• Title/Summary/Keyword: splitting strength

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Effect of Consolidation using Artificial Porous Material for Stone Cultural Property (인공 다공질체를 이용한 석조문화재 강화제의 처리효과)

  • Lee, Jae-Man;Lee, Myeong-Seong;Kim, Jae-Hwan;Lee, Mi-Hye
    • Journal of Conservation Science
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    • v.26 no.3
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    • pp.325-334
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    • 2010
  • In order to clarify the effect of consolidant, the artificial porous material with low intensity was manufactured using granite powder and Portland cement. We have prepared four kinds of alkoxysilane system consolidants, a acrylic resin and a epoxy resin and investigated about characteristics before and after consolidation. As a result of the research, Silres BS OH 100 was effective for density and surface hardness. SS-101 with hydrophobicity and Site SX-RO with hydrophilicity had the good durability over salts weathering. On the other hand, Syton HT-50 and Paraloid B72 were easily destructed by salt weathering because they were concentrated on surface area by the low penetration depth. Araldite 2020 was the most effective consolidant for improvement of physical properties.

A Study on the Electronic Properties and Redox Reaction of Europium(Ⅲ) Complexes in Aprotic Solvent (반 양성자성 용매속에서 Europium(Ⅲ) 착물에 대한 전자적 성질과 산화 · 환원 반응에 관한 연구)

  • Choe, Chil Nam;Son, Hyo Youl;Kim, Se Bong
    • Journal of the Korean Chemical Society
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    • v.40 no.1
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    • pp.65-71
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    • 1996
  • The chemical behaviour of the Eu(Ⅲ) complexes with organic ligands(tris[3-(trifluoromethylhydroxymethylene-camphorato)]) and tris[3-heptafluoropropylhydroxymethylene-camphorato)] has been investigated by the UV/vis-spectrophotometric, magnetic, and electrochemcial methods. The two or three energy absorption bands are observed by the spectra of these complexes. The magnitude of crystal field splitting energy, the spin pair energy and strength were obtained from the spectra of the complexes. These complexes are found to be delocalization, low-spin state, and strong bonding strenth of electron configuration. The magnetic dipolemoment are found to be diamagnetic. The redox reaction processes of complexes were investigated by cyclic voltammetry in aprotic solvent. The redox reaction processes of complexes are turned out to be single or double reaction with respect to one electron diffusion current.

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Application of Powdered Superplasticizer to Improve of Slump Loss Rate in Recycled Aggregate Concrete (재생 골재 콘크리트의 슬럼프 손실 개선을 위한 분말형 감수제의 활용)

  • Yang, Keun-Hyeok;Sim, Jae-Il;Lee, Jae-Sam;Chung, Heon-Soo
    • Journal of the Korea Concrete Institute
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    • v.18 no.5 s.95
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    • pp.649-656
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    • 2006
  • In this study, powered superplasticizer(PSP) agents to improve the slump loss rate of recycled aggregate concrete were developed. To evaluate the variation of fluidity against elapsed time and the mechanical properties, twenty four specimens whose main variables had the mixing condition of aggregates, such as natural and recycled gravels, and natural and recycled fine aggregates, were tested. The concrete slump with a liquid superplasticizer greatly decreased against the elapsed time and dropped by less than 50% of initial slump after two hours. However the concrete slump with the PSP agents hardly varied until after half an hour and maintained more than 85% of initial slump even after an hour. Also the PSP agents made the compressive, splitting tensile, and flexural strength of concrete increased and the shrinkage strain decreased. Considering the properties improvement of concrete, it can be recommended that optimum mixing amount of the PSP agents should be 5% of the amount of cement.

Slump and Mechanical Properties of Hybrid Steel-PVA Fiber Reinforced Concrete (강섬유와 PVA 섬유로 하이브리드 보강된 콘크리트의 슬럼프 및 역학적 특성)

  • Yang, Keun-Hyeok
    • Journal of the Korea Concrete Institute
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    • v.22 no.5
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    • pp.651-658
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    • 2010
  • Sixteen concrete mixes reinforced with hybrid steel-polybinyl alcohol (PVA) fibers and a control concrete mix with no fiber were tested in order to examine the effect of the micro and macro fibers on the slump and different mechanical properties of concrete. Main variables investigated were length and volume fraction of steel and PVA fibers. The measured mechanical properties of hybrid fiber reinforced concrete were analyzed using the fiber reinforcing index and compared with those recorded from monolithic steel or PVA fiber reinforced concrete. The initial slump of hybrid fiber reinforced concrete decreased with the increase of the aspect ratio and the volume fraction of fibers. In addition, splitting tensile strength, modui of rupture and elasticity, and flexural toughness index of concrete increased with the increase of the fiber reinforcement index. Modulus of rupture and flexural toughness index of hybrid fiber reinforced concrete were higher than those of monolithic fiber reinforced concrete, though the total volume fraction of hybrid fibers was lower than that of monolithic fiber. For enhancing the flexural toughness index of hybrid fiber reinforced concrete, using the steel fiber of 60 mm length was more effective than using the steel fibers combined with 60 mm and 30 mm lengths.

Experimental study on the mechanical property of coal and its application

  • Jiang, Ting T.;Zhang, Jian H.;Huang, Gang;Song, Shao X.;Wu, Hao
    • Geomechanics and Engineering
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    • v.14 no.1
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    • pp.9-17
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    • 2018
  • Brazilian splitting tests, uniaxial compression tests and triaxial compression tests are carried out on the coal samples cored from Shanxi group $II_1$ coal seam of Jiaozuo coal mine, Henan province, China, to obtain their property parameters. Considering the bedding has notable effect on the property parameter of coal, the samples with different bedding angles are prepared. The effects of bedding on the anisotropic characteristics of the coal seam are investigated. A geological geomechanical model is built based on the geology characteristics of the Jiaozuo coal mine target reservoir to study the effects of bedding on the fracture propagations during hydraulic fracturing. The effects of injection pressure, well completion method, in-situ stress difference coefficient, and fracturing fluid displacement on the fracture propagations are investigated. Results show bedding has notable effects on the property parameters of coal, which is the key factor affecting the anisotropy of coal. The hydraulic cracks trends to bifurcate and swerve at the bedding due to its low strength. Induced fractures are produced easily at the locations around the bedding. The bedding is beneficial to form a complicated fracture network. Experimental and numerical simulations can help to understand the effects of bedding on hydraulic fracturing in coalbed methane reservoirs.

The Development of Korean Rehabilitation Patient Group Version 1.0 (한국형 재활환자분류체계 버전 1.0 개발)

  • Hwang, Soojin;Kim, Aeryun;Moon, Sunhye;Kim, Jihee;Kim, Jinhwi;Ha, Younghea;Yang, Okyoung
    • Health Policy and Management
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    • v.26 no.4
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    • pp.289-304
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    • 2016
  • Background: Rehabilitations in subacute phase are different from acute treatments regarding the characteristics and required resource consumption of the treatments. Lack of accuracy and validity of the Korean Diagnosis Related Group and Korean Out-Patient Group for the acute patients as the case-mix and payment tool for rehabilitation inpatients have been problematic issues. The objective of the study was to develop the Korean Rehabilitation Patient Group (KRPG) reflecting the characteristics of rehabilitation inpatients. Methods: As a retrospective medical record survey regarding rehabilitation inpatients, 4,207 episodes were collected through 42 hospitals. Considering the opinions of clinical experts and the decision-tree analysis, the variables for the KRPG system demonstrating the characteristics of rehabilitation inpatients were derived, and the splitting standards of the relevant variables were also set. Using the derived variables, we have drawn the rehabilitation inpatient classification model reflecting the clinical situation of Korea. The performance evaluation was conducted on the KRPG system. Results: The KRPG was targeted at the inpatients with brain or spinal cord injury. The etiologic disease, functional status (cognitive function, activity of daily living, muscle strength, spasticity, level and grade of spinal cord injury), and the patient's age were the variables in the rehabilitation patients. The algorithm of KRPG system after applying the derived variables and total 204 rehabilitation patient groups were developed. The KRPG explained 11.8% of variance in charge for rehabilitation inpatients. It also explained 13.8% of variance in length of stay for them. Conclusion: The KRPG version 1.0 reflecting the clinical characteristics of rehabilitation inpatients was classified as 204 groups.

A Study on the Electronic Properties and Electrochemical Behavior of Rare Earch Metal(Ⅲ) Complexes (Ⅲ) (희토류금속(Ⅲ) 착물들의 전자적 성질과 전기화학적 거동에 관한 연구 (Ⅲ))

  • Choe, Chil Nam;Son, Hyo Yeol
    • Journal of the Korean Chemical Society
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    • v.38 no.8
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    • pp.590-597
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    • 1994
  • The chemical behavior of the trivalent lanthanide$(Pr^{3+}, Eu^{3+}, Gd^{3+} 그리고 Yb^{3+})$complexes with organo-ligand (2,2,6,6-tetramethyl-3,5-heptanedione) has been investigated by the use of UV/Vis-spectrophotometric, magnetics, and electrochemical method. The two or three energy absorption bands are observed by the spectra of these complexes. The magnetitude of crystal field splitting energy, the spin pairing energy and bond stength was obtained from the spectra of the complexes. These are found to be localization, low-spin (or high-spin state, and strong bonding strength. The magnetic dipole moment are found to be diamagnetic complexes (or paramagnetic). The electrochemical behavior of complexes was observed by the use of cyclic voltammetry in aprotic media. These reduction peaks were irreversible two and three step reduction processes by electron transfer.

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An Improved, Reliable and Practical Kinetic Assay for the Detection of Prekallikrein Activator in Blood Products

  • Shin, In-Soo;Shim, Yun-Bo;Hong, Choong-Man;Koh, Hyun-Chul;Lee, Seok-Ho;Hong, Seung-Hwa
    • Archives of Pharmacal Research
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    • v.25 no.4
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    • pp.505-510
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    • 2002
  • An improved kinetic assay for prekallikrein activator (PKA), a potential vasodilator, has been developed to be used as an indicator for quality control during production of human albumin preparations. It consists of two reaction stages. In the first stage, PKA and prekallikrein are incubated at $37^{\circ}C$ for 45 min to allow the transformation into kallikrein. Kallikrein, a serine protease, catalyzes the splitting of p-nitroaniline (pNA) from its substrate H-D-Pro-Phe-Arg-pNA(S-2302). The rate at which pNA is released was measured spectrophotometrically at 405 nm. Prekallikrein, a substrate of PKA was purified by DEAE ion-exchange chromatography and the major potential variations in the assay were optimized; pH 8.0 and 150 mM sodium chloride were chosen to give a proper ionic strength. Reaction times in the range of 10 to 360 min provided linear dose-response curves. The concentration of prekallikrein was adjusted to fall between 1:1 and 1:3 dilutions to generate a linear standard calibration curve. Under the optimized conditions, reproducibility was checked. In a precision test, the coefficient of variation (CV) stayed within ${\pm}4%$ and the dose-response curve showed a good correlation (${r^2}=0.999$). An accuracy test with an international standard of PKA afforded a mean recovery of 97.5%.

Dynamic failure features and brittleness evaluation of coal under different confining pressure

  • Liu, Xiaohui;Zheng, Yu;Hao, Qijun;Zhao, Rui;Xue, Yang;Zhang, Zhaopeng
    • Geomechanics and Engineering
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    • v.30 no.5
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    • pp.401-411
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    • 2022
  • To obtain the dynamic mechanical properties, fracture modes, energy and brittleness characteristics of Furong Baijiao coal rock, the dynamic impact compression tests under 0, 4, 8 and 12 MPa confining pressure were carried out using the split Hopkinson pressure bar. The results show that failure mode of coal rock in uniaxial state is axial splitting failure, while it is mainly compression-shear failure with tensile failure in triaxial state. With strain rate and confining pressure increasing, compressive strength and peak strain increase, average fragmentation increases and fractal dimension decreases. Based on energy dissipation theory, the dissipated energy density of coal rock increases gradually with growing confining pressure, but it has little correlation with strain rate. Considering progressive destruction process of coal rock, damage variable was defined as the ratio of dissipated energy density to total absorbed energy density. The maximum damage rate was obtained by deriving damage variable to reflect its maximum failure severity, then a brittleness index BD was established based on the maximum damage rate. BD value declined gradually as confining pressure and strain rate increase, indicating the decrease of brittleness and destruction degree. When confining pressure rises to 12 MPa, brittleness index and average fragmentation gradually stabilize, which shows confining pressure growing cannot cause continuous damage. Finally, integrating dynamic deformation and destruction process of coal rock and according to its final failure characteristics under different confining pressures, BD value is used to classify the brittleness into four grades.

Analysis of Shear Behavior of Reinforced ALWAC Beam Using Interface Elements (계면요소를 이용한 경량철근콘크리트 보의 전단거동해석)

  • Rhee, Inkyu;Kim, Woo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.1A
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    • pp.107-115
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    • 2006
  • A challenging topic was and still is the failure behavior of concrete beams without shear reinforcement. In spite of substantial experimental and theoretical efforts in the past, the mechanism of shear failure is not entirely understood. ALWAC is of importance to the current construction industry. Most of present concrete research focuses on high performance concrete, by which in meant a cost effective material that satisfies demanding performance requirements, including durability. The advantages of ALWAC are its reduced mass and improved thermal and acoustic insulation properties, while maintaining adequate strength. In spite of these advantages, its ultimate failure behavior has not been well defined for adequate design process. This paper will investigate mainly the shear behavior of reinforced ALWAC beam without web reinforcements numerically with experimental evidences.