Effect of Ti Addition on the Microstructure and High-Temperature Oxidation Property of AlCoCrFeNi High-Entropy Alloy

Gi‑Su Ham,Young‑Kyun Kim,Young Sang Na,Kee‑Ahn Lee 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.1

This study investigated the effect of Ti addition on microstructure and high-temperature oxidation property of AlCoCrFeNihigh-entropy alloy. Ti content was controlled at 0 at% and 1 at%. The two alloys were found to have BCC single phase, andthe average grain sizes of Ti0.0 and Ti1.0 were 47.3 μm and 49.7 μm, respectively, showing similarity. The EDS mappingof the inside of grains found that both alloys were characterized to be divided into Al-Ni element rich region and Cr–Feelement rich region. As a result of high-temperature oxidation test at 1100 °C, oxidation weight gains were measured atTi0.0: 0.75 mg/cm2 and Ti1.0: 0.17 mg/cm2, respectively. The results indicate that Ti addition largely improved high temperatureoxidation resistance of AlCoCrFeNi HEA. Ti1.0 alloy, in particular, showed remarkably more excellent 1100 °Chigh-temperature oxidation resistance than other previously reported major ones such as NiCrAl and FeCrAl. In the surfaceand cross-section observations after oxidation tests, both alloys were found to have Al2O3oxides mostly. While the Ti0.0material was observed to have Al2O3spallation macroscopically, the Ti1.0 alloy showed Al2O3spallation only in some localareas. In addition, a unique result was found in AlCoCrFeNiTix(x=0,1) alloy that BCC → FCC phase transformation was accelerated,and FCC phase layer was formed in the surficial area where Al element had been depleted due to high-temperatureoxidation. Moreover, as Ti was added, the thickness of FCC layer induced by high-temperature oxidation decreased. Basedon the results, it was also discussed on how to improve the high-temperature oxidation resistance of AlCoCrFeNiTixHEA.

Highly stable, rapid colorimetric detection of carbaryl pesticides by azo coupling reaction with chemical pre-treatment

Lee, Myung-Goo,Patil, Virendra,Na, Yun-Cheol,Lee, Doo Sung,Lim, Sung H.,Yi, Gi-Ra Elsevier 2018 Sensors and actuators. B Chemical Vol.261 No.-

<P><B>Abstract</B></P> <P>For rapid detection of carbaryl pesticides, we developed a simple colorimetric detection method based on azo-coupling reaction. Pretreating carbaryl pesticides with an organic base yielded 1-naphthol, which readily reacted with a diazonium salt with a dramatic color change. Since the resulting azo dye can further change color with the organic base used in the pretreatment, phosphoric acid was added to suppress the confounding colorimetric response. We report that this new colorimetric method can selectively detect carbaryl pesticides from other carbamate pesticides within a minute. Moreover, carbaryl can be detected below 10 parts per million (ppm), which is below its permissible exposure limit (∼15 ppm). Finally, we successfully estimated the concentrations of carbaryl pesticides on fruit samples in the presence of natural interferences.</P> <P><B>Highlights</B></P> <P> <UL> <LI> To detect carbaryl pesticides, simple colorimetric detection method is developed based on azo-coupling reaction. </LI> <LI> Carbaryl pesticide can be detected selectively within 1 min with other carbamates. </LI> <LI> Limit-of-detection for carbaryl is lower than permissible exposure level (∼15 ppm). </LI> <LI> The carbaryl concentration are estimated in real fruit samples with natural interferences. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Weighted PageRank Algorithm to Consider the Inter-Page Similarity

Sang-Yeon Lee,Young-Gi Kim,Keon-Myung Lee 한국콘텐츠학회 2014 한국콘텐츠학회 ICCC 논문집 Vol.- No.-

Endo- and Exocyclic Coordination of a 20-Membered N₂O₂S₂-Macrocycle and Cascade Complexation of a 40-Membered N₄O₄S₄-Macrocycle

Lee, Eunji,Lee, Seul-Gi,Park, In-Hyeok,Kim, Seulgi,Ju, Huiyeong,Jung, Jong Hwa,Ikeda, Mari,Habata, Yoichi,Lee, Shim Sung American Chemical Society 2018 Inorganic Chemistry Vol.57 No.11

<P>A 20-membered N<SUB>2</SUB>O<SUB>2</SUB>S<SUB>2</SUB>-macrocycle (<B>L</B><SUP><B>1</B></SUP>) and a 40-membered N<SUB>4</SUB>O<SUB>4</SUB>S<SUB>4</SUB>-macrocycle (<B>L</B><SUP><B>2</B></SUP>) were employed as a [1:1] and a [2:2] cyclization product, respectively, for the preparation of diverse types of supramolecular complexes including a cascade complex. Six complexes (<B>1</B>-<B>6</B>) of the smaller macrocycle <B>L</B><SUP><B>1</B></SUP> including discrete to continuous forms, mono- to heteronuclear, and endo- to exo- and endo/exocoordination were prepared and their coordination modes were discussed systemically. First, the reaction of <B>L</B><SUP><B>1</B></SUP> with CuI in the presence of trifluoroacetic acid afforded an exocyclic 1-D coordination polymer {[(μ<SUB>4</SUB>-Cu<SUB>4</SUB>I<SUB>4</SUB>)(H<B>L</B><SUP><B>1</B></SUP>)<SUB>2</SUB>](CF<SUB>3</SUB>COO)<SUB>2</SUB>}<SUB><I>n</I></SUB> (<B>1</B>). Meanwhile, the reaction of <B>L</B><SUP><B>1</B></SUP> with Cu(ClO<SUB>4</SUB>)<SUB>2</SUB>·6H<SUB>2</SUB>O afforded a typical endocyclic mononuclear complex [Cu<SUP>II</SUP>(<B>L</B><SUP><B>1</B></SUP>)](ClO<SUB>4</SUB>)<SUB>2</SUB>·H<SUB>2</SUB>O (<B>2</B>). In the reactions of <B>L</B><SUP><B>1</B></SUP> with CdX<SUB>2</SUB> (X = Br and I), isostructural sandwich-type complexes [Cd(<B>L</B><SUP><B>1</B></SUP>)<SUB>2</SUB>Br<SUB>2</SUB>] (<B>3</B>) and [Cd(<B>L</B><SUP><B>1</B></SUP>)<SUB>2</SUB>I<SUB>2</SUB>] (<B>4</B>) were isolated. The treatment of <B>L</B><SUP><B>1</B></SUP> with Hg(ClO<SUB>4</SUB>)<SUB>2</SUB> also afforded a sandwich-type complex [Hg(<B>L</B><SUP><B>1</B></SUP>)<SUB>2</SUB>](ClO<SUB>4</SUB>)<SUB>2</SUB> (<B>5</B>). One-pot reaction of <B>L</B><SUP><B>1</B></SUP> with a mixture of HgI<SUB>2</SUB> and CdI<SUB>2</SUB> afforded a dumbbell-type heteronuclear complex {[Cd(<B>L</B><SUP><B>1</B></SUP>)]<SUB>2</SUB>(μ-Hg<SUB>2</SUB>I<SUB>6</SUB>)}[Hg<SUB>2</SUB>I<SUB>6</SUB>] (<B>6</B>), in which the Cd(II) ion occupies the macrocyclic cavity. Further, such two endocyclic Cd(II) complex units are bridged by a square-type (μ-Hg<SUB>2</SUB>I<SUB>6</SUB>)<SUP>2-</SUP> cluster remaining another same cluster separately. The comparative NMR data exhibited a higher affinity of Cd(II) over Hg(II) toward <B>L</B><SUP><B>1</B></SUP>, in the parallel to the situation occurred in the solid state. Meanwhile, complexations of the extra-large macrocycle <B>L</B><SUP><B>2</B></SUP> is more challenging to afford some interesting dimercury(II) coordination products including a cascade complex. In solution, the dimercury(II) perchlorato complex of <B>L</B><SUP><B>2</B></SUP> as a metalloligand shows a preferential binding of dabco (1,4-diazabicyclo[2,2,2]octane), but its dimercury(II) iodo complex has a much smaller affinity for dabco. In order to explain these results, the solid dimercury(II) complexes with different anions [Hg<SUB>2</SUB>(<B>L</B><SUP><B>2</B></SUP>)X<SUB>4</SUB>] (<B>7</B>: X = I, <B>8</B>: X = ClO<SUB>4</SUB>) were prepared and characterized. Further, the dimercury(II) perchlorato complex <B>8</B> reacts with dabco to forms a cascade complex [Hg<SUB>2</SUB>(<B>L</B><SUP><B>2</B></SUP>)(μ-dabco)(ClO<SUB>4</SUB>)<SUB>2</SUB>](ClO<SUB>4</SUB>)<SUB>2</SUB>·2DMF·2ether (<B>9</B>), exhibiting its formation being metal-driven and coordinated anion-regulated. The observed cascade complexation both in solution and solid states is an example of the adaptive guest binding.</P><P>A 20-membered and a 40-membered macrocycles afforded a range of endo/exocoordinated supramolecular complexes including a cascade complex showing anion-regulated organic guest inclusion.</P> [FIG OMISSION]</BR>

A Study on Stable Motion Control of Humanoid Robot with 24 Joints Based on Voice Command

Lee, Woo-Song,Kim, Min-Seong,Bae, Ho-Young,Jung, Yang-Keun,Jung, Young-Hwa,Shin, Gi-Soo,Park, In-Man,Han, Sung-Hyun The Korean Society of Industry Convergence 2018 한국산업융합학회 논문집 Vol.21 No.1

We propose a new approach to control a biped robot motion based on iterative learning of voice command for the implementation of smart factory. The real-time processing of speech signal is very important for high-speed and precise automatic voice recognition technology. Recently, voice recognition is being used for intelligent robot control, artificial life, wireless communication and IoT application. In order to extract valuable information from the speech signal, make decisions on the process, and obtain results, the data needs to be manipulated and analyzed. Basic method used for extracting the features of the voice signal is to find the Mel frequency cepstral coefficients. Mel-frequency cepstral coefficients are the coefficients that collectively represent the short-term power spectrum of a sound, based on a linear cosine transform of a log power spectrum on a nonlinear mel scale of frequency. The reliability of voice command to control of the biped robot's motion is illustrated by computer simulation and experiment for biped walking robot with 24 joint.

Twinning and slip behaviors and microstructural evolutions of extruded Mg-1Gd alloy with rare-earth texture during tensile deformation

Lee, Sang Won,Kim, Sang-Hoon,Jo, Wan-Kuen,Hong, Won-Hwa,Kim, Woong,Moon, Byoung Gi,Park, Sung Hyuk Elsevier 2019 JOURNAL OF ALLOYS AND COMPOUNDS Vol.791 No.-

<P><B>Abstract</B></P> <P>An extruded Mg-1Gd alloy with a non-basal texture, whose basal poles are tilted 60.9° from the extrusion direction (ED), exhibits a high room-temperature tensile elongation of 37.2%. This study investigates the active deformation mechanisms and microstructural evolutions of this highly ductile extruded alloy during tensile deformation through <I>in situ</I> electron backscatter diffraction analysis. When tensile strain is applied along the ED, a small amount of {10-12} twins is formed at the early stage of deformation, and the twins gradually grow with increasing applied strain. However, {10-11} twins and {10-11}-{10-12} twins, which are generally observed in extruded Mg alloys with a typical basal fiber texture, are not formed during deformation. The tilted initial texture is favorable for basal slip, and therefore, basal slip is vigorously activated during tension. As a consequence, the average angle between the <I>c</I>-axis of the grains and the ED increases from 60.9° to 66.3° as the applied tensile strain increases from 0% to 30%. Prismatic slip is also activated during tension, which is confirmed by the gradual increase in the rotation angle of the prismatic poles around the <0001> axis during deformation. The activation of prismatic slip causes a significant reduction in the texture intensity of the alloy during deformation. The high ductility of the Mg-1Gd alloy is attributed mainly to the activation of {10-12} twinning, which is beneficial to elongation, instead of the activation of {10-11} twinning, which is detrimental to elongation, and the promoted activation of basal and non-basal slips. Furthermore, microstructural characteristics such as the fully recrystallized structure, large average grain size, and absence of second-phase particles also contribute to the high ductility of the alloy.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Tensile deformation behaviors of Mg-1Gd alloy with an RE texture are investigated. </LI> <LI> {10-12} Twins—not {10-11} twins detrimental to elongation—are formed under tension. </LI> <LI> Basal poles move away from the ED with deformation by the activation of basal slip. </LI> <LI> Lattice rotation by activation of prismatic slip causes gradual texture weakening. </LI> <LI> The alloy's high ductility is due mainly to the activation of twinning and slips. </LI> </UL> </P>

2 cases of chronic non-healing lesion on face: from hidden facial-lifting threads

( Gi-wook Lee ),( Yeona Kim ),( Sang-hyeon Won ),( Kyung-nam Bae ),( Jungsoo Lee ),( Kihyuk Shin ),( Hyunchang Ko ),( Byungsoo Kim ),( Moon-bum Kim ),( Hoonsoo Kim ) 대한피부과학회 2022 대한피부과학회 학술발표대회집 Vol.73 No.2

Semiautomated spleen volumetry with diffusion‐weighted MR imaging

Lee, Jeongjin,Kim, Kyoung Won,Lee, Ho,Lee, So Jung,Choi, Sanghyun,Jeong, Woo Kyoung,Kye, Heewon,Song, Gi‐,Won,Hwang, Shin,Lee, Sung‐,Gyu Wiley Subscription Services, Inc., A Wiley Company 2012 Magnetic resonance in medicine Vol.68 No.1

<P><B>Abstract</B></P><P>In this article, we determined the relative accuracy of semiautomated spleen volumetry with diffusion‐weighted (DW) MR images compared to standard manual volumetry with DW‐MR or CT images. Semiautomated spleen volumetry using simple thresholding followed by 3D and 2D connected component analysis was performed with DW‐MR images. Manual spleen volumetry was performed on DW‐MR and CT images. In this study, 35 potential live liver donor candidates were included. Semiautomated volumetry results were highly correlated with manual volumetry results using DW‐MR (<I>r</I> = 0.99; <I>P</I> < 0.0001; mean percentage absolute difference, 1.43 ± 0.94) and CT (<I>r</I> = 0.99; <I>P</I> < 0.0001; 1.76 ± 1.07). Mean total processing time for semiautomated volumetry was significantly shorter compared to that of manual volumetry with DW‐MR (<I>P</I> < 0.0001) and CT (<I>P</I> < 0.0001). In conclusion, semiautomated spleen volumetry with DW‐MR images can be performed rapidly and accurately when compared with standard manual volumetry. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.</P>

THE EXISTENCE THEOREM OF ORTHOGONAL MATRICES WITH <SUB>p</SUB> NONZERO ENTRIES

GI-SANG CHEON,SANG-GU LEE,SEOK-ZUN SONG 한국산업응용수학회 2000 Journal of the Korean Society for Industrial and A Vol.4 No.1

Hydration-induced rapid growth and regression after indirect revascularization of an anterior choroidal artery aneurysm associated with Moyamoya disease: A case report

Gi Yeop Lee,Byung-Kyu Cho,Sung Hwan Hwang,Haewon Roh,Jang Hun Kim 대한뇌혈관외과학회 2023 Journal of Cerebrovascular and Endovascular Neuros Vol.25 No.1

The prevalence of aneurysm formation in adults with Moyamoya disease (MMD) is higher than that in the general population. The treatment strategy is often individualized based on the patient’s disease characteristics. A 22-year-old man was diagnosed with MMD after presenting a small thalamic intracerebral and subarachnoid hemorrhage in the quadrigeminal cistern. Cerebral angiography revealed a small aneurysm (2.42 mm) in the left anterior choroidal artery. Since the hemodynamics in the left hemisphere was compromised, an indirect bypass surgery was performed. The patient’s condition deteriorated postoperatively because of poor perfusion of the internal carotid artery, and massive hydration was required. During neurocritical care, the aneurysm increased in size (5.33 mm). An observation strategy was adopted because of the distal aneurysmal location and the high risk involved. Subsequently, the patient recovered, and newly developed collateral flow appeared from the external carotid artery. Additionally, a dramatic size reduction of the aneurysm (1.51 mm) was noticed. Our case suggests that MMD-related dissecting aneurysms on a distal cerebral artery, which present a high risk of embolization, could be managed by indirectly reducing the hemodynamic burden. Massive hydration in such cases should be avoided or balanced to avoid the risk of rapid growth and aneurysm rupture.