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83.
Fernando P. Carvalho João M. Oliveira J. Vives i Batlle 《Marine pollution bulletin》2010,60(10):1734-1742
Mussels from the Portuguese coast collected during several seasons of the year have shown 210Po and 210Pb body burdens (Bq mussel−1) that increased with mussels’ body size but displayed significant decrease in radionuclide concentrations (Bq kg−1). For example, the increase of mussel size from 2.5 cm to 5.0 cm maximum shell length corresponded in average to a 50% decrease of 210Po activity concentration in soft tissues from 1065 Bq kg−1 (dw) to 540 Bq kg−1 (dw). A similar reduction in concentration was observed for 210Pb. The physiological condition of mussels, relating to fat and glycogen storage, had an effect on radionuclide concentrations, although the total body burden of radionuclide in mussels remained nearly constant throughout the year. These factors may play an important role in data interpretation for environmental monitoring programmes. Besides the mussel size and condition index, due to the inter-individual variation even inside narrow mussel size classes, the sample size, i.e., the number of specimens in one mussel sample is another key factor to be considered when obtaining environmentally representative radionuclide concentrations. 相似文献
84.
b值是研究地震活动的重要指标,其广泛应用于地震危险性分析和地震预测研究之中,与实际资料的完整性、样本量的大小、计算方法等因素有着重要的关系。常见的b值计算方法有最小二乘法和最大似然法,样本量的大小对这2种方法影响很大。本文利用蒙特卡罗模拟地震目录和汾渭地震带实际目录作为样本,从中抽取不同大小的样本量进行计算,研究不同样本量下这2种方法计算得到的b值与设定值或真实值之间的差别。结果表明,最小二乘法需要的最低样本量为1000,最大似然法为200;当样本量达不到要求时,计算出的b值是不可靠的;由于对样本量的要求不同,前者适用于计算区域的整体b值,而后者在研究某区域b值在时间轴上的变化方面更有优势。本研究为确定2种b值计算方法对样本量的最低要求提供了参考依据。 相似文献
85.
膨润土深加工的研究进展 总被引:14,自引:0,他引:14
由于膨润土具优良的物化性能、丰富的资源、低廉的价格,使得国内外有关科技人员对其深加工的方法和技术进行了大量的研究。在膨润土的提纯、钙基膨润土的钠化和活性白土的制备、各种有机膨润土的制备、膨润土凝胶的制备、用膨润土制备白炭黑等各种膨润土深加工的方法和技术,以及目前国际上研究的热点:柱撑粘土材料的制备和有机-无机纳米复合材料的制备等方面都有一定的进展。柱撑粘土是一种具有很高催化裂化活性的类分子筛新型固体酸催化材料,也是一种优良的新型环保材料。有机-无机纳米复合材料(纳米粘土)既具有粘土矿物的优良强度和尺寸稳定性,又具有聚合物断裂性能、可加工性和介电性能。膨润土的深加工技术开辟了非金属矿综合利用的新途径。 相似文献
86.
MARCO POLO: near earth object sample return mission 总被引:1,自引:0,他引:1
M. A. Barucci M. Yoshikawa P. Michel J. Kawagushi H. Yano J. R. Brucato I. A. Franchi E. Dotto M. Fulchignoni S. Ulamec 《Experimental Astronomy》2009,23(3):785-808
MARCO POLO is a joint European–Japanese sample return mission to a Near-Earth Object. This Euro-Asian mission will go to a
primitive Near-Earth Object (NEO), which we anticipate will contain primitive materials without any known meteorite analogue,
scientifically characterize it at multiple scales, and bring samples back to Earth for detailed scientific investigation.
Small bodies, as primitive leftover building blocks of the Solar System formation process, offer important clues to the chemical
mixture from which the planets formed some 4.6 billion years ago. Current exobiological scenarios for the origin of Life invoke
an exogenous delivery of organic matter to the early Earth: it has been proposed that primitive bodies could have brought
these complex organic molecules capable of triggering the pre-biotic synthesis of biochemical compounds. Moreover, collisions
of NEOs with the Earth pose a finite hazard to life. For all these reasons, the exploration of such objects is particularly
interesting and urgent. The scientific objectives of MARCO POLO will therefore contribute to a better understanding of the
origin and evolution of the Solar System, the Earth, and possibly Life itself. Moreover, MARCO POLO provides important information
on the volatile-rich (e.g. water) nature of primitive NEOs, which may be particularly important for future space resource
utilization as well as providing critical information for the security of Earth. MARCO POLO is a proposal offering several
options, leading to great flexibility in the actual implementation. The baseline mission scenario is based on a launch with
a Soyuz-type launcher and consists of a Mother Spacecraft (MSC) carrying a possible Lander named SIFNOS, small hoppers, sampling
devices, a re-entry capsule and scientific payloads. The MSC leaves Earth orbit, cruises toward the target with ion engines,
rendezvous with the target, conducts a global characterization of the target to select a sampling site, and delivers small
hoppers (MINERVA type, JAXA) and SIFNOS. The latter, if added, will perform a soft landing, anchor to the target surface,
and make various in situ measurements of surface/subsurface materials near the sampling site. Two surface samples will be collected by the MSC using
“touch and go” manoeuvres. Two complementary sample collection devices will be used in this phase: one developed by ESA and
another provided by JAXA, mounted on a retractable extension arm. After the completion of the sampling and ascent of the MSC,
the arm will be retracted to transfer the sample containers into the MSC. The MSC will then make its journey back to Earth
and release the re-entry capsule into the Earth’s atmosphere. 相似文献
87.
金矿样品分析中相关问题讨论 总被引:1,自引:0,他引:1
依据金矿石特性,探讨样品在分析过程中要特别注意的加工、测试取样量、样品焙烧、载体灰化等几个关键问题,认为只有处理好以上几个关键问题才能得到准确、可靠检测结果。 相似文献
88.
Variability of unconfined compressive strength in relation to number of test samples 总被引:1,自引:0,他引:1
Unconfined compressive strength is one of the most commonly used properties in rock engineering. Estimation or selection of an appropriate value of unconfined compressive strength for a given rock can be difficult as it can vary greatly within the same rock unit. Considering this large variability, unconfined compressive strength obtained by testing just a few samples is questionable. The purpose of this study was to investigate the variability of unconfined compressive strength for a given rock and, based on this information, determine the minimum number of samples required for obtaining a reliable value. Unconfined compressive strength values for approximately 50 NX-size (2.125 in./5.4 cm) core samples were determined for five different rock types. Statistical analyses were performed on subsets of cores to determine the minimum number of samples required to render a reliable estimate of the average strength of the entire set of cores. The results indicate that the minimum number of samples needed for strength determination depends on the statistical method used, the chosen confidence interval, and the acceptable deviation from the mean. For a 95% confidence interval and a 20% acceptable strength deviation from the mean, either 9 or 10 samples are needed to test for strength, depending on the statistical analysis used. 相似文献
89.
90.
本文在分析声控产生态势图必要性的基础上,提出了利用计算机及其外围设备和语音识别器构成声控指挥图形显示智能系统的设计思想、功能、数据流程和结构。 相似文献