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- 저자 : Zhiwu Huang (검색결과 5 건)
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Zhiwu Zhang,Youping Yi,Wen You,Shiquan Huang,Yonglin Guo,Hailin He 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.6
To investigate the quenching sensitivity of the 2195 Al–Li alloy rolled sheet and guide the design of the quenching process,the time–temperature-property (TTP) curves of this material were researched through interrupted quenching experiments. The differential scanning calorimetry (DSC) and transmission electron microscope (TEM) were used to characterize theevolution of precipitates during isothermal treatment. The results of this essay demonstrated that the nose temperature of 2195Al–Li alloy is around 370 °C and the temperature range of quenching sensitivity is 340 °C to 400 °C. The microstructureobservation revealed that the T1particles precipitate and grow rapidly at the temperature from 340 to 400 °C, which is dueto the high nucleation rate of phase and fast solute diffusion kinetics, especially at the nose temperature. The needle-shapedθ′/θ″ and T1particles grow up quickly as the isothermal preservation time prolonged, leading to the decrease of the supersaturatedsolid solution of the matrix. This will reduce the number of the age-induced precipitate and weaken the subsequentage hardening effect. Therefore, the rate of cooling should be increased in the quenching sensitivity range (340–400 °C) toinhibit the precipitation of the second phase and obtain excellent mechanical properties. While in other temperature ranges,the cooling rate should be decreased appropriately to reduce residual stress. The appropriate average cooling rate is recommendedto be around 13 °C s−1 at the temperature from 340 to 400 °C.
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Jianfeng Liu,Qing Peng,Zhiwu Huang,Weirong Liu,Heng Li 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.5
This paper proposes an optimal anti-locking control scheme so as to improve the braking performance of railway vehicles. The controlling effect of sliding mode control is improved, and the optimal slip ratio is achieved by extreme seeking algorithm. Firstly, a substitute function for the conventional sign function is proposed. Secondly, a closed loop observer for braking systems is used to enhance the estimation value of adhesion force, which can also be used for calculating reference speed. Finally Sliding Mode Controlbased controller needs to be entered a reference slip ratio called optimal slip ratio, which is searched by extreme seeking algorithm from the functional relationship between slip ratio and friction coefficient. Thus, the maximum adhesion is achieved despite wheel/ rail surface changes. The simulation result demonstrates the effect of real-time adjustment for braking torque, which guarantees the braking performance.
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Instability analysis under part-load conditions in centrifugal pump
Weixiang Ye,Renfang Huang,Zhiwu Jiang,Xiaojun Li,ZuChao Zhu,Xianwu Luo 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.1
In this study, a centrifugal pump with a specific speed of 39.12 m×min -1 ×m 3 s -1 is treated to analyze the flow instability under part-load conditions by numerical simulation and experimental test. For calculations, the RANS method, coupled with the k-ω SST turbulence model, is adopted. Numerical results at different operation points are compared with available experimental data, such as hydraulic performance and flow field information by particle image velocimetry. The numerical and experiment results agree well. The flow simulation indicates a strong reverse flow at the passage upstream impeller inlet, and the energy loss in the impeller is the largest under partload conditions among all flow components in the pump. In one impeller revolution, one blade-to-blade flow passage is always nearly blocked off by the rotating stall occurring at the impeller inlet for each instant, and the blockage induces a jet flow with large velocity at the next blade-to-blade flow passage along the rotational direction of the impeller. The blockage and the jet flow in the blade-to-blade flow passages will make the flow unstable inside the impeller and cause performance breakdown and pressure vibration under part-load conditions for the pump.
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Yingze Yang,Lu Xiong,Weirong Liu,Kai Gao,Zhiwu Huang 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.10
The inconsistent braking force will result in collision compacts between adjacent freight cars of heavy haul train, which utilizes ECP as brake system. Moreover, the rigid connection mode aggravates the negative effect. In practical applications, the brake pipe (BP) pressure sensor is used as the feedback in the closed loop brake force control of the ECP brake, but there is no sensor in the brake cylinder (BC), whose pressure is the control target, and these factors will contribute the longitudinal impacts among the freight cars. Therefore, an accurate and fast braking force control is extremely important for ECP brake. Firstly, as for the highly nonlinear ECP system of heavy haul train, an energy-based globally stable pressure observer for ECP brake is proposed. And then, according to the pressure of BC estimated by the observer, an enhanced sliding-mode control algorithm is applied to realize the fast and precise braking force control. Finally, experimental results are presented to demonstrate and validate effectiveness of the proposed observer and control algorithm.
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Zhiyong Zheng,Jun Peng,Kunyuan Deng,Kai Gao,Heng Li,Bin Chen,Yingze Yang,Zhiwu Huang 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
Lithium-ion battery remaining useful life (RUL) is a key parameter on battery management system. Many machine learning methods are applied to RUL predictions, but they generally suffer from two limitations: (i) the extracted features fail to reflect the information hidden in the historical degradation status, and (ii) the accuracy cannot be guaranteed in the evaluation of battery degradation due to the non-linearity. In this paper, a new prediction method is proposed combining the time window (TW) and Gradient Boosting Decision Trees (GBDT). First, the energy (VCE) and the fluctuation index (VFI) of voltage signal are verified and selected as features. Then, a TW based feature extraction method is designed to extract features from the historical discharge process. After that, GBDT is adopted to model the relation of features and RUL. The proposed method is implemented on a recognized battery degradation dataset, and the advantages in accuracy are proven.
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