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Methodology for determination of correction factors in direct gamma spectrometric measurement of radionuclides in sediments

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International Journal of Sediment Research 2017年第3期32卷 324-330页

作者： Esra uyar Alptug ?zer Yksel Rufiyet gven Haluk Ycel Ankara university Institute of Nuclear Sciences

In this study, the practical methodologies are described for the determination of the factors for the selfabsorption effect（Fs）, spectral interferences(Fcsi), and true coincidence summing effects(Fcoi), which are used in direct gamma-spectrometric measurement of radionuclides such as210Pb,238u,234Th,226Ra,214Pb,228Ac,208Tl,214Bi,137Cs and40K in samples. To validate the applied methods, certified reference materials（CRMs） of lake and stream sediments were measured with an n-type germanium（ge）detector-calibrated using a multinuclide reference source. The highest self-absorption correction factors ranged from Fs= 1.44-2.10 for 46.5 keV peak（210 Pb） and Fs= 1.25-1.60 for 63.3 keV peak(234Th) lying in the low energy region of the spectrum. The systematic influence was observed for 186.2 keV（226 Ra）peak due to spectral interferences with the 235 u contribution. For this peak, Fcsiis changed from 0.921 to0.955. Additionally, the present study su.gests that true coincidence summing（TCS） effects are not dominant, except for 208 T1 and 214 Bi for which Fcoiranged from 1.179 to 1.192 an ranged from 1.140 to1.151, respectively.

关键词： Correction factor Self-absorption Spectral interference True coincidence summing Sediment gamma-ray spectrometry

uniform and L-convergence of Logarithmic Means of Walsh-Fourier Series

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Acta Mathematica Sinica,English Series 2006年第2期22卷 497-506页

作者： g.gáT u.gOgINAVA Institute of Mathematics and Computer Science College of Nyiregyhaza Department of Mechanics and Mathematics Tbilisi State University

The （NSrlund） logarithmic means of the Fourier series of the integrable function f is：1/lnn-1∑k=1Sk（f）/n-k, where ln：=n-1∑k=11/k.In this paper we discuss some convergence and divergence properties of this logarithmic means of the Walsh-Fourier series of functions in the uniform, and in the L^1 Lebesgue norm. Among others, as an application of our divergence results we give a negative answer to a question of Móricz concerning the convergence of logarithmic means in norm.

关键词： Walsh system Norlund logarithmic means Convergence divergence properties

Semi-solid rheocasting of grain refined aluminum alloy 7075

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中国有色金属学会会刊：英文版 2010年第S3期20卷 832-836页

作者： u.A.CuRLE g.gOvenDER Materials Science and Manufacturing Council for Sci entific and Industrial Research(South Africa)

Near-net shape rheocasting with the Council for Scientific and Industrial Research Rheo casting system(CSIR-RCS) and a high pressure die casting machine was successfully performed on Al-5Ti-1B grain refined aluminum alloy *** refinement levels used were 0.03% Ti,0.13% Ti and 0.29% Ti(mass fraction).Tensile tests reveal that the ultimate tensile strengths,at all levels of grain refinement,are at least 97% of the specified *** at fracture increases with the increase of level of grain refinement although a maximum elongation is only 76% of the required minimum elongation in the case of 0.29% *** melting,during solution treatment,of the low melting point multinary eutectic causes porosity in the material and accounts for poor elongation results.0.03% Ti has a coarse eutectic structure forming larger pores while 0.29% Ti has a fine structure forming fine pores in the multinary *** 0.2% offset yield strengths of all the grain refinement levels are at least equal to or above the specified minimum and a decrease is observed with the increase of grain refinement *** is a clear reduction in grain size from 0.03% Ti to 0.29% Ti in the as-cast *** underlying grain structure develops in the T6 condition material which has an inverse size to the as-cast structure;coarse grained as-cast material results in fine grained T6 condition material after solution heat *** decrease in the offset yield strength as grain refinement increases correlates very strongly with the T6 grain sizes according to a Hall-Petch type relationship.

关键词： CSIR-RCS 7075 Al-5Ti-1B high pressure die casting F condition T6 condition incipient melting

Demonstration of Far-Infrared gaAs/AlgaAs Quantum Well Photodetectors for Broadband Wavelength Detection

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Chinese Physics Letters 2000年第12期17卷 921-923页

作者： SHEN Wen-Zhong Perera A.g.u Department of Applied Physics Shanghai Jiao Tong UniversityShanghai 200030 National Laboratory for Infrared Physics Shanghai Institute of Technical PhysicsShanghai 200083 Department of Physics and Astronomy Georgia State UniversityAtlantaGA 30303USA

We discuss the realization of broadband wavelength detection by demonstrating the longest cutoff wavelength(λc=28.6μm)far-infrared gaAs/AIgaAs quantum well infrared photodetectors(QWIPs).The responsivity is comparable to that of mid-infrared gaAs/AIgaAs and IngaAs/gaAs QWIPs,with a responsivity of 0.265 A/W and detectivity of 3.4x109 ***1/2/W at the peak wavelength of 26.9μm at *** on the temperature-dependent dark current and response results,it is expected that similar performance can be obtained at least up to 20 *** ways to expand the wavelength coverage are also addressed.

关键词： gaAs/AlgaAs Infrared Quantum

Linking electronic structure calculations to generalized stacking fault energies in multicomponent alloys

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npj Computational Materials 2020年第1期6卷 989-997页

作者： Anirudh Raju Natarajan Anton Van der ven Materials Department University of CaliforniaSanta BarbaraCA 93106USA

The generalized stacking fault energy is a key ingredient to mesoscale models of *** we develop an approach to quantify the dependence of generalized stacking fault energies on the degree of chemical disorder in multicomponent *** introduce the notion of a“configurationally-resolved planar fault”(CRPF)energy and extend the cluster expansion method from alloy theory to express the CRPF as a function of chemical occupation variables of sites surrounding the *** apply the approach to explore the composition and temperature dependence of the unstable stacking fault energy(uSF)in binary Mo–Nb ***-principles calculations are used to parameterize a formation energy and CRPF cluster *** Carlo simulations show that the distribution of uSF energies is significantly affected by chemical composition and *** formalism is broadly applicable to arbitrary crystal structures and alloy chemistries and will enable the development of rigorous models for deformation mechanisms in high-entropy alloys.

关键词： alloy alloys fault

白炭黑/有机硅烷及有机硅烷/聚合物反应的研究

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橡胶参考资料 2000年第2期30卷 30-38页

作者： u.grl 杨钧

本文是有关白炭黑/有机硅烷/橡胶反应体系的4篇论文中的第三篇,主要研究实际应用中白炭黑/有机硅烷反应的实现。在现场加入有机硅烷时混炼过程中发生的反应是形成强有力的橡胶/填料键合作用的先决条件之一。现在已经证实橡胶/

关键词：白炭黑有机硅烷高聚物反应研究混炼橡胶

新疆西南天山木扎尔特河一带低压泥质麻粒岩岩石学特征、独居石u-Th-Pb定年及其地质意义

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岩石学报 2009年第9期25卷 2271-2280页

作者：苟龙龙张立飞 g0u Peking univ Key Lab Orogen Belts & Crustal Evolut Minist Educ Sch Earth & Space Sci Beijing 100871 Peoples R China

古南天山洋闭合过程中,由于洋壳俯冲产生的岛弧岩浆作用加热大陆地壳,在新疆西南天山木扎尔特一带形成了一套低压高温泥质麻粒岩相变质岩石。本文用Theriak-Domino热力学软件对该套岩石中的堇青石榴夕线石黑云母片麻岩和含夕线石堇青石... 详细信息

古南天山洋闭合过程中,由于洋壳俯冲产生的岛弧岩浆作用加热大陆地壳,在新疆西南天山木扎尔特一带形成了一套低压高温泥质麻粒岩相变质岩石。本文用Theriak-Domino热力学软件对该套岩石中的堇青石榴夕线石黑云母片麻岩和含夕线石堇青石榴黑云母片麻岩进行了岩石学相平衡计算研究,得到它们峰期变质的温压条件分别是:T=630～674℃,P=5.2～5.5kbar和T=645～684℃,P=5.4～5.7kbar。并采用独居石Th-u-Pb电子探针定年方法,对样品WQ006中的3颗独居石进行了原位年龄测定(38个分析点),得到2组等时线年龄,分别是376±8Ma和280±8Ma(2σ)。结合独居石的岩相学特征,提出了新疆西南天山低压高温麻粒岩相峰期变质作用的时代为280±8Ma,而376±8Ma(2σ)可能为原沉积岩的原岩/成岩年龄。表明西南天山洋壳开始俯冲发生在晚古生代,进一步证明了西南天山造山带俯冲碰撞发生在晚二叠纪之后的观点。

关键词：新疆西南天山木扎尔特低压泥质麻粒岩相岩石学特征独居石定年地质意义 southwestern Tianshan region monazite dating China South Tianshan 黑云母片麻岩 electron microprobe 南天山洋峰期变质 phase equilibria

Cross Section of Heavy Ion Reaction （14.5 MeV/u） ^132Xe ＋ Bi

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Chinese Physics Letters 2006年第3期23卷 572-575页

作者： g. Sher M.I. Shahzad M. Hussain M. A. Rana E. u. Khan Physics Research Division PINSTECH P.O Nilore Islamabad Pakistan Department of Physics University of the Punjab Lahore Pakistan

We investigate the cross section of the heavy ion reaction （14.5 MeV/u） ^132Xe ＋ Bi by using a CR-39 plastic track detector. The target-detector assembly is exposed at uNILAC beam facility of gSI, germany. After etching under appropriate etching conditions, the detector is scanned for multipronged events produced as a result of interactions of projectile ions with target atoms. The elastic events are separated from binary events and used for the determination of the quarter-point angle. The quarter-point angle obtained is used to determine the total reaction cross section. The total experimental reaction cross section is determined by using statistics of inelastic events of two-pronged and higher multiplicity events. The experimental reaction cross sections determined by using elastic and inelastic data observed in the reaction under study are found to be in good agreement with the theoretically calculated value of reaction cross section using a sharp cutoff model.

关键词： SEQuENTIAL FISSION COuLOMB BARRIER TRACK DETECTORS NuCLEAR SCATTERINg PB-208

Implications of crude oil pollution on natural regeneration of plant species in an oil-producing community in the Niger Delta Region of Nigeria

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Journal of Forestry Research 2014年第4期25卷 915-921页

作者： u.D Chima g.Vure Department of Forestry and Wildlife Management University of Port Harcourt- Choba P.M.B. 5323 Port Harcourt Rivers State Nigeria

The study evaluated the impact of crude oil pollution on natu- ral regeneration of plant species in a major oil-producing community in the Niger Delta region of Nigeria. Three sites--unpolluted site （uS）, polluted and untreated site （PuS）, and polluted and treated site （PTS）-- were purposively chosen for the study. The seedling emergence method was used to evaluate soil seed banks in the various sites at two depths, 0 to 10 cm and 10 to 20 cm. Woody-plant species richness, abundance, and diversity were higher in the uS seed bank than in the PuS and PTS seed banks. The highest number of non-woody plants was observed in the uS, followed by the PTS, and then the PuS. Both species richness and diversity of non-woody plants were highest at the uS, followed by the PuS, and lowest in the PTS. Woody species in the uS seed bank were 87.5% and 80% dissimilar with those of the PuS and PTS at 0-10 cm and 10--20 cm respectively. No variation was observed between woody species in the PuS and PTS seed banks. Non-woody species at 0-10 em uS seed bank were 73.08% dissimilar with those of PuS at the two soil depths and 81.48/88.46% dissimilar with those of the 0-10/10-20 cm of the PTS respectively. At 10-20 cm, non-woody species of theuS were 69.66% dissimilar with those from each of the two soil depths in PuS; and 73.91/81.82% dissimilar with those of 0-10/10-20 cm of the PTS respectively. Non-woody species variation between the PuS and PTS was higher at 10-20 cm than 0-10 cm. The poor seed bank attributes at the polluted sites demonstrates that crude oil pollution negatively af- fected the natural regeneration potential of the native flora because soil seed banks serve as the building blocks for plant succession. Thorough remediation and enrichment planting are recommended to support the recovery process of vegetation in the polluted areas.

关键词： Ogoni land crude oil pollution remediation plant regeneration