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Positive and negative shear lag behaviors of composite twin-girder decks with varying cross-section

Science China(Technological Sciences) 2017年第1期60卷 116-132页

作者： zhu Li NIE jianguo JI WenYu Key Laboratory of Civil Engineering Safety and Durability of China Education Ministry Department of Civil Engineering Tsinghua University Beijing 100084 China

In steel-concrete composite twin-girder decks, wide concrete slab would undergo significant shear lag warping effect, including positive and negative. Some researchers have investigated the positive shear lag of composite decks by means of one-dimensional line model, while the studies on the negative shear lag have not yet been reported until now. In this study, a new one-dimensional analytical model of composite twin-girder decks is first proposed based on the model proposed by Dezi et al. Besides slab shear lag effect and partial connection at slab-girder interface which have been included in the model of Dezi et al., the particularity of the proposed model relies on its ability to account for variation characteristic of cross-section. Verification of the analytical model is later conducted through comparison of results from the analytical analysis and elaborate FE analysis for a simply supported composite deck with increasing depth and a two-span continuous one with decreasing depth. Finally, three kinds of structural forms of composite twin-girder decks, including cantilever, simply supported and continuous decks, are selected to carry out the analysis of positive and negative shear lag behaviors by means of the analytical model. The influences of cross-sectional variation characteristic and load type on positive and negative shear lag behaviors are mainly investigated. Additionally, a new definition on effective width for considering simultaneously positive and negative shear lag behaviors is proposed. The results from the proposed analytical model and EC4 specification are compared to provide suggestions for designers and checkers. In this study, the proposed analytical model can provide a powerful numerical tool for researchers to conduct the further investigation, and the analysis on shear lag and effective width can assist in design analysis of composite twin-girder decks.

关键词： steel-concrete composite twin-girder deck analytical model variation of cross-section positive and negative shear lagbehavior effective width

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Simulation of residual stresses and their effects on thermal barrier coating systems using finite element method

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Science China(Physics,Mechanics & Astronomy) 2015年第3期58卷 49-58页

作者： zhu jianguo CHEN Wei XIE HuiMin Faculty of Civil Engineering and Mechanics Jiangsu University School of Naval Architecture and Ocean Engineering Jiangsu University of Science and Technology Key Laboratory of Applied Mechanics (AML) Department of Engineering Mechanics Tsinghua University

Thermal barrier coating(TBC)systems are widely used in industrial gas-turbine ***,premature failures have impaired the use of TBCs and cut down their lifetime,which requires a better understanding of their failure *** the present study,experimental studies of isothermal cycling are firstly carried out with the observation and estimation of *** to the experimental results,a finite element model is established for the analysis of stress perpendicular to the TBC/BC *** residual stress distributions in TBC are obtained to reflect the influence of mechanical properties,oxidation,and interfacial *** calculated results show that the maximum tensile stress concentration appears at the peak of TBC and continues to increase with thermal *** of the microstructural characteristics of plasma-sprayed TBCs,cracks initialize in tensile stress concentration(TSC)regions at the peaks of TBC and propagate along the TBC/BC interface resulting in the spallation of ***,the inclusion of creep is crucial to failure prediction and is more important than the inclusion of sintering in the simulation.

关键词： residual stress failure mechanism finite element method thermal barrier coating

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Numerical Simulation on Pulverized Coal Combustion and NO_x Emissions in High Temperature Air from Circulating Fluidized Bed

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Journal of Thermal Science 2013年第3期22卷 261-268页

作者： jianguo zhu Ziqu Ouyang Qinggang Lu Institute of Engineering Thermophysics Chinese Academy of Sciences

High temperature air combustion is a prospecting technology in energy saving and pollutants reduction. Numerical simulation on pulverized coal combustion and NOx emissions in high temperature air from circulating fluidized bed was presented. The down-fired combustor, taken as the calculation domain, has the diameter of 220 mm and the height of 3000 mm. 2 cases with air staging combustion are simulated. Compared the simulation results with experimental data, there is a good agreement. It is found that the combustion model and NOx formation model are applicable to simulate the pulverized coal combustion and NOx emissions in high temperature air from circulating fluidized bed. The results show that there is a uniform temperature profile along the axis of the down-fired combustor. The NOx emissions are lower than those of ordinary pulverized coal combustion, and the NOx emissions are 390 mg/m3 and 352 mg/m3 in Case 1 and Case 2, respectively. At the range of 300-600 mm below the nozzle, the NO concentration decreases, mainly resulting from some homogeneous reactions and heterogeneous reaction. NO concentration has a little increase at the position of 800 mm below the nozzle as the tertiary air supplied to the combustor at the position of 600 mm below the nozzle.

关键词： Pulverized coal combustion Numerical simulation High temperature air NOx

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Characteristics of Preheating Combustion of Power Coal with High Coking Properties

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Journal of Thermal Science 2021年第4期30卷 1108-1115页

作者： ZHANG Yi zhu jianguo LYU Qinggang PAN Fei zhu Shujun Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

Yankuang coal with the high coking property is difficult to use through direct *** main purpose of this paper is to study the combustion characteristics and NO_(x)emissions of this type of coal using preheating combustion *** experimental results show that after the pulverized coal is preheated,the char residue characteristic is significantly reduced from 5 to *** the preheating process,the preheating temperature is stable at about 910°C,and the particle size of char after preheating is reduced,and the pore structure and specific surface areas are *** combustion temperature of preheated fuel is stable at around 1100℃,and the combustion efficiency can reach more than 99%under different *** the structure of the secondary air nozzles during the preheating combustion process can influence the characteristics of NO_(x)*** NO_(x)emission of the central nozzle is about 112 mg/Nm~(3)lower than that of the annular *** the tertiary air distribution modes can reduce the final NO_(x)emissions to 215 mg/Nm~3(@6%O_2),and the corresponding conversion ratio of fuel N to the final NO_(x)is 4.2%.The results of this experiment prove that the Yankuang coal can achieve stable combustion by preheating combustion technology,and this proposed a new way for the utilization of Yankuang coal.

关键词： Yankuang coal coking properties preheating combustion NO_(x)emissions

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Preheating Characteristics of Datong Coal in O2/CO2 and Air Atmospheres

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Journal of Thermal Science 2018年第4期27卷 341-348页

作者： zhu jianguo MA Hongzhou LIU Dianbin LI Jiarong Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100190 China University of Chinese Academy of Sciences Beijing 100049 China

Experimental studies were carried out to find the difference of preheating characteristics of Datong coal in O_2/CO_2 and air atmospheres by a circulating fluidized bed. It is found that pulverized coal could be both steadily preheated to above 800°C in the two different atmospheres, but the temperature distribution was more uniform along the riser in O_2/CO_2 atmosphere. During the preheating, the content of CO in the flue gas can reach 12.32% under the O_2/CO_2 atmosphere, far higher than that in air(5.94%). Simultaneously, the conversion rate of fixed carbon was higher in O_2/CO_2 atmosphere compared with that in air. It can be inferred the higher oxygen concentration and higher partial pressure of CO_2 have greatly accelerated the gasification reaction. The BET analysis indicated a number of large pores were transformed into micropores during the preheating progress, and the major contributors for overall pore volume of chars and specific surface area are the micro-pores and the mesopores with diameter ranging from 2 nm to 10 nm. The inner pore structure was more developed in O_2/CO_2 atmosphere.

关键词： circulating fluidized bed Datong coal preheating O2/CO2

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Experimental Study on Preheated Combustion of Pulverized Semi-coke

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Journal of Thermal Science 2015年第4期24卷 370-377页

作者： YAO Yao zhu jianguo LU Qinggang ZHOU Zuxu University of Chinese Academy of Sciences Institute of Engineering Thermophysics Chinese Academy of Sciences

In a test rig,pulverized semi-coke was preheated to 850℃in a circulating fluidized bed(CFB)and then cornbusted at 1100℃in a down-fired combustor(DFC).Experiments were conducted to reveal the effects of three secondary air nozzle cases(co-axial jet,top circular jet and wall circular jet)on the NO *** results show that the optimized secondary air nozzle can reduce NO emission.O_2 concentration profile is the major factor affecting NO generation and emission,which is led by the secondary air *** lower O_2 concentration led to the generation of lower initial *** NO emission at the exit of the DFC was reduced from 189 to 92mg/m^3(@6%O_2)with the decrease of initial *** peak of NO at 100 mm below the nozzle should be attributed to the oxidization of NH_3 in the syngas,rather than the oxidization of fuel-N in the *** low and well-distributed O_2 concentration contributes to the reduction of initial NO,which helps to reduce the NO *** combustion effieiencies of the eases of the co-axial jet,the top circular jet,and the wall circular jet are97.88%,98.94%and 98.74%,respectively.

关键词： Pulverized semi-coke Preheated combustion Secondary air nozzle NO emission.

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Preheating Combustion Characteristics of Ultra-Low Volatile Carbon-Based Fuel

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Journal of Thermal Science 2019年第4期28卷 772-779页

作者： zhu Shujun LYU Qinggang zhu jianguo LI Jiarong MAN Chengbo LIU Wen Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

Pulverized coal combustion technology with preheating solid fuel in a circulating fluidized bed was used for the combustion test of ultra-low volatile carbon-based *** paper first validated the feasibility and advantages of applying the combustion technology to this kind of *** carbon-based fuel could achieve a stable preheating process in this test *** the preheating,the apparent sensible heat of the fuel was significantly *** provided a necessary condition for the stable ignition and efficient combustion of the carbon-based fuel in the post-combustion *** relative proportions of CO,H2,and CH4 in preheated coal gas were very low,and the effect of high-temperature coal gas at the entrance of the post-combustion chamber was greatly impaired,indicating that the combustion process in post-combustion chamber was mainly the combustion of preheated *** the same time,the strong reducing atmosphere in the circulating fluidized bed also facilitated the reduction of fuel-nitrogen into N2,which resulted in low NOx *** this basis,with the combination of preheating combustion technology and air-staging combustion technology,the NOx emissions had drastically decreased when the burnout air distribution position moved down or varied from a single-layer distribution to a multi-layer distribution *** lowest original NOx emissions were 90.6 mg/m3(at 6%O2),and the combustion efficiency exceeded 97%,which ultimately achieved efficient and clean combustion of ultra-low volatile carbon-based fuel.

关键词： preheating combustion circulating fluidized bed ultra-low volatile carbon-based fuel air-staging Nox emissions

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Effect of La and Co-doping on microstructure and electrical properties of Bi FeO_3 thin films

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Chinese Science Bulletin 2014年第36期59卷 5205-5211页

作者： Jiagang Wu Dingquan Xiao jianguo zhu Department of Materials Science Sichuan University

Adding both La3+and Co3+was used to tune the microstructure and electrical properties of Bi Fe O3(BFO) thin films, and Bi1-xLaxFe0.90Co0.10O3 thin films were grown on the Sr Ru O3-buffered Pt-coated silicon substrates by a radio frequency sputtering. A polycrystalline structure with(110) orientation was shown in thin films, and their resistivity dramatically increases as the La3+content increases. Their dielectric constant increases,and dielectric loss decreases with increasing La3+*** addition, their ferroelectric and fatigue properties were enhanced with rising La3+content. The thin films with x = 0.03 have optimum electrical properties(e.g., remanent polarization 2Pr* 175.6 l C/cm2, coercive field2Ec* 699.5 k V/mm, dielectric constant er* 257 and tan d * 0.038), together with a good fatigue behavior. The impendence analysis of the films was conducted to identify the defects type during conductivity, and both hopping electrons and single-charged oxygen vacancies are mainly responsible for the conduction of grain and grain boundaries regardless of La3+content. As a result, the doping with both La3+and Co3+benefits the improvement in the electrical properties of BFO thin films.

关键词：电性能薄膜掺杂微结构抗疲劳性能 Co La 介电常数

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OPTIMUM DESIGN OF PROCESSING CONDITION AND EXPERIMENTAL INVESTIGATION OF GRATING FABRICATION WITH HOT EMBOSSING LITHOGRAPHY

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Acta Mechanica Solida Sinica 2009年第6期22卷 665-671页

作者： jianguo zhu Huimin Xie Minjin Tang Xiaojtm Li AML Department of Engineering Mechanics Tsinghua University Beijing 100084 China National Center for Nanoscienee and Technology Beijing 100084 China

The cross-section profiles of polymer deformation in the hot embossing lithography process were studied by finite element method for various temperature, time and pressure. In order to successfully fabricate high-frequency grating lines, an optimal imprint condition was selected and the related experiments were carried out. The fabricated gratings were illuminated by the SEM image and AFM analysis, which agree well with the simulated results. Therefore, the finite element methods are helpful for a better comprehension of the polymer flow phenomena governing the pattern definition and the design of optimum processing conditions for successful grating fabrication.

关键词： grating fabrication hot embossing lithography finite element experiment

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Defect passivation through electrostatic interaction for high performance flexible perovskite solar cells

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Journal of Energy Chemistry 2020年第7期29卷 173-177,I0006页

作者： Deyu Xin Shujie Tie Xiaojia Zheng jianguo zhu Wen-Hua Zhang Department of Materials Science Sichuan UniversityChengdu 610064SichuanChina Sichuan Research Center of New Materials Institute of Chemical MaterialsChina Academy of Engineering PhysicsChengdu 610200SichuanChina

The light weight,good bending resistance and low production cost make flexible perovskite solar cells(PSCs)good candidates in wearable electronics,portable charger,remote power,and flying *** power conversion efficiency(PCE)plays a crucial role on obtaining the high mass specific power of flexible ***,the performance for flexible PSCs is still having a large room to be ***,we added the 2-amino-5-cyanopyridine(ACP)molecule with a polar electron density distribution in the perovskite precursor solution to improve the performance of flexible *** cyano groups with electron-withdrawing ability are expected to passivate positively charged point defects,while amines with electron donating ability are expected to passivate negatively charged point defects in perovskite *** to the effective passivation of defects at the grain boundary and surface of perovskite films,the PCE of flexible PSCs is obviously increased from 16.9%to 18.0%.These results provide a universal approach to improve performance of flexible PSCs by healing the defects in perovskite films through electrostatic interactions.

关键词： Perovskite solar cell Flexible Electrostatic interaction Defect passivation Recombination

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