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Jonckheere I.G.C. Muys B. Coppin P.R. 《Geoscience and Remote Sensing Letters, IEEE》2005,2(3):296-300
A new methodology is presented to threshold high dynamic range hemispherical color photographs of forest canopies. It is based on the second derivative of brightness profiles along circular transects over the whole azimuthal range of angles at narrow annulus zenith rings. A fast, reliable, and objective way of extracting canopy forest parameters is described and illustrated for calculation of the monodirectional gap fraction around the zenith angle of 57.3/spl deg/, which is independent on average leaf angle distribution. 相似文献
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The concentration of ozone between 65 and 75 km has been determined from measurements of the attenuation of moonlight at 2570 Å made from a Moon-pointing rocket payload. The results support earlier rocket measurements, but are in marked disagreement with some recent data obtained by Hays and Roble using the stellar occultation technique. 相似文献
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Glas H. Jonckheere M. Mandal A. James-Williamson S. De Maeyer P. Deruyter G. 《Natural Hazards》2017,88(3):1867-1891
Natural Hazards - Flood risk assessments and damage estimations form integral parts of the disaster risk management in Jamaica, owing its vulnerability to hydrometeorological hazards. Although... 相似文献
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Konstanze Stübner Raymond Jonckheere Lothar Ratschbacher 《Geochimica et cosmochimica acta》2008,72(13):3184-3199
A simple atomistic Monte Carlo simulation suggests that there are up to four stages in the evolution of an etch pit in the (0 0 1)-surface of an idealised regular lattice. During the first stage, the etch pit is an inverted pyramid; its horizontal and vertical dimensions increase at a constant rate; the apparent horizontal (vh) and vertical (vd) growth rates are faster than during all subsequent stages but nevertheless less than the step retreat rate (vs) on account of surface etching (vv). The pyramid apex is truncated in the second stage; it is thereafter bounded by an expanding bottom plane and shrinking lateral walls; this is accompanied by a gradual decrease of vh; vd drops to a negative value indicating a slow decrease of the etch-pit depth; the bottom plane acquires a concave-up curvature; the outward curvature of the walls, initiated during the first stage, increases. During the third stage the etch pit consists of a single concave-up bottom plane; vh and vd decrease at declining rates; consecutive etch-pit profiles are scalable in the horizontal direction. The hypothetical fourth stage is inferred but not documented by the simulations; it sets in when vh is reduced to zero; unless this corresponds to an as yet unidentified steady-state condition, the etch pit from here on forth shrinks until it eventually disappears altogether. The sole cause for this succession is the process of stochastic rounding of confined steps and faces.The triangular footprint of recoil-track, fission-track, ion-track and dislocation etch pits in trioctahedral mica and its compliance with the monoclinic symmetries implies that the relevant periodic bond chains are O-Mg/Fe-O chains in the octahedral layer. The size distribution of etched recoil tracks is due to (1) depth variations resulting from the size distribution of the latent tracks, (2) the random truncation of the surface tracks, (3) the variable rate of etch-pit enlargement and (4) the fact that new tracks are exposed at the surface due to surface etching. The greater size of dislocation, fission-track and ion-track etch pits is due to their greater extent below the surface. The increase of the number of etched tracks with etching time due to bulk etching is non-linear because the bulk etch rate vv is not constant. The evolution of etch-pit shape with continued etching can also cause loss of tracks due to observation effects related to loss of contrast. 相似文献
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Raymond Jonckheere Daniel Heinz Bradley R. Hacker David Rafaja Lothar Ratschbacher 《地学学报》2019,31(3):263-270
This contribution reports Raman radiation damage measurements of zircons from the Kontinentale Tiefbohrung, on the western border of the Bohemian Massif. The mean wavenumbers (ω3) and widths (Γ3) of the ν3(SiO4) Raman band are constant down to 3 km, decrease (ω3) resp. increase (Γ3) between 3 and 5 km, and are again constant between 5 and 7 km. Uniform high Γ3 values associated with ω3 values close to those of undamaged zircon between 5 and 7 km are interpreted as due to residual damage predating the exhumation of the Bohemian Massif. A superimposed post‐exhumation signal indicates full damage retention down to 3 km depth, partial annealing between 3 and 5 km, and zero retention at greater depth. An attempt to calculate radiation damage ages gives results of a meaningful order of magnitude but also exposes difficulties associated with dating basement samples with complex damage accumulation and annealing histories. 相似文献
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一种裂变径迹密度统计的新方法 总被引：1，自引：0，他引：1
介绍了一种新的统计裂变径迹密度方法 ,比较和分析了新方法与传统标准方法的差异 ,得出新方法更为有效、准确的结论 相似文献
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Dating and forward modelling of the fission-track data of apatite samples from the Dereli–
ebinkarahisar region, south of Giresun in the Eastern Turkish Pontides, provides quantitative data on the regional tectonics resulting from the closure of neo-Thetys and the collision of Eurasia and Gondwana. The age vs. elevation profiles identified Senonian (80.7±3.2 to 62.4±2.5 Ma) slow uplift and denudation, interpreted as the result of the diapiric ascent of subduction-related plutons above the neo-Tethyan subduction zone beneath the Eurasian continent. This was followed by rapid differential uplift during the Palaeocene–Early Eocene (57.4±2.4 to 47.8±2.4 Ma), which juxtaposed granitoid units of different ages, compositions, and emplacement levels in the crust, and is thought to be related to the collision between the Pontide (Eurasian) and Anatolide (Gondwana) basements. The modelling results must be interpreted with caution, but appear to indicate a period of Mio-Pliocene (ca. 5 Ma) reheating related to volcanism associated with the westward escape of the Anatolian plate and uplift from the Pliocene (ca. 3.5 Ma) up to the present. 相似文献
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D. Boztuğ R. Jonckheere G. A. Wagner A. I. Erçin Z. Yeğingil 《International Journal of Earth Sciences》2007,96(5):875-886
The Kaçkar batholith in the Turkish eastern Pontides comprises several intrusive units with distinctive textural, mineralogical and geochemical characteristics. Their titanite and zircon fission-track ages confirm that the different lithodem units result from consecutive igneous episodes, establish their emplacement sequence and, together with geochemical data, help to relate them to their geodynamic context. The Çaml?kaya granitoid (112.4 ± 1.6 Ma) was emplaced during an immature-arc magmatic episode of early Cretaceous age. The S?rtyayla (57.1 ± 1.2 Ma) and Marselevat (52.9 ± 1.3 Ma) granitoids are late products of a late-Palaeocene mature-arc episode. The Ayder granitoid (46.4 ± 1.0 Ma) is the result of middle- to late-Eocene post-collisional magmatism related to slab break-off. The Halkal?ta? quartz diorite (43.7 ± 2.3 Ma) and the Güllüba? monzonite (38.1 ± 0.9 Ma) document a middle- to late-Eocene episode related to post-collisional extension. The data reveal the advantages of dense sampling, spanning a maximum range of elevations. Apart from the increased precision on the mean, redundant sampling allows to shift the basis for interpretation from a priori assumptions to a posteriori numerical criteria when using geochronometers with low to moderate closure temperatures, including apatite, titanite and zircon fission-tracks but also K–Ar (Ar–Ar) biotite, muscovite and K-feldspar. 相似文献
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本文分析了矿物自发裂变径迹的统计误差、自发与诱发裂变径数量的比值对姝影响，提出了自发裂变烃迹统计误差对ξ值的影响强于诱发裂变径迹、自发与诱发裂变径迹数量的比值对ξ值有显著影响的观点；利用ξ值计算矿物裂变径迹年龄时，正确识别和统计自发裂变径迹是提高裂变径迹年龄准确度的关键之一。 相似文献