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2019 Transactions of the American Nuclear Society, ANS 2019

作者： Wang, Xiaotong Yao, Weihua Luo, Ying Dong, Yuanyuan Science and Technology on Reactor System Design Technology Lab Nuclear Power Institute of China Chengdu China Nuclear Power Institute of China Chengdu China

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Weakening s-d orbital hybridization of metallic iridium by tungsten atoms for acidic water splitting

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Applied Catalysis A: General 2023年 649卷 1页

作者： Chang, Chaofeng Xie, Yuhua Luo, Fang Zhou, Shaowei Yang, Zehui Sustainable Energy Laboratory Faculty of Materials Science and Chemistry China University of Geosciences Wuhan 388 Lumo RD Wuhan430074 China State Key Laboratory for Hubei New Textile Materials and Advanced Processing Technology School of Materials Science and Engineering Wuhan Textile University Wuhan430200 China Power system and new energy China Ship Development and Design Center Wuhan430074 China

To economically realize proton electrolyte membrane water splitting technology, stable and high-performance oxygen evolution reaction (OER) electrocatalyst is significantly demanded. In this work, we invite tungsten atoms to metallic iridium (Ir) to weaken s-d hybridization of Ir-Ir bond due to the higher electronegativity accepting electron from Ir atoms;as a result, the adsorbed O* species become electrophilic favorable for the nucleophilic attack by H2O leading to 22 % decrement in energy barrier for the formation of OOH* species. Therefore, iridium-tungsten (IrW) electrocatalyst exhibits 3.7-fold higher turnover frequency (TOF) than metallic Ir at overpotential of 370 mV in acidic OER catalysis. Moreover, stable OER performance is recorded due to the high cohesive energy of tungsten atoms. Additionally, TOF of IrW electrocatalyst reaches 10.1 s−1 at overpotential of 100 mV in acidic hydrogen evolution reaction (HER) test, 7.6-time higher than Pt/C and metallic Ir. IrW electrocatalyst only needs 1.52 V to attain 10 mA cm−2 in acidic overall water splitting. © 2022 Elsevier B.V.

关键词： Chemical bonds

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The SIF model of Zr-4 cladding tube with axial cracks 14

The SIF model of Zr-4 cladding tube with axial cracks

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14th International Nuclear Fuel Cycle Conference, GLOBAL 2019 and Light Water reactor Fuel Performance Conference, TOP FUEL 2019

作者： Chen, L. Liu, L.L. Song, X.M. Pang, H. Xie, X.M. Zeng, X.G. Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China No.328 1st Section of Changshun Avenue Chengdu610213 China Sichuan University No.24 1st South Section of 1st Ring Road Chengdu610021 610213 China

The calculation of the stress intensity factor (SIF) on the axial cracking of the cladding tube is the basis for the study of the failure phenomena of delayed hydride cracking (DHC) and hydrogen embrittlement (HE). In most hydrogen failure models, especially the DHC model, an infinite or semi-infinite plate is used as the modeling basis. There is no doubt that cylindrical shell as a modeling object will make the calculation more accurate for nuclear fuel cladding. This work analyzes the influence of geometric conditions and the external load conditions on SIF of tubular components, respectively, based on virtual crack closure technique (VCCT), using single variable. Then the influence of crack length on SIF is analyzed under concentrated stress loading on the end of Zr-4 cladding tube by numerical analysis method. The approximate calculation formula of the stress intensity factor on the crack front is obtained and verified. Copyright © GLOBAL 2019 - International Nuclear Fuel Cycle Conference and TOP FUEL 2019 - Light Water reactor Fuel Performance *** rights reserved.

关键词： Stress analysis

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DC-Side Decoupling Method of DC-link Capacitor Reduction for Single Phase PWM Rectifier

DC-Side Decoupling Method of DC-link Capacitor Reduction for...

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Sustainable Power and Energy Conference (iSPEC)

作者： Jinxin Wang Peng Renyong Kailei Dai Zhiqiang Zhang Ting Zhang Junjie Zhao Qian Chen Jianjian Zhang Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu China Nuclear Power Institute of China Chengdu China

ISBN: (数字)9781728191645

ISBN: (纸本)9781728191652

The integrated charging system of Electric vehicle consists of a single-phase PWM rectifier and a Buck converter. When the single-phase PWM rectifier works with unit power factor, the dc-link voltage contains a large voltage harmonic of twice the grid frequency. Although the output voltage ripple can be controlled within the required range using the proper control of the Buck converter, the second-order harmonic on the dc-link capacitor is inevitable. This paper proposes a de-side decoupling method for the second-order harmonic problem of the dc-link voltage of the integrated charging system. A de-side decoupling half bridge is connected in parallel to absorb the ripple power of twice the grid frequency. This paper analyzes the operating principle of the de-side decoupling half bridge. Based on a theoretical analysis of the topology and the design procedure for controlling system, the proposed converter is designed and simulated. Finally, simulation results are given to verify the method.

关键词： Capacitors Rectifiers Bridge circuits Pulse width modulation Harmonic analysis Control systems Voltage control

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Experimental investigation of the transient pool boiling heat transfer on the quenching of vertical rodlet in water

Experimental investigation of the transient pool boiling hea...

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2020 International Conference on Nuclear Engineering, ICONE 2020, collocated with the ASME 2020 Power Conference

作者： Wang, Zefeng Deng, Jian Qian, Libo Cai, Rong Xiong, Jinbiao Zhong, Lei Ma, Yugao State Key Laboratory of Reactor System Design Technology Nuclear Power Institute of China 328 Changshun Road Shuangliu District Chengdu China School of Nuclear Science and Engineering Shanghai Jiao Tong University 800 DongChuan Road MinHang District Shanghai China

ISBN: (纸本)9780791883785

Quenching is an important phenomenon in the evaluation of an emergency core cooling system following a hypothetical loss of coolant accident (LOCA) in a nuclear reactor. In the present study, an experimental apparatus is designed and constructed with the purpose of conducting high-temperature transient pool boiling quenching experiments for zirconium (Zr-4) cylindrical test samples. Three thermocouples are inserted in the test sample to investigate the effect of axial distance on the minimum film boiling temperature. The Zr-4 rodlet is heated up to a temperature well above the minimum film boiling temperature (up to 600°C), and then plunged vertically in a quiescent pool of subcooled water. A data acquisition system is used to record the temperature of the embedded thermocouples with time. Data reduction is performed by an inverse heat conduction code to calculate the surface temperature and corresponding surface heat flux. A visualization study with a high-speed camera is conducted to record the quenching behavior on the test sample. It is found that the minimum film boiling temperature decreases with the axial distance, while the CHF temperature is relatively insensitive to the axial distance. The film boiling heat transfer coefficient decreases with surface temperature, and seems to be independent of axial distance. The quench front is observed to originate from the bottom and move upwards. It is found that the quench front velocity remains nearly constant in the lower region of the test sample, and significantly increases in the upper region. © 2020 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Surface temperature

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Autonomous driving through non-uniform steering angles nodes determination by deep learning

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Journal of Institute of Control, Robotics and systems 2019年第8期25卷 677-683页

作者： Kim, Soo Myung Kim, Tae Hyun Kim, Dong Hwan Dept. of Mechanical System and Design Engineering Seoul National University of Technology & Science Korea Republic of

In this work, an autonomous driving model using only one camera was implemented by combining a CNN (Convolutional Neural networks) and a YOLO (You Only Look Once) framework. Hyper-parameters in the structure were adjusted to improve driving performance. Autonomous driving in a corridor was performed by applying the improved model. An appropriate dropout and deep learning structure associated with non-uniform steering angle intervals as output is proposed. The proposed algorithm was implemented, and through experiments resulted in successful obstacle avoidance and stable driving. © ICROS 2019.

关键词： Autonomous vehicles

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Distributed reinforcement learning for privacy-preserving dynamic edge caching

arXiv

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arXiv 2021年

作者： Liu, Shengheng Zheng, Chong Huang, Yongming Quek, Tony Q.S. The School of Information Science and Engineering Southeast University Nanjing210096 China The Purple Mountain Laboratories Nanjing211111 China The Information System Technology and Design Pillar Singapore University of Technology and Design Singapore487372 Singapore

Mobile edge computing (MEC) is a prominent computing paradigm which expands the application fields of wireless communication. Due to the limitation of the capacities of user equipments and MEC servers, edge caching (EC) optimization is crucial to the effective utilization of the caching resources in MEC-enabled wireless networks. However, the dynamics and complexities of content popularities over space and time as well as the privacy preservation of users pose significant challenges to EC optimization. In this paper, a privacy-preserving distributed deep deterministic policy gradient (P2D3PG) algorithm is proposed to maximize the cache hit rates of devices in the MEC networks. Specifically, we consider the fact that content popularities are dynamic, complicated and unobservable, and formulate the maximization of cache hit rates on devices as distributed problems under the constraints of privacy preservation. In particular, we convert the distributed optimizations into distributed model-free Markov decision process problems and then introduce a privacy-preserving federated learning method for popularity prediction. Subsequently, a P2D3PG algorithm is developed based on distributed reinforcement learning to solve the distributed problems. Simulation results demonstrate the superiority of the proposed approach in improving EC hit rate over the baseline methods while preserving user privacy. © 2021, CC BY.

关键词： Mobile edge computing

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An Overview of Bearing Candidates for the Next Generation of Reusable Liquid Rocket Turbopumps

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Chinese Journal of Mechanical Engineering 2020年第2期33卷 43-55页

作者： Jimin Xu Changhuan Li Xusheng Miao Cuiping Zhang Xiaoyang Yuan Institute of Tribology School of Mechanical EngineeringHefei University of TechnologyHefei 230009China Aerospace Propulsion Institute China Aerospace Science and Technology CorporationXi’an 710100China Science Technology on Combustion Internal Flow and Thermal‑structure LaboratoryNorthwestern Polytechnical UniversityXi’an 710012China Superconducting Materials Research Center Laboratory Northwest Institute for Non-ferrous Metal ResearchXi’an 710016China Key Laboratory of Education Ministry for Modern Design and Rotor‑Bearing System Xi’an Jiaotong UniversityXi’an 710049China

There is a consensus in the aerospace field that the development of reusable liquid rockets can effectively reduce the launch *** pursuit of a long service life and reutilization highly depends on the bearing ***,the rolling element bearings(REBs)used in the existing rocket turbopumps present obvious and increasing limitations due to their mechanical contacting *** REBs,high rotational speed and long service life are two performance indexes that mutually restrict each *** go beyond the DN value(the product of the bearing bore and rotational speed)limit of REBs,the major space powers have conducted substantial explorations on the use of new types of bearings to replace the *** review discusses,first,the crucial role of bearings in rocket turbopumps and the related structural improvements of ***,with the prospect of application to the next generation of reusable liquid rocket turbopumps,the bearing candidates investigated by major space powers are summarized *** promising alternatives to REBs include fluid-film,foil,and magnetic bearings,together with the novel superconducting compound bearings recently proposed by our *** more than ten years of relevant research on fluid-film and magnetic bearings are also *** review is meaningful for the development of long-life and highly reliable bearings to be used in future reusable rocket turbopumps.

关键词： Aerospace Reusable liquid rocket turbopumps Rolling element bearings Bearing candidates Review

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Modification of severe accident analysis code for accident tolerant fuel (ATF) applications 27

Modification of severe accident analysis code for accident t...

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27th International Conference on Nuclear Engineering: Nuclear Power Saves the World!, ICONE 2019

作者： Xu, Tao Ma, Haifu Tian, Chao Wu, Yirui Yang, Junyun Wang, Kai Zhang, Bin Wang, Junlong Deng, Yaxin Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu Sichuan China School of Nuclear Science and Technology Xi'an Jiaotong University Xi'an Shaanxi China

ISBN: (纸本)9784888983051

After the Fukushima nuclear accident, we gradually realized the safety issues of the traditional UO2+Zr nuclear fuel system. Accident tolerance fuel (ATF) is a new generation fuel concept proposed to improve the performance of fuel elements against severe accidents, and can withstand the consequences of accidents for a long time while maintaining or improving their performance under normal operating conditions. Nowadays, the issue of the safe utilization of nuclear energy has attracted more and more attention. reactor severe accident simulation and analysis for ATF has also become one of the important research directions. MELCOR is a fully integrated engineering-grade computer code which can model severe accidents phenomena in light water reactors. However, the existing MELCOR code is only applicable for the UO2+Zr fuel system, and cannot simulate the behavior of the ATF. So it is necessary to modify the MELCOR code for ATF applications. Based on extensive investigation, multi-fuel and multi-cladding processing module and new physical properties of ATF are added to MELCOR. Also the heat transfer model, oxidation model and cladding failure model are modified, enabling the MELCOR code to calculate ATF behaviors. Afterwards, the model verification is carried out. Then the traditional UO2+Zr and five ATF combinations are applied to the traditional three-loop PWR nuclear power plant to perform the safety analysis under large break loss of coolant accident (LBLOCA). The calculation results show that ATFs have better accident tolerance ability than UO2+Zr fuel system used in the commercial PWR, and the temperature of the cladding rises more slowly. The cladding failure is also delayed to different extent. The ATF fuel system has a better performance under the severe accident condition. © 2018-2019 by JSME

关键词： Uranium dioxide

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Research on the effect of oil temperature on the performance of civil aircraft actuation system

Research on the effect of oil temperature on the performance...

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CSAA/IET International Conference on Aircraft Utility systems 2020, AUS 2020

作者： Kang, Rudong Li, Zhengqiang Huang, Jian Flight Control System Department Shanghai Aircraft Design and Research Institute COMAC Shanghai China Science and Technology Development Department Shanghai Aircraft Design and Research Institute COMAC Shanghai China

ISBN: (纸本)9781839535635

In order to research the influence of aviation hydraulic oil temperature change on the control performance of civil aircraft actuation system, a high-performance model is established by using Matlab for simulation analysis. Through the oil temperature-parameters controller, the influence of bulk modulus, density, viscosity on the system step response can be obtained. When the actuator in the active-disconnect state, the system gain can be simulated in different temperatures, and the frequency response performance correspond to the requirement. © 2020 Institution of Engineering and technology. All rights reserved.

关键词： Frequency response

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