A New Study on the Gap Effect of an Airfoil with Active Flap Control Based on the Overset Grid Method

Zhiyuan Hu,Guohua Xu,Yongjie Shi 한국항공우주학회 2021 International Journal of Aeronautical and Space Sc Vol.22 No.4

Rotors with active flap control have considerable potential in reducing vibration and noise and improving aerodynamic performance. However, due to the movement of the flap, there are unavoidable gaps between the components that will lead to significant changes in the aerodynamic characteristics. Moreover, considering the difficulties in motion modeling and the accuracy of the simulation of the flow field in such a narrow gap, carrying out related research is challenging; thus, there has been inadequate targeted research, and that which does exist requires supplementation. To carry out this challenging flow field simulation, the overset assembly algorithm proposed by the author in previous research is adopted in the present study. It is used to successfully assemble the narrow gap, and the accuracy of the simulation is fully verified by comparing the results with the actual experimental results and a grid study. Furthermore, to compensate for the lack of research and experiments on the gap effect, cases considering a complete range of gap widths from an absence of a gap to a width of 10% of the chord length are set up and carried out under the following three case groups: steady cases with a fixed trailing-edge deflection angle, unsteady cases in which only the trailing-edge flap is flapping, and full-motion cases characterized by the periodic flap of the main airfoil and the trailing-edge flap. The results show that the gap increases the drag of the trailing-edge flap and decreases aerodynamic efficiency, especially at low speeds and high angles of attack. Nevertheless, when the gap is unavoidable, there is a range of the gap width that makes unapparent the decrease of aerodynamic efficiency. Moreover, the decrease of aerodynamic efficiency can be reduced as much as possible by a well-designed gap region geometry to ensure that the airfoil and the trailing-edge flap fit together when moving.

Few-shot transfer learning with attention for intelligent fault diagnosis of bearing

Yao Hu,Qingyu Xiong,Qiwu Zhu,Zhengyi Yang,Zhiyuan Zhang,Dan Wu,Zihui Wu 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.12

The bearing is one of the key components in modern industrial equipment. In the past few years, many studies have been carried out on bearing diagnosis through datadriven methods. However, there are two practical problems. First, under actual working conditions, the lack of fault samples is a major factor that hinders the application of these methods in industrial environments. Second, there is a lack of full utilization of a priori knowledge in the current stage of methods using relational networks for fault diagnosis. It is manifested by the incompleteness of the relational network structure. To address these problems, we present a new diagnosis method based on few-shot learning, which is suitable for the environment where the data is scarce. In this method, we train the model with the data generated by the artificial damaged bearings instead of the data from the real bearing. We experimentally validate the performance improvement of the complete relational network structure. It is able to perform the few-shot learning task better. In addition, we also reduce the global feature discrepancy by introducing an attention mechanism to improve the performance of the model. And the impact of the number of layers of the attention mechanism on the model is also discussed in detail. In this paper, our model performs better under the same experimental conditions compared with other transfer learning models.

Characterization and functional analysis of Krtap11-1 during hair follicle development in Angora rabbits (Oryctolagus cuniculus)

Shuang Liang,Zhiyuan Bao,Bohao Zhao,Tong Zhou,Jiali Li,Ming Liu,Shuaishuai Hu,Naisu Yang,Yang Chen,Xinsheng Wu 한국유전학회 2020 Genes & Genomics Vol.42 No.11

Background Keratin-associated protein (KAP), the structural protein molecule of hair fibers, plays a key role in determiningthe physical properties of hair. Studies of Krtap11-1 have focused only on its localization. Functional studies of Krtap11-1in hair follicle development have so far not been reported. Objective This study aimed to provide evidence for the role of Krtap11-1 in skin and hair development. Methods Full-length cloning and analysis of Krtap11-1 were conducted to ascertain its function. Overexpression vectors andinterference sequences were constructed and transfected into RAB-9 cells. Quantitative real-time polymerase chain reaction(qRT-PCR) was used to investigate the hair follicle developmental stage of Krtap11-1, the expression of different tissues,and the effects on other hair follicle development-related genes. Results The full length of cloned Krtap11-1 was 947 bp. Krtap11-1 was confirmed to be a hydrophilic protein localizedmostly in mitochondria. The greatest mRNA expression was observed in skin. Using a follicle synchronization model, itwas found that Krtap11-1 mRNA expression levels first increased then decreased over the passage of time, principally duringhair follicle catagen and telogen. Following the overexpression of Krtap11-1, mRNA expression levels of the WNT-2,KRT17, BMP-2, and TGF-β-1 genes increased, and LEF-1 decreased (P < 0.05), the converse after the corresponding useof si-RNA interference. Conclusions Krtap11-1 exerts a promoting effect. The results provide novel insight into the relationship between hair follicledevelopment and Krtap11-1 gene expression.

Pole-to-Ground Fault Analysis for MMC-HVDC Grid

Zhen He,Jiabing Hu,Lei Lin,Zhiyuan He 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

Pole-to-ground (PTG) fault analysis is of vital importance for HVDC grid. However, many factors are not considered in the existing studies, such as the asymmetrical property of PTG fault, the coupling issue between dc transmission lines and the complexity of dc grid’s structure. This paper presents a PTG fault analysis method, which is based on common- and differential-mode (CDM) transformation. Similar to the symmetrical component method in ac system, the transformation decomposes the HVDC grid into CDM networks at first. Then, under the perspective of CDM components, a transfer impedance based analysis is performed to obtain the analytical expressions of PTG fault characteristics. The proposed PTG fault analysis method is applicable to arbitrary HVDC grid topologies. And the analytical expressions can give theoretical guidance for fault protection. The validity of the proposed PTG fault analysis method is verified by comparison with the simulation results in PSCAD/EMTDC.

Prevalence of Senecavirus A in pigs from 2014 to 2020: a global systematic review and meta-analysis

Xuhua Ran,Zhenru Hu,Jun Wang,Zhiyuan Yang,Zhongle Li,Xiaobo Wen 대한수의학회 2023 Journal of Veterinary Science Vol.24 No.3

Background: Senecavirus A (SVA), a member of the family Picornaviridae, is newly discovered, which causes vesicular lesions, lameness in swine, and even death in neonatal piglets. SVA has rapidly spread worldwide in recent years, especially in Asia. Objectives: We conducted a global meta-analysis and systematic review to determine the status of SVA infection in pigs. Methods: Through PubMed, VIP Chinese Journals Database, China National Knowledge Infrastructure, and Wanfang Data search data from 2014 to July 26, 2020, a total of 34 articles were included in this analysis based on our inclusion criteria. We estimated the pooled prevalence of SVA in pigs by the random effects model. A risk of bias assessment of the studies and subgroup analysis to explain heterogeneity was undertaken. Results: We estimated the SVA prevalence to be 15.90% (1,564/9,839; 95% confidence interval [CI], 44.75–65.89) globally. The prevalence decreased to 11.06% (945/8,542; 95% CI, 28.25–50.64) after 2016. The highest SVA prevalence with the VP1-based RT-PCR and immunohistochemistry assay was 58.52% (594/1,015; 95% CI, 59.90–83.96) and 85.54% (71/83; 95% CI, 76.68–100.00), respectively. Besides, the SVA prevalence in piglet herds was the highest at 71.69% (119/166; 95% CI, 68.61–98.43) (p < 0.05). Moreover, our analysis confirmed that the subgroups, including country, sampling year, sampling position, detected gene, detection method, season, age, and climate, could be the heterogeneous factors associated with SVA prevalence. Conclusions: The results indicated that SVA widely exists in various countries currently. Therefore, more prevention and control policies should be proposed to enhance the management of pig farms and improve breeding conditions and the environment to reduce the spread of SVA.