Effect of post annealing on the microstructure, mechanical properties, and failure of Mo_xW_1-xSi₂ heaters produced by self-propagating high-temperature synthesis

Cho, Myung-Yeon,Lee, Sung-Chul,Park, Chulhwan,Lee, Daeseok,Koo, Sang-Mo,Moon, Kyoung-Sook,Lee, Dong-Won,Oh, Jong-Min Elsevier 2019 INTERMETALLICS Vol.110 No.-

<P><B>Abstract</B></P> <P>High-performance tungsten molybdenum disilicide (Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB>) heating elements were prepared using a self-propagating high temperature synthesis process. The effect of post annealing on the degradation behavior of the alloy was experimentally investigated. Increasing the attrition milling time up to 20 min during powder preparation resulted in Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB> heaters with the highest density, which increased the fracture strength compared to samples with shorter attrition times. Such samples were annealed and evaluated as heating elements using accelerated degradation tests and failure analysis in order to compare their structural characteristics and flexural strength with as-fabricated samples. The annealed Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB> heater showed a relatively dense structure with few pores and no secondary phases, apart from a SiO<SUB>2</SUB> layer. This favorable structure prevented bubble formation, which can result in fracturing of the heater, as revealed by evaluation at high temperatures with various heating rates. The flexural strength of the annealed specimen was 2.5-times higher than that of the as-fabricated specimen, which was attributed to removal of secondary phases during annealing. Failure time and surface load analyses were used to investigate the fracture mechanism of the Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB> heaters in detail at 1790 °C by quantifying bubble formation and the presence of secondary phases.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Self-propagating high temperature synthesis of Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB> heaters demonstrated. </LI> <LI> Post-annealed Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB> heaters were highly dense, with good flexural strength. </LI> <LI> Bubble formation (the main cause of fracture) suppressed at ultra-high temperature (above 1700 °C). </LI> <LI> Surface load, failure time, and bubble formation used to study fracture mechanisms. </LI> </UL> </P>

광조사 시간에 따른 복합레진과 Ormocer의 중합수축에 관한 연구

정연정,민경산,이해형,조경모,조용범 大韓齒科保存學會 2003 Restorative Dentistry & Endodontics Vol.28 No.4

Ormocer has organic-inorganic compound polymers. One of advantages of ormocer is reduced polymerization shrinkage. The purpose of this study was to compare the amount of contraction shrinkage of composite resins and ormocers. Additionally, the time of each material when there is no further change of contraction shrinkage was analysed. Four brands of composite resins (P-60, Surefil, Z-250 and Denfil) and two brands of ormocers (Definite and Admira) were used. 20 seconds, 40 seconds and 60 seconds of curing times were given. Contraction shrinkage of them were measured using a linometer for 80 seconds. The effect of material and curing time to contraction shrinkage at the time of 80 seconds was analysed by two-way ANOVA. The effect of time to contraction shrinkage was analysed by one-way ANOVA, and the time when there was no further change of the contraction shrinkage was analysed. The results are as follows : 1. P-60, Dfinite, Z-250 and Denfil had no further change of contraction shrinkage from the time of 20 seconds, and Surefil and Admira had no further change of contraction shrinkage from the time of 10 seconds. 2. Statistical analysis revealed volumetric shrinkage varied among material (p<0.05). No significant difference of contraction shrinkage among different curing times was found, and there was no effect of interaction between materials and curing times to contraction shrinkage. 3. Dfinite and Admira showed the statistically same contraction shrinkage with those of Z-250 and P-60, which is higher than that of Surefil and lower than that of Denfil (p<0.05).

325 MHz 이동통신용 집중소자 Y형 서큘레이터의 설계

고연수,성원모,최학근 단국대학교 신소재기술연구소 1997 신소재 Vol.7 No.-

본 논문에서는 325 MHz 이동통신 기지국에 사용되는 집중소자 Y형 서큘레이터를 해석하고, 기존의 복잡한 수식을 통하여 설계하는 방법 대신 도표를 사용해 설계하는 간단한 설계방법을 제시하였다. 그리고, 실제 설계 제작하여 측정결과와 해석결과를 서로 비교 분석하였다. 설계방법은 % 대역폭과 페라이트 사이의 스트립선로의 고유인덕턴스 그리고 페라이트의 포화자화량과의 관계로부터 내부자계의 세기를 결정한 후 이로부터 입력 어드미턴스를 구해 외부의 정합회로를 결정하는 설계방법으로 전개하였다. 해석은 페라이트의 텐서투자율의 성분 μ와 k가 복소함수가 아니라고 가정하고(무손실이라고 하고), 정합회로까지 모두 고려한 등가회로에서 제 3포트를 격리포트로 하여 고유치 해석방법을 적용하여 손실 및 임피던스 그리고 산란행렬 고유치의 위상을 구하였다. 그리고, 이러한 해석방법으로부터 중심주파수 325 MHz에서 %대역폭, 포화자화량, 스트립선로의 고유인덕턴스와 내부자계의 관계를 밝혀서 도표로 제시함으로써 서큘레이터의 설계에 이용할 수 있게 하였다. 실제 제작된 서큘레이터는 중심주파수 325 MHz에서 반사손실이 -31dB, 아이솔레이션이 -32dB, 삽입손실이 -0.219dB로 나타내며, 해석을 통하여 얻은 결과와 거의 유사함을 알 수 있었다. In this paper, a new design method of Iumped-element Y circulator for 325 MHz mobile communication is proposed and the analysis results compared with the measured results. To develop the new design method, internal magnetic field intensity is derived from &bandwidth, characteristic inductance of stripline between two ferrites and saturation magnetization of ferrite to get the input admittance of circulator to obtain the external matching network. The analysis of circulator was based on the assuming that the circulator was lossless and the third port of its equivalent circuit was isolated, and the impedance and phase of scattering coefficient was calculated through the eigenvalues analysis. From this analysis, the relation among %bandwidth, saturation magnetization, characteristic inductance of stripline and internal magnetic field was found and the diagram for the design was suggested. Experimental results of fabricated circulator represent -31dB return loss. -32dB isolation and -0.219dB insertion loss at the center frequency 325MHz and support the theoretical prediction.

Kiwi fruit(Actinidia Chinensis Planch)의 種子發芽에 미치는 溫度와 床土의 影響

丁蓮圭,陳英旭,梁元模 順天大學校 1983 論文集 Vol.2 No.1

KIWI FRUIT(Chinese gooseberry)의 種子 發芽試驗에 있어서, 溫度別, 床土別試驗結果를 要約하면 다음과 같다. 1. 發芽率은 低溫區(15∼21℃)보다 高溫區(22∼28℃)에서 높았고 床土間에도 有意差가 있었으며 累積發芽率도 서로 다른 樣相을 보였다. 2. 發芽開始所要日數는 高溫區의 9.3日보다 低溫區가 21.7日로서 顯著히 길었으며 床土間에도 有意差가 認定되었다. 3. 高溫區의 第一本葉 出現開始所要日數는 23.7日, 第二本葉은 34.7日, 第三本葉은 모래+腐葉區에서만 40日째에 出現되었고 低溫區에서는 第一本葉이 30.7日이었으며 第二, 第三本葉은 出現되지 않았다. 4. 第一本葉에서 第二本葉 出現까지의 所要日數는 모래區에서 15日, 腐葉區에서 11日, 모래+腐葉區에서 7日이었다. 5. 最終本葉 出現數는 高溫區가 低溫區보다 많았으며 床土別로는 高溫區의 第一本葉및 第二本葉은 모래+腐葉區가 各各 85.3葉, 56葉으로서 가장 많았고 모래區가 各各 49.3葉, 4.7葉으로 가장 적었다. 低溫區의 第一本葉은 모래區가 25.3葉으로 가장 많았고 腐葉區가 8.7葉으로 가장 적었다. This experiment was carried out to investigate the effects of temperature and media on the seed germination of Kiwi Fruit. Germination temperature were controlled into two stages in growth chamber, low temperature (15∼21℃) and high temperature(22∼28℃). Three kinds of germination media that is sand, sand 50%+leafmold 50% and leafmold were used. Seeds of Kiwi Fruit, var "Hayward" were sowed on April, 21 in 1983. The results were summerised as follows: 1. The seed germination rate under high temperature treatment was higher than that of the low temperature, and the germination medias also made significant differences on the germination rate. Also, accumulated seed germination rates differred between the treatments. 2. Required time for the first germinating was 9.3 days in high temperature but 21.7 days in low temperature and the time requirement as to media was shorter in order of mention, leafmold, sand+leafmold and sand soil. 3. In high germination temperature, the first true leaf appeared at 23.7 days after sowing, the second did at 34.7 days and the third did at 40 days only in sand+leafmold germination media, however, in low temperature the first true leaf appeared at 30.7 days, but the second and the third did not appeared. 4. Required days from the first true leaf emergence to the second was shorter in oredr of mention, sand+leafmold, leafmold and sand soil. 5. True leaves finally emerged under high temperature was more than those under low temperature. And as for the variation in numbers among the germination media, the first leaves and the second leaves under high temperature were 85.3 leaves and 56.0 leaves(largest in number) in sand+leafmold media and 49.3 leaves and 4.7 leaves (smallest in number) in sand media. The first leaves under low temperature were 25.3 leaves(largest in number) in sand media and were 8.7 leaves (smallest in number) in leafmold media.

마찰기인 진동의 실험적 연구

김준모,최연선 成均館大學校 科學技術硏究所 1999 論文集 Vol.50 No.1

The dynamic characteristics of friction-induced vibration are investigated. The value of friction coefficient depends on material, relative velocity, and normal force. As a result, the governing equation of a mechanical system including friction effect is inherently nonlinear. In this research, friction-induced vibration characteristics of automotive brake lining pad are investigated by experiments and numerical simulation. The measured responses of pin-on-disk type apparatus which was designed and made for this research show limit cycles of quasi-harmonic vibrations and beating phenomena with the variation of the operation speed and the normal force of the system. Friction coefficient curve which depends on relative velocity was obtained by using Lienard method. Numerical integration was also performed by using the fitted friction coefficient curves. The numerical results of calculated amplitudes and mean displacements show good agreements with those of experiments. Throughout this research, most of the experimentally observed phenomena in friction-induced vibration were successfully explained theoretically and numerically.

오이의 品質向上과 運作障害 경감을 위한 有機物 施用 및 輪換式 栽培의 효과에 關한 硏究

丁蓮圭,梁承烈,梁元模 順天大學校 1984 論文集 Vol.3 No.1

處女地 沓田輪換 式栽培地, 3年 連作地, 5年 連作地에 園藝作物을 供試하여 各 土壤別로 標集施肥, 有機物, 및 이들의 조합處理를 함으로써 連作程度와 施肥方法에 따른 作物의 收量과 品質, 土壤의 鹽類濃度 및 土壤理化學性을 比較檢査 함으로써 現象을 하고 나아가서 連作障害를 輕減 또는 防止하기 위한 방안을 모색하기 위하여 몇가지 實驗을 수행하였던 바 그 결과를 모색하면 다음과 같다. 1. 供試土壤의 實驗前 pH는 連作年數가 길어질수록 낮아지는 경향이 있었으며 반대로 유기물, 인산, 마그네슘, K, Ca 등은 連作年數가 길어질수록 높았고 C.E.C.도 비슷한 結果를 나타냈다. 2. 土壤內의 E.C.는 試驗前의 경우, 處女地, 沓田輪換式栽培地가 名名 0.35, 0.56이었고 3年, 5年 連作地가 名名 1.20, 1.30으로 連作土壤이 월등하게 높았으며 施肥後의 경우에는 3.00에서 4.35사이로서 全체的으로 높은 수준이었으나 土壤間에 큰 差異가 없었고 降雨에 노출시켜 일정한 기간이 지난후에는 0.39에서 0.43사이로 土壤에 관계없이 원래의 상태로 쉽게 회복되었다. 3. 土壤의 連作程度나 施肥方法에 따른 오이의 蔓長, 莖의 굵기, 節間數는 處理問에差異가 없었으며 유기물이나 미량요소의 施用에 의한 뚜렷한 증가는 나타나지 않았다. 4. 오이의 收量은 5年 連作地가 가장 많았고 다음으로 處女地, 畓田輪換式栽培地, 3年 連作地 順이었는데 이것은 1果의 果重, 果長, 果俓의 증대보다 수확과수의 差異에 의한 것이었다. 5. 連作程度와 施肥方法에 따른 오이의 品質反應중 外的인 品質 즉, 1果의 果重, 果俓, 果長의 差異는 없었으나 內的인 品質중 Vitamin C 含量은 連作年數가 길어질수록 낮아졌다. This experiment was conducted to investigate the effect of application methods of organic material and minor elements, and difference of replanting year on the elevation of vegetable qualities and the reduction of replant-failure in cucumber plants which were cultivated under covering conditions. Used soils were Virgin soil, Paddy-Upland rotation soil, 3 year replanting soil, 5 year replanting soil. Application methods were Standard fertilizer, Standard fertilizer+Organic material, Standard fertilizer+Minor elements, Standard fertilizer+Organic material+Minor elements. Cucumber seeds were sown at August, 15 and transplanted at September, 15 in 1984. The results were summarized as follows; The pH value of the used soil before experiment was showed a decreasing tendency with extending the replanting year. On the other hand, the contents of the Organic material, ??, Mg, K, Ca and C.E.C. were increased with extending the replanting year. Before experiment, Electric Conductivity of 3 year replanting soil and 5 year replanting soil were notably higher than that of the non-replanting soil, Virgin soil and Paddy-Upland rotation soil. Their values were 1.20, 1.30, 0.35 and 0.56 mㆍmho respectively. But E.C. of the soil after fertilization was increased highly, from 3.00 to 4.35 mㆍmho with no relation of the replanting year. And after the soil being opened to the rainfall for about 4 weeks, the soil salinity was easily removed. Replanting year and fertilizer application methods didn't have an influence on the plant height, stem diameter and No. of node of cucumber plant. The yield was, however, affectected by it, not because of the fruit weight, diameter and length but because of the different quantity of the harvest fruits. Vitamin C content of cucumber fruit was decreased with extending the replanting year.

Numerical wind load estimation of offshore floating structures through sustainable maritime atmospheric boundary layer

Yeon, Seong Mo,Kim, Joo-Sung,Kim, Hyun Joe The Society of Naval Architects of Korea 2020 International Journal of Naval Architecture and Oc Vol.12 No.-

Wind load is one of the major design loads for the hull and mooring of offshore floating structures, especially due to much larger windage area above water than under water. By virtue of extreme design philosophy, fully turbulent flow assumption can be justified and the hydrodynamic characteristics of the flow remain almost constant which implies the wind load is less sensitive to the Reynolds number around the design wind speed than wind profile. In the perspective of meteorology, wind profile used for wind load estimation is a part of Atmospheric Boundary Layer (ABL), especially maritime ABL (MBL) and have been studied how to implement the profile without losing turbulence properties numerically by several researchers. In this study, the MBL is implemented using an open source CFD toolkit, OpenFOAM and extended to unstable ABL as well as neutral ABL referred to as NPD profile. The homogeneity of the wind profile along wind direction is examined, especially with NPD profile. The NPD profile was applied to a semi-submersible rig and estimated wind load was compared with the results from wind tunnel test.

Inter-ONU Bandwidth Scheduling by Using Threshold Reporting and Adaptive Polling for QoS in EPONs

Yeon-Mo Yang,김기선,정해원,안병하,이상욱 한국전자통신연구원 2005 ETRI Journal Vol.27 No.6

A dynamic bandwidth allocation (DBA) scheme, an inter–optical network unit (ONU) bandwidth scheduling, is presented to provide quality of service (QoS) to different classes of packets in Ethernet passive optical networks (EPONs). This scheme, referred to as TADBA, is based on efficient threshold reporting from, and adaptive polling order rearranging of, ONUs. It has been shown that the network resources are efficiently allocated among the three traffic classes by guaranteeing the requested QoS, adaptively rearranging the polling orders, and avoiding nearly all fragmentation losses. Simulation results using an OPNET network simulator show that TADBA performs well in comparison to the available allocation scheme for the given parameters, such as packet delay and channel utilization.

Observation of Molecular Self-assembly of Liquid Crystal Urethane-urea from 4,4-azodianilline

Yeon, Seong Mo,Cheong, In Woo,Kim, Jung Hyun 한국공업화학회 2004 응용화학 Vol.8 No.2

Liquid crystalline urethane-urea molecule (LCUU) was prepared via stepwise synthetic method from mono-methoxy poly(ethylene) glycol(M.W.=2000gmol^(-1)) (mPEG), 4,4'-methylenedi-p-phenyl diisocyanate (MDI), and 4,4'-azodianilline (ADA). In the 1st step, ADA and MDI were reacted to form NCO-terminated mesogenic molecular unit. In the 2nd step, the mesogenic unit was reacted with the excess amount of mPEG to form LCUU having urethane-urea linkage. Thermal analysis(DSC) and optical images (POM) revealed the liquid-crystal properties of the LCUU. The LCUU showed surface activity in water solution and CAC (critical aggregate concentration) of the LCUU in the presence of LiCF₃SO₃ was obtained by surface tension analysis. Near the CMC, the LCUU aggregates in the water-ethanol solution were observed by TEM and AFM analyses. The effect of reversible photo (UV) and thermal isomerization of ADA in the mesogenic unit on liquid crystal behavior of the LCUU will be discussed.

AI, IOT 기술을 활용한 자기계발 스마트 워치 & 어플 ‘MO:TIVE’

김소연 ( So-yeon Kim ),모하연 ( Ha-yeon Mo ),이유영 ( Yu-young Lee ),이예성 ( Ye-sung Lee ),최가현 ( Ga-hyun Choi ) 한국정보처리학회 2023 한국정보처리학회 학술대회논문집 Vol.30 No.2

‘MO:TIVE’는 AI 및 IoT를 활용하여 자기계발을 촉진하는 모바일 서비스로, 사용자 정보 학습과 정밀한 추천을 제공하며 생성형 AI를 활용한 개인화 조언을 제공한다. 이를 통해 사용자는 스마트 워치를 통해 자투리 시간을 효과적으로 활용하여 자기계발과 삶의 질을 향상을 기대할 수 있으며 지속적인 개선과 학습을 통해 더 나은 사용자 경험을 제공한다.