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A density functional theory study of methane activation on MgO supported NiM cluster: role of M on C–Hactivation

《化学科学与工程前沿（英文）》 2022年 第16卷 第10期   页码 1485-1492 doi: 10.1007/s11705-022-2169-8

摘要： Methane activation is a pivotal step in the application of natural gas converting into high-value added chemicals via methane steam/dry reforming reactions. Ni element was found to be the most widely used catalyst. In present work, methane activation on MgO supported Ni–M (M = Fe, Co, Cu, Pd, Pt) cluster was explored through detailed density functional theory calculations, compared to pure Ni cluster. CH4 adsorption on Cu promoted Ni cluster requires overcoming an energy of 0.07 eV, indicating that it is slightly endothermic and unfavored to occur, while the adsorption energies of other promoters M (M = Fe, Co, Pd and Pt) are all higher than that of pure Ni cluster. The role of M on the first C–H bond cleavage of CH4 was investigated. Doping elements of the same period in Ni cluster, such as Fe, Co and Cu, for C–H bond activation follows the trend of the decrease of metal atom radius. As a result, Ni–Fe shows the best ability for C–H bond cleavage. In addition, doping the elements of the same family, like Pd and Pt, for CH4 activation is according to the increase of metal atom radius. Consequently, C–H bond activation demands a lower energy barrier on Ni–Pt cluster. To illustrate the adsorptive dissociation behaviors of CH4 at different Ni–M clusters, the Mulliken atomic charge was analyzed. In general, the electron gain of CH4 binding at different Ni–M clusters follows the sequence of Ni–Cu (–0.02 e) < Ni (–0.04 e) < Ni–Pd (–0.08 e) < Ni–Pt (–0.09 e) < Ni–Co (–0.10 e) < Ni–Fe (–0.12 e), and the binding strength between catalysts and CH 4 raises with the CH4 electron gain increasing. This work provides insights into understanding the role of promoter metal M on thermal-catalytic activation of CH4 over Ni/MgO catalysts, and is useful to interpret the reaction at an atomic scale.

关键词： CH4 dissociation     Ni–M     C–H bond activation     charge transfer    

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Effect of noble metal nanoparticle size on C–N bond cleavage performance in hydrodenitrogenation: a study

《化学科学与工程前沿（英文）》 2023年 第17卷 第12期   页码 1986-2000 doi: 10.1007/s11705-023-2337-5

摘要： Breakage of the C–N bond is a structure sensitive process, and the catalyst size significantly affects its activity. On the active metal nanoparticle scale, the role of catalyst size in C–N bond cleavage has not been clearly elucidated. So, Ru catalysts with variable nanoparticle sizes were obtained by modulating the reduction temperature, and the catalytic activity was evaluated using 1,2,3,4-tetrahydroquinoline and o-propylaniline with different C–N bond hybridization patterns as reactants. Results showed a 13 times higher reaction rate for sp3-hybridized C–N bond cleavage than sp2-hybridized C–N bond cleavage, while the reaction rate tended to increase first and then decrease as the catalyst nanoparticle size increased. Different concentrations of terrace, step, and corner sites were found in different sizes of Ru nanoparticles. The relationship between catalytic site variation and C–N bond cleavage activity was further investigated by calculating the turnover frequency values for each site. This analysis indicates that the variation of different sites on the catalyst is the intrinsic factor of the size dependence of C–N bond cleavage activity, and the step atoms are the active sites for the C–N bond cleavage. When Ru nanoparticles are smaller than 1.9 nm, they have a strong adsorption effect on the reactants, which will affect the catalytic performance of the Ru catalyst. Furthermore, these findings were also confirmed on other metallic Pd/Pt catalysts. The role of step sites in C–N bond cleavage was proposed using the density function theory calculations. The reactants have stronger adsorption energies on the step atoms, and step atoms have d-band center nearer to the Fermi level. In this case, the interaction with the reactant is stronger, which is beneficial for activating the C–N bond of the reactant.

关键词： sp3/sp2-hybridized C–N bond     noble metal nanoparticle     catalytic active site     turnover frequency     DFT    

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Controllable synthesis of a large TS-1 catalyst for clean epoxidation of a C=C double bond under mild

《化学科学与工程前沿（英文）》 2023年 第17卷 第6期   页码 772-783 doi: 10.1007/s11705-022-2280-x

摘要： Development of a titanium silicalite-1 (TS-1) catalyst with good crystallinity and a four-coordinate Ti framework is critical for efficient catalytic oxidation reaction under mild conditions. Herein, a size-controlled TS-1 zeolite (TS-1#0.1ACh (acetylcholine)) was synthesized via steam-assisted crystallization by introducing acetylcholine as a crystal growth modifier in the preparation process, and TS-1#0.1ACh was also employed in epoxidations of different substrates containing C=C double bonds. The crystalline sizes of the as-synthesized TS-1#0.1ACh catalysts were controlled with the acetylcholine content, and characterization results showed that the particle sizes of highly crystalline TS-1#0.1ACh zeolite reached 3.0 μm with a good Ti framework. Throughout the synthetic process, the growth rate of the crystals was accelerated by electrostatic interactions between the connected hydroxyl groups of the acetylcholine modifier and the negatively charged skeleton of the pre-zeolites. Furthermore, the TS-1#0.1ACh catalyst demonstrated maximum catalytic activity, good selectivity and high stability during epoxidation of allyl chloride. Importantly, the TS-1#0.1ACh catalyst was also highly versatile and effective with different unsaturated substrates. These findings may provide novel, easily separable and large TS-1 catalysts for efficient and clean industrial epoxidations of C=C double bonds.

关键词： size-controlled TS-1     crystal modifier     steam-assisted crystallization     epoxidation    

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从氢原子质子化模型计算H2+的结构参数

陈景

《中国工程科学》 2004年 第6卷 第11期   页码 29-32

摘要：

对氢分子离子提出了氢原子质子化的结构模型，从微观时标和宏观时标分析了H2+中库仑吸引力和两核排斥力的动态平衡，认为氢原子畸变后的电子云在两核中点产生e/

关键词： 氢分子离子     键长     键能     力常数    

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Coronary leukocyte activation in relation to progression of coronary artery disease

null

《医学前沿（英文）》 2016年 第10卷 第1期   页码 85-90 doi: 10.1007/s11684-016-0435-1

摘要：

Leukocyte activation has been linked to atherogenesis, but there is little in vivo evidence for its role in the progression of atherosclerosis. We evaluated the predictive value for progression of coronary artery disease (CAD) of leukocyte activation markers in the coronary circulation. Monocyte and neutrophil CD11b, neutrophil CD66b expression and intracellular neutrophil myeloperoxidase (MPO) in the coronary arteries were determined by flow cytometry in patients undergoing coronary angiography. The primary outcome included fatal and nonfatal myocardial infarction or arterial vascular intervention due to unstable angina pectoris. In total 99 subjects who were included, 70 had CAD at inclusion (26 patients had single-vessel disease, 18 patients had two-vessel disease and 26 patients had three-vessel disease). The median follow-up duration was 2242 days (interquartile range: 2142–2358). During follow-up, 13 patients (13%) developed progression of CAD. Monocyte CD11b, neutrophil CD11b and CD66b expression and intracellular MPO measured in blood obtained from the coronary arteries were not associated with the progression of CAD. These data indicate that coronary monocyte CD11b, neutrophil CD11b and CD66b expression and intracellular MPO do not predict the risk of progression of CAD.

关键词： coronary artery disease     inflammation     integrin     myeloperoxidase     leukocyte activation    

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Effect of embedment length of untreated natural fibres on the bond behaviour in cement mortar

Gudimella RAMAKRISHNA, Sriraman PRIYADHARSHINI

《结构与土木工程前沿（英文）》 2018年 第12卷 第4期   页码 454-460 doi: 10.1007/s11709-017-0454-2

摘要： The present investigation is focused on studying the effects of various matrices with 1:3, 1:4 and 1:5 mortars and fibre types of sisal and coir on the bond behavior at various ages of curing, i.e., 24 h, 3 d, 7 d and 28 d. The other parameters included in the investigation are water/cement (w/c) ratio, sand gradation and embedment length of fibres. In addition, the type of failure of sisal and coir fibres for different mixes of mortars at various curing ages is also reported. From the results, it is seen that the bond strength is improving with respect to age of curing in case of sisal fibres, but decreases in case of coir fibres. The failure of fibres due to fibre fracture is observed in sisal fibres and fibre pullout is observed in coir fibres. The other varying parameters such as mortar mixes, sand gradation, w/c ratio and embedded length also showed significant effect on bond behaviour of sisal and coir fibre with the cement mortar mixes.

关键词： bond strength     cement mortar     natural fibre     pullout test     type of failure    

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Analysis of the double-layer α-Si:H emitter with different doping concentrations for α-Si:H/c-Si heterojunction

Haibin HUANG,Gangyu TIAN,Tao WANG,Chao GAO,Jiren YUAN,Zhihao YUE,Lang ZHOU

《能源前沿（英文）》 2017年 第11卷 第1期   页码 92-95 doi: 10.1007/s11708-016-0432-8

摘要： Double-layer emitters with different doping concentrations (DLE) have been designed and prepared for amorphous silicon/crystalline silicon (α-Si:H/c-Si) heterojunction solar cells. Compared with the traditional single layer emitter, both the experiment and the simulation (AFORS-HET, http://www.paper.edu.cn/html/releasepaper/2014/04/282/) prove that the double-layer emitter increases the short circuit current of the cells significantly. Based on the quantum efficiency (QE) results and the current-voltage-temperature analysis, the mechanism for the experimental results above has been investigated. The possible reasons for the increased current include the enhancement of the QE in the short wavelength range, the increase of the tunneling probability of the current transport and the decrease of the activation energy of the emitter layers.

关键词： double-layer emitter     α-Si:H/c-Si heterojunction solar cell     short circuit current     quantum efficiency     current-voltage-temperature    

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Modeling of alkali-silica reaction in concrete: a review

WANG, Q.C. SUN, C.H. ZHANG, D.R.J. OWEN

《结构与土木工程前沿（英文）》 2012年 第6卷 第1期   页码 1-18 doi: 10.1007/s11709-012-0141-2

摘要： This paper presents a comprehensive review of modeling of alkali-silica reaction (ASR) in concrete. Such modeling is essential for investigating the chemical expansion mechanism and the subsequent influence on the mechanical aspects of the material. The concept of ASR and the mechanism of expansion are first outlined, and the state-of-the-art of modeling for ASR, the focus of the paper, is then presented in detail. The modeling includes theoretical approaches, meso- and macroscopic models for ASR analysis. The theoretical approaches dealt with the chemical reaction mechanism and were used for predicting pessimum size of aggregate. Mesoscopic models have attempted to explain the mechanism of mechanical deterioration of ASR-affected concrete at material scale. The macroscopic models, chemo-mechanical coupling models, have been generally developed by combining the chemical reaction kinetics with linear or nonlinear mechanical constitutive, and were applied to reproduce and predict the long-term behavior of structures suffering from ASR. Finally, a conclusion and discussion of the modeling are given.

关键词： alkali-silica reaction (ASR)     modeling     concrete     mesoscopic     macroscopic    

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Uncertainty propagation analysis by an extended sparse grid technique

JIA, C. JIANG, C. M. FU, B. Y. NI, C. S. WANG, M. H. PING

《机械工程前沿（英文）》 2019年 第14卷 第1期   页码 33-46 doi: 10.1007/s11465-018-0514-x

摘要： In this paper, an uncertainty propagation analysis method is developed based on an extended sparse grid technique and maximum entropy principle, aiming at improving the solving accuracy of the high-order moments and hence the fitting accuracy of the probability density function (PDF) of the system response. The proposed method incorporates the extended Gauss integration into the uncertainty propagation analysis. Moreover, assisted by the Rosenblatt transformation, the various types of extended integration points are transformed into the extended Gauss-Hermite integration points, which makes the method suitable for any type of continuous distribution. Subsequently, within the sparse grid numerical integration framework, the statistical moments of the system response are obtained based on the transformed points. Furthermore, based on the maximum entropy principle, the obtained first four-order statistical moments are used to fit the PDF of the system response. Finally, three numerical examples are investigated to demonstrate the effectiveness of the proposed method, which includes two mathematical problems with explicit expressions and an engineering application with a black-box model.

关键词： uncertainty propagation analysis     extended sparse grid     maximum entropy principle     extended Gauss integration     Rosenblatt transformation     high-order moments analysis    

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Plasma enhanced chemical vapor deposition of excellent a-Si:H passivation layers for a-Si:H/c-Si heterojunction

Lei ZHAO,Wenbin ZHANG,Jingwei CHEN,Hongwei DIAO,Qi WANG,Wenjing WANG

《能源前沿（英文）》 2017年 第11卷 第1期   页码 85-91 doi: 10.1007/s11708-016-0437-3

摘要： The intrinsic a-Si:H passivation layer inserted between the doped a-Si:H layer and the c-Si substrate is very crucial for improving the performance of the a-Si:H/c-Si heterojunction (SHJ) solar cell. The passivation performance of the a-Si:H layer is strongly dependent on its microstructure. Usually, the compact a-Si:H deposited near the transition from the amorphous phase to the nanocrystalline phase by plasma enhanced chemical vapor deposition (PECVD) can provide excellent passivation. However, at the low deposition pressure and low deposition power, such an a-Si:H layer can be only prepared in a narrow region. The deposition condition must be controlled very carefully. In this paper, intrinsic a-Si:H layers were prepared on n-type Cz c-Si substrates by 27.12 MHz PECVD at a high deposition pressure and high deposition power. The corresponding passivation performance on c-Si was investigated by minority carrier lifetime measurement. It was found that an excellent a-Si:H passivation layer could be obtained in a very wide deposition pressure and power region. Such wide process window would be very beneficial for improving the uniformity and the yield for the solar cell fabrication. The a-Si:H layer microstructure was further investigated by Raman and Fourier transform infrared (FTIR) spectroscopy characterization. The correlation between the microstructure and the passivation performance was revealed. According to the above findings, the a-Si:H passivation performance was optimized more elaborately. Finally, a large-area SHJ solar cell with an efficiency of 22.25% was fabricated on the commercial 156 mm pseudo-square n-type Cz c-Si substrate with the open-circuit voltage ( ) of up to 0.732 V.

关键词： PECVD     high pressure and high power     a-Si:H microstructure     passivation     heterojunction solar cell    

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Liver surgery and transplantation in China: Progress and Challenges

LAU W Y, LAI E C H

《医学前沿（英文）》 2007年 第1卷 第1期   页码 1-5 doi: 10.1007/s11684-007-0001-y

摘要： From the limited but available information, we traced the history of developments of liver surgery and transplantation in China. Liver surgery first started in the late 1950s in China, and it soon flourished mainly because of the great demand in liver surgery and the emergence of a number of giants in liver surgery. We recognized and honoured the important contributions of these Chinese pioneers in portal hypertension, recurrent pyogenic cholangitis, hepatocellular carcinoma and liver transplantation.

关键词： transplantation     pyogenic cholangitis     available information     important     hypertension    

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Generation and repair of AID-initiated DNA lesions in B lymphocytes

null

《医学前沿（英文）》 2014年 第8卷 第2期   页码 201-216 doi: 10.1007/s11684-014-0324-4

摘要：

Activation-induced deaminase (AID) initiates the secondary antibody diversification process in B lymphocytes. In mammalian B cells, this process includes somatic hypermutation (SHM) and class switch recombination (CSR), both of which require AID. AID induces U:G mismatch lesions in DNA that are subsequently converted into point mutations or DNA double stranded breaks during SHM/CSR. In a physiological context, AID targets immunoglobulin (Ig) loci to mediate SHM/CSR. However, recent studies reveal genome-wide access of AID to numerous non-Ig loci. Thus, AID poses a threat to the genome of B cells if AID-initiated DNA lesions cannot be properly repaired. In this review, we focus on the molecular mechanisms that regulate the specificity of AID targeting and the repair pathways responsible for processing AID-initiated DNA lesions.

关键词： class switch recombination     somatic hypermutation     activation-induced deaminase     DNA repair     genomic instability    

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A Bayesian modeling approach to bi-directional pedestrian flows in carnival events

C. WONG, William H. K. LAM

《工程管理前沿（英文）》 2017年 第4卷 第4期   页码 483-489 doi: 10.15302/J-FEM-2017023

摘要： Bi-directional pedestrian flows are common at crosswalks, footpaths, and shopping areas. However, the properties of pedestrian movement may vary in urban areas according to the type of walking facility. In recent years, crowd movements at carnival events have attracted the attention of researchers. In contrast to pedestrian behavior in other walking facilities, pedestrians whose attention is attracted by carnival displays or activities may slow down and even stop walking. The Lunar New Year Market is a traditional carnival event in Hong Kong held annually one week before the Lunar New Year. During the said event, crowd movements can be easily identified, particularly in Victoria Park, where the largest Lunar New Year Market in Hong Kong is hosted. In this study, we conducted a video-based observational survey to collect pedestrian flow and speed data at the Victoria Park Lunar New Year Market on the eve of the Lunar New Year. Using the collected data, an extant mathematical model was calibrated to capture the relationships between the relevant macroscopic quantities, thereby providing insight into pedestrian behavior at the carnival event. Bayesian inference was employed to calibrate the model by using prior data obtained from a previous controlled experiment. Results obtained enhance our understanding of crowd behavior under different conditions at carnival events, thus facilitating the improvement of the safety and efficiency of similar events in the future.

关键词： pedestrian flow model     bi-directional interactions     empirical studies     Bayesian inference    

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H∞ control in the frequency domain for a semi-active floor isolation system

Yundong SHI, Tracy C BECKER, Masahiro KURATA, Masayoshi NAKASHIMA

《结构与土木工程前沿（英文）》 2013年 第7卷 第3期   页码 264-275 doi: 10.1007/s11709-013-0214-x

摘要： A floor isolation system installed in a single floor or room in a fixed base structure is designed to protect equipment. With this configuration, the input motions to the floor isolation from the ground motions are filtered by the structure, leaving the majority of the frequency content of the input motion lower than the predominant frequency of the structure. The floor isolation system should minimize the acceleration to protect equipment; however, displacement must also be limited to save floor space, especially with long period motion. Semi-active control with an control was adopted for the floor isolation system and a new input shaping filter was developed to account for the input motion characteristics and enhance the effectiveness of the control. A series of shake table tests for a semi-active floor isolation system using rolling pendulum isolators and a magnetic-rheological damper were performed to validate the control. Passive control using an oil damper was also tested for comparison. The test results show that the control effectively reduced acceleration for short period motions with frequencies close to the predominant frequency of the structure, as well as effectively reduced displacement for long period motions with frequencies close to the natural frequency of the floor isolation system. The control algorithm proved to be more advantageous than passive control because of its capacity to adjust control strategies according to the different motion frequency characteristics.

关键词： semi-active     floor isolation     H∞ control     MR damper     shaping filter     shaking table test    

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A ruptured recurrent small bowel gastrointestinal stromal tumour causing hemoperitoneum

null

《医学前沿（英文）》 2015年 第9卷 第1期   页码 108-111 doi: 10.1007/s11684-014-0344-0

摘要：

Hemoperitoneum is a rare and potentially life-threatening complication of GIST. We reported a 54-year-old man who developed disseminated intra-abdominal recurrence from a previously resected gastrointestinal stromal tumour (GIST) of the small bowel, and the patient presented with hemoperitoneum. Emergent debulking surgery was performed. A high dose imatinib was prescribed. Despite the presence of residual disease, the patient was well clinically 8 months after the operation. Even though, there is no evidence to support the routine use of debulking surgery in the management of GIST. In our patient, disease progression after second line targeted therapy and the absence of alternative treatment options for spontaneous rupture and hemoperitoneum prompted us to treat the patient aggressively. Resection of the ruptured GIST was carried out for control of bleeding and to prevent recurrent bleeding in this patient with good surgical risks. During the treatment decision-making, the patient’s general condition, the risk of surgery and the extent of dissemination were taken into consideration. In this patient who presented with spontaneous rupture of a small intestinal GIST, the novel use of targeted therapy and aggressive surgical treatment produced reasonably good survival outcome.

关键词： gastrointestinal stromal tumour     hemoperitoneum     small bowel GIST     small bowel neoplasm     imatinib    

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标题 作者 时间 类型 操作

A density functional theory study of methane activation on MgO supported NiM cluster: role of M on C–Hactivation

期刊论文

Effect of noble metal nanoparticle size on C–N bond cleavage performance in hydrodenitrogenation: a study

期刊论文

Controllable synthesis of a large TS-1 catalyst for clean epoxidation of a C=C double bond under mild

期刊论文

从氢原子质子化模型计算H2+的结构参数

陈景

期刊论文

Coronary leukocyte activation in relation to progression of coronary artery disease

null

期刊论文

Effect of embedment length of untreated natural fibres on the bond behaviour in cement mortar

Gudimella RAMAKRISHNA, Sriraman PRIYADHARSHINI

期刊论文

Analysis of the double-layer α-Si:H emitter with different doping concentrations for α-Si:H/c-Si heterojunction

Haibin HUANG,Gangyu TIAN,Tao WANG,Chao GAO,Jiren YUAN,Zhihao YUE,Lang ZHOU

期刊论文

Modeling of alkali-silica reaction in concrete: a review

WANG, Q.C. SUN, C.H. ZHANG, D.R.J. OWEN

期刊论文

Uncertainty propagation analysis by an extended sparse grid technique

JIA, C. JIANG, C. M. FU, B. Y. NI, C. S. WANG, M. H. PING

期刊论文

Plasma enhanced chemical vapor deposition of excellent a-Si:H passivation layers for a-Si:H/c-Si heterojunction

Lei ZHAO,Wenbin ZHANG,Jingwei CHEN,Hongwei DIAO,Qi WANG,Wenjing WANG

期刊论文

Liver surgery and transplantation in China: Progress and Challenges

LAU W Y, LAI E C H

期刊论文

Generation and repair of AID-initiated DNA lesions in B lymphocytes

null

期刊论文

A Bayesian modeling approach to bi-directional pedestrian flows in carnival events

C. WONG, William H. K. LAM

期刊论文

H∞ control in the frequency domain for a semi-active floor isolation system

Yundong SHI, Tracy C BECKER, Masahiro KURATA, Masayoshi NAKASHIMA

期刊论文

A ruptured recurrent small bowel gastrointestinal stromal tumour causing hemoperitoneum

null

期刊论文