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Boosting photocatalytic hydrogen production by creating isotype heterojunctions and single-atom active sites in highly-crystallized carbon nitride

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Science Bulletin 2022年第5期67卷 520-528,M0004页

作者： Shaohua Shen Jie Chen Yiqing Wang Chung-Li Dong Fanqi Meng Qinghua Zhang Yiliang Huangfu Zhi Lin Yu-Cheng Huang Yanrui Li Mingtao Li Lin Gu International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityXi’an 710049China School of Chemical Engineering and Technology Xi’an Jiaotong UniversityXi’an 710049China Department of Physics Tamkang UniversityNew Taipei City 25137TaiwanChina Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China

Carbon nitride-based photocatalysts hold an enormous potential in producing hydrogen.A strategy to simultaneously create isotype heterojunctions and active sites in highly-crystallized carbon nitride is anticipated to significantly boost the photocatalytic activity,but is yet to be ***,we find that cobalt salt added in the ionothermal synthesis can promote the phase transition of heptazine-based crystalline carbon nitride(CCN)to triazine-based poly(triazine imide)(PTI),rendering the creation of singleatom cobalt coordinated isotype CCN/PTI ***-CCN/PTI exhibits an appreciable apparent quantum yield of 20.88%at 425 nm for photocatalytic hydrogen production with a rate achieving3538μmol h^(-1)g^(-1)(λ>420 nm),which is 4.8 times that of CCN and 27.6 times that of *** high photocatalytic activity is attributed to the Type II isotype highly-crystallized CCN/PTI heterojunction for promoting charge carrier migration,and the single-atom Co sites for accelerating surface oxidation reaction.

关键词： Photocatalytic hydrogen production Single-atom cobalt Crystalline carbon nitride Poly(triazine imide) Isotype heterojunctions

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Life-Cycle-Based Multi-Objective Optimal Design and Analysis of Distributed Multi-Energy Systems for Data Centers

SSRN

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SSRN 2023年

作者： Ren, Xiaoxiao Han, Zijun Ma, Jinpeng Xue, Kai Chong, Daotong Wang, Jinshi Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi'An710049 China China Energy Construction Group Shaanxi Electric Power Design Institute Co. Ltd Xi’an710043 China

The widespread deployment of data centers has contributed to a dramatic increase in energy consumption and carbon emissions. To solve this problem, this study proposes a distributed multi-energy system (DMES) driven by solar, wind, geothermal and natural gas and its life-cycle-based multi-objective optimization model considered energy, economy and environment. This model employs an improved multi-objective grasshopper optimization algorithm (IMOGOA) based on the population variation mechanism and a novel operation strategy depending on load characteristics. On this basis, the effects of carbon tax, life span and indoor temperature set-point determined by improved predicted mean vote (PMV) on the system are further explored. Case studies are conducted on a practical data center in Qinghai, China. The results show that the IMOGOA is more suitable for the optimization of DMES than the commonly used algorithms. Besides, the supply of cooling, heating and electricity can meet the needs of the data center, and more than 30% of electricity is generated from renewable sources. Finally, the carbon tax, life span and indoor temperature set-points affect the optimization of the system. The methodology and results can be expected to be of great technical interest for the energy supply systems of data centers. © 2023, The Authors. All rights reserved.

关键词： Life cycle

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Assessing the predictions of A NOx kinetic mechanism on recent hydrogen and syngas experimental data 9

Assessing the predictions of A NOx kinetic mechanism on rece...

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9th International Conference on Modeling and Diagnostics for Advanved Engine Systems, COMODIA 2017

作者： Zhang, Yingjia Mathieu, Olivier Petersen, Eric Bourque, Gilles Li, Qianqian Curran, Henry Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Combustion Chemistry Centre National University of Ireland Galway Ireland Department of Mechanical Engineering Texas A and M University College StationTX United States Siemens Canada Limited 9545 Cote de Liesse Road MontrealQCH9P 1A5 Canada

A detailed chemical kinetic mechanism has been developed to describe the pyrolysis and oxidation of the hydrogen/NOx and syngas/NOx systems. The thermodynamic data of nitrogenous compounds have been updated based on t... 详细信息

关键词： Hydrogen

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Piv measurement of turbulent mixing layer flow with polymer additives

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2009年第4期30卷 608-610页

作者： Ning, Tao Guo, Fu-De Chen, Bin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Turbulent mixing layer flow with 200 mg/kg polymer additives was measured by PIV and compared with pure water cause. The velocity ratio between high and low speed is 4:1 and the velocity difference ranges from 0.25 m/s to 1.25 m/s. It is showed that large vortex structures exist in flow field with/without polymer addictives, but the coherent structure is much clearer and the large eddy will roll up earlier when polymer is added. Similar with pure water case, the Reynolds stress is decreasing and the vorticity is increasing with increasing the velocity difference. However, the width and range of Reynolds shear stress and vorticity are wider and larger.

关键词： Turbulent flow

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Research on holographic interference pattern of laser holographic interferometric technique

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Yi Qi Yi Biao Xue Bao/Chinese Journal of Scientific Instrument 2008年第SUPPL. 2期29卷 438-442页

作者： Guo, Ying He, Maogang Zhong, Qiu Zhang, Ying State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

The processing of interference fringe is the most important step in holographic interferometric technique. The interference fringe of mass diffusion were gathered and proposed, and 3 key steps in the process which reduce the precision mostly were improved in this paper. The improvements include the following steps: wavelet de-noise, frequency-domain wave filtering, phase unwrapping. The categories of noise were analyzed and some specific methods were used to reduce the noise. The improvements increased the precision greatly, and established a solid foundation for the using of laser holographic interferometric technique.

关键词： Wavelet transforms

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Effects of geometric parameters on steady laminar heal transfer in wavy channels

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Jisuan Wuli/Chinese Journal of Computational Physics 2007年第2期24卷 192-196页

作者： Xie, Gongnan Wang, Qiuwang Zeng, Min Luo, Laiqin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 110049 China

Periodically fully developed convective heat transfer characteristics in a two-dimensional wavy channel are investigated numerically with a constant wall temperature. The calculations are performed with Pr=0.7, Re=20-500 on non-orthogonal non-staggered grids generated by an elliptic equation system. A semi-implicit method for pressure linked equations revised (SIMPLER) algorithm in curvilinear body-fitted coordinates is employed. Effects of Reynolds number and geometric parameters, such as aspect ratio φ and shape ratio γ, on heat transfer and friction factor are studied. It shows that no recirculation region occurs through the whole channel at low Reynolds numbers, small aspect ratio or small shape ratio. With the increase of Reynolds number, aspect ratio or shape ratio, heat transfer is enhanced due to flow recirculation. Corresponding friction factor increases simultaneously.

关键词： Heat convection

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Pirani gauge based hermeticity monitoring for un-cooled micro bolometer array

Pirani gauge based hermeticity monitoring for un-cooled micr...

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2009 16th IEEE International Symposium on the Physical and Failure Analysis of Integrated Circuits, IPFA 2009

作者： Tao, Dong Bin, Xiao Anders, Elfving Zhaochu, Yang Nhut, Tran-Minh Einar, Halvorsen Nils, Høivik Norwegian Center of Expertise on Micro- and Nanotechnology Vestfold University College I.M.S.T./R.I. Tønsberg Norway SensoNor AS Knudsrødveien 7 N-3192 Horten Norway State Key Lab of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China

ISBN: (纸本)9781424439102

This paper presents a novel method to analyze the thermal conductance under vacuum environment for MEMS devices. The Si/Ge-based Pirani gauge introduced is developed for monitoring the package hermeticity of MEMS Bolometer array, which has the total same structure as the single bolometer pixel for the characteristic of functional material. Meanwhile the 'Extended Fourier's Law' is verified by free molecular theory and is applied into the thermal analysis of the micro-structure under the pressure below 100Pa. Thermal interaction between Focus Plane Arrays (FPAs) and Pirani gauge is checked to guarantee the normal performance as the influence from each side are under 2X lO-3K, which is acceptable for the products. This design can save the cost in fabrication significantly due to no extra process flow. The commercial value is affirmed by industry partner. ©2009 IEEE.

关键词： Bolometers

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Study on the characteristics of flowing organization in DMFC. Part II: A new scheme with plates staggered installed

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Taiyangneng Xuebao/Acta Energiae Solaris Sinica 2008年第10期29卷 1247-1251页

作者： Yin, Benhao He, Yaling Li, Xianglin Miao, Zheng State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Based on the investigations on the influences of geometrical parameters and symmetrical plates disposal scheme on DMFC performance, a new scheme that staggered channels arrangement was presented and studied in this work. The characteristics of fluid flow, proton transport and reaction rate distribution were well studied and contrasted to symmetrical scheme used in a cell unit. The effects of thickness of catalyst layer, backing layer and membrane on cell local average current density were investigated. After optimized design, a staggered scheme was put forward, and the higher potential output and greater limiting current density were obtained compared to the conventional symmetrical scheme. A new way to optimizing DMFC design and assembly was put forward.

关键词： Geometry

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Visualization Experiments and Piston Effect of Heat Transfer on Supercritical Carbon Dioxide in a Mini Vertical Upward flow

SSRN

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SSRN 2022年

作者： Lyu, Haicai Wang, Han Bi, Qincheng Niu, Fenglei School of Nuclear Science and Engineering North China Electric Power University Beijing102206 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University No.28 Xianning West Road Xi’an710049 China

The characteristics of supercritical heat transfer and flow patterns visualization were investigated experimentally. System parameters are pressure of 7.4 ~ 8.44 MPa, the mass flux of 600 ~ 1600 kg·m -2 ·s -1 and heat flux up to 319 kW·m -2 . The basic experimental data of heat transfer coefficient and frictional pressure drop were obtained. Local heat transfer coefficient was calculated with respect to the mass flux, heat flux and pressure. The scenario of in-tube supercritical carbon dioxide was presented by a high-resolution camera. Experimental results show that the heat transfer peak happens when the wall temperature is above the pseudo-critical temperature, and in-tube fluid is lower than the pseudo-critical temperature. Exciting phenomenon of critical opalescence is observed under the pressure of 7.4 MPa and a temperature of 31.68 ˚C. Rapid alternation of sky blue and milky white was captured in an extremely short period time, which may be related to Rayleigh scattering due to drastic density fluctuation. Piston effect of strongly uneven aggregation was formed due to the variation of thermal physical property, which can be used to exposit the mechanism of supercritical heat transfer peak near the pseudo-critical temperature. Ration of density and volumetric coefficient of expansion can be represented for the piston effect to produce the modified Jackson’s correlation, which owns the average error of -0.69% and root-mean-square error of 10.35%. © 2022, The Authors. All rights reserved.

关键词： Visualization

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Numerical study of heat transfer and fluid flow in a periodically wavy channel

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Jisuan Wuli/Chinese Journal of Computational Physics 2006年第1期23卷 93-97页

作者： Xie, Gong-Nan Wang, Qiu-Wang Luo, Lai-Qin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

The periodically fully developed laminar heat transfer and fluid flow in a two-dimensional wavy channel in a compact heat exchanger are investigated numerically. Calculations are performed at Pr = 0.7, in the range of Re = 100-1100 with non-orthogonal non-staggered grids. The Semi-Implicit Method for Pressure Linked Equations Revised (SIMPLER) algorithm in the curvilinear body-fitted coordinates is used. The effect of the wavy height and distance on momentum and heat transfer is studied. Performance of model parameters is evaluated. It is shown that the overall Nusselt numbers and friction factors increase with the increase of Reynolds numbers. The friction factors and overall Nusselt numbers increase as increasing the wavy height or decreasing the wavy distance. The overall Nusselt numbers increase significantly with the wavy height, especially at high Reynolds numbers. The best wavy height and distance are 1.15 mm and 13 mm, respectively.

关键词： Channel flow

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