Die Raumgruppe von Libethenit und Olivenit     

Eva Maria Walitzi 《Mineralogy and Petrology》1962,8(2):275-280

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Averaging Intervals For Spectral Analysis Of Nonstationary Turbulence     

George Treviño  Edgar L. Andreas 《Boundary-Layer Meteorology》2000,95(2):231-247

We formulate a method for determining the smallest time interval Tover which a turbulence time series can be averaged to decompose it intoinstantaneous mean and random components. From the random part the method defines the optimal interval (or averaging window) AW over which this part should be averaged to obtain the instantaneous spectrum. Both T and AW vary randomly with time and depend on physical properties of the turbulence. T also depends on the accuracy of the measurements and is thus independent of AW. Interesting features of the method are its real-time capability and the non-equality between AW and T.  相似文献   

Periodicities and irregularities of indices describing the daily pluviometric regime of the Fabra Observatory (NE Spain) for the years 1917–1999     

X. Lana  M. D. Martínez  C. Serra  A. Burgueño 《Theoretical and Applied Climatology》2005,82(3-4):183-198

Summary Several patterns of a daily pluviometric regime are obtained from an homogeneous set of daily rainfall recorded at the Fabra Observatory (NE Spain) for the period 1917–1999. Power spectral analyses of four annual pluviometric indices, determined from different daily rain amount percentiles, are performed. Periodicities of the quasi-biannual oscillation (QBO), North Atlantic Oscillation (NAO) and sunspot cycles are correlated in some cases with empirical spectral peaks of the indices exceeding Markov red-noise with a confidence level of 95%. Depending on the rainy day percentiles, a set of short periods (2.1–4.6 years), a second group of intermediate periods (5.5 and 9.2 years) and, finally, a third group of long periods of 11.8, 20.8 and 41.5 years can be distinguished. These periods are compared with those derived for other European and African emplacements. Additionally, the consecutive irregularity of every annual series is quantified by means of a concept similar to the entropy.  相似文献   

The influence of wind on measurements of seismic noise   总被引：4，自引：0，他引：4  

Marco Mucciarelli  Maria Rosaria Gallipoli  Domenico Di Giacomo  Francesco Di Nota  Enrico Nino 《Geophysical Journal International》2005,161(2):303-308

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Mixing Height Over Water And Its Role On The Correlation Between Temperature And Humidity Fluctuations In The Unstable Surface Layer   总被引：2，自引：2，他引：0  

Anna Maria Sempreviva  Sven-Erik Gryning 《Boundary-Layer Meteorology》2000,97(2):273-291

Results from an experimental investigation of themixing height over inner Danish waters carriedout from September 1990 to October 1992, are discussed.The statistical analysis of the mixed-layer height (z_i)over the sea does not exhibit the dailyvariation that is characteristic of the mixed layerover land, but it is nearly constant over a24-hour cycle. During summer, the mixed layer ishigher than during winter. A second inversionwas often observed.A case study of the development of the mixed layerover the sea under near-neutral and unstableatmospheric conditions during six consecutivedays is presented. A zero-order mixed-layer heightmodel is applied. In addition to momentum and heatfluxes the effect of subsidence was found to be importantfor the evolution of the mixed layer over the sea. Themodelled evolution of z_i compared successfullywith measurements.We have investigated the influence of themixed-layer height on the correlation coefficient R_qTbetween temperature and humidity fluctuations usingthe values obtained with the model.We found that the evolution of R_qT follows theevolution of the mixing height. An empirical modellinking the surface values of R_qT to z_i and the Obukhov scaling length L has been suggested. The modelreproduces the experimental features.  相似文献   

Statistical distribution and spectral analysis of rainfallanomalies for Barcelona (NE Spain)     

X. Lana  A. Burgueño 《Theoretical and Applied Climatology》2000,66(3-4):211-227

Summary  Rainfall anomaly patterns are obtained for the city of Barcelona from a statistical and a spectral point of view. The time series consists of monthly rainfall amounts recorded over 128 years without interruption. Monthly positive and negative anomalies, obtained as the difference between monthly amounts and monthly threshold values, are used for both types of analyses. The threshold levels are derived form the deciles of theoretical monthly rainfall distributions, which have been previously modelled by the gamma distribution. Positive and negative anomalies of the monthly rain amounts are investigated for these threshold levels. The statistical analysis is applied to each decile considered, yielding empirical exponential laws that can be used to forecast the cumulative number of episodes of consecutive months with either positive or negative anomalies equalling or exceeding a fixed length. A set of linear laws, relating the expected rainfall amount cumulated during an episode of a fixed length, is also deduced. It is worthy of mention that, independently of the decile considered, all the exponential and linear laws have satisfactory regression coefficients. At the same time, it has also been possible to establish the evolution of the coefficients of these laws with respect to the different deciles considered. The exponential laws for episodes of positive and negative anomalies are the starting point, together with two hypotheses, to model probabilities of repeated long episodes over an arbitrary number of years and their return periods in terms of the Poisson distribution model. Moreover, power spectra are derived for anomalies relative to the 50% decile at monthly and seasonal scale. The spectral estimates obtained are then compared with theoretical spectra deduced from possible Markovian or random behaviour of the time series of anomalies. Finally, the significant spectral peaks are discussed and compared with other significant spectral components deduced for some areas of the Mediterranean domain. Received November 11, 1999 Revised February 28, 2000  相似文献   

Screening of Mercury and Persistent Organochlorine Pollutants in Long-Finned Pilot Whale (Globicephala melas) in the Faroe Islands     

Maria Dam  Dorete Bloch 《Marine pollution bulletin》2000,40(12):1090-1099

Results of mercury and organochlorine analyses in pooled muscle and blubber samples representing in all 417 long-finned pilot whales (Globicephala melas) sampled in 1997 in the Faroe Islands are presented. The 28 pooled muscle samples from (in all) 9 pods were analysed for total mercury and the same number of pooled blubber samples were analysed for PCB (IUPAC CBs no. 28, 52, 99, 101, 105, 118, 128, 138, 153, 170, 180, 183 and 187), p,p′-DDT and metabolites and o,p′-DDT and metabolites, cis () and trans (γ)-chlordane, cis- and trans-nonachlor, oxychlordane, mirex, hexachlorobenzene, β-HCH and toxaphene (Parlars no. 26 (T2), 32, 50 (T12), 62 (T20) and 69.  相似文献   

The La Luna formation: chemostratigraphy and organic facies in the Middle Magdalena Basin     

A. Rangel  P. Parra  C. Nio 《Organic Geochemistry》2000,31(12):2694

A detailed geochemical study and a sequence stratigraphic interpretation have been conducted on a sedimentary sequence of the Upper Cretaceous La Luna Formation, in a section outcropping in the eastern flank of the Middle Magdalena Basin (MMB), Colombia. The goals were to evaluate geochemical variability related to lithofacies and organic facies changes, characterize depositional environment and investigate the possible relationship between geochemical data and sequence stratigraphic cycles. The La Luna Formation is composed of organic-rich sediments of monotonous appearance, with good to excellent potential for oil generation. Most of the bulk, petrographic and biomarker parameters display a relatively narrow range of variation. However, the geochemical variations are sufficient to differentiate organic facies types B, BC and C in the Salada Member, B and D in the Pujamana Member and B in the Galembo Member. Certain biomarker ratios are consistent within the La Luna Formation and are characteristic of its depositional environment, for example, average ratios of diasterane/sterane are lower than 1, Ts/Tm averages are less than 0.33, the C₃₅/C₃₄ hopane ratio is more than 0.92, and oleanane/C₃₀ hopane ratios range from 0.02 to 0.19. Regarding depositional condition indicators, the C₃₅/C₃₄ hopane ratio shows a good positive correlation with HI. This suggests that in carbonate environment changes in this parameter are more strongly related to redox condition than to changes in carbonate content. Regarding the possible relationship between organic matter characteristics and sea level changes, in regressive carbonate shelves during shallow stages, HI tends to increase and TOC tends to decrease, while in regressive siliciclastic shelves, both TOC and HI decrease continuously. Some biomarker ratios (oleanane/C₃₀ hopane, C₂₀/C₂₃ tricyclic, Ts/Tm) increase during base level falls. Regarding δ ¹³C/¹²C isotope composition, the aromatic fraction and whole bitumen display an isotopic shift associated to the main deepening event in the section.  相似文献   

Middle Terrace Deposits of the Tagus River in Alpiarça, Portugal, in Relation to Early Human Occupation     

Paolo Mozzi  Maria Teresa Azevedo  Elizabeth Nunes  Luis Raposo 《Quaternary Research》2000,54(3):359

The stratigraphy and sedimentology of the Q3 middle terrace alluvial sequence in the lower Tagus river valley, Portugal, were studied near the village of Alpiarça, approximately 40 km upstream from the estuarine area. Two main stratigraphic units were recognized, separated by an important uncomformity. The Lower Gravels unit (LG) consists of intercalations of medium to coarse gravel deposits, mainly quartzitic, with coarse sandy matrix, organized in tabular bodies. The overlying Upper Sands unit (US) consists of tabular sandy channel deposits and overbank fines, the latter containing well-developed paleosols and backswamp deposits, showing a general aggrading trend, apparently with varying rates; available data indicate that deposition of the US took place under temperate climatic conditions. Within US deposits are several paleolithic archaeological sites, the lower ones in the alluvial stratigraphy being Middle Acheulian, whereas those embedded in overlying deposits are, from bottom to top, Upper Acheulian and Micoquian. Some of these sites have been recently excavated. The quartzite artifacts were apparently abandoned by early humans on the flood plain surface during deposition of the US unit and were subjected to limited reworking during their incorporation in the alluvium. TL/OSL dating of sandy-silty sediments, though imprecise, support archaeological evidence pointing to an age of 150,000 to 70,000 yr B.P. for the US unit.  相似文献   

美国内华达Goldstrike矿区卡林型贝茨金矿同变形的富矿分带(续)          下载免费PDF全文

Stephen G. Peters  Gregory C. Ferdock  Maria B. Woitsekhowskay  Robert Leonardson  Jerry Rahn 《地质找矿论丛》2000,15(2):115-132

(接第 1期第 1 6页 )3　富矿分带与控制因素贝茨金矿中不同矿石矿物组合和蚀变类型的分布与构造背景、围岩岩石及在矿体中的位置有关。根据形态、矿物组成和地质背景可分出几种空间形式截然不同的矿石类型 ,彼此之间由废石或低含金量的岩石所分隔。富矿体的地球化学、矿物学、地质及冶金方面的分带在三维空间上是连续的。富矿体的形状和定位与 Peters向斜构造的特征 ,沉积岩的岩石组成以及闪长岩接触带的几何形态和厚度有关 (图 6 A,B)。根据对不同的矿石类型和围岩类型的研究结果 ,对不同的富矿体进行了分类和判别。 Pe-ters( 1 996 ,1 9…  相似文献