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Cao, Yi,Jung, Haemyeong,Song, Shuguang,Park, Munjae,Jung, Sejin,Lee, Jaeseok Oxford University Press 2015 Journal of petrology Vol.56 No.10
<P>The fore-arc mantle above a subducting slab is a unique site where complex partial melting, melt/fluid-rock interaction, and deformation of mantle rocks occur. To constrain these geological and geodynamic processes we analyzed the deformation microstructures, crystal preferred orientations (CPOs or fabrics), and water content in natural harzburgites that occur as exhumed massifs in the North Qilian suture zone, NW China. These harzburgites are very fresh, and have mineral assemblages of olivine (similar to 81-87 vol. %), orthopyroxene (similar to 11-17 vol. %), clinopyroxene (similar to 1-2 vol. %), and spinel (similar to 1 vol. %). Detailed analyses of mineral textures, CPO patterns, and rotation axis distributions suggest that the plastic deformation of olivine and pyroxene was accommodated by activating a series of slip systems of dislocation. The olivine (A-/D-type fabric) shows dominant (010)[100] and/or (001)[100] slip systems, as well as other minor [100]-glide, {0kl}[100], and [001]glide slip systems. The orthopyroxene shows dominant (100)[001] and subordinate (010)[001] slip systems, with minor (100)[010] and (100)[0vw] slip systems. The water content is extremely low in the orthopyroxene (38-44ppm by weight), equilibrated olivine (4-7 ppm), and bulk-rock samples (9-14 ppm). Previously published refractory mineral and whole-rock compositions, as well as estimated low-pressure(similar to 1-2 GPa), high-temperature (similar to 1100-1300 degrees C), low-stress (similar to 1-4 MPa) and water-poor conditions of deformation, suggest that these harzburgites represent a remnant of fossil fore-arc lithospheric mantle that was probably both formed (experienced partial melting and high-temperature melt/fluid-rock reaction) and deformed in a young and warm fore-arc mantle setting (i.e. juvenile subduction zone). Based on these results, a refined schematic model of olivine fabric distributions in subduction zones is proposed. In this model, the A-/D-type olivine fabrics are inferred to be prevalent in fore-arc lithospheric mantle. The opposing polarizing directions of A-/D-type olivine fabrics with other underlying anisotropic sources in the mantle wedge (e.g. B-type olivine fabrics and oriented serpentinite layers) may weaken the trench-parallel fast S-wave anisotropy contributed by the deformed fore-arc mantle, and thus provide an alternative explanation for the short or nearly null delay times of local shear-wave splitting (sourced from intra-slab earthquakes) that have been detected in some fore-arc regions. In addition, topotactic antigorite fabrics after the A-/D-type olivine fabric might play a minor role in contributing to the low P-and S-wave velocities, high V-p/V-s ratios, and large seismic anisotropies that are typically observed in fore-arc mantle.</P>
Cao, Yi,Jung, Haemyeong,Song, Shuguang Elsevier 2018 Tectonophysics Vol.722 No.-
<P><B>Abstract</B></P> <P>Though extensively studied, the roles of olivine crystal preferred orientations (CPOs or fabrics) in affecting the seismic anisotropies in the Earth's upper mantle are rather complicated and still not fully known. In this study, we attempted to address this issue by analyzing the seismic anisotropies [e.g., P-wave anisotropy (A<I>Vp</I>), S-wave polarization anisotropy (A<I>Vs</I>), radial anisotropy (<I>ξ</I>), and Rayleigh wave anisotropy (<I>G</I>)] of the Songshugou peridotites (dunite dominated) in the Qinling orogen in central China, based on our previously reported olivine CPOs. The seismic anisotropy patterns of olivine aggregates in our studied samples are well consistent with the prediction for their olivine CPO types; and the magnitude of seismic anisotropies shows a striking positive correlation with equilibrium pressure and temperature (P–T) conditions. Significant reductions of seismic anisotropies (A<I>Vp</I>, max. A<I>Vs</I>, and <I>G</I>) are observed in porphyroclastic dunite compared to coarse- and fine-grained dunites, as the results of olivine CPO transition (from A-/D-type in coarse-grained dunite, through AG-type-like in porphyroclastic dunite, to B-type-like in fine-grained dunite) and strength variation (weakening: A-/D-type → AG-type-like; strengthening: AG-type-like → B-type-like) during dynamic recrystallization. The transition of olivine CPOs from A-/D-type to B-/AG-type-like in the forearc mantle may weaken the seismic anisotropies and deviate the fast velocity direction and the fast S-wave polarization direction from trench-perpendicular to trench-oblique direction with the cooling and aging of forearc mantle. Depending on the size and distribution of the peridotite body such as the Songshugou peridotites, B- and AG-type-like olivine CPOs can be an additional (despite minor) local contributor to the orogen-parallel fast velocity direction and fast shear-wave polarization direction in the orogenic crust such as in the Songshugou area in Qinling orogen.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Seismic anisotropies of natural peridotites were calculated. </LI> <LI> Positive correlation between P-T conditions and seismic anisotropies was found. </LI> <LI> Seismic anisotropies vary with the transition of olivine CPOs. </LI> <LI> Seismic anisotropies vary from trench-parallel to -oblique during forearc cooling. </LI> <LI> B-/AG-type-like olivine CPOs contribute minor orogen-parallel seismic anisotropies. </LI> </UL> </P>
Shaodi Ouyang,Jinjun Liu,Xinyu Wang,Shuguang Song,Xueyu Hou,Teng Wu 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
Power electronic transformer(PET) has been the focus of interest in recent years. Compared with conventional low frequency transformers, PETs can offer many additional functions such as phase shifting, frequency shifting and reactive power/harmonic compensation. This paper proposes a single phase PET for the Scott railway power system. The PET achieves active power control which balances the Scott’s secondary currents. The PET also achieves reactive/harmonic compensation. The configuration and control strategy of the proposed PET is discussed. Simulation results from PLECS verifies the effectiveness of the proposed PET and its control strategy.
Jianping Shen,Siwei Zhang,Wei Wang,Shuguang Li,Song Zhang,Yujun Wang 한국광학회 2021 Current Optics and Photonics Vol.5 No.3
A tapered As 2 S 3 photonic crystal fiber (PCF) with four layers of air holes in a hexagonal array around the core is designed in this paper. Numerical simulation shows that the dispersion D decreases and the nonlinearity coefficient γ increases from the thick to the thin end along the tapered PCF. We simulate the midinfrared pulse compression in the tapered As 2 S 3 PCF using the adaptive split-step Fourier method. Initial Gaussian pulses of 4.4 ps and a central wavelength of 2.5 μm propagating in the tapered PCF arelocated in the anomalous dispersion region. With an average power of assumed input pulses at 3 mW and a repetition frequency of 81.0 MHz, we theoretically obtain a pulse duration of 56 fs and a compression factor of 78 when the pulse propagates from the thick end to the thin end of the tapered PCF. When confinement loss in the tapered PCF is included in the simulation, the minimum pulse duration reaches 72 fs; correspondingly, the maximum compression factor reaches 61. The results show that in the anomalous-dispersion region, midinfrared pulses can be efficiently compressed in a dispersion-decreasing and nonlinearity-increasing tapered As 2 S 3 PCF. Due to confinement loss in the tapered fiber, the efficiency of pulse compression is suppressed.