A Modifed Finite Control Set Model Predictive Control for 3L−NPC Grid−Connected Inverters Using Virtual Voltage Vectors

Jianguo Lyu,Binghui Ma,Han Yan,Zhendong Ji,Jinyong Ding 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.1

In order to improve the performance of a 3−level neutral point clamped (3L−NPC) grid−connected inverter with fnite control set model predictive control (FCS−MPC), this paper proposes a modifed FCS−MPC algorithm based on the rearranged control set (MFCS−MPC). By adding synthetic virtual voltage vectors to rearrange the fnite control set (FCS) of the 3L−NPC inverter, the frequency spectrum of output leg voltage becomes concentrated, which is benefted for decreasing total harmonic distortion (THD) of grid currents and makes it easier to design output flters for the grid−connected inverter. Moreover, based on switching state sequences of virtual voltage vectors, the modifed predictive model of the proposed method is established considering capacitor voltage diference. Besides, according to the location of the reference output voltage vector, a preselection step is incorporated into MFCS−MPC to narrow the control set for predictions, which avoids evaluating all candidate voltage vectors in the control set, and hence, the online computational burden is signifcantly reduced. A prototype of 3L−NPC grid−connected inverter is established to validate the proposed MFCS−MPC method and the experimental results show that this method has excellent static and dynamic performance, with a low THD for a wide range of modulation indexes.

Investigation into Rheological Properties of Magnetorheological Polishing Slurry Using α-Cellulose as an Additive Agent and its Polishing Performance

Jianguo Cao,Zongqiao Ma,Meng Nie 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.11

Magnetorheological finishing (MRF), considered as a promising polishing technique that can finish a nano-level smooth surface and free of surface or subsurface damage, has been widely utilized in ultra-smooth polishing of hard-to-machine materials. MRF process is mainly rely on shear stress to remove material. In this study, α-cellulose used as an additive agent to improve the rheological properties of magnetorheological polishing slurry (MRPS). The rheometer measurement results and polishing results showed that: (1) α-cellulose can enhance the shear stress of MRPS, but increased the apparent viscosity of MRPS. (2) α-cellulose can effectively improve the stability of MRPS, when the weight fraction of α-cellulose was 0.6 wt%, both stability and internal uniform of MRPS can be obtained. (3) If the weight fraction of α-cellulose was bigger than 0.6 wt%, the machining ability of MPRS was stable and the smooth polished surface can be obtained.

NUMERICAL STUDY ON THE SHAPED CHARGES

TIANBAO MA,CHENG WANG,JIANGUO NING 한국소성가공학회 2008 한국소성가공학회 컨퍼런스 Vol.2008 No.10

Osteogenic effect of magnesium oxychloride cement modified with phytic acid and loaded with strontium ranelate

Tingting Ma,Yijia Guan,Jinlun Feng,Yue Yang,Junying Chen,Wenjie Guo,Jianguo Liao,Yanru Zhang 한국생체재료학회 2023 생체재료학회지 Vol.27 No.00

Background Magnesium oxychloride cement has good mechanical properties, but poor water resistance. Methods Phytic acid, which can form chelate with Mg2+, was used to modify magnesium oxychloride cement, and the effects of phytic acid on the strength, in vitro degradation and biological activity of magnesium oxychloride cement were studied. Based on the preparation of phytic acid modified magnesium oxychloride cement with good water resistance and biological activity, osteoporosis treatment strontium ranelate was loaded on phytic acidmagnesium oxychloride cement, strontium ranelate/phytic acid-magnesium oxychloride cement was prepared. Results It was found that the compressive strength of 1.25 wt% phytic acid-magnesium oxychloride cement after soaking in SBF for 28 d could reach 40.5 ± 2.0 MPa, 13.33% higher than that of the control group (when phytic acid was 0 wt%), and the mass loss rate of all ages was lower than that of the control group. The water resistance of magnesium oxychloride cement was effectively improved by phytic acid. After loading with strontium ranelate, the water resistance of 1.25 wt% phytic acid-magnesium oxychloride cement was improved. Cell experiments showed that strontium ranelate could effectively promote cell proliferation and improve the expression of osteoblastrelated proteins. When strontium ranelate/phytic acid-magnesium oxychloride cement samples were implanted subcutaneously in rats for 4 w, no obvious inflammatory response was observed, and the material was tightly bound to the surrounding tissues. When bone cement was implanted into rat femur for 4 w, the bone cement was gradually wrapped and absorbed by new bone tissue, which grew from the outside to the inside, indicating that the bone cement containing strontium ranelate/phytic acid-magnesium oxychloride cement had excellent bone-forming ability. Conclusions In conclusion, the results indicated that strontium ranelate/phytic acid-magnesium oxychloride cement composite bone cement had a potential application prospect in clinical bone repair.

Reliability analysis based on the principle of maximum entropy and Dempster–Shafer evidence theory

Qiu Jiwei,Zhang Jianguo,Ma Yupeng 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.2

The Probability density functions (PDFs) of some uncertain parameters are difficult to determine precisely due to insufficient information. Only the varying intervals of such parameters can be obtained. A method of reliability analysis based on the principle of maximum entropy and evidence theory was proposed to address the reliability problems of random and interval parameters. First, the PDFs and cumulative distribution functions of interval parameters were obtained on the basis of the principle of maximum entropy and Dempster– Shafer evidence theory. Second, the normalized means and standard deviations of interval parameters were obtained using the equivalent normalization method. Third, two explicit iteration algorithms of reliability analysis were proposed on the basis of the advanced firstorder and second-moment method to avoid solving the limit state function and obtain the reliability index. Finally, the accuracy and efficiency of the proposed methods were verified through a numerical example and an engineering case.

Damage constitutive model of brittle rock considering the compaction of crack

Gu, Qingheng,Ning, Jianguo,Tan, Yunliang,Liu, Xuesheng,Ma, Qing,Xu, Qiang Techno-Press 2018 Geomechanics & engineering Vol.15 No.5

The deformation and strength of brittle rocks are significantly influenced by the crack closure behavior. The relationship between the strength and deformation of rocks under uniaxial loading is the foundation for design and assessment of such scenarios. The concept of relative crack closure strain was proposed to describe the influence of the crack closure behavior on the deformation and strength of rocks. Considering the crack compaction effect, a new damage constitutive model was developed based on accumulated AE counts. First, a damage variable based on the accumulated AE counts was introduced, and the damage evolution equations for the four types of brittle rocks were then derived. Second, a compaction coefficient was proposed to describe the compaction degree and a correction factor was proposed to correct the error in the effective elastic modulus instead of the elastic modulus of the rock without new damage. Finally, the compaction coefficient and correction factor were used to modify the damage constitutive model obtained using the Lemaitre strain equivalence hypothesis. The fitted results of the models were then compared with the experimental data. The results showed that the uniaxial compressive strength and effective elastic modulus decrease with an increase in the relative crack closure strain. The values of the damage variables increase exponentially with strains. The modified damage constitutive equation can be used to more accurately describe the compressive deformation (particularly the compaction stage) of the four types of brittle rocks, with a coefficient of determination greater than 0.9.

Influence of Alkalization Treatment on the Color Quality and the Total Phenolic and Anthocyanin Contents in Cocoa Powder

Yue Li,Song Zhu,Yun Feng,Feifei Xu,Jianguo Ma,Fang Zhong 한국식품과학회 2014 Food Science and Biotechnology Vol.23 No.1

The effects of alkalization treatments on color,colorimetric fractions, total polyphenol content, andanthocyanin content of cocoa powder were investigated. Adarker color and a lower total polyphenol content wereobtained for cocoa powder alkalized using a K2CO3solution than with an NaOH solution. A high temperatureand basic pH conditions favored formation of darkcomponents during alkalization due to sugar degradation,Maillard reactions, and anthocyanin polymerizing. Theanthocyanin content decreased with an increasing alkaliconcentration, suggesting that more anthocyanins weretransformed into brown polymers in darker cocoa powder. Cocoa powder with a heavy degree of alkalization had thelowest ratio of monomer anthocyanins to yellow/brownpolymer content. OD460/OD525 values for alkalized sampleswere higher than for non-alkalized samples. Cocoa powderpresented a better color quality after alkalization treatment.

Splenectomy improves liver fibrosis via tumor necrosis factor superfamily 14 (LIGHT) through the JNK/TGF-β1 signaling pathway

Liang Qing-shan,Xie Jian-Gang,Yu ChaoPing,Feng ZhuSheng,Ma JingChang,Zhang Yuan,Wang Dong,Lu JianGuo,Zhuang Ran,Yin Jikai 생화학분자생물학회 2021 Experimental and molecular medicine Vol.53 No.-

Splenectomy has been reported to improve liver fibrosis in patients with cirrhosis and hypersplenism. However, the mechanisms remain unclear. Tumor necrosis factor superfamily 14 (TNFSF14; also known as LIGHT) is highly expressed in the context of fibrosis and promotes disease progression in patients with fibrotic diseases such as pulmonary and skin fibrosis. Here, we determined whether splenectomy controls the production of LIGHT to improve liver fibrosis. Splenectomy reduced serum LIGHT levels in cirrhotic patients with hypersplenism and a ConA-induced liver fibrosis mouse model. Blocking LIGHT resulted in the downregulation of TGF-β1 in RAW264.7 cells. LIGHT treatment of RAW264.7 and JS1 cells in coculture regulated transforming growth factor-β1 (TGF-β1) expression through the activation of JNK signaling. Small interfering RNA-mediated silencing of lymphotoxin β receptor (LTβR) in macrophages resulted in pronounced decreases in the levels of fibrosis and αSMA in JS1 cells. These results indicated that LIGHT bound to LTβR and drove liver fibrosis in vitro. Blocking TGF-β1 abolished the effect of LIGHT in vitro. Furthermore, the administration of recombinant murine LIGHT protein-induced liver fibrosis with splenectomy, while blocking LIGHT without splenectomy improved liver fibrosis in vivo, revealing that the decrease in fibrosis following splenectomy was directly related to reduced levels of LIGHT. Thus, high levels of LIGHT derived from the spleen and hepatic macrophages activate JNK signaling and lead to increased TGF-β1 production in hepatic macrophages. Splenectomy attenuates liver fibrosis by decreasing the expression of LIGHT.