Velocity-Porosity Relationships: Predictive velocity model for cemented sands composed of multiple mineral phases.     

Mark A. Knackstedt  Christoph H. Arns  W. Val Pinczewski 《Geophysical Prospecting》2006,54(2):237-237

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GIOVE-A initial signal analysis     

Oliver Montenbruck  Christoph Günther  Sebastian Graf  Miquel Garcia-Fernandez  Johann Furthner  Hanspeter Kuhlen 《GPS Solutions》2006,10(2):146-153

In late December 2005 the GIOVE-A test satellite was launched by the European Space Agency (ESA) to secure the frequencies for the Galileo system and to provide a platform for testing the new navigation signals. We performed an initial assessment of these signals using the 30 m deep space antenna of the DLR ground station in Weilheim (Germany). The antenna gain raised the signals above the noise level, thus allowing a detailed analysis even without knowledge of the ranging codes. The present paper covers the analysis of the L1/E1 signals, which includes a discussion of the spectrum, the time domain signal and a decoding of the spreading codes for the Open Service.  相似文献   

Scalar Similarity for Relaxed Eddy Accumulation Methods     

Johannes Ruppert  Christoph Thomas  Thomas Foken 《Boundary-Layer Meteorology》2006,120(1):39-63

The relaxed eddy accumulation (REA) method allows the measurement of trace gas fluxes when no fast sensors are available for eddy covariance measurements. The flux parameterisation used in REA is based on the assumption of scalar similarity, i.e., similarity of the turbulent exchange of two scalar quantities. In this study changes in scalar similarity between carbon dioxide, sonic temperature and water vapour were assessed using scalar correlation coefficients and spectral analysis. The influence on REA measurements was assessed by simulation. The evaluation is based on observations over grassland, irrigated cotton plantation and spruce forest.Scalar similarity between carbon dioxide, sonic temperature and water vapour showed a distinct diurnal pattern and change within the day. Poor scalar similarity was found to be linked to dissimilarities in the energy contained in the low frequency part of the turbulent spectra ( < 0.01 Hz).The simulations of REA showed significant change in b-factors throughout the diurnal course. The b-factor is part of the REA parameterisation scheme and describes a relation between the concentration difference and the vertical flux of a trace gas. The diurnal course of b-factors for carbon dioxide, sonic temperature and water vapour matched well. Relative flux errors induced in REA by varying scalar similarity were generally below ± 10%. Systematic underestimation of the flux of up to − 40% was found for the use of REA applying a hyperbolic deadband (HREA). This underestimation was related to poor scalar similarity between the scalar of interest and the scalar used as proxy for the deadband definition.  相似文献   

Flux contribution of coherent structures and its implications for the exchange of energy and matter in a tall spruce canopy   总被引：2，自引：5，他引：2  

Christoph Thomas  Thomas Foken 《Boundary-Layer Meteorology》2007,123(2):317-337

The flux contribution of coherent structures to the total exchange of energy and matter is investigated in a spruce canopy of moderate density in heterogeneous, complex terrain. The study deploys two methods of analysis to estimate the coherent exchange: conditional averages in combination with wavelet analysis, and quadrant analysis. The data were obtained by high-frequency single-point measurements using sonic anemometers and gas analysers at five observation heights above and within the canopy and subcanopy, and represent a period of up to 2.5 months. The study mainly addresses the momentum transfer and exchange of sensible heat throughout the roughness sublayer, while results are provided for the exchange of carbon dioxide and water vapour above the canopy. The magnitude of the flux contribution of coherent structures largely depends on the method of analysis, and it is demonstrated that these differences are attributed to differences in the sampling strategy between the two methods. Despite the differences, relational properties such as sweep and ejection ratios and the variation of the flux contribution with height were in agreement for both methods. The sweep phase of coherent structures is the dominant process close to and within the canopy, whereas the ejections gain importance with increasing distance to the canopy. The efficiency of the coherent exchange in transporting scalars exceeds that for momentum by a factor of two. The occurrence of coherent structures results in a flux error less than 4% for the eddy-covariance method. Based on the physical processes identified from the analysis of the ejection and sweep phases along the vertical profile in the roughness sublayer, a classification scheme for the identification of exchange regimes is developed. This scheme allows one to estimate the region of the canopy participating in the exchange of energy and matter with the above-canopy air under varying environmental conditions.  相似文献   

α-Emitting mineral inclusions in apatite, their effect on (U-Th)/He ages, and how to reduce it     

Pieter Vermeesch  Diane Seward  Martin Wipf  Heinrich Baur 《Geochimica et cosmochimica acta》2007,71(7):1737-1746

U-Th rich mineral inclusions in apatite are often held responsible for erroneously old (U-Th)/He ages, because they produce “parentless” He. Three aspects associated with this problem are discussed here. First, simple dimensional considerations indicate that for small mineral inclusions, the parentless helium problem might not be as serious as generally thought. For example, a mineral inclusion that is 10% the length, width and height of its host apatite needs to be a thousand times more concentrated in U and Th to produce an equal amount of He. Therefore, single isolated inclusions smaller than a few μm are unlikely to contribute significant helium. For larger or more abundant inclusions, the parentless helium problem can be solved by dissolution of the apatite and its inclusions in hot HF. Second, besides creating parentless helium, inclusions also complicate α-ejection corrections. Mathematical exploration of this latter problem for spherical geometries reveals that for randomly distributed inclusions, the probability distribution of single-grain ages is predicted to have a sharp mode at the mean age, with tails towards younger and older ages. Multiple-grain measurements will yield accurate and precise age estimates if 10 or more randomly distributed α-emitting mineral inclusions are present in a sample. Third, thermal modeling indicates that mineral inclusions have a non-trivial but minor (<5 °C) effect on the closure temperature. These predictions were tested on apatites from rapidly cooled migmatites of Naxos (Greece) which contain abundant U-rich zircon inclusions. Thirty-seven samples were subjected to two kinds of treatment. The “pooled” age (i.e., the synthetic multi-grain age computed from a number of single-grain analyses) of four inclusion-free samples (13 apatites), prepared in HNO₃ is 10.9 Ma, close to apatite and zircon fission-track ages from the same rock. (U-Th)/He ages of 14 inclusion-bearing samples dissolved in HNO₃ range between 9 and 45 Ma, with a pooled age of 22.6 Ma. The ages of 19 HF-treated samples range between 5 and 16 Ma, with 10 of 14 single-grain samples between 9 and 13 Ma and a pooled age of 10.9 Ma. These observations agree with the theoretical predictions and support the addition of HF-treated apatite (U-Th)/He dating to the thermochronological toolbox.  相似文献   

Landscape governance: The “politics of scale” and the “natural” conditions of places     

Christoph Görg 《Geoforum》2007,38(5):954-966

Governance has become an iridescent concept in recent years. The term is widely used in almost all social-science disciplines as well as in the political process. The intention of this paper is not so much to clarify these sometimes vague meanings but to highlight some characteristics of environmental governance connected with the restructuring of the spatial dimensions of politics. It starts from the assumption that the quest for multi-level decision making is particularly pressing for environmental governance. However, multi-level governance raises concern about the constitution of various spatial levels and their relationships with each other, as discussed under the term of “politics of scale”. Moreover, it is argued that for environmental governance the spatial reference is strongly connected with another challenge, which concerns the question of how to deal with the biophysical conditions of particular places. The term landscape governance is introduced to tackle this question without referring to an ontologically given space. Thus, landscape governance deals with the interconnections between socially constructed spaces (the politics of scale) and “natural” conditions of places. For this task, the concept of societal relationships with nature is introduced and applied to the term “landscape” as a bridging concept between social and natural sciences. The paper illustrates the approach of landscape governance with examples of problem-oriented interdisciplinary research at the UFZ-Centre for Environmental research in Leipzig, Germany.  相似文献   

Preface     

Hartmut Heinrich  Wlodzimierz Krzyminski 《Ocean Dynamics》1998,50(2-3):107-107

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Ground freezing monitoring techniques     

D. Heinrich  G. Mller  H. Voort 《Engineering Geology》1979,13(1-4):455-471

Ground-freezing is used in mining and civil engineering to make water-bearing strata temporarily impermeable and to increase their compressive and shear strength by transforming joint water and interstitial water into ice. Freezing of rock or soil layers is achieved by means of an array of cased boreholes, through which a cold liquid is circulated in order to remove heat energy, comparable to cooling coils.

Frost expansion from the boreholes into the ground is monitored, for a better and more economic control of the freezing process. For this purpose, instruments for the determination of borehole deviation, for measurement of the temperature field and for an assessment of the degree of freezing with ultrasonic waves, have proved useful. These three techniques are described based on results obtained from field measurements.  相似文献   

Petrography and geochemistry of carbonate void-filling cements in fossil reefs     

Dr. Ibrahim A. Mirsal  Prof. Dr. Heinrich Zankl 《International Journal of Earth Sciences》1979,68(3):920-951

An Investigation of the distribution of Ca²⁺, Mg²⁺, Na⁺, Sr²⁺ and K⁺ as well as O¹⁸ and C¹³ in void-filling cements out of three fossil reefs — of Devonian and Triassic ages — shows a rhythmic fluctuation of these parameters in the successive layers. This reflects a similar change in the salinity conditions during cementation. It also leads to the presumption that the void filling process starts in early stages with a semi-closed system and later passes into a relatively closed one. Results obtained from factor analysis support this hypothesis.The original mineralogic constitution of the cements must have followed the rhythmic fluctuation of salinity with the result of forming alternative layers of aragonite and calcite. These lead, through inversion and grain growth, in later diagenetic stages to the formation of fibrous calcite.Blocky calcite represents the last stage of cementation. It crystallises out of exhausted solutions and shows no signs of inversion.Multivariate analysis of all investigated parameters reveals three factors. These were interpreted as representing Salinity, Temperature and original Mineralogy.

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Zusammenfassung Die Untersuchung der Verteilung von Ca²⁺, Mg²⁺, Na⁺, Sr²⁺ und K⁺, sowie O¹⁸ und C¹³ in Hohlraumzementen aus drei fossilen Riffen von devonischem und triadischem Alter zeigt eine rhythmische Schwankung in den sukzessiven Zementschalen. Die Schwankung der geochemischen Parameter reflektiert eine änderung der Salinitätsbedingungen. Dies wird unter der Annahme erklärt, daß die Ausfüllung der Hohlräume zuerst in einem halbgeschlossenen, später dann in einem relativ geschlossenen System stattfindet. Die Faktorenanalyse bestätigt diese Hypothese.Die Mineralogie der gebildeten Zemente folgt der rhythmischen Salinitätsschwankung und daraus entstand zunächst eine Wechsellagerung von calcitischen und aragonitischen Zementen.über Inversion und Sammelkristallisation bildet sich während der späteren Diagenese der fibröse Calcit, dessen rhythmische Gefügeabfolge von der ursprünglichen Mineralogie der Zemente diktiert wird. Als letzte Zementgeneration folgt blockiger Calcit aus ionenarmen Lösungen, wobei keine Umwandlung dieser Zementphase mehr erfolgt.Aus der Faktorenanalyse aller geochemischen Parameter ergeben sich drei Faktorengruppen, die die Salinität, Temperatur und ursprüngliche Bildungsmineralogie charakterisieren.

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Résumé L'examen de la répartition du Ca₂₊, Mg₂₊, Na₊, Sr₂₊ et K₊, ainsi que O¹⁸ et C¹³ dans le ciment de remplissage des vides de 3 récifs fossiles d'âge dévonien à triasique, montre une variation rythmique dans les couches successives du ciment. La variation des paramètres chimiques reflète un changement dans les conditions de la salinité. Ceci s'explique si l'on accepte que le remplissage des vides a eu lieu dans un milieu d'abord à moitié fermé, et plus tard relativement fermé. L'analyse des facteurs confirme cette hypothèse. La minéralogie du ciment formé est conforme à la variation rythmique de la salinité, d'où résulta une alternance de ciment calcitique et aragonitique.Après l'inversion et la recristallisation coalescente, il s'est formé, durant la diagenèse ultérieure de la calcite fibreuse, dont la succession structurale rythmique est dictée par la minéralogie originelle du ciment. Comme dernière génération de ciment, vient de la calcite en bloc provenant d'une solution pauvre en ions, sans qu'il s'en suive une transformation decette phase de cimentation.L'analyse des facteurs de tous les paramètres chimiques fait apparaÎtre trois groupes de facteurs qui caractérisent la salinité, la température et la minéralogie originelle de formation.

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, : Sa²⁺, Mg²⁺, Na²⁺, Sr²⁺ K⁺, ¹⁸O ¹³S . . , , , . . , . , . , , - . 3 , , .

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Die Beziehung zwischen Wind und Oberflächenströmung auf Grund von Triftkartenuntersuchungen     

Heinrich Neumann 《Ocean Dynamics》1966,19(6):253-266

Zusammenfassung Es wurden mehrere Tausend Trifkarten ausgeworfen. Ihr Weg vom Auswurfort zum Fundort wurde mit Hilfe einer elektronischen Rechenanlage durch Modellrechnungen verfolgt, bei denen das Windfeld über der Nordsee vorgegeben war. Die Rechnung wurde so variiert, daß tatsächliche und rechnerische Fundorte der Karten möglichst gut übereinstimmten. (Abb. 3.). Hiernach treiben die Triftkarten in Windrichtung mit 4,2 v. H. der Windgeschwindigkeit. Das nur aus dem Wind gewonnene Bild des Triftweges läßt sich verbessern, wenn zusätzlich Oberflächenströmungen angenommen werden. Durch rechnerische Experimente wurde ein zu diesem Windfaktor passendes Stromfeld für die Nordsee ermittelt (Abb. 15).

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Relation between wind and surface current derived from drift card investigations

Summary Several thousands of drift cards were released. Their route from the place of release to the place of retrieval was traced on an electronic computer by means of model computations where the wind field over the North Sea was preset. The computation was varied so to achieve the best possible agreement of actual and computational places of retrieval (Fig. 3). According to this, the cards are drifting in wind direction at 4.2 per cent of the wind velocity. The drift route exclusively derived from the wind can be improved by assuming, in addition, surface currents. Computational experiments delivered a current distribution in the North Sea corresponding to this wind factor (Fig. 15).

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Les relations entre vent et courant superficiel déduites des études par cartes-flotteurs

Résumé Plusieurs milliers de cartes-flotteurs ayant été lancées, leur trajet du point de lancement au point de recupération a été établi à l'aide d'une calculatrice électronique avec un programme de calcul dans lequel était introduit le champ des vents en mer du Nord. Le calcul était si détaillé que le meilleur accord possible a été trouvé entre les lieux réels et calculés de découverte des cartes (fig. 3). On constate que les cartes sont poussées dans la direction du vent avec une vitesse égale à 4,2% de celle du vent. La représentation obtenue pour les trajets de dérive à partir du vent seul peut être amélioré si on considère en plus les courants superficiels. La représentation calculée montre pour la mer du Nord un champ de courant en accord avec ce facteur de vent (fig. 15).

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