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- 저자 : Leilei Xu (검색결과 11 건)
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Leilei Xu,Xueying Wen,Mindong Chen,Chufei Lv,Yan Cui,Xianyun Wu,Cai-e Wu,Zhichao Miao,Xun Hu 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.100 No.-
The mesoporous nanosponge MFI silicate zeolite was facilely fabricated by employing the long chainammonium as the structure-directing agent. The zeolite with both mesoporous and microporouschannels were selected as the support of Ni-La catalysts for methanation of CO2. Various techniques wereused to characterize the catalysts systematically. The effects of the La2O3 promotor and pore morphologyof the support on the catalytic performance were carefully investigated. Our study demonstrated that Lapromoter could be beneficial to the increase of the surface basicity and the enhancement of the metallicNi dispersion. This would intensify the processes of the CO2 chemisorption and H2 dissociation in CO2methanation. Besides, we also found that the catalyst supported on mesoporous nanosponge MFI zeoliteperformed higher activity and better long-term stability than the reference catalysts supported on bulkMFI and MCM-48, suggesting that the synergistic effect between the mesoporous and microporouschannels displayed unique advantages. Kinetic study revealed that both the nanosponge structure andLa2O3 promoter contributed to decreasing the reaction activation energy. Therefore, the present highlydispersed Ni-La catalyst over mesoporous nanosponge MFI zeolite promised a potential catalystcandidate for low-temperature CO2 methanation reaction.
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The First Stage of Developing the Adolescent Friendship Social Capital Scale
Xu, Leilei Korean Association of Child Studies 2012 Child studies in Asia-Pacific context Vol.2 No.1
The purpose of the study was to generate the candidate items for the Adolescent Friendship Social Capital Scale. Both inductive and deductive approaches were used to generate the scale items. Halpern's conceptual map of social capital served as the theoretical basis of this scale, and guided the development of items. Semi-structured interviews with adolescents in Sydney, Melbourne and Beijing generated the initial pool of scale items. Twenty-six items were generated for the Adolescent Friendship Social Capital Scale. The items are organised in four theoretical constructs: Bonding Networks, Bridging Norms, Bridging Sanctions, and Linking Networks. Each item is a short statement followed by a five-point Likert scale anchored by 1= "Strongly disagree" and 5= "Strongly agree". The scale has several advantages over previous measures of adolescent friendship networks and friendship social capital. The scale has a strong and clear theoretical structure, the scale items demonstrate initial construct and content validity, and the format of the scale enables the collection of continuous data. However, in order to ensure the validity and reliability of the scale, another two stages of research need to be conducted in the future: scale development and scale evaluation.
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The First Stage of Developing the Adolescent Friendship Social Capital Scale
Leilei Xu 한국아동학회 2012 Child studies in Asia-Pacific context Vol.2 No.1
The purpose of the study was to generate the candidate items for the Adolescent Friendship Social Capital Scale. Both inductive and deductive approaches were used to generate the scale items. Halpern`s conceptual map of social capital served as the theoretical basis of this scale, and guided the development of items. Semi-structured interviews with adolescents in Sydney, Melbourne and Beijing generated the initial pool of scale items. Twenty-six items were generated for the Adolescent Friendship Social Capital Scale. The items are organised in four theoretical constructs: Bonding Networks, Bridging Norms, Bridging Sanctions, and Linking Networks. Each item is a short statement followed by a five-point Likert scale anchored by 1= "Strongly disagree" and 5= "Strongly agree". The scale has several advantages over previous measures of adolescent friendship networks and friendship social capital. The scale has a strong and clear theoretical structure, the scale items demonstrate initial construct and content validity, and the format of the scale enables the collection of continuous data. However, in order to ensure the validity and reliability of the scale, another two stages of research need to be conducted in the future: scale development and scale evaluation.
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A Study on Adaptive Direction Teaching-Learning-Based Optimization Algorithm
Xu Sun,Mengying He,Leilei Kong,Haoliang Qi 보안공학연구지원센터 2016 International Journal of u- and e- Service, Scienc Vol.9 No.4
In the real life learning process, the teacher communicates with the students for a better learning outcome. The teaching-learning-based optimization (TLBO) algorithm simulates this procedure and shows its great performance in solving the constrained and unconstrained nonlinear optimization problem. This paper presents an adaptive direction strategy(ADS )t o improve the searching ability for the TLBO algorithm. The improved algorithm is tested through searching the optimal points for a few typical testing functions. The testing result shows that the improved TLBO algorithm could obtain better optimal solutions in shorter time. Compared to the normal TLBO algorithm, the stability and effectiveness of the improved algorithm are increased greatly.
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Yiyu Shi,Leilei Xu,Mindong Chen,Bo Yang,Ge Cheng,Cai-e Wu,Zhichao Miao,Ning Wang,Xun Hu 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.105 No.-
In this work, the uniform Cu2O submicron-cubes were facilely synthesized by liquid phase reductionmethod. Then, the Cu2O submicron-cubes were further oxidized into Cu2O-CuO heterojunction with tunableCu2+/Cu+ ratios and CuO submicron-cubes by controlling the calcination temperature. The phasetransition period during calcination was real-time monitored by the in-situ XRD and in-situ DRIFTS. The obtained materials were investigated as the catalysts of CO oxidation. The results revealed thatthe Cu2O-CuO heterojunction catalysts performed much higher catalytic activities than the Cu2O andCuO counterparts. Because the synergistic effect of the heterojunction (Cu2+/Cu+) could increase the surfaceoxygen vacancy concentration. Furthermore, it was also found that only the Cu2O-CuO heterojunctionstructure with the appropriate Cu2+/Cu+ ratio behaved the optimum catalytic activity. The kineticstudies indicated that the apparent activation energy of CO oxidation was greatly affected by the Cu2+/Cu+ ratio. Therefore, these Cu2O-CuO submicron-cubes with heterostructure were considered as thepromising CO oxidation catalysts.
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High dispersion of supported metal catalysts on zeolitic mesopore walls
조창범,조장근,( Leilei Xu ),유룡 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1
Supported metal catalysts played a central role in many heterogeneous catalysis. Highly dispersed form of metal nanoparticles are generally preferred in terms of catalytic activity. High dispersion of supported metal nanoparticles can be readily achieved at low metal loading. However, supported metals become to be distributed in an inhomogeneous manner with increasing in loading amount. In this contribution, we reported that MFI zeolite nanosponges can support transition metal nanoparticles (e.g., Ni, Cu, Co) on the mesopore walls in a highly dispersed form at a very high content (~20 wt.%). Such a high dispersion might be attributed to three-dimensional interconnections of uniform mesopores and ordered arrangement of Si-OH groups onto the zeolitic mesopore walls. The MFI zeolite nanosponges supported on 20wt% Ni nanoparticles exhibited a high catalytic activity in CO<sub>2</sub> methanation reaction, as compared to MCM-48 supporting on 20wt% Ni nanoparticles.
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Yiran Wang,Chao Li,Shu Zhang,Leilei Xu,Xun Hu 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.110 No.-
Alcohols like ethanol and glycerol have been extensively investigated as potential feedstock for on-sitehydrogen production by steam reforming. The varied number of hydroxyl group in the alcohols inevitablyaffects the reaction intermediates generated and eventually properties of coke formed. In this study, fouralcohols (ethanol, ethylene glycol, 1-propanol and glycerol) with the single or multiple hydroxyl groupswere steam reformed, focusing on the influence of the hydroxyl group on the properties of the coke. Theresearch results showed that steam reforming of ethanol and glycerol produced more coke than that insteam reforming of 1-propanol or ethylene glycol, while the Ni/SBA-15 catalyst deactivated to a higherextent in steam reforming of ethylene glycol or glycerol with multiple hydroxyl group, due to the cokeof varied properties. The coke produced by steam reforming of ethanol and 1-propanol contained moredefective structures but more aromatic. However, the generated coke from the steam reforming of ethyleneglycol and glycerol had more aliphatic structures, especially in that from ethylene glycol. On theother hand, the carbon nanotubes formed by the steam reforming of ethanol or 1-propanol had thin wallthickness and smooth surface, while that in steam reforming of ethylene glycol and glycerol had thickwall and very rough surface, resulting from the distinct reaction intermediates formed.
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XIAOLI SUN,JIANGGUO GUAN,WEIDONG SHI,HAO TU,LEILEI XU,YAN YAN 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2014 NANO Vol.9 No.6
The Bi 2 O 3 sphere-like precursors were ¯rst synthesized through a simple hydrothermal reactionin the mixture of sodium cholate (SC) and hydrogen peroxide. Thermal decomposition of theseprecursors would result in the formation of the uniform porous Bi 2 O 3 nanospheres with diametersof ca. 80 nm in air at 500?C. The amount of added H 2 O 2 and the reaction time were found to playimportant roles in the formation of Bi 2 O 3 sphere-like precursors. The as-prepared porous Bi 2 O 3nanospheres exhibited a very excellent photocatalytic activity for the degradation of rhodamineB (RB) and methyl blue (MB) dyes under visible-light irradiation, which could be attributed totheir narrow band gap and high surface area.
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Fulin Wang,Qi Tao,Luoqiong Xiao,Jiahao Hu,Leilei Xu 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.5
A realistic finite element model considering the ploughing effect of cutting edge fillet was developed in high speed machining. Taking the hardened tool steel AISI D2 as the object of research, the cutting force and chip morphology were reasonably analyzed and compared with the actual results of cutting experiments, which verified the correctness of the model. Then, based on the model, the formation process of single serrated tooth was analyzed, while the effects of cutting heat and temperature field, material hardness and cutting speed on chip formation were explored. The research results indicate that: (1) The ploughing-effect has a great impact on the feed force, and for hardened tool steel AISI D2, the stagnation angle of 30 o is more appropriate. (2) Also, stress concentration appears and shear slipping occurs along the shear plane in the process of serrated chip formation. The strain rate on the shear slipping surface is much greater than other places and the temperature gradient perpendicular to the shear plane is relatively higher. (3) The cutting force becomes larger with increasing the hardness value of workpieces, which causes the chip to more likely to produce serrated chips. (4) The fluctuation of cutting force is more significant as the cutting speed increases, which puts forward higher requirements for the tool and machine tool.
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