A Hybrid Modulation Strategy with Reduced Switching Losses and Neutral Point Potential Balance for Three-Level NPC Inverter

Weidong Jiang,Yan Gao,Jinping Wang,Lei Wang 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.2

In this paper, carrier-based pulse width modulation (CBPWM), space vector PWM (SVPWM) and reduced switching losses PWM (RSLPWM) for the three-level neutral point clamped (NPC) inverter are introduced. In the case of the neutral point (NP) potential (NPP) offset, an asymmetric disposition PWM (ASPDPWM) strategy is proposed, which can output PWM sequences correctly and suppress the lower order harmonics of the inverter effectively. An NPP balance strategy based on carrier based PWM (CBPWM) is analyzed. A hybrid modulation strategy combining RSLPWM and the NPP balance based on CBPWM is proposed, and hysteresis control is adopted to switch between the two modulation strategies. An experimental prototype of the three-level NPC inverter is built. The effectiveness of the hybrid modulation is verified with a resistance-inductance load and a permanent magnetic synchronous motor (PMSM) load, respectively. The experimental results show that reduced switching losses and an acceptable NPP can be effectively achieved in the hybrid modulation strategy.

Unmanned Aerial Vehicle Targeting Based on Image Matching

Zhang Yan,Li Jianzeng,Li Deliang,Zhou Zidong,Du Yulong,Ji Weidong 보안공학연구지원센터 2016 International Journal of Multimedia and Ubiquitous Vol.11 No.1

Aiming at the problem of low accuracy of the target for one UAV (Unmanned Aerial Vehicle), an UAV target location method based on image matching is presented according to the data of video and photograph as well as the information of the digital map. Firstly, using the improved artificial matching method, the UAV aerial images are jointed based on the digital map to obtain the coordinates information. Then, the UAV video frame resolution containing the target is improved by the improving method of super-resolution reconstruction. Finally, making use of the improved SIFT algorithm, the video frames are registered with the aerial photo to complete the location of the target. Results prove that this method can achieve the target location without the UAV’s position and attitude information, while improving the precision and speed of target location, this method is an effective one for target location based on the image matching in the battlefield.

A Hybrid Modulation Strategy with Reduced Switching Losses and Neutral Point Potential Balance for Three-Level NPC Inverter

Jiang, Weidong,Gao, Yan,Wang, Jinping,Wang, Lei The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.12 No.2

In this paper, carrier-based pulse width modulation (CBPWM), space vector PWM (SVPWM) and reduced switching losses PWM (RSLPWM) for the three-level neutral point clamped (NPC) inverter are introduced. In the case of the neutral point (NP) potential (NPP) offset, an asymmetric disposition PWM (ASPDPWM) strategy is proposed, which can output PWM sequences correctly and suppress the lower order harmonics of the inverter effectively. An NPP balance strategy based on carrier based PWM (CBPWM) is analyzed. A hybrid modulation strategy combining RSLPWM and the NPP balance based on CBPWM is proposed, and hysteresis control is adopted to switch between the two modulation strategies. An experimental prototype of the three-level NPC inverter is built. The effectiveness of the hybrid modulation is verified with a resistance-inductance load and a permanent magnetic synchronous motor (PMSM) load, respectively. The experimental results show that reduced switching losses and an acceptable NPP can be effectively achieved in the hybrid modulation strategy.

Sizing Performance Improvement of Cotton Yarns Pretreated with UV Irradiation

Wenjun Yan,Bo Zhu,Weidong Gao 한국섬유공학회 2022 Fibers and polymers Vol.23 No.11

UV irradiation technology has the advantages of ease operation, affordable, and clean production. This paperfocused on the wettability improvement of cotton yarns by UV irradiation, and proposed UV irradiation pretreatment methodto improve the sizing performance of cotton yarns. The surface elemental composition and molecular structure before andafter UV irradiation were characterized. The effects of UV irradiation pretreatment intensity and time on apparent properties,weight, wettability and mechanical properties of raw cotton yarns were analyzed. The impact of UV irradiation pretreatmentprocess on sized yarns performance including mechanical properties, hairiness, yarn evenness and size pick-up were studied. Then, the mechanical properties of the sized yarns after alkali desizing were investigated. The results showed that UVirradiation pretreatment can introduce oxygen-containing polar groups on the cotton yarns. Meanwhile, it had a certaindegradation effect on the surface of the cotton yarns, which resulted in wax removed, roughness improvement and exposureof cellulose. The above reasons jointly caused the wettability improvement of raw cotton yarns after UV irradiation. Compared with the unpretreated sized ones, the breaking strength, breaking elongation and abrasion resistance of the UVirradiation pretreated sized yarns was greatly enhanced by 20.13 %, 20.54 % and 103.49 % respectively. The hairiness wasreduced by 88.23 %, and the yarn evenness was improved by 6.74 %. It presented the optimized sizing performance when theyarns were pretreated at UV irradiation intensity of 142.5 mW/cm2 for 120 min. After desizing, the decline amplitude waslittle between unpretreated and UV irradiation pretreated yarns.

PRECURSORS-DECOMPOSITED SYNTHESIS AND VISIBLE-LIGHT-RESPONSE PHOTOCATALYSTIC PROPERTIES OF UNIFORM POROUS Bi 2 O 3 NANOSPHERES

XIAOLI SUN,JIANGGUO GUAN,WEIDONG SHI,HAO TU,LEILEI XU,YAN YAN 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2014 NANO Vol.9 No.6

The Bi 2 O 3 sphere-like precursors were ¯rst synthesized through a simple hydrothermal reactionin the mixture of sodium cholate (SC) and hydrogen peroxide. Thermal decomposition of theseprecursors would result in the formation of the uniform porous Bi 2 O 3 nanospheres with diametersof ca. 80 nm in air at 500?C. The amount of added H 2 O 2 and the reaction time were found to playimportant roles in the formation of Bi 2 O 3 sphere-like precursors. The as-prepared porous Bi 2 O 3nanospheres exhibited a very excellent photocatalytic activity for the degradation of rhodamineB (RB) and methyl blue (MB) dyes under visible-light irradiation, which could be attributed totheir narrow band gap and high surface area.

Effect of FTY-720 on Pulmonary Fibrosis in Mice via the TGF-β1 Signaling Pathway and Autophagy

Jin Yuying,Liu Weidong,Gao Ge,Song Yilan,Liu Hanye,Li Liangchang,Zhou Jiaxu,Yan Guanghai,Cui Hong 한국응용약물학회 2023 Biomolecules & Therapeutics(구 응용약물학회지) Vol.31 No.4

We investigated whether FTY-720 might have an effect on bleomycin-induced pulmonary fibrosis through inhibiting TGF-β1 pathway, and up-regulating autophagy. The pulmonary fibrosis was induced by bleomycin. FTY-720 (1 mg/kg) drug was intraperitoneally injected into mice. Histological changes and inflammatory factors were observed, and EMT and autophagy protein markers were studied by immunohistochemistry and immunofluorescence. The effects of bleomycin on MLE-12 cells were detected by MTT assay and flow cytometry, and the related molecular mechanisms were studied by Western Blot. FTY-720 considerably attenuated bleomycin-induced disorganization of alveolar tissue, extracellular collagen deposition, and α-SMA and E-cadherin levels in mice. The levels of IL-1β, TNF-α, and IL-6 cytokines were attenuated in bronchoalveolar lavage fluid, as well as protein content and leukocyte count. COL1A1 and MMP9 protein expressions in lung tissue were significantly reduced. Additionally, FTY- 720 treatment effectively inhibited the expressions of key proteins in TGF-β1/TAK1/P38MAPK pathway and regulated autophagy proteins. Similar results were additionally found in cellular assays with mouse alveolar epithelial cells. Our study provides proof for a new mechanism for FTY-720 to suppress pulmonary fibrosis. FTY-720 is also a target for treating pulmonary fibrosis.

67-fs pulse generation from a mode-locked Tm,Ho:CLNGG laser at 2083 nm

Zhao, Yongguang,Wang, Yicheng,Chen, Weidong,Pan, Zhongben,Wang, Li,Dai, Xiaojun,Yuan, Hualei,Zhang, Yan,Cai, Huaqiang,Bae, Ji Eun,Choi, Sun Young,Rotermund, Fabian,Loiko, Pavel,Serres, Josep Maria,Mat The Optical Society 2019 Optics express Vol.27 No.3

Improvement of Microstructure, Mechanical Property and Corrosion Resistance of Mg–9Li–3Al–1Ca Alloy Through Centrifugal Casting

Zhenduo Ma,Qiang Peng,Guobing Wei,Yan Yang,Tiancai Xu,Weidong Xie,Gang Liu,Xiaodong Peng 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.11

The microstructure, mechanical property and corrosion behavior of gravity casting and centrifugal casting Mg–9Li–3Al–1Ca alloy were investigated. The results indicate that the Mg–9Li–3Al–1Ca alloy is mainly composed of α-Mg phases, β-Liphases and Al2Caphases. After centrifugal casting, the blocky and elongated α-Mg phases of the gravity casting alloy canbe refined and spheroidized. Meanwhile, the amount of α-Mg and AlLi phases increases, however, the number of Al2Caphases decreases. Besides, a strong texture of β-Li phase on the (200) plane can be formed. The microstructure refinementand the decrease of Al2Caphases lead to the improvement of comprehensive property. The property of centrifugal alloyshas gradient along radius direction because the strength of centrifugal force varies with the centrifugal radius. The centrifugalcasting Mg–9Li–3Al–1Ca alloy at outside exhibits excellent comprehensive properties. The ultimate tensile strengthand elongation of centrifugal casting alloy achieve the value of 198.3 MPa and 6.0%, corresponding to 83.6% and 300.0%increments compared with gravity casting ones, respectively. The corrosion current also decreases to 89.4 μA/cm2, whichattributes to the weakening of galvanic corrosion attributing to the decrease of number of Al2Caphases and the transformationof corrosion pattern caused by grain refinement.

Effect of Ignition Position and Sample Thickness on Flame Spread in Flexible Polyurethane Foam

Qi Yuan,Chang Li,Paul Amyotte,Lingfeng Wang,Chunmiao Yuan,Gang Li,Weidong Yan 한국고분자학회 2022 폴리머 Vol.46 No.4

Fire behavior of flexible polyurethane foam (FPUF) at different sample thicknesses and ignition positioningwas investigated. Effects on flame height, mass loss rate and other parameters were tested, and the flame propagationmechanism was analyzed. A method for predicting equivalent combustion diameter (D) values of the dynamic changeof liquid pool at different positions is proposed. Combined with data of sample mass loss rate, flame height can be predicted. Based on a transition state model, a method for predicting the fire risk of FPUF in late stage combustion by calculating the generation time of polyols is proposed. With edge ignition, FPUF burning produces an inclined surfaceduring the combustion process which enhances the length of the preheating zone by means of heat conduction and heatradiation. Flame spread rate (FSV) in FPUF with edge ignition was greater than with center point ignition.

Correlation Between Different Antidiarrheal Treatments and Changes in Chemical Components of Allii Sativi Bulbus Before and After Steaming Treatment Based on Flora Sequencing and In Vitro Experiments

Yarong Li,Yaqian Zhou,Huanjin Liu,Chenxu Wei,Shuli Chen,Zhengying Hua,Yan Xu,Yu Wu,Weidong Li 한국식품영양과학회 2022 Journal of medicinal food Vol.25 No.10

We investigated the changes in the main active ingredients and pharmacodynamic differences in the therapeutic effect of garlic before and after steaming and the correlation between them. The main active ingredients in raw garlic products (RGPs) and steamed garlic products (SGPs) were determined by high-pressure liquid chromatography and ultraviolet spectroscopy. Acute rapid diarrhea (AD) and antibiotic-induced diarrhea (DD) models were established in rats, and each group was treated with RGP and SGP, respectively. The main chemical components of garlic changed before and after steaming. Garlicin and alliinase were only found in RGP, whereas only alliin was found in SGP. Both RGP and SGP contained garlic polysaccharides. For in vivo experiments on AD, the average rate of loose stools was 100.00 ± 0.00, 31.55 ± 11.76, and 19.14 ± 6.62 in the RGP high-dose and SGP high-dose treatment groups, respectively; in DD, the rates were 91.11 ± 14.40, 19.33 ± 3.63, and 30.56 ± 4.30, respectively (P < .01, treatment vs. model groups). In AD, the average grade of loose stools was 2.33 ± 0.52 and 1.83 ± 0.75 in the model and RGP high-dose treatment groups, respectively (P < .05); in DD, the values were 2.17 ± 0.41 in the model group and 1.67 ± 0.52 in the SGP high-dose treatment group (P < .05). RGP had a better therapeutic effect on AD, mainly related to the antibacterial effect of garlicin in RGP. SGP had a better therapeutic effect on DD, mainly related to the alliin and garlic polysaccharide in SGP. This study could provide evidence to support the clinical use of garlic.