Experimental and numerical study on the dynamic behavior of a semi-active impact damper

Jiawei Zhang,Zheng Lu,Mengyao Zhou,Zhikuang Huang,Sami F. Masri 국제구조공학회 2023 Smart Structures and Systems, An International Jou Vol.31 No.5

Impact damper is a passive damping system that controls undesirable vibration with mass block impacting with stops fixed to the excited structure, introducing momentum exchange and energy dissipation. However, harmful momentum exchange may occur in the random excitation increasing structural response. Based on the mechanism of impact damping system, a semi-active impact damper (SAID) with controllable impact timing as well as a semi-active control strategy is proposed to enhance the seismic performance of engineering structures in this paper. Comparative experimental studies were conducted to investigate the damping performances of the passive impact damper and SAID. The extreme working conditions for SAID were also discussed and approaches to enhance the damping effect under high-intensity excitations were proposed. A numerical simulation model of SAID attached to a frame structure was established to further explore the damping mechanism. The experimental and numerical results show that the SAID has better control effect than the traditional passive impact damper and can effectively broaden the damping frequency band. The parametric studies illustrate the mass ratio and impact damping ratio of SAID can significantly influence the vibration control effect by affecting the impact force.

Design and analysis of mechanical flux‑weakening device of axial flux permanent magnet machines

Shaopeng Wang,Jiawei Lu,Bin Li,Chengcheng Liu,Youhua Wang,Gang Lei,Youguang Guo,Jianguo Zhu 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.4

Due to the low inductance of an axial flux permanent magnet machine (AFPMM), the constant power speed regulation range is small. A new mechanical flux-weakening method for single-rotor single-stator AFPMMs is proposed in this paper. By installing a mechanical flux-weakening device on one side of the stator and rotating it certain angle, the speed regulation of the flux-weakening can be realized. The device is simple in structure, easy to operate, and can be operated in the process of machine operation. The validity of the device is verified by applying it to a machine. Finite-element software is used to calculate and analyze the performances of two machines with the device.

Effect of motion path of downburst on wind-induced conductor swing in transmission line

Wenjuan Lou,Jiawei Wang,Yong Chen,Zhongbin Lv,Ming Lu Xu 한국풍공학회 2016 Wind and Structures, An International Journal (WAS Vol.23 No.3

In recent years, the frequency and duration of supply interruption in electric power transmission system due to flashover increase yearly in China. Flashover is usually associated with inadequate electric clearance and often takes place in extreme weathers, such as downbursts, typhoons and hurricanes. The present study focuses on the wind-induced oscillation of conductor during the process when a downburst is passing by or across a specified transmission line. Based on a revised analytical model recently developed for stationary downburst, transient three-dimensional wind fields of moving downbursts are successfully simulated. In the simulations, the downbursts travel along various motion paths according to the certain initial locations and directions of motion assumed in advance. Then, an eight-span section, extracted from a practical 500 kV ultra-high-voltage transmission line, is chosen. After performing a non-linear transient analysis, the transient displacements of the conductors could be obtained. Also, an extensive study on suspension insulator strings` rotation angles is conducted, and the electric clearances at different strings could be compared directly. The results show that both the variation trends of the transient responses and the corresponding peak values vary seriously with the motion paths of downburst. Accordingly, the location of the specified string, which is in the most disadvantageous situation along the studied line section, is picked out. And a representative motion path is concluded for reference in the calculation of each string`s oscillation for the precaution of wind-induced flashover under downburst.

Microstructure and Magnetic Properties of Plasma-Sprayed Fe<SUB>73.5</SUB>Cu1Nb₃Si<SUB>13.5</SUB>B₉ Coatings

Xiaojun Ni,Xihui Bo,Jiawei Wu,Jinhua Guo,Zhichao Lu,Shaoxiong Zhou 한국자기학회 2010 한국자기학회 학술연구발표회 논문개요집 Vol.2010 No.12

Effect of motion path of downburst on wind-induced conductor swing in transmission line

Lou, Wenjuan,Wang, Jiawei,Chen, Yong,Lv, Zhongbin,Lu, Ming Techno-Press 2016 Wind and Structures, An International Journal (WAS Vol.23 No.3

In recent years, the frequency and duration of supply interruption in electric power transmission system due to flashover increase yearly in China. Flashover is usually associated with inadequate electric clearance and often takes place in extreme weathers, such as downbursts, typhoons and hurricanes. The present study focuses on the wind-induced oscillation of conductor during the process when a downburst is passing by or across a specified transmission line. Based on a revised analytical model recently developed for stationary downburst, transient three-dimensional wind fields of moving downbursts are successfully simulated. In the simulations, the downbursts travel along various motion paths according to the certain initial locations and directions of motion assumed in advance. Then, an eight-span section, extracted from a practical 500 kV ultra-high-voltage transmission line, is chosen. After performing a non-linear transient analysis, the transient displacements of the conductors could be obtained. Also, an extensive study on suspension insulator strings' rotation angles is conducted, and the electric clearances at different strings could be compared directly. The results show that both the variation trends of the transient responses and the corresponding peak values vary seriously with the motion paths of downburst. Accordingly, the location of the specified string, which is in the most disadvantageous situation along the studied line section, is picked out. And a representative motion path is concluded for reference in the calculation of each string's oscillation for the precaution of wind-induced flashover under downburst.

Construction of antibacterial nano-silver embedded bioactive hydrogel to repair infectious skin defects

Qi Dong,Dan Zu,Lingqiang Kong,Sunfang Chen,Jun Yao,Jiawei Lin,Lei Lu,Bing Wu,Bin Fang 한국생체재료학회 2022 생체재료학회지 Vol.26 No.3

Background: Hydrogels loaded with antimicrobial agents have been widely used for treating infected wound defects. However, hydrogels derived from a porcine dermal extracellular matrix (PADM), containing silver nanoparticles (AgNPs), have not yet been studied. Therefore, we investigated the therapeutic effect of an AgNP-impregnated PADM (AgNP–PADM) hydrogel on the treatment of infected wounds. Methods: An AgNP–PADM hydrogel was synthesized by embedding AgNPs into a PADM hydrogel. We examined the porosity, moisture retention, degradation, antibacterial properties, cytotoxicity, antioxidant properties, and ability of the PADM and AgNP–PADM hydrogels to treat infected wounds in animals. Results: The PADM and AgNP–PADM hydrogels were pH sensitive, which made them flow dynamically and solidify under acidic and neutral conditions, respectively. The hydrogels also exhibited porous network structures, satisfactory moisture retention, and slow degradation. Additionally, the AgNP–PADM hydrogel showed a slow and sustained release of AgNPs for at least 7 days without the particle size changing. Thus, the AgNPs exhibited adequate antibacterial ability, negligible toxicity, and antioxidant properties in vitro. Moreover, the AgNP–PADM hydrogel promoted angiogenesis and healed infected skin defects in vivo. Conclusions: The AgNP–PADM hydrogel is a promising bioderived antibacterial material for clinical application to infected wound dressings

Sedimentology, geological modeling and prediction of the remaining oil distribution in a complicated fault-block reservoir in the Weicheng Oilfield, Dongpu Depression, China

Jinkun Yang,Weilu Li,Siyu Gao,Jinliang Zhang,Yi Zhang,Jiawei Lu 한국지질과학협의회 2019 Geosciences Journal Vol.23 No.5

Reservoirs in the Weicheng Oilfield, which occur in Paleogene Shahejie Formation Member 4 (Es4), were formed during the initial and strongly rifting stage of the Dongpu Depression. The geometry and distribution of sands of different types have controlled the heterogeneity of the reservoirs and have resulted in exploration challenges and relatively low recoveries. Based on various static and dynamic geological data including drilling, logging, seismic and production data, the microfacies features and distribution of Es4 were analyzed. Geostatistical three-dimensional (3-D) models and an integrated numerical simulation were constructed to quantify the geometry, spatial distribution and continuity of the reservoir sands and to predict the remaining oil distribution rules. Two depositional systems were recognized in Es4: terminal fans deposits in the lower part and partial shallow-lake deposits in the upper part. The three-dimensional geological model provided insights into the external and internal geometries, distributions and physical properties of the reservoir units. A sedimentary and connectivity feature analysis suggested four types of flow units: Type I units, which are primary sands of distributary channels and bars; Type II units, which are primary sands of proximal overbank and beaches; Type III units, which are sands of distal overbank; and Type IV units, which are mud flats and inter-beach-bar. The numerical simulation reproduced the changing process of the remaining oil, and the areas that have both high remaining oil saturations and reserve abundance, which are controlled by micro-facies and influenced by the structural trend and injection-production relations, comprise the key potential reservoirs: the sand pinch-out area, the imperfect pattern area and structural highs in Type I units and most of the areas in Type II units.