排序方式: 共有12条查询结果,搜索用时 31 毫秒
1.
V. D. Ashitkov A. S. Barabash S. G. Belogurov G. Carugno S. I. Konovalov I. O. Pilugin G. Puglierin R. R. Saakyan V. N. Stekhanov V. I. Umatov I. A. Vanushin 《Nuclear Physics B - Proceedings Supplements》1999,70(1-3)
First two runs with 138.7 g of 100Mo were done 9202 h and 238 h). Limits on half-lives for 0ν- and 0νχ0-decays of 100Mo were obtained, > 2.3 · 1021 y and 0.8 · 1020 y, respectively at 90% CL. Also the limit on the content of radioactive 42Ar in the natural Ar was obtained, < 5 · 10−21 g/g. Perspectives for the future are discussed. 相似文献
2.
MF Miller IA Franchi AS Sexton CT Pillinger 《Rapid communications in mass spectrometry : RCM》1999,13(13):1211-1217
The use of infrared laser-assisted fluorination to release oxygen from milligram quantities of silicates or other oxide mineral grains is a well-established technique. However, relatively few studies have reported the optimisation of this procedure for oxygen-17 isotope measurements. We describe here details of an analytical system using infrared (10 μm) laser-assisted fluorination, in conjunction with a dual inlet mass spectrometer of high resolving power ( approximately 250) to provide (17)O and (18)O oxygen isotope measurements from 0.5-2 mg of silicates or other oxide mineral grains. Respective precisions (1) of typically 0.08 and 0.04 per thousand are obtained for the complete analytical procedure. Departures from the mass-dependent oxygen isotope fractionation line are quantified by Delta(17)O; our precision (1) of such measurements on individual samples is shown to be +/-0.024 per thousand. In turn, this permits the offset between parallel, mass-dependent fractionation lines to be characterised to substantially greater precision than has been possible hitherto. Application of this system to investigate the (17)O versus (18)O relationship for numerous terrestrial whole-rock and mineral samples, of diverse geological origins and age, indicates that the complete data set may be described by a single, mass-dependent fractionation line of slope 0.5244+/- 0.00038 (standard error). Copyright 1999 John Wiley & Sons, Ltd. 相似文献
3.
泥沙输运模拟综述——现状及其发展趋势 总被引:1,自引:0,他引:1
随着流体力学中数值方法的飞速发展,计算模型已经成为研究流体运动,泥沙输运和不同环境(诸如河流,湖泊及沿海地区)中相应污染物归趋过程等方面非常有吸引力的工具,在过去的30多年里,发展了许多计算水动力学/泥沙输运模型.文章追溯当前具有代表性的(一维、二维、三维)模型的发展历程,描述他们各自的特点,优势及局限,力图作为对模型方面感兴趣读者的第一指南,同时也为大家讨论模型的局限性,未来的发展趋势和研究需求方面搭建一个平台.给出了模型的表达,时空特性,水动力学和沉积物的耦合方式,处理非恒定流,推移质和悬移质,泥沙交换过程,泥沙类型(粘性或非粘性)及非均匀泥沙输运的能力.总结了不同模型的应用实例,读者可以运用这些例子作为研究模型设置,模型率定及模型验证的参考.给出了选择泥沙输运模型应遵循的原则,模型输入及率定方面存在的问题及改进的途径.探讨了现有水动力学/泥沙输运模型在处理复杂湍流,泥沙携带,流动与输沙耦合,非均匀泥沙,离散和扩散系数,河岸来沙处理等方面的局限性及改进的方向.最后,对基于多相流思想的泥沙输运模型及其它一些交叉性问题作了评述与展望. 相似文献
4.
J. Suhonen J. Toivanen A. S. Barabash I. A. Vanushin V. I. Umatov R. Gurriarán F. Hubert Ph. Hubert 《Zeitschrift für Physik A Hadrons and Nuclei》1997,358(3):297-301
We apply the self-consistent renormalized proton-neutron QRPA (RQRPA) method to calculate the two-neutrino double beta (2νββ) decay matrix elements associated with the ground-state and excited-state transitions of the 82Se → 82Kr decay. The RQRPA method is an extension of the pnQRPA method and promotes the Pauli exclusion principle violated by the pnQRPA ground state and yields more stable nuclear matrix elements with increasing strength of the proton-neutron interaction. In the present work the RQRPA wave functions are also used to evaluate 2νββ-decay rates to excited final states. The resulting theoretical half lives are compared with the new stringent experimental limits obtained by using a HPGe detector and external sources of enriched selenium. 相似文献
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6.
IA Simpson R Bol ID Bull RP Evershed K Petzke SJ Dockrill 《Rapid communications in mass spectrometry : RCM》1999,13(13):1315-1319
Compound specific stable isotope analyses of managed soils using isotope ratio mass spectrometry have been undertaken as a means of determining early land use practices. delta (15)N amino acid signals demonstrate differences between manured grassland, unmanured grassland and continuous cereal cultivation under long-term experimental land use control conditions, with delta (15)N in hydrophobic amino acids providing the most distinctive signals. Analysis of early modern/medieval and of Bronze age anthropogenic soils from Orkney demonstrates that such signals are retained in archaeological contexts. delta (13)C analyses of n- alkanoic acid components of the fossil, Bronze Age, anthropogenic soils suggest a major terrestrial input to these soils, with uniform composition of formation materials. Surficial soils demonstrate the assimilation of isotopically lighter carbon, providing a means of assessing the mobility of the n- alkanoic acids within soils and sediments. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
7.
We propose a novel nonvolatile threshold adaptive transistor (TAT) for neuromorphic circuits. The threshold adaptive transistor is achieved by embedding a resistive random-access memory (RRAM) material stack between the gate electrode and gate dielectric. During operation, the embedded RRAM device is kept at a high resistance state, which makes it act as a nonvolatile capacitor. The threshold could be nonlinearly adjusted by the voltage pulses applied on the gate of the transistor. We quantitatively estimate the range of the capacitance variation of the RRAM device. The threshold voltage of the TAT is simulated and shows expected variation. The simulated output of an inverter using a TAT shows a nonlinear adaptive behavior. 相似文献
8.
Buoyancy driven flows of two Bingham fluids in an inclined ductare considered, providing a simplified model for many oilfieldcementing processes. The flows studied are near-uniaxial andstratified, with the heavy fluid moving down the incline, displacingthe lighter fluid upwards. Existence and uniqueness resultsare obtained for quite general flows and for those which satisfyan axial flow rate constraint. Parametric dependence of thesolutions on the axial pressure gradient is studied. Flows whichsatisfy a zero net axial flow constraint result from an axialpressure gradient which minimizes the viscous dissipation, butnot the plastic dissipation. A regularization method is usedto compute solutions to these problems for (more or less) arbitraryfluid-fluid interfaces and duct-cross sections. Examples relatedto a number of practical applications are presented. 相似文献
9.
R. Arnold C. Augier A. Barabash D. Blum V. Brudanin J. E. Campagne D. Dassié V. Egorov R. Eschbach J. L. Guyonnet F. Hubert Ph. Hubert S. Jullian O. Kochetov I. Kisel V. N. Kornoukov V. Kovalenko D. Lalanne F. Laplanche F. Leccia I. Linck C. Longuemare F. Mauger P. Mennrath H. W. Nicholson A. Nozdrin F. Piquemal O. Purtov J-L. Reyss F. Scheibling J. Suhonen C. S. Sutton G. Szklarz V. I. Tretyak V. Umatov I. Vanushin A. Vareille Yu. Vasilyev Ts. Vylov V. Zerkin 《Zeitschrift fur Physik C Particles and Fields》1996,72(2):239-247
The NEMO-2 tracking detector located in the Fréjus Underground Laboratory was designed as a prototype of the detector NEMO-3 to study 0ν and 2ν double-beta decay (ββ) physics. After ten months of nearly continuous running with an enriched cadmium source (0.92 mol·y of116Cd) aββ2ν half-life ofT 1/2=(3.75±0.35(stat)±0.21(syst))·1019 y was measured. Limits with 90% CL on the116Cd half-lives of 5.0·1021 y forββ0ν decay and of 1.2·1021 y forββ0νχ 0 decay with a Majoron (χ 0) were obtained. Theoretical predictions for 0ν and 2ν decays of116Cd are also presented. 相似文献
10.
Arnold R Augier C Baker J Barabash A Broudin G Brudanin V Caffrey AJ Caurier E Egorov V Errahmane K Etienvre AI Guyonnet JL Hubert F Hubert P Jollet C Jullian S Kochetov O Kovalenko V Konovalov S Lalanne D Leccia F Longuemare C Lutter G Marquet Ch Mauger F Nowacki F Ohsumi H Piquemal F Reyss JL Saakyan R Sarazin X Simard L Simkovic F Shitov Y Smolnikov A Stekl L Suhonen J Sutton CS Szklarz G Thomas J Timkin V Tretyak V Umatov V Vála L Vanushin I Vasilyev V Vorobel V Vylov Ts 《Physical review letters》2005,95(18):182302
The NEMO 3 detector, which has been operating in the Fréjus underground laboratory since February 2003, is devoted to the search for neutrinoless double-beta decay (beta beta 0v). The half-lives of the two neutrino double-beta decay (beta beta 2v) have been measured for 100Mo and 82Se. After 389 effective days of data collection from February 2003 until September 2004 (phase I), no evidence for neutrinoless double-beta decay was found from approximately 7 kg of 100Mo and approximately 1 kg of 82Se. The corresponding limits are T1/2(beta beta0v) > 4.6 x 10(23) yr for 100Mo and T1/2(beta beta 0v) > 1.0 x 10(23) yr for 82Se (90% C.L.). Depending on the nuclear matrix element calculation, the limits for the effective Majorana neutrino mass are < 0.7-2.8 e/v for 100Mo and < 1.7-4.9 eV for 82Se. 相似文献