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41.
F. Wagner H. -R. Wenk H. Kern P. Van Houtte C. Esling 《Contributions to Mineralogy and Petrology》1982,80(2):132-139
Carbonate rocks deform preferentially by twin gliding on e={01ˉ18} and slip on r ={10ˉ14} and f={02ˉ21}. In polycrystalline aggregates strong textures develop. We report on experimentally produced textures in triaxial
plane strain geometry with orthorhombic symmetry at 200° C and 400° C. Pole figure of the experimentally deformed specimens
are compared quantitatively with theoretical simulations based on the Taylor theory using both slip and mechanical twinning
as mechanisms. Agreement at low and high temperature is satisfactory and documents that models developed for f.c.c. metals
can be applied to low symmetry minerals provided that deformation mechanisms are known and that mechanical twinning is properly
accounted for. Comparison with experimental results indicates that strain was nearly homogeneous at the conditions considered
and the same may apply to many geological textures. Three texture types are described which are differentiated mainly by the
relative importance of e twinning. 相似文献
42.
Wagner José Barreto Ieda Scarminio Maria Cristina Solci Dílson Norio Ishikawa Melissa Tiemi Ogasawara Sônia Naomi Nomi Sônia Regina Giancoli Barreto 《洁净——土壤、空气、水》2007,35(3):239-245
Seventeen physical and chemical parameters were obtained from a hydroelectric reservoir located in a tropical region in the south of Brazil. Multivariate Principal Component Analysis (PCA) and Hierarchical Group Analysis (HGA) were used to identify the parameters discriminating the origin of water from the Tibagi and the Primeiro de Maio River, after it has passed the mixing region. The study was conducted during the dry and rainy seasons in July 2002 and February 2003 at three depths and three sampling sites located 0, 5, and 10 km away from the mixing region. The statistical methods showed to be appropriate for identifying the contribution of each tributary in the water mixing site of a complex water system. The most important discriminating parameter was the absorbance relation A(253 nm)/A(203 nm), followed by the concentrations of Fe(III), Mn(III), and Ni(II). An anthropogenic interference was found in the reservoir due to high Ni(II) and orthophosphate concentrations caused by a nearby town sewage discharge. The interference was more important during the dry periods due to the lower dispersion of the pollutants. Urgent initiatives should be taken from the state government to build treatment stations for the wastewater of the small cities around the Capivara hydroelectric reservoir to prevent the drinking water quality from deteriorating. 相似文献
43.
The tracking performance of a Phase Lock Loop (PLL) is affected by the influence of several error sources. In addition to thermal noise and dynamic stress error, oscillator phase noise can cause significant phase jitter which degrades the tracking performance. Oscillator phase noise is usually caused by two different effects: Allan deviation phase noise is caused by frequency instabilities of the receiver's reference oscillator and the satellite's frequency standard. It can be termed as system-inherent phase noise and is relevant for both static and dynamic applications. “External” phase noise, however, is caused by vibration and is a major problem for dynamic applications. In the context of this paper, both types of phase noise will be modeled and the resulting integrals will be evaluated for PLLs up to the third order. Besides, phase jitter induced by thermal noise and signal dynamics will also be discussed, thus providing all necessary formulas for analyzing the performance of a phase lock loop in case of different forms of stress. Since the main focus is centered on the effects of oscillator phase noise, the overall PLL performance is graphically illustrated with and without consideration of oscillator phase noise. © 2002 Wiley Periodicals, Inc. 相似文献
44.
Christian Tiberius Thomas Pany Bernd Eissfeller Peter Joosten Sandra Verhagen 《GPS Solutions》2002,6(1-2):96-99
In this short contribution it is demonstrated how integer carrier phase cycle ambiguity resolution will perform in near future,
when the US GPS gets modernized and the European Galileo becomes operational. The capability of ambiguity resolution is analyzed
in the context of precise differential positioning over short, medium and long distances. Starting from dual-frequency operation
with GPS at present, particularly augmenting the number of satellites turns out to have beneficial consequences on the capability
of correctly resolving the ambiguities. With a 'double' constellation, on short baselines, the confidence of the integer ambiguity
solution increases to a level of 0.99999999 or beyond.
Electronic Publication 相似文献
45.
The location requirements for emergency callers outside urban areas can hardly be fulfilled without global navigation satellite
systems (GNSS). Consequently, interest in positioning techniques based on use of a GNSS such as GPS or on the cellular network
infrastructure itself is growing rapidly in the mobile-telephone community. Moreover, the increasing demand for commercial
location-based services (LBS) has driven cellular-phone and network manufacturers to focus on positioning solutions which
are even more accurate than the regulatory mandates for positioning of emergency callers. One example of these upcoming LBS
is our PARAMOUNT project, which aims at improving user-friendly info-mobility services for hikers and mountaineers by combining
wireless communications (GMTS), satellite navigation (GNSS) and geographic information systems (GIS), based on a mobile client/server
architecture. The availability of mobile phones or PDAs with combined GNSS and cellular network-based wireless communication
on a high integration level is one primary demand of such LBS applications. Based on this, we will give some initial answers
to the question of whether mobile handset architecture synergies exist for the combination of GNSS with wireless location
in CDMA cellular wireless networks. In order to identify synergies, we will outline similarities and differences between wireless
communication and satellite navigation. In this respect, we pay particular attention to the so-called RAKE receiver architecture
employed in mobile CDMA cellular handsets. Our initial investigations will show that the RAKE receiver architecture, on which
mobile CDMA cellular handsets are based, will most likely be the one most suitable for achieving synergies between the two
positioning techniques within the same mobile handset architecture. Consequently, several receiver components could be used
to handle both types of signals (navigation and communications), resulting in a reduction of manufacturing costs and in a
decrease in energy consumption.
Electronic Publication 相似文献
46.
47.
The postglacial environmental development of Raffles Sø, East Greenland: inferences from a 10,000 year diatom record 总被引:1,自引:0,他引:1
Holger Cremer Bernd Wagner Martin Melles Hans-Wolfgang Hubberten 《Journal of Paleolimnology》2001,26(1):67-87
A 341 cm long sediment sequence was recovered from the unofficially named Raffles Sø on Raffles Ø, outer Scoresby Sund region, East Greenland. The sediment sequence consists in the upper part (0–230 cm) of a stratified gyttja enriched in organic carbon and biogenic silica whereas the lower core part (235–341 cm) is composed of terrigenous, consolidated glacio-limnic sediments. 14C-AMS measurements indicate that the sediment sequence represents the entire Holocene lake history from 10,030 calibrated radiocarbon years.The geochemical parameters (opal, total organic carbon (TOC), total nitrogen (TN)) and the total diatom concentration show similar developments during the Holocene, and reflect changes in biological production and nutrient input into the lake. These records clearly reveal a broad Holocene TOC-opal-maximum interval between 5200 and 1800 cal. yrs BP.The diatom flora consisted of 66 taxa representing 20 genera but only seven taxa were abundant and, sometimes, these were monospecifically dominant during the Holocene. In the sediment core from Raffles Sø four successive stratigraphical zones can be distinguished. Accumulation of diatom valves began at 9900 cal. yrs BP with a Stephanodiscus minutulus (Kütz.) Cleve and Möller dominated assemblage (stratigraphic zone 1) followed by a diatom flora dominated by Cyclotella pseudostelligera Hustedt and, less frequently, by Diatoma tenuis Agardh (9400 until 5900 cal. yrs BP, zone 2). Cyclotella sp. A, a taxon which belongs to the Cyclotella rossii-comensis-tripartita-complex, was the dominant floral element between 5200 and 1800 cal. yrs BP (zone 3). From 1800 cal. yrs BP, the periphytic taxa Fragilaria capucina var. gracilis (Østr.) Hustedt and F. capucina var. rumpens (Kütz.) Lange-Bertalot attained highest relative abundances, also almost monospecifically (zone 4).The distribution and composition of the diatom assemblages in the sediment record from Raffles Sø probably reflect past variations in the extent of the lake-ice cover during the growing season. More or less ice-free conditions during summer may have prevailed during the early Holocene until ca. 1800 cal. yrs BP, which allowed growth of planktonic diatoms (Cyclotella taxa) in the pelagic lake region. From 1800 cal. yrs BP, colder conditions lead to a perennial lake-ice cover with a small ice-free moat in summer which favored the growth of periphytic, littoral species (Fragilaria capucina varieties). 相似文献
48.
Helmcke DGZG University of Goettingen D Goettingen GermanyIngavat Helmcke Rc/o GZG University of Goettingen D Goettingen GermanyFeng QinglaiFaculty of Earth Sciences China University of Geosciences Wuhan Wagner B Heppe KGZG 《中国地质大学学报(英文版)》2001,12(3)
INTRODUCTIONTheSimaoregion (SWYunnan ,China) ,situatedbe tweentheAilaoshanbeltintheeastandtheLancangjiangzoneinthewest (Fig .1) ,isakeyareatochronologicallyconstrainlatePaleozoiccompressionaldeformationsandthusofprimein terestwhendiscussingtheplate tectonichi… 相似文献
49.
Martin Gast Wolfgang Schaaf Joerg Scherzer Rudolf Wilden Bernd U. Schneider Reinhard F. Hüttl 《Journal of Geochemical Exploration》2001,73(2):196
To analyze the development of pine ecosystems on lignite and pyrite containing mine soils, four pine stands with ages of 3–35 years were investigated in a chronosequence approach. Bulk precipitation, throughfall and soil solution in depths of 20, 40, 70 and 100 cm were studied over a three-year period to determine element fluxes in these forest ecosystems on extreme acidic and saline soils.Element budgets are controlled by the processes induced by pyrite oxidation such as intensive weathering of primary minerals, precipitation and leaching of secondary phases.Despite low water fluxes, element outputs can reach extraordinary high values due to very high concentrations in the soil solution. Although element outputs decrease drastically with stand age, respectively, site age, they exceed those of comparable pine stands on non-mine sites. Nitrogen release from the lignite fraction represents a special characteristic of the examined substrates. Nitrogen losses beneath the rooted zone can be 34 kg N ha−1 yr−1 in 100 cm depth. Element input and output in the examined ecosystems are far from balance. Closed cycling of nutrients seems to be recognizable in the case of potassium. 相似文献
50.
Summary The global power of the differences of altimetric sea heights at collocated points in the first 44 cycles of the Topex/Poseidon (T/P) mission, apparently shows the influence of errors in the major tides and long period ocean signals. Results show the principal semidiurnal tides (M2/S2 lumped together) in the Cartwright and Ray (1991) model are probably in error globally by 3–4 cm (rms). The dominant fluctuation in the differences over the 44 cycles (14 months total) arises from an annual signal of 4–6 cm (rms), significantly greater than long term climate data suggests (but with considerable uncertainty due to unresolved semiannual effects). 相似文献