-plane excitations. The polarization analysis of quasi-elastic scattering at 67 K shows in-plane spin fluctuations with XY symmetry, consistent with the disappearance of the in-plane gap above the Néel temperature . Our results suggest that jarosite is a promising candidate for studying the 2D XY universality class in magnetic systems. 相似文献
89.
S. Boag E. Babcock K.H. Andersen M. Becker T.R. Charlton W.C. Chen R.M. Dalgliesh S.D. Elmore C.D. Frost T.R. Gentile R. Lopez Anton S.R. Parnell A.K. Petoukhov M.W.A. Skoda T. Soldner 《Physica B: Condensed Matter》2009,404(17):2659-2662
We discuss the development and characterisation of a new in situ spin exchange optical pumping (SEOP) based 3He neutron spin filter polarisation device. We present results from a recent test of the prototype system developed with the Institut Laue-Langevin. The polariser was installed on the polarised reflectometer CRISP at ISIS in the analyser position. The 3He was pumped continuously in situ on the beamline. The system also integrated a 3He adiabatic fast passage spin flipper that allowed reversal of the 3He and therefore neutron polarisation state, allowing for measurement of all four polarisation cross-sections. The system was run for a number of days reaching a 3He polarisation of 63%. 相似文献
90.
We modulated the intensity of a neutron beam using Larmor precession techniques. We simulated triangular coils by using magnetised foils in electromagnets with rectangular pole shoes. Reversing the orientation of two of the magnetised foils in the spin-echo small-angle neutron scattering (SESANS)-instrument in Delft and changing the field settings was sufficient to obtain a modulation with a period in the order of 1 mm. We expect to be able to go to a modulation with a period of .This technique can be used to measure small-angle neutron scattering, analogous to the method used in SESANS, but with the advantage that all the manipulation of the neutron spin occurs before the sample. This means that the technique is insensitive to magnetic perturbations at the sample position. By positioning several of these devices after each other it will be possible to obtain a sharper modulation, or a modulation in two directions. 相似文献