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  • Articles  (10)
  • Geosciences  (10)
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  • Articles  (10)
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  • 1
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    Numerical simulation of acoustic field in logging-while-drilling borehole generated by linear phased array acoustic transmitter (2019)
    Oxford University Press
    Details
    Publication Date: 2019
    Description: 〈span〉〈div〉SUMMARY〈/div〉In actual monopole acoustic logging-while-drilling (LWD), the acquisition of formation velocities is rather difficult because of a strong collar wave interference. In this study, a method is proposed to enhance the amplitudes of formation gliding waves in an LWD borehole, based on the directional radiation technology of linear phased array (LPA) acoustic transmitters. Waveforms in the LWD borehole generated by a monopole acoustic transmitter and LPA acoustic transmitters are numerically simulated using the finite-difference method. The influence of the LPA parameters on the various waves in the LWD borehole is also analysed. The simulation results show that the guided waves in the LWD borehole generated by the LPA acoustic transmitter have the same type but different relative amplitudes compared to those generated by the monopole transmitter. The angular width and deflection angle of the main radiated acoustic beam in the borehole can be controlled by adjusting the LPA parameters. As the delay time between the excitation signals applied to adjacent elements is increased, the deflection angle of the main radiated acoustic beam in the borehole satisfies the generation conditions for the gliding compressional (〈span〉P〈/span〉) and shear (〈span〉S〈/span〉) waves, successively. When the delay time is set such that the deflection angle is equal to the first (or second) critical angle of the formation, the amplitude of the gliding 〈span〉P〈/span〉 (or 〈span〉S〈/span〉) wave is greatly enhanced. Moreover, the amplitude of the gliding 〈span〉P〈/span〉 (or 〈span〉S〈/span〉) wave increases linearly as the element number increases under such conditions. Therefore, compared to the monopole acoustic transmitter, the LPA acoustic transmitter can be utilized to effectively improve the reliability of the acoustic LWD tool in measuring formation velocities. This study establishes a theoretical foundation for the next-generation acoustic LWD tool development.〈/span〉
    Print ISSN: 2051-1965
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 2
    Electronic Resource
    Electronic Resource
    A new compact spin- and angle-resolving photoelectron spectrometer with a high efficiency (1998)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 5 (1998), S. 741-743 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A portable spin- and angle-resolving photoelectron spectrometer has been constructed, equipped with a newly developed compact retarding-potential Mott-scattering electron spin polarimeter with an efficiency of 1.9 × 10−4 for a gold target. Based on Monte Carlo calculations for the spin-dependent electron-scattering process and electron ray-tracing calculations, a novel design of the retarding-field electron optics with 0.59 sr collection solid angle for scattered electrons has been accomplished. Utilizing this spectrometer, the spin- and angle-resolved photoelectron spectra have been measured and the spin-dependent electronic structure of Ni(110), Ni(110)-p(2 × 1)O and Ni(110)-c(2 × 2)S along the {\overline {\Gamma S}} line of the Ni(110) surface Brillouin zone have been studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049597019067
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  • 3
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    Holocene shifts in riverine fine-grained sediment supply to the East China Sea Distal Mud in response to climate change (2014)
    Sage
    In: Holocene
    Details
    Publication Date: 2014-09-12
    Description: Holocene changes in fine-grained sediment supplies to the East China Sea outer shelf were uncovered, through the mineralogical and geochemical analysis of Core B3 in the East China Sea Distal Mud (ECSDM). Based on the lithology, accelerator mass spectrometry (AMS) 14 C dating, and sea-level change, Core B3 can be divided into two major units: transgressive stage (Unit 1: 12.5–6.8 kyr) and highstand stage (Unit 2: 6.8–0 kyr). Significant discrepancy of dolomite/calcite ratio in the fine fractions (〈16 µm) of Changjiang (dolomite/calcite = 3:1) and Huanghe (dolomite/calcite = 1:22) sediments was used as a new uniqueness provenance tracer to distinguish these two riverine sources. Both of the dolomite/calcite ratio and rare earth elements fractionation parameters in the fine-grained sediment indicated distinct provenance shifts of Core B3 during the Holocene. Unit 1 of Core 3 (12.5–6.8 kyr) mainly consists of the reworked and resuspension sediments of the East China Sea shelf during the Holocene transgression, while Unit 2 sediments (6.8–0 kyr) are most likely sourced from the Changjiang and Huanghe. Moreover, mixing curves of dolomite/calcite ratio reveal that the ECSDM continuously received the Changjiang sediment since 6.1 kyr with notable fluctuations, whereas the Huanghe sediment supply began in 6.8 kyr but abruptly stopped during 4.2–0.8 kyr and then appeared again since 0.8 kyr. Temporal changes of the Changjiang and Huanghe fine-grained sediment contribution to the ECSDM are closely related to the formation of modern oceanic circulation system since 6.8 kyr (shelf sea-level change), the ‘4.2 kyr’ climate event, and the followed transition to cold and dry climate condition in the northeastern China (global climate change), as well as the artificial shift of lower Huanghe course in ad 1128 in the war against invasion of the northern nomadic nation (human activities).
    Print ISSN: 0959-6836
    Electronic ISSN: 1477-0911
    Topics: Geography , Geosciences
    Published by Sage
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  • 4
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    Heat- and melt-fluxed melting of lower continental crust: Insights from two types of subduction-related granitoids in northeastern China and the implications for crustal reworking and growth (2019)
    Geological Society of America (GSA)
    Details
    Publication Date: 2019
    Description: 〈span〉Convergent plate boundaries are the primary location for the formation of continental crust by the intrusion of arc batholiths that contain essentially mantle-derived magmas. This paper presents two types of arc granitoids (enclave-free monzogranites and enclave-bearing granodiorites) in northeastern (NE) China to understand crustal evolution and growth in the eastern Asian continental margin. The monzogranites (189 Ma) show characteristics typical of upper continental crust, with high SiO〈sub〉2〈/sub〉 contents and enrichment of K, Rb, and Pb. These monzogranites have low 〈span〉I〈/span〉〈sub〉Sr〈/sub〉 (〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr) ratios (0.70378–0.70413) and positive ε〈sub〉Nd〈/sub〉 (t) (+2.2 to +2.3) and ε〈sub〉Hf〈/sub〉 (t) (+7.3 to +10.2) values. These features, combined with high zircon saturation temperatures (〈span〉T〈/span〉〈sub〉Zr〈/sub〉 〉 800 °C), suggest that the monzogranites were generated by the heat-fluxed melting of juvenile lower crust. In contrast, the granodiorites (171 Ma) contain abundant coeval mafic enclaves and show relatively low silica contents, low 〈span〉T〈/span〉〈sub〉Zr〈/sub〉 (748–799 °C), and particularly wide variation in ε〈sub〉Hf〈/sub〉 (t) (-3.5 to +5.6), implying a hybrid origin involving both mantle- and crust-derived components. Isotopic modeling indicates that mantle material accounts for around 60%–70% of the hybrid magmas by volume. The granodiorites have adakite-like signatures (e.g., Sr/Y 〉 21 and [La/Yb]〈sub〉N〈/sub〉 〉 15), which may have been primarily caused by a process of magma mixing and hornblende-dominated fractional fractionation, rather than through melting of a subducting slab or thickened lower crust. The two distinct granitoids (monzogranites and granodiorites) represent continental crustal reworking and growth, respectively, related to the subduction of the Paleo-Pacific Plate beneath the eastern Asian continental margin during the Jurassic.〈/span〉
    Print ISSN: 1941-8264
    Electronic ISSN: 1947-4253
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 5
    facet.materialart.
    Unknown
    Heat- and melt-fluxed melting of lower continental crust: Insights from two types of subduction-related granitoids in northeastern China and the implications for crustal reworking and growth (2019)
    Geological Society of America (GSA)
    Details
    Publication Date: 2019
    Description: 〈span〉〈div〉Abstract〈/div〉Convergent plate boundaries are the primary location for the formation of continental crust by the intrusion of arc batholiths that contain essentially mantle-derived magmas. This paper presents two types of arc granitoids (enclave-free monzogranites and enclave-bearing granodiorites) in northeastern (NE) China to understand crustal evolution and growth in the eastern Asian continental margin. The monzogranites (189 Ma) show characteristics typical of upper continental crust, with high SiO〈sub〉2〈/sub〉 contents and enrichment of K, Rb, and Pb. These monzogranites have low 〈span〉I〈/span〉〈sub〉Sr〈/sub〉 (〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr) ratios (0.70378–0.70413) and positive ε〈sub〉Nd〈/sub〉 (t) (+2.2 to +2.3) and ε〈sub〉Hf〈/sub〉 (t) (+7.3 to +10.2) values. These features, combined with high zircon saturation temperatures (〈span〉T〈/span〉〈sub〉Zr〈/sub〉 〉 800 °C), suggest that the monzogranites were generated by the heat-fluxed melting of juvenile lower crust. In contrast, the granodiorites (171 Ma) contain abundant coeval mafic enclaves and show relatively low silica contents, low 〈span〉T〈/span〉〈sub〉Zr〈/sub〉 (748–799 °C), and particularly wide variation in ε〈sub〉Hf〈/sub〉 (t) (−3.5 to +5.6), implying a hybrid origin involving both mantle- and crust-derived components. Isotopic modeling indicates that mantle material accounts for around 60%–70% of the hybrid magmas by volume. The granodiorites have adakite-like signatures (e.g., Sr/Y 〉 21 and [La/Yb]〈sub〉N〈/sub〉 〉 15), which may have been primarily caused by a process of magma mixing and hornblende-dominated fractional fractionation, rather than through melting of a subducting slab or thickened lower crust. The two distinct granitoids (monzogranites and granodiorites) represent continental crustal reworking and growth, respectively, related to the subduction of the Paleo-Pacific Plate beneath the eastern Asian continental margin during the Jurassic.〈/span〉
    Print ISSN: 1941-8264
    Electronic ISSN: 1947-4253
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 6
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    Unknown
    Flow slides run-out prediction using a sliding-consolidation model (2013)
    Springer
    Details
    Publication Date: 2013-08-29
    Print ISSN: 1612-510X
    Electronic ISSN: 1612-5118
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Published by Springer
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  • 7
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    A preliminary design of a knot undulator (2012)
    International Union of Crystallography
    Details
    Publication Date: 2012-11-10
    Description: The magnetic field configuration of the previously proposed knot undulator [Qiaoet al.(2009).Rev. Sci. Instrum.80, 085108] is realised in the design of a hybridized elliptically polarized undulator, which is presented. Although the details of the field distribution are not the same as those in the theoretical proposal, it is demonstrated that the practical knot undulator could work perfectly. In order to understand the minor discrepancies of the two, mathematical formulae of the synchrotron radiation are derived based on the Fourier transform of the magnetic field. From the results of calculations by simulation program, the discrepancies could be well interpreted by the corresponding formulae. The results show the importance of optimization of the end sections of the knot undulator to suppress the on-axis heat load. Furthermore, a study of the impact of the undulator on beam dynamics of the storage ring was conducted using the Shanghai Synchrotron Radiation Facility as an example and the results show that the knot undulator has little effect on the beam.
    Print ISSN: 0909-0495
    Electronic ISSN: 1600-5775
    Topics: Geosciences , Physics
    Published by International Union of Crystallography
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  • 8
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    Performance of the BL03U beamline at SSRF (2020)
    International Union of Crystallography
    Details
    Publication Date: 2020-07-28
    Description: The vacuum ultraviolet beamline BL03U with a photon energy range from 7 eV upwards has been constructed at the 3.5 GeV Shanghai Synchrotron Radiation Facility. Equipped with an APPLE-Knot undulator, this beamline is dedicated to angle-resolved photoemission spectroscopy. An energy-resolving power of higher than 4.6 × 104 has been achieved in the photon energy range 21.6–48 eV, which is almost the same as the theoretical estimation.
    Print ISSN: 0909-0495
    Electronic ISSN: 1600-5775
    Topics: Geosciences , Physics
    Published by International Union of Crystallography
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  • 9
    facet.materialart.
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    A new compact spin- and angle-resolving photoelectron spectrometer with a high efficiency (1998)
    International Union of Crystallography
    Details
    Publication Date: 1998-05-01
    Description: A portable spin- and angle-resolving photoelectron spectrometer has been constructed, equipped with a newly developed compact retarding-potential Mott-scattering electron spin polarimeter with an efficiency of 1.9 × 10−4 for a gold target. Based on Monte Carlo calculations for the spin-dependent electron-scattering process and electron ray-tracing calculations, a novel design of the retarding-field electron optics with 0.59 sr collection solid angle for scattered electrons has been accomplished. Utilizing this spectrometer, the spin- and angle-resolved photoelectron spectra have been measured and the spin-dependent electronic structure of Ni(110), Ni(110)-p(2 × 1)O and Ni(110)-c(2 × 2)S along the {overline {Gamma S}} line of the Ni(110) surface Brillouin zone have been studied.
    Print ISSN: 0909-0495
    Electronic ISSN: 1600-5775
    Topics: Geosciences , Physics
    Published by International Union of Crystallography
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  • 10
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    High temperature oxidation resistance improvement of carbon-carbon composite (1993)
    Elsevier
    Details
    Publication Date: 1993-01-01
    Print ISSN: 0008-6223
    Electronic ISSN: 1873-3891
    Topics: Chemistry and Pharmacology , Geosciences
    Published by Elsevier
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