On radioactive equilibrium in atmospheric aerosols at 700 and 1800 m a.s.l., as influenced by particle size and vertical mixing activity

Summary Data from simultaneous measurements of RaB and RaC concentration in atmospheric aerosols, taken at sites located roughly 700 and 1800 m a.s.l., are used to elucidate the relation of the ratio of the specific activities of RaB and RaC in aerosol particles on the one hand to the intensity of vertical mixing and the size of the aerosol particles on the other. The empirical relationships as found from a 15-month period of uninterrupted measurements are presented. Radioactive equilibrium is more nearly approached in aerosol particles of more than one micron in diameter than in smaller ones (including the smallest measurable sizes); this holds invariably — and for all height levels. The degree of approach to RaB/RaC equilibrium is the lowest for low altitude (700 m) and negligible vertical mixing: 65% to 75%. At the low-altitude site this figure increases to 80%–90% as the intensity of vertical mixing reaches higher levels. At 1800 m a.s.l., the degree of approach to RaB/RaC equilibrium is nearly 100% when vertical mixing is negligible, and declines with increased vertical mixing activity to a level of only 60–70% for conditions involving strong vertical mass exchange.

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Zusammenfassung Simultane Messungen der RaB- und RaC-Konzentration des atmosphärischen Aerosols an benachbarten Stationen in ca 700 und ca 1800 m a.s.l. werden benutzt um die Abhängigkeit des Verhältnisses der spezifischen Aktivitäten RaB/RaC auf Aerosolpartikeln von der Stärke des Vertikalaustausches, und von der Grösse der Aerosolpartikel abzuschätzen. Es werden die während einer 15-monatigen kontinuierlichen Meßperiode gesammelten empirischen Erfahrungen dargestelit. Die Annäherung an das radioaktive Gleichgewicht ist an Aerosolpartikeln vonD>1 m stets und unabhängig von der Seehöhe weiter fortgeschritten, als an den kleineren und kleinsten Partikeln. Der Grad der Gleichgewichtseinstellung RaB/RaC ist in niedriger Höhe (700 m) bei sehr schwachem Austausch am geringsten (65–75%) und steigt mit wachsender Austauschstärke bis zu einem Maximum von 80–90% an. Umgekehrt nimmt in 1800 m der Grad der Gleichgewichts-einstellung RaB/RaC von nahe 100% bei sehr schwachem Austausch bis auf 60–70% bei starkem Austausch ab.

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The research reported in this paper has been sponsored by the European Research Office, United States Army under Contract DAJA 37 67C 0254, and the Department of Defense of the Federal Republic of Germany.

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Physikalisch-Bioklimatische Forschungsstelle of the Fraunhofer Gesellschaft, in Garmisch-Partenkirchen. (Director: Dr.R. Reiter.)     

Upward flux of RaB and RaC in the planetary boundary layer as controlled by atmospheric microstructure

Summary Vertical mixing and transport processes are studied, and their variation as influenced by atmospheric fine-structure conditions investigated, using data gathered from simultaneous measurements of RaB and RaC concentration in the ambient air at three mountain stations located close to each other horizontally, but at markedly differing levels (730, 1780 and 2960 m). RaB was used as a tracer on account of the high sensitivity to variations of vertical-mixing activity evidenced by RaB abundance figures. Strong inversions between 700 and 2500 m a.s.l. create a zero condition at the higher level, where only 0.1% of the low-level RaB reading obtains; active turbulent mixing, on the other hand, leads to nearly equal RaB readings at the two levels. The vertical gradient of concentration of RaB is used to compute mean vertical-mass-exchange coefficients; the latter are studied in their relation to atmospheric structure characteristics. Statistical studies indicate that the barring effect of inversions is related solely to the magnitude of the inverse temperature gradient. Problems of radioactive equilibrium RaB-RaC are discussed, and the significance of aerosol particle size taken into consideration.

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Zusammenfassung Simultane Messungen der RaB- und RaC-Konzentration der Luft an 3 Bergstationen von geringem horizontalem Abstand aber mit relativ grossen Höhenunterschieden (Stationsniveau rund: 700, 1800 und 3000 m a.s.l.) werden benutzt um die vertikalen Mischungs-und Transportvorgänge und ihre Abhängigkeit von der atmosphärischen Feinstruktur zu studieren. Die RaB-Konzentration der Luft reagiert nämlich sehr empfindlich auf Schwankungen der Austauschintensität. Im Falle einer kräftigen Inversion zwischen 700 und 2500 m a.s.l. fällt die RaB-Konzentration über dieses Höhenintervall hinweg auf 0,1% des Basiswertes ab, bei turbulentem Austausch herrscht fast Konzentrationsgleichheit. Aus den vertikalen RaB-Konzentrationsgradienten werden mittlere vertikale Austauschkoeffizienten berechnet und diese zur atmosphärischen Struktur in Beziehung gesetzt. Es zeigte sich dabei, dass die Sperrwirkung einer Inversion nur durch die Steilheit der Temperaturänderung im Inversionsbereich bedingt ist. Probleme des radioaktiven Gleichgewichts zwischen RaB und RaC werden diskutiert. Auch die Bedeutung der Aerosolpartikelgrösse wird mit in Betracht gezogen.

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Paper presented at the XIVth General Assembly of the IUGG, meeting of the ICACR, Luzern, October 1967. The work has been sponsored by European Research Office, US Army, and Department of Defence of FRG     

Influence of soil to structure stiffness on the accuracy of the pushover method for underground structures

The pushover method for underground structures is a seismic analysis method featured by high calculation accuracy and a simple implementation process. The method has been widely used in seismic design and other related scientific research; however, the influence of different soil-structure flexibility ratios on the accuracy of this method is still not well understood. In this study, we select the cross-section structures beneath the Daikai subway station as the research object and establish 12 finite element analysis models with different soil-structure flexibility ratios using ABAQUS. All models are computed by the dynamic time-history method or the pushover method. Furthermore, the dynamic time-history solution result is taken as the standard solution, and the precision and application of the pushover analysis method are discussed based on the parameters of peak interlayer displacement and peak internal force of the middle column section. The results show that the soil-structure flexibility ratio has a significant influence on the calculation accuracy of the pushover method, and the calculation accuracy of this method is the most ideal when the soil-structure flexibility is equal to 1. The research results can provide significant references for the seismic design of underground structures or the improvement of simplified seismic analysis methods.     

Le teneur de l'air en petits et gros ions radioactifs

Résumé En assimilant à des petits ions les atomes RaA provenant de la désintégration du Radon présent dans l'air, on évalue par le calcul la fraction de ces particules fixées sur les poussières et les noyaux de condensation, ainsi que leur durée de fixation.Pour vérifier ces considérations, on compte les petits et gros ions radioactifs par la méthode deZeleny, en maintenant l'électrode axiale des tubes sous tension négative, les autres particules sont fixées par captation électrostatique ou avec un filtre papier et les activités des différents échantillons sont étudiées par comptage . On trouve une concentration de l'air en petits ions RaA de 1.5·10^–4 atome par cm³. Connaissant la teneur de l'air en Radon, et en admettant que l'équilibre radioactif est atteint entre le Radon et le Radium A qui en provient, on obtient par différence les concentrations de RaA fixée sur les autres particules.

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Summary The proportion and free life time of RaA atoms arising from the radioactivity of atmospheric radon, and catched by dust particles, large ions and condensation nuclei, is evaluated, with assumption that these atoms are identical to the ordinary small ions.Experimental verification of the calculation are made by catching small and large ions withZeleny tubes, axial electrode being negatively charged. Other particles being catched with electrical precipitation and filter paper, activities of different samples are measured by counting. 1.5·10^–4 per cm³ small ions RaA concentration is found. Knowing the air radon value concentration, and with the assumption of radioactive equilibrium only between radon and RaA in free air, it is possible to evaluate the concentration of RaA catched by other particles.

     

地球化学探测方法在西宁市城市活断层探测中的应用

在西宁市城市活断层探测工作中利用FD-3017RaA测氡仪开展了隐伏断层土壤气氡的探测,探讨了断层的气体地球化学特征及其确定隐伏断层的方法。在进行的8条测线上进行了土壤气氡的野外现场测量,共1384个点。结果表明,在8个地球化学剖面中确定了2处异常,由此确定了断层的大体位置,该处的人工浅层地震勘探结果也证实断层的存在和具体位置。土壤气氡测量法作为辅助探测手段在大城市活断层的探测工作中有一定的参考意义。     

Solution of the one-dimensional inverse magnetotelluric problem

Summary Methods of solving the inverse magnetotelluric problem are compared. Basic relations for Newton's method, the least-squares method and Marquardt's method are presented and the convergence properties of these methods are studied. The high effectiveness of Marquardt's method is demonstrated and its application to practical magnetotelluric data is discussed.     

A method to anchor floating chronologies in annually laminated speleothems with U–Th dates

Stalagmites occasionally present laminae which, when demonstrated to be annual, may be used to construct an annually resolved chronology. Such annually laminated records provide an opportunity to improve the precision of age models based on other dating techniques. Since annually laminated stalagmites sometimes present a complex stratigraphy with lateral variations in lamina thickness associated with changing macroscopic growth shapes, a procedure for lamina counting is developed here, which complements other methods of speleothem lamina counting. Regardless of the complexity of laminae, when the exact date of a laminated section is unknown, lamina counting provides a floating chronology. This paper describes a method to anchor floating chronologies in speleothems using the least-squares fit of the lamina counting to the radiometric dates (typically U–Th). The estimation of uncertainties in the age model is also considered, which accounts for uncertainties in the lamina counting as well as the fit of the lamina count to the radiometric dates. The uncertainty of this fit does not depend on the analytical uncertainty of the radiometric dates or the precision in the lamina counting, and simply considers all the available dates and their distance to the proposed age model. As an example, the method was applied to a stalagmite from Northern Spain and its accuracy was compared with the annually resolved and cross-dated Greenland chronology during the 8.2 ka event. Although this method has been described for stalagmites, it could be applied to other records in which cross-dating techniques would not be suitable.     

基于浓缩法的浮游植物定量数据稳定性与可靠性分析

浮游植物是水生生态系统中重要的初级生产者,相对准确地定量它们的数量是进一步进行水质评价和生态功能分析的基础.通过采集处于不同营养状态的水库和不同处理的围隔中的浮游植物,研究影响浓缩法定量浮游植物的因素,了解如何通过浓缩法来合理地定量浮游植物.分析浓缩倍数、样品的显微镜计数量、水体营养状态对浮游植物丰度、生物量及群落多样性等定量参数稳定性的影响,同时比较单个不同水体中重复(或平行)样品之间浮游植物丰度的差别.结果表明,基于浮游植物的显微镜计数效率与定量数据稳定性的综合考虑,选择计数4片×10格/片即可基本保证定量数据的稳定性;在保证正常镜检的基础上,考虑水体营养状态适当增加浓缩倍数能够提高定量数据的可靠性;在特别依赖生物量或稀有种进行水质评价时,处于不同营养水平的水体均需要增加样品的平行数来提高定量数据的可靠性.     

Measurements of the effective attachment coefficient between RaA ions and condensation nuclei

Summary To clarify the interaction between RaA ions and condensation nuclei, simultaneous measurements of the concentration of RaA ions (n _A), radon-222, and condensation nuclei (Z) were carried out at several stations. In some occasions, the diffusion coefficients of nuclei (D) were also measured. It was found that the correlation among them may be well expressed by the simple formula;q _A = _A n_A Z. The correlation between _A andD (or radius of nuclei) was also obtained.The effective attachment coefficient of RaA ions was compared with that of small ordinary ions, and it was presumed that about one fourth of RaA atoms formed on the decay of radon-222 is positively charged, and the rest is neutral.     

最小二乘Kirchhoff射线束叠前时间偏移

最小二乘偏移可以消除非规则采集、带限子波等因素对偏移结果的不利影响,提高成像剖面的分辨率和照明度,但巨大的计算成本严重制约了该方法的应用前景.本文基于地震数据的局部平面波合成/分解策略,对传统Kirchhoff时间正演/偏移的计算过程进行改进,发展了一种快速的最小二乘Kirchhoff射线束叠前时间偏移方法.同需要逐道数据映射运算的常规最小二乘Kirchhoff叠前时间偏移相比,本文方法不但具备相当的成像精度和反演收敛速度,同时由于数据的正/反向映射运算只需在稀疏的射线束中心位置进行,因此计算效率得到了大幅度的提升.文中给出的模型和实际数据算例证明了本方法的正确性和有效性.     

基于高紧支性移动最小二乘法的骨密度能谱探测技术研究

双能X射线骨密度仪系统具有测量精度高、时间短、剂量低等独特优势,是目前X射线骨密度测定技术的"金标准".本文采用半导体CdZnTe探测器模块搭建半导体光子计数骨密度能谱测量平台,针对CdZnTe半导体探测器信号特点,使用移动最小二乘算法进行不同材料高低能拟合校正.移动最小二乘算法通过权函数改变目标数据点周围节点对其影响...     

淡水浮游植物计数与定量方法

显微镜计数法是淡水浮游植物计数最常用的经典方法,是浮游植物生物量测定的基本方法,也是衡量其他测定方法准确性的依据.随着科技的发展,可见分光光度法、荧光分光光度法、流式细胞显微镜计数法、库尔特计数法等新型细胞计数法相继问世.对各种方法的特点进行比较,结果表明:光密度法、流式摄像机计数法、流式细胞仪法、叶绿素a法等仅能够分析测定浮游植物生物量,而显微镜法是测量浮游植物粒径的经典方法,不仅可以测定浮游植物生物量,还可以进行浮游植物的种类及群落结构分析.以上这些方法都可以用于浮游植物的计数与定量,可以根据不同的需求来选择最佳的浮游植物计数方法,如分析方便性、样本处理速率、样本大小等.但显微镜计数法在淡水生态学中具有不可替代的作用.     

Time-domain representation of frequency-dependent foundation impedance functions

Foundation impedance functions provide a simple means to account for soil–structure interaction (SSI) when studying seismic response of structures. Impedance functions represent the dynamic stiffness of the soil media surrounding the foundation. The fact that impedance functions are frequency dependent makes it difficult to incorporate SSI in standard time-history analysis software. This paper introduces a simple method to convert frequency-dependent impedance functions into time-domain filters. The method is based on the least-squares approximation of impedance functions by ratios of two complex polynomials. Such ratios are equivalent, in the time-domain, to discrete-time recursive filters, which are simple finite-difference equations giving the relationship between foundation forces and displacements. These filters can easily be incorporated into standard time-history analysis programs. Three examples are presented to show the applications of the method.     

Inversion of local S-wave velocity structures from average H/V ratios, and their use for the estimation of site-effects

H/V spectral ratios from microtremors areused to retrieve the S-velocity structurefrom a single ambient vibration record, byusing its relation to the ellipticity ofthe fundamental mode Rayleigh wave and theamplitude of observed H/V ratio.Constraints are needed in order to restrictthe possible range of solutions, and theinversion is applied to sites where thethickness of the unconsolidated sedimentsis approximately known from boreholeinformation. Within the uncertainty, theinverted structures agree well with theresults from other S-wave measuringtechniques such as downhole and cross-holemeasurements, and the analysis of ambientvibrations measured on an array.The influence of the inversion uncertaintyon site-amplification estimates forearthquakes is then investigated. For allinverted models, site response is computedfor a large number of events, which allowsto define the uncertainty by the aprioriunknown source position and mechanism of afuture earthquake. In most cases thevariability between the results obtainedfor the different models is much smallerthan the variability introduced by theunknown source position. The accuracy withwhich S-wave velocity structures can beretrieved from observed H/V ratios istherefore sufficient for an application ofthe method in seismic hazard analysis for aspecific site.     

Improved determination of heights using a conversion surface by combining gravimetric quasi-geoid/geoid and GPS-levelling height differences

The quasi-geoid/geoid can be determined from the Global Positioning System (GPS) ellipsoidal height and the normal/orthometric heights derived from levelling (GPS-levelling). In this study a gravimetric quasigeoid and GPS-levelling height differences are combined to develop a new surface, suitable for “levelling” by GPS. This new surface provides better conversion of GPS ellipsoidal heights to the national normal heights. Different combining procedures, a four-parameter solution, linear and cubic splines interpolations, as well as the least-squares collocation method were investigated and compared over entire Norway. More than 1700 GPS-levelling stations were used in this study. The combined surface provides significant accuracy improvement for the normal height transformation of GPS height data, as demonstrated by the post-fitting residuals. The best solution, based on the least-squares collocation, provided a conversion surface for the transformation of GPS heights into normal height in Norway with an accuracy of about 5 cm.     

JOINT INVERSION OF SEISMIC AND GEOELECTRIC DATA RECORDED IN AN UNDERGROUND COAL MINE1

Until the present time the ‘ rock-coal-rock’ layer sequence and offsets in coal-seams in underground coal mines have been detected with the aid of seismic waves and geoelectric measurements. In order to determine the geometrical and petrophysical parameters of the coal-seam situation, the data recorded using seismic and geoelectric methods have been inverted independently. In consequence, the inversion of partially inaccurate data resulted in a certain degree of ambiguity. This paper presents the first results of a joint inversion scheme to process underground vertical seismic profiling data, geolectric resistivity and resistance data. The joint inversion algorithm makes use of the damped least-squares method and its weighted version to solve the linearized set of equations for the seismic and geolectric unknowns. In order to estimate the accuracy and reliability of the derived geometrical and petrophysical layer parameters, both a model covariance matrix and a correlation matrix are calculated. The weighted least-squares algorithm is based on the method of most frequent values (MFV). The weight factors depend on the difference between measured data and those calculated by an iteration process. The joint inversion algorithm is tested by means of synthetic data. Compared to the damped least-squares algorithm, the MFV inversion leads to smaller estimation errors as well as lower sensitivities due to the choice of the initial model. It is shown that, compared to an independent inversion, the correlation between the model parameters is definitely reduced, while the accuracy of the parameter estimation is appreciably increased by the joint inversion process. Thus the ambiguity is significantly reduced. Finally, the joint inversion algorithm using the MFV method is applied to underground field data. The model parameters can be derived with a sufficient degree of accuracy, even in the case of noisy data.     

断层土壤氡观测方法的综合应用

为了对比有关土氡观测的稳定性及观测结果的映震能力,在原北川县政府断层气观测场地内建立了三组综合观测孔,进行ＲａＡ法,氡管仪法和α径迹蚀刻法测试实验。同时增加对地面空气中氡含量的测量,以便对比实验效果以确定几种方法的可信度。对连续１７个月三种方法的观测数据进行分析,测试的数据曲线同步性很好,年变规律清楚,观测资料与附近地震发生有较好的对应关系。     

Least-squares wave-path migration

We present a new least-squares migration method called least-squares wave-path migration. The proposed method combines an iterative conjugate-gradient solver with a stationary-phase wave-path migration operator. Numerical tests demonstrate that (i) least-squares wave-path migration is computationally more efficient than and almost as accurate as Kirchhoff least-squares migration, and (ii) many of the artefacts seen in wave-path migration images are suppressed after several conjugate-gradient iterations. Previous results have shown that 3D wave-path migration is up to 100 times faster than a standard 3D Kirchhoff migration, but sometimes at the cost of reduced quality. With the proposed least-squares wave-path migration method, the image quality in wave-path migration can be improved at an acceptable increase in computational cost.     

Die Anlagerung von natürlichen Radionukliden an Aerosolpartikel und Niederschlagselemente in der Atmosphäre

Zusammenfassung Es wird die Anlagerung der Zerfallsprodukte des, Radons und Thorons an das atmosphärische Aerosol infolge von Diffusion und elektrostatischer Dipolanziehung diskutiert. Die berechnete Grössenverteilung, des gebildeten, radioaktiven Aerosols stimmt weitgehend mit den Ergebnissen von Diffusionsmessungen überein. Die Aktivierung von Wolken-und Niederschlagselementen erfolgt im wesentlichen durch die Anlagerung trägerfreier, frisch gebildeter RaA-Atome; nur bei langlebigen Zerfallsprodukten spielt die Koagulation mit dem radioaktiven Aerosol eine Rolle. Die Anlagerungsgeschwindigkeit von RaA und ThB an fallende Regentropfen wurde durch Modellversuche bestimmt. Hiernach ist der Auswascheffekt von Regentropfen klein gegenüber der primären Aktivierung der Wolkenelemente. Es wird ein, Verfahren zur kontinuierlichen Messung der RaB- und RaC-Aktivität im Niederschlag beschrieben; die gemessene, mittlere spezifische Aktivität von 3·10^–5 c/cm³ kann mit Hilfe der angegebenen Aktivierungsprozesse befriedigend erklärt werden.

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Summary The attach of Rn- and Tn-decay-products to the atmospheric aerosol is discussed, taking into account diffusion and electrostatic forces. The computed size distribution of the produced radioactive aerosol agrees with the results of diffusion measurements. The activation of cloud and rain droplets with short-lived decay products happens chiefly due to the diffusion of fresh, carrier-free RaA-atoms. The collection efficiency of falling rain droplets for RaA and ThB was measured in model experiments; it is small compared to the activation of cloud elements. A method for the continuous measurement of RaB- and RaC-activity during rainfall is described; the measured, mean specific activity of 3·10^–5 c/cm³ can be explained by the theory of activation processes.

     

基于不等式约束的最小二乘法三维电阻率反演及其算法优化

基于光滑约束的最小二乘法是三维电阻率反演的主要方法,但该方法在某些情况下存在着多解性较强的问题,且普遍耗时较长,严重制约了三维反演方法的推广与发展.为改善上述问题,将表征模型参数变化范围的不等式约束作为先验信息引入最小二乘线性反演方法中,有效地改善了反演结果的精度,降低了反演的多解性问题.为了解决耗时较长的问题,基于预条件共轭梯度(PCG)算法和Cholesky分解法的特点提出了一套优化三维电阻率反演计算效率的计算方案.在该方案中,Cholesky分解法被用来求解敏感度矩阵计算中的多个点源场的正演问题,Cholesky分解法只需对总体系数矩阵进行一次分解,然后对不同的右端向量进行回代即可.将预条件共轭梯度法引入到三维电阻率反演方程的求解中,将雅可比迭代中的对角阵作为预处理矩阵,其具有求逆方便、无需内存空间的特点,有效地加快了收敛速度.对合成数据以及实测数据的反演算例表明,借助不等式约束和反演效率优化方案,最小二乘反演方法可得到较为精确的反演结果,有效地提高了反演计算效率,具有良好的推广前景.