Effect of Catalytic Properties on the Thermal Loads and Radiation Characteristics for Re-entry Capsules

Song Xiao-Xiao,Shuai Zhang,Gang Wang,Zhang Ji-Fa,Zheng Yao 한국항공우주학회 2024 International Journal of Aeronautical and Space Sc Vol.25 No.3

For the spectral characteristics of thermochemical nonequilibrium flow field gases and wall coating radiation, as well as the aerodynamic thermal loads of re-entry capsule Fire II, a finite-rate catalytic model combined with the multi-component chemical nonequilibrium N–S equation is developed. Based on this model, the effects of dissociation and recombination reactions of gas components on the wall coating temperature and heating flux are simulated. In addition, we investigate and analyze further the influence of the coating’s catalytic properties on the radiation spectral characteristic of the high-temperature nonequilibrium flow field and the wall coating radiation. The results show that the catalytic properties intensify the non-homogeneous recombination and exothermic processes near the wall surface. It results in a significant decrease in the number of component particles contributing to the radiative spectral intensity near the wall, which slightly reduces the flow field gas spectral radiation intensity. Meanwhile, the catalytic properties also increase the wall temperature and heating flux, significantly increasing the intensity of the wall radiation spectral in the near-infrared region.

Reliability Modeling and Analysis on Metallized Film Capacitors for MMC

Yao Ran,Zheng Meimei,Li Hui,Lai Wei,Wang Xiao,Long Haiyang 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

Metallized film capacitor’s (MFC’s) reliability directly affects the stable operation of MMC valve. Conventional reliability assessment method based on data statistics is limited. This paper studies the reliability modeling of MFC considering aging for the application condition of MMC valve. Firstly, the temperature field and electric field model of MFC is established, and the temperature and electric stress distribution are explored. Secondly, the lifetime model of MFC is established based on the electrical-thermal aging of dielectric films. Finally, the aging model of MFC is established from the aspect of equivalent series resistance. Results show that the aging rate of MFC increase with the service time going by, and increase sharply after 21 years. The failure rate of MFC is small at the beginning of operation, and there is a turning point in the 23rd year. Since then, the failure rate of MFC increases sharply. The lifetime of MFC is concentrated.

Structural and optical investigation of GaN grown by metal-organic Chemical Vapor Deposition

Xiao-Yong Gao,Liang-Yao Chen,Jing Li,Peng Zhou,Rong-Jun Zhang,Song-You Wang,Yue-Mei Yang,Yu-Xiang Zheng 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.44 No.32

Structural and optical properties of GaN grown on (0001)-oriented sapphire substrates by low pressure metal-organic chemical vapor deposition were investigated by XRD, ellipsometry, PL and other optical methods. The thickness of the GaN sample was about 1.5 m. Seen by XRD, the existence of the strong (0002) diraction peak with a very narrow FWHM value of 0.1 and the high order GaN (0004) diraction peak conrms a good quality of the GaN lms grown on sapphire substrate by using a multi-step growth procedure. Optical transparency of the GaN samples induces strong interference oscillations below E0 (3.44eV) in the measured dielectric function spectra and re ective spectra. In low temperature PL spectra, the red shift of the peak and decreased intensity of PL are visible. The former can be attributed to the involvement of band tail states, and the latter can be accounted for by the decreasing non-radiative recombination lifetime.

Study of the Correlation of Plasma Resonance and the Refractive Index to Dielectric Dispersion in the Complex Plane

Xiao-Yong Zhou,Yan Shen,Er-Tao Hu,Jian-Bo Chen,Yuan Zhao,Ming-Yu Sheng,Jing Li,Yu-Xiang Zheng,Hai-Bin Zhao,Liang-Yao Chen,Wei Li,Xun-Ya Jiang,이영백,David W. Lynch 한국광학회 2013 Current Optics and Photonics Vol.17 No.1

Based on the dispersive feature of the dielectric function of noble metals and the wave vector conservation in physics, both the plasma effect and the complex refractive index, which are profoundly correlated to the complex dielectric function and permeability, have been studied and analyzed. The condition to induce a bulk or a surface plasma in the visible region will not be satisfied, and there will be one solution for the real and the imaginary parts of the refractive index, restricting it only to region I of the complex plane. The results given in this work will aid in understanding the properties of light transmission at the metal/dielectric interface as characterized by the law of refraction in nature.

Dynamic temperature gradient and unfalsified control approach for machine tool thermal error compensation

Xiao-dong Yao,Zheng-Chun Du,Guang-yan Ge,Jian-Guo Yang 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.1

In this work, a novel machine tool thermal error modeling method based on dynamic temperature gradient is proposed, and a thermal error compensation method based on unfalsified control is developed. The dynamic temperature gradient is used to optimize the locations of temperature measuring points on the machine tool. Real-time compensation for the thermal error can be achieved using the developed compensation method by establishing the correlations between dynamic temperature gradient and thermal error in the machine tool. Different from traditional model-based methods, the developed compensation approach does not rely on an accurate model of the thermal error but instead uses online input/output data to adaptively select the best controller at any moment, thereby improving thermal error prediction accuracy and robustness. The effectiveness of the developed thermal error compensation method is demonstrated on a turning center, where the spindle thermal error is compensated during the manufacturing of 120 inner bore parts and 120 shaft parts. After compensation using the proposed approach, thermal errors are reduced from 27 µm to 9 µm for the inner bore parts and from 31 µm to 11 µm for the shaft parts, respectively.

Serum BMP-2 Up-regulation as an Indicator of Poor Survival in Advanced Non-small Cell Lung Cancer Patients

Fei, Zheng-Hua,Yao, Cheng-Yun,Yang, Xiao-Lei,Huang, Xin-En,Ma, Sheng-Lin Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.9

Purpose: High levels of bone morphogenetic protein (BMPs) have been reported in patients with lung cancer. This study was conducted to assess correlations between serum BMP-2 levels and prognostic outcome in patients with non-small-cell lung cancer (NSCLC). Methods: Blood samples from 84 patients with advanced NSCLC and 42 healthy controls were analyzed and quantitated for serum BMP-2 levels before and after two cycles of chemotherapy using a commercially available ELISA kit. Results: The median level of BMP-2 was 146.9 pg/ml in patients with NSCLC vs. 87.7 pg/ml in healthy controls (P<0.01). A significant correlation was observed between pretreatment serum BMP-2 level and ECOG PS, disease stage and number of organs with metastases (P<0.05). Serum BMP-2 level decreased significantly in patients who achieved objective response after two cycles of chemotherapy. Multivariate analysis showed that increased BMP-2 level and advanced clinical stage were significantly correlated with poor prognosis. Conclusion: Thes erum BMP-2 level is positively correlated with clinical stage, ECOG PS and metastatic burden and may serve as an independent negative predictor for prognosis. Decreased BMP-2 after chemotherapy could be a reliable marker for efficacy of treatment.

Control Method for Grid-Connected/Islanding Switching of Hybrid AC/DC Microgrid

Qu Zheng-Wei,Chong Zhen-Xiao,Wang Yun-Jing,Shi Zhe,Yao Yun-Xiao 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.1

For hybrid AC/DC microgrid (HMG) under master–slave control strategy, DGs usually adopt constant power control (P control) in gird-connected mode and at least one DG adopts constant voltage control (V control) in islanding mode. However, when unplanned islanding happens, the voltage and current of the HMG will experience remarkable fluctuations, which affects the system’s stability. This paper presents a control method to achieve smooth switching from grid-connected to islanding mode by introducing state tracking control between P control and V control. The state tracking control can make the current reference signal of the V control track that of the P control in grid-connected mode. When unplanned islanding happens, the mutation of the current reference signal can be tuned into a smooth transition by the voltage loop’s PI controller, and the transient oscillations can be eliminated to realize smooth switching. The effectiveness of the proposed control method is verified by simulation results using MATLAB/Simulink.

Control Method for Grid-Connected/Islanding Switching of Hybrid AC/DC Microgrid

Qu Zheng-Wei,Chong Zhen-Xiao,Wang Yun-Jing,Shi Zhe,Yao Yun-Xiao 대한전기학회 2023 Vol.18 No.1

For hybrid AC/DC microgrid (HMG) under master–slave control strategy, DGs usually adopt constant power control (P control) in gird-connected mode and at least one DG adopts constant voltage control (V control) in islanding mode. However, when unplanned islanding happens, the voltage and current of the HMG will experience remarkable fl uctuations, which aff ects the system’s stability. This paper presents a control method to achieve smooth switching from grid-connected to islanding mode by introducing state tracking control between P control and V control. The state tracking control can make the current reference signal of the V control track that of the P control in grid-connected mode. When unplanned islanding happens, the mutation of the current reference signal can be tuned into a smooth transition by the voltage loop’s PI controller, and the transient oscillations can be eliminated to realize smooth switching. The eff ectiveness of the proposed control method is verifi ed by simulation results using MATLAB/Simulink.

Ellipsometric Study of the Optical Properties of Silver Oxide Prepared by Reactive Magnetron Sputtering

Jian-Hong Qiu,Liang-Yao Chen,Jia-Ni Yu,Jing Li,Peng Zhou,Qing-Hai ong,ong-You Wang,Xiao-Yong Gao,Yue-Mei Yang,Yu-Xiang Zheng 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.2

A series of AgOx thin films were prepared by the DC-magnetron reactive-sputtering method at room temperature under different sputtering power and oxygen to argon ratio conditions. The optical properties of the AgOx films were studied by analysis of the spectroscopic ellipsometry data with the Tauc-Lorentz multi-oscillator model in the 1.5 4.5-eV photon-energy range. The spectra of absorption, XPS and PL were measured. The results indicate that the AgOx film changes from metallic to dielectric structure with increasing oxygen flux. Under the saturated oxidation condition after annealing, the dominating component will be Ag2O in the film to show indirect interband transitions occurring at about 0.57 eV and 2.43 eV, respectively, that are in agreement with the results of PL measurement and Lorentz analysis.

Hydrogen sulfide inhibits the growth of Escherichia coli through oxidative damage

Liu-Hui Fu,Zeng-Zheng Wei,Kang-Di Hu,Lan-Ying Hu,Yan-Hong Li,Xiao-Yan Chen,Zhuo Han,Gai-Fang Yao,Hua Zhang 한국미생물학회 2018 The journal of microbiology Vol.56 No.4

Many studies have shown that hydrogen sulfide (H2S) is both detrimental and beneficial to animals and plants, whereas its effect on bacteria is not fully understood. Here, we report that H2S, released by sodium hydrosulfide (NaHS), significantly inhibits the growth of Escherichia coli in a dose-dependent manner. Further studies have shown that H2S treatment stimulates the production of reactive oxygen species (ROS) and decreases glutathione (GSH) levels in E. coli, resulting in lipid peroxidation and DNA damage. H2S also inhibits the antioxidative enzyme activities of superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR) and induces the response of the SoxRS and OxyR regulons in E. coli. Moreover, pretreatment with the antioxidant ascorbic acid (AsA) could effectively prevent H2S-induced toxicity in E. coli. Taken together, our results indicate that H2S exhibits an antibacterial effect on E. coli through oxidative damage and suggest a possible application for H2S in water and food processing.