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  • Artikel  (393)
  • Copernicus  (235)
  • Elsevier  (81)
  • Institute of Physics (IOP)  (61)
  • Geological Society of America (GSA)  (16)
  • Geologie und Paläontologie  (393)
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  • Artikel  (393)
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  • 1
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    Design of a high-power density energy system for solar powered aircraft (2018)
    Institute of Physics (IOP)
    Details
    Publikationsdatum: 2018-10-31
    Beschreibung: Maximum energy utilization and high-power density are critical to solar powered aircraft energy system. SiC devices have the advantages of high frequency and high temperature and it is very promising in the aspect of the development of high temperature and high-power density converter. This paper designed a 1.2 kW SiC based power controller using interleaved two-switch buck-boost converter, analyzed the working process of the converter, put forward small signal model and discussed three mode control strategy, and achieved smooth switching among all modes and maximum utilization of power energy. Experimental results demonstrate that the converter module has the power density of 2.4 kW/kg.
    Print ISSN: 1755-1307
    Digitale ISSN: 1755-1315
    Thema: Geographie , Geologie und Paläontologie , Physik
    Publiziert von Institute of Physics (IOP)
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
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    Improved control strategy for PI-R current of DFIG considering voltage and current harmonics compensation (2016)
    Institute of Physics (IOP)
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    Publikationsdatum: 2016-09-27
    Beschreibung: With the rapid development of wind power generation, the related research of wind power control and integration issues has attracted much attention, and the focus of the research are shifting away from the ideal power grid environment to the actual power grid environment. As the main stream wind turbine generator, a doubly-fed induction generator (DFIG) is connected to the power grid directly by its stator, so it is particularly sensitive to the power grid. This paper studies the improvement of DFIG control technology in the power grid harmonic environment. Based on the DFIG dynamic model considering the power grid harmonic environment, this paper introduces the shortcomings of the common control strategy of DFIG, and puts forward the enhanced method. The decoupling control of the system is realized by compensating the coupling between the rotor harmonic voltage and harmonic current, improving the control performance. In addition, the simulation experiments on PSCAD/EMTDC are ca...
    Print ISSN: 1755-1307
    Digitale ISSN: 1755-1315
    Thema: Geographie , Geologie und Paläontologie , Physik
    Publiziert von Institute of Physics (IOP)
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
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    Cu isotopes reveal initial Cu enrichment in sources of giant porphyry deposits in a collisional setting (2018)
    Geological Society of America (GSA)
    In: Geology
    Details
    Publikationsdatum: 2018
    Beschreibung: 〈span〉Porphyry copper deposits (PCDs) represent the most important type of Cu reservoir on Earth, but the mechanism of Cu enrichment in PCDs is debated due to the lack of direct constraints. This issue may be resolved by the study of copper isotopes (δ〈sup〉65〈/sup〉Cu), which are strongly fractionated during formation and/or precipitation of sulfides. Here we report high-precision Cu-isotope data on a large set of porphyries, mafic magmatic enclaves (MMEs), and sulfide ores from PCDs in southern Tibet. For comparison, barren intrusions from southern Tibet were also analyzed. The fertile porphyries and MMEs from PCDs have high Cu contents and elevated δ〈sup〉65〈/sup〉Cu values compared with the barren intrusions and global average felsic rocks. These features are inconsistent with the known supergene processes after sulfide formation (e.g., leaching and weathering). Because sulfides formed from secondary Cu-rich fluids are enriched in heavy Cu isotopes, the elevated Cu contents and Cu-isotope ratios indicate that the Cu source for PCDs was a refertilized lithosphere enriched in sulfides. This suggests that initial Cu enrichment in magma sources could be a key step in the formation of giant PCDs in continental collision zones.〈/span〉
    Print ISSN: 0091-7613
    Digitale ISSN: 1943-2682
    Thema: Geologie und Paläontologie
    Publiziert von Geological Society of America (GSA)
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  • 4
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    The 2013 Lushan earthquake: Implications for seismic hazards posed by the Range Front blind thrust in the Sichuan Basin, China (2014)
    Geological Society of America (GSA)
    In: Geology
    Details
    Publikationsdatum: 2014-09-20
    Beschreibung: Thrust and reverse faults pose significant earthquake hazards in convergent plate margins around the world, but have proven difficult to study given the complex nature of their ruptures, which often involve multiple along-strike and vertically stacked fault segments. The 2013 M w 6.6 Lushan earthquake exemplified this complexity, rupturing a blind thrust fault in the southern Longmen Shan, which border the western Sichuan Basin in China. This event occurred 80 km south of the epicenter of the destructive 2008 M w 7.9 Wenchuan earthquake. The Wenchuan earthquake produced surface ruptures on two parallel fault splays, the Pengguan and Beichuan faults. In contrast, the Lushan earthquake was generated by a ramp in the Range Front blind thrust (RFBT), which is in the footwall of the Wenchuan rupture. We use seismic reflection profiles, petroleum wells, and relocated seismicity to construct a three-dimensional model of this imbricated fault system. Our model illustrates that the 2013 Lushan earthquake ruptured 〈10% of the RFBT, which extends for 250 km along the Longmen Shan range front and into the western Sichuan Basin. Analysis of growth strata in structures above the RFBT fault along strike shows clear evidence of Quaternary activity and constrains the middle Pleistocene to current slip rate at two locations on the fault. Single segment and multisegment fault rupture scenarios involving the RFBT suggest the potential for large earthquakes (M7.8) that would affect the densely populated western Sichuan Basin. Assessing the hazards posed by such complex thrust systems, which occur in convergent margins worldwide, requires subsurface characterization of fault segments that can be independently associated with geologic and seismologic evidence of fault activity.
    Print ISSN: 0091-7613
    Digitale ISSN: 1943-2682
    Thema: Geologie und Paläontologie
    Publiziert von Geological Society of America (GSA)
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
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    Temperature and leaf wax {delta}2H records demonstrate seasonal and regional controls on Asian monsoon proxies (2014)
    Geological Society of America (GSA)
    In: Geology
    Details
    Publikationsdatum: 2014-11-25
    Beschreibung: Orbital-scale precipitation isotope records can elucidate climate forcing mechanisms and provide benchmarks for climate model validation. The ability to differentiate the influence of temperature, seasonality, and vapor transport history on precipitation isotope proxies is critical to both objectives. We present a 300 k.y. leaf wax hydrogen isotope record from the South China Sea with the effects of local condensation temperature removed ( 2 H wax– T ). 2 H wax– T reflects annually integrated precipitation 2 H in the Pearl River catchment of southeast China. Depleted 2 H wax– T lags minimum precession (P min ) by 1.0 ± 0.7 k.y., reflecting the influence of maximum summer insolation and minimum winter insolation, with a minor influence of global ice volume, which lags P min by 3.3 ± 0.4 k.y. In contrast, annually integrated cave 18 O minima in central China, 1000 km north of our site, lag P min by 2.7 ± 0.3 k.y., in phase with ice volume minima. This phase indicates that precipitation 18 O in central China is more strongly influenced by ice volume forcing at the precession band, with a lesser influence of Northern Hemisphere insolation. Our new 2 H wax– T data demonstrate that precipitation isotopes in Asia have strong regional variability. Interpreting water isotope records within the context of regionally varying temperature, seasonality, and sensitivity to changing glacial boundary conditions is imperative to understanding Asian hydroclimatic change.
    Print ISSN: 0091-7613
    Digitale ISSN: 1943-2682
    Thema: Geologie und Paläontologie
    Publiziert von Geological Society of America (GSA)
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
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    Effect of unbalanced magnetic pull and hydraulic seal force on the vibration of large rotor-bearing systems (2014)
    Institute of Physics (IOP)
    Details
    Publikationsdatum: 2014-12-11
    Beschreibung: The influence of unbalanced magnetic pull (UMP) and hydraulic seal force on the vibration of large rotor-bearing systems is studied. The UMP caused by rotor eccentricity imposes important effects on rotating machinery, especially for large generators such as water turbine generator sets, because these machines operate above their first critical speed in some instances and are supported by oil film bearings. A magnetic stiffness matrix for studying the effects of the UMP is proposed. The magnetic stiffness matrix can be generated by decomposing the expression of air gap magnetic field energy. Two vibration models are constructed using the Lagrange equation. The difference between the two models lies in the boundary support condition: one has rigid support and the other has elastic bearing support. The influence of the magnetic stiffness and elastic support on the critical speed of the rotor is studied using Lyapunov nonlinear vibration stability theory. The vibration amplitude of...
    Print ISSN: 1755-1307
    Digitale ISSN: 1755-1315
    Thema: Geographie , Geologie und Paläontologie , Physik
    Publiziert von Institute of Physics (IOP)
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
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    Estimating soil total nitrogen contents from visible/near-infrared reflectance based on successive projections algorithm (2014)
    Institute of Physics (IOP)
    Details
    Publikationsdatum: 2014-03-19
    Beschreibung: The Visible/near-infrared reflectance (Vis/NIR) spectroscopy combined with multiple regression methods have been employed to assess various soil properties quantitatively. However, useless or irrelevant information in some bands worsen the performances of the calibrated models. Successive projections algorithm (SPA) is an effective technique for selecting informative variables, and its application potential in estimating soil contents using visible/near-infrared reflectance (Vis/NIR) spectroscopy has not been explored. This paper aimed to explore the effect of SPA combined with support vector machine regression (SVMR) on soil total nitrogen (TN) contents estimation using Vis/NIR spectroscopy. For this purpose, SPA-SVMR was compared with full spectrum based SVMR (FS-SVMR) for soil total nitrogen (TN) estimation, respectively. The results showed that the SPA-SVMR model (R 2 v = 0.58, RMSEV = 0.364) performed better than the FS-SVMR model (R 2 ...
    Print ISSN: 1755-1307
    Digitale ISSN: 1755-1315
    Thema: Geographie , Geologie und Paläontologie , Physik
    Publiziert von Institute of Physics (IOP)
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  • 8
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    The impact of climate change on summer maize phenology in the northwest plain of Shandong province under the IPCC SRES A1B scenario (2014)
    Institute of Physics (IOP)
    Details
    Publikationsdatum: 2014-03-19
    Beschreibung: Climate change will affect agricultural production. Combining a climate model and a crop growth model furnishes a good approach for analyzing this effect quantitatively. The purpose of this study is to analyze the effect of climate change on summer maize phenology in northwest Shandong province under the A1B climate scenario using a regional climate model and the CERES-Maize growth model. The results showed that the temperature would increase significantly during the maize growth season in the study region, that the increased temperature would shorten the maize growth stage and result in a potential yield loss using the current cultivar, and that it is critical to breed a heat-resistant and late-maturing cultivar to maintain the yield.
    Print ISSN: 1755-1307
    Digitale ISSN: 1755-1315
    Thema: Geographie , Geologie und Paläontologie , Physik
    Publiziert von Institute of Physics (IOP)
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  • 9
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    Evidence for insect-mediated skeletonization on an extant fern family from the Upper Triassic of China (2014)
    Geological Society of America (GSA)
    In: Geology
    Details
    Publikationsdatum: 2014-04-19
    Beschreibung: Leaf skeletonization represents a distinctive form of insect feeding behavior. It commonly occurs in angiosperm leaves after their initial appearance during the Early Cretaceous. This type of feeding behavior rarely has been documented in pre-Mesozoic fossils. We describe the earliest evidence of insect-skeletonized leaves of Dictyophyllum nathorstii Zeiller, affiliated with the extant fern family Dipteridaceae in the Late Triassic Yipinglang flora from southwestern China. The skeletonization generally is located adjacent to the pinna rachilla of the distal free portion of the leaf. In the skeletonized area, the interveinal tissue is completely removed, exposing the pinna rachilla, pinnule midveins, and lateral veins. Most nonvascular tissue has been removed between the vascular bundles, the latter forming polygonal meshes of varying size. Our report of insect-mediated skeletonization of fern leaves from southwestern China fills a spatiotemporal gap in the published data on the paleogeographical distribution and stratigraphic occurrence of plant–arthropod associations, and indicates an antagonistic relationship between a fern host and its insect herbivore.
    Print ISSN: 0091-7613
    Digitale ISSN: 1943-2682
    Thema: Geologie und Paläontologie
    Publiziert von Geological Society of America (GSA)
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
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    Effect of gas volume fraction on vortex motion in hydraulic turbine (2018)
    Institute of Physics (IOP)
    Details
    Publikationsdatum: 2018-07-31
    Beschreibung: In order to analyze the vortex motion in the flow channel of the hydraulic turbine impeller during the gas volume fraction change. Now, the pump with a specific speed of 55.7 is chosen as hydraulic turbine. On the basis of considering the gas compressibility, to take numerical calculation on the model under different flow rates and different gas volume fraction, to analyze the influence of gas volume fraction on vortex motion law in the impeller flow channel. Findings: When the flow rate is small, the relative velocity distribution in the impeller flow channel is uneven, the velocity field is chaotic, and there are obvious vortices, with the increase of the gas volume fraction, the vortices in the impeller flow channel gradually move to the inlet direction of the blade; With the increase of the flow rate, the flow in the channel of the hydraulic turbine impeller is unstable. Both the pressure surface and the suction surface of the blade appear vortices, the vortex region in the ...
    Print ISSN: 1755-1307
    Digitale ISSN: 1755-1315
    Thema: Geographie , Geologie und Paläontologie , Physik
    Publiziert von Institute of Physics (IOP)
    Standort Signatur Erwartet Verfügbarkeit
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