Study on Multi-Field Coupled Evolution Mechanism of Laser Irradiated 40Cr Steel Quenching Process Based on Phase Change Induced Plasticity

Chang Li,Hexin Gao,Xinxue Chen,Zhaotai Liu,Xing Han 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.8

40Cr is essential to steel for the manufacture of hardened gears, and optimizing its laser quenching process will be of greatsignificance for gear wear and life extension. However, the complete reliance on the experimental trial-and-error approachdoes not effectively reveal the mechanism of the evolution of the laser quenching process in disk laser. Numerical simulationprovides an effective way to obtain the transient evolution of the laser quenching process. In this paper, the temperaturechanges physical parameters of the quenched material are calculated based on the CALPHAD method. Establish a thermoelastic–plastic multi-field coupling model for the laser hardening process of the disk laser 40Cr gear steel. Perform thenumerical calculations on the transient temperature, martensite phase fraction, and the transformation-induced plasticitystress evolution of the 40Cr laser hardening process. Focus on the mechanism of the mutual coupling between phase changebehavior and plastic strain. Calculations show that there is heat accumulation during quenching, with a peak temperatureof 1448 K. Plastic stress has a “hump” distribution, with a peak value of 834 MPa, which is 1.25 mm from the center ofthe focal point. The experimental analyses of the 40Cr gear steel quenching microstructure and hardness distribution stateby the Axioskop2 scanning electron microscope, the KEYENCE VH-Z100R super depth of field 3D microscope, and theQ10M microhardness tester reveal the mechanical behavior of the material and the phase hardening law during the quenchingprocess. That provided an essential theoretical basis for effective prediction on quenching residual stress and optimizingindustrial production parameters.

Research on the Characteristic of Diesel Elastic-plate Impingement Spray

( Chang Yuan Wang ),( Yong Shang ),( Xiang Rong Li ),( Fu Shui Liu ),( Cheng Hui Yu ) 한국액체미립화학회 2010 한국액체미립화학회 학술강연회 논문집 Vol.2010 No.-

A series of experimental research results on the characteristic of diesel elastic-plate impingement spray using High Speed Photography camera are presented in this paper. The experiments were carried out in a constant volume chamber specially designed, which can hold a high ambiance pressure. The special fixed device was designed so that the elastic-plate can be fixed on the spray path, meanwhile the spray incident angle and height can be changed. The free jet spray and elastic-plate impingement spray was compared under the same experimental condition including different injection pressure and different background pressure. Experimental research showed that impingement spray droplets diffuse more quickly than free jet spray.

`당풍을 크게 갖춘(唐風大備)` 정지상 - 고려 한시사 상의 첫 고봉-

리우창 ( Liu Chang ) 연민학회 2016 연민학지 Vol.25 No.-

고려 왕조는 개국 200년 후 문화 발전의 전성기에 들어섰다. 이 기간에 작성된 시는 여러 가지 원인으로 대부분 산실되었는데, 오늘까지 전하는 시들은 거의 송시의 영향을 받아 송시의 품격을 보이고 있다. 시인들은 대부분 교제를 위해 시를 썼기 때문에 경치를 묘사하는데 심력을 쏟은 시인은 많지 않았다. 이에 당풍을 담은 작품으로 이름을 날린 시인이 이전에는 그다지 없었지만 한반도의 땅에서 당시풍도 지속적으로 발전해나갔다. 결과적으로 12세기 초에 이르러 정지상으로 인해 시풍이 바뀌게 되었다. 정지상은 시 자체에 집중하는 당시풍의 영향을 받아 세밀한 관찰을 통하여 밝은 경치와 여운을 담은 의경(意經)을 그려냈다. 이로 인하여 정지상의 시는 매우 높은 경지를 이루었으며 “고려 시 발전사 상 최초의 고봉”이라는 평가를 가할 수 있게 되었다. The cultural undertaking of Koryo Dynasty almost achieved a crest at 200 years of accumulation. The poems written at that time had nearly already ceased to exist, and most of the remainders were look like the poems of Song Dynasty. Compared to the scenery-description, these poems were mostly written for communication. The impact of Tang Dynasty on the Korean Peninsula was continuous, but there was no one famous for writing poems with the style of Tang. Until 12 century, Jeong Ji-sang emerged and things had changed. He became the first famous poet of Koryo Dynasty and one of the best poets in Korea history because of meticulous observation, bright scene and artistic conception

깊은 신경망 훈련 및 규제 기법을 이용한 요추 환자의 CT 영상에서 요추 분할

장민혜(Min Hye Chang),양정원(Jeongwon Yang),차보경(Bo Kyung Cha),김진성(Jin-Sung Kim),김은(Eun Kim),Yanting Liu,이경희(Kyeong-Hee Lee) 대한전자공학회 2021 대한전자공학회 학술대회 Vol.2021 No.6

In this paper, DNN training and regularization techniques have been explored for lumbar vertebrae segmentation in CT images of patients with degenerative lumbar spine disease. Combinations of loss function, learning rate schedule, normalization, dropout, moving average, weight decay, and squeeze-and-excitation were empirically tested. The results confirmed that the DNN with optimized training and regularization techniques can improve lumbar vertebrae segmentation without complex structural changes.

RO 및 NF막에서의 부식질에 의한 Fouling 및 미량오염물질의 제거

왕창근,차준철,이용현,김수동,류주환 대한상하수도학회 2004 상하수도학회지 Vol.18 No.1

This study investigated the phenomena of membrane fouling by NOM and the effect of the fouling on removal of micro-pollutants. NOM has a great effect on decline of permeate flux. Permeate flow rate was reduced by 88% in RO and 34.8% in NF for 323hr operation period. Removal rate of UV_(254), is 87.4% in RO and 78.5% in NF and removal rate of DOC is 42.7% in RO and 32.9% in NF for 2㎎/l humic acid. Removal efficiency of the micmpollutants by the RO and NF membranes fouled by humic acid was mostly lower than that by the new membrane. The concentration polarization which affects the flux and the rejection was thought to occur in the active layer of the membrane, as the membrane was getting fouled.

Perspectives on China-Africa Relationships in a context of

Changing World,Zhenke Zhang,Litao Liu 한양대학교 유럽-아프리카연구소 2022 글로벌 거버넌스와 문화 Vol.2 No.1

When talking about Sino-African relationships recently, few concern about China- Africa relationships in the context of the changing world. This study generally reviewed the background of the changing world and the evolution of China-Africa relations. For a long time, the Africa has been regarded as the hopeless continent. In the new century, the African countries experienced a transition from hopeless continent to rising Africa with more potentials. The state and private Chinese enterprises went to African countries not only for the crude oil and gas, the mining, and the forestry business, but also as important partner in infrastructure construction, joint enterprises as well as international trade partners. Most western views of China in Africa contained with negative attitude in the globalization era. The globalization and changing world gave the opportunity for China to improve the relations with African countries, especially in the economic relations. From 2009 to present, China became the top international trade partner in the whole Africa. There are also arguments with China in Africa in the future. The world is a complex socio-ecological system and corresponding with rapid changes, we provide the perspectives on the China-Africa relations in the context of changing world.

《浮生六記》追憶空間的建構與沈復的下層文人心態

LIU CHANG 한국중국어문학회 2019 中國文學 Vol.100 No.-

The academia has always maintained a strong interest in Fu Sheng Liu Ji since it was known to the world. However, current studies mostly focused on English versions translation, classification of works genres, the Image of the heroine Chen Yun, and depicting, which based on content of the works, the life of the lower literati in the mid-Qing Dynasty, yet no systematic discussion on the characteristic construction of memorial space has been carried out. Although real life was used as writing material, a careful reading will reveal that Shen Fu, the author, had the memories significantly split and reassembled, which was achieved through the repetition of fragmentary memory spaces. The intentionally constructed characters of these memory spaces, along with their combinations, and the mentality of the lower literati in the mid-Qing Dynasty are all worthy of further study, these aspects and their relations were discussed in this paper. The second chapter summarized, classified and described the types of memory spaces in the works. Two typical memory spaces were appeared, semi-closed dotted space and open linear space. The former was mainly in Gui Fang Ji Le and Xian Qing Ji Qu while the latter was in Kan Ke Ji Chou and Lang You Ji Kuai. The following discussion was on Shen Fu’s deliberately disconnecting the time chain, and the narrative ways of categorizing and linking these memory spaces. The third chapter revealed the mentality of the lower-class literati in the mid-Qing Dynasty, which hidden behind the special construction mode of Shen Fu’s memory spaces, was believed as a "active marginalization", and specifically manifested in defending the private space, as well as resisting the social space. Therefore, the paper holds that Fu Sheng Liu Ji is not a record of Shen Fu’s life, but a deliberate cutting and reorganizing of the memory spaces, and his active marginalization mentality contributes to the construction of such groups of memory spaces. 《부생육기(浮生六記)》가 발견된 이래, 학계는 줄곧 그에 대해 끊임없는 관심을 가지고 연구를 해 왔다. 그러나 기존의 연구 대부분은 번역본과, 작품 장르의 분류, 여주인공 진운(陳 芸)의 이미지, 작품의 내용으로부터 청나라 중기 하층 문인들의 삶을 조명하고, 묘사하는 등이러한 것에 대해서만 치중해왔다. 사실상 《부생육기》는 실제의 인생을 소재로 삼지만, 텍스트를 자세히 읽어보면 작가 심복(沈復)의 실제 기억을 편집하고, 이는 단편적인 기억공간의재현을 통해 이뤄진다는 것을 알 수 있다. 의도적으로 만들어진 공간들 자체의 특징, 이들 간의 조합 형식, 그리고 그 속에 드러난 청나라 중기 하층 문인들의 심리상태는 깊이 연구할만한 가치가 있는 요소들인데, 본문에서 이 몇 가지 요소에 대해 논의하고자 한다. 2장에서는 먼저 작품 속 추억의 공간 유형을 분류, 묘사하고자 한다. 전형적인 추억의 공간인 반폐쇄형 점 모양의 공간, 열린 형 선 모양의 공간 두 가지가 등장한다. 전자는 주로 앞의 《규방기락(閨房記樂)》과 《한정기취(閒情記趣)》에 나오는데, 후자는 뒤의 《감가기수(坎坷記 愁)》와 《랑유기쾌(浪遊記快)》에 나온다. 이어 심복에 의해 의도적으로 시간의 사슬을 끊고, 이들 추억의 공간을 분류한 후, 다시 연계하는 서술 방식에 대해 검토한다. 3장에서는 심복의특별한 추억의 공간을 구축하는 방식 뒤에 숨어 있는 청 중기 하층 문인의 모습을 보여줌으로써 폐쇄적이고 안정된 사적 공간을 지키는 것을 의미하는 ‘자발적 주변화'의 심리를 구현할것이다. 그래서 《부생육기》는 자신의 삶에 대한 실록이 아니라, 의도적으로 기억공간을 분류하고 재구성한 작품이다. 그리고 심복의 ‘자발적 주변화'라는 심리가 이러한 공간을 구축하게된 것이라고 할 수 있다.

《浮生六記》追憶空間的建構與沈復的下層文人心態

劉暢 ( Liu Chang ) 한국중국어문학회 2019 中國文學 Vol.100 No.-

The academia has always maintained a strong interest in Fu Sheng Liu Ji since it was known to the world. However, current studies mostly focused on English versions translation, classification of works genres, the Image of the heroine Chen Yun, and depicting, which based on content of the works, the life of the lower literati in the mid-Qing Dynasty, yet no systematic discussion on the characteristic construction of memorial space has been carried out. Although real life was used as writing material, a careful reading will reveal that Shen Fu, the author, had the memories significantly split and reassembled, which was achieved through the repetition of fragmentary memory spaces. The intentionally constructed characters of these memory spaces, along with their combinations, and the mentality of the lower literati in the mid-Qing Dynasty are all worthy of further study, these aspects and their relations were discussed in this paper. The second chapter summarized, classified and described the types of memory spaces in the works. Two typical memory spaces were appeared, semi-closed dotted space and open linear space. The former was mainly in Gui Fang Ji Le and Xian Qing Ji Qu while the latter was in Kan Ke Ji Chou and Lang You Ji Kuai. The following discussion was on Shen Fu’s deliberately disconnecting the time chain, and the narrative ways of categorizing and linking these memory spaces. The third chapter revealed the mentality of the lower-class literati in the mid-Qing Dynasty, which hidden behind the special construction mode of Shen Fu’s memory spaces, was believed as a "active marginalization", and specifically manifested in defending the private space, as well as resisting the social space. Therefore, the paper holds that Fu Sheng Liu Ji is not a record of Shen Fu’s life, but a deliberate cutting and reorganizing of the memory spaces, and his active marginalization mentality contributes to the construction of such groups of memory spaces.

5-Aza-2'-deoxycytidine Induces Hepatoma Cell Apoptosis via Enhancing Methionine Adenosyltransferase 1A Expression and Inducing S-Adenosylmethionine Production

Liu, Wei-Jun,Ren, Jian-Guo,Li, Ting,Yu, Guo-Zheng,Zhang, Jin,Li, Chang-Sheng,Liu, Zhi-Su,Liu, Quan-Yan Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.11

In hepatocellular cancer (HCC), lack of response to chemotherapy and radiation treatment can be caused by a loss of epigenetic modifications of cancer cells. Methionine adenosyltransferase 1A is inactivated in HCC and may be stimulated by an epigenetic change involving promoter hypermethylation. Therefore, drugs releasing epigenetic repression have been proposed to reverse this process. We studied the effect of the demethylating reagent 5-aza-2'-deoxycitidine (5-Aza-CdR) on MAT1A gene expression, DNA methylation and S-adenosylmethionine (SAMe) production in the HCC cell line Huh7. We found that MAT1A mRNA and protein expression were activated in Huh7 cells with the treatment of 5-Aza-CdR; the status of promoter hypermethylation was reversed. At the same time, MAT2A mRNA and protein expression was significantly reduced in Huh7 cells treated with 5-Aza-CdR, while SAMe production was significantly induced. However, 5-Aza-CdR showed no effects on MAT2A methylation. Furthermore, 5-Aza-CdR inhibited the growth of Huh7 cells and induced apoptosis and through down-regulation of Bcl-2, up-regulation of Bax and caspase-3. Our observations suggest that 5-Aza-CdR exerts its anti-tumor effects in Huh7 cells through an epigenetic change involving increased expression of the methionine adenosyltransferase 1A gene and induction of S-adenosylmethionine production.

Establishment of the Model Widely Valid for the Melting and Vaporization Zones in Selective Laser Melting Printings Via Experimental Verifications

Chang-Shuo Chang,Kuan-Ta Wu,Chang-Fu Han,Tsung-Wen Tsai,Sung-Ho Liu,Jen-Fin Lin 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.9 No.1

The thermally affected material properties operating in the three phases and porosity variations in the SS316L steel powder have been introduced to the numerical analyses for the transient volumetric heat source (Q) models developed for the solid powder, melting, and vaporization regions in the selective laser melting (SLM). The bulk Q is thus a function of these heat sources and their ratio defined for the liquid and vapor phases. The heat conduction developed for the solid powders with porosity strings the heat convection with Q as the moving heat source to solve two-dimensional temperature distributions efficiently without the confinement of operating conditions and phase presumption. The specimens with single- and multiple-track printings are prepared to investigate the effects of incident energy density (E) and power intensity (I o) on the geometries of single-track printings and the areal surface roughness (Sa) values of the multiple-track printings with 0 and 50% overlap ratios. Laser power and scanning velocity are the controlling factors for the melting pool depth D and width W . D and W become the governing factors for the keyhole with evaporations, which affects the height H of single track after solidification. The W and D results predicted by the theoretical models developed in this study have an error range, 5–20%, compared to the experimental ones, which is much lower than those reported in the literatures (Gusarov et al. in J Heat Transf 131(7):072101, 2009. https ://doi.org/10.1115/1.31092 45 ; Hussein et al. in Mater Des 52:638–647, 2013. https ://doi.org/10.1016/j.matde s.2013.05.070 ; Yin et al. Int J Adv Manuf Technol 83(9–12): 1847–1859, 2016. https ://doi.org/10.1007/s0017 0-015-7609-x ; Andreotta et al. in Finite Elem Anal Des 135: 36–43, 2017. https ://doi.org/10.1016/j.finel .2017.07.002 ). The contact angle ( ϕ * ) is defined as a function of single-track width ( W ) and solidification height ( H ). ϕ * and Sa are significantly reduced as an E is applied beyond its critical value (47.62–57.14 J/mm 3 ). Significant change in Sa is ascribed to the big difference in the morphology and its surface pattern when E or I o reaches its critical value.