Austenite Grain Growth Behavior of 30BF Steel Before Rough Rolling

Yong‑feng Chen,Jian‑bo Xie,Yan‑xin Wu,Jian‑xun Fu 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.4

To investigate the eff ect of heat treatment on the grain size of austenite in 30BF steel, the comparisons of the morphologiesand sizes of austenite grains between heating samples were made with a high-temperature electric resistance furnace, andthe austenite growth models were built with method of mathematics. The results show that most grains in original specimenwith the sizes below 70 μm uniformly distributed. At a heating rate ( v ) of 10 °C/s, the grain size ( d ) value under a certain time( t ) increased by 60–100 μm with raising temperature ( T ) from 850 to 1100 °C, whereas the d value under a certain T merelyincreased by 70–120 μm with raising time to 60 min. Under v = 0.1 °C/s, T = 850 °C, and t = 0 s, the occupied ratio of grainswith sizes of 40–50 μm was 0.165, whereas at 900 °C, the occupied ratio was 0.125. The evolutions of ln (d5.8− d5.80 ) with1/ T were in negative linear correlations, whereas the ln (d5.8− d5.80 ) with ln t were in positive linear correlations. To sum up,the grain growth behavior of steel was elucidated.

방한 중국관광객이 지각한 서울관광지이미지가 관광만족도와 충성도에 미친 영향에 관한 연구

진남,교광휘,이용일 남서울대학교 2009 남서울대학교 논문집 Vol.15 No.1

Typically we can not see it intangibly in the pre-purchase. When compared tourism product to other products, we swallow the uncertain and risk purchase in large quantity. Therefore, tourists' expectations for tourism attractions based on the image, active and intensive navigation through the tourists' information that they need to travel, they will get the positive and unique tourism attractions and they will select the good image.The study selected Chinese tourists as target population, and tried to find the impacts of tourism destination image of Seoul, tourism satisfaction & tourism loyalty to Seoul. Literature research and survey were used in this study.Among Chinese tourists' demographic characteristics, except gender, age, income, the other variables like educational level, marital level and jobs all have obvious differences with tourism destination image of Seoul.Multi- regression analysis also revealed that tourism destination image of Seoul has a positive correlation with tourism satisfaction & tourism loyalty. In the end the insufficiency of this study is put forward and recommendations on the future study are also given. Key Words : Seoul's Tourism Destination Image, Tourism Satisfaction, Tourism Loyalty, Chinese Tourist

1997~2000년에 발생된 황사에 관한 연구

정용승,김학성,낫짜가도르지 엘,적데어 디,첸 수잰 한국교원대학교 환경과학연구소 2002 환경연구논문집 Vol.- No.7

Joint monitoring of yellow sand (YS) phenomena occurred from 1997 to 2000 was carried out. It was found that the YS in source regions occurred in any time during the year, while the severe dust storms occurred frequently from March to May after the spring thaw. Wind erosion occurred usually with wind greater than about 8 ms^-1 in the source region in any seasons. However, severe YS phenomenon found to occur with wind greater than 15 ms^-1 at least for 3 hours or more. In source regions, YS occurred over 60∼120 days per year. In Korea, YS was found to occur 8∼12 cases per year with 12-22 YS days. It was recorded that maximum concentrations of TSP were 989∼1396 ㎍ m^-3 with PM10 values of 861∼996 ㎍ m^-3 and with the lowest visibility of 1.4∼1.6km. In Mongolia, however, it was observed that the number of dusty days decreased due to the increase in rainy days.

엉겅퀴로부터 분리한 Silymarin 및 Silybin이 Macrophages에 의한 사람 Low Density Lipoprotein의 산화에 대한 항산화 효과

류병호,이백천,정영기 동의대학교 기초과학연구소 1998 基礎科學硏究論文集 Vol.8 No.1

This study was undertaken to evaluate an antioxidative activity of silymarin and silybin obtained from Silybum marianum against oxidation of human low density lipoprotein (LDL). The electrophoretic mobility observed apparently was higher phase for LDL oxidized by macrophages compared to native LDL. Silymarin and silybin inhibited the copper-catalysed oxidation of human LDL in a dose-dependent manner. Silymarin and silybin at the concentration of 50μM/ml also inhibited the copper catalysed oxidation of LDL induced by the cell J774 and macrophages. LDL reisolated from the cell incubation in the presence of silymarin or silybin was degraded at rates similar with native LDL. Silymarin or silybin found to be potential inhibitors against oxidation of ^125I-LDL by macrophages and endothelial cells.

비부비동 반정성 유두종의 전산화 단층촬영상과 자기공명영상의 분석

배창훈,서영중,이석춘,천승민,백운희,정은채,송시연,김용대 영남대학교 의과대학 2005 Yeungnam University Journal of Medicine Vol.22 No.2

Background: Computed tomography (CT) is commonly used to evaluate the degree of sinus involvement in case of inverted papilloma (IP). However, CT cannot differentiate tumor from adjacent inflammatory mucosa or retained secretions. By contrast, magnetic resonance imaging (MRI) has been reported to be useful in distinguishing IP from paranasal sinusitis. This study investigated whether preoperative assessment with MRI and CT accurately predict the extent of IP. Materials and methods: CT and MRI were retrospectively reviewed in 9 case of IP. Patients were categorized into staged based on CT and MRI findings according to the staging system proposed by Krouse. The involvement of IP in each sinus was also assessed. Results: Differentiation of IP from inflammatory disease may be more successful in routine case where the inflammatory mucosa has low signal intensity on T1-weighted images and very high signal intensity on T2-weighted images. CT imaging could not differentiate tumor from adjacent inflammatory mucosa or retained secretions. Conclusion: Preoperative MRI of IP can predict the location and extent of the tumor involvement in the paranasal sinuses and sometimes predicts malignant changes.

Attenuation of Experimental Autoimmune Hepatitis in Mice with Bone Mesenchymal Stem Cell-Derived Exosomes Carrying MicroRNA-223-3p

Yong-Ping Chen,Feng-Bin Lu,Da-Zhi Chen,Lu Chen,En-De Hu,Jin-Lu Wu,Hui Li,Yue-Wen Gong,Zhuo Lin,Xiao-Dong Wang,Ji Li,Xiao-Ya Jin,Lan-Man Xu 한국분자세포생물학회 2019 Molecules and cells Vol.42 No.12

MicroRNA-223-3p (miR-223-3p) is one of the potential microRNAs that have been shown to alleviate inflammatory responses in pre-clinical investigations and is highly encased in exosomes derived from bone mesenchymal stem cells (MSC-exosomes). MSC-exosomes are able to function as carriers to deliver microRNAs into cells. Autoimmune hepatitis is one of the challenging liver diseases with no effective treatment other than steroid hormones. Here, we examined whether MSC-exosomes can transfer miR-223-3p to treat autoimmune hepatitis in an experimental model. We found that MSC-exosomes were successfully incorporated with miR-223-3p and delivered miR-223-3p into macrophages. Moreover, there was no toxic effect of exosomes on the macrophages. Furthermore, treatments of either exosomes or exosomes with miR-223-3p successfully attenuated inflammatory responses in the liver of autoimmune hepatitis and inflammatory cytokine release in both the liver and macrophages. The mechanism may be related to the regulation of miR-223-3p level and STAT3 expression in the liver and macrophages. These results suggest that MSC-exosomes can be used to deliver miR-223-3p for the treatment of autoimmune hepatitis.

A Secondary Resonance Soft Switching Half Bridge DC-DC Converter with an Inductive Output Filter

Chen, Zhang-yong,Chen, Yong The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.6

In this paper, a secondary resonance half-bridge dc-dc converter with an inductive output filter is presented. The primary side of such a converter utilizes asymmetric pulse width modulation (APWM) to achieve zero-voltage switching (ZVS) of the switches, and clamps the voltage of the switch to the input voltage. In addition, zero current switching (ZCS) of the output diode is achieved by a half-wave rectifier circuit with a filter inductor and a resonant branch in the secondary side of the proposed converter. Thus, the switching losses and diode reverse-recovery losses are eliminated, and the performance of the converter can be improved. Furthermore, an inductive output filter exists in the converter reduce the output current ripple. The operational principle, performance analysis and design equation of this converter are given in this paper. The analysis results show that the output diode voltage stress is independent of the duty cycle, and that the voltage gain is almost linear, similar to that of the isolation Buck-type converter. Finally, a 200V~380V input, 24V/2A output experimental prototype is built to verify the theoretical analysis.

Cav3.2 T-Type Ca2+ Channel-Dependent Activation of ERK in Paraventricular Thalamus Modulates Acid-Induced Chronic Muscle Pain.

Chen, Wen-Kwei,Liu, Ingrid Y,Chang, Ya-Ting,Chen, Yong-Cyuan,Chen, Chih-Cheng,Yen, Chen-Tung,Shin, Hee-Sup,Chen, Chien-Chang The Society 2010 The Journal of neuroscience Vol.30 No.31

<P>Treatments for chronic musculoskeletal pain, such as lower back pain, fibromyalgia, and myofascial pain syndrome, remain inadequate because of our poor understanding of the mechanisms that underlie these conditions. Although T-type Ca(2+) channels (T-channels) have been implicated in peripheral and central pain sensory pathways, their role in chronic musculoskeletal pain is still unclear. Here, we show that acid-induced chronic mechanical hyperalgesia develops in Ca(v)3.1-deficient and wild-type but not in Ca(v)3.2-deficient male and female mice. We also show that T-channels are required for the initiation, but not maintenance, of acid-induced chronic muscle pain. Blocking T-channels using ethosuximide prevented chronic mechanical hyperalgesia in wild-type mice when administered intraperitoneally or intracerebroventricularly, but not intramuscularly or intrathecally. Furthermore, we found an acid-induced, Ca(v)3.2 T-channel-dependent activation of ERK (extracellular signal-regulated kinase) in the anterior nucleus of paraventricular thalamus (PVA), and prevention of the ERK activation abolished the chronic mechanical hyperalgesia. Our findings suggest that Ca(v)3.2 T-channel-dependent activation of ERK in PVA is required for the development of acid-induced chronic mechanical hyperalgesia.</P>

A Secondary Resonance Soft Switching Half Bridge DC-DC Converter with an Inductive Output Filter

Zhang-yong Chen,Yong Chen 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.6

In this paper, a secondary resonance half-bridge dc-dc converter with an inductive output filter is presented. The primary side of such a converter utilizes asymmetric pulse width modulation (APWM) to achieve zero-voltage switching (ZVS) of the switches, and clamps the voltage of the switch to the input voltage. In addition, zero current switching (ZCS) of the output diode is achieved by a half-wave rectifier circuit with a filter inductor and a resonant branch in the secondary side of the proposed converter. Thus, the switching losses and diode reverse-recovery losses are eliminated, and the performance of the converter can be improved. Furthermore, an inductive output filter exists in the converter reduce the output current ripple. The operational principle, performance analysis and design equation of this converter are given in this paper. The analysis results show that the output diode voltage stress is independent of the duty cycle, and that the voltage gain is almost linear, similar to that of the isolation Buck-type converter. Finally, a 200V~380V input, 24V/2A output experimental prototype is built to verify the theoretical analysis.

EMI Noise Source Reduction of Single-Ended Isolated Converters Using Secondary Resonance Technique

Zhang-yong Chen,Yong Chen,Qiang Chen,Wei Jiang,Rongqiang Zhong 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.2

Aiming at the problems of large dv/dt and di/dt in traditional single-ended converters and high electromagnetic interference (EMI) noise levels, a single-ended isolated converter using the secondary resonance technique is proposed in this paper. In the proposed converter, the voltage stress of the main power switch can be reduced and the voltage across the output diode is clamped to the output voltage when compared to the conventional flyback converter. In addition, the peak current stress through the main power switch can be decreased and zero current switching (ZCS) of the output diode can be achieved through the resonance technique. Moreover, the EMI noise coupling path and an equivalent model of the proposed converter topology are presented through the operational principle of the proposed converter. Analysis results indicate that the common mode (CM) EMI noise and the differential mode (DM) EMI noise of such a converter are deduced since the frequency spectra of the equivalent controlled voltage sources and controlled current source are decreased when compared with the traditional flyback converter. Furthermore, appropriate parameter selection of the resonant circuit network can increase the equivalent impedance in the EMI coupling path in the low frequency range, which further reduces the common mode interference. Finally, a simulation model and a 60W experimental prototype of the proposed converter are built and tested. Experimental results verify the theoretical analysis.