Investigation of Quench Sensitivity and Microstructure Evolution During Isothermal Treatment in 2195 Al–Li Alloy

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.

Fault diagnosis method of rolling bearing based on deep belief network

Zhiwu Shang,Xiangxiang Liao,Rui Geng,Maosheng Gao,Xia Liu 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.11

A method based on the theory of deep learning and feature extraction and a fault diagnosis model of a rolling bearing based on deep belief network are proposed in this study considering the complex, nonlinear, and non-stationary vibration signal of the rolling bearing. To some extent, the method avoids the complex structure of deep neural network and can be easily trained. Experimental results show that the recognition rate of the method reaches 100 %. The method can identify various types of faults accurately and has good fault diagnosis capability, which can provide the convenience for maintenance.

Seismic Performance of Precast Concrete Columns with Improved U-type Reinforcement Ferrule Connections

Zhiwu Yu,Xiaoyong Lv,Yujie Yu,Faxing Ding,Xiaodan Peng 한국콘크리트학회 2019 International Journal of Concrete Structures and M Vol.13 No.7

This paper proposes a new kind of U-type reinforcement ferrule (URF) connection for the assembly of precast concrete (PC) components, which has a good fault-tolerance ability and low cost of construction with a simple postgrouting process. The modified connection features welded U ferrules, which can increase the bonding mechanism and internal stress transmission in the spliced region. A series of quasi-static cyclic tests were performed on URF-connected PC columns with different welding patterns. Comprehensive comparisons were performed on the load-bearing capacity, the plastic energy dissipation ability, the internal force transmission, the column ductility and the stiffness. The results indicated that PC columns with welded URF connections can ensure better lateral resistance than the cast-in-place concrete column. The weld type and length influence the connection performance, and the 15d-welded and full-length welded URF connections presented better connection performance and were suggested for the assembly of PC columns. Then, finite element analyses were performed to further reveal the working and failure mechanisms and the affecting mechanism of some working parameters. Parametric simulations indicated that the increase in the axial load ratio and the concrete strength in the postcast region had a slight but limited effect on improving the lateral resistance of the column connection.

Dynamic Output Feedback Robust MPC for LPV Systems Subject to Input Saturation and Bounded Disturbance

Xubin Ping,Zhiwu Li,Abdulrahman Al-Ahmari 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.3

For linear parameter varying (LPV) systems with unknown scheduling parameters and bounded disturbance,a synthesis approach of dynamic output feedback robust model predictive control (OFRMPC) with inputsaturation is investigated. By pre-specifying partial controller parameters, a main optimization problem is solvedby convex optimization to reduce the on-line computational burden. The main optimization problem guarantees thatthe estimated state and estimation error converge within the corresponding invariant sets such that recursive feasibilityand robust stability are guaranteed. The consideration of input saturation in the main optimization problemimproves the control performance. Two numerical examples are given to illustrate the effectiveness of the approach.

Tanshinone IIA Protects Endothelial Cells from H2O2-Induced Injuries via PXR Activation

Haiyan Zhu,Zhiwu Chen,Zengchun Ma,Hongling Tan,Chengrong Xiao,Xianglin Tang,Boli Zhang,Yuguang Wang,Yue Gao 한국응용약물학회 2017 Biomolecules & Therapeutics(구 응용약물학회지) Vol.25 No.6

Tanshinone IIA (Tan IIA) is a pharmacologically active substance extracted from the rhizome of Salvia miltiorrhiza Bunge (also known as the Chinese herb Danshen), and is widely used to treat atherosclerosis. The pregnane X receptor (PXR) is a nuclear receptor that is a key regulator of xenobiotic and endobiotic detoxification. Tan IIA is an efficacious PXR agonist that has a potential protective effect on endothelial injuries induced by xenobiotics and endobiotics via PXR activation. Previously numerous studies have demonstrated the possible effects of Tan IIA on human umbilical vein endothelial cells, but the further mechanism for its exerts the protective effect is not well established. To study the protective effects of Tan IIA against hydrogen peroxide (H2O2) in human umbilical vein endothelial cells (HUVECs), we pretreated cells with or without different concentrations of Tan IIA for 24 h, then exposed the cells to 400 μM H2O2 for another 3 h. Therefore, our data strongly suggests that Tan IIA may lead to increased regeneration of glutathione (GSH) from the glutathione disulfide (GSSG) produced during the GSH peroxidase-catalyzed decomposition of H2O2 in HUVECs, and the PXR plays a significant role in this process. Tan IIA may also exert protective effects against H2O2-induced apoptosis through the mitochondrial apoptosis pathway associated with the participation of PXR. Tan IIA protected HUVECs from inflammatory mediators triggered by H2O2 via PXR activation. In conclusion, Tan IIA protected HUVECs against H2O2-induced cell injury through PXR-dependent mechanisms.

Erratum to Tanshinone IIA Protects Endothelial Cells from H₂O₂-Induced Injuries via PXR Activation [Biomol Ther 25(6), 599-608 (2017)]

( Haiyan Zhu ),( Zhiwu Chen ),( Zengchun Ma ),( Hongling Tan ),( Chengrong Xiao ),( Xianglin Tang ),( Boli Zhang ),( Yuguang Wang ),( Yue Gao ) 한국응용약물학회 2024 Biomolecules & Therapeutics(구 응용약물학회지) Vol.32 No.2

Tanshinone IIA Protects Endothelial Cells from H₂O₂-Induced Injuries via PXR Activation

( Haiyan Zhu ),( Zhiwu Chen ),( Zengchun Ma ),( Hongling Tan ),( Chengrong Xiao ),( Xianglin Tang ),( Boli Zhang ),( Yuguang Wang ),( Yue Gao ) 한국응용약물학회 2017 Biomolecules & Therapeutics(구 응용약물학회지) Vol.25 No.6

Tanshinone IIA (Tan IIA) is a pharmacologically active substance extracted from the rhizome of Salvia miltiorrhiza Bunge (also known as the Chinese herb Danshen), and is widely used to treat atherosclerosis. The pregnane X receptor (PXR) is a nuclear receptor that is a key regulator of xenobiotic and endobiotic detoxification. Tan IIA is an efficacious PXR agonist that has a potential protective effect on endothelial injuries induced by xenobiotics and endobiotics via PXR activation. Previously numerous studies have demonstrated the possible effects of Tan IIA on human umbilical vein endothelial cells, but the further mechanism for its exerts the protective effect is not well established. To study the protective effects of Tan IIA against hydrogen peroxide (H₂O₂) in human umbilical vein endothelial cells (HUVECs), we pretreated cells with or without different concentrations of Tan IIA for 24 h, then exposed the cells to 400 μM H₂O₂ for another 3 h. Therefore, our data strongly suggests that Tan IIA may lead to increased regeneration of glutathione (GSH) from the glutathione disulfide (GSSG) produced during the GSH peroxidase-catalyzed decomposition of H₂O₂ in HUVECs, and the PXR plays a significant role in this process. Tan IIA may also exert protective effects against H₂O₂-induced apoptosis through the mitochondrial apoptosis pathway associated with the participation of PXR. Tan IIA protected HUVECs from inflammatory mediators triggered by H₂O₂ via PXR activation. In conclusion, Tan IIA protected HUVECs against H₂O₂-induced cell injury through PXR-dependent mechanisms.

A model for investigating vehicle-bridge interaction under high moving speed

Hanyun Liu,Zhiwu Yu,Wei Guo,Yan Han 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.77 No.5

The speed of rail vehicles become higher and higher over two decades, and China has unveiled a prototype highspeed train in October 2020 that has been able to reach 400 km/h. At such high speeds, wheel-rail force items that had previously been ignored in common computational model should be reevaluated and reconsidered. Aiming at this problem, a new model for investigating the vehicle-bridge interaction at high moving speed is proposed. Comparing with the common model, the new model was more accurate and applicable, because it additionally considers the second-order pseudo-inertia forces effect and its modeling equilibrium position was based on the initial deformed curve of bridge, which could include the influences of temperature, pre-camber, shrinkage and creep deformation, and pier uneven settlement, etc. Taking 5 km/h as the speed interval, the dynamic responses of the classical vehicle-bridge system in the speed range of 5 km/h to 400 km/h are studied. The results show that ignoring the second-order pseudo-inertia force will underestimate the dynamic response of vehicle-bridge system and make the high-speed railway bridge structure design unsafe.

A Wireless Power Transfer System Based on a Hybrid Transmitting Coil for Targeted Therapy Microrobots in the Intestine

Ding Han,Guozheng Yan,Zhiwu Wang,Pingping Jiang,Lin Yan 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.6

A wireless power transfer system for targeted therapy microrobots has been received more attention recently. However, it usually fails to work due to weak coupling caused by misalignment in position and angle between the transmitting coil and the receiving coil. It will not be tolerated even if it occurs at certain angles. To address this issue, a three-dimensional hybrid transmitting coil, combining a fixed Helmholtz coil pair and an adjustable curved rectangular coil pair, is proposed. Based on the novel structure, the proposed hybrid transmitting coil could produce a three-dimensional magnetic field, realizing well coupled with the receiving coil embedded on the microrobot at any posture. To verify the efficiency and practical applicability of the transmitting coil proposed in this paper, we build the coil model via both analytical calculation and simulation analysis. Finally, the designed hybrid transmitting coil is also implemented in the wireless power transfer system with a receiving coil. The magnetic field distribution indicates that a large and uniform magnetic field could be obtained. The experimental results demonstrate that in the central zone of the transmitting coil, 300 × 200 mm, the magnetic field distribution is uniform, which can meet the requirements of the microrobot system working area. And the maximum output efficiency and power can be reached at 5% and 1001 mW, respectively. What's more, the proposed hybrid transmitting coil has solved the weak coupling problem due to misalignment in position and angle with which the electromagnetic energy decays quickly.

Optimization and analysis of Helmholtz-like three-coil wireless power transfer system applied in gastrointestinal robots

Meng, Yicun,Wang, Zhiwu,Jiang, Pingping,Wang, Wei,Chen, Fanji,Yan, Guozheng The Korean Institute of Power Electronics 2020 JOURNAL OF POWER ELECTRONICS Vol.20 No.4

Wireless power transfer (WPT) systems based on magnetic resonance provides a possible method to supply energy for implantable medical devices, such as gastrointestinal robots and wireless capsule endoscopes. However, low power transfer efficiency (PTE) (most researches show it to be lower than 3%) and poor power received stability are the key limitation of WPT systems in such applications. Three-coil WPT systems are regarded as an effective method to improve the power transfer efficiency and power received of gastrointestinal robots. Thus, an analytical model of a three-coil inductive link was established in this paper. Then the power transfer efficiency of load coil was optimized by changing the coil turns and raising a novel coil configuration: a Helmholtz-like load coil. As a result, the power transfer efficiency and power deliver to load (PDL) of this three-coil WPT system are tremendously improved. To verify the proposed design, a prototype simulated the gastrointestinal robot working situation and it was implemented for an experimental test. The results obtained from the experimental test demonstrate that the proposed three-coil WPT system with 9 turns load coil and 40 turns receiving coil achieves a PTE of 4.32% and a PDL of 541.5 mW. Moreover, the best PTE attained by the novel Helmholtz-like load coil was 6.45% and the PDL was 845 mW.