Primary Side Constant Power Control Scheme for LED Drivers Compatible with TRIAC Dimmers

Junming Zhang,Ting Jiang,Lianghui Xu,Xinke Wu 전력전자학회 2013 JOURNAL OF POWER ELECTRONICS Vol.13 No.4

This paper proposes a primary side constant power control scheme for TRIAC dimmer compatible LED drivers. The LED driver is a Flyback converter operated in boundary conduction mode (BCM) to minimize the switching loss. With the proposed control scheme, the input power of the Flyback converter can be controlled by the TRIAC dimming angle, which is not affected by AC input voltage variations. Since the output voltage is almost constant for LED loads, the output current can be changed by controlling the input power with a given conversion efficiency. The isolated feedback circuit is eliminated with the proposed primary side control scheme, which dramatically simplifies the whole circuit. In addition, the input current automatically follows the input voltage due to the BCM operation, and the resistive input characteristic can be achieved which is attractive for TRIAC dimming applications. Experimental results from a 15W prototype verify the theoretical analysis.

Preparation of low density TiO_2/poly (methyl methacrylate) composite particles by emulsifier-free emulsion polymerization

Junming Liu,Lixin Cao,Ge Su,Wei Liu 한국물리학회 2011 Current Applied Physics Vol.11 No.6

Based on the 3-(trimethoxysilyl) propylmethacrylate (MPS) modified TiO_2 particles, the TiO_2/poly (methyl methacrylate) (PMMA) composite particles have been prepared successfully via emulsifier-free emulsion polymerization in water. A facile floating-sinking method is proposed to roughly evaluate the composite particles’ density. Chemical component of obtained composite particles was identified by Fourier transform infrared spectra (FTIR). The morphology and grain size of the composite particles were investigated by field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Thermal analysis of the composite particles was measured by differential thermal analysis-thermo gravimetric analysis (DTA-TGA). The zeta potential and electrophoretic mobility of composite particles with suitable density in water was measured by dynamic light scattering (DLS).

Simplified 2-D Analytical Model for Winding Loss Analysis of Flyback Transformers

Junming Zhang,Wei Yuan,Hulong Zeng,Zhaoming Qian 전력전자학회 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.6

The winding loss analysis of a flyback transformer is difficult and ambiguous because the primary side current and the secondary side current differs both in shape and phase, especially for DCM (Discontinuous Conduction Mode) operation. Meanwhile, the fringing field caused by the air gaps further makes the traditional 1-D loss analysis model not directly applicable. The paper gives a thorough investigation into the phase shift of winding currents, which indicates that the phase shift of the high order harmonics is still close to 180º out-of-phase. Based on the analysis, a simplified 2-D winding loss analytical model for flyback transformers considering the effects of low order harmonics is proposed. By neglecting the y components of the fringing field, the proposed model has an acceptable accuracy and a simple form that is similar to the conventional 1-D model. The power loss calculated with the proposed analysis model is verified by FEA (Finite Element Analysis) simulations and experimental results.

Mesenchymal Stem Cells Modified with Stromal Cell-Derived Factor 1б Improve Cardiac Remodeling via Paracrine Activation of Hepatocyte Growth Factor in a Rat Model of Myocardial Infarction

Junming Tang,Jianing Wang,Linyun Guo,Xia Kong,Jianye Yang,Fei Zheng,Lei Zhang,Yongzhang Huang 한국분자세포생물학회 2010 Molecules and cells Vol.29 No.1

Mesenchymal stem cells (MSCs) are a promising source for cell-based treatment of myocardial infarction (MI), but existing strategies are restricted by low cell survival and engraftment. We examined whether SDF-1 transfection improve MSC viability and paracrine action in infarcted hearts. We found SDF-1-modified MSCs effectively ex-pressed SDF-1 for at least 21days after exposure to hy-poxia. The apoptosis of Ad-SDF-1-MSCs was 42% of that seen in Ad-EGFP-MSCs and 53% of untreated MSCs. In the infarcted hearts, the number of DAPI-labeling cells in the Ad-SDF-1-MSC group was 5-fold that in the Ad-EGFP-MSC group. Importantly, expression of antifibrotic factor, HGF, was detected in cultured MSCs, and HGF expression lev-els were higher in Ad-SDF-MSC-treated hearts, compared with Ad-EGFP-MSC or control hearts. Compared with the control group, Ad-SDF-MSC transplantation significantly decreased the expression of collagens I and III and matrix metalloproteinase 2 and 9, but heart function was im-proved in d-SDF-MSC-treated animals. In conclusion, SDF-1–modified MSCs enhanced the tolerance of engrafted MSCs to hypoxic injury in vitro and improved their viability in infarcted hearts, thus helping preserve the contractile function and attenuate left ventricle (LV) remodeling, and this may be at least partly mediated by enhanced paracrine signaling from MSCs via antifibrotic factors such as HGF.

Primary Side Constant Power Control Scheme for LED Drivers Compatible with TRIAC Dimmers

Zhang, Junming,Jiang, Ting,Xu, Lianghui,Wu, Xinke The Korean Institute of Power Electronics 2013 JOURNAL OF POWER ELECTRONICS Vol.13 No.4

This paper proposes a primary side constant power control scheme for TRIAC dimmer compatible LED drivers. The LED driver is a Flyback converter operated in boundary conduction mode (BCM) to minimize the switching loss. With the proposed control scheme, the input power of the Flyback converter can be controlled by the TRIAC dimming angle, which is not affected by AC input voltage variations. Since the output voltage is almost constant for LED loads, the output current can be changed by controlling the input power with a given conversion efficiency. The isolated feedback circuit is eliminated with the proposed primary side control scheme, which dramatically simplifies the whole circuit. In addition, the input current automatically follows the input voltage due to the BCM operation, and the resistive input characteristic can be achieved which is attractive for TRIAC dimming applications. Experimental results from a 15W prototype verify the theoretical analysis.

Simplified 2-D Analytical Model for Winding Loss Analysis of Flyback Transformers

Zhang, Junming,Yuan, Wei,Zeng, Hulong,Qian, Zhaoming The Korean Institute of Power Electronics 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.6

The winding loss analysis of a flyback transformer is difficult and ambiguous because the primary side current and the secondary side current differs both in shape and phase, especially for DCM (Discontinuous Conduction Mode) operation. Meanwhile, the fringing field caused by the air gaps further makes the traditional 1-D loss analysis model not directly applicable. The paper gives a thorough investigation into the phase shift of winding currents, which indicates that the phase shift of the high order harmonics is still close to $180^{\circ}$ out-of-phase. Based on the analysis, a simplified 2-D winding loss analytical model for flyback transformers considering the effects of low order harmonics is proposed. By neglecting the y components of the fringing field, the proposed model has an acceptable accuracy and a simple form that is similar to the conventional 1-D model. The power loss calculated with the proposed analysis model is verified by FEA (Finite Element Analysis) simulations and experimental results.

A novel class of pyranocoumarin anti-androgen receptor signaling compounds.

Guo, Junming,Jiang, Cheng,Wang, Zhe,Lee, Hyo-Jeong,Hu, Hongbo,Malewicz, Barbara,Lee, Hyo-Jung,Lee, Jae-Ho,Baek, Nam-In,Jeong, Jin-Hyun,Kim, Dae-Keun,Kang, Kyung-Sun,Kim, Sung-Hoon,Lu, Junxuan American Association for Cancer Research 2007 Molecular Cancer Therapeutics Vol.6 No.3

<P>Androgen and the androgen receptor (AR)-mediated signaling are crucial for prostate cancer development. Novel agents that can inhibit AR signaling in ligand-dependent and ligand-independent manners are desirable for the chemoprevention of prostate carcinogenesis and for the treatment of advanced prostate cancer. We have shown recently that the pyranocoumarin compound decursin from the herb Angelica gigas possesses potent anti-AR activities distinct from the anti-androgen bicalutamide. Here, we compared the anti-AR activities and the cell cycle arrest and apoptotic effects of decursin and two natural analogues in the androgen-dependent LNCaP human prostate cancer cell culture model to identify structure-activity relationships and mechanisms. Decursin and its isomer decursinol angelate decreased prostate-specific antigen expression with IC(50) of approximately 1 mumol/L. Both inhibited the androgen-stimulated AR nuclear translocation and transactivation, decreased AR protein abundance through proteasomal degradation, and induced G(0/1) arrest and morphologic differentiation. They also induced caspase-mediated apoptosis and reactive oxygen species at higher concentrations. Furthermore, they lacked the agonist activity of bicalutamide in the absence of androgen and were more potent than bicalutamide for suppressing androgen-stimulated cell growth. Decursinol, which does not contain a side chain, lacked the reactive oxygen species induction and apoptotic activities and exerted paradoxically an inhibitory and a stimulatory effect on AR signaling and cell growth. In conclusion, decursin and decursinol angelate are members of a novel class of nonsteroidal compounds that exert a long-lasting inhibition of both ligand-dependent and ligand-independent AR signaling. The side chain is critical for sustaining the anti-AR activities and the growth arrest and apoptotic effects.</P>

A Novel Control Strategy for Improving the Performance of Hybrid Active Power Filters

Wen Junming,Zhang Miao,Lu Jianhang,Guan YiChuan,Wu Shiyu,Feng Chunshou 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.6

Hybrid active power filters (HAPF) are effective harmonic compensation devices. However, the inductor voltage is too low, so the DC-bus voltage can not get enough power flow. Thus, the compensation performance and stability of HAPF can be reduced. Theoretically, increasing the inductor voltage can improve the DC side control performance. Therefore, the relevant mathematical model is established, and systematic analysis is carried out. To improve the performance of HAPF, a new double closed-loop control strategy is proposed. To sum up, the main variable of the outer loop control is the inductor voltage. The current flow direction can be changed by changing the value of the inductance voltage to improve the inductance voltage and realize the stability of the DC-side voltage. Secondly, from the transfer function and the Bode Plots, the introduction of the inverter output current inner loop results in significant resonant spike suppression of the system. Compared with the self-excitation control method with voltage feedforward, this new control method is easy to implement and very effective in DC-bus control. Simulation and experimental results show that the compensation effect of HAPF is improved, the DC-side voltage is stable, and the system can operate safely and reliably.

Parameter Calibration of a Discrete Element Model for Three-Compartment Separation and Fragmentation of Castor Capsules During Harvesting

Hou Junming,Ren Zhaotan,Liu Deyu,Ma Zhi,Liu Xu,Wang Wei 한국농업기계학회 2023 바이오시스템공학 Vol.48 No.2

Purpose In order to analyze the damage of castor capsule during mechanical harvesting, it is necessary to establish a suitable model and obtain the parameters of discrete element model. Therefore, the study establishes a three-compartment separation and crushing discrete element model of castor; the contact parameters and bonding parameters of the model are calibrated. The TongBi No. 16 castor variety in harvest period was taken as the research object. The sizes of whole castor capsule and single part were measured; then, the moisture content of castor in harvest period was measured. Methods In order to obtain the inherent parameters of the capsule, the elastic modulus was measured by TMS pro professional food physical property analyzer. In order to realize the three-compartment separation and fragmentation of castor, a discrete element model combining the aggregation and bonding model was established. The contact parameters are calibrated by stacking angle and formed by lifting method. The contour curve of accumulation angle is obtained with MATLAB software. The results show that the stacking angle of physical test is 26.216°. Through Plackett–Burman test, the contact parameters that have a greater impact on the stacking angle are the static friction coefficient between castors and the dynamic friction coefficient between castors. After the steepest climbing test, the value range is selected. Finally, through response surface optimization, the optimal static and dynamic friction coefficients between castors are determined to be 0.41 and 0.05, respectively. Results In order to obtain accurate bonding parameters, it is carried out through compression test. In order to reduce the damage to single compartment in the process of compression, spherical compression head is used. The results show that the maximum destructive force is 52.65 N. In conducting the simulation tests, the Box-Behnken response surface design is applied to derive the optimal bonding parameters, the normal stiffness per unit area is 9.47× 107 N/m3, shear stiffness per unit area is 4.59× 107 N/m3, normal strength is 7.92× 103 Pa, and shear strength is 1.13× 104 Pa. Finally, the stacking angle test and cone compression test are carried out by the final calibrated parameters. The relative errors between the simulation and the actual test are 1.82% and 4.10%, respectively, which indicate that the calibration results are reliable. Conclusion This study can provide the support of discrete element simulation parameters for analyzing the mechanism of castor capsule damage during mechanized harvest.

Mesenchymal Stem Cells Modified with Stromal Cell-Derived Factor 1${\alpha}$ Improve Cardiac Remodeling via Paracrine Activation of Hepatocyte Growth Factor in a Rat Model of Myocardial Infarction

Tang, Junming,Wang, Jianing,Guo, Linyun,Kong, Xia,Yang, Jianye,Zheng, Fei,Zhang, Lei,Huang, Yongzhang Korean Society for Molecular and Cellular Biology 2010 Molecules and cells Vol.29 No.1

Mesenchymal stem cells (MSCs) are a promising source for cell-based treatment of myocardial infarction (MI), but existing strategies are restricted by low cell survival and engraftment. We examined whether SDF-1 transfection improve MSC viability and paracrine action in infarcted hearts. We found SDF-1-modified MSCs effectively expressed SDF-1 for at least 21days after exposure to hypoxia. The apoptosis of Ad-SDF-1-MSCs was 42% of that seen in Ad-EGFP-MSCs and 53% of untreated MSCs. In the infarcted hearts, the number of DAPI-labeling cells in the Ad-SDF-1-MSC group was 5-fold that in the Ad-EGFP-MSC group. Importantly, expression of antifibrotic factor, HGF, was detected in cultured MSCs, and HGF expression levels were higher in Ad-SDF-MSC-treated hearts, compared with Ad-EGFP-MSC or control hearts. Compared with the control group, Ad-SDF-MSC transplantation significantly decreased the expression of collagens I and III and matrix metalloproteinase 2 and 9, but heart function was improved in d-SDF-MSC-treated animals. In conclusion, SDF-1-modified MSCs enhanced the tolerance of engrafted MSCs to hypoxic injury in vitro and improved their viability in infarcted hearts, thus helping preserve the contractile function and attenuate left ventricle (LV) remodeling, and this may be at least partly mediated by enhanced paracrine signaling from MSCs via antifibrotic factors such as HGF.