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Prediction of Melt Pool Dimension and Residual Stress Evolution with Thermodynamically-Consistent Phase Field and Consolidation Models during Re-Melting Process of SLM

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Computers, Materials & Continua 2021年第1期66卷 87-112页

作者： Kang-hyun lee gun Jin Yun Department of Aerospace Engineering Seoul National UniversitySeoul08826South Korea Institute of Advanced Aerospace Technology Seoul National UniversitySeoul08826South Korea

Re-melting process has been utilized to mitigate the residual stress level in the selective laser melting(SLM)process in recent ***,the complex consolidation mechanism of powder and the different material behavior after the first laser melting hinder the direct implementation of the re-melting *** this work,the effects of re-melting on the temperature and residual stress evolution in the SLM process are investigated using a thermo-mechanically coupled finite element *** degree of consolidation is incorporated in the energy balance equation based on the thermodynamically-consistent phase-field *** drastic change of material properties due to the variation of temperature and material state is also *** the proposed simulation framework,the single-track scanning is simulated first to predict the melt pool dimension and validate the proposed model with the existing experimental *** obtained thermal histories reveal that the highest cooling rate is observed at the end of the local solidification time which acts as an important indicator for the alleviation of temperature ***,the scanning of a whole single layer that consists of multiple tracks is simulated to observe the stress evolution with several re-melting *** the full melting of powder material in the first scanning process,the increase of residual stress level is observed with one remelting ***,the predicted stress level with the re-melting process shows the variation trend attributable to the accumulated heat in the *** numerical issues and the detailed implementation process are also introduced in this paper.

关键词： Selective laser melting thermo-mechanical analysis Ti-6Al-4V additive manufacturing re-melting residual stress

The Characteristics of CLHS Driving for High Luminance Efficiency in AC PDP

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Plasma Science and Technology 2016年第11期18卷 1116-1122页

作者： gun-Su KIM Chi-hyung AHN Seok-hyun lee Department of Electrical and Electronic Engineering Youngsan UniversityYangsanGyeongnam 50510Korea Korea Railroad Research Institute Uiwang Gyeonggi 16105Korea School of Electrical Engineering Inha UniversityIncheon 22212Korea

This paper proposes a CLHS （Capacitor Less Half Sustain） driving method that is applied to a long gap panel to reduce the power consumption. In order to reduce the power consumption in moving images, the luminous efficiency should be improved at the low discharge load （〈25%）. The weight of reactive power consumption tends to increase as the low discharge load decreases. Thus, it is very important to improve the luminous efficiency at low discharge load. It is well known that a long gap panel improves the luminance and the luminous efficiency but it is very difficult to drive the panel due to high driving voltage. It is confirmed that the main factors which cause a long gap panel to increase the minimum driving voltages are not only a long discharge gap but also self-erasing discharge. Self-erasing discharge is generated between the address and sustain electrodes in a sustain period. The CLHS driving method can reduce the reactive power consumption in a sustain period because energy recovery capacitors were removed in the sustain circuit. The CLHS driving method can reduce the minimum driving voltage of the long gap panel because the self-erasing discharge was prevented. When the CLHS driving method was applied to the panel with an ITO gap of 100 μm, Vs and VA minimum voltages are reduced by about 9 V and 12 V compared with those of the normal driving method. The luminance and the luminous efficiency also increased by about 24.3% and 33.3% at the discharge load of 4% compared with those at the normal condition.

关键词： PDP plasma long gap CLHS

Small sphincterotomy combined with endoscopic papillary large balloon dilation versus sphincterotomy

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World Journal of Gastroenterology 2009年第34期15卷 4298-4304页

作者： hyun gun Kim Young Koog Cheon Young Deok Cho Jong Ho Moon Do hyun Park Tae Hoon lee hyun Jong Choi Sang-Heum Park Joon Seong lee Moon Sung lee Institute for Digestive Research Digestive Disease Center Soonchunhyang University College of Medicine

AIM： To compare small sphincterotomy combined with endoscopic papillary large balloon dilation （SES ＋ ELBD） and endoscopic sphincterotomy （EST） for large bile duct stones. METHODS： We compared prospectively SES ＋ ELBD （group A, n = 27） with conventional EST （group B, n = 28） for the treatment of large bile duct stones （≥ 15 mm）. When the stone could not be removed with a normal basket, mechanical lithotripsy was performed. We compared the rates of complete stone removal with one session and application of mechanical lithotripsy. RESULTS： No significant differences were observed in the mean largest stone size （A： 20.8 mm, B： 21.3 mm）, bile duct diameter （A： 21.4 turn, B： 20.5 ram）, number of stones （A： 2.2, B： 2.3）, or procedure time （A： 18 min, B： 19 rain） between the two groups. The rates of complete stone removal with one session was 85% in group A and 86% in group B （P = 0.473）. Mechanical lithotripsy was required for stone removal in nine of 27 patients （33%） in group A and nine of 28 patients （32%, P = 0.527） in group ***： SES ＋ ELBD did not show significant benefits compared to conventional EST, especially for the removal of large （≥ 15 mm） bile duct stones.

关键词： Sphincterotomy Endoscopic Balloon dilatation Cholelithiasis Lithotripsy

Impacts of optimization strategies on performance,power/energy consumption of a GPU based parallel reduction

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Journal of Central South University 2017年第11期24卷 2624-2637页

作者： Phuong Thi Yen lee Deok-Young lee Jeong-gun Smart Computing Lab. Department of Computer EngineeringHallym UniversityChuncheon 24252Korea College of General Education Hallym UniversityChuncheon 24252Korea

In the era of modern high performance computing, GPUs have been considered an excellent accelerator for general purpose data-intensive parallel applications. To achieve application speedup from GPUs, many of performance-oriented optimization techniques have been proposed. However, in order to satisfy the recent trend of power and energy consumptions, power/energy-aware optimization of GPUs needs to be investigated with detailed analysis in addition to the performance-oriented optimization. In this work, in order to explore the impact of various optimization strategies on GPU performance, power and energy consumptions, we evaluate performance and power/energy consumption of a well-known application running on different commercial GPU devices with the different optimization strategies. In particular, in order to see the more generalized performance and power consumption patterns of GPU based accelerations, our evaluations are performed with three different Nvdia GPU generations(Fermi, Kepler and Maxwell architectures), various core clock frequencies and memory clock frequencies. We analyze how a GPU kernel execution is affected by optimization and what GPU architectural factors have much impact on its performance and power/energy consumption. This paper also categorizes which optimization technique primarily improves which metric(i.e., performance, power or energy efficiency). Furthermore, voltage frequency scaling(VFS) is also applied to examine the effect of changing a clock frequency on these metrics. In general, our work shows that effective GPU optimization strategies can improve the application performance significantly without increasing power and energy consumption.

关键词： parallel reduction GPU code optimization power energy voltage frequency scaling

Zwitterion-assisted transition metal dichalcogenide nanosheets for scalable and biocompatible inkjet printing

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Nano Research 2020年第10期13卷 2726-2734页

作者： Hyeokjung lee Min Koo Chanho Park Madhumita Patel Hyowon Han Tae hyun Park Pawan Kumar Won-gun Koh Cheolmin Park Department of Materials Science and Engineering Yonsei University Seoul 03722Republic of Korea Department of Chemical and Biomolecular Engineering Yonsei UniversitySeoul 03722Republic of Korea

Inkjet printing of two-dimensional(2D)transition metal dichalcogenide(TMD)nanosheets fabricated by liquid-phase exfoliation(LPE)allows simple,mass-producible,and low-cost photo-electronic *** LPE processes involve toxic and environmentally hazardous solvents;however,dispersants have restricted the extent of applications of 2D-TMD ***,various 2D-TMD nanosheets,including MoS2,MoSe2,WS2,and WSe2,in addition to few-layered graphene,are inkjet-printed using a LPE process based on zwitterionic dispersants in *** with cationic and anionic species are water-soluble,while alkyl chain moieties associated with two ionic species adhere universally on the surface of TMD nanosheets,resulting in high throughput liquid exfoliation of the *** zwitterion-assisted TMD nanosheets in water are successtully employed as an ink without the need for additives to adjust the viscosity and surface tension of the ink for use in an office inkjet printer;this gives rise to A4 scale,large-area inkjet-printed images on diverse substrates,such as metals,oxides,and polymer substrates patchable onto human *** with conductive graphene nanosheet inks allowed the development of mechanically flexible,biocompatible-printed arrays of photodetectors with pixelated MoSe2 channels on a paper exhibiting a photocurrent ON/OFF ratio of approximately 1038 and photocurrent switching of 500 ms.

关键词： transition metal dichalcogenide nanosheets zwitterions zwitterion-assisted liquid-phase exfoliation scalable inkjet printing biocompatible

Does immunohistochemical staining have a clinical impact in early gastric cancer conducted endoscopic submucosal dissection?

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World Journal of Gastroenterology 2012年第33期18卷 4578-4584页

作者： Seong Ran Jeon Joo Young Cho Gene hyun Bok Tae Hee lee hyun gun Kim Won Young Cho So Young Jin Yeon Soo Kim Institute for Digestive Research Digestive Disease Center Soonchunhyang University College of Medicine Seoul 140-743 South Korea Department of Pathology Soonchunhyang University College of Medicine Seoul 140-743 South Korea Department of Internal Medicine Daejeon St. Mary's Hospital The Catholic University of Korea School of Medicine Daejeon 301-723 South Korea

AIM: To evaluate clinicopathologic parameters and the clinical significance related lymphovascular invasion (LVI) by immunohistochemical staining (IHCS) in endoscopic submucosal dissection (ESD). METHODS: Between May 2005 and May 2010, a total of 348 lesions from 321 patients (mean age 63 ± 10 years, men 74.6%) with early gastric cancer (EGC) who met indication criteria after ESD were analyzed retrospectively. The 348 lesions were divided into the absolute (n = 100, differentiated mucosal cancer without ulcer ≤ 20 mm) and expanded (n = 248) indica-tion groups after ESD. The 248 lesions were divided into four subgroups according to the expanded ESD indication. The presence of LVI was determined by factor Ⅷ-related antigen and D2-40 assessment. We compared LVI IHCS-negative group with LVI IHCSpositive in each group. RESULTS: LVI by hematoxylin-eosin staining (HES) and IHCS were all negative in the absolute group, while was observed in only the expanded groups. The positive rate of LVI by IHCS was higher than that of LVI by HES (n = 1, 0.4% vs n = 11, 4.4%, P = 0.044). LVI IHCS-positivity was observed when the cancer invaded to the mucosa 3 (M3) or submucosa 1 (SM1) levels, with a predominance of 63.6% in the subgroup that included only SM1 cancer (P < 0.01). In a univariate analysis, M3 or SM1 invasion by the tumor was significantly associated with a higher rate of LVI by IHCS, but no factor was significant in a multivariate analysis. There were no cases of tumor recurrence or metastasis during the median 26 mo follow-up. CONCLUSION: EGCs of the absolute group are immunohistochemically stable. The presence of LVI may be carefully examined by IHCS in an ESD expanded indication group with an invasion depth of M3 or greater.

关键词： Gastric cancer Endoscopic submucosal dis- section Immunohistochemical staining Lymphovascu- lar invasion Depth

Promoting dynamic recrystallization and improving strength and ductility of Mg-7Bi alloy through Al addition

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Journal of Magnesium and Alloys 2024年第8期12卷 3339-3356页

作者： gun Woong An Sang-Cheol Jin hyun Ji Kim Sumi Jo Sung Hyuk Park Department of Materials Science and Metallurgical Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Graduate School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea

This study investigated the influence of the addition of Al to a Mg-7Bi(B7,wt%)alloy,particularly its recrystallization behavior during extrusion and its resulting mechanical *** addition of 2 wt%Al to the B7 alloy resulted in a lower grain size,a reduction in the number density of fine Mg3Bi2 particles,and a higher area fraction of relatively coarse Mg3Bi2 particles in the extrusion *** microstructural changes increased the nucleation sites for recrystallization,reduced the Zener pinning effect,and enhanced particle-stimulated nucleation,all of which promoted dynamic recrystallization behavior during *** a result,the area fraction of recrystallized grains in the extruded alloy increased from 77%to 94%.The extruded B7 alloy exhibited a strongfiber texture,whereas the extruded Mg-7Bi-2Al(BA72)alloy had a weak-texture,which was attributed to the minimal presence of unrecrystallized grains and the dispersed orientation of the recrystallized *** tensile yield strength(TYS)of the extruded BA72 alloy was higher than that of the extruded B7 alloy(170 and 124 MPa,respectively),which resulted from the enhanced grain-boundary and solid-solution strengthening *** tensile elongation(EL)of the BA72 alloy also exceeded that of the B7 alloy(20.3%and 6.1%,respectively),the result of the uniform formation of fine twins under tension in the former and the formation of a few coarse twins among the unrecrystallized grains in the ***,the addition of a small amount of Al to the B7 alloy significantly improved both the strength and ductility of the extruded alloy,resulting in a remarkable increase in the product of the TYS and EL from 756 to 3451 MPa%and expanding its potential range of applications as a lightweight extruded structural component.

关键词： Mg-7Bi alloy Al addition Extrusion Recrystallization Microstructure

A Study on Classification and Detection of Small Moths Using CNN Model

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Computers, Materials & Continua 2022年第4期71卷 1987-1998页

作者： Sang-hyun lee Department of Computer Engineering Honam UniversityGwangsanguGwangju62399South Korea

Currently,there are many limitations to classify images of small *** addition,there are limitations such as error detection due to external factors,and there is also a disadvantage that it is difficult to accurately distinguish between various *** paper uses a convolutional neural network(CNN)algorithm to recognize and classify object images of very small moths and obtain precise data images.A convolution neural network algorithm is used for image data classification,and the classified image is transformed into image data to learn the topological structure of the *** improve the accuracy of the image classification and reduce the loss rate,a parameter for finding a fast-optimal point of image classification is set by a convolutional neural network and a pixel image as a *** a result of this study,we applied a convolution neural network algorithm to classify the images of very small moths by capturing precise images of the *** results showed that the accuracy of classification of very small moths was more than 90%.

关键词： Convolution neural network rectified linear unit activation function pooling feature map

A Study on Cascade R-CNN-Based Dangerous Goods Detection Using X-Ray Image

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Computers, Materials & Continua 2022年第11期73卷 4245-4260页

作者： Sang-hyun lee Department of Computer Engineering Honam UniversityGwangsanguGwangju 62399Korea

X-ray inspection equipment is divided into small baggage inspection equipment and large cargo inspection *** the case of inspection using X-ray scanning equipment,it is possible to identify the contents of goods,unauthorized transport,or hidden goods in real-time by-passing cargo through X-rays without opening *** this paper,we propose a system for detecting dangerous objects in X-ray images using the Cascade Region-based Convolutional Neural Network(Cascade R-CNN)model,and the data used for learning consists of dangerous goods,storage media,firearms,and *** addition,to minimize the overfitting problem caused by the lack of data to be used for artificial intelligence(AI)training,data samples are increased by using the CP(copy-paste)algorithm on the existing *** also solves the data labeling problem by mixing supervised and semi-supervised *** four comparative models to be used in this study are Faster Regionbased Convolutional Neural Networks Residual2 Network-101(Faster R-CNN_Res2Net-101)supervised learning,Cascade R-CNN_Res2Net-101_supervised learning,Cascade Region-based Convolutional Neural Networks Composite Backbone Network V2(CBNetV2)Network-101(Cascade R-CNN_CBNetV2Net-101)_supervised learning,and Cascade RCNN_CBNetV2-101_semi-supervised learning which are then compared and *** a result of comparing the performance of the four models in this paper,in case of Cascade R-CNN_CBNetV2-101_semi-supervised learning,Average Precision(AP)(Intersection over Union(IoU)=0.5):0.7%,AP(IoU=0.75):1.0%than supervised learning,Recall:0.8%higher.

关键词： Cascade R-CNN model faster R-CNN model X-ray screening equipment Res2Net supervised learning semi-supervised learning