Spindle Spinel CoFeCoO4 Microparticles/rGO as an Oxygen Reduction and Oxygen Evolution Catalyst

Bowen Wang,Nian Tao,Junchen Liu,Hao Wang,Yinxiao Du,Hujiang Yang,Yonggang Wang,Kai Huang,Ru Zhang,Ming Lei 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.4

The representative spinel-type materials AB2O4 (both A and B are transition metals) electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have been investigated and significant improvements have been achieved in the activity and durability for ORR and OER in the alkaline solution. But CoFeCoO4 was not explored widely like ZnCo2O4 (or NiCo2O4) as the ORR electrocatalyst for its relatively complicated atomic site occupation. CoFeCoO4 has a typical cubic spinel structure with Co2+ in the tetrahedron and Co3+ and Fe3+ in the octahedron. A mixture of Co3+ and Fe3+ in the B site makes the oxide have a wider overlap between transition metal 3d orbit and O 2p orbit, which can lead to an effective charge transfer in the rate-determining steps of ORR process and then enhance the ORR activity. The high electronic conductivity and specific surface area of rGO can accelerate charger transfer and provide more catalytic sites, which would contribute to a faster ORR process. In this work, the porous spindle CoFeCoO4 microparticles which were synthesized by hydrothermal technology, were assembled on the rGO surface to obtain the CoFeCoO4/rGO composite, which exhibited enhanced ORR activity and catalytic stability comparable to that of Pt/C. On the other hand, the OER catalytic activity of the prepared samples was also studied to explore the potential of CoFeCoO4/rGO as a bifunctional oxygen catalyst.

Preparation of new visible-light driven nanocomposite photocatalysts, X/NaTaO3/Er3+:YAlO3 (X = Ag, Au and Pt), for photocatalytic conversion of Cr(VI)

Bowen Li,Yidi Wang,Fangyuan Tian,Guanshu Li,Zhaohong Zhang,Jun Wang,Youtao Song 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.54 No.-

In order to expand the light response range of wide band-gap semiconductor photocatalyst (NaTaO3) for effective photocatalytic conversion of Cr(VI), an up-conversion luminescence agent (Er3+:YAlO3) is combined with NaTaO3 and a visible-light driven photocatalyst, NaTaO3/Er3+:YAlO3, is prepared. Moreover, several conduction band co-catalysts (Ag, Au and Pt) are deposited the surface of NaTaO3/Er3+: YAlO3, respectively, to facilitate the transfer rate of photo-generated electrons. X-ray diffractometer (XRD), energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM) analyses are employed to confirm the morphology, microstructure and composition of the prepared photocatalysts. In addition, UV–vis diffuse reflectance spectra are determined to explore the visible-light absorption properties of Er3+:YAlO3, NaTaO3, NaTaO3/Er3+:YAlO3 and X/NaTaO3/Er3+:YAlO3 (X = Ag, Au and Pt). Photoluminescence (PL) spectra are used to estimate the recombination rate of electron–hole pairs. The effects of irradiation time, photosource kind, solution acidity and used times on the photocatalytic capabilities of NaTaO3/Er3+:YAlO3 and X/NaTaO3/Er3+:YAlO3 (X = Ag, Au and Pt) are investigated in detail. The results show that the uses of up-conversion luminescence agent (Er3+:YAlO3) and co-catalysts (Ag, Au and Pt) can promote NaTaO3 to utilize visible-light to carry out the photocatalytic conversion of Cr(VI). Particularly, the prepared Au/NaTaO3/Er3+:YAlO3 nanocomposite with 1.0 wt% Au and 0.3:1.0 molar ratio of Er3+:YAlO3 and NaTaO3 shows the highest photocatalytic activity in conversion of Cr(VI).

A Novel Filtering Method Based on a Nonlinear Tracking Differentiator for the Speed Measurement of Direct-drive Permanent Magnet Traction Machines

Wang, Gaolin,Wang, Bowen,Zhao, Nannan,Xu, Dianguo The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.2

This paper presents a novel filtering method for speed measurements to improve the low-speed performance of the direct-drive permanent magnet traction machines for elevators. Based on the theory of nonlinear tracking differentiator (NTD), this method, which can act as a high performance filter of a raw speed signal, obtains a more accurate speed feedback signal when applying a low-resolution encoder. In addition, it can relieve the interference caused by the position derivative for speed sampling. By analyzing the frequency response of the NTD, the influence of its parameters on the performance of the speed filtering is investigated. Compared with different types of low-pass filters, the proposed method shows a shorter time delay and a stronger ability in terms of noise suppression when the parameters are selected carefully. In addition, when using the measured speed signal through a nonlinear tracking differentiator as the feedback of the system, the motor runs more steadily at low speeds. As a result, the riding comfort of a direct-drive elevator can be improved. The feasibility of the proposed strategy was verified on an 11.7kW elevator traction machine using a commercial inverter.

Nonlinear fatigue life prediction models based on material damage state correction

Bowen Wang,Qiwen Xue 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.12

The determination of the interaction factor of adjacent loads under variable amplitude loading is difficult. In this paper, two new nonlinear accumulation damage models are proposed based on the material damage state. Besides considering loading sequence, load interference, and mean stress effect, the proposed models consider the effect of material damage state and then modify the key parameter δ by introducing the load cycle ratio and the amount of material memory degradation in order to express the damage state. Verifying by different materials' test data and comparing with the existing models shows the proposed models good predictive ability and reliability. Further, in this method, there are no new variables introduced, no complex nested calculations, and only one conventional parameter that is easy to obtain by experimental fitting. Furthermore, the proposed models are convenient for fatigue life prediction in practical engineering problems.

Effect of packing structure on anisotropic effective thermal conductivity of thin ceramic pebble bed

Wang, Shuang,Wang, Shuai,Wu, Bowen,Lu, Yuelin,Zhang, Kefan,Chen, Hongli Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.7

Helium cooled solid breeder blanket as an important blanket candidate of the Tokamak fusion reactor uses ceramic pebble bed for tritium breeding. Considering the poor effective thermal conductivity of the ceramic breeder pebble bed, thin structure of tritium breeder pebble bed is usually adopted in the blanket design. The container wall has a great influence on the thin pebble bed packing structure, especially for the assembly of mono-sized particles, and thin pebble bed will appear anisotropic effective thermal conductivity phenomenon. In this paper, thin ceramic pebble beds composed of 1 mm diameter Li₄SiO₄ particles are generated by the EDEM 2.7. The effective thermal conductivity of different thickness pebble beds in the three-dimensional directions are analyzed by three-dimensional thermal network method. It is observed that thin Li₄SiO₄ pebble bed showing anisotropic effective thermal conductivity under the practical design size. Normally, the effective thermal conductivity along the bed vertical direction is higher than the horizontal direction due to the gravity effect. As the thickness increases from 10 mm to 40 mm, the effective thermal conductivity of the pebble bed gradually increases.

A Novel Filtering Method Based on a Nonlinear Tracking Differentiator for the Speed Measurement of Direct-drive Permanent Magnet Traction Machines

Gaolin Wang,Bowen Wang,Nannan Zhao,Dianguo Xu 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.2

This paper presents a novel filtering method for speed measurements to improve the low-speed performance of the direct-drive permanent magnet traction machines for elevators. Based on the theory of nonlinear tracking differentiator (NTD), this method, which can act as a high performance filter of a raw speed signal, obtains a more accurate speed feedback signal when applying a low-resolution encoder. In addition, it can relieve the interference caused by the position derivative for speed sampling. By analyzing the frequency response of the NTD, the influence of its parameters on the performance of the speed filtering is investigated. Compared with different types of low-pass filters, the proposed method shows a shorter time delay and a stronger ability in terms of noise suppression when the parameters are selected carefully. In addition, when using the measured speed signal through a nonlinear tracking differentiator as the feedback of the system, the motor runs more steadily at low speeds. As a result, the riding comfort of a direct-drive elevator can be improved. The feasibility of the proposed strategy was verified on an 11.7kW elevator traction machine using a commercial inverter.

A review on thermohydraulic and mechanical-physical properties of SiC, FeCrAl and Ti₃SiC₂ for ATF cladding

Qiu, Bowen,Wang, Jun,Deng, Yangbin,Wang, Mingjun,Wu, Yingwei,Qiu, S.Z. Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.1

At present, the Department of Energy (DOE) in Unite State are directing the efforts of developing accident tolerant fuel (ATF) technology. As the first barrier of nuclear fuel system, the material selection of fuel rod cladding for ATFs is a basic but very significant issue for the development of this concept. The advanced cladding is attractive for providing much stronger oxidation resistance and better in-pile behavior under sever accident conditions (such as SBO, LOCA) for giving more coping time and, of course, at least an equivalent performance under normal condition. In recent years, many researches on in-plie or out-pile physical properties of some suggested cladding materials have been conducted to solve this material selection problem. Base on published literatures, this paper introduced relevant research backgrounds, objectives, research institutions and their progresses on several main potential claddings include triplex SiC, FeCrAl and MAX phase material Ti3SiC2. The physical properties of these claddings for their application in ATF area are also reviewed in thermohydraulic and mechanical view for better understanding and simulating the behaviors of these new claddings. While most of important data are available from publications, there are still many relevant properties are lacking for the evaluations.

Photocatalytic conversion of nitrite in aqueous solution over nanocomposite photocatalyst Er3+:Y3Al5O12/BiPO4 using different photosources

Yidi Wang,Bowen Li,Guanshu Li,Yingying Huang,Dawei Fang,Jun Wang,Youtao Song 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.47 No.-

Three crystal phases of BiPO4 (HBIP, nMBIP and mMBIP), corresponding photocatalysts (Er3+:Y3Al5O12/HBIP, Er3+:Y3Al5O12/nMBIP and Er3+:Y3Al5O12/mMBIP) and their nanocomposite photocatalyst (Er3+:Y3Al5O12/(H-nM-mM)BIP) were prepared by hydrothermal, ultrasonic dispersion and liquid boilingmethods. The prepared photocatalysts were characterized by X-ray diffractometer (XRD), energydispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM) and UV–vis diffuse reflectancespectra (DRS). The catalytic activity of prepared photocatalysts was evaluated via photocatalyticconversion rate of nitrite under ultraviolet-light, visible-light and simulated solar-light irradiations. These three photocatalysts all exhibited excellent performance under simulated solar-light irradiationand reached 85.36%, 84.42% and 78.53% conversion rates, respectively, for Er3+:Y3Al5O12/mMBIP, Er3+:Y3Al5O12/nMBIP and Er3+:Y3Al5O12/HBIP. Particularly, Er3+:Y3Al5O12/(H-nM-mM)BIP was also found toplay a high catalytic activity, resulting in 78.68%, 70.04% and 82.57% conversion rates, respectively, underultraviolet-light, visible-light and simulated solar-light irradiation. In addition, the study of used timesshowed that the prepared photocatalysts can be effectively recycled without an apparent inactivation onthe photocatalytic activity. This research may provide a potential way for converting nitrite and othercontaminants by utilizing solar energy efficiently.

Development of a structure analytic hierarchy approach for the evaluation of the physical protection system effectiveness

Zou Bowen,Wang Wenlin,Liu Jian,Yan Zhenyu,Liu Gaojun,Wang Jun,Wei Guanxiang 한국원자력학회 2020 Nuclear Engineering and Technology Vol.52 No.8

A physical protection system (PPS) is used for the protection of critical facilities. This paper proposes a structure analytic hierarchy approach (SAHA) for the hierarchical evaluation of the PPS effectiveness in critical infrastructure. SAHA is based on the traditional analysis methods “estimate of adversary sequence interruption, EASI”. A community algorithm is used in the building of the SAHA model. SAHA is applied to cluster the associated protection elements for the topological design of complicated PPS with graphical vertexes equivalent to protection elements.

Research of Enterprise Private Cloud Computing Platform Based on OpenStack

Jiang Yunxia,Zhao Bowen,Wang Shuqi,Sun Dongnan 보안공학연구지원센터 2014 International Journal of Grid and Distributed Comp Vol.7 No.5

The demand for computing resources is growing, but the input costs of the enterprise information system construction of the traditional way is too high, and has not the high utilization of the resources. In order to solve this contradiction, the enterprise private cloud platform architecture has been put forward based on open source system. By analyzing the mainstream open source cloud projects, the basis to choose OpenStack has been given. From the perspective of classification of the enterprise personnel, combining with the components of OpenStack, this paper expounds manufacture of the virtual image and distribution, monitor, and use of the virtual machine. At last, the user interface design is also given.