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31.
From wind profile and wave measurements performed during the JONSWAP II experiment, relations between the dimensionless profile slope and the significant wave height are derived. It is shown that the wind profile is distorted by the waves especially in the vicinity of the water surface. The wave influence on the profile seems to be restricted to heights below about three wave heights. Above this level, the dimensionless profile slope is an approximately constant value corresponding to a drag coefficient of about 1.15 × 10–3. 相似文献
32.
Holger L. Fröhlich Lutz Breuer Hans‐Georg Frede Johan A. Huisman Kellie B. Vaché 《水文研究》2008,22(12):2028-2043
The link between spatiotemporal patterns of stream water chemistry and catchment characteristics for the mesoscale Dill catchment (692 km2) in Germany is explored to assess the catchment scale controls on water quality and to characterize water sources. In order to record the spatiotemporal pattern, ‘snapshot sampling’ was applied during low, mean and high flow, including 73 nested sites throughout the catchment. Water samples were analysed for the elements Li, B, Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Mo, Ba, Pb and U using inductively‐coupled‐plasma mass spectrometry, and for electric conductivity and pH. Principle component analysis and hierarchical cluster analysis were used to find typical element associations and to group water samples according to their hydrochemical fingerprints. This revealed regional hydrochemical patterns of water quality which were subsequently related to catchment attributes to draw conclusions about the controls on stream chemistry. It was found that various lithologic signals and anthropogenic point source inputs controlled the base flow hydrochemistry. During increased flows, stream waters were diluted causing additional hydrochemical variability in response to heterogeneous precipitation inputs and differences in aquifer storage capacities. The hydrochemical patterns further displayed in‐stream mixing of waters. This implied, that stream waters could be apportioned to the identified water sources throughout the catchment. The basin‐wide hydrochemical variability has the potential to outrange the tracer signatures typically inferred in studies at the hillslope scale and is able to strongly influence the complexity of the catchment output. Both have to be considered for further catchment scale tracer and modelling work. Despite the likelihood of non‐conservative behaviour, the minor and trace elements enhanced the rather qualitative discrimination of the various groundwater types, as the major cations were strongly masked by point source inputs. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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In experiments that are aimed at detecting astrophysical sources such as neutrino telescopes, one usually performs a search over a continuous parameter space (e.g. the angular coordinates of the sky, and possibly time), looking for the most significant deviation from the background hypothesis. Such a procedure inherently involves a “look elsewhere effect”, namely, the possibility for a signal-like fluctuation to appear anywhere within the search range. Correctly estimating the p-value of a given observation thus requires repeated simulations of the entire search, a procedure that may be prohibitively expansive in terms of CPU resources. Recent results from the theory of random fields provide powerful tools which may be used to alleviate this difficulty, in a wide range of applications. We review those results and discuss their implementation, with a detailed example applied for neutrino point source analysis in the IceCube experiment. 相似文献
35.
Jérôme Gattacceca Francis M. McCubbin Jeffrey N. Grossman Devin L. Schrader Nancy L. Chabot Massimo D'Orazio Cyrena Goodrich Ansgar Greshake Juliane Gross Katherine Helen Joy Mutsumi Komatsu Bingkui Miao 《Meteoritics & planetary science》2023,58(6):901-904
Meteoritical Bulletin 111 contains the 3094 meteorites approved by the Nomenclature Committee of the Meteoritical Society in 2022. It includes 11 falls (Antonin, Botohilitano, Cranfield, Golden, Great Salt Lake, Longde, Msied, Ponggo, Qiquanhu, Tiglit, Traspena), with 2533 ordinary chondrites, 165 HED, 123 carbonaceous chondrites (including 4 ungrouped), 82 lunar meteorites, 28 Rumuruti chondrites, 27 iron meteorites, 23 ureilites, 22 mesosiderites, 22 Martian meteorites, 21 primitive achondrites (one ungrouped), 17 ungrouped achondrites, 13 pallasites, 7 enstatite achondrites, 6 enstatite chondrites, and 5 angrites. Of the meteorites classified in 2022, 1787 were from Antarctica, 1078 from Africa, 180 from South America, 34 from Asia, 6 from North America, 4 from Europe, and 1 from Oceania. 相似文献
36.
Many geodetic applications require the minimization of a convex objective function subject to some linear equality and/or inequality constraints. If a system is singular (e.g., a geodetic network without a defined datum) this results in a manifold of solutions. Most state-of-the-art algorithms for inequality constrained optimization (e.g., the Active-Set-Method or primal-dual Interior-Point-Methods) are either not able to deal with a rank-deficient objective function or yield only one of an infinite number of particular solutions. In this contribution, we develop a framework for the rigorous computation of a general solution of a rank-deficient problem with inequality constraints. We aim for the computation of a unique particular solution which fulfills predefined optimality criteria as well as for an adequate representation of the homogeneous solution including the constraints. Our theoretical findings are applied in a case study to determine optimal repetition numbers for a geodetic network to demonstrate the potential of the proposed framework. 相似文献
37.
Abstract— The three major geochemical methods for impactor identification are evaluated with respect to their potential and limitations with regards to the precise detection and identification of meteoritic material in impactites. The identification of a projectile component in impactites can be achieved by determining certain isotopic and elemental ratios in contaminated impactites. The isotopic methods are based on Os and Cr isotopic ratios. Osmium isotopes are highly sensitive for the detection of minute amounts of extraterrestrial components of even <<0.05 wt% in impactites. However, this only holds true for target lithologies with almost no chemical signature of mantle material or young mantle‐derived mafic rocks. Furthermore, this method is not currently suitable for the precise identification of the projectile type. The Cr‐isotopic method requires the relatively highest projectile contamination (several wt%) in order to detect an extraterrestrial component, but may allow the identification of three different groups of extraterrestrial materials, ordinary chondrites, an enstatite chondrites, and differentiated achondrites. A significant advantage of this method is its independence of the target lithology and post‐impact alteration. The use of elemental ratios, including platinum group elements (PGE: Os, Ir, Ru, Pt, Rh, Pd), in combination with Ni and Cr represents a very powerful method for the detection and identification of projectiles in terrestrial and lunar impactites. For most projectile types, this method is almost independent of the target composition, especially if PGE ratios are considered. This holds true even in cases of terrestrial target lithologies with a high component of upper mantle material. The identification of the projectile is achieved by comparison of the “projectile elemental ratio” derived from the slope of the mixing line (target‐projectile) with the elemental ratio in the different types of possible projectiles (e.g., chondrites). However, this requires a set of impactite samples of various degree of projectile contamination. 相似文献
38.
A telescope based upon dark-lens diffractive optics would be a uniquely new instrument for solar astronomy. The image formation
process in such a telescope gives an intrinsically higher resolving power and a greatly reduced image intensity compared to
that of refracting or reflecting optical systems of similar lens dimension. This low image intensity would be an advantage
for solar observations made using a very large imaging element. After a brief overview of the history of solar instrument
development, a quantitative evaluation of the dark-lens diffracting solar telescope concept is presented, showing the potential
of this imaging method to meet or even to exceed the most demanding resolution goals currently being considered for future
space-borne solar telescopes. 相似文献
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Natural Hazards - In crisis situations, illiterates and people with other linguistic challenges are unable to understand text messages to inform or be informed of a situation. Pictographic... 相似文献