• Title/Summary/Keyword: influence surface

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Cause of Surface voids in Concrete Attached to an Aluminum Form, and Measures for Prevention

  • Noh, Sang-Kyun;Lee, Seung-Hoon;Han, Cheon-Goo
    • Journal of the Korea Institute of Building Construction
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    • v.13 no.5
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    • pp.457-464
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    • 2013
  • Traditionally, the material used for the form in reinforced concrete construction has been wood or steel. But recently, aluminum forms have been widely used in wall structures such as apartment buildings. Aluminum is light, easy to handle, and economically advantageous, but the hydrogen gas created due to its reaction with the alkali component in concrete gives rise to air pockets on the concrete's surface, and deteriorates the surface's finishability. In this research, to determine the influence of aluminum material on concrete, the cement paste W/C and its chemical reactivity in alkali and acid solution were analyzed. As a prevention plan, the influence of the number of applications of calcium hydroxide and various surface coating materials was analyzed. Through the analysis, it was found that the surface voids on the aluminum form are the result of the reaction of hydrogen gas with an alkali such as $Ca(OH)_2$. This can be prevented by the surface treatment of $Ca(OH)_2$, separating material and coating material. However, poor surface form and damages to the form are expected to cause quality degradation because of the aluminum-concrete interaction. Therefore, thorough surface treatment, rather than the type of separating material or coating material, is considered the most important target of management.

Determination of active failure surface geometry for cohesionless backfills

  • Altunbas, Adlen;Soltanbeigi, Behzad;Cinicioglu, Ozer
    • Geomechanics and Engineering
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    • v.12 no.6
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    • pp.983-1001
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    • 2017
  • The extent by which economy and safety concerns can be addressed in earth retaining structure design depends on the accuracy of the assumed failure surface. Accordingly, this study attempts to investigate and quantify mechanical backfill properties that control failure surface geometry of cohesionless backfills at the active state for translational mode of wall movements. For this purpose, a small scale 1 g physical model study was conducted. The experimental setup simulated the conditions of a backfill behind a laterally translating vertical retaining wall in plane strain conditions. To monitor the influence of dilative behavior on failure surface geometry, model tests were conducted on backfills with different densities corresponding to different dilation angles. Failure surface geometries were identified using particle image velocimetry (PIV) method. Friction and dilation angles of the backfill are calculated as functions of failure stress state and relative density of the backfill using a well-known empirical equation, making it possible to quantify the influence of dilation angle on failure surface geometry. As a result, an empirical equation is proposed to predict active failure surface geometry for cohesionless backfills based on peak dilatancy angle. It is shown that the failure surface geometries calculated using the proposed equation are in good agreement with the identified failure surfaces.

Evaporation Cooling of Water Droplet on Aluminum with Various Surface Roughness and Droplet Diameter in Conductive Condition (전도조건 하에서 표면조도와 액적 직경의 변화에 따른 알루미늄의 액적 증발 냉각)

  • Jang, C.S.;Choi, W.S.
    • Journal of the Korean Society for Heat Treatment
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    • v.18 no.6
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    • pp.375-382
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    • 2005
  • This paper presents the results of experimental investigation for the effect of heat conduction on the evaporation cooling of water droplet in the process of heat treatment. The experiments are mainly focused on the surface temperature, the surface roughness and the droplet diameter at aluminum. The range of surface temperature is from $80^{\circ}C$ to $140^{\circ}C$, surface roughness is from $R_a=0.18{\mu}m$ to $R_a=1.36{\mu}m$ and droplet diameter is from 2.4 mm to 3.0 mm. The results show that the total evaporation time is shorter for the larger surface roughness, the time averaged heat flux has maximum value for the larger surface roughness and exist the critical heat flux. The total evaporation time has a big influence on the evaporation region for the smaller droplet size, but the total evaporation time has not influence on the nuclear boiling region.

Influence of Selective Oxidation Phenomena in CGLs on Galvanized Coating Defects Formation

  • Gong, Y.F.;Birosca, S.;Kim, Han S.;De Cooman, B.C.
    • Corrosion Science and Technology
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    • v.7 no.1
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    • pp.1-5
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    • 2008
  • The gas atmosphere in continuous annealing and galvanizing lines alters both composition and microstructure of the surface and sub-surface of sheet steel. The formation and morphology of the oxides of alloying elements in High Strength Interstitial Free (HS-IF), Dual Phase (DP) and Transformation-Induced Plasticity (TRIP) steels are strongly influenced by the furnace dew point, and the presence of specific oxide may result in surface defects and bare areas on galvanized sheet products. The present contribution reviews the progress made recently in understanding the selective formation of surface and subsurface oxides during annealing in hot dip galvanizing and conventional continuous annealing lines. It is believed that the surface and sub-surface composition and microstructure have a pronounced influence on galvanized sheet product surface quality. In the present study, it is shown that the understanding of the relevant phenomena requires a combination of precise laboratory-scale simulations of the relevant technological processes and the use of advanced surface analytical tools.

Influence of Oxyfluorination on Properties of Polyacrylonitrile (PAN)- Based Carbon Fibers

  • Lim, In-Seub;Yoo, Seung-Hwa;Park, Il-Nam;Lee, Young-Seak
    • Carbon letters
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    • v.5 no.1
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    • pp.12-17
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    • 2004
  • In this study, the oxyfluorination of PAN-based carbon fibers was undertaken at room temperature using fluorine-oxygen mixtures, and the influence of oxyfluorination on properties was investigated. The surface characteristics of the modified fiber were determined by using X-ray photoelectron spectroscopy (XPS) and dynamic contact angle analyzer. The oxyfluorination of carbon fibers was one of the more effective methods to increase surface wettability by the formation of semicovalent C-F bond and C-O bond depending on reaction conditions. When oxygen mole fraction is increased from 0.5 to 0.9, it is probable that attached fluorine atoms at the surface of the fibers reacted with other components. As increased oxyfluorination time and decreased its pressures, semi-covalent peak is increased at 0.5 of oxygen mole fraction. The total surface free energy of oxyfluorinated carbon fibers decreased with increasing oxygen mole fraction over 0.5. These results indicate that the surface of carbon fibers became much more hydrophilic after the short oxyfluorination. The surface free energy of oxyfluorinated carbon fibers progressively decreased after 10 min treatment. The polar components of surface free energies were however, significantly higher for all oxyfluorinated samples than that for the untreated carbon fiber.

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Investigation of Effect of Input Ground Motion on the Failure Surface of Mountain Slopes

  • Khalid, Muhammad Irslan;Pervaiz, Usman;Park, Duhee
    • Journal of the Korean GEO-environmental Society
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    • v.22 no.7
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    • pp.5-12
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    • 2021
  • The reliable seismic stability evaluation of the natural slopes and geotechnical structures has become a critical factor of the design. Pseudo-static or permanent displacement methods are typically employed to evaluate the seismic slope performance. In both methods, the effect of input ground motion on the sliding surface is ignored, and failure surface from the limit equilibrium method is used. For the assessment of the seismic sensitivity of failure surface, two-dimensional non-linear finite element analyses are performed. The performance of the finite element model was validated against centrifuge measurements. A parametric study with a range of input ground motion was performed, and numerical results were used to assess the influence of ground motion characteristics on the sliding surface. Based on the results, it is demonstrated that the characteristics of input ground motion have a significant influence on the location of the seismically induce failure surface. In addition to dynamic analysis, pseudo-static analyses were performed to evaluate the discrepancy. It is observed that sliding surfaces developed from pseudo-static and dynamic analyses are different. The location of the failure surface change with the amplitude and Tm of motion. Therefore, it is recommended to determine failure surfaces from dynamic analysis

Influence of Grease Consistency on the Wear of Gear Surfaces

  • Li, Chen-Xiao;Park, Haneum;Lee, Chul-Hee
    • Tribology and Lubricants
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    • v.38 no.3
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    • pp.115-119
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    • 2022
  • This paper selected three kinds of grease with the same type but different consistency for the experiment. The purpose of the experiment is tested the effect of different consistency of grease on the wear of the gear surface. Different torque test groups were selected in the test, and the lubrication effect of different greases was tested in the test groups with the same torque. After each set of tests, the wear of the gear surfaces was observed and recorded. The data recorded in the experiment included the area of the wear area on the gear surface, the type of wear and the volume of wear. After the test, the gear surface roughness was measured. By calculating the wear volume, the effects of different concentrations of grease on the gear surface wear were compared. The experimental results show that under different stress conditions, the consistency of the grease has a great influence on the lubricating effect of the gear surface and the gear wear. Under the condition with low speed and high torque, different grease consistency affect the gear surface wear, the high consistency grease can reduce the wear of the gear surface, so that the gear can get better lubrication effect during the work.

Influence of Applied Electric Field on Low Temperature Degradation of Y-TZP (인가 전압이 Y-TZP의 저온열화에 미치는 영향)

  • 장주웅;이홍림;김대준;오남식;이득용
    • Journal of the Korean Ceramic Society
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    • v.34 no.12
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    • pp.1254-1260
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    • 1997
  • Influence of applied electric field on the low temperature degradation of 3 mol% YaO3 stabilized tetragonal zirconia polycrystals(3Y-TZP) was investigated using X-ray diffractometry of specimens aged under the dc field of 1.1 kV/mm in silicone oil both of 12$0^{\circ}C$-21$0^{\circ}C$. After the aging, the tetragonal to monoclinic phase transformation was observed only on the specimen surface of 3Y-TZP faced to the anode. This indicated that the surface was overcrowded with oxygen ions as a result of diffusion of oxygen vacancies toward the cathode-sided surface. To elucidate an influence of the applying time of the electric field on the extent of the degradation of 3Y-TZP in air, specimens were aged fore 0-2 hours under the electric field in the oil bath of 12$0^{\circ}C$ and then subsequently aged for 3h at 22$0^{\circ}C$ in air. The longer the specimens were aged under the field, the more extensive the transformation to the monoclinic phase was on the specimen surface faced to the cathode, probably originated from a high diffusion rate of oxygen ions due to a steep oxygen vacancy concentration gradient.

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A Case Study for Influence of Form-oil on Surface Condition of Steam-cured Concrete (증기양생 콘크리트 표면상태에 대한 박리제의 영향 사례연구)

  • Han, Sang Hoon;Yoon, Ju Yong;Hong, Ki Nam;Choi, Jae Wan;Lim, June Woo
    • Journal of the Korean Society of Safety
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    • v.28 no.1
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    • pp.52-56
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    • 2013
  • The purpose of this study is to evaluate the influence of form-oil on steam-cured concrete surface condition. Based, viscosity(high, medium, low) and flash point($26^{\circ}C$, $70^{\circ}C$) of form oil were considered as test variables. The digital image process method was applied for the extraction of air-void area from concrete surface. Test result showed that oil-based form oil reduced air-void by approximately 46% compared to water-based form oil, and the higher the viscosity was, the smaller air-void rate was. In addition, it was conformed that flash point of form oil had a considerable influence on the surface condition of steam-cured concrete.

Local Influence on Misclassification Probability

  • Kim, Myung-Geun
    • Journal of the Korean Statistical Society
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    • v.25 no.1
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    • pp.145-151
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    • 1996
  • The local behaviour of the surface formed by the perturbed maximum likelihood estimator of the squared Mahalanobis distance is investigated. The study of the local behaviour allows a simultaneous perturbation on the samples of interest and it is effective in identifying influential observations.

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