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Measuring magnetic declination with a compass, virtual globes and a global positioning system

International Journal of Digital Earth 2009年第1期2卷 31-43页

作者： William P.O’Brien Jr Physics Department Southwestern UniversityGeorgetownTexas78626USA

Earth’s magnetic declination was experimentally measured at 15 sites in western USA from Alaska to Texas;each site exhibited a large linear feature identifiable in virtual globe imagery(NASA’s World Wind or Google Earth).The difference between the geographic bearing of the linear feature measured directly on a virtual globe image and the magnetic bearing of the same linear feature measured on the ground with a compass defines the magnetic declination d for that *** all 15 sites,d values,determined by this differencing procedure,ranged from about 208 to 58 E and fell within 18(over half within 0.58)of expected *** positioning system(GPS)data recorded at most sites and plotted on virtual globe images aided in the identification of relevant *** straightforward method for determining magnetic declination using virtual globe software and a compass provides a contemporary geospatial field/laboratory activity that dramatically elucidates and contrasts features of magnetic and geographic coordinate systems for students in various disciplines involving geomagnetism,navigation,geography or spherical polar geometry.

关键词： Earth observation GPS magnetic declination geophysics

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Changes of Seed Germination during the Year

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Agricultural Sciences 2016年第3期7卷 164-174页

作者： Ladislav Bláha Jiří Hermuth Crop Research Institute Prague Czech Republic

It is possible to conclude that typical course of graph which analyse course of germinability during the year at every cultivar is observable. Germination usually shows a minimum in December, but mainly in January and in February. Maximum of germinability is observed in the spring and summer time. This phenomenon isn’t result of the dormancy or secondary dormancy because during of long term seed storage, germinability has similar curve every year, only number of germinative seeds stepwise decrease every year at every month of storage. Every species or cultivar of crops has a typical course of the germinability during the year. There are also species (crops), that have germination process during the year almost constant i.e., without variation during the year, but it is a minority of genotypes, rather exceptions. The annual course of germination is nearly identical to the annual course of the magnetic declination. From the theoretical practical view, there is possibility (but not certainty!) that in case of testing the seed germination at begin or end of year at genotypes with large variability of germinability during the year, that this phenomenon have negative impact on seed certification by companies producing seeds for cultivation practice in some species.

关键词： magnetic declination magnetic Field Influence of Magnetism Seed Germination Year Season

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The paleomagnetism and geological significance of Meso-proterozoic dyke swarms in the central North China Craton

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Science China Earth Sciences 2001年第2期44卷 185-192页

作者：侯贵廷李江海钱祥麟张宝兴 H.C.Halls Department of Geology Peking University Beijing 100871 China Department of Geoscience University of Toronto Canada

The Mesoproterozoic mafic dyke swarms are extensively distributedin the central North China Craton(NCC) including North Shanxi, Wutai and Lüliang areas, which are not deformed and metamorphic but high magnetic, so the dyke swarms become the mark to compare the high meta-morphic rock areas in magnetism. Based on the analysis of paleomagnetism of mafic dyke swarms in North Shanxi, Wutai and Lüliang areas, NCC inclined southward about 18° so that North Shanxi lifted up and rotated 10° left to Wutai area. The dyke swarms in Lüliang developed later than in North Shanxi and Wutai area. The NNW-trending and WNW-trending dyke swarms developed in Lüliang while the North China Plate moved northward consistently so that the paleomagnetism of dyke swarms in Lüliang is greatly different from North Shanxi and Wutai area.

关键词： Mesoproterozoic mafic dyke swarms paleomagnetism magnetic inclination magnetic declination apparent polar wander path

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