Effect of Different Cooling Rates in High Rheological Rate Forming Process on Mechanical Properties of Zr57Cu20Al10Ni8Ag5 Bulk Metallic Glass

Xiao‑Bo Mei,Bao‑Chuan Liu,Wei Jiang,Quan Xu,Qi‑Dong Zhang,Yu‑Bai Ma,Fang‑Qiu Zu 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.9

The influence of cooling rates on the mechanical properties of a Zr-based bulk metallic glass prepared with high rheologicalrate forming (HRRF) was investigated and compared with traditional suction cast methods. Amorphous samples of Zr57Cu-20Ni8Al10Ag5 were prepared in copper molds with different sizes in order to obtain different cooling rates for both HRRFand traditional cast methods. These specimens were subjected to compression experiments, including microhardness testing,X-ray diffraction testing and differential scanning calorimetry analysis. The results indicate that the plasticity of the samplesformed by HRRF are higher than that of the as-cast ones at the same cooling rates, while the microhardness manifests theopposite principle. As the cooling rate increases further, the difference in plasticity further increases between two methods,indicating that the plasticity of metallic glasses is more sensitive to cooling rates during the HRRF process. At the core ofthis phenomenon is the fact that HRRF methods can introduce more free volume into glasses than traditional cast methodswith an elevated cooling rate are able to.

Finite-time and Fixed-time Bipartite Consensus Tracking for Second-order Multi-agent Systems via an Integral Sliding-mode Approach

Xiao-Feng Zhao,Tao Han,Bo Xiao,Xi-Sheng Zhan,Huaicheng Yan 제어·로봇·시스템학회 2023 International Journal of Control, Automation, and Vol.21 No.12

This paper investigates the finite-time and fixed-time bipartite consensus tracking (Fin- and Fix-TBCT) problems for second-order multi-agent systems (MASs) under a signed directed communication network, in which both cooperative and competition exist. To achieve bipartite consensus tracking (BCT) within finite time and fixed time, two novel distributed control protocols utilizing integral sliding-mode control concept are presented and discussed, respectively. By virtue of Lyapunov stability and homogeneity with dilation, several sufficient conditions for achieving Fin- and Fix-TBCT for second-order MASs are obtained. Eventually, numerical simulation results are provided to verify the validity of the obtained theoretical results.

A direct-integration-based structural reliability analysis method using non-probabilistic convex model

Xiao-Bo Nie,Haibin Li 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.11

In practical structural reliability analysis, there is not only random uncertainty but also fuzzy uncertainty. Aiming at the fuzzy reliability of structure, a novel fuzzy reliability method is proposed based on direct integration method and ellipsoidal convex model. Firstly, the decomposition of fuzzy mathematics principle is used to convert fuzzy reliability model into non-probabilistic reliability model, in which fuzzy variables are converted into interval variables. The upper and lower bounds of interval variables are determined by the possibility distribution function on the membership value. Secondly, multidimensional ellipsoid convex models are constructed to quantify the uncertainty because of the complexity of non-probabilistic reliability. Finally, sigmoid function with adjustable parameter is introduced to direct integration method for approximating the step function, and then direct integration method is used to solve the fuzzy reliability. Numerical examples are investigated to demonstrate the effectiveness of the present method, which provides a feasible way for the structural fuzzy reliability analysis.

Nanoparticle Realgar Powders Induce Apoptosis in U937 Cells through Caspase MAPK and Mitochondrial Pathways

Xiao-bo Wang,Hui-yuan Gao,Bai-ling Hou,Jian Huang,Rong-gang Xi,Li-jun Wu 대한약학회 2007 Archives of Pharmacal Research Vol.30 No.5

Nanoparticle realgar powders (NRP) inhibited U937 cell growth in a time and dose-dependent manner. U937 cells treated with NRP showed typical characteristics of apoptosis including the morphological changes and DNA fragmentation. Caspase family inhibitor (z-VAD-fmk), caspase-8, -9 inhibitor (z-IETD-fmk, Ac-LEHD-CHO, respectively) and caspase-3 inhibitor (z- DEVD-fmk) partially prevented NRP -induced apoptosis. Moreover, the classical substrates of caspase-3, poly-ADP ribose polymerase (PARP) was degraded after U937 cells treatment with NRP. In addition, NRP increased the ratio of Bax/Bcl-2 protein expression. Although p38 inhibitor (SB203580) and ERK inhibitor (PD98059) failed to block cell death, JNK inhibitor (SP600125) had marked inhibitory effects on NRP -induced apoptosis. Furthermore, the phosphorylation of JNK was up-regulated, suggesting that JNK was responsible for NRP -induced apoptosis in U937 cells. These results suggested that the caspase, mitochondria and MAPK signal pathways were involved in NRP-induced U937 apoptosis.

LncRNA Taurine-Upregulated Gene 1 Promotes Cell Proliferation by Inhibiting MicroRNA-9 in MCF-7 Cells

Xiao-bo Zhao,Guo-sheng Ren 한국유방암학회 2016 Journal of breast cancer Vol.19 No.4

Purpose: This study was designed to investigate the role of taurine- upregulated gene 1 (TUG1) in MCF-7 breast cancer cells and the molecular mechanism involved in the regulation of microRNA- 9 (miR-9). Methods: The expression of TUG1 in breast cancer tissues and cells was evaluated using quantitative reverse transcription polymerase chain reaction. Cell viability was examined using a 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-Htetrazolium bromide (MTT) assay; cell cycle progression and apoptosis were analyzed using flow cytometry. A dual luciferase reporter assay was used to detect the relationship between TUG1 and miR-9. The expression of methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) was measured by western blot. Results: Higher expression of TUG1 was observed in breast cancer tissues and cell lines than in the corresponding controls. TUG1 knockdown reduced proliferation, suppressed cell cycle progression, and promoted apoptosis of MCF-7 cells. The dual luciferase reporter assay showed that TUG1 could negatively regulate the expression of miR-9. MiR-9 inhibition abrogated the effect of TUG1 knockdown on the proliferation, cell cycle progression, and apoptosis of MCF-7 cells. TUG1 positively regulated the expression of MTHFD2 in breast cancer cells. Conclusion: TUG1 knockdown was significantly associated with decreased cell proliferation and it promoted apoptosis of breast cancer cells through the regulation of miR-9.

Surface quality prediction model of nano-composite ceramics in ultrasonic vibration-assisted ELID mirror grinding

Bo Zhao,Fan Chen,Xiao-feng Jia,Chong-yang Zhao,Xiao-bo Wang 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.4

Ultrasonic vibration-assisted Electrolytic in-process dressing (ELID) grinding is a highly efficient and highly precise machining method. The surface quality prediction model in ultrasonic vibration-assisted ELID mirror grinding was studied. First, the interaction between grits and workpiece surface was analyzed according to kinematic mechanics, and the surface roughness model was developed. The variations in surface roughness under different parameters was subsequently calculated and analyzed by MATLAB. Results indicate that compared with the ordinary ELID grinding, ultrasonic vibration-assisted ELID grinding is superior, because it has more stable and better surface quality and has an improved range of ductile machining.

Preparation of Homogeneous Microstructure Pure Lead Metaniobate by Two-Step Sintering

Xiao-gang Zhao,Peng Liu,Bo Chao,Su Juan Liu,Ming Pang,Xiao-Ming Chen,Jian-Ping Zhou 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.1

The purpose of the present work is to obtain the Lead metaniobate ceramics with the orthorhombic phase via a two-step sintering method. The samples were first sintered at 1320°C for 10 min, and then sintered separately at 1260°C, 1220°C, and 1180°C for 4 h. All the ceramics show orthorhombic phase and homogeneous microstructure. It was found that the abnormal grain growth was restrained obviously.

Acoustic system design and experimental research on the ultrasonic forming grinding gear

Xiao-bo Wang,Mingqiang Wu,Jiangwei Jin,Bo Zhao 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.8

In order to obtain high-performance gear elements with integrated shape, using non-resonant theory, the gear grinding experiment and ultrasound-assisted grinding acoustic system were established. Firstly, a theoretical model founded on the non-resonant proposed methodology was constructed. The frequency equation and displacement characteristics of the vibration system were established based on the specified boundary conditions, and the geometric size of the ultrasonic amplitude with a design frequency of 20 kHz was established. The acoustic system was simulated employing finite element software, and the analysis revealed that its frequency range was 19648 Hz, which was consistent with the design outcome. Meanwhile, the amplitude of the end surface of the tool gear reaches 5.59 μm, and the vibration was stable. Secondly, according to the solution of geometric parameters, the acoustic performance test was carried out. The error between resonant frequency (20387 Hz) and design frequency was 1.93 %, and the amplitude was 4.5 μm, which met the requirements of ultrasonic assisted grinding gear. Finally, the grinding test was carried out. The study results show that compared to conventional gear grinding, ultrasonic supported grinding lessens the grinding force by 11.5 % to 35.4 % and, at most, lowers the grinding temperature by 22.5 %.

Theoretical Analysis and Optimization of Extrinsic Fabry-Perot Interferometer Optical-fiber Humidity-sensor Structures

Xiao Lei Yin,Ning Wang,Xiao Dan Yu,Yu Hao Li,Bo Zhang,Dai Lin Li 한국광학회 2021 Current Optics and Photonics Vol.5 No.6

The theoretical analysis and optimization of extrinsic Fabry-Perot interferometer (EFPI) opticalfiber humidity sensors are deeply investigated. For a typical dual-cavity structure composed of an optical fiber and a humidity-sensitive membrane (HSM), the changes in refractive index (RI) and initial length are discussed for polymer materials and porous oxide materials when relative humidity (RH) increases. The typical interference spectrum is simulated at different RH using MATLAB. The spectral change caused by changing HSM RI and initial length are simulated simutineously, showing different influences on humidity response. To deeply investigate the influence on RH sensitivity, the typical response sensitivity curves for different HSM lengths and air-cavity lengths are simulated. The results show that the HSM is the vital factor. Short HSM length can improve the sensitivity, but for HSM RI and length the influences on sensitivity are opposite, because of the opposite spectral-shift trend. Deep discussion and an optimization method are provided to solve this problem. According to analysis, an opaque HSM is helpful to improve sensitivity. Furthermore, if using an opaque HSM, a short air cavity and long HSM length can improve the sensor’s sensitivity These results provide deep understanding and some ideas for designing and optimizing highly sensitive EFPI fiber humidity sensors.

Bacterial and Fungal Diversity in the Starter Production Process of Fen Liquor, a Traditional Chinese Liquor

Xiao-Ran Li,En-Bo Ma,Liang-Zhen Yan,Han Meng,Xiao-Wei Du,Zhe-Xue Quan 한국미생물학회 2013 The journal of microbiology Vol.51 No.4

Fermented foods and beverages are important parts of human diet. Fen liquor, a Chinese liquor is a fermented beverage that uses a traditional fermentation process. Starters are the main microbial source and also provide nutrients for microorganisms during fermentation. In this study, starters of Fen liquor were produced through a complex traditional fermentation process. To investigate the community structure and the composition of microorganisms in the starter production process, bacterial 16S rRNA and fungal internal transcribed spacer (ITS) regions were sequenced using clone libraries and pyrosequencing, respectively. There was much higher diversity among the bacteria than among the fungi in the starter production process. Bacteria on the surface of the starters belonged mostly to the Lactobacillaceae family,while members of the Bacillacae family were dominant in the interior of the samples that lacked access to air and water. In the fungi population, diversity was high only in the raw material. In all other samples, nearly all of the fungal sequences were from Pichia kudriavzevii, a member of the Saccharomycetaceae family. Nearly all samples showed similar fungal community structures, indicating that there was little change in the fungal community. To the best of our knowledge, this is the first report to reveal the whole process of the starter production of Chinese traditional liquor. The findings obtained in this study provide new insights into understanding the composition of the microbial community during the traditional Chinese liquor starter production process and information about the production process control and monitoring.