Novel central‑tapped planar transformer structure with natural current‑sharing for LLC resonant converters

Cheng Gu,Qinsong Qian,Dalin Xu,Tianhao Tan 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.9

Planar transformers have been widely used in isolated power supplies. However, with a large current density, the parallel windings usually cannot share the current evenly. This uneven current-sharing may cause additional winding losses, and damage the performance of the power converter. In this paper, a novel central-tapped planar transformer structure is proposed. Regardless of whether it is in the first half cycle or the second half cycle, the proposed twelve-layer transformer can be simplified as four three-layer transformers connected in parallel. Moreover, there is a “shielding layer” between adjacent three-layer transformers. In addition, the proposed transformer structure is optimized with a symmetrical layer arrangement, and the skin effect and proximity effect can be further reduced. Simulation and experimental tests indicate that the optimized planar transformer can stably provide 476.1 W of output power at a frequency of 1.25 MHz. The peak efficiency of the optimized transformer is up to 99.2%, and there is no obvious hot spot on the PCB board. It is noteworthy that the temperature difference in the secondary windings is less than 5 °C, which means the current-sharing in the secondary windings works well.

Automatic resonant frequency tracking for DCX‑LLC based on magnetizing current cancellation

Cheng Gu,Qinsong Qian,Dalin Xu,Tianhao Tan 전력전자학회 2024 JOURNAL OF POWER ELECTRONICS Vol.24 No.1

The LLC resonant converter has been widely used as a DC-DC transformer (DCX) to provide a semi-regulated or unregulated bus voltage. However, due to circuit parameter variations, the switching frequency is usually different from the designed resonant frequency, which results in converter efficiency degradation. To achieve the highest efficiency under different scenarios, a novel primary-side regulation (PSR) scheme for LLCs based on magnetizing current cancellation is presented. The transformer magnetizing current component on the sampling resistor can be offset by the compensating current, which is generated by the auxiliary winding and the added compensating inductor. The effect of magnetizing current in the sampled primary resonant current can be effectively eliminated. Thus, the output current can be accurately estimated on the primary side of the LLC resonant converter. Finally, a prototype of a 20-60 V LLC is constructed to validate the theoretical analysis. In the experiment section, various scenarios are tested to assess the efficacy of the solution. It is shown that the LLC converter can always realize resonant frequency tracking with the highest transmission efficiency.

Functional study of Villin 2 protein expressed in Longissimus dorsi muscle of Korean native cattle in different growth stages

( Yong Cheng Jin ),( Jeng A Han ),( Cheng Xiong Xu ),( Sang Kee Kang ),( Sang Hun Kim ),( Kang Suk Seo ),( Du Hak Yoon ),( Yun Jaie Choi ),( Hong Gu Lee ) 생화학분자생물학회 2012 BMB Reports Vol.45 No.2

The aim of this study was to investigate protein profiles related to the induction of adipogenesis within the bovine longissimus dorsi muscle (BLDM) by proteomic analysis. We analyzed BLDM proteins at different growth stages to clarify the physiological mechanisms of marbled muscle development in 20 head of Korean native cattle (11 month: 10 head, 17 month: 10 head). BLDM proteins were analyzed by two-dimensional electrophoresis and image analysis. Villin 2 was specifically identified by mass spectrometry and a protein search engine. Villin 2 protein expression in BLDM decreased during the fat development stage in test steers. In a Western blot cell culture study of spontaneously immortal bovine muscle fibroblasts, the abundance of Villin 2 was shown to be down-regulated during differentiation into muscle. In 3T3-L1 mouse embryonic fibroblasts, Villin 2 was decreased during differentiation into adipocytes. The results suggest that Villin 2 may be related to the induction of transdifferentiation and adipogenesis in bovine longissimus dorsi muscle. [BMB reports 2012; 45(2): 102-107].

Effects of the Combination of Glucose, Chromium Picolinate, and Vitamin C on Lipid Metabolism in Steers

Lee, Hong-Gu,Yin, Jin-Long,Xu, Cheng-Xiong,Hong, Zhong-Shan,Lee, Zhe-Hu,Jin, Yong-Cheng,Choi, Chang-Weon,Lee, Do-Hyeung,Kim, Kyoung-Hoon,Choi, Yun-Jaie Asian Australasian Association of Animal Productio 2011 Animal Bioscience Vol.24 No.12

This study was conducted to examine the effects of glucose, chromium picolinate (CrP), and vitamin C (Vit C) on lipid metabolism in Korean native steers fitted with indwelling catheters. A total of 12 Korean native steers were randomly allocated to the following treatments: 1) normal control diet, 2) same as 1) +250 g of glucose by intravenous (IV) infusion, 3) same as 2)+13.5 g CrP administered orally, and 4) same as 3)+2.52 g Vit C by IV infusion. Glucose, Vit C, and CrP treatments were administered for five days. At days 1 and 3, serum insulin was higher in treated animals than in those fed the control diet (p<0.05). Serum non-esterified fatty acid (NEFA) concentration in the steers on treatment 2), control+13.5 g CrP, was lower than those on other treatments at 90 min post-infusion on days 1 and 3 (p<0.05). The expression of peroxisome proliferator-activated receptor-${\gamma}$ (PPAR${\gamma}$)2, stearoyl-CoA desaturase-1 (SCD), fatty acid synthase (FAS), and glucose transporter type 4 (Glut 4) in the longissimus muscle of steers on treatment 2 was higher than those on other treatments. In conclusion, the results suggest that CrP is associated with the regulation of gene expression involved in adipogenesis.

Expression of C4.4A is a Potential Independent Prognostic Factor for Patients with Gastric Cancer

Cheng, Da-Qing,Gu, Xiao-Dong,Li, Zhen-Yang,Xiang, Jian-Bin,Chen, Zong-You Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.9

C4.4A, a metastasis-associated gene, encodes a glycolipid-anchored membrane protein which is overexpressed in several human malignancies. However, there are few data available on C4.4A expression and its relationship with progression in gastric cancer. Our study was designed to explore the expression of C4.4A in gastric cancer and to correlate it with clinical outcome. C4.4A expression was studied by quantitative real-time RT-PCR and immunohistochemistry for assessment of correlations with clinicopathological factors. C4.4A mRNA expression was significantly up-regulated in gastric cancer as compared with noncancerous tissue (p<0.05)., being observed in 107 (88.4%) of the 121 gastric cancer cases by immunohistochemistry. We found that the expression of C4.4A mRNA was correlated with size of the tumor, depth of invasion, lymph node metastasis, distant metastasis and TNM stage. Moreover, patients with overexpression of C4.4A has a significantly worse survival (p<0.05). Further multivariable analysis indicated that the expression of C4.4A was an independent prognostic indicator for gastric cancer (p<0.05). In conclusion, overexpression of C4.4A correlates with metastatic potential of gastric cancer and C4.4A could be a novel independent prognostic marker for predicting outcome.

Characterization and Resistance Mechanisms of A 5-fluorouracil-resistant Hepatocellular Carcinoma Cell Line

Gu, Wei,Fang, Fan-Fu,Li, Bai,Cheng, Bin-Bin,Ling, Chang-Quan Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.9

Purpose: The chemoresistance of human hepatocellular carcinoma (HCC) to cytotoxic drugs, especially intrinsic or acquired multidrug resistance (MDR), still remains a major challenge in the management of HCC. In the present study, possible mechanisms involved in MDR of HCC were identified using a 5-fluorouracil (5-FU)-resistant human HCC cell line. Methods: BEL-7402/5-FU cells were established through continuous culturing parental BEL-7402 cells, imitating the pattern of chemotherapy clinically. Growth curves and chemosensitivity to cytotoxic drugs were determined by MTT assay. Doubling times, colony formation and adherence rates were calculated after cell counting. Morphological alteration, karyotype morphology, and untrastructure were assessed under optical and electron microscopes. The distribution in the cell cycle and drug efflux pump activity were measured by flow cytometry. Furthermore, expression of potential genes involved in MDR of BEL-7402/5-FU cells were detected by immunocytochemistry. Results: Compared to its parental cells, BEL-7402/5-FU cells had a prolonged doubling time, a lower mitotic index, colony efficiency and adhesive ability, and a decreased drug efflux pump activity. The resistant cells tended to grow in clusters and apparent changes of ultrastructures occurred. BEL-7402/5-FU cells presented with an increased proportion in S and G2/M phases with a concomitant decrease in G0/G1 phase. The MDR phenotype of BEL-7402/5-FU might be partly attributed to increased drug efflux pump activity via multidrug resistance protein 1 (MRP1), overexpression of thymidylate synthase (TS), resistance to apoptosis by augmentation of the Bcl-xl/Bax ratio, and intracellular adhesion medicated by E-cadherin (E-cad). P-glycoprotein (P-gp) might play a limited role in the MDR of BEL-7402/5-FU. Conclusion: Increased activity or expression of MRP1, Bcl-xl, TS, and E-cad appear to be involved in the MDR mechanism of BEL-7402/5-FU.

Expression of microRNA-218 and its Clinicopathological and Prognostic Significance in Human Glioma Cases

Cheng, Mao-Wei,Wang, Ling-Ling,Hu, Gu-Yu Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.5

Background: MicroRNAs are a class of noncoding RNAs which regulate multiple cellular processes during tumor development. The purpose of this report is to investigate the clinicopathological and prognostic significance of miR-218 in human gliomas. Materials and Methods: Quantitative RT-PCR (qRT-PCR) was conducted to detect the expression of miR-218 in primary normal human astrocytes, three glioma cell lines and 98 paired glioma and adjacent normal brain tissues.Associations of miR-218 with clinicopathological variables of glioma patients were statistically analyzed. Finally, a survival analysis was performed using the Kaplan-Meier method and Cox's proportional hazards model. Results: The expression level of miR-218 in primary normal human astrocytes was significantly higher than that in glioma cell lines (p<0.01). Also, the expression level of miR-218 in glioma tissues was significantly downregulated in comparison with that in the adjacent normal brain tissues (p<0.001). Statistical analyses demonstrated that low miR-218 expression was closely associated with advanced WHO grade (p=0.002) and low Karnofsky performance score (p=0.010) of glioma patients. Kaplan-Meier analysis with the log-rank test showed that patients with low-miR-218 expression had poorer disease-free survival and overall survival (p=0.0045 and 0.0124, respectively). Multivariate analysis revealed that miR-218 expression was independently associated with the disease-free survival (p=0.009) and overall survival (p=0.004) of glioma patients. Conclusions: Our results indicate that miR-218 is downregulated in gliomas and that its status might be a potential valuable biomarker for glioma patients.

Tribological behaviors of self-assembled 3-aminopropyltriethoxysilane films on silicon

Gu Qinlin,Cheng Xianhua 한국물리학회 2008 Current Applied Physics Vol.8 No.5

3-Aminopropyltriethoxysilane (APTES) thin films were prepared on the hydroxylated silicon substrate by a self-assembling process from formulated solution. Chemical compositions of the films were detected by X-ray photoelectron spectrometry (XPS). The thickness of the films was determined with an ellipsometer, while the morphologies of the original and worn surfaces of the samples were analyzed by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. The tribological properties of APTES thin films sliding against GCr15 steel ball were evaluated on a UMT-2MT reciprocating friction and wear tester. It was found that the macroscopic friction coefficients for coating times more than 1 h ranged from 0.177 to 0.3 whereas the value for short coating time was as high as 0.8. It was also found that the tribological behaviors of APTES films were sensitive to normal load and sliding velocity. SEM observation of the morphologies of worn surfaces indicates that the wear of silicon is characteristic of brittle fracture and severe abrasion. Differently, abrasion and micro-crack dominate the wear of APTES–SAM. The superior friction reduction and wear resistance of APTES films compared to the silicon substrate are attributed to good adhesion of the films to the substrate. 3-Aminopropyltriethoxysilane (APTES) thin films were prepared on the hydroxylated silicon substrate by a self-assembling process from formulated solution. Chemical compositions of the films were detected by X-ray photoelectron spectrometry (XPS). The thickness of the films was determined with an ellipsometer, while the morphologies of the original and worn surfaces of the samples were analyzed by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. The tribological properties of APTES thin films sliding against GCr15 steel ball were evaluated on a UMT-2MT reciprocating friction and wear tester. It was found that the macroscopic friction coefficients for coating times more than 1 h ranged from 0.177 to 0.3 whereas the value for short coating time was as high as 0.8. It was also found that the tribological behaviors of APTES films were sensitive to normal load and sliding velocity. SEM observation of the morphologies of worn surfaces indicates that the wear of silicon is characteristic of brittle fracture and severe abrasion. Differently, abrasion and micro-crack dominate the wear of APTES–SAM. The superior friction reduction and wear resistance of APTES films compared to the silicon substrate are attributed to good adhesion of the films to the substrate.

Constructing $G^1$ Quadratic B$\acute{e}$zier Curves with Arbitrary Endpoint Tangent Vectors

Gu, He-Jin,Yong, Jun-Hai,Paul, Jean-Claude,Cheng, Fuhua (Frank) Society for Computational Design and Engineering 2009 International Journal of CAD/CAM Vol.9 No.1

Quadratic B$\acute{e}$zier curves are important geometric entities in many applications. However, it was often ignored by the literature the fact that a single segment of a quadratic B$\acute{e}$zier curve may fail to fit arbitrary endpoint unit tangent vectors. The purpose of this paper is to provide a solution to this problem, i.e., constructing $G^1$ quadratic B$\acute{e}$zier curves satisfying given endpoint (positions and arbitrary unit tangent vectors) conditions. Examples are given to illustrate the new solution and to perform comparison between the $G^1$ quadratic B$\acute{e}$zier cures and other curve schemes such as the composite geometric Hermite curves and the biarcs.

Electrical properties and morphology of highly conductive composites based on polypropylene and hybrid fillers

Gu Zheming,Wang Gengchao,Zhang Ling,Cheng Qilin,Li Xiaohui,Wang Wendong,Jin Shilei,Li Chunzhong 한국공업화학회 2010 Journal of Industrial and Engineering Chemistry Vol.16 No.1

Electrically conductive polypropylene/hybrid filler (PP/GO–MWNTs) and PP/MWNTs composite have been prepared via melt blending PP with the hybrid filler (multiwalled carbon nanotubes (MWNTs) and graphite oxide (GO)) and the single filler (MWNTs), respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to research the interior morphology of the GO–MWNTs hybrid filler, and the dispersion of the hybrid filler in the PP matrix is also observed by SEM. The results show that a clear reduction in electrical resistivity and percolation threshold of PP/GO–MWNTs composite can be ascribed to the corporation of GO. The electrical properties of PP composites were improved owing to the effective conductive networks formed by hybrid filler.