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Mechanical Properties of High Strength Concrete with High Volume Mineral Admixture (다량의 혼화재를 사용한 고강도 콘크리트의 역학적 특성)

  • Baek, Chul-Woo;Park, Cho-Bum;Choi, Sung-Woo;Jo, Hyun-Tae;Ryu, Deuk-Hyun
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.2 no.3
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    • pp.180-187
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    • 2014
  • The purpose of this study is to evaluate on the mechanical properties of High Volume Mineral Admixture(HVMA) high strength concrete to reduce the amount use of Ordinary Potland Cement, to discover the optimized HVMA binder and to test HVMA concrete based on the change of W/B and curing temperature. The results were shown as follows: The HVMA binder using the mixture of combined heat power plant fly ash and anhydrous gypsum known as inorganic activators with the mixture of blast furnace slag and fly ash was optimized. The mixture of HVMA high strength concrete at 26% of W/B ratio had a good result on flow characteristic and mechanical properties. High strength HVMA concrete over 50MPa is possibly manufactured over curing temperature $20^{\circ}C$.

Effect of Gypsum on Hydration Properties of Natural Hydraulic Lime (천연 수경성 석회의 수화특성에 미치는 석고의 영향)

  • Moon, Ki-Yeon;Choi, Moon-Kwan;Cho, Kye-Hong;Cho, Jin-Sang;Ahn, Ji-Whan;Hong, Chang-Woo
    • Resources Recycling
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    • v.24 no.1
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    • pp.12-20
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    • 2015
  • In this study, change of hydration property with contents and type of gypsum in ternary natural hydraulic lime containing blast furnace slag and gypsum was investigated. Anhydrite, hemihydrate and dihydrate were added 3 % and 10 %, respectively in natural hydraulic lime adding blast furnace slag 20 %. Hydration and physical behavior due to solubility and reactivity of different types of gypsum were analyzed in early hydration. As a result of analysis of hydration properties, in all samples, hydrates such as ettringite and C-S-H were produced in early hydration, and amount of hydrates with increase of hydration time was increased. In the case of compressive strength, when contents of gypsum are 3 %, it was higher compressive strength than other specimens. At hydration 28 days, for addition of anhydrite and hemihydrate, compressive strength was more than adding dihydrate.

A Selection of High Pedestrian Accident Zones Using Traffic Accident Data and GIS: A Case Study of Seoul (교통사고 데이터와 GIS를 이용한 보행자사고 개선구역 선정 : 서울시를 대상으로)

  • Yang, Jong Hyeon;Kim, Jung Ok;Yu, Kiyun
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.34 no.3
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    • pp.221-230
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    • 2016
  • To establish objective criteria for high pedestrian accident zones, we combined Getis-ord Gi* and Kernel Density Estimation to select high pedestrian accident zones for 54,208 pedestrian accidents in Seoul from 2009 to 2013. By applying Getis-ord Gi* and considering spatial patterns where pedestrian accident hot spots were clustered, this study identified high pedestrian accident zones. The research examined the microscopic distribution of accidents in high pedestrian accident zones, identified the critical hot spots through Kernel Density Estimation, and analyzed the inner distribution of hot spots by identifying the areas with high density levels.

Study of Fundamental Properties of Latex-Modified Concrete Using Blast-furnace Slag (고로(高爐)슬래그 미분말(微粉末)을 사용(使用)한 라텍스개질(改質) 콘크리트의 기초물성(基礎物性) 연구(硏究))

  • Hong, Chang-Woo;Jeong, Won-Kyong;Kim, Kyeong-Jin
    • Resources Recycling
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    • v.15 no.2 s.70
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    • pp.10-17
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    • 2006
  • The purpose of this study was to evaluate the effects of blast-furnace slag on strength development and durability of latex-modified concrete (LMC) and ordinary portland cement concrete as slag contents. Main experimental variables were performed latex contents (0%, 10%, 15%) and slag contents (0%, 30%). The compressive and flexural strengths, chloride-ion rapid permeability and chemical attacks resistance were measured to analyze the characteristic of the developed LMC and BS-LMC(latex-modified concrete added blast-furnace slag) on hardened concrete. The test results showed that compressive and flexural strength of BS-LMC increased as the slag contents increased from 0% to 30% at the long term of curing. It considers blast furnace slag used when latex content was up to 10%. The permeability resistance of BS-LMC(latex 10%, blast 30%) was extremely good at the curing time 90 days. Also. the effects of added blast furnace slag on OPC and LMC were increased on the permeability and chemical attacks resistance.

A Study on the Frequency and Intensity Variations of Okhotsk High: Focused on the Korean Peninsula (오호츠크해고기압의 출현일과 강도의 변동에 관한 연구 -한반도에 영향을 미친 날을 중심으로-)

  • Cho, Li-Na;Lee, Seung-Ho
    • Journal of the Korean Geographical Society
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    • v.46 no.1
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    • pp.36-49
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    • 2011
  • This paper aims to investigate the frequency and intensity variations of Okhotsk high pressure system focused on the Korean Peninsula. Weather chart (00UTC), daily weather data and reanalysis data were used. The first occurrence date of Okhotsk high pressure system tends to be earlier in those years that surrounding land air temperature in April is high. The frequency of Okhotsk high has recently decreased, and its intensity tends to be stronger when the difference between sea surface temperature and surrounding land air temperature is big. The frequency of Okhotsk high in April, May, June and July increases when surrounding land air temperature is high, and its intensity grows when the difference between surrounding land air temperature and sea surface temperature is big. The frequency of Okhotsk high may increase and its intensity may increase when the first occurrence date comes earlier. In June, however, the reverse may apply.

Experimental Study on the Material Characteristics of Slag Cement with Various Phosphogypsum Materials (인산부산석고의 각 형태조건에 따른 슬래그 시멘트의 품질특성에 관한 실험적 연구)

  • Park, Jong-Tak;Oh, Hong-Seob
    • Journal of the Korea Concrete Institute
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    • v.21 no.6
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    • pp.729-735
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    • 2009
  • In this study, it is experimentally verified a feasibility of the wasted phosphogypsum ($CaSO_4/H_2O$) that is a byproduct from the phosphoric acid process of manufacturing fertilizers can be applied as an admixture in slag cement. For the test, phosphogypsum is modified as dihydrate, hemihydrate, type III anhydrite, and type II anhydrite, and then chemical characteristics and mechanical properties of various slag cements containing above mentioned gypsum materials were analyzed. The test results show that the gypsum made at high temperature has better quality with decrease of water-soluble phosphoric acid ($S-P_2O_5$) which has an effect on the quality of cement. And type II anhydrite shows superior quality in terms of drying shrinkage and the compressive strength of cement paste with hemihydrate at 56 days is higher than other gypsum material.

Improvement of Early Strength of Blast-Furnace Slag Blended Cement at Low Temperature (고로 슬래그 시멘트의 저온 조기 강도 증진)

  • 장복기;임용무;김윤주
    • Journal of the Korean Ceramic Society
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    • v.36 no.2
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    • pp.130-135
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    • 1999
  • The enhanced slag fineness and the batch water of low water-to-cement ratio(W/C) were employed in order to improve the early strength of blast-furnace slag blended cement at low temperature. A grinding aid was used to grind the blast-furnace slag into the fineness of 6,280$\textrm{cm}^2$/g (Blaine), and this fine slag was then homogeneously mixed with the ordinary Portland cement to produce the blast-furnace slag blended cement containing 40% slag by weight composition. On the other hand, the batch water could be reduced from W/C=0.50 (KS L 5105) to W/C=0.33 through a commercial, naphthalene type superplasticizer. Through the method mentioned above, the early strength of the blast-furnace slag blended cement at low temperature could be enhanced even somewhat higher than the Portland cement strength. And the microsturcture of the cement was studied by both the pore structure analysis and the A.C. impedance measurement.

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Strength and Durability of Polymer-Modified Mortars Using Ground Granulated Blast-Furnace Slag (고로슬래그 미분말을 혼입한 폴리머 시멘트 모르타르의 강도 및 내구성)

  • 주명기;김남길;연규석
    • Journal of the Korea Concrete Institute
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    • v.14 no.2
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    • pp.164-170
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    • 2002
  • Effect of the polymer-binder ratio and slag content on the properties of combined wet/dry-cured polymer-modified mortars using granulated blast-furnace slag are examined. Results shows that the flexural and compressive strengths of polymer-modified mortar using the slag tend to increase with increasing slag content, and reaches a maximum at a slag content of 40 %, and is inclined to increase with increasing polymer-binder ratio. Water absorption, carbonation depth and chloride ion penetration depth tend to decrease with increasing polymer-binder ratio and slag content. Accordingly, the incorporation of slag into polymer-modified mortars at a slag content of 40% is recommended for a combined wet/dry curing regardless of the types of polymer.

Forest Structure in Relation to Altitude and Part of Slope in a Valley Forest at Yeonaegol, Kyeryongsan National Park (계룡산국립공원 연애골지역 계곡부의 해발고와 사면부위에 따른 산림구조)

  • 박인협;서영권;이석면;이만용
    • Korean Journal of Environment and Ecology
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    • v.14 no.4
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    • pp.303-310
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    • 2001
  • 계룡산국립공원 연애골 계곡부(해발 170-630m)의 해발고와 사면부위에 따른 교목층과 아교목층의 산림구조를 조사하기 위하여 해발고와 사면부위에 따란 48개 조사구를 설정하였다. 계곡 정부를 제외할 때, 해발고가 높아짐에 따라 교목층의 밀도는 증가하는 반면 아교목층의 밀도는 감소하였으며, 교목층과 아교목층 전체의 밀도는 별차이가 없었다. 흉고단면적은 계곡 하부와 중부가 상부에 비하여 높았다. 해발고가 높아짐에 따라 중요치가 증가하는 경향을 보이는 수종은 산길나무, 팥배나무, 쇠물푸레 등이었으며, 감소하는 경향을 보이는 수종은 산벚나무, 졸참나무, 때죽나무, 갈참나무, 밤나무 등이었다. 사면 하부에서 갈수록 중요치가 증가하는 경향을 보이는 수종은 소나무, 신갈나무, 쪽동백나무, 쇠물푸레 드잉었으며, 감소하는 경향을 보이는 수종은 느티나무, 때죽나무, 비목나무, 고로쇠나무 등이었다. 해발고대별 종다양의 범위는 0.971~1.273이었으며, 종다양도와 종수는 계곡 중부가 계곡하부와 상부에 비하여 다소 낮았으나 균재도는 유사하였다. 계곡 정부를 제외한 해발고대간 유사도지수는 30.8~63.7%, 사면부위간 유사도지수는 69.8~79.5%로서 사면부위보다 해발고에 따른 종구성상태의 변화가 더 크게 나타났다. 수종별 중요치에 의한 Cluster 분석 결과 계곡 하부의 사면 상. 중, 하부에 위치한 때죽나무-소나무-낙엽활엽수군집, 계곡 중부의 사면 상, 중, 하부에 위치한 굴참나무-낙엽활엽수군집 계곡 상부의 상. 중. 하부에 위치한 물푸레나무-낙엽활엽수군집, 계곡 정부에 위치한 소나무-신갈나무군집 등 4개 유형군집으로 구분되었다. 종상관을 분석한 결과 느티나무, 물푸레나무, 고로쇠나무, 팽나무, 회나무 등 5개 수종간, 소나무, 쇠물푸레, 산철쭉 등 3개 수종간 유의적인 정의 상관을 보였다. 유의적인 정의 상관을 보인 느티나무, 물푸레나무, 회나무, 사람주나무 등 4개 수종 모두 소나무와 유의적인 부위 상관을 보였으며, 유의적인 정의 상관을 보인 졸참나무는 유의적인 정의 상관을 보인 물푸레나무, 사람주나무, 회나무와, 유의적인 부의 상관을 보였다.

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High-definition Video Enhancement Using Color Constancy Based on Scene Unit and Modified Histogram Equalization (장면단위 색채 항상성과 변형 히스토그램 평활화 방법을 이용한 고선명 동영상의 화질 향상 방법)

  • Cho, Dong-Chan;Kang, Hyung-Sub;Kim, Whoi-Yul
    • Journal of Broadcast Engineering
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    • v.15 no.3
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    • pp.368-379
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    • 2010
  • As high-definition video is broadly used in various system such as broadcast system and digital camcorder the proper method in order to improve the quality of high-definition video is needed. In this paper, we propose an efficient method to improve color and contrast of high-definition video. In order to apply the image enhancement method to high-definition video, scale-down video of high-definition video is used and the parameter for image enhancement method is computed from small size video. To enhance the color of high-definition video, we apply color constancy method. First, we separate the video into several scenes by cut detection method. Then, we apply color constancy to each scene with same parameter. To improve the contrast of high-definition video, we use union of original image and histogram equalized image, and weight is calculated based on sorting of histogram bins. Finally, the performance of proposed method is demonstrated in experiment section.