• 제목/요약/키워드: Function of MPA

검색결과 210건 처리시간 0.026초

Assessment of compressive strength of high-performance concrete using soft computing approaches

  • Chukwuemeka Daniel;Jitendra Khatti;Kamaldeep Singh Grover
    • Computers and Concrete
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    • 제33권1호
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    • pp.55-75
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    • 2024
  • The present study introduces an optimum performance soft computing model for predicting the compressive strength of high-performance concrete (HPC) by comparing models based on conventional (kernel-based, covariance function-based, and tree-based), advanced machine (least square support vector machine-LSSVM and minimax probability machine regressor-MPMR), and deep (artificial neural network-ANN) learning approaches using a common database for the first time. A compressive strength database, having results of 1030 concrete samples, has been compiled from the literature and preprocessed. For the purpose of training, testing, and validation of soft computing models, 803, 101, and 101 data points have been selected arbitrarily from preprocessed data points, i.e., 1005. Thirteen performance metrics, including three new metrics, i.e., a20-index, index of agreement, and index of scatter, have been implemented for each model. The performance comparison reveals that the SVM (kernel-based), ET (tree-based), MPMR (advanced), and ANN (deep) models have achieved higher performance in predicting the compressive strength of HPC. From the overall analysis of performance, accuracy, Taylor plot, accuracy metric, regression error characteristics curve, Anderson-Darling, Wilcoxon, Uncertainty, and reliability, it has been observed that model CS4 based on the ensemble tree has been recognized as an optimum performance model with higher performance, i.e., a correlation coefficient of 0.9352, root mean square error of 5.76 MPa, and mean absolute error of 4.1069 MPa. The present study also reveals that multicollinearity affects the prediction accuracy of Gaussian process regression, decision tree, multilinear regression, and adaptive boosting regressor models, novel research in compressive strength prediction of HPC. The cosine sensitivity analysis reveals that the prediction of compressive strength of HPC is highly affected by cement content, fine aggregate, coarse aggregate, and water content.

$\beta$-Sic-$TiB_2$복합체의 파괴인성과 전기전도도젠 미치는 YAG의 영향 (Effect of the YAG with fracture toughness and electric conductive of $\beta$-Sic-$TiB_2$)

  • 윤세원;주진영;신용덕;여동훈;박기엽
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2000년도 하계학술대회 논문집 C
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    • pp.1545-1547
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    • 2000
  • The mechanical and electrical properties of the hot-pressed and annealed $\beta$-Sic-$TiB_2$ electroconductive ceramic composites were investigated as function of the liquid forming additives of $Al_{2}O_{3}+Y_{2}O_3$. Phase analysis of composites by XRD revealed $\alpha$-SiC(6H), $TiB_2$, and YAG($Al_{5}Y_{3}O_{12}$). The relative density and the mechanical properties of composites were increased with increasing $Al_{2}O_{3}+Y_{2}O_3$ contents because YAG of reaction between $Al_{2}O_3$ and $Y_{2}O_3$ was increased. The Flexural strength showed the highest value of 432.5MPa for composites added with l2wt% $Al_{2}O_{3}+Y_{2}O_3$ additives at room temperature. Owing to crack deflection, crack bridging, phase transition and YAG of fracture toughness mechanism. the fracture toughness showed 7.1MPa${\cdot}m^{1/2}$. For composites added with l2wt% $Al_{2}O_{3}+Y_{2}O_3$ additives at room temperature The electrical resistivity and the resistance temperature coefficient respectively showed the lowest of 6.0${\sim}10^{-4}{\Omega}{\cdot}$ cm and 3.1${\times}10^{-3}/^{\circ}C$ for composite added with l2wt% $Al_{2}O_{3}+Y_{2}O_3$ additives at room temperature. The electrical resistivity of the composites was all positive temperature coefficient resistance(PTCR) in the temperature range of 25$^{\circ}C$ to 700$^{\circ}C$.

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BSCCO(2223) 다심 초전도 선재의 접합공정 연구 (A Study on Joining Method of BSCCO(223) Multifilamentary Tape)

  • 김정호;김규태;주진호;나완수
    • 한국전기전자재료학회논문지
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    • 제14권6호
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    • pp.511-517
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    • 2001
  • We evaluated the electrical properties of 37 multifilamentary jointed tapes processed by superconducting joint. In the superconducting joining method, a lap-joint was used. Tapes were selectively etched, and exposed superconducting cores of the two tapes were brought into contact with each other and then only the joined region was uniaxially pressed in the range of 1,000 to 2,50 MPa. The critical current ratio(CCR) and n-value of the jointed tape were evaluated as a function of uniaxial pressure and number of step in the contacting region. It was observed that the CCR was dependent on the number of step, but almost independent of uniaxial pressure. The highest critical current ratio and n-value were obtained to be 58% and 26%, respectively, for the jointed tape to the tape itself.

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Ni 첨가가 볼밀링한 MoSi$_2$분말성형체의 소결속도에 미치는 영향 (The Effect of Ni Addition on the Sintering Kinetics of Ball-milled Mosi$_2$ Powder Compacts)

  • 최선호;홍경태;김영도;문인형
    • 한국분말재료학회지
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    • 제5권4호
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    • pp.241-249
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    • 1998
  • Sintering kinetics of ball-milled $MoSi_2$ was studied with the addition of Ni. $MoSi_2$ powder with the average particle size of 1 $\mu\textrm{m}$ was obtained from ball-milling of 10 $\mu\textrm{m}$ powder. Small amount of Ni was added to the ball-milled $MoSi_2$ powder by salt solution and reduction method. The powder was compacted into cylindrical shape at 200 MPa and isothermally sintered in a $H_2$ atmosphere at the temperature range of 1100~$1400^{\circ}C$ for 3~600 minutes. The changes of linear shrinkage and sintered density were monitored as a function of sintering time. The microstructure was observed by using optical microscopy and scanning electron microscopy. Phases were identified by X-ray diffratometer and electro-probe micro analysis. Sintering kinetics of Ni-added powder was compared to as-milled powder and the apparent activation energy was calculated from Arrhenius plot.

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동결건조한 소의 치밀골에서 전해질용액의 침지시간에 따른 Strength와 Stiffness의 변화 (Changes of Strength and Stiffness of Freeze-Dried Bovine Cortical Bone according to Rehydration Time in Electrolyte Solution)

  • 김남수;장세웅;김희은;정인성;최성진;최인혁
    • 한국임상수의학회지
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    • 제20권4호
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    • pp.482-488
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    • 2003
  • Transplanted cortical bone grafts of freeze-dried bones also function as sustaining for defected bones, however, it has less strength and is fragile without rehydration. In this study, strength and stiffness of freeze-dried bone from bovine cortical bones were evaluated by three point bending test according to different time frames such as rehydration times of 0.5, 3, 6, 12 and 24 hrs in electrolyte solution and was compared with those of frozen bones. The strength and stiffness of frozen bone were $264.4\pm36.7$ MPa, $17.0\pm1.5$ GPa, respectively. The strength and stiffness of freeze-dried bone which fat was removed by treatments of chloroform-methanol solutions for 6 days, then was freeze-dried at $-80^{\circ}C$ and sterilized with ethylene oxide gas, were $224.9\pm27.6$ MPa, $19.2\pm2.8$ GPa, respectively. The strength and stiffness of feeze-dried bone were decreased 15.0% and increased 13.2% than these of frozen bone, respectively. The strength and stiffness of freeze-dried bone rehydrated for 6 hrs were restored to 96.0% strength and 99.2% stiffness of frozen bone. The rehydration time of freeze-dried bone which had the highest strength and stiffness was six hours and three hours, respectively. The results of the mathematica program for the variation of the strength and stiffness showed 3 hours and 30 minutes of rehydration time in electrolyte solution for the best condition in the strength and stiffness which was adequate to treat freeze-dried cortical bone.

Effects of the Addition of $La_2O_3$ on Mechanical Properties and Machinability of $Si_3N_4$ Ball

  • Sang Yang Lee;Sung Ho Kim;Soo Wohn Lee
    • The Korean Journal of Ceramics
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    • 제6권4호
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    • pp.364-369
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    • 2000
  • Silicon nitride with adding La$_2$O$_3$ was sintered by gas pressure sintering (GPS) technique at $1950^{\circ}C$, in $N_2$ gas at 3 MPa, for 2h. Mechanical properties such as hardness, flexural strength, and fracture toughness were determined as a function of the GPS holding time and the contents of La$_2$O$_3$ in silicon nitride. Also machinability of silicon nitride ball with various GPS holding time and amount of La$_2$O$_3$ was evaluated by magnetic fluid grinding (MFG) method. In this study it was found that machinability was influenced significantly with La$_2$O$_3$ contents. However, the different GPS holding time did not affect the machinability very much.

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$Al_2O_3+Y_2O_3 첨가량에 따른 {\beta}-SiC-ZrB_2$계 전도성 복합체의 특성 (The Properties of $\beta-SiC-ZrB_2$ Electroconductive Ceramic Composites with $Al_2O_3+Y_2O_3$Contents)

  • 신용덕;주진영;황철
    • 대한전기학회논문지:전기물성ㆍ응용부문C
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    • 제49권9호
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    • pp.516-522
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    • 2000
  • The mechanical and electrical properties of the hot-pressed and annealed $\beta-SiC-ZrB_2$ electroconductive ceramic composites were investigated as a function of the liquid forming additives of$Al_2O_3+Y_2O_3$ Phase analysis of composites by XRD revealed $\alpha-SiC(6H) ZrB_2\; and YAG(Al_5Y_3O_{12})$ The relative density of composites were increased with increased Al2O3+Y2O3 contents. The Flexural strength showed the highest value of 390.6MPa for composites added with 20wt% Al2O3+Y2O3 additives at room temperature. Owing to crack deflection crack bridging phase transition and YAG of fracture toughness mechanism the fracture toughness showed the highest value of 6.3MPa.m1/2 for composites added with 24wt% Al2O3+Y2O3 additives at room temperature. The resistance temperature coefficient showed the value of$ 2.46\times10^{-3}\;, 2.47\times10^{-3},\; 2.52\times10^{-3}/^{\circ}C$ for composite added with 16, 20, 24wt% Al2O3+Y2O3 additives respectively. The electrical resistivity of the composites was all positive temperature coefficient resistance(PTCR) in the temperature range of $256{\circ}C\; to\; 900^{\circ}C$.

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$Al_2O_3+Y_2O_3를 첨가한 {\beta}-SiC-TiB_2$ 복합체의 특성 (Properties of the $\beta-SiC-TiB_2$ Composites with $Al_2O_3+Y_2O_3$ additives)

  • 임승혁;신용덕;주진영;윤세원;송준태
    • 대한전기학회논문지:전기물성ㆍ응용부문C
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    • 제49권7호
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    • pp.394-399
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    • 2000
  • The mechanical and electrical properties of pressed and annealed $\beta-SiC-TiB_2$ electroconductive ceramic composites were investigated as a function of the liquid forming additives of $Al_2O_3+Y_2O_3$. Phase analysis of composites by XRD revealed $\alpha$-SiC(6H), TiB2, and (Al5Y3O12). Reaction between Al2O3 and $Y_2O_3$ formed YAG but the relative density decreased with increasing $Al_2O_3+Y_2O_3$ contents. The Flexural strength showed the value of 458.9 MPa for composites added with 4 wt% $Al_2O_3+Y_2O_3$ additives at room temperatures. Owing to crack deflection and crack bridging, the fracture toughness showed 6.2, 6.0 and 6.6 MPa.m1/2 for composites added with 4, 8 and 12 wt% Al2O3+Y2O3 additives respectively at room temperature. The resistance temperature coefficient showed the value of $3.6\times10^{-3},\; 2.9\times10^{-3}\; and\; 3.0\times10^{-3} /^{\circ}C$$^{\circ}C$ for composite added with 4, 8 and 12 wt% $Al_2O_3+Y_2O_3$additives respectively at room temperature. The electrical resistivity of the composites was all positive temperature coefficient resistance(PTCR) in the temperature range of $25^{\circ}C\; to\; 700^{\circ}$.

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$\beta$-Sic-$ZrB_2$계 복합체에 미치는 YAG의 영향 (Effect of YAG on $\beta$-Sic-$ZrB_2$ Composites)

  • 황철;주진영;신용덕;이종덕;진홍범
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2000년도 하계학술대회 논문집 C
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    • pp.1474-1476
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    • 2000
  • The mechanical and electrical properties of the hot-pressed and annealed $\beta$-Sic-$ZrB_2$ electroconductive ceramic composites were investigated as function of the liquid forming additives of $Al_{2}O_{3}+Y_{2}O_{3}$. Phase analysis of composites by XRD revealed $\alpha$-SiC(6H), $ZrB_2$, and YAG($Al_{5}Y_{3}O_{12}$). The relative density of composites were increased with increasing $Al_{2}O_{3}+Y_{2}O_{3}$ contents. The flexural strength showed the highest value of 390.6MPa for composites added with 20wt% $Al_{2}O_{3}+Y_{2}O_{3}$ additives at room temperature. Owing to crack deflection, crack bridging. phase transition and YAG of fracture toughness mechanism. the fracture toughness showed the highest value of 6.3MPa${\cdot}m^{1/2}$ for composites added with 24wt% $Al_{2}O_{3}+Y_{2}O_{3}$ additives at room temperature. The electrical resistivity of the composites was all positive temperature coefficient resistance (PTCR) in the temperature range of 25$^{\circ}C$ to 900$^{\circ}C$.

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액장 소결한 $\beta-SiC-TiB_2$계 전도성 복합체의 특성 (The Properties of $\beta-SiC-TiB_2$ Electroconductive Ceramic Composites Densified by Liquid-Phase Sintering)

  • 임승혁;신용덕;송준태
    • 대한전기학회논문지:전기물성ㆍ응용부문C
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    • 제49권9호
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    • pp.510-515
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    • 2000
  • The mechanical and electrical properties of the hot-pressed and annealed $\beta-SiC-TiB_2$ electroconductive ceramic composites were investigated as a function of the liquid forming additives of Al_2O_3+Y_2O_34. The result of phase analysis of composites by XRD revealed $\alpha-SIC(6H)\;TiB_2,\; and YAG(Al5Y3O12) crystal phase. The relative density and the mechanical properties of composites were increased with increasing $Al_2O_3+Y_2O_34 contents because YAG of reaction between $Al_2O_3\; and\; Y_2O_3$ was increased. The Flexural strength showed the highest value of 432.5MPa for composites added with 12wt% $Al_2O_3+Y_2O_34 additives at room temperature. Owing to crack deflection crack bridging phase transition and TAG of fracture toughness mechanism the fracture toughness showed 7.1MPa.m1/2 for composites added with 12wt% $Al_2O_3+Y_2O_34 additives at room temperature. The electrical resistivity and the resistance temperature coefficient showed the lowest of $6.0\times10-4\Omega.cm\; and\; 3.1\times10-3/^{\circ}C4 respectively for composite added with 12wt% \Omega additives at room temperature. The electrical resistivity of the composites was all positive temperature coefficient resistance (PTCR) in the temperature range of $25^{\circ}C\; to\; 700^{\circ}C$.

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