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51.
In this paper we have tested the potential application of X-rays as an irradiation source in Electron Spin Resonance dating of tooth enamel. A range of modern and fossil samples were used to assess the feasibility of dose estimations using this alternative irradiator. The use of a known laboratory additive dose allows the calculation of an absorption equivalent coefficient between gamma-rays and X-rays. The results show that equivalent doses obtained with gamma-rays on fossil powder enamel was frequently less than the doses obtained on fragments using only X-rays. This agrees with other studies that gamma irradiation can lead to age underestimation problems, and also indicates that X-ray sources could be more suitable for ESR dating. Here, we show that testing penetration attenuation for each individual irradiation source is required to accurately estimate the maximum enamel thickness and produce reliable protocols. We conclude that X-rays are an alternative irradiation source for ESR dating protocols, however, limitations remain in particular with alpha efficiency. 相似文献
52.
吐鲁番地区可利用太阳能资源分析 总被引：3，自引：0，他引：3
利用吐鲁番太阳能试验站实测数据,结合气象站同期观测资料,从斜面总辐射、法向直接辐射和散射辐射等3个方面分析了吐鲁番地区的可利用太阳能资源、变化特征及其可能原因。结果表明:最佳倾斜面总辐射年曝辐量比纬度倾斜面高1.4%,比水平面高23.16%,两组相对差值存在着截然相反的季节变化;法向直接辐射年曝辐量比水平面总辐射低17%,两者的相对差值冬、春季大而夏、秋季小,散射辐射年曝辐量占水平面总辐射的49%,散射比和太阳高度角的年变化是影响上述两种太阳能资源变化的主要因素;此外,气象站周围建筑物的遮挡可能使其水平面总辐射年曝辐量减少8%,而从气候平均态考虑,本文所用实测年的水平面总辐射也比近30年平均值低8%。 相似文献
53.
Dag O. Hessen JoLynn Carroll Berit Kjeldstad Anton A. Korosov Lasse H. Pettersson Dmitry Pozdnyakov Kai Sørensen 《Estuarine, Coastal and Shelf Science》2010
Spectral light attenuation profiles and concentrations of total and dissolved carbon (C), nutrients and chlorophyll a (Chla) were studied along transects running from the river mouth to the Kara Sea during late summer 2003 for the Yenisey and fall 2005 for the Ob estuaries. Earth Observation data were used to generate composite images of water color and Chla distribution over the estuaries and the Kara Sea to reveal the spatial impact of the river efflux in terms of optical properties. 相似文献
54.
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利用钴— 6 0放出的伽玛射线对中成药进行灭菌保鲜这一核技术 ,目前已被广泛应用。在灭菌过程中 ,对于不同的照射剂量、不同的辐照时间及辐射前后中成药中的微量元素是否会产生某些变化 ?有没有带来新的毒副作用 ,这是人们普遍关心的问题。本文就利用中子活化分析的方法对以上问题进行了探讨 相似文献
56.
The study presents a critical assessment of the possibility of global solar irradiation computation by using air temperature instead of sunshine duration with the classical Ångström equations. The reason for this approach comes from the fact that, although the air temperature is a worldwide measured meteorological parameter, this is rarely used in solar radiation estimation techniques. More than that, the literature is very silent concerning the testing of such models in Eastern Europe. Two new global solar irradiation models (to be called AEAT) related to solar irradiation under clear sky conditions and having the minimum and maximum daily air temperature as input parameters were tested and compared with others from the literature against data measured at five stations in Romania in the year 2000. The accuracy of AEAT is acceptable and comparable to that of the models which use sunshine duration or cloud amount as input parameters. Since temperature-based Ångström correlations are strongly sensitive to origin, the approach for AEAT as a tool for potential users is presented in detail. Additionally reported is a new method to increase the generality of AEAT concerning the extension of the geographical application area. Based on overall results it was concluded that air temperature successfully substitutes sunshine duration in the estimation of the available solar energy. 相似文献
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The coexistence of hydrogen-containing materials and radioactive substances in source rocks is universal. Few documents have researched whether the latter can radiate the former to generate hydrogen gas (H2) as well as the factors controlling this process. This work conducted a series of radiation experiments to address this issue. Samples were placed in sealed Pyrex glass containers and subject to cobalt (60Co) γ irradiation and components and contents of resultant gases were analyzed using gas-chromatography. The results show that all the samples released variable amounts of H2 after irradiation and that the yield (H2) of decane is lower than that of 3-tetradecylthiophene but higher than that of distilled water, which implies that a weaker H-X bond energy (X indicates O, C or other element) in homogeneous materials corresponds with increased yield (H2). The yields (H2) of samples decreased with the decreasing solutions concentrations in sequence from mixed salts solution, KCl solution, Yellow Sea water, oil field water, gypsum solution to distilled water. The experimental results also show that the yield (H2) of distilled water with montmorillonite is higher than that of distilled water with kaolinite, because due to the larger specific surface area, ion exchange capacity and more effective energy transfer effect of montmorillonite. Meanwhile, the irradiation of oxygen- and carbon-containing materials also releases O2 and CH4. The production of H2 via the irradiation of hydrogen-containing materials makes the involvement of exogenous H2 into hydrocarbon generation possible, which can enhance the hydrocarbon volume and optimize crude oil. 相似文献