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Yao, Hua,Li, Xuwen,Liu, Ying,Wu, Qian,Jin, Yongri The Korean Society of Ginseng 2016 Journal of Ginseng Research Vol.40 No.4
Background: Rare ginsenosides in Panax quinquefolius L. have strong bioactivities. The fact that it is hard to obtain large amounts of rare ginsenosides seriously restricts further research on these compounds. An easy, fast, and efficient method to obtain different kinds of rare ginsenosides simultaneously and to quantify each one precisely is urgently needed. Methods: Microwave-assisted extraction (MAE) was used to extract nine kinds of rare ginsenosides from P. quinquefolius L. In this article, rare ginsenosides [20(S)-Rh1, 20(R)-Rh1, Rg6, F4, Rk3, 20(S)-Rg3, 20(R)-Rg3, Rk1, and Rg5] were identified by high performance liquid chromatography (HPLC)-electrospray ionization-mass spectrometry. The quantity information of rare ginsenosides was analyzed by HPLC-UV at 203 nm. Results: The optimal conditions for MAE were using water as solvent with the material ratio of 1:40 (w/v) at a temperature of $145^{\circ}C$, and extracting for 15 min under microwave power of 1,600 W. Seven kinds of rare ginsenosides [20(S)-Rh1, 20(R)-Rh1, Rg6, F4, Rk3, Rk1, and Rg5] had high extraction yields, but those of 20(S)-Rg3 and 20(R)-Rg3 were lower. Compared with the conventional method, the extraction yields of the nine rare ginsenosides were significantly increased. Conclusion: The results indicate that rare ginsenosides can be extracted effectively by MAE from P. quinquefolius L. in a short time. Microwave radiation plays an important role in MAE. The probable generation process of rare ginsenosides is also discussed in the article. It will be meaningful for further investigation or application of rare ginsenosides.
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DUAL-MOTOR FULL-WEIGHT ELECTRIC POWER STEERING SYSTEM FOR COMMERCIAL VEHICLE
Yaohua Li,Qianlong Feng,Yangsen Zhang,Youfei Nan 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.3
In order to study the electric power steering system (EPS) which is suitable for the steering characteristics of commercial vehicles, the effect of weight on steering performance is analyzed, and a dual-motor full-weight EPS system is proposed. Firstly, the full-weight assist characteristics are studied, and two current distribution schemes and corresponding fault-tolerant control strategies are proposed according to the structural characteristics of dual-motor EPS system. By comparing with the traditional single-weight EPS system, it is proved that the full-weight EPS system improves the control stability and makes the driver get a better road feeling. Through the double line change test and step test, the effectiveness of the two current distribution schemes are verified, and it has better fault-tolerance performance. By comparison, the faulttolerance performance of scheme two is better than that of scheme one.
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Yaohua Yang,Hongwei Huang,Limin Sun 국제구조공학회 2017 Smart Structures and Systems, An International Jou Vol.19 No.3
System identification of structures is one of the important aspects of structural health monitoring. The accuracy and efficiency of identification results is affected severely by measurement noises, especially when the structure system is large, such as bridge structures, and when online system identification is required. In this paper, the least square estimation (LSE) method is used combined with the substructure approach for identifying structural parameters of a cable-stay bridge with large degree of freedoms online. Numerical analysis is carried out by first dividing the bridge structure into smaller substructures and then estimates the parameters of each substructure online using LSE method. Simulation results demonstrate that the proposed approach is capable of identifying structural parameters, however, the accuracy and efficiency of identification results depend highly on the noise sensitivities of loading region, loading pattern as well as element size.
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Yaohua Li,Jikang Fan,Yang Liu,Xiaoyu Wang 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.5
According to the position relationship between the vehicle and the obstacle, a new obstacle avoidance path planner was designed to solve the limitation of traditional local obstacle avoidance path planner in excessive obstacle avoidance. In order to improve the control accuracy of the path tracking controller and ensure the stability of the vehicle, a comprehensive evaluation index of path tracking performance considering control accuracy and driving stability was established. The optimal prediction time domain and control time domain parameters at different vehicle speeds were obtained, and an adaptive dual time domain parameter path tracking controller was designed. Based on the joint-simulation platform, the integrated structure of the planning layer and the control layer was simulated and verified. Simulation results show that the new obstacle avoidance function can avoid excessive obstacle avoidance while ensuring real-time performance, and improve the driving stability of the vehicle. The adaptive time-domain parameter path tracking controller has better comprehensive control performance and can improve driving safety under extreme conditions. The integrated structure of local obstacle avoidance path planning and path tracking control are beneficial for the vehicle to plan and accurately track the local obstacle avoidance path in multiple static obstacle scenes.
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Liu Yaohua,Li Rui,Li Sheng-Cai 한국응용곤충학회 2022 Journal of Asia-Pacific Entomology Vol.25 No.1
The multicolored Asian ladybird Harmonia axyridis Pallas is often used as a biological control agent against Aphis craccivora Koch, a key pest aphid of broad bean. Understanding consumption characteristics of biological control agents is critical for developing effective biological control programs. Here, under laboratory conditions we studied consumption patterns of H. axyridis on A. craccivora including functional response and intraspecific competition. All larvae (1st-, 2nd-, 3rd-, 4th-instar) and adults (male and female) of H. axyridis exhibited a Type II functional response to A. craccivora. We found H. axyridis females were superior to individuals of other developmental stages, based on three key parameters in functional response model, i.e. attack rate (a = 90.0%), handling time (T h = 2.7 min), and consumption threshold (N max = 526.7 individuals). Results from our analysis of intraspecific competition showed that when attacking A. craccivora, 4th-instar larvae of H. axyridis suffered from the greatest intraspecific competition (coefficient of mutual interference, m = 0.48). Our results show that 4th-instar larvae and adults of H. axyridis are most effective in controlling A. craccivora, and proper density of H. axyridis released will reduce intraspecific competition. This analysis reveals both prey-predator and predatorpredator interactions, and highlights the value of biological control in reducing pesticide use and protecting ecological environments.
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Study on Components Durability Test Conditions Based on Combined Clustering and Markov Chain Method
Li Yaohua,Liu Yang,Shao Pandeng,Li Zetian,Song Weiping 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.3
The process of obtaining durability test conditions of bus components is complicated. A way to build components durability test conditions based on driving cycle is proposed. Pure electric urban bus driving cycle in Xi \'an based on running data is constructed based on combined clustering and Markov chain method, and simulation model of pure electric urban bus is built. The load conditions of the motor output shaft are obtained through simulation and calculation based on load torque applied on the motor shaft from simulation results based on actual drive cycle. The damage calculation method of motor output shaft under different load is constructed according to the liner fatigue cumulative damage theory and the material S-N curve. The four-peak-valley rain-flow counting method is used to calculate the damage of motor output shaft and the corresponding cycle life of motor shaft under different load conditions is determined. The motor speed condition and torque condition corresponding to driving cycle with the shortest life are selected as the motor output shaft durability testcondition.
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Voltage Vector Selection Area of the Direct Torque Control for Permanent Magnet Synchronous Motor
Li, Yaohua,Ma, Jian,Yu, Qiang,Liu, Jingyu Journal of International Conference on Electrical 2012 Journal of international Conference on Electrical Vol.1 No.2
The control of stator flux, torque angle, excitation torque, reluctance torque and total torque of the direct torque control (DTC) for a permanent magnet synchronous motor (PMSM) are studied in this paper. Simplified expressions to represent the changes of these variables due to the application of a voltage vector are given. Finally, a voltage vector selection area and the implementation of a voltage vector selection strategy are proposed.
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Haichao Feng,Yaohua Guo,Xiaozhuo Xu,Caixia Gao,Liwang Ai 한국자기학회 2023 Journal of Magnetics Vol.28 No.4
In order to meet the demand of high-power density, high-precision positioning and low cost direct drive system in ropeless lifting, precision machining and other fields, the modular secondary structure with permanent magnet synchronous magnetization is adopted in this paper, and the secondary permanent magnet flux-switching linear machine (SPMFSLM) is proposed. Compared with the traditional primary permanent magnet fluxswitching linear machine (PPMFSLM), it reduces the thrust ripple and strengthens the primary structure. According to the topology and operation principle of the machine, starting from the air-gap magnetic field modulation principle and the convex tooth effect, the contribution of the air-gap flux density harmonics of the permanent magnet magnetic field and the armature magnetic field for the two machines to the average thrust is compared and analyzed, reflecting the similarities and differences between the two FSLMs in the thrust generation mechanism. In addition, the no-load characteristics for back-EMF and the thrust characteristics for two machines under equal load are calculated and compared. Finally, the multi-objective optimization of the key structural parameters of the machine is carried out by combining the response surface method (RSM) with the NSGAII algorithm. Then, the 3D simulation of the machine was carried out and cross-validated with the 2D results. Finally, a double-sided SPMFSLM (DS-SPMFSLM) is proposed from the practical point of view. The performance of DS-SPMFSLM is significantly superior to that of single-sided SPMFSLM, which verifies the advantages of the secondary permanent magnet structure scheme.
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