最新刊期
卷 0 ， 期 0 ， 2020
- 摘要：The geogas prospecting technique is a new method for finding concealed deposits by means of collecting and analysing trace-elements in ascending gas from underground. The experimental results of employing this method based on INAA at the Shuangliu-Chengdu-Deyang concealed fault zone are presented. Geogas anomalies are found almost on the top of the fault and the element combination may be some trace elements and petrogenic elements, such as W, Sb, La, Sm, Co, K, Na etc.关键词：Geogas prospecting technique;Concealed fault zone;INAA
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发布时间：2021-04-09 - 摘要：Crystal ultrafine particle （CUFP） films of the Fe-B alloys were prepared by the quick-cooling vapour-deposition method, and then studied by the positron annihilation technique. Results from the positron annihilation lifetime spectra agree with the three-state annihilation mode of positrons, The two-phase core-shell structure of CUFP of Fe-B alloy are determined, and it is inferred that the CUFP film possesses three-phase microstructure.关键词：Crystal ultrafine particle;Positron annihilation;Microstructure
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发布时间：2021-04-09 - 摘要：The percentage of living cells, division index and micronuclei frequency wereused to measure the biological effects of hepatoma SMMC-7721 cells irradiated withγ-rays. It is round that the living percentage is decreased significantly and themicronuclei frequency is increased with increasing dose. There is a negativecorrelation between the living percentage and the repair time for 0.68Gy, 6.8Gy and136Gy irradiation, while there is a positive correlation between the micronucleifrequency and the repair time for 6.8Gy and 68Gy irradiation. The division indexesvary irregularly with the dose or the repair time after irradiation, probably due to thenon-synchronization of the cells.关键词：γ-rays;Hepatoma;Micronuclei frequency;Percentage of living cells;Division index
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发布时间：2021-04-09 - 摘要：A delayed coincidence timing system consisting of two BaF2 scintillation detectors and a HPGe detector and operating in fast-slow coincidence mode has been set up.It is suitable for the measurement of lifetime in the ns and ps range for nuclear levels populated by EC decay and E0 transitions. The fast coincidences involve characteristic X-rays and cascade γ rays coming from correlated levels. The system has the advantage of both element and cascade choices. Radioactive isotope 152Eu has been measured, The half-lives of 1.395± 0.035 ns and 48± 10 ps are observed for 121.78keV and 366.48keV levels respectively. These results show that the system can be used for the elements of Z≥62 with EC decays.关键词：Electron capture decay;Triplle coincidence;Halft-life
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发布时间：2021-04-09 - 摘要：The "national target" of nuclear technique （NT）, as an applied fundamental research, should be located at the place indicated by President Jiang Zemin’s remark “fundamental research should supply the motive power and the achievement reserves for the economic development in the future” at the National Conference on Science and Technology. According to the requirements of the social economy growth for NT and the further advance （the inherent laws） of NT itself,the research of NT should be focused on the interface between NT and other disciplines in the domain of science. As NT is mingled with other disciplines, it is important to put the emphases on the deeper level and select the hot points of the disciplines. A strategic foresight for the long-term development is also essential. Another important thing is to establish a mechanism of the venture capital tallying with markets to promote the transformation of the achievement of NT into products.关键词：Nuclear technique;National target;Discipline interface;Transformation of science and technology to production;Venture capital
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发布时间：2021-04-09 - 摘要：Defects in electrodeposited nanocrystalline Ni and the effect of hydrogen on the positron lifetime have been studied by the positron annihilation technique. There exist three kinds of defects at the interface, i. e. the free volumes with a monovacancy, a cluster of 6-10 vacancies and a micro-void, respectively. It is found that the moderate and longest lifetimes will not be affected when the nano-Ni is annealed at 500℃ in vacuum for 2h, which suggests that the defects related to these lifetimes show surprisingly great thermal stability.关键词：Positron annihilation;Electrodeposited nano-Ni;Micro-defect
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发布时间：2021-04-09 - 摘要：A preconcentration-NAA method of measuring Y and all REEs in La series is described. The REE samples were melten with Na2O2 and interference elements were separated by ion exchange, PMBP extraction, formic acid antiextraction, etc. The determination of REEs was then completed by NAA on a miniatute reactor as neutron source. The whole 15 REEs including Y can be analysed by this method. In addition to higher precision （RSD<5%） and lower detection limits （10-6-10-8）, the accuracies for REE determination are greatly improved.关键词：PNAA;Mini-reactor;Yttrium;REE;Geological samples
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发布时间：2021-04-09 - 摘要：The surface reactions of metal uranium with CO at 25℃ and 200℃ have been studied by the X-ray photoelectron spectroscopy （XPS）. Adsorption of CO on the surface oxide layer will result in the U4f peak shifting to lower binding energy and the decreasing of oxygen content in surface oxides. The O/U ratio is decreased with increasing the exposure of CO to the surface layer. The investigation indicates that the CO atmosphere can suppress further oxidation on the surface of metal uranium.关键词：Uranium;Carbon monoxide;X-ray photoelectron spectroscopy
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发布时间：2021-04-09 - 摘要：Carbon nanotubes, prepared by using arc-discharge technique, were irradiated by 20MeV protons. By observing the irradiated samples with high-resolution transmission electron microscopy （TEM）, nanotube bundles were discovered. TheTEM image of three adjacent nanotubes jointed together shows that Van der Waals forces among adjacent nanotubes can deform them substantially, destroying the cylindrical symmetry,关键词：Carbon nanotube;Compress deformation;Irradiation
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发布时间：2021-04-09 - 摘要：Presented are the physical design, structure, fabrication and test result of the 476MHz subharmonic buncher, which is equipped on the high brightness injector of the Shanghai Free Electron Laser User Facility, The measurement results of the buncher are in good agreement with the design values.关键词：Subharmonic buncher;Resonator;External loading
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发布时间：2021-04-09 - 摘要：The recovery behavior of quenched-in defects in TiAl and Ti3Al alloys has been studied by the positron annihilation technique. It is shown that in a fully annealed sample there exists a certain number of grain boundaries in TiA1 alloy, and during quenching from high temperature, quite a lot of secondary defects such as vacancy clusters and vacancy-impurity complexes are produced. Because of the decomposition and transportation of defect complexes, the vacancy clusters aggregate further in the range of 300 to 600℃关键词：TiAl;Quenched-in defects;Isochronal annealing;Positron lifetime
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发布时间：2021-04-09 - 摘要：A fast-beam laser spectroscopy （FBLS） method, based on the relation between the resonant optical transition of ions and the ion energy through the Doppler effect has been suggested for measuring ion energy and the experimental details are described. The method can he applied in the energy range of leV-100MeV, and its accuracy is better than 2×10-3. The measurement of 144Nd+ -ion energy by this method is reported.关键词：Ion energy;Optical resonance;Collinear fast-beam laser spectroscopy
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发布时间：2021-04-09 - 摘要：Radiation effect in α-Al2O3 irradiated by neutrons （En≥1MeV） up to a fluence of 3×10￣20/cm2 has been studied by the positron annihilation lifetime technique. The voids of 0.7 nm were found in the irradiated α-Al2O3 after annealing at 850℃.关键词：α-Al2O3;Void;Positron annihilation;Positronium
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发布时间：2021-04-09 - 摘要：The metal hydrides Pd0.75 Ag0.25Hx and NbHx with hydrogen concentration x from 0 to 0.86 have been investigated by the positron annihilation method at temperatures from 77K to 300K. The experimental results are presented.关键词：Metal hydrides;Pd0.75Ag0.25Hx;NbHx;Positron annihilation
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发布时间：2021-04-09 - 摘要：The high molecular weight polystyrenes are synthesized by use of diethyl 2,3-dicyano-2,3 di（p-X substituted phenyl） succinate （X=H, CH3, C1） initiators. The influence of different initiators on the positron annihilation spectra are studied by comparing polystyrectes’ molecular weight and free volume. The results indicate that the decomposition rate of initiator has effect on free volume, but initiator’s density has no great effect on free volume.关键词：Initiators;Superhigh molecular weight polystyrenes;Positron lifetime spectra;Free volume
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发布时间：2021-04-09
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