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Effects of Epoxy Coating on the Bond Strength of Reinforcing Bars (철근과 콘크리트의 부착력에 대한 에폭시 피막의 영향)

  • ;Had;Darwin, David;McCabe, L. Steve
    • Proceedings of the Korea Concrete Institute Conference
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    • 1990.10a
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    • pp.79-82
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    • 1990
  • The results of a large-scale study to determine the effects of epoxy coating on the bond strength between deformed reinforcement and concrete are descrebed. Tests include beam-end specimens containing No. 5(16mm), No. 6 (19mm), No. 8(25mm), No. 11(32mm) bars with average coating thicknesses ranging from 3 to 17 mils(0.08-0.43mm). Three deformation patterns are evaluated. Specimens with covers of 1, 2, and 3 bar deameters are studied. Both top-cast and bottom-cast bars are tested. Epoxy coatings are found to significantly reduce bond strength. The severity of that reduction is a function of deformation pattern, bar size, and coating thickness. Design recommendations based on these observations differ from the modifications to the 1989 ACI Building Code.

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A Study of The Medical Classics in the '$\bar{A}yurveda$' (아유르베다'($\bar{A}yurveda$) 의경(醫經)에 관한 연구)

  • Kim, Kj-Wook;Park, Hyun-Kuk;Seo, Ji-Young
    • The Journal of Dong Guk Oriental Medicine
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    • v.10
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    • pp.119-145
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    • 2008
  • Through a simple study of the medical classics in the '$\bar{A}yurveda$', we have summarized them as follows. 1) Traditional Indian medicine started in the Ganges river area at about 1500 B. C. E. and traces of medical science can be found in the "Rigveda" and "Atharvaveda". 2) The "Charaka(閣羅迦集)" and "$Su\acute{s}hruta$(妙聞集)", ancient texts from India, are not the work of one person, but the result of the work and errors of different doctors and philosophers. Due to the lack of historical records, the time of Charaka(閣羅迦) or $Su\acute{s}hruta$(妙聞)s' lives are not exactly known. So the completion of the "Charaka" is estimated at 1st$\sim$2nd century C. E. in northwestern India, and the "$Su\acute{s}hruta$" is estimated to have been completed in 3rd$\sim$4th century C. E. in central India. Also, the "Charaka" contains details on internal medicine, while the "$Su\acute{s}hruta$" contains more details on surgery by comparison. 3) '$V\bar{a}gbhata$', one of the revered Vriddha Trayi(triad of the ancients, 三醫聖) of the '$\bar{A}yurveda$', lived and worked in about the 7th century and wrote the "$Ast\bar{a}nga$ $Ast\bar{a}nga$ hrdaya $samhit\bar{a}$ $samhit\bar{a}$(八支集) and "$Ast\bar{a}nga$ Sangraha $samhit\bar{a}$(八心集)", where he tried to compromise and unify the "Charaka" and "$Su\acute{s}hruta$". The "$Ast\bar{a}nga$ Sangraha $samhit\bar{a}$" was translated into Tibetan and Arabic at about the 8th$\sim$9th century, and if we generalize the medicinal plants recorded in each the "Charaka", "$Su\acute{s}hruta$" and the "$Ast\bar{a}nga$ Sangraha $samhit\bar{a}$", there are 240, 370, 240 types each. 4) The 'Madhava' focused on one of the subjects of Indian medicine, '$Nid\bar{a}na$' ie meaning "the cause of diseases(病因論)", and in one of the copies found by Bower in 4th century C. E. we can see that it uses prescriptions from the "BuHaLaJi(布唅拉集)", "Charaka", "$Su\acute{s}hruta$". 5) According to the "Charaka", there were 8 branches of ancient medicine in India : treatment of the body(kayacikitsa), special surgery(salakya), removal of alien substances(salyapahartka), treatment of poison or mis-combined medicines(visagaravairodhikaprasamana), the study of ghosts(bhutavidya), pediatrics(kaumarabhrtya), perennial youth and long life(rasayana), and the strengthening of the essence of the body(vajikarana). 6) The '$\bar{A}yurveda$', which originated from ancient experience, was recorded in Sanskrit, which was a theorization of knowledge, and also was written in verses to make memorizing easy, and made medicine the exclusive possession of the Brahmin. The first annotations were 1060 for the "Charaka", 1200 for the "$Su\acute{s}hruta$", 1150 for the "$Ast\bar{a}nga$ Sangraha $samhit\bar{a}$", and 1100 for the "$Nid\bar{a}na$". The use of various mineral medicines in the "Charaka" or the use of mercury as internal medicine in the "$Ast\bar{a}nga$ Sangraha $samhit\bar{a}$", and the palpation of the pulse for diagnosing in the '$\bar{A}yurveda$' and 'XiZhang(西藏)' medicine are similar to TCM's pulse diagnostics. The coexistence with Arabian 'Unani' medicine, compromise with western medicine and the reactionism trend restored the '$\bar{A}yurveda$' today. 7) The "Charaka" is a book inclined to internal medicine that investigates the origin of human disease which used the dualism of the 'Samkhya', the natural philosophy of the 'Vaisesika' and the logic of the 'Nyaya' in medical theories, and its structure has 16 syllables per line, 2 lines per poem and is recorded in poetry and prose. Also, the "Charaka" can be summarized into the introduction, cause, judgement, body, sensory organs, treatment, pharmaceuticals, and end, and can be seen as a work that strongly reflects the moral code of Brahmin and Aryans. 8) In extracting bloody pus, the "Charaka" introduces a 'sharp tool' bloodletting treatment, while the "$Su\acute{s}hruta$" introduces many surgical methods such as the use of gourd dippers, horns, sucking the blood with leeches. Also the "$Su\acute{s}hruta$" has 19 chapters specializing in ophthalmology, and shows 76 types of eye diseases and their treatments. 9) Since anatomy did not develop in Indian medicine, the inner structure of the human body was not well known. The only exception is 'GuXiangXue(骨相學)' which developed from 'Atharvaveda' times and the "$Ast\bar{a}nga$ Sangraha $samhit\bar{a}$". In the "$Ast\bar{a}nga$ Sangraha $samhit\bar{a}$"'s 'ShenTiLun(身體論)' there is a thorough listing of the development of a child from pregnancy to birth. The '$\bar{A}yurveda$' is not just an ancient traditional medical system but is being called alternative medicine in the west because of its ability to supplement western medicine and, as its effects are being proved scientifically it is gaining attention worldwide. We would like to say that what we have researched is just a small fragment and a limited view, and would like to correct and supplement any insufficient parts through more research of new records.

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Statistical Properties of Material Strength of Concrete, Re-Bar and Strand Used in Domestic Construction Site (국내 현장의 콘크리트, 철근 및 강연선 재료 강도에 대한 통계 특성 분석)

  • Paik, In-Yeol;Shim, Chang-Su;Chung, Young-Soo;Sang, Hee-Jung
    • Journal of the Korea Concrete Institute
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    • v.23 no.4
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    • pp.421-430
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    • 2011
  • As a fundamental study to introduce the reliability-based design code, a statistical study is conducted for the material strength data collected from domestic construction sites. In order to develop a rational design code based on statistics and reliability theory, it is essential to obtain the statistical properties of material strength. Material strength data for concrete, reinforcing bars, and prestressing strands which are used in domestic construction sites are collected and statistically analyzed. Then, the statistical properties are compared with those used in the process of the reliability-based calibration of internationally leading design codes. The statistical properties of the domestic data are such that the bias factor is relatively uniform between 1.13 and 1.20 and the coefficient of variation is below 0.10. Reinforcing bar data show difference among different manufacturers but there is not much difference among re-bar diameters. In the case of tendons, which are high strength materials, both of the domestic and foreign data show smaller values of the bias factor and the coefficient of variation than those of concrete and re-bar. Statistical distribution of all the material strength can be properly assumed as normal, log-normal, or Gumbel distribution after analyzing the classified data by individual construction site and manufacturer rather than the mixed data obtained from different sources in order to express the individual distribution of each structure.

Effect of Recycled Coarse Aggregate (RCA) Replacement Level on the Bond Behaviour between RCA Concrete and Deformed Rebars (순환 굵은골재의 혼입률에 따른 콘크리트와 이형철근의 부착 거동)

  • Jang, Yong-Heon;Choi, Ki-Sun;You, Young-Chan;Kim, Keung-Hwan;Yun, Hyun-Do
    • Journal of the Korea Concrete Institute
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    • v.22 no.1
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    • pp.123-130
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    • 2010
  • In this study, mixed recycled coarse aggregate (RCA) was produced by mixing RCA from waste concrete in order to evaluate a new method of RCA production. Bond strength between reinforcing bars and RCA concrete was qualitatively evaluated as a part of continuous studies to establish design code of reinforced concrete structural members using recycled aggregate. For practical application, specimens were manufactured with the ready mix RCA concrete. Parameters investigated include: concrete compressive strength (i.e 21, 27 and 40 MPa), replacement levels (i.e 0, 30, 60 and 100%), bar position (i.e vertical and horizontal) and bar location (75 and 225 mm). For the pull-out test, each specimen was in the form of a cube, with each side of 150 mm in length and a deformed bar, 16 mm in diameter, was embedded in the center of each specimen. From the test results, the most of HT type specimen with compressive strength of 21 and 27 MPa showed lower bond strength than the ones provided in CEB-FIP and considered in reinforcement location factor ($\alpha\;=\;1.3$). It was reasoned that bonded area of top bar specimen was reduced at the soffit of reinforcement because of bleed water of fresh concrete. Therefore the reinforcement location factor in current KCI design code should be reviewed and modified.

Optimal Gas Detection System in Cargo Compressor Room of Gas Fueled LNG Carrier (가스추진 LNG 운반선의 가스 압축기실에 설치된 가스검출장치의 최적 배치에 관한 연구)

  • Lee, Sang-Won;Shao, Yude;Lee, Seung-Hun;Lee, Jin-Uk;Jeong, Eun-Seok;Kang, Ho-Keun
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.25 no.5
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    • pp.617-626
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    • 2019
  • This study analyzes the optimal location of gas detectors through the gas dispersion in a cargo compressor room of a 174K LNG carrier equipped with high-pressure cargo handling equipment; in addition, we propose a reasonable method for determining the safety regulations specified in the new International Code of the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC). To conduct an LNG gas dispersion simulation in the cargo compressor room-equipped with an ME-GI engine-of a 174 K LNG carrier, the geometry of the room as well as the equipment and piping, are designed using the same 3D size at a 1-to-1 scale. Scenarios for a gas leak were examined under high pressure of 305 bar and low pressure of 1 bar. The pinhole sizes for high pressure are 4.5, 5.0, and 5.6mm, and for low pressure are 100 and 140 mm. The results demonstrate that the cargo compressor room will not pose a serious risk with respect to the flammable gas concentration as verified by a ventilation assessment for a 5.6 mm pinhole for a high-pressure leak under gas rupture conditions, and a low-pressure leak of 100 and 140 mm with different pinhole sizes. However, it was confirmed that the actual location of the gas detection sensors in a cargo compressor room, according to the new IGC code, should be moved to other points, and an analysis of the virtual monitor points through a computational fluid dynamics (CFD) simulation.

Development of Computer Program for Design of the Small Annular Linear Induction EM Pump (소형 환단면 선형유도전자펌프 설계를 위한 전산 프로그램 개발)

  • Kim, H.R.;Nam, H.Y.;Hwang, J.S.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.05b
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    • pp.137-140
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    • 2002
  • EM(ElectroMagnetic) pump is used for the purpose of transporting liquid sodium coolant with electrical conductivity in the LMR(Liquid Metal Reactor). In the present study, computer program for the pilot annular linear EM pump has been developed for the maximum flowrate with 200 l/min and maximum developing pressure with 3 bar. Firstly, Balance equation is induced by the equivalent circuit method which is commonly employed to analyze linear induction machines and the calculation of the hydraulic pressure drop. Then, design equation is converted to the computer program and optimum pump variables are determined by this code. The code is verified by the comparative analysis with the characteristic of the commercialized pump.

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Size Effect on Shear Strength of Reinforced High Strength Concrete Beams (고강도 철근콘크리트 보의 전단강도에 관한 크기효과)

  • 김진근;박연동
    • Proceedings of the Korea Concrete Institute Conference
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    • 1992.10a
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    • pp.155-160
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    • 1992
  • In this study , the size effect on diagonal shear failure of reinforced high strength concrete beams was investigated, For this purpose, ten singly reinforced high strength concrete beams without web reinforcement were tested for five different dimensions of effective depth which were varied from 67mm to 915mm. The compressive strength of concrete used in this study was 53.7 MPa. One type of reinforcing bar with nominal yield strength of 400 MPa was used. Test results were analyzed and compared with strength predicted by ACI code equation, Zutty's equation and Bazant &Kim's equation. As the results, ACI code equation was seriously unconservative for beams with d of 915mm. Bazant & Kim's equation predicted well the trend of test data. Within the scope of this study, there was no clear difference in size effect with variation of compressive strength of concrete.

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An Experimental Study on the Bond of Steel Fiber Reinforced High-Strength Lightweight Concrete (강섬유보강 고강도 경량콘크리트의 부착에 관한 실험적 연구)

  • 민준수;김상우;이시학;김용부
    • Proceedings of the Korea Concrete Institute Conference
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    • 1999.10a
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    • pp.613-616
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    • 1999
  • The bond between reinforcing bar and concrete is a significant factor to confirm that they behave uniformly in the reinforced concrete. Thus, the studies on this field have been conducted by many researchers. But for the high strength lightweight concrete few studies have been done. In this study, the steel fiber reinforced high strength lightweight concrete developed to complement the brittleness of the high strength lightweight concrete was studied experimentally to find the local bond stress. Total 20 specimens were tested and the measured test values were compared with those calculated according to ACI 318-95 code and CEB-FIP code, respectively. The results indicate that the maximum bond stress has been influenced by increment of volume fracture of steel fiber, compressive strength and cover, Especially steel fiber caused not only increment of bond strength but also ductile behaviro.

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Viscous Flow Analysis for the Rudder Section Using FLUENT Code (FLUENT 코드를 이용한 타 단면의 점성 유동 해석)

  • 부경태;한재문;송인행;신수철
    • Journal of the Society of Naval Architects of Korea
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    • v.40 no.4
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    • pp.30-36
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    • 2003
  • Lately, the cavitation and erosion phenomena in the rudder have been increased for high-speed container ships. However, cavitation is not prone to occur in model experiments because of low Reynolds number. In order to predict the cavitation phenomena, the - analysis of the viscous flow in the rudder gap is positively necessary In this study, numerical calculation was applied to the two-dimensional flow around the rudder gap using FLUENT code. The velocity and pressure field were numerically acquired and cavitation phenomena could be predicted. And the case that the round bar was installed in the rudder gap was analyzed. For reducing the acceleration force when fluid flow through the gap, modified rudder shape is proposed, It is shown that modified rudder shape restrain the pressure drop at the entrance of the gap highly both in the computational results and in the model experiment, and reduce the cavitation bubbles.

Visually Misprinted Ear Code Detection Method Using the Column Homogeneity of Bar Code (바 코드의 열 동질성을 이용한 시각적인 인쇄 오류가 있는 바 코드 검출 방법)

  • 이승재;김창화
    • Proceedings of the Korean Information Science Society Conference
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    • 2003.04c
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    • pp.271-273
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    • 2003
  • 본 논문에서는 바 코드리더로 그 정보를 읽어 낼 수 있지만, 시각적인 인쇄오류가 있는 바 코드를 고속으로 검출해 내는 방법을 제안한다. 바 코드는 해당 제품의 제품정보 및 키를 저장하기 위하여 주로 사용되어 왔다. 근래에 들어 바 코드의 활용범위가 점점 넓어지게 되면서 잘못 인쇄된 바 코드로 인하여 차후에 발생할 수 있는 시간적 경제적 손실을 줄이기 위하여 인쇄된 바 코드가 공장에서 나가기 전에 바 코드가 정확하게 인쇄되었는지를 검사하는 것이 중요하게 되었다. 특히 상품이 아니라 고객카드와 같이 바 코드 소유자의 정보를 저장하는 수단으로도 활용하는 경우는 개인이 자신의 카드를 소지하게 되므로 바 코드에 담겨있는 정보도 중요하지만 바 코드의 인쇄상태 또한 중요하다. 이는 바 코드리더로 제대로 읽혀진다 하더라도 시각적인 인쇄오류가 있는 경우 해당 고객으로부터 불만을 사게 되고 새 카드로 교체를 요구받게 되기 때문이다. 이 경우 회사의 이미지 실추는 물론 카드 교체에 따른 시간적 경제적 손실을 보게된다. 이에 본 논문에서는 바 코드의 높이가 모두 동일한 1차원(선형)바 코드를 대상으로 바 코드의 열 동질성을 이용한 시각적인 인쇄오류가 있는 바 코드를 검출해 내는 방법을 제안한다.

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