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Aligned Ion Conduction Pathway of Polyrotaxane‑Based Electrolyte with Dispersed Hydrophobic Chains for solid‑state Lithium–Oxygen Batteries

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Nano-Micro Letters 2025年第2期17卷 169-186页

作者： Bitgaram kim Myeong‑Chang sung Gwang‑Hee Lee Byoungjoon hwang sojung seo Ji‑Hun seo Dong‑Wan kim Department of Materials science and Engineering Korea University145 Anam‑RoSeongbuk‑GuSeoul 02841Republic of Korea school of Civil Environmental and Architectural EngineeringKorea University145 Anam‑RoSeongbuk‑GuSeoul 02841Republic of Korea Materials science and Chemical Engineering Center Institute for Advanced Engineering(IAE)Yongin 17180Republic of Korea

A critical challenge hindering the practical application of lithium–oxygen batteries(LOBs)is the inevitable problems associated with liquid electrolytes,such as evaporation and safety *** study addresses these problems by proposing a modified polyrotaxane(mPR)-based solid polymer electrolyte(sPE)design that simultaneously mitigates solvent-related problems and improves ***-sPE exhibits high ion conductivity(2.8×10^(−3)s cm^(−1)at 25℃)through aligned ion conduction pathways and provides electrode protection ability through hydrophobic chain *** this mPR-sPE into solid-state LOBs resulted in stable potentials over 300 *** situ Raman spectroscopy reveals the presence of an LiO_(2)intermediate alongside Li_(2)O_(2)during oxygen *** situ X-ray diffraction confirm the ability of the sPE to hinder the permeation of oxygen and moisture,as demonstrated by the air permeability *** present study suggests that maintaining a low residual solvent while achieving high ionic conductivity is crucial for restricting the sub-reactions of solid-state LOBs.

关键词： solid polymer electrolyte Lithium-oxygen batteries Polyrotaxane ion conductivity Hydrophobic chain

small Zeros of Additive Forms in several Variables

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Acta Mathematica sinica,English series 1998年第1期14卷 57-66页

作者： J. s. hwang Institute of Mathematics Academia Sinica Taipei Taiwan 11529 China

Let f（X） be an additive form defined by f（X）=f（x1. x2,…,xs）=σ1α1x1k+σα2x2k+…+σsαsxsk, where αo≠0 is integer, i=1, 2,…, s. In 1979, schmidt proved that if ε>0 then there is a large constant C（k, ε）... 详细信息

Let f（X） be an additive form defined by f（X）=f（xsub>1sub>. xsub>2sub>,…,xsub>ssub>）=σsub>1sub>αsub>1sub>xsub>1sub>sup>ksup>+σsub>αsub>sub>2sub>xsub>2sub>sup>ksup>+…+σsub>ssub>αsub>ssub>xsub>ssub>sup>ksup>, where αsub>osub>≠0 is integer, i=1, 2,…, s. In 1979, schmidt proved that if ε>0 then there is a large constant C（k, ε） such that for s≥C（k, ε） the equation f（X）=0 has a nontrivial integer solution in σsub>1sub>. σsub>2sub>,…σsub>ssub>, xsub>1sub>, xsub>2sub>…,xsub>ssub> satisfying σsub>isub>=±1 and |xsub>isub>|≤Asup>εsup>, i=1, 2.…,s where A=max|ai|. schmidt did not estimate this constant C（k. ε） since it would be extremely large. In this paper, we prove the following result: Theorem 1 If log A≤1/ε,then C（k,ε）≤max （2/ε,20）; if log A>1/ε,A is sufficiently larye and 1/2A≤5≤|asub>isub>|≤A,i=1. 2,…, s, then C（k,ε）≤csub>1sub>csub>2sub>sup>psup> and if the last condition is omitted, then C（k. ε）≤[4/ε]csub>1sub>csub>2sub>,where csub>1sub>={2k+1 for≤k≤11 [5ksup>2sup>log k] for k≥12, csub>2sub>=100csub>1sub>ksup>2sup>2sup>ksup>+csub>1sub>sup>2sup> and p=2[log 2csub>1sub>/ε]. We note that the inequality in the first case is sharp but not in the second case.

关键词： Additive form subset sums small zeros

Design Features and Commissioning of the Versatile Experiment spherical Torus (VEsT) at seoul National University

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Plasma science and Technology 2013年第3期15卷 244-251页

作者： k.J.CHUNG Y.H.AN B.k.JUNG H.Y.LEE C.sUNG Y.s.NA T.s.HAHM Y.s.hwang Department of Nuclear Engineering Seoul National University

A new spherical torus called VEsT （Versatile Experiment spherical Torus） is designed, constructed and successfully commissioned at seoul National University. A unique design feature of the VEsT is two partial solenoid coils installed at both vertical ends of a center stack, which can provide sufficient magnetic fluxes to initiate tokamak plasmas while keeping a low aspect ratio configuration in the central region. According to initial double null merging start-up scenario using the partial solenoid coils, apprdpriate p6wer supplies for driving a toroidal field coil, outer poloidal field coils, and the partial solenoid Coils are fabricated and successfully commissioned. For reliable start-up, a pre-ionization system with two cost-effective homemade magnetron power supplies is also prepared. In addition, magnetic and spectroscopic diagnostics with appropriate data acquisition and control systems are well prepared for initial operation of the device. The VEsT is ready for tokamak plasma operation by completing and commissioning most of the designed components.

关键词： spherical torus partial solenoids double null merging start-up

strain hardening rate dependency of deformation shape,strain distribution,and contact pressure during wire flat rolling

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Journal of Iron and steel Research International 2023年第3期30卷 475-486页

作者： Joong-ki hwang school of Mechatronics Engineering Korea University of Technology and EducationCheonan 31253Republic of Korea

The effect of the strain hardening exponent(n)of a material on the changes in shape,strain inhomogeneity,and contact pressure was investigated during wire flat rolling to understand its effect on the deformation behavior of a flat-rolled wire and to determine the optimal working conditions with *** deformation behaviors of wires with various n values were systematically compared using finite element *** shape of the deformed wire was found to depend on the n value of the *** the contact width and lateral spreading of the wire decrease with increasing n,resulting in a large reduction in area with the n *** strain homogeneity of the wire increases with the n value of the *** improvement in the strain homogeneity with the n value is attributable to two factors:a lower strain concentration in the central region and a higher overall elongation as n *** addition,the average effective strain of the wire cross section decreases with the n value of a material during wire flat *** contact pressure distribution on the surface of the wire differs significantly depending on the n *** materials with a low n value,the contact pressure exhibits a higher value at the entry and edge zones of the contact *** contrast,materials with high n values exhibit a higher contact pressure at the exit *** behavior can be explained by the strain hardening behavior of the material during wire flat rolling.

关键词： strain hardening exponent Wire flat rolling shape change strain inhomogeneity Contact pressure

Effect of drawing speed on microstructure distribution and drawability in twinning-induced plasticity steel during wire drawing

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Journal of Iron and steel Research International 2020年第5期27卷 577-587页

作者： Joong-ki hwang school of Mechanical Engineering Tongmyong UniversityBusan 48520Republic of Korea

The effect of drawing speed on temperature rise and microstructure distribution in twinning-induced plasticity(TWIP)steel during wire drawing has been investigated to improve drawability for wire rod *** wire drawing process is performed at room temperature,heat is generated due to the plastic deformation and friction at the wire-die *** steel wires subjected to the low drawing speed(LD)of 0.5 m/min and the high drawing speed(HD)of 5.0 m/min were analyzed using the numerical simulation and electron backscatter diffraction ***,the specimens subjected to the HD had a higher drawability by about 18%compared to the LD,which is totally different from the general behavior of plain carbon pearlitic *** LD wire had uniform temperature distribution along the radial direction during wire *** contrast,the HD wire had a temperature gradient along the radial direction due to the higher frictional effect at surface:the minimum temperature of 58℃ at center area and the maximum temperature of 143 C at surface *** higher stacking fault energy of HD wire at the surface area due to the high temperature rise retarded twinning rate,resulting in the prevention of fast exhaustion in ductility in comparison with the LD wires since the earlier depletion of twins at surface area is known as the main reason for the fracture of TWIP steel during wire ***,HD process delayed the fracture strain of wire and increased the uniformity of microstructure and mechanical properties along the radial direction.

关键词： Twinning-induced plasticity steel Wire drawing Deformation twin Drawing speed Temperature rise

Analysis on motion of Earth’s center of mass observed with CHAMP mission

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science China(Physics,Mechanics & Astronomy) 2008年第10期51卷 1597-1606页

作者： hwang CheinWay National Astronomical Observatories Chinese Academy of Sciences Department of Civil Engineering Chiao Tung University

Geocenter motion (GCM) is one important topic for constructing and maintaining the terrestrial reference frame and its applications. GCM is studied from CHAMP with the multi-step approach in this paper. Geometric orbits of CHAMP in 2001-2006 are precisely determined with the kinematic method only from the satel-lite-borne GPs zero-difference data. Then a GCM time series is estimated from the precise kinematic orbits based on the theory of satellite dynamics to fit the CHAMP’s real geometric orbits. We compare the series with the geocenter series used in ITRF2005. Then the GCM series are analyzed with Fourier transform and wavelet transformation. The mean motions within 6 years in TX, TY and TZ direc-tions are respectively 0.8 mm, 2.2 mm, and 7.9 mm. The trends of GCM in the three directions are 0.495 mm/a, -0.004 mm/a, and 1.309 mm/a, respectively. The long-term movement (2001-2006) indicates that the crustal figure is changing. The seasonal variations are the main component which may be excitated by the mass redistribution of Earth’s fluid layer, e.g. ocean, atmosphere and continental water. The inter-annual variations are also found in the GCM series measured with CHAMP.

关键词： geocenter motion CHAMP power spectral analysis wavelet transformation

Cartan-Fubini type extension of holomorphic maps respecting varieties of minimal rational tangents

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science China Mathematics 2015年第3期58卷 513-518页

作者： hwang JunMuk korea Institute for Advanced study

A fundamental result in the theory of minimal rational curves on projective manifolds is Cartan- Fubini extension theorem proved by hwang and Mok, which describes the extensibility of biholomorphisms between connected open subsets of two Fano manifolds of Picard number 1 which preserve varieties of minimal rational tangents （VMRT）, under a mild geometric assumption on the second fundamental forms of VMRT＇s. Hong and Mok have developed Cartan-Fubini extension for non-equidimensional holomorphic immersions from a connected open subset of a Pano manifold of Picard number 1 into a uniruled projective manifold, under the assumptions that the map sends VMRT＇s onto linear sections of VMRT＇s and it satisfies a mild geometric condition formulated in terms of second fundamental forms on VMRT＇s. In the current paper, we give a generalization of Hong and Mok＇s result, under the same condition on second fundamental forms, assuming only that the holomorphic immersions send VMRT＇s to VMRT＇s. Our argument is different from Hong and Mok＇s and is based on the study of natural foliations on the total family of VMRT＇s. This gives a substantially simpler proof than Hong and Mok＇s argument.

关键词： varieties of minimal rational tangents extension of holomorphic maps

A multi-subwaveform parametric retracker of the radar satellite altimetric waveform and recovery of gravity anomalies over coastal oceans

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science China Earth sciences 2010年第4期53卷 610-616页

作者： hwang CheinWay Department of Civil Engineering Chiao Tung University

The quality of satellite radar altimetric data is very important in studies of geodesy,geophysics,and *** coastal oceans,altimeter waveforms are contaminated by the terrain and physical environments so that the accuracy of altimeter data is lower than that over open *** we develop a new multi-subwaveform parametric retracker(MsPR) to improve the quality of altimeter data for the recovery of gravity anomaly in coastal *** least squares collocation method is used to recover the residual gravity anomaly over the coastal water from altimetric *** waveform data records from Geosat/GM around Taiwan Island are practically retracked with *** compared with the Taiwan geoid height,the results retracked by MsPR are more accurate than those retracked by the well-known β-5-parmeter method and from the geophysical data records(GDRs).The gravity anomalies over Taiwan coastal waters are calculated from the retracked altimeter data with the least squares *** we compared gravity anomalies computed using altimeter GDRs with the ship-borne gravity data over Taiwan coastal ocean,we found that the results from retracked data are more accurate than those from GDRs.

关键词： multi-subwaveform parametric retracker waveform retracking for radar satellite altimetry gravity anomaly least squares collocation Geosat/GM

Correlation of microstructure with tensile behavior and properties of API X70 pipeline steels subjected to strain aging

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Journal of Iron and steel Research International 2020年第3期27卷 319-324页

作者： sang-in Lee Byoungchul hwang Department of Materials science and Engineering Seoul National University of Science and TechnologySeoul 01811Republic of Korea

Variations in tensile behavior and properties after pre-strain and thermal aging were differently affected by strain aging phenomenon dependent on *** increasing polygonal ferrite fraction,decrement in uniform elongation is increased,and the increment in yield-to-tensile ratio is slightly decreased after pre-strain and thermal ***,it can be concluded that the polygonal ferrite has contradictory effects on strain aging resistance although the polygonal ferrite still contributes to improvement of uniform elongation after strain aging.

关键词： steel Microstructure strain aging Deformability Pipeline