Wyniki wyszukiwania - BazTech

1

Influence of NaCl Additive on the Reduction Process of MoO3 to Mo2C by High-Purity CO Gas

Que Biao-Hua, Wang Lu, Wang Bao, Chen Yi, Xue Zheng-Liang

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 2

787--796

EN

In this work, influence of NaCl additive on the transformation process of MoO3 to Mo2C under pure CO atmosphere in the range of room temperature to 1170 K was investigated. The results showed that transformation of MoO3 to Mo2C can be roughly divided into two stages: the reduction of MoO3 to MoO2 (the first stage) and the carburization of MoO2 to Mo2C (the second stage). As to the first stage, it was found that increasing the content of NaCl (from 0 to 0.5 wt.%) was beneficial for the increase of reaction rate due to the nucleation effect; while when the content of NaCl increased to 2 wt.%, the reaction rate will be decreased in turn. As to the second stage, the results showed that reaction rate was decreased with the increase of NaCl, which may be due to the formation of low-melting point eutectic. The work also found that morphology of as-prepared Mo2C was irregular and particle size of it was gradually increased with increasing the NaCl content. According to the results, the possible reaction mechanism was proposed.

2

Vibration transients of reservoir-pipe-valve system caused by water hammer

Miao Yang, Jiang Yuncheng, Qiu Zaihui, Pan Jun, Wang Lu, Han Zhenrong, Li Kun, Zhang Li, Zhang Xiaolu

Journal of Theoretical and Applied Mechanics

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2020

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Vol. 58 nr 4

1037--1048

EN

A severe oscillation, accompanied with an abnormal “click” sound, of a fuel feeding pipe system during valve closing, when the feeding flowrate reaches a certain value, is observed experimentally. A fluctuation model in which stiffness and damping coefficients of the vibration system are time varying is proposed. Each coefficient is composed of two parts, one of which is constant and the other is time varying. Based on this model, simulation transients of the vibration displacement, velocity and pressure in the pipe are presented. Simulations of the pressure transients are compared with experimental data detected by pressure transducer, which shows that both have fluctuations in the transient process at a large flowrate.

3

A new multi scale signed direct envelope inversion with more accurate amplitude polarity information

Luo Jingrui, Chen Guoxin, Wu Ru Shan, Wang Lu

Acta Geophysica

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2020

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Vol. 68, no. 5

1361--1371

EN

Subsurface parameter reconstruction using full waveform inversion is highly nonlinear with nonunique solutions. When the initial model with high precision is missing, the cycle skipping problem will be encountered, especially for the strong scattering media like salt structures. In order to adapt to the inversion of strong scattering media, direct envelope inversion (DEI) using directly the envelope Fréchet derivatives was proposed to avoid the weakly nonlinear assumption for the model updating. In the original DEI method, the envelope polarity is not considered. To further improve the efectiveness of DEI, signed envelope inversion with polarity detection can be used. In this work, we develop a new polarity detection technique on the basis of seismic attributes, which can provide more accurate polarity information for the seismic envelope. Based on the above technique, the new multi-scale signed DEI method is proposed. The new technique is applied to the SEG/EAGE salt model. The numerical examples verifed the efectiveness of this method.

4

Research on the road linear optimization design of bridge and tunnel connecting segment in the canyon

Wang Lu, Liu Yuwen, Chen Xiaoxin

Archives of Transport

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2019

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Vol. 52, iss. 4

81--93

EN

It is easy to skid and roll by centrifugal force and wind, which affects the safety of the vehicle. At the same time, the special location of bridge and tunnel connecting segment in the canyon will accelerate the wind, and make the transverse wind play a more important role in driving vehicles. Based on the acceleration effect of canyons on wind, the vehicle model is simulated by Carsim software, and the road and wind models are established. It is studied that the vehicle has different radius of circular curve under different wind levels, corresponding to different superelevation. The lateral acceleration, lateral deflection and transverse force coefficient are selected as the running state of the vehicle at different speeds to research the linear optimization design of bridge and tunnel connecting segment in the canyon. The result shows that when the wind force exceeds the fifth grade, it is possible for the vehicle to overturn under the limit minimum radius required by the standard value. In order to ensure the stability and safety of the vehicle, this paper considers the geographical position of bridge and tunnel connecting segment in the canyon and the relationship between the radius of the superelevation and circular curve. What’s more, it puts forward the optimal limit minimum radius of the circular curve with different wind grades of 5-9 grades. At the same time, when the road alignment cannot be optimized under the condition, this paper puts forward the speed limit that the vehicle safety can be guaranteed under different wind speed conditions. The speed limit can provide reference for traffic management and safety guarantee of mountain expressway.