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Reflection of a moving shock wave over an oblique shock wave

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Chinese Journal of Aeronautics 2021年第5期34卷 399-403页

作者： miaomiao wang Ziniu WU Department of Engineering Mechanics Tsinghua UniversityBeijing 100084China

The reflection of a moving shock wave over a wedge immersed in a still gas and the reflection of a wed ge induced steady shock wave over symmetrical and asymmetrical reflecting surfaces have received intensive considerations since more than 70 years *** we consider a different shock reflection problem—reflection of a moving shock wave over an initially steady oblique shock wave induced by a wedge immersed in supersonic *** the flow condition we considered,five moving triple points,with each connecting an incident shock wave,a reflected shock wave and a Mach stem,are *** using the reference frame co-moving with each triple point,the type of each shock wave of this triple point is *** present study is significant in that it treats a new shock reflection problem leading to a new shock reflection configuration and showing potential applications in supersonic flow with unsteady shock interaction.

关键词： Shock reflection Triple point Unsteady shock wave

Jackknife Model Averaging for Composite Quantile Regression

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Journal of Systems Science & Complexity 2024年第4期37卷 1604-1637页

作者： YOU Kang wang miaomiao ZOU Guohua School of Mathematical Sciences Capital Normal UniversityBeijing 100089China School of Chinese Materia Medica Beijing University of Chinese MedicineBeijing 100105China

In this paper,the authors propose a frequentist model averaging method for composite quantile regression with diverging number of *** from the traditional model averaging for quantile regression which considers only a single quantile,the proposed model averaging estimator is based on multiple *** well-known delete-one cross-validation or jackknife approach is applied to estimate the model *** resultant jackknife model averaging estimator is shown to be asymptotically optimal in terms of minimizing the out-of-sample composite final prediction *** studies are conducted to demonstrate the finite sample performance of the new model averaging *** proposed method is also applied to the analysis of the stock returns data and the wage data.

关键词： Asymptotic optimality composite quantile regression cross-validation model averaging

Theoretical insights into interfacial and electronic structures of NiOx/SrTiO3 photocatalyst for overall water splitting

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Journal of Energy Chemistry 2019年第6期28卷 138-148页

作者： miaomiao wang Shenmin Li Yang Lv Xin Zhou College of Environment and Chemical Engineering Dalian University

SrTiO3 is a promising candidate photocatalyst for overall water *** suitable cocatalysts,such as NiOx,the mixture of Ni and NiO,remarkably improve the photocatalytic ***,spatial locations and functions of components in NiOx/SrTiO3 are under ***,using first-principles density functional theory(DFT)calculations,we investigate the initial growth of Nin(n=1–4)and(NiO)n(n=1,2 and 4)clusters on stoichiometric(100)surfaces of SrTiO3,and explore interfacial and electronic structures of composite *** is found that Nin clusters are easier to undergo aggregation on SrO-termination than on *** adsorption of Nincluster on(100)surfaces elevates the Fermi level towards the conduction band,which may benefit the occurrence of hydrogen evolution *** structural similarity between(NiO)n cluster and surface has an essential effect on the most stable adsorption ***(NiO)n/SrTiO3 systems,the occupied states of(NiO)n cluster well overlap with those of(100)surfaces in the valence band maximum,which is in favor of the separation of photogenerated electrons and holes to SrTiO3 support and(NiO)n cluster,*** detailed DFT analysis provides important insights into the growth of NiOx on surfaces of SrTiO3and presents an explanation on the different models of NiOx/SrTiO3 photocatalyst proposed by experimental *** calculations build a basis for further investigations on the mechanism of photocatalytic water-splitting reaction in NiOx/SrTiO3composite system.

关键词： Semiconductor-based photocatalyst Density functional theory Cocatalyst Electronic structure calculation SrTiO3

Symmetric Mach reflection configuration with asymmetric unsteady solution

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Chinese Journal of Aeronautics 2023年第4期36卷 75-78页

作者： Chenyuan BAI miaomiao wang Ziniu WU Ministry of Education Key Laboratory of Fluid Mechanics Beihang UniversityBeijing 100083China Department of Engineering Mechanics Tsinghua UniversityBeijing 100084China

Symmetric Mach reflection in steady supersonic flow has been usually studied by solving a half-plane problem with the symmetric line treated as reflecting surface,thus losing the opportunity to discover antisymmetric flow *** in this paper we treat this problem as an entire-plane *** an unsteady numerical approach,we find that the two sliplines exhibit antisymmetric unsteadiness if the Mach stem height is small while the flow remains symmetric if the Mach stem height is *** mechanism by which disturbance,generated in the downstream of the flow duct between the two sliplines,propagates upstream is identified and it is also shown that the interaction between the transmitted expansion waves and the sliplines increases the amplitude of the unstable *** present study suggests a new type of compressible jet that deserves further studies.

关键词： Antisymmetric solution Mach reflection Shock reflection Supersonic flow

Analysis of the stress ratio of anisotropic rocks in uniaxial tests

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International Journal of Mining Science and Technology 2017年第3期27卷 531-535页

作者： wang miaomiao Li Pei Wu Xiaowa Xu Dan Key Laboratory of Shale Gas and Geoengineering Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China Institute of Geomechanics Chinese Academy of Geological Sciences Beijing 100081 China

The effect of structural discontinuities on the progressive failure process of anisotropic rocks should be paid particular *** crack damage stress σ_(cd),also considered as the yield strength,and the relationship between σ_(cd) and the uniaxial peak strength σ_(ucs) of anisotropic rocks for different orientations 8 of the isotropy planes with respect to the loading directions were investigated theoretically and experimentally.A theoretical relation of σ_(cd)/σ_(ucs) with the function of the shape parameter m was ***,uniaxial compression tests of shale samples were conducted for several inclinations θ.The test result of σ_(cd)/σ_(ucs) was close to the theoretical value for a given ***,both experimental results and theoretical solutions of σ_(cd)/σ_(ucs) were independent of the inclination θ while σ_(cd) andσ_(ucs) were strongly affected by θ.The strength ratio σ_(cd)/σ_(ucs) may therefore be an intrinsic property of anisotropic rocks and could be used to predict the failure of rock samples.

关键词： Anisotropic rocks Uniaxial compression test Brittle failure Crack damage stress Stress ratio

Microfibrous entrapped ZnO-CaO/Al_2O_3 for high efficiency hydrogen production via methanol steam reforming

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Particuology 2010年第3期8卷 225-230页

作者： Ying Tang Li Chen miaomiao wang Jianfeng Li Yong Lu Shanghai Key Laboratory of Green Chemistry and Chemical Processes Department of Chemistry East China Normal University Shanghai 200062 China

Sinter-locked microfibrous networks consisting of -3 vol.% of 8 p.m （dia.） nickel microfibers have been utilized to entrap -30vo1.% of 100-200 μm dia. porous AI203. ZnO and CaO were then highly dispersed onto the pore surface of entrapped A1203 by the incipient wetness impregnation method. Due to the unique combination of surface area, pore size/particle size, thermal conductivity, and void volume, the resulting microfibrous catalyst composites provided significant improvement of catalytic bed reactivity and utilization efficiency when used in methanol steam reforming. Roughly 260 mL/min of reformate, comprising 〉70% H2, 〈5% CO and trace CH4, with 〉97% methanol conversion, could be produced in a I cm3 bed volume of our novel microfihrous entrapped ZnO-CaO/Al2O3 catalyst composite at 470℃ with a high weight hourly space velocity （WHSV） of 15 h-1 using steam/methanol （1.3/1） mixture as feedstock. Compared to a packed bed of 100-200μm ZnO-CaO/Al2O3, our composite bed provided a doubling of the reactor throughput with a halving of catalyst usage.

关键词： Hydrogen Monolithic catalyst Methanol steam reforming ZnO CaO Fuel cells

An improved method that incorporates the estimated runoff for peak discharge prediction on the Chinese Loess Plateau

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International Soil and Water Conservation Research 2023年第2期11卷 290-300页

作者： Wenhai Shi miaomiao wang Donghao Li Xianwei Li Mengying Sun Key Laboratory of Subsurface Hydrology and Ecological Effects in Arid Region Chang'an UniversityMinistry of EducationChina School of Water and Environment Chang'an UniversityChina

An accurate prediction of peak discharge in watersheds is critical not only for water resource manage-ment,but also for understanding the complex relationships of hydrological *** this study,a modified peak discharge formula based on the Chemicals,Runoff,and Erosion from Agricultural Man-agement Systems(CREAMS)model was developed by introducing rainfall intensity and soil moisture *** reliability of the proposed method was tested with data from 1464 storm events in 41 watersheds and was applied to 256 storm events in five remaining typical watersheds using the opti-mized *** results indicate that the proposed method is highly accurate in terms of model efficiency,as determined by Nash-Sutcliffe efficiencies(NSEs)of 88.60%,74.04%,and 90.12%during the calibration,validation,and application cases,***,it performed better than the original and modified CREAMS ***,using the parameters derived from the initial 41 watersheds and the runoff estimated using the modified Soil Conservation Service curve number(SCS-CN)method,the proposed method was used to predict the peak discharge from the last five typical *** NSE(63.88-80.83%)and low root mean square error(RMSE)values(0.31-35.93 m^(3)s^(-1))were obtained for the five ***,the proposed peak discharge model,combined with the modified SCS-CN method,may accurately predict event-based peak discharge and runoff for general applications under various hydrological and geomorphic conditions in the Loess Plateau region.

关键词： Chemicals,Runoff,and Erosion from agricultural management systems (CREAMS) NRCS-CN Peak discharge Surface runoff Rainfall intensity

Exploring the mechanism of Ta_(3)N_(5)/KTaO_(3) photocatalyst for overall water splitting by first-principles calculations

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Journal of Energy Chemistry 2021年第5期30卷 353-364页

作者： Yanxia Ma Yumeng Fo miaomiao wang Xixi Liang Hao Dong Xin Zhou College of Environment and Chemical Engineering Dalian UniversityDalian 116622LiaoningChina School of Chemistry and Chemical Engineering Liaoning Normal UniversityDalian 116029LiaoningChina

The rational fabrication of heterostructures is one of efficient strategies for improving photocatalytic performance of semiconductor *** recently,Domen and co-workers found that Ta_(3)N_(5) single crystals grown on the surface of KTaO_(3) can accomplish photocatalytic overall water splitting for the first *** order to comprehend the underlying mechanism of this photocatalytic system,we have performed a systematic study based on density functional theory first-principles ***_(3)N_(5)(010)/KTaO_(3)(110)slab models have been built according to experimental observations by considering two common terminations of KTaO_(3)(110)surface,named as Ta_(3)N_(5)/O_(2) and Ta_(3)N_(5)/*** formations of interfacial bonds are thermodynamically stable,showing a covalent interaction between two components of a ***_(3)N_(5)/O_(2) has a higher mobility of photogenerated charge carriers and lower recombination rate of charge carriers than Ta_(3)N_(5)/*** light absorption of heterostructures displays the feature of KTaO_(3) in the short wavelength region and the characteristic of Ta_(3)N_(5) in the long wavelength *** calculated band offsets show that Ta_(3)N_(5)/O_(2) and Ta_(3)N_(5)/KTaO have distinct Type-II band alignments,with Ta_(3)N_(5) as the accumulator of photoinduced electrons in the former and the collector of photogenerated holes in the latter,*** difference in charge density and electrostatic potential between two components acts as a driving force to promote the transfer of electrons and holes to different domains of the interface,which is beneficial to extend the lifetime of photoinduced *** results demonstrate that the function of Ta_(3)N_(5) in Ta_(3)N_(5)/KTaO_(3) photocatalytic system is determined by the termination property of KTaO_(3)(110)surface,which provides a likely reason of the observed photocatalytic activity of overall water splitting achieved by Ta_(3)N_(5) synthesized by

关键词： Ta3N5 Density functional theory calculations Separation of photogenerated carriers Semiconductor-based photocatalyst Overall water splitting

Image motion and experimental study of a 0.1″space pointing measuring instrument for micro-vibration conditions

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Chinese Journal of Aeronautics 2023年第2期36卷 191-200页

作者： Lin LI Li YUAN Li wang miaomiao wang Xiaoxue GONG Jie SUI Yanpeng WU Ran ZHENG Space Optoelectronic Measurement and Perception Lab. Beijing Institute of Control EngineeringBeijing 100190China China Academy of Space Technology Beijing 100094China Science and Technology on Space Intelligent Control Laboratory Beijing 100094China University of Chinese Academy of Sciences Beijing 100049China Changchun Institute of Optics Fine Mechanics and PhysicsChinese Academy of SciencesChangchun 130033China Chang Guang Satellite Technology Co. Ltd.Changchun130102China

There exists an increasing need for Milli-Arc-Seconds(MAS)accuracy pointing measurement for current and future space *** meet the 0.1″space pointing measurement accuracy requirements of spacecraft in future,the influence of spacecraft micro-vibration on a 0.1″Space Pointing Measuring Instrument(SPMI)is studied.A Quasi-Zero Stiffness Device(QZSD)with adaptive adjustment and variable stroke was ***,a series of micro-vibration experiments of the SPMI were carried *** influence of the micro-vibration generated by Guidance Navigation Control(GNC)attitude control components under different attitudes on the SPMI was *** spread function of image motion in micro-vibration was also ***,the changes of image motion under the micro-vibration environment were evaluated by extracting the gray centroid of the images,and the experiment processes and results are deeply *** results show that the firstorder frequency of the QZSD system is 0.114 Hz,and it is induced by a double pendulum system;the image motion of single flywheel spinning reached 0.015 pixels;whilst the image motion reached 0.03 pixels when three flywheels are combined *** latest findings provide a beneficial theoretical and technical support for the development of spacecraft with 0·1″pointing accuracy.

关键词： Image motion Micro-vibration Milli-arc-seconds Quasi-zero stiffness device Space pointing measuring instrument