Synthesis of Co:MgAl2O4 nano-powders for saturable absorber

Wang Chuanyun,Yang Wei,Wang Zhiqi,Liu Bina,Li Shihua,Lu Taoa,,Li Xueren,Miao Weipeng,Luo Wei 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.2

Uniform Co:MgAl2O4 nano-powders for saturable absorber were prepared using inverse-drip co-precipitation method. Effectsof the precipitant and the metal ion solution on the composition and morphology of Co:MgAl2O4 nano-powders were studied. The results show that pure Co:MgAl2O4 nano-powders can be obtained, using the mixed solution of ammonium carbonate andammonia as the precipitant. The specific surface area of the particles reached 36 m2/g and the primary particle size was 39nm according to the SEM images and BET results.

Type synthesis of 3T2R decoupled hybrid mechanisms with large bearing capacity

Sen Wang,Shihua Li,Haoran Li,Yajie Zhou,Yongjie Wang,Xinyu Wang 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.4

This paper proposes a new synthesis method of three translational and two rotational (3T2R) decoupled hybrid mechanism with large bearing capacity, based on the screw theory and the atlas method. According to the degree of freedom and decoupled characteristics of the 3T and 2R mechanisms, the decoupled conditions for the 3T and 2R parallel mechanisms are proposed. The optimal conditions for the motion/force transmission performance of the 3T decoupled parallel mechanisms with redundant actuation is presented. A redundant actuated limb construction method is proposed to improve the load capacity of the hybrid mechanism. Following the design steps of the fully decoupled hybrid mechanism, 3T2R hybrid mechanisms with large load capacity are obtained. Kinematics and statics analysis verify the correctness of the proposed synthesis method. The mechanism synthesized by this method has a good application prospect in large load occasion.

Continuous Sliding Mode Control for Permanent Magnet Synchronous Motor Speed Regulation Systems Under Time-Varying Disturbances

Wang, Huiming,Li, Shihua,Yang, Jun,Zhou, XingPeng The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.4

This article explores the speed regulation problem of permanent magnet synchronous motor (PMSM) systems subjected to unknown time-varying disturbances. A continuous sliding mode control (CSMC) technique is introduced for the speed loop to enhance the robustness of PMSM systems and eliminate the chattering phenomenon caused by high-frequency switch function in the conventional control law. However, the high control gain of the CSMC law in the presence of strong disturbances leads to large steady-state speed fluctuations for PMSM systems. In many application fields, PMSM systems are affected by time-varying disturbances instead of constant disturbances. For example, electric bicycles are usually affected by changing environmental disturbances, including wind speeds, road conditions, etc. These disturbances may be in the form of constant, ramp, and parabolic disturbances. Hence, a generalized proportional integral (GPI) observer is employed to estimate these types of disturbances. Then, the disturbance estimation method and the aforementioned CSMC method are combined to establish a composite sliding mode control method called the CSMC+GPI method for the speed loop of PMSM systems. Contrary to the conventional sliding mode control technique, the proposed method completely eliminates the chattering phenomenon caused by the switching function in the conventional control law. Moreover, a small control gain for the CSMC+GPI method is chosen by feed-forwarding estimated values to the speed controller. Hence, the steady-state speed fluctuations are small. The effectiveness of the proposed control scheme is verified by simulation and experimental result.

Continuous Sliding Mode Control for Permanent Magnet Synchronous Motor Speed Regulation Systems Under Time-Varying Disturbances

Huiming Wang,Shihua Li,Jun Yang,XingPeng Zhou 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.4

This article explores the speed regulation problem of permanent magnet synchronous motor (PMSM) systems subjected to unknown time-varying disturbances. A continuous sliding mode control (CSMC) technique is introduced for the speed loop to enhance the robustness of PMSM systems and eliminate the chattering phenomenon caused by high-frequency switch function in the conventional control law. However, the high control gain of the CSMC law in the presence of strong disturbances leads to large steady-state speed fluctuations for PMSM systems. In many application fields, PMSM systems are affected by time-varying disturbances instead of constant disturbances. For example, electric bicycles are usually affected by changing environmental disturbances, including wind speeds, road conditions, etc. These disturbances may be in the form of constant, ramp, and parabolic disturbances. Hence, a generalized proportional integral (GPI) observer is employed to estimate these types of disturbances. Then, the disturbance estimation method and the aforementioned CSMC method are combined to establish a composite sliding mode control method called the CSMC+GPI method for the speed loop of PMSM systems. Contrary to the conventional sliding mode control technique, the proposed method completely eliminates the chattering phenomenon caused by the switching function in the conventional control law. Moreover, a small control gain for the CSMC+GPI method is chosen by feed-forwarding estimated values to the speed controller. Hence, the steady-state speed fluctuations are small. The effectiveness of the proposed control scheme is verified by simulation and experimental result.

Preparation and investigation of Dy³⁺-doped Ca₉LiGd_2/3(PO₄)₇ single-phase full-color phosphor

Liu, Shihua,Liu, Simei,Wang, Jingjing,Sun, Pengfei,Zhong, Yifan,Jeong, Jung Hyun,Deng, Bin,Yu, Ruijin Elsevier 2018 Materials research bulletin Vol.108 No.-

<P><B>Abstract</B></P> <P>Novel single-phased white-light-emitting Ca<SUB>9</SUB>LiGd<SUB>2/3</SUB>(PO<SUB>4</SUB>)<SUB>7</SUB>:<I>x</I>Dy<SUP>3+</SUP> (<I>x</I> = 0.02, 0.05, 0.10, 0.15, 0.20, 0.25, and 0.30) β-Ca<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>-type phosphate phosphors were synthesized. The phase structure, luminescence, and thermal stability of the phosphors were characterized by X-ray powder diffraction analysis, photoluminescence excitation and emission spectra, thermal quenching, and decay curves. XRD analysis confirmed the phase formation of Ca<SUB>9</SUB>LiGd<SUB>2/3</SUB>(PO<SUB>4</SUB>)<SUB>7</SUB>:Dy<SUP>3+</SUP> materials. Under the excitation of 352 nm, the emission of the Ca<SUB>9</SUB>LiGd<SUB>2/3</SUB>(PO<SUB>4</SUB>)<SUB>7</SUB>:0.20Dy<SUP>3+</SUP> sample centered at blue (488 nm) and yellow (580 nm), which corresponded to <SUP>4</SUP>F<SUB>9/2</SUB>–<SUP>6</SUP>H<SUB>15/2</SUB> transition and <SUP>4</SUP>F<SUB>9/2</SUB>–<SUP>6</SUP>H<SUB>13/2</SUB> transition. The optimum dopant concentration of Dy<SUP>3+</SUP> ions was around 20 mol%, and the critical transfer distance of Dy<SUP>3+</SUP> was calculated as 18 Å. The thermal-quenching temperature was above 500 K for Ca<SUB>9</SUB>LiGd<SUB>2/3</SUB>(PO<SUB>4</SUB>)<SUB>7</SUB>:0.20Dy<SUP>3+</SUP>. The developed phosphor has a great potential as a single-component white-light-emitting phosphor for UV-light-emitting diodes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel single-phased Ca<SUB>9</SUB>LiGd<SUB>2/3</SUB>(PO<SUB>4</SUB>)<SUB>7</SUB>:<I>x</I>Dy<SUP>3+</SUP> phosphor was firstly synthesized. </LI> <LI> Its structure, luminescent properties are well studied and characterized. </LI> <LI> It was promising as a single-component white-light-emitting phosphor for w-LEDs. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Incremental Passivity Based Control for DC-DC Boost Converters under Time-Varying Disturbances via a Generalized Proportional Integral Observer

Wei He,Shihua Li,Jun Yang,Zuo Wang 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1

In this paper, the voltage tracking control of a conventional DC-DC boost converter affected by unknown, time-varying circuit parameter perturbations is investigated. Based on the fundamental property of incremental passivity, a passivity based control law is designed. Then, to obtain a better disturbance rejection property, two generalized proportional integral (GPI) observers are employed to estimate the time-varying uncertainties in the output voltage and inductor current channels, and the estimated values are applied as feedforward compensation. Moreover, the global trajectory tracking performance of a system with disturbances is ensured under the composite controller. Finally, simulation and experiment studies are provided to demonstrate the feasibility and effectiveness of the proposed method. The results show that the proposed controller delivers a promising disturbance rejection capability as well as a good nominal tracking performance.

Effect of silicon carbide on carbonization and morphology behavior of coal tar pitch

Wenjuan Zhang,Shihua Song,Xianren Zeng,Genhui Teng,Qi Wang 한양대학교 세라믹연구소 2017 Journal of Ceramic Processing Research Vol.18 No.10

Coal tar pitch (CTP) is a quite promising candidate for the production of carbon materials. However, the application of CTP is restricted by its poor properties at elevated temperature. In this paper, silicon carbide was used to modify CTP and thecarbonization and morphology behavior of CTP and the CTP modified with silicon carbide were studied by thermogravimetry and differential scanning calorimetry (TG-DSC), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show silicon carbide and CTP can coalesce well when the ratio of silicon carbide to CTP is 12% and the carbonization yield of CTP at 900 o C increases from 35.86% to 40.56% after the modification of CTP. Further, the addition of silicon carbide to CTP can reduce the temperature at which the reaction of thermal polymerization happen during the carbonization process of CTP and can facilitate the carbonization of CTP. In addition, little pore distributes on the surface of the heat-treatment products after the modification of CTP with silicon carbide.

Ledley Solution Method for All Feasible State Feedback Stabilizers of Boolean Control Networks With Disturbances

Xinling Li,Shihua Fu,Jianjun Wang 제어·로봇·시스템학회 2024 International Journal of Control, Automation, and Vol.22 No.1

This paper addresses the robust stabilization problem of Boolean control networks with disturbance inputs (DBCNs) via the semi-tensor product (STP) of matrices, and designs all feasible state feedback stabilizers. Based on the algebraic form of DBCNs, some necessary and sufficient conditions are derived for the robust stabilization of DBCNs by Ledley antecedence solution technique. An algorithm is proposed to determine all complete families of robust reachable sets, moreover, all feasible state feedback stabilizers are obtained. Finally, two numerical examples are exploited to illustrate the effectiveness of the proposed results as well as the controller design scheme.

Polymorphic Forms of Furosemide Characterized by THz Time Domain Spectroscopy

Min Ge,Shihua Ma,Guifeng Liu,Wenfeng Wang 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.10

Terahertz time domain spectroscopy (THz-TDS) is applied in transmission to identify the five forms of modifications of furosemide and one commercial product from 0.3 THz to 1.6 THz at room temperature. The different absorption spectra of the different forms are sensitive to crystal structures. Density function theory (DFT) calculation was used to understand the vibrational modes of furosemide in the THz region. X-ray powder diffractometry (XRPD) was applied to confirm the different forms of modifications. The results demonstrate that THz-TDS is a potential analytical technique in investigating polymorphic forms in the pharmaceutical fields.

Incremental Passivity Based Control for DC-DC Boost Converters under Time-Varying Disturbances via a Generalized Proportional Integral Observer

He, Wei,Li, Shihua,Yang, Jun,Wang, Zuo The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1

In this paper, the voltage tracking control of a conventional DC-DC boost converter affected by unknown, time-varying circuit parameter perturbations is investigated. Based on the fundamental property of incremental passivity, a passivity based control law is designed. Then, to obtain a better disturbance rejection property, two generalized proportional integral (GPI) observers are employed to estimate the time-varying uncertainties in the output voltage and inductor current channels, and the estimated values are applied as feedforward compensation. Moreover, the global trajectory tracking performance of a system with disturbances is ensured under the composite controller. Finally, simulation and experiment studies are provided to demonstrate the feasibility and effectiveness of the proposed method. The results show that the proposed controller delivers a promising disturbance rejection capability as well as a good nominal tracking performance.