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Journal of Mountain Science 2018年第3期15卷 618-630页

作者： Artem A.RYBCHENKO Alena V.KADETOVA Elena A.KOZIREVA institute of the Earth's Crust Siberian Branch of Russian Academy of Sciences

Extreme and prolonged rainfall in the Tunka Ridge caused several debris flows in the vicinity of the Arshan village(Siberia, Russia) on June 28, 2014. These debris flows, in spite of similar geological conditions, had different velocity, peak discharge and alluvial fan volume values. The flow velocity was from 3.5 m/s to 19.6 m/s, the peak discharge ranged from 63 m3/s to 13566 m3/s, and the alluvial fan volume varied from 4.13×103 to 8.45×105 m3. Such a great range of values is due to the morphometric parameters of the debris flow basins. The article deals with the influence of morphometric parameters of debris flow basins, such as the basin area, the average slope, Melton ratio, relief ratio on the debris flow velocity, peak discharge and volume of alluvial fans. In this debris flow event the average values of slope angle and total basin relief of the debris flow basins did not affect the values of debris flow velocity, peak discharge and alluvial fan volume. The highest correlations were observed with the debris flow basin area that was connected with the water inflow volume into the debris flow basins during the rainfall. The unequal water distribution among debris flow basins also had an impact on the debris flow velocity, peak discharge and volume of alluvial fans.

关键词： Central Asia Debris flow Morphometric analysis Natural Hazards Tunka Ridge

Assessment of the Design Displacement Values at Seismic Fault Crossings and of Their Excess Probability

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Journal of Mountain Science 2011年第2期8卷 228-233页

作者： STROM Alexander IVASCHENKO Alexey KOZHURIN Andrey institute of Geospheres Dynamics of russian academy of sciences institute of Oceanology of russian academy of sciences Geological institute of russian academy of sciences

Line structures such as pipelines that cross active faults should be designed to retain leak-tightness if the design displacement (Ddesign) occurs. Principal approaches to the Ddesign and rupture kinematics assessment are described. They are based on relationships between earthquake magnitude, rupture length and displacement, and on the detailed field data on a specific fault that crosses the pipeline route. Since the future offset at the crossing may exceed the design value, the probability of a displacement occurrence where the safety of the structure can not be ensured should be estimated. Assessment method on such event probability is described and exemplified through active fault studies carried out at several pipeline projects in Russia.

关键词： Active Fault Surface Rupture Design Displacement Pipeline Sakhalin Island

On aerodynamic noises radiated by the pantograph system of high-speed trains

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Acta Mechanica Sinica 2013年第3期29卷 399-410页

作者： Hua-Hua Yu Jia-Chun Li Hui-Qin Zhang LMFS Institute of Mechanics Chinese Academy of Sciences

Pantograph system of high-speed trains become significant source of aerodynamic noise when travelling speed exceeds 300 km/h. In this paper, a hybrid method of non-linear acoustic solver （NLAS） and Ffowcs Williams-Hawkings （FW-H） acoustic analogy is used to predict the aerodynamic noise of pantograph system in this speed range. When the simulation method is validated by a benchmark problem of flows around a cylinder of finite span, we calculate the near flow field and far acoustic field surrounding the pantograph system. And then, the frequency spectra and acoustic attenuation with distance are analyzed, showing that the pantograph system noise is a typical broadband one with most acoustic power restricted in the medium-high frequency range from 200 Hz to 5 kHz. The aerodynamic noise of pantograph systems radiates outwards in the form of spherical waves in the far field. Analysis of the overall sound pressure level （OASPL） at different speeds exhibits that the acoustic power grows approximately as the 4th power of train speed. The comparison of noise reduction effects for four types of pantograph covers demonstrates that only case 1 can lessen the total noise by about 3 dB as baffles on both sides can shield sound wave in the spanwise direction. The covers produce additional aerodynamic noise themselves in the other three cases and lead to the rise of OASPLs.

关键词： Aerodynamic noise · NLAS · FW–H acoustic analogy · Pantograph system · High-speed train

Measurement of oil-water flow via the correlation of turbine flow meter, gamma ray densitometry and drift-flux model

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Journal of Hydrodynamics 2015年第4期27卷 548-555页

作者：李东晖许晶禹 LMFS Institute of Mechanics Chinese Academy of Sciences

The flow rate of the oil-water horizontal flow is measured by the combination of the turbine flow meter and the singlebeam gamma ray densitometry. The emphasis is placed on the effects of the pipe diameter, the oil viscosity and the slip velocity on the measurement accuracy. It is shown that the mixture flow rate measured by the turbine flow meter can meet the application requirement in the water continuous pattern（ o- w flow pattern）. In addition, by introducing the developed drift-flux model into the measurement system, the relative errors of measurements for component phase flow rates can be controlled within ±5%. Although more accurate methods for the flow rate measurement are available, the method suggested in this work is advantageous over other methods due to its simplicity for practical applications in the petroleum industry.

关键词： oil and water flow flow rate measurement turbine flow meter gamma ray densitometry drift-flux model

Underlying principle of efficient propulsion in flexible plunging foils

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Acta Mechanica Sinica 2014年第6期30卷 839-845页

作者： Xiao-Jue Zhu Guo-Wei He Xing Zhang LNM Institute of MechanicsChinese Academy of Sciences

Passive flexibility was found to enhance propulsive efficiency in swimming *** this study,we numerically investigate the roles of structural resonance and hydrodynamic wake resonance in optimizing efficiency of a flexible plunging *** results indicates that（1）optimal efficiency is not necessarily achieved when the driving frequency matches the structural eigenfrequency;（2）optimal efficiency always occurs when the driving frequency matches the wake resonant frequency of the time averaged velocity ***,the underlying principle of efficient propulsion in flexible plunging foil is the hydrodynamic wake resonance,rather than the structural *** addition,we also found that whether the efficiency can be optimized at the structural resonant point depends on the strength of the leading edge vortex relative to that of the trailing edge *** result of this work provides new insights into the role of passive flexibility in flapping-based propulsion.

关键词： Flexibility Propulsive efficiency Structural resonance Hydrodynamic wake resonance

Lagrangian statistics in isotropic turbulent flows with deterministic and stochastic forcing schemes

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Acta Mechanica Sinica 2015年第1期31卷 25-31页

作者： Jin-Cai Chen Guo-Dong Jin Jian Zhang LNM Institute of MechanicsChinese Academy of Sciences

Artificial input of energy into the flow is neces sary to create and maintain a statistically stationary isotropic turbulence for sampling in studying the statistics. Due to the nonlinear coupling among different Fourier modes through the triadic interaction, whether or not various forc ing schemes affect the statistics in turbulence is an impor tant and open question. We present detailed comparison of Lagrangian statistics of fluids particles in forced isotropic turbulent flows in 1283, 2563, and 5123 simulations, with Taylorscale Reynolds numbers in the range of 64-171, us ing a deterministic and a stochastic forcing scheme, respec tively. Several Lagrangian statistics are compared, such as velocity and acceleration autocorrelations, and moments of Lagrangian velocity increments. The differences in the La grangian statistics obtained from the two forcing schemes are shown to be small, indicating that the isotropic forcing schemes used have little effects on the Lagrangian statistics in the isotropic turbulence.

关键词： Isotropic turbulence Deterministic forcingscheme Stochastic forcing scheme Lagrangian statisticalquantities

Tunable band structures of polycrystalline graphene by external and mismatch strains

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Acta Mechanica Sinica 2012年第6期28卷 1539-1544页

作者： Jiang-Tao Wu Xing-Hua Shi Yu-Jie Wei LNM Institute of Mechanics Chinese Academy of Sciences

Lacking a band gap largely limits the application of graphene in electronic devices. Previous study shows that grain boundaries （GBs） in polycrystalline graphene can dra- matically alter the electrical properties of graphene. Here, we investigate the band structure of polycrystalline graphene tuned by externally imposed strains and intrinsic mismatch strains at the GB by density functional theory （DFT） calcu- lations. We found that graphene with symmetrical GBs typ- ically has zero band gap even with large uniaxial and biax- ial strain. However, some particular asymmetrical GBs can open a band gap in graphene and their band structures can be substantially tuned by external strains. A maximum band gap about 0.19 eV was observed in matched-armchair GB （5, 5） I （3, 7） with a misorientation of θ = 13° when the applied uniaxial strain increases to 9%. Although mismatch strain is inevitable in asymmetrical GBs, it has a small influence on the band gap of polycrystalline graphene.

关键词： Graphene Grain boundary Defects Strain and gap

Hierarchical structure observation and nanoindentation size effect characterization for a limnetic shell

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Acta Mechanica Sinica 2015年第3期31卷 364-372页

作者： Jingru Song Cuncai Fan Hansong Ma Yueguang Wei LNM Institute of Mechanics Chinese Academy of Sciences

In the present research, hierarchical structure observation and mechanical property characterization for a type of biomaterial are carried out. The investigated bioma- terial is Hyriopsis cumingii, a typical limnetic shell, which consists of two different structural layers, a prismatic ＂pillar＂ structure and a nacreous ＂brick and mortar＂ structure. The prismatic layer looks like a ＂pillar forest＂ with variationsection pillars sized on the order of several tens of microns. The nacreous material looks like a ＂brick wall＂ with bricks sized on the order of several microns. Both pillars and bricks are composed of nanoparticles. The mechanical properties of the hierarchical biomaterial are measured by using the nanoindentation test. Hardness and modulus are measured for both the nacre layer and the prismatic layer, respectively. The nanoindentation size effects for the hierarchical structural materials are investigated experimentally. The results show that the prismatic nanostructured material has a higher stiffness and hardness than the nacre nanostructured material. In addition, the nanoindentation size effects for the hierarchical structural materials are described theoretically, by using the trans-scale mechanics theory considering both strain gradient effect and the surface/interface effect. The modeling results are consistent with experimental ones.

关键词： Biomaterial Hierarchical structure - Mechan-ical property Nanoindentation size effect Trans-scalemechanics

Structure of the Intermetallic Compound Ni_3Al Synthesized under Compression of the Powder Mixture of Pure Elements Part Ⅰ: Phase Composition and Microstructure of Main Phase

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Journal of Materials Science & Technology 1999年第6期15卷 531-535页

作者： M. V. Fedorischeva, V.E.Ovcharenko, O.B.Perevalova and E. V. Kozlov(institute of Strength Physics and Materials Science, russian academy of sciences, Siberian branch, Tomsk, Russia) institute of Strength Physics and Materials Science Russian Academy of Sciences Siberian Branch Tomsk Russian Federation

It was shown by TEM and X-ray analysis that there are four types of grains of the main Ni3Al phase in the structure of the intermetallic obtained by the self-propagation high temperature method (SHS). Every type of grains has its own domain and dislocation structure. There are mono- and polydomains with and without dislocations. The grains of the main phase of monoand polydomains without dislocations and polydomains with dislocations were formed by diffusion in the solid phase. In these conditions NiAl3 phase is located on the grain boundary of the main phase. The Ni2Al3 phase is located at the triple joints of the main phase.

关键词： In Al Structure of the Intermetallic Compound Ni3Al Synthesized under Compression of the Powder Mixture of Pure Elements Part Phase Composition and Microstructure of Main Phase Ni

Structure of the Intermetallic Compound Ni_3Al Synthesized under Compression of the Powder Mixture of Pure Elements Part Ⅱ: Influence of Alloying by Boron on the Phase Composition and the Microstructure of Grains of the Main Phase

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Journal of Materials Science & Technology 2000年第1期16卷 15-18页

作者： M. V.Fedorischeva, V.E.Ovcharenko,O.B.Perevalova and E.V.Kozlov (institute of Strength Physics and Materials Science, russian academy of sciences, Siberian branch.Tomsk, Russia) institute of Strength Physics and Materials Science Russian Academy of Sciences Siberian Branch Tomsk Russian Federation

The Ni_3B phase was formed when boron (0.5 at. pct B) was added to the intermetallic of sto- ichiometric and off-stoichiometric (Ni-24 at. pct Al) compounds. In the alloy of stoichiometric composition the particles of Ni_3B phase has the size around 0.1μm and is located on the grain boundary of the main phase. The decreasing of concentrations of Al in the ofF-stoichiometric alloy leads to increase in the degree of the long-range order parameter, increasing the concen- trations of boron in the solid solution and decreasing its localization on the grain boundary. Microalloying of boron leads to increasing in the fraction of grain monodomains with disloca- tions up to 0.7 in the alloy of the off-stoichiometric composition and up to 1 in the alloy of the stoichiometric composition. It was established the correlation between the degree of the concentration inhomogeneity, average density of the dislocations and the average long range-order parameter.

关键词： Al Part Structure of the Intermetallic Compound Ni3Al Synthesized under Compression of the Powder Mixture of Pure Elements Ni