Investigation on Galloping of D-Shape Iced 6-Bundle Conductors in Transmission Tower Line

Mengqi Cai,Xiaohui Yang,Hanjie Huang,Linshu Zhou 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.6

The first comprehensive test base of electrical test transmission line in China has been established. Galloping response characteristics of real test tower-line system covered with D-shape ice model under natural wind load has been recorded. According to the structural details of the test tower-line, the detailed numerical model of the three spans tower-line system has been set up by nonlinear finite element method (FEM). Then, the digital stochastic wind field is presented. Galloping behaviors of the D-shape iced 6-bundle conductors in the test line under stochastic wind field is numerically simulated. Finally, the dynamic response of displacements, galloping traces, galloping modes, and frequencies are obtained. The numerical simulation results are consistent with the measured galloping characteristics results of the test transmission tower-line, which verifies the efficiency of the numerical model. It is demonstrated that the established FEM numerical method can be applied to investigate galloping behaviors of tower-line. Meanwhile, based on the numerical simulation results, the variation of stress and displacement of tower during galloping is also discussed.

Magnetohydrodynamic flows in a dis-aligned duct system under a uniform magnetic field

Luo, Yang,Zhu, Mengqi,Kim, Chang Nyung 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.2

<P>In the present study, three-dimensional Magnetohydrodynamic (MHD) Liquid-metal (LM) flows in a dis-aligned duct system under a uniform magnetic field are investigated by numerical method. Computational fluid dynamics (CFD) simulations are carried out to analyzed the characteristics of the MHD flows and to examine the inter-relationship of the LM velocity, current density, electric potential and pressure, using CFX. The duct system consists of two dis-aligned parallel channels (One inflow channel and one outflow channel) and one channel connecting the above channels. In the present study, cases with different lengths of the connecting channel are considered. Because of the inertial force therein, a velocity recirculation is found in the region just after the first turning, resulting in a region of peak value in electric potential together with complex distribution of the current. Also, another velocity recirculation is seen in the region just after the second turning, creating another region of peak value in electric potential. In a situation where the magnetic field is applied in a direction perpendicular to the plane of the main flow in a dis-aligned duct system, until the fluid reaches an edge, the velocity component parallel to the magnetic field converges, with an increasing in the peak value of the side layer velocity, and then, after the fluid passes the edge, the velocity component parallel to the magnetic field diverges, with a decrease in the peak value of the side layer velocity. Oppositely, until the fluid reaches a corner, the velocity component parallel to the magnetic field diverges, with a decrease in the peak value of the side layer velocity, and then, after the fluid passes the corner, the velocity component parallel to the magnetic field converges, with an increase in the peak value of the side layer velocity. It is found that this type of velocity pattern is closely associated with the current distribution in the region of right-angle segments in the sense that the magnitude of the electromotive component of electric current is proportional to the fluid velocity.</P>

Effects of 3D contraction on pebble flow uniformity and stagnation in pebble beds

Wu, Mengqi,Gui, Nan,Yang, Xingtuan,Tu, Jiyuan,Jiang, Shengyao Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.5

Pebble flow characteristics can be significantly affected by the configuration of pebble bed, especially for HTGR pebble beds. How to achieve a desired uniform flow pattern without stagnation is the top priority for reactor design. Pebbles flows inside some specially designed pebble bed with arc-shaped contraction configurations at the bottom, including both concave-inward and convex-outward shapes are explored based on discrete element method. Flow characteristics including pebble retention, residence-time frequency density, flow uniformity as well as axial velocity are investigated. The results show that the traditionally designed pebble bed with cone-shape bottom is not the most preferred structure with respect to flow pattern for reactor design. By improving the contraction configuration, the flow performance can be significantly enhanced. The flow in the convex-shape configuration featured by uniformity, consistency and less stagnation, is much more desirable for pebble bed design. In contrast, when the shape is from convex-forward to concave-inward, the flow shows more nonuniformity and stagnation in the corner although the average cross-section axial velocity is the largest due to the dominant middle pebbles.

Prediction of the remaining time and time interval of pebbles in pebble bed HTGRs aided by CNN via DEM datasets

Wu Mengqi,Liu Xu,Gui Nan,Yang Xingtuan,Tu Jiyuan,Jiang Shengyao,Qian Zhao 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.1

Prediction of the time-related traits of pebble flow inside pebble-bed HTGRs is of great significance for reactor operation and design. In this work, an image-driven approach with the aid of a convolutional neural network (CNN) is proposed to predict the remaining time of initially loaded pebbles and the time interval of paired flow images of the pebble bed. Two types of strategies are put forward: one is adding FC layers to the classic classification CNN models and using regression training, and the other is CNNbased deep expectation (DEX) by regarding the time prediction as a deep classification task followed by softmax expected value refinements. The current dataset is obtained from the discrete element method (DEM) simulations. Results show that the CNN-aided models generally make satisfactory predictions on the remaining time with the determination coefficient larger than 0.99. Among these models, the VGG19þDEX performs the best and its CumScore (proportion of test set with prediction error within 0.5s) can reach 0.939. Besides, the remaining time of additional test sets and new cases can also be well predicted, indicating good generalization ability of the model. In the task of predicting the time interval of image pairs, the VGG19þDEX model has also generated satisfactory results. Particularly, the trained model, with promising generalization ability, has demonstrated great potential in accurately and instantaneously predicting the traits of interest, without the need for additional computational intensive DEM simulations. Nevertheless, the issues of data diversity and model optimization need to be improved to achieve the full potential of the CNN-aided prediction tool

열전 발전과 열전 가열/냉각을 위한 열전 모듈의 설계 모델링 연구

김창녕(Chang Nyung Kim),Yang Lluo,Mengqi Zhu 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.6

A Novel Fixed Twin-Rotor Unmanned Aerial Vehicle with Variable Angle Louver Rudder

Yixin Zhang,Jianfeng Zhou,Shaoping Wang,Mengqi Yang,Shaoshi Li 제어로봇시스템학회 2021 제어로봇시스템학회 국제학술대회 논문집 Vol.2021 No.10

A novel fixed twin-rotor unmanned aerial vehicle (UAV) based on the variable angle louver rudder (VALR) is developed in this work. In view of the mechanical characteristics under the action of the louver rudder, specific kinematics and dynamics models are derived. The aerodynamic characteristics of the UAV are studied through computational fluid dynamics simulation, and a ground measurement system is designed to analyze the aerodynamic characteristics of the prototype. An attitude control model is proposed, and maneuvers such as take-off, landing, hovering, and braking are realized through flight experiments, which verify the feasibility of the prototype design. This research shows that the new layout with the VALR system, combined with the advantages of rudder control and vector control, can reduce the structural complexity and deadweight of the UAV while ensuring flight stability and improving maneuverability. Moreover, the novel UAV has higher energy efficiency and economy.

Functional mechanisms for diabetic nephropathy-associated genetic variants

Hong Xu,Chengxin Gong,Yonghu Xu,Yongfang Fan,Xingzi Liu,Chaopeng Xiong,Luling He,Changle Liu,Shenqiang Rao,Wen Xiao,Lu Ding,Lan Tang,Fangfang Hu,Mengqi Xiong,Mei Yang,Shangdong Liang 한국유전학회 2016 Genes & Genomics Vol.38 No.7

Diabetic nephropathy (DN) is one of the major complications of diabetes. A tremendous amount of genetic variations have been identified to be associated with DN. However, most of them only generate from statistical associations at the DNA level, generally without direct functional evidence regarding their association mechanisms underlying DN. Based on the publicly available datasets and resources, this study performed integrative analyses (expression quantitative trait loci analysis, differential gene expression analysis and functional prediction analysis) to detect the molecular functional mechanisms underlying the associations for DN. Among 150 selected (P\E-4) genetic associations that were archived in the public databases, two single nucleotide polymorphisms (SNPs) (rs3135377 and rs9469220) have been found to act as cis-effect regulators of the ‘‘identified’’ gene (HLADRA and HLA-DRB1). These eQTL genes have differential expression signals in the DN-associated cell groups. These SNPs were predicted as regulatory sites by utilizing online prediction tools. Our data suggest potential mechanistic links underlying the association between DN and two identified SNPs. These results could help us to have a deeper understanding of the functional relevance of genetic variants with susceptibility to DN, which is useful for pursuit of in-depth validation studies to dissect their involvements and molecular functional mechanisms in DN.