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NaF-FeF2 nanocomposite： New type of Na-ion battery cathode material

Nano Research 2017年第12期10卷 4388-4397页

作者： Insang Hwang Sung-Kyun Jung Eun-Suk Jeong Hyunchul Kim Sung-Pyo Cho kyojin ku Hyungsub Kim Won-Sub Yoon Kisuk Kang Department of Materials Science and Engineering Research Institute of Advanced Materials (RIAM) Seoul National University Seoul 08826 Republic of Korea Department of Energy Science (DOES) Sungkyunkwan University Suwon 16419 Republic of Korea National Center for Inter-University Research Facilities Seoul National University Seou108826 Republic of Korea Neutron Science Division HANARO Korea Atomic Energy Research Institute Daejeon 34057 Republic of Korea Center for Nanoparticle Research Institute for Basic Science (IBS) Seoul National University Seou108826 Republic of Korea

Na-ion batteries （NIBs） are considered one of the most attractive alternatives for Li-ion batteries （LIBs） because of the natural abundance of Na and the similarities between the NIB technology and the well-established LIB technology. However, the discovery of high-performance electrode materials remains a key factor in the success of NIBs. Herein, we propose a new type of cathode material for NIBs based on a nanocomposite of an alkali metal fluoride （NaF） and a transition metal fluoride （FeF2）. Although neither of these components is electrochemically active with Na, the nanoscale mixture of the two can deliver a reversible capacity of -125 mAh/g in the voltage range of 1.2--4.8 V vs. Na/Na＋ via an Fe2＋/Fe3＋ redox couple. X-ray absorption spectroscopy reveals that the reversible Na storage is aided by the F-ions due to the decomposition of NaF, which are absorbed on the surface of FeF2, promoting the redox reaction of Fe and triggering the gradual transformation of the mother structure （FeF2） into a new （FeFB-like） host structure for the Na ions. This unique Na-ion storage phenomenon, which is reported for the first time, will introduce an avenue for designing novel cathode materials for NIBs.

关键词： nanocomposite Na-ion batteries NaF FeF2 cathode

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Occurrence of anionic redox with absence of full oxidation to Ru^(5+) in high-energy P2-type layered oxide cathode

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Journal of Energy Chemistry 2023年第9期84卷 153-161页

作者： Jinho Ahn Hyunyoung Park Wonseok Ko Yongseok Lee Jungmin Kang Seokjin Lee Sangyeop Lee Eunji Sim Kyuwook Ihm Jihyun Hong Jung-Keun Yoo kyojin ku Jongsoon Kim Department of Energy Science Sungkyunkwan UniversitySuwon 16419Republic of Korea SKku Institute of Energy Science and Technology(SIEST) Sungkyunkwan UniversitySuwon 16419Republic of Korea Nano&Interface Research Team Pohang Accelerator LaboratoryPohang 37673Republic of Korea Department of Smart Fabrication Technology Sungkyunkwan UniversitySuwon 16419Republic of Korea Energy Materials Research Center Korea Institute of Science and Technology(KIST)14 Gil 5 Hwarang-roSeongbuk-guSeoul 02792Republic of Korea Carbon Composites Department Composites Research DivisionKorea Institute of Materials Science(KIMS)797 ChangwondaeroChangwon 51508Republic of Korea Department of Materials Science and Engineering Hanbat National UniversityDaejeon 34158Republic of Korea

The anionic redox has been widely studied in layered-oxide-cathodes in attempts to achieve highenergy-density for Na-ion batteries(NIBs).It is known that an oxidation state of Mn^(4+) or Ru^(5+) is essential for the anionic reaction of O^(2-)/O~-to occur during Na^(+) de/***,here,we report that the anionic redox can occur in Ru-based layered-oxide-cathodes before full oxidation of Ru^(4+)/Ru^(5+).Combining studies using first-principles calculation and experimental techniques reveals that further Na^(+) deintercalation from P2-Na_(0.33)[Mg_(0.33)Ru_(0.67)]O_(2) is based on anionic oxidation after 0.33 mol Na^(+) deintercalation from P2-Na_(0.67)[Mg_(0.33)Ru_(0.67)]O_(2) with cationic oxidation of Ru^(4+)/Ru^(4.5+).Especially,it is revealed that the only oxygen neighboring 2Mg/1 Ru can participate in the anionic redox during Na^(+) de/intercalation,which implies that the Na-O-Mg arrangement in the P2-Na_(0.33)[M9_(0.33)Ru_(0.67)]O_(2) structure can dramatically lower the thermodynamic stability of the anionic redox than that of cationic *** the O anionic and Ru cationic reaction,P2-Na_(0.67)[Mg_(0.33)Ru_(0.67)]O_(2) exhibits not only a large specific capacity of~172 mA h g^(-1) but also excellent power-capability via facile Na^(+) diffusion and reversible structural change during charge/*** findings suggest a novel strategy that can increase the activity of anionic redox by modulating the local environment around oxygen to develop high-energy-density cathode materials for NIBs.

关键词： Na-ion batteries P2-type cathode Anionic redox Local environment First-principles calculation

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The Mystery 40 Hz:Unraveling the Efficacy of Rhythmic Stimulation in Alzheimer's Disease

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Neuroscience Bulletin 2024年第6期40卷 831-834页

作者： Yixuan ku Guangdong Provincial Key Laboratory of Brain Function and Disease Center for Brain and Mental Well-beingDepartment of PsychologySun Yat-sen UniversityGuangzhou510006China Peng Cheng Laboratory Shenzhen518000China

Promises and Challenges of Rhythmic *** advances in research have made significant strides in understanding the potential of 40 Hz rhythmic optogenetic stimulation for the treatment of Alzheimer's disease(AD).A pivotal study conducted by Iaccarino et al.(2016)unveiled that targeted stimulation of interneurons at this specific frequency results in a remarkable reduction ofβ-amyloid levels in a mouse model of AD[1].

关键词： stimulation Alzheimer

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Selective reduction of NO by photo-SCR with ammonia in an annular fixed-film photoreactor

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Frontiers of Environmental Science & Engineering 2012年第2期6卷 149-155页

作者： YiangChen CHOU Young ku Department of Chemical Engineering Taiwan University of Science and Technology Taipei 10607 China

Gaseous NO was photocatalytically reduced at room temperature by photo-assisted selective catalytic reduction （photo-SCR） with ammonia over TiO2 in this study. NO reduction efficiency and N2 selectivity were determined from gases composition at the outlet stream of photoreactor. Effect of operating conditions, e.g. light intensity and inlet concentrations of ammonia and oxygen, on the NO reduction efficiency and N2 selectivity were discussed to determine the feasible operating condition for photocatalytic reduction of NO. Experimental results showed that selective catalytic reduction of NO with ammonia over TiO2 in the presence of oxygen was a spontaneous reaction in dark. The photoirradiation on the TiO2 surface caused remarkable photocatalytic reduction of NO to form N2, NO2, and N20 under 254 nm UV illuminations, while almost 90% of N2 selectivity was achieved in this study. The ammonia and oxygen molecules played the roles of reductant and oxidant for NO reduction and active sites regeneration, respectively. The reduction of NO was found to be increased with the increase of inlet ammonia and oxygen concentrations until specific concentrations because of the limited active sites on the surface of TiO2. The kinetic model proposed in this study can be used to reasonably describe the reaction mechanism of photo-SCR.

关键词： photo-SCR photocatalysis NO reduction,Eley-Rideal model

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SOLUTION OF THE ENSO DELAYED OSCILLATOR WITH HOMOTOPY ANALYSIS METHOD

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Journal of Hydrodynamics 2009年第1期21卷 131-135页

作者： WU Zi-ku School of Science Qingdao Agriculture University Qingdao 266109 China

An ENSO delayed oscillator is considered. The E1 Nino atmospheric physics oscillation is an abnormal phenomenon involved in the tropical Pacific ocean-atmosphere interactions. The conceptual oscillator model should consider the variations of both the eastern and western Pacific anomaly patterns. Using the homotopy analysis method, the approximate expansions of the solution of corresponding problem are constructed. The method is based on a continuous variation from an initial trial to the exact solution. A Maclaurin series expansion provides a successive approximation of the solution through repeated application of a differential operator with the initial trial as the first term. This approach does not require the use of perturbation parameters and the solution series converges rapidly with the number of terms. Comparing the approximate analytical solution by homotopy analysis method with the exact solution, we can find that the homotopy analysis method is valid for solving the strong nonlinear ENSO delayed oscillator model.

关键词： ENSO delayed oscillator homotopy analysis method strong nonlinear

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Mixture flow of particles and power-law fluid in round peristaltic tube

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Applied Mathematics and Mechanics(English Edition) 2019年第6期40卷 805-822页

作者： Hailin YANG Jianzhong LIN Xiaoke ku Institute of Fluid Engineering School of Aeronautics and AstronauticsZhejiang University

The erythrocyte and blood flowing in the blood vessel can be treated as the two-phase flow of the mixture of particles and a power-law fluid in a peristaltic *** the present work, the peristaltic transport of a power-law fluid and the suspension of particles in a tube is investigated by a perturbation method using the long wavelength approximation. The influence of different parameters on the velocity profile and streamlines is explored. Results show that there is a deflection of the flow field when the power-law index n = 0.5 or 1.5 compared with the Newtonian fluid where the trapping zone is symmetric to a certain cross section. The flux rate and reflux of the material are identified,and the conditions under which the reflux appears are determined. Moreover, a reflux phenomenon occurs near the wall. The trapping zone is related to not only the tube geometry and the flow flux but also the fluid properties. Both the length and width of the trapping zone increase with an increase in θ or φ. The trapping zone is more difficult to produce in the shear-thinning fluid than the shear-thickening fluid.

关键词： peristaltic transport two-phase flow power-law fluid perturbation method trapping phenomenon

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Motion and orientation of cylindrical and cubic particles in pipe flow with high concentration and high particle to pipe size ratio

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第5期9卷 664-671页

作者： Xiao-ke ku Jian-zhong LIN Department of Mechanics Zhejiang University Hangzhou 310027 China College of Metrology Technology and Engineering China Jiliang University Hangzhou 310018 China

Lattice Boltzmann method was used to numerically investigate the motion and orientation distribution of cylindrical and cubic particles in pipe flow with high concentration and high particle to pipe size ratio. The transient impulse model of 3D collisions between particles and between particle and wall is proposed. The numerical results are qualitatively in agreement with and quantitatively comparable to the experiment data. The results show that the increases of both the cylindrical particle to pipe size ratio and the particle aspect ratio decrease the rotation about all axes. All rotations of cubic particles decrease with increasing the particle concentration. The cubic particles, rotating more drastically in the flow with large Reynolds number, rotate faster than the cylindrical particles with the same size. The cylindrical particles align with the flow direction more obviously with decreasing Reynolds numbers. However, the orientations of cubic particles are spread all over the range with no significant difference in magnitude, and the Reynolds numbers have no obvious effect on the orientations of cubic particles.

关键词： Particulate flow Angular velocity Orientation Lattice Boltzmann method

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Nearly degenerate ground states of a checkerboard antiferromagnet and their bosonic interpretation

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Science China(Physics,Mechanics & Astronomy) 2024年第1期67卷 84-89页

作者： Haiyuan Zou Fan Yang Wei ku Key Laboratory of Polar Materials and Devices(MOE) School of Physics and Electronic ScienceEast China Normal UniversityShanghai 200241China Department of Physics Beijing Institute of TechnologyBeijing 100081China Tsung-Dao Lee Institute Shanghai 200240China Key Laboratory of Artificial Structures and Quantum Control(Ministry of Education) Shanghai 200240China Shanghai Branch Hefei National LaboratoryShanghai 201315China

The spin-1/2 model system with antiferromagnetic(AF) couplings on a J1-J2checkerboard lattice, known as the planar pyrochlore model, is strongly frustrated and associated with a two-to-one dimensional crossover. Using the Projected Entangled Simplex States tensor network ansatz, we identify a large number of nearly degenerate states in the frustrated region(J_(1)

关键词： tensor networks frustrated magnetism dimensional crossover degenerate states

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Bi-directional and concurrent proof of ownership for stronger storage services with de-duplication

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Science China(Information Sciences) 2018年第3期61卷 84-94页

作者： Taek-Young YOUN ku-Young CHANG Electronics and Telecommunications Research Institute

In storage service, data de-duplication is a specialized technique for eliminating duplicate copies of repeating data in storage. Especially, client-side de-duplication has more merits than server-side deduplication since they can improve both the space efficiency and the communication bandwidth. For secure client-side de-duplication, we need a way to prove the ownership of a file to be stored. In the upload step,the server should verify the ownership of a client to give the right of the file without uploading it. On the contrary, the client also want to verify the retrievability for the file since he will delete it from his storage after protocol execution. Existing proof of ownership techniques have been designed for server's need. In this paper, we first point out that we need the second property in client's view point, and give a very simple and practical solution which can support the server and the client to prove that they have the same file. We first describe a generic strategy which can help us to construction a bi-directional and concurrent proof of ownership technique from an ordinary proof of ownership technique, and then give an efficient hash-based scheme with security proof in the random oracle model.

关键词： cloud storage secure de-duplication data out-source proof of ownership bi-directional and concurrent proof

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The amazing world of light nuclei

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Science Bulletin 2024年第21期69卷 3303-3304页

作者： Aslıkuşoğlu Department of Physics Faculty of ScienceIstanbul UniversityVezneciler/Fatih34134 IstanbulTurkey

Light nuclei are few-body quantal systems and historically their spectra were theﬁrst to be studied *** a recent review,the existing experimental data from the stable N¼Z doubly-odd nuclei and spectroscopic studies have been discussed,as well as the b decay of the corresponding isobaric multiplets[1].The description of nuclear many-body systems derived fromﬁrst principles remains one of the most challenging research areas over the past decades because of the complex nature and limited knowledge of fundamental forces among nucleons,emerging from either meson-exchange theory or quantum chromodynamics(QCD).

关键词： meson decay spectroscopic

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