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61.
F. M. Karawajew A. F. Dričko H. Greupner K.-H. Sucker 《Isotopes in environmental and health studies》2013,49(11):396-399
In der Arbeit wird über eine Empfehlung zur Methodik der Weitergabe der Aktivitätseinheit für umschlossene γ-Strahlungsquellen von den Normalen der metrologischen Slaatsämter der UdSSR (WNIIM) und der DDR (ASMW) an Normale niederer Ordnung berichtet. Die Weitergabe der Aktivitätseinheit geschieht durch Vergleich mittels Ionisationskammern. Die Empfehlung bezieht sich auch auf solche Fälle, in denen neben dem Hauptnuklid ein Verunreinigungsnuklid in der Quelle enthalten ist, sowie auf solche, bei denen unterschiedlicher Aufbau der zu vergleichenden Quellen vorliegt. Auβerdem umfaβt die Empfehlung die Methode der Fehlerrechnung. 相似文献
62.
Iodine and tellurium isotopes produced in the fission of 232Th with 30.5 MeV alpha particles were separated using a method of sublimation in an air stream and the independent yields of 130I, 131I, 132m,gI, 133I 134I, 134m,gTe, 133mTe and 134Te (cumulative) were determined by means of high resolution Ge(Li) γ-ray spectrometry. A Gaussian fit to the experimental data was used to obtain the width parameter σz and the most probable charge Zp of the nuclear charge distribution in the isobaric chains 130 – 131. The most probable masses for fission fragments with Z = 52 and Z = 53 were also deduced from the measured fission yields. 相似文献
63.
The ultrasonic velocity of the alkali-borosilicate with different transition metal oxides (TMO) has been studied using the pulse echo technique. The elastic moduli such as elastic constant and bulk modulus have been obtained from the experimental data. Changes in the structure with different gamma irradiation doses have been investigated by using FTIR spectroscopy and ultrasonic studies. The results show that structural changes in the BO3 to BO4 due to TMO and irradiation are obtained. 相似文献
64.
I. I. Bashter 《辐射效应与固体损伤》2013,168(3-4):351-364
Abstract The fast neutron and gamma ray spectra measured behind different thickness of steel scrap concrete with density of 4 g/cm3 have been studied. The mix proportions by weight of this type of concrete were 1 cement: 6.89 steel scrap: 2.9 sand and 0.5 Water. Comparison with a standard ordinary concrete of density 2.3 g/cm3 have been carried out. The measurements were made using a collimated beam of both gamma rays and neutrons emitted from one of the horizontal channel of the Egyptian Research Reactor-1. A fast neutron and gamma ray spectrometer with a stilbene crystal was used to measure the spectra of fast neutrons and gamma rays. Pulse shape discrimination using the zero cross over technique was used to separate the photon pulses from the electron pulses. The equation due to Schmidt has been modified and applied for determining the neutron effective removal cross sections (~R) for steel scrap, ordinary, hematite–serpentine, ilmenite–limonite and ilmenite concretes. This equation gives results which are in good agreement with the measured values. The derived empirical equation in a previous work to calculate the neutron integral flux behind different thicknesses of different types of concretes, gives good results for steel scrap concrete under investigation comparing with the corresponding experimental data. Total neutron macroscopic cross sections, linear attenuation coefficients for gamma rays and the half-value layers for both radiations at different energies have been obtained for steel scrap concrete and comparing with the corresponding values of ordinary concrete. The results show that steel scrap concrete is better than ordinary, hematite–serpentine, ilmenite–limonite and ilmenite concretes from the radiation shielding point of view. 相似文献
65.
F. P. Heßberger 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(1):33-37
Isotopes of elements up to Z = 113 have been synthesized
using medium heavy projectiles and target nuclei around doubly
magic 208Pb. Synthesis of still heavier elements in reactions
of 48Ca projectiles with actinide target nuclei has been
reported. To obtain more information about production mechanism of
transfermium isotopes nuclear reaction studies including
investigations of massive transfer were resumed at SHIP, GSI.
Nuclear structure investigations at SHIP have been concentrated so
far mainly on systematic investigations of low lying Nilsson
levels in odd-mass nuclei. Recently this field has been extended
to decay studies of isomeric states in nobelium nuclei at E* > 1 MeV. 相似文献
66.
探索原子核的壳层演化,验证奇特核的幻数结构是香港大学核物理研究的重要方向。目前,科研团队利用在束伽玛谱学技术已经研究了30Ne的N=20幻数消失和78Ni(Z=28,N=50)附近原子核的双幻数结构,而即将开展的53,56Ca在束伽玛谱学实验会对新幻数N=34的定量研究,以及到N=40核的壳层演化提供重要的数据。下一步的研究目标是探索100Sn(N=Z=50)的奇特结构,特别是研究它的第一个2+激发态与其邻近原子核的低激发态性质。100Sn处于质子滴线以及核天体快质子俘获路径上,因此,它的幻数结构及其临近原子核单粒子性能研究将会极大增强对核力和核合成机制的认识。为了进一步提高物理实验统计,香港大学在数量上增加了30% NaI(Tl)晶体从而全面升级了DALI2伽玛探测阵列。此外,为了探索远离稳定线核区的新物理,开展更高精度在束伽玛谱学实验,香港大学与中国科学院近代物理研究所、中国原子能科学研究院计划合作研制基于溴化镧晶体的新一代伽玛探测器阵列。这套阵列主要在兰州重离子加速器(HIRFL)和将来建成的强流重离子加速器(HIAF)等大科学装置上开展实验,从而在奇特核研究方面取得大量重要的成果,促进科研人员全面认识、理解核力以及天体核合成过程。Exploring the evolution of shell closures and examining the magicity of extremely exotic nuclei are the main research interests of HKU (University of Hong Kong) experimental nuclear physics group. The group has employed in-beam gamma-ray spectroscopy technique to investigate the vanishing of N=20 magicity in 30Ne (N=20) and the strong magicity in nuclei around 78Ni (Z=28, N=50). The approved future's experiment on spectroscopy of 53,56Ca, proposed by HKU, will give quantitative information for the "magic index" of N=34 and shell evolution toward N=40. The next goal is to investigate the structure of 100Sn (N=Z=50), particularly the energy of the first 2+ state, and the low-lying states in the neighboring nuclei. 100Sn lies on the proton drip-line and on the astrophysical rp-process path. Characterizing the magicity of 100Sn and the nature of single-particle states in its neighboring nuclei is therefore essential to the fundamental understanding of nuclear forces and nucleo-synthesis. To significantly increase the data statistics for our physics goals, HKU group has prepared the upgrade of gamma-ray spectrometer DALI2 with 30% more NaI(Tl) detectors integrated into a new array configuration. On the other hand, next significant insights into the structure of nuclei would require new gamma-ray detection array capable for higher precision gamma-ray spectroscopy. HKU group in collaboration with IMP and CIAE therefore proposes to construct a new-generation gamma-ray detection array based on the novel scintillator LaBr3(Ce) to explore the new physics in nuclei far from the valley of stability. Utilizing the radioactive beams at the Chinese large-scale facilities such as the Heavy Ion Research Facility in Lanzhou (HIRFL) in IMP and the future's High Intensity heavy-ion Accelerator Facility (HIAF), this novel LaBr3(Ce) array would lead to a significant boost to the frontiers of exotic-nuclei research, which will guide scientists towards the comprehensive and even beyond-traditional understanding of nuclear forces and nucleosynthesis. 相似文献
67.
Ganesh Prasad Yogesh Prasad G. S. Gusain Manjari Badoni J. M. S. Rana R. C. Ramola 《Indian Journal of Physics》2009,83(6):887-892
Radon was measured in soil-gas and groundwater in the Budhakedar area of Tehri Garhwal, India in summer and winter to obtain
the seasonal variation and its correlation with radon exhalation rate. The environmental surface gamma dose rate was also
measured in the same area. The radon exhalation rate in the soil sample collected from different geological unit of Budhakedar
area was measured using plastic track detector (LR-115 type II) technique. The variation in the radon concentration in soil-gas
was found to vary from 1098 to 31,776 Bq.m−3 with an average of 7456 Bq.m−3 in summer season and 3501 to 42883 Bq.m−3 with an average of 17148 Bq.m−3 in winter season. In groundwater, it was found to vary from 8 to 3047 Bq.l−1 with an average value 510 Bq.l−1 in summer and 26 to 2311 Bq.l−1 with an average value 433 Bq.L−1 in winter. Surface gamma dose rate in the study area varied from 32.4 to 83.6 μR.h−1 with an overall mean of 58.7 μ-R.h−1 in summer and 34.6 to 79.3 μR.h−1 with an average value 58.2 μR.h−1 in winter. Radon exhalation rate from collected soil samples was found to vary from 0.1 × 10−5 to 5.7 × 10−5 Bq.kg−1.h−1 with an average of 1.5 × 10−5 Bq.kg−1.h−1 in summer season and 1.7 × 10−5 to 9.6 × 10−5 Bq.kg−1.h−1 with an average of 5.5 × 10−5 Bq.kg−1.h−1. A weak negative correlation was observed between radon exhalation rate from soil and radon concentration in the soil. Radon
exhalation rate from the soil was also not found to be correlated with the gamma dose rate, while it shows a positive correlation
with radon concentration in water in summer season. Inter-correlations among various parameters are discussed in detail.
相似文献
68.
The triggering of long-lived isomeric nuclei by non-radiative excitation to a relatively short-lived mediating state is considered.
Coulomb triggering in inelastic scattering of heavy ions, a transfer of triggering energy from resonant electron transitions
of atomic shell (NEET) and triggering by capture of a free electron into a bound atomic state (NEEC) are discussed. Cross
sections for the above processes of non-radiative triggering are presented and the relative efficiencies of these different
triggering mechanisms are discussed. Numerical estimates are presented for the selected isomers.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
69.
Amogh Deshpande Srikanth K. Iyer 《Central European Journal of Operations Research》2009,17(2):219-228
We consider an enhancement of the credit risk+ model to incorporate correlations between sectors. We model the sector default rates as linear combinations of a common set
of independent variables that represent macro-economic variables or risk factors. We also derive the formula for exact VaR contributions at the obligor level. 相似文献
70.
The space of obstacles (i.e. p-quasi upper semicontinuous functions) is endowed with a distance which is topologically equivalent to the -convergence. We find the metric completion of this space and we give some application for minimization problems of cost functionals depending on obstacles via their level sets. An element of the completion is a decreasing and
p
-continuous on the left mapping Rt
t
, where
t
are positive Borel measures vanishing on sets of zero p-capacity. 相似文献