3D quasi-transient thermo-mechanical analysis for vehicle brake disc

Biao Hu,Xingyan Zhang,Yang Liu,Junjie Yan,Xiaobing Liu,Xin Wang,Richard Sun 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.2

An alternative numerical method is developed to predict the thermo-mechanical behavior of brake disc during braking. Steady-state aerodynamic simulation for entire vehicle with variant speeds are conducted to analyze the convective heat transfer characteristic of the disc surface. Then the transient heat transfer boundary of the disc is obtained by interpolating the steady-state simulation results. Based on that, the transient thermo-mechanical coupled simulation for brake disc is performed via finite element method. With those work, the characteristics of transient temperature field and stress field of the brake disc are analyzed. Meanwhile, the characteristic of contact pressure distribution on friction interface is also obtained. The results show that during the braking process, for any node in the friction areas of the brake disc surface, its temperature rise curve fluctuates like a sawtooth. The temperature field has a significant effect on the stress field of the brake disc, both in distribution and variation. To verify the numerical method and validate the simulation results, a full-scale vehicle brake-thermalperformance test is carried out. By comparison, the simulation results show good agreement with the experimental results. The proposed numerical method enables an efficient and economical way to predict and evaluate the thermo-mechanical behavior of the brake disc in early phase of vehicle development.

Low pH stress responsive transcriptome of seedling roots in wheat (Triticum aestivum L.)

Haiyan Hu,Jie He,Junjie Zhao,Xingqi Ou,Hongmin Li,Zhengang Ru 한국유전학회 2018 Genes & Genomics Vol.40 No.11

Soil acidification is one of major problems limiting crop growth and especially becoming increasingly serious in China owing to excessive use of nitrogen fertilizer. Only the STOP1 of Arabidopsis was identified clearly sensitive to proton rhizotoxicity and the molecular mechanism for proton toxicity tolerance of plants is still poorly understood. The main objective of this study was to investigate the transcriptomic change in plants under the low pH stress. The low pH as a single factor was employed to induce the response of the wheat seedling roots. Wheat cDNA microarray was used to identify differentially expressed genes (DEGs). A total of 1057 DEGs were identified, of which 761 genes were up-regulated and 296 were downregulated. The greater percentage of up-regulated genes involved in developmental processes, immune system processes, multi-organism processes, positive regulation of biological processes and metabolic processes of the biological processes. The more proportion of down-regulation genes belong to the molecular function category including transporter activity, antioxidant activity and molecular transducer activity and to the extracellular region of the cellular components category. Moreover, most genes among 41 genes involved in ion binding, 17 WAKY transcription factor genes and 17 genes related to transport activity were up-regulated. KEGG analysis showed that the jasmonate signal transduction and flavonoid biosynthesis might play important roles in response to the low pH stress in wheat seedling roots. Based on the data, it is can be deduced that WRKY transcription factors might play a critical role in the transcriptional regulation, and the alkalifying of the rhizosphere might be the earliest response process to low pH stress in wheat seedling roots. These results provide a basis to reveal the molecular mechanism of proton toxicity tolerance in plants.

Effects of Isosorbide on the Microphase Separation and Properties of Waterborne Polyurethane Coatings

Jun Hu,Can Tao,Aining Yuan,Junjie Bao,Qin Cheng,Gewen Xu,Yiping Huang 한국고분자학회 2019 폴리머 Vol.43 No.2

Series of waterborne polyurethanes (WPUs) containing poly(tetra methylene glycol) (PTMG), 4,4-dicyclohexylmethane diisocyanate (HMDI), 2,2-dimethylolpropionic acid (DMPA), 2,2,4-trimethyl-1,3-pentanediol (TMPD), isosorbide (ISO) and ethylenediamine (EDA) were synthesized. The effects of ISO on the structure and properties of WPUs were studied by gel permeation chromatography (GPC), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), dynamic mechanical analyzer (DMTA), X-ray diffraction (XRD), thermogravimetry (TG), mechanical test, chemical resistance and hardness test. The deconvolution analysis of FTIR of WPUs revealed that the hydrogen bond interaction in the WPUs increased with the increase of ISO content. Furthermore, the degree of microphase separation was increased with the increase of hydrogen bond interaction, which was confirmed by DSC, XRD and DMTA test. The results demonstrated that the addition of ISO can increase the hydrogen bond interaction between the hard and hard segments in WPUs, which improved the mechanical properties of the WPU films. The highest tensile strength was obtained of 59.67 MPa when the content of isosorbide was 10.35 wt%. Moreover, the ISO was helpful to improve the chemical resistance and hardness of the coatings by the comprehensive performance analysis.

Molecular dynamics simulation of tensile behavior of diffusion bonded Ni/Al nanowires

Zhenjiang Hu,Junjie Zhang,Yong Da Yan,Jiuchun Yan,Tao Sun,김동철,강성원 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.1

Interfaces play key roles in determining mechanical properties of materials. In current work we perform molecular dynamics simulations of diffusion bonding to evaluate the effect of temperature on the morphology of the Ni/Al interface and the strength of the diffusion bonded Ni/Al nanowires. The centro-symmetry parameter is adopted to identify defect atoms generated. Simulation results show that the thickness of the Ni/Al interface has strong dependence on the temperature of diffusion bonding. Following uniaxial tension tests indicate that the yield strength of Ni/Al nanowires is smaller than both the single crystalline Ni and Al nanowires, because of the Ni/Al interface acting as dislocation source and the mobilization of pre-existing dislocations at high temperature. It is shown that the mechanical properties of diffusion bonded Ni/Al nanowires strongly depend on the temperature.

A Neutral-Point Voltage Balance Controller for the Equivalent SVPWM Strategy of NPC Three-Level Inverters

Lyu, Jianguo,Hu, Wenbin,Wu, Fuyun,Yao, Kai,Wu, Junji The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6

Based on the space vector pulse width modulation (SVPWM) theory, this paper realizes an easier SVPWM strategy, which is equivalently implemented by CBSPWM with zero-sequence voltage injection. The traditional SVPWM strategy has no effect on controlling the neutral-point voltage balance. In order to solve the neutral-point voltage unbalance problem for neutral-point-clamped (NPC) three-level inverters, this paper proposes a neutral-point voltage balance controller. The proposed controller realizes controlling the neutral-point voltage balance by dynamically calculating the offset superimposed to the three-phase modulation waves of an equivalent SVPWM strategy. Compared with the traditional SVPWM strategy, the proposed neutral-point voltage balance controller has a strong ability to balance the neutral-point voltage, has good steady-state performance, improves the output waveforms quality and is easy for digital implementation. An experiment has been carried out on a NPC three-level inverter prototype based on a digital signal processor-complex programmable logic device (DSP-CPLD). The obtained experimental results verify the effectiveness of the proposed neutral-point voltage balance controller.

A New DPWM Method to Suppress the Low Frequency Oscillation of the Neutral-Point Voltage for NPC Three-Level Inverters

Lyu, Jianguo,Hu, Wenbin,Wu, Fuyun,Yao, Kai,Wu, Junji The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.5

In order to suppress the low frequency oscillation of the neutral-point voltage for three-level inverters, this paper proposes a new discontinuous pulse width modulation (DPWM) control method. The conventional sinusoidal pulse width modulation (SPWM) control has no effect on balancing the neutral-point voltage. Based on the basic control principle of DPWM, the relationship between the reference space voltage vector and the neutral-point current is analyzed. The proposed method suppresses the low frequency oscillation of the neutral-point voltage by keeping the switches of a certain phase no switching in one carrier cycle. So the operating time of the positive and negative small vectors is equal. Comparing with the conventional SPWM control method, the proposed DPWM control method suppresses the low frequency oscillation of the neutral-point voltage, decreases the output waveform harmonics, and increases both the output waveform quality and the system efficiency. An experiment has been realized by a neutral-point clamped (NPC) three-level inverter prototype based on STM32F407-CPLD. The experimental results verify the correctness of the theoretical analysis and the effectiveness of the proposed DPWM method.

Loss of Pten synergizes with c-Met to promote hepatocellular carcinoma development via mTORC2 pathway

Zhong Xu,Junjie Hu,Hui Cao,Maria G Pilo,Antonio Cigliano,Zixuan Shao,Meng Xu,Silvia Ribback,Frank Dombrowski,Diego F Calvisi,Xin Chen 생화학분자생물학회 2018 Experimental and molecular medicine Vol.50 No.-

Hepatocellular carcinoma (HCC) is a deadly malignancy with limited treatment options. Activation of the AKT/mTOR cascade is one of the most frequent events along hepatocarcinogenesis. mTOR is a serine/threonine kinase and presents in two distinct complexes: mTORC1 and mTORC2. While mTORC1 has been extensively studied in HCC, the functional contribution of mTORC2 during hepatocarcinogenesis has not been well characterized, especially in vivo. Pten expression is one of the major mechanisms leading to the aberrant activation of the AKT/mTOR signaling. Here, we show that concomitant downregulation of Pten and upregulation of c-Met occurs in a subset of human HCC, mainly characterized by poor prognosis. Using CRISPR-based gene editing in combination with hydrodynamic injection, Pten was deleted in a subset of mouse hepatocytes (sgPten). We found that loss of Pten synergizes with overexpression of c-Met to promote HCC development in mice (sgPten/c-Met). At the molecular level, sgPten/c-Met liver tumor tissues display increased AKT and mTOR signaling. Using Rictor conditional knockout mice, we demonstrate that sgPten/c-Met-driven HCC development strictly depends on an intact mTORC2 complex. Our findings therefore support the critical role of mTORC2 in hepatocarcinogenesis. sgPten/c-Met mouse model represents a novel valuable system that can be used for the development of targeted therapy against this deadly malignancy.

A Neutral-Point Voltage Balance Controller for the Equivalent SVPWM Strategy of NPC Three-Level Inverters

Jianguo Lyu,Wenbin Hu,Fuyun Wu,Kai Yao,Junji Wu 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6

Based on the space vector pulse width modulation (SVPWM) theory, this paper realizes an easier SVPWM strategy, which is equivalently implemented by CBSPWM with zero-sequence voltage injection. The traditional SVPWM strategy has no effect on controlling the neutral-point voltage balance. In order to solve the neutral-point voltage unbalance problem for neutral-point-clamped (NPC) three-level inverters, this paper proposes a neutral-point voltage balance controller. The proposed controller realizes controlling the neutral-point voltage balance by dynamically calculating the offset superimposed to the three-phase modulation waves of an equivalent SVPWM strategy. Compared with the traditional SVPWM strategy, the proposed neutral-point voltage balance controller has a strong ability to balance the neutral-point voltage, has good steady-state performance, improves the output waveforms quality and is easy for digital implementation. An experiment has been carried out on a NPC three-level inverter prototype based on a digital signal processor-complex programmable logic device (DSP-CPLD). The obtained experimental results verify the effectiveness of the proposed neutral-point voltage balance controller.

New DPWM Method to Suppress the Low Frequency Oscillation of the Neutral-Point Voltage for NPC Three-Level Inverters

Jianguo Lyu,Wenbin Hu,Fuyun Wu,Kai Yao,Junji Wu 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.5

In order to suppress the low frequency oscillation of the neutral-point voltage for three-level inverters, this paper proposes a new discontinuous pulse width modulation (DPWM) control method. The conventional sinusoidal pulse width modulation (SPWM) control has no effect on balancing the neutral-point voltage. Based on the basic control principle of DPWM, the relationship between the reference space voltage vector and the neutral-point current is analyzed. The proposed method suppresses the low frequency oscillation of the neutral-point voltage by keeping the switches of a certain phase no switching in one carrier cycle. So the operating time of the positive and negative small vectors is equal. Comparing with the conventional SPWM control method, the proposed DPWM control method suppresses the low frequency oscillation of the neutral-point voltage, decreases the output waveform harmonics, and increases both the output waveform quality and the system efficiency. An experiment has been realized by a neutral-point clamped (NPC) three-level inverter prototype based on STM32F407-CPLD. The experimental results verify the correctness of the theoretical analysis and the effectiveness of the proposed DPWM method.

Low-loss carrier-stored IGBT with p-type Schottky diode-clamped shielding layer

Yi, Bo,Zhao, Qing,Zhang, Qian,Cheng, JunJi,Huang, HaiMeng,Pan, YiLan,Hu, XiaoRan,Xiang, Yong The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.8

A novel carrier-stored trench bipolar transistor (CSTBT) with heavily doped carrier-stored layer (CSL) is proposed and investigated by TCAD tools. The voltage of CSL is shielded by a buried p-type layer (P-bury) whose potential is clamped by a p-type Schottky Barrier Diode (pSBD) in series-connection with a PN diode. Hence, the CSL can be heavily doped, and the trade-off between on-state voltage drop (V_on) and turn-off loss (E_off) is substantially improved. Compared with that of a conventional CSTBT with floating P-base (FP-CSTBT), the E_off of the proposed CSTBT is reduced by 27.9% at V_on=1.1 V. Owing to the shielding effect of the P-bury layer, the saturation current density of the proposed CSTBT is reduced by 52% compared with that of the FP-CSTBT. Consequently, significantly enlarged short-circuit safe operation area is obtained, and the short-circuit withstand time (t_sc) is increased to 12.8 s at ultra-low V_on (~1.1 V).