检索结果-南通市图书馆

Fe–N–C single atom catalysts for the electrochemical conversion of carbon,nitrogen and oxygen elements

在线全文

学校读者我要写书评

暂无评论

Materials Reports(Energy) 2022年第3期2卷 22-37页

作者： Jian Huang qiao zhang Jie Ding Yueming Zhai The Institute for Advanced Studies Wuhan UniversityWuhan430072China School of Chemical and Biomedical Engineering Nanyang Technological University62 Nanyang DriveSingapore637459Singapore

Single atom catalysts(SACs)are constituted by isolated active metal centers,which are heterogenized on inert supports such as graphene,porous carbon,and amorphous *** thermal stability,electronic properties,and catalytic activities of the metal center can be controlled via manipulating the neighboring heteroatoms such as nitrogen,oxygen,and *** to the atomical dispersion of the active catalytic centers,the amount of metal required for catalysis can be ***,new possibilities are offered to easily control the selectivity of a given transformation process as well as to improve turnover frequencies and turnover numbers of target *** them,Fe–N–C single atom catalysts own special electronic structure,and have been widely used in many fields of *** review aims to summarize the synthesis of Fe–N–C based on anchoring individual iron atoms on carbon/*** spin-related properties of Fe–N–C catalysts are described,including the relation between spin and electron structure of Fe–N x as well as the coupling between electronic structure of Fe–N x and electronic(orbit)of CO_(2),N_(2)and O_(2).Next,mechanistic investigations conducted to un-derstand the specific behavior of Fe–N–C catalysts are highlighted,including C,N,O ***,some issues related to the future developments of Fe–N–C are put forward and corresponding feasible solutions are offered.

关键词： Single atom catalysts Fe-N-C synthesis Spin Electrochemical conversion CO_(2)reduction reaction Nitrogen reduction reaction Oxygen reduction reaction

Extreme meteorological disaster effects on grain production in Jilin Province, China

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Integrative Agriculture 2017年第2期16卷 486-496页

作者： XU Lei zhang qiao zhang Jing ZHAO Liang SUN Wei JIN Yun-xiang Key Laboratory of Agri-lnformation Service Technology Ministry of Agriculture/Agricultural Information Institute Chinese Academy of Agricultural Sciences Beijing 100081 P.R. China

Extreme meteorological disaster effects on grain production is mainly determined by the interaction between danger degree of hazard-induced factors and vulnerability degree of hazard-affected bodies. This paper treats physical exposure, sensitivity of the response to the impact, and capabilities of disaster prevention and mitigation as a complex system for vulnerability degree of hazard-affected bodies, which included the external shocks and internal stability mechanism. Hazard-induced factors generate external shocks on grain production systems though exposure and sensitivity of hazard-affected body, and the result can be represented as affected area of grain. By quantile regression model, this paper depicts the quantitative relationship between hazard-induced factors of extreme meteorological disaster and the affected area in the tail of the distri- bution. Moreover, the model of production function have also been utilized to expound and prove the quantitative relationship between the affected area and final grain output under the internal stability mechanism of the agricultural natural resources endowment, the input factors of agricultural production, and the capacity of defending disaster. The empirical study of this paper finds that impact effects of drought disaster to grain production system presents the basic law of ＂diminishing marginal loss＂, namely, with the constant improvement of the grade of drought, marginal affected area produced by hazard-induced factors will be diminishing. Scenario simulation of extreme drought impact shows that by every 1% reduction in summer average rainfall, grain production of Jilin Province will fell 0.2549% and cut production of grain 14.69% eventually. In re- sponse to ensure China＇s grain security, the construction of the long-term mechanism of agricultural disaster prevention and mitigation, and the innovation of agricultural risk management tools should be also included in the agricultural policy agenda.

关键词： extreme meteorological disaster grain production danger degree of hazard-induced factors vulnerability degreeof hazard-affected bodies Jilin Province in China

Stress and strain analysis on the anastomosis site sutured with either epineurial or perineurial sutures after simulation of sciatic nerve injury

在线全文

学校读者我要写书评

暂无评论

Neural Regeneration Research 2012年第29期7卷 2299-2304页

作者： Guangyao Liu qiao zhang Yan Jin Zhongli Gao Department of Orthopedics China-Japan Union Hospital Jilin University Changchun 130031 Jilin Province China Department of Ophthalmology Second Hospital Jilin University Changchun 130041 Jilin Province China

The magnitude of tensile stress and tensile strain at an anastomosis site under physiological stress is an important factor for the success of anastomosis following suturing in peripheral nerve injury treatment. Sciatic nerves from fresh adult cadavers were used to create models of sciatic nerve injury. The denervated specimens underwent epineurial and perineurial suturing. The elastic modulus （40.96 ＋ 2.59 MPa） and Poisson ratio （0.37 ＋ 0.02） of the normal sciatic nerve were measured by strain electrical measurement. A resistance strain gauge was pasted on the front, back left, and right of the edge of the anastomosis site after suturing. Strain electrical measurement results showed that the stress and strain values of the sciatic nerve following perineurial suturing were lower than those following epineurial suturing. Scanning electron microscopy revealed that the sciatic nerve fibers were disordered following epineurial compared with perineurial suturing. These results indicate that the effect of perineurial suturing in sciatic nerve injury repair is better than that of epineurial suturing.

关键词： sciatic nerve injury epineurial suture perineurial suture strain electrical measurement anastomosis site tensile stress tensile strain elastic modulus Poisson ratio biomechanics peripheral nerve injury neural regeneration

A facile synthesis of 2-substituted-2,3-dihydro-4(1H)-quinazolinones in 2,2,2-trifluoroethanol

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2007年第6期18卷 656-658页

作者： Rong zhang qiao Bai Ling Xu Yan Hui Wang Department of Life Science and Technology Beijing University of Chemical TechnologyBeijing 100029China Institute of Materia Medica Chinese Academy of Medical Sciences&Peking Union Medical CollegeBeijing 100050China

2-Substituted-2,3-dihydro-4(1H)-quinazolinones were obtained in high yields by condensation of anthranilamide with aryl, alkyl or heteroaryl aldehydes or ketones in the refluxing 2,2,2-trifluoroethanol without any cat... 详细信息

关键词： 2,3-Dihydro-4(1H)-quinazolinone Trifluoroethanol (TFE) Fluorinated solvent

Encapsulation of Supported Pt Nanoparticles with Mesoporous Silica for Increased Catalyst Stability

在线全文

学校读者我要写书评

暂无评论

Nano Research 2011年第1期4卷 115-123页

作者： Ilkeun Lee qiao zhang Jianping Ge Yadong Yin Francisco Zaera Department of Chemistry University of Califomia Riverside CA 92521 USA

A new synthetic strategy has been developed to encapsulate supported Pt nanoparticles in heterogeneous catalysts to prevent their sintering. Model catalysts were first prepared by dispersing -3-nm Pt nanoparticles on -120-nm silica beads. These were then covered with a fresh layer of mesoporous silica, a few tens of nanometers thick, and etched to re-expose the metal surface to the reaction mixtures. TEM images were used to confirm the success of each of the synthesis steps, and both CO titrations and kinetic measurements for the catalytic conversion of cis- and trans-2-butenes with hydrogen were employed to test the degree of re-activation of the catalyst obtained after the etching treatment, which had to be tuned to give simultaneous maximum activity and maximum catalyst stability. The resulting encapsulated platinum nanoparticles were shown to resist sintering during calcination at temperatures as high as 1075 K, whereas the unprotected catalysts were seen to sinter by 875 K.

关键词： Supported catalyst resistance to sintering carbon monoxide adsorption olefin conversion surface-protected etching mesoporous silica

Influence of thermal inhibitor position and temperature on vortex-shedding-driven pressure oscillations

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2013年第3期26卷 544-553页

作者： Su Wanxing Li Shipeng zhang qiao Li Junwei Ye Qingqing Wang Ningfei School of Aerospace Engineering Beijing Institute of Technology China Academy of Space Technology

Vortex-acoustic coupling is one of the most important potential sources of combustion instability in solid rocket motors （SRMs）. Based on the Von Karman Institute for Fluid Dynamics （VKI） experimental motor, the influence of the thermal inhibitor position and temperature on vortex-shedding-driven pressure oscillations is numerically studied via the large eddy simulation （LES） method. The simulation results demonstrate that vortex shedding is a periodic process and its accurate frequency can be numerically obtained. Acoustic modes could be easily excited by vortex shedding. The vortex shedding frequency and second acoustic frequency dominate the pressure oscillation characteristics in the chamber. Thermal inhibitor position and gas temperature have little effect on vortex shedding frequency, but have great impact on pressure oscillation amplitude. Pressure amplitude is much higher when the thermal inhibitor locates at the acoustic velocity anti-nodes. The farther the thermal inhibitor is to the nozzle head, the more vortex energy would be dissipated by the turbulence. Therefore, the vortex shedding amplitude at the second acoustic velocity antinode near 3/4L （L is chamber length） is larger than those of others. Besides, the natural acoustic frequencies increase with the gas temperature. As the vortex shedding frequency departs from the natural acoustic frequency, the vortex-acoustic feedback loop is decoupled. Consequently, both the vortex shedding and acoustic amplitudes decrease rapidly.

关键词： Combustion instability Pressure oscillation Solid rocket motor Vortex-acoustic coupling Vortex shedding

Effects of Different Processes on Phases and Service Performance of FeSiMg8RE5 Alloy

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2004年第Z1期22卷 201-205页

作者： Jia Yanhua zhang Hong Wang Zidong Xue Shouhong qiao Zhen zhang Xianheng Beijing Science and Technology University Beijing 100083 China No. 1 Rare Earth Plant Baotou Iron and Steel Company Baotou 014010 China Beijing Science and Technology University Beijing 100083 China Beijing Science and Technology University Beijing 100083 China No. 1 Rare Earth Plant Baotou Iron and Steel Company Baotou 014010 China No. 1 Rare Earth Plant Baotou Iron and Steel Company Baotou 014010 China No. 1 Rare Earth Plant Baotou Iron and Steel Company Baotou 014010 China

The difference of nodularizer in phase morphology and service performance by three processes was *** three processes include directly pressing magnesium into molten alloy stirring by nitrogen gas and no stirring from 5 t arc furnace and melting magnesium in the intermediate frequency *** microstructure patterns were observed by scanning electron microscope, and composition of phases was measured by energy dispersive spectrometer method.X-ray diffraction method was used to determine the phase structure of the *** results show that spheroidizing reaction time and violent degree of nodularizers are influenced by grain size and distribution uniformity of siliconizing magnesium phase; spheroidizing reaction degree can be mitigated and spheroidizing time be increased by using N2 stirring in pressing magnesium from arc furnace.

关键词： nodularizer rare earth magnesium ferrumsilicium alloy phase structure

Granite is an Effective Helium Source Rock: Insights from the Helium Generation and Release Characteristics in Granites from the North Qinling Orogen, China

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Geologica Sinica(English Edition) 2020年第1期94卷 114-125页

作者： zhang Wen LI Yuhong ZHAO Fenghua ZHOU Zheng HAN Wei ZHOU Junlin zhang qiao Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources Laboratory of Isotope ThermochronologyInstitute of GeologyChinese Academy of Geological SciencesBeijing 100037China Xi’an Center China Geological SurveyXi’an 710054China College of Geoscience and Surveying Engineering China University of Mining and TechnologyBeijing 100083China Lancaster Environment Centre Lancaster UniversityLancasterLA14YQUK

Global helium(He) shortage is a challenging problem;however, the types of helium source rock and the mechanisms of He generation and release therein remain still poorly understood. In this study, in order to evaluate the potential of granite as an effective helium source rock, we collected granitic samples from the North Qinling Orogen, Central China, in the south of the helium-rich Weihe Basin. The helium generation and release behaviors in granite were studied through analysis of U and Th concentrations, EMPA images, and He and Ar concentrations and isotopic ratios extracted by crushing and stepwise heating. The results indicate that Ar has a better retention and a lower mobility than He. 3 He/4 He ratios released by crushing and stepwise heating are 0.016–0.056 RA and 0.003–0.572 RA, respectively, where RA is the atmospheric 3 He/4 He of 1.4×10-6, reflecting a crustal and radiogenic source. Helium concentrations extracted by the two ways are 0.13–0.95 ucm3 STP/g and 7.82–115.62 ucm3 STP/g, respectively, suggesting that matrix-sited He accounts for more than 98% of total helium preserved in granite. In addition, the total generated He amounts in granites are calculated based on the measured U and Th concentrations in granitic samples. Dividing the preserved He quantities by the generated He amounts, it turned out that less than 10% of He produced since the formation of the granite is preserved in the rock over geological time, suggesting that more than 90% generated He can be transferred to the Weihe Basin. Temperature and fracture are the two critical factors controlling He release. Based on the relationship between He diffusivity of granites and temperature and the He closure temperatures of a variety of U-and Th-rich minerals(27–250°C), we estimate that He can be partially released out of granite at the depths 7800 m. Fractures provide effective transfer of free He from deep source rocks to shallow reservoirs. Finally,

关键词： granite helium source rock helium diffusivity crushing stepwise heating

Effect of spatial configuration on adhesion of 1,2-disubstituted cyclohexane derivatives

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2023年第8期34卷 196-200页

作者： qiao zhang Yuhang Yin Jingfu Song Gai Zhao Shengyi Dong College of Chemistry and Chemical Engineering Hunan UniversityChangsha 410082China State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Spatial configuration has a significant effect on chemical ***,the importance of spatial configuration in supramolecular adhesive materials has been frequently *** this study,the effects of the spatial configuration on cohesion and adhesion were *** to the diversities of the chemical structures and assembly patterns,1,2-disubstituted cyclohexane derivatives were used in this combined experimental and theoretical *** self-sorting assembly of enantiopure isomers improved cohesion but had a negative effect on *** contrast,racemic mixtures displayed stronger adhesion ***,it was proven that the cis-configuration was more favorable for supramolecular adhesion than the *** addition,the influence of the spatial configuration of 1,2-disubstituted cyclohexane derivatives could be effectively mitigated by hydrogen bond donors or *** addition of natural acids yielded three-dimensional polymeric networks,in which the spatial configuration was not the decisive factor for supramolecular adhesion.

关键词： Spatial configuration Supramolecular adhesive material Assembly Cohesion Adhesion