Velocity Control of Permanent Magnet Stepper Motor Using Nonsingular Terminal Sliding Mode Controller

WEIMING YANG(양위명),Yong Woo Jeong(정용우),Chung Choo Chung(정정주) 제어로봇시스템학회 2019 제어로봇시스템학회 국내학술대회 논문집 Vol.2019 No.5

Template-free hydrothermal synthesis of hollow alumina microspheres and its excellent catalytic properties for thiolation

WeiMing Wang,Shuai Peng,XinTian Chen,YingMing Chen,Chuang Peng,Dong Zeng,Jun Xiong,Hao Liu,XiXian Yang,Ming Li 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.118 No.-

In view of the important industrial application value of alumina supports in the field of oil refining andreforming, it is of great significance to develop a simple and economical synthesis method for the hierarchicalporous alumina. Herein, the hollow microsphere alumina was hydrothermally synthesized withouttemplate. The surface of the hollow microsphere alumina supports has a raised fluffy structure, themicrosphere diameter is about 5 8 lm, and the thickness of the shell is about 1 lm. The morphologyevolution process from solid microspheres to core–shell microspheres with spindle-shaped nanoclusters,and then to hollow fluffy microspheres with protruding surface was observed by investigating the effectof hydrothermal synthesis temperature on the morphology of microspheres. Because of its specific morphologyand surface characteristics, the microsphere can better disperse the active component KW toprepare KW/Al2O3 catalyst and used in the thiolation to methyl mercaptan. Compared with our previouslyused catalysts prepared from commercial alumina, this KW/Al2O3 catalyst was not only able togreatly reduce the amount of active component, but also exhibited higher CH3SH selectivity. On the10KW/Al catalyst, the CH3SH selectivity reached 66.2 % at 340 C, which was about 10 % higher than thatof the previous commercial alumina catalyst. This work can provide theoretical basis and practical guidancefor the reasonable design of new alumina support and high efficiency methyl mercaptan catalyst.

Enzymatic Desymmetrization of 3-(4-Fluorophenyl)glutaric Anhydride through Enantioselective Alcoholysis in Organic Solvents

Weiming Liu,Yi Hu,Yang Zhang,Yan Ma,He Huang 한국생물공학회 2014 Biotechnology and Bioprocess Engineering Vol.19 No.3

The enzymatic desymmetrization of 3-(4-fluorophenyl)glutaric anhydride (3-FGA) was investigatedthrough lipase-catalyzed enantioselective alcoholysis inorganic solvents. An immobilized Lipase B from CandidaAntarctica (Novozym 435) was found to be an efficientbiocatalyst for the enantioselective alcoholysis of 3-FGA. Methyl tert-butyl ether (MTBE) and methanol were chosenas the suitable reaction medium and acyl acceptor,respectively. The optimum reaction temperature, molarratio of methanol to 3-FGA and 3-FGA concentration were25oC, 2:1 and 100 mM, respectively. Under these conditions,complete conversion was achieved and methyl (S)-3-(4-fluorophenyl)glutarate ((S)-MFG) was obtained in a moderateee value of 80%. Furthermore, the reaction was performedon a gram scale and the ee value of (S)-MFG was enrichedto 96% after treatment with a toluene/hexane (2/1, v/v)mixture.

The Significantly Enhanced Mechanical and Tribological Performances of the Dual Plasma Nitrided and PVD Coated Ti6Al4V Alloy

Jiaqiang Yang,Kai Le,Hui Chen,Xu Zhao,Xiaodong Xie,Yong Luo,Shusheng Xu,Weiming Liu 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.4

In this work, plasma pre-nitriding technique has been employed to enhance the bearing capacity for the TiN coating deposited on Ti6Al4V alloy by magnetron sputtering. The composition, morphology and mechanical property of the as-prepared samples were studied by the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), Vickers micro-hardness tester and nanoindentater. The tribological properties are investigated using a rotary tribometer under dry sliding and oil lubrication, and the mechanism was also discussed in details. The results show that the plasma nitriding treatment produced a nitrided layer with thickness of 85 μm on the surface of Ti6Al4V alloy, which significantly enhanced the mechanical properties. Therefore, the as-prepared TiN coated sample with plasma pre-nitriding treatment exhibit more excellent mechanical properties possessing the maximum hardness values (26 GPa) and exceptional load bearing capacity (74 N) compared to single TiN-coated Ti6Al4V. Moreover, the tribological properties of sample with plasma pre-nitriding treatment was also significantly improved, which was attributed to the synergistic effect of the superior bearing performance of nitriding layer and the high hardness of TiN coating. Additionally, wear mechanisms were discussed in terms of wear track morphology after sliding test.

A NONSTANDARD FINITE DIFFERENCE METHOD APPLIED TO A MATHEMATICAL CHOLERA MODEL

Liao, Shu,Yang, Weiming Korean Mathematical Society 2017 대한수학회보 Vol.54 No.6

In this paper, we aim to construct a nonstandard finite difference (NSFD) scheme to solve numerically a mathematical model for cholera epidemic dynamics. We first show that if the basic reproduction number is less than unity, the disease-free equilibrium (DFE) is locally asymptotically stable. Moreover, we mainly establish the global stability analysis of the DFE and endemic equilibrium by using suitable Lyapunov functionals regardless of the time step size. Finally, numerical simulations with different time step sizes and initial conditions are carried out and comparisons are made with other well-known methods to illustrate the main theoretical results.

A nonstandard finite difference method applied to a mathematical cholera model

Shu Liao,Weiming Yang 대한수학회 2017 대한수학회보 Vol.54 No.6

In this paper, we aim to construct a nonstandard finite difference (NSFD) scheme to solve numerically a mathematical model for cholera epidemic dynamics. We first show that if the basic reproduction number is less than unity, the disease-free equilibrium (DFE) is locally asymptotically stable. Moreover, we mainly establish the global stability analysis of the DFE and endemic equilibrium by using suitable Lyapunov functionals regardless of the time step size. Finally, numerical simulations with different time step sizes and initial conditions are carried out and comparisons are made with other well-known methods to illustrate the main theoretical results.

Plastic Deformation Mechanism of Ductile Fe50Ni30P13C7 Metallic Glass

Kangkang Geng,Weiming Yang,Jinyong Mo,Haishun Liu,Feng Wei,Zhanguo Ma,Yucheng Zhao,Akihisa Inoue 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.2

Shear band (SB) multiplication is considered as an essential characteristic of the plastic deformation in metallic glasses(MGs). In this work, the evolutionary characteristics of SBs and serrated behavior in ductile Fe50Ni30P13C7MGs werestudied by the finite element method simulation. The study demonstrated that the stress field would redistribute and becomeinhomogeneous during SB sliding, where the stress perpendicular to the original SB gradually accumulates until reachingthe magnitude of yielding strength and triggering new SBs. The results of simulation are in good agreement with the SBsintersection morphologies observed in SEM images and the serration flows on the stress–strain curves. Furthermore, severalfactors affecting stress field distribution in MGs, such as contact friction, aspect ratio, and boundary confinement, werealso analyzed and discussed. The overall results indicate that the ductility of Fe-based MGs could be achieved without anyinhomogeneous structure, and scientifically explicate the dependence of SB multiplication on both material properties andloading condition, which can provide us with a deeper understanding on plastic deformation mechanism of MGs.

Novel Strategy for Reducing Residual Stress in Titanium Alloy Parts Obtained via Additive Manufacturing

Xinfa Sun,Yucheng Zhao,Weiming Yang,Wenyu Li,Dengfeng Yang,Haishun Liu 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.12

The additive manufacturing of titanium alloy parts has important scientific significance and practical value. Controllingthe distribution of residual stress caused by the high cooling rate and temperature gradient is the key to regulating the performanceof devices obtained from additive manufacturing. In this work, the effects of the interlayer scanning angle on theresidual stress in Ti–6Al–4V parts manufactured by selective laser melting were investigated by finite element simulations. We studied how changing the interlayer deflection angle alleviated residual stress under different energy inputs. The resultsshowed that the residual stress in the z-direction was reduced by the deflection angle of 67° and 90°, and the non-uniformdistribution of residual stress was reduced by a deflection angle of 67°. The combination of a chessboard pattern and interlayerdeflection angle greatly alleviated the generation of residual stress. This work has important guiding significance forthe additive manufacturing design of high-quality and high-performance titanium alloy devices.

Study on activity of the signaling pathways regulating hepatocyte differentiation during rat liver regeneration

Cuifang Chang,Cunshuan Xu,Weiming Zhao,Jing Yang,Menghua Li,Yun Zhou 한국통합생물학회 2014 Animal cells and systems Vol.18 No.6

To understand the mechanism of hepatocyte differentiation during rat liver regeneration (LR) at the genetranscription level, Rat Genome 230 2.0 Array was used to determine the gene expression changes ofhepatocytes. Then the genes associated with cell differentiation and their signaling pathways were searched byNCBI, QIAGEN and KEGG webs, and their signaling activities were calculated by spectral function Ep(t)based on the expression profiles. The key genes associated with the signaling pathways and cell differentiationwere analyzed and verified by the same kind extraction method. The mechanism of hepatocyte differentiationduring rat LR was analyzed by Ingenuity Pathway Analysis 9.0 (IPA). The results showed that 42 signalingpathways regulated cell differentiation and the Ep(t) values of IL-9 signaling pathway and its JAK/STAT andPI3K/AKT branches, PEDF signaling pathway and its NF-κB and Ras/ERK branches were significantlyincreased in the progression phase (6–72 h after partial hepatectomy [PH]) of rat LR, and the Ep(t) values ofhepatocyte differentiation were also significantly increased. ERK/MAPK signaling pathway was significantlyincreased in the priming (0.5–6 h after PH) and progression phase, and hepatocyte differentiation were alsosignificantly increased. In conclusion, among the 42 signaling pathways that regulated cell differentiation, thesignaling activity of IL-9 signaling pathway and its JAK/STAT and PI3K/AKT branches, PEDF signalingactivity and its NF-κB and Ras/ERK branches, and ERK/MAPK signaling activity were significantly increasedand promoted hepatocyte differentiation in rat LR. Meanwhile, the expression of MYC involved in mentionedsignaling pathways and expression of AGT, BCL2, IL10, CCND1, PLAT, and NF1 related to celldifferentiation were increased significantly.

Serial Frozen Fecal Microbiota Transplantation in the Treatment of Chronic Intestinal Pseudo-obstruction: A Preliminary Study

( Lili Gu ),( Chao Ding ),( Hongliang Tian ),( Bo Yang ),( Xuelei Zhang ),( Yue Hua ),( Yifan Zhu ),( Jianfeng Gong ),( Weiming Zhu ),( Jieshou Li ),( Ning Li ) 대한소화기기능성질환·운동학회(구 대한소화관운동학회) 2017 Journal of Neurogastroenterology and Motility (JNM Vol.23 No.2

Background/Aims Chronic intestinal pseudo-obstruction (CIPO) is a serious, life-threatening motility disorder that is often related to bacterial overgrowth. Fecal microbiota transplantation (FMT) results in restoration of the normal intestinal microbial community structure. We investigated the efficacy of FMT in the treatment of CIPO patients. Methods Nine patients (age 18-53 years) with CIPO were enrolled in this prospective, open-label study. Patients received FMT for 6 consecutive days through nasojejunal (NJ) tubes and were followed up for 8 weeks after treatment. We evaluated the rate of clinical improvement and remission, feeding tolerance of enteral nutrition, and CT imaging scores of intestinal obstructions. Lactulose hydrogen breath tests were performed before FMT and 8 weeks after FMT to evaluate for the presence small intestinal bacterial overgrowth (SIBO). Results FMT significantly alleviated bloating symptoms, and symptoms of pain were relieved 2 weeks after FMT. Enteral nutrition administered through a NJ tube after FMT was well-tolerated by 66.7% (6/9) of patients. CT scores of intestinal obstructions were significantly reduced after FMT (P = 0.014). SIBO was eliminated in 71.0% (5/7) of patients. Conclusions This pilot study demonstrated the safety of using FMT. FMT may relieve symptoms in selected patients with CIPO. FMT may also improve patient tolerance of enteral nutrition delivered via a NJ tube. (J Neurogastroenterol Motil 2017;23:289-297)