检索结果-内蒙古大学图书馆

A mixed discontinuous Galerkin method with symmetric stress for Brinkman problem based on the velocity-pseudostress formulation

引用

COMPUTER METHODS IN APPLIED MECHANICS AND engineering 2020年 368卷

作者： Qian, Yanxia Wu, Shuonan Wang, Fei Xi An Jiao Tong Univ Sch Math & Stat Xian 710049 Shaanxi Peoples R China Peking Univ Sch Math Sci Beijing 100871 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

The Brinkman equations can be regarded as a combination of the Stokes and Darcy equations which model transitions between the fast flow in channels (governed by Stokes equations) and the slow flow in porous media (governed by Darcy's law). The numerical challenge for this model is the designing of a numerical scheme which is stable for both the Stokes-dominated (high permeability) and the Darcy-dominated (low permeability) equations. In this paper, we solve the Brinkman model in n dimensions (n = 2, 3) by using the mixed discontinuous Galerkin (MDG) method, which meets this challenge. This MDG method is based on the pseudostress-velocity formulation and uses a discontinuous piecewise polynomial pair (P) under bar (S)(k+1)-P-k (k >= 0), where the stress field is symmetric. The main unknowns are the pseudostress and the velocity, whereas the pressure is easily recovered through a simple postprocessing. A key step in the analysis is to establish the parameter-robust inf-sup stability through specific parameter-dependent norms at both continuous and discrete levels. Therefore, the stability results presented here are uniform with respect to the permeability. Thanks to the parameter-robust stability analysis, we obtain optimal error estimates for the stress in broken (H) under bar (div)-norm and velocity in L-2-norm. Furthermore, the (L) under bar (2) error estimate for pseudostress is derived under certain conditions. Finally, numerical experiments are provided to support the theoretical results and to show the robustness, accuracy, and flexibility of the MDG method. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Brinkman model Mixed discontinuous Galerkin method Pseudostress Parameter-robust stability

来源：评论

学校读者我要写书评

暂无评论

A review of research and development of supercritical carbon dioxide Brayton cycle technology in nuclear engineering applications

引用

NUCLEAR engineering AND DESIGN 2020年 368卷 110767-110767页

作者： Wu, Pan Ma, Yunduo Gao, Chuntian Liu, Weihua Shan, Jianqiang Huang, Yanping Wang, Junfeng Zhang, Dan Ran, Xu Xi An Jiao Tong Univ Sch Nucl Sci & Technol 28 Xianning West Rd Xian Shaanxi Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Nucl Power Inst China CNNC Key Lab Nucl Reactor Thermal Hydraul Technol Chengdu 610041 Peoples R China Nucl Power Inst China Sci & Technol Reactor Syst Design Technol Lab Chengdu 610041 Peoples R China

Supercritical carbon dioxide (S-CO2) Brayton cycle has many advantages including high power conversion efficiency at mediate temperature, compact configuration, high system simplicity and low efficiency loss using dry cooling, which make it well suited to nuclear reactor applications. S-CO2 power cycle can be used as power conversion system for almost all the nuclear power systems including small modular reactor (SMR), Generation IV reactor and fusion reactor. It can also be used as a self-propellant and self-sustaining decay heat removal system to enhance the safety of existing commercial nuclear power plant. An update of research activities is needed to identify the unique research interests and challenges of S-CO2 power cycle based nuclear applications. This paper is a review of the research activities which have been carried out for S-CO2 power cycle based nuclear applications worldwide. The characteristics of S-CO2 power cycle are presented first to explain the distinctive features of this power cycle. Then the progresses in the experimental study of integrated S-CO2 Brayton cycle test loops are reviewed comprehensively to shed a light on its technical maturity in laboratory. Moreover, a review of various research areas concerning S-CO2 power cycle working as power conversion system or heat removal system for nuclear applications are carried out. Based on these review works, the challenges and perspectives are discussed and highlighted in the paper. Conclusions can be achieved that S-CO2 Brayton cycle is a promising option to broaden nuclear energy's application scope.

关键词： Brayton cycle Supercritical carbon dioxide Nuclear engineering Safety analysis Control strategy

来源：评论

学校读者我要写书评

暂无评论

Efficient electroreduction of NO3-to NH3 via the tandem catalysis of CeOx/ B-Cu2O NWs

引用

APPLIED CATALYSIS B-ENVIRONMENT AND ENERGY 2025年 378卷

作者： Yao, Zhimin Lin, Changzheng Gao, Jiaxiang Feng, Jiangtao Li, Mingtao Yan, Wei Zhang, Wenlong Wang, Hongjie Hebei Univ Sch Ecoenvironm Hebei Key Lab Close To Nat Restorat Technol Wetlan Baoding 071002 Peoples R China MOE Engn Res Ctr Ecol Safety & Conservat Beijing Tianj Baoding Peoples R China Xi An Jiao Tong Univ Sch Energy & Power Engn Dept Environm Sci & Engn 28 Xianning West Rd Xian 710049 Peoples R China Xi An Jiao Tong Univ Int Res Ctr Renewable Energy IRCRE State Key Lab Multiphase Flow Power Engn MFPE 28 Xianning West Rd Xian 710049 Peoples R China

Electrocatalytic nitrate reduction (eNitRR) has emerged as a carbon-free method for sustainable ammonia synthesis and wastewater treatment. However, the complex reaction intermediates and sluggish hydrogenation kinetics remain the key barriers of eNitRR. Herein, this work presented tandem catalysis strategy and developed a B-doped Cu2O nanowires decorated with CeOx to address the two critical issues. Our work presents a highperformance CeOx/B-Cu2O NWs catalyst for eNitRR, achieving an ammonia yield of 2.137 mmol h-1 cm-2 and a Faraday efficiency of 98.8 %, which are superior to those of most previously reported catalysts. At a voltage of-0.5 V vs. RHE, cyclic tests with 8 cycles verified the exceptional stability of the catalyst. In-depth in-situ characterization and density functional theory (DFT) computations demonstrated that doping with boron (B) enhances the adsorption of *NO3 due to the interactions between metallic and non-metallic components. Subsequently, the incorporation of CeOx modifies the electronic structure of Cu2O, thereby promoting hydrolysis and ensuring a sufficient supply of active hydrogen. Moreover, we report the successful development of an innovative Zn-NO3 battery, demonstrating remarkable performance characteristics with an open-circuit voltage of 1.182 V and an exceptional peak power density reaching 21.91 mW cm-2. Furthermore, by integrating eNitRR with an air stripping process, we successfully recovered high-purity NH4Cl products, providing a practical pathway for converting nitrate in wastewater into valuable ammonia-based products. This work provides comprehensive insights into the mechanism of tandem catalysis for eNitRR through the B doping and CeOx heterostructure.

关键词： Electrocatalytic nitrate reduction to ammonia Tandem catalysis Cu-based catalysts Heterostructure Density-functional theory

来源：评论

学校读者我要写书评

暂无评论

Electromagnetic-conductance measurement method for the flow rate and void fraction of gas-liquid two-phase flows

引用

Measurement: Sensors 2020年 10-12卷

作者： Chang, Fucheng Hu, Zitu Li, Xi Feng, Zongrui Ni, Shiyao Li, Huixiong State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an710049 China

Gas-liquid two-phase flow systems are widely existed in many engineering systems and industrial processes, and measurement techniques for two-phase flows are crucial in a diverse range of engineering applications. Most of the existing measurement techniques usually brought extra resistance to the flow in the branch pipes and, to some extent, influenced the original distribution of the gas-liquid two-phase flows in the parallel T-junction system. In order to study the distribution characteristics of two-phase flow in vertically parallel T-junctions, the electromagnetic-conductance measurement method was developed to measure the void fraction and liquid flow rate of the gas-liquid two-phase flow in the branch pipes. Electromagnetic-conductance measurement technique has the advantages of high response rate, satisfactory accuracy and low disturbance on the flow field of gas-liquid two-phase flows. In order to calibrate the conductance measurement method, experiments were carried out with the liquid velocity range of 0.2–2 m·s-1, the gas velocity range of 0–50 m·s-1 and the volume void fraction range of 0–0.99. Through the calibration experiments, the relationship between the resistance value of each conductivity sensor and the volume void fraction of two-phase fluid was decided to be established as a logistic function. By the error analysis of the calibration results, 75.9% of experimental results of the void fraction in the gas-liquid two-phase flow fell within the ±20% error bands. The electromagnetic-conductance measurement method proposed in this paper could provide a reference for accurate and non-interference measurement of two-phase flow in parallel T-junctions. © 2020 The Authors

关键词： Two phase flow

来源：评论

学校读者我要写书评

暂无评论

Preliminary study of system design and safety analysis methodology for supercritical carbon dioxide Brayton cycle direct-cooled reactor system

引用

ANNALS OF NUCLEAR ENERGY 2020年 147卷

作者： Gao, Chuntian Wu, Pan Shan, Jianqiang Huang, Yanping Zhang, Jibin Wang, Lianjie Xi An Jiao Tong Univ Sch Nucl Sci & Technol 28 Xianning West Rd Xian Shaanxi Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Nucl Power Inst China CNNC Key Lab Nucl Reactor Thermal Hydraul Technol Chengdu 610041 Peoples R China Nucl Power Inst China Sci & Technol Reactor Syst Design Technol Lab Chengdu 610041 Peoples R China

Due to advantage of compact component and simply layout, supercritical CO2 (s-CO2) Brayton cycle is considered as power conversion system for small modular reactors (SMRs). The safety performance of SMRs coupling with s-CO2 Brayton cycle, especially for s-CO2 Brayton cycle direct cooled reactor, is quite different from that of conventional reactor systems. Safety analysis is essential work before the system design of a newly proposed reactor system is finalized. In this paper, preliminary system design and safety analysis methodology is proposed for a direct cooled reactor system (SCFR-300). System characteristic is clarified through simulation and analysis. Conceptual design of overall plant system is developed based on its unique characteristics. 35 initial accident events are obtained through main logic diagram. The system design and protection logic, and safety analysis methodology determined in this study will be used in further safety analysis. This work will provide helpful implications for safety performance evaluation for s-CO2 direct cooled reactor systems. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： Supercritical CO2 Brayton cycle Reactor safety analysis Supercritical CO2 cooled reactor Deterministic safety analysis Safety system design

来源：评论

学校读者我要写书评

暂无评论

Birnessite-type short rod-like MnO2 achieving propane low-temperature destruction: Benign synthesis strategy and reaction mechanism determination

引用

APPLIED SURFACE SCIENCE 2021年 559卷

作者： Jian, Yanfei Feng, Xiangbo Tian, Mingjiao Jiang, Zeyu He, Chi Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Univ Chinese Acad Sci Natl Engn Lab VOCs Pollut Control Mat & Technol Beijing 101408 Peoples R China

Developing economical and robust noble metal-free materials for obstinate light alkane low-temperature decomposition is of great significance. Here, birnessite-type short rod-like MnO2 was firstly prepared by facile mixing KMnO4 and ascorbic acid under ambient conditions and employed in propane catalytic decomposition. Experimental results revealed that abundant oxygen vacancies and high valent Mn4+ species, superior reducibility, and high surface oxygen mobility guarantee the remarkable low-temperature activity of MnO2-SR, over which 90% of propane can be oxidized (T-90) at temperature as low as 225 degrees C, achieving a temperature reduction over 70 degrees C compared with that of delta-MnO2 (T-90 = 300 degrees C) and alpha-MnO2 (T-90 = 355 degrees C). In situ diffuse reflectance infrared Fourier transform spectroscopy revealed that the dissociation and activation of propane molecules is the decisive step in propane oxidation. Gaseous propane is slowly oxidized by adsorbed oxygen directly to the final mineralization products at low temperature region (<200 degrees C);at high temperature region (>200 degrees C) however, propane molecules are firstly dissociated and activated before oxidized to carbonate intermediate products over active oxygen, and then eventually oxidized to carbon dioxide and water.

关键词： MnO2 Oxygen vacancy Propane Catalytic oxidation Intermediates Activation route

来源：评论

学校读者我要写书评

暂无评论

Practical DMSO-promoted selective hydrolysis-oxidation of lignocellulosic biomass to formic acid attributed to hydrogen bonds

引用

GREEN CHEMISTRY 2021年第18期23卷 7041-7052页

作者： Guo, Yan-Jun Li, Shi-Jun Sun, Yuan-Li Wang, Lei Zhang, Wen-Min Zhang, Ping Lan, Yu Li, Yang Xi An Jiao Tong Univ Ctr Organ Chem Frontier Inst Sci & Technol Xian 710054 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710054 Peoples R China Zhengzhou Univ Coll Chem Zhengzhou 450052 Peoples R China Hubei Univ Technol Inst Pulp & Paper Technol Wuhan 430068 Peoples R China Xianyang Normal Univ Coll Chem & Chem Engn Xianyang 712000 Peoples R China

Formic acid (HCO2H) is widely used in various chemical processes, applied in fuel cells, and considered as a promising candidate for hydrogen storage. Currently, industrial production of HCO2H mainly depends on fossil resources using multiple processes. Practical HCO2H production from renewable resources for the potential industrial application is rare. Herein, we demonstrate practical dimethyl sulfoxide (DMSO) (1 v%)-promoted selective hydrolysis-oxidation of lignocellulosic biomass to HCO2H, which is demonstrated by recycling experiments of near 10 gram-scale wheat straw with constantly high efficiencies. Mechanism studies on the major unit of lignocellulosic biomass, glucose, disclose that the high selectivity and yield of HCO2H are attributed to the hydrogen bonds of DMSO with generated gem-diol groups from the reaction of glucose, or the intermediates of glycolaldehyde and glyoxal with water (H2O). The formation of hydrogen bonds is indicated both by DFT calculations and IR experiments.

关键词： Dimethyl sulfoxide

来源：评论

学校读者我要写书评

暂无评论

Fraunhofer-type signal for underwater measurement of copper sample using collinear long-short double-pulse laser-induced breakdown spectroscopy

引用

SPECTROCHIMICA ACTA PART B-ATOMIC SPECTROSCOPY 2020年 168卷

作者： Cui, Mincha Deguchi, Yoshihiro Wang, Zhenzhen Tanaka, Seiya Xue, Bowen Yao, Changfeng Zhang, Dinghua Northwestern Polytech Univ MIIT Key Lab High Performance Mfg Aero Engine Xian 710072 Peoples R China Shaanxi Univ Technol Shaanxi Key Lab Ind Automat Hanzhong 723000 Peoples R China Tokushima Univ Grad Sch Adv Technol & Sci Tokushima Tokushima 7708501 Japan Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The collinear long-short double-pulse laser-induced breakdown spectroscopy (long-shrot DP-LIBS) is used to detect the underwater copper sample. Fraunhofer-type signal is acquired with very short gate delay parameter, which is the first time to be reported that the collinear long-short DP-LIBS can generate Fraunhofer-type signal from underwater target. It is found that the early structure of underwater plasma is similar to the solar structure. According to the plasma image of early stage, a cold shell with low emission intensity is wrapped around a hot core with strong emission intensity. During early period, the continuum radiation from the hot core is absorbed by the copper atoms in plasma edge, causing Fraunhofer-type absorption at Cu I 324.754 nm and Cu I 327.396 nm. The experimental results show that the absorption intensity of Fraunhofer-type lines possesses a well signal stability in early stage. RSD% of signal is 1.5% with 10 ns delays and 5.3% with 30 ns delays at Cu I 324.754 nm, and RSD% is 2.7% with 10 ns delays and 3.3% with 30 ns delays at Cu I 327.396 nm. The present results sugget that the Fraunhofer-type signal generated by collinear long-short DP-LIBS is possible to be used for further underwater quantitative measurement.

关键词： LIBS Collinear long-short double-pulse Fraunhofer-type lines Underwater Copper

来源：评论

学校读者我要写书评

暂无评论

Experimental study on the droplet characteristics in the spray tip region: Comparison between the free and impinging spray

引用

EXPERIMENTAL THERMAL AND FLUID SCIENCE 2021年 121卷

作者： Zhan, Cheng Luo, Hongliang Chang, Feixiang Nishida, Keiya Ogata, Youichi Tang, Chenglong Feng, Zehao Huang, Zuohua Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Hiroshima Univ Grad Sch Adv Sci & Engn 1-4-1 Kagamiyama Higashihiroshima Hiroshima 7398527 Japan

In this work, we compared the microscopic characteristics of the free and impinging spray tip using double-pulse laser particle image analysis technique. Droplet population density, diameters, and velocities were experimentally resolved for both the free and impinging spray at three spray tip penetration positions (STP = 32, 37 and 42 mm) under three injection pressures (10, 20 and 30 MPa). Results showed that firstly, wall impingement will delay the arrival timing of the spray tip at a specific spray tip penetration location. The droplets were less populated in the impinging spray compared to the free spray especially at downstream positions. The population density between the impinging and the free spray is more profound at higher injection pressure. Secondly, for fixed injection pressure, more small droplets are observed in upstream region after impingement, while this effect becomes weak at downstream positions. The droplet diameter distribution of the impinging spray is less sensitive to the increase of injection pressure, compared to the free spray. Sauter mean diameter significantly reduces at higher injection pressure for both the free and impinging spray. Finally, the smaller droplet velocity was observed in the impinging spray due to the dissipation of spray momentum during interaction with the wall plate. Based on the droplet size and velocity, gas phase Weber number was further calculated. Compared to the free spray, the Weber number distribution of droplets in the impinging spray concentrates in significantly smaller values at all injection pressures and observation locations.

关键词： Spray impingement Free spray Microscopic characteristics Spray tip

来源：评论

学校读者我要写书评

暂无评论

Mass-produced metallic multiwalled carbon nanotube hybrids exhibiting high N-type thermoelectric performances

引用

JOURNAL OF MATERIALS CHEMISTRY A 2021年第6期9卷 3341-3352页

作者： Wang, Yizhuo Lu, Zhongxu Hu, Qiujun Qi, Xia Li, Qing Wu, Ziping Zhang, Hao-Li Yu, Choongho Wang, Hong Xi An Jiao Tong Univ Frontier Inst Sci & Technol Xian 710054 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710054 Peoples R China Jiangxi Univ Sci Technol Sch Mat Sci & Engn Ganzhou 341000 Peoples R China Lanzhou Univ Coll Chem & Chem Engn State Key Lab Appl Organ Chem SKLAOC Lanzhou 730000 Peoples R China Texas A&M Univ Dept Mech Engn College Stn TX 77843 USA ZhejiangYunFeng New Mat Technol Co Ltd 755 Hongji St Jinhua 321015 Zhejiang Peoples R China

Finding a stable n-type flexible thermoelectric (TE) material with a high power factor and mass production is a challenge for wearable TE devices. In this paper, we report that metallic multiwalled carbon nanotubes (MWCNTs) and their hybrids are converted from p-type to n-type with an n-type dopant, 1,3-dimethyl-2-phenyl-2,3-dihydro-1h-benzoimidazole (NDMBI), with a high n-type Seebeck coefficient. The maximum power factor of the n-type hybrid is 195 mW m(-1) K-2 at 373 K which is 2-3 orders higher than those of most n-type MWCNT based organic materials in the literature. This high TE performance may be attributed to the high n-type Seebeck coefficient of MWCNTs derived from the effective n-type doping. The theoretical calculation results indicate that the effective n-type doping could increase the Seebeck coefficients of metallic MWCNTs without sacrificing their electrical conductivities when their Fermi level shifts to approach the one-dimensional van Hove singularity. The results suggest that the trade-off relationship between the electrical conductivity and the Seebeck coefficient of one-dimensional metallic materials could be solved, which are promising candidates for preparing large scalable, low-cost, and high-performance flexible TE devices for wearable electronics. This may promote the evolution of developing high performance organic and inorganic TE materials with metallic one-dimensional nanomaterials.

关键词： Seebeck coefficient

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：