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ZHAO, Binjuan,ZHANG, Chenghu,ZHAO, Youfei,FU, Yanxia,LIU, Qi,CHEN, Huilong Korean Society for Fluid machinery 2018 International journal of fluid machinery and syste Vol.11 No.1
To improve the design of the splitter blade in the centrifugal pump impeller, inner flow numerical simulations are performed on the centrifugal pump impeller without splitter blades firstly, inner flow diagnoses are performed based on the theory of the boundary vorticity dynamics, and distributions of the boundary vorticity flux (BVF), friction force as well as vorticity on the inner walls of the impeller are carefully analyzed to find the location of bad flows and their dynamic sources. Later, according to the inner flow diagnosis results, splitter blades are designed and reformed for the original impeller. The inner flow filed in the impellers equipped with the preliminary splitter blade and reformed splitter blade are numerically simulated and diagnosed. Finally, comparisons are made among the three impellers, and it is found that, compared to the original impeller (impeller 0), the BVF, friction force and vorticity distribution in the impeller equipped with the preliminary splitter blade (impeller 1) has no obvious improvement, although the pump head increases, the efficiency decreases; the BVF, friction force and vorticity distribution in the impeller equipped with the reformed blade (impeller 2) has improved obviously, BVF peak decreases evidently and BVF distributes more uniformly, flow separation is inhibited, the hydraulic force acting on the impeller increases, with the pump head and efficiency increasing dramatically. It is proven that, flow diagnosis based on the theory of the boundary vorticity dynamics is an effective supplemental way for the design of the splitter blade in the centrifugal pump impeller, and will provide reference for the design of other turbo machinery as well.
CFD-DEM modeling of snowdrifts on stepped flat roofs
Zhao, Lei,Yu, Zhixiang,Zhu, Fu,Qi, Xin,Zhao, Shichun Techno-Press 2016 Wind and Structures, An International Journal (WAS Vol.23 No.6
Snowdrift formation on roofs should be considered in snowy and windy areas to ensure the safety of buildings. Presently, the prediction of snowdrifts on roofs relies heavily on field measurements, wind tunnel tests and numerical simulations. In this paper, a new snowdrift modeling method by using CFD (Computational Fluid Dynamics) coupled with DEM (Discrete Element Method) is presented, including material parameters and particle size, collision parameters, particle numbers and input modes, boundary conditions of CFD, simulation time and inlet velocity, and coupling calculation process. Not only is the two-way coupling between wind and snow particles which includes the transient changes in snow surface topography, but also the cohesion and collision between snow particles are taken into account. The numerical method is applied to simulate the snowdrift on a typical stepped flat roof. The feasibility of using coupled CFD with DEM to study snowdrift is verified by comparing the simulation results with field measurement results on the snow depth distribution of the lower roof.
Quickest Spectrum Sensing Approaches for Wideband Cognitive Radio Based On STFT and CS
( Qi Zhao ),( Wei Qiu ),( Boxue Zhang ),( Bingqian Wang ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.3
This paper proposes two wideband spectrum sensing approaches: (i) method A, the cumulative sum (CUSUM) algorithm with short-time Fourier transform, taking advantage of the time-frequency analysis for wideband spectrum. (ii)method B, the quickest spectrum sensing with short-time Fourier transform and compressed sensing, shortening the time of perception and improving the speed of spectrum access or exit. Moreover, method B can take advantage of the sparsity of wideband signals, sampling in the sub-Nyquist rate, and it is more suitable for wideband spectrum sensing. Simulation results show that method A significantly outperforms the single serial CUSUM detection for small SNRs, while method B is substantially better than the block detection based spectrum sensing in small probability of the false alarm.
Qi Zhao,Xiujuan Yu,Xiuwen Cheng,Juan Wu 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.6
Sulfur-free exfoliated graphite (EG) with large exfoliated volume (760 mL g-1) was prepared throughchemical oxidation, followed by microwave exfoliation. SEM results indicated that well-developednetwork pores in the worm-like structure of EG could be clearly observed. XPS results displayed thatsome functional groups were yielded on the surface of the as-prepared EG. Moreover, the capacity of EGwas evaluated by the adsorption of rodamine B and 4-chlorophenol aqueous solution. Results showedthat EG exhibited high adsorption capacity for RhB and 4-CP, which could be attributed to the functionalgroups and well-developed network pores in the worm-like EG.
The infertile individual analysis based on whole-exome sequencing in chinese multi-ethnic groups
Zhao Qiongzhen,Li Yanqi,Liang Qi,Zhao Jie,Kang Kai,Hou Meiling,Zhang Xin,Du Renqian,Kong Lingyin,Liang Bo,Huang Weidong 한국유전학회 2023 Genes & Genomics Vol.45 No.4
Background Infertility is a common and rapidly growing health issue around the world. The genetic analysis based on the infertile population is crucial for intervention and treatment. Objective To find candidate gene locus led to azoospermia in Chinese multi-ethnic groups and provide theoretical guidance for the diagnosis of genetic diseases to progressively aggravated infertility patients and sterile offspring with ART. Methods The study based on whole-exome sequencing (WES) was presented for genetic characteristic analysis of multi-ethnics and identification of variants related to infertility in Xinjiang area of China. Results The frequency of pathogenic variants showed significant ethnic differences among four main ethnics in Xinjiang. The population structure analysis confirmed that the Hui was close to the Han population, the Kazak was close to the Uygur population, and there are three ancestry components in the four ethnics. In addition, ten candidate variants potentially regulated azoospermia were detected, and KNTC1 (rs7968222: G > T) was chosen to validate the association. Through the analysis in the valid group, the frequency of rs7968222 (G > T) has a significant difference in the azoospermia population (11.76%, 8/68) and normospermia population (4.63%, 35/756) (P < 0.001). Interestingly, the proportion of people with abnormal follicle-stimulating hormone (FSH) level in the group carrying rs7968222 (G > T) was significantly higher than non-carriers (P < 0.05). Therefore, rs7968222 may regulate spermatogenesis through affecting hormone level. Conclusion Our study establishes the genetics analysis of Northwest China and finds a candidate gene locus KNTC1 (rs7968222: G > T), which is one of the genetic susceptibility factors for male azoospermia.
Texture Evolution of Hot Rolled Al–Cu–Mg–Zr Alloy During Annealing
Qi Zhao,Zhiyi Liu 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.12
Texture growth and relative mechanism of Al–Cu–Mg–(Zr) alloy during annealing have been investigated by three dimensionalOrientation Distribution Functions (ODFs), Electron Back Scattered Diffraction (EBSD) and Transmission ElectronMicroscopy (TEM). The results show that Zr addition in Al–Cu–Mg alloy restricts the preferable growth of recrystallizedGoss grain, and fails to improve the total intensity of Goss texture. Recrystallized Goss is difficult to nucleate within Brassorientation even after full recrystallization, and Copper and S grains cannot preferably transform into Cube grains in Al–Cu–Mg–Zr alloy. Instead, the growth of random textures is favorable at the expense of deformed Brass, Copper and S textures. These phenomena can be well explained by relating to the disappearance of Σ5, Σ7 and Σ9 boundaries caused by Al3Zrpinningdislocation. In addition, it is found that the Brass texture of Al–Cu–Mg–Zr alloy can be enhanced at specific annealingtemperature, which is attributed to the formation of recrystallized Brass grains. Lastly, the deformed Goss of Al–Cu–Mg–Zralloy is energy-unstable as compared with Brass during annealing, and these deformed Goss grains will subsequently evolveinto recrystallized Brass or random orientations.
Image-processing Based Adaptive Human-computer Interaction System
Qi-Jie Zhao,Da-Wei Tu,Zhi-Hua Huang 한국과학기술원 인간친화 복지 로봇 시스템 연구센터 2007 International Journal of Assistive Robotics and Me Vol.8 No.3
In this paper, we have taken into account some impact factors on Infrared TVbased eye gaze input system, and proposed some solutions to these problems. In order to improve the adaptation of eye-gaze input modality to large variation of environment light and its lighteness, a set of image capturing equipment and image thresholding model has been put forward. Furthermore, some control strategies and methods have been proposed to decrease the influences on the eye gaze system caused by users head movement. At last, some experiments have been done to verify the feasibility of the strategies and methods. The results have shown that the system permits user’s head freely move in certain conditions. Moreover, higher accuracy can be gotten for eye gaze input.