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Zihua Liu,Hao Zhou,Hao Fang,Mingxi Zhou 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.6
Perforated plates have been widely used to attenuate harmful noise. An impedance tube was used to evaluate the sound absorption capacities of four cases of dual perforated plates with multiple apertures traversed by bias flow. The radius of small holes on the plates was 1.0 mm, and the radii of large holes were 1.5 mm, 2.0 mm, 2.5 mm, and 3.0 mm, respectively. The effects of the frequency and amplitude of the incident sound wave, the cavity depths, and the bias flow velocity on the sound attenuation effect of these cases were experimentally studied. The maximum sound absorption coefficient of dual perforated plates with the large difference in hole size was 0.93. On the other hand, the dual plates with the small aperture difference is more adaptable to the change of the bias flow velocity, and the maximum sound absorption coefficient was close to 1.
Zihua Liu,Di Wang,Ren Liang,Dechang Cai,Yong Ouyang,Zhikang Lin 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.9
In this paper, a single-equation drift-flux type model for gas-lead-bismuth eutectic (LBE) two-phase flow analysis in the LBE fast reactor steam generator tube rupture (SGTR) accident is established. As the area-averaged superficial gas velocity increases, the calculated exponent P in the Bankoff model increases, and the distribution parameter C 0 decreases. The reliability of the model is confirmed by comparing the predicted results with a total of 76 sets of open experimental data from a bubble-column case and a gas lift pump case. The relative deviation between the predicted and experimental values of the void fraction is within 20 %. The model proposed in this paper helps to realize the early warning and analysis of SGTR accidents in LBE fast reactors, and can provide theoretical and technical guidance for the safety design and evaluation of LBE fast reactors.
Liu JunHe,Zhao Zhong,Yan Yan,Ali Abid,Ahmed Zeeshan,He DaHan,Yu Mingfu,Hang Jia,Perven Misbah,Nazir Tamsila,Tayyib Muhammad,Zhao ZiHua 한국응용곤충학회 2021 Journal of Asia-Pacific Entomology Vol.24 No.4
An alfalfa grassland landscape was divided into 36 plots during 2014 season in Yuanzhou District of Guyuan city in Ningxia Hui Autonomous Region of P.R. China. In these three times repeated experiments, treatment of habitat fragmentation was divided into two grades: continuity (H = 0.0) and fragmentation (H = 1.0), and their habitat loss rate was divided into 6 grades: 90, 80, 70, 50, 20 and 0%. Considering habitat loss 0% of the plot as the reference, as a result of sweeping net and visual methods, results showed that the flight distance of the Harmonia axyridis was much higher than that of the Hippodamia variegata both in fragmentation and continuous habitats. In the alfalfa landscape, H. axyridis moved more by flying, while H. variegata moved more by crawling. There was a threshold effect that affected the movement behavior of lady beetles between 70 and 100% of the habitat loss. The population of the two species of lady beetles in the continuous habitat was higher than that in the habitat fragmentation and was more obvious in 70 and 50% plots of the habitat loss. The dispersal rate of the two species of lady beetles inside plots was higher than outside of the experimental plots, which reflected the low diffusivity of the ladybeetle. Habitat fragmentation affected the dispersal, migration and construction of two species of lady beetles on different spatial scales by disturbing the spread of natural enemies and searching for prey.
Advances in Fog Microphysics Research in China
Duanyang Liu,Zihua Li,Wenlian Yan,Yi Li 한국기상학회 2017 Asia-Pacific Journal of Atmospheric Sciences Vol.53 No.1
Fog microphysical research in China based on field experiments obtained many important results in recent 50 years. With the fast development of China's economy, urbanization in the last 30 years, special features of fog microphysical structure also appeared, which did not appear in other countries. This article reviews the fog microphysical research around China, and introduces the effect of urbanization on fog microphysical structure and the microphysical processes as well as macroscopic conditions of radiation fog droplet spectral broadening. Urbanization led to an increase in fog droplet number concentration but decreases in fog liquid water content (LWC) and fog droplet size, as well as a decrease in visibility in large cities. Observations show that the radiation fog could be divided into wide-spectrum one, which is all extremely dense fog with the spectral width more than 40 μm, and narrow-spectrum one, most of which is dense fog with the spectral width less than 22 μm, according to droplet spectral distribution. During developing from dense fog to extremely dense fog, the widespectrum radiation fog is characterized by explosive deepening, that is, within a very short time (about 30 min), the droplet concentration increase by about one order of magnitude, droplet spectral broadening across 20 μm, generally up to 30-40 μm, or even 50 μm. As a result, water content increased obviously, visibility decreased to less than 50 m, when dense fog became extremely dense fog.
Lili Pan,Zihua Chen,Wenxiu De,Guangjie Yang,Xikui Liu 한국고분자학회 2016 Macromolecular Research Vol.24 No.4
The past decades have witnessed significant advance in the synthesis of covalent organic frameworks (COFs), however, their formation and morphology revolution mechanism have been rarely reported. Here, through an acid modulated dynamic covalent chemistry approach, pure and uniform micro-octahedral covalent imine frameworks were obtained for the first time. Formation mechanism based on the stacking of initially formed two-dimensional nanoplates followed by surface smoothing enabled by the dynamic nature of imine bonding was proposed. Furthermore, we revealed for the first time that nonstoichiometric method can be applied to the synthesis of covalent organic frameworks. Thus we provide novel strategy for the morphology control COFs which will surely facilitate their application in energy-related area.
Hao Zhou,Zihua Liu,Hao Fang,Chengfei Tao,Mingxi Zhou,Liubin Hu 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.11
Perforated plates have been widely used in combustors to attenuate harmful sounds. In this study, the acoustic absorption capability of plates with heterogeneously distributed holes under bias flow was evaluated in an impedance tube, and the sound attenuation effect of each plate located in the liquid fuel combustor inlet section was experimentally studied. The perforated plate with heterogeneously distributed large holes showed the best control effect under the designed experimental conditions. After control, the peak dynamic pressure in the chamber and plenum decreased by 90 % and 75 %, respectively, and the reduction in the heat release fluctuation was 60 %. When the primary air flow rate deviated from the optimal value, the plate with large holes still reduced the pressure amplitude in the chamber by approximately 70 %. It was also found that installing the perforated plate with a back cavity had the dual effect of gaining and damping combustion instability.
Control of thermoacoustic instability of liquid-spray flame with porous sound absorber
Hao Zhou,Hao Fang,Dongliang Wei,Zihua Liu,Zhaowen Wang,Hanxiao Meng 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.8
A kind of porous sound absorber was studied to control the thermoacoustic oscillation of liquid mist flame, which combined natural fibrous materials and perforated plate. It could optimize the sound absorption characteristics of fibrous materials by adding perforated plate and air cavity. The influences of the interlayer and back cavity depth of two kinds of fibrous materials with the mass of 20, 30, 40 g were investigated experimentally in an impedance tube and applied to control the oscillating ethanol flame. The results showed that the best depth of interlayer and back cavity were 20 cm and 30 cm, respectively. The addition of two kinds of fiber sandwich structures could reduce the amplitude of the sound pressure oscillation in the combustion chamber by 89.2 % and 92.6 %, as well as 88.0 % and 91.2 % in the plenum chamber, meanwhile, restrained the flame heat release fluctuation by 73 %. It was proved that the porous sound absorber could act as a damp in the acoustic transmission path and suppress the sound source.