共查询到20条相似文献，搜索用时 47 毫秒
1.
Z. M. Malkin 《Astronomy Reports》2014,58(6):415-425
Corrections to the IAU 2000/2006 parameters of the theory of precession and nutation are calculated using five different series—two individual series and three combined series that have been used in the literature for this purpose. A comparison of the sets of corrections obtained using the different datasets indicates significance systematic differences between them, which often substantially exceed the corresponding random errors. At the same time, existing studies have usually used data obtained from one or two series chosen by the authors without special justification. When refining the theory of precession and nutation, it is necessary to consider and compare various available series of VLBI data if one wishes to reduce the systematic errors in an improved model. 相似文献
2.
Ab initio LDF theory has been used to derive interatomic potentials for the Si-O and O-O interaction in α-quartz. The potentials have been used to study the lattice dynamical properties of α-quartz from 1 atm to 12.5 Gpa pressure. The results are compared with other calculated and experimentally derived potentials. 相似文献
3.
4.
松辽分水岭东段白土山组成因与时代 总被引：3，自引：1，他引：3
综合考虑松辽分水岭东段地区白土山组的地层分布、沉积特征、地貌部位及第四纪以来松辽分水岭的演化过程、松辽水系的变迁，认为其为河流冲积物，形成时代为早更新世早期。 相似文献
5.
常用化学风化指标诸如帕克风化指数（WIP）、化学蚀变指数（CIA）、成分变异指数（ICV）、CIX指数和αAlE常被用于评价源区化学风化强度,但利用以上化学风化指标评价化学风化强度时要考虑不同指标的控制因素,否则会导致风化评价结果失真。文章认为以最常用化学风化指标探究源区化学风化过程时,应在了解源区地质信息的情况下,选取合适的的细粒物质或悬浮物作为样品减弱粒度的控制作用,通过酸处理去除杂质,再利用Sc/Th-CIA 判别图反映物源信息,Th/Sc-Zr/Sc判别图进一步判别沉积分异和沉积再旋回的控制作用,进而选取ICV＞1的样品排除再旋回作用的干扰,用A-CN-K图或Panahi（2000）提出的公式进行钾交代作用的校正,最终通过CIA计算得出源岩化学风化强度。为确保准确反映源区风化情况,利用SPSS进行CIA受控因子分析,进而构建研究区的特征风化指标。 相似文献
6.
The quality of aggregate used as buildings materials is defined by European Standard test methods. According to the agreement
within the European Economic Area, each individual country decides test methods of current interest. Among the Nordic countries,
the Los Angeles-, micro-Deval- and the Nordic test are the most common methods used to decide the mechanical properties of
the aggregate. The three test methods are all drum test where the degradation of the material occur by rotation between the
test material and steel balls together with, or without water. The mechanical test methods are empirical and are believed
to express either resistance to fragmentation or wearing. The results of this study show that analysing the particle size
distribution of a material after the drum testing give indication of which type and degree of degradation the test material
is exposed to. Knowledge of the type of degradation for the test methods is important compared to the understanding of the
real breakdown of the aggregate for instance used in road construction. 相似文献
7.
Devonshire marbles: history of the industry and the geology of these classic British ornamental stones 
下载免费PDF全文
下载免费PDF全文 Gordon Walkden 《Geology Today》2017,33(6):224-232
Devonshire ‘marbles’ come from Mid– to Late Devonian limestones of south Devon, UK. They are not true marbles in the geological sense but were nonetheless tectonically buried during the Variscan orogenesis. They retain abundant palaeontological and sedimentological characters, overstamped by limited to extensive veining, deformation and brecciation. Recent work has revealed how these marbles have been used to decorate a wealth of buildings in Britain and overseas. There were two distinct industries, one that produced decorative marble for architectural use, and one that produced portable artefacts such as specimen marble tables and ornaments. The stones used in these two sister industries can be very different, a result of different sourcing of the same Devonshire limestones. A third industry sought to slice and polish local limestone pebbles to reveal their diverse coral, stromatoporoid and other fossil contents, and was aimed at tourists, collectors and museums. The history and early development of the marble industry are explored and the distinct characteristics of the stones used in Devonshire marble inlay are explained. The stones used in the parallel architectural trade are analysed elsewhere. 相似文献
8.
为进一步查明南屯煤矿奥陶系石灰岩含水层的水文地质条件,正确评价奥陶系石灰岩含水层对下组煤开采的影响,本次研究利用井下现有的水文地质观测孔,对奥陶系石灰岩含水层进行了群孔放水试验,进行三个落程的放水,并应用GMS软件进行数值模拟分析,计算水文地质参数,预计奥陶系石灰岩疏水量。该结果表明,奥陶系石灰岩含水层放水基本上对十四灰含水层没有产生较大的影响,对奥陶系石灰岩水尽量采用避让措施,通过物探等手段寻找导水通道,并及时对其进行处理。 相似文献
9.
Eliseev A. V. Ploskov A. N. Chernokulsky A. V. Mokhov I. I. 《Doklady Earth Sciences》2019,485(1):273-278
Doklady Earth Sciences - A modification of the commonly used Price–Rind scheme for lightning flash frequency (LFF), which can be used in calculations with large spatial and time steps, has... 相似文献
10.
Infill-sampling design and the Cost of classification errors 总被引：2，自引：0，他引：2
The criterion used to select infill sample locations should depend on the sampling objective. Minimizing the global estimation variance is the most widely used criterion and is suitable for many problems. However, when the objective of the sampling program is to partition an area of interest into zones of high values and zones of low values, minimizing the expected cost of classification errors is a more appropriate criterion. Unlike the global estimation variance, the cost of classification errors incorporates both the sample locations and the sample values into an objective infill-sampling design criterion. 相似文献
11.
12.
Non-parallelism between the effect of microbial flocculants on sewerage disposal and the flocculation rate 总被引：2，自引：1，他引：2
1 IntroductionMicrobial flocculant (MBF) is one of the naturalmacromolecular organic compounds, which is producedby some microorganisms and has a high flocculationfunction ( Cheng Wen et al., 2003). It has beencalled“the third-generation flocculant”beca… 相似文献
13.
Steel wire mesh held by a pattern of bolts can be used to stabilize a rock slope. Knowledge of the force-displacement response of steel mesh is essential in the design of this support system. Laboratory tests have been used to test mesh that is held to rigid steel frames. These testing conditions differ from how steel mesh is held in the field by bolts. The existing laboratory test data may underestimate the deformation and overestimate the load-bearing capacity of the steel mesh. This paper focuses on the response of the high tensile strength steel mesh held by commonly used bolt patterns. Discrete element models were used to study the force-displacement response of the steel mesh pinned by bolts. The influences of different bolt patterns and varying ratios of bolt spacing on the effectiveness of steel wire mesh were analyzed. Relationships between the resistance force of steel mesh and bolt density at various mesh deformations were developed. These relationships can help engineers choose the bolt spacing and provide an estimate of the resistance force that a steel mesh can mobilize at a desired deformation limit for a given bolt pattern. 相似文献
14.
Clarkina Postbitteri的首现不适合作为乐平统底界的定义，蓬莱滩剖面上6j的底界也不适合作为乐平统底界的全球界线层型剖面点（GSSP），乐平统底界的定义应是Clarkina postbitteri-C.dukouensis连续的演化系列中C.dukouensis的首次出现，精确的位置在蓬莱滩剖面6k之底。 相似文献
15.
Radiowave and gas-emanation geophysical methods have long been used to study the upper segment of a geological section, i.e., at the depths of the first tens of meters. This work deals with the improvement of these methods and the accuracy of the results of works due to the use of the new techniques and technology of other electrical prospecting methods. A complex of geophysical and geochemical methods based on studying the Earth’s radio fields (the ERF method) and the emanation fields of radon or other gases in the soil (EM) has been developed and widely tested. The proposed methods were tested during the study of the zones of natural and anthropogenic risks (landslides, karsts, etc.) at fuel and energy-sector objects (pipelines, their construction sites, etc.). They can be used to solve other engineering and hydrogeological tasks related to the upper segment of a geological section. 相似文献
16.
N. K. Andreeva N. A. Kagramanyan T. N. Kheraskova 《Lithology and Mineral Resources》2000,35(4):373-389
New data on the stratigraphy and composition of the Devonian rocks of the Moscow Syneclise were used. Facies-paleogeographic
schemes were compiled for the Lochkovian, Eifelian, Givetian, early-middle Frasnian, late Frasnian, and early-late Famennian
evolutionary stages of the Moscow Syneclise. Seven sedimentation cycles were developed due to sealevel fluctuations and structural
rearrangements in the paleooceanic basins surrounding the East European Platform at that time. The inference was made on the
structural heterogeneity of the platform basement and on differentiated movements as well as on the strike-slip fault nature
of some fragments of the basement relative to each other in the Devonian. 相似文献
17.
M. A. Levitan M. V. Bourtman L. L. Demina M. Yu. Chudetsky F. Schoster 《Lithology and Mineral Resources》2005,40(5):408-419
Recent sedimentary environments and facies of the southern Kara Sea are described. Lithological, mineralogical, geochemical, and micropaleontological indicators are used to characterize the facies variability. Some mechanisms of mineralogical and geochemical differentiation, which contribute to the facies zonation, are revealed. 相似文献
18.
以长江中下游防洪系统为对象,在大型复杂防洪系统洪水运动数值模拟基础上,成功地将面向长江中下游防洪规划论证需求的洪水演进数学模型转化为面向长江防洪系统江湖水沙调控需求的长江中下游江湖水沙调控数学模型.为适应江湖水沙调控和评估的要求,提出了基于水动力学的闸坝调度计算模式.此外,还对河网分汊泥沙分配模式进行了深入研究.通过长江中下游防洪规划及其洞庭湖区"控支强干"方案论证模拟计算,较好地解决了防洪措施蓄泄后效评估和工程优化调控模式等关键难题,为防洪规划方案的制定提供了定量依据,主要成果已应用于长江中下游防洪规划方案. 相似文献
19.
3D geological models are created to integrate a set of input measurements into a single geological model. There are many problems with this approach, as there is uncertainty in all stages of the modelling process, from initial data collection to the approach used in the modelling scheme itself to calculate the geological model. This study looks at the uncertainty inherent in geological models due to data density and introduces a novel method to upscale geological data that optimises the information in the initial dataset. This method also provides the ability for the dominant trend of a geological dataset to be determined at different scales. By using self-organizing maps (SOM's) to examine the different metrics used to quantify a geological model, we allow for a larger range of metrics to be used compared to traditional statistical methods, due to the SOM's ability to deal with incomplete datasets. The classification of the models into clusters based on the geological metrics using k-means clustering provides a useful insight into the models that are most similar and models that are statistical outliers. Our approach is guided and can be calculated on any input dataset of this type to determine the effect that data density will have on a resultant model. These models are all statistical derivations that represent simplifications and different scales of the initial dataset and can be used to interrogate the scale of observations. 相似文献
20.
青藏铁路抛石护坡和保温材料复合路基温度场特征非线性分析 总被引：1，自引：1，他引：0
采用多孔介质中流体的连续性方程、动量方程及能量方程,针对青藏铁路的气温和地质条件,对抛石护坡路基(无保温材料)及其在靠近路基顶部增设保温材料后的温度场特征进行了分析和比较.结果表明:在年平均气温为-4.0℃的青藏高原多年冻土区,考虑未来50 a气温上升2.6℃条件下,抛石护坡路基对其下部多年冻土可起到一定的保护作用;但由于气温升高的影响,路基中心处出现终年融化夹层;计算中发现当抛石护坡达到一定厚度时,单纯依靠增加抛石护坡厚度并不能明显增加其对路基中心处的降温效果;而增设保温材料后的抛石护坡路基可有效减小路基中出现的融化夹层,确保冻土路基的稳定.因此,建议在高温多年冻土区使用抛石护坡路基结构时,应考虑使用保温材料作为一种对抛石护坡路基进行保温补强的措施. 相似文献